bluuebunny/crossref_metadata_2025 huggingface dataset:
Glycols, Propylene Glycols
Authors: Martin Alton E. , Murphy Frank H.
Published: July 2004

The propylene glycol family of chemical compounds consists of monopropylene glycol (PG), dipropylene glycol (DPG), and tripropylene glycol (TPG). These chemicals are manufactured as copoducts and are used commercially in a large variety of applications. They are available as highly purified products which meet well‐defined manufacturing and sales specifications. All commercial production is via the hydrolysis of propylene oxide.

The propylene glycols are clear, viscous, colorless liquids that have very little odor, a slightly bittersweet taste, and low vapor pressures. The most important member of the family is monopropylene glycol, also known as 1,2‐propylene glycol, 1,2‐dihydroxypropane, 1,2‐propanediol, methylene glycol, and methyl glycol. All of the glycols are totally miscible with water.

Propylene glycol, when produced according to the U.S. Food and Drug Administration good manufacturing practice guidelines at a registered facility, meets the requirements of the U.S. Food, Drug, and Cosmetic Act. It is listed in the regulation as a direct additive for specified foods and is classified as generally recognized as safe (GRAS). In addition, it meets the requirements of the
Food Chemicals Codex
and the specifications of the
U.S. Pharmacopeia XXIII.
Because of its low human toxicity and desirable formulation properties it has been an important ingredient for years in food, cosmetic, and pharmaceutical products.
Propylene Oxide
Authors: Trent David L.
Published: July 2004

Propylene oxide, a commercially important chemical worldwide, is very reactive, finding application in many derivative businesses. Use is primarily as an intermediate for a wide array of products, such as polyether polyols for the polyurethane industry; propylene glycol for food, cosmetics, and heat‐transfer fluids; polyglycols as lubricants, antifoam agents, and metalworking fluids; glycol ethers for protective coatings, inks, and cleaners; and isopropanolamines for adhesives, corrosion inhibitors, and agricultural products.

Propylene oxide is produced by two process chemistries. The first, and oldest, is the chlorohydrin process. Epoxidation by caustic or milk of lime produces the epoxide. The second process involves the oxidation of an organic such as isobutane or ethylbenzene to the corresponding hydroperoxide, then epoxidation of propylene using the hydroperoxide to the epoxide and an alcohol. The alcohol,tert‐butanol or 1‐phenylethanol, is further processed to provide the commercially viable coproducts, such as methyl‐tert‐butyl ether and styrene. The global capacity for propylene oxide is about half from the chlorohydrin process and a quarter each from the hydroperoxide processes producingtert‐butanol and styrene as coproducts. These and several other potentially commercial processes are discussed.
n
‐Propyl Alcohol
Authors: Unruh J. D. , Pearson D.
Published: July 2004

n
‐Propyl alcohol (1‐propanol) is used primarily as a specialty solvent for printing inks or as a chemical intermediate. The predominant derivatives of
n
‐propyl alcohol are the acetate ester and
n
‐propylamines. The latter are used in herbicide production. Smaller‐volume uses of
n
‐propyl alcohol are as a flavor or fragrance in foods and as feed additive. 1‐Propanol is manufactured in most of the Western world by hydroformylation of ethylene followed by hydrogenation of propanal. The hydroformylation or oxo process is catalyst‐driven. This process is described. In South Africa, 1‐propanol is also produced from coal through Fischer‐Tropsch processes.
Prostaglandins
Authors: Collins Paul W.
Published: July 2004

Prostaglandins are a family of naturally occurring substances found in animals and humans. They are produced from 20 carbon fatty acidsin vivoand play important and diverse roles in both health and disease. Unlike circulating hormones, prostaglandins are synthesized and released by most tissues, act near their site of synthesis, and then are rapidly inactivated by metabolic enzymes. They are among the most potent substances known and exert regulatory influences on virtually all tissues and organs.

Because of their diverse biological effects and their potential as therapeutic agents, prostaglandins underwent intense scrutiny following their structural elucidation and availability in the early 1960s. Both academic and industrial laboratories studied their biosynthesis, metabolism, physiological and pharmacological effects, and their chemical and physical properties. The total synthesis of prostaglandins presented formidable challenges. Because of their structural and stereochemical complexity and chemical instability, they provided a strong impetus to the development of new synthetic methodologies. The prostaglandins and many analogues are available by total synthesis and some have reached the marketplace as therapeutic agents. Examples are prostaglandin E1(PGE1), used in cardiovascular and reproductive indications; analogues of prostaglandin F2 α, used in estrus synchronization in farm animals; misoprostol, an analogue of PGE1, used in the treatment of ulcers; prostacyclin and some of its analogues, used for cardiovascular diseases; and latanoprost, used in the treatment of glaucoma.
Protein Engineering
Authors: Davis June P. , Copeland Robert A.
Published: July 2004

