bluuebunny/crossref_metadata_2025 huggingface dataset:
Blue‐emitting poly[(m‐phenylene vinylene)‐alt‐(o‐phenylene vinylene)]s: The effect of regioregularity on the optical properties
Authors: Liao Liang , Pang Yi , Ding Liming , Karasz Frank E.
Published: July 2003

Poly[(m‐phenylene vinylene)‐alt‐(o‐phenylene vinylene)]s with different contents of cis‐/trans‐CHCH (3 and 6) have been synthesized through Wittig condensation. The polymers exhibit good solubility in common organic solvents such as toluene and tetrahydrofuran. A comparison of the optical properties has been made between 3 and its phenyl regioisomers containing either p‐phenylene or m‐phenylene units. The results show that the regiochemistry of the phenyl ring can be a useful tool for tuning the emission color of π‐conjugated polymers because the extension of π conjugation can only partially be achieved through an o‐phenylene bridge. Although both polymers 3 and 6 exhibit comparable low fluorescence quantum efficiencies (≈0.18) in solution, their films are highly luminescent, showing a broad emission band near 456 nm (blue color). Electroluminescence results show that the device of polymer 3, which has a higher content of trans‐CHCH linkages, is about 20 times more efficient than that of 6. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2650–2658, 2003
Monomer reactivity ratios and glass‐transition temperatures of copolymers based on dimethyl amino ethyl methacrylate and two structural hydroxy‐functional acrylate isomers
Authors: Martín‐Gomis L. , Cuervo‐Rodriguez R. , Fernández‐Monreal M. C. , Madruga E. L. , Fernández‐García M.
Published: July 2003

Two chemical structural isomers, 2‐hydroxyethyl methacrylate and ethyl α‐hydroxymethyl acrylate, were copolymerized with dimethyl amino ethyl methacrylate in bulk at 50 °C with 1.0 × 10−2 mol/L 2,2′‐azobisisobutyronitrile as an initiator. Experiments showed differences in the values of the monomer reactivity ratios due to electronic or steric contributions to the cross‐propagation reaction. The homopolymer glass‐transition temperature (Tg), along with the intramolecular and intermolecular structure and Johnston's equation, enabled a description of the experimental variations of the copolymer Tg. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2659–2666, 2003
Cationic polymerization of styrene on the surface of graphite expanded
Authors: Wang Wen‐Ping , Pan Cai‐Yuan
Published: July 2003

Cationic polymerization of styrene initiated by the CO+ClO group on the surface of expanded graphite (EG) was carried out for modifying the surface properties of graphite. The initiating sites were achieved by the reaction of EG with SOCl2 and followed by AgClO4. Subsequently, the cationic polymerization of styrene was conducted to afford polystyrene brush on EG. The influence factors, such as polymerization time and temperature, on the polymerization including the grafting ratio and efficiency were investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2715–2721, 2003
Characterization and properties of chemically modified Corchorus capsularis jute fiber via pulping and grafting: Infrared, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, X‐ray diffraction, biodegradation, and superabsorbency
Authors: Sahoo Prafulla K. , Rana Pradeep K. , Sarkar Nandalal Deb , Sahoo Anusmita , Swain Sarat K.
Published: July 2003

Jute fiber (Corchorus capsularis, JRC‐321 variety), an environmentally and ecologically friendly product, was chemically modified by the cooking alkaline sulfite process to unbleached and bleached pulps, which were further modified via graft copolymerization with acrylamide monomer with a complex initiating system: CuSO4/glycine/KHSO5. The above samples were characterized and morphologically analyzed by IR, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and X‐ray diffraction. The biodegradability and superabsorbency of the samples were also evaluated for their novel commercial importance as jute‐based superabsorbents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2696–2703, 2003
Ring‐opening polymerization and block copolymerization of L‐lactide with divalent samarocene complex
Authors: Cui Dongmei , Tang Tao , Bi Wuguo , Cheng Jianhua , Chen Wenqi , Huang Baotong
Published: July 2003

Divalent samarocene complex [(C5H9C5H4)2Sm(tetrahydrofuran)2] was prepared and characterized and used to catalyze the ring‐opening polymerization of L‐lactide (L‐LA) and copolymerization of L‐LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L‐LA was retained. The structure of the block copolymer of CL/L‐LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)‐b‐P(L‐LA) copolymer were monitored with real‐time hot‐stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL‐b‐P(L‐LA) copolymer was demonstrated through AFM observation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2667–2675, 2003
Controlled/living polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with tert‐butyl methacrylate by atom transfer radical polymerization
Authors: Gan Leong‐Huat , Ravi Palaniswamy , Mao Bao Wei , Tam Kam‐Chiu
Published: July 2003

Polymerization of 2‐(diethylamino)ethyl methacrylate (DEAEMA) via homogeneous atom transfer radical polymerization under various reaction conditions is described. The effects of the initiators and solvents were examined. With 1,1,4,7,10,10‐hexamethyl triethylenetetramine/copper(I) chloride/p‐toluenesulfonyl chloride as the ligand/catalyst/initiator system in methanol, poly(DEAEMA) with a polydispersity index as low as 1.07 was synthesized. Kinetic studies demonstrated the polymerization was very well controlled and exhibited the living characteristic of the process. Well‐defined block copolymers of DEAEMA and tert‐butyl methacrylate (tBMA) were successfully synthesized. The copolymers could be synthesized with equally good results by starting with either p(DEAEMA) or p(tBMA) as the macroinitiators. However, only the macroinitiators terminated with chlorine should be used. The corresponding macroinitiators with bromine as a transferable group did not yield well‐defined copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2688–2695, 2003
Synthesis and properties of fluorosilicone with perfluorooctylundecyl side chains
Authors: Furukawa Y. , Yoneda T.
Published: July 2003

