Monkman-grant analysis of creep fracture in dispersion-strengthened and particulate-reinforced aluminum

The tensile creep fracture properties of coarse- and fine-grained dispersion-strengthened-cast aluminum (DSC-Al) with 25 vol pct of submicron alumina dispersoids are presented for temperatures between 335 °C and 500 °C and stresses between 30 and 100 MPa. The primary, secondary, and tertiary creep strains are analyzed in terms of the minimum creep rate, applied stress, and temperature. Good agreement with the original and the modified Monkman-Grant relationships is found for the failure time of DSC-Al and other aluminum materials reinforced with dispersoids or particulates. The origin of the Monkman-Grant relationships for these materials is discussed in terms of stress exponents, specific interfacial areas, and ratio of secondary strain to failure strain.     

Phase Relations in the Bi–Sr–Ca–Cu–M–O (M = Y, Dy, Ho, Er, Tm, Yb, Lu) Systems

The phase relations in the Bi–Sr–Ca–Cu–M–O (M = Y, Dy, Ho, Er, Tm, Yb, Lu) systems near Bi₂Sr₂CaCu₂O_{8+ x} (Bi-2212) were studied between 850 and 990°C. The results demonstrate that larger sized rare earths (Y, Dy, Ho, Er) substitute on the Ca site in Bi-2212, leading to the formation of CaO. Smaller sized rare earths (Tm, Yb, Lu) replace lesser amounts of Ca and form Sr₂MBiO₆phases. In the material of nominal composition Bi₂Sr₂Ca_0.85M_0.15Cu₂O_{8 + x} + 0.25Sr₂YBiO₆prepared via melt processing, a major fraction of the Y atoms substitute for Ca in Bi-2212, resulting in a low-T _cmultiphase superconductor. In the analogous Yb system, a Bi-2212–Sr₂YbBiO₆composite with T _c= 87 K is obtained.     

Mental health policy: Observations from Europe.

Reviews policies and practices based on a study of 5 European countries (Switzerland, England, Denmark, Sweden, and the Netherlands) with respect to deinstitutionalization and community support and rehabilitation services, health and social security benefits, financing mechanisms, and care for the homeless and young adult chronic populations. Common trends in European mental health and social welfare policies are summarized. Relative to the US, the coordinated system of care in these countries is supported by a strong social welfare system allowing for community-based care administered by the mental health service system. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maltose hydrolysis kinetics with glucoamylase immobilized in porous glass fibers in a tubular flow reactor

Glucoamylase has been covalently immobilized in controlled pore glass fibers packed parallel to the axis of a tubular reactor. Flow kinetic studies have been carried out for a range of flow rates and substrate concentrations at 50°C and pH 4.5. Diffusion control has been found negligible with high flow rates and substrate concentrations. The apparent Michaelis constant was three orders of magnitude higher than that of the free enzyme. As flow rate and substrate concentration decrease, the extent of diffusion control increased up to a moderate degree. The immobilized glucoamylase was more stable than the free enzyme when incubated at 50°C.     

Accelerant‐promoted free radical polymerization of methacrylates by stabilized nitroxide unimolecular initiators: synthesis and characterization

BACKGROUND: This investigation evaluates the effectiveness of initiator adducts for living and controlled polymerization of methacrylates, crosslinking of dimethacrylates and thermal stabilities of the resulting polymers. Adducts of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy with benzoyl peroxide and with azobisisobutyronitrile were prepared and evaluated as stabilized unimolecular initiators for the free radical polymerization of methacrylate monomers using sulfuric acid as catalyst. The monomers used were methyl methacrylate, triethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA). RESULTS: Successful polymerization was achieved at 70 and 130 °C with reaction times ranging from 45 min to 120 h. The dispersity (D) of poly(methyl methacrylate) (PMMA) was 1.09–1.28. The livingness and extent of control over polymerization were confirmed with plots of M_n evolution as a function of monomer conversion and of the first‐order kinetics. The glass transition temperature (T_g) for PMMA was 123–128 °C. The degradation temperature (T_d) for PMMA was 350–410 °C. T_d for poly(TEGMA) was 250–310 °C and for poly(EBPADMA) was 320–390 °C. CONCLUSION: The initiators are suitable for free radical living and controlled polymerization of methacrylates and dimethacrylates under mild thermal and acid‐catalyzed conditions, yielding medium to high molecular weight polymers with low dispersity, high crosslinking and good thermal stability. Copyright © 2008 Society of Chemical Industry     

Comparison of residual stress predictions and measurements using excimer laser layer removal

Residual stresses in injection molded polymer parts can have a major effect on product performance and are therefore often undesirable. Two different models for residual stress formation in injection molded products exist in the literature. The first model assumes that stresses in molded parts are identical with free quench stresses. Deviations are attributed to molecular orientation effects. The second model assumes that no slip occurs and that stresses are related to the holding pressure. Careful measurements should be able to differentiate between these models. In this study the layer removal stress measurement technique was improved by using an excimer laser for the milling operation. In that way stress relaxation during measurements was avoided and thin layers of uniform thickness could be removed. Both resolution and measurement accuracy were greatly improved. Stress distributions in polycarbonate plates molded under low holding pressures turned out to be of the free quenching type, whereas those molded under higher pressures were of the pressure type. All stress distributions could be predicted by a recent theory that comprises the two models as limiting cases.     

The effect of silicide on ESD performance of transistors

In this paper a new model for localized breakdown in NMOSTs under ESD stress is developed, which accounts for the reduced ESD strength in silicided devices. The model explains the impact of a stabilizing drain resistance on second breakdown current for both silicided and unsilicided protections.     

Oerlikon Schlafhorst：引领短纤纺纱技术

欧瑞康赐来福公司作为短纤领域的行业标杆，坚持不断创新，潜心致力于最先进纺纱和络筒设备的研发，旨在为客户提供最具经济效益的纺纱和络筒解决方案。     

Biological properties of iron oxide nanoparticles for cellular and molecular magnetic resonance imaging

Superparamagnetic iron-oxide particles (SPIO) are used in different ways as contrast agents for magnetic resonance imaging (MRI): Particles with high nonspecific uptake are required for unspecific labeling of phagocytic cells whereas those that target specific molecules need to have very low unspecific cellular uptake. We compared iron-oxide particles with different core materials (magnetite, maghemite), different coatings (none, dextran, carboxydextran, polystyrene) and different hydrodynamic diameters (20-850 nm) for internalization kinetics, release of internalized particles, toxicity, localization of particles and ability to generate contrast in MRI. Particle uptake was investigated with U118 glioma cells und human umbilical vein endothelial cells (HUVEC), which exhibit different phagocytic properties. In both cell types, the contrast agents Resovist, B102, non-coated Fe(3)O(4) particles and microspheres were better internalized than dextran-coated Nanomag particles. SPIO uptake into the cells increased with particle/iron concentrations. Maximum intracellular accumulation of iron particles was observed between 24 h to 36 h of exposure. Most particles were retained in the cells for at least two weeks, were deeply internalized, and only few remained adsorbed at the cell surface. Internalized particles clustered in the cytosol of the cells. Furthermore, all particles showed a low toxicity. By MRI, monolayers consisting of 5000 Resovist-labeled cells could easily be visualized. Thus, for unspecific cell labeling, Resovist and microspheres show the highest potential, whereas Nanomag particles are promising contrast agents for target-specific labeling.