The use of GPS-arrays in detecting shock-acoustic waves generated during rocket launchings

This paper is concerned with the form and dynamics of shock-acoustic waves (SAW) generated during rocket launchings. We have developed a method for determining SAW parameters (including angular characteristics of the wave vector, and the SAW phase velocity, as well as the direction towards the source) using GPS-arrays whose elements can be chosen out of a large set of GPS-stations of the global GPS network. The application of the method is illustrated by a case study of ionospheric effects from launchings of launch vehicles (LV) Proton and Space Shuttle from space-launch complexes Baikonur and Kennedy Space Center (KSC) in 1998 and 1999 (a total of five launchings). The study revealed that, in spite of a difference of LV characteristics, the ionospheric response for all launchings had the character of an N - wave corresponding to the form of a shock wave, regardless of the disturbance source (rocket launchings, industrial explosions). The SAW period T is 270--360 s, and the amplitude exceeds the standard deviation of TEC background fluctuations in this range of periods under quiet and moderate geomagnetic conditions by factors of 2 to 5 as a minimum. The angle of elevation of the SAW wave vector varies from 30 degree to 60 degree, and the SAW phase velocity (900-1200 m/s) approaches the sound velocity at heights of the ionospheric F-region maximum.Comment: EmTeX-386, 23 pages, 6 figure

Breve resenha histórica sobre a normalização contabilística nacional

Este trabalho tem por objetivo apresentar os resultados de uma revisão da literatura sobre o processo de normalização contabilística em termos nacionais, de modo a enquadrar a situação atual. A metodologia seguida traduziu-se numa revisão da literatura e na análise de conteúdo de diversos artigos e textos, assim como de documentos diretamente relacionados com a temática em análise. Conclui-se pela identificação e caracterização do atual cenário de normalização contabilística. Pretende se com isto ajudar a perceber qual a evolução da normalização contabilística em Portugal, qual a situação atual e evolução provável

Tree species regeneration after logging in temperate rainforest, Tasmania

Selective mechanized logging for Athrotaxis selaginoides in temperate rainforest south of Rosebery in western Tasmania has resulted in a maze of logging tracks and associated destruction of part of the forest by firing. Mapping and analysis of regeneration of A. seleginoides, Phyllocladus aspleniifolius, Eucryphia lucida and Nothofagus cunninghamii at sites logged ten and twenty years previous to the study suggest that little successful tree establishment can be expected on areas where the topsoil has been removed by bulldozers, although the sides of the tracks where this material has been piled promise a restoration of the forest canopy. A. selaginoides and P. aspleniifolius establish in low densities after logging but appear to have low apparent rates of mortality in contrast to E. lucida and N. cunninghamii which establish in high densities, but have high apparent rates of mortality

Ionospheric effects of the solar flares of September 23, 1998 and July 29, 1999 as deduced from global GPS network data

This paper presents data from first GPS measurements of global response of the ionosphere to solar flares of September 23, 1998 and July 29, 1999. The analysis used novel technology of a global detection of ionospheric effects from solar flares (GLOBDET) as developed by one of the authors (Afraimovich E. L.). The essence of the method is that use is made of appropriate filtering and a coherent processing of variations in total electron content (TEC) in the ionosphere which is determined from GPS data, simultaneously for the entire set of visible (over a given time interval) GPS satellites at all stations used in the analysis. It was found that fluctuations of TEC, obtained by removing the linear trend of TEC with a time window of about 5 min, are coherent for all stations and beams to the GPS satellites on the dayside of the Earth. The time profile of TEC responses is similar to the time behavior of hard X-ray emission variations during flares in the energy range 25-35 keV if the relaxation time of electron density disturbances in the ionosphere of order 50-100 s is introduced. No such effect on the nightside of the Earth has been detected yet.Comment: EmTeX-386, 13 pages, 5 figure

Dynamics of continental deformation in Asia

International audienceThe relevance of plate tectonics concepts to the description of deformation of large continental areas like Asia is subject to much debate. For some, the deformation of continents is better described by rigid motion of lithospheric blocks with strain concentrated along narrow fault zones. For others, it is better described by viscous flow of a continuously deforming solid in which faults play a minor role. Discriminating these end-member hypotheses requires spatially dense measurements of surface strain rates covering the whole deforming area. Here we revisit the issue of the forces and rheological structure that control present-day deformation in Asia. We use the ‘‘thin sheet'' theory, with deformation driven by the balance of boundary and buoyancy stresses acting on a faulted lithosphere with laterally varying strength. Models are validated against a recent, homogeneous, GPS velocity field that covers most of Asia. In the models, deformation in compressional areas (Himalayas, Tien Shan, Altay) is well reproduced with strong coupling at the India/Eurasia plate contact, which allows for boundary forces to transfer into Asia. Southeastward motions observed in north and south China, however, require tensional, oceanward directed stresses, possibly generated by gravitational potential energy gradients across the Indonesian and Pacific subductions. Model and observed strain rates show that a large part of Asia undergoes no resolvable strain, with a kinematics apparently consistent with block- or plate-like motions. Internal strain, possibly continuous, is limited to high-elevation, mechanically weaker areas. Lateral variations of lithospheric strength appear to control the style of deformation in Asia, with a dynamics consistent with the thin sheet physical framework

Lecture et bibliothèques publiques : actes du colloque, Hénin-Beaumont, 20-21 novembre 1981

« Document numérisé pour l\u27ENSSIB » - Ce document s\u27adresse aux professionnels des bibliothèques, et plus largement, aux acteurs de la vie culturelle. Il s\u27agit des actes du colloque consacré à la lecture et aux bibliothèques publiques qui s\u27est tenu à Hénin-Beaumont les 20 et 21 novembre 1981. Ce document aborde l\u27ensemble des questions et problèmes liés au développement de la lecture et des bibliothèques publiques, spécialement en région Nord - Pas-de-Calais. Les différentes interventions dressent un état des lieux de la situation régionale en la matière afin de réfléchir aux actions à mener en faveur de la lecture publique et d\u27élaborer une stratégie de développement efficace avec la participation de tous les acteurs du monde culturel de la région. L\u27intérêt de cet ouvrage réside dans cette vocation régionale qui permet d\u27appréhender concrètement la question de la lecture publique dans un contexte donné. Certes, cette étude précise ne peut être généralisée au niveau national, mais elle offre l\u27opportunité de comprendre les enjeux de la lecture publique au niveau local, ainsi que les réflexions et problèmes qu\u27ils sous-tendent. Par ailleurs, quelques tableaux font référence à d\u27autres régions françaises, amenant des comparaisons intéressantes

Role of mantle flow in Nubia-Somalia plate divergence

Present-day continental extension along the East African Rift System (EARS) has often been attributed to diverging sublithospheric mantle flow associated with the African Superplume. This implies a degree of viscous coupling between mantle and lithosphere that remains poorly constrained. Recent advances in estimating present-day opening rates along the EARS from geodesy offer an opportunity to address this issue with geodynamic modeling of the mantle-lithosphere system. Here we use numerical models of the global mantle-plates coupled system to test the role of present-day mantle flow in Nubia-Somalia plate divergence across the EARS. The scenario yielding the best fit to geodetic observations is one where torques associated with gradients of gravitational potential energy stored in the African highlands are resisted by weak continental faults and mantle basal drag. These results suggest that shear tractions from diverging mantle flow play a minor role in present-day Nubia-Somalia divergence.This work was supported by NSF award EAR-0538119 to E.C. D.S.S. was supported by NSF graduate research fellowship EAR-2009052513. G.I. acknowledges support from the Ringwood Fellowship at the Australian National University