排序方式： 共有28条查询结果，搜索用时 343 毫秒
21.
Graziella Mura 《International Journal of Salt Lake Research》1994,3(2):201-219
Ecological studies onArtemia are still sparse, particularly in the Mediterranean area. The paper provides information on the main life-history traits of a bisexualArtemia strain in solar saltworks at Sant'Antioco, in the Province of Cagliari (southern Sardinia, Italy). Data on age class composition, reproductive mode and status, fecundity and other features are discussed in relation to environmental conditions and compared with previous studies. 相似文献
22.
Graziella Pizzichini 《Astrophysics and Space Science》1981,75(1):205-210
One of the most recent discoveries on gamma-ray bursts was the fact that one, or possibly two, of them had a pulsed emission with a periodicity of 8 and 4 s. The intensity of successive peaks decreased exponentially with time. We can speculate that the energy range and/or the lack of sensitivity are probably the reasons why periodicities were not discoverded in some other bursts. In fact, many time-histories show a double or multiple peak structure. If they were periodic, the distance between successive peaks would be equal to the period. Based on this extremely simplified assumption, a search on all available gamma-ray burst time-histories shows that most the periodicities above 1 s should be contained within an interval between 1 and 9 s, with a maximum at approximately 3 s.Paper presented at the Symposium on Cosmic Gamma-Ray Bursts held at Toulouse, France, 26–29 November, 1979. 相似文献
23.
A digital landslide database has been created for Nicaragua to provide the scientific community and national authorities with
a tool for landslide-hazard assessment, emergency management, land-use planning, development of early warning systems, and
the implementation of public and private policies. The Instituto Nicaragüense de Estudios Territoriales (Nicaraguan Geosciences
Institute, INETER) began to compile the database in a digital format in 2003 as part of a comprehensive geographical information
system for all types of geohazards. Landslide data have been obtained from a variety of sources including newspapers, technical
reports, and landslide inventory maps. Inventory maps are largely based on fieldwork and aerial-photo analyses conducted by
foreign development agencies in collaboration with INETER and other Nicaraguan institutions. This paper presents the sources
of landslide information, introduces the database, and presents the first analyses of the data at national and regional scales.
The database currently contains spatial information for about 17,000 landslides that occurred in mountainous and volcanic
terrains. Information is mainly recorded for the period 1826–2003, with a large number of events that occurred during the
disastrous Hurricane Mitch in October 1998. The oldest historical event is dated at 1570, some events are recorded as prehistorical,
and other events have unknown dates of occurrence. Debris flows have been the most common types of landslides, both in volcanic
and nonvolcanic areas, but other types, including rockfalls and slides, have also been identified. Intense and prolonged rainfall,
often associated with tropical cyclones, and seismic and volcanic activity represent the most important landslide triggers.
At a regional scale, the influence of topographic (elevation, slope angle, slope aspect) and lithologic parameters on the
occurrence of landslides was analyzed. The development of the database allowed us to define the state of knowledge on landslide
processes in the Nicaragua and to provide a preliminary identification of areas affected by landslides. 相似文献
24.
Core and surface sediments from the Tonalli River, a tributary of the artificial lake, Lake Burragorang, in the Blue Mountains National Park, New South Wales, Australia, were studied to evaluate the spatio-temporal distribution of pollutants from the Yerranderie silver-lead-zinc mine site, abandoned in the late 1920s. A sediment core was collected in the mouth of the Tonalli River, at its junction with Lake Burragorang, and surface sediment samples were collected in the Tonalli River and its tributaries. The concentrations of Pb, As, Zn, Cu, Cd, Hg and Ag in the sediments were determined by ICP-MS and ICP-AES techniques. Temporal variability of metal concentrations was established through 210Pb dating of the core sediments and compared with published historical records, rainfall records and bushfire data. Metal concentrations in core sediments showed an overall increase around the year 1950 as well as increases coincident with heavy rainfall. Spatially, metal concentrations were up to 400 times the guideline limit around mine sites but decreased rapidly with distance downstream of the mines. 相似文献
25.
We studied north Tyrrhena Terra, an approximately 39,000 km2 area, located in the transition region straddling the Amenthes and Mare Tyrrhenum Mars Chart quadrangles 14 and 22, respectively. The study area comprises ancient terrains with infilled craters, ridges and valleys. Interpretation of orbiter data of ancient terrains is inherently difficult, but valuable information can be obtained using multiple datasets and analyzing various geological features. Using data from the High Resolution Stereo Camera on board Mars Express, complemented by Mars Global Surveyor MOLA DEM and MOC Narrow Angle datasets, we observed and interpreted surface morphologies at a scale suitable for geologic investigation. Morphometric examination of a 31 km diameter large impact crater indicated that tectonism and volcanism were responsible for its morphologic modification. Small impact crater depth/diameter relationships indicated that smooth surfaces of valleys are composed of highly consolidated material. Surface cracks and lobate fronts further suggested that the rocks are volcanic. Examination of tectonic features revealed that in the study area: a dominant NW-SE fabric is related to a ridge/bench-scarp-valley repetition consistent with synthetic and antithetic normal faulting; a NNW-SSE lineament represents the surface expression of normal faulting post-dating all other tectonic features. A weak NE-SW fabric is observable as small sublinear depressions, and at the contact between units internal to one large crater. One 20 km diameter crater in the study area was interpreted to be a caldera, infilled by thick volcanic rock layers. Identification of wrinkle ridges further indicated that thick layered lava flows infilled the main depressions of the study area. The available evidence suggests that the study area underwent multiple episodes of extension and volcanism. 相似文献
26.
27.
Rosana?Menéndez-DuarteEmail author Jorge?Marquínez Graziella?Devoli 《Environmental Geology》2003,44(3):290-300
The heavy rains associated with Hurricane Mitch triggered off a number of slope instability processes in several Central American countries. Different instability processes have been acknowledged for the various mountainous regions of Nicaragua. An enormous movement of the Casita Volcano slopes resulted in numerous deaths and some deep movements have been reactivated. On the other hand, numerous shallow mass movements and debris flows have given rise to great material loss throughout a large part of Nicaraguan mountains.Mapping the shallow mass movements in an area of Central Nicaragua clearly reveals the close ties between their distribution and some geomorphological factors. A susceptibility model has been constructed for shallow mass movements based on field mapping of the shallow mass movement distribution, the geomorphological map as well as the digital slope and accumulated flow models. A logistical regression analysis was applied. The study area has been categorized into three classes of relative landslide susceptibility. Given that phenomena of this nature occur much more frequently in the high susceptibility class, 94% of the shallow mass movements that have been used to test the model are in the high and medium susceptibility classes . The geological and geomorphological conditions of the study area are representative of a large sector of the central Nicaraguan region. Consequently, the methodology followed in this paper is deemed to constitute a useful tool, both regarding the design of new infrastructures, and as a guide to the urban development of the area. 相似文献
28.
AXIOM: advanced X-ray imaging of the magnetosphere 总被引：1，自引：0，他引：1
Graziella Branduardi-Raymont Steve F. Sembay Jonathan P. Eastwood David G. Sibeck Tony A. Abbey Patrick Brown Jenny A. Carter Chris M. Carr Colin Forsyth Dhiren Kataria Steve Kemble Steve E. Milan Chris J. Owen Lisa Peacocke Andy M. Read Andrew J. Coates Michael R. Collier Stan W. H. Cowley Andrew N. Fazakerley George W. Fraser Geraint H. Jones Rosine Lallement Mark Lester F. Scott Porter Tim K. Yeoman 《Experimental Astronomy》2012,33(2-3):403-443
Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission. 相似文献