Gas-driven hydrogen permeation in the surface-limited regime

Gas-driven permeation of hydrogen through metal membranes in the surface-limited regime (SLR) is analyzed. An analytical solution for the concentration and permeation flux as a function of time is given for permeation through the asymmetric membrane having different conditions on the inlet and outlet sides. The features of the steady state and transient permeation are discussed. Comparison of calculations with an experiment on deuterium permeation through vanadium, which is available from literature, is performed. It has been demonstrated that the parameters, extracted from the measurements of the permeation rate in SLR are very uncertain. Even the calculations with opposite asymmetries can be equally well adjusted to the experiment. Non-zero initial conditions in SLR experiments are additional source of uncertainty. Measurements of the accumulation in a closed volume instead of the permeation rate can seriously mislead in the interpretation of the experiment. Complementary experiments on permeation in two opposite directions and measurements of permeation decay could increase the reliability of the data obtained.     

Current distribution in superconducting multistrands for ac use before and after quenching

A superconducting multistranded cable is used to realize high current capacity for ac use. The critical current value of the cable is reported to be less than the simple summation of the individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using seven-strand superconducting cable and 7x7 cable. The following experimental results are derived: (1) the quenching is initiated at one strand in the cable; (2) the current in the quenched strand is transferred into the other strands; (3) an avalanche of quenching is induced among the strands; and (4) the central strand is quenched finally among the strands. The critical current values of the 7- and 7 × 7-stranded cables also are measured. These values are in good agreement with the predicted values based on the mutual inductance among the strands. It is concluded that the unbalance of the current distribution in the superconducting multistrands can be one of the promising causes for the degradation of the critical current value.     

Opportunities for international collaboration in superconducting electronics

It is said that international collaborations in superconducting electronics have become particularly important to share research risks and resources. The present status of technologies, recent cooperative research activities, and some comments on future cooperations in superconducting electronics are described.     

The effect of pituitary adenylate cyclase activating polypeptide (PACAP) on amylase secretion from guinea pig pancreatic acini

Beta-lactamase production is one of the major mechanisms of resistance amongst bacteria especially the enteric bacilli. The purpose of this study is to assess the in-vitro activity of Sulperazon, a combination of cefoperazone and an irreversible beta-lactamase inhibitor, sulbactam, against the cefoperazone resistant isolates of aerobic gram-negative bacilli. A total of 92 such strains were tested. It was found that at a concentration of < or = 8 mg/l of sulbactam added to cefoperazone 82% of Klebsiella spp, 100% of E. coli, 100% of Enterobacter spp, 33% of Pseudomonas aeruginosa, 67% of Pseudomonas spp and 62% of Acinetobacter spp that were resistant to cefoperazone alone were susceptible to the combination. Hence it is concluded that the addition of sulbactam to cefoperazone does expand the spectrum of the in-vitro activity of cefoperazone.     

Partial discharge characteristics of inverter-fed motor coil samples under ac and surge voltage conditions

This work investigates the partial discharge (PD) characteristics of twisted pair samples for inverter-fed motor coil under ac and surge voltage conditions. It also discusses the difference in the PD inception characteristics of a twisted pair under 60-Hz voltage and surge voltages with a steep wave front. The PDIV under ac voltage was measured and was found to agree well with the theoretical value using electric field analysis and Paschen's law. The PDIV under surge voltage was measured for different repetition rates and the PDIV for 60-pps repetition was found to be lower than those for 6 pps and for the single shot, which suggested that the electrical insulation performance would be influenced by the repetition rate. The PDIV under surge voltages was 1.5 to 1.8 and 2.3 to 2.7 times higher than those under AC voltage application for the used and virgin samples, respectively.     

Superconducting digital electronics

Single-flux quantum logic (SFQ) circuits, in which a flux quantum is used as an information carrier, have the possibility for opening the door to a new digital system operated at over 100-GHz clock frequency at extremely low power dissipation. The SFQ logic system is a so-called pulse logic, which is completely different from the level logic for semiconductors like CMOS, so circuit design technologies for SFQ logic circuits have to be newly developed. Recently, much progress in basic technologies for designing SFQ circuits and operating circuits at high speeds has been made. With advances in these design tools, large-scale circuits including more than several thousand junctions can be easily operated with the clock frequency of more than several tens of gigahertz. High-end routers and high-end computers are possible applications of SFQ logic circuits because of their high throughput nature and the low power dissipation of SFQ logic. In this paper, recent advances of SFQ circuit design technologies and recent developments of switches for high-end routers and microprocessors for high-end computers that are considered possible applications for SFQ logic will be described.     

Measurement of erosion yields for a SiC surface on H+, D+ and Ar+ bombardment

Changes in the distribution of silicon solute in a 99.8% pure nickel crystal after 75 keV Ni⁺ ion bombardment at 16°C and 500°C, are reported. The concentration depth profiles were measured by simultaneous sputter-profiling and secondary ion mass spectrometry (SIMS). At 16°C the results are satisfactorily explained by the formation and subsequent migration to sinks of nickel interstitial-silicon complexes. The same mechanisms can be used to explain the results obtained at 500°C but the effect observed could also be due to the migration of vacancy-silicon complexes to sinks and the possibility that both mechanisms occur simultaneously cannot be ruled out.