Experimental Evaluation of a Coarse-Grained Switch Scheduler

Modern high performance routers rely on sophisticated interconnection networks to meet ever increasing demands on capacity. Regulating the flow of packets through these interconnects is critical to providing good performance, particularly in the presence of extreme traffic patterns that result in sustained overload at output ports. Previous studies have used a combination of analysis and idealized simulations to show that coarse-grained scheduling of traffic flows can be effective in preventing congestion, while ensuring high utilization. In this paper, we study the performance of a coarse-grained scheduler in a real router with a scalable architecture similar to those found in high performance commercial systems. Our results are obtained by taking fine-grained measurements of an operating router that provide a detailed picture of how the scheduling algorithm behaves under a variety of conditions, giving a more complete and realistic understanding of the short time-scale dynamics than previous studies could provide. We also examine computation and communication overheads of our scheduler implementation to assess its resource usage and to provide the basis for an analysis of how the resource usage scales with system size

A rapid, sensitive enrichment PCR to detect Salmonella and ETEC infections in pigs

Salmonella and Escherichia coli infections, particularly enterotoxigenic E. coli (ETEC), are a problem in piglet production. In addition, Salmonella is a major concem in the pork industry as a carrier state can be induced post infection allowing the pathogen to spread across the pig herd, onto many carcasses at slaughter and into the human food chain. Detection methods for these pathogens are currently highly laborious, with Salmonella detection taking over 5 days to give a verified positive result. Identification of ETEC isolates involves detecting the presence of toxin or fimbriae (or their genes by PCR), particularly F4, the most common fimbriae in piglet ETEC infection. Altemative methods such as real time PCR are unable to detect low levels of infection directly from the sample. Enrichment PCR assays have been successfully implemented for the detection of pathogens in foodstuffs, however, faecal material often is inhibitory to PCR based methods

The clinical and cost effectiveness of surgical interventions for stones in the lower pole of the kidney : the percutaneous nephrolithotomy, flexible ureterorenoscopy and extracorporeal shockwave lithotripsy for lower pole kidney stones randomised controlled trial (PUrE RCT) protocol

PUrE is a UK Collaborative Trial funded by the National Institute for Health Research Health Technology Assessment (NIHR HTA) Programme (project no. 13/152/02). The Health Services Research Unit is funded by the Chief Scientists Office of the Scottish Government Health Directorates. The views and opinions expressed herein are those of the authors and do not necessarily reflect those of the Health Technology Assessment Programme, the National Institute of Health Research, the National Health Service or the Department of Health. The funder (through their peer-review and funding board review process) approved the study proposal but had no role in the collection, analysis or interpretation of data or writing of the report.Peer reviewedPublisher PD

Expressions 1992

https://openspace.dmacc.edu/expressions/1014/thumbnail.jp

Searching for a Stochastic Background of Gravitational Waves with LIGO

The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new limit is $\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.Comment: 37 pages, 16 figure

Advanced Technology Large-Aperture Space Telescope (ATLAST): A Technology Roadmap for the Next Decade

The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation of UVOIR space observatory with a primary aperture diameter in the 8-m to 16-m range that will allow us to perform some of the most challenging observations to answer some of our most compelling questions, including "Is there life elsewhere in the Galaxy?" We have identified two different telescope architectures, but with similar optical designs, that span the range in viable technologies. The architectures are a telescope with a monolithic primary mirror and two variations of a telescope with a large segmented primary mirror. This approach provides us with several pathways to realizing the mission, which will be narrowed to one as our technology development progresses. The concepts invoke heritage from HST and JWST design, but also take significant departures from these designs to minimize complexity, mass, or both. Our report provides details on the mission concepts, shows the extraordinary scientific progress they would enable, and describes the most important technology development items. These are the mirrors, the detectors, and the high-contrast imaging technologies, whether internal to the observatory, or using an external occulter. Experience with JWST has shown that determined competitors, motivated by the development contracts and flight opportunities of the new observatory, are capable of achieving huge advances in technical and operational performance while keeping construction costs on the same scale as prior great observatories.Comment: 22 pages, RFI submitted to Astro2010 Decadal Committe

Last-Minute Bidding in Sequential Auctions with Unobserved, Stochastic Entry

We present a model of repeated, ascending price auctions for homogeneous goods with unobserved, stochastic entry. Bidders have unit demands; they exit if they win, and bid again if they lose. We show that, in equilibrium, entrants always bid in the next-toclose auction and bidders always bid at the last minute. The more bidders present, the lower is the continuation value of future auctions, so bidders avoid revealing themselves until the end of the auction. Using a dataset of calculator auctions on eBay, we present evidence that losers of an auction bid again in future auctions. Ordering the auctions by closing time, we show that last-minute bidding is not merely the result of bidders going to the next-to-close auction. Instead, bidding is concentrated at the end of the period in which the auction is the next to close.