bluuebunny/crossref_metadata_2025_split huggingface dataset:
HPLC analysis and pharmacokinetics of icariin in rats
Authors: Cheng Shan , Qiu Feng , Wang Shuhui , He Junqi 
Published: April 2007

AbstractAs a prerequisite to the determination of pharmacokinetic parameters of icariin in rats, an HPLC method using UV detection was developed and validated. Icariin and the internal standard, quercetin, were extracted from plasma samples using ethyl acetate after acidification with 0.05 mol/L NaH2PO4 solution (pH 5.0). Chromatographic separation was achieved on an Agilent XDB C18 column (250×4.6 mm id, 5 μm) equipped with a Shim‐pack GVP‐ODS C18 guard column (10×4.6 mm id, 5 μm) using a mobile phase of ACN/water/acetic acid (31:69:0.4 v/v/v) at a flow rate of 1.0 mL/min. Detection was at 277 nm. The calibration curve was linear from 0.05 to 100.0 μg/mL with 0.05 μg/mL as the lower LOQ (LLOQ) in plasma. The intra‐ and interday precisions in terms of RSD were lower than 5.7 and 7.8% in rat plasma, respectively. The accuracy in terms of relative error (RE) ranged from –1.6 to 3.2%. The extraction recoveries of icariin and quercetin were 87.6 and 80.1%, respectively. The main pharmacokinetic parameters for rats were determined after a single intravenous administration of 10 mg/kg icariin: t1/2, 0.562 ± 0.200 h; AUC0–∞, 8.73 ± 2.23 μg·h/mL; CLTOT, 20.10 ± 5.80 L/kg·h; VZ, 1.037 ± 0.631 L/kg; MRT0–∞, 0.134 ± 0.040 h; and Vss, 0.170 ± 0.097 L/kg.
Mediators of control beliefs, stressful life events, and adaptive behavior in school age children: The role of appraisal and social support
Authors: Jackson Yo , Kim Kerri L. , Delap Chris 
Published: April 2007

AbstractThe authors examine the role of appraisal and social support as mediators of the relation between control beliefs and adaptive behavioral outcome. Using the responses from 297 children, ages 8 to 12 years old, the results suggest two significant mediational pathways. Social support was a mediator of the relation between unknown control for negative events and adaptive behavior and the relation between unknown control for positive events and adaptive behavior. Negative appraisal demonstrated no mediation relations. The role of social support and negative appraisal in the display of adaptive behavior and the implications for further model testing are discussed.
Randomized clinical trial for treatment of chronic nightmares in trauma‐exposed adults
Authors: Davis Joanne L. , Wright David C. 
Published: April 2007

AbstractNightmares and sleep disturbance are fundamental concerns for victims of trauma. This study examined the efficacy of a manualized cognitive–behavioral treatment (CBT) for chronic nightmares in trauma‐exposed individuals via a randomized clinical trial. Participants were randomly assigned to a treatment group or wait‐list control group, with 27 participants completing the treatment. At the 6‐month follow‐up assessment, 84% of treated participants reported an absence of nightmares in the previous week. Significant decreases were also reported in symptoms of depression and posttraumatic stress, fear of sleep, and number of sleep problems, while sleep quality and quantity improved. The present study adds to the growing literature indicating this brief CBT as a first‐line treatment for trauma‐exposed individuals with chronic nightmares.
Bacterial Translocation During Liver Transplantation
Authors: Abdala Edson , Baía Carlos Eduardo Sandoli , Mies Sérgio , Massarollo Paulo Celso Bosco , de Paula Cavalheiro Norma , Baía Vania Regina Mollo , Inácio Conceição Aparecida Félix , Sef Henry Corazza , Barone Antonio Alci 
Published: April 2007

