Validation Approach for a Spatially and Temporally Resolved Fault Arc Model

This paper presents a method to validate arc models for fault arc applications by examining the effect of changed boundary conditions on arc parameters, e.g. voltage and pressure build-up. The study shows the impact of ignition location on arc voltage and pressure build-up and prediction accuracy of the presented model. The results indicate insufficient accuracy in predicting arc voltage during dynamic phases, while the pressure build-up prediction aligns well with the experimental results

Corrosion of Orthodontic Brackets: Cost, Cold Worked, and Powdered Metal

The purpose of this study is to evaluate the relative corrosion rates of 316-L stainless steel cast metal, cold worked, and powdered metal brackets. This is done using potentiodynamic anodic polarization to measure the voltage difference between the samples and a reference electrode. Corrosion layers effect current flow and by plotting how the current responds to an applied voltage it is possible to determine the corrosion rate of a sample. The point at where the applied voltage breaks down the passivation or oxidation layer is recorded and the relative corrosion rate is figured using the formula: Corrosion Rate (mpy) (in milliinches per year) = [(k) (Icorr) Equivalent Weight] /Density. (K is a known constant and Icorr is current density in microamps per cm2) The results indicate that the powdered metal samples had the smallest relative corrosion rate with .2256mpy, cast metal was next with .4639mpy, and cold worked had the greatest corrosion rate with 2.8135mpy

\u3ci\u3eEchinococcus\u3c/i\u3e spp. Tapeworms in North America

Alveolar and cystic echinococcosis are emerging and re-emerging in Europe, Africa, and Asia. The expansion of Echinococcus spp. tapeworms in wildlife host reservoirs appears to be driving this emergence in some areas. Recent studies suggest a similar phenomenon may be occurring in North America. We describe the context of Echinococcus spp. research in North America, with a specific focus on the contiguous United States. Although studies were conducted in the United States throughout the 1900s on various sylvatic and domestic Echinococcus spp. tapeworm cycles, data are lacking for the past ≈30 years. We review previous research, provide analysis of more recent focal studies, and suggest that Echinococcus spp. tapeworms, in particular E. canadensis, may be underrecognized. As a result, we suggest that additional research and surveillance be conducted for these tapeworms in wildlife host reservoirs across the United States

Influence of Oxygen-containing Filling Gas Mixtures on the Interruption Capability of MV Load Break Switches

Nowadays SF6 is commonly used as filling gas for medium voltage load break switches due to its outstanding insulating and arc-quenching properties. However, due to its high global warming potential the interrupting performance of alternative eco-friendly gases are investigated for such devices. This contribution investigates the thermal interruption capability of a medium voltage load break switch using two different oxygen-containing gas mixtures: dry air and a mixture of nitrogen, oxygen and carbon dioxide. The findings indicate an improved performance in comparison to pure nitrogen when considering an admixture of oxygen. In gas mixtures containing 80\% nitrogen, the addition of oxygen results in an enhanced thermal interruption capability compared to an equivalent proportion of carbon dioxide

Simulative Comparison of Radiation Model Parameterizations for Direct Current Arcs in a Busbar Setup

The influence of different methods for calculating mean absorption coefficients on the mean arc voltage and velocity of an arc moving in air along parallel busbars is investigated in a numerical arc simulation. The radiation model used is the discrete ordinate method. Planck, hybrid and Rosseland mean calculations for a three- and six-band selection are discussed. Compared with the experimental results from a published paper, the Planck mean for six bands shows the most promising results

Prevalence of internal parasites in beef cows in the United States: Results of the National Animal Health Monitoring System’s (NAHMS) beef study, 2007–2008

During the United States Department of Agriculture (USDA) National Animal Health Monitoring System’s (NAHMS) 2007–2008 beef study, 567 producers from 24 US States were offered the opportunity to collect fecal samples from weaned beef calves and have them evaluated for the presence of parasite eggs (Phase 1). Participating producers were provided with instructions and materials for sample collection. Up to 20 fresh fecal samples were collected from each of the 99 participating operations. Fresh fecal samples were submitted to one of 3 randomly assigned laboratories for evaluation. Upon arrival at the laboratories, all samples were processed for the enumeration of strongyle, Nematodirus, and Trichuris eggs using the modified Wisconsin technique. The presence or absence of coccidian oocysts and tapeworm eggs was also noted. In submissions where the strongyle eggs per gram exceeded 30, aliquots from 2 to 6 animals were pooled for DNA extraction. Extracted DNA was subjected to genus level polymerase chain reaction (PCR) identification for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. In this study, 85.6% of the samples had strongyle type, Nematodirus, and Trichuris eggs. Among the samples evaluated, 91% had Cooperia, 79% Ostertagia, 53% Haemonchus, 38% Oesophagostomum, 18% Nematodirus, 7% Trichuris, and 3% Trichostrongylus. The prevalence of coccidia and tapeworm eggs was 59.9% and 13.7%, respectively

Effectiveness of current anthelmintic treatment programs on reducing fecal egg counts in United States cow-calf operations

During the United States Department of Agriculture (USDA) National Animal Health Monitoring System’s (NAHMS) 2007–2008 beef study, producers from 24 states were offered the opportunity to evaluate their animals for internal parasites and for overall responses to treatment with anthelmintics. A lapse of 45 d was required between initial sampling and any previous treatments. Choice of anthelmintic (oral benzimidazoles, and both injectable and pour-on endectocides) was at the discretion of the producer so as not to alter the local control programs. Fresh fecal samples were collected from 20 animals, or from the entire group if less than 20, then randomly assigned to 1 of 3 participating laboratories for examination. Analyses consisted of double centrifugation flotation followed by enumeration of strongyle, Nematodirus, and Trichuris eggs (the presence of coccidian oocysts and tapeworm eggs was also noted). Where strongyle eggs per gram (epg) exceeded 30, aliquots from 2 to 6 animals were pooled for egg isolation and polymerase chain reaction (PCR) analysis for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. Results from 72 producers (19 States) indicated that fecal egg count reductions were , 90% in 1/3 of the operations. All operations exhibiting less than a 90% reduction had used pour-on macrocyclic lactones as the anthelmintic treatment. While some of these less than expected reductions could have been the result of improper drug application, PCR analyses of the parasite populations surviving treatment, coupled with follow-up studies at a limited number of sites, indicated that less than expected reductions were most likely due to anthelmintic resistance in Cooperia spp. and possibly Haemonchus spp