bluuebunny/crossref_metadata_2025 huggingface dataset:
Photodetectors
Authors: Borrello Sebastian R. , Wadsworth Mark V.
Published: August 2004

Photodetectors, based on photon absorption or thermal emission, are made from semiconductor materials that are very sensitive in the spectral range from ultraviolet to far infrared. Detector figures of merit such as responsivity, noise, noise equivalent power and detectivity, and ideal performance and cooling requirements are given. Modes of operation include charge‐coupled device, photovoltaic diode, photoconductor, and bolometer. Most semiconductor detectors operate as photon detectors where the minimum photon energy detected is defined by a discrete activation energy of the semiconductor. However, micromachined bolometers and superlattice infrared detectors are in development for thermal imaging and chemical spectroscopy. Materials and detector types are discussed.

Detector material preparation technologies are presented for intrinsic detectors where the photon absorption coefficient is high, and for the low absorption coefficient detectors such as impurity‐doped Ge or Si. Fabrication technology making possible large photodetector focal planes that detect photons and perform signal processing are integrated structures either in monolithic form or in hybrid form. The monolithic arrays range up to 106detectors. The hybrid focal planes, mostly for infrared detection, contain up to 105. Photodetector arrays have been developed for imaging across the spectrum and are used in CCD cameras, chemical spectroscopy, missile seekers, and night vision equipment.
Fluorine‐Containing Polymers, Poly(Vinyl Fluoride)
Authors: Ebnesajjad S. , Snow L. G.
Published: August 2004

Homopolymers and copolymers of vinyl fluoride are based on free‐radical polymerization of vinyl fluoride and comonomers, usually under high pressure. Du Pont first commercialized a poly(vinyl fluoride)‐based film in 1961 under the trade name Tedlar. Poly(vinyl fluoride) homopolymers and copolymers have excellent resistance to sunlight degradation, chemical attack, water absorption, and solvent; they have a high solar energy transmittance rate. These properties have resulted in the utilization of poly(vinyl fluoride) (PVF) film and coating in outdoor and indoor functional and decorative applications. These films are used where exceptional high temperature stability, outdoor longevity, stain resistance, adherence, and release properties are required.
Coating Processes, Powder Technology
Authors: Richart Douglas S.
Published: August 2004

The coating processes used to apply coating powders all employ a fusion coating method. The individual power particles are melted and fused together to form a continuous coating useful in thin film, decorative, or thicker film functional applications. Application methods include the use of fluidized beds, electrostatic sprays employing both corona discharge and triboelectric guns, electrostatic fluidized beds, and hot flocking. Both thermoplastic coating powders based on nylon, plasticized PVC, or several fluoropolymers, as well as thermosetting coating powders are used. Thermosetting coating powders based on epoxy resins, epoxy‐polyester combinations, polyester‐TGIC cured, polyesters cured with blocked isocyanates, and acrylic resins are described. Properties of powder coatings are described as are the test methods and regulations regarding the coating powder. Methods of manufacturing coating powders include melt‐mixing and dry‐blending processes. Usage of powder coatings for both industrial and architectural applications is increasing worldwide.
Bleaching Agents, Pulp and Paper
Authors: McDonough Thomas
Published: August 2004

Worldwide, more than

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of pulp is bleached annually, making the pulp and paper industry one of the largest consumers of bleaching chemicals. The principal objective in bleaching any type of pulp is usually to increase the whiteness of the pulp, as measured by its brightness, which is defined as reflectance measured at a wavelength of 457 nm. Virtually all of the color of any pulp resides in its lignin component. Because concurrent cellulose damage would seriously weaken the fibers, pulping is therefore terminated when 5–8% of the original lignin remains. Bleaching effluent is typically contaminated with chloride ion and chlorine compounds, making it difficult or impossible to recycle it to the recovery system because of potential for corrosion. It is therefore necessary to treat and discharge the bleaching effluent. Associated environmental concerns are presently causing rapid changes in bleaching technology. With the exception of caustic, all important chemical pulp bleaching agents are oxidants, eg, chlorine, Cl
2
; chlorine dioxide, ClO
2
; calcium hypochlorite, Ca(OCl)
2
; hydrogen peroxide, H
2
O
2
; oxygen, O
2
; and ozone, O
3
. Research in progress points to the possible commercialization of several other chemical pulp bleaching technologies: chemical pretreatments to improve the selectivity of oxygen bleaching, enzymatic pretreatments to facilitate subsequent delignification, and recycling of bleach plant effluents. Much new high yield pulping technology has been developed, including production of thermomechanical pulp (TMP) and chemithermomechanical pulp (CTMP). Because little material is lost in these processes, and the pulps have a very high lignin content, it is not feasible to bleach them by removing all of the lignin, as in chemical pulp bleaching. Instead, the lignin must be decolorized, a process sometimes referred to as brightening. Only two brightening agents, hydrogen peroxide and sodium hydrosulfite (sodium dithionite), are of commercial importance. Because pulp bleaching agents are, for the most part, reactive oxidizing agents, appropriate precautions must be taken in their handling and use. Hazards associated with pulp bleaching agents include their potential for damage resulting from contact with skin or eyes, their ability, as oxidizers, to cause fires or explosions. Additional information on health and safety aspects should be sought by consulting material safety data sheets. Most suppliers of bleaching chemicals provide on‐site training sessions by experts on the safe use and handling of their products, upon request.
Release Agents
Authors: Owen Michael J.
Published: August 2004

