bluuebunny/crossref_metadata_2025 huggingface dataset:
MRI of the basement membrane using charged nanoparticles as contrast agents
Authors: Bennett Kevin M. , Zhou Hua , Sumner James P. , Dodd Stephen J. , Bouraoud Nadia , Doi Kent , Star Robert A. , Koretsky Alan P.
Published: August 2008

The integrity of the basement membrane is essential for tissue cellular growth and is often altered in disease. In this work a method for noninvasively detecting the structural integrity of the basement membrane, based on the delivery of cationic iron‐oxide nanoparticles, was developed. Cationic particles accumulate due to the highly negative charge of proteoglycans in the basement membrane. The kidney was used to test this technique because of its highly fenestrated endothelia and well‐established disease models to manipulate the basement membrane charge barrier. After systemic injection of cationic or native ferritin (CF or NF) in rats, ex vivo and in vivo MRI showed selective accumulation of CF, but not NF, causing a 60% reduction in signal intensity in cortex at the location of individual glomeruli. Immunofluorescence and electron microscopy demonstrated that this CF accumulation was localized to the glomerular basement membrane (GBM). In a model of GBM breakdown during focal and segmental glomerulosclerosis, MRI showed reduced single glomerular accumulation of CF, but a diffuse accumulation of CF in the kidney tubules caused by leakage of CF through the glomerulus. Cationic contrast agents can be used to target the basement membrane and detect the breakdown of the basement membrane in disease. Magn Reson Med 60:564–574, 2008. © 2008 Wiley‐Liss, Inc.
Fat‐water separated delayed hyperenhanced myocardial infarct imaging
Authors: Goldfarb James W.
Published: August 2008

Fat deposition associated with myocardial infarction (MI) has been reported as a commonly occurring phenomenon. Magnetic resonance imaging (MRI) has the ability to efficiently detect MI using T1‐sensitive contrast‐enhanced sequences and fat via its resonant frequency shift. In this work, the feasibility of fat‐water separation applied to the conventional delayed hyperenhanced (DHE) MI imaging technique is demonstrated. A three‐point Dixon acquisition and reconstruction was combined with an inversion recovery gradient‐echo pulse sequence. This allowed fat‐water separation along with T1 sensitive imaging after injection of a gadolinium contrast agent. The technique is demonstrated in phantom experiments and three subjects with chronic MI. Areas of infarction were well defined as conventional hyperenhancement in water images. In two cases, fatty deposition was detected in fat images and confirmed by precontrast opposed‐phase imaging. Magn Reson Med 60:503–509, 2008. © 2008 Wiley‐Liss, Inc.
Positive contrast visualization of nitinol devices using susceptibility gradient mapping
Authors: Vonken Evert‐jan P.A. , Schär Michael , Stuber Matthias
Published: August 2008

MRI visualization of devices is traditionally based on signal loss due toT2* effects originating from local susceptibility differences. To visualize nitinol devices with positive contrast, a recently introduced postprocessing method is adapted to map the induced susceptibility gradients. This method operates on regular gradient‐echo MR images and maps the shift ink‐space in a (small) neighborhood of every voxel by Fourier analysis followed by a center‐of‐mass calculation. The quantitative map of the local shifts generates the positive contrast image of the devices, while areas without susceptibility gradients render a background with noise only. The positive signal response of this method depends only on the choice of the voxel neighborhood size. The properties of the method are explained and the visualizations of a nitinol wire and two stents are shown for illustration. Magn Reson Med 60:588–594, 2008. © 2008 Wiley‐Liss, Inc.
In vivo 1H NMR measurement of glycine in rat brain at 9.4 T at short echo time
Authors: Gambarota Giulio , Xin Lijing , Perazzolo Chiara , Kohler Ingrid , Mlynárik Vladimír , Gruetter Rolf
Published: August 2008

Glycine is an amino acid present in mammalian brain, where it acts as an inhibitory and excitatory neurotransmitter. The two detectable protons of glycine give rise to a singlet at 3.55 ppm that overlaps with the more intense myo‐inositol resonances, and its measurement has traditionally required specific editing efforts. The aim of the current study was to reduce the signal intensity of myo‐inositol relative to that of glycine by exploiting the fast signal J‐evolution of the myo‐inositol spin system when using a single spin‐echo localization method we recently introduced. Glycine was detected at TE = 20 ms with an average Cramér‐Rao lower bound (CRLB) of 8.6% ± 1.5% in rat brain (N = 5), at 9.4 T. The concentration of glycine was determined using LCModel analysis at 1.1 ± 0.1 mM, in good agreement with biochemical measurements previously reported. We conclude that at high magnetic fields, glycine can be measured at a relatively short echo time (TE) without additional editing efforts. Magn Reson Med 60:727–731, 2008. © 2008 Wiley‐Liss, Inc.
Prospective self‐gating for simultaneous compensation of cardiac and respiratory motion
Authors: Buehrer Martin , Curcic Jelena , Boesiger Peter , Kozerke Sebastian
Published: August 2008

