bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and solution properties of temperature‐sensitive copolymers based on NIPAM
Authors: Zhang Xiaofei , Zhou Li , Zhang Xi , Dai Hua 
Published: December 2009

AbstractA kind of temperature‐sensitive water‐soluble polymers P(NIPAM‐HEMA‐AM) of N‐isopropylacrylamide (NIPAM), hydroxyethyl methacrylate (HEMA) and acrylamide (AM) were synthesized by free radical aqueous solution copolymerization. The polymers were characterized by Fourier transform infrared spectrum (FTIR) method. Solution properties, such as the influences of monomer ratios and additives on the low critical soluble temperature (LCST) of the polymer solutions as well as the viscosity‐temperature properties were studied. The results show that the polymer concentrations have no significant influence on the LCST of polymer solutions. The incorporation of HEMA units leads to a lower LCST, while AM units to a higher LCST. The additions of small molecules such as salt and surfactant also have significant effect on the LCST, the addition of NaCl decreases the LCST, while the addition of sodium dodecylbenzenesulfonate (SDBS) increases the LCST. The apparent viscosity of polymer solutions depends on temperature. The 1.5 wt % aqueous solutions of P(NIPAM‐HEMA‐AM) exhibits good thermo‐thickening behavior over 55°C, whereas the 0.8 wt % aqueous solutions do not show this behavior during the heating process. The aqueous solutions of P(NIPAM‐HEMA‐AM) are viscoelastic fluids, and the viscoelasticities mainly depend on temperature. Both the storage modulus (G') and loss modulus (G'') of 1.5 wt % polymer solutions increase with temperature. Over 55°C, G' exceeds G'', and the polymer solutions are elasticity‐dominated. In contrast, below 55°C, G'' is larger than G', and the polymer solutions are viscosity‐dominated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Mechanical and acoustic performance of compression‐molded open‐cell polypropylene foams
Authors: McRae Joe D. , Naguib Hani E. , Atalla Noureddine 
Published: December 2009

AbstractOpen‐cell materials are lightweight and multifunctional capable of absorbing acoustic energy and supporting mechanical load. The acoustic and mechanical performance of open‐cell materials can be optimized through processing. In this article, the relationships between processing parameters and acoustic and mechanical performance are shown for polypropylene (PP) foams. PP foam samples are fabricated using a combined compression molding and particulate leaching process. The results from a parametric study showed that both salt size and salt to polymer ratio affect the acoustic and mechanical performance of open‐cell PP foams. As salt size increases, cell size increased and cell density decreased. The salt to polymer ratio had opposite affect on cell density, and increasing the salt to polymer mass ratio increased the open‐cell content. The airflow resistivity decreased significantly by increasing the cell size, which means that foam samples with smaller cell size have better sound absorption. When foam samples were thin, smaller cell sizes produced better sound absorption; however, as thickness of the sample increases, medium cell size offered the best acoustic performance. The compressive strength of the foams was increased by increasing the relative density. Acoustic performance results from the parametric study were compared to the Johnson‐Allard model with good agreement. Finally, optimal cellular morphologies for acoustic absorption and mechanical performance were identified. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
A study on the nonuniform deformation of PTFE membrane during its tentering transverse stretching
Authors: Guo Yu‐Hai , Chen Jian‐Yong , Gao Jing‐Xin , Zhang Hua‐Peng , Feng Xin‐Xing 
Published: December 2009

AbstractTo understand the deformation of biaxially stretched polytetrafluoroethylene (PTFE) membrane during the tenter frame transverse stretching process, a finite element analysis (FEA) model was established to study the stress and displacement distribution during the transverse stretching. The morphology, pore size, and mechanical properties of the membrane were also characterized. It has been found from the experimental and FEA simulation results that the tentering transverse stretching of PTFE membrane is a nonuniform stretching, the stress and displacement distribution of the PTFE membrane during tentering is nonuniform because of the nonuniform deformation and the ease of yield and plastic deformation originated from the specific structure of the virgin PTFE particles. The nonuniform thickness and pore size distribution across the membrane width resulted from this nonuniform deformation was also characterized and discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Non‐isothermal cold crystallization kinetics and morphology of PET + SAN blends
Authors: Wellen Renate M. R. , Rabello Marcelo S. 
Published: December 2009

