33,377 research outputs found

    Approach to the Continuum Limit of the Quenched Hermitian Wilson-Dirac Operator

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    We investigate the approach to the continuum limit of the spectrum of the Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge SU(2) and SU(3) backgrounds. For this we study the spectral flow of the Hermitian Wilson-Dirac operator in the range 0m20\le m\le 2. We find that the spectrum has a gap for 0<mm10 < m \le m_1 and that the spectral density at zero, ρ(0;m)\rho(0;m), is non-zero for m1m2m_1\le m\le 2. We find that m10m_1\to 0 and, for m0,ρ(0;m)0m \ne 0, \rho(0;m)\to 0 (exponential in the lattice spacing) as one goes to the continuum limit. We also compute the topological susceptibility and the size distribution of the zero modes. The topological susceptibility scales well in the lattice spacing for both SU(2) and SU(3). The size distribution of the zero modes does not appear to show a peak at a physical scale.Comment: 19 pages revtex with 9 postscript figures included by eps

    Variable conductance heat pipe technology

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    Research and development programs in variable conductance heat pipe technology were conducted. The treatment has been comprehensive, involving theoretical and/or experimental studies in hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, and materials compatibility, in addition to the principal subject of variable conductance control techniques. Efforts were not limited to analytical work and laboratory experimentation, but extended to the development, fabrication and test of spacecraft hardware, culminating in the successful flight of the Ames Heat Pipe Experiment on the OAO-C spacecraft

    The use of computer-generated color graphic images for transient thermal analysis

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    Color computer graphics techniques were investigated as a means of rapidly scanning and interpreting large sets of transient heating data. The data presented were generated to support the conceptual design of a heat-sink thermal protection system (TPS) for a hypersonic research airplane. Color-coded vector and raster displays of the numerical geometry used in the heating calculations were employed to analyze skin thicknesses and surface temperatures of the heat-sink TPS under a variety of trajectory flight profiles. Both vector and raster displays proved to be effective means for rapidly identifying heat-sink mass concentrations, regions of high heating, and potentially adverse thermal gradients. The color-coded (raster) surface displays are a very efficient means for displaying surface-temperature and heating histories, and thereby the more stringent design requirements can quickly be identified. The related hardware and software developments required to implement both the vector and the raster displays for this application are also discussed

    Beneficial effects of childhood selective dorsal rhizotomy in adulthood

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    Background: Selective dorsal rhizotomy (SDR) has been used to treat children with spastic cerebral palsy (CP) for over three decades. However, little is known about the outcomes of childhood SDR in adults.  Objectives: 1) To study the effects of childhood SDR on the quality of life and ambulatory function in adult life. 2) To determine late side effects of SDR in adults.   Methods: Adults (> 17.9 years) who underwent SDR in childhood (2 - 17.9 years) between 1987 and 2013 were surveyed in 2015. Patients completed a survey, including questions on demographic information, quality of life, health, surgical outcomes, motor function, manual ability, pain, braces/orthotics, post-SDR treatment, living situation, education level, work status, and side effects of SDR.  Results: In our study population of 294 patients (18.0 - 37.4 years), patients received SDR during the ages of 2.0 - 17.9 years and were followed up 2.2 to 28.3 years after surgery. Eighty-four percent had spastic diplegia, 12% had spastic quadriplegia, and 4% had spastic triplegia. The majority (88%) of patients reported improved post-SDR quality of life and 1% considered the surgery detrimental. Most (83%) would recommend the procedure to others and 3% would not. However, patients who would not recommend SDR to others ambulated with a walker or were not ambulatory at all prior to SDR. The majority (83%) of patients improved (30%) or remained stable (53%) in ambulation. Twenty-nine percent of patients reported pain, mostly in the back and lower limbs, with a mean pain level of 4.4 ± 2.4 on the Numeric Pain Rating Scale (NPRS). Decreased sensation in small areas of the lower limbs was reported by 8% of patients, though this did not affect daily life. Scoliosis was diagnosed in 28%, with 40% of these patients pursuing treatment. Whether scoliosis was related to SDR is not clear, though scoliosis is known to occur in patients with CP and also in the general population. Only 4% of patients underwent spinal fusion.  Orthopedic surgeries were pursued by 59% of patients. The most common orthopedic surgeries were hamstring lengthenings (31%), Achilles tendon lengthenings (18%), adductor lengthenings (16%), and derotational osteotomies (16%). Twenty-four percent of all patients later underwent hip surgery and 8% had surgeries on their knees.  Conclusion: Results of this study indicate that the beneficial effects of childhood SDR extend to adulthood quality of life and ambulatory function without late side effects of surgery

