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501.
502.
M. F. Correia M. A. F. da Silva Dias M. R. da Silva Aragão 《Meteorology and Atmospheric Physics》2006,94(1-4):103-113
Summary Sobradinho Lake lies in the S?o Francisco River Basin, in one of the most arid regions in Northeastern Brazil, within a land
stretch categorized as the Lower-middle S?o Francisco, situated at about 40 km away from the municipality of Petrolina (09°23′S–40°30′W)
in the state of Pernambuco. The dam, in its full capacity, consists of a lake of approximately 4,214 km2; 280 km in length, the width of which varies from 5 to 50 km. The dam storage capacity is that of 34.1 billion m3 of water. Being situated in a semi-arid region, the dam brought about significant development to local irrigated agriculture.
The caatinga ecosystem has, for that matter, undergone considerable changes. Statistical analysis techniques applied to data collected
before and after the filling of the lake, made it possible both to make an assessment of the impact of the dam construction
on the region meteorology and to diagnose the variability of such an impact on environmental conditions. Results showed that
the dam has brought about considerable changes to regional meteorology. The alterations were observed to be more significant
as regards atmospheric humidity and wind speed. 相似文献
503.
L. S. Farenzena P. Iza R. Martinez F. A. Fernandez-Lima E. Seperuelo Duarte G. S. Faraudo C. R. Ponciano M. G. P. Homem A. Naves de Brito K. Wien E. F. da Silveira 《Earth, Moon, and Planets》2005,97(3-4):311-329
Experimental results on fast ion collision with icy surfaces having astrophysical interest are presented. 252Cf fission fragments projectiles were used to induce ejection of ionized material from H2O, CO2, CO, NH3, N2, O2 and Ar ices; the secondary ions were identified by time-of-flight mass spectrometry. It is observed that all the bombarded frozen gas targets emit cluster ions which have the structure XnR±, where X is the neutral ice molecule and R± is either an atomic or a molecular ion. The shape of the positive or negative ion mass spectra is characterized by a decreasing yield as the emitted ion mass increases and is generally described by the sum of two exponential functions. The positive ion water ice spectrum is dominated by the series (H2O)nH3O+ and the negative ion spectrum by the series (H2O)nOH− and (H2O)nO−. The positive ion CO2 ice spectrum is characterized by R+ = C+, O+, CO+, O2+ or CO2+ and the negative one by R− = CO3−. The dominant series for ammonia ice correspond to R+ = NH4+ and to R− = NH2−. The oxygen series are better described by (O3)nOm+ secondary ions where m = 1, 2 or 3. Two positive ion series exist for N2 ice: (N2)nN2+ and (N2)nN+. For argon positive secondary ions, only the (Ar)nAr+ series was observed. Most of the detected molecular ions were formed by one-step reactions. Ice temperature was varied from ∼20 K to complete sublimation. 相似文献
504.
505.
G. Cristiani G. Martinez C. H. Mandrini C. G. Giménez De Castro C. W. Da Silva M. G. Rovira P. Kaufmann 《Solar physics》2007,240(2):271-281
Using magnetograms, EUV and Hα images, Owens Valley Solar Array microwave observations, and 212-GHz flux density derived from
the Solar Submillimeter Telescope data, we determine the spatial characteristics of the 1B/M6.9 flare that occurred on November
28, 2001, starting at 16:26 UT in active region (AR) NOAA 9715. This flare is associated with a chromospheric mass ejection
or surge observed at 16:42 UT in the Hα images. We compute the coronal magnetic field under the linear force-free field assumption,
constrained by the photospheric data of the Michelson Doppler Imager and loops observed by the Extreme Ultraviolet Imaging
Telescope. The analysis of the magnetic field connectivity allows us to conclude that magnetic field reconnection between
two different coronal/chromospheric sets of arches was at the origin of the flare and surge, respectively. The optically thick
microwave spectrum at peak time shows a shape compatible with the emission from two different sites. Fitting gyrosynchrotron
emission to the observed spectrum, we derive parameters for each source.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
506.
G.L. Granato G. DeZotti L. Silva L. Danese M. Magliocchetti 《Astrophysics and Space Science》2002,281(1-2):497-500
In view of the extensive evidence of tight inter-relationships between spheroidal galaxies (and galactic bulges) with massive
black holes hosted at their centers, a consistent model must deal jointly with the evolution of the two components. We describe
one such model, which successfully accounts for the local luminosity function of spheroidal galaxies, for their photometric
and chemical properties, for deep galaxy counts in different wavebands, including those in the (sub)-mm region which proved
to be critical for current semi-analytic models stemming from the standard hierarchical clustering picture, for clustering
properties of SCUBA galaxies, of EROs, and of LBGs, as well as for the local mass function of massive black holes and for
quasar evolution. Predictions that can be tested by surveys carried out by SIRTF are presented.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
507.