A series of fluorosilicone (FLS) homopolymers with 4,4,5,5,6,6,7,7,8,8, 9,9,10,10,11,11,11‐heptadecafluoroundecylmethylsiloxane [C8F17CH2CH2CH2(CH3) SiO; HDFUSiO] and copolymers based on dimethylsiloxane [(CH3)2SiO] were prepared by the hydrosilylation of 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11‐heptadecafluoro‐1‐undecene (C8F17CH2CHCH2) with poly(hydromethylsiloxane)s. Thermal characterization showed that the decomposition of fluoroalkyl side chains occurred at about 245 °C. Side‐chain crystallization was observed for FLSs with more than 30 mol % HDFUSiO. The refractive index decreased with increasing HDFUSiO content. The dielectric constant increased with increasing HDFUSiO content. The liquid surface tension of the FLS containing 10 mol % HDFUSiO was as low as that of the highly fluorinated FLSs. FLSs with HDFUSiO and trichlorosilylethyl side chains (Cl3SiCH2CH2) were also prepared so that their solid surface tension (surface free energy) could be measured. The surface free energy of these FLSs decreased with increasing Cl3SiCH2CH2 content, but the sliding angle of a water droplet and the contact‐angle hysteresis adversely increased. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2704–2714, 2003
Thermotropic liquid‐crystalline polymers containing five‐membered heterocyclic groups. X. Relationships between structures of semirigid polyesters based on three disubstituted 2,5‐diphenyl‐1,3,4‐thiadiazoles and thermotropic liquid‐crystalline and optical properties
Authors: Sato Moriyuki , Nakashima Shinji , Uemoto Yuko
Published: July 2003

Thermotropic liquid‐crystalline (LC) semirigid polyesters based on three terphenyl analogues of 1,3,4‐thiadiazole (2,5‐diphenyl‐1,3,4‐thiadiazole)s (DPTD) linking undecamethyleneoxy chain at different substituted positions were synthesized from three disubstituted (4,4′‐, 3,4′‐, and 3,3′‐) dioxydiundecanols of DPTD and four diesters, and the relationships between polymer structures and LC and optical properties were investigated. DSC measurements, texture observations, and wide‐angle X‐ray analyses revealed that the polymers composed of DPTD moiety having a more linear molecular structure and 1,4‐phenylene unit or short aliphatic chain tend to exhibit LC smectic C and/or A phases. The following observations were made: (1) the emergence of smectic C and/or A phases in all the polymers on the basis of 4,4′‐disubstituted DPTD, (2) formation of enantiotropic smectic C and/or A phases in the polymers containing a 1,4‐phenylene unit in the main chain, (3) formation of a more stable smectic C phase in the polymers having a short aliphatic [(CH2)4] chain, and (4) a decrease of the mesomorphic property of the polyesters in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD. Solution and solid‐state ultraviolet–visible and photoluminescent spectra indicated that all the polyesters display maximum absorbances and blue emissions arising from the DPTD moiety, whose peak maxima were shifted to lower wavelengths in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD as well as the aforementioned LC property. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2676–2687, 2003
Direct copolymerization of sulfonated poly(phthalazinone arylene ether)s for proton‐exchange‐membrane materials
Authors: Gao Yan , Robertson Gilles P. , Guiver Michael D. , Jian Xigao , Mikhailenko Serguei D. , Wang Keping , Kaliaguine Serge
Published: July 2003

Sulfonated poly(phthalazinone ether ketone) (SPPEK) copolymers and sulfonated poly(phthalazinone ether sulfone) (SPPES) copolymers containing pendant sodium sulfonate groups were prepared by direct copolymerization. The reaction of disodium 3,3′‐disulfonate‐4,4′‐difluorobenzophenone (SDFB‐Na), 4,4′‐difluorobenzophenone (DFB), and 4‐(4‐hydroxyphenyl)‐1(2H)‐phthalazinone (DHPZ) at 170 °C in N‐methyl‐2‐pyrrolidione containing anhydrous potassium carbonate gave SPPEKs. SPPESs were similarly obtained with 3,3′‐disulfonate‐4,4′‐difluorophenyl sulfone, 4‐fluorophenyl sulfone (DFS), and DHPZ as monomers. The sulfonic acid groups, being on deactivated positions of the polymer backbone, were expected to be hydrolytically more stable than postsulfonated polymers. Fourier transform infrared and 1H NMR were used to characterize the structures and degrees of sulfonation of the sulfonated polymers. Membrane films of SPPEKs with SDFB‐Na/DFB molar feed ratios of up to 60/40 and SPPESs with sulfonated 4‐fluorophenyl sulfone/DFS molar feed ratios of up to 50/50 were cast from N,N‐dimethylacetamide polymer solutions. Membrane films in acid form were then obtained by the treatment of the sodium‐form membrane films in 2 N sulfuric acid at room temperature. An increase in the number of sulfonate groups in the copolymers resulted in an increased glass‐transition temperature and enhanced membrane hydrophilicity. The sodium‐form copolymers were thermally more stable than their acid forms. The proton conductivities of the acid‐form copolymers with sulfonated monomer/unsulfonated monomer molar feed ratios of 0.5 and 0.6 were higher than 10−2 S/cm and increased with temperature; they were less temperature‐dependent than those of the postsulfonated products. SPPESH‐50 showed higher conductivity than the corresponding postsulfonated poly(phthalazinone ether sulfone). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2731–2742, 2003
Synthesis and characterization of poly(diethylsiloxane) and its copolymers with different diorganosiloxane units
Authors: Liu Lihua , Yang Shiyan , Zhang Zhijie , Wang Qian , Xie Zemin
Published: July 2003

