bluuebunny/crossref_metadata_2025_split huggingface dataset:
A DFT and AIM analysis of the spin–spin couplings across the hydrogen bond in the 2‐fluorobenzamide and related compounds
Authors: Alkorta Ibon , Elguero José , Limbach Hans‐Heinrich , Shenderovich Ilja G. , Winkler Tammo 
Published: April 2009

AbstractIn 1975 a large number of coupling constants were measured in 2‐fluorobenzamide labeled with15N. Some of them were assigned to couplings through intramolecular NH···F hydrogen bonds (HBs). These couplings change dramatically when CDCl3is replaced by DMSO‐d6. In this theoretical paper we provide density functional theory (DFT) calculations that justify the existence of a weak HB in the absence of solvent, while solvents that act as HB acceptors break down the intramolecular hydrogen bond (IMHB) of 2‐fluorobenzamide. Atoms in molecules (AIM) analyses and Steiner‐Limbach plots were used to analyze the structure of the compounds. Copyright © 2009 John Wiley & Sons, Ltd.
Development of functional LH Receptors on pig cumulus–oocyte complexes cultured in vitro by a novel two‐step culture system
Authors: Procházka Radek , Nĕmcová Lucie , Nagyová Eva , Scsuková Son̆a , Mlynarc̆íková Alz̆beta 
Published: April 2009

AbstractWe show in the present study that freshly isolated pig cumulus–oocyte complexes (COCs) display a limited response to LH, as assessed by the expression of hyaluronan synthase 2 (Has2) mRNA, activation of protein kinase A (PKA), production of hyaluronic acid (HA) and progesterone, cumulus cell expansion and resumption of meiosis. These data indicate that freshly isolated COCs do not possess a sufficient number of functional LH receptors (LHR). However, the expression of Lhr significantly increased during the culture of COCs in vitro in a medium supplemented with FSH. Assuming that the effect of FSH on LHR induction is mediated via cAMP signaling pathways, we developed a new culture system, in which the COCs were pre‐cultured for 72 hr in a medium supplemented with dbcAMP. The pre‐cultured COCs remained in the germinal vesicle stage, their cumulus investment underwent a dramatic increase in size and gap junctions between the cumulus cells were preserved. The stimulation of such COCs with either FSH or LH led to the resumption and completion of meiosis, activation of PKA, expression of Has2, synthesis of large amounts of HA and progesterone, and extensive expansion of cumulus cells. We conclude that the formation of functional LHR is stimulated in cumulus cells during the culture in vitro in a cAMP‐dependent pathway. The dbcAMP‐treated COCs thus represent a new model in which the resumption of meiosis and cumulus expansion can be induced exclusively by the action of recombinant LH. Mol. Reprod. Dev. 76: 751–761, 2009. © 2009 Wiley‐Liss, Inc.
Methodology for Kinetic Modeling of Atom Transfer Radical Polymerization
Authors: D'hooge Dagmar R. , Reyniers Marie‐Françoise , Marin Guy B. 
Published: April 2009

AbstractA methodology for kinetic modeling of atom transfer radical polymerization is developed allowing to calculate the monomer conversion, the fraction of polymer molecules having end group functionality, the full molar mass distribution (MMD) of the dormant polymer and the number, mass, and z based average molar mass of the dead and dormant polymer. The developed methodology is based on an extension of the method of moments and allows an accurate description of the contribution of the polymer molecules with a high molar mass to the MMD of the polymer. Diffusional limitations on all considered reaction steps are systematically accounted for. Simulation results are in good agreement with experimental observations. Moreover, the methodology allows a detailed description of the broadness and the skewness of the MMD of the polymer.magnified image
Gradient Copolymers by ATRP in Semibatch Reactors: Dynamic Monte Carlo Simulation
Authors: Al‐Harthi Mamdouh , Khan Masihullah J. , Abbasi Sarfraz H. , Soares João B. P. 
Published: April 2009

