bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase equilibria of precursor‐derived Si–(B–)C–N ceramics
Authors: Seifert Hans Jürgen , Peng Jianqiang , Golczewski Jerzy , Aldinger Fritz
Published: August 2002

Phase equilibria and phase reactions of precursor‐derived ceramics of the Si–C–N and the Si–B–C–N systems at temperatures higher than 1700 K are described. CALPHAD (CALculation of PHAse Diagrams) results confirm quantitatively the data from thermogravimetry and differential thermal analysis of precursor‐derived Si–C–N ceramics. A model for explanation of the thermal stability of specific Si–B–C–N precursor ceramics was developed. Phase reactions of polymeric precursors of the Si–C–N–H system were calculated and compared with analyses concerning the composition of the solid ceramic and gaseous products from thermolysis at a temperature of 1323 K. The results­show that a semi‐quantitative description of­the thermolysis process is possible. Copyright­© 2001 John Wiley & Sons, Ltd.
Superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone‐drawn under critical necking tension
Authors: Suzuki Akihiro , Kawada Takashi
Published: August 2002

The superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone‐drawn under a critical necking tension (σc) were studied. σc was defined as the minimum tension needed to generate a neck at a given drawing temperature (Td) and was measured over a temperature range of 70–120°C. The σc value increased rapidly with decreasing Td in the temperature range below 85°C, but the temperature dependence of σc was small above 85°C. The neck profile relied on Td, becoming more shapely with decreasing Td. A neck with a gradual decrease in diameter was observed in the fibers drawn at 100°C and above. The draw ratio increased significantly with increasing Td above 90°C, but birefringence decreased. Density decreased gradually with increasing Td, and fiber drawn at 120°C had a density of 1.347 g/cc. Wide‐angle X‐ray diffraction photographs of the fibers drawn at 100°C and below showed reflections due to crystallites, but a photograph of the fiber obtained at 120°C showed a ring‐like amorphous halo. The storage modulus (E′) at 25°C increased progressively with decreasing Td, and the fiber drawn at 70°C had the maximum E′ value among the fibers drawn at a series of Td's. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 179–185, 2002
Effects of a Nd—Fe—B magnetic filler on the crystallization of poly(phenylene sulfide)
Authors: Guschl Peter C. , Kim Hyun Seog , Otaigbe Joshua U.
Published: August 2002

The crystallization of poly(phenylene sulfide) (PPS) in a polymer–magnetic Nd—Fe—B powder suspension was studied. Isothermal crystallization behavior was analyzed by way of differential scanning calorimetry, and the kinetics were described via the Avrami equation. The Avrami parameters and the crystallization times were strongly affected by both the particle size and the presence of a coupling agent coated on the filler particles. The small Nd—Fe—B particles exhibited long induction and half‐times, whereas the large particles tended to have short crystallization times. Particles ranging from 38 to 150 μ appeared to have similar crystallization times and to have no significant change in the value of Avrami index with melt crystallization temperature. As a result of these analyses, the dynamic mechanical properties were determined to correlate the fundamental polymer crystallization characteristics and the physical properties of the PPS binder. The enhancement of the wetting of the filler to the binder was promoted through the coupling agent, as confirmed by dynamic mechanical testing performed on the samples. The storage modulus typically decreased because of the presence of the uncoated small particles. Conversely, the loss modulus was enhanced because of the presence of the coated small particles in the PPS binder. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1091–1102, 2002
Blends of high‐density polyethylene with solid silicone additive
Authors: Muñoz P Ma. Patricia , Werlang Moisés M. , Yoshida I. Valéria P. , Mauler Raquel S.
Published: August 2002

Silicone masterbatch (SMB) is a pelletized formulation containing 50% of an ultrahigh molecular‐weight polydimethylsiloxane dispersed in polyethylene. This SMB is designed to be used as an additive in polyethylene‐compatible systems to impart benefits such as processing improvement and modification of surface characteristics. In this work, binary blends of high‐density polyethylene (HDPE) and SMB were prepared by melt‐mixing technique to study the influence of this masterbatch on the processing and mechanical properties of HDPE. Ternary blends were also prepared by the addition of silane‐grafted polyethylene (HDPE‐VTES) as compatibilizer. The blends were analyzed by melting flow rate (MFR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests. Data of final torque and MFR showed that SMB improved the processability of pure HDPE. DSC results showed differences in crystalline behavior between binary and ternary blends. In the former, the degree of crystallinity increased up to 10 wt % of SMB content; beyond this concentration, it decreased. In ternary blends, a reverse behavior was observed. The morphologic study showed silicone particles uniformly distributed in HDPE matrix. With high SMB concentration, the addition of HDPE‐VTES significantly reduced the size of silicone particles. In the range of SMB composition studied, the mechanical properties of blends lower slightly compared to pure HDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2347–2354, 2002
Effect of polycarbonate–poly(methyl methacrylate) graft copolymer as a modifier improving the surface hardness of polycarbonate
Authors: Okamoto Masaya
Published: August 2002

