Seismic study of stellar convective regions: the base of the convective envelope in low-mass stars     

Mário J. P. F. G. Monteiro  Jørgen Christensen-Dalsgaard  Michael J. Thompson 《Monthly notices of the Royal Astronomical Society》2000,316(1):165-172

The possibility of observing solar-type oscillations on other stars is of great relevance to investigating the uncertain aspects of the internal structure of stars. One of these aspects is the convective overshoot that takes place at the borders of the envelopes of stars of mass similar to, or lower than, the Sun. It affects the temperature stratification, mixing, rotation and magnetic-field generation. Asteroseismology can provide an observational test for the studies of the structure of such overshoot regions.
The seismic study of the transition in the Sun, located at the base of the convection zone, has been successful in determining the characteristics of this layer in the Sun. In this work we consider the extension of the analysis to other solar-type stars (of mass between 0.85 and 1.2 M_⊙) in order to establish a method for determining the characteristics of their convective envelopes. In particular, we hope to be able to establish seismologically that a star does indeed possess a convective envelope, to measure the size of the convective region and also to constrain the properties of an overshoot layer at the bottom of the envelope. The limitations in terms of observational uncertainties and stellar characteristics, and the detectability of an overshoot layer, are discussed.  相似文献   

Comparison Between Kriging Variance and Interpolation Variance as Uncertainty Measurements in the Capanema Iron Mine, State of Minas Gerais—Brazil     

Marcelo Monteiro da Rocha  Jorge Kazuo Yamamoto 《Natural Resources Research》2000,9(3):223-235

The Capanema Mine, an iron ore deposit, is located in the central portion of the Quadrilátero Ferrífero, State of Minas Gerais, southeastern Brazil. Mine development data from approximately 7000 drillholes were used for a comparative study between kriging variance and interpolation variance as uncertainty measurements associated with ordinary kriging estimates. As known, the traditional kriging variance does not depend on local data and, therefore, does not measure the actual dispersion of data. On the other hand, the interpolation variance measures adequately the local dispersion of data used for an ordinary kriging estimate. This paper presents an application of the concept of interpolation variance for measuring uncertainties associated with ordinary kriging estimates of Fe and silica grades. These data were selected for their distinct statistical characteristics with Fe presenting a negatively skewed distribution and, consequently, a low dispersion, and silica a positively skewed distribution and, therefore, a high variability. Comparative studies between the two uncertainty measurements associated with ordinary kriging estimates of Fe and silica proved the superiority of the interpolation variance as a reliable and precise alternative to the kriging variance.  相似文献   

Plasma steroid levels in female flounder (Platichthys flesus) after chronic dietary exposure to single polycyclic aromatic hydrocarbons     

P. R. R. Monteiro  M. A. Reis-Henriques  J. Coimbra 《Marine environmental research》2000,49(5)

The chronic effects of polycyclic aromatic hydrocarbons (PAHs) on ovary development, total hepatic lipids and plasma sex- and corticosteroid levels in female flounder (Platichthys flesus) were examined. Sexually mature feral female flounder were exposed via the diet to phenanthrene (0.5, 2.5 or 12.5 nmol/g food) or chrysene (0.4 nmol/g food) for 12 weeks, during the previtellogenic phase of the annual reproductive cycle. PAH exposure did not directly affect germ cell development since no structural and/or developmental differences were observed between control and exposed fish. On the contrary, all treatments resulted in altered plasma steroid levels. The most pronounced effect was the significant decrease in plasma 17β-estradiol to 19±11%, 27±7%, 63±20% and 61±12% in relation to control fish, respectively, in flounders exposed to 12.5, 2.5 or 0.5 nmol phenanthrene/g food and 0.4 nmol chrysene/g food. Impaired ovarian growth was not observed, most likely because experiments were ended before the period of vitellogenesis, even though a non-significant general decline in total hepatic lipids could be observed. Moreover, all exposed flounders, except fish fed with the highest amount of phenanthrene, showed a negative correlation between plasma 17β-estradiol and 17α-hydroxyprogesterone levels (r=−0.46). One possible explanation is that PAH action may be mediated by a specific inhibition of steroidogenic enzymes. These findings provide evidence that selected PAHs are antiestrogenic xenobiotics with the capability to impair female teleost reproductive function.  相似文献   

Effect of tooth spacing and mesh size on the catch of the Portuguese clam and razor clam dredge   总被引：1，自引：1，他引：0  

Gaspar  M. B.; Castro  M.; Monteiro  C. C. 《ICES Journal of Marine Science》1999,56(1):103-110

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Presence of Anthropogenic Markers in Water: A Case Study of the Guaporé River Watershed,Brazil          下载免费PDF全文

Marilia Camotti Bastos  Danilo Rheinheimer dos Santos  José A. Monteiro de Castro Lima  Thibaut le Guet  Maria A. Santanna dos Santos  Renato Zanella  Elodie Aubertheau  Leslie Mondamert  Laurent Caner  Jérôme Labanowski 《洁净——土壤、空气、水》2018,46(3)

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Probabilistic models for structures with bilinear demand-intensity relationships     

Gerard J. O'Reilly  Ricardo Monteiro 《地震工程与结构动力学》2019,48(2):253-268

An extension to the existing SAC/FEMA expressions to estimate mean annual frequency of exceedance (MAFE) for a given limit state is described. In specific, this study pertains to structural systems whose demand versus seismic intensity relationship cannot be reasonably represented by a linear fit in logspace, but rather a bilinear fit over the entire range of structural response. Using a predefined limiting intensity, the median demand is separated into two distinct zones of response. These expressions are derived using a second-order polynomial hazard model fit and can be considered a further extension of the closed-form expressions available in the literature. The steps in the derivation are described along with an example application of the proposed expressions. Comparing different models shows that the MAFE can be significantly misrepresented when using a linear demand-intensity model for systems whose behaviour deviates from this assumption in logspace. Similarly, a logarithmic function demand-intensity fit is examined and seen not to be suitable in the specific situations focused on here. Furthermore, significant underestimation or overestimation is observed when using local fits in the vicinity of the behaviour transition point, which highlights the need for such a bilinear model when assessing the structural performance at the transition point's vicinity. Adopting a bilinear model is shown to better represent structural systems with complex response characteristics, also allowing the use of a single demand model for the entire range of response. This is at the same time still compatible with the existing framework for performance-based seismic design and assessment.  相似文献