AbstractWe developed a dynamic Monte Carlo model for ATRP in semibatch reactors. Semibatch reactors can be used to produce gradient copolymers even if the difference between the reactivity ratios of the comonomers is not significant by using different comonomer feed policies. The model was used to predict average molecular weights, polydispersity index, copolymer composition and complete distributions of molecular weight, chemical composition, and comonomer sequence length at any polymerization time. Two case studies, poly[styrene‐co‐(methyl methacrylate)] and poly[acrylonitrile‐co‐(methyl methacrylate)], were chosen to demonstrate the effect of comonomer feed compositions on the final chemical composition distribution of the copolymer.magnified image
Kinetics and Molecular Weight Development of Dithiolactone‐Mediated Radical Polymerization of Styrene
Authors: Soriano‐Moro Jesús Guillermo , Jaramillo‐Soto Gabriel , Guerrero‐Santos Ramiro , Vivaldo‐Lima Eduardo 
Published: April 2009

AbstractCalculations of polymerization kinetics and molecular weight development in the dithiolactone‐mediated polymerization of styrene at 60 °C, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator and γ‐phenyl‐γ‐butirodithiolactone (DTL1) as controller, are presented. The calculations were based on a polymerization mechanism based on the persistent radical effect, considering reverse addition only, implemented in the PREDICI® commercial software. Kinetic rate constants for the reverse addition step were estimated. The equilibrium constant (K = kadd/k‐add) fell into the range of 105–106 L · mol−1. Fairly good agreement between model calculations and experimental data was obtained.magnified image
A placebo arm is not always necessary in clinical trials of amyotrophic lateral sclerosis
Authors: Gordon Paul H. 
Published: April 2009

AbstractRiluzole is currently the only approved medication for amyotrophic lateral sclerosis (ALS). While other potential neuroprotective agents have been tested in clinical trials, none has been effective, and few symptomatic treatments have been studied. Randomized placebo‐controlled trials are necessary to establish the effectiveness of a drug, but an increasing number of potential therapies combined with limited resources means that only a few drugs at a time can be tested for efficacy in ALS. Therefore, priority must be given to agents that show an advantage in early phase trials before proceeding to Phase III efficacy trials. New strategies are being used to screen different agents, along with their correct dose, in a variety of neurological illnesses, including ALS. Early phase trial designs conducted without a placebo arm improve efficiency, reduce cost, and appeal to patients. Dose‐ranging, futility, and selection trials are examples of Phase I and II trial designs that can be conducted without placebo groups. Muscle Nerve, 2009
Can we eliminate placebo in ALS clinical Trials?
Authors: Simmons Zachary 
Published: April 2009

AbstractAmyotrophic lateral sclerosis (ALS) is a fatal disease with limited treatment options. Controlled studies are a necessary part of Phase II and Phase III assessments of proposed therapies. Due to the relatively small number of patients with ALS, several study designs have been proposed to improve the efficiency of Phase II studies. Some of these advocate the use of historical controls in place of placebo controls. However, the characteristics of historical controls may not mirror those of patients in the treatment group. Novel study designs can be used to decrease the number of patients required for Phase II studies. The use of placebo controls rather than historical controls in these novel study designs likely leads to better predictions of treatments that will be successful in Phase III studies. There is general agreement on the necessity of placebo controls in Phase III studies. Muscle Nerve, 2009
Fast planar slides. A closed‐form thermo‐hydro‐mechanical solution
Authors: Pinyol N. M. , Alonso E. E. 
Published: April 2009

AbstractHeat‐induced excess pore pressures on the failure surface of a planar slide have been calculated by solving the mass and heat balance equations on the shear band. The set of differential equations and the equation of motion of the slide have been solved in closed form for the case of incompressible fluid and incompressible soil skeleton. The solution describes the accelerated motion of the slide. It has been compared with the numerical solution when soil and water stiffness terms are not disregarded. A case study, based on a well‐known translational slide (Cortes slide) has been solved. Numerical and analytical solutions are compared. Results of a sensitivity analysis indicate that the permeability of the shear band is the key parameter to control the onset of a rapid motion. For a band permeability above a threshold value, in the vicinity of 10−15m2 (10−8m/s), fast accelerated motions are very unlikely. Copyright © 2009 John Wiley & Sons, Ltd.
Asymmetric spin‐echo (ASE) spiral improves BOLD fMRI in inhomogeneous regions
Authors: Brewer Kimberly D. , Rioux James A. , D'Arcy Ryan C. N. , Bowen Chris V. , Beyea Steven D. 
Published: April 2009

