bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanocomposites, Polymer–Clay
Authors: Lefebvre Jean‐Marc
Published: October 2003

Polymer–clay nanocomposites are a new class of filled polymers in which disc‐shaped, 1‐nm‐thick, clay platelets are dispersed in a polymer matrix. The unique combination of large interfacial area and small interparticle distances, obtained at low filler loadings, is responsible for a material response unexpected from what is observed in conventional microcomposites. This shows in a panel of property enhancement which includes strength, stiffness, heat and dimensional stability, as well as barrier and fire‐retardant behavior. The significant challenge is to gain a basic understanding of elaboration–structure–property relationships for these highly promising materials.
Optical Properties
Authors: Galiatsatos Vassilios
Published: October 2003

In studying the interaction of light with polymers one discovers a multitude of exciting phenomena. Thorough knowledge of these phenomena yields thories and instrumentation that can be applied to a wide spectrum of academic and industrial subjects. Most markets served by polymers benefit from understanding of optical properties of polymers. This article provides an overview of some of the theory and properties central to the subject. It covers most properties that are of fundamental importance and macroscopic properties directly important to industrial applications. Examples of computational methods are given. Definitions, testing methods, references, and examples accompany each property to further help understanding.
Packaging, Flexible
Authors: Wooster Jeffrey J.
Published: October 2003

Flexible packaging can come in many forms, from the simple to the extremely complex. Whatever its form its purpose is to protect a product from the time of its manufacture until it is used by the ultimate consumer. The performance requirements that must be met in order to protect a given product ultimately determine the type of packaging that is used. These requirements are used in the selection of polymers, film structures, and packaging methods. The listed applications and packaging types in this article show the range of uses of flexible packaging. As the development of new materials and packaging machinery continues, the number of uses for flexible packaging is sure to grow as well.
Plasticizers
Authors: Wadey Brian L.
Published: October 2003

Plasticizers are added to materials to make the material softer, more flexible, and easier to process. There are four theories of plasticization along with various interaction parameters. The largest family of plasticizers are phthalate esters. These are used mainly to plasticize poly (vinyl chloride) (PVC). Phthalate esters are made by the reaction of phthalic anhydride with various chain length alcohols. These alcohols can be branched or linear in nature. Other families of plasticizers such as trimellitates and adipates can be manufactured by changing the acid component of the reaction. Polymeric plasticizers are made through polycondensation reaction of an acid, glycol, and either an alcohol or an acid. The choice of plasticizer affects the end property performance of flexible PVC. Polymers other than PVC can also be plasticized to improve flexibility. Worldwide plasticizer production and consumption is illustrated as are the health, safety, and environmental aspects of plasticizers.
Polyamides, Plastics
Authors: Palmer Robert J.
Published: October 2003

Polyamides (nylons) are important engineering plastics as well as being well known for fiber applications. This article covers the properties, manufacture, processing, and use of polyamide plastics together with information on specifications, sales, pricing, and suppliers. Materials discussed include nylon‐6,6, nylon‐6, nylon‐6,9, nylon‐6,12, nylon‐11, nylon‐12, nylon‐4,6, amorphous nylon, and other semiaromatic nylons. Physical properties described are crystallinity, thermal properties, moisture absorption, electrical properties, and flammability. Chemical properties are hydrolysis/polycondensation, thermal degradation, oxidation, uv aging, and effect of chemicals and solvents. Manufacture is described including solid‐state polymerization, compounding, and pultrusion. Compounding also includes a review of additives and modifications covering lubricants, nucleants, stabilizers, impact modifiers, flame retardants, plasticizers, reinforcements, nanocomposites, and polymer blends. The following processing routes are detailed: injection molding, extrusion, film, tubing and pipe, monofilament, rods and profiles, wire and cable coating, blow molding, rotomolding, reaction injection molding, powder coating, and also assembly techniques. Uses and automotive, electrical/electronic, consumer, and industrial applications are described. A discussion of recycling is followed by a summary of economic aspects including suppliers, sales, and pricing. Specifications, standards, and quality control are also reviewed with an indication of appropriate test methods.
Polycyanoacrylates
Authors: Woods John
Published: October 2003

Cyanoacrylates are important materials in the production of rapidly curing structural adhesives. The monomers are generally low viscosity liquids, which are prepared in a two‐step process by a base‐catalyzed condensation of paraformaldehyde and cyanoacetate, followed by thermally induced depolymerization of the resultant oligomer under acidic conditions. The monomers are highly reactive toward basic materials and undergo extremely rapid anionic polymerization on contact with catalytic amounts of even weakly nucleophilic compounds or species. The polymers are amorphous materials that are readily depolymerized at elevated temperatures. They are generally soluble in polar aprotic solvents, although polymer solutions are unstable in the presence of basic materials. Adhesives are by far the most important end use for cyanoacrylates and they are widely used for component assembly and repair. The adhesive products are characterized by high rates of curing, high adhesive strength, and good adhesion to a wide range of different materials. They are becoming increasingly important materials as tissue adhesives and sealants for various surgical procedures.
Polyphosphazenes
Authors: Wycisk Ryszard , Pintauro Peter P.
Published: October 2003

An overview of polyphosphazene science is given. A brief history of over 100 years of synthetic developments is presented, from the work of Stokes to the latest cationic condensation polymerization, followed by discussions of blending, cross‐linking, and functionalization. Applications of polyphosphazenes as elastomers, solid polymer electrolytes, membranes, and flame retardants are reviewed. Biomedical research is referenced and hybrid polyphosphazenes and polymers containing cyclophosphazenes are also covered briefly.