Owen, Michael J. (Dow Corning Corp.). Release agents are used to minimize adhesion between surfaces in many industrial processing and handling operations such as extrusion, molding, transferring, and packaging. They function either by lessening intermolecular interactions between surfaces or by preventing close contact. Consequently, they are either low surface‐tension materials such as fatty acid derivatives, natural and synthetic waxes, and polymers such as polytetrafluoroethylene and polydimethylsiloxane, or particulate solids such as silica or mica. The principal classes of materials used are waxes, fatty acid metal soaps, other long‐chain alkyl derivatives, polymers, and fluorinated compounds. These are formulated into products of various forms, including solvent solutions, emulsions, and films. They are widely used in the metal, glass, rubber, plastics, furniture, and food industries. Some key material transfer processes critically dependent on release agent technology include hot stamping foils, pressure‐sensitive adhesives, photocopying, transfer coatings, and transfer printing of textiles. Growth is modest, but new products are evolving. The trend is from solvent to waterbourne systems, and from single‐application products to semipermanent types. Vol. 21, pp. 207–218, 31 refs. to June 1994.
Toluenes, Ring‐Chlorinated
Authors: Lin Henry C. , Krishnamurti Ramesh
Published: August 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.
Silver and Silver Alloys
Authors: Etris Samuel F.
Published: August 2004

The workability, beauty, and bacteriocidal effects of silver have made it a most desirable metal since ancient times. The combination of desirable properties and the total resistance of silver to the formation of oxides has established its position as a critical metal for a myriad of advanced technology applications. Silver also imparts the properties to the many metals with which it forms commercially important alloys. Among its many important salts, the halides stand as unique photosensitive salts, providing the basis for high quality photography as well as for photochromic glass.

More obscure properties of silver such as its high thermal reflectivity are also being fully exploited. For example, silver is used to provide energy‐saving domestic window glass. The unique interaction of silver and oxygen is being used to advantage in the superconductor industry. The superior fatigue resistance and lubricity of silver make it an essential component of high performance jet engines.
Antibacterial Agents, Sulfonamides
Authors: Foye William O.
Published: August 2004

Sulfonamides derived from sulfanilamide (p‐aminobenzenesulfonamide) are commonly referred to as sulfa drugs. The sulfa drugs are still important as antimicrobials, although they have been replaced in many systemic infections by the natural and semisynthetic antibiotics. They are of great value in Third‐World countries where problems of storage and lack of medical personnel make appropriate use of antibiotics difficult. They are especially useful in urinary tract infections, particularly the combination of sulfamethoxazole with trimethoprim, and the combination of sulfamethoxazole with trimethoprim is of value in treatment of a number of specific microbial infections. The introduction of this combination (cotrimoxazole) in the late 1960s (1973 in the United States) resulted in increased use of sulfonamides. The sulfas also remain clinically useful in the treatment of chancroid, lymphogranuloma venereum, trachoma, inclusion conjunctivitis, and the fungus‐related nocardiosis. The sulfone, dapsone, remains an accepted treatment for all forms of leprosy. Currently used sulfas vary widely in their absorption, distribution, and excretion patterns. Some of those in clinical practice, past or present, are sulfanilamide, sulfacetamide, sulfadiazine, sulfadimethoxine, sulfaguanidine, sulfisomidine, sulfisoxazole, sulfamethazine, sulfamethizole, sulfamethoxazole, sulfamethoxypyridazine, sulfamoxole, sulfaphenazole, sulfapyridine, sulfapyrazine, and sulfathiazole. The action of the sulfa drugs and related sulfones is bacteriostatic rather than bactericidal. Numerous studies have been made to find a correlation between the physicochemical properties of the sulfonamides and their bacteriostatic activity. Degree of ionization, lipid–water solubility, electron distribution values, and protein binding have all been observed. One of the principal disadvantages of sulfonamide therapy is the emergence of drug‐resistant strains of bacteria. The most common method for the preparation of sulfonamides is by the action ofN‐acetylsulfanilyl chloride with the appropriate amine. A small percentage of patients treated with sulfa drugs have shown toxic effects, such as drug fever, rashes, mild peripheral neuritis, and mental disturbance. In 1966 the FDA required that two long‐acting sulfas, sulfamethoxypyridazine and sulfadimethoxine carry a label warning of the possibility of death due to Stevens‐Johnson syndrome, an extremely severe dermatologic reaction. Blood dyscrasias are quite uncommon, but if they occur may be serious enough to cause discontinuance of the therapy. Administration of sulfas can cause hypersensitivity reactions, but in general, use of sulfonamide therapy is considered relatively safe.
Carboxylic Acids, Survey
Authors: Bagby M. O.
Published: August 2004

Carboxylic acids from formic (C‐1) to the 22‐carbon fatty acids and selected examples of higher carbon number (C‐30) are reviewed. Available physical properties are tabulated for normal saturated and selected unsaturated and substituted aliphatic acids. The physical properties as well as chemical properties are discussed briefly.
Acrylonitrile Polymers, Survey and SAN
Authors: Ball Lawrence E. , Curatolo Benedict S.
Published: August 2004