    EVALUATION OF A TURBIDITY METER FOR USE AT THE DEFENSE WASTE PROCESSING FACILITY

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    Savannah River Remediation&#x27;s (SRR&#x27;s) Defense Waste Processing Facility (DWPF) Laboratory currently tests for sludge carry-over into the Recycle Collection Tank (RCT) by evaluating the iron concentration in the Slurry Mix Evaporator Condensate Tank (SMECT) and relating this iron concentration to the amount of sludge solids present. A new method was proposed for detecting the amount of sludge in the SMECT that involves the use of an Optek turbidity sensor. Waste Services Laboratory (WSL) personnel conducted testing on two of these units following a test plan developed by Waste Solidification Engineering (WSE). Both Optek units (SN64217 and SN65164) use sensor model AF16-N and signal converter model series C4000. The sensor body of each unit was modified to hold a standard DWPF 12 cc sample vial, also known as a &#x27;&#x27;peanut&#x27;&#x27; vial. The purpose of this testing was to evaluate the use of this model of turbidity sensor, or meter, to provide a measurement of the sludge solids present in the SMECT based upon samples from that tank. During discussions of the results from this study by WSE, WSL, and Savannah River National Laboratory (SRNL) personnel, an upper limit on the acceptable level of solids in SMECT samples was set at 0.14 wt%. A &#x27;&#x27;go/no-go&#x27;&#x27; decision criterion was to be developed for the critical turbidity response, which is expressed in concentration units (CUs), for each Optek unit based upon the 0.14 wt% solids value. An acceptable or a &#x27;&#x27;go&#x27;&#x27; decision for the SMECT should reflect the situation that there is an identified risk (e.g. 5%) for a CU response from the Optek unit to be less than the critical CU value when the solids content of the SMECT is actually 0.14 wt% or greater, while a &#x27;&#x27;no-go&#x27;&#x27; determination (i.e., an Optek CU response above the critical CU value, a conservative decision relative to risk) would lead to additional evaluations of the SMECT to better quantify the possible solids content of the tank. A sludge simulant was used to develop standards for testing both Optek units and to determine the viability of a &#x27;&#x27;go/no-go&#x27;&#x27; CU response for each of the units. Statistical methods were used by SRNL to develop the critical CU value for the &#x27;&#x27;go/no-go&#x27;&#x27; decision for these standards for each Optek unit. Since only one sludge simulant was available for this testing, the sensitivity of these results to other simulants and to actual sludge material is not known. However, limited testing with samples from the actual DWPF process (both SRAT product samples and SMECT samples) demonstrated that the use of the &#x27;&#x27;go/no-go&#x27;&#x27; criteria developed from the sludge simulant testing was conservative for these samples taken from Sludge Batch 7b (SB7b), the sludge batch currently being processed. While both of the Optek units performed very reliably during this testing, there were statistically significant differences (although small on a practical scale) between the two units. Thus, testing should be conducted on any new unit of this Optek model to qualify it before it is used to support the DWPF operation

    Urban Tourism Research. Developing an Agenda

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    The study of urban tourism and associated focus on urban tourist precincts is a growing area of interest as practitioners, researchers and policy makers seek to understand the phenomenon of tourism within the urban environment. In Australia research in this area has lacked integration and has not engaged sufficiently with the contextual setting of the urban environment. This paper reports on a study that was undertaken to identify the important areas that should be included in an urban tourism research agenda. This paper has three aims: to review the literature on urban tourism; to outline the process that was undertaken to identify areas for urban tourism research; and to present a conceptual framework that can be used to focus future urban tourism research. © 2008 Elsevier Ltd. All rights reserved

    Variable Conductance Heat Pipe Technology

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    A research and development program in variable conductance heat pipe technology is reported. The project involved: (1) theoretical and/or experimental studies in hydrostatics, (2) hydrodynamics, (3) heat transfer into and out of the pipe, (4) fluid selection, and (5) materials compatibility. The development, fabrication, and test of the space hardware resulted in a successful flight of the heat pipe experiment on the OAO-3 satellite. A summary of the program is provided and a guide to the location of publications on the project is included

    The first North American records of the synanthropic spider \u3ci\u3eCithaeron praedonius\u3c/i\u3e O. P.-Cambridge (Araneae: Gnaphosoidea: Cithaeronidae), with notes on its biology

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    Cithaeron praedonius O. P.-Cambridge 1872 (Araneae: Gnaphosoidea: Cithaeronidae) is an Old World species with a distribution from The Gambia, western Africa, and Greece to Malaysia and Australia. In the New World, it was recently found in Brazil, and is now reported for the first time in North America, in the United States. Multiple individuals of both sexes and various life stages, including multiple eggsacs, have been found in a home in Port Richey, Pasco County, Florida. An adult female was found on the outside wall of the house feeding on another spider, suggesting that C. praedonius are no longer contained as a spot introduction in this one house. Observations in captivity indicate that this species may prefer feeding on other spiders. The eggsac and molting nest are described for the first time, and the first records on fecundity are reported

    Domain Wall Fermions with Exact Chiral Symmetry

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    We show how the standard domain wall action can be simply modified to allow arbitrarily exact chiral symmetry at finite fifth dimensional extent. We note that the method can be used for both quenched and dynamical calculations. We test the method using smooth and thermalized gauge field configurations. We also make comparisons of the performance (cost) of the domain wall operator for spectroscopy compared to other methods such as the overlap-Dirac operator and find both methods are comparable in cost.Comment: revtex, 37 pages, 11 color postscript figure
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