Constraining Holocene sea‐surface conditions in the south‐western Black Sea using dinoflagellate cysts

This paper presents two dinoflagellate cyst records from the south‐western shelf of the Black Sea. A new site, MAR05‐13, from the Sakarya shelf is described and placed into context with site MAR02‐45, ～250 km distant on the Thracian shelf. The records provide a centennial resolution of surface water conditions in the Holocene. Analysis of the data suggests that the surface salinity of the south‐western shelf increased in a gradual and progressive manner. In the period ～11 000–9000 cal a BP the assemblages suggest surface‐water salinities between 7–13 psu. The initial arrival of euryhaline species, ～8100 cal a BP, is linked to the reconnection of the Black Sea and Marmara Sea. The suggested surface water changes related to the reconnection took approximately 1000 years. Following this initial change in assemblages, a further increase in the number of euryhaline species is noted between 5000 and 4000 cal a BP. This is linked to the establishment of more saline surface‐water conditions, close to present‐day values. The record for MAR05‐13 highlights the complexity of the changes in cyst assemblages during the mid‐Holocene. Copyright © 2012 John Wiley & Sons, Ltd.     

Emerging coral diseases: a temperature‐driven process?

In the last few decades there has been a surge in research focusing on coral disease. While climate change, specifically rising sea surface temperature, has been proposed as a major and growing driver of the emergence of marine diseases, to date a solid connection between disease epizootics and elevated sea surface temperature has not been established. However, a wealth of data now exists, compiled from many different perspectives, that may support such a connection. In this work we provide a comprehensive review targeting one coral disease, black band disease, that spans the infection process, pathobiology, and epizootiology, and links specific mechanisms of the disease process to increasing temperatures. This temperature‐driven pattern of infection can be expanded to include similar processes associated with other temperature‐related coral diseases. The conclusions presented here are based upon the results of many studies using a diverse suite of approaches that have been synthesized to argue that the emergence and continuing spread of black band disease is linked to warming sea surface temperatures. In summary, as global ocean temperatures increase seasonally and over decades, the environment shifts to become more favorable for the growth of potentially pathogenic microorganisms endemic to the immediate environment of the reef. The increase in the relative number of potential pathogens in the microbial community produces microenvironments conducive to the growth of other potential pathogens, leading to infection by a polymicrobial consortium. This consortium is easily perturbed by a (seasonal) temperature decrease, but remains associated with the coral host and can be reactivated with a subsequent seasonal increase in temperature, resulting in a cycle of temperature‐dependent disease emergence.     

Multiple controls on the paleoenvironment of the Early Cambrian marine black shales in the Sichuan Basin,SW China: Geochemical and organic carbon isotopic evidence

In order to understand the paleoenvironment of the Early Cambrian black shale deposition in the western part of the Yangtze Block, geochemical and organic carbon isotopic studies have been performed on two wells that have drilled through the Qiongzhusi Formation in the central and southeastern parts of Sichuan Basin. It shows that the lowest part of the Qiongzhusi Formation has high TOC abundance, while the middle and upper parts display relative low TOC content. Redox-sensitive element (Mo) and trace elemental redox indices (e.g., Ni/Co, V/Cr, U/Th and V/(V + Ni)) suggest that the high-TOC layers were deposited under anoxic conditions, whereas the low-TOC layers under relatively dysoxic/oxic conditions. The relationship of the enrichment factors of Mo and U further shows a transition from suboxic low-TOC layers to euxinic high-TOC layers. On the basis of the Mo-TOC relationship, the Qiongzhusi Formation black shales were deposited in a basin under moderately restricted conditions. Organic carbon isotopes display temporal variations in the Qiongzhusi Formation, with a positive excursion of δ¹³C_org values in the lower part and a continuous positive shift in the middle and upper parts. All these geochemical and isotopic criteria indicate a paleoenvironmental change from bottom anoxic to middle and upper dysoxic/oxic conditions for the Qiongzhusi Formation black shales. The correlation of organic carbon isotopic data for the Lower Cambrian black shales in different regions of the Yangtze Block shows consistent positive excursion of δ¹³C_org values in the lower part for each section. This excursion can be ascribed to the widespread Early Cambrian transgression in the Yangtze Block, under which black shales were deposited.     

滇东北下寒武统黑色岩系钼、镍矿床特征及找矿前景

滇东北地区钼镍多金属矿床主要产于下寒武统筇竹寺组黑色页岩、黑色粉砂岩地层中,矿体与围岩界线明显,呈似层状、层状产出,为层控矿床。矿体厚度薄、品位高,但往深部有变富、变厚的趋势.     