Although the limitless derivatization possibilities along with the attractiveness of the inorganic P–N backbone has generated enormous scientific interest in polyphosphazenes, current synthetic routes are characterized by high costs of the substrates, high instability of the intermediate polydichlorophosphazene, and sensitivity of the resultant polyphosphazene to the synthesis conditions. The need for costly process equipment must also be taken into account when assessing the cost of synthesizing polyphosphazenes on a commercial scale. Initial manufacturing efforts by Firestone, Ethyl Corporation, and Elf Atochem were terminated, but various polyphosphazene derivatives are available from custom synthesis companies. Therefore, polyphosphazenes should be considered still under the development stage.
Poly(trimethylene terephthalate)
Authors: Chuah Hoe H.
Published: October 2003

Poly(trimethylene terephthalate) (PTT) is a newly commercialized odd‐numbered aromatic polyester made by the melt polycondensation of 1,3‐propanediol and terephthalic acid. It has a melting point of 228°C and a glass‐transition temperature of 45°C. PTT crystallizes into triclinic unit cell with two chemical repeating units in the
c
‐axis. The three methylene units are arranged in
gauche–gauche
conformation. Crystal and amorphous densities are 1432 and 1295 kg/m
3
, respectively. PTT crystallization rate is in between those of poly(ethylene terephthalate) and poly(butylene terephthalate), with a crystallization half‐time of 2.4 min at 180°C. A rapidly quenched PTT shows cold crystallization at about 65°C, which could affect its drawing behavior if crystallization were to occur during hot drawing. Heat of fusion of 100% crystalline PTT is 30 ± 2 kJ/mol. Isotropic PTT has a flexural modulus of 2.76 GPa and a tensile strength of 67.6 MPa. The notched Izod impact is 48 J/m. Current commercial applications are in textile and carpet fibers. Applications in monofilament, nonwoven, film, and engineering thermoplastics are under development. PTT is processed at 250–270°C. Melt viscosity of a 0.92 dl/g intrinsic viscosity fiber grade PTT is about 240 Pa·s at 265°C. PTT fibers are soft and have very good hand. It also has excellent elastic recovery similar to nylon fiber and is stain‐resistant. The fibers are disperse‐dyed at atmospheric boil without using a carrier.
Polyurethanes
Authors: Ulrich Henri
Published: October 2003

The properties of thermoplastic and thermoset polyurethanes are discussed. The subjects include flexible and rigid polyurethane foams, poly(urethane isocyanurate) foams, thermoplastic polyurethane elastomers, thermoset cast and reaction injection molding elastomers, engineering thermoplastics, liquid crystalline polyurethanes, and polyurethane containing interpenetrating polymer networks. Principal raw materials, such as isocyanates, polyether polyols, and polyester polyols, as well as catalysts, fire retardants, and surfactants are described. The manufacture of flexible foam, rigid foam, coatings, adhesives, sealants, and elastomers are included, as is the use of polyurethane ionomers in aqueous dispersions and blocked isocyanates in one‐component and powder coating applications. The global trend in polyurethanes is a shift from toluene diisocyanate‐based formulations to polymeric isocyanate and 4,4′‐methylenebis(phenyl isocyanate) whenever possible, and substitution of chlorinated fluorocarbon blowing agents by hydrochlorofluorocarbons, hydrofluorocarbons, or hydrocarbons. Recycling of polyurethanes, health and safety factors, including toxicity and safe handling of isocyanates and tertiary amine catalysts, as well as principal uses of polyurethanes and market information are all discussed.
Release Agents
Authors: Owen Michael J.
Published: October 2003

Release agents are used in a wide variety of industries to control or eliminate the adhesion between surfaces. Key product requirements and trends are reviewed and a classification based on chemical type is presented. The mechanisms of release are reviewed, emphasizing the importance of minimizing both the strength of the interaction across the interface and the degree of contact. The dominant role of materials such as those based on aliphatic hydrocarbon and fluorocarbon entities or particulate solids is thus explained. Simple thermodynamic arguments are presented, stressing the need for release surfaces to have lower surface energies than the substrates they are designed to function with. Industrial applications are succinctly summarized, focusing on the specific needs of each particular application and the types of release agents currently used therein. The categories considered are metal, glass, rubber, plastics, textiles, adhesive transfer processes, furniture, and food. Economic aspects and health and safety factors are also briefly considered.
Rotational Molding
Authors: Dodge Phillip T. , Andrzejewski Steve , Mahan Duane
Published: October 2003

Rotational molding, also referred to as rotomolding, is one of the oldest plastics processing techniques. This article introduces the reader to the manufacturing process, including equipment, molds, and secondary operations required to produce parts. In‐depth resin requirements and comparison are also discussed.
Semicrystalline Polymers
Authors: Li Christopher Y. , Cheng Stephen Z. D.
Published: October 2003

