Ice in the Southern Coalsack     

R. G.Smith †  R. D.Blum †  D. E.Quinn  K.Sellgren  D. C. B.Whittet † 《Monthly notices of the Royal Astronomical Society》2002,330(4):837-843

To better understand the conditions under which ice mantles form on grains in molecular clouds, three globules in the Southern Coalsack have been searched for the presence of H₂O ice. Given the total lack of star formation in the Coalsack, it is an ideal site for studying unprocessed icy molecular mantles. In our sample of eight field stars lying behind the Coalsack we detect strong H₂O ice absorption in the lines of sight to two stars and possible weak absorption in four others. We estimate H₂O ice column densities or upper limits for these lines of sight. Compared to dark clouds such as Taurus, the Coalsack H₂O ice column densities are lower than expected given the quiescent nature of the Coalsack region. It is possible that the chemical evolution of the Coalsack may simply be at too early a stage for significant ice mantles to appear on the grains, except perhaps in the densest parts of some of the globules. Alternatively, the presence or absence of ice absorption may be related to the distribution of dust along each line of sight, specifically, the relative contributions of dense globules and a more extended diffuse component. For example, our observations are consistent with an ice threshold extinction similar to that observed in the Taurus dark cloud if extinction amounting to   A _V∼5  towards Globules 2 and 3 arises in the extended component. Globule 1 appears to have no extended component.  相似文献   

Irradiation of dust in molecular clouds. I. UV doses     

A. G. Yeghikyan 《Astrophysics》2009,52(2):288-299

The radiation fluxes inside molecular clouds owing to a neighboring class A star or to isotropic interstellar irradiation are calculated. Radiation within the interval 912 ? < λ < 2067 ? is found to penetrate deeply enough to ensure a radiation dose for water ice on the order of 100 eV/amu or more over the lifetime of the clouds, whether a star formation region is present or not. The possibility is discussed of using these results for an astrophysical interpretation of published data from laboratory experiments on irradiation of ices of the type H₂O:CH₃OH:NH₃:CO. The resulting radiation-chemical transformation of complex organic materials may play an important role in the prebiological evolution of the dust component of molecular clouds. Translated from Astrofizika, Vol. 52, No. 2, pp. 311–324 (May 2009).  相似文献   

四川后高坪地区晚泥盆世植物和遗迹化石的新发现   总被引：2，自引：0，他引：2  

张立军  龚一鸣 《地层学杂志》2009,33(2)

在扬子板块西缘后高坪地区新发现植物化石Cyclostigma kiltorkense(平圆印木)和Lepidodendropsis hirmeri(希氏拟鳞木),以及遗迹化石Zoophycos(动藻迹)和Chondrties(丛藻迹),据此及相关地层和沉积相标志,确定该地层时代为晚泥盆世,沉积环境为由早期为滨岸较粗碎屑岩和浅海中上部细碎屑岩沉积,晚期为碳酸盐台地相。  相似文献   

Properties of the high-mass star forming region IRAS 22475＋5939     

Xiao-Lan Liu  Jun-Jie Wang 《天体物理学报》2012,(7):845-856

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Amino acids produced from the ultraviolet/extreme-ultraviolet irradiation of naphthalene in a H₂O+NH₃ ice mixture     

Y.-J. Chen  M. Nuevo  T.-S. Yih  W.-H. Ip  H.-S. Fung  C.-Y. Cheng  H.-R. Tsai  C.-Y. R. Wu 《Monthly notices of the Royal Astronomical Society》2008,384(2):605-610

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Molecular Structure of Kerogen in the Longmaxi Shale: Insights from Solid State NMR,FT‐IR,XRD and HRTEM     