AbstractThe influence of small amounts of poly(styrene‐co‐acrylonitrile) (SAN) on the non‐isothermal cold crystallization behavior and morphology of poly(ethylene terephthalate) (PET) was investigated by dynamic‐mechanical thermal analysis, differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy. The results indicated that SAN had a limited solubility in the amorphous phase of PET although in a larger scale a phase separation occurred. The addition of 1 wt % of SAN promoted a significant reduction in the crystallization rate of PET, acting as an antinucleating agent. The kinetics parameters were determined applying both the Ozawa and Mo approaches. Mo's model described the crystallization evolution better than the Ozawa one because it is possible to analyze the kinetic parameters in similar range of crystallinity degrees. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Role of internal additives in the friction and wear of carbon‐fiber‐reinforced polyimide
Authors: Samyn Pieter , De Baets Patrick , Schoukens Gustaaf 
Published: December 2009

AbstractPolyimide composites should function in sliding contacts under high temperatures, but the interference of carbon fibers with sliding mechanisms is difficult to predict: they often increase the coefficients of friction and act abrasively but show lubricating properties under other conditions. The friction and wear behavior of thermoplastic polyimides reinforced with short carbon fibers and filled with solid internal lubricant (polytetrafluoroethylene) or silicon oil was investigated in this study with a reciprocating cylinder‐on‐plate tester under 50 N at 0.3 m/s with steel counterfaces that were heated at 23–260°C. We concluded that polytetrafluoroethylene additives effectively reduced the coefficients of friction over the entire temperature range, especially under thermally controlled sliding conditions at 120°C, whereas the internal silicon oil increased the coefficients of friction. The wear rates of the fiber‐reinforced polyimide significantly decreased with respect to those of the thermoplastic polyimide, whereas additional fillers slightly increased the wear rates. We further analyzed the role of internal additives by considering the deformation and maximum polymer surface temperature during sliding. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Mechanical and thermal properties of EVA blended with biodegradable ethyl cellulose
Authors: Girija B. G. , Sailaja R. R. N. , Biswas Sharmistha , Deepthi M. V. 
Published: December 2009

AbstractIn this study, biodegradable blend of Poly (Ethylene‐co‐Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two‐stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Accelerated crystallization of poly(L‐lactide) by physical aging
Authors: Tsuji Hideto , Sawada Mariko 
Published: December 2009

AbstractThe low‐temperature physical aging of amorphous poly(L‐lactide) (PLLA) at 25–50°C below glass transition temperature (Tg) was carried out for 90 days. The physical aging significantly increased the Tg and glass transition enthalpy, but did not cause crystallization, regardless of aging temperature. The nonisothermal crystallization of PLLA during heating was accelerated only by physical aging at 50°C. These results indicate that the structure formed by physical aging only at 50°C induced the accelerated crystallization of PLLA during heating, whereas the structure formed by physical aging at 25 and 37°C had a negligible effect on the crystallization of PLLA during heating, except when the physical aging at 37°C was continued for the period as long as 90 days. The mechanism for the accelerated crystallization of PLLA by physical aging is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Investigations on the electrical and structural properties of PVA doped with (NH4)2SO4
Authors: Hassan M. A. , Gouda M. E. , Sheha E. 
Published: December 2009

AbstractSolid polymer electrolytes based on poly(vinyl alcohol) (PVA) complexed with ammonium sulfate (NH4)2SO4 at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by X‐ray diffraction (XRD) studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with the increase of ammonium sulfate added up to 5 wt %, after which the degree of crystallinity increases. The complexation of the salt with the polymer was confirmed by Fourier transform infrared (FTIR) spectroscopy. Electrical conductivity was measured in the temperature range of 303–373 K. The conductivity was found to obey Arrhenius formula. The dielectric permittivity ε′ was studied as function of temperature and frequency, respectively.The data showed increasing in ε′ values with the increase in temperature while decreased with increase in frequency for polymer electrolyte system up to 10% of ammonium sulfate added. For values of addition greater than 10%, ε′ is independent of both temperature and frequency. The ac conductivity is found to obey the power relation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Optimal investment and consumption with stochastic dividends
Authors: Wang Xikui , Wang Yan 
Published: December 2009