The crystalline state in polymers is distinguished from that in other materials by the fact that polymer crystals are not in a single phase having 100% crystallinity, but are only partially crystallized; therefore, they are called semicrystalline polymers. In a bulk semicrystalline polymer, one can find both crystalline and amorphous regions, and the crystalline region may form different aggregates in shapes in different length scales. These length scales are identified as follows: crystal unit cells in a length scale of a few tenth to one nanometer; single lamellar crystals having at least one dimension size less than a few tens of nanometers; lamellar aggregates in a length scale of a few hundreds of nanometers. Crystallinity is a concept in the macroscopic scale. Each structural or morphological level influences the ability of a polymer to respond to its environment. As a result, macroscopic properties are critically associated with different structural and morphological levels, which complicates structure–property relationships. This article, focuses on the formation mechanisms of the crystalline structures and morphologies in these length scales and tries to explore their interrelationships and interdependencies in semicrystalline polymers.
Smart Materials
Authors: Benee L. S. , Snowden M. J. , Chowdhry B. Z.
Published: October 2003

The nature and properties of “smart” colloidal microgels are reviewed. Detailed descriptions including mechanistic information are reported with respect to the preparation of a number of physically different microgel structures including homopolymers, copolymers, polyelectrolyte, and core–shell type materials. The principal techniques used for the characterization of microgels are described, including dynamic light scattering and differential scanning calorimetery. Microgel properties are reviewed with respect to temperature sensitivity, pH sensitivity, colloid stability, rheological behavior, osmotic deswelling, and the influence of copolymers on microgels. Applications of these types of materials are also discussed and, include drug delivery devices, binding/adsorption agents, and catalytic compounds.
Stabilization
Authors: Al‐Malaika S.
Published: October 2003

This review of the fundamental aspects of polymer stabilization technology covers aspects of oxidative degradation of polymers, and the deleterious effects of oxygen and the environment: temperature, sunlight, ozone, atmospheric pollutants, water, mechanical stress, adventitious metal, and metal ion contaminants. The role of antioxidants in polymer stabilization with examples to illustrate the basic mechanisms of action and the range of chemical and physical factors that affect performance are discussed. Different classes of antioxidants that act by different and complementary mechanisms are covered. Also included are examples of recent developments and progress in areas of application where melt, heat, and light stabilizers are generally employed, as well as in more targeted areas that benefit specifically from the use of time‐control stabilizers, high molar mass antioxidants, reactive (polymerizable or graftable) antioxidants, and biological antioxidants.
Styrene–Butadiene Copolymers
Authors: Demirors Mehmet
Published: October 2003

Styrene–butadiene (SB) copolymers are the largest volume, and hence industrially most significant, copolymers currently in use. They are typically divided into three classes. Styrene–butadiene rubbers (SBRs) are mostly used for tire applications. SBRs are manufactured both by emulsion process and by solution process, utilizing anionic polymerization. High impact polystyrene (HIPS), the largest by volume of the three, is a thermoplastic resin and is used in food packaging, consumer electronics, and appliances. HIPS is manufactured by grafting of the polybutadiene rubber in solution during the production of polystyrene. SB block copolymers are utilized in the manufacture of transparent, impact‐resistant polystyrene as well as impact modification in other areas. SB block copolymers are exclusively manufactured by anionic polymerization of styrene and butadiene.
Vinyl Fluoride Polymers (PVF)
Authors: Ebnesajjad Sina
Published: October 2003

Homopolymers and copolymers of vinyl fluoride are inert. They posses unique chemical and weather resistance characteristics in addition to good mechanical properties. These polymers can be rendered adherable by flame and corona discharge techniques. These attributes have spurred the application of poly(vinyl fluoride) films and coatings in indoor and outdoor functional and decorative uses. This article provides a review of methods of manufacture, properties, polymerization chemistry, fabrication techniques, applications, and economy of these polymers.
Vinylidene Fluoride Polymers
Authors: Humphrey J. S. , Amin‐Sanayei R.
Published: October 2003

Poly(vinylidene fluoride), PVDF, [CH2CF2]n, is the addition polymer of vinylidene fluoride, VDF, CH2CF2. It has achieved a high level of usage during the past 40 years based upon the excellent resistance to chemicals, weathering elements, and oxidants, as well as for special properties such as piezoelectric characteristics and fire resistance. It is a tough, high temperature thermoplastic finding use, eg, in super heated steam environments. It may be fabricated by a variety of techniques, including solvent‐based or water‐based dispersion processes as well as typical melt extrusion and radiation cross‐linking processes. It is available from a variety of manufacturers. Copolymerization technology has produced thermoplastic resins with excellent flexibility.
Wool
Authors: Christoe John R. , Denning Ron J. , Evans David J. , Huson Mickey G. , Jones Leslie N. , Lamb Peter R. , Millington Keith R. , Phillips David G. , Pierlot Anthony P. , Rippon John A. , Russell Ian M.
Published: October 2003

Wool, the fibrous coating from sheep, is the most important animal fiber used by the textile industry. It has been used continuously for several thousand years, the earliest type of fabric made from wool probably being a felt. Although the relative importance of wool as a textile fiber has declined with the increasing use of synthetic fibers, it remains important in some sectors of the market. This article discusses raw wool specification, fiber growth, its complex morphological and chemical structure, and the physical properties that make wool unique among textile fibers. Also discussed are the processing steps used to transform raw wool into consumer products, namely, scouring, carbonizing, carding, spinning, setting, dyeing, bleaching, printing, and treatments to reduce felting shrinkage, insect damage, and flammability. A new textile fiber made from wool (Optim™, CSIRO) is also described.
Dendronized Polymers
Authors: Schlüter A. Dieter , Rabe Jürgen P.
Published: October 2003

