Winter Grazing in a Grass-Fed System: Effect of Stocking Density and Sequential Use of Autumn-Stockpiled Grassland on Performance of Yearling Steers

Winter grazing can help reduce the need for purchased feeds in livestock production systems, when finishing cattle on pasture. Our objective was to evaluate the influence of stocking density and grazing stockpiled forage on performance of yearling steers during winter. Three grasslands were winter grazed for two years: I, naturalized pastureland, and II and III, sown and managed for hay production during the growing season but grazed in winter. Two stocking densities were used: low 7.41 and high 12.35 steers ha−1. Herbage mass was estimated before and after each grazing event, and disappearance (consumption, weathering, and trampling) was the difference between both. Forage mass and residual differed by stocking density (SD), year (YR), and grazing interval (GI), and disappearance differed by YR and GI. Grass and dead constituents of botanical composition differed by YR and GI. No differences were found for legumes and forbs. CP differed by YR and GI, and NDF and ADF differed only by YR. Steer average daily gain was 0.15 kg d−1 in 2011 and 0.68 kg d−1 in 2012 and varied by YR and GI. Acceptable gains in 2012 may be a product of environmental conditions that influenced herbage mass and nutritive value during stockpile and animal behavior during winter

Developement of real time diagnostics and feedback algorithms for JET in view of the next step

Real time control of many plasma parameters will be an essential aspect in the development of reliable high performance operation of Next Step Tokamaks. The main prerequisites for any feedback scheme are the precise real-time determination of the quantities to be controlled, requiring top quality and highly reliable diagnostics, and the availability of robust control algorithms. A new set of real time diagnostics was recently implemented on JET to prove the feasibility of determining, with high accuracy and time resolution, the most important plasma quantities. With regard to feedback algorithms, new model–based controllers were developed to allow a more robust control of several plasma parameters. Both diagnostics and algorithms were successfully used in several experiments, ranging from H-mode plasmas to configuration with ITBs. Since elaboration of computationally heavy measurements is often required, significant attention was devoted to non-algorithmic methods like Digital or Cellular Neural/Nonlinear Networks. The real time hardware and software adopted architectures are also described with particular attention to their relevance to ITER.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Comparison of Two Low-Input Cow/Calf Production Systems on Temperate Grassland

Two systems of grass farming were compared in an eight-year experiment in West Virginia, USA. The grassland consisted primarily of cocksfoot (Dactylis glomerara L.), Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb.), and red (Trifolium pretense L.) and white clover (T. repens L.). The objective was to compare two systems of beef cow calf production. The experiment was a randomized complete block with two replicated treatments. The grassland of treatment 1 (system 1) was overseeded with legumes, grazing started 1 wk earlier and continued 1 wk later than treatment 2 (system 2) and calves were allowed to forward creep graze. The hay land of treatment 2 received 56 kg N ha-1, at the start of the growing season. Response was measured as calf weaning weight, hay production, and pre-grazing herbage accumulation. Each treatment/replicate (experimental unit) was assigned 6.5 ha divided into three grassland managements units: pasture, buffer and meadow. Pasture was grazed and not cut for hay. First growth of buffer and meadow was harvested as hay. Subsequently, buffer was grazed, meadow was again harvested, followed by late season grazing. Management units were divided into four paddocks. Animals occupied a paddock for 7 days resulting in 4-week grazing cycles from May to mid-November. Eight cow/calf pairs grazed each treatment/replicate (stocking rate 1.23 cow calves ha-1 ). Calves, born in March, were weaned in late September. System 1 calves gained 1.18 kg dy-1 (P \u3c 0.04 SE=0.01) compared with those on System 2 which gained 1.14 kg dy-1. Annual hay production on System 2 was 5784 kg ha-1, significantly more than on System 1 (P \u3c 0.01 SE=107). However, in System 1 extending the grazing season reduced the amount of hay required annually by 1680 kg ha-1. System 1 hay had a greater proportion of legume (9 vs. 3%, P \u3c 0.01 SE=0.5) and a lesser proportion of grass (75 vs. 85%, P \u3c 0.01 SE=0.7) than those of system 2

