bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoreinforcement of flexible epoxy using layered silicate
Authors: Ratna D. , Chakraborty B. C. , Dutta H. , Banthia A. K. 
Published: November 2006

AbstractFlexible epoxy matrices, having a good vibration damping capability, were nanoreinforced using an organoclay. The nanocomposites were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The effect of matrix flexibility on the reinforcing effect was investigated. It was found that the reinforcing effect increased with an increase in flexibility of the matrix. The reinforcement is achieved without any sacrifice in flexibility and Tg. In addition, a reduction in solvent diffusion and flammability has been demonstrated. DMA study indicates that the height of the loss peak, decreases with incorporation of the clay because of the intercalation. Nevertheless, the nanocomposite samples having up to 10 wt% of the clay show a high damping capability as evident from the tan δmax values. POLYM. ENG. SCI., 46:1667–1673, 2006. © 2006 Society of Plastics Engineers
Natural rubber–polyurethane block copolymers: Nonlinear structural variations with NCO/OH ratio
Authors: Gopakumar S. , Nair M.R. Gopinathan 
Published: November 2006

AbstractA series of segmented block copolymers was prepared by the chain extension of hydroxyl terminated liquid natural rubber (HTNR) with polyurethane oligomers derived from toluene diisocyanate (TDI) and 1,3‐butane diol at varying NCO/OH ratio. The previously reported two‐step method of synthesis was modified to get improved products. This was done by optimizing the formation of polyurethane oligomers in the first step of the synthesis. All the samples were characterized by solubility testing, DSC, tensile testing, etching studies, and SEM. The data obtained were correlated to the structural features of the block copolymers. It was found that NCO/OH ratio played an important role in determining the structural variations in the block copolymers. POLYM. ENG. SCI. 46:1812–1821, 2006. © 2006 Society of Plastics Engineers
Preparation and properties of the self‐crosslinked acrylic rubber via gamma ray initiated emulsion polymerization
Authors: Geng Hongwei , Wang Mozhen , Ge Xuewu , Wang Weiwei 
Published: November 2006

AbstractIn this study, a series of self‐crosslinked acrylic rubbers were prepared by gamma ray initiated emulsion copolymerization. Acrylic acid and N‐hydroxymethl acrylamide were used as the cure‐site monomers. The vulcanizing properties, tensile properties, and dynamic mechanical analysis of the self‐crosslinked acrylic rubbers were investigated. It was found that the curing characteristics could be influenced significantly by the content and species of the cure‐site monomers. Improvement in mechanical properties like tensile strength, modulus and elongation at break was observed in the prepared self‐crosslinked rubber. The structure‐property correlation of the self‐crosslinked acrylic rubber was discussed. POLYM. ENG. SCI. 46:1748–1753, 2006. © 2006 Society of Plastics Engineers.
Multiplex shear stress‐induced nucleation in dynamic microcellular foaming process
Authors: Zhu Wenli , Zhou Nanqiao , Wu Hongwei 
Published: November 2006

AbstractThe effect of multiplex shear stress on the cell nucleation during microcellular foaming process was investigated using a dynamic foaming experimental apparatus. The multiplex oscillatory shear, which is different from previous one‐dimensional screw shear in a “stable” extrusion foaming process, is applied to the polymer melt through an axially vibrated rotor. The experimental results show that, by superimposing an axial vibration on the rotating rotor, the cell density increases and cell size decreases significantly when the shear rate is low. Both the uniformity of cell size and cell distribution are improved under vibration when compared with that without vibration regardless of how the shear rate changes. In addition, a simplified nucleation model based on shear energy has been carried out to qualitatively investigate the effect of both the simple steady shear and the multiplex oscillatory shear on the cell nucleation. Experiments and theoretical predictions all show that cell nucleation could be greatly improved by superimposing the oscillatory shear when the nucleation driving force induced by the steady shear is insufficient. Finally, the shear heat generated by excessive shear and strong vibration should be considered carefully although the isothermal condition was supposed in the present model. POLYM. ENG. SCI. 46:1728–1738, 2006. © 2006 Society of Plastics Engineers.
Rheokinetics of ring‐opening metathesis polymerization of norbornene‐based monomers intended for self‐healing applications
Authors: Larin G. E. , Bernklau N. , Kessler M. R. , DiCesare J. C. 
Published: November 2006

