bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinked, electrospun chitosan–poly(ethylene oxide) nanofiber mats
Authors: Vondran Jennifer L. , Sun Wei , Schauer Caroline L. 
Published: April 2008

AbstractMechanical characterization of nanofiber mats is an underexplored area in biomaterial engineering. In this study, a chitosan–poly(ethylene oxide) copolymer blend was electrospun and crosslinked with glutaraldehyde (GA) for various time periods. The tensile and compressive mechanical integrity of the nanofibers was analyzed with increasing exposure to vapor crosslinking. Solubility, scanning electron microscopy characterization, Fourier transform infrared, uniaxial tensile tests, and nanoindentation analyses were used to identify these trends. The mechanical studies confirmed that the GA vapor crosslinking increased the stiffness and decreased the ductility of the electrospun mats. Increased exposure time to crosslinking led to changes in the mat surface color and resistance to dissolution. Scanning electron microscopy fiber counts verified that exposure to GA vapor crosslinking increased the average fiber diameter. By the use of vapor phase deposition, mechanical properties continued to change throughout the study. The crosslinking exposure time could be chosen to accommodate in vivo mechanical loading. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Microcellulose fibers‐filled epoxy foams
Authors: Stefani P. M. , Perez C. J. , Alvarez V. A. , Vazquez A. 
Published: April 2008

AbstractThe dynamic‐mechanical behavior of epoxy foams reinforced with microcellulose fibers was investigated. Microcellulose fibers were obtained from sisal fibers by a several step process which includes chlorination, alkaline extraction, and bleaching. To analyze the effect of cellular structure on DMA properties, unreinforced and reinforced unfoamed epoxy samples were also used. SEM experiments demonstrated that the addition of microfiber modified the final morphology, decreasing the average cell size and increasing the number of cells per volume unit. The dynamic‐mechanical behavior of the reinforced samples, unfoamed epoxy and foamed epoxy, showed improvements with respect to the unreinforced ones, but the effect was remarkable in the second case. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis, Cytotoxicity and Protein Kinase C Inhibition of Arylpyrrolylmaleimides
Authors: Xu Gui‐Qing , Zhang Chong , Zhang Lei , Zhou Xing‐Lu , Yang Bo , He Qiao‐Jun , Hu Yong‐Zhou 
Published: April 2008

AbstractA series of novel arylpyrrolylmaleimides was synthesized and evaluated for their in‐vitro cytotoxicity against various human cancer cell lines and their protein‐kinase C inhibitory activity. Some of the compounds showed high or moderate cytotoxic activity against the tested cell lines. Compound 6b is the most promising compound against the tested cancer cell lines; 6d and 6e showed moderate protein‐kinase C inhibition. Structure–activity relationships are discussed based on the experimental data obtained.
Novel bioabsorbable salicylate‐based polymer as a drug‐eluting stent coating
Authors: Jabara Refat , Chronos Nicolas , Robinson Keith 
Published: April 2008

AbstractBackground: Permanent polymers used in current drug‐eluting stents (DES) can trigger chronic inflammation and hypersensitivity reactions, which may contribute to the increased risk of late thrombosis and rebound restenosis. Therefore, optimal polymer selection and the use of completely absorbable but biocompatible polymers are expected to minimize these risks. Objectives: We sought to evaluate a novel, potentially innately anti‐inflammatory, bioabsorbable salicylate‐based polymer as a DES coating, in a clinically relevant animal model. Methods: Four types of stents were implanted in pig coronary arteries using QCA to optimize stent apposition: bare metal stents (BMS); salicylic acid/adipic acid bioabsorbable polymer‐only coated metal stents (SA/AA); biostable polymeric sirolimus‐eluting stents (Cypher™); and metal stents coated with salicylic acid/adipic acid bioabsorbable polymer containing sirolimus (SA/AA + S). The dose density of sirolimus was 8.3 μg/mm of stent length (similar to Cypher™) with in vitro studies demonstrating elution over 30 days and complete polymer degradation in 37 days. Animals underwent angiographic restudy and were terminated at 1 month for complete histopathologic and histomorphometric analyses. Results: Both SA/AA + S and Cypher™ stents had significantly lower angiographic % stenosis when compared with BMS and SA/AA polymer‐only groups (6 ± 4% and 5 ± 4% vs. 15 ± 7% and 16 ± 5%, respectively, P < 0.001). Intimal thickness was lower for SA/AA + S and Cypher™ than for BMS (0.14 ± 0.06 and 0.13 ± 0.04 mm vs. 0.23 ± 0.05 mm, respectively, P < 0.001). Histologic % area stenosis was also lower for SA/AA + S and Cypher™ when compared with BMS (22 ± 7% and 23 ± 6% vs. 33 ± 5%, respectively, P < 0.001). There was a strong trend toward reduced inflammatory response in the SA/AA and SA/AA + S when compared with BMS and Cypher™ groups (P = 0.072). Conclusions: This study shows favorable vascular compatibility and efficacy for a novel bioabsorbable salicylate‐based polymer as a DES coating, and supports further research and development of this unique class of polymer materials for applications in cardiovascular devices. © 2008 Wiley‐Liss, Inc.
Tuning the Nucleophilicity in Cyclopropenylidenes
Authors: Schoeller Wolfgang W. , Frey Guido D. , Bertrand Guy 
Published: April 2008

