bluuebunny/crossref_metadata_2025 huggingface dataset:
Free vibrations of solid and hollow wedge beams with rectangular or circular cross‐sections and carrying any number of point masses
Authors: Wu Jong‐Shyong , Chiang Lieh‐Kwang
Published: May 2004

Since the literature relating to the natural frequencies and mode shapes of the double‐tapered wedge beams carrying multiple point masses is rare, the object of this paper is to present some information in this aspect. First of all, the closed‐form solutions in terms of the Bessel functions for the natural frequencies and normal mode shapes of the ‘bare’ wedge beams (without carrying any point masses) were determined. Next, the partial differential equation of motion for the ‘loading’ wedge beams (carrying any number of point masses) were transformed into the matrix equation by using the expansion theorem and the foregoing natural frequencies and normal mode shapes of the ‘bare’ wedge beam. Finally, the eigenvalue equation associated with the last matrix equation was solved to give the natural frequencies and the mode shapes of the ‘loading’ wedge beams. The formulation of this paper is available for the solid and hollow wedge beams with square, rectangular or circular cross sections. In other words, the taper ratio for the width and that for the depth may be equal or unequal. All the numerical results were compared with the existing literature or the conventional finite element method results and good agreement was achieved. Copyright © 2004 John Wiley & Sons, Ltd.
Expression of Fhit, cell adhesion molecules and matrix metalloproteinases in atypical adenomatous hyperplasia and pulmonary adenocarcinoma
Authors: Kerr Keith M , MacKenzie Suzi J , Ramasami Sharmini , Murray Graeme I , Fyfe Nicky , Chapman Andrea D , Nicolson Marianne C , King George
Published: May 2004

Invasive parenchymal‐type lung adenocarcinoma develops from atypical adenomatous hyperplasia (AAH), through an intermediate in situ stage of bronchioloalveolar carcinoma (BAC). We examined the expression of the putative tumour suppressor gene product Fhit, cell adhesion molecules CD44v6, E‐cadherin and β‐catenin, and matrix metalloproteinase 2 and its inhibitor, TIMP‐2, in a range of AAH lesions, BACs and invasive adenocarcinomas, to determine the changes in molecular expression associated with this form of neoplastic progression. Sections of formalin‐fixed wax‐embedded archival tissue were stained by standard Immunohistochemical techniques and scored semi‐quantitatively, resulting in a grading of negative/low‐ or high‐level staining. Fhit protein was retained at high levels in over 90% of AAH and 83% of BAC, but was found in only 6% of stromally invasive tumours (p < 0.0001). CD44v6 staining was high‐level in 64% of AAH but fell to 26% in stromally invasive tumour (p = 0.007). E‐cadherin and β‐catenin showed the opposite, with more high‐level staining as adenocarcinoma developed (p < 0.001). High‐level MMP‐2 and TIMP‐2 expression was relatively infrequent in AAH (32% and 40% respectively), rose in BAC (89% each) but fell in stromally invasive tumour (31% and 17% respectively) (p < 0.01). Unlike in central bronchial carcinogenesis, loss of Fhit expression is a relatively late event in this putative progression of lung adenocarcinogenesis, and has potential as a surrogate marker of invasion, which could be of value in screening patients for lung cancer. Loss of CD44v6 expression follows the convention of falling adhesion molecule expression as malignancy develops. Increased expression of E‐cadherin and β‐catenin may reflect increased cell–cell contact as tissue architecture changes in the transition from AAH to adenocarcinoma. Loss of MMP‐2 and TIMP‐2 in stromally invasive tumour may reflect a particular role for MMP‐2 at the BAC stage, with later down‐regulation of this particular enzyme. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Vascular endothelial growth factor (VEGF)‐A and platelet‐derived growth factor (PDGF) play a central role in the pathogenesis of digital clubbing
Authors: Atkinson Stephen , Fox Stephen B
Published: May 2004

Digital clubbing is associated with many unrelated serious diseases but its pathogenesis remains a clinical enigma. It has been hypothesized that platelet clusters impacting in the distal vasculature mediate the morphological changes of clubbing. Since the multifunctional cytokines vascular endothelial growth factor (VEGF) and platelet‐derived growth factor (PDGF) are released on platelet aggregation and are hypoxically regulated, the present study has examined their role in clubbing using immunohistochemistry. Basic fibroblast growth factor (bFGF), transforming growth factor‐beta 1 (TGF‐β1), microvessel density, carbonic anhydrase IX (CAIX), hypoxia inducible factor (HIF)‐1α, and HIF‐2α were also measured. There was a significant increase in VEGF (p = 0.01), pKDR (p = 0.03), PDGF (p = 0.017), and HIF‐1α and HIF‐2α (p = 0.004 and p = 0.004, respectively) expression together with a significant increase in microvessel density (p = 0.03) in the stroma in clubbed digits compared with controls. There was no difference in CAIX (p = 0.25), TGF‐β1 (p = 0.66) or bFGF (p = 0.18) between affected and control groups. These findings suggest that VEGF and PDGF are released after platelet impaction and that their expression is hypoxically enhanced in the stroma after capillary occlusion. VEGF may synergize with PDGF in inducing the stromal and vascular changes present in digital clubbing. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Apparent activation energy of degradation of poly[acrylonitrile‐co‐(N‐vinylpyrrolidone)]
Authors: Chen Hou , Wang Cheng‐guo , Cai Hua‐su , Cui Chuan‐sheng
Published: May 2004

