bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of charge hopping between redox center molecules in a polymer membrane based on percolation theory
Authors: Shiroishi Hidenobu , Ishikawa Kazunori , Hirano Kazuhiro , Kaneko Masao 
Published: January 2005

AbstractCharge propagation in a polymer membrane dispersing redox center molecules was studied using Monte‐Carlo simulation. The charge propagation was visualized using a uniform sphere sites model. The fraction of charge‐transported sites (R
CT) increased above concentration called percolation threshold. The charge transfer in a Nafion® membrane confining [(bpy)2 (H2O)RuORu(H2O)(bpy)2]4+ (abbreviated to Nafion [Ru‐O‐Ru]) as well as in a polymer pendant $\hbox{Ru(bpy)}_{3}^{2+}$ membrane was investigated with a potential‐step chronoamperospectrometry (PSCAS), and the behavior was compared with the simulation The relationship between charge hopping distance and critical percolation concentration (c
p) was obtained from the percolation theory and applied to the actual systems. The charge hopping distance between molecules was estimated as 2.04 nm for Nafion[Ru‐O‐Ru] system and 1.71 nm for polymer pendant $\hbox{\it Ru(bpy)}_{3}^{2+}$. When the charge propagation takes place by charge hopping mechanism, a slow diffusion of the redox centers increases R
CT at the concentration below c
p, but decreases at the concentration above c
p. Although the c
p becomes ambiguous with increasing diffusion coefficient (D
phys), it was suggested that c
p value doesn't change. Copyright © 2001 John Wiley & Sons, Ltd.
Improved procedure for the quality control of Hypericum perforatum L.
Authors: Poutaraud Anne , Lobstein Annelise , Girardin Philippe , Weniger Bernard 
Published: January 2005

AbstractA new, fast and reliable procedure for the quantification of the major compounds of Hypericum perforatum L. has been developed. Four naphthodianthrones (protopseudohypericin, pseudohypericin, protohypericin, hypericin) and two phloroglucinols (hyperforin, adhyperforin) were assayed by HPLC using a short (17 min) linear gradient, with hypericin and hyperforin as external standards. Extraction of dried plant material with methanol in the dark at room temperature for 2 h led to a complete recovery of phloroglucinols but only a partial recovery of the naphthodianthrone derivatives. Treatment of plant material with water:ethanol (40:60, v/v) in a water bath shaker at 80°C led to the total extraction of hypericins, but a 10% loss of total hyperforins was also observed. The two extraction methods, applied successively to the same sample, allowed the complete extraction of all compounds of interest. A 5 min exposure of the crude extract of H. perforatum to sunlight (1 E/m2) induced a 96% loss of hyperforins, whereas the dry plant material lost only 20% of hyperforins after 2 h exposure to sunlight (24 E/m2). Copyright © 2001 John Wiley & Sons, Ltd.
A claims data approach to defining an episode of care
Authors: Schulman Kevin A. , Yabroff K. Robin , Kong Janet , Gold Karen F. , Rubenstein L. Elizabeth , Epstein Andrew J. , Glick Henry 
Published: January 2005

AbstractObjectiveTo utilize health services research techniques in developing an episode of care using an administrative data set. This method is demonstrated for an episodic clinical condition, migraine.Data SourcesMedicaid administrative data set of 3,372 patients with a diagnosis of migraine (ICD‐9‐CM 346.0, 346.1) in the state of Pennsylvania between May 1990 and March 1992.Study DesignThe duration of a migraine episode was measured by assessing the magnitude of resource utilization and the proportion of patients with charges in the period after the index migraine as compared to the period before the index migraine. A confidence interval (CI) was developed around each measure using bootstrap techniques.Data Collection MethodsAll charge data were extracted daily for a 113‐day observation period surrounding each index migraine in order to observe the duration of impact of a migraine diagnosis on resource utilization.Principal FindingsThe lower limits of both the 95% and 99% CIs for the difference in charges are greater than 0 for three weeks. The lower limits of both CIs for the difference in the proportion of patients with charges are above 0 for six weeks.ConclusionsOur analysis demonstrates that a health services research framework can be used to define an episode of care for a chronic disease category such as migraine. This method can be used to evaluate episodes of care for clinical studies of limited or episodic conditions and to complement clinical expertise in developing time horizons for clinical trials. Copyright © 1999 Health Research and Education Trust. Reprinted in 2001 by John Wiley & Sons, Ltd.
High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene
Authors: Mansencal Rachel , Haidar Bassel , Vidal Alain , Delmotte Luc , Chezeau Jean‐Michel 
Published: January 2005

