Seven Wonders "Hair Food" Cocktail
Seven Wonders "Hair Food" Cocktail
The following drink contains Protein, Choline, Inositol, Pantothenic Acid,
Biotin, Vitamin E and Zinc:
The seven ingredients' nutritionists most often recommend for growing healthy hair.
8 Fl oz Plain Yoghurt
8 Fl oz Orange Juice
3 Tablespoons Wheat Germ
3 Tablespoons Brewers Yeast
1 Tablespoon Lecithin Crystals
1 Teaspoon Vitamin C Crystals
1 Raw Egg Yolk
1 Tablespoon Unflavored Gelatine Powder
Honey to Taste (optional)
Combine all the ingredients and blend until smooth. If a blender is not available put all the ingredients into a jar with a lid and shake vigorously.
This tonic makes a quick and nutritious breakfast and will work wonders for your hair.
This cocktail should help just about everyone, and you will certainly notice a difference to your hair once you try it.
Another recommended regime for hair loss which has proved to be very effective is a supplement of the Amino Acids, Zinc and Vitamin C.
This supplement is particularly good for people who go on crash diets and find a problem with hair loss, or problems which are less obvious such as women who are losing hair as a result of birth control pills and subsequent vitamin and mineral deficiencies.
The following drink contains Protein, Choline, Inositol, Pantothenic Acid,
Biotin, Vitamin E and Zinc:
The seven ingredients' nutritionists most often recommend for growing healthy hair.
8 Fl oz Plain Yoghurt
8 Fl oz Orange Juice
3 Tablespoons Wheat Germ
3 Tablespoons Brewers Yeast
1 Tablespoon Lecithin Crystals
1 Teaspoon Vitamin C Crystals
1 Raw Egg Yolk
1 Tablespoon Unflavored Gelatine Powder
Honey to Taste (optional)
Combine all the ingredients and blend until smooth. If a blender is not available put all the ingredients into a jar with a lid and shake vigorously.
This tonic makes a quick and nutritious breakfast and will work wonders for your hair.
This cocktail should help just about everyone, and you will certainly notice a difference to your hair once you try it.
Another recommended regime for hair loss which has proved to be very effective is a supplement of the Amino Acids, Zinc and Vitamin C.
This supplement is particularly good for people who go on crash diets and find a problem with hair loss, or problems which are less obvious such as women who are losing hair as a result of birth control pills and subsequent vitamin and mineral deficiencies.
how can we can prevent Hair loss
Vitamins and minerals play a vital role in the function of the body, the use of certain vitamins can most certainly play a major part in helping to maintain a healthy head of hair.
Introduction
The human body is an amazingly complex and wonderful machine, but it cannot function without a supply of food.
The nutrients in food are needed for energy, movement, heat, growth, repair, hair growth and sometimes reproduction. The body needs to be able to digest the foods it takes in so that it can be used in various ways.
There are six basic types of nutrients and two basic non-nutrients found in food. The six nutrients are carbohydrate, fat, protein, vitamins, minerals, trace elements; the two non-nutrients are fibre and water. Generally speaking most foods contain several nutrients, in varying amounts. Carrots, for instance, contain a little protein, a trace of fat, some carbohydrate, a good deal of water, a little sugar, fibre, and a selection of vitamins and minerals such as potassium, sodium, calcium, iron, zinc, vitamins B6, C and E, folic acid, biotin and pantothenic acid, etc. We need a combination of all the above nutrients to maintain a normal and healthy body.
Para-Aminobenzoic Acid
(PABA) as this vitamin is commonly known is one of the lesser known members of the B complex family, has been shown to be an anti-grey hair vitamin. In tests in black animals that were feed with a diet deficient of PABA, they developed grey hair, when the animals were reintroduced to the vitamin, normal hair colour was restored
Research on humans with grey hair being given 200mg of PABA after each meal produced results that showed that a study of the hair afterwards resulted in a seventy per cent result of the hair returning to its original colour. Other research claims that PABA combined with folic acid also helps restore hair to its original colour.
Deficiency of PABA, Biotin, Folic Acid and Pantothenic Acid appears to affect hair colour. Hair colour can normally be restored with a diet rich in the B vitamins and in the few cases where colour is not restored the hair will improve in quality and strength of growth.
PABA and the B vitamins are found in foods such as liver, kidney, whole grain and yeast. The richest source being liver.
Inositol
Inositol is also a member of the B vitamin group. It is a compound occurring in the brain, muscles, liver, kidney and eyes.
In laboratory animals, a diet lacking Inositol produced baldness, but when the vitamin was added to the food of these animals, the hair grew back again. It was also observed that male animals lost hair twice as fast as female animals. The result of this experiment would suggest that males require a higher Inositol intake than females. An Inositol deficient diet can also cause eczema, a form of skin irritation.
One doctor in a series of experiments prescribed Inositol together with other sources of B vitamins to all his balding patients. In almost all case's hair loss was arrested, in some case's hair growth was noticeable in as little as one month. In one case hair recovery was total and not one bald spot remained.
Inositol, also appears to reduce the amount of cholesterol in the blood.
Biotin
Biotin often called vitamin H, is yet another B complex component. Biotin is a proven hair growth vitamin and a preventative to excessive hair loss. It appears to metabolise fatty acids. Fatty acids are a valuable growth factor in numerous processes in the body including the hair.
Biotin is also seen as an aid in preventing hair turning grey.
Biotin is found in egg yolks. Raw egg whites actually hinder effectiveness, but when the albumen (egg white) is cooked, the culprit - a substance called avidin is destroyed by heat. Biotin is also present in liver, milk, yeast and kidney.
Balding men might find that a Biotin supplement may keep their hair longer.
Zinc
In laboratory tests animals fed with a zinc supplement showed signs of more hair growth, as opposed to loss of hair in animals that were deprived of zinc in their feed. It was discovered that there was a change in the hair protein structure when zinc was deficient in the diet.
Severe zinc deficiency in humans has been shown to produce baldness and scalp problems that were reversed when zinc was returned to the diet.
Zinc has also been shown to stop hair turning grey. One doctor taking zinc for a year reversed the grey hairs which returned to their original colour.
Zinc can be depleted by high stress levels. For a good source of zinc, wheat germ is the best, other sources are brewer's yeast, pumpkin seeds, oysters and mussels, shrimps and egg yolks.
One delightful effect of zinc is that it has long been regarded as an aphrodisiac, and as such it can be very beneficial for your sex life, which is not a bad side effect to have.
Protein
Protein is a basic ingredient in many hair shampoos and conditioners and is also the major ingredient of hair itself, which is at least ninety per cent protein. Whilst this should not necessarily be the main ingredient in your diet, its importance should not be ignored.
In controlled tests volunteers, supplementing their diets with protein in the form of 14g of gelatine daily, found it increased the thickness of individual hair strands by as much as 45 per cent in only two months.
Diet can influence both hair growth and quality and gelatine has exhibited one of the highest specific dynamic effects of any food or supplement.
Given that a strong hair is a healthy hair, the study noted that the gelatine induced increases in the diet constituted an improvement in the mechanical properties of the hair, including strength. When the volunteers stopped eating the gelatine, their hair returned to its original diameter within six months.
Vitamin E
A Canadian physician who started going grey was able to reverse the process by taking 800iu of vitamin E in capsule form daily. At the age of 68 after some 15 years of taking vitamin E he still has a healthy head of thick black hair, and is the envy of men half his age.
Vitamin E has also been shown to retard the ageing process. It has been suggested that grey hair is a symptom of body degeneration so a supplement of vitamin E can only be beneficial whether you have grey hair or not.
The best natural sources of vitamin E are wheat germ, Soya beans, broccoli, brussel sprouts, spinach and eggs.
Choline
Choline is a B vitamin like nutrient that's useful in counter acting the effects of stress. Recently scientists in America were able to induce toxic levels of stress in baby animals by limiting the amount of choline in their diets.
Choline supplements prescribed to balding patients produced significant results to prove choline's worth in hair loss. Lecithin is a very good source of choline, at it also supplies inositol, a B complex vitamin with a particular affinity with choline, these two vitamins work together well.
Foods rich in choline are egg yolks, yeast, liver and wheat germ.
Vitamin A
A deficiency of Vitamin A will cause dry hair and rough skin. Vitamin A is stored in the liver and if large doses (50,000 - 100,000 iu daily) are taken for a prolonged period the liver cannot store the A vitamin, and it can build up in the body to give unpleasant side effects which include nausea, headaches, hair loss, drowsiness and weight loss.
The R.D.A. for vitamin A is 2,500 iu.
Pantothenic Acid
Pantothenic Acid also known as Calcium Pantothenate is considered to be important to the health of the skin and scalp. Pantothenic acid is necessary for the well being of every body cell and neither carbohydrate nor fat can be changed into energy without it.
This nutrient is also important for the functioning of the adrenal glands that produce much of the male sex hormones.
Volunteers who were feed on a diet deficient of pantothenic acid showed increased vulnerability to infection and adrenal levels dropped, blood pressure also dropped and constipation developed.
Animals lacking this nutrient in their diet became grey haired and the follicles started to waste away.
This supplement is most often found in B complex formulas.
This nutrient is obtained from liver, kidney, egg yolks, whole grains, milk and potatoes.
Introduction
The human body is an amazingly complex and wonderful machine, but it cannot function without a supply of food.
The nutrients in food are needed for energy, movement, heat, growth, repair, hair growth and sometimes reproduction. The body needs to be able to digest the foods it takes in so that it can be used in various ways.
There are six basic types of nutrients and two basic non-nutrients found in food. The six nutrients are carbohydrate, fat, protein, vitamins, minerals, trace elements; the two non-nutrients are fibre and water. Generally speaking most foods contain several nutrients, in varying amounts. Carrots, for instance, contain a little protein, a trace of fat, some carbohydrate, a good deal of water, a little sugar, fibre, and a selection of vitamins and minerals such as potassium, sodium, calcium, iron, zinc, vitamins B6, C and E, folic acid, biotin and pantothenic acid, etc. We need a combination of all the above nutrients to maintain a normal and healthy body.
Para-Aminobenzoic Acid
(PABA) as this vitamin is commonly known is one of the lesser known members of the B complex family, has been shown to be an anti-grey hair vitamin. In tests in black animals that were feed with a diet deficient of PABA, they developed grey hair, when the animals were reintroduced to the vitamin, normal hair colour was restored
Research on humans with grey hair being given 200mg of PABA after each meal produced results that showed that a study of the hair afterwards resulted in a seventy per cent result of the hair returning to its original colour. Other research claims that PABA combined with folic acid also helps restore hair to its original colour.
Deficiency of PABA, Biotin, Folic Acid and Pantothenic Acid appears to affect hair colour. Hair colour can normally be restored with a diet rich in the B vitamins and in the few cases where colour is not restored the hair will improve in quality and strength of growth.
PABA and the B vitamins are found in foods such as liver, kidney, whole grain and yeast. The richest source being liver.
Inositol
Inositol is also a member of the B vitamin group. It is a compound occurring in the brain, muscles, liver, kidney and eyes.
In laboratory animals, a diet lacking Inositol produced baldness, but when the vitamin was added to the food of these animals, the hair grew back again. It was also observed that male animals lost hair twice as fast as female animals. The result of this experiment would suggest that males require a higher Inositol intake than females. An Inositol deficient diet can also cause eczema, a form of skin irritation.
One doctor in a series of experiments prescribed Inositol together with other sources of B vitamins to all his balding patients. In almost all case's hair loss was arrested, in some case's hair growth was noticeable in as little as one month. In one case hair recovery was total and not one bald spot remained.
Inositol, also appears to reduce the amount of cholesterol in the blood.
Biotin
Biotin often called vitamin H, is yet another B complex component. Biotin is a proven hair growth vitamin and a preventative to excessive hair loss. It appears to metabolise fatty acids. Fatty acids are a valuable growth factor in numerous processes in the body including the hair.
Biotin is also seen as an aid in preventing hair turning grey.
Biotin is found in egg yolks. Raw egg whites actually hinder effectiveness, but when the albumen (egg white) is cooked, the culprit - a substance called avidin is destroyed by heat. Biotin is also present in liver, milk, yeast and kidney.
Balding men might find that a Biotin supplement may keep their hair longer.
Zinc
In laboratory tests animals fed with a zinc supplement showed signs of more hair growth, as opposed to loss of hair in animals that were deprived of zinc in their feed. It was discovered that there was a change in the hair protein structure when zinc was deficient in the diet.
Severe zinc deficiency in humans has been shown to produce baldness and scalp problems that were reversed when zinc was returned to the diet.
Zinc has also been shown to stop hair turning grey. One doctor taking zinc for a year reversed the grey hairs which returned to their original colour.
Zinc can be depleted by high stress levels. For a good source of zinc, wheat germ is the best, other sources are brewer's yeast, pumpkin seeds, oysters and mussels, shrimps and egg yolks.
One delightful effect of zinc is that it has long been regarded as an aphrodisiac, and as such it can be very beneficial for your sex life, which is not a bad side effect to have.
Protein
Protein is a basic ingredient in many hair shampoos and conditioners and is also the major ingredient of hair itself, which is at least ninety per cent protein. Whilst this should not necessarily be the main ingredient in your diet, its importance should not be ignored.
In controlled tests volunteers, supplementing their diets with protein in the form of 14g of gelatine daily, found it increased the thickness of individual hair strands by as much as 45 per cent in only two months.
Diet can influence both hair growth and quality and gelatine has exhibited one of the highest specific dynamic effects of any food or supplement.
Given that a strong hair is a healthy hair, the study noted that the gelatine induced increases in the diet constituted an improvement in the mechanical properties of the hair, including strength. When the volunteers stopped eating the gelatine, their hair returned to its original diameter within six months.
Vitamin E
A Canadian physician who started going grey was able to reverse the process by taking 800iu of vitamin E in capsule form daily. At the age of 68 after some 15 years of taking vitamin E he still has a healthy head of thick black hair, and is the envy of men half his age.
Vitamin E has also been shown to retard the ageing process. It has been suggested that grey hair is a symptom of body degeneration so a supplement of vitamin E can only be beneficial whether you have grey hair or not.
The best natural sources of vitamin E are wheat germ, Soya beans, broccoli, brussel sprouts, spinach and eggs.
Choline
Choline is a B vitamin like nutrient that's useful in counter acting the effects of stress. Recently scientists in America were able to induce toxic levels of stress in baby animals by limiting the amount of choline in their diets.
Choline supplements prescribed to balding patients produced significant results to prove choline's worth in hair loss. Lecithin is a very good source of choline, at it also supplies inositol, a B complex vitamin with a particular affinity with choline, these two vitamins work together well.
Foods rich in choline are egg yolks, yeast, liver and wheat germ.
Vitamin A
A deficiency of Vitamin A will cause dry hair and rough skin. Vitamin A is stored in the liver and if large doses (50,000 - 100,000 iu daily) are taken for a prolonged period the liver cannot store the A vitamin, and it can build up in the body to give unpleasant side effects which include nausea, headaches, hair loss, drowsiness and weight loss.
The R.D.A. for vitamin A is 2,500 iu.
Pantothenic Acid
Pantothenic Acid also known as Calcium Pantothenate is considered to be important to the health of the skin and scalp. Pantothenic acid is necessary for the well being of every body cell and neither carbohydrate nor fat can be changed into energy without it.
This nutrient is also important for the functioning of the adrenal glands that produce much of the male sex hormones.
Volunteers who were feed on a diet deficient of pantothenic acid showed increased vulnerability to infection and adrenal levels dropped, blood pressure also dropped and constipation developed.