Abstract
The aim of this study was to evaluate the bacterial translocation in liver transplantation (LT), comparing the conventional and the piggyback methods. A total of 32 patients were randomized into the 2 groups. Samples of blood were collected from the radial artery, portal vein (PV) and hepatic vein (HV), in up to 120 minutes postreperfusion. The samples were sent for endotoxin level, as well as samples up to 2 minutes post-perfusion were sent to culture. Hepatic artery and PV blood flows were measured at postreperfusion collection times. The results analyzed were: endotoxin concentration, its quantity, and hepatic clearance. The statistical treatment consisted of analyzing each group's mean profile. The analysis for endotoxin concentration in the radial artery was the deviation related to presurgery measure, and in the PV the deviation related to preclamping (PC) measure. The overall mean level of endotoxin concentration was 0.99 EU/mL in the artery, 1.30 EU/mL in the PV, and 1.22 EU/mL in the HV. The deviation was significant in the portal (P = 0.0031), but not in the artery samples (P = 0.2092). We detected a significant quantity of endotoxin in the artery and in the portal and the HVs (P < 0.001). There was no difference between the 2 groups and no hepatic clearance of endotoxin was detected either (P = 0.1515). All the cultures were negative. In conclusion, the study detected a significant translocation of endotoxin, but not of bacteria. The study also detected the absence of endotoxin hepatic clearance in both the piggyback and the conventional methods without any difference between them. Liver Transpl 13:488–496, 2007. © 2007 AASLD.
Biotechnological Production of Spider‐Silk Proteins Enables New Applications
Authors: Vendrely Charlotte , Scheibel Thomas 
Published: April 2007

AbstractThe outstanding mechanical properties of spider silks have motivated many researchers to establish biotechnological production techniques which are necessary to provide sufficient amounts of silk proteins for industrial applications. Based on recent developments in genetic engineering, two strategies for the recombinant production of spider‐silk proteins have been established which are discussed in detail. Further, protein‐design strategies are described, enabling the combination of silk properties with additional biological, chemical, or technical features. We highlight the potential of engineered and recombinantly‐produced spider‐silk proteins to provide the basis for a new generation of biomaterials.magnified image
A New Network Composite Material Based on Soy Dreg Modified with Polyurethane Prepolymer
Authors: Chen Yun , Zhang Lina , Deng Rui , Cui Yejian 
Published: April 2007

AbstractA series of biodegradable, soy‐protein‐based, composite materials was prepared by introducing castor‐oil‐based polyurethane prepolymer (PUP) into soy dreg (SD) without the addition of plasticizers, via extrusion and a compression‐molding process. The effects of the NCO/OH molar ratio and the PUP content on the structure and properties of the resulting materials were studied by Fourier‐transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, tensile testing, swelling experiments, and biodegradability testing. The results revealed that the NCO group in the PUP played a vital role in improving the compatibility and elasticity, as a result of the formation of a cross‐linking network structure with the NH2, NH, and OH groups in SD containing protein and cellulose. Increasing the NCO/OH molar ratio to 2.0 resulted in an enhancement of the degree of cross‐linking, leading to a higher tensile strength (24 MPa), glass‐transition temperature (52 °C) and water‐resistivity of the composite materials. The unreacted SD also served as a filler in the cross‐linked networks and enhanced the tensile strength of the composites. The biodegradation testing showed that the composites exhibited biodegradability under the condition of fungus culture.magnified image
Polymeric Nanocomposites for Tribological Applications
Authors: Burris David L. , Boesl Benjamin , Bourne Gerald R. , Sawyer W. Gregory 
Published: April 2007

AbstractPolymer nanocomposites operate in applications where fluid and grease lubricants fail, and have superior tribological performance to traditional polymer composites. Nanoparticle fillers have been a part of notable reductions in the wear rate of the polymer matrix at very low loadings. Despite instances of remarkable wear reductions at unprecedented loadings (3 000 times at 0.5% loading in one case), there is a lack of general agreement within the literature on the mechanisms of wear resistance in these nanocomposites. In addition, results appear to vary widely from study to study with only subtle changes of the filler material or blending technique. The apparent wide variation in tribological results is likely a result of processing and experimental differences. Tribology is inherently complex with no governing laws for dry sliding friction or wear, and the state of the art in polymeric nanocomposites tribology includes many qualitative descriptors of important system parameters, such as particle dispersion, bulk mechanical properties, debris morphology, and transfer film adhesion, morphology, composition, and chemistry. The coupling of inherent tribological complexities with the complicated mechanics of poorly characterized nanocomposites makes interpretation of experimental results and the state of the field extremely difficult. This paper reviews the state of the art in polymeric nanocomposites tribology and highlights the need for more quantitative studies. Examples of such quantitative measurements are given from recent studies, which mostly involve investigation of polytetrafluoroethylene matrix nanocomposites.magnified image
Influence of Cure Regime on the Strain Development in an Epoxy Resin as Monitored by a Fiber Bragg Grating Sensor
Authors: Harsch Margit , Karger‐Kocsis József , Herzog Florian 
Published: April 2007