Synthesis, properties, and application of the novel class of comb polymers with dendritic side chains (dendronized polymers) are discussed. Different synthetic strategies are discussed and compared. The assembly and manipulation of homo‐ and amphiphilic representatives are treated with an emphasis on interfacial issues. The combination of neutron scattering data in solution, molecular dynamics simulations in vacuum, and scanning force microscopical investigations of ultrathin layers as well as individualized representatives of dendronized polymers adsorbed on highly oriented pyrolytic graphite show that dendronized polymers can be considered rigid, nano‐sized molecular objects with cylindrical shapes, depending on structure, size, and density of attachment. Although experiments were only recently started accordingly, it has already become obvious that this class of polymers, because of their size and shape and potential to be equipped with various surface functionalities and patterns, links the worlds of materials science and bioscience.
Cyclopentadiene and Dicyclopentadiene
Authors: Cheung T. T. Peter
Published: October 2003

Cyclopentadiene (CPD) and dicyclopentadiene (DCPD), which occur as by‐products in the steam cracking process in ethylene plants, are the major ingredients in the production of hydrocarbon resins, unsaturated polyester resins, elastomers, pesticides, flame retardants, and a host of specialty chemicals. The versatility of CPD as the building block in so many chemicals stems from the high reactivity of its conjugated double bonds. They react readily with dienophiles, compounds with ethylenic or acetylenic unsaturation, to give Diels–Alder adducts, with oxygen and halogen to give oxygenates and halide derivatives. Cyclopentadiene dimerizes readily, via the Diels–Alder mechanism, to DCPD at ambient conditions. The dimerization is highly exothermic. Because of its reactivity, CPD is normally available only in the stable dimer form. Pure CPD can be producedin situby the thermal cracking of the DCPD at a temperature near the normal boiling point of the DCPD.
Perfluorinated Polymers, Tetrafluoroethylene–Perfluorodioxole Copolymers
Authors: Gangal Subhash V.
Published: October 2003

Copolymers of tetrafluoroethylene–perfluorodioxole are perfluorinated amorphous polymers and have unusual combination of properties. These polymers, commonly known as Teflon AF, have high temperature stability, excellent chemical resistance, low surface energy, low water absorption, high limiting oxygen index, solubility at ambient temperature in fluorinated solvents, high transparency, and low refractive index. They are stiffer and have high gas permeability. The glass‐transition temperature is sensitive to polymer composition and the structure of the dioxole monomer. These polymers can be processed by various solution processing techniques such as spin coating, dip coating, spraying, or casting. Melt‐processing techniques like extrusion and injection molding are used. They are used to provide antireflective coatings, low dielectric coatings, pellicles in electronic chips, plastic optical fiber, and in gas separation membrances.
Urethane Coatings
Authors: Wicks Zeno W.
Published: October 2003

Various classes of urethane coatings are discussed: two package solventborne, moisture cure, blocked isocyanate, uralkyd, aqueous polyurethane dispersion, and two‐package waterborne coatings. Major end uses include architectural paints, especially varnishes; coatings for automobiles, both OEM and refinish; and maintenance coatings.
Ferroelectric Liquid Crystalline Elastomers
Authors: Zentel Rudolf
Published: October 2003

Ferroelectric LC‐elastomers represent an interesting class of material because they combine the ordering of liquid crystalline ferroelectric phases and the rubber elasticity of polymer networks. Switching of the electric polarization leads to deformation of the polymer network, equivalent to stretching a spring, and creates a stress in the network of polymer chains.

The interaction of mesogens and the network can be varied by using different topologies of net points: Crosslinking is carried out either within the siloxane sublayers (leading to fast switching elastomers) or between the siloxane sublayers (resulting in an elastomer that favors the ferroelectric switching state in which the cross‐linking reaction took place).

Because the orientation of the smectic phase couples to the polymer network, electromechanical measurements show a piezoelectric effect. Mechanical deformation leads to polarization or an external electric field to deformation of the sample. Applying the electric field parallel to the smectic layer structure leads to an extremly high electrostrictive strain.
Flash Devolatilization
Authors: Nauman Bruce
Published: October 2003

Flash devolatilization is a highly efficient method for removing volatile components from a polymer melt. A dispersed spray or an open‐celled form exposes a large surface area and enables a close approach to thermodynamic equilibrium. The process is highly scalable in the sense that the residual volatile content is insensitive to flow rate. The typical apparatus consists of a heat exchanger, flash chamber, and gear pump. Flash devolatilization also contributes to the effectiveness of devolatilizing extruders and wiped file evaporators. Foaming agents can be used to increase the surface area available for mass transfer.
Microemulsion Polymerization
Authors: Chern Chorng‐Shyan
Published: October 2003

