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11.
Tao An Xiao-Yu Hong Wen-Xia Feng Jun-Hui Zhao Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai National Astronomical Observatories Chinese Academy of Sciences Beijing Harvard-Smithsonian Center for Astrophysics Garden Street MS Cambridge MA 《中国天文和天体物理学报》2004,4(6):527-532
We observed 1938-155, a broad line radio galaxy (BLRG), with the Very Large Array (VLA) at 90cm with an angular resolution of 6.8" × 4.0". The source consists of two components separated by 4 arcsec (- 20kpc, for H0 = 65km s-1 Mpc-1, q0 = 0.5) along the SE-NW direction. Both components show steep-spectra with a similar spectral index α - 0.83 ± 0.07 (Sv ∝ v-α). The bright double components are surrounded by a low-brightness cocoon. The radio properties of the two bright components are consistent with the hot spots produced by twin jets. An upper limit of - 0.0008 for the core dominance parameter (R) is inferred, suggesting there is no prominent radio core in the source. Assuming a modest viewing angle 30f77, a jet velocity is estimated - 0.07 c, based on the jet to counter-jet brightness ratio (J). The lower limit in jet speed inferred is consistent with no Doppler beaming effect on the jet. The radio galaxy 1938-155 could be an exceptional BLRG with no prominent radio core or jet. 相似文献
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Editorial: human dynamics in the mobile and big data era 总被引：1，自引：0，他引：1
14.
Lutz creek is a small (9.69 ha) catchment located on Barro Colorado Island (BCI), a 1500-ha island in Lake Gatún, the principal freshwater reservoir (425 ha, 26 m above sea level) of the Panama Canal watershed in central Panama. In 1972, a concrete V-notch weir was installed on the creek, located at 9°09′42.8358″N, 79°50′15.6699″W, and hydrological record keeping began. The island was first established as a research station in 1923 and precipitation data collection was initiated in 1925. A meteorological tower, installed in 1972 and located a few meters from the weir, is currently instrumented to collect air temperature, relative humidity, wind speed and direction, evapotranspiration and solar radiation. In addition, since 1972, gravimetric soil moisture has been measured at least biweekly at 10 sites located throughout the Lutz Catchment above the location of the weir. Data collection and the administration of BCI are the responsibility of the Smithsonian Tropical Research Institute (STRI; https://stri.si.edu ) which funds the data collection and storage. Data are in the public domain, entitled ‘Lutz Watershed And Meteorological Tower’ and are available at the STRI Physical monitoring website https://biogeodb.stri.si.edu/physical_monitoring/ . 相似文献
15.
E. Grün Z. Sternovsky M. Horanyi V. Hoxie S. Robertson J. Xi S. Auer M. Landgraf F. Postberg M.C. Price R. Srama N.A. Starkey J.K. Hillier I.A. Franchi P. Tsou A. Westphal Z. Gainsforth 《Planetary and Space Science》2012,60(1):261-273
The Stardust mission returned two types of unprecedented extraterrestrial samples: the first samples of material from a known solar system body beyond the moon, the comet 81P/Wild2, and the first samples of contemporary interstellar dust. Both sets of samples were captured in aerogel and aluminum foil collectors and returned to Earth in January 2006. While the analysis of particles from comet Wild 2 yielded exciting new results, the search for and analysis of collected interstellar particles is more demanding and is ongoing.Novel dust instrumentation will tremendously improve future dust collection in interplanetary space: an Active Cosmic Dust Collector is a combination of an in-situ dust trajectory sensor (DTS) together with a dust collector consisting of aerogel and/or other collector materials, e.g. such as those used by the Stardust mission. Dust particles’ trajectories are determined by the measurement of induced electrical signals when charged particles fly through a position sensitive electrode system. The recorded waveforms enable the reconstruction of the velocity vector with high precision.The DTS described here was subject to performance tests at the Heidelberg dust accelerator at the same time as the recording of impact signals from potential collector materials. The tests with dust particles in the speed range from 3 to 40 km/s demonstrate that trajectories can be measured with accuracies of ～1° in direction and ～1% in speed. The sensitivity of the DTS electronics is of the order of 10?16 C and thus the trajectory of cosmic dust particles as small as 0.4 μm size can be measured. The impact position on the collector can be determined with better than 1 mm precision, which will ease immensely the task of locating sub-micron-sized particles on the collector. Statistically significant numbers of trajectories of interplanetary and interstellar dust particles can thus be collected in interplanetary space and their compositions correlated with their trajectories. 相似文献
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Seismic demand estimation for a structure is a critical issue for seismic performance assessment so that the potential damage can be estimated realistically. Many researchers proposed simplified methods to estimate the demand of a structure under strong ground motions. However, most of them did not consider degradation and collapse potential of the structures. Even some of theme considered the degradation effect, stiffness and strength degradation effects were considered separately without collapse potential caused by dynamic instability. In this study, collapse potential of SDOF systems caused by dynamic instability with stiffness and strength degradation has been investigated. Nonlinear time history analyses were performed, using an energy-based, strength and stiffness degraded hysteretic model that considers the collapse potential, with 160 earthquake acceleration time histories. An equation was proposed for the estimation of collapse period of SDOF systems as a function of certain strength reduction factor, ductility level and post-capping stiffness ratio. Finally, effects of parameters of the considered hysteretic model and local site conditions on the collapse period were investigated. 相似文献