With the use of macromonomers that have a dicarboxyl group, polycarbonate–poly(methyl methacrylate) (PC–PMMA) graft copolymers were prepared, and the relationship between the length of PMMA branches and Vickers hardness of the graft copolymer was investigated. With the use of the PC–PMMA graft copolymer as a modifier to improve the surface hardness of PC, Vickers hardness of PC/PC–PMMA blend polymers was examined. PC/PC–PMMA blend polymers are more transparent than PC/PMMA blend polymers. PC/PC–PMMA blend polymers are superior in Vickers hardness to PC/PMMA blend polymers, although the content of PMMA in PC/PC–PMMA blend polymers is smaller than that of PC/PMMA blend polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2774–2779, 2002; DOI 10.1002/app.10252
Enhancement of the luminescent intensity of the novel system containing Eu3+‐β‐diketonate complex doped in the epoxy resin
Authors: Parra Duclerc Fernandes , Brito Hermi Felinto , Matos Jivaldo Do Rosário , Dias Luís Carlos
Published: August 2002

Photoluminescent properties of the europium tris(thenoyltrifluoroacetonate) dihydrate [Eu(TTA)3(H2O)2] incorporated in epoxy resin in the solid state are reported. The polymeric Eu3+ complex and the precursor compound were characterized by elemental analysis, thermogravimetry (TG), differential scanning calorimetry (DSC), infrared spectroscopy, nuclear magnetic resonance (NMR), and electronic spectroscopy. Due to efficient energy transfer from the polymer to the rare earth ion, the polymer phosphorescence intensity was observed to decrease with an increase of the Eu3+ ion concentration. High values of the Ω2 intensity parameter were obtained, reflecting the hypersensitive character of the 5D0 → 7F2 transition and indicating that the Eu3+ ions are in a highly polarizable chemical environment. This is consistent with systems containing epoxy resin that generally show a higher value for the Ω4 parameter as a consequence of the difference in the basicity of the oxygen donor from the polymer. Lifetime measurement (τ = 0.442 ms) suggests that the Eu3+ luminescence has a higher efficiency than in the case of hydrated compound (τ = 0.260 ms). The emission quantum efficiency shows higher luminescence for the polymer containing 1% of Eu3+‐β‐diketonate complex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2716–2726, 2002
Wetting properties of polystyrene ionomers treated with plasma source ion implantation
Authors: Kim Joon‐Seop , Hong Min‐Chul , Nah Yeon Hwa , Lee Yeonhee , Han Seunghee , Lim Hyun Eui
Published: August 2002

The wetting properties of polystyrene‐based ionomers treated with plasma source ion implantation (PSII) were investigated by the measurement of water contact angles. When sulfonated ionomers were aged for a few days, the hydrophobic recovery for the ionomers became much slower than that for the nonionic polymers. However, when the samples were aged over 20 days, the water contact angle of the ionomers converged with that of the nonionic polymer. Thus, it was concluded that the ionic interaction between the ionic groups and the presence of ionic groups together resulted in the slow hydrophobic recovery and that the aging effect was significant for the ionomers. For the methacrylate ionomer of low ion content, on the other hand, it was found that the PSII treatment produced only a small change in hydrophobic recovery behavior. Thus, it was suggested that the low ionic content coupled with the small size of the ionic unit might cause changes only of a very insignificant degree in hydrophobic recovery behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2500–2504, 2002
Influence of mechanical stresses on the hydrolytic aging of standard and low styrene unsaturated polyester composites
Authors: Autran M. , Pauliard R. , Gautier L. , Mortaigne B. , Mazeas F. , Davies P.
Published: August 2002

Standard and low styrene emission glass fiber‐reinforced unsaturated polyester (FRP) composites were aged by immersion under flexural and tension loads, to evaluate modifications to the mechanical properties as a function of exposure time under stress. The application of a mechanical load does not modify either the quantity of the absorbed water or the diffusion coefficients significantly. For an applied stress of less than 10% of the fiber strength, the influence on aging is small, but for larger applied stresses, the rate of reduction in the mechanical properties is accelerated and, in some cases, premature rupture is observed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2185–2195, 2002
Formation of integrally skinned asymmetric polyetherimide nanofiltration membranes by phase inversion process
Authors: Kim In‐Chul , Yoon Hyung‐Gu , Lee Kew‐Ho
Published: August 2002

Integrally skinned asymmetric polyetherimide (PEI) membranes were prepared by the phase inversion process from casting solution containing dimethylformamide (DMF) as a solvent and 1,4‐dioxane as a cosolvent. Deionized water was used as a coagulation medium in preparing asymmetric membranes. The effect of 1,4‐dioxane was investigated by measuring casting solution properties, permeation properties, and membrane structures. Various effects of polymer concentration, evaporation time, and coagulation bath temperature were also studied. Low miscibility of 1,4‐dioxane with coagulant (water) resulted in reducing membrane pore size. The molecular weight cutoff values of asymmetric membranes could be controlled by changing the amount of 1,4‐dioxane in the casting solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1300–1307, 2002; DOI 10.1002/app.10452
Preparation and adsorption behavior for metal of chitosan crosslinked by dihydroxy azacrown ether
Authors: Yang Zhikuan , Zhuang Li , Tan Gongrong
Published: August 2002