Protein engineering aims to provide insights into the interplay of forces that relate protein structure to stability and function. Genetic engineering techniques allow the identity of an amino acid residue within a protein to be altered, typically replacing one residue systematically with others that differ in only one functional aspect, such as size, charge, hydrogen‐bonding capacity, etc. De novo design of proteins is being used to help understand the forces that stabilize specific protein structural motifs. Applications of de novo protein design to the construction of α‐helical bundles and all β‐sheet proteins are discussed. The power of mutagenic analysis for the identification of the structural determinants of biological function are illustrated through protein engineering studies of the proteolytic enzyme subtilisin, and of the G‐protein‐coupled β‐adrenergic receptor. Methods that allow for the replacement of an amino acid residue within a protein by unnatural amino acids are described.
Psychopharmacological Agents
Authors: Martin J. R. , Godel T. , Hunkeler W. , Jenck F. , Moreau J.‐L. , Sleight A. J. , Widmer U.
Published: July 2004

Martin, James R.; Godel, T.; Hunkeler, W.; Jenck, F.; Moreau, J‐L.; Sleight, A. J.; and Widmer, U. (F. Hoffmann‐La Roche Ltd.). A number of important advances have occurred in the understanding and the treatment of disorders of the central nervous system including mood disorders, schizophrenia, anxiety disorders, insomnia, substance use disorders, and dementias. The plethora of novel drugs act by means of diverse neurobiological mechanisms and represent a great diversity of chemical structures. Along with improvements in the therapeutic index of anxiolytics, sedative–hypnotics, antidepressants, and antipsychotics, some progress has also been made in the search for drugs effective in the treatment of substance use disorders, as well as Alzheimer's disease and other dementias. Nonetheless, such improvements in symptomatic therapy have not been accompanied by the discovery of effective etiological and pathophysiological interventions. It is from here that the successful psychopharmacological agents of the future must come.
Pulp
Authors: Genco Joseph M.
Published: July 2004

Pulp, the raw material used in the production of paper, paperboard, fiberboard, and other similar manufactured products, is produced from wood and nonwood plant matter by separating cellular components using mechanical and/or chemical methods. Wood is the dominant source of fiber used in the manufacture of pulp in the western hemisphere. Nonwood fiber sources are used in those locations where wood is in short supply or for pulps requiring special characteristics. In addition to wood, recovered (recycled) fiber represents a growing segment of the overall fiber supply worldwide.

Commercial pulp is classified according to the method of manufacture as mechanical, chemical, chemimechanical, and semichemical. Economic factors, product requirements, and desired fiber properties determine the method of pulping. Mechanical pulps, produced through the application of mechanical energy, give rise to materials having high yield, small average particle size, high opacity, and excellent printing characteristics. Mechanical pulps have some undesirable properties such as low tensile strength and lack of permanence. Chemical pulps are produced by digesting wood using chemicals to remove lignin, extractives, and low molecular weight polysaccharides, frequently resulting in the loss of wood solids which are dissolved during the pulping and bleaching processes. Chemical pulps are used in the bleached or the unbleached state and are composed of longer, stronger fibers that are more stable than mechanical pulps, but have lower yields and less desirable print qualities. Chemimechanical and semichemical pulps are produced in hybrid processes based on the application of both chemicals and mechanical energy.

Wood solids originating in the pulping process are recovered in the form of steam and electrical energy. Pulping chemicals are also recovered for reuse in the manufacturing process. Environmental management includes improvements in chemical recovery, process modification to minimize the use of elemental chlorine, and the treatment of process waste streams.
Pumps
Authors: Nelik Lev
Published: July 2004

Pumps are used in a wide range of industrial applications in the chemical processing industries. Pumping equipment varies widely in terms of pump type, size, and materials of construction. The two principal pump types, kinetic, which is mainly centrifugal, and positive displacement, are presented and basic operating parameters such as capacity, head, power, efficiency, and specific speed are defined. Fundamentals of operation are discussed, selection guidelines given, and examples of pump applications and reliability concerns provided. Pump auxiliaries such as couplings and seals, as well as effects of cavitation, recirculation, internal hydraulic forces, wear, and corrosion, are described. Cost approximation methodology is presented along with a list of manufacturers.
Silicon, Pure
Authors: Runyan W. R.
Published: July 2004

Elemental silicon, a metal, does not occur in nature, but as the oxide is a constituent of various rocks comprising about 28% of the earth's crust. There are three naturally occurring stable isotopes and several radioactive ones. Except at very high pressures, silicon has a diamond cubic structure and is a semiconductor.

