银河系卫星星系研究进展

对银河系内卫星星系进行全面的"人口普查"具有重要的意义。目前已经发现了二十几个卫星星系,其光度范围分布很广,最暗的矮星系比球状星体还暗。叙述了卫星星系的光度分布、空间分布和动力学性质。总结了观测和理论研究进展,并讨论了星流和伽玛射线在研究银河系结构和暗物质性质方面的贡献。表明了卫星星系的统计分布能用来很好地限制冷暗物质理论和星系形成的相关物理过程,同时指出当前研究的局限性和可能的发展方向。     

Numerical modelling of the vertical structure and dark halo parameters in disc galaxies

The non‐linear dynamics of bending instability and vertical structure of a galactic stellar disc embedded into a spherical halo are studied with N‐body numerical modelling. Development of the bending instability in stellar galactic disc is considered as the main factor that increases the disc thickness. Correlation between the disc vertical scale height and the halo‐to‐disc mass ratio is predicted from the simulations. The method of assessment of the spherical‐to‐disc mass ratio for edge‐on spiral galaxies with a small bulge is considered. Modelling of eight edge‐on galaxies: NGC 891, NGC 4738, NGC 5170, UGC 6080, UGC 7321, UGC 8286, UGC 9422 and UGC 9556 is performed. Parameters of stellar discs, dark haloes and bulges are estimated. The lower limit of the dark‐to‐luminous mass ratio in our galaxies is of the order of one within the limits of their stellar discs. The dark haloes dominate by mass in the galaxies with very thin stellar discs (NGC 5170, UGC 7321 and UGC 8286) (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Metallicity and kinematical clues to the formation of the Local Group

The kinematics and elemental abundances of resolved stars in the nearby Universe can be used to infer conditions at high redshift, trace how galaxies evolve and constrain the nature of dark matter. This approach is complementary to direct study of systems at high redshift, but I will show that analysis of individual stars allows one to break degeneracies, such as between star formation rate and stellar Initial Mass Function, that complicate the analysis of unresolved, distant galaxies (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Primordial black holes

Primordial black holes (PBHs) are a profound signature of primordial cos-mological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to re-strict a wide range of particle physics models, predicting an enhancement of the ul-traviolet part of the spectrum of density perturbations, early dust-like stages, first or-der phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflation-ary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.     

Urbanised beaches of the Ligurian coastal area (NW Mediterranean): A classification based on organic-matter characteristics and hydrolytic enzymatic activities

The beaches of Liguria have been intensively affected by human activities for over a century, transforming nearly the entire coastline from natural to urbanised and significantly upsetting beach ecological properties. The present study aims to investigate 9 Ligurian beaches characterised by different degree of urbanisation, to test if and to what extent the organic-matter (OM) recycling processes can be linked to the human activity. Swash zone sediment, sampled during the spring–summer–autumn period, when the anthropogenic influence is at its maximum due to tourism, was analysed for OM features and recycling processes. Multivariate statistical analyses showed that huge amounts of detrital OM accumulated in the more urbanised sites, where the anthropogenic influence was at its peak, deriving from higher inhabitant number and density, from the presence of crowded roads very near to the swash zone and sewage treatment plants. The presence of torrent outlets on the beaches provided further OM accumulation. Lipids, carbohydrates and degraded autotrophic pigments were the OM fractions mainly responsible of the differentiation, and rather constant, high labile phosphorus contents were found in the more urbanised sites. The high activity values of the hydrolytic enzymes indicate the response of the microbial system to the OM accumulation in the urban sites. However, a decoupling of the trends of some enzymatic activities (namely glucosidase and lipase) and their target OM was observed in the highly urbanised conditions.     

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here ‘DIN’ is the sum of ammonium, nitrite and nitrate.) After  30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher proportion of the decomposed particulate N was converted into inorganic N. It can be concluded that during the first days and weeks of early diagenesis the magnitude and composition of the flux of decompositional dissolved N-compounds from sediments into the overlying water was influenced by non-linear interactions of OM substrates of different degradability. Given these experimental results it is likely that the relative spatial distributions of OM of differing degradability in sediments control the magnitude and composition of the return flux of dissolved N-bearing compounds from sediments into the overlying water column.     

高速Ia型超新星的蓝色超出: 星周介质的尘埃散射

Ia型超新星起源于碳氧白矮星在质量接近钱德拉塞卡极限时的热核爆炸,并被广泛地用作宇宙学距离的标准烛光.然而, Ia型超新星的前身星系统和爆炸机制还存在很多不明确的地方.近几十年来, Ia型超新星的星周环境得到了越来越多的关注.星周介质的空间分布性质为探究Ia型超新星的物理起源提供了重要线索.同时星周尘埃的散射会在Ia型超新星晚期的光变曲线、光谱和偏振等方面产生可观测效应.光谱上正常的Ia型超新星可以分成两类:喷射物速度正常和高速Ia型超新星.对比两者的光变曲线可以发现高速Ia型超新星在光极大后几个月内有明显颜色偏蓝的超出.该蓝色超出可以通过星周介质中的尘埃散射拟合得到.同时, Ia型超新星晚期光谱的拟合可以限制星周尘埃的颗粒大小等性质,晚期的偏振信号可以有效地限制星周尘埃的空间分布.拟合结果表明针对Ia型超新星晚期的多次图像偏振观测是揭示其星周尘埃环境特征的重要手段.     

微塑料添加对小麦苗期生长及干物质分配的影响

土壤环境中微塑料污染已成为全球关注的环境问题。关于微塑料对于植物生长的直接影响和由于土壤理化性状改变的间接影响研究已逐步开展,但针对小麦的研究鲜见报道。试验选择两个旱地小麦品种(甘春27和禾尚头)作为研究对象,选取高密度聚乙烯作为微塑料添加,设置3种质量浓度(0、1、4 g·kg^-1)开展盆栽试验,对不同微塑料组合处理下小麦的出苗率、株高、全株生物量和地上/地下干物质分配进行了分析。结果表明：(1)微塑料添加对两个品种出苗率没有影响。(2)禾尚头在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高46.7%、8.5%,甘春27在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高28.7%、17.2%;甘春27整体比禾尚头在3种浓度处理下全株生物量分别高24.9%、9.6%、1.5%。(3)不同试验处理条件下,甘春27将更多的干物质分配在地上植株的构建,其在地下(根系)和地上(茎叶)部分的分配比例整体小于禾尚头。整体上,适度微塑料添加可...     

水下荧光光谱探测装置控制系统的设计与实现

海水中有色可溶性有机物(CDOM,Chromophoric Dissolved Organic Matter,常称之为黄色物质)是影响海洋水色的三大成分之一,海水中CDOM的研究具有重要的意义。本文针对CDOM水下原位探测激光诱导荧光光谱探测装置开发了一套控制系统,该控制系统分为水上甲板控制和水下数据采集两部分,水上甲板控制部分通过8芯电缆与水下数据采集部分实现供电及通信,水下数据采集部分以PC104嵌入式工控机为核心,控制整体采集部分的工作,甲板控制部分通过远程控制软件来操控PC104以实现水下数据的采集和存储。实验室环境测试及近海现场实验表明,该系统能够可靠完成水下荧光光谱装置的控制和数据的采集及通信需求,实现海水中有色可溶性有机物的水下原位探测。