bluuebunny/crossref_metadata_2025_split huggingface dataset:
O6‐alkylguanine‐DNA alkyltransferase gene polymorphisms and the risk of primary lung cancer
Authors: Chae Myung Hwa , Jang Jin‐Sung , Kang Hyo‐Gyoung , Park Jae Hyung , Park Jung Min , Lee Won Kee , Kam Sin , Lee Eung Bae , Son Ji‐Woong , Park Jae Yong 
Published: December 2005

AbstractO6‐alkylguanine‐DNA alkyltransferase (AGT) plays an important role in the repair of O6‐alkylguanine adducts, which are major mutagenic lesions produced by environmental carcinogens. Polymorphisms in the AGT gene may affect the capacity to repair DNA damage and thereby have influence on individual's susceptibility to smoking‐related cancer. To test this hypothesis, we investigated the potential association of AGT polymorphisms (485C > A, Leu53Leu (C > T) and Leu84Phe] with the risk of lung cancer in a Korean population. The AGT genotypes were determined in 432 lung cancer patients and in 432 healthy controls who were frequency‐matched for age and gender. The 485 AA genotype was associated with a significantly increased risk for overall lung cancer as compared with the 485 CC genotype and the combined 485 CC + CA genotype, respectively (adjusted odds ratio (OR) = 1.83, 95% confidence interval (CI) = 1.12–2.99, P = 0.02, and Bonferroni corrected P‐value (Pc) = 0.04; and adjusted OR = 1.67, 95% CI = 1.05–2.66, P = 0.03, respectively). When the lung cancer cases were categorized by the tumor histology, the 485 AA genotype was associated with a significantly increased risk of adenocarcinoma (AC) and small cell carcinoma (SmCC), respectively, as compared with the combined 485 CC + CA genotype (adjusted OR = 2.54, 95% CI = 1.39–4.66, P = 0.003; and adjusted OR = 2.19, 95% CI = 1.06–4.55, P = 0.04, respectively). However, the genotype distributions of the Leu53Leu and Leu84Phe polymorphisms were not significantly different between the lung cancer cases and the controls. On a promoter assay, the 485C > A polymorphism did not have an effect on the promoter activity of the AGT gene. These results suggest that the effect of the AGT 485C > A polymorphism on the risk of lung cancer may be secondary to linkage disequilibrium (LD) with either another AGT variant or with a true susceptibility gene, and that the AGT 485C > A polymorphism could be used as a marker for the genetic susceptibility to lung cancer. © 2005 Wiley‐Liss, Inc.
Cyclooxygenase isozymes are expressed in human myeloma cells but not involved in anti‐proliferative effect of cyclooxygenase inhibitors
Authors: Ding Jie , Tsuboi Kazuhito , Hoshikawa Hiroshi , Goto Rieko , Mori Nozomu , Katsukawa Michiko , Hiraki Emi , Yamamoto Shozo , Abe Masahiro , Ueda Natsuo 
Published: December 2005

AbstractConsidering possible tumorigenic activity of cyclooxygenase (COX) isozymes in myeloma, we examined expression levels of COX‐1 and ‐2 in seven human myeloma cell lines (ARH‐77, IM‐9, RPMI‐8226, HPC, HS‐Sultan, TSPC‐1, and U‐266). As analyzed by reverse transcriptase‐polymerase chain reaction (RT‐PCR), all the cell lines constitutively expressed COX‐1, while COX‐2 levels markedly varied among different cell lines. Induction of COX‐2 by phorbol ester was observed in RPMI‐8226 and HPC cells. In contrast, COX‐2 was constitutively expressed in ARH‐77 and IM‐9 cells. Moreover, the high expression level of COX‐2 protein in ARH‐77 cells was verified by Western blotting. Intact cells of ARH‐77 converted 14C‐labeled arachidonic acid to prostaglandin E2, F2α, and D2, and this activity was dose‐dependently inhibited by selective COX‐2 inhibitors (SC‐58125 and NS‐398), a non‐selective COX inhibitor (indomethacin), and relatively high concentrations of a selective COX‐1 inhibitor (SC‐560). These COX inhibitors also suppressed the proliferation of ARH‐77 cells, but significant suppression was seen only at 100 µM, a much higher concentration than those sufficient for the COX inhibition. Moreover, proliferation of the myeloma cells lacking COX‐2 was also suppressed by 100 µM of SC‐58125. These results suggested that the anti‐proliferative effect of the COX inhibitors is independent of the inhibition of COX‐2. © 2005 Wiley‐Liss, Inc.
Phosphodiesterase 5 (PDE 5) inhibitors for the treatment of male erectile disorder: Attaining selectivity versus PDE6
Authors: Pissarnitski Dmitri 
Published: December 2005

