High-repetition rate sealed-off pseudospark switches for pulsedmodulators

Experimental results of high-repetition-rate pseudospark switch testing are reported. Typical test parameters are hold-off voltage of about 20 kV, peak currents on the order of 10 kA, and pulse durations between 50 and 100 ns. The discharge circuit, with discrete ceramic capacitors up to 10.8 nF total, produced a ringing discharge with peak currents on the order of 10 kA. Current reversal under these conditions was up to 80% of the peak current. A sealed-off, ceramic-metal pseudospark switch with integral deuterium reservoir tested in this setup achieved repetition rates of up to 1.8 kHz without latching or triggering failures. Some 10⁷ shots have been performed without degradation of the switch performance     

HPLC-PDA detection of cylindrospermopsin--opportunities and limits

The cyanobacterial hepatotoxic alkaloid cylindrospermopsin (CYL) is of increased concern to public health due to the spreading of its main producer, Cylindrospermopsis raciborskii, around the globe. Here we present results of an evaluation of the possibility to analyse environmental samples for their content of CYL based on HPLC with photo diode array detection as an alternative to costly LC-MS approaches. A gradient from 0% to 50% aqueous methanol (+0.05% trifluoroacetic acid) in 20 min proved to be highly reproducible with respect to peak height, peak area, and retention time of purified CYL. Good linearity of peak area response was found for 1-300 ng CYL on column. For a good performance the duration of equilibration prior to individual runs was crucial. Extraction from cell material (culture and bloom) was efficiently done with pure water in one extraction step and CYL contents determined matched well with results previously obtained by LC-MS. When different seston matrices were added to cultured cells to mimic realistic environmental samples, however, peaks eluting close to CYL in chromatograms restrained the performance. The data presented show a limitation of HPLC-PDA analysis for trace amounts of CYL in environmental samples but also underline the potential of an inexpensive and fast analysis for various purposes.     

Industrial scale production of hydrogen from natural gas,naphtha and coal

This paper reviews the three major routes for the production of hydrogen from fossil fuels.Today there is considerable interest in the production of hydrogen via the gasification of coal. Existing processes and developments are listed.The partial oxidation processes which utilize feedstocks ranging from light hydrocarbons to heavy fuel oil are attractive due to feedstock flexibility.Hydrogen production based on the steam reforming of light hydrocarbons has become the most widely used process as a result of, in general, better economics.     

Tribology of SiC/SiC Ceramic Matrix Composites in Liquid Oxygen in Relation to the Design of Hydrostatic Bearings

This paper reports on the characterisation of ceramic matrix composites (CMCs) for bearing applications in liquid oxygen (LOX). Compatibility tests were performed to determine the safety and feasibility of subsequent research operations. Tribological tests were then made on a pin‐on‐disc apparatus using LOX as the working environment. The measurement of friction and wear allowed a comparison between different kinds of CMCs and 440C steel materials. As a logical progression a real geometry test rig is now being built. The design of a hybrid journal bearing has been finished and the manufacturing of the rig components started.     

Hypothetical intertemporal choice and real economic behavior: Delay discounting predicts voucher redemptions during contingency-management procedures.

Delay discounting rates are predictive of drug use status, the likelihood of becoming abstinent, and a variety of health behaviors. Rates of delay discounting may also be related to other relevant behaviors associated with addiction, such as the frequency at which individuals redeem contingency management voucher earnings. This study examined the discounting rates of 152 participants in a buprenorphine treatment program for opioid abuse. Participants received up to 12 weeks of buprenorphine treatment combined with contingency management. Participant's drug use was measured via urine specimens submitted three times a week. Successive negative urine specimens were reinforced with increasing amounts of money. After each negative urine specimen, a participant could either redeem his or her earnings or accumulate it in an account. Analysis of the frequency of redemptions showed that participants with higher rates of delay discounting at study intake redeemed their earnings significantly more often than participants with lower rates of discounting. Age and income also predicted redemption rates. We suggest that delay discounting rates can be used to predict redemption behaviors in a contingency management treatment program and that these findings are consistent with the recent theory of the competing neurobehavioral decision systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Innervation territories of single sympathetic C fibers in human skin

Microneurography techniques were used to record action potentials from unmyelinated nerve fibers (C fibers) in the cutaneous fascicles of the peroneal nerve in healthy volunteers. C units were identified by their long latency responses to electrical stimulation of their terminals in the skin. Their responsiveness to mechanical or heat stimuli applied to the skin or to sympathetic reflex provocation tests was determined by transient slowing of conduction velocity following activation (marking technique). In a sample of 381 C units, 59 were unresponsive to mechanical and thermal stimulation of their endings, but responded to sympathetic reflex provocation tests, e.g., arousal or deep inspiration. They were classified as sympathetic efferent units. On average, conduction velocities of sympathetic units were lower (0.78 +/- 0.12 m/s, mean +/- SD) than those of mechano-heat (CMH) or mechanoresponsive (CM) afferent C units (0.91 +/- 0.14 m/s). Endings of most of the sympathetic units were located in the skin of toes or in the foot dorsum. Innervation territories of 16 sympathetic units were mapped by means of conditioning transcutaneous electrical stimuli. Twelve units had one continuous skin territory, whereas two units had two and two other units had three and five separate territories, respectively. The mean innervated area was 128 mm2 (range: 24-350 mm2). Innervation territories of sympathetic units were of approximately the same size in different skin regions on the lower leg, foot, or toes. Based on responses to whole body cooling and warming, two units were tentatively classified as vasoconstrictor and sudomotor units, respectively. Eleven units were tested for responsiveness to iontophoresis of acetylcholine in their innervation territories. In five of them, activity was induced that was not due to central reflex activity but instead due to antidromic activation from the peripheral terminals. Iontophoresis of saline or histamine was ineffective. These findings confirm the existence of excitatory cholinergic receptors in the terminal membrane of some sympathetic units, possibly sudomotors.     

Maintenance of sister-chromatid cohesion at the centromere by the Drosophila MEI-S332 protein

Sister-chromatid cohesion is essential for the faithful segregation of chromosomes during cell division. Recently biochemical analysis with Xenopus extracts suggests that cohesion is established during S phase by a cohesion complex but that other proteins must maintain it in mitosis. The Drosophila melanogaster MEI-S332 protein is present on centromeres in mitosis and meiosis and is essential for cohesion at the centromeres in meiosis II. Here, we analyze the timing of MEI-S332 assembly onto centromeres and the functional domains of the MEI-S332 protein. We find that MEI-S332 is first detectable on chromosomes during prometaphase, and this localization is independent of microtubules. MEI-S332 contains two separable functional domains, as mutations within these domains show intragenic complementation. The carboxy-terminal basic region is required for chromosomal localization. The amino-terminal coiled-coil domain may facilitate protein-protein interactions between MEI-S332 and male meiotic proteins. MEI-S332 interacts with itself in the yeast two-hybrid assay and in immunoprecipitates from Drosophila oocyte and embryo extracts. Thus it appears that MEI-S332 assembles into a multimeric protein complex that localizes to centromeric regions during prometaphase and is required for the maintenance of sister-chromatid cohesion until anaphase, rather than its establishment in S phase.