AbstractConstant shear rate rheokinetics was used to evaluate the polymerization of four norbornene‐based monomer systems as candidate healing agents in self‐healing composites: endo‐dicyclopentadiene (endo‐DCPD), exo‐DCPD, 5‐ethylidene‐2‐norbornene (ENB), and a 1:1 volume mixture of endo‐DCPD:ENB. The ruthenium catalyst induced ring‐opening metathesis polymerization of the healing agent candidates were measured experimentally under isothermal conditions while the influences of several different variables were considered (e.g., test temperature, catalyst concentration, catalyst form). Analyzing the increase in viscosity during the polymerization, comparisons of the reaction kinetics of the different monomers were quantified by defining two parameters, tt and Δt, which correspond to the polymerization initiation and propagation rates respectively. Generally, ENB shows the fastest polymerization kinetics, and endo‐DCPD the slowest. POLYM. ENG. SCI. 46:1804–1811, 2006. © 2006 Society of Plastics Engineers
The effect of screw geometry on melt temperature profile in single screw extrusion
Authors: Kelly A.L. , Brown E.C. , Coates P.D. 
Published: November 2006

AbstractExperimental observations of melt temperature profiles and melting performance of extruder screws are reported. A novel temperature sensor consisting of a grid of thermocouple junctions was used to take multiple temperature readings in real time across melt flow in a single screw extruder. Melt pressure in the die and power consumption were also monitored. Three extruder screws at a range of screw speeds were examined for a commercial grade of low density polyethylene. Results showed melt temperature fields at low throughputs to be relatively independent of screw geometry with a flat‐shaped temperature profile dominated by conduction. At high throughputs, melting performance and measured temperature fields were highly dependent upon screw geometry. A barrier‐flighted screw with Maddock mixer achieved significantly better melting than single flighted screws. Low temperature “shoulder” regions were observed in the temperature profiles of single‐flighted screws at high throughput, due to late melting of the solid bed. Stability of the melt flow was also dependent upon screw geometry and the barrier‐flighted screw achieving flow with lower variation in melt pressure and temperature. Dimensionless numbers were used to analyze the relative importance of conduction, convection, and viscous shear to the state of the melt at a range of extrusion conditions. Polym. Eng. Sci. 46:1706–1714, 2006. © 2006 Society of Plastics Engineers
Evaluation of agreement between physicians' notation of ‘no evidence of disease’ (NED) and patients' report of cancer status
Authors: Oates Carolyn T. , Sloane Richard , Ingram Sally S. , Seo Pearl H. , Cohen Harvey J. , Clipp Elizabeth C. 
Published: November 2006

AbstractThis study examines extent of agreement between oncologists' and cancer patients' reports of current cancer status. Participants with history of cancer were given a comprehensive geriatric assessment in which they were asked whether they had cancer at the present time. This was compared to cancer status concurrently recorded by their physicians in the chart. 75.5% of patients whose physicians reported ‘no evidence of disease’ (NED) reported that they currently had cancer. 30% of them were anxious and 27% were depressed. Among patients for whom both the patient and physician reported no cancer, only 12.5% were anxious and 7% depressed. Compared to patients with concordant responses, those who discrepantly reported they had cancer had significantly more comorbid illnesses, medications, and pain, and lower levels of social, emotional, and physical functioning. Moreover, equal levels of distress and dysfunction were found between those who reported cancer but had NED and those who reported cancer and did have active disease by physician notation. Although conclusions about cause and effect are limited due to study design, findings suggest that some patients might suffer unnecessarily from lack of understanding about current disease status. These findings also suggest the need for improved physician–patient communication and symptom recognition/management. Copyright © 2006 John Wiley & Sons, Ltd.
Cryogenic landforms in the Sierras de Alvear, Fuegian Andes, subantarctic Argentina
Authors: Valcárcel‐Díaz Marcos , Carrera‐Gómez Pedro , Coronato Andrea , Castillo‐Rodríguez Francisco , Rabassa Jorge , Pérez‐Alberti Augusto 
Published: November 2006

