The role of dispersed particles in strengthening and fracture mechanisms in a Mo-ZrC alloy processed by mechanical alloying

The tensile properties of a ZrC particle-dispersed Mo, which was processed by spark plasma sintering with mechanically alloyed powder, were investigated at room temperature and at elevated temperatures of 1170 to 1970 K. The Mo-ZrC alloy showed much higher strength at room temperature than a fully recrystallized pure Mo. The high strength of Mo-ZrC is mainly attributed to a very small grain size (about 3 μm). The main role of the ZrC particle is not to increase strength due to the particle-dislocation interaction, but to limit grain growth during sintering and to attain the very small grain size. The elongation at room temperature of Mo-ZrC was much lower than that of pure Mo. This is probably related to the higher interstitial contents. However, Mo-ZrC showed a large elongation of 180 pct at 1970 K and 6.7×10⁻⁴ s⁻¹. It was suggested that the ZrC particles stabilized the fine-grained microstructure yet provided no cavitation sites at 1970 K; as a result, the large elongation was attained.     

The soluble N-ethylmaleimide-sensitive factor attached protein receptor complex in growth cones: molecular aspects of the axon terminal development

Soluble N-ethylmaleimide-sensitive factor attached protein (SNAP) receptor (SNARE) mechanisms are thought to be involved in two important processes in axonal growth cones: (1) membrane expansion for axonal growth and (2) vesicular membrane fusion for mature synaptic transmission. We investigated the localization and interactions among the proteins involved in SNARE complex formation in isolated growth cone particles (GCP) from forebrain. We demonstrated that the SNARE complex is present in GCPs morphologically without synaptic vesicles (SVs) and associated with growth cone vesicles. However, the apparently SV-free GCP was lacking in the regulatory mechanisms inhibiting SNARE complex formation proposed in SV fusion, i.e., the association of synaptotagmin with the SNARE complex, and vesicle-associated membrane protein (VAMP)-synaptophysin complex formation. The core components of the SNARE complex (syntaxin, SNAP-25, and VAMP) accumulated for several days before postnatal day 7, when SVs first appeared, and preceded the accumulation of marker proteins such as synaptophysin, SV2, and V-ATPase. Our present results suggest that the SNARE mechanism for vesicular transmitter release is not fully functional in growth cones before the appearance of SVs, but the SNARE mechanism is working for membrane expansion in growth cones, which supports our recent report. We concluded that the regulation of the SNARE complex in growth cones is different from that in mature presynaptic terminals and that this switching may be one of the key steps in development from the growth cone to the presynaptic terminal.     

Effect of annealing on d.c. conductivity of V2O5-SnO-TeO2 glasses

The d.c. conductivity (σ) of V₂O₅-SnO-TeO₂ glasses prepared by the press-quenching method was studied at temperatures from room temperature (RT) to 473 K, and the effect of annealing on σ was investigated. The conductivity of 50V₂O₅·20SnO·30TeO₂ glass was determined to be 3.98×10⁻⁴ Scm⁻¹ at 473 K and was unchanged for annealing (6–48 h) at 493 K, lower than T_g = 501 K, while its density increased with annealing time. These glasses were found to be n-type semiconductors, and the conduction was confirmed to be due to adiabatic small polaron hopping for V₂O₅ ≧ 50 mol%, and non-adiabatic for V₂O₅ < 50 mol%. The activation energy for conduction, W, decreased with annealing time. Variations in oxygen molar volume of the glasses with annealing time inferred a change in glass structure, from loosely to closely packed, resulting in a decrease in vanadium ion spacing with annealing. This caused an increase in the polaron band width, producing a decrease in polaron hopping energy and W. The effect of annealing time on the density of 50V₂O₅·20SnO·30TeO₂ glass was explained adequately by Winter's formula.     

Evaluation of the Fatigue Characteristics of Laser-processed Hot Work Tool Steel Based on Reliability

It is reported that laser-processing is effective to repair the heat checks, which are fine shallow cracks on a surfaceof die-casting dies.     

Preparation of yttrium-90-labeled human macroaggregated albumin for regional radiotherapy

Helicobacter pylori and non-steroidal anti-inflammatory drugs are two of the most common causes of peptic ulceration. The aim of this review is to assess the possible inter-relationships between Helicobacter pylori and non-steroidal anti-inflammatory drugs in the pathogenesis of gastric and duodenal erosions and ulcers, with the aim of assessing if the presence of Helicobacter pylori is likely to increase the likelihood of non-steroidal anti-inflammatory drug-related gastroduodenal symptoms and lesions, and if eradication of Helicobacter pylori may reduce or prevent non-steroidal anti-inflammatory drug lesions. There appears to be more likelihood of dyspeptic symptoms in patients on long-term non-steroidal anti-inflammatory drugs when Helicobacter pylori is present. The balance of evidence also suggests that peptic ulcers and erosions in patients on long-term non-steroidal anti-inflammatory drugs may be more likely to occur in patients who are Helicobacter pylori positive compared to those who are Helicobacter pylori negative. Although Helicobacter pylori and non-steroidal anti-inflammatory drugs both increase the risk of peptic ulcer bleeding, the risk does not appear to be additive. There is increasing evidence from prospective studies that eradication of Helicobacter pylori may reduce the incidence of ulcers in patients on non-steroidal anti-inflammatory drugs. More prospective long-term studies are required. If Helicobacter pylori is confirmed to be a factor in this respect, it will aid in the targeting of patients at greatest risk of developing ulcers in patients on long-term non-steroidal anti-inflammatory drugs. Those at greatest risk are elderly patients, especially females, smokers, patients with a previous ulcer history, severe or debilitating arthritis or who have other chronic diseases. The addition of Helicobacter pylori to this list and its subsequent eradication may improve the outlook for these patients and help in the effective targeting of patients at greatest risk who are on long-term non-steroidal anti-inflammatory drugs.