AbstractFunctional MRI (fMRI) is of limited use in areas such as the orbitofrontal and inferior temporal lobes due to the presence of local susceptibility‐induced field gradients (SFGs), which result in severe image artifacts. Several techniques have been developed to reduce these artifacts, the most common being the dual‐echo spiral sequences (spiral‐in/out and spiral‐in/in). In this study, a new multiple spiral acquisition technique was developed, in which the later spiral acquisitions are acquired asymmetrically with the peak of a spin‐echo causing increased R2‐weighting but matched R2′‐weighting. This sequence, called asymmetric spin‐echo (ASE) spiral, has demonstrated significant improvements in minimizing the signal loss and increasing the image quality as well as optimal blood‐oxygen‐level‐dependent (BOLD)‐weighting. The ASE spiral is compared to conventional spiral‐out using both signal‐to‐noise ratio (SNR) and whole brain fMRI activation volumes from a breath‐hold task acquired at 4 Tesla. The ASE dual spiral has exhibited SNR increases of up to 300% in areas where strong SFGs are present. As a result, the ASE spiral is highly efficient for recovering lost activation in areas of SFGs, as demonstrated by a 16% increase in the total number of activated voxels over the whole brain. Post spin‐echo ASE spiral images have decreasing SNR due to R2 signal losses, however the increase in R2‐weighting leads to a higher percentage of signal changes producing ASE spiral images with equivalent contrast‐to‐noise ratio (CNR) for each echo. The use of this sequence allows for recovery of BOLD activation in areas of SFG without sacrificing the CNR over the whole brain. Copyright © 2009 John Wiley & Sons, Ltd.
An optimal‐order error estimate on an H1‐Galerkin mixed method for a nonlinear parabolic equation in porous medium flow
Authors: Chen Huan‐Zhen , Wang Hong 
Published: April 2009

AbstractWe present an H1‐Galerkin mixed finite element method for a nonlinear parabolic equation, which models a compressible fluid flow process in subsurface porous media. The method possesses the advantages of mixed finite element methods while avoiding directly inverting the permeability tensor, which is important especially in a low permeability zone. We conducted theoretical analysis to study the existence and uniqueness of the numerical solutions of the scheme and prove an optimal‐order error estimate for the method. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010
On the computation of the solution of perturbed nonlinear Schrödinger equations
Authors: Subaşı Murat 
Published: April 2009

AbstractWe introduce a numerical treatment for solving nonlinear Schrödinger equations in the form
$i\, \psi_{t} + a_{0}\psi_{xx} - v (x) \psi - a_{1} |\psi|^{2}\psi = f (x, \, t),$
where f(x,t) is an arbitrary function, being perturbative, dependent on ψ. For this purpose, we developed a MAPLE® procedure and examined the effectiveness of the method on two problems. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010
An efficient explicit/implicit domain decomposition method for convection‐diffusion equations
Authors: Zhu Liyong , Yuan Guangwei , Du Qiang 
Published: April 2009

AbstractA nonoverlapping domain decomposition method for some time‐dependent convection‐diffusion equations is presented. It combines predictor‐corrector technique, modified upwind differences with explicit/implicit coupling to provide intrinsic parallelism, and unconditional stability while improving the accuracy. Both rigorous mathematical analysis and numerical experiments are carried out to illustrate the stability, accuracy, and parallelism. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010
Effect of film thickness controlled by ink‐jet printing method on the optical properties of an electroluminescent polymer
Authors: Wang Meng , Yang Gui‐Zhong , Wang Min , Liu Tianxi 
Published: April 2009