AbstractA preliminary survey of periglacial landforms found in the Monte Alvear region of the Fuegian Andes, subantarctic Argentina has revealed the presence of nivation hollows, subnival ‘boulder’ (clast) pavements, protalus ramparts, debris lobes, patterned ground and cryo‐ejected clasts. With the exception of debris lobes and cryo‐ejected clasts, all the landforms show some degree of activity and are, therefore, considered as indicators of present‐day cryonival morphodynamics at higher elevations in these mountains. A number of small tors, while not necessarily periglacial in origin, are also apparently experiencing cryogenic weathering. Copyright © 2006 John Wiley & Sons, Ltd.
Mechanisms of guanosine triphosphate hydrolysis by Ras and Ras‐GAP proteins as rationalized by ab initio QM/MM simulations
Authors: Grigorenko Bella L. , Nemukhin Alexander V. , Shadrina Maria S. , Topol Igor A. , Burt Stanley K. 
Published: November 2006

AbstractThe hydrolysis reaction of guanosine triphosphate (GTP) by p21ras (Ras) has been modeled by using the ab initio type quantum mechanical–molecular mechanical simulations. Initial geometry configurations have been prompted by atomic coordinates of the crystal structure (PDBID: 1QRA) corresponding to the prehydrolysis state of Ras in complex with GTP. Multiple searches of minimum energy geometry configurations consistent with the hydrogen bond networks have been performed, resulting in a series of stationary points on the potential energy surface for reaction intermediates and transition states. It is shown that the minimum energy reaction path is consistent with an assumption of a two‐step mechanism of GTP hydrolysis. At the first stage, a unified action of the nearest residues of Ras and the nearest water molecules results in a substantial spatial separation of the γ‐phosphate group of GTP from the rest of the molecule (GDP). This phase of hydrolysis process proceeds through the low barrier (16.7 kcal/mol) transition state TS1. At the second stage, the inorganic phosphate is formed in consequence of proton transfers mediated by two water molecules and assisted by the Gln61 residue from Ras. The highest transition state at this segment, TS3, is estimated to have an energy 7.5 kcal/mol above the enzyme–substrate complex. The results of simulations are compared to the previous findings for the GTP hydrolysis in the Ras‐GAP (p21ras–p120GAP) protein complex. Conclusions of the modeling lead to a better understanding of the anticatalytic effect of cancer causing mutation of Gln61 from Ras, which has been debated in recent years. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Dust collector explosion prevention and control
Authors: Going John E. , Lombardo Tony 
Published: November 2006

AbstractThe handling of fine particles of a combustible material is a major and inevitable part of many industrial processes. The objective may be fugitive and emission controls or the collection of a product. The challenge will increase as the use of finer particles increases. The risks will increase simultaneously as the hazard properties such as ignitability increase with the reduction of particle size. Dust collectors are a component, if not the most common component, of particle handling and are also often the origin or termination of an explosion. The design of dust collector protection is a systematic process that includes and requires process information as well as protection objectives. The theory of protection and the selection of protection techniques will be reviewed. The practice of dust collector protection is often less routine because of many physical and process complications. Examples of both simple and complicated applications are presented with brief illustrations of the consequence of no or inadequate protection. © 2006 American Institute of Chemical Engineers Process Saf Prog 2007
Structure, ferromagnetism and magnetotransport of epitaxial (Ga,Mn)As/GaAs structures
Authors: Brunner K. , Gould C. , Schmidt G. , Molenkamp L. W. 
Published: November 2006

