Geophysical,socio-demographic characteristics and perception of flood vulnerability in Accra,Ghana   总被引：1，自引：1，他引：0  

Samuel Nii Ardey Codjoe  Samuel Afuduo 《Natural Hazards》2015,77(2):787-804

  相似文献   

Interacting Ricci-like holographic dark energy     

F. Arévalo  P. Cifuentes  Samuel Lepe  Francisco Peña 《Astrophysics and Space Science》2014,352(2):899-907

In a flat Friedmann–Lemaitre–Robertson–Walker background, a scheme of dark matter–dark energy interaction is studied considering a holographic Ricci-like model for the dark energy. Without giving a priori some specific model for the interaction function, we show that this function can experience a change of sign during the cosmic evolution. The parameters involved in the holographic model are adjusted with Supernova data and we obtained results compatible with the observable universe.  相似文献   

The nature of the molecular gas system in the core of NGC 1275     

R. J. Wilman  A. C. Edge  R. M. Johnstone 《Monthly notices of the Royal Astronomical Society》2005,359(2):755-764

  相似文献   

Powerful, obscured active galactic nuclei among X-ray hard, optically dim serendipitous Chandra sources     

P. Gandhi  C. S. Crawford  A. C. Fabian  R. M. Johnstone 《Monthly notices of the Royal Astronomical Society》2004,348(2):529-550

  相似文献   

The February 1986 solar activity: A comparison of GIOTTO,VEGA-1, and IMP-8 solar wind measurements with MHD simulations     

M. Dryer  Z. K. Smith  A. J. Coates  A. D. Johnstone 《Solar physics》1991,132(2):353-371

Large disturbances in the interplanetary medium were observed by several spacecraft during a period of enhanced solar activity in early February 1986. The locations of six solar flares and the spacecraft considered here encompassed more than 100° of heliolongitude. These flares during the minimum of cycle 21 set the stage for an extensive multi-spacecraft comparison performed with a two-dimensional, magnetohydrodynamic (MHD) numerical experiment. The plasma instruments on the European Space Agency (ESA)'s GIOTTO spacecraft, on its way to encounter Comet Halley in March 1986, made measurements of the solar wind for up to 8 hours per day during February. We compare solar wind measurements from the Johnstone Plasma Analyzer (JPA) experiment on GIOTTO with the MHD simulation of the interplanetary medium throughout these events. Using plasma data obtained by the IMP-8 satellite in addition, it appears that an extended period of high solar wind speed is required as well as the simulated flares to represent the interplanetary medium in this case. We also compare the plasma and magnetometer data from VEGA-1 with the MHD simulation. This comparison tends to support an interpretation that the major solar wind changes at both GIOTTO and VEGA-1 on 8 February, 1986 were due to a shock from a W05° solar flare on 6 February, 1986 (06:25 UT). The numerical experiment is considered, qualitatively, to resemble the observations at the former spacecraft, but it has less success at the latter one.  相似文献   

A problem of discrete approximations to an arbitrarily varying one-dimensional seismic model     

Samuel H. Gray 《Geophysical Journal International》1984,78(2):431-437

  相似文献   

A statistical study of environmental factors controlling concentrations of heavy metals in the burrowing bivalve Scrobicularia plana and the polychaete Nereis diversicolor     

Samuel N. Luoma  G.W. Bryan 《Estuarine, Coastal and Shelf Science》1982,15(1):95-108

Multiple regression analyses indicate that the most important factors controlling Ag, Cd, Co, Cu, Pb and Zn concentrations in the estuarine bivalve Scrobicularia plana and the polychaete Nereis diversicolor are the concentrations of these metals in surface sediments and the partitioning of sediment-bound metals between different sediment constituents. Extraction of the sediments with 1-n HCl provides more information about the bioavailability of the metals than do extractions with five other techniques. Biologically available Cd and Co in solution contribute significantly to Cd and Co concentrations in both Scrobicularia and Nereis. Concentrations of Ag in Scrobicularia are reduced where Cu concentrations in sediments are high. An unexplained increase in concentrations of Cu in Scrobicularia at specific stations in six estuaries suggests that under certain very anoxic conditions the availability of copper may be exceptionally high.  相似文献   

Fast solar electrons,interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft     

Hector Alvarez  Robert P. Lin  Samuel J. Bame 《Solar physics》1975,44(2):485-501

IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons.  相似文献   

Soil feedback drives the mid-Holocene North African monsoon northward in fully coupled CCSM2 simulations with a dynamic vegetation model   总被引：1，自引：0，他引：1  

Samuel Levis  Gordon B. Bonan  Céline Bonfils 《Climate Dynamics》2004,23(7-8):791-802

We explore climate-vegetation interactions in mid-Holocene North Africa with a suite of community climate system model (CCSM2) simulations. The CCSM includes synchronously coupled atmosphere, ocean, sea ice, land, and vegetation models. The CCSMs present-day precipitation for North Africa compares well with simulations of other models and observations. Mid-Holocene data reveal a wetter and greener Sahara compared to the present. The CCSM exhibits a greater, closer to the expected, precipitation increase than other models, and in response, grasses advance from 18.75° to 22.5°N in much of North Africa. Precipitation is enhanced locally by the northward advance of grasses, but suppressed regionally mainly due to an insufficient albedo decrease with the expansion of vegetation. Prior studies have always lowered the surface albedo with the expansion of vegetation in North Africa. In the CCSMs mid-Holocene simulations, the albedo decreases more because wetter soils are simulated darker than drier soils than due to expanding vegetation. These results isolate albedo as the key ingredient in obtaining a positive precipitation-vegetation feedback in North Africa. Two additional simulations support this conclusion. In the first simulation, the deserts sandy soil textures are changed to loam to represent increased organic matter. Soil water retention and grass cover increase; albedo decreases somewhat. Precipitation responds with a small, yet widespread, increase. In the second simulation, a darker soil color is prescribed for this region. Now the monsoon advances north about 4°. These results illustrate a North African monsoon highly sensitive to changes in surface albedo and less sensitive to changes in evapotranspiration.  相似文献   

Climate change, adaptation and economic growth     

Alex Bowen  Sarah Cochrane  Samuel Fankhauser 《Climatic change》2012,113(2):95-106

This paper explores the links between economic growth and the impacts of climate change. Inclusive, pro-poor growth is central to the development of low-income countries. There is also a broad consensus that growth and development are important to reduce vulnerability to climate change. Growth does not automatically reduce vulnerability, only the right kind of growth does. The paper aims to develop a better understanding of what the ??right kind of growth?? may be. We find that many growth policies, such as investment in skills and access to finance, indeed reduce vulnerability to climate change. However, climate change calls for some adjustments in growth policy. In particular, investment in infrastructure and efforts to stimulate entrepreneurship and competitive markets must take more of a risk management perspective and recognise climate risks.  相似文献