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Selected AbstractsEffect of melt processing conditions on the morphology and properties of nylon 6 nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 11 2007F. Chavarria Nylon 6 (PA-6) organoclay nanocomposites were prepared by melt processing using three different twin screw extruders (TSEs). The effect of mixing conditions, feed port location, residence time, and number of extrusion passes on the morphology and mechanical properties of the nanocomposites were examined. Wide-angle X-ray scattering, transmission electron microscopy (TEM), and mechanical property data are reported. Particle analyses were performed on the TEM images to quantitatively characterize the extent of exfoliation. The amount of shear and the mixing conditions created by TSEs have a significant effect on the morphology and properties of PA-6 nanocomposites. Morphology and mechanical property results show that (1) melting the polymer before coming into contact with the organoclay followed by a low level of shear and (2) maintaining a medium level of shear throughout the extruder with a longer residence time lead to extremely high platelet dispersion and matrix reinforcement for PA-6 nanocomposites. Nanocomposites formed in a DSM microcompounder showed similar morphologies and modulus trends as those obtained with conventional TSEs; thus, this microcompounder is a good alternative for nanocomposite research especially when only small amounts of material are available. POLYM. ENG. SCI., 47:1847,1864, 2007. © 2007 Society of Plastics Engineers [source] Upstream Solutions: Does the Supplemental Security Income Program Reduce Disability in the Elderly?THE MILBANK QUARTERLY, Issue 1 2008PAMELA HERD Context: The robust relationship between socioeconomic factors and health suggests that social and economic policies might substantially affect health, while other evidence suggests that medical care, the main focus of current health policy, may not be the primary determinant of population health. Income support policies are one promising avenue to improve population health. This study examines whether the federal cash transfer program to poor elderly, the Supplemental Security Income (SSI) program, affects old-age disability. Methods: This study uses the 1990 and 2000 censuses, employing state and year fixed-effect models, to test whether within-state changes in maximum SSI benefits over time lead to changes in disability among people aged sixty-five and older. Findings: Higher benefits are linked to lower disability rates. Among all single elderly individuals, 30 percent have mobility limitations, and an increase of $100 per month in the maximum SSI benefit caused the rate of mobility limitations to fall by 0.46 percentage points. The findings were robust to sensitivity analyses. First, analyses limited to those most likely to receive SSI produced larger effects, but analyses limited to those least likely to receive SSI produced no measurable effect. Second, varying the disability measure did not meaningfully alter the findings. Third, excluding the institutionalized, immigrants, individuals living in states with exceptionally large benefit changes, and individuals living in states with no SSI supplements did not change the substantive conclusions. Fourth, Medicaid did not confound the effects. Finally, these results were robust for married individuals. Conclusions: Income support policy may be a significant new lever for improving population health, especially that of lower-income persons. Even though the findings are robust, further analyses are needed to confirm their reliability. Future research should examine a variety of different income support policies, as well as whether a broader range of social and economic policies affect health. [source] Analytical study of mine closure behaviour in a poro-visco-elastic mediumINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2008H. Wong Abstract This paper is interested in the hydro-mechanical behaviour of an underground cavity abandoned at the end of its service life. It is an extension of a previous study that accounted for a poro-elastic behaviour of the rock mass (Int. J. Comput. Geomech. 2007; DOI: 10.1016/j.compgeo.2007.11.003). Deterioration of the lining support with time leads to the transfer of the loading from the exterior massif to the interior backfill. The in situ material has a poro-visco-elastic constitutive behaviour while the backfill is poro-elastic, both saturated with water. This loading transfer is accompanied by an inward cavity convergence, thereby compressing the backfill, and induces an outward water flow. This leads to a complex space,time evolution of pore pressures, displacements and stresses, which is not always intuitive. In its general setting, a semi-explicit solution to this problem is developed, using Laplace transform, the inversion being performed numerically. Analytical inversion leading to a quasi-explicit solution in the time domain is possible by identifying the characteristic creep and relaxation times of volumetric strains with those of the deviatoric strains, on the basis of a parametric study. A few numerical examples are given to illustrate the hydro-mechanical behaviour of the cavity and highlight the influence of key parameters (e.g. stiffness of backfill, lining deterioration rate, etc.). Further studies accounting for more general material behaviours for the backfill and external ground are ongoing. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mammal community structure in relation to disturbance and resource gradients in southern AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2009Märtha Wallgren Abstract The arrangements of mammals differ along environmental gradients, such as of disturbance and resources. We examined how mammal community composition in the Kalahari, Botswana, varied in relation to disturbance and resource gradients. We predicted that livestock-keeping villages are disturbances and pans are resources for wildlife, that the responses of mammals to disturbance and resources depend on their functional types and that increased disturbance over time has reduced the numbers and distributions of wildlife. The methods involved road-side counts of mammals >0.2 kg and trapping of small mammals, <0.2 kg. The disturbance gradient was more important than the resource gradient for explaining the distribution of mammals >0.2 kg. Communities in low disturbance-high resource areas were most diverse regarding species and functional types. Small mammal species richness and abundances were unaffected by villages, but increased with distance from pans. Villages were particularly deterring to large wild herbivores, functionally similar to livestock. Most large wild herbivores had decreased since 1975,1983. We conclude that large and medium-sized mammals are highly affected by large-scale disturbance gradients, while small mammals are most dependent on small-scale variation in resources, probably shelter and food. Increased disturbance over time leads to decreasing ranges and numbers of the large wild herbivores. Résumé Les associations de mammifères diffèrent selon des gradients environnementaux tels que ceux des perturbations et des ressources. Nous avons examiné comment la composition de la communauté de mammifères variait dans le Kalahari, au Botswana, en fonction des gradients de perturbations et de ressources. Nous avions prédit que les villages qui gardent du bétail sont des perturbations, et les pans des ressources pour la faune sauvage, que les réponses des mammifères à ces deux facteurs dépendaient de leur type de fonctionnement, et que les perturbations croissant avec le temps avaient réduit l'abondance et la distribution de la faune sauvage. Les méthodes employées comprenaient les comptages le long de la route de tous les mammifères de plus de 0,2 kg et le piégeage des petits mammifères de moins de 0,2 kg. Le gradient de perturbation était plus important que celui des ressources pour expliquer la distribution des mammifères >0,2 kg. Les communautés vivant dans les zones de faibles perturbations et d'abondantes ressources étaient plus diverses au point de vue du nombre d'espèces et de types fonctionnels. La richesse en espèces de petits mammifères et leur abondance n'étaient pas affectées par les villages mais augmentaient avec la distance par rapport au pan. Les villages étaient particulièrement dissuasifs pour les grands herbivores sauvages qui étaient, fonctionnellement, semblables au bétail. La plupart des grands herbivores sauvages ont diminué depuis 1975,1983. Nous concluons que les herbivores grands et moyens sont fort affectés par les gradients de perturbations à grande échelle alors que les petits mammifères sont surtout dépendants des variations à petite échelle des ressources, probablement les abris et la nourriture. Les perturbations croissant avec le temps entraînent une réduction des domaines vitaux et du nombre des grands herbivores sauvages. [source] Galvanisches Verzinken von MagnesiumlegierungenMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 2 2007H. Pokhmurska magnesium alloy; zinc coating; electro plating of zinc; corrosion behaviour Abstract Magnesiumlegierungen sind sehr korrosionsanfällig, was ihre Anwendung unter korrosiven Bedingungen einschränkt. Eine Möglichkeit, um Magnesium vor aggressiven Umweltbedingungen zu schützen, ist das Beschichten. Es werden Ergebnisse über das Korrosionsverhalten der aus verschiedenen Elektrolyten galvanisch verzinkten Magnesiumknetlegierung AZ31 gezeigt. Die Bewertung der Korrosionsprozesse in chloridhaltigen Lösungen erfolgte durch elektrochemische Messungen. Durch einstündige Auslagerung der beschichteten Proben wurde festgestellt, dass dicke und dichte galvanische Zinkschichten auf AZ31 die Korrosionseigenschaften verbessern. Eine Erhöhung der Immersionszeit führt jedoch zu einer Verschlechterung der Korrosionseigenschaften. Elektrolytische Zinkschichten, die durch einen konsekutiven alkalisch / sauren Prozess erzeugt