Entropy Evolution of the Gas in Cooling Flow Clusters

We emphasise the importance of the gas entropy in studying the evolution of cluster gas evolving under the influence of radiative cooling. On this basis, we develop an analytical model for this evolution. We then show that the assumptions needed for such a model are consistent with a numerical solution of the same equations. We postulate that the passive cooling phase ends when the central gas temperature falls to very low values. It follows a phase during which an unspecified mechanism heats the cluster gas. We show that in such a scenario the small number of clusters containing gas with temperatures below about 1 keV is simply a consequence of the radiative cooling.Comment: Contribution to Proceedings of `The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies', Charlottesville, VA, USA. May 31 -- June 4, 2003. Editors: Reiprich, T. H., Kempner, J. C., and Soker, N. Requires included style fil

Elastic Reciprocity and Symmetry Constraints on the Stress Field Due to a Surface-Parallel Distribution of Dislocations

Elastic reciprocity and geometric symmetry are used to constrain the expressions for stresses due to introduction of line dislocations near a half-space surface. Specifically, a relationship is shown to exist between the changes induced by dislocations of orthogonal Burgers vectors (normal and parallel to the free surface). These results are used to address inconsistencies of solutions in the literature.Earth and Planetary SciencesEngineering and Applied Science

A critical assessment of different transmethylation procedures commonly employed in the fatty acid analysis of aquatic organisms

Several transmethylation procedures have been used for fatty acid analysis of aquatic organisms although the suitability of the applied procedures has rarely been tested. The aim of this study was to demonstrate how different derivatization procedures can affect the result of fatty acid analysis. Different transmethylation procedures based on the acidic catalysts boron trifluoride, concentrated sulphuric acid and anhydrous hydrochloric acid were applied to cold-pressed copepod oil and Atlantic salmon flesh lipids rich in wax esters and triacylglycerols, respectively. The results show that 1) the use of unsuitable catalysts and/or incubation conditions may influence the data obtained which can lead to inaccurate conclusions about the presence of fatty acids in aquatic organisms/ecosystems 2) different derivatization procedures based on the same catalyst can produce diverging results and 3) the efficiency of a selected catalyst/procedure should be verified (e.g. by thin-layer chromatography) to ensure the complete transmethylation of fatty acids

Experimental Design for the Gemini Planet Imager

The Gemini Planet Imager (GPI) is a high performance adaptive optics system being designed and built for the Gemini Observatory. GPI is optimized for high contrast imaging, combining precise and accurate wavefront control, diffraction suppression, and a speckle-suppressing science camera with integral field and polarimetry capabilities. The primary science goal for GPI is the direct detection and characterization of young, Jovian-mass exoplanets. For plausible assumptions about the distribution of gas giant properties at large semi-major axes, GPI will be capable of detecting more than 10% of gas giants more massive than 0.5 M_J around stars younger than 100 Myr and nearer than 75 parsecs. For systems younger than 1 Gyr, gas giants more massive than 8 M_J and with semi-major axes greater than 15 AU are detected with completeness greater than 50%. A survey targeting young stars in the solar neighborhood will help determine the formation mechanism of gas giant planets by studying them at ages where planet brightness depends upon formation mechanism. Such a survey will also be sensitive to planets at semi-major axes comparable to the gas giants in our own solar system. In the simple, and idealized, situation in which planets formed by either the "hot-start" model of Burrows et al. (2003) or the core accretion model of Marley et al. (2007), a few tens of detected planets are sufficient to distinguish how planets form.Comment: 15 pages, 9 figures, revised after referee's comments and resubmitted to PAS

Incorporation and metabolism of fatty acids by desaturation and elongation in the nematode, Panagrellus redivivus

The free-living nematode Panagrellus redivivus can be mass produced in monoxenic solid culture on Saccharomyces cerevisiae and therefore could be useful as a live food for marine fish or crustacean larvae in the rapidly expanding aquaculture industry. However, this will depend on their lipid and fatty acid composition and so this was investigated in mass produced P. redivivus grown on S. cerevisiae in three different media. Live nematodes were also incubated with [1-14C]-labelled fatty acids and their desaturation and elongation determined. The combined results from the growth trials on different media and the metabolic studies with labelled fatty acids indicated the presence of Δ9, Δ12, Δ6 and Δ5 fatty acid desaturase activities, and elongase activities active towards C18, C16 and shorter chain fatty acids. The presence of Δ15, and therefore the ability to produce n-3 polyunsaturated fatty acids, was suggested by the compositional data, but could not be conclusively established from metabolic studies

The Evolution of Legal Risks Pertaining to Patch Management and Vulnerability Management

This article begins with an overview, in non-technical terms, of the tools generally available and processes implemented for vulnerability management and patch management. Section II identifies some of the evolving security standards that regulators and plaintiffs may rely on to show that companies are legally required to have vulnerability management and patch management. Section III identifies U.S. legal implications of vulnerability management and patch management and factors that a court and regulators may consider

The Triple-S framework: ensuring scalable, sustainable, and serviceable practices in educational technology

Educational institutions are increasingly investing into digital delivery, acquiring new devices, and employing novel software and services. The rising costs associated with maintenance, in combination with increasing redundancy of older technologies, presents multiple challenges. While lesson content itself may not have changed, the educational landscape constantly evolves, where tertiary institutions are incorporating new modes of content delivery, hybrid-style learning, and interactive technologies. Investments into digital expansions must be taken with caution, particularly prior to the procurement of technology, with a need for the proposed interventions’ scalability, sustainability, and serviceability to be considered. This article presents the Triple-S framework for educators, administrators, and educational institutions, and outlines examples of its application within curricula. The paper synthesises research evidence to provide the foundation underlying the key principles of the Triple-S framework, presenting a useful model to use when evaluating digital interventions. Utilising the framework for decisions regarding the acquisition of educational technology, devices, software, applications, and online resources can assist in the assurance of viable and appropriate investments