AbstractInk‐jet printing (IJP) represents a highly promising liquid processed polymer deposition method for the film preparation of functional polymers in photo‐electronic devices. In this report, the results on the IJP of a fluorene‐based electroluminescent polymer, poly(9,9‐dihexylfluorene‐alt‐2,5‐dioctyloxybenzene) (PF6OC8), from a piezoelectric droplet generator are presented. The polymer film thickness has been found to show an approximate linear relation with the number of droplets per unit area; it is thus convenient to control the film thickness by the space of printed dots in IJP process. In comparison, spin coating approach is also used to prepare polymer films with different thicknesses by varying solution concentration and spinning speed. However, it is found that spin coating is difficult to control the film thickness quantitatively. The influence of film thickness on the photoluminescence (PL) properties of PF6OC8 films prepared by IJP and spin coating is comparatively investigated. For both ink‐jet printed and spin coated films, the intensity of PL spectra first increases and then decreases with increase in the film thickness, probably due to the exciton quenching in thicker films. When the polymer film thickness is at nanoscale, the major peak in the PL spectrum is the 0–0 vibronic emission at about 420 nm, and with increase in the film thickness, the 0–1 vibronic peak at about 440 nm becomes dominant. The red‐shifted PL spectra with increase in film thickness show the change from the 2D exciton state to the 3D one. Copyright © 2009 John Wiley & Sons, Ltd.
Brittle–ductile transition in the PETG/PC blends by adding PTW elastomer
Authors: Zhang Xinlan , Wang Ke , Li Bo , Chen Feng , Fu Qiang 
Published: April 2009

AbstractIn this paper, an elastomer containing epoxy groups, ethylene‐butylacrylate‐glycidylmethacrylate (PTW), was used as toughening modifier for the poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG)/polycarbonate (PC) blends. A remarkable improvement of toughness was achieved by addition of only 5 wt% PTW. In particular, an obvious brittle–ductile (B–D) transition in impact toughness was found when the PTW content increased from 3 to 5 wt%. The toughening mechanism and observed B–D transition have been explored in detail, combining with electronic microscopy observation, melt rheological investigation and dynamic mechanical analysis (DMA). It is suggested that the B–D transition can be attributed to a better interfacial adhesion between different phases, and importantly, to a continuum percolation dispersed‐phases network formed at appropriate PTW content, in which PC particles are connected with each other by PTW phase. Our present study offers new, profound insight on the toughening mechanism for the elastomer modified amorphous/amorphous plastic blends. Copyright © 2009 John Wiley & Sons, Ltd.
Metal complexes of natural and synthetic fabrics grafted with vinyl monomers by gamma irradiation
Authors: Hassan Mahmoud S. , Atteia Rehab M. , Zohdy Maged H. 
Published: April 2009

AbstractGraft copolymers of natural and synthetic fabrics with acrylic acid (AAc) prepared by gamma irradiation were transformed into metal complexes of the divalent metal ions of cobalt, nickel, and copper. The factors that affect the grafting process without affecting the physical properties of fabrics and homogeneous grafting were studied. These factors involved inhibitor (FeCl2) concentration, solvent composition, AAc concentration, and irradiation dose. The results showed that the appropriate irradiation dose in all cases was 20 kGy, whereas the inhibitor concentration was 0.1 wt% in the case of cotton and 0.2 wt% in the case of cotton/polyester blend and polyester fabrics. The suitable solvent composition was H2O (90%)/MeOH(10%) in the case of cotton and H2O (90%)/MeOH(10%) in the cotton/polyester blend and polyester fabrics. On the other hand, the suitable AAc concentration was 30% in the case of cotton and 50% in the cotton/polyester blend and polyester fabrics. The homogenous grafting and subsequent distribution of metal complexation was illustrated by a method based on the measurement of color parameters. Moreover, the effect of radiation grafting and metal complexation on the water absorption and mechanical properties of fabrics was investigated. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers
Thermal decomposition behavior of poly(ethylene 2,6‐naphthalate)/silica nanocomposites
Authors: Kim Jun Young , Kim Duk Ki , Kim Seong Hun 
Published: April 2009

AbstractPoly(ethylene 2,6‐naphthalate) (PEN) nanocomposites reinforced with silica nanoparticles were prepared by direct melt compounding. Dynamic thermogravimetric analysis was conducted on the PEN/silica nanocomposites to clarify the effect of silica nanoparticle on the thermal decomposition behavior of the resultant nanocomposites. There is a significant dependence of thermal decomposition behavior for PEN/silica nanocomposites on the content of silica nanoparticles and heating rate. The variation of the activation energy for thermal decomposition reflected the improvement of the thermal stability of the PEN/silica nanocomposites. The unique characteristics of silica nanoparticles resulted in physical barrier effect against the thermal decomposition, leading to the enhancement of the thermal stability of the PEN/silica nanocomposites. The incorporation of silica nanoparticles into the PEN matrix increased the storage modulus of the PEN/silica nanocomposites and made it possible for them to sustain higher modulus at higher temperature relative to pure PEN. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers
Effects of the accelerated freeze‐thaw cycling on physical and mechanical properties of wood flour‐recycled thermoplastic composites
Authors: Adhikary Kamal Babu , Pang Shusheng , Staiger Mark P. 
Published: April 2009