AbstractCyclopropenylidenes are Hückel aromatic π systems in which one of the ring atoms is a carbene center. Quantum chemical calculations at the density functional level of theory, supplemented by coupled‐cluster calculations, indicate that there is a sizeable energy separation between the lowest‐energy singlet and triplet states of these species. Amino groups considerably increase the energy difference between these two states, whereas electron‐withdrawing substituents decrease it. The 1,1‐dimerization products of cyclopropenylidenes, namely, triafulvalenes, have been investigated. The calculations show that, without steric hindrance and considerable electronic stabilization, cyclopropenylidenes are kinetically unstable and dimerize. Different substituents (alkyl, silyl, terphenyl, amino, and phosphoraneiminato) were probed to tune the frontier orbital energies of cyclopropenylidenes. Accordingly, it is predicted that by a suitable choice of substituents at the olefinic positions, cyclopropenylidenes can be more nucleophilic than their five‐membered ring congeners, namely, imidazol‐2‐ylidenes.
Transport Processes at α‐Quartz–Water Interfaces: Insights from First‐Principles Molecular Dynamics Simulations
Authors: Adeagbo Waheed A. , Doltsinis Nikos L. , Klevakina Ksenia , Renner Jörg 
Published: April 2008

AbstractCar–Parrinello molecular dynamics (CP–MD) simulations are performed at high temperature and pressure to investigate chemical interactions and transport processes at the α‐quartz–water interface. The model system initially consists of a periodically repeated quartz slab with O‐terminated and Si‐terminated (1000) surfaces sandwiching a film of liquid water. At a temperature of 1000 K and a pressure of 0.3 GPa, dissociation of H2O molecules into H+ and OH− is observed at the Si‐terminated surface. The OH− fragments immediately bind chemically to the Si‐terminated surface while Grotthus‐type proton diffusion through the water film leads to protonation of the O‐terminated surface. Eventually, both surfaces are fully hydroxylated and no further chemical reactions are observed. Due to the confinement between the two hydroxylated quartz surfaces, water diffusion is reduced by about one third in comparison to bulk water. Diffusion properties of dissolved SiO2 present as Si(OH)4 in the water film are also studied. We do not observe strong interactions between the hydroxylated quartz surfaces and the Si(OH)4 molecule as would have been indicated by a substantial lowering of the Si(OH)4 diffusion coefficient along the surface. No spontaneous dissolution of quartz is observed. To study the mechanism of dissolution, constrained CP–MD simulations are done. The associated free energy profile is calculated by thermodynamic integration along the reaction coordinate. Dissolution is a stepwise process in which two SiO bonds are successively broken. Each bond breaking between a silicon atom at the surface and an oxygen atom belonging to the quartz lattice is accompanied by the formation of a new SiO bond between the silicon atom and a water molecule. The latter loses a proton in the process which eventually leads to protonation of the oxygen atom in the cleaved quartz SiO bond. The final solute species is Si(OH)4.
Importance of Home Visits in Peritoneal Dialysis
Authors: Kazancioglu Rumeyza , Ozturk Savas , Yucel Lamia , Guvenc Sinem , Ekiz Serpil , Dogan Sevel 
Published: April 2008