Differential scanning calorimetry results of the degradation of poly[acrylonitrile‐co‐(N‐vinylpyrrolidone)] in air are presented. The apparent activation energy of degradation was calculated using Kissinger's method. The effect of copolymerization conditions on the apparent activation energy was studied. Increasing the dimethylformamide concentration in the solvent mixture led to a rapid increase in the degradation apparent activation energy. The apparent activation energy decreased rapidly with increase in the comononer N‐vinylpyrrolidone concentration, and this change becomes less prominent as the weight ratio of N‐vinylpyrrolidone/acrylonitrile rises above 5/95. The apparent activation energy also increases with increasing copolymerization temperature. Copyright © 2004 Society of Chemical Industry
Ozonation of unstretched natural rubber film from Hevea brasiliensis studied by ozone consumption and 13C NMR
Authors: Rodrigues FHA , Santos EF , Feitosa JPA , Ricardo NMPS , Heatley F
Published: May 2004

Unstretched films of natural rubber (NR) from Hevea brasiliensis were exposed to ozone flow of 15 ml min−1 from 4 to 300 min. The efficiency of reaction was determined by ozone consumption of NR films. Plots of reacted ozone mass versus film thickness show that the ozone penetration and the ozone reaction progressed into deeper layers (170 µm) than described in the literature (∼0.5 µm). The previous proposed model based on viscometry measurements was corroborated by ozone consumption results. The effect of thickness on the O3/NR stoichiometric ratio indicated that the diffusion process that controls the ozonation in unstretched film does not consist of the boundary progression behind which all reactive sites have been saturated. Ozonation in unstretched rubber film, while being less efficient than ozonolysis in solution, does have a reaction efficiency of the same order of magnitude. NMR spectroscopy was used to characterise the products formed by ozonation. Copyright © 2004 Society of Chemical Industry
Dielectric behaviour and relaxation in poly(propylene glycol)–water mixtures studied by time domain reflectometry
Authors: Sengwa RJ
Published: May 2004

Dielectric behaviour of poly(propylene glycol) (PPG) of number‐average molecular weight 2000 g mol−1 and binary mixtures of PPG with water (PPG–W) of various concentrations were carried out in the frequency range 10 MHz to 4 GHz at 25 °C. The dielectric dispersion and absorption curves related to the orientational motion of these molecules in the binary mixtures are described by a single relaxation time using Debye's model. The values of static dielectric constant εo, high frequency limiting dielectric constant ε∞, and dielectric relaxation time τo were determined for PPG and PPG–W mixtures. The values of the dielectric parameters were used to explore the nature of homogeneous and heterogeneous dynamic networks formed through hydrogen bonding in the binary mixtures of PPG and water molecules with concentration variation. The dielectric studies of PPG molecules were also carried out in the same frequency range at four temperatures, namely 25, 35, 45 and 55 °C. The temperature‐dependent relaxation times were used to evaluate the thermodynamical parameters for the dielectric relaxation processes. The dielectric relaxation free energy of activation ΔFτ for PPG molecules was found in the range ∼4.5 to 4.7 kcal mol−1, which corresponds to the activation energy needed for the breakage of hydrogen bonds. Furthermore, the large negative value of the entropy ΔSτ of PPG molecules confirms that the configuration involved in dipolar orientation has an activated state, which is more ordered than in the normal state. Copyright © 2004 Society of Chemical Industry
Preparation and structural study of polypropylene–talc gradient materials
Authors: Wu Gang , Wen Bianying , Hou Shaohua
Published: May 2004

Polypropylene (PP)–talc composites with proper spatial gradients were prepared by gradually varying the component ratio of PP and talcum powder during the extrudion process. The gradient variations of composition, structural and physical properties along the radius direction of a cylindrical sample were studied by wide angle x‐ray diffraction (WAXD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and tensile testing. The WAXD and TG results indicate that the content of either component shows a monotonic change along the radius direction. With increasing radius, a gradually decreased percentage of PP was observed, while that of the talc filler gradually increased. A gradually varying stacking density of the talcum powder in the PP matrix was also observed by the SEM images for the sliced specimens sampled at different positions. As a result of such variations in both component and structure, the physical properties, including the mechanical performance and thermal behaviour of the PP–talc composites, gradually varied along the radius direction. The experimental data show that a polymeric gradient material (PGM), with significantly different structures and properties existing on both sides, can be prepared by using this unique process. Copyright © 2004 Society of Chemical Industry
Preparation of vinyl polymers bearing photo‐labile diethylthiocarbamoylthiyl (S2CNEt2) groups via ATRP
Authors: Li Peng , Qin Shu‐Hui , Qin Dong‐Qi , Qiu Kun‐Yuan
Published: May 2004

