Factors affecting the operation of laser-triggered gas switch (LTGS) with multi-electrode spark gap

Multi-electrode spark switches can be used for switching applications at elevated voltages or for command triggering. Symmetrical field graded electrodes allow the electrical stress across individual gaps to be controlled, thus maximising the hold off voltage and reducing switch pre-fire. The paper considers some aspects of multielectrode switch design and their influence on switching behavior. Non-symmetrical, uni-directional electrode topologies can be employed with advantages over traditional symmetrical design. The choice of working gas and gas pressure can influence switching performance in terms of delay-time and jitter. Transient analysis of switch characteristics has been undertaken in order to understand multi-electrode switching

Categories of insight and their correlates: An exploration of relationships among classic-type insight problems, rebus puzzles, remote associates and esoteric analogies.

A central question in creativity concerns how insightful ideas emerge. Anecdotal examples of insightful scientific and technical discoveries include Goodyear's discovery of the vulcanization of rubber, and Mendeleev's realization that there may be gaps as he tried to arrange the elements into the Periodic Table. Although most people would regard these discoveries as insightful, cognitive psychologists have had difficulty in agreeing on whether such ideas resulted from insights or from conventional problem solving processes. One area of wide agreement among psychologists is that insight involves a process of restructuring. If this view is correct, then understanding insight and its role in problem solving will depend on a better understanding of restructuring and the characteristics that describe it. This article proposes and tests a preliminary classification of insight problems based on several restructuring characteristics: the need to redefine spatial assumptions, the need to change defined forms, the degree of misdirection involved, the difficulty in visualizing a possible solution, the number of restructuring sequences in the problem, and the requirement for figure-ground type reversals. A second purpose of the study was to compare performance on classic spatial insight problems with two types of verbal tests that may be related to insight, the Remote Associates Test (RAT), and rebus puzzles. In doing so, we report on the results of a survey of 172 business students at the University of Waikato in New Zealand who completed classic-type insight, RAT and rebus problems

Gold(I)-Catalysed Direct Thioetherifications Using Allylic Alcohols: an Experimental and Computational Study

A gold(I)-catalysed direct thioetherification reaction between allylic alcohols and thiols is presented. The reaction is generally highly regioselective (S(N)2′). This dehydrative allylation procedure is very mild and atom economical, producing only water as the by-product and avoiding any unnecessary waste/steps associated with installing a leaving or activating group on the substrate. Computational studies are presented to gain insight into the mechanism of the reaction. Calculations indicate that the regioselectivity is under equilibrium control and is ultimately dictated by the thermodynamic stability of the products

The training of healthcare professionals: An expense or an investment?

Background. There is little information on the financial return of investment when funding the tertiary education of healthcare professionals (HCPs) in South Africa (SA).Objectives. To assess the cost-benefit of the Umthombo Youth Development Foundation (UYDF) scholarship scheme, which has supported the training of HCPs from rural areas in KwaZulu-Natal Province, SA, for the past 19 years, and to establish whether it is a worthwhile investment.Methods. This was an economic analysis to estimate the costs and economic value of UYDF’s investment in the training of HCPs, using a deterministic model developed in Excel 2010 (Microsoft, USA) to analyse the UYDF’s historical, numerical and economic data. Costs were measured in monetary terms, and a rate of return on investment was calculated over the working life of HCPs who had been supported by the UYDF.Results. With a >90% pass rate, the total cost of training the 254 graduates supported by the UYDF from 2009 to 2015 was estimated to be ZAR186 million. Graduates are expected to generate an estimated ZAR15 billion in lifetime earnings, which is equal to ZAR4 billion at 2015 prices, and represents an internal rate of return of 63%. Income tax paid on future earnings will be ~ZAR4 billion, assuming a 20 - 30% tax rate.Conclusions. The analysis has shown that the cost of HCPs’ education, where the annual pass rate is >90%, and >98% of graduates are employed, is an excellent investment. Consideration should be given to finding ways of improving the pass rate at institutions of higher learning and ensuring that graduates obtain meaningful employment if such returns on investment are to be seen on a national level

