bluuebunny/crossref_metadata_2025_split huggingface dataset:
Virus Filtration Membranes Prepared from Nanoporous Block Copolymers with Good Dimensional Stability under High Pressures and Excellent Solvent Resistance
Authors: Yang Seung Yun , Park Jihoon , Yoon Jinhwan , Ree Moonhor , Jang Sung Key , Kim Jin Kon 
Published: April 2008

AbstractWe introduce a nanoporous membrane suitable for virus filtration with good dimensional stability under high pressures maintaining high selectivity. The membrane consists of a double layer: The upper layer is a nanoporous film with pore size of ∼17 nm and a thickness of ∼160 nm, which was prepared by polystyrene‐block‐poly(methyl methacrylate) copolymer (PS‐b‐PMMA) where PMMA block was removed by ultraviolet irradiation followed by rinsing with acetic acid. The nanoporous block copolymer film was combined with a conventional micro‐filtration membrane to enhance mechanical strength. The membrane employed in this study did not show any damage or crack even at a pressure of 2 bar, while high selectivity was maintained for the filtration of human rhinovirus type 14 which has a diameter of ∼30 nm and is a major pathogen of the common cold in humans. Furthermore, due to crosslinked PS matrix during the UV irradiation, the nanoporous membrane showed excellent resistance to all organic solvents. This could be used under harsh filtration conditions such as high temperature and strong acidic (or basic) solution.
Effect of Charge Density on Energy‐Transfer Properties of Cationic Conjugated Polymers
Authors: Pu Kan‐Yi , Fang Zhen , Liu Bin 
Published: April 2008

AbstractCationic conjugated polymers (CCPs) with different charge densities are synthesized via Suzuki polymerization. The CCPs show similar optical properties in aqueous solutions but obvious difference in fluorescence resonance energy transfer (FRET) to Texas Red‐labeled single‐stranded DNA (ssDNA‐TR). Both CCP and TR fluorescence quenching are revealed to influence the energy‐transfer process. The difference in quantum yields of CCP/ssDNA complexes highlights the importance of polymer side‐chain structures and charge density. A CCP with a high charge density and ethylene oxide as the side chain provides the highest quantum yield for CCP/ssDNA complexes, which favors FRET. TR quenching within the CCP/ssDNA complexes is predominantly determined by the CCP charge density. In contrast to the other two polymers, the CCP with low charge density provides the most‐intense polymer‐sensitized TR emission, which is due to the collective response of more optically active polymer units around TR and the minimized TR self‐quenching within the CCP/ssDNA‐TR complexes. These studies provide a new guideline for improving the signal amplification of conjugated‐polymer‐based optical sensors.
Third‐Order Nonlinear Optical Response of Gold‐Island Films
Authors: Xenogiannopoulou Evangelia , Iliopoulos Kostas , Couris Stelios , Karakouz Tanya , Vaskevich Alexander , Rubinstein Israel 
Published: April 2008

AbstractFilms of gold nanoscaled islands with thicknesses ranging between 0.5 and 15 nm were prepared by thermal evaporation onto untreated and aminosilane‐pretreated glass substrates. Post‐deposition annealing was found to modify the morphological characteristics of the islands (e.g., average island area and height, inter‐island distance, etc.), resulting in changes of the localized surface plasmon resonance (SPR) characteristics and, therefore, modifying the nonlinear optical (NLO) response of the films. The NLO response of both unannealed and annealed (20 h at 200 °C) films was studied by means of the optical Kerr effect (OKE), using 35 ps, 532 nm laser excitation, while measurements performed by means of the Z‐scan technique allowed for the determination of both the nonlinear refraction and absorption characteristics of the films. The results are discussed and compared with other reports.
Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids
Authors: Kuschel Andreas , Polarz Sebastian 
Published: April 2008

AbstractAn interesting class of materials is mesoporous organosilica materials containing a bridging, organic group along the pore‐surface. Such materials are prepared from silsesquioxane precursors of the type (R′O)3Si‐R‐Si(OR′)3 where R is the bridging organic group of interest, in combination with a lyotropic phase as a template for the generation of the pores. A new silsesquioxane precursor, 1,3‐bis‐(trialkoxysilyl)‐5‐bromobenzene, and the related mesoporous organosilica material containing bromobenzene groups located at the pore walls are presented in the current publication. The latter precursor allows access to the derivatization reactions known for halogenated aromatic compounds. Materials containing phenyl derivatives can be obtained either by chemical modifications starting from the mentioned precursor on the molecular scale, or the modifications can be performed directly at the surfaces of the porous material. Materials with surfaces containing benzoic acid, styrene, and phenylphosphonic acid are described.
Asymmetric Organocatalysis: From Infancy to Adolescence
Authors: Dondoni Alessandro , Massi Alessandro 
Published: April 2008