A new type of crosslinked chitosan was prepared using Dihydroxy azacrown ether as the crosslinking agent. Its structure was confirmed by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state 13C nuclear magnetic resonance (NMR) analysis, and X‐ray diffraction analysis. Its static adsorption properties for Ag+, Cd2+, Hg2+, and Co2+ were studied. The experimental results showed that the Dihydroxy azacrown ether crosslinked chitosan has good adsorption capacities and high selectivity for adsorption of Ag+ with the coexistence of Hg2+ and Co2+. The selectivity coefficients of crosslinked chitosan are k/ = 5.47, k/ = 4.64, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 530–535, 2002
Quantitative analysis of star‐branched polymers by multidetector size‐exclusion chromatography
Authors: Balke Stephen T. , Mourey Thomas H. , Robello Douglas R. , Davis Tammy A. , Kraus Alexander , Skonieczny Krzysztof
Published: August 2002

The object of this study is to develop multidetector size‐exclusion chromatography (SEC) methods to determine the number of arms per molecule across the molecular size distribution of star‐branched polymers. An empirical fit between the intrinsic viscosity molecular contraction factor g‘ and the number of arms f is used as an alternative to converting g‘ values to root mean square radii ratios used by random walk models. The quantitative analysis of star polymer distributions by SEC is then reduced to understanding factors unique to the accurate measurement of g‘ across the molecular size distribution. Two methods of analyzing SEC data are then tested: (1) the “conventional method” utilizing values of weight‐average molecular weight and intrinsic viscosity at each retention volume and (2) the method of component chromatograms. The latter is a new method useful when only a few different types of branching are present. It depends on fitting each detector's chromatograms as the sum of component chromatograms. Plotting the intrinsic viscosity of the branched polymer versus that of the linear polymer at the same molecular weight was useful for diagnosing problems. The conventional method was defeated by axial dispersion in the narrow chromatograms and the homogeneity of branching in the samples. The component chromatogram method avoids the axial dispersion problem but its value depends on how accurately the component peaks reflected the true situation. In this study, the method provided the most reasonable values when component peaks were grouped together. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 552–570, 2002
Synthesis and properties of poly(ester ether) multiblock copolymers/organomontmorillonite hybrid nanocomposite
Authors: Li Chun‐Cheng , Zhang Dong , Li Zhen‐Yi
Published: August 2002

In this article, poly(ester ether) multiblock copolymer/organomontmorillonite hybrid nanocomposites were prepared via an intercalation polymerization process. The resulting hybrid nanocomposites were characterized by X‐ray diffraction, differential scanning calorimeter, and transmission electron microscopy. The results proved that the organomontmorillonite (organo‐MMT) could be exfoliated into ∼ 50‐nm thickness and dispersed in the poly(ester ether) multiblock copolymer (TPEE) matrix during the intercalation polymerization process. TPEE/organo‐MMT nanocomposites showed excellent mechanical properties compared with the unfilled TPEE. When the organo‐MMT content was about 3–5 wt %, MMT could enhance the strength, modulus, and hardness of TPEE without sacrificing its elongation at break. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1716–1720, 2002; DOI 10.1002/app.10552
Mechanical and morphological properties of white rice husk ash filled polypropylene/ethylene‐propylene‐diene terpolymer thermoplastic elastomer composites
Authors: Siriwardena S. , Ismail H. , Ishiaku U. S. , Perera M. C. S.
Published: August 2002

The performance of white rice husk ash (WRHA) as filler for polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic elastomer (TPE) composites was investigated. The composites with different filler loadings were prepared in a Brabender plasticorder internal mixer. Both unvulcanized and dynamically vulcanized composites were prepared. Mixing and vulcanization processes of the composites were monitored through the typical Brabender torque‐time curves. The mechanical properties and morphology of the composites were also studied. The Brabender torque curves revealed that the dynamic vulcanization process employed was successful and incorporation of filler has no adverse effect on the processibility of the composites. Incorporation of WRHA improves the tensile modulus and flexural modulus and lowers tensile strength, elongation at break, tear strength, and toughness of both types of composites. Dynamic vulcanization significantly enhances the mechanical and TPE properties of the composites. Dynamic mechanical analysis (DMA) study revealed the existence of two phases in both types of composites. It further shows that neither dynamic vulcanization nor filler agglomeration has played a prominent role in the compatibility of the composites. Thermogravimetric investigation shows that dynamic vulcanization or WRHA loading has not adversely affected the thermal stability of the composites. The scanning electron micrographs provide evidence for the tendency to form filler agglomerates with increasing filler loading, better filler dispersion of dynamically vulcanized composites over unvulcanized composites, and effective vulcanization of elastomer phase of the composites in the presence of filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 438–453, 2002
Three‐dimensional imaging of large compressive deformations in elastomeric foams
Authors: Kinney J. H. , Marshall G. W. , Marshall S. J. , Haupt D. L.
Published: August 2002

Specimens of silica‐reinforced polysiloxane foam pads were three‐dimensionally imaged during axial compressive loading to densification. The foams' behavior was highly nonlinear and showed the three characteristic regions of linear elastic, elastic buckling, and densification. A finite‐element technique, based upon conversion of the image voxels to finite elements, was used to calculate the mechanical properties of the foams. The results were compared with conventional mechanical testing and theory. The finite‐element calculations were in excellent agreement with experimental stress–strain data over the entire range of compressive loading. Theoretical models, on the other hand, overestimated the stiffness of the foam above the elastic buckling stress by not correctly predicting the abruptness of the transition from elastic buckling to densification. Three‐dimensional analysis of the deformed microstructures indicated that there was a critical foam density beyond which the cell morphology suddenly changed from open‐celled to closed‐celled and that this “phase”‐like transition was responsible for the abrupt increase in stiffness near densification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1746–1755, 2001
Synthesis and properties of organosoluble polyimide/clay hybrids
Authors: Hsiao Sheng‐Huei , Liou Guey‐Sheng , Chang Li‐Ming
Published: August 2002

