Microstructural development and radiation hardening of neutron irradiated Mo-Re alloys

Stress-relieved specimens and recrystallized specimens of pure Mo and Mo-Re alloys with Re contents of 2, 4, 5, 10, 13 and 41 wt% were neutron irradiated up to 20 dpa at temperatures from 681 to 1072 K. On microstructural observation, sigma phase and chi phase precipitates were found in all irradiated Mo-Re alloys. Voids were observed in all irradiated specimens, and dislocation loops and dislocations were observed in the specimens that were irradiated at lower temperatures. On Vickers hardness testing, all of the irradiated specimens showed hardening. Especially Mo-41Re were drastically embrittled after irradiation at 874 K or below. From these results, the authors discuss about the relation between microstructure development and radiation hardening and embrittlement, and propose the optimum Re content and thermal treatment for Mo-Re alloys to be used under irradiation conditions.     

The solution structure of human endothelin-2 a 1H-NMR and CD study

OBJECTIVE: Peroxynitrite (ONOO-) is an oxidant formed from the rapid reaction of superoxide and nitric oxide (NO) at sites of inflammation. The literature reports conflicting data on the effects of ONOO- in biological systems, with both NO- and oxidant-dependent effects having been demonstrated. The aim of this study was to investigate these distinct mechanisms through examining molecular aspects of the effects of ONOO- on human platelets, a system in which we have previously shown that ONOO- has both pro- and anti-aggregatory effects. METHODS: Platelet function was assessed by measuring platelet P-selectin expression flow cytometrically, intraplatelet Ca2+ concentrations, and by light aggregometry. A colorimetric method was used to measure extracellular platelet membrane thiols. The contribution of NO and cGMP to the pharmacological effects of ONOO- was investigated using an inhibitor of the soluble guanylate cyclase (sGC), 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), and the NO scavenger oxy-haemoglobin. RESULTS: Peroxynitrite (50-400 microM) caused a concentration-dependent increase in the number of platelets expressing P-selectin, an increase in intraplatelet Ca2+ concentrations and a decrease in platelet membrane thiols. Peroxynitrite-induced P-selectin expression was augmented by ODQ. In contrast, when P-selectin expression was elicited by collagen, ONOO- acted as an inhibitor of this process, an effect that was further enhanced by the addition of 1% plasma, ODQ or oxy-haemoglobin abolished this inhibitory effect. Finally, low concentrations (50-100 microM) of ONOO- inhibited collagen-induced platelet aggregation, an effect that was reversed by oxy-haemoglobin. CONCLUSIONS: Peroxynitrite exerts dual effects on platelets, which are either activating or inhibitory due to the conversion of ONOO- to NO or NO donors. Peroxynitrite-induced platelet activation seems to be due to thiol oxidation and an increase in intracellular Ca2+. It is important to note that inhibitory, NO-dependent effects occur at lower concentrations than the activating effects. These data are then consistent with the conflicting literature, showing both damaging and cytoprotective effects of ONOO- in biological systems. We hypothesize that the conversion of ONOO- to NO is the critical factor determining the outcome of ONOO- exposure in vivo.     

Equivalent transformations for the mixed lumped Brune-type sectionand uniform transmission line

As an analytical method for nonuniform transmission lines (NTLs) equivalent transformations are extended to a more general case, namely a mixed lumped Brune-type section and a uniform transmission line (unit element, UE). Circuits consisting of a cascade connection of a lumped Brune section and a UE are equivalent to one consisting of a cascade connection of a nonuniform transmission line whose characteristic impedance distribution is expressed with a trigonometric function and a lumped Brune section. This equivalent transformation method is easily applied to a circuit consisting of a lumped C section and a UE. The equivalent circuit is a circuit consisting of an NTL and a lumped C section. In this case, the characteristic impedance distribution of the NTL may be expressed in terms of a hyperbolic function. Exact network functions of the NTLs are easily obtained from the equivalent circuits without solving the telegrapher's equation. By considering the limiting case of these equivalent transformations, equivalent transformations for circuits consisting of a cascade connection of a lumped resonance circuit and a circuit and a uniform transmission line are derived     

Microstructural characteristics of an ultrafine grain metal processed with equal-channel angular pressing

Equal-channel angular pressing is a procedure for producing a fully dense material with an ultrafine grain size, typically in the submicrometer or nanometer range, by subjecting the material to a very high plastic strain. This paper describes the principle of equal-channel angular pressing and illustrates the capability of the technique by reference to a series of detailed experiments conducted on an Al-3%Mg solid solution alloy in which the grain size was successfully reduced by equal-channel angular pressing from an initial size of ˜500 μm in the hot-rolled condition to a final size of ˜0.2 μm.     