AbstractWe use the statistical model of bandit processes to formulate and solve two kinds of optimal investment and consumption problems. The payoffs from the investment are dividend payments with fixed return rates, but the payment frequency is stochastic following a Poisson distribution. The financial market consists of assets which follow Poisson distributions with known or unknown intensity rates. Two kinds of consumption patterns are defined and the optimality of the myopic strategy, the Gittins index strategy, and the play‐the‐winner strategy are discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Does CTCF mediate between nuclear organization and gene expression?
Authors: Ohlsson Rolf , Lobanenkov Victor , Klenova Elena 
Published: December 2009

AbstractThe multifunctional zinc‐finger protein CCCTC‐binding factor (CTCF) is a very strong candidate for the role of coordinating the expression level of coding sequences with their three‐dimensional position in the nucleus, apparently responding to a “code” in the DNA itself. Dynamic interactions between chromatin fibers in the context of nuclear architecture have been implicated in various aspects of genome functions. However, the molecular basis of these interactions still remains elusive and is a subject of intense debate. Here we discuss the nature of CTCF‐DNA interactions, the CTCF‐binding specificity to its binding sites and the relationship between CTCF and chromatin, and we examine data linking CTCF with gene regulation in the three‐dimensional nuclear space. We discuss why these features render CTCF a very strong candidate for the role and propose a unifying model, the “CTCF code,” explaining the mechanistic basis of how the information encrypted in DNA may be interpreted by CTCF into diverse nuclear functions.
Proteomics enhances evolutionary and functional analysis of reproductive proteins
Authors: Findlay Geoffrey D. , Swanson Willie J. 
Published: December 2009

AbstractReproductive proteins maintain species‐specific barriers to fertilization, affect the outcome of sperm competition, mediate reproductive conflicts between the sexes, and potentially contribute to the formation of new species. However, the specific proteins and molecular mechanisms that underlie these processes are understood in only a handful of cases. Advances in genomic and proteomic technologies enable the identification of large suites of reproductive proteins, making it possible to dissect reproductive phenotypes at the molecular level. We first review these technological advances and describe how reproductive proteins are identified in diverse animal taxa. We then discuss the dynamic evolution of reproductive proteins and the potential selective forces that act on them. Finally, we describe molecular and genomic tools for functional analysis and detail how evolutionary data may be used to make predictions about interactions among reproductive proteins.
Parallel evolution of segmentation by co‐option of ancestral gene regulatory networks
Authors: Chipman Ariel D. 
Published: December 2009

AbstractDifferent sources of data on the evolution of segmentation lead to very different conclusions. Molecular similarities in the developmental pathways generating a segmented body plan tend to suggest a segmented common ancestor for all bilaterally symmetrical animals. Data from paleontology and comparative morphology suggest that this is unlikely. A possible solution to this conundrum is that throughout evolution there was a parallel co‐option of gene regulatory networks that had conserved ancestral roles in determining body axes and in elongating the anterior‐posterior axis. Inherent properties in some of these networks made them easily recruitable for generating repeated patterns and for determining segmental boundaries. Phyla where this process happened are among the most successful in the animal kingdom, as the modular nature of the segmental body organization allowed them to diverge and radiate into a bewildering array of variations on a common theme.
Determination of eflornithine enantiomers in plasma by precolumn derivatization with o‐phthalaldehyde‐N‐acetyl‐l‐cysteine and liquid chromatography with UV detection
Authors: Jansson‐Löfmark R. , Römsing S. , Albers E. , Ashton M. 
Published: December 2009

