Time-reversal-noninvariant, parity-conserving nuclear interactions

The work that has been done in compound nucleus studies of time-reversal-noninvariant (TRNI), parity-conserving (PC) NN interactions is reviewed. The general form of TRNI PC meson-exchange potentials that can be constrained by such studies is discussed a la Simonius. The competing limits that can be obtained from atomic electric dipole moments produced by weak radiative corrections to long-ranged TRNI PNC interactions are then explored. Both classes of constraints limit the magnitude of typical TRNI PC matrix elements to about 10{sup {minus}3} of those for strong interactions. These limits are contrasted with those recently obtained from short-ranged one- and two-loop weak radiative corrections

Onset of the aerobic nitrogen cycle during the Great Oxidation Event

The rise of oxygen on the early Earth (about 2.4 billion years ago)1 caused a reorganization of marine nutrient cycles2, 3, including that of nitrogen, which is important for controlling global primary productivity. However, current geochemical records4 lack the temporal resolution to address the nature and timing of the biogeochemical response to oxygenation directly. Here we couple records of ocean redox chemistry with nitrogen isotope (15N/14N) values from approximately 2.31-billion-year-old shales5 of the Rooihoogte and Timeball Hill formations in South Africa, deposited during the early stages of the first rise in atmospheric oxygen on the Earth (the Great Oxidation Event)6. Our data fill a gap of about 400 million years in the temporal 15N/14N record4 and provide evidence for the emergence of a pervasive aerobic marine nitrogen cycle. The interpretation of our nitrogen isotope data in the context of iron speciation and carbon isotope data suggests biogeochemical cycling across a dynamic redox boundary, with primary productivity fuelled by chemoautotrophic production and a nitrogen cycle dominated by nitrogen loss processes using newly available marine oxidants. This chemostratigraphic trend constrains the onset of widespread nitrate availability associated with ocean oxygenation. The rise of marine nitrate could have allowed for the rapid diversification and proliferation of nitrate-using cyanobacteria and, potentially, eukaryotic phytoplankton

A 50-year record of NOx and SO2 sources in precipitation in the Northern Rocky Mountains, USA

Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ15N, ) and sulfur (δ34S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ34S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington. The remaining δ34S values were similar to the isotopic composition of coal from southern Wyoming. The δ15N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and all fall within the δ15N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S. emissions data from 1950 to the mid-1970s

Gesundheitliche Bewertung von 35 Sprengstoff-typischen Verbindungen und Abbauprodukten

Oral toxicity data of 35 typical explosive chemicals (nitrobenzenes, nitrotoluenes, nitroanilines, nitroxylenes, esters of nitric acid) have been compiled, and for most of these compounds a toxicological assessment is given. The assessment is based on the 'Proposal on a standardized toxicological evaluation of chemicals from contaminated sites' by Dieter et al. (Chemosphere 20, 1990, 75-90). For each of the discussed substances a special monography has been compiled. (WEN)SIGLEAvailable from TIB Hannover: RO 2237(1994,6) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekNiedersaechsisches Landesamt fuer Oekologie, Hildesheim (Germany); Saechsisches Staatsministerium fuer Umwelt und Landesentwicklung, Dresden (Germany); Regierungspraesidium Giessen (Germany)DEGerman