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Coupling fluvial processes and landslide distribution toward geomorphological hazard assessment: a case study in a transient landscape in Japan 总被引：1，自引：0，他引：1
Ching-Ying Tsou Masahiro Chigira Yuki Matsushi Narumi Hiraishi Noriyuki Arai 《Landslides》2017,14(6):1901-1914
This study quantified the relationship among deep-seated gravitational slope deformations (DGSDs), landslides, and river rejuvenation in the upper reaches of the Kumano River in the Kii Mountains of Japan, an area of frequent bedrock landslides. River profiles and hillslope landforms were examined, and high-resolution digital elevation models (DEMs) were used to identify DGSDs and landslides. Many of the deep-seated landslides were associated with rainstorms in 1889 and 2011. Landslide volumes were related to landslide areas on the basis of 52 deep-seated landslides that failed during the 2011 rainfall, providing basic data for landscape denudation and sediment yield. River rejuvenation occurred stepwise, incising moderate relief paleosurfaces and forming two series of knickpoints and V-shaped inner gorges that are up to 400-m deep. More than 65% of DGSDs and 75% of the landslides were located in association with the incised inner gorges along the peripheries of the paleosurfaces or were entirely contained within the inner gorges. DGSDs and landslides associated with the incised inner valley slopes tended to be larger than those developed within the paleosurfaces and may be long-term transient hillslope responses to river incision. Hillslope undercutting caused by rejuvenated river incision may play an important role in long-term slope stability and distribution of mass movements, and could serve as an indicator of landslide hazard. 相似文献
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In Florida, issues related to alterations of estuarine salinity caused by freshwater withdrawal have recently gained increasing attention. We examined nekton community structure in the Suwannee River estuary (1997–2000) and investigated the relationship between environmental factors and the abundance of fisheries resources. We compared nekton community structure and environmental factors seasonally and annually using multidimensional scaling (MDS) ordination and cluster analysis and observed a strong seasonal pattern. This pattern was consistent among years and closely paralleled those for temperature and river discharge. Representative species for cold seasons includedLeiostomus xanthurus andLagodon rhomboides, and those for warm seasons includedMembras martinica andAnchoa hepsetus. Species that contributed most to the dissimilarity in community structures between wet and dry seasons were abundant and generally preferred lower salinity (e.g.,L. xanthurus, Eucinostomus spp., andMenidia spp.). A period of low freshwater inflow during the latter portion of our study coincided with both decreases and increases in the abundances of some dominant and some economically important species. We have established a baseline which will assist in measuring the effects of long-term changes in freshwater input on the nekton communities of the Suwannee River estuary, but our ability to predict these effects is still limited. 相似文献
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C. I. Nnamchi M.Sc. J. A. N. Obeta MS.c. Ph.D. L. I. Ezeogu Ph.D. 《International Journal of Environmental Science and Technology》2006,3(2):181-190
Twenty-four bacteria capable of utilizing naphthalene, as their sole source of carbon and energy for growth were isolated from three different sites in Nsukka, Nigeria. By standard bacteriological methods, these bacteria were characterized taxonomically as belonging to the genus Pseudomonas, Burkholderia or Actinomycetes. Two of the isolates, which showed the highest growth during screening as demonstrated by an increase in their optical densities (OD600) and identified as Pseudomonas aeruginosa and Burkholderia cepacia respectively, were also able to grow in anthracene and carbazole, but not very much so in 2,4-dichlorophenol and D-camphor. The isolates showed a concentration-dependent growth in all the compounds they grew in. There were visible changes in the colour of the growth medium of the isolates during their incubation, suggesting the production of different metabolites. There were also changes in their medium pH during growth. These studies demonstrate the possession by the bacterial species of novel degradative systems. 相似文献
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Ralf Srama Thomas Stephan Eberhard Grün Norbert Pailer Anton Kearsley Amara Graps Rene Laufer Pascale Ehrenfreund Nicolas Altobelli Kathrin Altwegg Siegfried Auer Jack Baggaley Mark J. Burchell James Carpenter Luigi Colangeli Francesca Esposito Simon F. Green Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Neil McBride Georg Moragas-Klostermeyer Harald Krüger Pasquale Palumbo Andre Srowig Mario Trieloff Peter Tsou Zoltan Sternovsky Oliver Zeile Hans-Peter Röser 《Experimental Astronomy》2009,23(1):303-328
The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We
propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth.
SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board
allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important
constraints for subsequent laboratory analysis.
The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and
inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and
October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection
period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area
of 1 m2. At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule.
SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar
samples by latest laboratory technologies. 相似文献