Geochemical significance of lipids and lipid-derived substructures interlaced in kerogen

Young kerogens isolated from seven freshwater lakes, six river mouths and four marine surface sediments were subjected to pyrolysis in vacuo. Their pyrolysates were trapped and separated subsequently for determination of hydrocarbons, fatty acids and alcohols. The abundances, carbon number distributions of long (C₁₂) polymethylene chain lipid compounds and relative abundances of pristenes are proposed as possible indices applicable to discrimination between young kerogens from freshwater lacustrine and marine sediments. Some oil-shale kerogens of Eocene and Permian age were pyrolyzed in the same way, where the chain-length distributions of the pyrolysis products showed similar trends as those observed for the pyrolysis of young kerogens.     

中国青年国际义工旅行者的旅游动机及其影响因素

以参加过国际义工旅行的26名中国青年旅行者为研究对象,基于半结构访谈所获取的数据,对青年国际义工旅行者旅游动机特征及其影响因素进行质性分析。在已有文献和调研资料的基础上,根据动机性质和联系将义工旅行的出行动机划分为利他动机和自我动机。其中,利他动机指义工旅行者对目的地援助的期望;自我动机指义工旅行者以自我兴趣和需求为中心。研究发现：1）国际义工旅行者的旅游动机呈现出自我需求主导的特征;2）不同动机主导下的国际义工旅行者都存有利他和自我的双重影响因素。影响义工旅行者动机的因素包括：平台宣传建构的目的地旅游形象、项目内容、个人能力和家庭影响等;3）国际义工旅行是一种责任旅游,不仅包含对目的地的责任同样也是对个人的责任。     

UV-B辐射对海带幼孢子体生长和生理的影响

探讨UV-B辐射对海带幼孢子体的影响,运用实验生态学的方法,研究了高(93.6 J·m-2·d-1)、中(46.8 J·m-2·d-1 )、低(11.7 J·m-2·d-1)3个剂量的UV-B辐射对海带幼孢子体生长和生理状况的影响.辐射处理期间(第2～10天),3个辐射剂量处理组的海带幼孢子体体长和体重的相对增长率显著低于对照组(0 J·m-2·d-1);第6～10天期间,低剂量处理组和高剂量处理组的叶绿素a(Chl-a)含量与对照组相比呈现出完全相反的变化趋势,前者显著高于对照组,后者显著低于对照组;中、高剂量处理组的ATP酶活性在整个实验期间均显著低于对照组,而低剂量组与对照组无显著差异.氮(N)、磷(P)元素缺乏与中剂量UV-B联合作用条件下的海带幼孢子体体长、体重相对增长率与中剂量单独处理组无显著差异;辐射处理初期(第2～4天),N、P缺乏与中剂量UV-B辐射共同处理组的ATP酶活性明显高于单独辐射处理组,后期(第10天)则显著低于单独辐射处理组;N、P元素缺乏加剧了中剂量UV-B辐射对海带幼孢子体Chl-a含量的影响效应,N、P缺乏与中剂量UV-B辐射共同处理组的Chl-a含量显著低于中剂量UV-B辐射处理组.在高剂量UV-B辐射处理的同时,附加一定强度的光合有效辐射(photosynthetically active radiation,PAR,400～700 nm)能在一定程度上减轻UV-B辐射对海带幼孢子体生长和生理状况的影响程度.     

关于高校学报青年编辑培养的几点思考

为了紧跟时代步伐,成为与时俱进,新世纪优秀的出版人,从职业素质的培养、出版业务知识的培养、专业知识的培养及综合知识的培养、人际关系的培养5个方面对高校学报青年编辑的培养进行了探讨。     

条斑紫菜孢子体与配子体光合系统Ⅱ(PSⅡ)稳定性研究

膜蛋白是生物领域研究中的热点和难点。在光合作用研究中,对于藻类个体发育过程中光合膜蛋白结构和功能的变化所知甚少,其中的一个限制因素是能否纯化得到大量高活性的稳定且均一的光合膜蛋白。作者从条斑紫菜(Porphyra yezoensis)孢子体和配子体中分离纯化得到光合系统(PSⅡ)复合物,并研究了其完整性和放氧活性。结果表明,孢子体和配子体的PSⅡ复合物,在4℃条件下保存比在-80℃下保存放氧活性高,稳定性高。配子体PSⅡ复合物,在-80℃保存第6天就已经没有放氧活性,而孢子体PSⅡ复合物仍有放氧活性。对4℃下保存的PSII复合物进行分子筛柱层析,室温吸收光谱测定以及放氧活性测定,发现随着放氧活性逐渐降低,蛋白大分子有聚合现象。室温吸收光谱表明经过长期的保存,吸收峰向短波长方向偏移,叶绿素易降解成为脱镁叶绿素     