High purity silicon is used primarily for its semiconducting properties and is the primary constituent of silicon diodes, transistors, and integrated circuits. Ordinary metallurgical‐grade silicon is made by reducing quartz sand with coke in an electric furnace. That silicon may then be used to produce a silicon compound such as a chlorosilane that is relatively easy to purify. After purification, the compound is reduced to give high purity, semiconductor‐grade silicon, where most of the impurities are in the parts per billion range. Purification methods are discussed and properties of the electronics‐grade silicon given.
Pyrotechnics
Authors: Conkling John A.
Published: July 2004

Pyrotechnics involves the combination of science and art to chemically generate heat, and from that heat create light, color, audible effects, and gas pressure for entertainment, emergency signaling, and military applications. The civilian side of pyrotechnics includes fireworks, highway flares (fusees), air bag inflators, and special effects devices for the entertainment industry. Military and aerospace pyrotechnics include a wide range of devices for illumination, signaling, obscuration, and gas generation. A pyrotechnic mixture typically contains one or more oxygen‐rich oxidizers and one or more fuels, which undergo an exothermic reaction when heated to the ignition temperature of the mixture. The heat that is produced then creates the desired pyrotechnic effect. The selection of the chemicals used in a pyrotechnic composition, as well as the particle sizes of the chemicals and the degree of intimacy to which the composition is blended, determine in large part the speed of the pyrotechnic reaction. Safety in all aspects of manufacturing and using pyrotechnic mixtures and devices is important.
Quinolines and Isoquinolines
Authors: Finley K. Thomas
Published: July 2004

The fusion of a pyridine and a benzene ring produces two heterocyclic aromatic systems, usually referred to by their common names, quinoline and isoquinoline. Besides the chemistry to be expected, this combination opens a wide range of additional possibilities. It is therefore not surprising that both quinoline and isoquinoline have been the subject of extensive studies ranging from the theoretical to the most actively applied. The dye and photographic industries, the metallurgical, analytical, and polymer sciences all provide extensive examples. However, it continues to be the medical field and the pharmaceutical industry which provide the principal driving force for an impressive array of studies of the synthesis and properties of molecules containing these structures. The toxicity of these compounds is sufficient to warrant care in their handling.
Quinones
Authors: Finley K. Thomas
Published: July 2004

Quinones, possessing two α,β‐unsaturated carbonyl groups usually in a six‐carbon atom ring, represent a unique structural unit. Their centrality in the synthesis of such important commercial substances as dyes and pharmaceuticals has resulted in extensive study of a variety of synthons. In living matter they are ubiquitous and vital to human metabolism. Quinones are of special interest to biochemists and to both synthetic and theoretical organic chemists. The types of reactions most often reported are nucleophilic addition, photochemistry, cycloaddition, electrophilic addition, radical alkylation, electrochemistry, oxidation, and nucleophilic substitution. The synthesis of quinones is usually accomplished through oxidation of phenols or anilines. A wide variety of oxidants have been used, but quinones of higher oxidation potential are often the reagent of choice. Quinones of low molecular weight should be treated with care in their storage and handling.
Antibacterial Agents, Quinolones
Authors: Kadow John. F. , Barrett J.F. , Beaulieu D. , Dougherty T.J. , Meanwell N.A. , Ohemeng‐Paratek K.A. , Ryan B.
Published: July 2004

Quinolone carboxylic acids are totally synthetic antibacterial agents. Initial compounds possessed relatively limited clinical utility. Since the 1980s, the discovery of fluoroquinolones with better safety profiles and broader spectrums of activity have made this class of antibacterial agents one of the most important in clinical usage. New des‐F(6)‐quinolone analogues are expected to provide improved activity against gram‐positive organisms and as a result, members of this class should become true broad spectrum antibiotics of major clinical importance.
Radioactive Elements
Authors: Beres Laszlo
Published: July 2004

This article is an overview of radioactive tracers technology focusing on compounds labeled with hydrogen‐3 (tritium), carbon‐14, sulfur‐35, phosphorus‐32, phosphorus‐33, and iodine‐125. The general approaches for the synthesis of labeled compounds, such as organic chemical methods and biochemical techniques, are described. The factors affecting the stability of labeled compounds are discussed, along with methods of detection and quantitation of the commonly used radioactive isotopes. Considerations in the safe handling of radioactive tracers and regulatory issues related to working with radioactive materials are summarized. The uses and applications of labeled compounds in biomedical research, pharmaceutical development, gene analysis, and agricultural experiments are discussed.
Radioisotopes
Authors: Helmer Richard G.
Published: July 2004

Radioisotopes, also called nuclides or radionuclides, are not stable, but rather decay to more stable elements or other atoms by emission of high energy radiation. Study of radioisotopes has led to increased understanding of the forces of nature, especially those forces such as those prevalent in nuclei binding exhibited solely in the microscopic world. Naturally occurring radioisotopes are used to determine the ages of materials, as radiopharmaceuticals or radiation sources or tracers in medicine, for nondestructive evaluation, for the tracking of groundwater or air flow, and for scientific analysis.