Microemulsion polymerization involves free‐radical polymerization in ultrafine monomer droplets (1–10 nm in diameter) dispersed in a continuous phase. The resultant polymer colloids generally exhibit small latex particles (10 nm in diameter) and very high polymer molecular weight (10
6
– 10
7
g/mol), which cannot be achieved by conventional emulsion polymerization. This article presents a concise review of the formation and microstructure of the thermodynamically stable microemulsion. The structural characteristic of the initial microemulsion has a significant influence on the subsequent polymerization inside monomer droplets. Polymerization kinetics and nucleation and growth of latex particles are the focuses of this work. Microemulsion droplets are the primary loci of particle nucleation and particle nuclei are generated continuously throughout the polymerization. Only a few polymer chains are produced in one latex particle. In contrast, the continuous phase or bicontinuous phase of microemulsion may also serve as the locus of polymerization and this unique technique allows the preparation of various novel polymeric materials.
Miscibility
Authors: Arrighi V. , Cowie J. M. G.
Published: October 2003

The phase behavior of polymers whether in solution or in mixtures with other polymeric components, differs considerably from that of small molecules. In this article a description of the basic principles of polymer solution and blend thermodynamics is given.
Microcellular Plastics
Authors: Suh Nam P.
Published: October 2003

Microcellular plastics (MCPs) refer to any plastic with tiny bubbles of less than about 50 μm. They are made by subjecting polymers with a large amount of dissolved gas to a thermodynamic instability so as to nucleate a large number of cells instantaneously. MCPs have been extruded and injection‐molded in order to make various industrial products. This article reviews the fundamental theory for design of MCPs and their processing methods. It also discusses the design of equipment, including the die or mold, for MCP processing. The performance of MCPs and the advantages of using MCPs are demonstrated. Some of their industrial applicatons are also highlighted.
Vinyl Acetal Polymers
Authors: Wade Bruce
Published: October 2003

Vinyl acetal polymers are terpolymers, with units of vinyl acetate, vinyl alcohol, and vinyl acetal reflecting the three reactions required for their manufacture. Manufacture involves several stages including vinyl acetate polymerization and either sequential or concurrent hydrolysis of poly(vinyl acetate) to poly(vinyl alcohol) and acetalization with an aldehyde in the presence of an acid catalyst. Only poly(vinyl butyral) and to a lesser extent poly(vinyl formal) continue to be made in sizeable commercial quantities. These polymers form hard, unpliable materials that are difficult to process without using solvents or plasticizers. Plasticized poly(vinyl butyral) interlayer for laminated safety glass is by far the largest single application for this class of polymers. Poly(vinyl butyral) provides flexible toughness over a wide range of temperatures and at a lower cost than vinyl acetal polymers derived from longer chain aldehydes. Where stiffer performance at higher temperatures is required, poly(vinyl formal) provides significant property advancement. Applications for vinyl acetal resins make use of their optical clarity, high pigment and filler binding capacity, and excellent adhesion to a variety of surfaces.
Biomolecules at Interfaces
Authors: Van Tassel Paul R.
Published: October 2003

Biomolecules such as proteins, peptides, amino acids, polysaccharides, lipids, and nucleic acids tend to reside at interfaces. This simple fact carries immense consequences in nature and affords substantial opportunities in biotechnology. In this article, several important technological applications and intriguing intellectual challenges that motivate the study of biomolecules at interfaces are introduced. Significant discussion is directed toward applications in biomaterials and biosensors, and open questions on issues of irreversibility and history‐dependent behavior are addressed. In addition, a number of theoretical tools and experimental methods critical to advancing the study of biomolecules at interfaces are presented. Theoretical descriptions at the site, particle, colloidal, polymer, and atomistic level—as well as optical, piezoelectric, and scanning probe experimental techniques—are described and speculation is made upon their potential to broaden our application and/or deepen our understanding of biomolecules at interfaces.
Intercalation Polymerization
Authors: Duguet Etienne , Rey Stéphanie , Robles Josepha Maria Merida
Published: October 2003

Polymer‐layered nanocomposites are made of the alternation of inorganic slabs and polymer layers. They may be obtained through (1) the synthesis of the mineral slabs from soluble precursors in a macromolecular solution, (2) mineral slab exfoliation and their subsequent restacking after adsorption of macromolecules (encapsulative precipitation), (3) the direct intercalation of macromolecules in the interslab space, (4) the intercalation of monomer molecules and theirin situsimultaneous or subsequent polymerization. In this article, the main layered inorganic lattices, which readily undergo intercalation reaction, and the corresponding intercalation driving forces are described. The synthesis of polymer‐layered nanocomposites are presented essentially from the viewpoint of the polymer chemist. The polymerization mechanisms, the molecular weight distribution, and the interslab arrangement of the intercalated macromolecules are discussed. Among the original properties of such polymer‐layered nanocomposites, a special emphasis is made on their enhanced ionic or electron conductivity and their thermal stability.
Identification of a metabolic network structure representative of arthrospira (spirulina) platensis metabolism
Authors: Cogne Guillaume , Gros J.‐B. , Dussap C.‐G.
Published: October 2003

A comprehensive network structure for the autotrophic growth of Arthrospira platensis is proposed. The metabolic network was built up with 121 reactions and 134 metabolites including biomass synthesis, production of a growth‐associated exopolysaccharide, and energy aspects. The model supports the existence of a metabolic shunt of PEP to pyruvate through PEP carboxylase, NAD+‐dependent malate dehydrogenase and malic enzyme to convert NADH,H+ into NADPH,H+. A limit in Arthrospira growth metabolism due to NADH,H+ balancing is evidenced, explaining why the maximal light‐dependent mass yield of the growth‐associated exopolysaccharide was 0.51 kg EPS kg−1 biomass, consistent with experimental results. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 667–676, 2003.
Use of stable emulsion to improve stability, activity, and enantioselectivity of lipase immobilized in a membrane reactor
Authors: Giorno L. , Li N. , Drioli E.
Published: October 2003