WANG Xiaoqi  ZHU Yanming  LIU Yu  LI Wu 《《地质学报》英文版》2019,93(4):1015-1024

Kerogen plays an important role in shale gas adsorption, desorption and diffusion. Therefore, it is necessary to characterize the molecular structure of kerogen. In this study, four kerogen samples were isolated from the organic-rich shale of the Longmaxi Formation. Raman spectroscopy was used to determine the maturity of these kerogen samples. High-resolution transmission electron microscopy (HRTEM), 13C nuclear magnetic resonance (13C NMR) , X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to characterize the molecular structure of the shale samples. The results demonstrate that VReqv of these kerogen samples vary from 2.3% to 2.8%, suggesting that all the kerogen samples are in the dry gas window. The macromolecular carbon skeleton of the Longmaxi Formation kerogen is mainly aromatic (fa’=0.56). In addition, the aromatic structural units are mainly composed of naphthalene (23%), anthracene (23%) and phenanthrene (29%). However, the aliphatic structure of the kerogen macromolecules is relatively low (fal*+falH=0.08), which is presumed to be distributed in the form of methyl and short aliphatic chains at the edge of the aromatic units. The oxygen-containing functional groups in the macromolecules are mainly present in the form of carbonyl groups (fac=0.23) and hydroxyl groups or ether groups (falO=0.13). The crystallite structural parameters of kerogen, including the stacking height (Lc=22.84 ?), average lateral size (La=29.29 ?) and interlayer spacing (d002=3.43 ?), are close to the aromatic structural parameters of anthracite or overmature kerogen. High-resolution transmission electron microscopy reveals that the aromatic structure is well oriented, and more than 65% of the diffractive aromatic layers are concentrated in the main direction. Due to the continuous deep burial, the longer aliphatic chains and oxygen-containing functional groups in the kerogen are substantially depleted. However, the ductility and stacking degree of the aromatic structure increases during thermal evolution. This study provides quantitative information on the molecular structure of kerogen samples based on multiple research methods, which may contribute to an improved understanding of the organic pores in black shale.  相似文献   

我国新记录绿潮物种Ulva laetevirens的比较叶绿体基因组学研究     

王静  王毅超  王洪淑  刘峰  陈楠生 《海洋与湖沼》2021,52(5):1201-1213

在全球范围内广泛暴发的石莼属绿潮既包括大规模暴发的跨海域绿潮,也包括小规模暴发的局地绿潮。我国有关绿潮致灾物种的研究对象主要集中于黄海绿潮浒苔,而针对局地绿潮致灾物种的研究尚处于起步阶段。针对局地绿潮物种的鉴定和分布调查是有效预防和监测潜在大规模绿潮暴发的重要环节。本文对2020年11月初于山东烟台第一海水浴场暴发的石莼属绿潮进行了初步研究。经随机采样获得了12株藻体,根据tufA分子标记初步将其中11株鉴定为Ulvalaetevirens。本研究完成了U. laetevirens的一个代表性株系CNS00533的叶绿体基因组构建和解析。叶绿体基因组为110 889 bp,含有71个蛋白编码基因、27个tRNA基因和3个rRNA基因(rrl、rrn和rrn5)。烟台海域U.laetevirens株系叶绿体基因组基因组成和排列顺序与爱尔兰海域U.laetevirens株系MT179351完全一致,DNA序列相似性为99.8%,进一步证明CNS00533为U.laetevirens。此外,U.laetevirens的烟台株系与爱尔兰株系的叶绿体基因组也存在差异,烟台株系比爱尔兰株系多了5个I型内含子和1个II型内含子,导致叶绿体基因组长度增加7kb。CNS00533与U.rigidaMT179352叶绿体基因组之间存在多个不同的长片段插入序列(763—2 346 bp), DNA序列相似性也较低(93.1%);与U. australis MT179348相比差异更大,存在一个较大(覆盖45个基因)的基因组反转事件。在基于71个蛋白编码基因的遗传进化树中, CNS00533与U. laetevirens MT179351聚类在一枝,与U. rigida MT179352遗传距离较近,与U. australis MT179348的遗传距离很远,表明U. laetevirens、U. rigida和U. australis为石莼属的3个不同物种。2020年11月烟台海域局地绿潮事件的原因种U. laetevirens在我国近海绿潮事件中首次报道,本研究对该物种的分子进化分析将有助于对我国近海绿潮监测、物种鉴定提供数据支持和理论依据。  相似文献   