AbstractBACKGROUNDPeritoneal dialysis (PD) is a treatment option that enables patients to perform dialysis in their own homes without being separated from social life. This study assessed the training provided by the PD unit to patients practicing self‐treatment at home.METHODSThirty‐two patients (13 women, 19 men; mean age: 44.3 ± 15.3 years) answered a training assessment form comprising 31 questions during home visits. The answers were evaluated according to the incomplete/complete information system and assessed by percentage statistics.RESULTSThe mean number of correct answers was 26.4 ± 3.28/31 (81%). Questions related to feeding, constipation, changing room, peritonitis, infections, medication, and material were those most often incorrectly answered.CONCLUSIONSMany patients were observed to perceive the said information in a detailed manner. Lack of information about food to be avoided proved the importance of a dietitian. Also, patients focused only on peritonitis and had incomplete knowledge about the symptoms of and how to prevent place‐of‐exit and tunnel infections. This indicates that training should be repeated and tested at predetermined intervals.
Copper‐Catalyzed Asymmetric Allylic Alkylation
Authors: Falciola Caroline A. , Alexakis Alexandre 
Published: April 2008

AbstractOver the past decade, much effort has been put on designing efficient chiral ligands and screening of the different parameters that govern the main challenges of asymmetric SN2′ reactions, namely chemo‐, regio‐ and enantioselectivity. This review traces the evolution of the methodologies for creating stereogenic centers through asymmetric copper‐catalyzed allylic alkylation with the use of different organometallic reagents and their subsequent applications. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Separation of cytokinin isomers with a partial filling‐micellar electrokinetic chromatography‐mass spectrometry approach
Authors: Ge Liya , Tan Swee Ngin , Yong Jean W. H. , Hua Lin , Ong Eng Shi 
Published: April 2008

AbstractA new method based on partial filling‐MEKC (PF‐MEKC) directly coupled to ESI‐MS was developed for the simultaneous separation and determination of 13 structurally similar cytokinins, including various geometric and positional isomers of cytokinins. On the basis of the resolution of the neighboring isomer peaks, different parameters (i.e., pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF‐MEKC separation. Under optimum conditions, the separation of 13 cytokinin standards was accomplished within 25 min. MS/MS with multiple reaction monitoring detection was carried out to obtain sufficient selectivity. PF‐MEKC‐MS/MS allowed for the direct identification and confirmation of the cytokinins present in banana (Musa spp.) pulp sample after extraction and purification. Finally, trans‐zeatin riboside (ZR) and trans‐zeatin (Z) were unambiguously identified in banana pulp. It is anticipated that the current PF‐MEKC‐MS method can be applied to analyze cytokinins in a wide range of biological samples.
In‐line solid‐phase extraction preconcentration in capillary electrophoresis‐tandem mass spectrometry for the multiresidue detection of quinolones in meat by pressurized liquid extraction
Authors: Lara Francisco J. , García‐Campaña Ana M. , Alés‐Barrero Fermín , Bosque‐Sendra Juan M. 
Published: April 2008

AbstractWe have developed and validated a CE‐MS/MS method using an in‐line SPE device (analyte concentrator, AC) to determine eight quinolones of veterinary use whose maximum residue levels in animal edible tissues are established by the EU Council Regulation 2377/90, i.e., danofloxacin, sarafloxacin, ciprofloxacin, marbofloxacin, enrofloxacin, difloxacin, oxolinic acid, and flumequine. Different parameters affecting the AC performance, such as its design (in this case frit‐free), the kind of sorbent (Oasis® MCX), sample pH, volume, and composition of the elution plug and injection time were studied. The method was validated using standard solutions obtaining LODs between 17 and 59 ng/L. Finally, a pressurized liquid extraction (PLE) method was developed to determine these antibiotics in chicken muscle samples. The whole analytical method was validated in terms of linearity (r2 ≥ 0.992), recoveries (63–112%), repeatability and intermediate precision (RSD ≤ 20%), LODs (40–140 ng/kg) and LOQs (130–470 ng/kg), showing the usefulness of the combination of in‐line SPE‐CE‐MS/MS with PLE for the identification and simultaneous quantification of eight regulated quinolone antibiotics in chicken muscle at very low concentration levels.
Negative effect of [bmim][PF6] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention
Authors: Zhang Yun , Huang Xirong , Li Yuezhong 
Published: April 2008