AbstractThe role of phosphodiesterase type 5 (PDE5) in the mechanism of male erection has been well understood, and several drugs inhibiting this enzyme are being used for the treatment of erectile dysfunction (ED). Discovery of inhibitors with improved selectivity versus other PDE isozymes could lead to drugs with improved safety profile. Achievement of selectivity versus PDE6, co‐inhibition of which results in disturbances of color perception, remains the most challenging aspect of current drug discovery programs. The present review describes several case studies, where significant (>100 fold) selectivity versus PDE6 has been attained via investigation of structure–activity relationships (SAR). Special attention is given to the chemical routes leading to novel chemotypes and allowing efficient exploration of their SAR's. Strategies for attaining inhibitor selectivity discussed below may be applicable for other drug discovery programs. © 2005 Wiley Periodicals, Inc. Med Res Rev
Compressible Navier–Stokes equations with vacuum state in the case of general pressure law
Authors: Fang Daoyuan , Zhang Ting 
Published: December 2005

AbstractIn this paper, we consider the one‐dimensional compressible isentropic Navier–Stokes equations with a general ‘pressure law’ and the density‐dependent viscosity coefficient when the density connects to vacuum continuously. Precisely, the viscosity coefficient µ is proportional to ρθ and 0<θ<1, where ρ is the density. And the pressure P = P(ρ) is a general ‘pressure law’. The global existence and the uniqueness of weak solutions is proved, and a decay result for the pressure as t→ + ∞ is given. It is also proved that no vacuum states and no concentration states develop, and the free boundary do not expand to infinite. Copyright © 2006 John Wiley & Sons, Ltd.
Photon transport with a localized source in locally convex spaces
Authors: Lisi Meri , Totaro Silvia 
Published: December 2005

AbstractThis paper deals with the study of a mathematical model of photon transport in an interstellar cloud where a localized source is present. The source is represented by a Dirac delta functional. The problem is studied in the setting of locally convex spaces. By means of the theory of semigroups on locally convex spaces and the adjoint approach, we prove existence and uniqueness of the solution. Copyright © 2006 John Wiley & Sons, Ltd.
Optimal control of non‐linear chemical reactors via an initial‐value Hamiltonian problem
Authors: Costanza V. , Neuman C. E. 
Published: December 2005

AbstractThe problem of designing strategies for optimal feedback control of non‐linear processes, specially for regulation and set‐point changing, is attacked in this paper. A novel procedure based on the Hamiltonian equations associated to a bilinear approximation of the dynamics and a quadratic cost is presented. The usual boundary‐value situation for the coupled state–costate system is transformed into an initial‐value problem through the solution of a generalized algebraic Riccati equation. This allows to integrate the Hamiltonian equations on‐line, and to construct the feedback law by using the costate solution trajectory. Results are shown applied to a classical non‐linear chemical reactor model, and compared against suboptimal bilinear‐quadratic strategies based on power series expansions. Since state variables calculated from Hamiltonian equations may differ from the values of physical states, the proposed control strategy is suboptimal with respect to the original plant. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis, characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites
Authors: Jia Qingming , Zheng Maosheng , Shen Renjie , Chen Hongxiang 
Published: December 2005

Abstractorganoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (Tg) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry
Synthesis and characterization of new ferroelectric liquid‐crystalline cyclic oligosiloxanes containing methyleneoxymethylene spacers
Authors: Sołtysiak Joanna T , Czupryński Krzysztof , Drzewiński Witold 
Published: December 2005