乌鲁木齐冬季黑碳气溶胶污染特征初步研究

利用2010年2月乌鲁木齐大气成分观测站黒碳仪观测数据,结合散射系数及常规观测资料,对乌鲁木齐冬季黑碳气溶胶浓度变化特征进行了分析,并通过气流后向轨迹进行了来源分析。结果表明：(1)观测期间BC质量浓度日平均值为12707±4673 ng.m-3,浓度变化范围为4916~22997 ng.m-3,散射系数日均值为1086±561Mm-1,变化范围为350~2232 Mm-1。BC质量浓度和散射系数日均值变化趋势基本一致;(2)BC质量浓度日变化具有明显的峰值和谷值,峰值分别出现在9~11时和20~22时,谷值分别出现在4~6时和16~18时,散射系数与BC质量浓度日变化趋势基本一致,相对其有一定的滞后。春节期间燃放烟花爆竹对空气污染物浓度上升有明显作用,显著影响BC质量浓度日变化规律;(3)乌鲁木齐冬季大气层结稳定,污染物不易扩散,风速和降水对黑碳气溶胶浓度具有明显的稀释作用。在乌鲁木齐特殊的地形和气象条件下,本地源排放与来自周边城市群污染物输送的叠加使得污染更加严重。     

Towards a new standard model for black hole accretion

We briefly review recent developments in black hole accretion disk theory, emphasizing the vital role played by magnetohydrodynamic (MHD) stresses in transporting angular momentum. The apparent universality of accretion-related outflow phenomena is a strong indicator that large-scale MHD torques facilitate vertical transport of angular momentum. This leads to an enhanced overall rate of angular momentum transport and allows accretion of matter to proceed at an interesting rate. Furthermore, we argue that when vertical transport is important, the radial structure of the accretion disk is modified at small radii and this affects the disk emission spectrum. We present a simple model demonstrating how energetic, magnetically-driven outflows modify the emergent disk emission spectrum with respect to that predicted by standard accretion disk theory. A comparison of the predicted spectra against observations of quasar spectral energy distributions suggests that mass accretion rates inferred using the standard disk model may be severely underestimated.     

黑洞熵可以量子化吗?

在黑洞蒸发的最后阶段其残余质量为Planck质量的量级,因而所对应的黑洞熵为2πk_B量级,在Bekenstein工作的基础上作者导出在吸积物质的过程中黑洞的最小熵增为2πk_B,这一最小熵增又限制能参与吸积物质的黑洞的质量下限为Planck质量的量级,因而所对应的最小黑洞熵也为2πk_B这一量级。作者进一步指出:黑洞的最小熵及最小熵增不受引力常数G变化的影响,因此上述结论在极早期宇宙中也能成立,在上述分析的基础上作者提出一个猜想:黑洞熵可以量子化,其量子单位为2πk_B。     

Why the fundamental plane of black hole activity is not simply a distance driven artifact

The fundamental plane of black hole activity is a non-linear correlation among radio core luminosity, X-ray luminosity and mass of all accreting black holes, both of stellar mass and supermassive, found by Merloni et al. [Merloni, A., Heinz, S., di Matteo, T. 2003. MNRAS 345, 1057 (MHD03)] and, independently, by Falcke et al. [Falcke, H., Körding, E., Markoff, S., 2004. A& A 414, 895]. Here we further examine a number of statistical issues related to this correlation. In particular, we discuss the issue of sample selection and quantify the bias introduced by the effect of distance in two of the correlated quantities. We demonstrate that the fundamental plane relation cannot be a distance artifact, and that its non-linearity must represent an intrinsic characteristic of accreting black holes. We also discuss possible future observational strategies to improve our understanding of this correlation.     

吸积盘谱讨论

本文用数值方法讨论了吸积盘谱与黑体谱的形状和谱指数。结果表明:对于吸积盘用F_v∝v~(1/3)作为其特征谱是不合适的;同时Frank等(1985)所得到的解析式F_v∝v~2也是不正确的。     

The iron Kα lines as a tool for magnetic field estimations in non-flat accretion flows

Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton indicate the existence of broad X-ray emission lines of ionized heavy elements in their spectra. Such spectral lines were discovered also in X-ray spectra of neutron stars and X-ray afterglows of GRBs. Recently, Zakharov et al. [MNRAS 342 (2003) 1325] described a procedure to estimate an upper limit of the magnetic fields in regions from which X-ray photons are emitted. The authors simulated typical profiles of the iron Kα line in the presence of magnetic field and compared them with observational data in the framework of the widely accepted accretion disk model. Here we further consider typical Zeeman splitting in the framework of a model of non-flat accretion flows, which is a generalization of previous consideration into non-equatorial plane motion of particles emitting X-ray photons. Using perspective facilities of space borne instruments (e.g., Constellation-X mission) a better resolution of the blue peak structure of iron Kα line will allow to evaluate the magnetic fields with higher accuracy.