Immunosuppressant deoxyspergualin induces apoptotic cell death in dividing cells

Type 1 diabetes is associated with autoimmunity to insulin. Genetic susceptibility to type 1 diabetes is polygenic and includes the INS VNTR-IDDM2 locus which may regulate the expression of insulin in pancreas and thymus. In order to determine whether insulin autoimmunity could be attributed to a genetic susceptibility conferred by the INS VNTR-IDDM2 locus, peripheral blood T cell proliferation to human insulin and insulin autoantibodies (IAA) was measured in patients with new onset type 1 diabetes and control subjects. IAA were detected in 21 of 53 patients and in none of 25 control subjects, while T cell responses were low (stimulation index range 0.4-7.2) and similar in both groups. Both antibody and T cell responses were higher in younger subjects and IAA were more prevalent in patients with the HLA-DR4 allele. No relationship was observed between humoral and cellular responses to insulin. No association was found between the INS VNTR-IDDM2-susceptible allele and insulin autoimmunity. Increased T cell responses and IAA were found in patients with either the diabetes-susceptible or the diabetes-protective INS VNTR-IDDM2 locus genotypes, and increased T cell responses were also found in control subjects with either susceptible or protective INS VNTR-IDDM2 locus genotypes. This study confirms that primary T cell proliferative responses to insulin are low and detectable also in control subjects. The detection of T cell proliferation and autoantibodies to insulin in subjects with and without the protective INS VNTR-IDDM2 locus genotypes does not support the hypothesis of an allele-specific capacity for tolerance induction which could determine a susceptibility to develop autoimmunity against the insulin protein and subsequently diabetes.     

Structure and mechanical properties of a Fe90Zr10 amorphous alloy

The structure of a Fe₉₀Zr₁₀ amorphous alloy was investigated by means of small angle X-ray scattering as well as large-angle diffraction measurements. For as-quenched specimens, SAXS was found to be relatively weak, but spread over a wide scattering angle. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 0.6 nm. When the specimen was heat treated below the crystallization temperature, the amorphous structure changed to a more stable dual structure consisting of pure iron and a structure similar to Fe₃Zr. By prolonged heat treatment, the iron-rich regions crystallized initially from the amorphous state. An apparent correspondence was found to exist between the changes in the amorphous structure and in the mechanical properties. The microscopic phase separation within the amorphous state resulted in an increase of ultimate tensile strength and fracture toughness. The deterioration of mechanical properties was suggested to be attributed to the gradual crystallization of iron-rich regions.     

Ray matrix for Gaussian beam propagation in a nonlinear medium: experimental results

The validity of a ray-matrix formulation of Gaussian beam propagation in a liquid nonlinear medium exhibiting self-defocusing is examined experimentally. By comparing the measured spot size of a Gaussian laser beam passing through the medium with the calculated spot size, it was found that the theory is consistent with the experimental results as long as the waist position of the input beam is not close to the exit surface of the medium.     

Control of Bubble Size and Location in Nano‐/Microscale Cellular Poly(propylene)/Rubber Blend Foams

Plastic foam with nano‐/micro‐scale cellular structures was prepared from a poly(propylene) (PP)/propylene‐ethylene copolymer (PER) blend by controlling bubble nucleation sites and bubble growth in disperse PER domains. Batch foaming experiments using a CO₂ pressure quench method were conducted at room temperature. The bubble size and location were highly controlled in disperse PER domains by exploiting the differences in CO₂ solubility and viscoelasticity between the PER domains and the PP matrix. The average cell diameter of PP/PER blend foams can be controlled within 0.5–2 µm by the PP/PER ratio, depressurization rate, and foaming temperature.

     

Low-loss deflection prism for a laser beam with Brewster angle

A low-loss deflection prism for a laser beam is proposed, and its various characteristics such as beam quality, transmittance, deflection angle, and polarization state are presented. The prism having a trapezoidal form is made from BK7 glass and is designed for a He-Ne laser beam. When a p-polarized beam is incident on the slant surface of the prism at the Brewster angle, the totally reflected and transmitted beam is deflected by 90 degrees, and the measured transmittance is nearly 98%. The theoretical transmittances of the proposed prism are compared with those of a Pellin-Broca prism.