Multicolor (BV RIJHK) observations of the BL Lac object S5 0716+714 carried out irom 2001–2004 indicate that the spectral energy distribution
of the slowly varying component remained constant over the entire wavelength interval and over the three-year observation
period. The distribution can be represented by the power law Fv ∼ v−1.12, providing evidence that this component has a synchrotron nature. The color characteristics of very rapid variability detected
on several nights are the same as those for the slowly varying component. An analysis of published data on the color variability
of the object for previous years indicates that the color characteristics of the slowly varying component are stable, independent
of the time intervals considered and the characteristic variability time scales. 相似文献
The Corbetti Caldera area, a recent volcanic complex in the Main Ethiopian Rift Valley, is described. In the area, most of the volcanic products are peralkaline pyroclastics (ignimbrites and pumice). The volcanological history of this complex has been reconstructed. It comprises fissure eruptions, which were followed by a volcano-tectonic collapse. Finally the activity resumed with the birth of two recent peralkaline volcanoes (Urji and Chabbi) inside the caidera. Both these volcanoes are at present in a fumarolic stage. Relations between the tectonic of the Rift Valley and the volcanological evolution of the Caldera Corbetti Area are discussed. 相似文献
Ciona intestinalis sp. A (Tunicata, Ascidiacea) is a marine invertebrate with a widespread distribution and high invasive potential, yet little is known about its ecology. Here, the macrodynamics of demographic and reproductive trends were first determined using archive data covering 2002–2012. Species abundance in the central Tyrrhenian Sea (Campania, Italy ‐ NW Mediterranean) displayed Poisson distribution across 2002–2008, massive die‐off in 2009/2010 and population recovery in 2011/2012. We defined the seasonal ranges of sea surface temperature in which sampling size, animal size and reproductive status reached their highest values. In 2003/2004, self and non‐self fertilization appeared to follow reverse trends across the year. The long‐term recording run here on Ciona intestinalis sp. A provides novel insights into its population biology and ecology, and represents a valuable tool for sampling management and research planning. 相似文献
Identifying urban flooding risk hotspots is one of the first steps in an integrated methodology for urban flood risk assessment and mitigation. This work employs three GIS-based frameworks for identifying urban flooding risk hotspots for residential buildings and urban corridors. This is done by overlaying a map of potentially flood-prone areas [estimated through the topographic wetness index (TWI)], a map of residential areas and urban corridors [extracted from a city-wide assessment of urban morphology types (UMT)], and a geo-spatial census dataset. A maximum likelihood method (MLE) is employed for estimating the threshold used for identifying the flood-prone areas (the TWI threshold) based on the inundation profiles calculated for various return periods within a given spatial window. Furthermore, Bayesian parameter estimation is employed in order to estimate the TWI threshold based on inundation profiles calculated for more than one spatial window. For different statistics of the TWI threshold (e.g. MLE estimate, 16th percentile, 50th percentile), the map of the potentially flood-prone areas is overlaid with the map of urban morphology units, identified as residential and urban corridors, in order to delineate the urban hotspots for both UMT. Moreover, information related to population density is integrated by overlaying geo-spatial census datasets in order to estimate the number of people affected by flooding. Differences in exposure characteristics have been assessed for a range of different residential types. As a demonstration, urban flooding risk hotspots are delineated for different percentiles of the TWI value for the city of Addis Ababa, Ethiopia. 相似文献
The Ingurtosu Pb-Zn mine, situated in the southwestern part of Sardinia, has been in production from the beginning of the last century up to 1968. The orebody consists of galena/sphalerite/barite/siderite veins in Ordovician arenaceous and phyllitic sediments, near the contact with a Hercynian batholith.
Abundant tailings were collected in a pond from which they were discharged during the winter months into the sea via the Rio Naracauli stream. Today this area of outstanding scenic beauty, is degraded by tailings and waste rock scattered all along the stream.
Material derived from mining activities was studied for grain size, mineralogical and geochemical composition. The Rio Naracauli was sampled over a length of ten kilometers at regular intervals.
The results can be summarized as follows: (a) tailings contain a varying, but often quite high, percentage of Pb; lower percentages were found for Zn and Cd; (b) a sharp increase in dissolved Zn, Cd and Pb was observed in the Rio Naracauli where it leached the tailings; and (c) tailings and waste rocks should be recycled or revegetated. 相似文献
Acta Geotechnica - During recent seismic events, such as 2010 Darfield and 2016 Ecuador earthquakes, widespread liquefaction has been observed in sand deposits with silt content. Nevertheless, the... 相似文献