OH masers in the Milky Way and Local Group galaxies in the SKA era

The intense line emission of OH masers is a perfect tracer of regions where new stars are born aswell as of evolved stars, shedding large amounts of processed matter into the interstellar medium. From SKA deep surveys at 18 cm, where the maser lines from the ground-state of the OH molecule arise, we predict the discovery of more than 20000 sources of stellar and interstellar origin throughout the Galaxy. The study of this maser emission has many applications, including the determination of magnetic field strengths from polarisation measurements, studies of stellar kinematics using the precisely determined radial velocities, and distance determinations from VLBI astrometry. A new opportunity to study shocked gas in different galactic environments is expected to arise with the detection of lower luminosity masers. For the first time, larger numbers of OH masers will be detected in Local Group galaxies. New insights are expected in structure formation in galaxies by comparing maser populations in galaxies of different metallicity, as both their properties as well as their numbers depend on it. With the full capabilities of SKA, further maser transitions such as from excited OH and from methanol will be accessible, providing new tools to study the evolution of star-forming regions in particular.Comment: Contribution to the conference on "Advancing Astrophysics with the Square Kilometre Array" for the SKA science book, Giardini-Naxos, Sicily, June 2014; in Proceedings of Science, 14 page

The Case for UBUNTU Linux Operating System Performance and Usability for Use in Higher Education in a Virtualized Environment

The use of Linux based Operating Systems (OS) in the classroom is increasing, but there is little research to address usability differences between Windows and Linux based OSs. Moreover, studies related to the ability for students to navigate effectively between Ubuntu 14.04 Long Term Support (LTS) and Windows 8 OSs are scant. This research aims to bridge the gap between modern Linux and Windows Oss, as the former represents a viable alternative to eliminate licensing costs for educational institutions. Preliminary findings, based on the analysis of the System Usability Scale results from a sample of 14 students, demonstrated that Ubuntu users did not require technical support to use the system, while the majority found little inconsistency in the system and regarded it as well integrated

An investigation into the use of additive manufacture for the production of metallic bipolar plates for polymer electrolyte fuel cell stacks

The bipolar plate is of critical importance to the efficient and long lasting operation of a polymer electrolyte fuel cell (PEMFC) stack. With advances in membrane electrode assembly design, greater attention has been focused on the bipolar plate and the important role it plays. Although carbon composite plates are a likely candidate for the mass introduction of fuel cells, it is metallic plates made from thin strip materials which could deliver significant advantages in terms of part cost, electrical performance and size. However, there are some disadvantages. Firstly, interfacial stability of the metal interconnect is difficult to achieve. Secondly, and the issue addressed here, is the difficultly and cost in developing new plate designs when there are very significant tooling costs associated with manufacture. The use of selective laser melting (SLM: an additive manufacturing technique) was explored to produce metallic bipolar plates for PEMFC as a route to inexpensively test several plate designs without committing to tooling. Crucial to this was proving that, electrically, bipolar plates fabricated by SLM behave similarly to those produced by conventional manufacturing techniques. This research presents the development of a small stack to compare the short term performance of metallic plates made by machining against those made by SLM. Experimental results demonstrate that the cell performance in this case was unaffected by the manufacturing method used and it is therefore concluded that additive manufacturing could be a very useful tool to aid the rapid development of metallic bipolar plate designs

The use of additive manufacture for metallic bipolar plates in polymer electrolyte fuel cell stacks

The bipolar plate is of critical importance to the efficient and long lasting operation of a polymer electrolyte fuel cell (PEMFC) stack. With advances in membrane electrode assembly (MEA) design greater attention has been focused on the bipolar plate and the important role it plays in performance and durability. Although carbon composite plates are a likely candidate for the mass introduction of fuel cells, it is metallic plates made from thin strip materials (typically 0.2 mm thick stainless strip) which could deliver significant advantages in terms of part cost, electrical performance and size. However, there are some disadvantages. Firstly, interfacial stability of the metal interconnect is difficult to achieve leading to migration of ions into the MEA and also an increase in contact resistance. Secondly, and the issue addressed here, is the difficultly and cost in developing new plate designs when there are very significant tooling costs associated with manufacture. The use of selective laser melting (SLM: an additive manufacturing technique) was explored to produce metallic bipolar plates for PEMFC as a route to inexpensively test several plate designs without committing to tooling. Crucial to this was proving that, electrically, bipolar plates fabricated by SLM behave similarly to those produced by conventional manufacturing techniques. This research presents the development of a small stack to compare the short term performance of metallic (316L stainless steel) plates made by machining against those made by SLM. Polarisation curves and impedance experiments were conducted. These demonstrate that the cell performance was unaffected by the manufacturing method used and that the pure resistive content of the impedance spectra, a proportion of which could be attributed to contact resistance between the MEA and plate, was very similar. It is concluded that additive manufacturing could be a very useful tool to aid the rapid development of metallic bipolar plate designs. However, when making direct comparisons with very space efficient designs, some challenges exist in the generation of very thin planar forms which would be most representative of sheet metal parts