Segmented cardiac acquisitions generally require the use of an electrocardiogram (ECG) in combination with a breathhold or a respiratory navigator placed on the diaphragm. These techniques necessitate patient cooperation and increase the complexity of cardiac imaging. The ECG signal may be distorted inside the magnet by interferences from radiofrequency and gradient action. Breathhold acquisition limits the total scan time, while navigators on the diaphragm might not fully reflect respiratory‐induced motion of the heart. To overcome some of these problems, several self‐gating (SG) or “wireless” techniques have recently been presented. All of these approaches, however, are based on either cardiac triggering or respiratory gating, or the data are processed retrospectively, reducing the efficiency of data acquisition. In this work a prospective SG approach for free‐breathing imaging is presented that requires neither ECG gating nor respiratory navigation. The motion data used for cardiac triggering and respiratory gating are extracted from the repeatedly acquired k‐space center. Based on computer simulations and in vivo data of the heart, it is shown that cardiac as well as respiratory motion can be accurately extracted in real time. Using the method proposed, the scan efficiency could be significantly increased while preserving image quality relative to retrospective SG approaches. Magn Reson Med 60:683–690, 2008. © 2008 Wiley‐Liss, Inc.
Reproducibility study of whole‐brain 1H spectroscopic imaging with automated quantification
Authors: Gu Meng , Kim Dong‐Hyun , Mayer Dirk , Sullivan Edith V. , Pfefferbaum Adolf , Spielman Daniel M.
Published: August 2008

A reproducibility study of proton MR spectroscopic imaging (1H‐MRSI) of the human brain was conducted to evaluate the reliability of an automated 3D in vivo spectroscopic imaging acquisition and associated quantification algorithm. A PRESS‐based pulse sequence was implemented using dualband spectral‐spatial RF pulses designed to fully excite the singlet resonances of choline (Cho), creatine (Cre), and N‐acetyl aspartate (NAA) while simultaneously suppressing water and lipids; 1% of the water signal was left to be used as a reference signal for robust data processing, and additional lipid suppression was obtained using adiabatic inversion recovery. Spiral k‐space trajectories were used for fast spectral and spatial encoding yielding high‐quality spectra from 1 cc voxels throughout the brain with a 13‐min acquisition time. Data were acquired with an 8‐channel phased‐array coil and optimal signal‐to‐noise ratio (SNR) for the combined signals was achieved using a weighting based on the residual water signal. Automated quantification of the spectrum of each voxel was performed using LCModel. The complete study consisted of eight healthy adult subjects to assess intersubject variations and two subjects scanned six times each to assess intrasubject variations. The results demonstrate that reproducible whole‐brain 1H‐MRSI data can be robustly obtained with the proposed methods. Magn Reson Med 60:542–547, 2008. © 2008 Wiley‐Liss, Inc.
Multiple‐profile homogeneous image combination: Application to phase‐cycled SSFP and multicoil imaging
Authors: Çukur Tolga , Lustig Michael , Nishimura Dwight G.
Published: August 2008

Signal inhomogeneities in MRI often appear as multiplicative weightings due to various factors such as field‐inhomogeneity dependencies for steady‐state free precession (SSFP) imaging or receiver sensitivities for coil arrays. These signal inhomogeneities can be reduced by combining multiple data sets with different weights. A sum‐of‐squares combination is typically used due to its simplicity and near‐optimal signal‐to‐noise ratio (SNR). However, this combination may lead to residual signal inhomogeneity. Alternatively, an optimal linear combination of the data can be performed if the weightings for individual data sets are estimated accurately. We propose a nonlinear combination to improve image‐based estimates of the individual weightings. The signal homogeneity can be significantly increased without compromising SNR. The improved performance of the method is demonstrated for SSFP banding artifact reduction and multicoil (phased‐array and parallel) image reconstructions. Magn Reson Med 60:732–738, 2008. © 2008 Wiley‐Liss, Inc.
Domain decomposition of stochastic PDEs: Theoretical formulations
Authors: Sarkar Abhijit , Benabbou Nabil , Ghanem Roger
Published: August 2008

We present a novel theoretical framework for the domain decomposition of uncertain systems defined by stochastic partial differential equations. The methodology involves a domain decomposition method in the geometric space and a functional decomposition in the probabilistic space. The probabilistic decomposition is based on a version of stochastic finite elements based on orthogonal decompositions and projections of stochastic processes. The spatial decomposition is achieved through a Schur‐complement‐based domain decomposition. The methodology aims to exploit the full potential of high‐performance computing platforms by reducing discretization errors with high‐resolution numerical model in conjunction to giving due regards to uncertainty in the system. The mathematical formulation is numerically validated with an example of waves in random media. Copyright © 2008 John Wiley & Sons, Ltd.
Medizinische Chemie und molekulare Hemmmechanismen der Tyrosinkinase‐Inhibitoren. Schwerpunkt pharmazeutischer Forschung
Authors: Holm Melanie , Lehmann Frank , Laufer Stefan
Published: August 2008

Die meisten Prozesse einer Zelle werden durch Proteinphosphorylierungen reguliert, wohingegen anormale Phosphorylierung ein Grund für oder eine Konsequenz von Krankheiten ist. Ein stetig steigendes Interesse an der Entwicklung von oral applizierbaren, aktiven Proteinkinase‐Hemmstoffen hat mittlerweile zur Zulassung der ersten Wirkstoffe geführt. Proteinkinasen sind inzwischen die zweitwichtigste Gruppe der Wirkstoff‐Targets nach den G‐Protein‐gekoppelten Rezeptoren. Nach Schätzungen zielen heutzutage 30 bis 35 % aller präklinischen Wirkstofffindungsprogramme auf Proteinkinasen ab.
Compressive strength of gamma‐irradiated polymer concrete
Authors: Martínez‐Barrera Gonzalo , Villarruel Uriel Texcalpa , Vigueras‐Santiago Enrique , Hernández‐López Susana , Brostow Witold
Published: August 2008