Poly(diethylsiloxane) and its copolymers with various kinds of R1R2SiO (R1 = R2 = methyl or phenyl, or R1 = methyl and R2 = phenyl) units have been prepared by the equilibrium polymerization of cyclosiloxanes. All the polymers have been characterized by 1H and 29Si NMR, gel permeation chromatography, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The results indicate that a random distribution of different units has been obtained in the structures of copolymers containing 50 mol % diethylsiloxane units content. DSC and DMA show that the presence of 2.5 mol % diphenylsiloxane units or 5.0 mol % methylphenylsiloxane units in the copolymer can disrupt the crystallinity and lead to noncrystalline copolymers with low glass‐transition temperatures (ranging from −133 to −137 °C according to DSC). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2722–2730, 2003
Methane plasma polymerization by low‐temperature cascade arc discharge for enhanced adhesion of primer to thermoplastic olefins
Authors: Lin Yung‐Sen , Yasuda Hirotsugu K.
Published: July 2003

Improvement of primer adhesion to thermoplastic olefins (TPOs) by methane plasma polymerization with a low‐temperature cascade arc discharge was investigated. Methane plasma with a low‐temperature cascade arc plasma torch can be used for improving the primer adhesion to TPOs. Tape‐adhesion tests (ASTM 3359‐92a method) demonstrated this improvement, with a rating of 0 for untreated TPOs and 5 for methane plasma‐polymerized TPOs at certain plasma conditions even for aging at 60 °C and 80% relative humidity for 5 days. The adhesion to primer for the soft, flexible TPOs (ETA‐3041c and ETA‐3101) was easily enhanced. The adhesion to primer for the hard and brittle TPOs (ETA‐3183) needs to optimize the plasma conditions to pass the dry‐ and wet‐adhesion test with methane plasmas. To relate the surface characteristics of methane plasma‐polymerized TPOs to adhesion performance with primer, the wettability and polarity of TPOs were evaluated by the contact‐angle measurements of primer and deionized water to TPOs. TPO surface morphology was evaluated with scanning electron microscopy. The surface composition was characterized with electron spectroscopy for chemical analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2004–2021, 2003
Spherulite morphology studies of N‐alkyl chitosan films cast from formic acid solutions
Authors: Dong Yanming , Sakurai Kensuke , Wu Yusong , Kondo Yukie
Published: July 2003

The films of N‐ethyl chitosan were prepared via the solution‐casting technique with formic acid as a solvent. The solutions with different concentrations (35 and 40 wt %) were prepared previously from dilute solution (1 wt %) via evaporating process. The crystalline morphology of these films was investigated by means of polarized optical microscopy and scanning electron microscopy. Normal spherulites with a low growth rate formed in the casting films. The different morphologies of spherulite appeared in the films cast from the solutions with different concentrations. After further crystallizing for a few days, the spherulites were decorated by thousands of needlelike extended‐chain crystals, which had a typical size of ∼50 μm (length) × 2∼5 μm (width) × 1∼2 μm (height) in the central part of the spherulite, but a typical size of ∼5 μm (lenght)× 1∼2 μm (width) × 1∼2 μm (height) in the fringe part of the spherulite. The real concentration for crystallization was determined to be 65–82 wt%. Thus, the crystallization actually appeared in supersaturated solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2033–2038, 2003
Determination of the rheological behavior of epoxy–amine thermosets by dynamic mechanical analysis: Isothermal methods versus nonisothermal methods
Authors: Cuevas J. M. , Laza J. M. , Correa M. , Vilas J. L. , Rodríguez M. , León L. M.
Published: July 2003

The reticulation process of an epoxy resin using an amine as a cure agent was studied at different temperatures and concentrations of the cure agent with dynamic mechanical thermal analysis. The study was performed under both isothermal and nonisothermal conditions, and a temperature–time–transformation diagram was obtained. The measurements from the two modes gave similar results, although the nonisothermal mode required fewer experiments. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1965–1977, 2003
Characterization of the interaction of poly(ethylene oxide) with nanosize fumed silica: Surface effects on crystallization
Authors: Ding Jiang , Maitra Prithwiraj , Wunder Stephanie L.
Published: July 2003

