An eigenfunction method for particle acceleration at ultra-relativistic shocks

We adapt and modify the eigenfunction method of computing the power-law spectrum of particles accelerated at a relativistic shock front via the first-order Fermi process (Kirk, J.G., Schneider, P., Astrophysical Journal 315, 425 (1987)) to apply to shocks of arbitrarily high Lorentz factor. The power-law index of accelerated particles undergoing isotropic small-angle scattering at an ultrarelativistic, unmagnetized shock is found to be s=4.23 +/- 0.2 (where s=d\ln f/ d\ln p, with f the Lorentz-invariant phase-space density and p the momentum), in agreement with the results of Monte-Carlo simulations. We present results for shocks in plasmas with different equations of state and for Lorentz factors ranging from 5 to infinity.Comment: 4 pages, 2 figures, contribution to the Proceedings of the 5th Huntsville GRB Symposiu

The Integration of Rural Households into Ruminant Livestock Industries in China

A major determinant of rural development in China is the way by which rural households integrate with rural industries. Three forms of integration market integration, vertical integration and integration through local groups are investigated. Policy measures that may facilitate household integration, household specialisation and market segmentation are identified. Findings for the ruminant livestock sector are widely applicable to other agricultural industries in China.China, rural development, livestock, markets, vertical integration, Livestock Production/Industries, Q13, Q18, L1,

Particle Acceleration at Ultra-Relativistic Shocks and the Spectra of Relativistic Fireballs

We examine Fermi-type acceleration at relativistic shocks, and distinguish between the initial boost of the first shock crossing cycle, where the energy gain per particle can be very large, and the Fermi process proper with repeated shock crossings, in which the typical energy gain is of order unity. We calculate by means of numerical simulations the spectrum and angular distribution of particles accelerated by this Fermi process, in particular in the case where particle dynamics can be approximated as small-angle scattering. We show that synchrotron emission from electrons or positrons accelerated by this process can account remarkably well for the observed power-law spectra of GRB afterglows and Crab-like supernova remnants. In the context of a decelerating relativistic fireball, we calculate the maximum particle energy attainable by acceleration at the external blast wave, and discuss the minimum energy for this acceleration process and its consequences for the observed spectrum.Comment: To appear in Proceedings of the 5th Huntsville Gamma-Ray Burst Symposium. LaTeX, 6 pages, 2 figures, uses aipproc.sty and epsfi

The natural resources of Bolinas Lagoon: their status and future

This publication is an integral part of the Department's high-priority inventory and assessment of coastal marshland and tideflat resources. It is intended as a guide for citizens, planners, administrators, and all others interested in the use and development of coastal lands and waters. Although the resources and problems of Bolinas Lagoon have probably been the subject of more biological and physical investigations than any small estuarine area of the California coast, many of the pertinent reports and information are not readily available to the public. Consequently, it is one purpose of this report to summarize the lagoon's history, ecological attractions, educational values and the problems facing its continued existence. At the same time, it should provide concerned citizens with a knowledge of the sources of additional and more specific information. Publication of this report is consistent with the obligation of the Department of Fish and Game to do everything in its power to protect and maintain the State's fish and wildlife resources. Therefore, its purpose transcends local issues on pollution and development, and the Department is, in fact, submitting a report to the people on the status and future of part of its inheritance and the dowry of coming generations. The report is the third of a scheduled series. It follows similar releases on Upper Newport Bay (Orange County) and Goleta Slough (Santa Barbara county) in March and June of 1970. Documentation of the resources of other critical areas is in progress. There will be future reports of this nature on Elkhorn Slough, Morro Bay, Tomales Bay, Humboldt Bay, and highly threatened marshlands in southern California. (137 pp.