Low-Cost, Minimum-Size Satellites for Demonstration of Formation Flying Modes at Small, Kilometer-Size Distances

In-flight demonstration of close-range formation flying modes is discussed with emphasis on low cost, based on spacecraft design simplicity and minimum size, and hence minimum launch cost. Piggy-back launch of three identical demonstration spacecraft is the preferred option. This demonstration includes comprehensive collection and analysis, on the ground, of relative motion data derived from GPS signals that are received by the participating satellites. In addition to realistically reflecting the known Keplerian and non-Keplerian characteristics as part of the flight dynamics analysis, an important concern is to demonstrate the less well-known effects of differential drag perturbations. These can be deliberately induced by small aerodynamic cross section variations on the satellites. Results of the demonstration mission will benefit currently projected and other future missions that require close-formation flying, e.g., radar and visual observation missions, by proving feasibility, assisting detailed and comprehensive operations planning, and helping diminish their potential risks

Effect of GTP and Ca2+ on inositol 1,4,5-trisphosphate induced Ca2+ release from permeabilized rat exocrine pancreatic acinar cells

The effects of Ca2+ and GTP on the release of Ca2+ from the inositol 1,4,5-trisphosphate (IP3) sensitive Ca2+ compartment were investigated with digitonin permeabilized rat pancreatic acinar cells. The amount of Ca2+ released due to IP3 directly correlated with the amount of stored Ca2+ and was found to be inversely proportional to the medium free Ca2+ concentration. Ca2+ release induced by 0.18 μM IP3 was half maximally inhibited at 0.5 μM free Ca2+, i.e. at concentrations observed in the cytosol of pancreatic acinar cells. GTP did not cause Ca2+ release on its own, but a single addition of GTP (20 μM) abolished the apparent desensitization of the Ca2+ release which was observed during repeated IP3 applications. This effect of GTP was reversible. GTPγS could not replace GTP. Desensitization still occurred when GTPγS was added prior to GTP. The reported data indicate that GTP, stored Ca2+ and cytosolic free Ca2+ modulate the IP3 induced Ca2+ release. EGTA, Ethylene-glycol-bis (2-aminoethylether)-N,N,N′,N′- tetra acetic acid; GTPγS, Guanosine 5′-O-[3-thio]triphosphate; GDPβS, Guanosine 5′-O-[2-thio]diphosphate; IP3, Inositol 1,4,5-trisphosphate; IP2, Inositol 1,4-bisphosphate; IP4, Inositol 1,3,4,5-tetrakisphosphate; MOPS, Morpholinopropane sulfonic acid; HEPES, 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid; pHMB, Parahydroxymercuribenzoat

RQF publication quality measures: methodoligical issues

The Research Quality Framework uses Thomson-ISI citation benchmarks as its main set of objective measures of research quality. The Thomson-ISI measures rely on identifying a core set of journals in which the major publications for a discipline are to be found. The core for a discipline is determined by applying a nontransparent process that is partly based on Bradford&rsquo;s Law (1934). Yet Bradford was not seeking measures about quality of publications or journals. How valid then is it to base measures of publication quality on Bradford&rsquo;s Law? We explore this by returning to Bradford&rsquo;s Law and subsequent related research asking &lsquo;what is Bradford&rsquo;s Law really about?&rsquo; We go further, and ask &lsquo;does Bradford&rsquo;s Law apply in Information Systems?&rsquo; We use data from John Lamp&rsquo;s internationally respected Index of Information Systems Journals to explore the latter question. We have found that Information Systems may have a core of journals only a subset of which is also in the list of Thomson-ISI journals. There remain many unanswered questions about the RQF metrics based on Thomson-ISI and their applicability to information systems.<br /