A NEW“TETRASPORANGIAL”SPECIES OF LIAGORA(RHODOPHYTA,NEMALIALES)FROM HAWAIT     

Isabella A. Abbott 《中国海洋湖沼学报》1995,(4)

A new species of Liagora,L.perennis sp.nov.from Hawai’i,is described.Unlike dpecies of this genus in China,it is carpotetrasporangial,and at the place of expected carposporangia bears cruciately di-vided tetrasporangia,a detail which differentiates it from the usual species of Liagora without tetraspores that have been reported in China.Notes are provided on other Liagora species that have an impact on the taxonomy of species found in China.  相似文献   

Life's origin: the cosmic, planetary and biological processes     

Scattergood T  Des Marais D  Jahnke L 《The Planetary report》1987,7(6):4-5

From elements formed in interstellar furnaces to humans peering back at the stars, the evolution of life has been a long, intricate and perhaps inevitable process. Life as we know it requires a planet orbiting a star at just the right distance so that water can exist in liquid form. It needs a rich supply of chemicals and energy sources. On Earth, the combination of chemistry and energy generated molecules that evolved ways of replicating themselves and of passing information from one generation to the next. Thus, the thread of life began. This chart traces the thread, maintained by DNA molecules for much of its history, as it weaves its way through the primitive oceans, gaining strength and diversity along the way. Organisms eventually moved onto the land, where advanced forms, including humans, ultimately arose. Finally, assisted by a technology of its own making, life has reached back out into space to understand its own origins, to expand into new realms, and to seek other living threads in the cosmos.  相似文献   

岩体三维节点偶对分析及其应用          下载免费PDF全文

王思敬  张菊明 《地质科学》1991,(3):277-287

本文讨论了节点偶对分析的三维扩展。节点偶对分析是针对摩擦滑动节理单元的约束边界进行的序列矢量判定。在三维节理单元的分析中,几何约束和相应的力学判据极为复杂,采用节点偶对等效结合力方法才能迎刃而解。文中对三维转向节理模型的分析得到合理的结果,它表明本文所提出的方法可成功地应用于节理岩体的有限元分析。  相似文献   

Heterodyne spectroscopy of the 158 micron C II line in M42     

Boreiko RT  Betz AL  Zmuidzinas J 《The Astrophysical journal》1988,325(2):L47-L51

We have obtained velocity-resolved spectra of the 12C II 157.8 microns 2P3/2-2P1/2 fine structure line in the M42 region of Orion. Observations at 0.8 km s-1 resolution with a laser heterodyne spectrometer show multiple velocity components in some locations, with typical linewidths of 3-5 km s-1. Spectra of theta 1C and BN-KL also show weak emission from the F = 2-1 hyperfine component of the equivalent 13C II line. From the observed 12C II/13C II line intensity ratios, we deduce that the 12C II emission is optically thick with tau approximately 5 at both positions. Excitation temperatures of 128 K and 90 K, together with column densities of approximately 1 x 10(19) cm-2 and approximately 4 x 10(18) cm-2, are derived for theta 1C and BN-KL, respectively.  相似文献   

南极威尔克斯地SGR钻孔处雪冰转化过程中的密度变化特征          下载免费PDF全文

韩建康  N.W.杨 《极地研究》1988,1(1):13-24

本文着重描述了SGR钻孔处冰盖上的积雪在密实化过程中的特征变化,并对该过程进行了分段的和全面的回归分析.结果表明,冰盖密度随深度增大,但增长幅度随深度减小.作者提出密度变化减小度的概念.计算得出的所研究冰芯钻取点的密度变化减小度为-0.15kg/m~3·m~2,粒雪成冰前的密实速率平均值为4.08kg/m~3·a.本文得到的冰盖密度变化“临界点”与以往报道的有所不同.分析这一现象时,作者强调当积雪还在活动层时冰盖温度的影响,并以此解释密度剖面的异常变化以及离差的回升.特别指出,积雪的密度变化具有气候学意义,它在一定程度上能够反映出积雪形成及变化过程中气候变化的某些信息.本文由密度变化确定的钻孔点雪冰转化深度为50米.  相似文献   