AbstractA bioanalytical method for indirect determination of eflornithine enantiomers in 75 μL human plasma has been developed and validated. l‐ and d‐eflornithine were derivatized with o‐phthalaldehyde and N‐acetyl‐L‐cysteine to generate diastereomers which were separated on two serially connected Chromolith Performance columns (RP‐18e 100 × 4.6 mm i.d.) by a isocratic flow followed by a gradient flow for elution of endogenous compounds. The diastereomers were detected with UV (340 nm). The between‐day precisions for L‐ and D‐eflornithine in plasma were 8.4 and 2.3% at 3 μm, 4.0 and 5.1% at 400 μm, and 2.0 and 3.7% at 1000 μm. The lower limit of quantification was determined to be 1.5 μm, at which precision was 14.9 and 9.9% for L‐ and D‐eflornithine, respectively. Copyright © 2009 John Wiley & Sons, Ltd.
Synthesis and Anti‐HIV Activity of [ddN]‐[ddN] Dimers and Benzimidazole Nucleoside Dimers
Authors: Li Guo‐Rui , Liu Jun , Pan Qin , Song Zhi‐Bin , Luo Feng‐Ling , Wang Shao‐Ru , Zhang Xiao‐Lian , Zhou Xiang 
Published: December 2009

AbstractIn an attempt to combine the HIV‐inhibitory capacity of different 2′,3′‐dideoxynucleoside (ddN) analogs, we have designed and synthesized several dimers of [AZT]‐[AZT] and [AZT]‐[d4T]. In addition, we also synthesized the dimers of 1‐(1H‐benzimidazol‐1‐yl)‐1‐deoxy‐β‐D‐ribofuranose. The in vitro anti‐HIV activity of these compounds on a pseudotype virus, pNL4‐3.Luc.R‐E‐, in the 293T cells has been determined. Among these compounds, 2,2′‐(propane‐1,3‐diyl)bis[1‐(β‐D‐ribofuranosyl)‐1H‐benzimidazole] (3) showed the highest anti‐HIV activity with similar effect as AZT.
Sinuladiterpenes A–F, New Cembrane Diterpenes from Sinularia flexibilis
Authors: Lo Kuang‐Liang , Khalil Ashraf Taha , Kuo Yao‐Haur , Shen Ya‐Ching 
Published: December 2009

AbstractChromatographic investigation of the octocoral Sinularia flexibilis afforded six new cembrane diterpenes, sinuladiterpenes A–F (1–6, resp.), in addition to four known cembranolides, 11‐episinulariolide acetate, 11‐dehydrosinulariolide, 11‐episinulariolide, and sinulariolide. Their structures were elucidated by spectroscopic analysis, especially 2D‐NMR and HR‐ESI‐MS. Compound 2 exhibited significant in vitro cytotoxic activity against human colon adenocarcinoma (WiDr) cell line.
Synthesis and DNA‐Cleavage Activities of Dinuclear Copper(II) Complexes of Urea‐Bridged Macrocyclic Polyamines
Authors: Yue Yang , Li Jing , Zhang Ji , Zhang Zhong‐Wei , Lin Hong‐Hui , Chen Shan‐Yong , Yu Xiao‐Qi 
Published: December 2009

AbstractTwo dinuclear macrocyclic polyamine copper(II) (CuII) complexes, which have two cyclen units linked by urea, were synthesized as DNA‐cleavage agents. The structures of these new dinuclear complexes were identified by HR‐ESI‐MS and IR analyses. The catalytic activities of DNA cleavage of these dinuclear CuII complexes were subsequently studied. The results show that 6a was the better catalyst in the DNA‐cleavage process than 6b. The effects of reaction time and concentration of complexes were also investigated. The results indicate, that the CuII complexes could catalyze the cleavage of supercoiled DNA (pUC 19 plasmid DNA; Form I) under physiological conditions to produce selectively nicked DNA (Form II; no Form III was produced) with high yields (nearly 100%) in short time in the absence of reductant or oxidant.
In silicoStructural Study of Random Amino Acid Sequence Proteins Not Present in Nature
Authors: Prymula Katarzyna , Piwowar Monika , Kochanczyk Marek , Flis Lukasz , Malawski Maciej , Szepieniec Tomasz , Evangelista Giovanni , Minervini Giuseppe , Polticelli Fabio , Wiśniowski Zdzisław , Sałapa Kinga , Matczyńska Ewa , Roterman Irena 
Published: December 2009

