Asymmetric injection of cathodic arc plasma into a macroparticle filter

The cathodic arc plasmas produced by cathode spots usually include macroparticles, which is undesirable for many applications. A common way of removing macroparticles is to use curved solenoid filters which guide the plasma from the source to the substrate. In this work, an arc source with relatively small cathode is used, limiting the possible locations of plasma production. The relative position of cathodic arc source and macroparticle filtered was systematically varied and the filtered plasma current was recorded. It was found that axis-symmetric plasma injection leads to maximum throughput only if an anode aperture was used, which limited the plasma to near-axis flow by scraping off plasma at larger angles to the axis. When the anode aperture was removed, more plasma could enter the filter. In this case, maximum filtered ion current was achieved when the plasma was injected off-axis, namely offset in the direction where the filter is curved. Such behavior was anticipated because the plasma column in the filter is known to be shifted by ExB and centrifugal drift as well as by non-axis-symmetric components of the magnetic field in the filter entrance and exit plane. The data have implications for plasma transport variations caused by different spot locations on cathodes that are not small compared to the filter cross section

Hybrid gas-metal co-implantation with a modified vacuum arc ion source

Energetic beams of mixed metal and gaseous ion species can be generated with a vacuum arc ion source by adding gas to the arc discharge region. This could be an important tool for ion implantation research by providing a method for forming buried layers of mixed composition such as e.g. metal oxides and nitrides. In work to date, we have formed a number of mixed metal-gas ion beams including Ti+N, Pt+N, Al+O, and Zr+O. The particle current fractions of the metal-gas ion components in the beam ranged from 100% metallic to about 80% gaseous, depending on operational parameters. We have used this new variant of the vacuum arc ion source to carry out some exploratory studies of the effect of Al+O and Zr+O co-implantation on tribology of stainless steel. Here we describe the ion source modifications, species and charge state of the hybrid beams produced, and results of preliminary studies of surface modification of stainless steel by co-implantation of mixed Al/O or Zr/O ion beams. 5 figs, 21 refs

Monitoring international migration flows in Europe. Towards a statistical data base combining data from different sources

The paper reviews techniques developed in demography, geography and statistics that are useful for bridging the gap between available data on international migration flows and the information required for policy making and research. The basic idea of the paper is as follows: to establish a coherent and consistent data base that contains sufficiently detailed, up-to-date and accurate information, data from several sources should be combined. That raises issues of definition and measurement, and of how to combine data from different origins properly. The issues may be tackled more easily if the statistics that are being compiled are viewed as different outcomes or manifestations of underlying stochastic processes governing migration. The link between the processes and their outcomes is described by models, the parameters of which must be estimated from the available data. That may be done within the context of socio-demographic accounting. The paper discusses the experience of the U.S. Bureau of the Census in combining migration data from several sources. It also summarizes the many efforts in Europe to establish a coherent and consistent data base on international migration. The paper was written at IIASA. It is part of the Migration Estimation Study, which is a collaborative IIASA-University of Groningen project, funded by the Netherlands Organization for Scientific Research (NWO). The project aims at developing techniques to obtain improved estimates of international migration flows by country of origin and country of destination

A Sensitive High-Throughput Assay for Evaluating Host-Pathogen Interactions in Cryptococcus neoformans Infection

Background: Cryptococcus neoformans causes serious disease in immunocompromised individuals, leading to over 600,000 deaths per year worldwide. Part of this impact is due to the organism’s ability to thwart what should be the mammalian hosts ’ first line of defense against cryptococcal infection: internalization by macrophages. Even when C. neoformans is engulfed by host phagocytes, it can survive and replicate within them rather than being destroyed; this ability is central in cryptococcal virulence. It is therefore critical to elucidate the interactions of this facultative intracellular pathogen with phagocytic cells of its mammalian host. Methodology/Principal Findings: To accurately assess initial interactions between human phagocytic cells and fungi, we have developed a method using high-throughput microscopy to efficiently distinguish adherent and engulfed cryptococci and quantitate each population. This method offers significant advantages over currently available means of assaying hostfungal cell interactions, and remains statistically robust when implemented in an automated fashion appropriate for screening. It was used to demonstrate the sensitivity of human phagocytes to subtle changes in the cryptococcal capsule, a major virulence factor of this pathogen. Conclusions/Significance: Our high-throughput method for characterizing interactions between C. neoformans and mammalian phagocytic cells offers a powerful tool for elucidating the relationship between these cell types durin

Modelling And Simulation Of The Operational Impacts And Value Of Distributed Renewable Resources In Electric Power Systems

Distributed renewable resources are, together with other novel decentralised power technologies, likely to play an increasingly important role in electric power systems. There are however, a number of operational issues that need addressing before their widespread use. These resources can have variable and somewhat unpredictable power outputs, while the presence of numerous small, and probably independently owned, plants distributed throughout the network has important implications for overall system coordination. This paper outlines the development of an object oriented software modelling and simulation tool for exploring power system operation with distributed resources. Initial studies with the tool have focussed on price-induced coordination and storage optimisation. INTRODUCTION Distributed resources are likely to play an increasingly important role in electric power systems. They include: . renewable energy from photovoltaics, solar thermal, wind, small hydro and biomass, . nov..

Optimised operation of electrical distribution systems with PV and storage using evolutionary programming

Distributed electrical resources seem likely to play an increasingly important role in power systems. This paper presents a novel approach for optimising energy storage operation in electric distribution systems with renewable energy sources. Initial studies presented here indicate that evolutionary programming can determine near optimal solutions for simple power system problems with a single energy storage. This evolutionary approach appears to offer important advantages over conventional techniques for exploring decentralised coordination of power system operation when there are high levels of distributed resources. Introduction Distributed electrical resources are increasingly cost effective as well as environmentally less damaging alternatives to conventional large-scale power generation. These resources include: . renewable energy from photovoltaics, solar thermal, wind, small hydro and biomass, . novel fossil fuelled generation including gas turbines and fuel cells, . energ..