Polymer concrete (PC) was developed by using different concentrations of silica sand as aggregate and a commercial unsaturated preaccelerated (orthophtalic) polyester resin. The PC specimens were submitted to gamma radiation at several dosages: 5, 10, 50, 100, and 150 kGy. Mechanical performance was evaluated including the compressive strength, the compressive strain at yield point, and the compression modulus of elasticity. As expected, mechanical properties depend on both the resin concentration and the applied radiation dose. Improvement achieved in mechanical properties is related to the morphological characteristics observed by scanning electron microscopy. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Influence of erodent particle types on solid particle erosion of polyphenylene sulphide composite under low particle speed
Authors: Sari Nejat Y.
Published: August 2008

The influence of erodent particle types on solid particle erosion of randomly oriented short glass fiber and mineral particle reinforced polyphenylene sulphide (PPS) was investigated. The solid particle erosion studies were carried out using low speed solid particle erosion test rig with 150 to 212‐μm brown fused aluminum oxide (Al2O3), 150 to 200‐μm silica sand and 150 to 250‐μm glass bead. Glass bead eroding particles appear spherical in shape whereas aluminum oxide and silica sand eroding particles have sharp and angular edges. The erosion tests were conducted at six different contact angles of 15, 30, 45, 60, 75, and 90°, respectively. The results showed a strong dependence of the eroding particle types on the erosive wear behavior of PPS composite. The peak erosion rate occurred at 45° contact angle for silica sand eroding particles while the peak erosion rate occurred at 30° contact angle for aluminum oxide and glass bead particles. The morphologies of eroded surfaces were characterized by the scanning electron microscopy. In case of aluminum oxide and silica sand, the erosive wear mechanism occurs firstly by the erosion of matrix, followed by the fracture of un‐supported fibers and their detachment; however, the erosive wear mechanism occurs different for glass bead particles. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Simultaneous determination of 76As, 122Sb and 153Sm in Chinese medicinal herbs by epithermal neutron activation analysis
Authors: Chen Chien‐Yi
Published: August 2008

Optimal conditions for the simultaneous determination of As, Sb and Sm in Chinese medicinal herbs using epithermal neutron activation analysis were investigated. The minimum detectable concentrations of 76As, 122Sb and 153Sm in lichen and medicinal herbs depended on the weight of the irradiated sample, and irradiation and decay durations. Optimal conditions were obtained by wrapping the irradiated target with 3.2 mm borated polyethylene neutron filters, which were adopted to screen the original reactor fission neutrons and to reduce the background activities of 38Cl, 24Na and 42K. Twelve medicinal herbs, commonly consumed by Taiwanese children as a diuretic treatment, were analysed since trace elements, such as As and Sb, in these herbs may be toxic when consumed in sufficiently large quantities over a long period. Various amounts of medicinal herbs, standardised powder, lichen and tomato leaves were weighed, packed into polyethylene bags, irradiated and counted under different conditions. The results indicated that about 350 mg of lichen irradiated for 24 h and counted for 20 min following a 30–60 h decay period was optimal for irradiation in a 1011 n/cm s epithermal neutron flux. The implications of the content of the studied elements in Chinese medicinal herbs are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Polyester containing isocyanate groups—Modified epoxy resin: Rheological, dynamic‐mechanical, and impact properties
Authors: Soares Bluma G. , Gonçalez Viviane , Galimberti Rurik , Barcia Fabio L. , Sirqueira Alex S.
Published: August 2008

Low molar mass hydroxyl‐terminated polyester was functionalized with isocyanate groups (NCO) and used to improve the impact resistance of epoxy resin (ER) cured with triethylene tetramine (TETA). The effect of polyester‐based modifiers (with or without NCO groups) on the curing rate of epoxy/TETA system was investigated by rheological techniques. It was found that the functionalized polyester decreased the gel time, indicating an accelerating effect of the curing process. In addition, significant improvement in impact resistance of the epoxy network was achieved, with low detrimental effect on the glass transition temperature and stiffness. The modified epoxy systems did not present phase‐separated morphology discernible by scanning electron microscopy, even after the curing process. The glass transition temperature of the epoxy networks was also investigated by dynamic‐mechanical analysis. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Electrodes modified with polyaminophenols: Immobilization of purines and pyrimidines
Authors: Franco Diego L. , Afonso André S. , Ferreira Lucas F. , Gonçalves Rafael A. , Boodts Julien F.C. , Brito‐Madurro Ana G. , Madurro João M.
Published: August 2008

This work describes the preparation of polymers potentiodynamically formed on surface of graphite electrode by anodic oxidation of 2, 3, or 4‐aminophenol monomers, as well as incorporation and detection of purine and pyrimidine bases on these modified electrodes. The electrochemical behavior of the formed films was studied by cyclic voltammetry and electrochemical impedance spectroscopy. These analyses indicate that poly‐4‐aminophenol presents the highest charge transfer rate. The surface morphology was studied by SEM and AFM. These analyses showed that the polymers present globular morphology. The immobilization and detection of purines and pyrimidines on graphite electrodes modified with poly‐aminophenols was studied by differential pulse voltammetry. It was possible to show, for the first time, that the oxidation of purine and pyrimidine bases and their mixtures takes place on modified electrodes covered with polymeric films. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
New polyaniline/polycardanol conductive blends characterized by FTIR, NIR, and XPS
Authors: Souza Fernando Gomes , Pinto José C. , Rodrigues Marcus V. , Anzai Thiago K. , Richa Priscila , Melo Príamo A. , Nele Márcio , Oliveira Geiza E. , Soares Bluma Guenther
Published: August 2008