AbstractAfter an initial period of validating asymmetric organocatalysis by using a wide range of important model reactions that constitute the essential tools of organic synthesis, the time has now been reached when organocatalysis can be used to address specific issues and solve pending problems of stereochemical relevance. This Review deals with selected studies reported in 2006 and the first half of 2007, and is intended to highlight four main aspects that may be taken as testimony of the present status and prospective of organocatalysis: a) chemical efficiency; b) discovery of new substrate combinations to give new asymmetric syntheses; c) development of new catalysts for specific purposes by using mechanistic findings; and d) applications of organocatalytic reactions in the asymmetric total synthesis of target natural products and known compounds of biological and pharmaceutical relevance.
Preparation and characterization of poly(vinyl alcohol) and gelatin blend films
Authors: Pawde S. M. , Deshmukh Kalim , Parab Sanmesh 
Published: April 2008

AbstractPoly(vinyl alcohol) (PVA) is a water‐soluble polymer that has been studied intensively because of several interesting physical properties that are useful in technical applications, including biochemical and medical applications. In this article, we report the effects of the addition of gelatin on the optical, microstructural, thermal, and electrical properties of PVA. Pure and PVA/gelatin blend films were prepared with the solution‐casting method. These films were further investigated with Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, and dielectric measurements. The FTIR spectrum shows a strong chemical interaction between PVA and gelatin molecules with the formation of new peaks. These peaks are due to the presence of gelatin in the blend films. The DSC results indicate that the addition of gelatin to PVA changes the thermal behavior, such as the melting temperature of PVA, and this shows that the blends are compatible with each other. This also shows that the interaction of gelatin and PVA molecules changes the crystallite parameters and the degree of crystallinity, and this supports the XRD results. The UV–vis optical study also reflects the formation of the complex and its effect on the microstructure of the blend film. Moreover, the addition of gelatin also gives rise to changes in the electrical properties of PVA/gelatin blend films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Instant modification of graphite nanosheets by the grafting of a styrene oligomer under microwave radiation
Authors: Li Jianping , Lin Hongfei , Zhao Weifeng , Chen Guohua 
Published: April 2008

AbstractInstant grafting polymerization of styrene initiated by microwave radiation on the surface of graphite nanosheets (GNs) was carried out. The stability of the modified GN dispersions in different solvents indicated significant changes in the surface properties of GNs. In comparison with GNs without modification, the modified GNs showed more stable suspensions in a nonpolar organic solvent such as toluene and were more likely to form a precipitate when dispersed in distilled water, a polar solvent. Fourier transform infrared and thermogravimetric analysis were used to confirm the functionalized GNs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Molecular weight evaluation of depolymerized poly(ethylene terephthalate) using intrinsic viscosity
Authors: Li Kaixiang , Song Xiaofang , Zhang Dong 
Published: April 2008

AbstractA series of poly(ethylene terephthalate) (PET) depolymerization experiments versus time was proceeded under optimal experimental conditions with microwave radiation, in which the temperature was 220°C, the pressure was 200 psi, the microwave power was 260 W, and the ratio of water to PET was 10 : 1. The relative viscosity of the feedstock PET grain and the residual solid products from depolymerization reaction at six different time, respectively, was measured in the solution of 60/40 (w/w) phenol/1,1,2,2‐tetrachloroethane. Then the approximate intrinsic viscosity was calculated from linear and exponential extrapolation of reduced viscosity. Molecular weights were calculated by Mark‐Houwink's equation, with values of K and α taken from the literatures. The results show that the molecular weights fell dramatically with increasing of reaction time, namely the number average molecular weight from 2.57 × 104 of the feedstock PET to 372 of the remained solid product at 240 min, and the weight average molecular weight of the samples fell from 3.89 × 104 to 408 correspondingly. The intrinsic viscosity decreased greatly with reaction, while the distribution of molecular weight turned to be steady. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Phase inversion process to prepare quasi‐solid‐state electrolyte for the dye‐sensitized solar cells
Authors: Zhang Jing , Han Hongwei , Xu Sheng , Wu Sujuan , Zhou Conghua , Yang Ying , Zhao Xingzhong 
Published: April 2008