Acrylonitrile has found its way into a great variety of polymeric compositions based on its polar nature and reactivity. Some of these areas include adhesives and binders, antioxidants, medicines, dyes, electrical insulations, emulsifying agents, graphic arts materials, insecticides, leather, paper, plasticizers, soil‐modifying agents, solvents, surface coatings, textile treatments, viscosity modifiers, azeotropic distillations, artificial organs, lubricants, asphalt additives, water‐soluble polymers, hollow spheres, cross‐linking agents, and catalyst treatments. Styrene–acrylonitrile (SAN) resins possess many physical properties desired for thermoplastic applications. They are characteristically hard, rigid, and dimensionally stable with load bearing capabilities. Modifiers may include uv stabilizers, flow and processing aids, and reinforcing agents. SAN resins show considerable resistance to solvents and are insoluble in carbon tetrachloride, ethyl alcohol, gasoline, and hydrocarbon solvents. Polar solvents such as acetone, chloroform, and pyridine will dissolve SAN. The properties of SAN are significantly altered by water absorption. Commercially, SAN is manufactured by three processes: emulsion, suspension, and continuous bulk. Acrylonitrile copolymerizes readily with many electron‐donor monomers other than styrene. Hundreds of acrylonitrile copolymers have been reported. Copolymers of acrylonitrile and methyl acrylate and terpolymers of acrylonitrile, styrene, and methyl methacrylate are used as barrier polymers. Environmentally degradable polymers are useful in packaging. The largest portion of SAN (80%) is incorporated into ABS resins, and their markets are inexorably joined. SAN resins themselves appear to pose few health problems, and they have been approved by the FDA for food packaging use.
Carbides, Survey
Authors: Oyama S. Ted , Kieffer Richard
Published: August 2004

Carbon reacts with many elements of the Periodic Table to form a diverse group of compounds known as carbides, some of which are extremely important in technology. For example, calcium carbide, CaC2, is a source of acetylene; silicon carbide, SiC, and boron carbide, B4C, are used as abrasives; tungsten carbide, WC, titanium carbide, TiC, and tantalum (niobium) carbide, TaC(NbC), find use as structural materials at extremely high temperatures or in corrosive atmospheres. Cementite, Fe3C, and the multimetallic complexes (Co,W)6C, (Cr,Fe,Mo)23C6, and (Cr,Fe)7C3are the components in tool steels and Stellite‐type alloys responsible for their hardness, wear resistance, and excellent cutting performance. There are also emerging applications of these materials as catalysts. Binary compounds of carbon are divided into four main groups: the salt‐like, metallic, diamond‐like, and volatile compounds of carbon. The nature of the bonding is correspondingly of ionic, metallic, semiconductor, or covalent character, but these divisions are not rigid and there are a number of transitional cases. A number of compounds, although containing carbon, fit only marginally in the category of carbides. This includes the acetylides and the alkali metal–graphite compounds, the coordination and organometallic compounds, ML. Carbides are generally prepared by the direct reaction of carbon with metals or metal‐like materials at elevated temperatures. Their most outstanding properties are extreme hardness and physical strength combined with high temperature stability.
Alcohols, Higher Aliphatic, Survey and Natural Alcohols Manufacture
Authors: Peters Richard A.
Published: August 2004

The monohydric aliphatic alcohols of six or more carbon atoms are generally referred to as higher alcohols. Historically, the higher alcohols were derived from natural fats, oils, and waxes and were called fatty alcohols, but now similar alcohols are widely available from synthetic processes using petrochemical feedstocks. Although the natural and synthetic alcohols are used interchangeably for many applications, for some applications the distinction still remains. The detergent range alcohols are used mainly as sulfate, ethoxy, and ethoxysulfate derivatives in a wide variety of detergent and surfactant applications. Most higher alcohols of commercial importance are primary alcohols; secondary alcohols have more limited specialty uses. Typical reactions of the higher alcohols include esterification, sulfation, etherification, halogenation, dehydration, oxidation, and amination. In the United States, most detergent range alcohol production is by synthetic processes. Most manufacturers sell a portion of their alcohol product on the merchant market, retaining a portion for internal use, typically for the manufacture of plasticizers. The higher alcohols are among the less toxic of commonly used chemicals. Fatty alcohols are produced by hydrogenolysis of methyl esters or fatty acids in the presence of a heterogeneous catalyst. There are three principal hydrogenolysis processes in worldwide use. Each process typically uses a copper chromite or copper‐zinc catalyst that is modified to meet the needs of the individual producer. The detergent range alcohols and their derivatives have a wide variety of uses in consumer and industrial products. The major use is as surfactants in detergents and cleaning products. They also are used extensively in cosmetics and pharmaceuticals. The plasticizer range alcohols are utilized primarily in plasticizers, but they also have a wide range of other uses.
Thermoplastic Elastomers
Authors: Holden Geoffrey
Published: August 2004

Thermoplastic elastomers have many of the physical properties of vulcanized rubbers but can be processed as thermoplastics. This unique behavior has opened a new field of polymer science and technology. Since their commercial introduction in the 1960s, thermoplastic elastomers have become a significant part of the polymer industry. They are used in applications as diverse as adhesives, footwear, medical devices, automobile parts, and asphalt modification. Many of them are block copolymers with alternating hard and soft segments. The thermoplastic elastomers with polystyrene hard segments are the larget group and probably the most versatile; they can be produced over a wide range of hardness values and applied either in the molten state or from solution. Other examples are block copolymers with elastomers, either vulcanized or unvulcanized, in which the two components are intimately mixed together, but in most cases still remain as separate phases. Thermoplastic elastomers of this type are generally used as replacements for vulcanized rubbers. This article reviews the synthesis, morphology, structure‐property relationships, and commercial applications of thermoplastic elastomers of all types.
Tungsten and Tungsten Alloys
Authors: Penrice Thomas W.
Published: August 2004