Electrically conducting composites based on polyaniline‐H2SO4/polycardanol were prepared with a mechanical mixing method. The influence of the composition on the electrical performance of the composites was evaluated. Materials were characterized by Fourier Transform Infrared Analysis and Near Infrared Analysis. X‐Ray Photoelectron Spectroscopy analyses were used to explain the different electrical behavior of these composites. The bioconductive materials showed low percolation thresholds and low electrical resistances, allowing for use as pressure sensing materials. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Thermogravimetric and spectrometric characterizations of poly(styrene‐co‐divinylbenzene) containing phosphinic and phosphonic acid groups
Authors: de Santa Maria Luiz Claudio , Souza Marcelo A.V. , Santos Fábio R. , Rubenich Lorna M.S. , Ferreira Maria D.J.F. , Sá Rita M.P.
Published: August 2008

Derivatized poly(styrene‐co‐divinylbenzene) resins have been prepared from the commercial crosslinked polystyrene by the aromatic electrophilic substitution reaction using PCl3/AlCl3 or PCl5/AlCl3, followed by base‐promoted hydrolysis. The unmodified copolymer and their phosphored derivatives have been characterized by thermogravimetric (TG) analysis to evaluate their thermal stability in nitrogen atmosphere. The influence of phosphorylation and phosphonation of crosslinked copolymer on its thermal behavior was evaluated. The TG and DTG curves of modified copolymers have clearly shown two thermal degradation stages. The modified copolymers have presented higher thermal stability than unmodified one, showing that the introduction of phosphinic or phosphonic acid groups modifies their kinetic pathways. The decomposition temperatures and thermal stability were dependent on the phosphorous amount incorporated on the commercial resin. The modified copolymers were also evaluated by spectrometric method (FTIR, using KBr pellet). The phosphorous content of the modified copolymers was determined by colorimetric method based on sodium molybdate reagent (determination at 830 nm). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Interphase phenomena in nanoparticulate filled polyurethane/poly(vinyl acetate) polymer systems
Authors: Vrsaljko Domagoj , Leskovac Mirela , Blagojević Sanja Lučić , Kovačević Vera
Published: August 2008

Polyurethane (PU) and poly(vinyl acetate) (PVAc) are partially miscible polymers. The aim of this study was to investigate the influence of untreated and surface pretreated calcium carbonate (CaCO3) on the interphase properties of PU/PVAc polymer blends with possible compatibilization effects when the conditions of effective adhesion are achieved. With the aim to modify interface between filler and matrices, CaCO3 was pretreated by grafting PVAc on the filler surface using 60Co γ‐ray irradiation polymerization of vinyl acetate. A series of the PU/PVAc blends without and with the addition of CaCO3 were prepared using a Brabender plasticorder at 140°C. Surface characterization of the PU and PVAc polymers as well as the untreated and surface pretreated CaCO3 fillers was carried out by determination of the surface free energy. The adhesion between CaCO3 and phases in the polymer blends was predicted on the basis of the calculated adhesion parameters (interfacial free energy, spreading coefficient and work of adhesion) obtained from the surface free energy of components. Thermal and mechanical properties were investigated by tensile strength measurements and differential scanning calorimetry (DSC). The adhesion parameters were correlated with the mechanical and thermal properties as well as phase morphology observations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Surface studies of corona treated polydimethylsiloxane‐block‐polystyrene hybrid copolymer films
Authors: Bayley G.M. , Mallon P.E.
Published: August 2008

Linear hybrid block copolymers of polydimethylsiloxane (PDMS) and polystyrene (PS) were synthesized using living sequential anionic polymerization. Sample films of these block copolymers were thermally annealed for 48 hr at 120°C to promote phase segregation and allow for the preferential surface segregation of PDMS. The films were then exposed to corona discharge for 30 min. Optical microscopy and scanning electron microscopy (SEM) were used to identify surface cracks due to the formation of a silica‐like glassy layer after corona exposure. Slow positron beam studies were used to evaluate the degradation phenomenon and provide the first evidence of silica‐like degradation layers forming on the surface of PDMS containing hybrid polymer films, after corona exposure. It also allowed determination of the thickness of the glassy layer. Contact angle measurements also showed the first evidence that the same hydrophobic loss and recovery phenomenon for the corona treated hybrid polymer films occurs, as with pure PDMS samples. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Settling rates for flocculation of iron and manganese ore‐containing suspensions by cationic glycogen
Authors: Brostow Witold , Hagg Lobland Haley E. , Pal Sagar , Singh Ram P.
Published: August 2008

Novel flocculants have been synthesized on the basis of glycogen. The efficiency of cationic glycogen can be explained in terms of Singh's qualitative easy approachability model (EAM). The jar test was used previously to evaluate flocculation efficacy, but we have recently shown that a plot of interface height vs. settling times provides a better measure. In accord with the EAM, a one‐to‐one correspondence between settling velocity and radius of gyration of flocculants in various solutions has been demonstrated, providing quantitative proof of the EAM. Now the flocculation efficacy of cationic glycogen is evaluated by determination of settling times in both iron and manganese ore suspensions and compared with the performance of other polymer flocculants. Its superior flocculation efficacy over commercial flocculants and other flocculants synthesized by us is demonstrated. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Melt processing and filler/matrix interphase in carbon nanotube reinforced poly(ether‐ester) thermoplastic elastomer
Authors: Broza Georg , Schulte Karl
Published: August 2008