Direct synthesis of vinyl polymers functionalized with photo‐labile diethylthiocarbamoylthiyl (S2CNEt2) groups was reviewed via three living polymerization procedures: normal atom‐transfer radical polymerization (ATRP), reverse ATRP and photo ATRP. The S2CNEt2 group was transferred by mediating the dormant–active species equilibrium in the course of polymerization and eventually ω‐terminating the resulting polymer chain. ATRP of methyl methacrylate (MMA) was successfully performed with a p‐toluenesulfonyl chloride/Cu(S2CNEt2)/2,2′‐bipyridine(bpy) or benzoyl peroxide (BPO)/Cu(S2CNEt2)/bpy initiation system. The oxidized complex, Cu(S2CNEt2)Cl/bpy, catalyzed the reverse ATRP of vinyl monomers initiated with BPO or 2,2′‐azobisisobutyronitrile (AIBN), producing tailor‐made polymers with ω‐S2CNEt2 groups and a narrow molecular‐weight distribution. Without external ligands, the living polymerization of vinyl monomers was achieved under the thermal initiation of diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS) in conjunction with Fe(S2CNEt2)3 catalyst. Photo ATRP of MMA and styrene was first realized in the presence of 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA)/Fe(S2CNEt2)3 under UV irradiation at ambient temperature. Copyright © 2004 Society of Chemical Industry
Solvent‐specific swelling behavior of poly(allylamine) gel
Authors: Yasumoto Naoko , Hata Yosuke , Satoh Mitsuru
Published: May 2004

Poly(allylamine) (PAlAm) gel was prepared by γ‐ray irradiation. Swelling behavior of the charged PAlAm gels having Cl− and NO3− counter‐ions (PAlAmHCl and PAlAmHNO3, respectively) was investigated in aqueous organic solvent mixtures as functions of solvent species (dimethylsulfoxide (DMSO), methanol (MeOH), ethanol (EtOH), 2‐propanol (2PrOH), tert‐butanol (tert‐BuOH), acetone, tetrahydrofuran (THF) and dioxane) and the concentration. With increasing solvent concentration, the gels (except for the DMSO system) showed a sharp deswelling comparable to the volume phase transition. The solvent specificity for the PAlAmHNO3 gel transition was correlated with the dielectric constant of the organic solvents, while that for the PAlAmHCl gel suggested that solvency for the counter anion is another important factor. Copyright © 2004 Society of Chemical Industry
Reaction of poly(vinyl butyral) with tetraethyl orthosilicate: grafting of siloxane chains and new composites
Authors: Annenkov Vadim V , Danilovtseva Elena N , Filina Elena A , Mikhaleva Albina I , Skotheim Terie A , Trofimov Boris A
Published: May 2004

New graft copolymers with side polysiloxane chains were synthesized by sol–gel reaction of acid‐catalyzed hydrolysis of tetraethyl orthosilicate in the presence of poly(vinyl butyral). The grafting is realized by exchange reaction of the alkoxyl moieties in siloxane and acetal groups. When the reaction is carried out in non‐hydroxylic solvent (1,1‐dimethoxyethane) inter‐etherification with participation of the residual hydroxyl groups of poly(vinyl butyral) is also important. The copolymers obtained contain free silanol groups which are active in complexing with polymeric bases by hydrogen bonds, with formation of new composites. Copyright © 2004 Society of Chemical Industry
DC electrical conductivity of some oligoazomethines
Authors: El‐Shekeil Ali , Al‐Aghbari Sama
Published: May 2004

Six aromatic oligoazomethines were synthesized containing seven benzene rings each. The terminal rings were substituted with different groups, namely, H, Cl, NO2, OH, OCH3 and CH3. The synthesis was carried out by condensing the para‐substituted benzaldehydes with benzidine to give the three‐ring compound, which was then condensed with terephthaldehyde to give the respective seven‐benzene‐ring oligomers. The oligomers were characterized by elemental analysis, electronic spectra, Fourier‐transform infrared and thermal analysis. The oligomers were used to investigate the effects of their molecular structure on their electronic spectra, as well as their thermal, electronic and electrical properties. The different conformers were reported and compared. The DC electrical conductivity variation of oligoazomethines was studied in the temperature range 300–500 K after annealing for 24 h at 100 °C and after doping with 5% I2. An attempt was made to relate the DC electrical conductivity, electronic properties and thermal properties to the chain length, substituted groups and coplanarity. The fairly low conductivity obtained was attributed to the non‐linearity of the rings in the chain. The different groups (neutral, electron withdrawing or electron donating) attached at the ends of the oligomer showed no influence upon the conductivity of the different oligomers. The action of doping gave almost the same enhancement as that noticed in the case of a long‐chain polymer. The DC electrical conductivity was interpreted using the band energy model. The seven‐benzene‐ring oligomer gave the same DC electrical conductivity as the long‐chain polymer. Copyright © 2004 Society of Chemical Industry
Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers
Authors: Du Xusheng , Xiao Min , Meng Yuezhong , Hay Allan S
Published: May 2004