Tungsten, discovered in 1755 and produced as a metal in 1783, is notable for having a very low vapor pressure, the highest melting point of any metal, and the highest tensile strength of any metal above 1650°C. It has been used formerly in the manufacture of high speed steels and as a metal filament in electric lamps, where it was fabricated by powder metallurgy using the Coolidge process. The largest modern application is in the manufacture of cemented carbide cutting tools. Tungsten is rated as a strategic material in the U.S. economy.

Tungsten occurs in a number of mineral forms, the most important being scheelite and wolframite. The beneficiation and hydrometallurgy are described, together with the principal intermediate compounds used to make the metal powder by hydrogen reduction. Technically it is possible to process compacted powder by arc or electron‐beam melting, but commercially the power metallurgy process of compaction, sintering, and working is used exclusively.

The largest reserves of ores occur in China, which has, in more recent years, become the principal source of supply not only for ores but for metal powder and intermediates at prices that have caused most U.S. mines to be closed. About 65% of tungsten usage is as tungsten carbide in cutting and mining tools. The instability of the market as well as economic and environmental factors have favored development of recycling processes. Used cutting tools can be treated with molten zinc and both are recovered tungsten carbide and cobalt binder as mixed powders after vacuum‐distilling off the zinc. It is estimated that 25% of cutting tools are recycled in this way in the United States.

Tungsten alloyed with nickel and iron is used for a range of high density compositions that find applications as counterweights in aircraft, as armor‐piercing penetrators, and for collimators and shielding in x‐ray machines. These alloys are characterized by high density and high modulus, which make them suitable for use in critical dynamic structures. Tungsten forms only a few alloys; tungsten–rhenium is important for thermocouples and as a tough lamp filament alloy. Insoluble tungsten has relatively low toxicity, but aerosols with cobalt and with impurities found in mining can have some effect and require controls of exposure level.
Tungsten Compounds
Authors: Penrice Thomas W.
Published: August 2004

Tungsten combines with many other elements to form simple stable compounds. It readily polymerizes but the chemistry of aqueous solutions is very complex. This is exemplified by the large number of polytungstates. The chemical uses of tungsten have increased substantially in more recent years.

The hexacarbonyl has potential as a lubricant additive and as a dye and pigment. The halides are useful as a starting materials in the chemical vapor deposition of tungsten. The oxides are important intermediate products in the stepwise reduction in hydrogen to the metal. Tungsten bronzes constitute a series of well‐defined nonstoichiometric compounds. The sodium tungsten bronzes are interesting not only for their intense color range but exhibit both positive and negative coefficient of resistance as the sodium:tungsten ratio changes. Sodium tungsten bronzes help the catalytic oxidation of carbon monoxide and reformer gas in fuel cells.

The tungstates are an important class of materials. The metatungstates are important starting materials for production of tungsten catalysts because of the high solubility in water. Ammonium paratungstate is the intermediate material of choice between chemical recovery from ores and the reduction to tungsten metal. The interstitial compounds, particularly with carbon, represent the largest application for tungsten in cemented carbides. Tungsten compounds, especially the oxides, sulphides, and heteropoly complexes, form stable catalysts for a variety of chemical processes in the petroleum industry and in chemical synthesis. Other uses include fireproofing of textiles, as additives in lubricants and antifreeze solutions, in inks and dyes, as phosphors in fluorescent lights, and for improvement of conductivity of tin oxide coatings on aircraft windows. Because soluble tungsten compounds show varying degrees of toxicity, exposures in the workplace are regulated.
What Really Happens in Cohorts
Authors: Maher Michelle A.
Published: August 2004

Togetherness, academic help, peer support—all good things for a college student, right? Mostly. Michelle Maher followed several students co-enrolled in a cohort around for almost a year to discover what's good, what's not so good, and what we can do with both.
Gone Fishing
Authors: Pence Mary E. Springer
Published: August 2004

Based on what they knew about today's generation of college students and sound educational practice, the orientation staff at the University of Louisville reoriented its program using a philosophy from Seattle's world-famous fish market.
Supercritical water oxidation of a carbon particle by Schlieren photography
Authors: Sugiyama Masakazu , Tagawa Sumiko , Ohmura Hisao , Koda Seiichiro
Published: August 2004