Multiblock poly(ether‐ester) thermoplastic elastomers (PBT/PTMO) are based on semicrystalline poly(butylene terephthalate) (PBT) and amorphous oxytetramethylene (PTMO) blocks. The copolymer was compounded with a filler content up to 10 wt% multi wall carbon nanotubes (MWCNTs) via a masterbatch process, which included milling, high shear mixing in the melt, and extrusion using a twin‐srew extruder. From the compound several compositions of PBT/PTMO with 0.1–2.0 wt% of MWCNTs were prepared. Differential scanning calorimeter analysis showed that the fillers enhance initiation of recrystallisation, i.e. accelerate the nucleation of crystalline segments of PBT/PTMO. The morphology of the obtained nano‐composites shows that MWCNTs are well dispersed in the matrix. Only some discrete nanotubes, apparently protruding from the matrix, could be distinguished on the fracture surface, still covered with a thin interphase matrix layer of PBT/PTMO. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Adsorption of polymers used in drilling fluids on the inner surfaces of carbon steel pipes
Authors: Spinelli Luciana S. , Aquino Aline S. , Lucas Elizabete , d'Almeida Arnaldo R. , Leal Rafael , Martins André L.
Published: August 2008

Polymers in drilling fluids tend to adhere to the inside surfaces of metal pipes, improving the lubricity characteristics of the fluid. The present study evaluated the adsorption of polymers from their aqueous solutions on metal surfaces by means of visual observation and contact angle measurements. The polymers tested were xanthan gum, starch, and partially hydrolyzed polyacrylamide (PHPA). The contact angle measurements were carried out to enable calculating the adhesion and adsorption energy. The visual observation, although not furnishing quantitative data, agreed with the results of the contact angle measurements. The results show that the tendency of these polymers to be adsorbed on metal surfaces varies as follows: starch > PHPA > xanthan gum. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Characterization of grooves in scratch resistance testing
Authors: Brostow Witold , Chonkaew Wunpen , Mirshams Reza , Srivastava Ashish
Published: August 2008

For a number of polymers with different chemical structures and different properties we have determined scratch resistance and sliding wear (15 scratches along the same groove). We have measured cross section areas after scratching, namely the groove and side top‐ridge areas. Nanohardness after scratching was determined using nanoindentation testing both inside and outside the scratching and sliding wear grooves. Three modes of sliding wear are seen: plowing, cutting with debris formation, and densification. The dominating mode depends on the material and is reflected in nanohardness. In polycarbonate (PC) the nanohardness inside and outside the groove are practically the same; the indenter just plows the material aside without debris formation or densification. Thus, the old measure of wear as the weight of the debris formed is not usable for PC; grooves are present but there is no loosened material. By contrast, in brittle materials such as polystyrene there is debris formation and nanohardness inside the groove decreases after 15 scratching runs. A third type of behavior is seen in polyethylene and polypropylene, namely densification caused by scratching; as a result, nanohardness inside the groove increases after 15 passes of the indenter. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Microhybrids of metal powder incorporated in polymeric matrices: Friction, mechanical behavior, and microstructure
Authors: Brostow Witold , Buchman Alisa , Buchman Eli , Olea‐Mejia Oscar
Published: August 2008

The polymers used as a matrix were low density polyethylene (LDPE) and a thermoplastic elastomer (TPE). The metal particles were Al, Ag, and Ni with micrometer diameters. The metal concentration varied from 0 to 10 wt%. Dynamic and static frictions on tetrafluoropolyethylene and stainless steel as sliding surfaces were determined and tensile tests were performed. Secondary electron and backscattered electron SEM images were taken to determine microstructures of the hybrids. Addition of metal powder to the matrix results in reduction to a minimum of the tensile elastic modulus for low metal concentrations, and increase in the modulus with further addition of metal particles. For the TPE, the tensile modulus exceeds that of the pure material. Small metal particles increase the modulus at lower concentrations than larger ones. Hardness varies with the filler concentration, similarly as tensile modulus does. Backscattered electron SEM images show uniform dispersion of the metal particles at the surfaces and in the bulk. The contrast is enhanced by large differences in atomic numbers between the fillers and the matrices. Ni microparticles in LDPE cause crack arrest seen in SEM. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of the filler characteristics on the miscibility of styrene‐butadiene rubber and nitrile‐butadiene rubber blends
Authors: Pérez León D. , Sierra Ligia , López Betty L.
Published: August 2008

Styrene‐butadiene rubber (SBR) and nitrile‐butadiene rubber (NBR) blends are immiscible. Fillers can be used as compatibilizers. The SBR + NBR blends reinforced with a mesoporous silica and a precipitated silica are characterized by studying their miscibility by the determination of rubber bound, their changes in heat capacity at each glass transition temperature, and their mechanical performance. NBR is preferentially located at the silica surface improving its dispersion. Larger rubber + filler as well as SBR + NBR interphases are obtained for the blends reinforced with the mesoporous silica, whose high surface area and organized porous structure allow a better polymer + filler interaction. The reinforced blends present higher strength at break than each reinforced polymer alone. The best performance is attained for blends reinforced with mesoporous silica. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Environmental stress cracking behavior of bottle and fiber grade poly(ethylene terephthalate) in contact with aqueous amine solutions
Authors: Sanches Nadir de B. , Dias Marcos L. , Pacheco Elen B.A.V.
Published: August 2008