Poly(ethylene oxide) (PEO) of 4600 molar mass (PEO‐4600) was crystallized from methanol in the presence of hydrophilic fumed silicas (A380, A200, and OX50) with nominal surface areas of 380, 200, and 50 m2/g and a hydrophobic fumed silica (R812s) modified with methyl groups. The composites were characterized by thermogravimetric analysis and differential scanning calorimetry. The inhibition of crystallization and the tendency for chain reorganization after melting were in the order of A380 > A200 > OX50 > R812s, respectively, that is, both were least for the hydrophobic silica and increased with increasing specific surface area for the hydrophilic silica. The interaction of PEO with the silica increased in the melt state as compared with the solution‐cast samples, resulting in enhanced suppression of crystallization. The following took place at a high silica content: (1) crystallization occurred at crystallization temperatures [Tc < Tc (bulk)], suggesting that the silica inhibited crystallization; (2) crystallites with melt temperatures [Tm < Tm (bulk)] were observed, indictive of smaller and/or less perfect crystals; and (3) melt entropies [ΔSm (surface) < ΔSm (bulk)] suggested that the interaction of surface silanols, SisOH, with PEO decreased both the melt entropy and crystallite size/perfection. Crystallinity was observed in solution‐cast composites when there were greater than ∼0.03 PEO molecules/nm2 for native and ∼0.01 PEO molecules/nm2 for methylated fumed silica, similar to reported plateau equilibrium adsorption values from methanol. These results were consistent with a model in which PEO interacted more strongly with native fumed silica as compared with hydrophobically modified silica because of hydrogen bonding of the ether oxygens of PEO with the acidic silanols, preventing chain mobility and crystallization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1978–1993, 2003
Block copolymer modified novolac epoxy resin
Authors: Guo Qipeng , Dean Jennifer M. , Grubbs Robert B. , Bates Frank S.
Published: July 2003

The phase behavior of uncured and cured mixtures containing stoichiometric amounts of Epon164 novolac epoxy resin and 4,4′‐methylenedianiline combined with a nearly symmetric poly(methyl acrylate‐co‐glycidyl methacrylate‐b‐polyisoprene) diblock copolymer was investigated with small‐angle X‐ray scattering and transmission electron microscopy. A series of morphologies were documented as a function of the copolymer concentration, which ranged from pure diblock to 2.5 wt % in the thermoset resin. Ordered lamellae bordered a wide multiphase region followed by disordered wormlike micelles that transformed continuously into vesicles at the lowest compositions. The thermal curing of this pentafunctional epoxy system to complete conversion had little impact on the phase behavior of the mixtures, and this was consistent with previous experiments with difunctional epoxy and the same hardening agent. However, changing the epoxy component led to gross changes in the phase behavior that were interpreted with the concept of a wet‐to‐dry brush transition. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1994–2003, 2003
Effect of surface‐grafted ionic groups on the performance of cellulose‐fiber‐reinforced thermoplastic composites
Authors: Cai Xiaolin , Riedl Bernard , Ait‐Kadi A.
Published: July 2003

The influence of the surface chemistry of the cellulose fiber and polymer matrix on the mechanical and thermal dynamic mechanical properties of cellulose‐fiber‐reinforced polymer composites was investigated. The cellulose fiber was treated either with a coupling agent or with a coupling‐agent treatment followed by the introduction of quaternary ammonium groups onto the fiber surface, whereas the polymer matrix, with opposite polar groups such as polystyrene incorporated with sulfonated polystyrene and poly(ethylene‐co‐methacrylic acid), was compounded with the fiber. The grafting of the fiber surface was investigated with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Experimental results showed that an obvious improvement in the mechanical strength could be achieved for composites with an ionic interface between the fiber and the polymer matrix because of the adhesion enhancement of the fiber and the matrix. The improved adhesion could be ascribed to the grafted ionic groups at the cellulose‐fiber surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2022–2032, 2003
Characterization of polyethylene with partially random chlorine substitution
Authors: Stephens C. H. , Yang H. , Islam M. , Chum S. P. , Rowan S. J. , Hiltner A. , Baer E.
Published: July 2003

A series of chlorine‐containing polymers were prepared by ring‐opening metathesis polymerization (ROMP) followed by hydrogenation. This synthesis route was chosen specifically so that chain microstructures would be obtained that resembled copolymers of ethylene and vinyl chloride. The chlorine content was varied by the copolymerization of 5‐chlorocyclooctene and cyclooctene. Differential scanning calorimetry, light microscopy, tapping‐mode atomic force microscopy, wide‐angle X‐ray diffraction (WAXD), and density were employed to characterize the polymers. The copolymers had certain restrictions on the length of the methylene sequence between substituted carbons, however, ROMP copolymerization introduced enough variation in the methylene sequence length that model copolymers with the equivalent of 14 mol % vinyl chloride or less closely resembled random copolymers of ethylene and vinyl chloride. These materials organized as spherulites and exhibited the orthorhombic crystal form. Constraints on the placement of chlorine atoms strongly affected the crystallization of polymers with more than the equivalent of 14 mol % vinyl chloride. More regular chlorine substitution along the polyethylene chain translated into better ordered crystal structures with sharp melting peaks. The granular morphology of these materials at ambient temperature was interpreted as fringed micellar crystals. The WAXD patterns provided definitive evidence that chains in the fringed micelle took the hexagonal crystal form. The lower density hexagonal form facilitated the crystallization of short ethylene sequences and accommodated chlorine atoms more easily than the orthorhombic form. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2062–2070, 2003
Solidlike transition of melt‐intercalated biodegradable polymer/clay nanocomposites
Authors: Lim Sung T. , Lee Chung H. , Choi Hyoung J. , Jhon Myung S.
Published: July 2003