The flow pattern around a carbon particle (∼ 3.5 mm in diameter) during the supercritical water oxidation (SCWO) process (25 MPa, 723 K, 3.6 wt % O2 concentration) was visualized for the first time by the use of Schlieren optics and a SCWO reactor equipped with transparent sapphire windows. To link Schlieren images with flow fields, computational fluid dynamics (CFD) simulations were executed, assuming temperature‐dependent density of supercritical water and heat of a surface reaction, and then the obtained density fields around the particle were numerically converted to Schlieren images. Numerically obtained Schlieren images agreed well with observed images, confirming that the CFD simulation was able to predict the flow field in SCWO processes. Such a combined approach of CFD and flow visualization revealed that, in SCWO of solid substances with a fast reaction rate, the heat of surface reaction increased the temperature of the fluid and induced an upward flow from the particle with higher fluid temperature than that of the surroundings. Such flow can increase reaction rates by enhancing the mass transfer of O2 to solids. Therefore, a flow field in SCWO is an important factor controlling the progress of reaction and it can be reasonably predicted by CFD simulations. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2082–2089, 2004
Clinicopathological correlates in frontotemporal dementia
Authors: Hodges John R. , Davies R. Rhys , Xuereb John H. , Casey Barney , Broe Melissa , Bak Thomas H. , Kril Jillian J. , Halliday Glenda M.
Published: August 2004

The term frontotemporal dementia (FTD) encompasses a range of clinical syndromes that are believed not to map reliably onto the spectrum of recognized pathologies. This study reexamines the relationships between clinical and pathological subtypes of FTD in a large series from two centers (n = 61). Clinical subtypes defined were behavioral variant FTD (n = 26), language variants (semantic dementia, n = 9; and progressive nonfluent aphasia, n = 8), and motor variants (corticobasal degeneration, n = 9; and motor neuron disease, n = 9), although most cases presented with a combination of behavioral and language problems. Unexpectedly, some behavioral cases (n = 5) had marked amnesia at presentation. The pathological subtypes were those with tau‐immunopositive inclusions (with Pick bodies, n = 20; or without, n = 11), those with ubiquitin immunopositive inclusions (n = 16), and those lacking distinctive histology (n = 14). Behavioral symptoms and semantic dementia were associated with a range of pathologies. In contrast, other clinical phenotypes had relatively uniform underlying pathologies: motor neuron disease predicted ubiquitinated inclusions, parkinsonism and apraxia predicted corticobasal pathology, and nonfluent aphasia predicted Pick bodies. Therefore, the pathological substrate can be predicted in a significant proportion of FTD patients, which has important implications for studies targeting mechanistic treatments. Ann Neurol 2004
Hemispheric mediation of spatial attention: Pseudoneglect after callosal stroke
Authors: Wolk David A. , Coslett H. Branch
Published: August 2004

Study of patients with callosal lesions can provide insight into the mediation of spatial attention‐intention by each hemisphere. Two patients with anterior callosal strokes bisected lines to the left of midline with the left hand and to the right of midline with the right in both a visual and tactile bisection task. The patients demonstrated a similar pattern of performance on pointing to body‐midline in space. These results are consistent with the notion that each hemisphere supports spatial attention‐intention toward contralateral space and that the corpus callosum is critical in the integration of such information. Ann Neurol 2004
Crystallographic report: Di(p‐fluorobenzyl)tin bis(N,N‐dimethyldithiocarbamate)
Authors: Yin Han‐Dong , Wang Chuan‐Hua
Published: August 2004

The tin atom in (p–FC6H4CH2)2(S2CNMe)2 is in a skewed‐trapezoidal bipyramidal geometry defined by two sets of sulfur donors derived from the dithiocarbamate ligands and two carbon atoms from the tin‐bound p‐fluorobenzyl substituents; CSnC is 129.2(2)°. Copyright © 2004 John Wiley & Sons, Ltd.
Ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst
Authors: Karabulut Solmaz , Çetinkaya Sevil , Düz Bülent , İmamoǧlu Yavuz
Published: August 2004

The ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst (WCl6e−AlCH2Cl2) is described. In addition, the influence of reaction conditions on the polymerization yield was determined. The resulting polymer has been characterized by NMR, IR, gel permeation chromatography and differential scanning calorimetry. The glass transition temperature and melting point of the polydodecenamer are 19.6°C and 70.0°C respectively. Furthermore, cyclododecene has been polymerized into a low‐molecular‐weight polymer (12.0 × 103) with a polydispersity of 2.06 in high yields (94%). IR and NMR analysis indicate that the polydodecenamer has a high trans content (60%). Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Crystal structure of tris(2,6‐di‐tert‐butyl‐4‐methylphenolato‐O) (tetrahydrofuran‐O) erbium toluene solvate
Authors: Xu Xiaoping , Yao Yingming , Zhang Yong , Shen Qi
Published: August 2004

A low‐coordinate aryloxo erbium complex, [(ArO)3Er(THF)](MePh), has been synthesized by the reaction of anhydrous ErCl3 with three equivalents of NaOAr in tetrahydrofuran. The central erbium atom is coordinated by three oxygen atoms of the aryloxo ligands and one oxygen atom of the tetrahydrofuran molecule, resulting in a distorted tetrahedron. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Bis[tris(morpholindithiocarbamato)bismuth(III)]
Authors: Yin Han‐Dong , Wang Chuan‐Hua
Published: August 2004

The dimeric and centrosymmetric structure of {Bi[S2CN(CH2CH2)2O]3}2 features chelating dithiocarbamate ligands and intermolecular BiS interactions, so that a distorted pentagonal bipyramidal S7 coordination geometry results. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Diisopropylammonium [3‐(2‐thienyl)‐2‐sulfanylpropenoato]triphenylstannate
Authors: Casas José S. , Couce Marıa D. , Sánchez Agustín , Sordo José , Varela José M. , Vázquez‐López Ezequiel M.
Published: August 2004