AbstractA quasi‐solid‐state electrolyte for the dye‐sensitized solar cells was prepared following the phase inversion process. The microporous polymer electrolyte based on poly(vinylidene fluoride‐co‐hexafluoropropylene) (P(VDF‐HFP)) hybrid with different amount of TiO2 nanoparticles were prepared. The surface morphologies, the differential scanning calorimetry, and the ionic conductivity of the microporous polymer electrolyte were tested and analyzed. The results indicated that the microporous polymer electrolyte with TiO2 nanoparticles modification exhibited better ionic conductivity compared with the original P(VDF‐HFP) polymer electrolyte. The optimal ionic conductivity of 0.8 mS cm−1 is obtained with the 30 wt % TiO2 nanoparticles modification. When assembled with the 30 wt % TiO2 nanoparticles modified quasi‐solid‐state electrolyte, the dye‐sensitized TiO2 nanocrystalline solar cell exhibited the light to electricity conversion efficiency of 2.465% at light intensity of 42.6 mW cm−2, much better than the performance of original P(VDF‐HFP) microporous polymer electrolyte DSSC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Morphology and mechanical properties of natural rubber and styrene‐grafted natural rubber latex compounds
Authors: Arayapranee Wanvimon , Rempel Garry L. 
Published: April 2008

AbstractThe mechanical properties of natural rubber latex (NRL) modified with styrene‐grafted natural rubber (styrene‐GNR) latex were investigated. Styrene‐GNR was first synthesized via emulsion copolymerization using cumene hydroperoxide/tetraethylene pentamine as an initiator. The styrene‐GNR latex produced was mixed with NRL with various latex compounding contents and then prevulcanization was carried out. The mechanical properties and heat, weathering, and ozone resistance of the natural rubber (NR) and styrene‐GNR latex compounds were investigated as a function of the grafted NR content. The results indicated that the tensile and tear strength were decreased, whereas Young's modulus and hardness were increased at high content of styrene‐GNR. Addition of styrene‐GNR improved the resistance of the compounds to heat and weathering ageing. The ozone resistance of the compound containing styrene‐GNR is superior to that of the NR‐rich compound. The results indicated that NR/styrene‐GNR latex compounds maintained good antiageing properties required for outdoor applications. The tensile fracture surface examined by scanning electron microscopy confirmed a shift from ductility failure to brittle with an increase of the styrene‐GNR content in the compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Statistical analysis of personal radiofrequency electromagnetic field measurements with nondetects
Authors: Röösli Martin , Frei Patrizia , Mohler Evelyn , Braun‐Fahrländer Charlotte , Bürgi Alfred , Fröhlich Jürg , Neubauer Georg , Theis Gaston , Egger Matthias 
Published: April 2008

AbstractExposimeters are increasingly applied in bioelectromagnetic research to determine personal radiofrequency electromagnetic field (RF‐EMF) exposure. The main advantages of exposimeter measurements are their convenient handling for study participants and the large amount of personal exposure data, which can be obtained for several RF‐EMF sources. However, the large proportion of measurements below the detection limit is a challenge for data analysis. With the robust ROS (regression on order statistics) method, summary statistics can be calculated by fitting an assumed distribution to the observed data. We used a preliminary sample of 109 weekly exposimeter measurements from the QUALIFEX study to compare summary statistics computed by robust ROS with a naïve approach, where values below the detection limit were replaced by the value of the detection limit. For the total RF‐EMF exposure, differences between the naïve approach and the robust ROS were moderate for the 90th percentile and the arithmetic mean. However, exposure contributions from minor RF‐EMF sources were considerably overestimated with the naïve approach. This results in an underestimation of the exposure range in the population, which may bias the evaluation of potential exposure‐response associations. We conclude from our analyses that summary statistics of exposimeter data calculated by robust ROS are more reliable and more informative than estimates based on a naïve approach. Nevertheless, estimates of source‐specific medians or even lower percentiles depend on the assumed data distribution and should be considered with caution. Bioelectromagnetics. Bioelectromagnetics 29:471–478, 2008. © 2008 Wiley‐Liss, Inc.
Cytotoxic Triterpenoids from the Root Bark of Helicteres angustifolia
Authors: Pan Min‐Hsiung , Chen Chiu‐Ming , Lee Shwu‐Woan , Chen Zong‐Tsi 
Published: April 2008

AbstractThree new triterpenoids, 3β‐acetoxy‐27‐[(E)‐cinnamoyloxy]lup‐20(29)‐en‐28‐oic acid methyl ester (1), 3β‐acetoxy‐27‐[(4‐hydroxybenzoyl)oxy]lup‐20(29)‐en‐28‐oic acid (2), and 3β‐acetoxy‐27‐[(4‐hydroxybenzoyl)oxy]olean‐12‐en‐28‐oic acid methyl ester (3), together with nine known triterpenoids, 4–12, were isolated from the root bark of Helicteres angustifolia. The structures of these compounds were established on the basis of spectroscopic methods including 2D‐NMR experiments. All twelve compounds were tested for their cytotoxic activities against human colorectal cancer (COLO 205), human hepatoma (Hep G2), and human gastric cancer (AGS) cell lines in vitro. Among them, compounds 2, 3, 3β‐O‐[(E)‐coumaroyl]betulinic acid (6), and pyracrenic acid (7) showed significant cytotoxic activities against human cancer cells COLO 205 and AGS.
Anthracene Carboxyimides and Their Dimers
Authors: Langhals Heinz , Schönmann Gertrud , Polborn Kurt 
Published: April 2008