The enantiocatalytic performance of immobilized lipase in an emulsion membrane reactor using stable emulsion prepared by membrane emulsification technology was studied. The production of optical pure (S)‐naproxen from racemic naproxen methyl ester was used as a model reaction system. The O/W emulsion, containing the substrate in the organic phase, was fed to the enzyme membrane reactor from shell‐to‐lumen. The enzyme was immobilized in the sponge layer (shell side) of capillary polyamide membrane with 50 kDa cut‐off. The aqueous phase was able to permeate through the membrane while the microemulsion was retained by the thin selective layer. Therefore, the substrate was kept in the enzyme‐loaded membrane while the water‐soluble product was continuously removed from the reaction site. The results show that lipase maintained stable activity during the entire operation time (more than 250 h), showing an enantiomeric excess (96 ± 2%) comparable to the free enzyme (98 ± 1%) and much higher compared to similar lipase‐loaded membrane reactors used in two‐separate phase systems (90%). The results demonstrate that immobilized enzymes can achieve high stability as well as high catalytic activity and enantioselectivity. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 677–685, 2003.
Crude aminoacylase from aspergillus sp. is a mixture of hydrolases
Authors: Bode Moira L. , van Rantwijk Fred , Sheldon Roger A.
Published: October 2003

A range of cross‐linked enzyme aggregates (CLEAs) was prepared from commercially available aminoacylase I. Results from three test reactions showed that aminoacylase does not possess aminolysis or alcoholysis activity, both previously ascribed to this enzyme. This result was confirmed using aminoacylase purified by chromatographic techniques, which leads us to conclude that the previously observed acylations of esters and amines is due to other enzymes present as impurities in the crude aminoacylase I. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 710–713, 2003.
Genetically engineered binding proteins as biosensors for fermentation and cell culture
Authors: Ge Xudong , Tolosa Leah , Simpson Jen , Rao Govind
Published: October 2003

The signal‐transduction properties and the potential applications of two engineered binding proteins from E. coli were extensively studied. Both proteins have a single cysteine mutation in their polypeptide chains, which allow the introduction of an environmentally sensitive fluorophore: ANS for glucose‐binding protein (GBP) and acrylodan for glutamine‐binding protein (QBP). Both proteins respond to their ligands in the micromolar range. The proteins can be stored at 4°C for at least 5 months. Apparent binding constant, protein concentration, and fluorophore are three major factors that affect the biosensor's responsive ranges. The binding of the ligand is quick and reversible in solution, but the unfavorable dissociation equilibrium and mass‐transfer resistance for encapsulated proteins can delay the response to several minutes and the recovery to hours. Simulated results show that using dialysis tubing with a diameter of 1 mm or less is possible to reduce the recovery time to less than 30 minutes. The potential applications of GBP were studied in yeast fermentation and E. coli fermentations in three different scales: 150 mL, 5 mL, and 100 μL. The results were compared with an YSI 2700 Chemistry Analyzer. Although the latter could not give reliable results for the E. coli fermentations as the glucose concentration in LB medium is close to its lower detection limit, the glucose biosensor presented here was successfully applied to each situation. Glutamine‐binding protein was tested in cell cultures of two different scales (100 mL and 100 μL) and the results were also compared with those obtained with YSI. Both QBP and YSI gave good results for the 100‐mL cell culture, but the relatively large sample volume requirement of YSI (at least 5 μL) prevented it from being used in the 100‐μL cell culture. Because of their small sample volume requirements (less than 1 μL) and high sensitivity, the assays described here might find wide applications in high‐throughput bioprocessing. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 723–731, 2003.
Metabolic characteristics of an isocitrate dehydrogenase defective derivative of escherichia coli BL21(DE3)
Authors: Aoshima Miho , Ishii Masaharu , Yamagishi Akihiko , Oshima Tairo , Igarashi Yasuo
Published: October 2003

A 7.8 kb fragment containing isocitrate dehydrogenase (ICDH) gene and its flanking regions was cloned from Escherichia coli BL21(DE3) and sequenced. Unlike the case of the K‐12 strain, the e14 element was not found. The nucleotide divergence between these two strains was about 2%. Using the cloned fragment, ICDH defective mutant strain, MA1935, was generated from BL21(DE3). Although MA1935 accumulated citrate, citrate synthase activity was not repressed but was rather high. In addition, isocitrate lyase was not highly induced at the stationary phase. MA1935 was shown to be a good host strain for ICDH gene expression. © 2003 Wiley Periodicals Inc. Biotechnol Bioeng 84: 732–737, 2003.
Prospects for diffusion enhancement of signal and resolution in magnetic resonance microscopy
Authors: Pennington Charles H.
Published: October 2003

