A Simple Method for Estimating Alfalfa Fiber Content in the Field

Predictive equations for alfalfa (Medicago sativa L.) quality (PEAQ) based on length of the longest stem and maturity stage of the most mature stem in a sample were developed and validated for estimating neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations in alfalfa. The objective of this research was to validate PEAQ with a simplified maturity scale when estimating fiber content. Alfalfa samples varying in height and maturity were collected throughout the growing season from fields across six states in USA. Observed NDF and ADF values (determined via wet chemistry) were regressed on estimated values. The estimated values were calculated with PEAQ using the Kalu and Fick maturity scale (stages 2 to 6) and using a modified 3-stage scale consisting of vegetative stage (Kalu and Fick stage 2.0), bud stage (stage 3.5, i.e. averaged Kalu and Fick bud stages 3 and 4), and flower stage (stage 5.5, i.e. averaged Kalu and Fick flower stages 5 and 6). Regression equations for NDF and ADF were slightly biased (b 1.0 and/or y-intercept 0) for two of the three datasets regardless of the staging scale used. Prediction errors were similar regardless of the staging scale, ranging from 16.8 to 25.4 g kg-1 for NDF and 14.3 to 19.3 g kg-1 for ADF. We conclude that the 3-stage maturity scale can be used effectively in these equations for estimating alfalfa fiber content based on a combination of stem length and maturity

Pasture Weaning and Forage Barley to Extend the Grazing Season for Replacement Heifers

In a two-year study at the SDSU Cow/Calf Teaching and Research Unit, Brookings, SD, heifer calves were allotted to two weaning management treatments in early October at an average age of 202 days. The pasture-weaned group was separated from their dams and grazed grass pasture across the fence from their dams for two weeks. Then, until early December, they grazed “Robust” barley (forage type) that had been no-till planted into oat stubble in early August. The drylot-weaned group was fed a traditional weaning diet of grass hay, corn, and protein supplement from weaning until early December. The effect of management on heifer weight gain depended on year. In the first year, pasture-weaned heifers gained more than the drylot group during the first two weeks after weaning. Due to less than ideal pasture conditions in the second year, the drylot group gained more than the pasture weaned group for two and four weeks after weaning. In both years, gains from weaning to the end of the grazing period in December and to the following April were similar between management systems. Pasture weaning appeared to cause less stress for both cows and calves, but no differences in disease symptoms were observed. Antibody titers for IBR, BVD type 1 and BVD type 2 were determined at weaning and two and four weeks after weaning to measure the development of immunity from vaccinations administered two months prior to and at weaning. At two weeks after weaning in the second year of the study, antibody titer for BVD type 1 was greater for the drylot group than the pasture-weaned group. By four weeks after weaning the pasture-weaned heifers had antibody titers similar to the drylot group. The results of this study indicate that pasture weaning combined with small grain pasture to extend the grazing system can be an effective alternative for managing replacement heifers compared to a traditional drylot weaning system

A Critical Appraisal and Evaluation of Modern PDFs

We review the present status of the determination of parton distribution functions (PDFs) in the light of the precision requirements for the LHC in Run 2 and other future hadron colliders. We provide brief reviews of all currently available PDF sets and use them to compute cross sections for a number of benchmark processes, including Higgs boson production in gluon-gluon fusion at the LHC. We show that the differences in the predictions obtained with the various PDFs are due to particular theory assumptions made in the fits of those PDFs. We discuss PDF uncertainties in the kinematic region covered by the LHC and on averaging procedures for PDFs, such as advocated by the PDF4LHC15 sets, and provide recommendations for the usage of PDF sets for theory predictions at the LHC.Comment: 70 pages pdflatex, 19 figures, 17 tables; final versio

Seasonal Variation in Terrestrial Invertebrate Subsidies to Tropical Streams and Implications for the Feeding Ecology of Hart’s Rivulus (Anablepsoides hartii)

Terrestrial invertebrates are important subsidies to fish diets, though their seasonal dynamics and importance to tropical stream consumers are particularly understudied. In this year-round study of terrestrial invertebrate input to two Trinidadian headwater streams with different forest canopy densities, we sought to (a) measure the mass and composition of terrestrial inputs with fall-in traps to evaluate the influences of seasonality, canopy cover, and rainfall intensity, and; (b) compare terrestrial and benthic prey importance to Anablepsoides hartii(Hart’s Rivulus), the dominant invertivorous fish in these streams, by concurrently measuring benthic and drifting invertebrate standing stocks and the volume and composition of invertebrates in Rivulus guts throughout the year. The biomass of terrestrial invertebrate fall-in was 53% higher in the wet versus dry season; in particular, ant input was 320% higher. Ant biomass fall-in also increased with the density of canopy cover among sampling locations within both streams. Greater precipitation correlated with increased ant inputs to the more open-canopied stream and increased inputs of winged insects in the more closed canopy stream. Concurrently, the biomass of benthic invertebrates was reduced by more than half in the wet season in both streams. We detected no differences in the total volume of terrestrial prey in Rivulus diets between seasons, though ants were a greater proportion of their diet in the wet season. In contrast, benthic prey were nearly absent from Rivulus diets in the wet season in both streams. We conclude that terrestrial invertebrates are a substantial year-round prey subsidy for invertivores in tropical stream ecosystems like those we studied, which may contrast to most temperate streams where such terrestrial inputs are significantly reduced in the cold season. Interestingly, the strongest seasonal pattern in these tropical streams was observed in benthic invertebrate biomass which was greatly reduced and almost absent from Rivulus diets during the wet season. This pattern is essentially the inverse of the pattern observed in many temperate streams and highlights the need for additional studies in tropical ecosystems to better understand how spatial and temporal variation in terrestrial subsidies and benthic prey populations combine to influence consumer diets and the structure of tropical stream food webs