Animals lacking this nutrient in their diet became grey haired and the follicles started to waste away.
This supplement is most often found in B complex formulas.
This nutrient is obtained from liver, kidney, egg yolks, whole grains, milk and potatoes.
Plasticizers for plastics | Triphenyl phosphate | Safer plasticizers
Plasticizer
Plasticizers are additives that increase the plasticity or fluidity the material to which they are added, these include plastics, cement, concrete and clay bodies. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different. The plasticizers for plastics soften the final product increasing its flexibility. Plasticizers for concrete soften the mix before it hardens, increasing its workability, and are usually not intended to affect the properties of the final product after it hardens.
Plasticizers for plastics
Plasticizers for plastics are additive, most commonly phthalates, that give hard plastics like PVC the desired flexibility and durability. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing of the "free volume"), and thus significantly lowering the glass transition temperature for the plastic and making it softer. For plastics such as PVC, the more plasticiser added, the lower its cold flex temperature will be. This means that it will be more flexible, though its strength and hardness will decrease as a result of it. Some plasticizers evaporate and tend to concentrate in an enclosed space; the "new car smell" is caused mostly by plasticizers evaporating from the car interior.
Dicarboxylic/tricarboxylic ester-based plasticizers
Phthalate-based plasticizers are used in situations where good resistance to water and oils is required. Some common phthalate plasticizers are:
Bis(2-ethylhexyl) phthalate (DEHP), used in construction materials, food packaging, children toys, medical devices, and cling wrap
Diisononyl phthalate (DINP), found in garden hoses, shoes, toys, and building materials
Bis(n-butyl)phthalate (DnBP, DBP), used for cellulose plastics, food wraps, adhesives, perfumes and also in cosmetics - about a third of nail polishes, glosses, enamels and hardeners contain it, together with some shampoos, sunscreens, skin emollients, and insect repellents
Butyl benzyl phthalate (BBzP) is found in vinyl tiles, traffic cones, food conveyor belts, artificial leather and plastic foams
Diisodecyl phthalate (DIDP), used for insulation of wires and cables, car undercoating, shoes, carpets, pool liners
Di-n-octyl phthalate (DOP or DnOP), used in flooring materials, carpets, notebook covers, and high explosives, such as Semtex. Together with DEHP it was the most common plasticizers, but now is suspected of causing cancer
Diisooctyl phthalate (DIOP), all-purpose plasticizer for polyvinyl chloride, polyvinyl acetate, rubbers, cellulose plastics and polyurethane.
Diethyl phthalate (DEP)
Diisobutyl phthalate (DIBP)
Di-n-hexyl phthalate, used in flooring materials, tool handles and automobile parts
Trimellitates are used in automobile interiors and other applications where resistance to high temperature is required. They have extremely low volatility.
Trimethyl trimellitate (TMTM)
Tri-(2-ethylhexyl) trimellitate (TEHTM-MG)
Tri-(n-octyl,n-decyl) trimellitate (ATM)
Tri-(heptyl,nonyl) trimellitate (LTM)
n-octyl trimellitate (OTM)
Adipate-based plasticizers are used for low-temperature or resistance to ultraviolet light. Some examples are:
Bis(2-ethylhexyl)adipate (DEHA)
Dimethyl adipate (DMAD)
Monomethyl adipate (MMAD)
Dioctyl adipate (DOA)
Sebacate-based plasticiser
Dibutyl sebacate (DBS)
Maleates
Dibutyl maleate (DBM)
Diisobutyl maleate (DIBM)
Other plasticisers
Benzoates
Epoxidized vegetable oils
Sulfonamides
N-ethyl toluene sulfonamide (o/p ETSA), ortho and para isomers
N-(2-hydroxypropyl) benzene sulfonamide (HP BSA)
N-(n-butyl) benzene sulfonamide (BBSA-NBBS)
Organophosphates
Tricresyl phosphate (TCP)
Tributyl phosphate (TBP)
Glycols/polyethers
Triethylene glycol dihexanoate (3G6, 3GH)
Tetraethylene glycol diheptanoate (4G7)
Polymeric plasticizers
Some other chemicals working as plasticizers are nitrobenzene, carbon disulfide and β-naphthyl salicylate. Plasticizers, such as DEHP and DOA, were found to be carcinogens and endocrine disruptors.
Safer plasticizers
Safer plasticizers with better biodegradability and less biochemical effects are being developed. Some such plasticizers are:
Acetylated monoglycerides; these can be used as food additives
Alkyl citrates, used in food packagings, medical products, cosmetics and children toys
Triethyl citrate (TEC)
Acetyl triethyl citrate (ATEC), higher boiling point and lower volatility than TEC
Tributyl citrate (TBC)
Acetyl tributyl citrate (ATBC), compatible with PVC and vinyl chloride copolymers
Trioctyl citrate (TOC), also used for gums and controlled release medicines
Acetyl trioctyl citrate (ATOC), also used for printing ink
Trihexyl citrate (THC), compatible with PVC, also used for controlled release medicines
Acetyl trihexyl citrate (ATHC), compatible with PVC
Butyryl trihexyl citrate (BTHC, trihexyl o-butyryl citrate), compatible with PVC
Trimethyl citrate (TMC), compatible with PVC
Plasticizers for energetic materials
For energetic materials, especially propellants (eg. smokeless powders), plasticizers based on nitrates are frequently employed. Some such plasticizers are:
Nitroglycerine (NG)
Butanetriol trinitrate (BTTN)
Dinitrotoluene (DNT)
Metriol trinitrate (METN)
Diethylene glycol dinitrate (DEGN)
Bis(2,2-dinitropropyl)formal (BDNPF)
Bis(2,2-dinitropropyl)acetal (BDNPA)
2,2,2-Trinitroethyl 2-nitroxyethyl ether (TNEN)
Due to the secondary alcohol groups, NG and BTTN have relatively low thermal stability. METN, DEGN, BDNPF and BDNPA have relatively low energies. NG and DEGN have relatively high vapor pressure.
Plasticizers for concrete production
Superplasticizers are chemical admixtures that can be added to concrete mixtures to improve workability. Strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture very unworkable and difficult to mix, necessitating the use of plasticizers and superplasticizers.
Superplasticizers are also often used when pozzolanic ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high strength concrete and fiber reinforced concrete.
Adding 2% superplasticizer per unit weight of cement is usually sufficient. However, note that most commercially available superplasticizers come dissolved in water, so the extra water added has to be accounted for in mix proportioning. Adding an excessive amount of superplasticizer will result in excessive segregation of concrete and is not advisable. Some studies also show that too much superplasticizer will result in a retarding effect.
Plasticizers are commonly manufactured from lignosulfonates, a by-product from the paper industry. Superplasticizers have generally been manufactured from sulfonated naphthalene formaldehyde or sulfonated melamine formaldehyde, although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate based plasticisers and naphthalene and melamine based superplasticisers disperse the flocculated cement particles through a mechanism of electrostatic repulsion (see colloid). In normal plasticisers, the active substances are adsorbed on to the cement particles, giving them a negative charge, which leads to repulsion between particles. Naphthalene and melamine superplasticisers are organic polymers. The long molecules wrap themselves around the cement particles, giving them a highly negative charge so that they repel each other.
Polycarboxylate Ethers (PCE), the new generation of superplasticisers are not only chemically different from the older sulphonated melamine and naphthalene based products but their action mechanism is also different, giving cement dispersion by steric stabilisation, instead of electrostatic repulsion. This form of dispersion is more powerful in its effect and gives improved workability retention to the cementitious mix. Furthermore, the chemical structure of PCE allows for a greater degree of chemical modification than the older generation products, offering a range of performance that can be tailored to meet specific needs.
In ancient times, the Romans used blood as a superplasticizer for their concrete mixes.
Plasticisers can be obtained by your local concrete manufacturerHousehold washing up liquid may also be used as a simple plasticizer.
ORGANO PHOSPHATE ESTERS
Triphenyl Phosphate (T.P.P)
Chemical Name : Triphenyl Phosphate
Uses
Polyester fibers, Poly Carbonate triacetate,
NC, Photographic films, Cellulose acetate,
ethyl cellulose & cellulose acetate butyrate.
Typical properties :
Physical appearance :White flake
Phosphorus content: wt % 9.5
Specific gravity @ 60° C / 60 ° C :1.220
Melting Point °C :48° C
Acidity as phosphoric acid: % 0.003
Applications :
PAC’S TPP ( Triphenyl Phosphate ), a white flake having low iron content, meets the known specification of all major manufacturers of photographic safety film, It is a recognized organophosphorus flame retardant used in films sheetings, mouldings and certain coatings. Others important properties are its toughening ability and extremely low volatility in cellulose acetate and triacetate, its good resistance to extremely low volatility in cellulose Acetate and triacetate its good resistance to moisture, and its lack of odour. In most applications, it is combined with other plasticizers but it can be used as a primary flame retardant plasticizers in cast triacetate film and sheeting. These products are clear, tough and tack free, It also improves dimensional stability and dielectric strength. Other applications are in moulded acetate products and in coating based in nitrocellulose , ethyl cellulose and cellulose acetate butyrate.PAC’ S TPP when used in large proportions is usually combined with a solvent plasticizer to avoid crystallization and a consequent separation, as it is a solid at room temperature. It is more compatible with cellulose triacetate than with secondary cellulose acetate, but can be incorporated in the latter up to about 30 phr without separation. In secondary cellulose acetate, cellulose acetate butyrate, and ethyl cellulose, for film sheeting or moulding material, it is generally combined with other more active plasticizer such as dimethyl phthalate, dimethoxy ethyl phthalate or diethyl phthalate. It can be used alone in cast triacetate film and sheeting, where, as a very approximate guide, the top limit is 35 phr, or less ( 20-25 phr) under severe service conditions. The approximate top limit in melt-extruded sheeting of film is 15 phr of triphenyl phosphate, and injection moulding material it is about 20 phr. Triphenyl phosphate is compatible with cellulose nitrate in amounts up to equal proportions of plasticizer and resin.
Other films and sheetings :
Triphenyl phosphate as a plasticizer toughens cellulose acetate and imparts a good balance of properties in other films and sheeting. A solvent plasticizer is generally used along with triphenyl phosphate will reduce cold flow and improved tensile strength. Impact strength is correspondingly reduced. Ultraviolet-light stability is average. Whereas phthalate plasticizers and triacetin tend to increase the flammability of a cellulose acctate composition, triphenyl phosphate reduces flammability considerably. Cellulose acetate sheeting containing 20 phr or more triphenyl phosphate will not continue to burn when ignited and the flame withdrawnMoulding compostions : Typical moulding applications of triphenyl phosphate are in cellulose acetate, cellulose acetate butyrate, and vinyl copolymer compound which are used in records, vacuum cleaner parts, housings for clocks and appliances, and parts for Christmas tree lighting sets. Triphenyl phosphate is recommended for use in compounds for records based on vinyl chloride-vinyl acetate copolymer for several reasons. Up to 50 % by weight of fillers must be added to the resin to prevent heat distortion, and up to 5 phr triphenyl phosphate is added to wet these fillers. Its wetting actions is possible because it melts at a slightly lower temperature than the resin. It also functions as a surface – active agent in the calendaring process, and as an internal lubricant improving flow characteristics when the records is moulded. As a plasticizer, it controls brittleness in the final product. Its heat stability, low water absorption and low volatility are all advantages over other plasticizer that has been used in these applications.
Benefits :
It is used principally as a non-solvent plasticizer for cellulose acetate films having up to 80% retentivity and giving flexibility and toughness to the films An excellent catalyst/inhibitor/chain terminator for the growing polymer chain for the manufacture of polyester fibre An excellent fire retardant and plasticizer for synthetic resins viz. Phenol formal-dehyde, decorative laminated sheets etc. It is also used in making stencil blanks, dopes films, varnishes, enamels, plastics, lacquers and for impregnating roofing paper
Tricresyl Phosphate (T.C.P.)
Phosphorus Flame Retardant
TCP ( Tricresyl Phosphate ) is a low viscosity synthetic phosphate ester, Tricresyl Phosphate finds uses in wide variety of applications as Flame retardant plasticizer.
Uses
Leather cloth (PVC) : Upholstery, Book binding, Seat covers
Utility articles : Footwear, Raincoats, Handbags, Fiber glass cellulose acetate
Extruded articles : Cables (PVC & rubber), hoses, flexible pipe, coal mining, conveyor belts
Coatings : Nitrocellulose lacquers, phenolic resins, lube oils
Typical properties :
Physical appearance:Clear Liquid
Phosphorus content:wt % 8.4
Specific gravity @ 25° C :1.17±0.01
Boiling Point (decomposes )°C :415° C
Flash Point °C :220°C
Solubility (G/100 g Solvent) :Water Insoluble ,Completely soluble in Toluene, Methyl Ethyl Ketone, Methanol
TCP is recommended for use in plastisols for fabrics coating & other applications where its low, stable viscosity offers improved processing. TCP can give a driver finish to coated fabrics. TCP has high plasticizing efficiency that enables formulator to achieve better flame retardance at lower cost. It can also be used as flame retardant in phenolic laminatesThe use of proper equipment is recommended. Excess exposure to the product should be avioded. Wash thoroughly after handling.
Product should be stored in cool, dry and well ventilated area away from incompatible materials.
Unless stated, shelf life of the product will be 12 months from the date of packing. For additional handling & toxicological information, consult PAC Material safety Data sheet. Triaryl Phosphate (T.A.P.)
Phosphorus Flame RetardantTAP ( Triaryl Phosphate ) is a low viscosity synthetic Triaryl phosphate ester, Triaryl Phosphate finds uses in wide variety of application as Flame retardant plasticizer
Plasticizers are additives that increase the plasticity or fluidity the material to which they are added, these include plastics, cement, concrete and clay bodies. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different. The plasticizers for plastics soften the final product increasing its flexibility. Plasticizers for concrete soften the mix before it hardens, increasing its workability, and are usually not intended to affect the properties of the final product after it hardens.
Plasticizers for plastics
Plasticizers for plastics are additive, most commonly phthalates, that give hard plastics like PVC the desired flexibility and durability. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing of the "free volume"), and thus significantly lowering the glass transition temperature for the plastic and making it softer. For plastics such as PVC, the more plasticiser added, the lower its cold flex temperature will be. This means that it will be more flexible, though its strength and hardness will decrease as a result of it. Some plasticizers evaporate and tend to concentrate in an enclosed space; the "new car smell" is caused mostly by plasticizers evaporating from the car interior.
Dicarboxylic/tricarboxylic ester-based plasticizers
Phthalate-based plasticizers are used in situations where good resistance to water and oils is required. Some common phthalate plasticizers are:
Bis(2-ethylhexyl) phthalate (DEHP), used in construction materials, food packaging, children toys, medical devices, and cling wrap
Diisononyl phthalate (DINP), found in garden hoses, shoes, toys, and building materials
Bis(n-butyl)phthalate (DnBP, DBP), used for cellulose plastics, food wraps, adhesives, perfumes and also in cosmetics - about a third of nail polishes, glosses, enamels and hardeners contain it, together with some shampoos, sunscreens, skin emollients, and insect repellents
Butyl benzyl phthalate (BBzP) is found in vinyl tiles, traffic cones, food conveyor belts, artificial leather and plastic foams
Diisodecyl phthalate (DIDP), used for insulation of wires and cables, car undercoating, shoes, carpets, pool liners
Di-n-octyl phthalate (DOP or DnOP), used in flooring materials, carpets, notebook covers, and high explosives, such as Semtex. Together with DEHP it was the most common plasticizers, but now is suspected of causing cancer
Diisooctyl phthalate (DIOP), all-purpose plasticizer for polyvinyl chloride, polyvinyl acetate, rubbers, cellulose plastics and polyurethane.