The main gas-phase constituents of Titan's upper atmosphere, N2 and CH4, are photolyzed and radiolyzed by solar photons and magnetospheric electrons, respectively. The primary products of these chemical interactions evolve to heavier organic compounds that are likely to associate into the particles of haze layers that hide Titan's surface. The different theories and models that have been put forward to explain the characteristics and properties of the haze composites require a knowledge of their optical properties, which are determined by the complex refractive index. We present a new set of values for refractive index n and extinction coefficient k calculated directly from the transmittance and reflectance curves exhibited by a laboratory analogue of Titan's aerosols in the 200-900 nm range. Improvements in the aerosol analogue quality have been made. The effects of variables such as the uncertainty in sample thickness, aerosol porosity, and amount of scattered light on the final n and k values are assessed and discussed. Within the studied wavelength domain, n varies from 1.53 to 1.68 and k varies from 2.62×10−4 to 2.87×10−2. These final n and k values should be considered as a new reference to modelers who compute the properties of Titan's aerosols in trying to explain the atmospheric dynamics and surface characteristics. 相似文献
508.
António J.C. da Silva 《Astrophysics and Space Science》2004,290(1-2):167-176
Observations with the SZ effect constitute a powerful new tool for investigating clusters and constraining cosmological parameters. Of particular interest is to investigate how the SZ signal correlates with other cluster properties, such as the mass, temperature and X-ray luminosities. In this presentation we quantify these relations for clusters found in hydrodynamical simulations of large scale structure and investigate their dependence on the effects of radiative cooling and pre-heating. 相似文献
509.
Wolf Uwe Reimold Natalia Hauser Alisson Lopes Oliveira Ana Rita Pereira Maciel Steven Goderis Lidia Pittarello Wencke Wegner Mario Fischer-Goedde Christian Koeberl Vinciane Debaille Carolinna Silva Maia de Souza 《Meteoritics & planetary science》2023,58(7):907-944
Genesis and emplacement of Vredefort Granophyre, the impact melt rock exposed on the Vredefort Dome, the erosional remnant of the central uplift of the Vredefort impact structure, South Africa, have long been debated. This debate was recently reinvigorated by the discovery that besides the previously known felsic variety of >66 wt% SiO2, a second, somewhat more mafic phase of <66 wt% SiO2 occurs along a Granophyre dike on farms Kopjeskraal and Eldorado in the northwest sector of the dome. Two hypotheses have been put forward to explain the genesis and emplacement of this second phase: (1) successive injections of impact melt into extensional fractures opened in the course of central uplift formation/crater modification, with melts of distinct compositions derived from a differentiating impact melt body in the crater, and (2) generation of the more mafic phase as a product of admixture/assimilation of a mafic country rock component, either the so-called epidiorite of possible Ventersdorp Supergroup affiliation or the Dominion Group meta-lava (DGL), to Felsic Granophyre. In the latter model, contamination with mafic country rock would have occurred during downward intrusion and stoping into and below the crater floor. The so-called Mafic Granophyre has previously only ever been sampled on a single site (Farm Kopjeskraal). In this study, samples of Granophyre occurring along the southerly extension of this dike on farm Rensburgdrif, and from a second dike on the Rietkuil property further southwest were investigated by field work, and petrographic, geochemical, and isotopic analysis. The mafic phase indeed occurs in the interior of the dike at Rensburgdrif, and also on Rietkuil. New geochemical and Sr-Nd isotope data support the hypothesis that the Mafic Granophyre composition represents a mixture between Felsic Granophyre and a mafic country rock. A 20% admixture of epidiorite or DGL to Felsic Granophyre provides an excellent match for the chemical composition of the Mafic Granophyre. The Sr-Nd isotope data indicate that this admixture likely involved the epidiorite component rather than DGL. Together with earlier Sr-Nd-Os-Se isotopic data, and other geochemical data, these results further support formation of the Mafic Granophyre by local assimilation/admixture of epidiorite to Felsic Granophyre. 相似文献
510.
Michel Michaelovitch de Mahiques Samara Cazzoli y Goya Maria Carolina da Silva Nogueira de Matos Rodrigo Augusto Udenal de Oliveira Bianca Sung Mi Kim Paulo Alves de Lima Ferreira Rubens Cesar Lopes Figueira Marcia Caruso Bícego 《国际泥沙研究》2021,36(2):317-327
The current study aims to do a comparative analysis of the results obtained with two End-Member(EM)grain-size modeling techniques(AnalySize and BasEMMA)and the Environmental Sensitive Grain-Size(ESGS)modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf.The methods were compared using grain-size data from the south Brazilian shelf,and the results are discussed here.It is the first time that the concept of ESGS,in its present form,is utilized outside China.The results show that despite its relative ease of use,the ESGS is not fully comparable to the EM analyses,and only two grain-size ESGS classes were recognized as analogous to EMs.The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques.A comparative analysis between the two EM techniques revealed advantages in the BasEMMA,especially in the better correlation of the end-members with the original grain size distribution.The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred. 相似文献