The nuclear physic properties of radioisotopes and the various radiation particles are summarized, including half‐lives, decay constants, angular momentum, and parities. The modes of nuclear decay and the accompanying radiation are described, as are combined nuclear and atomic processes, and atomic decays and corresponding radiations. Decay data for useful radioisotopes are given.
Radiopaques
Authors: Lin Youlin
Published: July 2004

Lin, Youlin (Mallinckrodt Medical, Inc.). Medical examination of soft tissues or organs by nonsurgical means often requires the introduction of a special agent that makes the detection system responsive to detail in the tissue of interest. Radiopaques, often called x‐ray contrast media, are examples of such diagnostic agents. Radiopaques are categorized according to specific applications, such as angiography, urography, myelography, cholecystography, cholangiography, gastrointestinal radiography, computed tomography, arthrography, and hysterosalpingography. The importance, chemistry, and kinds of radiopaques developed for the types of medical imaging are presented. The evolution of research efforts from high osmolality contrast media (HOCM) to low osmolality contrast media (LOCM) is emphasized. Historical perspectives, cost considerations, and future outlooks in contrast media development are briefly outlined. Physical constants, such as osmolality, water solubility, viscosity and partition coefficient, and median lethal dose in animal studies are cited and compared for selected contrast agents. Sources are listed for commercial radiopaque suppliers in the United States. Vol. 20, pp. 906–930, 129 refs. to December 1995.
Radioprotective Agents
Authors: Murray David , McBride William H.
Published: July 2004

Developments in understanding agents having activity for the prevention and treatment of radiation injuries are discussed. Chemical radioprotectors have long been dominated by thiol compounds and their phosphorothioate derivatives. Advances have been made to understanding the fundamental mechanisms by which these agents protect against cell killing. The finding that thiols also protect against radiation‐induced mutations and transformation has generated considerable interest. Mutations may be expressed as undesirable late effects in radiotherapy. Such effects are reviewed herein, as is the enormous literature that has accumulated relating to preclinical and clinical studies of the effects of phosphorothioates in animals and humans. A number of nonthiol radioprotective agents, including protease inhibitors, vitamins, metalloelements, and calcium antagonists, are also discussed. There has been a virtual explosion of interest in biological, as opposed to chemical, modifiers of radiation injury. These biologics include cytokines such as interleukin 1 and granulocyte colony‐stimulating factor, eicosanoids such as prostaglandins and leukotrienes, and steroids/glucocorticoids such as dexamethasone and methylprednisolone. In addition, an array of immunomodulatory agents such as glucan and endotoxin have been described, which act by nonspecifically enhancing immunological and hemopoietic responses. Although some of these biologics act best when given prior to irradiation, many of them can modulate radiation injury when given after irradiation, presumably by affecting the recovery and repopulation of critical tissue elements. Biologics thus afford an opportunity for therapeutic intervention following accidental radiation exposure as well as in radiation therapy. Demonstrations of a potential therapeutic advantage from combining chemical radioprotectors, which decrease the extent of initial damage, with nonthiol biologics, which accelerate tissue recovery, provides an attractive approach to radioprotection which also minimizes toxicity.
Raman Spectroscopy
Authors: Christensen Kenneth A. , Todd Elizabeth A. , Morris Michael D.
Published: July 2004

Raman spectroscopy involves the detection of inelastic light scattering resulting from molecular vibrations. Industrial applications of this technique are growing in areas such as process and quality control, materials characterization and reliability, and environmental and industrial hygiene monitoring. Simple as well as large inorganic and organic compounds, polymers, films, and surfaces may be investigated using Raman. Samples, which may be solid, gaseous, or liquid, are easily prepared. Even aqueous solutions may be examined. Instrumentation utilizing visible or near infrared laser sources, modern dispersive spectrographs or interferometers, fiber‐optic and/or microprobes, and highly sensitive detection systems are described.
Nuclear Reactor Types
Authors: Murray Raymond L.
Published: July 2004

Nuclear reactors may be classified by purpose or use, key components, method of heat extraction, power level or neutron flux, or arrangement of component materials. Commercial reactors are also classified by the companies involved in design and building of the facility. Reactors used for power generation, either heat or electrical, propulsion, whether naval vessels or spacecraft, radioisotope production, materials testing, basic research, and training are discussed. The development of nuclear reactors is presented, including information gleaned from the two principal nuclear accidents of the 1980s.

The pressurized lightwater reactor is the most common power generation reactor in the United States, but the boiling water reactor is also used. In Canada, heavy‐water reactors are usually employed. These and other reactors, such as the molten salt and the fast breeder reactor, are described.
Recreational Surfaces
Authors: Orofino T. A. , Sweenie H. G.
Published: July 2004

Grass‐like and other artificial recreational surfaces designed for sports use are described in terms of types, construction, materials and components, and performance characteristics. Also included are installation techniques and listings of current commercial products. For grass‐like turf products the principal assembly techniques are tufting and knitting. Fiber‐forming polymers such as polyolefins, polyamides, and polyesters processed to provide high strength combined with appropriate elongation are suitable materials for the turf surface and backing fibers. Other materials are utilized for backing finish, including acrylic, polyurethane, and vinyl polymers. Track surfaces, another important category of recreational surfaces, typically employ polyurethanes via pour‐in‐place techniques. Shock absorption and resiliency are important performance properties of recreational surfaces. High return of impact energy is desirable on track surfaces, whereas substantial hysteresis loss is needed with grass‐like surfaces for safety under body impact. The turf surfaces typically are overlaid on a foamed elastomer underpad for this purpose. Artificial recreational surfaces were introduced in the early 1960s and remain important commercial products in the 1990s, represented by numerous manufacturers.
Recycling, Plastics
Authors: Borchardt John K.
Published: July 2004