AbstractThis work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent‐extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [1H] high‐resolution high‐speed magic‐angle spinning solid‐state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2‐polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface.© 2001 Society of Chemical Industry
Synthesis and characterization of novel biodegradable poly(carbonate‐co‐phosphate)s
Authors: Wang Xu‐Li , Zhuo Ren‐Xi , Liu Li‐Jian 
Published: January 2005

AbstractA series of aliphatic poly(carbonate‐co‐phosphate)s was synthesized in bulk using aluminium isopropoxide as initiator by ring‐opening polymerization with various cyclic carbonates (trimethylene carbonate (TMC) and 5,5‐dimethyltrimethylene carbonate (DTC)) and cyclic phosphates (ethylene ethyl phosphate (EEP), ethylene isobutyl phosphate (EIBP), ethylene lauryl phosphate (ELP) and ethylene stearyl phosphate (ESP)). The influence of reaction conditions such as polymerization time, polymerization temperature and initiator concentration on the yield and molecular weight were investigated. The substituent effect of the cyclic monomers on the polymerization was also studied, and the results indicate that the substituents exert a marked influence on the molecular weight of the copolymers obtained. The comonomer reactivity ratios were determined (TMC 0.88 and EEP 1.17). The copolymers with backbone chains rich in phosphate content exhibit better hydrophilicity than that of TMC homopolymer, and the degradation rate of the copolymers increases with the increase of phosphate content therein.© 2001 Society of Chemical Industry
Role of silane coupling agents for performance improvement of poly(vinyl acetate)/tetraethyl orthosilicate hybrid composites prepared by a sol–gel process
Authors: Jang Jyongsik , Bae Joonwon , Kang Doohwan 
Published: January 2005

AbstractSilica based poly(vinyl acetate)/inorganic hybrid composites were prepared via a sol–gel process under acidic conditions. Because the phase behaviour of the hybrids is greatly affected by weak interactions such as hydrogen bonding between organic polymer and inorganic network, two types of silane coupling agent (vinyl trimethoxysilane and 3‐(trimethoxysilyl)propyl methacrylate) were used to introduce specific interactions and to control phase behaviour in the interface between polymer and silica. The interfacial interactions between polymer and inorganic segment in the presence of silane have been investigated by Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that the thermal stability of organic components in the hybrids is enhanced by addition of silane coupling agents. Scanning electron micrographs reveal that silica particles are homogeneously dispersed in the organic matrix as a result of the specific interactions.© 2001 Society of Chemical Industry
Preparation of novel soluble poly(ester imide)s containing a trimellitimide moiety and their use as modifiers for aromatic diamine‐cured epoxy resin
Authors: Iijima Takao , Hamakawa Shuichi , Tomoi Masao 
Published: January 2005