Diethyl phthalate (DEP)
Diisobutyl phthalate (DIBP)
Di-n-hexyl phthalate, used in flooring materials, tool handles and automobile parts
Trimellitates are used in automobile interiors and other applications where resistance to high temperature is required. They have extremely low volatility.
Trimethyl trimellitate (TMTM)
Tri-(2-ethylhexyl) trimellitate (TEHTM-MG)
Tri-(n-octyl,n-decyl) trimellitate (ATM)
Tri-(heptyl,nonyl) trimellitate (LTM)
n-octyl trimellitate (OTM)
Adipate-based plasticizers are used for low-temperature or resistance to ultraviolet light. Some examples are:
Bis(2-ethylhexyl)adipate (DEHA)
Dimethyl adipate (DMAD)
Monomethyl adipate (MMAD)
Dioctyl adipate (DOA)
Sebacate-based plasticiser
Dibutyl sebacate (DBS)
Maleates
Dibutyl maleate (DBM)
Diisobutyl maleate (DIBM)
Other plasticisers
Benzoates
Epoxidized vegetable oils
Sulfonamides
N-ethyl toluene sulfonamide (o/p ETSA), ortho and para isomers
N-(2-hydroxypropyl) benzene sulfonamide (HP BSA)
N-(n-butyl) benzene sulfonamide (BBSA-NBBS)
Organophosphates
Tricresyl phosphate (TCP)
Tributyl phosphate (TBP)
Glycols/polyethers
Triethylene glycol dihexanoate (3G6, 3GH)
Tetraethylene glycol diheptanoate (4G7)
Polymeric plasticizers
Some other chemicals working as plasticizers are nitrobenzene, carbon disulfide and β-naphthyl salicylate. Plasticizers, such as DEHP and DOA, were found to be carcinogens and endocrine disruptors.
Safer plasticizers
Safer plasticizers with better biodegradability and less biochemical effects are being developed. Some such plasticizers are:
Acetylated monoglycerides; these can be used as food additives
Alkyl citrates, used in food packagings, medical products, cosmetics and children toys
Triethyl citrate (TEC)
Acetyl triethyl citrate (ATEC), higher boiling point and lower volatility than TEC
Tributyl citrate (TBC)
Acetyl tributyl citrate (ATBC), compatible with PVC and vinyl chloride copolymers
Trioctyl citrate (TOC), also used for gums and controlled release medicines
Acetyl trioctyl citrate (ATOC), also used for printing ink
Trihexyl citrate (THC), compatible with PVC, also used for controlled release medicines
Acetyl trihexyl citrate (ATHC), compatible with PVC
Butyryl trihexyl citrate (BTHC, trihexyl o-butyryl citrate), compatible with PVC
Trimethyl citrate (TMC), compatible with PVC
Plasticizers for energetic materials
For energetic materials, especially propellants (eg. smokeless powders), plasticizers based on nitrates are frequently employed. Some such plasticizers are:
Nitroglycerine (NG)
Butanetriol trinitrate (BTTN)
Dinitrotoluene (DNT)
Metriol trinitrate (METN)
Diethylene glycol dinitrate (DEGN)
Bis(2,2-dinitropropyl)formal (BDNPF)
Bis(2,2-dinitropropyl)acetal (BDNPA)
2,2,2-Trinitroethyl 2-nitroxyethyl ether (TNEN)
Due to the secondary alcohol groups, NG and BTTN have relatively low thermal stability. METN, DEGN, BDNPF and BDNPA have relatively low energies. NG and DEGN have relatively high vapor pressure.
Plasticizers for concrete production
Superplasticizers are chemical admixtures that can be added to concrete mixtures to improve workability. Strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture very unworkable and difficult to mix, necessitating the use of plasticizers and superplasticizers.
Superplasticizers are also often used when pozzolanic ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high strength concrete and fiber reinforced concrete.
Adding 2% superplasticizer per unit weight of cement is usually sufficient. However, note that most commercially available superplasticizers come dissolved in water, so the extra water added has to be accounted for in mix proportioning. Adding an excessive amount of superplasticizer will result in excessive segregation of concrete and is not advisable. Some studies also show that too much superplasticizer will result in a retarding effect.
Plasticizers are commonly manufactured from lignosulfonates, a by-product from the paper industry. Superplasticizers have generally been manufactured from sulfonated naphthalene formaldehyde or sulfonated melamine formaldehyde, although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate based plasticisers and naphthalene and melamine based superplasticisers disperse the flocculated cement particles through a mechanism of electrostatic repulsion (see colloid). In normal plasticisers, the active substances are adsorbed on to the cement particles, giving them a negative charge, which leads to repulsion between particles. Naphthalene and melamine superplasticisers are organic polymers. The long molecules wrap themselves around the cement particles, giving them a highly negative charge so that they repel each other.
Polycarboxylate Ethers (PCE), the new generation of superplasticisers are not only chemically different from the older sulphonated melamine and naphthalene based products but their action mechanism is also different, giving cement dispersion by steric stabilisation, instead of electrostatic repulsion. This form of dispersion is more powerful in its effect and gives improved workability retention to the cementitious mix. Furthermore, the chemical structure of PCE allows for a greater degree of chemical modification than the older generation products, offering a range of performance that can be tailored to meet specific needs.
In ancient times, the Romans used blood as a superplasticizer for their concrete mixes.
Plasticisers can be obtained by your local concrete manufacturerHousehold washing up liquid may also be used as a simple plasticizer.
ORGANO PHOSPHATE ESTERS
Triphenyl Phosphate (T.P.P)
Chemical Name : Triphenyl Phosphate
Uses
Polyester fibers, Poly Carbonate triacetate,
NC, Photographic films, Cellulose acetate,
ethyl cellulose & cellulose acetate butyrate.
Typical properties :
Physical appearance :White flake
Phosphorus content: wt % 9.5
Specific gravity @ 60° C / 60 ° C :1.220
Melting Point °C :48° C
Acidity as phosphoric acid: % 0.003
Applications :
PAC’S TPP ( Triphenyl Phosphate ), a white flake having low iron content, meets the known specification of all major manufacturers of photographic safety film, It is a recognized organophosphorus flame retardant used in films sheetings, mouldings and certain coatings. Others important properties are its toughening ability and extremely low volatility in cellulose acetate and triacetate, its good resistance to extremely low volatility in cellulose Acetate and triacetate its good resistance to moisture, and its lack of odour. In most applications, it is combined with other plasticizers but it can be used as a primary flame retardant plasticizers in cast triacetate film and sheeting. These products are clear, tough and tack free, It also improves dimensional stability and dielectric strength. Other applications are in moulded acetate products and in coating based in nitrocellulose , ethyl cellulose and cellulose acetate butyrate.PAC’ S TPP when used in large proportions is usually combined with a solvent plasticizer to avoid crystallization and a consequent separation, as it is a solid at room temperature. It is more compatible with cellulose triacetate than with secondary cellulose acetate, but can be incorporated in the latter up to about 30 phr without separation. In secondary cellulose acetate, cellulose acetate butyrate, and ethyl cellulose, for film sheeting or moulding material, it is generally combined with other more active plasticizer such as dimethyl phthalate, dimethoxy ethyl phthalate or diethyl phthalate. It can be used alone in cast triacetate film and sheeting, where, as a very approximate guide, the top limit is 35 phr, or less ( 20-25 phr) under severe service conditions. The approximate top limit in melt-extruded sheeting of film is 15 phr of triphenyl phosphate, and injection moulding material it is about 20 phr. Triphenyl phosphate is compatible with cellulose nitrate in amounts up to equal proportions of plasticizer and resin.
Other films and sheetings :
Triphenyl phosphate as a plasticizer toughens cellulose acetate and imparts a good balance of properties in other films and sheeting. A solvent plasticizer is generally used along with triphenyl phosphate will reduce cold flow and improved tensile strength. Impact strength is correspondingly reduced. Ultraviolet-light stability is average. Whereas phthalate plasticizers and triacetin tend to increase the flammability of a cellulose acctate composition, triphenyl phosphate reduces flammability considerably. Cellulose acetate sheeting containing 20 phr or more triphenyl phosphate will not continue to burn when ignited and the flame withdrawnMoulding compostions : Typical moulding applications of triphenyl phosphate are in cellulose acetate, cellulose acetate butyrate, and vinyl copolymer compound which are used in records, vacuum cleaner parts, housings for clocks and appliances, and parts for Christmas tree lighting sets. Triphenyl phosphate is recommended for use in compounds for records based on vinyl chloride-vinyl acetate copolymer for several reasons. Up to 50 % by weight of fillers must be added to the resin to prevent heat distortion, and up to 5 phr triphenyl phosphate is added to wet these fillers. Its wetting actions is possible because it melts at a slightly lower temperature than the resin. It also functions as a surface – active agent in the calendaring process, and as an internal lubricant improving flow characteristics when the records is moulded. As a plasticizer, it controls brittleness in the final product. Its heat stability, low water absorption and low volatility are all advantages over other plasticizer that has been used in these applications.
Benefits :
It is used principally as a non-solvent plasticizer for cellulose acetate films having up to 80% retentivity and giving flexibility and toughness to the films An excellent catalyst/inhibitor/chain terminator for the growing polymer chain for the manufacture of polyester fibre An excellent fire retardant and plasticizer for synthetic resins viz. Phenol formal-dehyde, decorative laminated sheets etc. It is also used in making stencil blanks, dopes films, varnishes, enamels, plastics, lacquers and for impregnating roofing paper
Tricresyl Phosphate (T.C.P.)
Phosphorus Flame Retardant
TCP ( Tricresyl Phosphate ) is a low viscosity synthetic phosphate ester, Tricresyl Phosphate finds uses in wide variety of applications as Flame retardant plasticizer.
Uses
Leather cloth (PVC) : Upholstery, Book binding, Seat covers
Utility articles : Footwear, Raincoats, Handbags, Fiber glass cellulose acetate
Extruded articles : Cables (PVC & rubber), hoses, flexible pipe, coal mining, conveyor belts
Coatings : Nitrocellulose lacquers, phenolic resins, lube oils
Typical properties :
Physical appearance:Clear Liquid
Phosphorus content:wt % 8.4
Specific gravity @ 25° C :1.17±0.01
Boiling Point (decomposes )°C :415° C
Flash Point °C :220°C
Solubility (G/100 g Solvent) :Water Insoluble ,Completely soluble in Toluene, Methyl Ethyl Ketone, Methanol
TCP is recommended for use in plastisols for fabrics coating & other applications where its low, stable viscosity offers improved processing. TCP can give a driver finish to coated fabrics. TCP has high plasticizing efficiency that enables formulator to achieve better flame retardance at lower cost. It can also be used as flame retardant in phenolic laminatesThe use of proper equipment is recommended. Excess exposure to the product should be avioded. Wash thoroughly after handling.
Product should be stored in cool, dry and well ventilated area away from incompatible materials.
Unless stated, shelf life of the product will be 12 months from the date of packing. For additional handling & toxicological information, consult PAC Material safety Data sheet. Triaryl Phosphate (T.A.P.)
Phosphorus Flame RetardantTAP ( Triaryl Phosphate ) is a low viscosity synthetic Triaryl phosphate ester, Triaryl Phosphate finds uses in wide variety of application as Flame retardant plasticizer
Paterno-Büchi Reaction
Paterno-Büchi Reaction
In this reaction photoinduced oxetane is formed by the photochemical [2+2] cycloaddition of a carbonyl with an olefin.
In this reaction photoinduced oxetane is formed by the photochemical [2+2] cycloaddition of a carbonyl with an olefin.
Mechanism:
The possible transitions (C=O) are shown below:
Once the carbonyl ground state has been photoexcited, either a singlet or triplet state may be formed:
Either type of transition (n,π* and π,π*) and electronic state (singlet, triplet) may participate in the first stage of this reaction, which is rationalized by invoking diradical intermediates:
Breaking of the new σ-bonds requires more energy, and the reverse reaction is not possible using same light frequency.
Application:
Diatropic ring | Ring currents in large [4n + 2]-annulenes
Ring currents in large [4n + 2]-annulenes
Alessandro Soncini, Patrick W. Fowler and Leonardus W. Jenneskens
Reported computational results for large [4n + 2]-annulenes indicate a falling off of aromaticity in D3h geometries but its retention in D6h geometries, as diagnosed on both energetic and magnetic criteria. Ipsocentric pseudo- mapping of the current density induced by a perpendicular external magnetic field shows that ring currents follow this trend.
Diatropic ring currents are quenched in D3h geometries but survive in D6h geometries of [4n + 2]-annulenes (4n + 2 = 30, 42, 54, 66). Ipsocentric orbital contributions explain this distinction in terms of the translational/diatropic, rotational/paratropic selection rules for current in monocycles, coupled with an account of differential angular-momentum mixing in D3h and D6h symmetries. The orbital model rationalises the differences between D6h and D3h geometries, accounts for the decay of aromaticity with ring size for D3h[4n + 2]-annulenes, and predicts trends for anti-aromatic [4n]-annulenes in the two symmetry groups.
Alessandro Soncini, Patrick W. Fowler and Leonardus W. Jenneskens
Reported computational results for large [4n + 2]-annulenes indicate a falling off of aromaticity in D3h geometries but its retention in D6h geometries, as diagnosed on both energetic and magnetic criteria. Ipsocentric pseudo- mapping of the current density induced by a perpendicular external magnetic field shows that ring currents follow this trend.
Diatropic ring currents are quenched in D3h geometries but survive in D6h geometries of [4n + 2]-annulenes (4n + 2 = 30, 42, 54, 66). Ipsocentric orbital contributions explain this distinction in terms of the translational/diatropic, rotational/paratropic selection rules for current in monocycles, coupled with an account of differential angular-momentum mixing in D3h and D6h symmetries. The orbital model rationalises the differences between D6h and D3h geometries, accounts for the decay of aromaticity with ring size for D3h[4n + 2]-annulenes, and predicts trends for anti-aromatic [4n]-annulenes in the two symmetry groups.
• Mass Spectrometry | Ultraviolet-Visible Spectroscopy | Infrared Spectroscopy
Spectroscopy
The spectroscopic techniques described below do not provide a three-dimensional picture of a molecule, but instead yield information about certain characteristic features. A brief summary of this information follows:
• Mass Spectrometry: Sample molecules are ionized by high energy electrons. The mass to charge ratio of these ions is measured very accurately by electrostatic acceleration and magnetic field perturbation, providing a precise molecular weight. Ion fragmentation patterns may be related to the structure of the molecular ion.
• Ultraviolet-Visible Spectroscopy:
Absorption of this relatively high-energy light causes electronic excitation. The easily accessible part of this region (wavelengths of 200 to 800 nm) shows absorption only if conjugated pi-electron systems are present.
• Infrared Spectroscopy:
Absorption of this lower energy radiation causes vibrational and rotational excitation of groups of atoms. within the molecule. Because of their characteristic absorptions identification of functional groups is easily accomplished.
The spectroscopic techniques described below do not provide a three-dimensional picture of a molecule, but instead yield information about certain characteristic features. A brief summary of this information follows:
• Mass Spectrometry: Sample molecules are ionized by high energy electrons. The mass to charge ratio of these ions is measured very accurately by electrostatic acceleration and magnetic field perturbation, providing a precise molecular weight. Ion fragmentation patterns may be related to the structure of the molecular ion.
