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261.
The minor planet 164 Eva passed through opposition on December 1, 1975 with a magnitude Bopp = 11.3 mag. Photoelectric observations at the Observatory of Torino, Italy, were carried out in two nights on Oct. 27/28 and Nov. 11, each with a run of about 3 hr. Two further successful photoelectric observations were carried out at the OHP, France, each with a run of about 6 hr. From all observed parts of the lightcurve a resulting synodic period of rotation of about 27.3 hr can be deduced, with a range of the total amplitude of at least Δm = 0.07 mag. With this period of 27.3 hr the minor planet 164 Eva is one more long period object, falling now between 654 Zelinda (H. J. Schober, 1975, Astron. Astrophys.44, 85–89) and 139 Juewa (J. Goguen et al., 1976, Icarus29, 137–142), at the high end in the histogram of the distribution of minor planet rotation periods. 相似文献
262.
The study of the region 348°l12°, +3°b+17° reveals strong kinematic asymmetries of the interstellar gas, with a notorious predominance of positive radial velocities, referred to the LSR. The principal cause of this is a very intense source, a ridge-like object (Ridge) which presents very special characteristics and seems to be identical with Lindblad's feature A. It should, therefore, be related to Gould's Belt. The object's velocity dependence onl is in good agreement with Lindblad's model. It can be easily followed into high northern latitudes and also into low southern latitudes, as well as into values ofl remarkably lower and higher than those considered in this work. It seems also highly probable that feature A presents both the cold as well as the hot component of the interstellar medium. In that case, the mean optical depth and the mean spin temperature of the cold component would be
and
K in the region considered here.Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET).The Instituto operates under an agreement between the CONICET, the CIC and the Universities of Buenos Aires and La Plata, and with the support of the Carnegie Institution of Washington. 相似文献
263.
The origin of the Tongkeng-Changpo tin deposit,Dachang metal district,Guangxi, China: clues from fluid inclusions and He isotope systematics 总被引:6,自引:0,他引:6
Cai Minghai Mao Jingwen Liang Ting Franco Pirajno Huang Huilan 《Mineralium Deposita》2007,42(6):613-626
Tongkeng-Changpo is the largest tin deposit within the giant Dachang polymetallic tin ore field in Guangxi, southern China,
which is part of a large skarn system associated with Cretaceous granitoids. The Tongkeng-Changpo mineralization consists
of veins and stockworks in the upper levels and replacement stratiform orebodies (mantos) at lower levels. Based on textural
relationships, three major mineralizing stages can be recognized: stage I with cassiterite, sulphides, stannite, tourmaline,
and quartz; stage II with cassiterite, sulphides, sulphosalts, quartz, and calcite; and stage III with calcite as the main
phase. The study of fluid inclusions has shown that there are two main fluid types: CO2 and NaCl-H2O. Homogenization temperatures are 270 to 365°C, 210 to 240°C, and 140 to 190°C for stages I, II, and III, respectively. Salinities
range from 1 to 7 wt.% NaCl equiv. in the early ore stage and 3 to 10 wt.% NaCl equiv. in the late stages. Laser Raman Spectroscopy
indicates that the inclusion fluids in stages I and II were of carbono-aqueous composition, with minor amounts of CH4 and H2S, whereas those in stage III were aqueous. Helium isotopic analyses of inclusion fluids indicate that the 3He/4He ratios in the ore veins are in between 1.2 to 2.9 Ra (Ra = 1.4 × 10−6, modern atmospheric ratio), and range from 1.6 to 2.5 Ra in the stratiform orebodies. This range of 3He/4He ratios is significantly higher than that of crustal fluids (0.01–0.05 Ra). The similar characteristics of fluid inclusions
and their He isotopic composition, as well as age constraints, indicate that the ore veins and stratiform orebodies of the
Tongkeng-Changpo deposit formed from the same hydrothermal system, likely related to granite intrusions of the Mesozoic Yanshanian
tectono-thermal event. In addition, the high R/Ra ratios indicate a mantle contribution in the ore fluids. 相似文献
264.
Franco PIRAJNO 《《地质学报》英文版》2007,81(2)
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (~160 Ma),Ⅰ-type granite in the middle stage (~130 Ma) and anorogenic A-type granite in the late stage (~115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at~115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between~160 Ma and~115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons. 相似文献
265.