AbstractThe three‐dimensional structures of a set of ‘never born proteins’ (NBP, random amino acid sequence proteins with no significant homology with known proteins) were predicted using two methods: Rosetta and the one based on the ‘fuzzy‐oil‐drop’ (FOD) model. More than 3000 different random amino acid sequences have been generated, filtered against the non redundant protein sequence data base, to remove sequences with significant homology with known proteins, and subjected to three‐dimensional structure prediction. Comparison between Rosetta and FOD predictions allowed to select the ten top (highest structural similarity) and the ten bottom (the lowest structural similarity) structures from the ranking list organized according to the RMS‐D value. The selected structures were taken for detailed analysis to define the scale of structural accordance and discrepancy between the two methods. The structural similarity measurements revealed discrepancies between structures generated on the basis of the two methods. Their potential biological function appeared to be quite different as well. The ten bottom structures appeared to be ‘unfoldable’ for the FOD model. Some aspects of the general characteristics of the NBPs are also discussed. The calculations were performed on the EUChinaGRID grid platform to test the performance of this infrastructure for massive protein structure predictions.
Chemical and Genetic Differentiation of Ligularia hodgsonii in Japan and China
Authors: Torihata Atsushi , Chao Xun , Kuroda Chiaki , Hanai Ryo , Hirota Hiroshi , Gong Xun 
Published: December 2009

AbstractThe chemical composition of the root extract and neutral base sequences of L. hodgsonii samples collected in Japan and China were examined. From the Japanese and the Chinese samples, 6β‐(angeloyloxy)furanoeremophilan‐15‐oic acid (2) and 3β‐acetoxy‐6β‐[(2‐methylbutanoyl)oxy]furanoeremophilan‐10β‐ol (3) were isolated as the major component, respectively. The sequence of the internal transcribed spacers (ITSs) of the ribosomal RNA gene was different in the Japanese and the Chinese samples. In contrast to the significant genetic difference, chemical diversity was limited to the positions of O‐functionalities on the furanoeremophilane skeleton, supporting our hypothesis that the production of furanoeremophilanes is ecologically advantageous.
abeo‐Taxane Diterpenoids from the Taiwanese Yew Taxus sumatrana
Authors: Wang Shih‐Sheng , Abd El‐Razek Mohamed H. , Chen Yi‐Cheng , Chien Ching‐Te , Guh Jih‐Hwa , Kuo Yao‐Haur , Shen Ya‐Ching 
Published: December 2009

AbstractChemical investigation of the acetonic extract of the leaves and twigs of Taxus sumatrana (Taxaceae) led to the isolation of four new taxane diterpene esters, taiwantaxins A–D (1–4, resp.). Their structures were determined primarily on the basis of 1D‐ and 2D‐NMR techniques as well as MS. Compound 1 is a rearranged taxane diterpenoid possessing an opened oxetane ring moiety containing C(4), C(5), and C(20). The metabolites 2 and 3 belong to a 5/6/6 taxene system having a rare five‐membered γ‐lactone ring comprising C(8), C(9), C(10), and C(19). Compound 4 is an example of a taxane diterpene containing a 6/8/6 ring system with a tetrahydrofuran ring comprising C(2), C(3), C(4), and C(20). The 11(15→1)abeo‐taxane diterpenoids, taiwantaxins A–C (1–3, resp.) are lacking an O‐bearing functionality at either C(13) or C(14). Compound 2 showed significant cytotoxic activity against human PC‐3 tumor cells.
A Novel Cytotoxic Cerium Complex: Aquatrichloridobis(1,10‐phenanthroline)cerium(III) (KP776). Synthesis, Characterization, Behavior in H2O, Binding towards Biomolecules, and Antiproliferative Activity
Authors: Biba Florian , Groessl Michael , Egger Alexander , Jakupec Michael A. , Keppler Bernhard K. 
Published: December 2009

AbstractThe lanthanide complex aquatrichloridobis(1,10‐phenanthroline)cerium(III) [Ce(phen)2(H2O)Cl3] (KP776) was fully characterized by elemental analysis, IR‐, and 1H‐ and 13C‐NMR spectroscopy, as well as TG/DTA measurements, and its behavior in H2O, important for the application as a chemotherapeutic, was studied. In addition, the binding of KP776 to nucleotides and single serum proteins was investigated by capillary electrophoresis, whereas binding to proteins in human plasma was observed by ICP‐MS. The compound shows promising anticancer properties in vitro: proliferation of human cancer cell lines is strongly inhibited with IC50 values in the very low micromolar range.