Social geography of risk: The role of time,place and antiretroviral therapy in conceptions about the sexual risk of HIV in Kahe,Kilimanjaro, Tanzania

The epidemiological pattern of HIV/AIDS in Africa and Tanzania is characterized by geographical variations in HIV prevalence. Despite the geographical variations, heterosexual contact remains the predominant mode of HIV transmission. The article examines the interrelationships of social, spatial and temporal issues in explaining the sexual risk of HIV/AIDS amongst youths in rural Tanzania. Drawing on discussions with young people, the authors employ a comparative approach to establish categories of social practices that explain HIV risk. HIV risk is largely influenced by social interaction as youths engage in routine day-to-day activities in different geographical locales. The availability of antiretroviral treatment ushered in new dynamics in locally available strategies to manage the risk of HIV infection. Gender relations appear to have an underlining influence in determining the timing and place of risk as well as ways of controlling risk. The study participants emphasized both social and biomedical interventions to manage and control sexual activity and risk. Youth-focused and community-wide interventions addressing HIV prevention, care and treatment need to recognize the fact that the HIV epidemic in Tanzania is increasingly becoming a rural phenomenon structured by a wide range of local, national and global processes.     

Disk wind in young binaries with low-mass secondary components: Optical observational manifestations

We consider a model of a young binary with a low-mass secondary component. Mass accretion from the remnants of the protostellar cloud onto the binary components is assumed to take place in accordance with current models; i.e., it proceeds mainly onto the low-mass component. The accretion is accompanied by mass outflow (disk wind), whose low-velocity component can be partially captured by the primary component. As a result, an asymmetric common envelope is formed. Its densest part is involved in the orbital motion of the secondary and can periodically shield the primary component of the binary from the observer. Assuming a standard dust-to-gas ratio for the disk wind (1: 100), we calculated the possible photometric effects from such eclipses and showed that they could be observed even at moderate accretion rates onto the low-mass binary component, ∼10⁻⁸–10⁻⁹ M _⊙ per year. In this case, the parameters of the minima depend on the model of the disk wind, on the ratio of its characteristic velocity to the orbital velocity of the secondary, and on its orbital inclination to the line of sight. These results can form the basis for interpreting a wide range of phenomena observed in young stars, such as the activity cycles in UX Ori stars, the unusually broad minima in some young eclipsing systems, etc., and for searching for substellar objects and massive protoplanets. In addition, the peripheral parts of the gas and dust disk around a young binary can fall within the shadow zone produced by the opaque part of the common envelope. In such cases, a shadow from the common envelope must be observed on the disk; this shadow must move over the disk following the orbital motion of the low-mass component. Detection and investigation of such structures in the images of protoplanetary disks may become a method of searching for protoplanets and studying binaries at early stages of their evolution.     

年轻石笋平均沉积速率的确定——多方法探讨

石笋凭借其准确的年代学和对洞穴外界环境的敏感响应,已经成为第四纪研究的重要力量。亚洲季风区轨道-千年尺度石笋δ18O指示亚洲季风强弱的变化,但是在更短的时间尺度上,石笋δ18O则可能受到其他因素的影响,因此近现代、能与器测记录进行对比的石笋记录研究是衔接现代气候与古气候的关键环节。而这关键环节中的关键问题就是确定石笋的沉积年代。寻找一种适合于无生长纹层、低U含量石笋样品的年代方法对于解决石笋沉积年代有着重要的推动作用。本研究选择广西桂林茅茅头大岩一正在生长的年轻石笋。由于低U含量、高232 Th含量,U系-230 Th定年不成功。利用210Pb定年计算出平均沉积速率为1.96±0.23mm/a,但由于多层晶间孔隙的存在,计算结果偏小。由于石笋中14 C基本为核爆产生,AMS 14 C测试结果计算石笋平均沉积速率为2.10mm/a,但由于未测量到核爆前14 C数据,其值可能仍偏小。由于前人研究指出桂林地区石笋记录能记录夏季风降水,结合桂林多年降水数据,综合计算出该石笋平均沉积速率为2.44mm/a,生长时限为2009—1968年。平均沉积速率和沉积时代的确定,为后续的石笋现代气候研究,进而与古气候衔接提供了重要的研究基础。     

An advanced irradiation facilities and its usage

1 INTRODUCTION Carrier type gamma irradiation, a new tech- nology have been developed rapidly in recent dec- ades in industry, agriculture, and science and tech- nology. In Qingdao Irradiation Center (QIC), a car- rier-type irradiator in overlapping sourc…