The High Resolution X-ray Spectrum of SS 433 using the Chandra HETGS

We present observations of SS 433 using the Chandra High Energy Transmission Grating Spectrometer. Many emission lines of highly ionized elements are detected with the relativistic blue and red Doppler shifts. The lines are measurably broadened to 1700 km/s (FWHM) and the widths do not depend significantly on the characteristic emission temperature, suggesting that the emission occurs in a freely expanding region of constant collimation with opening angle of 1.23 +/- 0.06 deg. The blue shifts of lines from low temperature gas are the same as those of high temperature gas within our uncertainties, again indicating that the hottest gas we observe to emit emission lines is already at terminal velocity. Fits to the emission line fluxes give a range of temperatures in the jet from 5e6 to 1e8 K. We derive the emission measure as a function of temperature for a four component model that fits the line flux data. Using the density sensitive Si XIII triplet, the characteristic electron density is 1e14 cm^{-3}, where the gas temperature is about 1.3e7 K. Based on an adiabatic expansion model of the jet, the electron densities drop from ~2e15 to 4e13 cm^{-3} at distances of 2e10 to 2e11 cm from the apex of the jet cone. The jet mass outflow rate is 1.5e-7 Msun / yr. The kinetic power is 3.2e38 erg/s, which is x1000 larger than the unabsorbed 2-10 keV X-ray luminosity. The bremsstrahlung emission associated with the lines can account for the entire continuum; we see no direct evidence for an accretion disk. The image from zeroth order shows extended emission at a scale of ~2", aligned in the general direction of the radio jets.Comment: 28 pages, 12 figures (1, 4, 5, and 6 are color), to appear in the Astrophysical Journa

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Abiotic O_2 Levels on Planets around F, G, K, and M Stars: Effects of Lightning-produced Catalysts in Eliminating Oxygen False Positives

Over the last few years, a number of authors have suggested that, under certain circumstances, molecular oxygen (O_2) or ozone (O_3) generated by abiotic processes may accumulate to detectable concentrations in a habitable terrestrial planet's atmosphere, producing so-called "false positives" for life. But the models have occasionally disagreed with each other, with some predicting false positives, and some not, for the same apparent set of circumstances. We show here that photochemical false positives derive either from inconsistencies in the treatment of atmospheric and global redox balance or from the treatment (or lack thereof) of lightning. For habitable terrestrial planets with even trace amounts of atmospheric N_2, NO produced by lightning catalyzes the recombination of CO and O derived from CO_2 photolysis and should be sufficient to eliminate all reported false positives. Molecular oxygen thus remains a useful biosignature gas for Earth-like extrasolar planets, provided that the planet resides within the conventional liquid water habitable zone and has not experienced distinctly non-Earth-like, irrecoverable water loss

Insights into the O-Acetylation Reaction of Hydroxylated Heterocyclic Amines by Human Arylamine N-Acetyltransferases: A Computational Study

A computational study was performed to better understand the differences between human arylamine N-acetyltransferase (NAT) 1 and 2. Homology models were constructed from available crystal structures and comparisons of the active site residues 125, 127, and 129 for these two enzymes provide insight into observed substrate differences. The NAT2 model provided a basis for understanding how some of the common mutations may affect the structure of the protein. Molecular dynamics simulations of the human NAT models and the template structure (NAT from Mycobacterium smegmatis) were performed and showed the models to be stable and reasonable. Docking studies of hydroxylated heterocyclic amines in the models of NAT1 and NAT2 probed the differences exhibited by these two proteins with mutagenic agents. The hydroxylated heterocyclic amines were only able to fit into the NAT2 active site, and an alternative binding site by the P-loop was found using our models and will be discussed. Additionally, quantum mechanical calculations were performed to study the O-acetylation reaction of the hydroxylated heterocyclic amines N-OH MeIQx and N-OH PhIP. This study has given us insight into why there are substrate differences among isoenzymes and explains some of the polymorphic activity differences