• Ultraviolet-Visible Spectroscopy:
Absorption of this relatively high-energy light causes electronic excitation. The easily accessible part of this region (wavelengths of 200 to 800 nm) shows absorption only if conjugated pi-electron systems are present.
• Infrared Spectroscopy:
Absorption of this lower energy radiation causes vibrational and rotational excitation of groups of atoms. within the molecule. Because of their characteristic absorptions identification of functional groups is easily accomplished.
Types of Phospholipid | Phosphoglycerides | Sphingomyelin
Phospholipid
Phosphatidyl choline is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
Phospholipids are a class of lipids, and a major component of all biological membranes, along with glycolipids, cholesterol and proteins. Understanding of the aggregation properties of these molecules is known as lipid polymorphism and forms part of current academic research.
Components
They are built upon to a nitrogen-containing alcohol like ethanolamine or an organic compound such as choline. The "head" of the phospholipid is polar and the "tails" are non-polar.
Types of Phospholipid
Phosphoglycerides
In phosphoglycerides, the carboxyl group of each fatty acid is esterified to the hydroxyl groups on carbon-1 and carbon-2 of the glycerol molecule. The phosphate group is attached to carbon-3 by an ester link. This molecule, known as a phosphatidate, is present in small quantities in membranes, but is also a precursor for the other phosphoglycerides.
In phosphoglyceride synthesis, phosphatidates must be activated first. Phospholipids can be formed from an activated diacylglycerol or an activated alcohol.
Phosphatidyl serine and phosphatidyl inositol are formed from a phosphoester linkage between the hydroxyl of an alcohol (serine or inositol) and cytidine diphosphodiacylglycerol (CDP-diacylglycerol).
In animals, plants and yeast the synthesis of phospatidyl ethanolamine, the alcohol is phosphorylated by ATP first, and subsequently reacts with cytidine triphosphate (CTP) to form the activated alcohol (CDP-ethanolamine). The alcohol then reacts with a diacylglycerol to form the final product. In bacteria, the serine moiety of Phosphatidyl serine is decarboxylated to give phospatidyl ethanolamine.
In mammals, phosphatidyl choline can be synthesized via two separate pathways; a series of reactions similar to phosphatidyl ethanolamine synthesis, and the methylation of phosphatidyl ethanolamine, which is catalyzed by phosphatidyl ethanolamine methyltransferase, an enzyme produced in the liver.
Phosphatidyl ethanolamine is the major component of cephalin.
Sphingomyelin
The backbone of sphingomyelin is sphingosine, an amino alcohol formed from palmitate and serine. The amino terminal is acylated with a long-chain acyl CoA to yield ceramide. Subsequent substitution of the terminal hydroxyl group by phosphatidyl choline forms sphingomyelin.
Sphingomyelin is also present in all eukaryotic cell membranes, especially the plasma membrane, and is particularly concentrated in the nervous system because sphingomyelin is a major component of myelin, the fatty insulation wrapped around nerve cells by Schwann cells or oligodendrocytes. Multiple sclerosis is a disease characterised by deterioration of the myelin sheath, leading to impairment of nervous conduction.
Amphipathic character
Due to its polar nature, the head of a phospholipid is hydrophilic (attracted to water); the lipophilic (or often known as hydrophobic) tails are not attracted to water. When placed in water, phospholipids form one of a number of lipid phases. In biological systems this is restricted to bilayers, in which the lipophilic tails line up against one another, forming a membrane with hydrophilic heads on both sides facing the water. This allows it to form liposomes spontaneously, or small lipid vesicles, which can then be used to transport materials into living organisms and study diffusion rates into or out of a cell membrane.
This membrane is partially permeable, capable of elastic movement, and has fluid properties, in which embedded proteins (integral or peripheral proteins) and phospholipid molecules are able to move laterally. Such movement can be described by the Fluid Mosaic Model, that
describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Cholesterol contributes to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.
Phosphatidyl choline is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
Phospholipids are a class of lipids, and a major component of all biological membranes, along with glycolipids, cholesterol and proteins. Understanding of the aggregation properties of these molecules is known as lipid polymorphism and forms part of current academic research.
Components
They are built upon to a nitrogen-containing alcohol like ethanolamine or an organic compound such as choline. The "head" of the phospholipid is polar and the "tails" are non-polar.
Types of Phospholipid
Phosphoglycerides
In phosphoglycerides, the carboxyl group of each fatty acid is esterified to the hydroxyl groups on carbon-1 and carbon-2 of the glycerol molecule. The phosphate group is attached to carbon-3 by an ester link. This molecule, known as a phosphatidate, is present in small quantities in membranes, but is also a precursor for the other phosphoglycerides.
In phosphoglyceride synthesis, phosphatidates must be activated first. Phospholipids can be formed from an activated diacylglycerol or an activated alcohol.
Phosphatidyl serine and phosphatidyl inositol are formed from a phosphoester linkage between the hydroxyl of an alcohol (serine or inositol) and cytidine diphosphodiacylglycerol (CDP-diacylglycerol).
In animals, plants and yeast the synthesis of phospatidyl ethanolamine, the alcohol is phosphorylated by ATP first, and subsequently reacts with cytidine triphosphate (CTP) to form the activated alcohol (CDP-ethanolamine). The alcohol then reacts with a diacylglycerol to form the final product. In bacteria, the serine moiety of Phosphatidyl serine is decarboxylated to give phospatidyl ethanolamine.
In mammals, phosphatidyl choline can be synthesized via two separate pathways; a series of reactions similar to phosphatidyl ethanolamine synthesis, and the methylation of phosphatidyl ethanolamine, which is catalyzed by phosphatidyl ethanolamine methyltransferase, an enzyme produced in the liver.
Phosphatidyl ethanolamine is the major component of cephalin.
Sphingomyelin
The backbone of sphingomyelin is sphingosine, an amino alcohol formed from palmitate and serine. The amino terminal is acylated with a long-chain acyl CoA to yield ceramide. Subsequent substitution of the terminal hydroxyl group by phosphatidyl choline forms sphingomyelin.
Sphingomyelin is also present in all eukaryotic cell membranes, especially the plasma membrane, and is particularly concentrated in the nervous system because sphingomyelin is a major component of myelin, the fatty insulation wrapped around nerve cells by Schwann cells or oligodendrocytes. Multiple sclerosis is a disease characterised by deterioration of the myelin sheath, leading to impairment of nervous conduction.
Amphipathic character
Due to its polar nature, the head of a phospholipid is hydrophilic (attracted to water); the lipophilic (or often known as hydrophobic) tails are not attracted to water. When placed in water, phospholipids form one of a number of lipid phases. In biological systems this is restricted to bilayers, in which the lipophilic tails line up against one another, forming a membrane with hydrophilic heads on both sides facing the water. This allows it to form liposomes spontaneously, or small lipid vesicles, which can then be used to transport materials into living organisms and study diffusion rates into or out of a cell membrane.
This membrane is partially permeable, capable of elastic movement, and has fluid properties, in which embedded proteins (integral or peripheral proteins) and phospholipid molecules are able to move laterally. Such movement can be described by the Fluid Mosaic Model, that
describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Cholesterol contributes to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.
Heat Temperature and the Particle Theory | Expanding and Contracting
Heat, Temperature, and the Particle Theory
What actually is the difference between water at 20ºC and water at 50ºC?
What is the difference between heat and temperature?
How are these questions related?
Can any one hypothesis answer both questions?
The Particle Theory
Scientists over the years came up with many ideas, or hypotheses, to try to explain the difference between heat and temperature. One such hypothesis was thought of by Lavoisier. He suggested that heat might be a substance with mass, which he called caloric. But Lavoisier's idea was not supported by experimental observations, and scientists looked for other ways to explain heat.
Scientists now use the kinetic molecular theory, or particle theory, to explain heat and temperature and the difference between, say, 20ºC and 50ºC. The particle theory is based on a model that suggests that all matter is made up of tiny particles too small to be seen. According to this model, these particles are always moving- they have energy. The more energy they have, the faster they move. So far, all the evidence is made up of moving particles. That is why we call the particle model for matter a theory.
So what is the difference between heat and temperature? According to the particle theory, heat is energy, and it is transferred from hotter substances to colder ones. Temperature is a measure of the average energy level of the particles in a substance.
Both hot and cold water are made up of moving particles, some moving quickly, and some moving slowly. But on average, the particles move faster in hot water than in cold water.
Expanding and Contracting
The particle theory is a useful model to explain why substances expand when they are heated and contract when they are cooled. At high temperatures, particles have more energy, move more quickly, and have more collisions. As a result, they take up more space, and the substance expands. At lower temperatures, particles have less energy, move more slowly, and have fewer collisions. They take up less space, and the substance contracts.
Self Check
In your own words, describe the difference between heat and temperature.
Two cups contain the same amount of water. a) What device would be best for comparing the average energy of the particles of each sample of water? b) Explain how this device would help you compare the energies of the particles.
Apply
Use the particle theory to explain how an outdoor thermometer works.
What actually is the difference between water at 20ºC and water at 50ºC?
What is the difference between heat and temperature?
How are these questions related?
Can any one hypothesis answer both questions?
The Particle Theory
Scientists over the years came up with many ideas, or hypotheses, to try to explain the difference between heat and temperature. One such hypothesis was thought of by Lavoisier. He suggested that heat might be a substance with mass, which he called caloric. But Lavoisier's idea was not supported by experimental observations, and scientists looked for other ways to explain heat.
Scientists now use the kinetic molecular theory, or particle theory, to explain heat and temperature and the difference between, say, 20ºC and 50ºC. The particle theory is based on a model that suggests that all matter is made up of tiny particles too small to be seen. According to this model, these particles are always moving- they have energy. The more energy they have, the faster they move. So far, all the evidence is made up of moving particles. That is why we call the particle model for matter a theory.
So what is the difference between heat and temperature? According to the particle theory, heat is energy, and it is transferred from hotter substances to colder ones. Temperature is a measure of the average energy level of the particles in a substance.
Both hot and cold water are made up of moving particles, some moving quickly, and some moving slowly. But on average, the particles move faster in hot water than in cold water.
Expanding and Contracting
The particle theory is a useful model to explain why substances expand when they are heated and contract when they are cooled. At high temperatures, particles have more energy, move more quickly, and have more collisions. As a result, they take up more space, and the substance expands. At lower temperatures, particles have less energy, move more slowly, and have fewer collisions. They take up less space, and the substance contracts.
Self Check
In your own words, describe the difference between heat and temperature.
Two cups contain the same amount of water. a) What device would be best for comparing the average energy of the particles of each sample of water? b) Explain how this device would help you compare the energies of the particles.
Apply
Use the particle theory to explain how an outdoor thermometer works.
Carotenoids
Carotenoids
Carotenoids are familiar to all of us through the orange-red colours of popular foods like oranges, tomatoes and carrots, and the yellow colours of many flowers.
They are also added as colorants to many manufactured foods, drinks and animal feeds, either in the form of natural extracts (e.g annatto) or as pure compounds manufactured by chemical synthesis. The production of carotenoids by biotechnology is of increasing interest. Carotenoids are essential to plants for photosynthesis, acting in light-harvesting and, especially, in protection against destructive photooxidation. Without carotenoids photosynthesis in an oxygenic atmosphere would be impossible.
But carotenoids are not simply pigments of terrestrial plants. They occur widely in bacteria, fungi and algae, where they can be useful taxonomic markers. The production of carotenoids in seaweed runs to hundreds of million tons per year.
Some animals use carotenoids for coloration, especially birds (yellow and red feathers), fish (g.g. goldfish and salmon) and a wide variety of invertebrate animals, where complexation with protein may modify their colour to blue, geen or purple.
Carotenoids are important factors in human health. The essential role of beta-carotene and others as the main dietary source of vitamin A has been known for many years. More recently, protective effects of carotenoids against serious disorders such as cancer, heart disease and degenerative eye disease have been recognized, and have stimulated intensive resarch into the role of carotenoids as antioxidants and as regulators of the immune response system.
Currents carotenoid research encompasses a wide veriety of fields and interests including plant physiology, food science, environmental science, taxonomy, industrial chemical synthesis, biotechnology and medical research. All the work must be based on a solid foundaation of carotenoid chemistry and reliable methods for handling and analysing these rather unsatble substances.
CAROTENOIDS?
Of the various classes of pigments in Nature the carotenoids are among the mostwidespread and important ones, especially due to their most varied functions.In 1831 Wackenroder isolated carotene from carrots and in 1837 Berzelius namedthe yellow pigments from autumn leaves xanthophylls. This marks the beginning ofcarotenoid research and since then continuous developments have taken place.Because of their ubiquitous occurrence, different functions (see below), and interestingproperties carotenoids are the subject of interdisciplinary research in chemistry, bio-chemistry, biology, medicine, physics, and many other branches of science.
Carotenoids can help you to:
Minimize the risk for certain types of cancer;
Reduce the risk for CVD's;
Help to avoid catarracts.
They further:
Have an important role in photosynthesis;
Are powerful antioxidants in Nature;
Are used to attract animals (and humans) with their color.
OCCURRENCE
As already mentioned, the carotenoids are a class of natural pigments that is very widespread and it was demonstrated that they occur in all the three domains of life, i.e. in the eubacteria, the archea and in the eucarya. A rich source for carotenoids are the algae and more than 100 carotenoids have been isolated and characterized from these organisms. For humans the most important source for carotenoids are plants, where often the brilliant colors of the carotenoids are masked by chlorophyll, e.g. in green leaves. The carotenoids are responsible for the beautiful colors of many fruits (pine-apple, citrus fruits, tomatoes, paprika, rose hips) and flowers (Eschscholtzia, Narcissus), as well as the colors of many birds (flamingo, cock of rock, ibis, canary), insects (lady bird), and marine animals (crustaceans, salmon). Normally carotenoids occur in low concentrations, but this varies enormously from one source to another. The total carotenoid production in nature has been estimated at about 100'000'000 tons a year. Recently it was demonstrated by the analysis of serum and human breast milk that up to 50 dietary carotenoids from fruits and vegetables may be absorbed and metabolized by humans.
Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives (xanthophylls). They consist of eight isoprenoid units joined in such a manner that the arrangement of isoprenoid units is reversed at the center of the molecule so that the two central methyl groups are in a 1,6-position relationship and the remaining nonterminal methyl groups are in a 1,5-position relationship. All carotenoids may be formally derived from the acyclic C40H56 structure (I) (Fig. 1), having a long central chain of conjugated double bonds, by (I) hydrogenation, (2) dehydrogenation, (3) cyclization, or (4) oxidation, or any combination of these processes. The class also includes compounds that arise from certain rearrangements or degradations of the carbon skeleton (I), provided that the two central methyl groups are retained.
About 600 carotenoids have been isolated from natural sources; they are listed with their trivial and semisystematic names in Key to Carotenoids (Pfander, 1987) and in the Appendix of Carotenoids, Volume 1A (Kull & Pfander 1995) which also includes literature references for their spectroscopic and other properties. It must be pointed out, however, that for many of the carotenoids listed the structure (this term includes the stereochemistry) is still uncertain and in all these cases a reisolation, followed by structural elucidation with all the modern spectroscopic methods (especially high resolution nuclear magnetic resonance (NMR) spectroscopy) is absolutely necessary. About 370 of the naturally occurring carotenoids are chiral, bearing from one to five asymmetric carbon atoms, and in most cases one carotenoid occurs only in one configuration in Nature.