A soluble polyimide prepared from 7,7′‐bis(4‐aminophenoxy)‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobichroman and 4,4′‐hexafluoroisopropylidenediphthalic anhydride was mixed with organo‐modified montmorillonite or synthetic mica in N,N‐dimethylacetamide. The content of the clay minerals was 1, 2, and 4 wt %, respectively. Transparent, flexible, and tough films could be cast from the hybrid solutions. The hybrid films were characterized with wide‐angle X‐ray scattering (WAXS), transmission electron microscopy, thermomechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. The WAXS results revealed that the montmorillonite was dispersed more homogeneously than the synthetic mica in the polyimide matrix. In both polyimide/clay hybrids the addition of clay caused thermal expansion coefficients to decrease, and the thermal stability was slightly enhanced. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2067–2072, 2001
Crystallization and nematic–isotropic transition activation energies measured using the Kissinger method
Authors: Sha W.
Published: August 2002

The activation energies for crystallization in poly(3‐hydroxybutyrate) and for nematic–isotropic transition in liquid–crystalline polyesters have been calculated based on data obtained with a dielectric method and differential scanning calorimetry (DSC), respectively. This study explores the feasibility of using a modified Kissinger method to calculate the activation energies of these transitions. It has been found that the activation energy for crystallization in poly(3‐hydroxybutyrate) is 109 kJ/mol. The activation energy for nematic–isotropic transition in the liquid crystals is 487 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2535–2537, 2001
Polymerization of methyl methacrylate with a thermal iniferter: Diethyl 2,3‐dicyano‐2,3‐di(p‐tolyl)succinate
Authors: Qin Shu‐Hui , Qiu Kun‐Yuan , Westmoreland David G. , Lau Willie , Wu Shuguang , Swift Graham
Published: August 2002

A hexa‐substituted ethane type compound, diethyl‐2,3‐dicyano‐2,3‐di(p‐tolyl)succinate (DCDTS), was successfully synthesized and used for initiation of methyl methacrylate (MMA) polymerization. The reaction demonstrated the characteristics of a “living” polymerization; i.e., both the yield and the molecular weight of the resulting polymers increased linearly with increasing reaction time, the molecular‐weight distribution of PMMA obtained was ∼1.60 and almost unaffected by the conversion, and the resultant polymer can be chain extended by adding fresh MMA. End group analysis of the resultant PMMA confirmed that DCDTS behaves as a thermal iniferter for MMA polymerization. A block copolymer was prepared from the resultant PMMA, which contains a hexa‐substituted CC bond functional end group. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2566–2572, 2001
Preparation and physical properties of N‐defunctionalized derivatives of poly(aspartic acid)
Authors: Katritzky Alan R. , Yao Jiangchao , Qi Ming , Qiu Guofang , Bao Weilang , Yang Baozhen , Denisko Olga , Davis Shannon , Zhang Jingen
Published: August 2002

A number of N‐substituted poly(aspartic acid)s was prepared under mild conditions using the silylation–alkylation technique. Their physical properties were studied. Free swelling capacity (FSC) tests were performed for polymers obtained by crosslinking the parent poly(aspartic acid) as well as its defunctionalized derivatives. The hypothesis that H‐bonding is critical in superabsorbency was demonstrated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 85–90, 2001
Preparation and phenol captivating properties of polyvinylpyrrolidone‐montmorillonite hybrid materials
Authors: Gultek Ahmet , Seckin Turgay , Onal Yunus , Icduygu M. Galip
Published: August 2002

Montmorillonite minerals were modified in two distinct steps in order to remove hydroxlated toxicants from the aqueous environment. At first, the montmorillonite minerals were acrylated with the silylating agent γ‐methcaryloxypropyl trimethoxysilane to give a product denoted as TAY‐10. In the second step these materials readily reacted with vinylpyrrolidone to form copolymers covalently bonded to the clay. All hybrid materials were characterized by FTIR spectroscopy, thermogravimetry, X‐ray diffractometry, SEM, and differential thermal analysis. The original montmorillonite structure was maintained for the copolymer modified surfaces. Different loadings of polyvinylpyrrolidone (PVP) were examined to arrive at the optimal conditions for the removal of toxicants from the aqueous environment. The presence of the PVP enhanced the adsorption capacity of the clay toward phenolic compounds from solution as evidenced by the retention percent that was as high as 98.9%. These results demonstrated the feasibility of utilizing a PVP modified clay as a thermally recyclable adsorbent for environmental pollutants. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 512–519, 2001
Crosslinkable positive‐tone photoresist comprising polymers with pendant carboxyl groups
Authors: Liu Jui‐Hsiang , Shi Chih‐Hung , Chen We‐Tin
Published: August 2002

