Smooth transitions from Schwarzschild vacuum to de Sitter space

We provide an infinity of spacetimes which contain part of both the Schwarzschild vacuum and de Sitter space. The transition, which occurs below the Schwarzschild event horizon, involves only boundary surfaces (no surface layers). An explicit example is given in which the weak and strong energy conditions are satisfied everywhere (except in the de Sitter section) and the dominant energy condition is violated only in the vicinity of the boundary to the Schwarzschild section. The singularity is avoided by way of a change in topology in accord with a theorem due to Borde..Comment: revtex4, two figures. Final form to appear in Phys. Rev.

Modeling and experimental results for condensing supercritical CO2 power cycles.

This Sandia supported research project evaluated the potential improvement that 'condensing' supercritical carbon dioxide (S-CO{sub 2}) power cycles can have on the efficiency of Light Water Reactors (LWR). The analytical portion of research project identified that a S-CO{sub 2} 'condensing' re-compression power cycle with multiple stages of reheat can increase LWR power conversion efficiency from 33-34% to 37-39%. The experimental portion of the project used Sandia's S-CO{sub 2} research loop to show that the as designed radial compressor could 'pump' liquid CO{sub 2} and that the gas-cooler's could 'condense' CO{sub 2} even though both of these S-CO{sub 2} components were designed to operate on vapor phase S-CO{sub 2} near the critical point. There is potentially very high value to this research as it opens the possibility of increasing LWR power cycle efficiency, above the 33-34% range, while lowering the capital cost of the power plant because of the small size of the S-CO{sub 2} power system. In addition it provides a way to incrementally build advanced LWRs that are optimally designed to couple to S-CO{sub 2} power conversion systems to increase the power cycle efficiency to near 40%

How Malthusian Ideology crept into the Newsroom: British tabloids and the coverage of the ‘underclass’

This article argues that Malthusianism as a series of discursive regimes, developed in the Victorian-era, serves in times of austerity to reproduce an elite understanding of social exclusion in which those in a state of poverty are to blame for their own situation. It highlights that Malthusianism is present in the public discourse, becoming an underlining feature in news coverage of the so-called ‘underclass’. Our findings broadly contradict the normative claim that journalism ‘speaks truth to power’, and suggest instead that overall as a political practice, journalism tends to reproduce and reinforce hegemonic discourses of power. The piece is based on critical discourse analysis (CDA), which has been applied to a significant sample of news articles published by tabloid newspapers in Britain which focussed on the concept of the ‘underclass’. By looking at the evidence, the authors argue that the ‘underclass’ is a concept used by some journalists to cast people living in poverty as ‘undeserving’ of public and state support. In so doing, these journalists help create a narrative which supports cuts in welfare provisions and additional punitive measures against some of the most vulnerable members of society

Scaling considerations for a multi-megawatt class supercritical CO2 brayton cycle and commercialization.

Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop

Number of closed strings emitted from a decaying D-brane

We have calculated in the covariant gauge the total number of massless closed strings emitted from a decaying Dp-brane using fermionization technology on the time component of the boundary state. This verifies the computation carried out in the less well known temporal gauge despite differences in renormalization schemes. In addition we have attempted to use the fermionic technique to calculate the total number of closed strings emitted. Our result is difficult to interpret due to the ambiguity involved with rotating it back to Minkowski space.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

CO2-based mixtures as working fluids for geothermal turbines.

Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for application to a variety of heat sources, including geothermal, solar, fossil, and nuclear power. This work is centered on the supercritical CO{sub 2} (S-CO{sub 2}) power conversion cycle, which has the potential for high efficiency in the temperature range of interest for these heat sources and is very compact-a feature likely to reduce capital costs. One promising approach is the use of CO{sub 2}-based supercritical fluid mixtures. The introduction of additives to CO{sub 2} alters the equation of state and the critical point of the resultant mixture. A series of tests was carried out using Sandia's supercritical fluid compression loop that confirmed the ability of different additives to increase or lower the critical point of CO{sub 2}. Testing also demonstrated that, above the modified critical point, these mixtures can be compressed in a turbocompressor as a single-phase homogenous mixture. Comparisons of experimental data to the National Institute of Standards and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties (REFPROP) Standard Reference Database predictions varied depending on the fluid. Although the pressure, density, and temperature (p, {rho}, T) data for all tested fluids matched fairly well to REFPROP in most regions, the critical temperature was often inaccurate. In these cases, outside literature was found to provide further insight and to qualitatively confirm the validity of experimental findings for the present investigation