196,255 research outputs found
Supersymmetry of the C-metric and the general Plebanski-Demianski solution
No full textWe derive the necessary and sufficient conditions under which the general Plebanski-Demianski (PD) solution of Einstein-Maxwell theory with a negative cosmological constant admits Killing spinors. We consider in detail two different scaling limits of the PD metric. The first of these limits removes the acceleration parameter, and leads to the Carter-Plebanski solution. In this case, the integrability conditions for Killing spinors were obtained by Alonso-Alberca, Meessen and Ortin in hep-th/0003071, and we show that these are not only necessary, but also sufficient for the existence of Killing spinors. This fills also a gap in hep-th/9808097, where the integrability conditions for supersymmetry of the Kerr-Newman-AdS black hole were worked out, but the Killing spinor was not constructed explicitely. The second scaling limit eliminates the rotation parameter, and leads to the cosmological C-metric, which describes accelerated black holes in AdS. Also in this case, the supersymmetry conditions are obtained, and it is shown that they follow from the ones of the general PD solution by scaling the parameters appropriately. In all cases, we determine the three-dimensional base space that appears in the classification scheme of hep-th/0307022, and prove that for the 1/2-supersymmetric Reissner-Nordstrom-AdS spacetime, this base is unique. A Wick-rotation of our results leads to gravitational instantons that generalize the ones constructed recently by Martelli, Passias and Sparks in arXiv:12124618 to U(1)xU(1) symmetry. These instantons are shown to admit an integrable almost complex structure. Finally, our work may open the possibility to systematically construct generalizations of the PD metric that include scalar fields with a potential in matter-coupled gauged supergravity
Exact results on analogue gravity in optical Plebanski-Tamm media
No full textExact results concerning ray-tracing methods in Plebanski-Tamm media are derived. In particular, Hamilton equations describing the propagation of quasi-plane wave electromagnetic fields in the geometrical optics regime are explicitly written down in terms of the 3-metric representing the properties of the optical analogue, anisotropic medium. We exemplify our results by obtaining the trajectories of light in the resulting analogue medium recreating G\"odel's universe
Gravedad análoga en medios ópticos de Plebanski-Tamm
No full textEste trabajo se enfoca en el estudio de un modelo de analogía óptico-gravitatoria para un espacio-tiempo que presenta una singularidad de curvatura fuerte. Para ello, utilizando el formalismo de Plebanski-Tamm, se obtuvieron las relaciones constitutivas para el medio óptico análogo y se resolvieron en forma exacta las ecuaciones para el campo electromagnético en dicho medio, en distintos casos de interés. Se obtuvieron soluciones en las que el campo electromagnético está perfectamente definido en todo el espacio, incluso en la singularidad, donde el espacio-tiempo presenta invariantes de curvatura divergentes
Natural Regulatory T Cells and Persistent Viral Infection
No full textShuo Li, Eric J. Gowans, Claire Chougnet, Magdalena Plebanski, and Ulf Dittme
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
The power of effective study design in animal Experimentation: Exploring the statistical and ethical implications of asking multiple questions of a data set
No full textOne of the chief advantages of using highly standardised biological models including model organisms is that multiple variables can be precisely controlled so that the variable of interest is more easily studied. However, such an approach often obscures effects in sub-populations resulting from natural population heterogeneity. Efforts to expand our fundamental understanding of multiple sub-populations are in progress. However, such stratified or personalised approaches require fundamental modifications of our usual study designs that should be implemented in Brain, Behavior and Immunity (BBI) research going forward. Here we explore the statistical feasibility of asking multiple questions (including incorporating sex) within the same experimental cohort using statistical simulations of real data. We illustrate and discuss the large explosion in sample numbers necessary to detect effects with appropriate power for every additional question posed using the same data set. This exploration highlights the strong likelihood of type II errors (false negatives) for standard data and type I errors when dealing with complex genomic data, where studies are too under-powered to appropriately test these interactions. We show this power may differ for males and females in high throughput data sets such as RNA sequencing. We offer a rationale for the use of alternative experimental and statistical strategies based on interdisciplinary insights and discuss the realworld implications of increasing the complexities of our experimental designs, and the implications of not attempting to alter our experimental designs going forward.R.A. Ankeny, A.L. Whittaker, M. Ryan, J. Boer, M. Plebanski, J. Tuke, S.J. Spence
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
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