AbstractIn this paper, the effects of different cure regimes on the strain development in an anhydride‐cured epoxy resin were investigated by fiber optical measurements. The course of the strain signal was detected by an embedded fiber Bragg grating sensor in the unconstrainedly curing epoxy. The build‐up of strain was detected for various cure regimes differing in the dwelling times of the first isothermal step, heating rates to the cure temperature, and final curing temperatures, respectively. Characteristic points (gelation, vitrification) of the cure regimes were identified by conversion‐ and Tg‐determinations via DSC and assigned to changes of the FBG signal. The fiber Bragg sensing technique allowed us to find those variables of the cure regimes which mostly affect the strain development and thus, the level of the residual strain. It was established that the dwelling time and heating rate to the cure temperature influence markedly the residual strain whereas the cure temperature affects this value to a lesser extent for the selected cure regimes. So, the above parameters should be selected properly for an optimum cure regime characterized by the build‐up of a minimum residual strain.magnified image
Exponential attractor for a planar shear‐thinning flow
Authors: Pražák Dalibor 
Published: April 2007

AbstractWe study the dynamics of an incompressible, homogeneous fluid of a power‐law type, with the stress tensor T = ν(1 + µ|Dv|)p−2Dv, where Dv is a symmetric velocity gradient. We consider the two‐dimensional problem with periodic boundary conditions and p ∈ (1, 2). Under these assumptions, we estimate the fractal dimension of the exponential attractor, using the so‐called method of 𝓁‐trajectories. Copyright © 2007 John Wiley & Sons, Ltd.
Apple polyphenols diminish the phosphorylation of the epidermal growth factor receptor in HT29 colon carcinoma cells
Authors: Fridrich Diana , Kern Melanie , Pahlke Gudrun , Volz Nadine , Will Frank , Dietrich Helmut , Marko Doris 
Published: April 2007

AbstractPreviously, we showed that an apple juice extract (AE) potently inhibits the protein tyrosine kinase (PTK) activity of the epidermal growth factor receptor (EGFR). In the present study, an apple pomace extract (APE) was found to exceed the EGFR inhibitory properties of AE in a cell‐free system. The impact of the extracts on the phosphorylation status of the EGFR in intact cells (HT29) was sensitive to catalase, added to suppress the accumulation of hydrogen peroxide. In the absence of catalase, the formation of hydrogen peroxide was observed, achieving 1.1 ± 0.1 μM (AE) and 1.5 ± 0.1 μM (APE) after 45 min of incubation. In the presence of catalase, suppressing the hydrogen peroxide level to the solvent control, APE effectively suppressed EGFR phosphorylation, even exceeding the effects of AE. Both extracts inhibited the growth of HT29 cells, albeit the enhanced EGFR inhibitory properties of APE compared to AE were not reflected by a higher growth inhibitory potential. The results clearly show that the effect of apple extracts on the EGFR and cell growth are not simply artefacts of hydrogen peroxide formation. However, the formation of hydrogen peroxide has to be considered to modulate and/or mask cellular responses to apple extracts.
Hyperstructured polyacetylene
Authors: Akagi Kazuo 
Published: April 2007

AbstractCurrent progress in the synthesis and properties of conjugated polymers is presented by focusing on recently put forward hyperstructured helical polyacetylene. Interfacial polymerization of acetylene has been carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*‐LC) and Ziegler–Natta catalyst. Since the chiral nematic liquid crystal is composed of nematic liquid crystal and a chiral compound such as axially chiral binaphthyl derivative with R‐ or S‐configuration, the screw directions of the polyacetylene chain and fibril bundle and even the spiral morphology are rigorously controlled by selecting the chirality of the chiral compound. Surprisingly, the screw directions of the fibril and the bundle of fibrils in helical polyacetylene were found to be opposite to that of N*‐LC. It is worthwhile to emphasize that the hierarchical spiral morphology involving the primary to higher order structure is generated in a synthetic polymer such as polyacetylene by using N*‐LC as an asymmetric polymerization solvent. Copyright © 2007 Society of Chemical Industry
Anionic synthesis of dimethylamino‐functionalized polystyrenes and poly (methyl methacrylates) using 1 ‐ (4‐dimethylaminophenyl) ‐ 1 ‐ phenylethylene
Authors: Quirk Roderic P. , Zhu Lin‐Fang 
Published: April 2007