Propagation of cosmic-ray nucleons in the Galaxy

We describe a method for the numerical computation of the propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the halo propagation region is determined, using recent 10Be/9Be measurements, as >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration models. For convection models we set an upper limit on the velocity gradient of dV/dz < 7 km/s/kpc. The radial distribution of cosmic-ray sources required is broader than current estimates of the SNR distribution for all halo sizes. Full details of the numerical method used to solve the cosmic-ray propagation equation are given.Comment: 15 pages including 23 ps-figures and 3 tables, latex2e, uses emulateapj.sty (ver. of 11 May 1998, enclosed), apjfonts.sty, timesfonts.sty. To be published in ApJ 1998, v.509 (December 10 issue). More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.html Some references are correcte

Excitations in the Halo Nucleus He-6 Following The Li-7(gamma,p)He-6 Reaction

A broad excited state was observed in 6-He with energy E_x = 5 +/- 1 MeV and width Gamma = 3 +/- 1 MeV, following the reaction Li-7(gamma,p)He-6. The state is consistent with a number of broad resonances predicted by recent cluster model calculations. The well-established reaction mechanism, combined with a simple and transparent analysis procedure confers considerable validity to this observation.Comment: 3 pages of LaTeX, 3 figures in PostScript, approved for publication in Phys. Rev. C, August, 200

The Influence of Network Topology on Sound Propagation in Granular Materials

Granular materials, whose features range from the particle scale to the force-chain scale to the bulk scale, are usually modeled as either particulate or continuum materials. In contrast with either of these approaches, network representations are natural for the simultaneous examination of microscopic, mesoscopic, and macroscopic features. In this paper, we treat granular materials as spatially-embedded networks in which the nodes (particles) are connected by weighted edges obtained from contact forces. We test a variety of network measures for their utility in helping to describe sound propagation in granular networks and find that network diagnostics can be used to probe particle-, curve-, domain-, and system-scale structures in granular media. In particular, diagnostics of meso-scale network structure are reproducible across experiments, are correlated with sound propagation in this medium, and can be used to identify potentially interesting size scales. We also demonstrate that the sensitivity of network diagnostics depends on the phase of sound propagation. In the injection phase, the signal propagates systemically, as indicated by correlations with the network diagnostic of global efficiency. In the scattering phase, however, the signal is better predicted by meso-scale community structure, suggesting that the acoustic signal scatters over local geographic neighborhoods. Collectively, our results demonstrate how the force network of a granular system is imprinted on transmitted waves.Comment: 19 pages, 9 figures, and 3 table

A large pseudoautosomal region on the sex chromosomes of the frog Silurana tropicalis

Sex chromosome divergence has been documented across phylogenetically diverse species, with amphibians typically having cytologically nondiverged (“homomorphic”) sex chromosomes. With an aim of further characterizing sex chromosome divergence of an amphibian, we used “RAD-tags” and Sanger sequencing to examine sex specificity and heterozygosity in theWestern clawed frog Silurana tropicalis (also known as Xenopus tropicalis). Our findings based on approximately 20 million genotype calls and approximately 200 polymerase chain reaction-amplified regions across multiple male and female genomes failed to identify a substantially sized genomic region with genotypic hallmarks of sex chromosome divergence, including in regions known to be tightly linked to the sex-determining region.Wealso foundthat expression andmolecular evolutionof genes linked to the sex-determining region did not differ substantially from genes in other parts of the genome. This suggests that the pseudoautosomal region, where recombination occurs, comprises a large portion of the sex chromosomes of S. tropicalis. These resultsmay in part explainwhy African clawed frogs have such a high incidence of polyploidization, shed light onwhy amphibians have a high rate of sex chromosome turnover, and raise questions about why homomorphic sex chromosomes are so prevalent in amphibians

QED Radiative Corrections for Parton Distributions

I discuss radiative corrections due to the emission of photons from quarks which contribute to deep inelastic lepton--nucleon scattering as well as to $pp$ collisions at high energies. These corrections are dominated by quark-mass singularities which have to be absorbed into the parton distribution functions. Observable effects appear as a modification of the $Q^2$ dependence of the distribution functions. Numerical results indicate, however, that these QED corrections are negligible except at extremely large $Q^2$ and large $x$. Therefore it is safe to neglect the single and multiple photon effects in $pp$ scattering at LHC energies.Comment: 13 pages, uuencoded latex with postscript, 3 figures include

Diphoton Production at Hadron Colliders and New Contact Interactions

We explore the capability of the Tevatron and LHC to place limits on the possible existence of flavor-independent $q \bar q \gamma\gamma$ contact interactions which can lead to an excess of diphoton events with large invariant masses. Assuming no departure from the Standard Model is observed, we show that the Tevatron will eventually be able to place a lower bound of 0.5-0.6 TeV on the scale associated with this new contact interaction. At the LHC, scales as large as 3-6 TeV may be probed with suitable detector cuts and an integrated luminosity of $100 fb^{-1}$.Comment: LaTex, 12pages plus 5 figures(available on request), SLAC-PUB-657