The title compound comprises trigonal bipyramidal SnPh3(tspa) anions and iPr2NH2 cations linked into centrosymmetric dimers by NH·O hydrogen bonds. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: A two‐dimensional zinc phosphate framework: [H3N(CH2)3NH3]0.5[Zn2(PO4)(HPO4)]
Authors: Wang Lei , Li Guanghua , Ma Jingjing , Feng Shouhua
Published: August 2004

The two‐dimensional zinc phosphate [H3N(CH2)3NH3]0.5[Zn2(PO4)(HPO4)], has been synthesized hydrothermally using 1,3‐diaminopropane as the template. Its structure contains an inorganic framework with three‐, four‐, or six‐membered rings, built from PO4, PO3(OH) and ZnO4 tetrahedral moieties sharing vertexes. The protonated 1,3‐diaminopropane molecules interact with the framework through hydrogen bonds. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: [(η5‐C5H5)Fe(CO)2]2Ga3Cl3(OSiMe2OSiMe2O)2: a diiron complex of a tetracyclic trigallasiloxane
Authors: Bunn Natalie R. , Aldridge Simon , Jones Cameron
Published: August 2004

The structure of the penta‐metallic diiron trigallasiloxane, [(η5‐C5H5)Fe(CO)2]2Ga3Cl3(OSiMe2 OSiMe2O)2, reveals two distinct gallium coordination environments and FeGa bond lengths (2.3258(6) Å), consistent with bonding of the iron centres to four‐coordinate gallyl ligands. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: 6‐Mercaptopurinate complex of tribenzyltin(IV), (PhCH2)3Sn(C5H3N4S)Sn(PhCH2)3OMe
Authors: Ma Chunlin , Sun Jiafeng
Published: August 2004

The title complex displays a binuclear structure in which the geometries of tin atoms are different: one is cis‐trigonal bipyramidal (with a C3NS donor set) and the other is trans‐trigonal bipyramidal (C3NO). Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Bis[N,N‐dimethyl‐N′‐(pyrid‐2‐ylmethyl)‐ethylenediamine]zinc(II) diperchlorate
Authors: Bian He‐Dong , Yu Qing , Liang Hong , Yan Shi‐Ping , Liao Dai‐Zheng , Cheng Peng , Jiang Zong‐Hui
Published: August 2004

The zinc(II) atom in the centrosymmetric complex is in a distorted N6 octahedral geometry defined by two tridentate ligands. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Dibenzyltin(IV) bis(N,N‐dibenzyldithiocarbamate)
Authors: Yin Han‐Dong , Xue Sheng‐Cai
Published: August 2004

A distorted octahedron C2S4 geometry is found for the tin atom in the title compound; CSnC is 136.61(19)°. Copyright © 2004 John Wiley & Sons, Ltd.
Studies on the catalysis of the reaction of organotin phenoxides with bis(2,2,2‐trichloroethyl) azodicarboxylate by lithium perchlorate
Authors: Kinart Wojciech J. , Kinart Cezary M. , Tran Quang T. , Oszczȩda Rafał , Nazarski Ryszard B.
Published: August 2004

Organotin phenoxides, which are distinctly more active than the corresponding phenols, react at room temperature with bis(2,2,2‐trichloroethyl) azodicarboxylate to produce para‐substituted phenolic hydrazides in high yields. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and characterization of some penicillins modified with germanium‐containing moieties
Authors: Imafuku Yoko , Takeuchi Yoshito
Published: August 2004

Penicillin derivatives, penicillin G (1), penicillin V (2) and ampicillin (3), were modified with germanium‐containing moieties and their structures were confirmed based on NMR spectroscopy and MALDI‐TOF. Their antibacterial ability was tested. None of these exhibited activity stronger than the parent penicillins. Copyright © 2004 John Wiley & Sons, Ltd.
Modification of low energy polymer surfaces by immobilization of fluorinated carboxylates with zirconium‐based coupling agents
Authors: Textor Torsten , Schollmeyer Hauke , Bahners Thomas , Schollmeyer Eckhard
Published: August 2004

After the photochemical generation of carboxylates onto surfaces of several aromatic polymers, complexes based on zirconyl‐(IV)‐acetylacetonate are immobilized. These zirconium compounds tend to form strong bonds to carboxylates. Subsequently, zirconium modified surfaces are treated with solutions of a highly fluorinated lithium carboxylate yielding oil‐ and water‐repellent surfaces. It is shown that combined with excimer‐UV‐laser‐induced micro structuring, the treatments lead to super‐repellent surfaces showing contact angles of water up to 160°. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 789–795, 2004
Influence of ammonium polyphosphate on the mechanism of thermal degradation of an acrylic binder resin
Authors: Drevelle Christophe , Duquesne Sophie , Le Bras Michel , Lefebvre Jérôme , Delobel René , Castrovinci Andrea , Magniez Carole , Vouters Moïse
Published: August 2004

The thermal behavior of an acrylic binder resin used in back coatings for textile applications was studied. The influence of the crystalline form of the fire‐retardant additive on the thermal behavior was investigated. This resin formed a carbon char during its thermal degradation, so it may be assumed that it acts as a charring agent in intumescent systems with ammonium polyphosphate (APP) as the acid source. Thermogravimetric and spectroscopic analyses of acrylic binder resin/APP mixtures demonstrated the influence of the crystalline form of APP. The degradation mechanism of the binder resin could be described by ring closure and the formation of unsaturations. APP leads to the formation of a phosphocarbon structure that is thermally stable, whatever the crystalline form was of APP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 717–729, 2004
Effects of the blend ratio and crosslinking systems on the curing behavior, morphology, and mechanical properties of styrene–butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends
Authors: Radhakrishnan C. K. , Sujith A. , Unnikrishnan G. , Thomas Sabu
Published: August 2004