Plastics comprise 9.3% of the 200 millions tons of municipal solid waste collected in the United States. Although the recycling rate of plastics seems low, U.S. plastics production in 1993 was 70 billion pounds while 700 million pounds was recycled. Both economic and governmental regulation are driving recycling. This article deals with the various plastics that can be recycled. Separation of commingled materials is discussed. Plastics discussed include poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and other miscellaneous compounds. Economics and disposal statistics are also given.
Refractories
Authors: Leigh H. David
Published: July 2004

Almost all industrial processes use or depend on refractory materials that resist the action of hot environments. The many forms, constituent substances, uses, and analyses common to industrial refractories are presented. Uses include linings for furnaces, cement kilns, crucibles, and chemical tanks. A large variety of forming techniques can be used to produce refractories of virtually any conceivable shape. The most common of these techniques are discussed. Historically, refractories were simply naturally occurring stone minerals found to be useful in rudimentary smelting and refining processes. More sophisticated use of raw mineral deposits, beneficiated mineral deposits, and the development of synthetic minerals has led to an array of refractory compositions. The principles governing the performance of refractories have been well established. Reactions with high temperature process liquids, gases, and other refractories is discussed. Sophisticated refractory systems to achieve greater performance characteristics are continually under development.
Refrigeration
Authors: Sibley Howard W.
Published: July 2004

This article covers the broad area of vapor compression refrigeration and the refrigerants used in applications requiring temperatures in the range of

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to 4°C. Systems described are domestic refrigerator/freezers, commercial refrigeration systems, cold storage warehousing, industrial applications, and transport refrigeration. The basic refrigeration components common to all categories are described and then followed by discussion of unique cycle configurations or design considerations for each category, respectively. Because of the significant ramifications associated with refrigerant effects on environmental parameters, namely, ozone depletion and global warming, discussion of changes necessary in refrigerant selection and availability is provided. Associated with all vapor compression refrigeration systems is the need for compressor lubrication. The interaction of the lubricant and refrigerant is discussed as well as the impact of new refrigerants on lubricant selection.
Refractory Coatings
Authors: Thorpe Merle
Published: July 2004

Refractory coatings are protective surface layers of high melting materials used primarily for high temperature applications or to prevent abrasion or corrosion. These coatings may be composed of metals, alloys, or intermetallic compounds; metallic oxides, carbides, borides, nitrides, etc; or ceramic or metal–ceramic composites. Many specific coatings are described. Uses of refractory coatings range from application to the surfaces of parts in the aerospace and automotive industries, where high temperature protection is of importance, to lens coatings where the protective layer must be optically pure, yet abrasion resistant. Some prosthetic devices also require these coatings.

Coating technology has advanced rapidly since the early 1980s resulting in improved coating quality, reproducibility, and application rates and techniques. The various coating technologies ranging from thermal spray to chemical vapor deposition are discussed. Methods for evaluating coatings are presented.
Refractory Fibers
Authors: Waugh R. A.
Published: July 2004

Waugh, Richard A. (Thermal Ceramics). Oxide and nonoxide refractory fibers have become essential materials for use in modern industrial and commercial applications. These technologically advanced fibrous products are manufactured by thermal or chemical processes and generally can be used at temperatures up to 2800°C. Chemical composition and processing technology determine the chemical and physical properties of these refractory fibers. This article reviews manufacturing processes and properties for silicon carbide, silicon nitride, boron nitride, carbon, silica, polycrystalline, and aluminosilicate refractory fibers. Applications are also discussed.
Refractory Boron Compounds
Authors: Wentorf Robert H.
Published: July 2004