Poly(methacrylic acid‐co‐t‐butylmethacrylate‐co‐bornylmethacrylate) was synthesized and its application to a crosslinkable positive photoresist was investigated. The existence of pendant alicyclic bornyl groups increased the thermostability of copolymers; however, a decrease in the acid‐catalyzed deprotection of pendant t‐butyl groups led to a decrease in the sensitivity of the positive‐tone photoresist. The thermostability of the relief polymeric patterns of the positive‐tone photoresist was appreciably improved effectively because of the acid‐catalyzed dehydration crosslinking of pendant carboxyl groups. Thermogravimetric properties of binder resins, exposure characteristics, and sensitivity and resolution of the photoresist were all investigated. Lithographic evaluation of the curable positive‐tone photoresists was also estimated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1014–1020, 2001
Hydrogel of biodegradable cellulose derivatives. II. Effect of some factors on radiation‐induced crosslinking of CMC
Authors: Wach Radoslaw A. , Mitomo Hiroshi , Yoshii Fumio , Kume Tamikazu
Published: August 2002

The effects of high‐energy radiation on sodium carboxymethylcellulose (CMC) with a degree of substitution of 2.2 were investigated. Moderate CMC concentrations formed hydrogels by intermolecular crosslinking. Significant influences on the results of irradiation, in addition to the concentration, were the dose and dose rate and the presence of oxygen in the surrounding atmosphere. Up to a 95% gel fraction was obtained from 50 and 60% CMC solutions irradiated by an electron beam. CMC hydrogels swelled by absorbing more than 800 g of water per gram of dry gel at a low applied dose. Swelling tests of CMC hydrogels in salt solutions and in media of various pHs showed that the swelling decreased with the salt concentration and was lower at acidic pH values. Radiation yields of crosslinking and scission were calculated on the basis of gel–sol analysis. Crosslinked CMC, in the form of the hydrogel, was degraded by the action of cellulase enzyme, thereby entering the class of environmentally friendly polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3030–3037, 2001
Postpolymerization of quaternary ammonium acrylate polymer produced by electropolymerization
Authors: Lin Thong‐Yueh , Chen Min‐Hua , Chou Tse‐Chuan
Published: August 2002

Postpolymerization of dimethylaminoethylmethacrylate‐methyl chloride (DMAEM‐MC) electropolymerization, with Sn+2/EDTA as initiator, was studied. The factors that affect the stable average molecular weight of the polymer (MW∞) created by postpolymerization were investigated. The results indicate that the major factors affecting the MW∞ are the current density, pHi value, and the [Sn+2]i/[EDTA]i ratio. On the other hand, original reaction temperature, initial initiator concentration, and initial monomer concentration are minor factors affecting the postpolymerization polymer. Increasing the current density decreases the MW∞ at fixed operating conditions. The optimum [Sn+2]i /[EDTA]i ratio to obtain the highest MW∞ mainly depends on the pHi value. At 3.25 and 4.00 pHi values, the optimum [Sn+2]I/[EDTA]i ratio is 5.00. However, at 1.75 and 2.50 pHi values, the optimum ratios are 1.00 and 2.00, respectively. The results also reveal that increasing the original reaction temperature, initial initiator concentration, and initial monomer concentration increases the molecular weight. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1071–1076, 2001
Influence of degree of deacetylation on critical concentration of chitosan/dichloroacetic acid liquid‐crystalline solution
Authors: Dong Yanming , Xu Congyi , Wang Jianwei , Wu Yusong , Wang Mian , Ruan Yonghong
Published: August 2002

We prepared chitosans with various degrees of deacetylation (DDAs) by mixing completely deacetylated chitosan and acetic anhydride at room temperature without serious degradation and O‐substitution. We obtained a standard curve to measure DDA by plotting the IR absorbance ratio of A1560/A2880 against the known DDAs (from 1–100%) of 10 specimens. The effect of DDA on the critical concentration (C*) of chitosan/dichloroacetic acid solutions required to form mesophase was investigated by optical methods. A maximum C* value of 23 wt % appeared at a relative medium DDA (∼20%). The effect was explained by the disordering of chains with medium composition ratios of the copolymer of glucosamine and N‐acetyl glucosamine. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1204–1208, 2002
Use of focal species in marine conservation and management: a review and critique
Authors: Zacharias Mark A. , Roff John C.
Published: August 2002

1. Focal species (i.e. indicators, keystones, umbrellas, and flagships) have been advocated for the management and conservation of natural environments.

2. The assumption has been that the presence or abundance of a focal species is a means to understanding the composition and/or state of the more complex community.

3. We review the characteristics of focal species, and evaluate their appropriateness and utility judged against conservation objectives.

4. It appears that indicator species (of both composition and condition) may be of greatest general utility, and that several types of focal species may exhibit useful indicator properties.

Copyright © 2001 John Wiley & Sons, Ltd.
Conservation of otter (Lutra lutra) in a Mediterranean area: the importance of habitat quality and temporal variation in water availability
Authors: Prenda José , López‐Nieves Pedro , Bravo Rafael
Published: August 2002

1. This study analyses quantitatively the association between habitat characteristics and annual variation in water availability on otter (Lutra lutra L.) distribution in a large Mediterranean area (13 717 km2) in southern Spain.

2. There was a strong positive correlation between habitat quality, estimated after the two first components of a principal component analysis of a matrix of habitat variables×sites, and an index of otter presence/absence, otter presence being most commonly associated with unpolluted and undisturbed sites surrounded by woodland.