Abstractω‐Dimethylaminopolystyrenes can be synthesized in quantitative yields by reacting poly(styryl)lithium with 1‐(4‐dimethylaminophenyl)‐1 ‐phenylethylene (1). The resulting polymeric dimethylamino‐substituted 1,1‐diphenylalkyllithium was terminated with methanol or reacted with butadiene to form a diblock copolymer, poly(styrene‐b‐butadiene), with the dimethylamino group at the interface between the blocks. α‐Dimethylaminopolystyrene and α‐dimethylaminopoly‐(methyl methacrylate) were synthesized by using the adduct of 1 with sec‐butyllithium as initiator, α,ω‐Bis(dimethylamino)polystyrene was prepared by using the functionalized initiator and then terminating the resulting dimethylaminopoly‐(styryl)lithium with 1. The amine‐functionalized polymers were characterized by end‐group titration, size exclusion chromatography, thin‐layer chromatography, vapor phase osmometry, elemental analysis and both 1H and 13C NMR spectroscopy. All experimental evidence is consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative.
Synthesis and viscoelastic properties of α,ω‐diquaternary ammonium polybutadiene lonomers
Authors: Roberts Caroline , Lindsell W. Edward , Soutar Ian 
Published: April 2007

AbstractTelechelic ionomeric elastomers with quaternary ammonium groups (Me2RN+) attached terminally to polybutadiene (M̄n ∼ 2.7 × 103; M̄w/M̄n = 1.27; containing 62% 1,4‐linkages) have been synthesised by an anionic technique using a functionalised initiator and terminator, followed by quaternisation of the resulting α,ω‐bis(dimethylamino)polybutadiene. By using differing alkyl halides for quaternisation and by ion exchange chromatography, a series of dialkylated telechelic cationomers has been produced containing alkyl groups, R = Me, Et, n‐Pr, n‐Bu or n‐C5H11 with counter anions X = I−, Br−, PF or SO. The glass transition temperatures, Tg, of these cationomers are c. 6°C higher than for the precursor, non‐quaternised polymer but are essentially unchanged with variations in groups R or anions X. Dynamic mechanical thermal analyses of the cationomers have been carried out and a secondary transition, Ti, associated with relaxation of ionic cross‐linking interactions, observed. Values of Ti decrease as the size of R increases from C1 to C5, and as the anion X is changed from Br− to I− to PF or SO to PF.Activation energies can be derived from the frequency dependence of Ti values or from the temperature dependence of shift parameters, obtained from the master curves of the dependence on frequency of the shear storage (G') and loss (G') moduli; these activation energies are dependent on the nature of the counter anion, being greatest for the polymer containing the dinegative SO, but are essentially unchanged by the variations in alkyl group, R, implemented in this study. Other results of the dynamic mechanical analyses on the cationomeric elastomers are discussed in relation to their ionic cross‐linking.
Polymerization and copolymerization using high intensity ultrasound
Authors: Price Gareth J. , Daw Melanie R. , Newcombe Nicholas J. , Smith Paul F. 
Published: April 2007

AbstractAbstract: High intensity ultrasound has been used to prepare homopolymers and copolymers of styrene, methyl methacrylate and n‐butyl methacrylate. High molecular weight homopolymers are formed rapidly during sonication and are then subjected to a degradation process. The copolymers prepared by this method have similar structure and properties to those prepared using AIBN as an initiator.
Reaction of the epoxide groups of the copolymer trimethylolpropane trimethacrylate‐glycidyl methacrylate with aliphatic amino compounds
Authors: Walenius Maria , Flodin Per 
Published: April 2007

AbstractFunctional macroporous polymers have been synthesized from copolymers of trimethylolpropane trimethacrylate (TRIM) and glycidyl methacrylate (GMA). The accessibility of the epoxy groups has been investigated by reaction with dialkylamines and diamines of different chain lengths. The obtained yield of reacted amine was approximately 80% for small molecules. The yield, and accessibility, decreased when the chain length or bulkiness of the reagent increased. The swelling ability in water of the functional polymers increased compared with the original copolymer.
Modelling of urethane formation
Authors: Jönsson Kersti , Flodin Per 
Published: April 2007