Borides have metallic characteristics such as high electrical conductivity and positive coefficients of electrical resistivity. Many of them, particularly the borides of metals of Groups 4 (IVB), 5 (VB), and 6 (VIB), the MB6compounds of Groups 2(II) and 13(III), and the borides of aluminum and silicon, have high melting points, great hardness, low coefficients of thermal expansion, and good chemical stability. Borides are inert toward nonoxidizing acids; however, a few, such as Be2B and MgB2, react with aqueous acids to form boron hydrides. Most borides dissolve in oxidizing acids such as nitric or hot sulfuric acid and they are also readily attacked by hot alkaline salt melts or fused alkali peroxides. In dry air, borides are relatively resistant to oxidation. On a commercial scale, borides are prepared by the reduction of mixtures of metallic and boron oxides using aluminum, magnesium, carbon, boron, or boron carbide, followed by purification. Borides can also be synthesized by vapor‐phase reaction or electrolysis. They are used for resistance‐heated boats (with boron nitride), for aluminum evaporation, and for sliding electrical contacts. Boron and carbon form one compound, boron carbide, B4C, although excess boron may dissolve in boron carbide, and a small amount of boron may dissolve in graphite. Boron carbide has a rhombohedral structure consisting of an array of nearly regular icosahedra, each having twelve boron atoms at the vertices and three carbon atoms in a linear chain outside the icosahedra. A descriptive chemical formula would be B12C3. Boron carbide is resistant to most acids but is rapidly attacked by molten alkalies. Hot‐pressed boron carbide finds use as wear parts, sandblast nozzles, seals, and ceramic armor plates. Boron carbide is used in the shielding and control of nuclear reactors. Boron and nitrogen form one compound, boron nitride, BN, which may exist in a hexagonal, graphite‐like form, hBN, or in two denser forms having tetrahedrally bonded B and N atoms on a cubic (zinc‐blend) or a hexagonal (wurtzite) lattice. Hot‐pressed hBN is useful for high temperature electric or thermal insulation, vessels, etc, and for special materials such as III‐V semiconductors. The greatest use of cubic boron nitride is as an abrasive under the name Borazon.
Repellents
Authors: Carlson D. A.
Published: July 2004

Repellents, the first line of defense that can be readily used as personal protection, affect insects by disrupting their natural behavior of bloodseeking through biting of humans and animals. The best overall repellent, effective against many species of pest mosquitoes but not all malaria mosquitoes, isN,N‐diethyl‐m‐toluamide (DEET). Commercial products containing DEET are available which are reasonably comfortable for the user and can protect against pests for hours before retreatment on skin. Clothing treatment has become more popular for mosquito protection, using DEET or synthetic pyrethroids. A few compounds, including two cyclohexyl carboxamides, are under development and may eventually replace DEET in the U.S. military system. A 1993 database search showed 27 active ingredients in 212 EPA‐registered products as repellents or feeding depressants. Repellents including DEET are effective, as are synthetic pyrethroids when treated onto clothing to intoxicate ticks. Chemical cockroach repellents are available, but newer compounds are also under development. Methyl anthranilate, a grape‐flavored food additive, is an effective bird repellent when tested against geese, ducks, and gulls; methiocarb is an insecticide that repels birds from food crops; 4‐aminopyridine is a repellent–toxicant that is lethal when used in baits. No consistently repellent compounds are known for deer, however, thiram is registered in Georgia, and Chaperone is registered with EPA for use against deer and rabbits.
Furnaces, Electric, Resistance Furnaces
Authors: Walton Robert R.
Published: July 2004

The most widely used and best known resistance furnaces are indirect‐heat resistance furnaces or electric resistor furnaces. They are categorized by a combination of four factors: batch or continuous; protective atmosphere or air atmosphere; method of heat transfer; and operating temperature. The primary method of heat transfer in an electric furnace is usually a function of the operating temperature range. The three methods of heat transfer are radiation, convection, and conduction. Radiation and convection apply to all of the furnaces described. Conductive heat transfer is limited to special types of furnaces.

Operating temperature ranges are classified as low, medium, and high; there is no standard or precise definition of these ranges. Generally, a low temperature furnace operates below 760°C, medium temperature ranges from 760– 1150°C, and furnaces operating above 1150°C are high temperature furnaces. The term oven should be used when temperatures are below 760°C, and the word furnace applied for higher temperatures.

Electric furnaces are used for annealing, brazing, carburizing, galvanizing, forging, hardening, melting, sintering, enameling, and tempering metals, most notably aluminum, copper, iron and steel, and magnesium alloys.
Reverse Osmosis
Authors: Bhattacharyya D. , Mangum W. C. , Williams M. E.
Published: July 2004

Reverse osmosis is a highly effective separation technology used industrially in several areas, including desalination of seawater and brackish water and wastewater treatment. Membrane materials and types of modules used in reverse osmosis, as well as theoretical bases and operational aspects, are presented. A discussion of flux limiting conditions caused by concentration polarization and membrane fouling is included, as is that of the pretreatments required for process feed streams. The application of reverse osmosis for the separation of hazardous organic compounds from aqueous systems, for wastewater treatment, desalination, ultrapure water production, and food processing are reviewed in terms of membrane performance. The concept of nanofiltration and its applications are also discussed. General design considerations and economics are reviewed.
Fluorine Compounds, Inorganic, Rhenium
Authors: Meshri Dayal T.
Published: July 2004

Of the six known binary rhenium fluorides, rhenium hexafluoride and rhenium heptafluoride are those that are commercially available. Rhenium also form a series of oxyfluorides. Preparation and properties are described. Rhenium hexafluoride finds use in the electronics, semiconductor, and laser industries as a substrate for their rhenium or rhenium alloy films.
Toluenes, Ring‐Chlorinated
Authors: Khandare Pravin , Spohn Ron
Published: July 2004