AbstractPoly(ester imide)s, prepared by the reaction of phthalic anhydride, N‐(4‐carboxyphenyl) trimellitimide and 1,2‐ethanediol, were used to improve the toughness of bisphenol‐A diglycidyl ether epoxy resin cured with 4,4′‐diaminodiphenyl sulfone (DDS). The poly(ester imide)s include poly(ethylene phthalate‐co‐ethylene N‐(1,4‐phenylene) trimellitimide dicarboxylate)s (PESIs) having 10, 20 and 30 mol% trimellitimide (TI) units, respectively. PESIs having 10 and 20 mol% TI units were effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt% of PESI (20 mol% TI unit,
M
W 19300 g mol−1) led to a 55% increase in the fracture toughness (KIC) of the cured resin (with an increase in flexural strength and modulus) and the modified resin had a particulate morphology. PESI having 30 mol% TI units was not effective because of degradation of the modifier by DDS. The toughening mechanism is discussed in terms of morphological and dynamic viscoelastic behaviour of the modified epoxy resin system.© 2001 Society of Chemical Industry
Gellan/poly(vinyl alcohol) hydrogels: characterization and evaluation as delivery systems
Authors: Cascone Maria Grazia , Barbani Niccoletta , Maltinti Simona , Lazzeri Luigi 
Published: January 2005

AbstractBioartificial polymeric materials in the form of hydrogels were prepared starting from blends of poly(vinyl alcohol) (PVOH) with gellan, using a procedure based on freeze–thawing cycles. The effect exerted by gellan on the properties of these materials was investigated. The materials were loaded with human growth hormone (GH) and the release of the drug was evaluated. The results obtained indicated that gellan favours the crystallization process of PVOH allowing the formation of a material with a more homogeneous and stable structure than that of pure PVOH hydrogels. Both the PVOH melting enthalpy and the elastic modulus increased with increasing gellan content in the hydrogels; in addition, the higher the gellan content in the samples, the lower was the amount of PVOH released. Gellan/PVOH hydrogels were able to release GH and the release was affected by the content of the biological component. The amount of GH released was within a physiological range.© 2001 Society of Chemical Industry
Polymerization of styrene with a simple rare earth metal initiator
Authors: Hayakawa Toshiyuki , Nakayama Yuusho , Yasuda Hajime 
Published: January 2005

AbstractThe catalytic activity in the polymerization of styrene has been examined using commercially available simple rare earth metal compounds such as Sm(OiPr)3, Sm(acac)3, Sm(OCOMe)3, SmI2(THF)2 or SmCl3 coupled with Et3Al or methylaluminoxane (MAO). Among these compounds, the Sm(OiPr)3/AlEt3 system shows the highest catalytic activity, especially in the presence of a minor amount of toluene at 60 °C. The random copolymerization of styrene with methyl methacrylate suggests that the present polymerization proceeds with a radical polymerization mechanism. (C5Me5)SmCl3Na(THF) and (C5Me5)SmCl3Li(THF) systems exhibit relatively low catalytic activity, even in the presence of AlEt3.© 2001 Society of Chemical Industry
Compatibilization of SBR/NBR blends using chemically modified styrene‐co‐butadiene rubber Part 2. Effect of compatibilizer loading
Authors: Ramesan M T , Alex Rosamma 
Published: January 2005

AbstractThe present work focuses on the compatibization of styrene‐co‐butadiene rubber (SBR)/acrylonitrile‐co‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐co‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data.© 2001 Society of Chemical Industry
Fracture behaviour of acrylonitrile–butadiene rubber/clay nanocomposite
Authors: Nah Changwoon , Ryu Hyune Jung , Han Sang Hyub , Rhee John M , Lee Myong‐Hoon 
Published: January 2005

AbstractA new fracture behaviour is described for acrylonitrile–butadiene rubber/clay nanocomposite. The nanocomposite is prepared by melt mixing the organo‐treated montmorillonite into the rubber matrix, together with a peroxide curative, and crosslinked by conventional compression moulding for typical rubbers. A considerable enhancement in stiffness is observed without serious sacrifice in ultimate strength. A totally different tear morphology of a series of regularly‐spaced tear ridges parallel to the direction of tearing was observed instead of the typical ‘cross‐hatched morphology’ of conventional rubber composites.© 2001 Society of Chemical Industry
Aeration of fishponds by photovoltaic power
Authors: Applebaum J. , Mozes D. , Steiner A. , Segal I. , Barak M. , Reuss M. , Roth P. 
Published: January 2005