The environmental stress cracking (ESC) resistance of commercial virgin bottle and fiber grade poly(ethylene terephthalate) (PET) in contact with aqueous amine solutions was investigated. The ESC resistance, in terms of time to failure, was evaluated taking into account some factors, such as test temperature, molar volume (Vo) of the ESC agent, and molecular weight and degree of crystallinity (Xc) of PET. The specimens were tested in flexural mode using a constant load flexural creep test apparatus and also in tensile mode using a dynamometer. After the creep tests, the specimens were photographed with a digital camera and analyzed by scanning electron microscopy (SEM). It was found that ESC resistance was higher with the increase of ESC agent molar volume as well as with the increase of molecular weight and degree of crystallinity of PET. The highest temperature (60°C) lowered the ESC resistance of the specimens, except for the crystalline specimens in n‐butylamine that exhibited a higher ESC resistance at 60°C, which can probably be attributed to the induced crystallization of the remaining amorphous phase by the plasticizing effect of n‐butylamine. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Thermal and low‐field NMR study on poly(vinylidene fluoride) and their physical mixtures with poly(methyl methacrylate)
Authors: Freire Estevão , Bianchi Otavio , Forte Maria Madalena C. , Preto Mônica , Monteiro Elisabeth E.C. , Tavares Maria Inês B.
Published: August 2008

Blends with various proportions of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) were prepared using melt mixing and studied by oscillatory mechanical measurements and low‐field NMR spectroscopy to evaluate the influence of the processing method. The polymers and its blends were processed using a conventional low shear mixing chamber (LSM) and a high shear mixer (HSM). The behavior of all blends lies among those of the pure components, considering the two methods of characterization, and the data suggest phase separation between the two components. The hydrogen spin‐lattice relaxation time of the PVDF/PMMA blends were measured and correlated with the components phases. The results are a contribution to data reported previously in the literature using different analytical methods. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Evaluation of microarray surfaces and arraying parameters for autoantibody profiling
Authors: Balboni Imelda , Limb Cindy , Tenenbaum Jessica D. , Utz Paul J.
Published: August 2008

Autoantigen microarrays are being used increasingly to study autoimmunity. Significant variation has been observed when comparing microarray surfaces, printing methods, and probing conditions. In the present study, 24 surfaces and several arraying parameters were analyzed using >500 feature autoantigen microarrays printed with quill pins. A small subset of slides, including FAST®, PATH®, and SuperEpoxy2, performed well while maintaining the sensitivity and specificity of autoantigen microarrays previously demonstrated by our laboratory. By optimizing the major variables in our autoantigen microarray platform, subtle differences in serum samples can be identified that will shed light on disease pathogenesis.
Effect of endgroup modification on dynamic viscoelastic relaxation and motion of hyperbranched poly(ether ketone)s
Authors: Choi Jeongsoo , Chung Jae Woo , Jang Seung‐Hyun , Kwak Seung‐Yeop
Published: August 2008

Fluoro‐terminated hyperbranched poly(ether ketone) (FHPEK) was synthesized and its end groups were modified with alkyl compounds of different chain lengths, i.e., hexyloxy (C6), dodecyloxy (C12), and octadecyloxy, (C18), to produce alkyl‐modified HPEKs (HPEK‐C6, HPEK‐C12, and HPEK‐C18, respectively). Master curves were constructed by using the time‐temperature superposition principle. The horizontal shift factors, aT, used for the construction of the master curves were fit using the William‐Landel‐Ferry (WLF) equation. From the fitting parameters, the apparent activation energy, Ea, was estimated. With increasing alkyl chain length, the Ea values were found to decrease in the order FHPEK > HPEK‐C6 > HPEK‐C12, and then increase for HPEK‐C18. The average relaxation time, τHN, was determined by fitting of the dynamic moduli G′(ω) and G″(ω) to the empirical Havriliak‐Negami equation. Similarly, the τHN values decreased in the order of FHPEK > HPEK‐C6 > HPEK‐C12, and then increased for HPEK‐C18. This indicates that the endgroup modification with short alkyl chains (C6, C12) increased the molecular mobility due to the internal plasticization effect of these alkyl chains. Modification with the longer alkyl chain (C18) retarded the molecular motion through an antiplasticization effect caused by summation of nonpolar hydrophobic interactions between long hydrocarbon chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2079–2089, 2008
Association of genetic polymorphisms at 8q24 with the risk of prostate cancer in a Japanese population
Authors: Terada Naoki , Tsuchiya Norihiko , Ma Zhiyong , Shimizu Yosuke , Kobayashi Takashi , Nakamura Eijiro , Kamoto Toshiyuki , Habuchi Tomonori , Ogawa Osamu
Published: August 2008

BACKGROUND

Genetic factors, as well as a combination of environmental factors, contribute to the risk of prostate cancer (PC). Recently, genome‐wide linkage studies found several independent single nucleotide polymorphisms (SNPs) that are strongly associated with PC on chromosome 8q24.

METHODS

We analyzed two of these SNPs, rs1447295 and rs6983267, to examine association with the risk of PC in Japanese men. These SNPs were examined by a mismatch PCR‐RFLP method in 507 PC patients (286 aggressive and 221 non‐aggressive) and in 511 non‐PC patients (124 benign prostatic hyperplasia and 387 normal male controls) and the allele frequencies were then compared between groups.