Blends of styrene–butadiene rubber (SBR) and poly(ethylene‐co‐vinyl acetate) (EVA) with different ratios were prepared with a two‐roll mixing mill and were vulcanized by three different crosslinking systems, namely, sulfur (S), dicumyl peroxide, and a mixture consisting of S and peroxide (mixed). The vulcanization behavior of the blends was analyzed from the rheographs. The mechanical properties, including stress–strain behavior, tensile strength, elongation at break, modulus, hardness, and abrasion resistance, of the blends were examined. The morphology of the prepared blends was studied with scanning electron microscopy with special reference to the effects of the blend ratio and crosslinking systems. A relatively cocontinuous morphology was observed for the 20/80 SBR/EVA composition. The mechanical properties increased with increasing EVA content up to 60–80%, for all of the vulcanizing modes. The tensile fracture surfaces were analyzed under a scanning electron microscope to understand the failure mechanism. Various theoretical models were applied to explain the properties of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 827–837, 2004
Synthesis and structural characterization of a new polysiloxane with second‐order nonlinear optical effect
Authors: Li Zhen , Qin Jingui , Yang Zhou , Ye Cheng
Published: August 2004

A new polysiloxane (P2), with a high density of the indole‐based chromophore and carbazolyl side groups, was prepared. Thus a polysiloxane (P1), with indole and carbazolyl groups as side chains, was first synthesized through a hydrosilylation reaction, and then the post‐azo coupling of p‐nitrobenzenediazonium fluoroborate toward the indole ring gave the mulifunctional indole‐based chromophore‐functionalized polysiloxane (P2). Molecular structural characterization for the polymers was determined by 1H‐NMR, IR, and UV–visible spectra, gel permeation chromatography, and differential scanning calorimetry. The polymers were easily soluble in common organic solvents. The poled film of P2 revealed a resonant d33 value of 27 pm/V by second‐harmonic generation measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 769–774, 2004
Water‐dispersible conducting nanocomposites of binary polymer systems. I. Poly(N‐vinylcarbazole)–polyaniline–Al2O3 nanocomposite system
Authors: Maity Arjun , Biswas Mukul
Published: August 2004

The chemical oxidative polymerization of a mixture of N‐vinylcarbazole (NVC) and aniline (ANI), by FeCl3 in aqueous medium, produced an insoluble polymer that contained polyaniline (PANI), along with some residual poly‐N‐vinylcarbazole (PNVC) not extractable with benzene. This insoluble PNVC–PANI composite could be obtained as a stable suspension in water when the above polymerization was conducted in the presence of nanodimensional Al2O3. Alternatively, PNVC–(PANI–Al2O3) composite could also be produced by precipitating a THF solution of preformed PNVC onto a PANI–Al2O3 suspension. Likewise PANI–(PNVC–Al2O3) could be obtained by polymerizing ANI onto an aqueous suspension of PNVC–Al2O3. The inclusion of either of these monomer units in the resultant polymer was confirmed by FTIR analysis. SEM analyses revealed formation of a lumpy aggregate, and TEM analyses confirmed particle sizes of the PNVC–PANI–Al2O3 composite to be in the 52–200 nm range. Thermogravimetric stability was in the order: PANI–Al2O3 < PNVC–PANI–Al2O3 < PNVC–Al2O3. The dc conductivity values (S/cm) followed the trend: PNVC–Al2O3 (10−7) < PNVC–PANI–Al2O3 (1.5 × 10−4) ≈ PANI–Al2O3 (1.1 × 10−4) < PNVC–PANI (1 × 10−3) at ambient temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 803–811, 2004
Gas permeabilities of NH3‐plasma‐treated polyethersulfone membranes
Authors: Iwa T. , Kumazawa H. , Bae S.‐Y.
Published: August 2004

The effect of NH3‐plasma treatment on glassy polyethersulfone (PES) membranes upon the diffusion process for CO2, O2, and N2. was investigated from the permeability measurements. The permeation behavior for O2 and CO2 in untreated and NH3‐plasma‐treated PES membranes was simulated well in terms of the dual‐mode mobility model. For O2 transport, NH3‐plasma treatment on PES membrane had a little influence on the diffusion process of Langmuir species and very little influence on the diffusion process of Henry's law species. For CO2 transport, it promoted the transport of Henry's law mode but had very little influence on the transport process of Langmuir species. Both the mean permeability coefficient to CO2 and the ideal separation factor for CO2 relative to N2 took maximum values at a treatment power of 40 W. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 758–762, 2004
Microemulsion copolymerization of methyl methacrylate with acrylonitrile
Authors: Reddy G. V. Ramana , Kumar C. Ramesh , Sriram R.
Published: August 2004