AbstractFishponds in aquaculture farms are usually located in remote areas, far from grid supply lines. Aeration of ponds for growing aquatic animals (e.g., fish) is required to prevent mortality and to intensify production, especially when feeding is practical, and in warm regions. Aeration systems with photovoltaic power supply may be the appropriate technology from an ecological and economic point of view. In addition, photovoltaic power is very suitable for remote developing regions, owing to its simplicity and low maintenance. The purpose of the present study was to demonstrate an aeration system using a paddle wheel connected to a permanent magnet DC motor, and powered by a photovoltaic power supply. The study was carried out on the coastal area in the center of Israel. The aeration system operated satisfactorily for the demonstration period of more than two years. Copyright © 2001 John Wiley & Sons, Ltd.
Impact of light‐induced recombination centres on the current–voltage characteristic of czochralski silicon solar cells
Authors: Schmidt Jan , Cuevas Andrés , Rein Stefan , Glunz Stefan W. 
Published: January 2005

AbstractWe have investigated the effect of the light‐induced deep‐level recombination centre specific to boron‐doped, oxygen‐contaminated Czochralski (Cz) silicon on the current–voltage characteristic of Cz silicon solar cells by means of numerical simulation and experiment. The device simulation predicts the occurrence of a shoulder in the current–voltage curve after activating the characteristic recombination centre. The physical reason for the non‐ideal diode behaviour, characterised by a local ideality factor greater unity, is the strongly injection‐level‐dependent bulk lifetime produced by the deep‐level centre. The increased ideality factor causes a degradation in fill factor with the magnitude of degradation depending on the doping concentration of the Cz silicon base. In order to verify the theoretical predictions experimentally, we have performed measurements on high‐efficiency Cz silicon solar cells. Current–voltage curves recorded before and after light degradation clearly show the theoretically predicted change in shape and the reduction in fill factor. An excellent quantitative agreement between calculation and experiment is obtained for the subtracted current–voltage curves measured after and before illumination. Copyright © 2001 John Wiley & Sons, Ltd.
Textured monocrystalline thin‐film Si cells from the porous silicon (PSI) process
Authors: Brendel Rolf , Auer Richard , Artmann Hans 
Published: January 2005

AbstractWe have fabricated a textured monocrystalline Si solar cell with a thickness of 15·5 μm and a confirmed efficiency of 12·2% using porous silicon (PSI) for layer transfer. The PSI process avoids photolithography and high‐temperature oxidation. The cell has a surface that is textured with randomly positioned inverted pyramids for light trapping. The device does not yet fully exploit the light‐trapping capability of this film shape, owing to a small back‐surface reflectance. Copyright © 2001 John Wiley & Sons, Ltd.
Purification and proteomic analysis of outer membrane vesicles from a clinical isolate of Leptospira interrogans serovar Copenhageni
Authors: Nally Jarlath E. , Whitelegge Julian P. , Aguilera Rodrigo , Pereira Martha M. , Blanco David R. , Lovett Michael A. 
Published: January 2005

