辽宁省中晚元古代—中生代页岩的化学元素丰度及其演化特征

作者利用全省不同地质时代和不同地质构造单元内的页岩41种元素的分析数据,计算出辽宁省全域内的页岩元素丰度休系。同时探讨了元素从中、晚元古代至中生代的演化规律,指出Ca、Cd、Sb、As、Na、Mn、P、Sr的元素丰度随时间序列的演化不断增长,B、F、K、Rb、W、Mg则显示出降低的趋势。某些元素比值从老至新表现出明显的规律性变化,如Sr/Ba、Ca/Mg值的演化具有阶段性,K/Na、Th/U值的演化具有方向性,Al/Ti值的演化则具有周期性。     

Anharmonicity effects in bounce motion of particles

Equations for parallel motion for a particle trapped in a magnetic field have been considered and improved solutions of differential equations have been derived. The expressions for the change in energy of the particle (Δw) and diffusion coefficient (D_ww) have been presented in a simple form using the improved solution.     

Can the unresolved X-ray background be explained by the emission from the optically-detected faint galaxies of the GOODS project?

The emission from individual X-ray sources in the Chandra Deep Fields and XMM – Newton Lockman Hole shows that almost half of the hard X-ray background above 6 keV is unresolved and implies the existence of a missing population of heavily obscured active galactic nuclei (AGN). We have stacked the 0.5–8 keV X-ray emission from optical sources in the Great Observatories Origins Deep Survey (GOODS; which covers the Chandra Deep Fields) to determine whether these galaxies, which are individually undetected in X-rays, are hosting the hypothesized missing AGN. In the 0.5–6 keV energy range, the stacked-source emission corresponds to the remaining 10–20 per cent of the total background – the fraction that has not been resolved by Chandra . The spectrum of the stacked emission is consistent with starburst activity or weak AGN emission. In the 6–8 keV band, we find that upper limits to the stacked X-ray intensity from the GOODS galaxies are consistent with the ∼40 per cent of the total background that remains unresolved, but further selection refinement is required to identify the X-ray sources and confirm their contribution.     

The distribution of absorption in AGN detected in the XMM–Newton observations of the CDFS

We have used very deep XMM–Newton observations of the Chandra Deep Field -South to examine the spectral properties of the faint active galactic nucleus (AGN) population. Crucially, redshift measurements are available for 84 per cent (259/309) of the XMM–Newton sample. We have calculated the absorption and intrinsic luminosities of the sample using an extensive Monte Carlo technique incorporating the specifics of the XMM–Newton observations. 23 sources are found to have substantial absorption and intrinsic X-ray luminosities greater than 10⁴⁴ erg s⁻¹, putting them in the 'type-2' QSO regime. We compare the redshift, luminosity and absorption distributions of our sample to the predictions of a range of AGN population models. In contrast to recent findings from ultradeep Chandra surveys, we find that there is little evidence that the absorption distribution is dependent on either redshift or intrinsic X-ray luminosity. The pattern of absorption in our sample is best reproduced by models in which ∼75 per cent of the AGN population is heavily absorbed at all luminosities and redshifts.     

恒星临边昏暗系数的测定

介绍一种新的一级挖和二级近似描述恒星大气临边昏境现象方法,其临边昏境系数可通过有关物理量的直接测量或测量流量和辅助量恒星表面温度的方法间接给出。与太阳观测比较和数值模型大气方法比较,均显示新方法能够以很精确的方式描述恒星临边昏境关系,或确定其相应系数 方法对太阳观测的１７６个数据比较了统计方差,其中直接法的一级挖和二级挖分别为０．３８％和０．２６％;间接法的方差与此相近而略大;与数值模型大气比较其     

Neutrino Tomography – Learning About The Earth’s Interior Using The Propagation Of Neutrinos

Because the propagation of neutrinos is affected by the presence of Earth matter, it opens new possibilities to probe the Earth’s interior. Different approaches range from techniques based upon the interaction of high energy (above TeV) neutrinos with Earth matter, to methods using the MSW effect on the oscillations of low energy (MeV to GeV) neutrinos. In principle, neutrinos from many different sources (sun, atmosphere, supernovae, beams etc.) can be used. In this talk, we summarize and compare different approaches with an emphasis on more recent developments. In addition, we point out other geophysical aspects relevant for neutrino oscillations.     

Non-local diffusion and the chemical structure of molecular clouds

Observations of fluctuations in the redshifted 21-cm radiation from neutral hydrogen (H  i ) are perceived to be an important future probe of the universe at high redshifts. Under the assumption that at redshifts   z ≤ 6  (post-reionization era) the H  i traces the underlying dark matter with a possible bias, we investigate the possibility of using observations of redshifted 21-cm radiation to detect the bispectrum arising from non-linear gravitational clustering and from non-linear bias. We find that the expected signal is ∼ 0.1  mJy at  325  MHz ( z = 3.4)  for the small baselines at the Giant Metrewave Radio Telescope, the strength being a few times larger at higher frequencies  (610 MHz, z = 1.3)  . Further, the magnitude of the signal from the bispectrum is predicted to be comparable to that from the power spectrum, allowing a detection of both in roughly the same integration time. The H  i signal is found to be uncorrelated beyond frequency separations of ∼1.3 MHz whereas the continuum sources of contamination are expected to be correlated across much larger frequencies. This signature can in principle be used to distinguish the H  i signal from the contamination. We also consider the possibility of using observations of the bispectrum to determine the linear and quadratic bias parameters of the H  i at high redshifts, this having possible implications for theories of galaxy formation.