基于网络药理学和分子对接探讨左金丸治疗肝癌的作用机制          下载免费PDF全文

雷彩云  刘人杰  田立峰 《应用海洋学学报》2021,37(11):178

目的：运用网络药理学和分子对接方法探讨左金丸治疗肝癌的作用机制。方法：从TCMSP和BATMAN-TCM数据库获取左金丸的化合物及其相应靶点,检索GeneCards、OMIM和TTD 3个数据库获得肝癌的相关靶基因,取两者靶基因交集得到左金丸治疗肝癌的预测靶基因;运用Cytoscape 3.7.1软件构建左金丸-化合物-靶点-肝癌和PPI网络图;运用R软件对预测靶基因进行GO和KEGG富集分析;最后运用分子对接技术对关键化合物和靶点进行验证。结果：共获取左金丸35个化合物及173个相应靶点,左金丸与肝癌的共同靶点有103个。PPI结果表明AKT1、MAPK1、TP53、JUN和RELA可能为左金丸治疗肝癌的关键靶点。富集分析示左金丸可能通过乙型肝炎、卡波西肉瘤相关疱疹病毒感染、人巨细胞病毒感染、丙型肝炎、MAPK信号通路、肝癌等信号通路抗肝癌。分子对接结果示槲皮素和黄连素均能与AKT1和MAPK1稳定结合。结论：本研究初步揭示了左金丸通过多成分、多靶点、多通路治疗肝癌的作用机制,为后续左金丸治疗肝癌提供理论参考。  相似文献   

基于网络药理学-分子对接探索大黄牡丹汤治疗大肠癌的作用机制          下载免费PDF全文

梁子成  文璐  陈泓秀 《应用海洋学学报》2021,37(10):177

目的：利用网络药理学-分子对接技术探索经方大黄牡丹汤治疗大肠癌的作用机制。方法：通过TCMSP、TCMID数据库获得大黄牡丹汤药物成分,通过PubChem、Swisstarget prediction数据库获得药物成分对应靶点,分析GSE113513芯片获得差异基因,随即获取大黄牡丹汤与大肠癌的共同靶点。利用R、Cytoscape、Autodock软件进行PPI、GO、KEGG、分子对接等分析。结果：获得大黄牡丹汤靶点561个,大肠癌差异基因1227个,共同靶点71个。共同靶点的通路富集分析显示主要与PPAR、p53等信号通路相关,Reactome机制分析显示大黄牡丹汤治疗大肠癌主要通过影响信号转导、免疫系统、疾病等产生作用,分子对接结果显示大肠癌核心靶点与大黄牡丹汤主要成分亲和力较好,能够有效自由结合。结论：经方大黄牡丹汤可通过多层次、多途径、多靶点发挥对大肠癌的治疗作用。  相似文献   

海洋有害藻华研究进展   总被引：3，自引：0，他引：3  

林森杰  姬南京  罗昊 《海洋与湖沼》2019,50(3):495-510

浮游植物不仅是食物链的基础环节,也在生物地球化学循环中起着重要作用。然而,某些种类在一定条件下会过度增殖富集形成有害藻华(因造成水色变为红、绿、褐、金等颜色,所以俗称为赤潮、绿潮、褐潮、金潮等),结果严重影响当地经济、海洋生态系统、全球生物地球化学循环甚至人类健康。近年来,随着水体富营养化、全球气候变化等现象加剧,有害藻华(Harmful Algal Bloom,HAB)的暴发规模和频次呈逐年增加趋势,且相关研究已成为环境生态学领域的热点。本文主要以典型海洋HAB生物为线索,从物种分布、生物监测、主要影响因素、分子机制及防治等方面概述了近十年HAB的主要研究进展,总结了现有研究的优点和不足,并对未来HAB研究做了相关展望。近十年的研究进展主要体现在:(1)不断有新的HAB物种被发现或鉴定,HAB藻类系统分类也不断被更新;(2)鉴定、检测方法包括DNA分析、生物传感器研发应用等有较大改进;(3)藻类毒素生物合成通路的研究有一定进展;(4)在HAB生态学与海洋学研究持续发展的基础上,分子机制及现代组学发展较迅速。然而, HAB发生的关键环境诱因和生物学(特别是生化与分子)机制仍然不是很清楚,缺乏一个可用来预测HAB暴发的关键因子。笔者认为,一方面是因为HAB的复杂性、种类及生态系统的特异性,另一方面是研究缺乏系统性与完整性。因此未来有必要加强对每一个重要的HAB原因种开展系统、持续的研究,类似于生物科学领域里的模式种研究,并且有必要开展综合性的研究,如实验室单种培养、中尺度模拟及现场生态研究相结合,整合现代组学、传统生理生态学和现场实时连续观测等技术。  相似文献