AbstractThe formation of polyurethanes has been followed by in‐situ 1H NMR. The experimental data have been used in a mathematical model. The model was found to be representative for a major part of the reaction. The Arrhenius preexponential factors and activation energies for the formation reactions were calculated based on the model.
Approaches to the synthesis of novel photoactive side chain liquid crystalline polymers containing analogues of the cinnamate ester group
Authors: Whitcombe Michael J. , Gilbert Andrew , Mitchell Geoffrey R. 
Published: April 2007

AbstractA series of chain liquid crystalline copolymers of 4‐cyanophenyl 4′‐(6‐methacryloyloxyhexyloxy)benzoate and 2‐methacryloyloxyethyl β‐(1‐naphthyl)‐propenoate were prepared by free radical polymerization. The corresponding polyacrylates could not be prepared in the same way and an alternative method was used for their preparation involving the synthesis of copolymers of the mesogenic monomer and 2‐hydroxyethyl acrylate followed by treatment of the resulting polymers with β‐(1‐naphthyl)propenoyl chloride. The materials are of interest as photoactive liquid crystalline polymers. The effect of introducing a bulky nonmesogenic group into a liquid crystalline copolymer generally lowers the clearing temperature and raises Tg but also gives rise to contrasting phase behaviour in these two series of polymers. Polymethacrylates which show mesomorphism have sharp transitions and continue to exhibit a highly ordered smectic phase over the bulk of their liquid crystal range. Polyacrylates, on the other hand, exhibit a weakening and broadening‐out of their thermal transitions consistent with a lowering of order. These results emphasize the effect of the polymer backbone on phase behaviour.
New self‐crosslinkable polyethers
Authors: Eldin Sameer H. 
Published: April 2007

AbstractNew alkylene‐polyethers, OPh(CH2)nPhOPhXPh with X = SO2, CO are described that undergo an unexpected crosslinking reaction at temperatures ≧ 250°C. HNMR indicates the participitation of methylene groups in the vicinity of the aromatic ring and of the phenyl rings of the diarylsulphone moiety in this crosslinking reaction.The crosslink density can be regulated via copolyaddition with bisphenol A. Polyethers of the general structure OPhRPhOPhXPh with R = (CH2)6 + C(CH3)2, X = SO2, CO are easily processable, impact and solvent resistant. ESR measurements correlate with the HNMR findings and identify the crosslinking as a radical reaction.A crosslink mechanism is proposed and substantiated by the synthesis of specific model polymers.
Effect of reaction conditions on poly (methyl methacrylate) molecular weight as polymerized in aqueous media by the redox system Ce(IV)‐isobutyl alcohol
Authors: Fernández M. D. , Fernández M. J. , Guzmán G. M. 
Published: April 2007

AbstractPolymerization of methyl methacrylate initiated by ceric ammonium nitrate in combination with isobutyl alcohol has been investigated in aqueous nitric acid. The effects of conversion, isobutyl alcohol, Ce(IV) and monomer concentrations, as well as temperature on polymer molecular weight have been studied. Molecular weight distributions obtained by size exclusion chromatography showed several shoulders and a high dispersity index which seemed to be related to the fact that the polymer precipitated continuously during the reaction. Average molecular weights increased initially as conversion increased, while an increase in the isobutyl alcohol and Ce(IV) concentrations up to a certain value caused the molecular weight to decrease. The average molecular weights increased with increasing monomer concentration, but decreased with a rise in temperature. These effects are in agreement with a reaction mechanism involving the oxidation of isobutyl alcohol by Ce(IV) via complex formation, decomposition of the complex giving rise to a primary radical, initiation, propagation, and bimolecular termination of the polymeric radicals and oxidative termination of the primary radical by Ce(IV).
Mechanical properties and dynamic mechanical relaxations of ethylene/alpha‐olefin copolymers
Authors: Benavente Rosario , Pereá José M. , Bello Antonio , Pérez Ernesto , Martínez Carmen , Aguilar Carmelo 
Published: April 2007

AbstractThe tensile drawing behaviour and the viscoelastic relaxations of three different copolymers of ethylene, containing 1‐butene, 1‐hexene and 4‐methyl‐1‐pentene as comonomer, have been studied. The composition of the copolymers is increasingly poorer in comonomer following the above order. However, they show similar mechanical properties, both large‐strain and small‐strain dynamic mechanical, because the minor differences which have been found can generally be explained by the thermal and mechanical histories of the samples. Thus, it seems that the higher disrupting effect produced in the copolymer structure by the comonomers of greater size and volume is counterbalanced by the corresponding smaller concentration, and that only thermal treatment produces appreciable differences in properties.