3. After univariate analysis, the main freshwater habitat features were statistically different between sites with otters and sites lacking them. In general, otters occurred in medium‐sized fluvial habitats, with high bankside vegetation cover, unpolluted, with low or very low human disturbance and surrounded by forests or dehesas (Mediterranean‐like savannah).

4. Water availability, inferred from the water balance, strongly influenced otter distribution and the type of water body used the most. As water availability increased so did the otter distribution range and during these periods they tended to colonize low‐order streams. During periods of water shortage, otters were usually found in high‐order streams and reservoirs, the only sites that kept water.

5. This work shows that otter distribution in Mediterranean areas is strongly influenced by two factors — man‐induced habitat degradation and natural variability in water availability. The addition of the second factor to the first one introduces additional risks to the survival of otter populations in Mediterranean areas compared with more northerly and humid areas. Copyright © 2001 John Wiley & Sons, Ltd.
Anatomy and three‐dimensional reconstructions of the brain of the white whale (Delphinapterus leucas) from magnetic resonance images
Authors: Marino Lori , Murphy Timothy L. , Deweerd Amy L. , Morris John A. , Fobbs Archibald J. , Humblot Nathalie , Ridgway Sam H. , Johnson John I.
Published: August 2002

Magnetic resonance imaging offers a means of observing the internal structure of the brain where traditional procedures of embedding, sectioning, staining, mounting, and microscopic examination of thousands of sections are not practical. Furthermore, internal structures can be analyzed in their precise quantitative spatial interrelationships, which is difficult to accomplish after the spatial distortions often accompanying histological processing. For these reasons, magnetic resonance imaging makes specimens that were traditionally difficult to analyze, more accessible. In the present study, images of the brain of a white whale (Beluga) Delphinapterus leucas were scanned in the coronal plane at 119 antero‐posterior levels. From these scans, a computer‐generated three‐dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three‐dimensional space, was then resectioned in orthogonal planes to produce corresponding series of “virtual” sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of such structures as the corpus callosum, internal capsule, cerebral peduncles, cerebral ventricles, certain thalamic nuclear groups, caudate nucleus, ventral striatum, pontine nuclei, cerebellar cortex and white matter, and all cerebral cortical sulci and gyri. Anat Rec 262:429–439, 2001. © 2001 Wiley‐Liss, Inc.
Spatial distribution of cell adhesion molecules on the peritoneal surface in the cecal perforation‐induced peritonitis
Authors: Johkura Kohei , Liang Yan , Cui Li , Ogiwara Naoko , Sasaki Katsunori
Published: August 2002

For understanding the immunological functions of the peritoneum, spatial localization of integrins and their ligands was studied by immuno‐SEM on the peritoneal surface of mice with cecal perforation‐induced peritonitis. The cecal peritoneum 24 hr after perforation was stained with specific antibodies against LFA‐1, Mac‐1, VLA‐4, ICAM‐1, VCAM‐1, and fibronectin diluted with cold University of Wisconsin (UW) solution in conjunction with immuno‐gold labeling. The spatial localization of those cell adhesion molecules was detected by backscatter electron (BSE) imaging with field emission scanning electron microscope (FESEM). Numerous leukocytes with diverse surface ultrastructure were observed on the peritoneal surface by FESEM. Some leukocytes were in contact with mesothelial cells, and others adhered to the exposed underlying connective tissue. The BSE imaging showed the ubiquitous distribution of Mac‐1 on all membrane domains of leukocytes, i.e., cell body, ruffles, and microvilli. In contrast, predominant expressions of LFA‐1 and VLA‐4 were discernible on ruffles/microvilli of some leukocytes. The mesothelial cells remaining in the inflamed area expressed both ICAM‐1 and VCAM‐1 on their microvilli. The fibronectin was detected on presumable collagen fibers and/or fibrin over the exposed smooth muscle layer as well as on fibrin extending between leukocyte aggregation. The spatial microlocalization of integrins was clarified on the leukocytes emigrated in peritonitis, and their ligands were detected on the inflamed peritoneum. Anat Rec 264:219–227, 2001. © 2001 Wiley‐Liss, Inc.
Combining and selecting characteristics of information use
Authors: Ruthven Ian , Lalmas Mounia , van Rijsbergen Keith
Published: August 2002

In this article we report on a series of experiments designed to investigate the combination of term and document weighting functions in information retrieval. We describe a series of weighting functions, each of which is based on how information is used within documents and collections, and use these weighting functions in two types of experiments: one based on combination of evidence for ad hoc retrieval, the other based on selective combination of evidence within a relevance feedback situation. We discuss the difficulties involved in predicting good combinations of evidence for ad hoc retrieval, and suggest the factors that may lead to the success or failure of combination. We also demonstrate how, in a relevance feedback situation, the relevance assessments can provide a good indication of how evidence should be selected for query term weighting. The use of relevance information to guide the combination process is shown to reduce the variability inherent in combination of evidence.
An expressive and efficient language for XML information retrieval
Authors: Chinenyanga Taurai Tapiwa , Kushmerick Nicholas
Published: August 2002

