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排序方式: 共有123条查询结果,搜索用时 953 毫秒
1.
Leaños-Castañeda O Gold-Bouchot G Van Der Kraak G Lister A Ceja-Moreno V Simá-Alvarez R 《Marine environmental research》2004,58(2-5):337-342
The objective of this study was to determine if tamoxifen or an aromatase inhibitor (4-hydroxyandrostenedione; 4-OHA) affected plasma concentrations of o,p' -DDT and its metabolites, o,p'-DDD and o,p'-DDE, in mature tilapia. Male and female tilapia were injected 6 times intraperitoneally with o,p'-DDT (40 mg/kg) alone or in combination with 4-OHA (2 mg/kg) over a 12 day period. An additional group of male fish was injected with tamoxifen (5 mg/kg) plus o,p'-DDT. At the end of the treatment period, plasma samples were extracted and analyzed by GC/ECD. Females injected only with o,p'-DDT had significantly higher levels of o,p'-DDT compared with males. Interestingly, females and males treated concomitantly with o,p'-DDT and 4-OHA or tamoxifen had significantly lower concentrations of plasma o,p'-DDT (about 50%) compared with fish treated with only o,p'-DDT. These initial results suggest that an interaction between endocrine-active compounds occurs in vivo in tilapia and may involve alterations in metabolism of o,p'-DDT. 相似文献
2.
Norhakim Yusof Raul Zurita-Milla Menno-Jan Kraak Bas Retsios 《International journal of geographical information science》2016,30(8):1486-1506
Wind speed and direction vary over space and time due to the interactions between different pressures and temperature gradients within the atmospheric layers. Near the earth’s surface, these interactions are modulated by topography and artificial structures. Hence, characterizing wind behaviour over large areas and long periods is a complex but essential task for various energy-related applications. In this study, we present a novel approach to discover wind patterns by integrating sequential pattern mining and interactive visualization techniques. The approach relies on the use of the Linear time Closed pattern Miner sequence algorithm in conjunction with a time sliding window that allows the discovery of all sequential patterns present in the data. These patterns are then visualized using integrated 2D and 3D coordinated multiple views and visually explored to gain insight into the characteristics of the wind from a spatial, temporal and attribute (type of wind pattern) point of view. This proposed approach is used to analyse 10 years of hourly wind speed and direction data for 29 weather stations in the Netherlands. The results show that there are 15 main sequential patterns in the data. The spatial task shows that weather stations located in the same region do not necessarily experience similar wind pattern. For within the selected time interval, similar wind patterns can be observed in different stations and in the same station at different times of occurrence. The attribute task discovered that the repetitive occurrences of chosen pattern indicate as regular wind behaviour at different weather stations that persisted continuously over time. The results of these tasks show that the proposed interactive discovery facilitates the understanding of wind dynamics in space and time. 相似文献
3.
Raul Borges Guimarães 《New Zealand geographer》2007,63(2):97-105
Abstract: This paper offers a geographical perspective on the way in which health regions have been defined and established in São Paulo as part of overall Brazilian health policy. To accomplish this, I first situate the Brazilian case in the international debate over the regionalization of health services. Second, I examine health regionalization in the case of São Paulo and show how the process is dynamic and complex, involving geographical scales that go well beyond the administrative boundaries of Brazilian municipalities. 相似文献
4.
Two-dimensional asymptotic iterative elastic inversion 总被引:3,自引:0,他引:3
Side Jin Raul Madariaga Jean Virieux Gilles Lambaré 《Geophysical Journal International》1992,108(2):575-588
5.
Jonathan Irwin Suzanne Aigrain Simon Hodgkin Keivan G. Stassun Leslie Hebb Mike Irwin Estelle Moraux Jerome Bouvier Aude Alapini Richard Alexander D. M. Bramich Jon Holtzman Eduardo L. Martín Mark J. McCaughrean Frédéric Pont P. E. Verrier María Rosa Zapatero Osorio 《Monthly notices of the Royal Astronomical Society》2007,380(2):541-550
We present a general recipe for constructing N -body realizations of galaxies comprising near spherical and disc components. First, an exact spherical distribution function for the spheroids (halo and bulge) is determined, such that it is in equilibrium with the gravitational monopole of the disc components. Second, an N -body realization of this model is adapted to the full disc potential by growing the latter adiabatically from its monopole. Finally, the disc is sampled with particles drawn from an appropriate distribution function, avoiding local-Maxwellian approximations. We performed test simulations and find that the halo and bulge radial density profile very closely match their target model, while they become slightly oblate due to the added disc gravity. Our findings suggest that vertical thickening of the initially thin disc is caused predominantly by spiral and bar instabilities, which also result in a radial re-distribution of matter, rather than scattering off interloping massive halo particles. 相似文献
6.
Ten eclipsing binaries, identified in the scope of the CoRoT Space Mission, were selected for analysis. The photometric light curves were processed and analyzed, resulting in the first study of eclipsing binary candidates with their possible photometric solution, in the context of the above-mentioned Space Mission. The selected targets are detached and overcontact systems, for which we computed 2MASS temperatures, in addition to different physical parameters, including orbital period, orbit inclination angle, and temperatures, radius and luminosity ratios. This study reveals a large diversity of eclipsing binary systems obtained from the CoRoT data. 相似文献
7.
8.
María Rosa Zapatero Osorio José Caballero Eduardo L. Martín Víctor J.S. Béjar Rafael Rebolo 《Astrophysics and Space Science》2004,292(1-4):673-679
We have monitored S Ori 45, a young, low-mass (20 M j up) brown dwarf of the σ Orionis cluster (~3 Myr, 352 pc), using optical and near-infrared filters. S Ori 45 (spectral type M8.5) is found to be multi-periodic with a dominant modulation at 2.5–3.5 h, and a short modulation at about 46 min. We ascribe the longer of these modulations to a rotation period. After comparing these results with observations of more massive cluster brown dwarfs and field brown dwarfs, we conclude that substellar objects present rotational and angular momentum evolution. We have also obtained intermediate-resolution near-infrared spectroscopy of S Ori 70, which is a T-class, free-floating planetary candidate member in the σ Orionis cluster. Its observed spectrum has been compared to data of field brown dwarfs of similar types and to theoretical spectra computed for different surface temperatures and gravities. We conclude that S Ori 70 has a significantly cool, low-gravity atmosphere. This supports the young age of this object and its membership in the cluster. From state-of-the-art evolutionary models, the mass of S Ori 70 is estimated at 3 times the Jovian mass (+5 ?2 M j up), challenging current stellar/substellar formation models. S Ori 70 remains the lowest mass object so far identified in any open cluster. 相似文献
9.
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