The prospects for and practical requirements of the “diffusion enhancement of signal and resolution” (DESIRE) scheme proposed by Lauterbur as a method to enhance the sensitivity, spatial resolution, and contrast in magnetic resonance (MR) microscopy and localized MR spectroscopy is assessed. The method, which still has not been implemented, promises signal enhancements of 1–2 orders of magnitude in imaging or localized spectroscopy on the scale of ∼10 microns and requires magnetic field gradient strengths (∼10 T/m) that are not unreasonable. I emphasize the development of an understanding of the physical principles involved in this unfamiliar, “real‐space” imaging method. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part A 19A: 71–79, 2003.
Thermal relaxation and coherence dynamics of spin 3/2. I. Static and fluctuating quadrupolar interactions in the multipole basis
Authors: van der Maarel Johan R.C.
Published: October 2003

The relaxation dynamics of the spin 3/2 density operator in the presence of fluctuating and static quadrupolar interactions is reviewed. The nuclear magnetic resonance (NMR) line shapes are analyzed for any value of the static quadrupolar interaction, ranging from isotropic systems to systems exhibiting large splitting far exceeding the line widths. Pulse sequences optimized for the elimination of line broadening due to an inhomogeneous static quadrupolar interaction and for the detection of nuclei involved in slow molecular motion and/or in anisotropic, liquid crystalline environment are discussed. In Part II, the dynamics of spin 3/2 in the presence of a (pulsed) radio frequency (RF) field is reviewed. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part A 19A: 97–116, 2003.
Involvement of the liver by multiple myeloma as nodular lesions: A case diagnosed by fine‐needle aspiration and immunocytochemistry
Authors: Fernandez‐Flores A. , Fortes J. , Smucler A. , Orduña M. , Pol A.
Published: October 2003

Liver involvement by multiple myeloma as space‐occupying lesions is a rare condition with only a few cases reported in the literature. We present a case of a 68‐year‐old man with a prostatic adenocarcinoma who developed a multiple myeloma as a second primary malignancy. Hepatic nodules were discovered in the tomographic study. Fine‐needle aspiration of one of the hepatic lesions showed a pleomorphic plasmacytoid tumor. Immunocytochemistry using p63 and kappa‐chain antibodies was useful in determining the plasmacytic nature of the cells. Diagn. Cytopathol. 2003;29:280–282. © 2003 Wiley‐Liss, Inc.
Rhabdoid meningioma: Cytopathologic findings in cerebrospinal fluid
Authors: Parwani Anil V. , Mikolaenko Irina , Eberhart Charles G. , Burger Peter C. , Rosenthal Dorothy L. , Ali Syed Z.
Published: October 2003

Rhabdoid meningioma is a recently described, rare, WHO Grade III intracranial tumor with an aggressive growth pattern and increased risk of recurrence. We describe the cytopathologic findings on cerebrospinal fluid of one such case in a 26‐yr‐old female who underwent resection of a left temporo‐parietal mass. Cerebrospinal fluid contained abundant malignant cells with a prominent “rhabdoid” phenotype, i.e., large cells, eccentric nuclei, single prominent nucleoli, and dense eosinophilic cytoplasm. Although rhabdoid meningioma has a characteristic cytomorphology, the differential diagnosis of this tumor would involve metastatic adenocarcinoma, metastatic malignant melanoma, and other tumors with “rhabdoid” features (such as an atypical teratoid/rhabdoid tumor). Diagn. Cytopathol. 2003;29:297–299. © 2003 Wiley‐Liss, Inc.
Borderline nuclear change in cervical smears: Five‐year follow‐up
Authors: Grace A. , Maguire G. , Doherty S. , Thornhill M. , O'Dowd J. , Leader M. , Kay E.
Published: October 2003

Borderline nuclear changes (BNC) account for 5–20% of cervical smears, and their outcome is unpredictable. Current management involves repeat smears at 6‐mo intervals, for a further 12 mo with referral for colposcopy, if the changes persist. Given the uncertainty surrounding the natural history of BNC and the claim that many patients are further investigated unnecessarily and potentially “overtreated,” the aim of this study was to determine the outcome for patients with a diagnosis of BNC to define whether the management protocol is appropriate for this patient group in our laboratory. A total of 808 patients with BNC were followed up. There was a 4.05% progression to high‐grade dyskaryosis, and most of these were detected within the first year of follow‐up. This at least justifies the early and intense follow‐up of this patient group until a reliable “triage tool” is adopted to pre‐select those patients with BNC who will progress or revert to negative. Diagn. Cytopathol. 2003;29:267–269. © 2003 Wiley‐Liss, Inc.
Metastatic lobular mammary carcinoma diagnosed in cervicovaginal smears: A case report
Authors: Rau Aarathi R. , Saldanha Prema , Raghuveer C. V.
Published: October 2003

Lobular carcinoma of the breast uncommonly metastasizes to the cervix. We report a case of lobular carcinoma of the breast with an abnormal cervicovaginal smear caused by metastasis in the cervix. We also discuss the differential diagnosis of primary genital and secondary adenocarcinomas in abnormal cervicovaginal smears. Diagn. Cytopathol. 2003;29:300–302. © 2003 Wiley‐Liss, Inc.
Parameter‐uniform numerical methods for a laminar jet problem
Authors: Ansari Ali R. , Hegarty Alan F. , Shishkin Grigori I.
Published: October 2003