Several languages for querying and transforming XML, including XML‐QL, Quilt, and XQL, have been proposed. However, these languages do not support ranked queries based on textual similarity, in the spirit of traditional IR. Several extensions to these XML query languages to support keyword search have been made, but the resulting languages cannot express IR‐style queries such as “find books and CDs with similar titles.” In some of these languages keywords are used merely as boolean filters without support for true ranked retrieval; others permit similarity calculations only between a data value and a constant, and thus cannot express the above query. WHIRL avoids both problems, but assumes relational data. We propose ELIXIR, an expressive and efficient language for XML information retrieval that extends XML‐QL with a textual similarity operator that can be used for similarity joins, so ELIXIR is sufficiently expressive to handle the sample query above. ELIXIR thus qualifies as a general‐purpose XML IR query language. Our central contribution is an efficient algorithm for answering ELIXIR queries that rewrites the original ELIXIR query into a series of XML‐QL queries to generate intermediate relational data, and uses WHIRL to efficiently evaluate the similarity operators on this intermediate data, yielding an XML document with nodes ranked by similarity. Our experiments demonstrate that our prototype scales well with the size of the query and the XML data.
Effect of 0.25 T static magnetic field on microcirculation in rabbits
Authors: Gmitrov Juraj , Ohkubo Chiyoji , Okano Hideyuki
Published: August 2002

We showed previously in rabbits that 0.2 and 0.35 T static magnetic field (SMF) modulated systemic hemodynamics by arterial baroreceptors. We now have measured the effect of 0.25 T SMF on microcirculation within cutaneous tissue of the rabbit ear lobe by the rabbit ear chamber (REC) method. Forty experimental runs (20 controls and 20 SMF) were carried out in eight different rabbits with an equal number of control and SMF experiments on each individual. Rabbits were sedated by pentobarbital sodium (5 mg/kg/h, i.v.) during the entire 80 min experiment. SMF was generated by four neodium‐iron‐boron alloy (Nd2‐Fe14‐B) magnets (15 × 25 × 30 mm, Neomax, PIP ‐ Tokyo Co., Ltd., Tokyo, Japan), positioned around the REC on the observing stage of an optical microscope. The direct intravital microscopic observation of the rabbit's ear microvascular net, along with simultaneous blood flow measurement by microphotoelectric plethysmography (MPPG), were performed PRE (20 min, baseline), DURING (40 min), and POST (20 min) magnetic field exposure. The control experiments were performed under the same conditions and according to the same time course, but without magnetic field. Data were analyzed comparing MPPG values and percent change from baseline in the same series, and between corresponding sections of control and SMF runs. In contrast to control series (100 ± 0.0%–90.0 ± 5.4%–87.7 ± 7.1%, PRE–EXPOSURE–POST), after magnetic field exposure we observed increased blood flow (100 ± 0.0%–117.8 ± 9.6%*–113.8 ± 14.0%, *P < 0.05) which gradually decreased after exposure cessation. We propose that long exposure of a high level nonuniform SMF probably modifies microcirculatory homeostasis through modulation of the local release of endothelial neurohumoral and paracrine factors that act directly on the smooth muscle of the vascular wall, presumably by affecting ion channels or second messenger systems. Bioelectromagnetics 23:224–229, 2002. © 2002 Wiley‐Liss, Inc.
Reactions of keratinocytes to in vitro millimeter wave exposure
Authors: Szabo Imre , Rojavin Mikhail A. , Rogers Thomas J. , Ziskin Marvin C.
Published: August 2002

The effects of millimeter waves (MW) on human keratinocytes were studied in vitro using the HaCaT keratinocyte cell line. MW‐induced modulation of keratinocyte function was studied in proliferation, adhesion, chemotaxis, and interleukin‐1β (IL‐1β) production assays. Spontaneous proliferation, adhesion to tissue culture plate, random migration, and IL‐8‐ and RANTES induced chemotaxis were not affected by exposure of cells to millimeter waves under the following conditions: frequency, 61.22 GHz; SAR, 770 W/kg; duration of exposure, 15–30 min. However, MW irradiation resulted in a modest but statistically significant increase in the intracellular level of IL‐1β. These data suggest that exposure of human skin (with keratinocytes being the major component of epidermis) to MW can cause activation of basal keratinocytes resulting in an elevated level of IL‐1β production. Bioelectromagnetics 22:358–364, 2001. © 2001 Wiley‐Liss, Inc.
Paradox of Bcl‐2 (and p53): why may apoptosis‐regulating proteins be irrelevant to cell death?
Authors: Blagosklonny Mikhail V.
Published: August 2002

Although the Bcl‐2 family members and p53 are involved in the regulation of apoptosis, the status of apoptotic machinery (eg caspases) plays a major role in determining the mode and timing of cell death. If the apoptotic machinery is lost, inhibited, or intrinsically inactivated, the “death stars”, Bcl‐2 and p53, may become irrelevant to cell death. In this light, high levels of Bcl‐2 may indicate that downstream apoptotic pathways are still functional. This explains why Bcl‐2 overexpression can be a marker of chemosensitivity and favorable prognosis in certain cancers and why retention of wild‐type p53 may manifest inactivation of caspases in aggressive cancers. BioEssays 23:947–953, 2001. © 2001 John Wiley & Sons, Inc.
Near‐IR spectroscopic imaging for skin hydration: The long and the short of it
Authors: Attas E. Michael , Sowa Michael G. , Posthumus Trevor B. , Schattka Bernhard J. , Mantsch Henry H. , Zhang Shuliang L.
Published: August 2002