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry
Equilibrium swelling and solvation studies on crosslinked polyacrylamides
Authors: Joseph Mary , Mathew Tessymol , S Devipriya , Chen Yu , Kuriakose Sunny
Published: May 2004

Polyacrylamide (PA) crosslinked with four different crosslinking agents, triethyleneglycol dimethacrylate (TEGDMA), N,N′‐methylene bisacrylamide (NNMBA), hexanediol dimethacrylate (HDDMA) and divinylbenzene (DVB), with mole percents ranging from 5 to 20, was prepared by solution polymerization and subjected to swelling and solvation studies. Solubility parameters and cohesive energy density were determined from swelling studies. Molecular weight between crosslinks for these systems were determined by Flory–Rehner analysis. There is a discontinuous volume change for 10% NNMBA and HDDMA crosslinked PA, 15% TEGDMA crosslinked PA and 10 and 15% DVB crosslinked PA in solvent mixtures of acetic acid and water due to phase change occurring at this stage. The hydrogels exhibit inhomogeneous crosslink distribution due to multiple crosslinking, cyclization and network irregularity owing from arising from entanglements. As the percentage of crosslinking increases, crosslinks become more homogeneous due to a decrease in entanglements. Copyright © 2004 Society of Chemical Industry
Infrared study on in situ polymerization of zinc dimethacrylate in poly(α‐octylene‐co‐ethylene) elastomer
Authors: Lu Yonglai , Liu Li , Shen Deyan , Yang Cheng , Zhang Liqun
Published: May 2004

An infrared spectroscopic method was used to follow the course of in situ polymerization of zinc dimethacrylate (ZDMA) in poly(α‐octylene‐co‐ethylene) elastomer (POE). The integral intensity of the 831 cm−1 band, ie the out‐of‐plane deformation mode of CH, was used to determine the residual amount of ZDMA in composites cured at 165°C for different times, through which the course of in situ polymerization of ZDMA in POE was traced and the dynamic curve determined. The curing course of the ZDMA/POE/peroxide system at 165°C was examined with a rheometer and compared with the course of in situ polymerization. The results surprisingly show that the in situ polymerization of ZDMA is almost complete at the beginning stage of curing, and that substantial crosslinking starts subsequently. Scanning electron microscopy and transmission electron microscopy observations on morphologies of ZDMA/POE composites cured at 165°C for different times were carried out and confirmed the results of infrared experiments. Combining all the investigations, it was deduced that a competition exists between in situ polymerization and crosslinking in the composites. Covalent crosslinking rather than ionic bond crosslinks are the major types of crosslinks structures in ZDMA/POE composites, and its total density is lower than that of carbon‐ black‐reinforced POE. Copyright © 2004 Society of Chemical Industry
Influence of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) on miscibility and properties of atactic poly(methyl methacrylate)
Authors: Cimmino Sossio , D'Alma Edoardo , Di Lorenzo Maria , Silvestre Clara
Published: May 2004

Miscibility and properties of two atactic poly(methyl methacrylate)‐based blends [containing 10 and 20% of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)] have been investigated as a function of thermal treatments. Differential scanning calorimetry and dynamic mechanical thermal analysis of blends quenched in liquid nitrogen or ice/water, after annealing at T > 190 °C, showed a single glass transition temperature, indicating miscibility of the components for the time‐temperature history. Two glass transition temperatures, equal to those of the pure components, are instead found for blends after annealing at T < 190 °C. Scanning electron microscopy confirmed the homogeneity for the former quenched blends and phase separation for the latter. These results indicate the presence of an upper critical solution temperature (UCST). Tensile experiments, performed on two series of samples annealed at temperatures above and below the UCST, showed that the copolyester induces a decrease of Young's modulus and stresses at yielding and break points, and a marked increase of elongation at break. Differences in tensile properties between the two series of annealed blends are accounted for by the physical state of the components at room temperature after annealing above or below the UCST. Copyright © 2004 Society of Chemical Industry
Self‐assembled ultra‐thin films fabricated from diazoresin and phenol–formaldehyde resin via H‐bonding interaction
Authors: Yang Zhaohui , Chen Jinyu , Cao Weixiao
Published: May 2004

A photosensitive ultra‐thin film has been fabricated from diazoresin (DR) and various phenol‐formaldehyde resins (PR) through a self‐assembly technique (SA). The driving force is confirmed to be a hydrogen‐bonding (H‐bonding) interaction between the diazonium groups of DR and the phenolic hydroxy groups of PR. Under exposure of UV‐light or immersion in an alkaline solution, the hydrogen‐bonds between layers will be converted to covalent bonds. As a result, the stability of the film towards polar solvents improves dramatically. Copyright © 2004 Society of Chemical Industry
Synthesis of graft copolymer from copolymerization of styrene‐terminated poly(ethylene oxide) macromonomer and styrene with CpTiCl3/methylaluminoxane catalyst
Authors: Endo Kiyoshi , Sugita Tomoaki
Published: May 2004

Copolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl3/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl3/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004
Abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds to initiate radical and cationic photopolymerizations
Authors: Tanaka Kenta , Nakamura Kanako , Yoshioka Nariyoshi , Kameyama Atsushi , Igarashi Tetsutaro , Sakurai Tadamitsu
Published: May 2004

This study explored the abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds, which absorb long‐wavelength light (>350 nm), to photochemically initiate radical and cationic polymerizations. It was found that the irradiation of the title compounds initiates the radical polymerization of styrene whereas the cationic polymerization of oxetane proceeds in the presence of these photoinitiators to a negligible extent. The behavior of 9‐anthrylmethyloxyl and amidyl radicals in the photopolymerization process of styrene was discussed based on 1H NMR, UV, and fluorescence spectral data. In addition, the photoinitiation ability of the anthrylmethyloxyl end group was also investigated by using its model compound. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2859–2865, 2004
Synthesis and characterization of an azobenzene‐ and acrylamide‐based photoresponsive copolymer and gel
Authors: Moniruzzaman M. , Fernando G. F. , Talbot J. D. R.
Published: May 2004

This article reports the synthesis and characterization of a new type of copolymer consisting of acrylamide and trans‐4‐methacroyloxyazobenzene and their gel. Free‐radical polymerization initiated with 2,2′‐azobisisobutyronitrile was used to conduct the synthesis although N,N′‐methylene bisacrylamide was used as a crosslinking agent for the gel synthesis. Despite the insolubility of the different monomers in a single solvent, a certain ratio of water/tetrahydrofuran (THF) enabled the propagating species to stay in the solution and thus to facilitate chain growth. The solubility, Fourier transform infrared spectra, and solid‐state 13C NMR investigations revealed that two monomers in the copolymer were chemically bonded. The compositions of the incorporated acrylamide and azobenzene in the copolymer and the gel were determined by NMR spectroscopy. Because the potential actuating behavior of such materials was due to the volume change involved in reversible solvent uptake, the sorption and evaporation of the gel were also investigated and showed that the gel could absorb about 460% water, which corresponded to a polymer content of the weight gel of 18% and was compatible with thermogravimetric analysis of a saturated gel that revealed about 83 wt % of a swollen gel was lost within 12 h. Finally, photoinduced trans–cis isomerization kinetics of the copolymer was investigated in a 30:70 mixture of water and THF against irradiation time. A photostationary state was reached within 5.5 min with a corresponding conversion of 70% of the trans isomer to the cis form. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2886–2896, 2004
New approaches for the synthesis of hindered C60‐containing polyphosphazenes via functionalized intermediates
Authors: Li Zhen , Qin Jingui , Xu Xiaojuan
Published: May 2004

Two new approaches were developed to synthesize C60‐containing polyphosphazenes. Accordingly, two new reactive macromolecular intermediates (P4 and P8) were obtained from poly(dichlorophosphazene) by the direct nucleophilic substitution reaction. In one approach, a predesigned amimo end–functionalized polyphosphazene (P4) was prepared and then reacted with C60 molecules in chlorobenzene to yield C60‐containing polyphosphazene; in the other approach, a polyphosphazene containing 4‐methyl phenoxy groups as side chains was first prepared, and then part of the 4‐methyl groups were converted to azidomethyl groups (in P8), which reacted with C60 to yield C60‐containing polyphosphazene. The polymers were characterized by 1H NMR, 13C NMR, IR, and UV–visible spectra and by gel permeation chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2877–2885, 2004
Synthesis and properties of novel conjugated poly(silylacetylene silazane)s
Authors: Hu Ji Dong , Zheng Zhi Min , Ma Teng , Zhang Zhi Jie , Ye Jian Ping , Wang Duo Yuan , Xie Ze Min
Published: May 2004

A series of novel conjugated polymers, poly(silylacetylene silazane)s having different substituents, were prepared by ammonolysis of the corresponding α,ω‐dichlorosilyleneacetylene oligomers. The structures and properties of the poly(silylacetylene silazane)s were characterized by Fourier transform infrared, 1H, 13C, 29Si NMR, and elemental analyses, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and spectrofluorophotometry. The resulting polymers had good thermal properties and were moderately fluorescent. Their thermal stability was improved, and obvious red shift was observed when a phenyl substituent was attached on a silicon atom of polymers in the emission spectra. These polymers have the potential to be used as light‐emitting materials with good thermal stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2897–2903, 2004
Elastic modulus of single‐walled carbon nanotube/poly(methyl methacrylate) nanocomposites
Authors: Putz Karl W. , Mitchell Cynthia A. , Krishnamoorti Ramanan , Green Peter F.
Published: May 2004