Synthetic biodegradable aliphatic polyester (BAP) intercalated into organoclay was prepared by melt compounding, and its solidlike characteristics were investigated via several rheological test modes: steady shear rotation, oscillation, and creep testing. Structural investigations with X‐ray diffraction and transmission electron spectroscopy were also performed for a better understanding of the characteristic rheological behaviors. The creep, recovery, and stress modulus exhibited a solidlike transition of BAP/clay nanocomposites that depended on the clay content. An increase in the zero shear rate viscosity and a shifting of the crossover point (storage modulus vs loss modulus) to a lower frequency were also observed with increasing clay contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2052–2061, 2003
Electrical and mechanical behavior of filled elastomers. I. The effect of strain
Authors: Yamaguchi K. , Busfield J. J. C. , Thomas A. G.
Published: July 2003

Electrical and mechanical property tests have been used to examine the changes in the carbon black network structure that occur in a filled elastomer at large strains in tension and compression. These changes have been examined both in materials that have no previous loading history and in test pieces that have been subjected to a specific known prestrain. When a previously unstrained, filled elastomer specimen is stretched to moderate extensions, the electrical resistivity increases. This is ascribed to the breakdown of the carbon black network structure. At higher tensile extensions, the resistivity decreases. This reduction in the electrical resistivity is attributed to the alignment of the shaped carbon black aggregates under strain. During unloading, the resistivity behavior is different from that during loading, with the final unloaded electrical resistivity being significantly higher than that measured in the unstrained elastomer. This dramatic change in the electrical properties after unloading is in marked contrast to the relatively modest changes observed in the mechanical behavior. After the first cycle, the electrical behavior becomes much more reversible, and this indicates that the bulk of the damage experienced by the carbon black network is developed during the first cycle. After unloading from a large strain, the electrical anisotropy is small, whereas the mechanical anisotropy is more marked. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2079–2089, 2003
Depth profile analysis of polyimide film treated by potassium hydroxide
Authors: Okumura H. , Takahagi T. , Nagai N. , Shingubara S.
Published: July 2003

The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003
Specific reversible melting of polymers
Authors: Androsch R. , Wunderlich B.
Published: July 2003

Temperature‐modulated differential scanning calorimetry can detect a certain amount of reversible latent heat in flexible macromolecules. In short, one can identify a reversible melting in such polymers earlier thought to exhibit only fully irreversible crystallization and melting. Details of the reversible melting of isotactic polypropylene and ethylene‐1‐octene copolymers of low and medium densities have newly been measured and linked to the crystallization, annealing, or melting temperature. It is possible to assign the experimental reversibility of melting to specific crystal fractions that ultimately melt irreversibly at higher temperatures; that is, it is suggested that reversible melting mainly occurs only between the temperatures of their formation and their zero‐entropy‐production melting temperature, at which they change to a melt of the same degree of metastability. This is supported by the almost complete absence of reversibility below the temperature of crystal formation and the observation of a distinct relationship between the amount of irreversibly by annealing reorganized material and reversibility in the case of isotactic polypropylene. A given crystal fraction, characterized by its formation temperature and zero‐entropy‐production melting temperature, has a specific reversibility of the melt‐to‐crystal transition, which is represented by the ratio of the reversible latent heat to the total enthalpy change when the crystal fraction of interest ultimately melts. This specific reversibility is, for ethylene‐1‐octene copolymers, at least 25% at temperatures in the primary crystallization range, and this indicates that the reversible contribution to the total of the melting processes is much larger than expected from simple calculations by the excess apparent reversible heat capacity being referred to the heat of fusion of the polymer, as is commonly done. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2039–2051, 2003
In vivo preservation of steroid specificity in CWR22 xenografts having a mutated androgen receptor
Authors: Shao Tsang C. , Li Huiling , Eid Wael , Ittmann Michael , Unni Emmanual , Cunningham Glenn R.
Published: July 2003

Background

In vitro studies of CWR22 tumor cells lack steroid specificity. We sought to determine if CWR22 xenografts also lack steroid specificity.

Methods

We injected castrated nude mice with CWR22 tumor cells (6 × 106 cells) and implanted Alzet osmotic pumps that delivered approximately 1 mg steroid/kg body weight/day.

Results

Serum PSA levels were detectable in intact mice and castrated mice treated with testosterone (T), but not in those treated with estradiol (E2), progesterone (P), or flutamide (F). T maintained mean tumor weight similar to that in intact mice (P = NS). We observed no tumors in castrated mice or mice treated with E2, P, or F, and tumor histology was consistent with weights.

Conclusions

The mutation of the androgen receptor (H874Y) that occurs in the CWR22 xenograft model of human prostate cancer does not significantly affect in vivo steroid specificity for E2, P, or F. Prostate 57: 1–7, 2003. © 2003 Wiley‐Liss, Inc.
Possibility of re‐screening intervals of more than one year in men with PSA levels of 4.0 ng/ml or less
Authors: Ito Kazuto , Yamamoto Takumi , Ohi Masaru , Takechi Hiroyuki , Kurokawa Kohei , Suzuki Kazuhiro , Yamanaka Hidetoshi
Published: July 2003

BACKGROUND

The optimal re‐screening interval is one of the most important issues to evaluate the effectiveness of screening for prostate cancer.

