Deflection of Highly Relativistic Particles in a Gravitational Field

A novel approach to the calculation of the deflection of highly relativistic test particles in gravitational fields is described. We make use of the light-like boosts of the gravitational fields of the sources. Examples are given of the deflection of highly relativistic particles in the Schwarzschild and Kerr gravitational fields, in the field of a static, axially symmetric, multipole source and in the field of a cosmic string. The deflection of spinning particles is also discussed.Comment: 18 pages, 2 figures, accepted for publication in Classical and Quantum Gravit

Dynamics of N removal over annual time periods in a suburban river network

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): G03038, doi:10.1029/2007JG000660.River systems are dynamic, highly connected water transfer networks that integrate a wide range of physical and biological processes. We used a river network nitrogen (N) removal model with daily temporal resolution to evaluate how elevated N inputs, saturation of the denitrification and total nitrate removal processes, and hydrologic conditions interact to determine the amount, timing and distribution of N removal in the fifth-order river network of a suburban 400 km2 basin. Denitrification parameters were based on results from whole reach 15NO3 tracer additions. The model predicted that between 15 and 33% of dissolved inorganic nitrogen (DIN) inputs were denitrified annually by the river system. Removal approached 100% during low flow periods, even with the relatively low and saturating uptake velocities typical of surface water denitrification. Annual removal percentages were moderate because most N inputs occurred during high flow periods when hydraulic conditions and temperatures are less favorable for removal by channel processes. Nevertheless, the percentage of annual removal occurring during above average flow periods was similar to that during low flow periods. Predicted river network removal proportions are most sensitive to loading rates, spatial heterogeneity of inputs, and the form of the removal process equation during typical base flow conditions. However, comparison with observations indicates that removal by the river network is higher than predicted by the model at moderately high flows, suggesting additional removal processes are important at these times. Further increases in N input to the network will lead to disproportionate increases in N exports due to the limits imposed by process saturation.This work was funded by NSF-DEB- 0614282, NSF-OCE-9726921, NSF-DEB-0111410, and NSF-BCS- 0709685

Evolution des pratiques vaccinales entre 2007 et 2010 chez les patients infectés par le VIH (une étude prospective auprès des centres hospitaliers de la COREVIH d'Alsace)

STRASBOURG-Medecine (674822101) / SudocSudocFranceF