ALMA Measurements of Circumstellar Material in the GQ Lup System

We present ALMA observations of the GQ Lup system, a young Sun-like star with a substellar mass companion in a wide-separation orbit. These observations of 870 $\mu$m continuum and CO J=3-2 line emission with beam size $\sim0.3''$ ($\sim45$ AU) resolve the disk of dust and gas surrounding the primary star, GQ Lup A, and provide deep limits on any circumplanetary disk surrounding the companion, GQ Lup b. The circumprimary dust disk is compact with a FWHM of $59\pm12$ AU, while the gas has a larger extent with a characteristic radius of $46.5\pm1.8$ AU. By forward-modeling the velocity field of the circumprimary disk based on the CO emission, we constrain the mass of GQ Lup A to be $M_* = (1.03\pm0.05)*(d/156\text{ pc})$ $M_\odot$, where $d$ is a known distance, and determine that we view the disk at an inclination angle of $60.5^\circ\pm0.5^\circ$ and a position angle of $346^\circ \pm1^\circ$. The $3\sigma$ upper limit on the 870 $\mu$m flux density of any circumplanetary disk associated with GQ Lup b of $<0.15$ mJy implies an upper limit on the dust disk mass of $<0.04$ $M_\oplus$ for standard assumptions about optically thin emission. We discuss proposed mechanisms for the formation of wide-separation substellar companions given the non-detection of circumplanetary disks around GQ Lup b and other similar systems.Comment: 11 pages, 4 figure

The potential for dietary factors to prevent or treat osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease-modifying drugs. It is a leading cause of disability in the UK. Increasing age and obesity are both major risk factors for OA and the health and economic burden of this disease will increase in the future. Focusing on compounds from the habitual diet that may prevent the onset or slow the progression of OA is a strategy that has been under-investigated to date. An approach that relies on dietary modification is clearly attractive in terms of risk/benefit and more likely to be implementable at the population level. However, before undertaking a full clinical trial to examine potential efficacy, detailed molecular studies are required in order to optimise the design. This review focuses on potential dietary factors that may reduce the risk or progression of OA, including micronutrients, fatty acids, flavonoids and other phytochemicals. It therefore ignores data coming from classical inflammatory arthritides and nutraceuticals such as glucosamine and chondroitin. In conclusion, diet offers a route by which the health of the joint can be protected and OA incidence or progression decreased. In a chronic disease, with risk factors increasing in the population and with no pharmaceutical cure, an understanding of this will be crucial

Pulsed ultraviolet light decontamination of artificially-generated microbiological aerosols

Airborne transmission of infectious organisms is a major public health concern, particularly within healthcare and communal public environments. Methods of environmental decontamination utilising pulsed ultraviolet (UV) light are currently available, however it is important that germicidal efficacy against airborne contamination is established. In this study bacterial aerosols were generated and exposed to short duration pulses (~20 µs) of UV-rich light emitted from a xenon-filled flashlamp. The lamp was operated using a 1 kV solid–state pulsed power source, with a pulse frequency of 1 Hz, and output energy of 20 J/pulse. Post-treatment, air samples were extracted from the chamber and the surviving fraction was enumerated using standard microbiological culture methods. Results demonstrate successful aerosol inactivation, with a 92.1% reduction achieved with only 5 pulses of UV-rich light (P=<0.0002). Inactivation using continuous UV light was also investigated in order to quantify the comparative efficacy of these antimicrobial light sources. Overall, results provide evidence of the comparative efficacy of pulsed and continuous UV light for inactivation of airborne bacterial contamination. For practical application, given the safety restrictions limiting its application for decontamination of unoccupied environments, or within sealed enclosures such as air handling units, the reduced treatment times with PUV provides significant operational advantages over continuous light treatment