RESULTS

The rs1447295 A allele was associated with susceptibility to PC (PC vs. non‐PC: P = 0.041; OR, 1.28; 95%CI = 1.01–1.61), and was more significantly associated with disease in aggressive PC (aggressive PC vs. normal controls, P = 0.013; OR, 1.43; 95%CI = 1.08–1.90). The rs6983267 G allele did not show significant association with susceptibility to PC (PC vs. non‐PC: P = 0.967; OR, 1.00; 95%CI = 0.83–1.21). However, it was associated with disease in non‐aggressive PC (non‐aggressive PC vs. normal controls: P = 0.0068; OR, 1.43; 95%CI = 1.10–1.85).

CONCLUSIONS

The two SNPs at 8q24 were associated with an increased risk of prostate cancer and contributed to tumor aggression in Japanese men. Prostate 68: 1689–1695, 2008. © 2008 Wiley‐Liss, Inc.
Imaging the effects of castration on bone turnover and hormone‐independent prostate cancer colonization of bone
Authors: Cross N.A. , Fowles A. , Reeves K. , Jokonya N. , Linton K. , Holen I. , Hamdy F.C. , Eaton C.L.
Published: August 2008

INTRODUCTION

Tumor populations may selectively colonize bone that is being actively remodeled. In prostate cancer patients, androgen deprivation directly inhibits tumor growth initially, whilst induced bone loss may facilitate tumor colonization of bone by androgen‐insensitive cells. We have tested this hypothesis using a xenograft model of early growth of prostate cancer in bone.

METHODS

PC3 cells transfected with Green fluorescent protein (GFP) were injected into castrated and non‐castrated athymic mice via intrabial and intracardiac routes. In vivo tumor growth was monitored daily and animals sacrificed 6–9 days following initial GFP‐based detection of tumors. Tumor bearing and contra‐lateral non‐tumor bearing tibias were analyzed extensively by micro‐CT and histology/immunohistochemistry for the presence of tumor cells and the effects of tumor and/or castration on bone cells and bone structure evaluated.

RESULTS

GFP‐positive tumors in bone were visible from 12 days post‐injection following intratibial injection, allowing tumors <1 mm diameter to be monitored in live animals. Castration did not affect tumor frequency, tumor volume, or time to initial appearance of tumors injected via intratibial or intracardiac routes. Castration decreased trabecular bone volume in all mice. Significant tumor‐induced suppression of numbers of osteoblasts, coupled with increased numbers of activated osteoclasts, was evident in both intact animals and castrated animals.

CONCLUSIONS

In vivo GFP imaging allows the detection of early tumor growth at intra‐osseous sites. Castration induces bone loss, but PC3‐GFP cells are also capable of inducing bone remodeling in intact animals at early time points, independently of pre‐existing castration‐induced alterations to bone. Prostate 68: 1707–1714, 2008. © 2008 Wiley‐Liss, Inc.
Induction of FLIP expression by androgens protects prostate cancer cells from TRAIL‐mediated apoptosis
Authors: Raclaw Kristin A. , Heemers Hannelore V. , Kidd Emily M. , Dehm Scott M. , Tindall Donald J.
Published: August 2008

BACKGROUND

Prostate tumors initially regress in response to androgen‐ablation therapy. However, most cancers eventually relapse with an androgen‐depletion‐independent (ADI) phenotype that is often more aggressive than the original androgen‐dependent (AD) tumor. Importantly, most relapsed tumors still rely upon androgen receptor (AR) activity for proliferation and survival. The cellular Fas/FasL‐associated death domain protein‐like inhibitory protein (FLIP) inhibits activation of procaspase‐8 by death receptor‐mediated signaling at the cell surface. In the current study, we examined the androgenic regulation of FLIP and its contribution to protecting prostate cancer cells from death receptor‐mediated apoptosis.

METHODS

FLIP expression in tissues from intact and castrated rats as well as androgen‐treated prostate cancer cell lines (LNCaP, C4‐2, LNCaP‐Rf, and DU‐145) was monitored via Real‐Time RT‐PCR and immunoblot. Induction of apoptosis by TRAIL, the death receptor ligand, was determined via microscopic observation and cell counting of fragmented nuclei following fixation and staining with Hoechst 33285.

RESULTS

FLIP mRNA and protein expression was reduced following castration in multiple rat tissues, including dorsolateral prostate and seminal vesicles. Androgenic induction of FLIP mRNA and protein was observed in isogenic AD LNCaP and ADI LNCaP‐Rf cells, but not the isogenic ADI C4‐2 cell line. Protection from TRAIL‐induced apoptosis by androgen was completely blocked when LNCaP‐Rf cells were depleted of endogenous FLIP via siRNA transfection.

CONCLUSIONS

Androgenic protection from TRAIL‐induced apoptosis is predominantly via enhanced transcription of FLIP in prostate cancer cells. Loss of androgen‐sensitivity in ADI prostate cancer cells highlights this pathway as a potential target for future therapy of prostate cancer. Prostate 68: 1696–1706, 2008. © 2008 Wiley‐Liss, Inc.
The dietary bioflavonoid, quercetin, selectively induces apoptosis of prostate cancer cells by down‐regulating the expression of heat shock protein 90
Authors: Aalinkeel Ravikumar , Bindukumar B. , Reynolds Jessica L. , Sykes Donald E. , Mahajan Supriya D. , Chadha Kailash C. , Schwartz Stanley A.
Published: August 2008

BACKGROUND

Human and animal studies have suggested that diet‐derived flavonoids, in particular quercetin may play a beneficial role by preventing or inhibiting oncogenesis, but the underlying mechanism remains unclear. The aim of this study is to evaluate the effect(s) of quercetin on normal and malignant prostate cells and to identify the target(s) of quercetin's action.