The preparation, physical and chemical properties, and applications on mono‐, di‐, tri‐, tetra‐, and pentachlorotoluenes are reviewed. Reactions of chlorotoluenes are classified into those involving the aromatic ring, the methyl group, and the halogen. The reactions involving the methyl group are widely used to synthesize a variety of functionalized chloroaromatic compounds. Some of the recent applications of these compounds are based on replacement of the halogen by other functional groups catalyzed by transition‐metal compounds. Monochlorotoluenes are obtained generally by reaction of toluene with chlorine under a variety of homogeneous and heterogeneous conditions. The higher chlorotoluenes are obtained usually by chlorination of the lower chlorinated analogues. Many detailed studies have been conducted to evaluate the toxicological properties of chlorotoluenes. Ring‐chlorinated toluenes find principal applications in the pesticide, pharmaceutical, peroxide, dye, and other industries.p‐Chlorotoluene is an especially valuable starting material to prepare numerous, industrially useful intermediates.
Rubber, Natural
Authors: Baker C. S. L. , Fulton W. S.
Published: July 2004

Baker, C. S. L., and Fulton, W. S. (Malaysian Rubber Producers' Research Association). This article provides an overview of natural rubber, derived from the tree

Hevea brasiliensis

. It summarizes the history of natural rubber with the seedlings planted in Malaysia in 1877, through to the production figures of the present day. It discusses latex collection and its coagulation to give the various types of dry natural rubber grades. The latter are individually described, up to the modern technically specified grades. Raw rubber properties, such as crystallization, storage hardening, cure behavior, and plasticity retention index are covered, followed by treatment of the chemistry and technology of natural rubber. The technical advantages of natural rubber, blends with synthetic rubber, the various vulcanization systems available with the resulting key properties, and antidegradant agents are each outlined. For completeness of coverage of natural rubber, modified forms are discussed, with their attendant change in properties, including those of thermoplastic natural rubber.

Blends and application areas are followed by a final section on natural rubber latex. Latex preparation, concentration, and properties are described, together with an indication of consumption patterns and principal product groups. The concern over protein allergy in latex gloves and condoms is addressed and an explanation on the apparent explosion of interest in this phenomena is given.
Recycling, Rubber
Authors: P. Paul John
Published: July 2004

An overview of the uses for worn out scrap and reject rubber parts and articles, primarily tires, is presented. Uses and processing of worn out scrap and reject rubber include scrap rubber as a final source, pyrolysis of scrap rubber, depolymerization, rubber–asphalt modification, cryogenic pulverizing and mechanical tire shredding, rubber reclaiming, civil engineering, and tire retreading.

Scrap rubber as a fuel source (burning rubber, sometimes known as tire‐derived fuel) in cement kilns, electric utilities, pulp and paper mills, and dedicated tire‐to‐energy plants is discussed.

Processes for pyrolyzing rubber into oil and char are described, as are projects using rubber in asphalt and legislation being enacted to encourage the use of asphalt in rubber. Methods for cryogenically pulverizing and grinding tires are included. Methods of devulcanizing rubber using digesters, and heater or pan and reclaimator processes are presented. Uses of scrap rubber in civil engineering include erosion control retaining walls, fill material, and athletic and playing surfaces.
Rubidium and Rubidium Compounds
Authors: Wagner Frank S.
Published: July 2004

The article provides an overview of the properties, preparation, and chemistry of the element rubidium. Physical properties of rubidium are provided. The chemistry of the element is discussed in terms of its preparation, basic inorganic chemistry, chelating complexes, and metal–fulleride compounds. Packaging and current shipping information is included. Suppliers of rubidium metal and compounds are listed, along with pricing. Owing to the chemical reactivity of rubidium, safe handling and storage procedures for the metal are discussed. Available toxicological data are given for a number of common rubidium compounds. Although rubidium and its compounds have limited commercial application, some uses are reviewed. References to review articles, monographs, and books on rubidium and the alkali metals are also provided.
Nuclear Power Facilities, Safety
Authors: Taylor J. J.
Published: July 2004

Safety has played a dominant role in the ability to generate electricity by nuclear means because large quantities of highly radioactive fission products are generated with the energy from fission. Strict control is maintained over these radioactive materials to assure that public and worker health and safety are protected. The basic safety principles, defense‐in‐depth design philosophy, and key safety design features which apply to all nuclear facilities are discussed. Specific examples are given from nuclear power plant design. The methods of assessment of safety are described, both for self‐assessment and independent assessment. The roles of industry and government in the assessment process are outlined. Comparative risks of nuclear power are substantially lower than most other methods of generating electricity.