Dynamic mechanical analysis, nuclear magnetic resonance, and thermogravimetric analysis experiments were performed on pure poly(methyl methacrylate) and on in situ polymerized single‐walled carbon nanotube (SWNT)/PMMA nanocomposites. The addition of less than 0.1 wt % SWNT to PMMA led to an increase in the low‐temperature elastic modulus of approximately 10% beyond that of pure PMMA. The glass‐transition temperature and the elastic modulus at higher temperatures of the nanocomposites remained unchanged from those of pure PMMA. These changes were associated with excessive cohesive interactions between the large‐surface area nanotubes and PMMA and were not due to changes in the microstructural features of the polymer during synthesis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2286–2293, 2004
Analysis of the biaxial stress–strain behavior of poly(dimethylsiloxane) networks from the viewpoint of the slip–link model of rubber elasticity
Authors: Meissner Bohumil , Matějka Libor
Published: May 2004

The biaxial stress–strain dependence on melt‐ and solution‐end‐linked poly(dimethylsiloxane) networks has recently been measured and found to be well represented by the Edwards–Vilgis (EV) slip‐link theory of rubber elasticity, with its connectivity term being exclusively given by the theoretical contribution of chemical crosslinks. This article shows that this result of the rigorously applied EV theory is due to the narrow strain range of the data tested and that with biaxial measurements extending to high strains (stretch ratio ≳ 3), an acceptably satisfactory data representation can only be obtained if the concept of the connectivity term being rigorously calculated from structural considerations is abandoned and all four parameters of the slip‐link theory are allowed to be adjusted. In that case, however, the values of the inextensibility parameter are significantly lower than the molecularly based expectations, and the infinite‐strain moduli (extrapolated on the assumption of infinite extensibility) are distinctly higher than the values based on structural considerations. This finding may be explained, in conformity with Thirion and Weil, if we assume that some of the trapped entanglements do not slide and behave in a junctionlike manner. The idea of entanglements contributing to the connectivity term was suggested by Mullins, Moore, and Watson and, more recently, was put forward by Klüppel in the framework of the tube theory. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2318–2328, 2004
π‐complexes of polystyrene with silver salts and their use as facilitated olefin transport membranes
Authors: Kim Jong Hak , Won Jongok , Kang Yong Soo
Published: May 2004

π‐Complexes of silver salts with polystyrene (PS) were prepared and tested in the separation of propylene/propane mixtures. After the incorporation of silver ions into the PS matrix, both the pure propylene gas permeance of the membrane and its olefin selectivity with respect to the propylene/propane mixtures were remarkably higher than those of the pure PS membrane, demonstrating facilitated propylene transport through the solid‐state membrane. The remarkable separation performance of the PS/silver salt membranes was attributable to the unusually high solubility of the silver salts in the PS matrix, which was possibly due to the formation of π‐complexes between the silver ion and aromatic CC bond of PS. The coordination properties and dissolution behavior of the silver salts in PS were investigated with Fourier transform infrared, Fourier transform Raman, and X‐ray photoelectron spectroscopy. The values for the intersegmental d‐spacing, determined by wide‐angle X‐ray scattering, also showed that significant transient crosslinks arose between the PS chains when the silver salts were added to the PS matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2263–2269, 2004
Numerical simulation of the tensile modulus of nanoclay‐filled polymer composites
Authors: Zhu Linjie , Narh K.A.
Published: May 2004

A numerical simulation model that incorporates three phases, polymer matrix, interlayer, and clay platelet, was developed to predict the tensile modulus of nanoclay‐filled polymer composites. The interlayer was introduced to account for the fact that the mechanical properties of the polymer near the clay surface are different from those of the polymer matrix. The effects of the properties of interlayers, the structure of clay clusters, and platelet distributions upon the modulus of elasticity of the nanocomposites, were studied. The simulation results show that a decrease in the interlayer modulus, as well as an increase in the interlayer thickness, would decrease the modulus of the nanocomposites. Furthermore, it was found that the maximum strain, located in the interlayer near the end of the clay platelet, increases significantly with decreasing interlayer modulus. The effects of the distribution of clay platelets upon composite modulus were interpreted in terms of two parameters, platelet overlap length, and the lateral distance between platelets. Comparison of simulation results with experimental data from the literature has confirmed the reliability of the numerical simulation method used in the present study. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2391–2406, 2004
A stereochemical microstructure‐based attempt to explain the dielectric behavior of poly(vinyl chloride) (PVC)
Authors: Guarrotxena N. , Del Val J.J. , Elicegui A. , Millan J.
Published: May 2004