AbstractBACKGROUND: [bmim][PF6] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF6], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF6] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF6] on YADH by microemulsifying [bmim][PF6].RESULTS: The activity of YADH in the homogeneous solution formed by H2O, CH3CH2OH and [bmim][PF6] decreased rapidly with the increase of the molar fraction of [bmim][PF6]. The inhibitory effect of [bmim][PF6] on YADH was probably caused by the competition of the imidazole group of [bmim][PF6] with the coenzyme NAD+ for the binding sites on YADH. In a water‐in‐[bmim][PF6] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF6] and avoided the direct inactivation of [bmim][PF6] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L−1 min−1.CONCLUSION: [bmim][PF6] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry
Spanish experience with German psychology prior to World War I
Authors: Mülberger Annette 
Published: April 2008

AbstractAn increase in interest for German scientific psychology followed the rise of liberalism in late nineteenth‐century Spain. This paper deals with Spanish scholars' endeavors to participate in German psychology: It outlines the intellectual and institutional background of Spanish preoccupation with German philosophy and psychology, and deals with the personal experience and testimony of two Spanish philosophers, Eloy Luis André and Juan Vicente Viqueira López, who traveled to Leipzig, Berlin, and Göttingen between 1909 and 1914 to gain firsthand experience in the nascent science of psychology in Germany at that time. © 2008 Wiley Periodicals, Inc.
Rapid magnetic resonance elastography of muscle using one‐dimensional projection
Authors: Bensamoun Sabine F. , Glaser Kevin J. , Ringleb Stacie I. , Chen Qingshan , Ehman Richard L. , An Kai‐Nan 
Published: April 2008

AbstractPurposeTo demonstrate the feasibility of 1D MR elastography (MRE) to rapidly assess skeletal muscle stiffness in vivo.Materials and MethodsShear waves were induced in the vastus medialis muscle (VM) using a pneumatic driver at 90 Hz and 2D MRE data were collected. Spatially selective excitations were used to produce 1D projections of MRE data oriented along the direction of propagating waves in the muscle. Data were collected with the thigh muscles relaxed and contracted at 20% maximum voluntary contraction (MVC) and the knee flexed at 30°.ResultsThe muscle stiffness measured at rest and in contraction with 1D MRE was 3.69 ± 0.80 kPa and 9.52 ± 2.74 kPa, respectively, and 4.36 ± 0.98 kPa and 9.22 ± 1.29 kPa, respectively, with the 2D MRE technique.ConclusionMuscle stiffness measured using 1D MRE was in agreement with 2D MRE while reducing the scan time by a factor of 4. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Psychometric properties of the Retrospective Self Report of Inhibition (RSRI) in a representative German sample
Authors: Rohrbacher Heike , Hoyer Jürgen , Beesdo Katja , Höfler Michael , Bittner Antje , Lieb Roselind , Wittchen Hans‐Ulrich 
Published: April 2008

AbstractThe present study examined the internal consistency, factorial structure, and construct validity of the German version of the Retrospective Self Report of Inhibition (RSRI), a questionnaire measure of behavioral inhibition. The research was based on data from a German prospective‐longitudinal community study of 3021 adolescents and young adults (aged 14–24 years at baseline). Diagnostic assessment was based on the DSM‐IV/M‐CIDI and general psychopathological distress was assessed with SCL‐90‐R. Results of confirmatory factor analysis indicated adequate fit of the two‐factor model, suggested by the authors of the original version. Indices of internal consistency of the RSRI and its subscales ‘social/school’ and ‘fear/illness’ were shown to be sufficient for the total sample and even higher in subgroups of subjects with certain DSM‐IV diagnoses. Associations with variables such as mental distress, parental psychopathology, and DSM‐IV disorders were in line with theoretical assumptions and confirm different aspects of the validity (convergent, concurrent, predictive) of the instrument. The psychometric properties of the German RSRI were found to be comparable to those of the English version. The applicability of this questionnaire in German‐speaking countries is therefore recommended for adolescents and young adults. Copyright © 2008 John Wiley & Sons, Ltd.
A posteriori estimates for the Stokes eigenvalue problem
Authors: Lovadina Carlo , Lyly Mikko , Stenberg Rolf 
Published: April 2008