AbstractThis study investigated durability performance of wood‐plastic composites (WPCs) that were exposed to accelerated cycling of water immersion followed by freeze thaw (FT). The WPCs used in this study were made of high‐density polyethylene (HDPE) or polypropylene (PP) with radiata pine (Pinus radiata) wood flour using hot‐press molding. These two types of plastics included both recycled and virgin forms in the formulation. In the experiments, surface color, flexural properties, and dimensional stability properties (water absorption and thickness swelling) were measured for the FT cycled composites and the control samples. Interface microstructures and thermal properties of the composites were also investigated. The results show that the water absorption and the thickness swelling of the composites increased with the FT weathering. In the meantime, the flexural strength and stiffness decreased. Scanning electron microscopy (SEM) images of the fractured surfaces confirmed a loss of interface bonding between the wood flour and the polymer matrix. Differential scanning calorimetry (DSC) showed a decrease in crystallization enthalpy and crystallinity of the wood flour‐plastic composites as compared with the neat PP and HDPE samples. The crystallinity of the FT cycled composites using the virgin plastics (vPP and vHDPE) increased; however, the composites with the recycled plastics decreased in comparison with corresponding control samples. In general, the properties of the composites were degraded significantly after the accelerated FT cycling. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Effects of silane grafting on the morphology and thermal stability of poly(ethylene terephthalate)/clay nanocomposites
Authors: Xu Xinfeng , Ding Yanfen , Wang Feng , Wen Bin , Zhang Junhua , Zhang Shimin , Yang Mingshu 
Published: April 2009

AbstractAn alkylammonium intercalated montmorillonite (A‐MMT) was modified by edge grafting with 3‐glycidoxypropyltrimethoxysilane. In comparison with poly(ethylene terephthalate) (PET)/A‐MMT, the resultant grafted clay, S‐A‐MMT, exhibited improved miscibility with PET matrix and revealed better dispersion state in the melting compounded PET/S‐A‐MMT nanocomposites. As a result, the PET/S‐A‐MMT nanocomposite had slower degradation rate owing to the enhanced clay barrier effect. Meanwhile, the nanocomposite exhibited lower degradation onset temperature under nitrogen because of the clay catalysis effect, which can be explained by the decreasing degradation reaction energy calculated from Coats–Redfern method of degradation kinetics. In the other hand, nanocomposite with better clay dispersion state exhibited increasing thermal oxidative stability due to clay barrier effect of hindering oxygen to diffuse in, which accorded with the continuous and compact char surface formed during polymer degradation. The clay catalysis and barrier effect of silicate layers were presented directly in isothermal oxidative TGA experiment. Furthermore, the mechanical and crystallization properties of PET/clay nanocomposites were investigated as well. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Influence of modified carbon nanotube on physical properties and crystallization behavior of poly(ethylene terephthalate) nanocomposite
Authors: Kim Jun Young , Choi Hee Jun , Kang Chang Soo , Kim Seong Hun 
Published: April 2009

AbstractPoly(ethylene terephthalate) (PET) nanocomposites reinforced with a very small quantity of modified carbon nanotube (CNT) were prepared by melt compounding using a twin‐screw extruder. The introduction of carboxylic acid groups on the surfaces of the nanotube leads to the enhanced interactions between the nanotube and the polymer matrix through hydrogen bonding formation. The thermal stability, mechanical, and rheological properties of the PET nanocomposites are strongly dependent on the interfacial interactions between the PET and the modified CNT as well as the dispersion of the modified CNT in the PET. The introduction of the nanotube can significantly influence the non‐isothermal crystallization behavior of the PET nanocomposites. This study demonstrates that a very small quantity of the modified CNT can substantially improve the thermal stability and mechanical properties of the PET nanocomposites, depending on the dispersion of the modified CNT and the interfacial interactions between the polymer matrix and the modified CNT. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers