bluuebunny/crossref_metadata_2025 huggingface dataset:
Glass Transition and Interfacial Segmental Dynamics in Polymer-Particle Composites
Authors: Robertson C. G. , Roland C. M.
Published: February 2011

We review the literature concerned with the effect of proximity to a filler surface on the local segmental mobility of polymer chains. This mobility is commonly assessed from either the glass transition temperature, Tg, or the segmental relaxation times measured by mechanical, dielectric, or NMR spectroscopy. Published studies report increases, decreases, or no change in Tg upon the addition of carbon black, silica, and other reinforcing fillers. Similarly, the segmental relaxation times have been found to increase or be invariant to the presence of nanometer-sized particles. Some of these discrepancies can be ascribed to ambiguous methods of data analysis; others likely reflect the variation in filler-polymer interaction among different systems. There are unequivocal examples of polymers that have segmental dynamics and glass transitions unaffected by nano-particle reinforcement. However, the general principles governing the behavior remain to be clarified, with further work, focusing on the micromechanics at the particle interface, required for resolution of this important aspect of rubber science and technology.
Fiber Adhesion to Rubber Compounds
Authors: Wennekes W. B. , Datta R. N. , Noordermeer J. W. M. , Elkink F.
Published: February 2011

The present paper provides an overview of literature published on fiber-rubber composites. A brief history of Fibers used in rubber applications is given. The emphasis is on the adhesion between fiber materials and rubber compounds. Special attention is given to the standard RFL-treatment and the double-dip treatment used for aramid and polyester Fibers to enhance the adhesion with rubber compounds. Some alternatives to the RFL-treatment are described: fiber surface roughening, adhesion promoter additives to the rubber compound, impregnated Fibers and plasma treatment.
Effect of Fillers on Wet Skid Resistance of Tires. Part I: Water Lubrication Vs. Filler-Elastomer Interactions
Authors: Wang Meng-Jiao , Kutsovsky Yakov
Published: February 2011

From results of testing materials using a new filler, it was recognized that the wet skid resistance of tires is determined not only by dynamic properties of the tread compounds, but also by elastohydrodynamic lubrication, especially on the micro scale. By reviewing the basic concepts of friction under dry and wet conditions, and friction coefficients of possible model materials that are at the worn surface of tire tread compounds and road surface, it is inferred that after skid testing under wet conditions, the top skin of the worn surface contains some bare silica for silica-filled compounds, but the carbon black aggregates remain covered by rubber film. This inference is supported by measuring the surface energies of the fillers, analyzing the properties of filled vulcanizates, and direct investigation of worn surface of the compounds after skid test by AFM. The different surface compositions between silica- and carbon black-filled vulcanizates would lead to different effects on micro-elastohydrodynamic lubrication, hence wet skid resistance, which will be the topic of next report of this study.
Chemically Modified Emulsion SBR in Tire Treads
Authors: Thielen Georges
Published: February 2011

A series of Emulsion SBRs (E-SBR) with polar and nonpolar third co-monomers are studied in silica filled compounds. The applied third co-monomers include polar types such as acrylonitrile (ACN), hydroxypropyl methacrylate (HPMA) and 1-vinylpyridine (VP) and nonpolar types such as isoprene and 1,3-pentadiene. The impact of the third co-monomers on compound reinforcement, hysteresis, abradability and viscoelastic properties is studied for single polymer compounds as well as polymer blends with 1,4-cis-polybutadiene (cis-BR) and Natural Rubber (NR). Changes in miscibility of the polymer blends are studied via viscoelastic temperature sweeps and via Atomic Force Microscopy (AFM). All blends show a miscibility behavior in agreement with Hildebrand solubility parameter predictions. The nonpolar co-monomers lead to an increased miscibility while the polar co-monomers reduce the miscibility with cis-BR and NR. These changes only show up in blend Tg's and viscoelastic response and stay associated with a heterogeneous AFM blend structure with different degrees of mixed phase compositions. The impact of the third co-monomers is more pronounced in the case of cis-BR than in the case of NR blends in this study. The preferred chemically modified ESBR is the one with 3% HPMA showing improved performance relative to unmodified ESBR and unmodified Solution SBR (SSBR).
Population Balance Kinetic Model for Interaction of 2-Bisbenzothiazole-2-2'Disulfide (MBTS) with Sulfur
Authors: Goyal Ayush , Patkar Priyan , Medvedev Grisha , Venkatasubramanian Venkat , Caruthers James M. , Cao Jun , Midkiff Samuel P.
Published: February 2011

The first step in accelerated vulcanization is the formation of the active sulfurating species via the incorporation of sulfur by an accelerator like benzothiazole. Several mechanisms for the pick-up of sulfur by the accelerator have been proposed, including lumped pick-up of the full S8 species, sequential pick-up of individual sulfur atoms in S8 and numerous proposals where the stoichiometry is not clearly specified. For the reaction of MBTS with S8 Gradwell, et al. observed that benzothiazole terminated sulfurating species with lower sulfur rank form in greater concentrations than the sulfurating species with higher sulfur rank, where a sequential sulfur pick-up mechanism was then postulated. A detailed kinetic model will be developed to describe the Gradwell, et al. data. Density functional theory (DFT) simulations were used to provide information on the thermochemistry of the various reaction intermediates. The DFT simulations indicated that both sequential and lumped S8 pick-up are thermodynamically feasible. Population balance models have been developed that explicitly account for all polysulfidic species that are present in the MBTS+S8 reaction system. The chemically consistent population balance model includes the following reactions: (i) dissociation of polysulfides, including the opening of S8 rings, to form radical pairs, (ii) combination of a pair of persulfenyl radicals, (iii) reaction of a persulfenyl radical with a polysulfide. The effect of chain length on the kinetic constants for these reactions was determined from the DFT simulations, where the bonds that are close to the benzothiazole groups have significantly different rates of reaction. It is shown that (i) lumped sulfur pick-up alone is not thermodynamically consistent, and (ii) sequential sulfur pickup alone can not adequately describe the experimental data of Gradwell, et al.; however, a chemically consistent model with both sequential and lumped sulfur pick-up can explain the data. The identification of the above mechanism and the associated distribution of sulfurating species of different sulfur rank provide the starting point for a quantitative kinetic description of the accelerated vulcanization.
Production and Properties of Yulex® - The Natural Solution to Latex Allergy
Authors: Cornish Katrina , Williams Jali , Hall Julie L. , McCoy Raymond G.
Published: February 2011

Natural rubber is an irreplaceable raw material vital to industry, transportation, medicine and defense, largely produced from clonal plantations of Hevea brasiliensis in Southeast Asia. Additional rubber-producing crops are greatly desired to increase biodiversity, protect supplies, and provide a safe alternative for people suffering from Type I latex protein allergy. Basic and applied research approaches were used to make the production of latex (Yulex® latex) from Parthenium argentatum (guayule) a commercial reality. In contrast to Hevea brasiliensis, from which rubber latex is tapped by hand from laticifers, guayule latex rubber is contained within individual bark parenchyma cells. Processing involves disrupting these cells to release the rubber particles, and then purifying the latex. As in the Hevea industry, latex concentration can be achieved by centrifugation and/or by creaming agents. An artificially produced guayule natural rubber latex is then produced, under the material name of “Yulex® latex”. The Yulex Pilot Plant has been constructed, optimized and automated, and extracts then purifies latex from guayule shrub without detectable losses. The natural rubber polymers in guayule latex are high molecular weight and products made from this material have the desired high performance properties. Because guayule latex contains very little protein, all of which is hydrophobic and bound to the rubber phase, and because none of the protein cross-reacts with Type I latex allergy to Hevea latex products, its use is initially aimed towards the high-value medical products marketplace. Clinical and performance trials continue to ensure that guayule processing provides a safe, high performance, non-allergenic natural rubber latex that is safe for human use.
Temperature Controlled Dispersion of Poly(N-Isopropyl Acrylamide) Treated Silica Clusters
Authors: Bava Luciana , Feke Donald L. , Manas-Zloczower Ica , Rowan Stuart J.
Published: February 2011

The dispersion of particle agglomerates is affected by the presence of any chemical additives incorporated within the agglomerate structure. Traditional additives change the particle-particle and particle-matrix interactions to a degree that depends primarily on the chemical nature of the additive and its concentration within the agglomerate. A new generation of additives, based on polymeric systems that respond to external stimuli, allows the adjustment of interparticle interactions by manipulating the variable to which the additive is responsive. In this study, dispersion tests in simple shear flow are used to examine the effect of a thermally responsive additive, poly(N-isopropyl acrylamide) (PNIPAM), on the dispersion behavior of silica agglomerates. The temperature sensitivity of the dispersion mechanisms and kinetics for silica clusters treated with either linear or crosslinked PNIPAM has been examined.
Synthesis and Characterization of Styrene-Butadiene Rubber-Clay Nanocomposites with Enhanced Mechanical and Gas Barrier Properties
Authors: Meneghetti P. , Shaikh S. , Qutubuddin S. , Nazarenko S.
Published: February 2011

Five styrene-butadiene rubber (SBR)/clay nanocomposite or hybrid systems were synthesized via mechanical mixing of SBR using a Brabender mixer and a 2-roll mill in the presence of unmodified sodium montmorillonite (Na-MMT) clay, MMT modified with octadecylamine (C18amine), MMT modified with a zwitterionic surfactant, octadecyldimethyl betaine (C18DMB), and MMT modified with a polymerizable cationic surfactant, vinylbenzyl octadecyldimethyl ammonium chloride (VODAC) or vinylbenzyl dodecyldimethyl ammonium chloride (VDAC). The surfactant chain length and functional groups affected the dispersion of clay nanolayers in the matrix and the overall properties of the nanocomposites. X-ray diffraction (XRD) revealed peaks corresponding to intercalated structures; transmission electron microscopy (TEM) observations agreed well with XRD assessment of the composites. SBR/VODAC-MMT system exhibited the best dispersion among the nanocomposites studied. VODAC-MMT was partially exfoliated in SBR matrix and the average aspect ratio of the nanolayer stacks or aggregates was high (20). Depending on the amount of clay, considerable mechanical reinforcement and gas barrier enhancement were achieved in nanocomposites over pure rubber. Tensile strength in excess of 18MPa was observed in SBR nanocomposites with 30 phr C18 organoclays. The storage modulus at 25C increased by a factor of four by incorporating 10 phr VODAC-MMT in SBR. The most pronounced oxygen barrier enhancement was again observed in SBR/VODAC-MMT nanocomposite with the reduction of permeability by 60% at silicate volume fraction of 0.06. The superior performance of nanocomposites containing VODAC-MMT is attributed to the presence of the vinyl-benzyl group and 18 carbon-atom tail in the surfactant leading to high compatibility with SBR and nano-scale dispersion in the SBR matrix.
Synthesis and Characterization of Chemically Crosslinked Styrene-Butadiene Rubber Nanogels and their Effect on Various Properties of the Rubber
Authors: Mitra Suman , Chattopadhyay Santanu , Bhowmick Anil K.
Published: February 2011

Nano-sized styrene-butadiene rubber (SBR) latex gels were prepared by pre-vulcanizing SBR latex with different sulfur to accelerator ratios. These gels were characterized by swelling studies, dynamic light scattering, atomic force microscopy, mechanical and dynamic mechanical properties. With the increase in sulfur to accelerator ratio, the gels had higher amount of crosslink density and gel content. Particle size distribution did not alter much in the crosslinked gels. Incorporation of these nanogels into raw SBR led to the considerable drop in viscosity of the gel filled systems under capillary melt flow conditions. However, the reduction in viscosity was found to be dependent on the loading and crosslink density of the nanogels. Energy dispersive X-ray mapping of sulfur was used to check the dispersion of these gels into raw SBR matrix. The die swell values of gel filled SBR were much lower than that of the raw SBR. The reduction in principal normal stress difference values combined with the reinforcement effect of the gels was found to be responsible for the lowering of die swell values. Scanning electron photomicrographs of extrudates of gel filled systems showed much-improved surface smoothness compared to the unfilled SBR. The mechanical and dynamic mechanical properties also showed excellent improvement in modulus with the addition of gels in the raw rubber. A new empirical relationship was proposed to explain the reinforcement properties of nanogels as viscoelastic fillers.
Modeling of an Elastomeric Friction Damper
Authors: Li C. G. , Wang S. W. , Lu H. Y.
Published: February 2011

Frictional resistance of a hollow rubber cylinder steadily sliding inside a rigid sleeve has been studied theoretically and reported here. This is inspired by a new class of elastomeric friction damper consisting of an unbonded rubber cylinder, axially compressed and radially expanding to contact an outer rigid sleeve and generate friction. By considering the force equilibrium of each thin section of the rubber cylinder and adapting the principle of superposition, the tri-bological problem was decomposed into three fundamental sub-problems, which were solved consecutively. The results shed lights on the functional effects of various design parameters such as part dimensions, friction coefficient, and Young's modulus on the total friction force. Finite element analyses were also performed, and the results were compared with the closed-form solutions.
On the ABAQUS FEA Model of Finite Viscoelasticity
Authors: Ciambella J. , Destrade M. , Ogden R. W.
Published: February 2011

Predictions of the QLV (Quasi-Linear Viscoelastic) constitutive law are compared with those of the ABAQUS viscoelastic model for two simple motions in order to highlight, in particular, their very different dissipation rates and certain shortcomings of the ABAQUS model.
Dynamic Nanofishing of Single Polymer Chains
Authors: Nakajima Ken , Nishi Toshio
Published: February 2011

Single molecule force spectroscopy (SMFS) realized by atomic force microscope (AFM) on a single polymer chain (static nanofishing), where a polymer chain is picked up and pulled at its chemically modified terminals, only gives structural information such as persistence length and contour length. Beyond this technique, dynamic nanofishing, where an AFM cantilever is imposed on the forced oscillation at its resonant frequency (∼10 kHz), enables us to investigate more fruitful information. The method gave extension-dependent changes of entropic elasticity and frictional coefficient with solvent molecules for mono-disperse living-polymerized polystyrene (PS). The solvent temperature dependence revealed that the frictional coefficient could be correlated with macroscopic “intrinsic viscosity.” Another novel technique, nanofishing at fast pulling rate (fast nanofishing), exhibited internal entanglement of a single PS chain and its subsequent relaxation.
Adhesion of Steel Tire Cord to Rubber
Authors: Vanooij William J. , Harakuni Prasan B. , Buytaert Guy
Published: February 2011

This paper reviews the literature on rubber-brass bonding that has been published in approximately the last decade. Previous reviews of this topic by Van Ooij were published in 1979, 1984, 1991 and 2001. The scientific and technical literature is reviewed exhaustively; the patent literature is reviewed in a more selective way. Only U.S. patents are covered, and then only those that clearly propose new processes or materials. Emphasis in this review is on those papers that have contributed to an increased understanding of the mechanisms of rubber-brass bonding as it is of importance to the performance of brass-plated tire cords. Another major component of this review is the literature on compounding for brass adhesion. Literature on tire failure, tire design, or steel cord construction, is not included. This paper is concluded by an updated adhesion model that can be distilled from the recent literature.
Effects of Bio-Fuels on Common Static Sealing Elastomers
Authors: Walker F. J.
Published: February 2011

The purpose of this investigation was to explore the effects of bio-fuels on several common static sealing elastomers. This study explored ethanol-enriched gasoline and soy-based diesel. Exposed to these fuels were fifteen common static sealing elastomer compounds. These were comprised of eight FKM compounds, and two NBR compounds. In addition, other compositions were also included in the study. These comprised VMQ, FVMQ, AEM di-polymer, HNBR and a high temperature ACM. The percentage of ethanol enrichment was varied from zero to 100 percent. The bio-diesel section of this study examined comparative effects of conventional low-sulfur diesel, twenty percent soy diesel, and 100 percent soy diesel. Effects on conventional mechanical properties of hardness, tensile strength, elongation and volume change were measured.
A Numerical Model for Edge Effect Correction of the Mooney Rheometer
Authors: Montes Sergio A.
Published: February 2011

The flow of a power law fluid within the cavity of a multi-speed Mooney rheometer is studied by means of finite difference techniques with the aim of quantifying the edge effects that occur in the vicinity of the rotor corner. As expected, a significant concentration of shear stress occurs near the rotor edge. As the power law index varies, significant stagnation zones are found within the cavity, which combined with thin-shearing behavior near the moving surfaces, yield complex shear rate distributions. However, when torque is calculated, the edge effect can be described by a factor which is numerically very similar to a factor obtained from one-dimensional models described in the literature. Comparison of theoretical predictions and experimental data was found to be satisfactory.
Characterization of the Steel Tire Cord - Rubber Interface
Authors: Buytaert Guy , Coornaert Frederik , Dekeyser Willem
Published: February 2011

Brass-coated steel cords are extensively used as reinforcement material in radial tires, high-pressure hydraulic hoses and heavy duty conveyor belts. Bonding between rubber and steel cord is obtained via the formation of an adhesion interface layer during the curing process. The adhesion build-up mechanism involves the chemical reaction of sulfurating species contained in the rubber skim compound and copper of the brass coating, forming a CuxS layer at the rubber-brass interface. Advances in mechanistic investigations are presented, using analytical techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), atomic force microscopy (AFM) and optical microscopy (OM). XPS and AES provide chemical in-depth information, whereas OM and AFM highlight the morphology of the resulting interfacial layers. These investigations improve the understanding of the adhesion mechanism, both for adhesion buildup and for bond degradation.
Cyclic Stress Relaxation (Csr) of Filled Rubber and Rubber Components
Authors: Asare S. , Thomas A. G. , Busfield J. J. C.
Published: February 2011

Under repeated stressing it is well known that rubber materials exhibit cyclic stress relaxation (CSR). Previous work has shown that the amount of relaxation observed from cycle to cycle is significantly greater than that expected from static relaxation measurements. The reduction in the stress attained on the second and successive loading cycles as compared to the stress attained on the first cycle in a stress strain cyclic test of fixed amplitude has been measured for elastomer test pieces and engineering components. It is seen that the peak force, under cyclic testing to a specific maximum displacement, plotted against the number of cycles on logarithmic scales produces a straight line graph, whose slope correlates to the rate of cyclic stress relaxation per decade. The rate of cyclic stress relaxation was found to increase with displacement amplitude in all modes of deformation. Plotting the rate of stress relaxation per decade against the maximum average strain energy attained in the cycle reduces the data measured in different deformation modes for both simple test pieces and components to a single curve. This approach allows the cyclic stress relaxation in a real component to be predicted from simple laboratory tests.
Assessing Effect of the Migration of A Paraffin Wax on the Surface Free Energy of Natural Rubber
Authors: Ansarifar A. , Critchlow G. W. , Guo R. , Ellis R. J. , Haile-Meskel Y. , Doyle B.
Published: February 2011

The effect of the migration of paraffin wax on the surface free energy of natural rubber (NR) was investigated. The rubber was mixed with the wax and then stored at ambient temperature for up to 168 hrs before its surface free energy was measured using contact angle measurement. Static secondary ion mass spectrometry was also used to provide a chemical fingerprint of the rubber surfaces. The surface free energy decreased as a function of storage time because of the migration of the wax to the rubber surface. The highest rate of reduction was recorded up to 3 hrs and thereafter, the surface free energy decreased at a much slower rate, reaching a plateau after 48 hrs in storage. In total, the surface free energy reduced by approximately 46% as a result of the migration of the wax to the rubber surface. The reduction in surface free energy could adversely affect ability of the rubber to stick to itself and to other dissimilar elastomers.
Compression of Rubber Disks Between Frictional Surfaces
Authors: Gent A. N. , Discenzo F. M. , Suh J. B.
Published: February 2011

An approximate analysis is given of the axial compression and retraction of a rubber disk sandwiched between two rigid frictional surfaces. The rubber is assumed to be linearly-elastic and incompressible, and Coulomb's law of sliding friction is assumed to apply. The amount of interfacial slipping during compression is calculated and the distributions of normal and shear stress are determined. The overall compressive stiffness is then evaluated for disks with a wide range of aspect ratio a/h, where a is the radius and h is the thickness, and for several values of friction coefficient. Force-displacement relations during retraction are obtained and the energy expended in frictional sliding is calculated in some representative cases. It is found to be a large fraction (about one-half) of the input energy for disks of large aspect ratio, compressed between low-friction surfaces. Finite element analysis (FEA) was carried out for disks with various aspect ratios and friction coefficients. Stress distributions and force-displacement relations are compared with the analytical results. Agreement is generally good, even though the stress singularity at the edge of the disk is ignored in the analysis. It appears to have little influence away from the edge.
The Effect of Thermal Boundary Condition on the Crosslink Density Distribution and the Curing Time of the Thick Cylindrical Dampers
Authors: Saeb Mohammad R. , Mostafaiyan Mehdi
Published: February 2011

Optimization of curing process conditions of elastomers so as to achieve a part with homogeneous network is of crucial importance. One of the indicative parameters in the curing process is state of cure (SOC) that is investigated in this study in order to verify the influence of thermal boundary conditions on the curing of a cylindrical damper based on NR.. Furthermore, the newly introduced parameter of state of reversion (SOR) is defined, and this parameter will be set as a controlling parameter in the curing time; in order to avoid the unfavorable phenomenon of thermal decomposition. In this work, the curing process is numerically modeled using a finite element code which is developed by authors and results are compared with experimental results, as a verification step for validity of the code. Employing this code, the curing process is subjected to various molding temperatures, and it is demonstrated that a constant temperature of mold for elastomeric parts of high thickness will not result in a homogeneous crosslink network, unless the curing time is very long. Therefore, a varying with time temperature profile for mold is proposed that leads to a decreased curing cycle time, while giving complete SOC at a lower SOR value, simultaneously.
Die Pressure Losses During Injection Molding of Rubber Mixes
Authors: Arrillaga A. , Zaldua A. M. , Atxurra R. M. , Farid A. S. , Farid A. S.
Published: February 2011

In order to fill the mold in a rubber injection molding process, it is necessary to inject the material into the closed mold. Rubber is usually injected under ram speed control, but it can be also injected under pressure control. In the present study, we have recorded the signals of pressure at three points during the filling of a spiral shape part. The behaviors of two rubber compounds have been studied using a variety of combinations of process conditions (including mold temperature, mass temperature, ram speed and injection molding with and without pressure holding stage). In all conditions, the transducer located in proximity to the gate exhibits pressure decay at the last stage of mold filling. Initial CAE simulations have been carried out using Moldflow software to check the capability of this sort of software to calculate pressure decay during the filling stage.
Energetics of Organomanganese Compounds
Authors: Liebman Joel F. , Slayden Suzanne W.
Published: February 2011

Diverse aspects of the energetics of organomanganese compounds are considered in this chapter. Bond energies, enthalpies of formation and enthalpies of reaction are discussed. Classical combustion calorimetry plays only a small role compared to reaction calorimetry and techniques from contemporary ion energetics. While carbonyl, cyano, cyclopentadienyl, and benzene derivatives dominate the discussion, species with numerous other σ and/or π‐bonded ligands also appear. Quantitation is given whenever possible.
A bubbling fluidization model using kinetic theory of rough spheres
Authors: Shuai Wang , Zhenhua Hao , Huilin Lu , Goudong Liu , Jiaxing Wang , Pengfei Xu
Published: February 2011

Collisional motion of inelastic rough spheres is analyzed on the basis of the kinetic theory for flow of dense, slightly inelastic, slightly rough sphere with the consideration of gas–solid interactions. The fluctuation kinetic energy of particles is introduced to characterize the random motion of particles as a measure of the translational and rotational velocities fluctuations. The kinetic energy transport equation is proposed with the consideration of the redistribution of particle kinetic energy between the rotational and translational modes and kinetic energy dissipation by collisions. The solid pressure and viscosity are obtained in terms of the particle roughness and restitution coefficient. The partition of the random‐motion kinetic energy of inelastic rough particles between rotational and translational modes is shown to be strongly affected by the particle restitution coefficient and roughness. Hydrodynamics of gas–solid bubbling fluidized beds are numerically simulated on the basis of the kinetic theory for flow of rough spheres. Computed profiles of particles are in agreement with the experimental measurements in a bubbling fluidized bed. The effect of roughness on the distribution of energy dissipation, kinetic energy, and viscosity of particles is analyzed. © 2011 American Institute of Chemical Engineers AIChE J, 2012
Subgrid scale scalar variance in high‐Schmidt‐number turbulence
Authors: Kurose Ryoichi , Takagaki Naohisa , Michioka Takenobu , Kohno Naoki , Komori Satoru
Published: February 2011

The subgrid scale (SGS) variance for a high‐Schmidt‐number passive scalar of Sc >> 1 is measured using a high‐resolution planar laser‐induced fluorescence technique in a grid‐generated turbulent liquid flow, and the values of the model coefficients in the scale‐similarity model and the scalar‐gradient model used for estimating the SGS scalar variance are experimentally evaluated. The results show that for both models, the measured values are much larger than the well‐known values obtained in the previous studies done for non‐high‐Sc scalars of Sc ≅ 1. Similarly, the measured value of the model coefficient in the scalar‐gradient model tends to be larger than the value estimated by the dynamic procedure. The increases in the measured values of the model coefficients for the high‐Sc scalar can be explained by the presence of the viscous‐convective range showing a nearly (−1)‐slope in the high‐wavenumber range of the power spectrum of concentration fluctuation. © 2011 American Institute of Chemical Engineers AIChE J, 2012
Thyroid abnormalities in patients treated with lenalidomide for hematological malignancies: Results of a retrospective case review
Authors: Figaro M. Kathleen , Clayton Warren , Usoh Chinenye , Brown Kara , Kassim Adetola , Lakhani Vipul T. , Jagasia Shubhada
Published: February 2011

Lenalidomide is an antiangiogenic drug associated with hypothyroidism. We describe a case‐series of lenalidomide use in hematological cancers and the prevalence of thyroid abnormalities. We reviewed medical records of patients treated with lenalidomide at a single center form 2005 to 2010 and extracted demographic, clinical, and laboratory data. Of 170 patients with confirmed lenalidomide use (age 64.9±15 years), 148 were treated for multiple myeloma and 6% had thyroid abnormalities attributable only to lenalidomide. In patients with a previous diagnosis of thyroid dysfunction, the addition of lenalidomide therapy was associated with a higher incidence of subsequent TFTF abnormality (17%) as compared to patients with no previous diagnosis of thyroid dysfunction (6%) (P=0.0001). Many patients (44%) with pre‐existing disease and a change in thyroid function before or while on lenalidomide had no further follow‐up of their thyroid abnormalities, Of 20 patients who did not undergo any thyroid finction testing either before starting or while on lenalidomide for a median of 9.4 months (±6.5), 35% developed new symptoms compatible with hypothyroidism, including worsened fating, constipation or cold intolerance. Symptoms of thyroid dysfunction overlap with side effects of lenalidomide. Thyroid hormone levele are not regularly evaluated in patients on lenalidomide. While on this treatment, thyroid abnormalities can occur in patients with no previous diagnoses and in patients with pre‐existing abnormalities. Because symptoms of thyroid dysfunction could be alleviated by appropriate treatment, thyroid function should be evaluated during the course of lenalidomide to improve patients quality of life. Am. J. Hematol. 2011. © 2011 Wiley‐Liss, Inc.
Nonfasting triglycerides, cholesterol, and ischemic stroke in the general population
Authors: Varbo Anette , Nordestgaard Børge G. , Tybjærg‐Hansen Anne , Schnohr Peter , Jensen Gorm B. , Benn Marianne
Published: February 2011

Objective:

Current guidelines on stroke prevention have recommendations on desirable cholesterol levels, but not on nonfasting triglycerides. We compared stepwise increasing levels of nonfasting triglycerides and cholesterol for their association with risk of ischemic stroke in the general population.

Methods:

A total of 7,579 women and 6,372 men from the Copenhagen City Heart Study with measurements of nonfasting triglycerides and cholesterol at baseline in 1976–1978 were followed for up to 33 years; of these, 837 women and 837 men developed ischemic stroke during follow‐up, which was 100% complete.

Results:

The fluctuation of nonfasting triglycerides and cholesterol over 15 years was similar. In both women and men, stepwise increasing levels of nonfasting triglycerides were associated with increased risk of ischemic stroke. Compared to women with triglycerides <1 mmol/liter, multivariate adjusted hazard ratios ranged from 1.2 (95% confidence interval [CI], 0.9–1.7) for triglyceride levels of 1.00–1.99 mmol/liter to 3.9 (95%CI, 1.3–11.1) for triglyceride levels ≥5 mmol/liter (trend: p < 0.001); corresponding hazard ratios in men ranged from 1.2 (95%CI, 0.8–1.7) to 2.3 (95%CI, 1.2–4.3) (p = 0.001). Increasing cholesterol levels were not associated with risk of ischemic stroke except in men with cholesterol levels ≥9.00 mmol/liter vs <5.00 mmol/liter, with a hazard ratio of 4.4 (95%CI, 1.9–10.6).

Interpretation:

In women, stepwise increasing levels of nonfasting triglycerides were associated with increasing risk of ischemic stroke while increasing cholesterol levels were not. In men, these results were similar except that cholesterol ≥9.00 mmol/liter was associated with increased risk of ischemic stroke. ANN NEUROL, 2011
Diethanol amine‐functionalized polymer‐supported palladium (0) complex as catalyst for Suzuki cross‐coupling reaction in water
Authors: He Ying , Wang Liang , Cai Chun
Published: February 2011

Diethanol amine‐functionalized polymer‐supported palladium (0) complex as catalyst for Suzuki cross‐coupling reaction in water was synthesized and characterized. The catalyst exhibits excellent catalytic activity and stability in the Suzuki cross‐coupling reaction. Various aryl bromides were coupled with aryl boronic acids in water, under air, and in the presence of 0.5 mol % of the catalyst to afford corresponding cross‐coupled products in high yields at 100°C. Furthermore, the heterogeneous catalyst can be readily recovered by simple filtration and reused for several times only with a slight decrease in its activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Drug release behaviors of a novel pH/temperature‐responsive chitosan‐poly(N‐acryloylglycinate) hydrogel
Authors: Deng Kuilin , Dong Lirong , Li Qian , Gou Yubo , Zhang Pengfei , Ren Xiaobo , Zhong Haibin
Published: February 2011

A pH/temperature and degradable‐responsive hydrogel (PSMEA) was prepared from chitosan (CS),N‐acryloylglycine methyl ester (NAGME),N‐acryloylglycine ethyl ester (NAGEE), acrylic acid (AA), andN‐methylenebisacrylamide (NMBA). The swelling properties of PSMEA were systematically investigated at different temperatures, pH, and CS contents. It was found that the PSMEA demonstrated obvious pH and temperature‐responsive natures. The caffeine‐release behaviors showed that only 42.9% caffeine was released from PSEMA in pH 2.1 phosphate buffer solution (PBS) after 360 min, whereas more than 71.5% caffeine was gradually diffused into pH 7.4 PBS over the same time interval. In addition, the caffeine release was much higher at 37.0°C than that at 14.0°C in PBS medium. The apparent degradability of PSMEA was also observed in the pH 7.4 PBS at 37.0°C through the chemical cleavage of CS. As seen from the results, PSEMA seems to be a potential application in the drug‐delivery system controlled by the external pH value and temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of BSA‐loaded microspheres based on polyanhydrides
Authors: Yu Yang , Lu Tingli , Zhao Wen , Sun Weiguang , Chen Tao
Published: February 2011

A series of biodegradable PEG‐containing polyanhydrides composed of sebacic acid, 1, 6‐bis(p‐carboxyphenoxy) hexane, and poly (ethylene glycol) (PEG) were used as matrix material for BSA‐loaded microspheres. The effects of polymer composition on the microsphere size, entrapment efficiency, in vitro degradation, and in vitro protein release were studied. Microspheres in the size range of 0.8–10 μm were fabricated via a modified double emulsion method and were characterized using scanning electron microscopy. As the content or the molecular weight of PEG was increased in the copolymer, a proportional increase was found in the particle size and the efficiency of BSA entrapment. The in vitro degradation rate of particles could be controlled by varying the polymer composition, increasing as the PEG proportion increased. In vitro release studies of BSA from polyanhydride microspheres revealed that the increased amounts of PEG within microspheres could accelerate the release rate of protein. These studies indicate that the PEG‐containing polyanhydrides hold potential for protein delivery applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effects of TDI and FA‐703 on physico‐mechanical properties of polyurethane dispersion
Authors: Negim S. M. , Bahruddin S. , Mahyuddin R. , Idiris M. S.
Published: February 2011

A series of water dispersion polyurethanes dispersions (PUDs) were prepared by polyaddition reaction using isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), and triol (trade name FA‐703). Various formulations were designed to investigate the effects of process variables such as TDI and FA‐703 on the physico‐mechanical properties of PUD. IR spectroscopy was used to check the end of polymerization reaction and characterization of polymer. Evolution of the particle size distribution, contact angle, Tg, molecular weight, viscosity, and mechanical properties of the emulsion‐cast films were significantly affected by variable content of TDI and FA‐703. Average particle size of the prepared polyurethane emulsions and contact angle decrease with increase of content of FA‐703 and TDI. Molecular weight, Tg, tensile strength, tear strength, hardness, viscosity and elongation at break increase with increase of content of FA‐703 and TDI. The increase of molecular weight, tensile strength, tear strength and elongation at break properties are interpreted in terms of increasing hard segments, chain flexibility, and phase separation in high content of FA‐703 and TDI‐based polyurethane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Viscoelastic properties of polypropylene/organo‐clay nano‐composites prepared using miniature lab mixing extruder from masterbatch
Authors: Ali Mohammad Al‐haj , Elleithy Rabeh H.
Published: February 2011

Polypropylene (PP) was melt blended with nano organo‐clay masterbatch at different ratios; namely 5, 10, and 15 wt % of nano‐clay. The effect of organo‐clay content on the viscoelastic properties of the nano‐composite was studied. A miniature laboratory mixing extruder, LME, was used to blend the nano organo‐clay masterbatch with PP at 260°C and 250 rpm. The blend was pelletized first, and then a thin ribbon was extruded. Two viscoelastic tests were performed; frequency sweep at constant temperature of 80°C, and temperature sweep at constant frequency of 1.0 rad/s. As the loading of nano‐clay increased, the storage modulus, G', and the thermal resistance increased as well. Different viscoelastic models were tried and 3‐elements Maxwell model was found to describe well the viscoelastic properties of the nano‐composites. The ratio of the complex modulus to the corresponding matrix modulus at different frequencies was found to vary proportional to the nanoclay loading. This dependency was described reasonably well by modified Guth model using particle aspect ratio of 12.1. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermal stability of polyoxymethylene and its blends with poly(ethylene‐methylacrylate) or poly(styrene‐butadiene‐styrene)
Authors: Wang Qian
Published: February 2011

Polyoxymethylene (POM) copolymer and its blends with poly(ethylene‐methylacrylate) (EMA) or poly(styrene‐butadiene‐styrene) (SBS) up to 5 wt % were conducted to thermooxidative ageing in oven at 140°C for 111 days. POM showed continued degradation as seen from the gradual decrease in the crystallization temperature from differential scanning calorimetry (DSC) study, while no change in Fourier transform infrared spectra (FTIR) and low weight loss were observed (2.5% after 111 days' ageing). The POM degradation was characterized by the initial increase of crystallinity due to crystal perfection, which then kept nearly unchanged until 35 days' ageing, and lastly increased again to result in embrittlement and decrease in tensile strength. Increase in the tensile stress and strain was observed up to 35 days' ageing. POM blends with SBS or EMA had similar degradation behavior as POM, but addition of SBS accelerated the POM degradation significantly, while POM blend with 1 or 3% EMA just showed slightly lower thermal stability than POM. Degradation in POM and SBS/POM occurred in amorphous phase while EMA/POM degraded in both amorphous and crystal phase. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effects of chlorpyrifos exposure on kidney Notch2–Jagged1 pathway of early prenatal embryo
Authors: Chen Wenqing , Jiang Hong , Wang Minmin , Jin Juan , Feng Shi , Bi Yan , Wang Huiping , Mao Youying , Shou Zhangfei , Chen Jianghua
Published: February 2011

Aims: To evaluate the effects of this insecticide on the embryonic development of kidney and to assess the important role of Notch2–Jagged1 pathway in this duration. Methods and results: Chlorpyrifos (CPF) 5 mg/kg/d were administrated on gestation 7.5–11.5 day by subcutaneous injection. On gestation 16.5 day, the normal embryo kidney developed through S shape duration to the original kidney, which had the nephrons and could start to secret the urine. But for the CPF‐treated mice, the embryo kidney developed much more slowly, they did not show the S shape and the nephrons. The Notch2–Jagged1 pathway should be expressed stronger in the normal embryo kidney on gestation 16.5 day, but for the CPF‐treated mice we found the obvious weak pathway staining. Conclusions: CPF broke the Notch2–Jagged1 pathway during the embryo kidney development, and the Notch2–Jagged1 pathway plays an important role in the S shape to original kidney formation duration. Birth Defects Res (Part B) 92:97–101, 2011. © 2011 Wiley‐Liss, Inc.
An improved LC‐MS/MS method for the determination of taspoglutide in plasma and urine using orthogonal HILIC–RP column switching, ultra‐performance LC separation and ‘wrong‐way‐round’ electrospray ionization
Authors: Heinig Katja , Wirz Thomas , Yuan Moucun , Tingler Michael , Mylott William
Published: February 2011

The synthetic peptide drug taspoglutide, developed for treatment of diabetes, must be quantified at low pg/mL levels in biological samples. This manuscript describes the improvement of a previous method, featuring orthogonal hydrophilic interaction to reversed‐phase chromatography column switching and tandem mass spectrometric detection. Signal‐to‐noise ratio was enhanced and isobaric interferences were reduced by ultra‐performance separation using a basic mobile phase in ‘wrong‐way‐round’ ionization mode and monitoring a selective fragment ion. Tedious solid‐phase extraction cleanup was abandoned in favor of simple protein precipitation. Urine required the addition of surfactants to prevent adsorptive drug loss. Dissociation of complexes with possibly formed anti‐drug antibodies was achieved with formic acid. Lower limits of quantitation (LLOQ) were 4 pg/mL in human plasma and 10 pg/mL in urine using a 250 μL sample, and an LLOQ of 50 pg/mL was obtained in animal plasma using 50 μL. Precision, accuracy and incurred samples reproducibility fulfilled regulatory requirements. Simultaneous determination of unlabeled and stable isotope labeled taspoglutide, interesting for clearance studies in which both compounds are co‐administered, was realized using a structural analog as internal standard. The described method offered excellent sensitivity with low sample consumption, reasonable throughput, moderate costs and high robustness for routine analysis. Copyright © 2011 John Wiley & Sons, Ltd.
Celecoxib determination in different layers of skin by a newly developed and validated HPLC‐UV method
Authors: Praça Fabíola Silva Garcia , Bentley Maria Vitória Lopes Badra , Lara Marilisa Guimarães , Pierre Maria Bernadete Riemma
Published: February 2011

A simple, rapid and sensitive analytical procedure for the measurement of celecoxib (CXB) levels in skin samples after in vitro penetration studies was developed and validated. In vitro permeability studies in porcine skin were performed for quantification of CXB at different layers of skin, the stratum corneum (SC) and epidermis plus dermis (EP + D) as well as in the acceptor solution (AS) to assess CXB permeation through skin. CXB was quantified by HPLC using a C18 column and UV detection at 251 nm. The mobile phase was methanol–water 72:28 (v/v) and the flow‐rate was 0.8 mL/min. The CXB retention time was 5 min. The assay was linear for CBX in the concentration range of 0.1–3.0 μg/mL in the AS (drug permeated through skin) and 5.0–50.0 μg/mL for drug retained in SC and [EP + D] in vitro. The linear correlation coefficients for the different calibration curves were equal or greater than 0.99. Intra‐ and inter‐assay variabilities were below 8.0%. Extraction of CXB from skin samples showed recoveries higher than 95.0% after 15 min of ultrasonic sound and centrifugation at 2500 rpm for 3 min. The method was considered appropriate for the assay of CXB in skin samples, after in vitro cutaneous penetration studies. Copyright © 2011 John Wiley & Sons, Ltd.
Effects of passivation and postannealing on the photoluminescence properties of MgO/SiO2 core‐shell nanorods
Authors: Jin Changhyun , Lee Jungkeun , Park Sunghoon , Lee Chongmu
Published: February 2011

MgO nanorods were grown by the thermal evaporation of Mg3N2 powders on the Si (100) substrate coated with a gold thin film. The MgO nanorods grown on the Si (100) substrate were a few tens of nanometers in diameter and up to a few hundreds of micrometers in length. MgO/SiO2 core‐shell nanorods were also fabricated by the sputter‐deposition of SiO2onto the MgO nanorods. Transmission electron microscopy (TEM) and X–ray diffraction (XRD) analysis results indicated that the cores and shells of the annealed core‐shell nanorods were a face‐centered cubic‐type single crystal MgO and amorphous SiO2, respectively. The photoluminescence (PL) spectroscopy analysis results showed that SiO2 coating slightly decreased the PL emission intensity of the MgO nanorods. The PL emission of the MgO/SiO2 core‐shell nanorods was, however, found to be considerably enhanced by thermal annealing and strongly depends on the annealing atmosphere. The PL emission of the MgO/SiO2 core‐shell nanorods was substantially enhanced in intensity by annealing in a reducing atmosphere, whereas it was slightly enhanced by annealing in an oxidative atmosphere. The origin of the PL enhancement by annealing in a reducing atmosphere is discussed with the aid of energy‐dispersive X‐ray spectroscopy analyses. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)