AbstractThe synthesis of side‐chain liquid‐crystalline oligocyclosiloxanes containing methyleneoxymethylene spacers, two different mesogenic cores (including biphenyl phenyl carboxylate or biphenyl fluorophenyl carboxylate groups) and chiral tails is presented. Differential scanning calorimetry, optical polarizing microscopy and X‐ray diffraction measurements reveal liquid‐crystalline properties for all of the synthesized monomers and oligomers. All cyclic oligosiloxanes exhibit enantiotropic smectic A and chiral smectic C phases. The mesogenic properties of the cyclic oligomers and side‐chain liquid‐crystalline precursor are discussed. Copyright © 2005 Society of Chemical Industry
High‐yield controlled syntheses of polysilanes by the Wurtz‐type reductive coupling reaction
Authors: Jones Richard G , Holder Simon J 
Published: December 2005

AbstractThe factors that determine the Wurtz‐type reductive coupling of dichloroorganosilanes by alkali metals are reviewed. A strong recommendation is advanced for carrying out all such polysilane syntheses in tetrahydrofuran at ambient temperature, conditions under which the reaction gives far higher yields and generally much narrower product molecular weight distributions. The higher yields are attributed to the ability of the solvent to sequester the sodium ion and thereby stabilize the anionic chain carriers. The bimodal molecular weight distributions of the product polymers, which are ubiquitous when such reactions are carried out in high‐boiling‐point aromatic solvents under reflux, as is common practice, are attributed to it being a defect‐diffusion‐controlled polymerization at the alkali metal surface. The narrower molecular weight distributions that result from syntheses in tetrahydrofuran are attributed to the suppression of defect diffusion rates at lower temperatures. Copyright © 2005 Society of Chemical Industry
Flame‐retarding effects of dialkyl‐p‐vinylbenzyl phosphonates in copolymers with acrylonitrile
Authors: Wyman Paul , Crook Vincent , Ebdon John , Hunt Barry , Joseph Paul 
Published: December 2005

AbstractSeveral dialkyl‐p‐vinylbenzyl phosphonates have been synthesized and free‐radically copolymerized with acrylonitrile to give copolymers with phosphorus contents ranging from 1 to 14 wt%. The flammability and thermal degradation characteristics of these copolymers have been assayed by limiting oxygen index and thermogravimetric methods. It has been found that, despite the negative effect of the vinylbenzyl entity upon the stability of polyacrylonitrile, the incorporation of a small percentage of phosphonate has a significant effect on retarding combustion of the copolymers. The differing effects of the polymerizable function (backbone group) and the pendant phosphonate on thermal stability and flame retardance are deconvoluted by comparison of the behaviours of the acrylonitrile–dialkyl‐p‐vinylbenzyl phosphonate copolymers with the corresponding acrylonitrile–styrene copolymers. The increased flammability and reduced char formation in acrylonitrile–styrene copolymers, compared with those of polyacrylonitrile itself, are shown to recover in the presence of pendant phosphorus groups, and the particular effects of these groups are discussed. Copyright © 2005 Society of Chemical Industry
Isothermal cure kinetics and thermodynamics of an epoxy–nickel–diamine system
Authors: Ghaemy M , Rostami AA , Omrani A 
Published: December 2005

AbstractA study was conducted on the cure kinetics and thermodynamics of a nickel‐containing epoxy polymer obtained by the polymerization of diglycidyl ether of bisphenol A (DGEBA) with a nickel catalyst of diethylenetriamine (Dien) under isothermal condition. The apparent activation energy (Ea) was determined for the whole conversion range by the model‐free iso‐conversional approach. Isothermal kinetic parameters were estimated using an autocatalytic cure mechanism proposed by Kamal. The model gives a good description of curing kinetics at various temperatures prior to the onset of vitrification. Using the rate constants from the kinetic analysis and transition state (TS) theory, thermodynamic parameters such as enthalpy, entropy and Gibbs free energy changes were also calculated. The thermodynamic functions were shown to be very sensitive parameters for evaluation of the cure reaction. Copyright © 2005 Society of Chemical Industry
Phase morphology of functionalized polyester polyurethanes. Effect of functional group concentration
Authors: Čulin Jelena , Šmit Ivan , Veksli Zorica , Anžlovar Alojz , Žigon Majda 
Published: December 2005