Ensembles of 1-year-long experiments with a relatively high-resolution ECMWF model were conducted in order to investigate the impact of modified land surface properties on local, regional and large-scale atmospheric circulations. The modifications consisted of changes to land cover and increased albedo over the northern part of South America. In many respects the experimental design resembles the setting of classical deforestation experiments. The local model response to imposed modifications, which includes a reduction in precipitation as well as in evaporation and an increase in surface temperature, was found to be stronger in dry (July–September, JAS) than in wet (January–March, JFM) season, and in the ensemble with higher albedo value. Local drying is discussed in terms of locally generated overturning that resembles a direct thermal circulation. The effects of this circulation seem to be dominant over the reduction in large-scale moisture supply from the adjacent ocean. On large scales, changes to the Pacific branch of the Walker circulation lead, through modified divergent flow, to a tropics-wide impact on precipitation. In addition to South America, the largest changes are seen in the south Pacific convergence zone in JFM, while the impact on the Atlantic inter-tropical convergence zone is stronger in JAS. In the extratropics, there is little change in precipitation. In the upper troposphere, a distinctive teleconnection wave-pattern could be seen in the Pacific/North American region during JFM. A notable feature in the upper-air model response in JAS is a wave train extending from South America, over the northern Atlantic into Europe. With regard to the interaction between the land surface response and model systematic errors, our results suggest that the erroneous shift of the downward branch of the Pacific/South American Walker circulation is likely to be a cause, rather than a consequence, of the rainfall deficit over South America in the model climatology. 相似文献
266.
267.
Linear Amplification of Horizontal Strong Ground Motion in Zagreb (Croatia) for a Realistic Range of Scaled Point Sources 总被引:2,自引:0,他引:2
Marijan Herak Ivan Lokmer Franco Vaccari Giuliano F. Panza 《Pure and Applied Geophysics》2004,161(5-6):1021-1040
— The linear amplification of the larger horizontal component of strong ground motion along a selected profile in the city of Zagreb is estimated by examining the synthetic waveforms corresponding to a suite of 16 realistically chosen scaled point sources. The accelerograms, computed for the average bedrock model by modal summation, are propagated through local laterally heterogeneous anelastic models by the finite-difference algorithm. The ratio of peak ground acceleration (PGA) and of the response spectra (RS), obtained by using local and bedrock models, define the PGA and RS amplification AMP(PGA) and AMP(RS), respectively. Even variations of the order of commonly observed uncertainties of only dip and rake angles of the causative fault show that both AMP(PGA) and AMP(RS) vary at some sites by more than a factor of two. It follows that, especially for strongly laterally heterogeneous structures, local effects must be determined for each of the relevant sources considering all associated uncertainties as completely as possible. Such a conclusion certainly holds for the case of the microzonation of Zagreb, where the local geology is quite complex, and the seismicity is not confined to a single seismic source zone. 相似文献
268.
269.
Novoa S Chust G Sagarminaga Y Revilla M Borja A Franco J 《Marine pollution bulletin》2012,64(4):739-750
The implementation of water quality European Directives requires an intensification of water quality monitoring, within the limits of the Exclusive Economic Zone. Remote sensing technologies can provide a valuable tool for frequent, synoptic, water-quality observations, over large areas. The aim of this study is to assess the ecological status of Basque coastal water bodies using satellite imagery from MODIS sensor, together with optical and chlorophyll-ain situ measurements. Thus, sea surface satellite-derived chl-a algorithms, the OC3 M, OC5 and a Local empirical algorithm, were compared against in situ measurements using satellite in situ match-ups, 90th Percentile (P90) monthly values for the 2005-2010 period. The OC5 algorithm corresponded most accurately with in situ measurements performed in the area, hence, it was selected. A P90 chlorophyll-a map was created with this algorithm to apply the classification scheme required by the directives. The classification of water bodies, based upon satellite-derived chlorophyll-a, could improve considerably the assessment of water quality. 相似文献
270.
A reflection/refraction seismic experiment performed in 1991 in the western Po plain gave basic data to constrain the interpretation of the crustal structures across the Alps/Apennines junction zones. Two different seismic domains, north and south of the western supposed prosecution of the Villalvernia-Varzi line, are evidenced from the interpretation of the data. The boundary between the two domains is characterized by strong lateral variations from southern high to northern low velocity layers. The northward abrupt deepening of the refractor/reflector basement is followed at depth by a similar deepening of the crust/mantle boundary. The geological interpretation evidences domains with coherent and independent evolution at surface level juxtaposed along oblique discontinuities cutting across the crust. A peculiar feature is the presence of both crust and mantle north-verging wedges into the crustal structure and the overthrust at depth of the 'alpine' metamorphic crust onto the 'apenninic' nappes (Monferrato region). 相似文献