Rules for the nomenclature of carotenoids (semisystematic names) have been published by the International Union of Pure and Applied Chemistry (IUPAC) and IUPAC-International Union of Biochemists (IUB) Commissions on Nomenclature (1975). For the most common carotenoids trivial names are normally used. If these trivial names are used in a paper, the semisystematic name should always be given, in parentheses or in a footnote, at the first mention. All specific names are based on the stem name carotene, which corresponds to the structure and numbering in II (Fig. 2). 
The name of a specific compound is constructed by adding two Greek letters as prefixes (Figure 3) to the stem name carotene; the Greek letter prefixes are cited in alphabetical order.
Carotenoids are familiar to all of us through the orange-red colours of popular foods like oranges, tomatoes and carrots, and the yellow colours of many flowers.
They are also added as colorants to many manufactured foods, drinks and animal feeds, either in the form of natural extracts (e.g annatto) or as pure compounds manufactured by chemical synthesis. The production of carotenoids by biotechnology is of increasing interest. Carotenoids are essential to plants for photosynthesis, acting in light-harvesting and, especially, in protection against destructive photooxidation. Without carotenoids photosynthesis in an oxygenic atmosphere would be impossible.
But carotenoids are not simply pigments of terrestrial plants. They occur widely in bacteria, fungi and algae, where they can be useful taxonomic markers. The production of carotenoids in seaweed runs to hundreds of million tons per year.
Some animals use carotenoids for coloration, especially birds (yellow and red feathers), fish (g.g. goldfish and salmon) and a wide variety of invertebrate animals, where complexation with protein may modify their colour to blue, geen or purple.
Carotenoids are important factors in human health. The essential role of beta-carotene and others as the main dietary source of vitamin A has been known for many years. More recently, protective effects of carotenoids against serious disorders such as cancer, heart disease and degenerative eye disease have been recognized, and have stimulated intensive resarch into the role of carotenoids as antioxidants and as regulators of the immune response system.
Currents carotenoid research encompasses a wide veriety of fields and interests including plant physiology, food science, environmental science, taxonomy, industrial chemical synthesis, biotechnology and medical research. All the work must be based on a solid foundaation of carotenoid chemistry and reliable methods for handling and analysing these rather unsatble substances.
CAROTENOIDS?
Of the various classes of pigments in Nature the carotenoids are among the mostwidespread and important ones, especially due to their most varied functions.In 1831 Wackenroder isolated carotene from carrots and in 1837 Berzelius namedthe yellow pigments from autumn leaves xanthophylls. This marks the beginning ofcarotenoid research and since then continuous developments have taken place.Because of their ubiquitous occurrence, different functions (see below), and interestingproperties carotenoids are the subject of interdisciplinary research in chemistry, bio-chemistry, biology, medicine, physics, and many other branches of science.
Carotenoids can help you to:
Minimize the risk for certain types of cancer;
Reduce the risk for CVD's;
Help to avoid catarracts.
They further:
Have an important role in photosynthesis;
Are powerful antioxidants in Nature;
Are used to attract animals (and humans) with their color.
OCCURRENCE
As already mentioned, the carotenoids are a class of natural pigments that is very widespread and it was demonstrated that they occur in all the three domains of life, i.e. in the eubacteria, the archea and in the eucarya. A rich source for carotenoids are the algae and more than 100 carotenoids have been isolated and characterized from these organisms. For humans the most important source for carotenoids are plants, where often the brilliant colors of the carotenoids are masked by chlorophyll, e.g. in green leaves. The carotenoids are responsible for the beautiful colors of many fruits (pine-apple, citrus fruits, tomatoes, paprika, rose hips) and flowers (Eschscholtzia, Narcissus), as well as the colors of many birds (flamingo, cock of rock, ibis, canary), insects (lady bird), and marine animals (crustaceans, salmon). Normally carotenoids occur in low concentrations, but this varies enormously from one source to another. The total carotenoid production in nature has been estimated at about 100'000'000 tons a year. Recently it was demonstrated by the analysis of serum and human breast milk that up to 50 dietary carotenoids from fruits and vegetables may be absorbed and metabolized by humans.
Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives (xanthophylls). They consist of eight isoprenoid units joined in such a manner that the arrangement of isoprenoid units is reversed at the center of the molecule so that the two central methyl groups are in a 1,6-position relationship and the remaining nonterminal methyl groups are in a 1,5-position relationship. All carotenoids may be formally derived from the acyclic C40H56 structure (I) (Fig. 1), having a long central chain of conjugated double bonds, by (I) hydrogenation, (2) dehydrogenation, (3) cyclization, or (4) oxidation, or any combination of these processes. The class also includes compounds that arise from certain rearrangements or degradations of the carbon skeleton (I), provided that the two central methyl groups are retained.
About 600 carotenoids have been isolated from natural sources; they are listed with their trivial and semisystematic names in Key to Carotenoids (Pfander, 1987) and in the Appendix of Carotenoids, Volume 1A (Kull & Pfander 1995) which also includes literature references for their spectroscopic and other properties. It must be pointed out, however, that for many of the carotenoids listed the structure (this term includes the stereochemistry) is still uncertain and in all these cases a reisolation, followed by structural elucidation with all the modern spectroscopic methods (especially high resolution nuclear magnetic resonance (NMR) spectroscopy) is absolutely necessary. About 370 of the naturally occurring carotenoids are chiral, bearing from one to five asymmetric carbon atoms, and in most cases one carotenoid occurs only in one configuration in Nature.
Rules for the nomenclature of carotenoids (semisystematic names) have been published by the International Union of Pure and Applied Chemistry (IUPAC) and IUPAC-International Union of Biochemists (IUB) Commissions on Nomenclature (1975). For the most common carotenoids trivial names are normally used. If these trivial names are used in a paper, the semisystematic name should always be given, in parentheses or in a footnote, at the first mention. All specific names are based on the stem name carotene, which corresponds to the structure and numbering in II (Fig. 2). The name of a specific compound is constructed by adding two Greek letters as prefixes (Figure 3) to the stem name carotene; the Greek letter prefixes are cited in alphabetical order.The oxygenated carotenoids (xanthophylls) are named according to the usual rules of organic chemical nomenclature. The functions most frequently observed are hydroxy, methoxy, carboxy, oxo, and epoxy. In addition, carotenoids with triple bonds are also known. Important and characteristic carotenoids (Fig. 4) are lycopene (gamma,gamma-carotene) (I), beta-carotene (beta,beta-carotene) (III), alpha-carotene ((6’R)-beta,epsilon-carotene) (IV), beta-cryptoxanthin ((3R)-beta,beta-caroten-3-ol) (V), zeaxanthin ((3R,3'R)-beta,beta carotene-3,3'-diol) (VI), lutein ("xanthophyll", (3R,3'R,6'R)-beta,epsilon -carotene-3,3'-diol) (VII), neoxanthin ((3S,5R,6R,3'S,5'R,6'S)-5',6'-epoxy-6,7-didehydro-5,6,S',6'-tetrahydro-beta,beta-carotene-3,5,3'-triol) (VIII), violaxanthin ((3S,5R,6R,3’S,5'R,6'S)-5,6,5',6'-diepoxy-5,6,5',6'-tetrahydro-beta,beta-carotene-3,3'-diol) (IX), fucoxanthin ((3S,5R,6S,3'S,5'R,6'R)-5,6-epoxy-3,3',5'-trihydroxy-6',7'-didehydro-5,6,7,8,5',6'-hexahydro-beta,beta-caroten-8-one 3'-acetate) (X), canthaxanthin (beta,beta-carotene-4,4'-dione) (XI), and astaxanthin ((3S,3'S)-3,3'-dihydroxy-beta,beta-carotene-4,4'-dione) (XII).
Derivatives in which the carbon skeleton has been shortened by the formal removal of fragments from one or both ends of a carotenoid are named apo- and diapocarotenoids, respectively, e.g. beta-apo-8'-carotenal (8'-apo-beta-caroten-8'-al) (XIII). Other structural variations are encountered in the norcarotenoids, in which one or more carbon atoms have been eliminated from within the typical C40-skeleton. A prominent example is the C37-skeleton of peridinin ((3S,5R,6R,3’S,5’R,6’R)-epoxy-3,5,3’-trihydroxy-6,7-didehydro-5,6,5’,6’-tetrahydro-10,11,20-trinor-beta,beta-caroten-19’,11’-olide 3-acetate) (XIV) characteristic of diatoms.
Carotenoids are synthesized in Nature by plants and many microorganisms. Animals can metabolize carotenoids in a characteristic manner, but they are not able to synthesize carotenoids.
Carotenoids, being terpenoids, are synthesized from the basic C5-terpenoid precursor, isopentenyl diphosphate (IPP) (XVII) (Fig.1). This compound is converted to geranylgeranyl diphosphate (C20) (XVIII). The dimerization of XVIII leads to phytoene (7,8,11,12,7’,8’,11’,12’-octahydro-gamma,gamma-carotene) (XIX) and the stepwise dehydrogenation via phytofluene (15Z,7,8,11,12,7’,8’-hexahydro-gamma,gamma-carotene (XX), zeta-carotene (7,8,7’,8’-tetrahydro-gamma,gamma-carotene) (XXI), and neurosporene (7,8-dihydro-gamma,gamma-carotene) (XXII) gives lycopene (I). Subsequent cyclizations, dehydrogenations, oxidations, etc., lead to the individual naturally occurring carotenoids, but little is known about the biochemistry of the many interesting final structural modifications that give rise to the hundreds of diverse natural carotenoids.
Carotenoids, being terpenoids, are synthesized from the basic C5-terpenoid precursor, isopentenyl diphosphate (IPP) (XVII) (Fig.1). This compound is converted to geranylgeranyl diphosphate (C20) (XVIII). The dimerization of XVIII leads to phytoene (7,8,11,12,7’,8’,11’,12’-octahydro-gamma,gamma-carotene) (XIX) and the stepwise dehydrogenation via phytofluene (15Z,7,8,11,12,7’,8’-hexahydro-gamma,gamma-carotene (XX), zeta-carotene (7,8,7’,8’-tetrahydro-gamma,gamma-carotene) (XXI), and neurosporene (7,8-dihydro-gamma,gamma-carotene) (XXII) gives lycopene (I). Subsequent cyclizations, dehydrogenations, oxidations, etc., lead to the individual naturally occurring carotenoids, but little is known about the biochemistry of the many interesting final structural modifications that give rise to the hundreds of diverse natural carotenoids.
There are now exciting prospects for rapid progress through the application of molecular genetics techniques in combination with other biochemical and chemical approaches. The benefits of this are not purely academic. The industrial production of natural carotenoids through microbial biotechnology is already established and expanding, mainly through the exploitation of some microalgae (particularly Dunaliella) which can synthesize large amount of carotenoid.
Advantages and Disadvantages of Fuel Cells
With respect to other energy conversion systems, fuel cells have advantages and disadvantages:
ADVANTAGES
Zero Emissions: a fuel cell vehicle only emits water vapour if fueled with pure hydrogen, while if it has an on board reformer for the hydrogen production we have to take into account its emissions. The vehicle is a really no-noise vehicle, except for the noise of the auxiliaries (pumps, fan etc.);
High efficiency: Since fuel cells do not use combustion, their efficiency is not linked to their maximum operating temperature. As a result, the efficiency of the power conversion step (the actual electrochemical reaction as opposed to the actual combustion reaction) can be significantly higher than that of thermal engines. In addition fuel cells also exhibit higher part-load efficiency and do not display a sharp drop in efficiency as the powerplant size decreases. Heat engines operate with highest efficiency when run at their design speed and ex-hibit a rapid decrease in efficiency at part load.
Rapid load-following: Fuel cells exhibit good load-following characteristics. Fuel cell sys-tems, however, are comprised of predominantly mechanical devices each of which has its own response time to changes in load demand. Nonetheless, fuel cell systems that operate on pure hy-drogen tend to have excellent overall response.
Low temperatures: Fuel cell systems suitable for automotive applications operate at low temperatures. This is an advantage in that the fuel cells re-quire little warmup time, high temperature hazards are reduced, and the thermodynamic efficiency of the electro-chemical reaction is inherently better.
Reduced number of energy tranformations: When used as an electrical energy generating device, fuel cells require fewer energy transformations than those as-sociated with a heat engine. When used as a mechanical energy generating device, fuel cells require an equal number of conversions, although the specific transformations are different and efficiencies are higher.
Refueling time: Fuel cell systems do not require recharging. Rather, fuel cell systems must be re-fueled, which is faster than charging a battery and can provide greater range depend-ing on the size of the storage tank.
DISADVANTAGES
Hydrogen: Ironically, hydrogen which is of such benefit environmentally when used in a fuel cell, is also its greatest liability in that it is difficult to manufacture and store. Current manufacturing processes are expensive and energy in-tensive, and often derive ultimately from fossil fuels.
Contaminants sensitivity: Fuel cells require relatively pure fuel, free of specific con-taminants. These contaminants include sulfur and car-bon compounds, and residual liquid fuels (depending on the type of fuel cell) that can deactivate the fuel cell catalyst effectively destroying its ability to operate. None of these contaminants inhibit combustion in an internal combustion engine.
High-cost catalyst: Fuel cells suitable for automotive applications typically require the use of a platinum catalyst to promote the power generation reaction. Platinum is a rare metal and is very expensive.
Ice: Fuel cells must not freeze with water inside. Fuel cells generate pure water during the power generating reaction and most fuel cells suitable for automotive applications use wet reactant gases. Any residual water within the fuel cells can cause irreversible expansion damage if permitted to freeze. During operation, fuel cell systems generate sufficient heat to prevent freezing over normal ambient temperatures, but when shut down in cold weather the fuel cells must be kept warm or the residual water must be removed before freezing.
New technology: Fuel cells are an emerging technology. As with any new technology, reductions in cost, weight and size concurrent with increases in reliability and lifetime remain pri-mary engineering goals.
Lack of infrastructures: An effective hydrogen infrastructure has yet to be established.
ADVANTAGES
Zero Emissions: a fuel cell vehicle only emits water vapour if fueled with pure hydrogen, while if it has an on board reformer for the hydrogen production we have to take into account its emissions. The vehicle is a really no-noise vehicle, except for the noise of the auxiliaries (pumps, fan etc.);
High efficiency: Since fuel cells do not use combustion, their efficiency is not linked to their maximum operating temperature. As a result, the efficiency of the power conversion step (the actual electrochemical reaction as opposed to the actual combustion reaction) can be significantly higher than that of thermal engines. In addition fuel cells also exhibit higher part-load efficiency and do not display a sharp drop in efficiency as the powerplant size decreases. Heat engines operate with highest efficiency when run at their design speed and ex-hibit a rapid decrease in efficiency at part load.
Rapid load-following: Fuel cells exhibit good load-following characteristics. Fuel cell sys-tems, however, are comprised of predominantly mechanical devices each of which has its own response time to changes in load demand. Nonetheless, fuel cell systems that operate on pure hy-drogen tend to have excellent overall response.
Low temperatures: Fuel cell systems suitable for automotive applications operate at low temperatures. This is an advantage in that the fuel cells re-quire little warmup time, high temperature hazards are reduced, and the thermodynamic efficiency of the electro-chemical reaction is inherently better.
Reduced number of energy tranformations: When used as an electrical energy generating device, fuel cells require fewer energy transformations than those as-sociated with a heat engine. When used as a mechanical energy generating device, fuel cells require an equal number of conversions, although the specific transformations are different and efficiencies are higher.
Refueling time: Fuel cell systems do not require recharging. Rather, fuel cell systems must be re-fueled, which is faster than charging a battery and can provide greater range depend-ing on the size of the storage tank.
DISADVANTAGES
Hydrogen: Ironically, hydrogen which is of such benefit environmentally when used in a fuel cell, is also its greatest liability in that it is difficult to manufacture and store. Current manufacturing processes are expensive and energy in-tensive, and often derive ultimately from fossil fuels.
Contaminants sensitivity: Fuel cells require relatively pure fuel, free of specific con-taminants. These contaminants include sulfur and car-bon compounds, and residual liquid fuels (depending on the type of fuel cell) that can deactivate the fuel cell catalyst effectively destroying its ability to operate. None of these contaminants inhibit combustion in an internal combustion engine.
High-cost catalyst: Fuel cells suitable for automotive applications typically require the use of a platinum catalyst to promote the power generation reaction. Platinum is a rare metal and is very expensive.
Ice: Fuel cells must not freeze with water inside. Fuel cells generate pure water during the power generating reaction and most fuel cells suitable for automotive applications use wet reactant gases. Any residual water within the fuel cells can cause irreversible expansion damage if permitted to freeze. During operation, fuel cell systems generate sufficient heat to prevent freezing over normal ambient temperatures, but when shut down in cold weather the fuel cells must be kept warm or the residual water must be removed before freezing.
New technology: Fuel cells are an emerging technology. As with any new technology, reductions in cost, weight and size concurrent with increases in reliability and lifetime remain pri-mary engineering goals.
Lack of infrastructures: An effective hydrogen infrastructure has yet to be established.
Molten Carbonate Fuel Cells
Molten Carbonate Fuel Cells
Molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and coal-based power plants for electrical utility, industrial, and military applications. MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide (LiAlO2) matrix. Since they operate at extremely high temperatures of 650°C (roughly 1,200°F) and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs.
Improved efficiency is another reason MCFCs offer significant cost reductions over phosphoric acid fuel cells (PAFCs). Molten carbonate fuel cells can reach efficiencies approaching 60 percent, considerably higher than the 37-42 percent efficiencies of a phosphoric acid fuel cell plant. When the waste heat is captured and used, overall fuel efficiencies can be as high as 85 percent.
Unlike alkaline, phosphoric acid, and polymer electrolyte membrane fuel cells, MCFCs don't require an external reformer to convert more energy-dense fuels to hydrogen. Due to the high temperatures at which MCFCs operate, these fuels are converted to hydrogen within the fuel cell itself by a process called internal reforming, which also reduces cost.
Molten carbonate fuel cells are not prone to carbon monoxide or carbon dioxide "poisoning" —they can even use carbon oxides as fuel—making them more attractive for fueling with gases made from coal. Because they are more resistant to impurities than other fuel cell types, scientists believe that they could even be capable of internal reforming of coal, assuming they can be made resistant to impurities such as sulfur and particulates that result from converting coal, a dirtier fossil fuel source than many others, into hydrogen.
The primary disadvantage of current MCFC technology is durability. The high temperatures at which these cells operate and the corrosive electrolyte used accelerate component breakdown and corrosion, decreasing cell life. Scientists are currently exploring corrosion-resistant materials for components as well as fuel cell designs that increase cell life without decreasing performance.
Alkaline Fuel Cells | disadvantage of fuel
Alkaline Fuel Cells
Alkaline fuel cells (AFCs) were one of the first fuel cell technologies developed, and they were the first type widely used in the U.S. space program to produce electrical energy and water onboard spacecraft. These fuel cells use a solution of potassium hydroxide in water as the electrolyte and can use a variety of non-precious metals as a catalyst at the anode and cathode. High-temperature AFCs operate at temperatures between 100°C and 250°C (212°F and 482°F). However, newer AFC designs operate at lower temperatures of roughly 23°C to 70°C (74°F to 158°F)
AFCs' high performance is due to the rate at which chemical reactions take place in the cell. They have also demonstrated efficiencies near 60 percent in space applications.
The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide (CO2 ). In fact, even the small amount of CO2 in the air can affect this cell's operation, making it necessary to purify both the hydrogen and oxygen used in the cell. This purification process is costly. Susceptibility to poisoning also affects the cell's lifetime (the amount of time before it must be replaced), further adding to cost.
Cost is less of a factor for remote locations such as space or under the sea. However, to effectively compete in most mainstream commercial markets, these fuel cells will have to become more cost-effective. AFC stacks have been shown to maintain sufficiently stable operation for more than 8,000 operating hours. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues. This is possibly the most significant obstacle in commercializing this fuel cell technology.
Alkaline fuel cells (AFCs) were one of the first fuel cell technologies developed, and they were the first type widely used in the U.S. space program to produce electrical energy and water onboard spacecraft. These fuel cells use a solution of potassium hydroxide in water as the electrolyte and can use a variety of non-precious metals as a catalyst at the anode and cathode. High-temperature AFCs operate at temperatures between 100°C and 250°C (212°F and 482°F). However, newer AFC designs operate at lower temperatures of roughly 23°C to 70°C (74°F to 158°F)
AFCs' high performance is due to the rate at which chemical reactions take place in the cell. They have also demonstrated efficiencies near 60 percent in space applications.
The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide (CO2 ). In fact, even the small amount of CO2 in the air can affect this cell's operation, making it necessary to purify both the hydrogen and oxygen used in the cell. This purification process is costly. Susceptibility to poisoning also affects the cell's lifetime (the amount of time before it must be replaced), further adding to cost.
Cost is less of a factor for remote locations such as space or under the sea. However, to effectively compete in most mainstream commercial markets, these fuel cells will have to become more cost-effective. AFC stacks have been shown to maintain sufficiently stable operation for more than 8,000 operating hours. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues. This is possibly the most significant obstacle in commercializing this fuel cell technology.
Microbial fuel cell | Mediator Microbial Fuel Cell
Microbial fuel cell
A microbial fuel cell (MFC) or biological fuel cell is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature. Micro-organisms catabolize compounds such as glucose (Chen, et al., 2001), acetate[citation needed] or wastewater (Habermann & Pommer, 1991). The electrons gained from this oxidation are transferred to an anode, where they depart through an electrical circuit before reaching the cathode. Here they are transferred to a high potential electron acceptor such as oxygen. As current now flows over a potential difference, power is generated directly from biofuel by the catalytic activity of bacteria. (Rabaey & Verstraete, 2005)
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Microbial fuel cell
A microbial fuel cell is a device that converts chemical energy to electrical energy by the catalytic reaction of microorganisms (Allen and Bennetto, 1993). A typical microbial fuel cell consists of anode and cathode compartments separated by a cation specific membrane. In the anode compartment, fuel is oxidized by microorganisms, generating electrons and protons. Electrons are transferred to the cathode compartment through an external electric circuit, and the protons are transferred to the cathode compartment through the membrane. Electrons and protons are consumed in the cathode compartment, combining with oxygen to form water. In general, there are two types of microbial fuel cell, mediator and mediator-less microbial fuel cell. Biological fuel cells take glucose and methanol from food scraps and convert it into hydrogen and food for the bacteria.
Mediator Microbial Fuel Cell
Most of the microbial cells are electrochemically inactive. The electron transfer from microbial cells to the electrode is facilitated by mediators such as thionine, methyl viologen (methyl blue), humic acid, neutral red and so on (Delaney et al., 1984; Lithgow et al., 1986). Most of the mediators available are expensive and toxic.
Mediator-less Microbial Fuel Cell
Mediator-less microbial fuel cells have been engineered at the Korea Institute of Science and Technology [1], by a team led by Kim, Byung Hong[2]. A mediator-less microbial fuel cell does not require a mediator but uses electrochemically active bacteria to transfer electrons to the electrode (electrons are carried directly from the bacterial respiratory enzyme to the electrode). Among the electrochemically active bacteria are, Shewanella putrefaciens (Kim et al., 1999a), Aeromonas hydrophila (Cuong et al., 2003), and others.
Mediator-less MFCs are a much more recent development and due to this the factors that affect optimum operation, such as the bacteria used in the system, the type of ion membrane, and the system conditions such as temperature, are not particularly well understood. Bacteria in mediator-less MFCs typically have electrochemically-active redox enzymes such as cytochromes on their outer membrane that can transfer electrons to external materials (Min, et al., 2005).
Generating electricity
When micro-organisms consume a substrate such as sugar in aerobic conditions they produce carbon dioxide and water. However when oxygen is not present they produce carbon dioxide, protons and electrons as described below (Bennetto, 1990):
C12H22O11 + 13H2O ---> 12CO2 + 48H+ + 48e- Eqt. 1
Microbial fuel cells use inorganic mediators to tap into the electron transport chain of cells and steal the electrons that are produced. The mediator crosses the outer cell lipid membranes and plasma wall; it then begins to liberate electrons from the electron transport chain that would normally be taken up by oxygen or other intermediates. The now-reduced mediator exits the cell laden with electrons that it shuttles to an electrode where it deposits them; this electrode becomes the electro-generic anode (negatively charged electrode). The release of the electrons means that the mediator returns to its original oxidised state ready to repeat the process. It is important to note that this can only happen under anaerobic conditions, if oxygen is present then it will collect all the electrons as it has a greater electronegativity than the mediator.
A number of mediators have been suggested for use in microbial fuel cells. These include natural red, methylene blue, thionine or resorfuin (Bennetto, et al., 1983).
This is the principle behind generating a flow of electrons from most micro-organisms. In order to turn this into a usable supply of electricity this process has to be accommodated in a fuel cell.
In order to generate a useful current it is necessary to create a complete circuit, not just shuttle electrons to a single point.
The mediator and micro-organism, in this case yeast, are mixed together in a solution to which is added a suitable substrate such as glucose. This mixture is placed in a sealed chamber to stop oxygen entering, thus forcing the micro-organism to use anaerobic respiration. An electrode is placed in the solution that will act as the anode as described previously.
In the second chamber of the MFC is another solution and electrode. This electrode, called the cathode is positively charged and is the equivalent of the oxygen sink at the end of the electron transport chain, only now it is external to the biological cell. The solution is an oxidizing agent that picks up the electrons at the cathode. As with the electron chain in the yeast cell, this could be a number of molecules such as oxygen. However, this is not particularly practical as it would require large volumes of circulating gas. A more convenient option is to use a solution of a solid oxidizing agent.
Connecting the two electrodes is a wire (or other electrically conductive path which may include some electrically powered device such as a light bulb) and completing the circuit and connecting the two chambers is a salt bridge or ion-exchange membrane. This last feature allows the protons produced, as described in Eqt. 1 to pass from the anode chamber to the cathode chamber.
The reduced mediator carries electrons from the cell to the electrode. Here the mediator is oxidized as it deposits the electrons. These then flow across the wire to the second electrode, which acts as an electron sink. From here they pass to an oxidising material.
Uses
Power generation
Microbial fuel cells have a number of potential uses. The first and most obvious is harvesting the electricity produced for a power source. Virtually any organic material could be used to ‘feed’ the fuel cell. MFCs could be installed to waste water treatment plants. The bacteria would consume waste material from the water and produce supplementary power for the plant. The gains to be made from doing this are that MFCs are a very clean and efficient method of energy production. A fuel cell’s emissions are well below regulations (Choi, et al., 2000). MFCs also use energy much more efficiently than standard combustion engines which are limited by the Carnot Cycle. In theory a MFC is capable of energy efficiency far beyond 50% (Yue & Lowther, 1986).
However MFCs do not have to be used on a large scale, as the electrodes in some cases need only be 7 μm thick by 2 cm long (Chen, et al., 2001). The advantages to using a MFC in this situation as opposed to a normal battery is that it uses a renewable form of energy and would not need to be recharged like a standard battery would. In addition to this they could operate well in mild conditions, 20°C to 40°C and also at pH of around 7 (Bullen, et al., 2005). Although more powerful than metal catalysts, they are currently too unstable for long term medical applications such as in pacemakers (Biotech/Life Sciences Portal).Further uses
Since the current generated from a microbial fuel cell is directly proportional to the strength of wastewater used as the fuel, an MFC can be used to measure the strength of wastewater (Kim, et al., 2003). The strength of wastewater is commonly evaluated as biochemical oxygen demand (BOD) values. BOD values are determined incubating samples for 5 days with proper source of microbes, usually activate sludge collected from sewage works. When BOD values are used as a real time control parameter, 5 days' incubation is too long. An MFC-type BOD sensor can be used to measure real time BOD values. Oxygen and nitrate are preferred electron acceptors over the electrode reducing current generation from an MFC. An MFC-type BOD sensors underestimate BOD values in the presence of these electron acceptors. This can be avoided by inhibiting aerobic and nitrate respirations in the MFC using terminal oxydase inhibitors such as cyanide and azide [Chang, I. S., Moon, H., Jang, J. K. and Kim, B. H. (2005) Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors. Biosensors and Bioelectronics 20, 1856-1859.] This type of BOD sensor is commercially available.
Current research practices
Currently, most researchers in this field are biologists rather than electrochemists or engineers. This has prompted some researchers (Menicucci, 2005) to point out some undesirable practices, such as recording the maximum current obtained by the cell when connecting it to a resistance as an indication of its performance, instead of the steady-state current that is often a degree of magnitude lower. Sometimes, data about the value of the used resistance is scanty, leading to non-comparable data.
History
At the turn of the last century, the idea of using microbial cells in an attempt to produce electricity was first conceived. M. C. Potter was the first to perform work on the subject in 1912 (Potter, 1912). A professor of botany at the University of Durham Potter managed to generate electricity from E. Coli, however the work was not to receive any major coverage. In 1931 however Barnet Cohen drew more attention to the area when he created a number of microbial half fuel cells that, when connected in series, were capable of producing over 35 volts, though only with a current of 2 milliamps (Cohen, 1931). More work on the subject came with a study by DelDuca et al. who used hydrogen produced by the fermentation of glucose by Clostridium butyricum as the reactant at the anode of a hydrogen and air fuel cell. Unfortunately, though the cell functioned it was found to be unreliable due to the unstable nature of the hydrogen production from the micro-organisms(Delduca, et al., 1963). Although this issue was later resolved in work by Suzuki et al. in 1976 (Karube, et al., 1976) the current design concept of a MFC came into existence a year later with work once again by Suzuki (Karube, et al., 1977).
Even by the time of Suzuki’s work in the late seventies little was understood about how these microbial fuel cells functioned, however the idea was picked up and studied later in more detail first by MJ Allen and then later by H. Peter Bennetto both from King's College London. Bennetto saw the fuel cell as a possible method for the generation of electricity for third world countries. His work, starting in the early 1980s helped build an understanding of how fuel cells operate and until his retirement was seen by many as the foremost authority on the subject.
It is now known that electricity can be produced directly from the degradation of organic matter in a microbial fuel cell, although the exact mechanisms of the process are still to be fully understood. Like a normal fuel cell an MFC has both an anode and a cathode chamber. The anaerobic anode chamber is connected internally to the cathode chamber by an ion exchange membrane, the circuit is completed by an external wire.In May of 2007, the University of Queensland, Australia, completed its prototype MFC, as a cooperative effort with Fosters Brewing Company. The prototype, a 10 liter design, converts the brewery waste water into carbon dioxide, clean water, and electricity. With the prototype proven successful, plans are in effect to produce a 660 gallon version for the brewery, which is estimated to produce 2 kilowatts of power. While it is a negligible amount of power, the production of clean water is of utmost importance to Australia, which is experiencing its worst drought in over 100 years.