AbstractSoluble anthracenedicarboxyimides have been prepared and undergo a photodimerisation of the anthracene skeleton, which is important for their application as antitumour agents, such as azonafides. Reaction under strongly alkaline conditions causes CC coupling to form soluble dimeric fluorescent dyes with bathochromic absorption and fluorescence in the NIR region. These dyes are of special interest because of their absorption at longer wavelengths.
Potential‐Energy and Free‐Energy Surfaces of Glycyl‐Phenylalanyl‐Alanine (GFA) Tripeptide: Experiment and Theory
Authors: Valdes Haydee , Spiwok Vojtech , Rezac Jan , Reha David , Abo‐Riziq Ali G. , de Vries Mattanjah S. , Hobza Pavel 
Published: April 2008

AbstractThe free‐energy surface (FES) of glycyl‐phenylalanyl‐alanine (GFA) tripeptide was explored by molecular dynamics (MD) simulations in combination with high‐level correlated ab initio quantum chemical calculations and metadynamics. Both the MD and metadynamics employed the tight‐binding DFT‐D method instead of the AMBER force field, which yielded inaccurate results. We classified the minima localised in the FESs as follows: a) the backbone‐conformational arrangement; and b) the existence of a COOH⋅⋅⋅OC intramolecular H‐bond (families CO2Hfree and CO2Hbonded). Comparison with experimental results showed that the most stable minima in the FES correspond to the experimentally observed structures. Remarkably, however, we did not observe experimentally the CO2Hbonded family (also predicted by metadynamics), although its stability is comparable to that of the CO2Hfree structures. This fact was explained by the former's short excited‐state lifetime. We also carried out ab initio calculations using DFT‐D and the M06‐2X functional. The importance of the dispersion energy in stabilising peptide conformers is well reflected by our pioneer analysis using the DFT‐SAPT method to explore the nature of the backbone/side‐chain interactions.
ChemInform Abstract: Asymmetric Nitroaldol Reaction Catalyzed by a Chromium(III)—Salen System.
Authors: Kowalczyk Rafal , Sidorowicz Lukasz , Skarzewski Jacek 
Published: April 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Preparation of Novel Azabicyclic Amines and α7 Nicotinic Acetylcholine Receptor Activity of Derived Aryl Amides.
Authors: Walker Daniel P. , Acker Brad A. , Jacobsen E. Jon , Wishka Donn G. 
Published: April 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Marine Diterpenoids with a Briarane Skeleton from the Okinawan Soft Coral Pachyclavularia violacea
Authors: Ito Hisanaka , Iwasaki Junya , Sato Yuki , Aoyagi Miwako , Iguchi Kazuo , Yamori Takao 
Published: April 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Chlorinated Briarane‐Type Diterpenoids from the Gorgonian Coral Ellisella robusta (Ellisellidae).
Authors: Sung Ping‐Jyun , Chiang Michael Y. , Tsai Wei‐Tse , Su Jui‐Hsin , Su Yu‐Mine , Wu Yang‐Chang 
Published: April 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: The Catalytic Asymmetric Strecker Reaction: Ketimines Continue to Join the Fold
Authors: Connon Stephen J. 
Published: April 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The motor activity of mammalian axonemal dynein studied in situ on doublet microtubules
Authors: Lorch David P. , Lindemann Charles B. , Hunt Alan J. 
Published: April 2008

AbstractFlagellar dynein generates forces that produce relative shearing between doublet microtubules in the axoneme; this drives propagated bending of flagella and cilia. To better understand dynein's role in coordinated flagellar and ciliary motion, we have developed an in situ assay in which polymerized single microtubules glide along doublet microtubules extruded from disintegrated bovine sperm flagella at a pH of 7.8. The exposed, active dynein remain attached to their respective doublet microtubules, allowing gliding of individual microtubules to be observed in an environment that allows direct control of chemical conditions. In the presence of ATP, translocation of microtubules by dynein exhibits Michaelis‐Menten type kinetics, with Vmax = 4.7 ± 0.2 μm/s and Km = 124 ± 11 μM. The character of microtubule translocation is variable, including smooth gliding, stuttered motility, oscillations, buckling, complete dissociation from the doublet microtubule, and occasionally movements reversed from the physiologic direction. The gliding velocity is independent of the number of dynein motors present along the doublet microtubule, and shows no indication of increased activity due to ADP regulation. These results reveal fundamental properties underlying cooperative dynein activity in flagella, differences between mammalian and non‐mammalian flagellar dynein, and establish the use of natural tracks of dynein arranged in situ on the doublet microtubules of bovine sperm as a system to explore the mechanics of the dynein‐microtubule interactions in mammalian flagella. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.