METHODS

Between 1992 and 2000, 7,026 men aged 50–78 with baseline PSA levels of 4.0 ng/ml or lower underwent screening for prostate cancer twice or more. The risk of developing prostate cancer relative to elapsed years and baseline PSA levels were investigated.

RESULTS

Prostate cancer was detected in a total of 127 cases (1.8%). The detection rate of prostate cancer was high between 1.6% and 5.5% at 1 year after baseline PSA measurements in men with baseline PSA levels of 2.1–4.0 ng/ml. In men with baseline PSA levels of 1.1– 2.0 ng/ml, the detection rate increased from 0.06% to 1.02% with passed years. The proportion of stage ≥T3 was high at 63% in prostate cancer cases detected between 3 and 4 years after baseline PSA levels being 1.1–2.0 ng/ml. In men with baseline PSA levels of 1.0 or lower, the cumulative detection rate of prostate cancer was low at 0.01% within 3 years, however, the detection rate increased to 0.34% after 5 or more years from baseline PSA measurements.

CONCLUSIONS

The re‐screening interval was recommended to be 1, 1–2, and 3–5 years for men with baseline PSA levels of 2.1–4.0 ng/ml, 1.1–2.0 ng/ml, and 1.0 ng/ml or lower, respectively. Prostate 57: 8–13, 2003. © 2003 Wiley‐Liss, Inc.
Apoptosis levels increase after castration in the CWR22 human prostate cancer xenograft
Authors: Smitherman Andrew B. , Gregory Christopher W. , Mohler James L.
Published: July 2003

Background

The role of apoptosis in the regression of human prostate cancer after androgen deprivation therapy remains controversial. Detection of caspase‐3, an ubiquitous effector of apoptosis, is a highly specific technique for in vivo evaluation of apoptosis.

Methods

Apoptotic rates were evaluated in the androgen‐dependent CWR22 human prostate cancer xenograft in tumors that represented time points throughout the progression from androgen‐stimulated to recurrent prostate cancer. Caspase‐3 levels in formalin‐fixed, paraffin‐embedded specimens were quantified using immunohistochemical detection and video image analysis. Western blot analysis was used to confirm the results of immunodetection.

Results

Expression of caspase‐3 reached a maximum on day 2 after castration, decreased on day 6, and remained low until tumor recurrence. The percentage of tumor area expressing caspase‐3 increased from 2.51 ± 0.44% in tumors from intact mice to 20.84 ± 1.75% on day 2 after castration. Among immunopositive cells, the intensity of caspase‐3 expression measured using the mean optical density (MOD) increased 45% (0.3762 ± 0.003 to 0.5461 ± 0.001) on day 2 after castration compared to levels detected in tumors from intact mice.

Conclusions

Apoptosis contributes to tumor regression after castration in the CWR22 human prostate cancer xenograft model. Prostate 57: 24–31, 2003. © 2003 Wiley‐Liss, Inc.
Extensive analysis of the 13q14 region in human prostate tumors: DNA analysis and quantitative expression of genes lying in the interval of deletion
Authors: Latil Alain , Chêne Laurent , Mangin Philippe , Fournier Georges , Berthon Philippe , Cussenot Olivier
Published: July 2003

BACKGROUND

Loss of heterozygosity (LOH) on chromosome arm 13q14 is one of the most consistent genetic alterations in sporadic prostate cancer. This alteration may be involved in prostate oncogenesis through inactivation of one or more tumor suppressor genes (TSGs). Candidate gene expression is an approach to focus the search for TSGs in this region.

METHODS

We tested 41 human sporadic prostate tumors for 13q14 LOH by using seven polymorphic markers overlapping the critical region and used a real‐time quantitative RT‐PCR assay to study the same tumors for expression of the 31 genes located in this genomic region (localized by the Human Genome Project Working Draft).

RESULTS

Allelic loss on at least one locus was found in 18 (41%) of the 41 tumor DNAs. Only four genes (ITM2B, CHC1L, KIAA0970, and LOC51131), located in the region most frequently deleted in prostate carcinoma, showed a significant difference in expression between normal and neoplastic prostate tissues.

CONCLUSIONS

Given their location in the LOH hotspot, as indicated by our genomic analysis, ITM2B, CHC1L, KIAA0970, and LOC51131 are candidate tumor suppressor genes in this region. ITM2B that showed a significant association (P < 0.005) between expression and LOH at the corresponding locus could, furthermore, be the main target of the observed LOH at 13q in prostate tumors. Prostate 57: 39–50, 2003. © 2003 Wiley‐Liss, Inc.
C16 ceramide accumulates following androgen ablation in LNCaP prostate cancer cells
Authors: Eto Masatoshi , Bennouna Jaafar , Hunter Oriana C. , Hershberger Pamela A. , Kanto Tatsuya , Johnson Candace S. , Lotze Michael T. , Amoscato Andrew A.
Published: July 2003

Background

Adenocarcinoma of the prostate is the most frequently diagnosed non‐cutaneous cancer and the second leading cause of cancer‐related deaths among men in the United States. The most successful therapies to date for this tumor have involved some form of androgen ablation. However, these therapies become ineffective as the tumor evolves to an androgen‐insensitive state. Ceramide is a lipid second messenger that has been shown to mediate growth arrest or cell death when added exogenously to prostate cancer cells. As a first step toward understanding the events that lead to the transition of prostate cancer cells to an androgen‐independent state, we considered investigating the effect of androgen ablation on endogenous ceramide levels in androgen‐sensitive and androgen‐insensitive prostate cancer cells.