The specific safety characteristics of the nuclear power plant that generates the electricity, and of the nuclear fuel cycle, which functions to produce nuclear fuel and dispose of radioactive wastes are each given. Special focus is placed on the safe disposal of spent fuel and radioactive waste. The basic radiation exposure and health standards which establish the foundation of public and worker protection are cited. The safety of future nuclear power plants is summarized.
Sedimentation
Authors: Svarovsky Ladislav
Published: July 2004

Sedimentation as it applies to gravitational settling of solid particles is discussed. Other aspects included are the pretreatment of slurries to improve settling rates and the enhancement of settling by slow cyclonic action. The fundamental principles of sedimentation are reviewed for free, hindered, and zone settling of solids. The effects of coagulation and flocculation are also presented in terms of how these affect the gravity sedimentation process. A discussion of the batch settling tests on real suspension and the way industrial settlers are sized, as well as a review of clarifiers and thickeners, is included.
Selenium and Selenium Compounds
Authors: Hoffmann J. E. , King M. G.
Published: July 2004

Selenium, the 30th most abundant element, lies between sulfur and tellurium in Group 16 (IVA) of the Periodic Table. There are no ores mined for selenium value. Rather, selenium is recovered throughout the world as a by‐product in the refining of sulfide‐bearing copper minerals. Those processes are discussed.

The chemical and physical properties of selenium are often similar to those of sulfur but are sufficiently different to account for specialized industrial applications. Both inorganic and organic compounds are known. Principal markets for selenium include those as decolorizing agents in glass, photoreceptors for xerography, stable high temperature pigments, free machining additives for steel and brass, and as a nutritional additive to animal and human diets. Selenium deficiency occurs in some parts of the world and diseases relating to this deficiency have been discovered.
Light Generation Semiconductor Lasers
Authors: Temkin Henryk
Published: July 2004

Semiconductor lasers are versatile and easy to use devices having a wide range of applications that include consumer products such as compact disc players and high speed telecommunications networks. The basic concepts needed to understand their operation, from ap–njunction to conditions needed to reach threshold, to the design of double heterostructures, are presented as is a description of lattice matched and strained quantum wells. Materials systems composed principally of Group 13–15 (III–V) elements used for the fabrication of near‐infrared and visible lasers are discussed. Band gaps and lattice constants are given for these systems and for Group 2–16 and 12–16 (II–III) systems. The design and performance characteristics of specific laser types ranging from high power laser arrays to narrow linewidth distributed feedback lasers are presented.
Sensors
Authors: Hughes R. C. , Ricco A. J. , Butler M. A. , Martin S. J.
Published: July 2004

Hughes, R. C.; Ricco, A. J.; Butler, M. A.; and Martin, S. J. (Sandia National Laboratories). Sensor technology is being revolutionized by advances in microelectronics and optoelectronics. Thus, modern sensor systems almost always include data acquisition capabilities. Rapid advances in sensor technology have increased the difficulty of the task of finding the best sensor system for a given application. A generic scheme for decision‐making is presented. Sensors, generally far from perfect, are often expected to function in hostile environments and to be immune to interference. A variety of sensor technologies are discussed. The most common is silicon processing technology, in which the sensing elements are micromachined into the same chip as the integrated circuit. Also possible are hybrid chips joined after the integrated circuit is formed. Photodetectors, smart sensors, and chemical sensors may be based on silicon processing technology. Other technologies involve the use of acoustic waves, optical fibers, electrochemical systems, and semiconducting metal oxides.
Shape‐Memory Alloys
Authors: Vaidyanathan R.
Published: July 2004

Shape‐memory alloys (SMAs) when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape‐memory. This strain recovery can occur against large forces, resulting in their use as actuators. Associated with this behavior is the superelastic or pseudoelastic effect (SE) wherein large and completely recoverable strains are generated mechanically rather than thermally. Whereas the alloys are primarily nonferrous, some ferrous alloys also exhibit shape memory. Applications of SMAs include those as tubes and valves in piping systems for power plants, ships, and the petroleum industry; use as explosive bolts in the aerospace and construction industry; as packaging devices for electronic materials; and as dental materials, prosthetics, and biomedical devices. Shape‐memory alloys may be found in sensors in automobiles, in consumer products, and generally in smart materials and adaptive structures.
Silicon Compounds, Silicon Esters
Authors: Arkles Barry
Published: July 2004

Silicon esters are silicon compounds that contain an oxygen bridge from silicon to an organic group, ie, Si–OR. The most prevalent is tetraethoxysilane. The applications for tetraalkoxysilanes are classified roughly by whether the Si–OR bond is expected to remain intact or be hydrolyzed in the final application. Applications in which the Si–OR bond is hydrolyzed include as binders for foundry‐mold sands used in investment and thin‐shell castings; as binders for refractories; and as resins, coatings, sol–gel glasses, cross‐linking agents, and adhesion promoters. Applications in which the Si–OR bond remains intact include as heat‐transfer and hydraulic fluids. The hydrolysis reaction, which yields polymers of silicic acid that can be dehydrated to silicon dioxide, is of considerable commercial importance. The chemistry and properties of alkoxysilanes and related acyloxysilanes and aspects of commercial production and utilization are reviewed. Sol–gel technology is discussed.