AbstractThe severe pulmonary form of leptospirosis (SPFL) is an especially serious and rapid disease process characterized by alveolar hemorrhage and acute respiratory failure. The outer membrane of Leptospira facilitates direct interactions with the environs and likely contains important constituents involved during infection, transmission, survival, and adaptation to environmental conditions, including putative vaccinogen and diagnostic candidates. Outer membrane vesicles (OMVs) were purified by incubation in low‐pH citrate buffer, treatment in a French press, and centrifugation over a continuous sucrose gradient. OMVs characterized by two‐dimensional gel electrophoresis (2‐DE) contained the previously described outer membrane proteins OmpL1, Qlp42, LipL32, LipL41, LipL36 and Loa22. In addition, unknown, hypothetical and putative outer membrane proteins were identified. High‐performance liquid chromatography (HPLC) coupled with mass spectrometry and fraction collection (LC‐MS+) measured the intact mass profile of the major outer membrane protein, LipL32, and the putative lipoprotein Qlp42. In contrast to a predicted molecularmass of 27 653.5 Da for LipL32 after cleavage of its signal peptide, intact mass proteomics measured the mass as ranging from 28 468 to 28 583 Da, consistent with lipidation of LipL32. In contrast to a predicted molecular mass of 39.8 kDa for Qlp42, the actual mass was measured as 24 811 and 26 461 Da consistent with a 30 kDa doublet observed on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) gels and processing of the N‐terminus of the mature protein. These studies indicate that purified OMVs are highly compatible with proteomics technologies including 2‐DE and intact mass proteomics using LC‐MS+ that facilitates definition of actual molecular masses of intact outer membrane proteins, and heterogeneity associated with them.∁
A proteomic approach to characterize protein shedding
Authors: Ahram Mamoun , Adkins Joshua N. , Auberry Deanna L. , Wunschel David S. , Springer David L. 
Published: January 2005

AbstractShedding (i.e. proteolysis of ectodomains of membrane proteins) plays an important pathophysiological role. In order to study the feasibility of identifying shed proteins, we analyzed serum‐free media of human mammary epithelial cells by mass spectrometry following induction of shedding by the phorbol ester, 4β‐phorbol 12‐myristate 13‐acetate (PMA). Different means of sample preparation, including biotinylation of cell surface proteins, isolation of glycosylated proteins, and preparation of crude protein fractions, were carried out to develop the optimal method of sample processing. The collected proteins were digested with trypsin and analyzed by reversed‐phase capillary liquid chromatography interfaced to an ion‐trap mass spectrometer. The resulting peptide spectra were interpreted using the program SEQUEST. Analyzing the sample containing the crude protein mixture without chemical modification or separation resulted in the greatest number of identifications, including putatively shed proteins. Overall, 45 membrane‐associated proteins were identified including 22 that contain at least one transmembrane domain and 23 that indirectly associate with the extracellular surface of the plasma membrane. Of the 22 transmembrane proteins, 18 were identified by extracellular peptides providing strong evidence they originate from regulated proteolysis or shedding processes. We combined results from the different experiments and used a peptide count method to estimate changes in protein abundance. Using this approach, we identified two proteins, syndecan‐4 and hepatoma‐derived growth factor, whose abundances increased in media of cells treated with PMA. We also detected proteins whose abundances decreased after PMA treatment such as 78 kDa glucose‐regulated protein and lactate dehydrogenase A. Further analysis using immunoblotting validated the abundance changes for syndecan‐4 and 78 kDa glucose‐regulated protein as a result of PMA treatment. These results demonstrate that tandem mass spectrometry can be used to identify shed proteins and to estimate changes in protein abundance.
1,4‐Naphthoquinonediazide‐2‐carboxylic acid: a diazo compound with a long‐lived triplet excited state
Authors: Bucher Götz , Wandel Holger , Sander Wolfram 
Published: January 2005

AbstractLaser flash photolysis (308 nm) of 1,4‐naphthoquinonediazide‐2‐carboxylic acid 1 in 2‐methyltetrahydrofuran (MTHF) leads to the detection of a long‐lived (5.3 μs) triplet excited state, whose triplet energy, obtained by measuring the phosphorescence spectrum of 1 in an Ar‐ matrix at 10 K, is ca 55 kcal mol−1 (1 kcal­= 4.184 KJ). The first triplet excited state of 1 is quenched efficiently by 1,3‐dienes and molecular oxygen. By calculating the spin density distribution it can be shown that 31 is not a typical naphthalene triplet, as it bears significant spin density at the diazo moiety. Copyright © 2001 John Wiley & Sons, Ltd.