AbstractIn this review, we describe the structural, magnetic and magnetotransport properties of one of the most advanced ferromagnetic semiconductor material systems, (Ga,Mn)As/GaAs heterostructures and nanostructures. Molecular beam epitaxy at low substrate temperature is applied to deposit epitaxial layers without MnAs cluster formation but with homogeneous incorporation of substitutional Mn up to about 8% content and with concomitant hole carrier densities in the 1021 cm–3 range. Epitaxial strain, Mn content, p‐doping and defects that are related to low‐temperature growth may strongly influence the ferromagnetic properties, like Curie temperature, remanent magnetization and magnetic anisotropy. This is well understood within the Zener model for ferromagnetic ordering of Mn ions that is mediated by p–d exchange interaction with free holes in the complex, anisotropic valence band states. The interplay of ferromagnetism and electronic band structure manifests in the various magnetotransport phenomena, like anomalous Hall effect and spin valve tunneling transport. In particular, tunneling structures reveal many novel features, such as the tunneling anisotropic magnetoresistance (TAMR), that highlight the interplay of magnetic and electronic properties and may be pathways to future spintronics devices. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanically controlled preparation of protein intermediates in single molecule experiments
Authors: Berkemeier Felix , Schlierf Michael , Rief Matthias 
Published: November 2006

AbstractSingle molecule mechanical experiments allow the controlled manipulation of proteins and the population of intermediate states within their high dimensional energy landscape. Here we report single molecule refolding measurements of domain 4 from the protein ddFilamin using a novel digital control scheme. First, the protein is unfolded mechanically to an intermediate state. An on‐line detection scheme then detects population of the intermediate and rapidly switches to refolding conditions. This control scheme allows direct measurement of the refolding kinetics. A comparison to the results from conventional single molecule refolding schemes allows important conclusion on the structural relation between unfolding and refolding intermediates in this protein domain. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Infrared imaging with InAs/GaSb type‐II superlattices
Authors: Walther M. , Weimann G. 
Published: November 2006

AbstractInAs/GaSb short period superlattices (SLs) with broken gap typ‐II band alignment are very well suited for the fabrication of high performance infrared camera systems for the second atmospheric window (3–5 µm). High resolution focal plane arrays for single‐ and dual‐colour applications based on InAs/GaSb SLs have been fabricated. Those camera systems reveal excellent performance data which are comparable and even superior to state of the art thermal imaging systems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic properties of MnAs‐on‐GaAs(001) films
Authors: Ploog K. H. , Däweritz L. , Engel‐Herbert R. , Hesjedal T. 
Published: November 2006

AbstractStrained MnAs films on GaAs(001) grown by molecular beam epitaxy exhibit unique micro‐magnetic properties due to the strain‐mediated coexistence of hexagonal ferromagnetic α‐MnAs and orthorhombic paramagnetic β‐MnAs arranged in selforganized periodic stripe patterns. To explore the internal structure of the magnetization, which is not accessible by the magnetic imaging techniques AFM and XMCDPEEM, detailed micromagnetic simulations are needed. Otherwise, physically unreasonable models would be developed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical excitations of quasi‐one‐dimensional systems: carbon nanotubes versus polymers and semiconductor wires
Authors: Prezzi D. , Molinari E. 
Published: November 2006

AbstractWe review the main characteristics of optical excitations of semiconductor nanotubes, as obtained from accurate ab‐initio theories and model calculations as well as experimental evidence, and discuss them in light of the previous understanding of other quasi‐one‐dimensional semiconducting systems. We point out striking similarities of nanotubes with III–V quantum wires and conjugated polymers, especially (i) the clear excitonic nature of absorption, very far from the single‐particle behaviour; (ii) its manifestations in optical spectra, where excitonic peaks are accompanied by a strong intensity reduction at the onset of the free‐particle continuum; (iii) the strategies that allow experimental access to exciton binding energies. The recent theoretical and experimental evidence obtained on semiconducting single‐walled nanotubes converges quantitatively to a picture of strongly bound excitons (about 0.3–1.0 eV for nanotubes with 0.4–1.0 nm diameter). We discuss its implications and list a few open issues of relevance to fundamental understanding and optoelectronic applications. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Supported membranes on polyelectrolyte layers studied by X‐ray reflectometry
Authors: Reich Christian , Neff Petra A. , Bausch Andreas R. , Rädler Joachim O. , Nickel Bert 
Published: November 2006