A microbial fuel cell (MFC) or biological fuel cell is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature. Micro-organisms catabolize compounds such as glucose (Chen, et al., 2001), acetate[citation needed] or wastewater (Habermann & Pommer, 1991). The electrons gained from this oxidation are transferred to an anode, where they depart through an electrical circuit before reaching the cathode. Here they are transferred to a high potential electron acceptor such as oxygen. As current now flows over a potential difference, power is generated directly from biofuel by the catalytic activity of bacteria. (Rabaey & Verstraete, 2005)
//
Microbial fuel cell
A microbial fuel cell is a device that converts chemical energy to electrical energy by the catalytic reaction of microorganisms (Allen and Bennetto, 1993). A typical microbial fuel cell consists of anode and cathode compartments separated by a cation specific membrane. In the anode compartment, fuel is oxidized by microorganisms, generating electrons and protons. Electrons are transferred to the cathode compartment through an external electric circuit, and the protons are transferred to the cathode compartment through the membrane. Electrons and protons are consumed in the cathode compartment, combining with oxygen to form water. In general, there are two types of microbial fuel cell, mediator and mediator-less microbial fuel cell. Biological fuel cells take glucose and methanol from food scraps and convert it into hydrogen and food for the bacteria.
Mediator Microbial Fuel Cell
Most of the microbial cells are electrochemically inactive. The electron transfer from microbial cells to the electrode is facilitated by mediators such as thionine, methyl viologen (methyl blue), humic acid, neutral red and so on (Delaney et al., 1984; Lithgow et al., 1986). Most of the mediators available are expensive and toxic.
Mediator-less Microbial Fuel Cell
Mediator-less microbial fuel cells have been engineered at the Korea Institute of Science and Technology [1], by a team led by Kim, Byung Hong[2]. A mediator-less microbial fuel cell does not require a mediator but uses electrochemically active bacteria to transfer electrons to the electrode (electrons are carried directly from the bacterial respiratory enzyme to the electrode). Among the electrochemically active bacteria are, Shewanella putrefaciens (Kim et al., 1999a), Aeromonas hydrophila (Cuong et al., 2003), and others.
Mediator-less MFCs are a much more recent development and due to this the factors that affect optimum operation, such as the bacteria used in the system, the type of ion membrane, and the system conditions such as temperature, are not particularly well understood. Bacteria in mediator-less MFCs typically have electrochemically-active redox enzymes such as cytochromes on their outer membrane that can transfer electrons to external materials (Min, et al., 2005).
Generating electricity
When micro-organisms consume a substrate such as sugar in aerobic conditions they produce carbon dioxide and water. However when oxygen is not present they produce carbon dioxide, protons and electrons as described below (Bennetto, 1990):
C12H22O11 + 13H2O ---> 12CO2 + 48H+ + 48e- Eqt. 1
Microbial fuel cells use inorganic mediators to tap into the electron transport chain of cells and steal the electrons that are produced. The mediator crosses the outer cell lipid membranes and plasma wall; it then begins to liberate electrons from the electron transport chain that would normally be taken up by oxygen or other intermediates. The now-reduced mediator exits the cell laden with electrons that it shuttles to an electrode where it deposits them; this electrode becomes the electro-generic anode (negatively charged electrode). The release of the electrons means that the mediator returns to its original oxidised state ready to repeat the process. It is important to note that this can only happen under anaerobic conditions, if oxygen is present then it will collect all the electrons as it has a greater electronegativity than the mediator.
A number of mediators have been suggested for use in microbial fuel cells. These include natural red, methylene blue, thionine or resorfuin (Bennetto, et al., 1983).
This is the principle behind generating a flow of electrons from most micro-organisms. In order to turn this into a usable supply of electricity this process has to be accommodated in a fuel cell.
In order to generate a useful current it is necessary to create a complete circuit, not just shuttle electrons to a single point.
The mediator and micro-organism, in this case yeast, are mixed together in a solution to which is added a suitable substrate such as glucose. This mixture is placed in a sealed chamber to stop oxygen entering, thus forcing the micro-organism to use anaerobic respiration. An electrode is placed in the solution that will act as the anode as described previously.
In the second chamber of the MFC is another solution and electrode. This electrode, called the cathode is positively charged and is the equivalent of the oxygen sink at the end of the electron transport chain, only now it is external to the biological cell. The solution is an oxidizing agent that picks up the electrons at the cathode. As with the electron chain in the yeast cell, this could be a number of molecules such as oxygen. However, this is not particularly practical as it would require large volumes of circulating gas. A more convenient option is to use a solution of a solid oxidizing agent.
Connecting the two electrodes is a wire (or other electrically conductive path which may include some electrically powered device such as a light bulb) and completing the circuit and connecting the two chambers is a salt bridge or ion-exchange membrane. This last feature allows the protons produced, as described in Eqt. 1 to pass from the anode chamber to the cathode chamber.
The reduced mediator carries electrons from the cell to the electrode. Here the mediator is oxidized as it deposits the electrons. These then flow across the wire to the second electrode, which acts as an electron sink. From here they pass to an oxidising material.
Uses
Power generation
Microbial fuel cells have a number of potential uses. The first and most obvious is harvesting the electricity produced for a power source. Virtually any organic material could be used to ‘feed’ the fuel cell. MFCs could be installed to waste water treatment plants. The bacteria would consume waste material from the water and produce supplementary power for the plant. The gains to be made from doing this are that MFCs are a very clean and efficient method of energy production. A fuel cell’s emissions are well below regulations (Choi, et al., 2000). MFCs also use energy much more efficiently than standard combustion engines which are limited by the Carnot Cycle. In theory a MFC is capable of energy efficiency far beyond 50% (Yue & Lowther, 1986).
However MFCs do not have to be used on a large scale, as the electrodes in some cases need only be 7 μm thick by 2 cm long (Chen, et al., 2001). The advantages to using a MFC in this situation as opposed to a normal battery is that it uses a renewable form of energy and would not need to be recharged like a standard battery would. In addition to this they could operate well in mild conditions, 20°C to 40°C and also at pH of around 7 (Bullen, et al., 2005). Although more powerful than metal catalysts, they are currently too unstable for long term medical applications such as in pacemakers (Biotech/Life Sciences Portal).Further uses
Since the current generated from a microbial fuel cell is directly proportional to the strength of wastewater used as the fuel, an MFC can be used to measure the strength of wastewater (Kim, et al., 2003). The strength of wastewater is commonly evaluated as biochemical oxygen demand (BOD) values. BOD values are determined incubating samples for 5 days with proper source of microbes, usually activate sludge collected from sewage works. When BOD values are used as a real time control parameter, 5 days' incubation is too long. An MFC-type BOD sensor can be used to measure real time BOD values. Oxygen and nitrate are preferred electron acceptors over the electrode reducing current generation from an MFC. An MFC-type BOD sensors underestimate BOD values in the presence of these electron acceptors. This can be avoided by inhibiting aerobic and nitrate respirations in the MFC using terminal oxydase inhibitors such as cyanide and azide [Chang, I. S., Moon, H., Jang, J. K. and Kim, B. H. (2005) Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors. Biosensors and Bioelectronics 20, 1856-1859.] This type of BOD sensor is commercially available.
Current research practices
Currently, most researchers in this field are biologists rather than electrochemists or engineers. This has prompted some researchers (Menicucci, 2005) to point out some undesirable practices, such as recording the maximum current obtained by the cell when connecting it to a resistance as an indication of its performance, instead of the steady-state current that is often a degree of magnitude lower. Sometimes, data about the value of the used resistance is scanty, leading to non-comparable data.
History
At the turn of the last century, the idea of using microbial cells in an attempt to produce electricity was first conceived. M. C. Potter was the first to perform work on the subject in 1912 (Potter, 1912). A professor of botany at the University of Durham Potter managed to generate electricity from E. Coli, however the work was not to receive any major coverage. In 1931 however Barnet Cohen drew more attention to the area when he created a number of microbial half fuel cells that, when connected in series, were capable of producing over 35 volts, though only with a current of 2 milliamps (Cohen, 1931). More work on the subject came with a study by DelDuca et al. who used hydrogen produced by the fermentation of glucose by Clostridium butyricum as the reactant at the anode of a hydrogen and air fuel cell. Unfortunately, though the cell functioned it was found to be unreliable due to the unstable nature of the hydrogen production from the micro-organisms(Delduca, et al., 1963). Although this issue was later resolved in work by Suzuki et al. in 1976 (Karube, et al., 1976) the current design concept of a MFC came into existence a year later with work once again by Suzuki (Karube, et al., 1977).
Even by the time of Suzuki’s work in the late seventies little was understood about how these microbial fuel cells functioned, however the idea was picked up and studied later in more detail first by MJ Allen and then later by H. Peter Bennetto both from King's College London. Bennetto saw the fuel cell as a possible method for the generation of electricity for third world countries. His work, starting in the early 1980s helped build an understanding of how fuel cells operate and until his retirement was seen by many as the foremost authority on the subject.
It is now known that electricity can be produced directly from the degradation of organic matter in a microbial fuel cell, although the exact mechanisms of the process are still to be fully understood. Like a normal fuel cell an MFC has both an anode and a cathode chamber. The anaerobic anode chamber is connected internally to the cathode chamber by an ion exchange membrane, the circuit is completed by an external wire.In May of 2007, the University of Queensland, Australia, completed its prototype MFC, as a cooperative effort with Fosters Brewing Company. The prototype, a 10 liter design, converts the brewery waste water into carbon dioxide, clean water, and electricity. With the prototype proven successful, plans are in effect to produce a 660 gallon version for the brewery, which is estimated to produce 2 kilowatts of power. While it is a negligible amount of power, the production of clean water is of utmost importance to Australia, which is experiencing its worst drought in over 100 years.
Phosphoric-acid fuel cell
Phosphoric-acid fuel cell
Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte. The electrodes are made of carbon paper coated with a finely-dispersed platinum catalyst, which make them expensive to manufacture. They are not affected by carbon monoxide impurities in the hydrogen stream. Phosphoric acid solidifies at a temperature of 40 °C, making startup difficult and restraining PAFCs to continuous operation.
However, at an operating range of 150 to 200 °C, the expelled water can be converted to steam for air and water heating. Phosphoric acid fuel cells have been used for stationary applications with a combined heat and power efficiency of about 80%, and they continue to dominate the on-site stationary fuel cell market.
The primary manufacturer of PAFC technology is UTC Power (also known as UTC Fuel Cells), a unit of United Technologies (NYSE: UTX). As of 2005, there were close to 300 "PureCell" 200 kW units by UTC Power in service globally.
Scheme of a Phosphoric-acid fuel cell
Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte. The electrodes are made of carbon paper coated with a finely-dispersed platinum catalyst, which make them expensive to manufacture. They are not affected by carbon monoxide impurities in the hydrogen stream. Phosphoric acid solidifies at a temperature of 40 °C, making startup difficult and restraining PAFCs to continuous operation.
However, at an operating range of 150 to 200 °C, the expelled water can be converted to steam for air and water heating. Phosphoric acid fuel cells have been used for stationary applications with a combined heat and power efficiency of about 80%, and they continue to dominate the on-site stationary fuel cell market.
The primary manufacturer of PAFC technology is UTC Power (also known as UTC Fuel Cells), a unit of United Technologies (NYSE: UTX). As of 2005, there were close to 300 "PureCell" 200 kW units by UTC Power in service globally.
Methanol fuel cell | Fuel cell design | archetypal hydrogen–oxygen proton exchange
Fuel cell
Methanol fuel cell. The actual fuel cell stack is the layered cubic structure in the center of the image
A fuel cell is an electrochemical energy conversion device. It produces electricity from external supplies of fuel (on the anode side) and oxidant (on the cathode side). These react in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.
Fuel cells are different from batteries in that they consume reactant, which must be replenished, while batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and relatively stable.
Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include air, chlorine and chlorine dioxide.[1]
//
Fuel cell design
In essence, a fuel cell works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel through a circuit, hence converting them to electrical power. Another catalytic process takes the electrons back in, combining them with the protons and the oxidant to form waste products (typically simple compounds like water and carbon dioxide).
In the archetypal hydrogen–oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that "polymer electrolyte membrane" and "proton exchange membrane" result in the same acronym.)
On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water — in this example, the only waste product, either liquid or vapor.
In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.
Construction of a low temperature PEMFC: Bipolar plate as electrode with in-milled gas channel structure, fabricated from conductive plastics (enhanced with carbon nanotubes for more conductivity); Porous carbon papers; reactive layer, usually on the polymer membrane applied; polymer membrane.
The materials used in fuel cells differ by type. The electrode–bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.
A typical PEM fuel cell produces a voltage from 0.6 to 0.7 at full rated load. Voltage decreases as current increases, due to several factors:
Activation loss
Ohmic loss (voltage drop due to resistance of the cell components and interconnects)
Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage)[2]
To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn, this design is referred to as a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.
Methanol fuel cell. The actual fuel cell stack is the layered cubic structure in the center of the imageA fuel cell is an electrochemical energy conversion device. It produces electricity from external supplies of fuel (on the anode side) and oxidant (on the cathode side). These react in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.
Fuel cells are different from batteries in that they consume reactant, which must be replenished, while batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and relatively stable.
Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include air, chlorine and chlorine dioxide.[1]
//
Fuel cell design
In essence, a fuel cell works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel through a circuit, hence converting them to electrical power. Another catalytic process takes the electrons back in, combining them with the protons and the oxidant to form waste products (typically simple compounds like water and carbon dioxide).
In the archetypal hydrogen–oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that "polymer electrolyte membrane" and "proton exchange membrane" result in the same acronym.)
On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water — in this example, the only waste product, either liquid or vapor.
In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.
Construction of a low temperature PEMFC: Bipolar plate as electrode with in-milled gas channel structure, fabricated from conductive plastics (enhanced with carbon nanotubes for more conductivity); Porous carbon papers; reactive layer, usually on the polymer membrane applied; polymer membrane.
The materials used in fuel cells differ by type. The electrode–bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.
A typical PEM fuel cell produces a voltage from 0.6 to 0.7 at full rated load. Voltage decreases as current increases, due to several factors:
Activation loss
Ohmic loss (voltage drop due to resistance of the cell components and interconnects)
Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage)[2]
To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn, this design is referred to as a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.
Mechanism of Sonogashira Coupling
Sonogashira Coupling
Mechanism
This coupling of terminal alkynes with aryl or vinyl halides is performed with a palladium catalyst, a copper(I) cocatalyst, and an amine base. Typically, the reaction requires anhydrous and anaerobic conditions, but newer procedures have been developed where these restrictions are not important.
Mechanism
Passerini Reaction
Passerini Reaction
This three-component reaction between a carboxylic acid, a carbonyl compound such as a ketone or aldehyde, and an isocyanide, offers direct access to α-hydroxy carboxamides.
Mechanism
The Passerini Reaction proceeds rapidly if the reaction is performed in aprotic solvents at room temperature. High yields are obtained with high concentrations of the starting materials in the reaction mixture.
From these findings, it is assumed that the Passerini Reaction does not follow an ionic pathway. Hydrogen bonding is believed to play a crucial role in the formation of the presumed cyclic transition state for this reaction.
This three-component reaction between a carboxylic acid, a carbonyl compound such as a ketone or aldehyde, and an isocyanide, offers direct access to α-hydroxy carboxamides.