A poly(vinylchloride) (PVC) obtained by bulk polymerization at 70 °C was modified through substitution reaction with sodium benzenethiolate (NaBT) in cyclohexanone solution at 25 °C, at various conversions up to 15 mol %. According to earlier work, this allows to change, in a controlled way, the stereochemical microstructure in terms of mainly the content of mmr (meso, meso, racemic) tetrad termini of isotactic sequences of at least one heptad in length, and of its likely chain conformations. The samples were all studied by Dielectric Relaxation Spectroscopy, which allows to measure the real and the imaginary parts of the complex dielectrical constant in a frequency range between 1 and 106 Hz, and a temperature range between 100 and 600 K. Most of the changes in the physical quantities that can be analyzed by this technique were found to parallel the changes in stereochemical microstructure with substitution extent. The temperature of the maximum of the dipolar losses, which relates to the temperature range where α relaxation occurs, appeared to increase somewhat up to 0.7% molar conversion. Then the tendency is towards stabilization. The relaxation time τ(T) as deduced from the Havriliak‐Negami (NH) function, tends to decrease between 0 and 0.7 substitution percent, and to increase afterwards. The evolution of the Ngai's β parameter with substitution degree is also highly illustrative. It clearly decreases up to 0.7% and then it increases rapidly up to 7% and slowly afterwards. These changes are discussed by taking into account that 0.7 and 7% substitution extents agree with the removal of mmr under GTTG−TT conformation and of the same structure under GTGTTT conformation, respectively. From the results, some original correlations between stereochemical microstructure and molecular dynamic behaviors are proposed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2337–2347, 2004
Effects of physical aging on solubility, diffusivity, and permeability of propane and n‐butane in poly(4‐methyl‐2‐pentyne)
Authors: Nagai Kazukiyo , Sugawara Akihito , Kazama Shingo , Freeman Benny D.
Published: May 2004

The effects of physical aging on the solubility, diffusivity, and permeability of propane and n‐butane in a hydrocarbon‐based disubstituted polyacetylene, poly(4‐methyl‐2‐pentyne) (PMP), were studied. As the relative pressure of propane and n‐butane increased, the solubility of both hydrocarbons increased. Like other glassy polymers, the sorption isotherms for propane and n‐butane in all PMP films were concave to the relative pressure axis, indicating dual‐mode sorption behavior. The diffusion of propane and n‐butane in PMP followed typical Fickian diffusion in a plane sheet. The propane diffusivity in both the unaged and aged films increased with increasing concentration of propane sorbed in the film. The n‐butane diffusivity in aged films also increased with increasing n‐butane concentration. However, unaged films showed the opposite behavior: the diffusivity decreased with increasing n‐butane concentration. These diffusion phenomena are a consequence of the interplay between thermodynamic and mobility factors. The permeabilities of propane and n‐butane decreased monotonically with increasing penetrant concentration, similar to the behavior observed in other common glassy polymers. The relaxation of the nonequilibrium excess free volume in PMP films induced the decrease in both solubility and diffusivity. As a result, the permeability of propane and n‐butane in PMP decreased upon physical aging. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2407–2418, 2004
Transport and magnetic properties of delafossite CuAl1−xMnxO2 ceramics
Authors: Kim Hyoun Soo , Lee Byoung Seon , Ji Sung Hwa , Kim Hyojin , Kim Dojin , Ihm Young Eon , Choo Woong Kil
Published: May 2004

We report on the transport and magnetic properties of Mn‐doped CuAlO2 ceramics (CuAl1−xMnxO2, 0 ≤ x ≤ 0.05) fabricated by standard solid solution method in an air atmosphere at a sintering temperature of 1150 °C. The equilibrium solubility of Mn ions in CuAlO2 was found to be as low as 3 mol%. Non‐doped CuAlO2 ceramics were semiconducting with a hole concentration of ∼5.8 × 1016 cm−3 and an increase of Mn ion rapidly reduced the hole concentration. The magnetization measurements for all CuAl1−xMnxO2 samples showed paramagnetic behaviors and a negative value of the Curie–Weiss temperature corresponding to antiferromagnetic exchange coupling between Mn ions in delafossite CuAlO2 lattice. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of γ‐Fe2O3 nanoparticles made by coprecipitation method
Authors: Jeong Jong‐Ryul , Lee Seung‐Jun , Kim Jong‐Duk , Shin Sung‐Chul
Published: May 2004

We have synthesized maghemite (γ‐Fe2O3) nanoparticles using chemical coprecipitation technique through a typical pipette drop method (pipette diameter: 2000 μm) and a piezoelectric nozzle method (nozzle size: 50 μm). The size distribution of the maghemite nanoparticles prepared by the pipette drop method is from 5 nm to 8 nm. However, the nanoparticles made by the piezoelectric nozzle method show smaller size and very narrow size distribution from 3 nm to 5 nm. Zero‐Field‐Cooled (ZFC)/Field‐Cooled (FC) magnetization and magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer from 5 K to 300 K to investigate the magnetic properties of nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles with the blocking temperature of 119.5 K and 94.3 K for the nanoparticles made by the pipette drop method and the piezoelectric nozzle method, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin transport in an FM/Bi/FM junction
Authors: Lee K. I. , Jeun M. H. , Chang J. Y. , Han S. H. , Ha J. G. , Lee W. Y.
Published: May 2004

The spin transport in a spin‐valve device incorporating Bi thin film and two ferromagnetic (FM) contacts is presented. The non‐local output voltage is found to depend upon the relative magnetization state of the two FM electrodes, indicating that the spin‐polarized electrons are injected from the first FM (injector) into Bi and are detected by the second FM (detector) due to spin accumulation. The observed Hanle effect supports the spin injection and detection in our device. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and magnetism of CrAu3 nano films: density functional study
Authors: Kwon Youngsoo , Cho Sunglae , Hong Soon C.
Published: May 2004