werden, stabilisieren die Schicht und verbessern somit die Korrosionsbeständigkeit des beschichteten AZ31. Zinc-Plating of Magnesium Alloys Magnesium alloys are highly susceptible to corrosion that limits their application when exposure to corrosive service conditions is needed. One of the ways to prevent corrosion is to coat the magnesium-based substrate to avoid a contact with an aggressive environment. Results concerning corrosion behaviour of wrought AZ31 magnesium alloy with electrolytic zinc coatings deposited from different electrolyte solutions are described. Evaluation of corrosion processes in chlorides containing solutions was performed by electrochemical measurements. It was found that thick and dense electrolytic zinc coatings formed on AZ31 significantly improve the corrosion behaviour of magnesium alloy after one hour immersion of zinc coated magnesium alloys in corrosive media. Further increase of immersion time leads to relatively fast decrease of corrosion properties. Electrolytic zinc coatings obtained in consecutive alkaline / acidic process demonstrate an improvement of corrosion resistance of coated AZ31. The time to coating degradation strongly increases. [source] On spherical harmonics expansion type modelsfor electron,phonon collisionsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2003J.-P. Bourgade Abstract In this paper, we give the rigorous derivation of a diffusion model for semiconductor devices, the starting point being a microscopic description of electron transport by means of a kinetic equation of Boltzmann type. The limit of a small mean free path at a large time leads to a diffusion equation of ,SHE' type (spherical harmonics expansion). We deal with a collision operator that models interactions between electron and phonons. This induces a peculiar form for the diffusion tensor: electron,phonon collisions happen to be discontinuous in energy and inelastic, and, as a consequence, the diffusion tensor appears as an infinite dimensional matrix. Copyright © 2003 John Wiley & Sons, Ltd. [source] Hochdurchsatz-Methoden in der Festkörperchemie.CHEMIE IN UNSERER ZEIT (CHIUZ), Issue 5 2007Schneller zum Ziel Abstract Hochdurchsatz-Methoden zeichnen sich gegenüber konventionellen Methoden durch eine größere Effizienz aus. Mittlerweile steht im Bereich der Anorganischen Festkörperchemie und der Materialwissenschaften eine Vielzahl von Werkzeugen zur Verfügung, um die Entdeckung und Optimierung von Materialien durch Verwendung von HD-Methoden schneller voranzutreiben. Für alle Arbeitstechniken gilt: Das Ausmaß der Automatisierung, Parallelisierung und Miniaturisierung sowie die Integration aller Einzelschritte in einen Gesamtprozess bestimmt die Effizienz einer HD-Methodik. Durch eine systematische Untersuchung des Parameterraumes und durch sorgfältige Datenevaluierung (möglichst Software-gestützt) können Trends gefunden werden, die zu einem besseren Verständnis der untersuchten Systeme beitragen. Der vorgestellte Ansatz zur HD-Untersuchung von Solvothermalreaktionen erlaubt die automatisierte Synthese und Charakterisierung von bis zu 48 Produkten ohne die Proben einzeln manipulieren zu müssen. Der geringe Reagenzienverbrauch zusammen mit der Möglichkeit, die Reaktionen unter identischen Prozessparametern (Temperatur, Zeit, Druck, usw.) durchführen zu können, ermöglichen die systematische Untersuchung eines größeren Parameterraumes. An Hand zahlreicher Beispiele haben wir das Potential von Hochdurchsatz- Methoden bei der Entdeckung neuer Verbindungen, der Optimierung von Reaktionen, beim Auffinden von Reaktionstrends sowie der Untersuchung des Einflusses von Prozessparametern gezeigt. High-throughput (HT) methods applied to materials discovery have attracted much attention over the last few years because they permit a fast and efficient investigation of parameter space while consuming only small amounts of starting materials. Nowadays, many different HT techniques in solid state science are employed in order to accelerate the discovery and optimization of materials. The degree of parallelisation, automation, and miniaturization determines the efficiency of a HT methodology. Systematic investigation of parameter space and careful data analysis allow the identification of reaction trends and may give important guidance in better understanding of reaction systems. The described HT methodology for solvothermal reactions allows the systematic investigation of 48 different hydrothermal reactions at a time. The methodology includes automatic dispensing of solids and liquids, followed by homogenization, pH measurement, synthesis, isolation, washing as well as automated phase analysis by X-ray diffraction without the manipulation of individual samples. The focus of this article is on the application of HT methods in the investigation of the parameter space in solid state sciences. Based on selected examples, the power of HT methods in the discovery of new compounds, the optimization of reactions, the identification of reaction trends, as well as the investigation of the influence of process parameters is described. The large amount of data obtained in a short time leads to an improvement towards the understanding of the role that synthesis and process parameters play in the formation of compounds and materials. [source] BEHAVIOUR OF THE ANTI-OXIDANT DEFENCE SYSTEM AND HEME OXYGENASE-1 PROTEIN EXPRESSION IN FRUCTOSE-HYPERTENSIVE RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2006Ariel H Polizio SUMMARY 1Addition of fructose to a rat diet for various periods of time leads to hypertension, hyperinsulinaemia and dyslipidaemia and provides a model for testing oxidative stress parameters in the animals. 