The Impact of Glucuronidation on the Bioactivation and DNA Adduction of the Cooked-Food Carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b] pyridine in vivo

UDP-glucuronosyltransferases (UGTs) catalyze the glucuronidation of many different chemicals. Glucuronidation is especially important for detoxifying reactive intermediates from metabolic reactions, which otherwise can be biotransformed into highly reactive cytotoxic or carcinogenic species. Detoxification of certain food-borne carcinogenic heterocyclic amines (HAs) is highly dependent on UGT1A-mediated glucuronidation. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most mass abundant carcinogenic HA found in well-done cooked meat, is extensively glucuronidated by UGT1A proteins. In humans, CYP1A2 catalyzed N-hydroxylation and subsequent UGT1A-mediated glucuronidation is a dominant pathway in the metabolism of PhIP. Therefore, changes in glucuronidation rates could significantly alter PhIP metabolism. To determine the importance of UGT1A-mediated glucuronidation in the biotransformation of PhIP, UGT1A proficient Wistar and UGT1A deficient Gunn rats were exposed to a single 100 {micro}g/kg oral dose of [{sup 14}C]-PhIP. Urine was collected over 24 h and the PhIP urinary metabolite profiles were compared between the two strains. After the 24 h exposure, livers and colon were removed and analyzed for DNA adduct formation by accelerator mass spectrometry. Wistar rats produced several PhIP and N-hydroxy-PhIP glucuronides that accounted for {approx}25% of the total amount of recovered urinary metabolites. In the Gunn rats, PhIP and N-hydroxy-PhIP glucuronides were reduced by 68-92%, compared to the Wistar rats, and comprised only 4% of the total amount of recovered urinary metabolites. PhIP-DNA adduct analysis from the Gunn rats revealed a correlation between reduced PhIP and N-hydroxy-PhIP glucuronide levels in the urine and increased hepatic DNA adducts, compared to the Wistar rats. These results indicate that UGT1A-mediated glucuronidation of PhIP and N-hydroxy-PhIP is an important pathway for PhIP detoxification. Failure to form glucuronide conjugates results in increases in PhIP bioactivation and DNA adduct formation, which can potentially lead to increases in tumor formation. Therefore, diminished UGT1A activity could pose a significant risk for the development of certain cancers from exposure to PhIP

Individualization of piperacillin dosing for critically ill patients: Dosing software to optimize antimicrobial therapy

Piperacillin-tazobactam is frequently used for empirical and targeted therapy of infections in critically ill patients. Considerable pharmacokinetic (PK) variability is observed in critically ill patients. By estimating an individual's PK, dosage optimization Bayesian estimation techniques can be used to calculate the appropriate piperacillin regimen to achieve desired drug exposure targets. The aim of this study was to establish a population PK model for piperacillin in critically ill patients and then analyze the performance of the model in the dose optimization software program BestDose. Linear, with estimated creatinine clearance and weight as covariates, Michaelis-Menten (MM) and parallel linear/MM structural models were fitted to the data from 146 critically ill patients with nosocomial infection. Piperacillin concentrations measured in the first dosing interval, from each of 8 additional individuals, combined with the population model were embedded into the dose optimization software. The impact of the number of observations was assessed. Precision was assessed by (i) the predicted piperacillin dosage and by (ii) linear regression of the observed-versus-predicted piperacillin concentrations from the second 24 h of treatment. We found that a linear clearance model with creatinine clearance and weight as covariates for drug clearance and volume of distribution, respectively, best described the observed data. When there were at least two observed piperacillin concentrations, the dose optimization software predicted a mean piperacillin dosage of 4.02 g in the 8 patients administered piperacillin doses of 4.00 g. Linear regression of the observed-versus-predicted piperacillin concentrations for 8 individuals after 24 h of piperacillin dosing demonstrated an r2 of > 0.89. In conclusion, for most critically ill patients, individualized piperacillin regimens delivering a target serum piperacillin concentration is achievable. Further validation of the dosage optimization software in a clinical trial is required. Copyrigh