Methods

To investigate the mechanisms of growth arrest/apoptosis in androgen‐sensitive (LNCaP) and insensitive (DU‐145, PC–3) cells, we used various methods including nonyl acridine orange (NAO) staining, propidium iodide (PI) staining/cell‐cycle analysis, lipid analysis, and Western blotting assays.

Results

In this study, we demonstrate that androgen ablation drives G0/G1‐phase cell‐cycle arrest followed by progressive apoptosis in vitro, in LNCaP cells. Lipid analysis indicated an increase in C16 ceramide, which was generated via the de novo pathway as revealed by blockade of ceramide synthase by fumonisin B1. The addition of 5α‐dihydrotestosterone (DHT) or fumonisin B1 rescued LNCaP cells from apoptosis induced by androgen ablation, and decreased levels of intracellular C16 ceramide. Neither apoptosis nor an increase in C16 ceramide was observed in androgen‐independent cell lines following androgen ablation. Prostate 57: 66–79, 2003. © 2003 Wiley‐Liss, Inc.
Induction of cellular and humoral immune responses to tumor cells and peptides in HLA‐A24 positive hormone‐refractory prostate cancer patients by peptide vaccination
Authors: Noguchi Masanori , Kobayashi Kazuhiko , Suetsugu Norie , Tomiyasu Katsurou , Suekane Shigetaka , Yamada Akira , Itoh Kyogo , Noda Shinshi
Published: July 2003

Background

To assess the safety and immune response of a peptide‐based immunotherapy for patients with hormone‐refractory prostate cancer, a phase I clinical trial was conducted.

Methods

This study first investigated whether cytotoxic T‐lymphocyte (CTL) precursors reacting to peptide with vaccine candidates (14 peptides for HLA‐A24 positive patients) were detectable in the pre‐vaccination peripheral blood mononuclear cells (PBMCs) of ten patients with hormone‐refractory prostate cancer. Patients were then vaccinated subcutaneously with only those peptides to which pre‐vaccination PBMCs reacted (CTL precursor‐oriented peptide vaccine) for up to four kinds of peptides.

Results

Overall vaccinations were generally well tolerated, but most patients (nine of ten) developed grade 1 local redness and swelling at the injection site. Increased CTL response to both peptides and cancer cells were observed in four of ten patients. Anti‐peptide IgG antibodies were also detected in post‐vaccination sera of seven of ten patients. One patient achieved a partial response with an 89% decrease in PSA. Stable disease was demonstrated in five of ten patients (50%) for the median duration of 2 months (range, 2–5 months). There were no objective responses of measurable lesions.

Conclusions

Increase in cellular and humoral immune responses, and decrease in PSA level in some patients support further development of peptide‐based immunotherapy for hormone refractory prostate cancer. Prostate 57: 80–92, 2003. © 2003 Wiley‐Liss, Inc.
Increased growth factor production in a human prostatic stromal cell culture model caused by hypoxia
Authors: Berger Andreas P. , Kofler Kurt , Bektic Jasmin , Rogatsch Hermann , Steiner Hannes , Bartsch Georg , Klocker Helmut
Published: July 2003

BACKGROUND

Local hypoxia may be one of the triggers of embryonic reawakening of the stroma and subsequent hyperplastic growth in the prostate. Using a cell culture model of human prostatic stromal cells, we investigated the effects of hypoxia on activation of hypoxia‐inducible factor 1 (HIF 1) and on the production of growth factors.

METHODS

Primary prostatic stromal cells were grown in normal and hypoxic (1% O2) atmosphere. Activation of HIF 1 was evaluated after different time intervals by Western blot. Induced secretion of growth factors VEGF, FGF‐7, TGF‐β, IL 8, and FGF‐2 were analyzed by ELISA. To confirm the in vitro findings we also performed immunohistochemistry of HIF 1α as well as pro‐collagen I, collagens I, III, and IV in the benign tissue of radical prostatectomy specimens.

RESULTS

HIF 1 is activated in a time‐dependent manner, already starting 1 hr after exposure of stromal cells to hypoxic conditions. Secretion of VEGF, FGF‐7, TGF‐β, FGF‐2, and IL 8 is increased under hypoxic in vitro conditions in comparison to normoxia. Levels of TGF‐β, VEGF, and IL 8 were rapidly and statistically significantly increased in the supernatant of hypoxic cells. Consistent with the in vitro findings, immunohistochemistry of HIF 1α in (benign prostatic hyperplasia) BPH tissue revealed strong HIF 1α nuclear staining in hyperplastic areas. No difference was observed in the collagen pattern between hyperplastic and normal prostate tissue.