AbstractWe consider the Stokes eigenvalue problem. For the eigenvalues we derive both upper and lower a‐posteriori error bounds. The estimates are verified by numerical computations. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Renewable resource‐based poly (m‐phenylenevinylene)s and their statistical copolymers: Synthesis, characterization, and probing of molecular aggregation and Forster energy transfer processes
Authors: Cyriac Anish , Amrutha S. R. , Jayakannan M. 
Published: April 2008

AbstractWe report a novel poly (m‐phenylenevinylene)s and their copolymers based on renewable resource starting material 3‐pentadecylphenol to trace the Forster energy transfer process and molecular aggregation in the π‐conjugated polymers. The new bisylide monomer was polymerized with bisaldehyde (or benzaldehyde) under Wittig‐Horner reaction conditions to prepare poly [(4‐methoxy‐6‐pentadecyl‐1, 3‐phenylenevinylene)‐alt‐(1, 3‐phenylenevinylene)] (m‐PPV) and its para‐counterpart poly [(4‐methoxy‐6‐pentadecyl‐1, 3‐phenylenevinylene)‐alt‐(1, 4‐phenylenevinylene)] (p‐PPV) and oligo‐phenylenevinylene model compound 4‐methoxy‐6‐pentadecyl‐1, 3‐distyrylbenzene (OPV). A series of with m‐ or p‐conjugated segments were also prepared by varying the m‐ and p‐content from 0 to 100% in the feed. The selective excitation of m‐conjugated segments in the copolymer by 310 nm light showed emission properties of pure p‐conjugated segments indicating the efficient Forster energy transfer process in segmented copolymers. Both solution quantum yields and the emission intensities increase up to 75% of para‐content in the copolymers. In the solid state, the increase in the p‐incorporation in the copolymer decreases the photoluminescent intensity almost by four times as compared to that of pure meta‐substituted PPV. The excitation spectra of the polymers confirmed a new peak at 400 nm corresponding to the aggregated polymer chains in the film, which is absent in the solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3241–3256, 2008
Synthesis of star poly(1,3‐cyclohexadiene): Grafting reaction of poly(1,3‐cyclohexadienyl)lithium onto C60
Authors: Natori Itaru , Natori Shizue 
Published: April 2008

AbstractThe grafting reaction of poly(1,3‐cyclohexadienyl)lithium onto fullerene‐C60 (C60) was strongly affected by the nucleophilicity of poly(1,3‐cyclohexadiene) (PCHD) carbanions and the polymer chain microstructure, and progressed via step‐by‐step reactions. A star‐shaped PCHD, having a maximum of four arms, was obtained from poly(1,3‐cyclohexadienyl)lithium composed of all 1,4‐cyclohexadiene (1,4‐CHD) units. The rate of the grafting reaction was accelerated by the addition of amine. The grafting density of PCHD arms onto C60 decreased with an increase in the molar ratio of 1,2‐cyclohexadiene (1,2‐CHD) units. The electron‐transfer reaction from PCHD carbanions to C60 did not occur in either a nonpolar solvent or a polar solvent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3282–3293, 2008.
Morphological investigation on melt crystallized polylactide homo‐ and stereocopolymers by enzymatic degradation with proteinase K
Authors: He Yong , Wu Tong , Wei Jia , Fan Zhongyong , Li Suming 
Published: April 2008

AbstractPolylactide (PLA) homo‐ and stereocopolymers containing 100, 98, 96, 94, and 92% L‐lactyl units, respectively, were synthesized by ring opening polymerization of L‐lactide and DL‐Lactide, using zinc lactate as catalyst. Differential scanning calorimetric analysis measurements show that incorporation of D‐lactyl units leads to decrease of the crystallization rate of the copolymers. However, the crystallization mechanism and the amount of crystallizable fraction are not affected. The enzymatic degradation was performed at 37 °C in a pH 8.6 Tris buffer containing proteinase K. Two distinct morphologies were obtained by melt crystallization for PLA films with ca. 80 μm of thickness. It is confirmed that proteinase K can degrade both the free and confined amorphous regions. Lamella stacks in spherulites retain their orientation during enzymatic degradation. PLA crystal morphologies are affected by the content of D‐lactyl units. Factors such as the nucleus location and the D‐lactyl units' exclusion as amorphous fraction were considered to elucidate the observed PLA spherulite morphologies. Infrared spectroscopy and mass loss measurements were also combined to better understand the degradation behaviors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 959–970, 2008