The application of low crude protein wheat-soyabean diets to growing and finishing pigs: 2. The effects on nutrient digestibility, nitrogen excretion, faecal volatile fatty acid concentration and ammonia emission from boars

peer-reviewedThis study received financial support from Telltech Ltd. (Wicklow, Ireland) and Enterprise Ireland (Dublin, Ireland).Diets containing 132, 152, 183 and 206 g/kg crude protein (CP) were fed to growing and finishing boars to evaluate the effect on nutrient digestibility, N balance, faecal volatile fatty acids (VFA) and ammonia-N (NH3–N) emission. Dietary CP concentration was adjusted by altering the ratio of wheat:soyabean meal. Lysine, threonine, tryptophan and total sulphur-containing amino acids were included in all diets at concentrations equivalent to that in the highest CP diet. All diets were formulated to provide 9.7 MJ/kg of net energy. Urine and faeces were collected from 16 boars (4 boars per treatment) housed in metabolism crates. Collections were performed at 72, 80 and 87 kg live weight. NH3–N emission was measured over 10 days using a laboratory scale procedure. Reducing the concentration of dietary CP decreased N intake (linear, P < 0.01), the excretion of urinary N, ammoniacal N and total N (linear, P < 0.001; cubic, P < 0.001) and the emission of NH3–N (linear, P < 0.001; cubic, P < 0.01). Total N excretion and NH3–N emission decreased 8.7% and 10.1% per 10 g/kg reduction in dietary CP concentration between 205.6 and 131.9 g/kg, respectively. There was no interaction between dietary CP concentration and collection period. N balance differed between the collection periods and less NH3–N was emitted at 87 kg than at 72 kg. Decreasing dietary CP reduced faecal VFA concentration (linear, P < 0.05) and the molar proportions of acetic and butyric acids (quadratic, P < 0.01).Enterprise Irelan

Liquid-Vapor Equilibrium of Multicomponent Cryogenic Systems

Liquid-vapor and solid-vapor equilibria at low to moderate pressures and low temperatures are important in many solar system environments, including the surface and clouds of Titan, the clouds of Uranus and Neptune, and the surfaces of Mars and Triton. The familiar cases of ideal behavior are limiting cases of a general thermodynamic representation for the vapor pressure of each component in a homogeneous multicomponent system. The fundamental connections of laboratory measurements to thermodynamic models are through the Gibbs-Duhem relation and the Gibbs-Helmholtz relation. Using laboratory measurements of the total pressure, temperature, and compositions of the liquid and vapor phases at equilibrium, the values of these parameters can be determined. The resulting model for vapor-liquid equilibrium can then conveniently and accurately be used to calculate pressures, compositions, condensation altitudes, and their dependencies on changing climatic conditions. A specific system being investigated is CH4-C2H6-N2, at conditions relevant to Titan's surface and atmosphere. Discussed are: the modeling of existing data on CH4-N2, with applications to the composition of Titan's condensate clouds; some new measurements on the CH4-C2H6 binary, using a high-precision static/volumetric system, and on the C2H6-N2 binary, using the volumetric system and a sensitive cryogenic flow calorimeter; and describe a new cryogenic phase-equilibrium vessel with which we are beginning a detailed, systematic study of the three constituent binaries and the ternary CH4-C2H6-N2 system at temperatures ranging from 80 to 105 K and pressures from 0.1 to 7 bar

Coulomb Drag between One-Dimensional Wigner Crystal Rings

We consider the Coulomb drag between two metal rings in which the long range Coulomb interaction leads to the formation of a Wigner crystal. The first ring is threaded by an Ahranov Bohm flux creating a persistent current J_0. The second ring is brought in close proximity to the second and due to the Coulomb interaction between the two rings a drag current J_D is produced in the second. We investigate this system at zero temperature for perfect rings as well as the effects of impurities. We show that the Wigner crystal state can in principle lead to a higher ratio of drag current to drive current J_D/J_0 than in weakly interacting electron systems.Comment: 12 pages, 10 figure

Building economic decision-making capabilities of Chinese wool textile mills

Agribusiness,