CONCLUSIONS

Prostatic stromal cells respond to hypoxia by upregulation of secretion of several growth factors suggesting that hypoxia can trigger prostatic growth. Therefore, hypoxia might be a key factor contributing to the pathogenesis of BPH. Prostate 57: 57–65, 2003. © 2003 Wiley‐Liss, Inc.
Condensation and pattern formation in cold exciton gases
Authors: Butov L. V.
Published: July 2003

Excitons are Bose particles with small mass. Exciton Bose–Einstein condensation is expected to occur at a few degrees Kelvin. Experimentally, an exciton temperature well below 1 Kelvin is achieved in coupled quantum wells (CQWs). In this contribution, we review briefly experiments that show a strong enhancement of the exciton scattering rate with increasing exciton concentration revealing bosonic stimulation of exciton scattering, which is a signature of a degenerate Bose‐gas of excitons. Novel experiments with exciton condensation in potential traps, pattern formation in exciton system and macroscopically ordered exciton state are also reviewed briefly.
When should we say we have observed Bose condensation of excitons?
Authors: Snoke D. W.
Published: July 2003

I consider what evidence would give an uncontestable claim to observation of Bose condensation of excitons, and discuss recent observations of rings of luminescence in coupled quantum wells in relation to this.
Optical tracking of high‐density cooled excitons in potential traps in Cu2O
Authors: Naka N. , Nagasawa N.
Published: July 2003

The density distribution of cold exciton clouds generated into a strain‐induced potential well by two‐photon excitation in Cu2O is studied at 2 K. The potential shapes of the double well are examined by two‐photon diagnostics. The motion of the exciton clouds is tracked by time‐resolved luminescence imaging and spectral imaging. We find that an anomalous spike appears on the center of the well in a specific excitation condition, i.e. ΔE = −5.0 meV, where ΔE is the detuning of the two‐photon excitation energy from the orthoexciton level under zero stress. The origin of the spike has been discussed in view of bosonic stimulation of the excitons into the ground state.
Exciton ionization in semiconductors
Authors: Koch Stephan W. , Hoyer Walter , Kira Mackillo , Filinov Vladimir S.
Published: July 2003

Two theoretical approaches, a dynamic density‐matrix approach and an equilibrium Monte‐Carlo technique, are combined to give new insight into the ionization behaviour of incoherent excitons in direct‐gap semiconductor heterostructures. In contrast to the widely spread picture of the excitonic Mott transition as an unbinding transition where the correlation length of a bound electron‐hole pair gradually increases until an ionized plasma is formed, the number of incoherent excitons is found to decrease continuously while the mean separation between electrons and holes within the remaining bound pairs is hardly changed, i.e., the pairs remain well correlated. In fact, the remaining excitons have a mean electron‐hole separation even below that of an isolated single pair.
Implementation of an all‐optical spin‐based quantum computer
Authors: Pazy E. , Calarco T. , D'Amico I. , Zanardi P. , Rossi F. , Zoller P.
Published: July 2003

An all‐optical implementation scheme of a spin‐based quantum computer is presented. Our quantum memory consists of the spin of electrons confined to quantum dots. Utilizing the Pauli blocking effect we are able to have ultra‐fast control and read out of the electronic spin degrees of freedom by conditionally coupling them with charged excitations of the quantum dot. Imperfections effecting gate operations are discussed and we show that final readout can still be performed by a quantum‐jump technique even in the presence of hole mixing, when the Pauli‐blocking selection rule is violated.
Phonon‐induced damping of Rabi oscillations in semiconductor quantum dots
Authors: Förstner Jens , Weber Carsten , Danckwerts Juliane , Knorr Andreas
Published: July 2003

The phonon‐induced dephasing dynamics of semiconductor quantum dots during nonlinear optical excitation is studied using quantum kinetic equations. We find that despite the decoherence process Rabi oscillations occur even for relatively long pulse durations and that their signatures in pump‐probe experiments only get suppressed for high input pulse areas.
The influence of four‐particle correlations on the parametric polariton amplification
Authors: Savasta Salvatore , Di Stefano Omar , Girlanda Raffaello
Published: July 2003

We present a microscopic theory of parametric polariton amplification in semiconductor microcavities including the influence of exciton–exciton correlations beyond mean‐field. The complexity induced by the Coulomb interaction between electrons determines the noninstantaneous character of exciton–exciton collisions. We find that the observed great enhancement of gain when increasing the polariton splitting origins from the unique interplay of the noninstantaneous nature of exciton–exciton interactions with the strong coupling regime giving rise to polaritons.
Resonant second‐harmonic generation and mode dispersion in photonic crystal waveguides
Authors: Andreani L. C. , Guizzetti G. , Patrini M. , Vecchi G. , Malvezzi A. M. , Businaro L. , Romanato F. , Di Fabrizio E. , Passaseo A.
Published: July 2003

Linear and nonlinear optical measurements on GaAs/AlGaAs photonic crystal waveguides with square lattice are reported. Second‐harmonic generation in reflection shows a resonant enhancement when the pump beam is frequency‐ and momentum‐matched to a photonic mode in the slab. A full three‐dimensional theory of waveguide‐embedded photonic crystals allows to determine the dispersion of photonic modes and the intrinsic radiative losses of quasi‐guided modes lying above the light line.