University of Rhode Island

About: University of Rhode Island is a education organization based out in Kingston, Rhode Island, United States. It is known for research contribution in the topics: Population & Bay. The organization has 11464 authors who have published 22770 publications receiving 841066 citations. The organization is also known as: URI & Rhode Island College of Agriculture and the Mechanic Arts.

Respiration of Escherichia coli in the Mouse Intestine

Abstract: Mammals are aerobes that harbor an intestinal ecosystem dominated by large numbers of anaerobic microorganisms. However, the role of oxygen in the intestinal ecosystem is largely unexplored. We used systematic mutational analysis to determine the role of respiratory metabolism in the streptomycin-treated mouse model of intestinal colonization. Here we provide evidence that aerobic respiration is required for commensal and pathogenic Escherichia coli to colonize mice. Our results showed that mutants lacking ATP synthase, which is required for all respiratory energy-conserving metabolism, were eliminated by competition with respiratory-competent wild-type strains. Mutants lacking the high-affinity cytochrome bd oxidase, which is used when oxygen tensions are low, also failed to colonize. However, the low-affinity cytochrome bo3 oxidase, which is used when oxygen tension is high, was found not to be necessary for colonization. Mutants lacking either nitrate reductase or fumarate reductase also had major colonization defects. The results showed that the entire E. coli population was dependent on both microaerobic and anaerobic respiration, consistent with the hypothesis that the E. coli niche is alternately microaerobic and anaerobic, rather than static. The results indicate that success of the facultative anaerobes in the intestine depends on their respiratory flexibility. Despite competition for relatively scarce carbon sources, the energy efficiency provided by respiration may contribute to the widespread distribution (i.e., success) of E. coli strains as commensal inhabitants of the mammalian intestine.

A Comparison of Satellite and In Situ–Based Sea Surface Temperature Climatologies

Abstract: The purpose of this study is to present a satellite-derived sea surface temperature (SST) climatology based on Pathfinder Advanced Very High Resolution Radiometer (AVHRR) data and to evaluate it and several other climatologies for their usefulness in the determination of SST trends. The method of evaluation uses two longterm observational collections of in situ SST measurements: the 1994 World Ocean Atlas (WOA94) and the Comprehensive Ocean‐Atmosphere Data Set (COADS). Each of the SST climatologies being evaluated is subtracted from each raw SST observation in WOA94and COADS to produce several separate long-term anomaly datasets. The anomaly dataset with the smallest standard deviation is assumed to identify the climatology best able to represent the spatial and seasonal SST variability and therefore be most capable of reducing the uncertainty in SST trend determinations. The satellite SST climatology was created at a resolution of 9.28 km using both day and night satellite fields generated with the version 4 AVHRR Pathfinder algorithm and cloud-masking procedures, plus an erosion filter that provides additional cloud masking in the vicinity of cloud edges. Using the statistical comparison method, the performance of this ‘‘Pathfinder 1 erosion’’ climatology is compared with the performances of the WOA94 18 in situ climatology, the Reynolds satellite and in situ blended 1 8 analysis, version 2.2 of the blended 18 Global Sea-Ice and Sea Surface Temperature (GISST) climatology, and the in situ 58 Global Ocean Surface Temperature Atlas (GOSTA). The standard deviation of the anomalies produced using the raw WOA94 in situ observations and the reference SST climatologies indicate that the 9.28-km Pathfinder 1 erosion climatology is more representative of spatial and seasonal SST variability than the traditional in situ and blended SST climatologies. For the anomalies created from the raw COADS observations, the Pathfinder1 erosion climatology is also found to minimize variance more than the other climatologies. In both cases, the 58 GOSTAclimatology exhibits the largest anomaly standard deviations. Regional characteristics of the climatologies are also examined by binning the anomalies by climatological temperature classes and latitudinal bands. Generally, the Pathfinder 1 erosion climatology yields lower anomaly variances in the mid- and high latitudes and the Southern Hemisphere, but larger variances than the 18 climatologies in the warm, Northern Hemisphere low-latitude regions.

Performance of multiprocessor interconnection networks

Abstract: A tutorial is provided on the performance evaluation of multiprocessor interconnection networks, to guide system designers in their design process. A classification of parallel/distributed systems is followed by a classification of multiprocessor interconnection networks. Basic terminology for performance evaluation is presented. The performance of crossbar interconnection networks, multistage interconnection networks, and multiple-bus systems is then addressed, and a comparison is made along them. >