Magnetism of some CrAu3 nano films [free standing CrAu(001) monolayer, 1(CrAu)/1Au/1(CrAu)(001), 1(CrAu)/3Au/1(CrAu)(001), 1Au/1(CrAu)/1Au, and 1(CrAu)/1Au/1(CrAu)/1Au/1(CrAu)] were investigated using the FLAPW method with the PBE‐version of GGA for exchange‐correlation potential. The nano films were calculated to be stable in an in‐plane antiferromagnetic state. 1(CrAu)/1Au/1(CrAu)/ 1Au/1(CrAu) was calculated to be stable in L12 G‐type antiferromagnetic structure. The calculated magnetic moments of Cr are about 3.9 μB and 3.7 μB at the surface and in the center layer, respectively. For comparison, calculations on bulk CrAu3 have been done for plausible magnetic structures (PM, FM, and some AFM states) for L12 and D022 crystal structures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DFT‐EPR study of radiation‐induced radicals in α‐D‐glucose
Authors: Pauwels Ewald , Van Speybroeck Veronique , Vanhaelewyn Gauthier , Callens Freddy , Waroquier Michel
Published: May 2004

The structures of two radiation‐induced radicals in solid‐state α‐D‐glucose have been identified by means of single‐molecule density function theory (DFT) calculations. Using the original crystalline structure as input, several radical models were created and their geometries optimized. Subsequently, electron paramagnetic resonance (EPR) parameters were calculated. During these calculations, the global orientation of the radical structure was kept fixed with respect to the crystal axes reference frame. This was essential to allow for an easy analysis of the hyperfine tensor principal directions, besides the isotropic and anisotropic coupling constants. By comparing these calculated EPR parameters with their experimentally determined counterparts, a plausible identification of two carbon‐centered glucose radicals was possible. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
DFT studies on key intermediates in thiamin catalysis
Authors: Friedemann Rudolf , Tittmann Kai , Golbik Ralph , Hübner Gerhard
Published: May 2004

The diphosphate ester (ThDP) of thiamin (vitamin B1) is an important cofactor of enzymes within the carbohydrate metabolism. From experiments of site‐specific variants and nuclear magnetic resonance (NMR) studies, it is known that the protonation of the N1′ atom is a significant step in the coenzyme activation by the enzymatic environment. Therefore, we have performed density functional theory (DFT) calculations on the B3LYP/6‐31G* level of N1′H and N1′CH3 thiamin as model systems to study the protonation and methylation effect on the structure and the electronic properties of the 4′‐amino group. The relaxed rotational barriers related to the C4′‐4′N bond are correlated with findings of 1H NMR studies and proton/deuterium exchange experiments. Moreover, the effect of N1′ protonation was studied in more detail on the hydroxyethyl‐thiamin carbanion (HETh−), a key intermediate during catalysis of some ThDP‐dependent enzymes. The relaxed rotational barriers related to the C2C2α bond and the reaction coordinates of the proton transfer 4′NH→C2α of HETh− and N1′H‐HETh− show that they are significantly determined by the protonation at N1′ of HETh−. The influence of the apoenzyme environment on the active coenzyme conformation is modeled in a very simple way. The characteristic torsion angles ΦT and ΦP are considered to be restricted in terms of their values in the corresponding enzyme as well as free optimization parameters. Frequency calculations were performed to characterize the minima and transition state structures, respectively. The applicability of the DFT method was checked by comparing calculations on the MP2‐HF‐SCF/6‐31G* level. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Random covering of an interval and a variation of Kingman's coalescent
Authors: Bertoin Jean
Published: May 2004

We consider the covering of [0, 1] by a large number of small random intervals. We show that a simple variation of Kingman's coalescent describes the emergence of macroscopic connected components. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
Simply generated trees, B‐series and Wigner processes
Authors: Mazza Christian
Published: May 2004

We consider simply generated trees, like rooted plane trees, and consider the problem of computing generating functions of so‐called bare functionals, like the tree factorial, using B‐series from Butcher's theory. We exhibit a special class of functionals from probability theory: the associated generating functions can be seen as limiting traces of product of semi‐circular elements. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
Reconciling sustainability and growth: criteria, indicators, policies
Authors: Spangenberg Joachim H.
Published: May 2004

Sustainable development is based on the integration of four dimensions: the economic, the environmental, the social and the institutional. For the economic dimension in particular, growth has been considered an essential element of sustainable development.

This paper discusses the relationship of social, environmental and institutional sustainability objectives to economic growth and derives social and environmental criteria for growth to be sustainable.

One of the most sophisticated sustainability studies developed for Germany is introduced, demonstrating the need and the possibility to reconcile economic, social, environmental and institutional objectives. Integrated politics taking into account all four dimensions when drafting policy plans are a necessary precondition for this behalf.

Based on two sustainability scenarios with a different emphasis (growth, integration) five core action zones for policy making are identified.

The criteria derived can be used as yardsticks assessing policy proposals at an early stage regarding their impact on key sustainability objectives. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.