We consider the classical problem of a two‐dimensional laminar jet of incompressible fluid flowing into a stationary medium of the same fluid. The equations of motion are the same as the boundary layer equations for flow past an infinite flat plate, but with different boundary conditions. Numerical experiments show that, using appropriate piecewise‐uniform meshes, numerical solutions together with their scaled discrete derivatives are obtained which are parameter (i.e., viscosity ν) robust with respect to both the number of mesh nodes and the number of iterations required for convergence. While the method employed is non‐conservative, we show with the aid of numerical experiments that the loss in conservation of momentum is minimal. Copyright © 2003 John Wiley & Sons, Ltd.
Highly efficient transgene‐independent recombination directed by a maternally derived SOX2CRE transgene
Authors: Vincent Stéphane D. , Robertson Elizabeth J.
Published: October 2003

Summary: The Cre/loxP site‐specific recombination system is a powerful tool that allows gene inactivation in a tissue‐ and time‐specific manner. Several reports have shown that the Sox2Cre transgenic strain provides a very efficient means to delete gene function from the early epiblast (Hayashi et al.: Gene Expr Patterns 2:93–97, 2002; Vincent et al.: Genes Dev 17:1646–1662, 2003). Routinely, male studs carrying one null allele of the gene of interest and the Cre transgene are crossed to females homozygous for the conditional allele. Normally, excision is observed only in the progeny inheriting both the Cre transgene and the conditional allele. Here we report that when the Sox2Cre transgene is inherited maternally, excision occurs in all offspring irrespective of whether they carry the Cre transgene. Thus, Sox2Cre females provide a generally useful tool for rapid and efficient removal of loxP flanked sequences in vivo. genesis 37:54–56, 2003. © 2003 Wiley‐Liss, Inc.
Subtractive hybridisation screen identifies sexually dimorphic gene expression in the embryonic mouse gonad
Authors: McClive P.J. , Hurley T.M. , Sarraj M.A. , van den Bergen J.A. , Sinclair A.H.
Published: October 2003

The sex of most mammals is determined by the action of SRY. Its presence initiates testis formation resulting in male differentiation, its absence results in ovary formation and female differentiation. We have used suppression subtraction hybridisation between 12.0–12.5 days postcoitum (dpc) mouse testes and ovaries to identify genes that potentially lie within the Sry pathway. Normalised urogenital ridge libraries comprising 8,352 clones were differentially screened with subtracted probes. A total of 272 candidate cDNAs were tested for qualitative differential expression and localisation by whole mount in situ hybridisation; germ cell‐dependent or ‐independent expression was further resolved using busulfan. Fifty‐four genes were identified that showed higher expression in the testis than the ovary. One novel gene may be a candidate for interactions with WT1, based on its localisation to Sertoli cells and map position (16q24.3). genesis 37:84–90, 2003. © 2003 Wiley‐Liss, Inc.
Differential requirements for the neurogenic gene almondex during Drosophila melanogaster development
Authors: Michellod Marie‐Agnès , Forquignon Françoise , Santamaria Pedro , Randsholt Neel B.
Published: October 2003

During early development, the neurogenic genes of Drosophila melanogaster are involved in the control of cell fates in the neurectoderm; almondex (amx) belongs to this category of genes. We have identified the amx locus and rescued the amx embryonic neurogenic phenotype with a 1.5 kb DNA fragment. Using a small deficiency, we generated a new amx mutant background called amxm, which is a null allele. Besides the characteristic neurogenic maternal effect caused by loss of amx, amxm flies display a new imaginal phenotype resembling loss of function of Notch. We describe amx‐induced misregulation of the Notch pathway target E(spl) m7 in embryos and genetic interactions between amx and Notch pathway mutants in adult flies. These data show that wildtype amx acts as a novel positive regulator of the Notch pathway and is required at different levels during development. genesis 37:113–122, 2003. © 2003 Wiley‐Liss, Inc.
Proximal upstream region of zebrafish bone morphogenetic protein 4 promoter directs heart expression of green fluorescent protein
Authors: Shentu Hsuan , Wen Hui‐Ju , Mour Her Guor , Huang Chang‐Jen , Wu Jen‐Leih , Hwang Sheng‐Ping L.
Published: October 2003

We examined the activity of the bone morphogenetic protein 4 (BMP4) promoter in zebrafish embryos via transient and stable transgenic expression analyses in order to obtain a better understanding of the regulation of BMP4 tissue‐specific expression. Transient expression studies showed that the 9.0‐kb BMP4 promoter/upstream region drove green fluorescent protein (GFP) expression mainly in the heart. Deletion analyses indicated the existence of multiple regulatory elements in the 7.5‐kb BMP4 promoter/proximal upstream region. In addition, a coinjection experiment further demonstrated the 2.4‐kb Bgl II–Hind III DNA region contains major positive regulatory elements. In addition, stable transgenic lines were established to further confirm the heart‐specificity of this segment in BMP4 promoter. The results showed that GFP was mainly localized in the myocardium of developing ventricles of 48‐hpf (hours postfertilization), 72‐hpf, and 100‐hpf transgenic F1 embryos. Together, these results indicate that the 7.5‐kb BMP4 promoter/proximal upstream region specifically contains regulatory elements for BMP4 expression in the heart, while regulatory elements for other endogenous BMP4‐expressing tissues may reside in more distal regions and/or in introns. genesis 37:103–112, 2003. © 2003 Wiley‐Liss, Inc.