MechanismThe Passerini Reaction proceeds rapidly if the reaction is performed in aprotic solvents at room temperature. High yields are obtained with high concentrations of the starting materials in the reaction mixture.
From these findings, it is assumed that the Passerini Reaction does not follow an ionic pathway. Hydrogen bonding is believed to play a crucial role in the formation of the presumed cyclic transition state for this reaction.
Mechanism of Strecker Synthesis
Strecker Synthesis
The Strecker Synthesis is a preparation of α-aminonitriles, which are versatile intermediates for the synthesis of amino acids via hydrolysis of the nitrile.
Mechanism of Strecker Synthesis
The reaction is promoted by acid, and HCN must be supplied or generated in situ from cyanide salts - in the latter case, one equivalent of acid is consumed in the reaction.
The reaction is promoted by acid, and HCN must be supplied or generated in situ from cyanide salts - in the latter case, one equivalent of acid is consumed in the reaction.
The first step is probably the condensation of ammonia with the aldehyde to form an imine:
The cyanide adds as a nucleophile to the imine carbon, generating the α-aminonitrile:
This product may optionally be hydrolysed to the corresponding α-aminoacid:
Hantzsch pyridine synthesis
Hantzsch pyridine synthesis
The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multi-component organic reaction between an aldehyde such as formaldehyde, 2 equivalents of a β-keto ester such as ethyl acetoacetate and a nitrogen donor such as ammonium acetate or ammonia.. The initial reaction product is a dihydropyridine which can be oxidized in a subsequent step to a pyridine. The driving force for this second reaction step is aromatization.
A 1,4-dihydropyridine dicarboxylate is also called a 1,4-DHP compound or a Hantzsch compound. These compounds are an important class of calcium channel blockers and as such commercialized in for instance nifedipine, amlodipine or nimodipine.
The reaction has been demonstrated to proceed in water as reaction solvent and with direct aromatization by ferric chloride or potassium permanganate in a one-pot synthesis.
The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multi-component organic reaction between an aldehyde such as formaldehyde, 2 equivalents of a β-keto ester such as ethyl acetoacetate and a nitrogen donor such as ammonium acetate or ammonia.. The initial reaction product is a dihydropyridine which can be oxidized in a subsequent step to a pyridine. The driving force for this second reaction step is aromatization.
A 1,4-dihydropyridine dicarboxylate is also called a 1,4-DHP compound or a Hantzsch compound. These compounds are an important class of calcium channel blockers and as such commercialized in for instance nifedipine, amlodipine or nimodipine.
The reaction has been demonstrated to proceed in water as reaction solvent and with direct aromatization by ferric chloride or potassium permanganate in a one-pot synthesis.
The Hantzsch dihydropyridine synthesis is found to benefit from microwave chemistry.
Funny Chemical Dictionary
From: Xkarlk#NoSpam.POBoxes.comX (Karl)
Disclaimer: I didn't write this, I'm just reposting it.
THE LAST WORD
The Ultimate Scientific Dictionary
Activation Energy: The useful quantity of energy available in one cup of
coffee.
Atomic Theory: A mythological explanation of the nature of matter, first
proposed by the ancient Greeks, and now thoroughly discredited by modern
computer simulation. Attempts to verify the theory by modern computer
simulation have failed. Instead, it has been demonstrated repeatedly
that computer outputs depend upon the color of the programmer's eyes, or
occasionally upon the month of his or her birth. This apparent
astrological connection, at last, vindicates the alchemist's view of
astrology as the mother of all science.
Bacon, Roger: An English friar who dabbled in science and made
experimentation fashionable. Bacon was the first science popularizer to
make it big on the banquet and talk-show circuit, and his books even
outsold the fad diets of the period.
Biological Science: A contradiction in terms.
Bunsen Burner: A device invented by Robert Bunsen (1811-1899) for
brewing coffee in the laboratory, thereby enabling the chemist to be
poisoned without having to go all the way to the company cafeteria.
Butyl: An unpleasant-sounding word denoting an unpleasant-smelling
alcohol.
CAI: Acronym for "Computer-Aided Instruction". The modern system of
training professional scientists without ever exposing them to the
hazards and expense of laboratory work. Graduates of CAI-based programs
are very good at simulated research.
Cavendish: A variety of pipe tobacco that is reputed to produce
remarkably clear thought processes, and thereby leads to major
scientific discoveries; hence, the name of a British research laboratory
where the tobacco is smoked in abundance.
Chemical: A substance that:
1) An organic chemist turns into a foul odor;
2) an analytical chemist turns into a procedure;
3) a physical chemist turns into a straight line;
4) a biochemist turns into a helix;
5) a chemical engineer turns into a profit.
Chemical Engineering: The practice of doing for a profit what an organic
chemist only does for fun.
Chromatography: (From Gr. chromo [color] + graphos [writing]) The
practice of submitting manuscripts for publication with the original
figures drawn in non-reproducing blue ink.
Clinical Testing: The use of humans as guinea pigs. (See also
PHARMACOLOGY and TOXICOLOGY)
Compound: To make worse, as in: 1) A fracture; 2) the mutual
adulteration of two or more elements.
Computer Resources: The major item of any budget, allowing for the
acquisition of any capital equipment that is obsolete before the
purchase request is released.
Eigen Function: The use to which an eigen is put.
En: The universal bidentate ligand used by coordination chemists. For
years, efforts were made to use ethylene-diamine for this purpose, but
chemists were unable to squeeze all the letters between the corners of
the octahedron diagram. The timely invention of en in 1947
revolutionized the science.
Evaporation Allowance: The volume of alcohol that the graduate students
can drink in a year's time.
Exhaustive Methylation: A marathon event in which the participants
methylate until they drop from exhaustion.
First Order Reaction: The reaction that occurs first, not always the one
desired. For example, the formation of brown gunk in an organic prep.
Flame Test: Trial by fire.
Genetic Engineering: A recent attempt to formalize what engineers have
been doing informally all along.
Grignard: A fictitious class of compounds often found on organic exams
and never in real life.
Inorganic Chemistry: That which is left over after the organic,
analytical, and physical chemists get through picking over the periodic
table.
Mercury: (From L. Mercurius, the swift messenger of the gods) Element
No. 80, so named because of the speed of which one of its compounds
(calomel, Hg2Cl2) goes through the human digestive tract. The element
is perhaps misnamed, because the gods probably would not be pleased by
the physiological message so delivered.
Monomer: One mer. (Compare POLYMER).
Natural Product: A substance that earns organic chemists fame and glory
when they manage to systhesize it with great difficulty, while Nature
gets no credit for making it with great ease.
Organic Chemistry: The practice of transmuting vile substances into
publications.
Partition Function: The function of a partition is to protect the lab
supervisor from shrapnel produced in laboratory explosions.
Pass/Fail: An attempt by professional educators to replace the
traditional academic grading system with a binary one that can be
handled by a large digital computer.
Pharmacology: The use of rabbits and dogs as guinea pigs. (See also
CLINICAL TESTING, TOXICOLOGY).
Physical Chemistry: The pitiful attempt to apply y=mx+b to everything in
the universe.
Pilot Plant: A modest facility used for confirming design errors before
they are built into a costly, full-scale production facility.
Polymer: Many mers. (Compare MONOMERS).
Prelims: (From L. pre [before] + limbo [oblivion]) An obligatory ritual
practiced by graduate students just before the granting of a Ph.D. (if
the gods are appeased) or an M.S. (if they aren't).
Publish or Perish: The imposed, involuntary choice between fame and
oblivion, neither of which is handled gracefully by most faculty
members.
Purple Passion: A deadly libation prepared by mixing equal volumes of
grape juice and lab alcohol.
Quantum Mechanics: A crew kept on the payroll to repair quantums, which
decay frequently to the ground state.
Rate Equations: (Verb phrase) To give a grade or a ranking to a formula
based on its utility and applicability. H=E, for example, applies to
everything everywhere, and therefore rates an A. pV=nRT, on the other
hand, is good only for nonexistent gases and thus receives only a D+,
but this grade can be changed to a B- if enough empirical virial
coefficients are added.
Research: (Irregular noun) That which I do for the benefit of humanity,
you do for the money, he does to hog all the glory.
Sagan: The international unit of humility.
Scientific Method: The widely held philosophy that a theory can never be
proved, only disproved, and that all attempts to explain anything are
therefore futile.
SI: Acronym for "Systeme Infernelle".
Spectrophotometry: A long word used mainly to intimidate freshman
nonmajors.
Spectroscope: A disgusting-looking instrument used by medical
specialists to probe and examine the spectrum.
Toxicology: The wholesale slaughter of white rats bred especially for
that purpose. (See also CLINICAL TESTING, PHARMACOLOGY).
X-Ray Diffraction: An occupational disorder common among physicians,
caused by reading X-ray pictures in darkened rooms for prolonged
periods. The condition is readily cured by a greater reliance on blood
chemistries; the lab results are just as inconclusive as the X-rays, but
are easier to read.
Ytterbium: A rare and inconsequential element, named after the village
of Ytterby, Sweden (not to be confused with Iturbi, the late pianist and
film personality, who was actually Spanish, not Swedish). Ytterbium is
used mainly to fill block 70 in the periodic table. Iturbi was used
mainly to play Jane Powell's father.
Disclaimer: I didn't write this, I'm just reposting it.
THE LAST WORD
The Ultimate Scientific Dictionary
Activation Energy: The useful quantity of energy available in one cup of
coffee.
Atomic Theory: A mythological explanation of the nature of matter, first
proposed by the ancient Greeks, and now thoroughly discredited by modern
computer simulation. Attempts to verify the theory by modern computer
simulation have failed. Instead, it has been demonstrated repeatedly
that computer outputs depend upon the color of the programmer's eyes, or
occasionally upon the month of his or her birth. This apparent
astrological connection, at last, vindicates the alchemist's view of
astrology as the mother of all science.
Bacon, Roger: An English friar who dabbled in science and made
experimentation fashionable. Bacon was the first science popularizer to
make it big on the banquet and talk-show circuit, and his books even
outsold the fad diets of the period.
Biological Science: A contradiction in terms.
Bunsen Burner: A device invented by Robert Bunsen (1811-1899) for
brewing coffee in the laboratory, thereby enabling the chemist to be
poisoned without having to go all the way to the company cafeteria.
Butyl: An unpleasant-sounding word denoting an unpleasant-smelling
alcohol.
CAI: Acronym for "Computer-Aided Instruction". The modern system of
training professional scientists without ever exposing them to the
hazards and expense of laboratory work. Graduates of CAI-based programs
are very good at simulated research.
Cavendish: A variety of pipe tobacco that is reputed to produce
remarkably clear thought processes, and thereby leads to major
scientific discoveries; hence, the name of a British research laboratory
where the tobacco is smoked in abundance.
Chemical: A substance that:
1) An organic chemist turns into a foul odor;
2) an analytical chemist turns into a procedure;
3) a physical chemist turns into a straight line;
4) a biochemist turns into a helix;
5) a chemical engineer turns into a profit.
Chemical Engineering: The practice of doing for a profit what an organic
chemist only does for fun.
Chromatography: (From Gr. chromo [color] + graphos [writing]) The
practice of submitting manuscripts for publication with the original
figures drawn in non-reproducing blue ink.
Clinical Testing: The use of humans as guinea pigs. (See also
PHARMACOLOGY and TOXICOLOGY)
Compound: To make worse, as in: 1) A fracture; 2) the mutual
adulteration of two or more elements.
Computer Resources: The major item of any budget, allowing for the
acquisition of any capital equipment that is obsolete before the
purchase request is released.
Eigen Function: The use to which an eigen is put.
En: The universal bidentate ligand used by coordination chemists. For
years, efforts were made to use ethylene-diamine for this purpose, but
chemists were unable to squeeze all the letters between the corners of
the octahedron diagram. The timely invention of en in 1947
revolutionized the science.
Evaporation Allowance: The volume of alcohol that the graduate students
can drink in a year's time.
Exhaustive Methylation: A marathon event in which the participants
methylate until they drop from exhaustion.
First Order Reaction: The reaction that occurs first, not always the one
desired. For example, the formation of brown gunk in an organic prep.
Flame Test: Trial by fire.
Genetic Engineering: A recent attempt to formalize what engineers have
been doing informally all along.
Grignard: A fictitious class of compounds often found on organic exams
and never in real life.
Inorganic Chemistry: That which is left over after the organic,
analytical, and physical chemists get through picking over the periodic
table.
Mercury: (From L. Mercurius, the swift messenger of the gods) Element
No. 80, so named because of the speed of which one of its compounds
(calomel, Hg2Cl2) goes through the human digestive tract. The element
is perhaps misnamed, because the gods probably would not be pleased by
the physiological message so delivered.
Monomer: One mer. (Compare POLYMER).
Natural Product: A substance that earns organic chemists fame and glory
when they manage to systhesize it with great difficulty, while Nature
gets no credit for making it with great ease.
Organic Chemistry: The practice of transmuting vile substances into
publications.
Partition Function: The function of a partition is to protect the lab
supervisor from shrapnel produced in laboratory explosions.
Pass/Fail: An attempt by professional educators to replace the
traditional academic grading system with a binary one that can be
handled by a large digital computer.
Pharmacology: The use of rabbits and dogs as guinea pigs. (See also
CLINICAL TESTING, TOXICOLOGY).
Physical Chemistry: The pitiful attempt to apply y=mx+b to everything in
the universe.
Pilot Plant: A modest facility used for confirming design errors before
they are built into a costly, full-scale production facility.
Polymer: Many mers. (Compare MONOMERS).
Prelims: (From L. pre [before] + limbo [oblivion]) An obligatory ritual
practiced by graduate students just before the granting of a Ph.D. (if
the gods are appeased) or an M.S. (if they aren't).
Publish or Perish: The imposed, involuntary choice between fame and
oblivion, neither of which is handled gracefully by most faculty
members.
Purple Passion: A deadly libation prepared by mixing equal volumes of
grape juice and lab alcohol.
Quantum Mechanics: A crew kept on the payroll to repair quantums, which
decay frequently to the ground state.
Rate Equations: (Verb phrase) To give a grade or a ranking to a formula
based on its utility and applicability. H=E, for example, applies to
everything everywhere, and therefore rates an A. pV=nRT, on the other
hand, is good only for nonexistent gases and thus receives only a D+,
but this grade can be changed to a B- if enough empirical virial
coefficients are added.
Research: (Irregular noun) That which I do for the benefit of humanity,
you do for the money, he does to hog all the glory.
Sagan: The international unit of humility.
Scientific Method: The widely held philosophy that a theory can never be
proved, only disproved, and that all attempts to explain anything are
therefore futile.
SI: Acronym for "Systeme Infernelle".
Spectrophotometry: A long word used mainly to intimidate freshman
nonmajors.
Spectroscope: A disgusting-looking instrument used by medical
specialists to probe and examine the spectrum.
Toxicology: The wholesale slaughter of white rats bred especially for
that purpose. (See also CLINICAL TESTING, PHARMACOLOGY).
X-Ray Diffraction: An occupational disorder common among physicians,
caused by reading X-ray pictures in darkened rooms for prolonged
periods. The condition is readily cured by a greater reliance on blood
chemistries; the lab results are just as inconclusive as the X-rays, but
are easier to read.
Ytterbium: A rare and inconsequential element, named after the village
of Ytterby, Sweden (not to be confused with Iturbi, the late pianist and
film personality, who was actually Spanish, not Swedish). Ytterbium is
used mainly to fill block 70 in the periodic table. Iturbi was used
mainly to play Jane Powell's father.