Near‐IR spectroscopic methods have been developed to determine the degree of hydration of human skin in vivo. Noncontact reflectance spectroscopic imaging was used to investigate the distribution of skin moisture as a function of location. A human study in a clinical setting has generated quantitative data showing the effects of a drying agent and a moisturizer on delineated regions of the forearms of eight volunteers. Two digital imaging systems equipped with liquid‐crystal tunable filters were used to collect stacks of monochromatic images at 10‐nm intervals over the 650–1050 and 960–1700 nm wavelength bands. Synthetic images generated from measurements of water absorption band areas at three different near‐IR wavelengths (970, 1200, and 1450 nm) showed obvious differences in the apparent distribution of water in the skin. Changes resulting from the skin treatments were much more evident in the long‐wavelength images than in the short‐wavelength ones. The variable sensitivity of the method at different wavelengths has been interpreted as being the result of different penetration depths of the IR light used in the reflectance studies. © 2002 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 67: 96–106, 2002
Peroxidase activity of in vitro‐selected 2′‐amino RNAs
Authors: Teramoto Naozumi , Ichinari Hisashi , Kawazoe Naoki , Imanishi Yukio , Ito Yoshihiro
Published: August 2002

Peroxidase activities of RNAs containing 2′‐amino groups, which were selected as aptamers binding to N‐methylmesoporphyrin IX, were investigated. Some clones promoted the oxidation reaction of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) with hydrogen peroxide (H2O2) in the presence of iron(III)‐protoporphyrin (hemin), whereas others did not. Each of them had a different substrate specificity. One of the active clones promoted the oxidation of o‐dianisidine and β‐nicotinamide adenine dinucleotide reduced form (NADH) with H2O2 5 and 15 times faster than hemin only, respectively. On the other hand, one clone that was inactive on oxidation of ABTS exhibited the same level of activity on oxidation of o‐dianisidine as that shown by the clone active on ABTS but no activity on NADH. By in vitro selection, we can produce various types of peroxidase‐like non‐natural RNAs. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 463–468, 2001.
The effect of dissolved oxygen (DO) concentration on the glycosylation of recombinant protein produced by the insect cell–baculovirus expression system
Authors: Zhang Fuming , Saarinen Mark A. , Itle Laura J. , Lang Sybil C. , Murhammer David W. , Linhardt Robert J.
Published: August 2002

The effect of dissolved oxygen concentration on human secreted alkaline phosphatase (SEAP) glycosylation by the insect cell–baculovirus expression system was investigated in a well‐controlled bioreactor. Oligomannose‐type N‐linked glycans (i.e., Man2 to Man6 and Man3F) were present in SEAP produced by Spodoptera frusiperda Sf‐9 (Sf‐9) and Trichoplusia ni BTI‐Tn‐5B1‐4 (Tn‐5B1‐4) insect cell lines. The relative amounts of the most highly processed glycans (i.e., Man3F and Man2 in the SEAP from Sf‐9 and Tn‐5B1‐4 cells, respectively) were significantly higher at 50% of air saturation than at either 10% or 190% of air saturation. That is, glycan processing was inhibited at both low and high dissolved oxygen concentrations. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 219–224, 2002.
A GFP‐based screen for growth‐arrested, recombinant protein‐producing cells
Authors: Yuk Inn H. Y. , Wildt Stefan , Jolicoeur Mario , Wang Daniel I. C. , Stephanopoulos Gregory
Published: August 2002

The growth of anchorage‐dependent Chinese hamster ovary (CHO) cells is arrested upon serum deprivation; however, a portion of these cells remain viable for extended time periods in serum‐free culture. This work presents a strategy to both rapidly generate a heterogeneous population of CHO cells as well as to select for subpopulations that remain robust and continue to produce recombinant protein when their growth is arrested. Stable expression of recombinant proteins in mammalian cells is often a tedious and time‐consuming process because only a small percentage of transfected cells will express sufficient quantities of protein. To overcome the limitations associated with standard transformation and selection methods, bicistronic retroviral expression technology was used. First, bicistronic retroviral constructs encoding for both interferon gamma (IFN‐γ), the model therapeutic protein, and green fluorescent protein (GFP), the quantitative selectable marker, were generated. Next, recombinant retroviruses were obtained from transient transfection of a helper‐cell line and were used to infect susceptible CHO cells. Cells with the bicistronic expression module stably integrated into their genome fluoresce green and could thereby be easily isolated by fluorescence‐activated cell sorting. Upon subjecting successfully infected cells to serum withdrawal, significant declines in cell viability and GFP expression occurred. After imposing this selection pressure on the cells for 8 days, GFP producers were isolated from the survivors by fluorescence‐activated cell sorting and expanded. To evaluate the effectiveness of the screening process, the selected cells were exposed to a second round of serum deprivation. Unlike the original cell population from which it was derived, the subpopulation remained robust and continued to stably express both GFP and IFN‐γ throughout the extended period of serum‐free culture. Within 2 weeks, cells selected for recombinant protein production under serum‐free conditions were successfully generated and isolated. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 79: 74–82, 2002.