METHODOLOGY

We addressed this question using cells in culture and investigated whether quercetin affects key biological processes responsible for tumor cell properties such as cell proliferation and apoptosis and also studied the effect of quercetin on the proteome of prostate cancer cells using difference gel electrophoresis (DIGE) to assess changes in the expression of relevant proteins.

RESULTS

Our findings demonstrate that quercetin treatment of prostate cancer cells results in decreased cell proliferation and viability. Furthermore, we demonstrate that quercetin promotes cancer cell apoptosis by down‐regulating the levels of heat shock protein (Hsp) 90. Depletion of Hsp90 by quercetin results in decreased cell viability, levels of surrogate markers of Hsp90 inhibition (intracellular and secreted), induced apoptosis and activation of caspases in cancer cells but not in normal prostate epithelial cells. Knockdown of Hsp90 by short interfering RNA also resulted in induction apoptosis similar to quercetin in cancer cells as indicated by annexin V staining.

CONCLUSION

Our results demonstrate that quercetin down‐regulates the expression of Hsp90 which, in turn, induces inhibition of growth and cell death in prostate cancer cells while exerting no quantifiable effect on normal prostate epithelial cells. Prostate © 2008 Wiley‐Liss, Inc.
Single‐beam pumped coherent anti‐Stokes Raman scattering on carbon nanotubes
Authors: Lefrant Serge , Buisson Jean‐Pierre , Mevellec Jean‐Yves , Baltog Ioan , Baibarac Mihaela
Published: August 2008

Giant optical fields locally generated in nanoscale metal structures through the local excitation of surface plasmons underlie a variety of nonlinear optical processes. Using silver and gold rough metallic films, reproducible enhancements of the Raman signal on various materials including carbon nanotubes have been demonstrated. In addition, an abnormal anti‐Stokes Raman emission, reminiscent of Coherent anti‐Stokes Raman Scattering (CARS), is accurately observed on nanometric thin films. We demonstrate that under a tight focusing of the excitation light, a CARS‐type emission, resulting from a wave mixing process between the incident laser light and Stokes Raman light generated by a SERS mechanism, is produced. The results which corroborate the CARS emission are the following: a square relation between the CARS signal intensity and the film thickness; a square relationship between the CARS signal intensity and the exciting laser intensity; a dependence of the CARS intensity on the numerical aperture (NA) of the microscope objective used for the detection of the anti‐Stokes signal; a polarization ratio in the anti‐Stokes side always greater in comparison with that measured for an usual Stokes Raman signal. We demonstrate also that this mechanism may contribute to a clear identification of the state of the observed nanotubes, i.e. in isolated or bundled forms, even when tubes are in powders. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory of ultrafast intraband relaxation in carbon nanotubes
Authors: Hirtschulz Matthias , Milde Frank , Malic Ermin , Thomsen Christian , Reich Stephanie , Knorr Andreas
Published: August 2008

Ultrafast intraband carrier relaxation in carbon nanotubes can be described by Carbon Nanotube Bloch Equations (CNBE) treating the Coulomb interaction beyond the Hartree‐Fock level to include carrier‐carrier scattering. We obtain equations of motion for carrier densities and two‐particle carrier correlations that are solved numerically. The complex non‐Markovian relaxation dynamics of hot electrons is calculated for various carbon nanotubes of different diameter and chirality. All calculated nanotubes show an ultrafast relaxation to equilibrium within approximately 100 femtoseconds. The observed relaxation is only weakly dependent on chirality, but depends on the diameter of the nanotube. With increasing diameter of the CNT the relaxation is slowed down, because of the weaker Coulomb interaction in larger diameter CNT. Additionally, we find oscillations of the electron plasma that are due to memory effects in the electron equilibration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local measurement of charge density in carbon nanotubes by Raman spectroscopy
Authors: Freitag Marcus , Tsang James , Avouris Phaedon
Published: August 2008

The energies of the Raman G‐band transitions in both metallic and semiconducting CNTs are renormalized by the electron‐phonon interaction, leading to energy shifts in Raman spectra of gated CNT devices. In addition in metallic CNTs, the linewidth decreases sharply upon electrostatic doping because the Γ‐point phonon can no longer decay into electron‐hole pairs when the Fermi level is removed by more than 1/2 the phonon energy from the K‐point. Raman spectroscopy can therefore be used to locally measure charge density and capacitance of individual CNTs in a nanotube field‐effect transistor. Experiments under bias reveal breaks in nanotubes and depleted nanotube segments close to the contacts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ge‐doping dependence of gamma‐ray induced germanium lone pair centers in Ge‐doped silica
Authors: Alessi Antonino , Agnello Simonpietro , Gelardi Franco Mario , Boscaino Roberto
Published: August 2008

We report an experimental study on the γ irradiation effects in Ge‐doped sol‐gel silica samples doped with Ge from 102 up to 104 part per million molar. The samples were exposed to the radiation generated by a 60Co source up to an accumulated dose value of 10 MGy. Our data evidence that the γ irradiation significantly increases the number of Germanium Lone Pair Centers (GLPC). Such defects are induced with a concentration that depends on the Ge content of the employed material in those samples where no optical activity related to GLPC was detected before irradiation. Furthermore an increase of the GLPC concentration was detected also in a sample that already contains this defect after the production. These findings show that, in addition to the GLPC bleaching effect already reported in the literature, γ rays can generate such defects and a range of doses exists in which the generation processes overcome the bleaching processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)