2In the present study, oxidative stress generation, the soluble and enzymatic defence system and heme oxygenase-1 (HO-1) protein expression were investigated in the heart, liver and kidney of rats fed fructose for a period of 1 or 8 months. 3Compared with the control group, fructose-hypertensive rats showed increased in lipid peroxidation only in the heart after both 1 and 8 months of fructose treatment. Changes in the behaviour of the soluble and enzymatic defence system and HO-1 protein expression were different depending on the organ. Increased or unaltered activities of anti-oxidant enzymes were found in the liver and kidney, respectively. Induction of HO-1 prevented the generation of oxidative stress in the liver, where the activity of anti-oxidant defence enzymes was not reduced. Increased expression of HO-1 protein was not able to prevent the generation of oxidative stress in the heart, where fructose treatment diminished the activity of anti-oxidant enzymes. 4The results of the present study demonstrate that upregulation of HO-1 may prevent the generation of oxidative stress only when the anti-oxidant defence system is still operative. [source] Cover Picture: Fortschritte der Physik 11,12 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11-12 2009Article first published online: 9 NOV 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 10 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 10 2009Article first published online: 14 SEP 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 9 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9 2009Article first published online: 21 AUG 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 5,7 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009Article first published online: 27 MAY 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 3,4 /2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 3-4 2009Article first published online: 23 MAR 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 1,2 /2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 1-2 2009Article first published online: 9 FEB 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Synchrotron X-ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p,-bibenzoate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Ernesto Pérez Abstract Time-resolved synchrotron X-ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p,-bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110,°C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained. Scattering profiles corresponding to sample PDEB85 in a melting experiment. [source] Surface properties of hydrosilylated polyolefins annealed in supercritical carbon dioxidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2008S.-H. Zhu Abstract Two hydrosilylated polyolefin compounds are obtained by reacting polypropylene (PP) and polyethylene (PE) with di- and multi-functional hydride-terminated poly(dimethylsiloxane) (dH-PDMS and mH-PDMS), respectively. The PDMS-rich surface layers on these two samples show different Si concentrations but similar thicknesses. Samples of these materials are annealed in supercritical carbon dioxide (scCO2) at various temperatures and pressures for different periods of time. On the PP/dH-PDMS sample, an increase in the annealing temperature does not affect the Si concentration up to 120°C. However, the Si concentration is sharply reduced at T,=,150°C at which point the surface appears to be covered by SiO2 particles. Annealing the PP/dH-PDMS sample for short times leads to submicron scale SiO2 particle formation on the surface. The particles form aggregated clusters that spread all over the surface uniformly when the annealing time is extended. However, Si concentration on the PE/mH-PDMS sample surface is enhanced as the annealing temperature increases, reaching a maximum at an annealing temperature of 100°C. No particle formation is observed on the PE/mH-PDMS sample surface. The contact angle of both samples is found to increase with annealing temperature. Increasing the scCO2 pressure leads to a higher Si concentration on the surfaces of both samples. On the other hand, increasing the CO2 pressure leads to opposite trends in contact angle with the PP/dH-PDMS sample exhibiting an increasing contact angle and the PE/mH-PDMS sample exhibiting a decreasing one. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||