Variations in the HCN/HNC abundance ratio in the Orion molecular cloud     

Goldsmith PF  Irvine WM  Hjalmarson A  Elldér J 《The Astrophysical journal》1986,310(1):383-391

We have used observations of the rare isotopes of HCN and HNC to determine the relative abundance of these two chemical isomers along the central ridge of the Orion molecular cloud. The abundance ratio [HCN]/[HNC] decreases by more than an order of magnitude from the relatively warm plateau and hot core sources toward the KL nebula to the colder, more quiescent clouds to the north and south. Even in the cooler regions, however, the ratio is an order of magnitude larger than that found in previous investigations of cold dark clouds. We determine the kinetic temperature in the regions we have studied from new observations of methylacetylene (CH3CCH), together with other recent estimates of the gas temperature near KL. The results suggest that the warmer portions of the cloud are dominated by different chemical pathways than those in the general interstellar cloud material.  相似文献   

《徐霞客游记》的科学性和时代性——怒江、腾冲地区的实地验证   总被引：2，自引：0，他引：2  

陈述彭 《地理研究》1986,5(4):1-11

作者选取本人身历其境作过工作的怒江、腾冲地区来验证《徐霞客游记》,从徐氏进步的地理概念、游记严谨的逻辑结构、游记作者观察的细致深入等方面论述了徐霞客的献身精神和不朽贡献。  相似文献   

Population development in Greater Santiago between 1970 and 1982: an analysis of district census results     

Bahr J  Mertins G 《Erdkunde》1985,39(3):218-238

"An attempt is made in the light of an analysis of population changes occurring in several sub-districts of Greater Santiago in the period between the last population censuses of 1970 and 1982, based on small-area census units (distritos and communas) to draw attention to the effects on the spatial growth of the city resulting from changed conditions in the political and juridical sphere since the change of power in 1973." The effect of changes in government policy concerning the liberalization of the property market and the illegal occupation of land are noted. (summary in ENG)  相似文献   

湖北徐家山锑矿床流体包裹体特征及其意义     

沈能平  彭建堂  袁顺达  张东亮  胡瑞忠  王国强 《矿床地质》2008,27(5):570-578

文章利用激光拉曼光谱和显微测温学方法,对湖北徐家山锑矿床成矿期的石英、重晶石和方解石中的流体包裹体进行了研究。研究表明,这些矿物中的流体包裹体主要有纯液体包裹体和液体包裹体(气相 液相)2类,其液体包裹体的气相成分为H2O±CO2±N2;石英、重晶石和方解石的均一温度分别为134~258℃、154~259℃和145~230℃,主要集中于150~200℃;流体的盐度w(NaCleq)和密度分别集中于3%~6%和0.90~0.96g/cm3。流体包裹体资料揭示出该矿床为典型的中低温热液锑矿床,其成矿流体为中低温、低盐度、中等密度热液。结合H、O、Sr、Pb同位素等研究结果,进一步推断该成矿热液主要是经深部循环演化的大气降水。  相似文献   

The Nordic geological surveys： Geology for society in practice   总被引：1，自引：0，他引：1  

Morten Smelror Andreas AhlstrФm Lena Ekelund Jens Morten Hansen Keijo Nenonen Anette K. Mortensen 《《幕》》2008,31(1):193-200

Since the mid-nineteenth century., when the first of the Nordic Geological Surveys were established, they have generated a substantial amount of information on the Earth＇s crust, its natural resources, its processes, and on the geological history of Nordic areas. The collective mission of the geological surveys is to carry out ＂Geology for Society＂, by doing research and providing services, and by making geological information and data easily accessible to all the varied end users in industry, government agencies, government institutes, public administrations, technical offices, academia and research institutes, as well as for private individuals. The present paper gives a brief overview of a few, selected, research areas and projects currently undertaken by the Nordic geological surveys. These serve as practical examples of how the Nordic geological surveys address important societal problems and challenges that require geological input for their solution.  相似文献