AbstractSegmented polyester polyurethanes (PU) were prepared based on polycaprolactone as a soft segment and a hard segment containing isophoronediisocyanate and chain extenders 2,2′‐bis‐(hydroxymethyl) propionic acid and 1,4‐butanediol with different molar ratios. The changes of crystallinity and morphology due to the incorporation of carboxylic functional groups in the hard segment were monitored by wide‐angle X‐ray diffraction, optical microscopy and differential scanning calorimetry. The concentration of functional groups varied from 0 to 0.45 mmol g−1. The phase separation, the degree of crystallinity and the size of spherulites depend on the interactions imposed by functional groups. A critical level of the concentration of functional groups (0.25 mmol g−1) at which the crystallizability reaches its maximum was observed. Copyright © 2005 Society of Chemical Industry
Ethylene polymerization using a novel MgCl2/SiO2‐supported Ziegler–Natta catalyst
Authors: Wang Jianfeng , Wang Li , Gao Haoqi , Wang Wenqin , Wang Wei , Zhao Zhenrong , Sun Tianxu , Feng Lianfang 
Published: December 2005

AbstractA novel MgCl2/SiO2‐supported Ziegler–Natta catalyst was prepared using a new one‐pot ball milling method. Using this catalyst, polyethylenes with different molecular weight distributions were synthesized. The effects of the [Si]/[Mg] ratio, polymerization temperature and [Al]/[Ti] ratio on the catalytic activity, the kinetic behaviour and the molecular weight and the polydispersity of the resultant polymer were studied. It was found that the polydispersity index of the polymer could be adjusted over a wide range of 5–30 through regulating the [Si]/[Mg] ratio and polymerization temperature, and especially when the [Si]/[Mg] ratio was 1.70, the polydispersity index could reach over 25. This novel bi‐supported Ziegler–Natta catalyst is thus useful for preparing polyethylene with a required molecular weight distribution using current equipment and technological processes. Copyright © 2005 Society of Chemical Industry
Microstructure and thermal properties of ethylene‐(vinyl acetate) copolymer/rectorite nanocomposites
Authors: Fang Pengfei , Chen Zhe , Zhang Shaoping , Wang Shaojie , Wang Liying , Feng Jiwen 
Published: December 2005

AbstractEthylene‐(vinyl acetate) copolymer (EVA)/rectorite nanocomposites were prepared by direct melt extrusion of EVA and organo‐rectorite. The microstructures and thermal properties of EVA nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), solid‐state nuclear magnetic spectroscopy, positron annihilation spectroscopy, thermal gravimetric analysis (TGA) and dynamic mechanical analysis techniques. XRD pattern and SEM images show that the intercalated structure is formed and rectorite is finely dispersed in EVA matrix. When organoclay content of the hybrid increases to 7.5 wt%, or pristine rectorite was used instead of organoclay, the crystallization behavior of EVA nanocomposite changes greatly and the ratio of the monoclinic to orthorhombic crystal increases significantly. The relative fractional free volume of the nanocomposite decreases with the increasing organo‐rectorite content, and the values of damping factor (tan δ) for all nanocomposites are lower than that of pure EVA. These facts illuminate that intercalated structure restricts the segment motion and mobilization of polymer chain. TGA results of EVA nanocomposites in air indicate that deacylation of EVA is accelerated because of the catalytic effect and the thermal degradation of the main chain is delayed owing to the barrier effect of silicate layers. Copyright © 2005 Society of Chemical Industry
Time‐resolved luminescence anisotropy studies of the relaxation behaviour of polymers. 2. On the intramolecular mobility of poly(butyl methacrylate) in dilute solution
Authors: Soutar Ian , Swanson Linda 
Published: December 2005

AbstractTime‐resolved anisotropy measurements (TRAMS) have been used to study the relaxation behaviour of poly(butyl methacrylate) (PBMA) in dilute solution both in toluene and dichloromethane. Various fluorescent labels (residues from copolymerisation of BMA with ca 0.3 mol% of acenaphthylene (ACE), 1‐vinylnaphthalene (VN), 1‐naphthylmethyl methacrylate, 9‐phenyanthrylmethyl methacrylate, and 9‐anthrylmethyl methacrylate (AMMA)) were used. It was found that, as expected, ACE and VN provided information on the segmental motion of PBMA. The fluorescence anisotropies of the various ester labels reflected the influence of motion, independent of that of the PBMA backbone, upon the observed relaxation behaviour. The motion of AMMA, in particular, could be resolved, with confidence, into components corresponding to segmental relaxation of both the polymer and ester group motion. Clearly, in this system, motion of the labelled ester is not fully cooperative with that of the polymer backbone, even at the high test frequencies to which these fluorescence measurements correspond. Copyright © 2005 Society of Chemical Industry
Photoinitiated cationic polymerization of urethane vinyl ether crystalline monomers
Authors: Zeng Zhaohua , Yang Jianwen , Pang Laixing , Chen Yonglie 
Published: December 2005

AbstractPhotoinitiated cationic polymerization of crystalline monomers based on urethane vinyl ether has been investigated by means of differential photocalorimetry (DPC). The crystalline monomers in the melt state polymerized rapidly by exposure to UV light in the presence of a cationic photoinitiator such as an iodonium salt, sulfonium salt or iron arene salt. The kinetics of the cationic photopolymerization process were studied by following kp[M+] as a function of conversion. High conversions, of around 90 %, were obtained for most of the systems investigated. The efficiency of the cationic photoinitiators in initiating the polymerization of the vinyl ether monomers was in the order: iodonium salt > iron arene salt > sulfonium salt. Monomers modified with different saturated alcohols had different activities in photopolymerization, although they all carry the same functional group, i.e. vinyl ether. Copyright © 2005 Society of Chemical Industry
Synthesis of amphiphilic poly(methyl methacrylate)‐block‐poly(methacrylic acid) diblock copolymers by atom transfer radical polymerization
Authors: Yuan Jun , Shi Yan , Fu Zhifeng , Yang Wantai 
Published: December 2005

AbstractAtom transfer radical polymerization (ATRP) of 1‐(butoxy)ethyl methacrylate (BEMA) was carried out using CuBr/2,2′‐bipyridyl complex as catalyst and 2‐bromo‐2‐methyl‐propionic acid ester as initiator. The number average molecular weight of the obtained polymers increased with monomer conversion, and molecular weight distributions were unimodal throughout the reaction and shifted toward higher molecular weights. Using poly(methyl methacrylate) (PMMA) with a bromine atom at the chain end, which was prepared by ATRP, as the macro‐initiator, a diblock copolymer PMMA‐block‐poly [1‐(butoxy)ethyl methacrylate] (PMMA‐b‐PBEMA) has been synthesized by means of ATRP of BEMA. The amphiphilic diblock copolymer PMMA‐block‐poly(methacrylic acid) can be further obtained very easily by hydrolysis of PMMA‐b‐PBEMA under mild acidic conditions. The molecular weight and the structure of the above‐mentioned polymers were characterized with gel permeation chromatography, infrared spectroscopy and nuclear magnetic resonance. Copyright © 2005 Society of Chemical Industry
Investigations of parasitic shunt resistance in n‐type buried contact solar cells
Authors: Guo Jiun‐Hua , Cousins Peter J. , Cotter Jeffrey E. 
Published: December 2005

AbstractIt has been shown thatn‐type laser‐grooved buried contact solar cells exhibit a high‐efficiency potential, both on interdigitated backside buried contact (IBBC) and double‐sided buried contact (DSBC) cell structures. As the IBBC solar cell contains heavily doped, compensated regions, the shunt mechanisms are more complicated, and are different from those of the conventional front‐collecting‐junction solar cells. In this paper, several shunting mechanisms hindering the performances of then‐type buried contact solar cells are investigated and discussed. The main shunting routes inn‐type IBBC solar cells are concluded as follows: (1) the emitter contact metal touching the n‐type substrate, which is either due to nonuniform boron deposition or diffusion‐induced misfit dislocations; (2) the base contact metal touching thep+emitter, attributed to either the phosphorus groove diffusion being unable to compensate for the boron emitter diffusion, or the junction depth located in the diffusion overlap regions not deep enough to prevent nickel from spiking through the groove diffusion. The shunt resistance of the IBBC cells increased by more than two orders of magnitude after eliminating the shunt mechanisms discussed in this study. This led to an improvement in fill factor from 0·71–0·73 to 0·74–0·76, and an increase of average absolute efficiency of more than 0·65%. Copyright © 2005 John Wiley & Sons, Ltd.