The microemulsion (ME) and conventional emulsion (CE) copolymerizations of methyl methacrylate (MMA) with acrylonitrile (AN) are carried out at 70°C by employing n‐butyl cellosolve as cosurfactant along with sodium lauryl sulfate as surfactant in the reaction medium and potassium persulfate as initiator. The copolymers are characterized by FTIR, NMR, TG/DTA, and GPC techniques. The reactivity ratios are evaluated by employing Fineman‐Ross, Kellen‐Tüdös (K‐T), and Mayo‐Lewis integration methods. The K‐T method yields reactivity ratios, rMMA and rAN, for the ME copolymerization of MMA and AN of 1.06 ± 0.01 and 0.14 ± 0.01, and those for the CE copolymerization of MMA and AN are 2.19 ± 0.01 and 0.14 ± 0.01, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 739–747, 2004
Surface‐modified silica nanoparticle–reinforced poly(ethylene 2,6‐naphthalate)
Authors: Ahn Seon Hoon , Kim Seong Hun , Lee Seung Goo
Published: August 2004

The effect of stearic acid modification on the dispersity of silica nanoparticles and the adhesion between the filler and polymer matrix with stearic acid concentration were investigated. The wettability of silica nanoparticles was improved by the addition of stearic acid. The presence of adsorbed stearic acid on the surface of the silica nanoparticles reduced the interaction between silica nanoparticles, and reduced the size of agglomerates with increasing concentration. Silica nanoparticle–reinforced poly(ethylene 2,6‐naphthalate) (PEN) composites were melt‐blended to investigate their mechanical properties and the processability of the composites. The torque and total torque values of the composites decreased with increasing silica nanoparticle content. The tensile moduli of the composites reinforced with unmodified silica nanoparticles increased with increasing silica content, whereas the tensile strength and elongation decreased. However, the stearic acid–modified silica nanoparticle–reinforced PEN composites exhibited increased elongation and decreased tensile moduli with increasing content because stearic acid, which adsorbs onto the surface of the silica nanoparticles in layers thicker than a monolayer, acts as a plasticizer during the melt‐compounding stage. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 812–818, 2004
Isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide)
Authors: Liu Hongzhi , Yang Guisheng , He Aihua , Wu Meiyan
Published: August 2004

The isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide) (PA‐10T) was studied by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization process. The commonly used Avrami equation and the one modified by Jeziorny were used, respectively, to describe the primary stage of isothermal and nonisothermal crystallization. The Avrami exponent n was evaluated to be in the range of 2.36–2.67 for isothermal crystallization, and of 3.05–5.34 for nonisothermal crystallization. The Ozawa analysis failed to describe the nonisothermal crystallization behavior, whereas the Mo–Liu equation, a combination equation of Avrami and Ozawa formulas, successfully described the nonisothermal crystallization kinetics. In addition, the value of crystallization rate coefficient under nonisothermal crystallization conditions was calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 819–826, 2004
TERC is not a major gene in human neural tube defects
Authors: Benz Lisa P. , Swift Frances E. , Graham Felicia L. , Enterline David S. , Melvin Elizabeth C. , Hammock Preston , Gilbert John R. , Speer Marcy C. , Bassuk Alexander G. , Kessler John A. , George Timothy M. ,   and the NTD Collaborative Group
Published: August 2004

BACKGROUND

Neural tube defects (NTDs) are the second most common birth defects, after congenital heart defects. Telomerase, the reverse transcriptase that maintains telomere DNA, has been shown to be important for neural tube development and bilateral symmetry in the brain. In knockout mice null for the telomerase RNA component (TERC), telomere loss results in the failure of neural tube closure, primarily at the forebrain and midbrain.

METHODS

We investigated TERC for variants that may predispose to human NTDs in 477 NTD cases with a variety of phenotypic presentations.

RESULTS

Two novel single nucleotide polymorphisms were identified in the human TERC sequence but showed no association with the NTD phenotype.

CONCLUSIONS

Variants in TERC are unlikely to be a major risk factor for the most common form of human NTDs, lumbosacral myelomeningocele. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Searching for folding initiation sites of staphylococcal nuclease: A study of N‐terminal short fragments
Authors: Dai Jixun , Wang Xu , Feng Yingang , Fan Guibao , Wang Jinfeng
Published: August 2004

The N‐terminal short fragments of staphylococcal nuclease (SNase), SNase20, SNase28, and SNase36, corresponding to the sequence regions, Ala1–Gly20, Ala1–Lys28, and Ala1–Leu36, respectively, as well as an 8‐residue peptide (Ala17–Ile18–Asp19–Gly20–Asp21–Thr22–Val23–Lys24) have been synthesized. The conformational states of these fragments were investigated using CD and NMR spectroscopy in aqueous solution and in trifluoroethanol (TFE)–H2O mixture. SNase20 containing a sequence corresponding to a bent peptide in native SNase shows a transient population of bend‐like conformation around Ala12–Thr13–Leu14 in TFE–H2O mixture. The sequence region of Ala17–Thr22 of SNase28 displays a localized propensity for turn‐like conformation in both aqueous solution and TFE—H2O mixture. The conformational ensemble of SNase36 in aqueous solution includes populated turn‐like conformations localized in sequence regions Ala17–Thr22 and Tyr27–Gln30. The analysis suggests that these sequence regions, which form the regular secondary structures in native protein, may serve as the folding nucleation sites of SNase fragments of different chain lengths starting from the N‐terminal end. Thus, the formation of bend‐ and turn‐like conformations of these sequence regions may be involved in the early folding events of the SNase polypeptide chain in vitro. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004