AbstractSupported lipid membranes on polymer layers were investigated by X‐ray reflectivity in aqueous environment using a microfluidic setup. Polyallylamine hydrochloride and poly(sodium 4‐styrenesulfonate) were used for building up multilayer architectures with alternating charge distribution.First results from synchrotron reflectivity experiments demonstrate that such polyelectrolyte layers can act as aqueous spacers with almost negligible electron density contrast as compared to water. Lipid membranes on top of such polymer spacers are expected to show only minor structural denaturation. Thus this model system is proposed as a step towards decoupling lipid membranes from solid substrates. The accessibility to such biological systems using high‐resolution X‐ray reflectivity and the possibility to insert well‐defined spacers with minimum contrast are highly competitive to established methods of neutron reflectivity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of end grafted DNA molecules and possible biosensor applications
Authors: Sendner C. , Kim Yong W. , Rant U. , Arinaga K. , Tornow M. , Netz R. R. 
Published: November 2006

AbstractPolymers that are terminally attached to solid supports, so called brushes, form the basis for a wide variety of different applications in colloidal and biophysical sciences. For grafted charged chains a conducting surface allows to manipulate the brush structure by applying electric fields across the brush. The dynamics of oligomeric DNA molecules under the action of repulsive and attractive surface electric fields is studied by Brownian dynamics simulations including hydrodynamic effects and compared to experimental results. The difference in flexibility between double and single stranded DNA molecules leads to a change in the switching dynamics when repeatedly reversing the surface charge. This effect allows to detect hybridization of surface anchored DNA. Similar kinetic changes occur when other molecules bind terminally to DNA, opening the possibility to use end grafted polymers for general biosensing applications. We in particular discuss the influence of the adsorbate size and change on the switching dynamics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transistor based study of the electrolyte/SiO2 interface
Authors: Gentil Cédric , Côte Denis , Bockelmann Ulrich 
Published: November 2006

AbstractAn experimental and theoretical study of the silica surface in aqueous environment is presented. The current/voltage characteristics of silicon field effect transistors are measured as a function of the salt concentration of a KCl solution in contact with the SiO2 gate oxide. We find that a model assuming constant interface charge can describe the global trend of the measured salt dependence. A refined model, allowing for a varying interface charge, provides a quantitative description of the measurements. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Label‐free detection of DNA using field‐effect transistors
Authors: Ingebrandt Sven , Offenhäusser Andreas 
Published: November 2006

AbstractElectronic DNA sensors based on field‐effect transistor arrays operating in liquid environment, offer an alternative method for the detection of biomolecular binding events, without the requirement to label the target molecules. These semiconductor devices are sensitive to electrical charge variations that occur at the surface/electrolyte interface. Using such devices, the hybridization reaction of oligonucleotides with complementary single‐stranded oligonucleotides, which are immobilized on the oxide surface of the transistor gate, can be detected. The detection principle is based on the intrinsic charge of the nucleic acid molecules in liquid environment. In this article we present a summary of the ‘DNA BioFET’ project, which has been conducted in our group in recent years. We compare an electrostatic and a covalent immobilization protocol for the probe DNA. Most important for reliable signal readout is the use of a differential approach, for which a DNA microarray represents an ideal bioassay. With our FET setup we can either use a chip‐to‐chip reference with two electrically identical chips, which are coated with different probe sequences. A more sophisticated method, which makes use of the DNA microarray technology, was established with an aligned microspotting system enabling the coating of different channels out of the microarray with different probe sequences. So far our current chip design uses 16 channels enabling first proof‐of‐principle experiments. The detection method itself, however, offers the possibility to be up scaled to many thousands of sensor spots like currently used in fluorescence based DNA microarray chips. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)