Irish on the move     

King R  Mcgrath F  Shuttleworth I  Strachan A 《Geography review》1989,3(3):23-27

Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour."  相似文献   

贝加尔裂谷系及邻区断裂现今活动变化及成因(英文)     

S.I. Sherman　E.A.Gorbunova 《地学前缘》2008,15(3):337-347

已有的地质和地球物理方法无法对年、月、旬等现今时间尺度上的断层活动变化进行有效预测。运用基于地震活动定量指数运算程序的地理信息技术可以解决这个问题。这种方法被应用于贝加尔裂谷系(BRS)及邻区的研究当中。研究发现,断层活动变化发生在以几年为周期的时间尺度上,这无法用区域应力场的变化进行合理解释。沿着穿越贝加尔裂谷系的剖面编制了活动断层图以及地震活动定量指数曲线。提出的这种方法可以根据地震活动定量指数对活动断层进行仔细的分类,从而为解决地震中期预报相关问题开辟了重要途径。这种方法还被用来研究断层现今活动的时空变化和形成机制。研究发现,在实时尺度上断层活动具有高频发生的特征,这种现象可能是由于脆性岩石圈板内和块体内部运动产生的慢变形波的干扰导致的。利用变形波的通过速度可以对活动断层进行分组,各组具有不同的地质和地球物理特征参数,同时还可以对变形波波前的方向以及某一区域内主要断层在实时间隔内(地质上的瞬间)的活动情况进行预测。  相似文献   

The population of Croatia     

Sterc S  Crkvencic I 《GeoJournal》1996,38(4):417-424

Croatia is a Central European and Mediterranean state, located in contact with and under the influence of various spheres of civilization, which for centuries have penetrated and conflicted on and around the territory of Croatia. Such a position has resulted in various influences which did not always have a positive effect on the development of Croatia. The gradual narrowing and decrease of the Croatian ethnic territory, as well as the presence of national minorities in it, was also a result of the aforementioned position and outside influences (ulji 1993/1994).The demographic structure of Croatia indicates a series of specificities which were primarily conditioned by the historical development of Croatia and which is particularly expressed in constant emigration since the end of the nineteenth century, the relatively large direct and indirect losses to the population during and immediately after the First and Second World Wars, emigration as a type of population movement in all inter-census periods after 1945, the appearance of a natural decline and the aging of the population on almost one half of the state territory.  相似文献   

Evidence of ancient life at 207 m depth in a granitic aquifer     

Pedersen K  Ekendahl S  Tullborg EL  Furnes H  Thorseth I  Tumyr O 《Geology》1997,25(9):827-830

The results of electron-microscopy investigations of calcite precipitated in a water-conducting fracture in a ca. 1800 Ma granitic rock from 207 m below sea level at the island of Aspo on the southeastern (Baltic) coast of Sweden are compared with measurements of carbon, oxygen, and sulfur isotope composition of the calcite and embedded pyrite. Parts of the calcite had extremely low delta 13C values, indicative of biological activity, and contained bacteria-like microfossils occurring in colonies and as typical biofllms. X-ray microanalysis demonstrated these fossils to be enriched in carbon. Our results provide evidence for ancient life in deep granitic rock aquifers and suggest that the modern microbial life found there is intrinsic. Modeling historical and present geochemical processes in deep granitic aquifers should, therefore, preferably include biologically catalyzed reactions. The results also suggest that the search for life on other planets, e.g., Mars, should include subsurface material.  相似文献   

同位素地球化学、岩石地球化学——密坑山锡矿同位素年代学研究的启示     

邱检生  蒋少涌胡建 McInnes B I A 凌洪飞 《云南地质》2006,25(4):436-437

密坑山锡矿田位于江西省会昌县西南约40km处。该区为一晚中生代破火山，火山岩为上侏罗统鸡笼嶂组流纹质凝灰熔岩及火山碎屑岩，火山口周围环状及放射状断裂发育，火山口中心为浅成相的密坑山似斑状钾长花岗岩中央岩株侵入体所充填。上世纪80年代以来，在该岩体与流纹质凝灰熔岩的内外接触带相继发现了岩背、淘锡坝、苦竹岽、矿背、上湾等一批大、中型锡多金属矿床或矿点，表明这一岩体对成矿具有重要的制约作用。  相似文献   

探地雷达(GPR)在海南岛东北部海岸带调查中的应用 ^*   总被引：2，自引：0，他引：2  

殷勇  朱大奎  I.P.Martini 《第四纪研究》2006,26(3):462-469

对海南岛东北部海岸带调查采用了探地雷达(GPR)研究海岸带沙体的结构、展布和沉积序列,取得了很好的效果。文章通过和有限的露头资料对比以及对反射波形态、结构的研究,确定了海滩脊、海岸沙丘的反射特征以及潜水面的位置。雷达图像显示五龙港古海滩脊由亚水平、不连续、高振幅和透镜状反射波组成;木兰头海岸沙丘已受到人类活动的扰动,短的、陡倾斜反射可能代表未受扰动的海岸风成沙的前积层。研究表明探地雷达是一种可靠、快速和经济的地球物理方法,在砂砾质海岸可产生高质量、高分辨率和连续的反射剖面,值得加以推广。  相似文献   

The application of GPR to barrier-lagoon sedimentation study in Boao of Hainan Island     

YIN Yong  ZHU Dakui  TANG Wenwu  Martini I. Peter 《地理学报(英文版)》2002,12(3)

Sedimentary successions and internal structure of the coastal barrier-lagoon system of Boao, eastern Hainan Island were studied through utilizing data from test holes and trenches and ground-penetrating-radar (GPR) profiles. During late Pleistocene, fluvial and delta plains developed over an unevenly eroded bedrock during low sea level stand, followed by the formation of littoral and lagoon facies and defined coastal barrier-lagoon-estuary system during the post-glacial uppermost Pleistocene-lower Holocene eustatic rise of the sea level, and the upper Holocene high stand. GPR results show that Yudaitan, a sandy coastal bar backed by a low-laying land (shoal) just east of the active lagoon, is a continuous, parallel and slightly-wavy reflectors indicating homogeneous sandy or sandy gravel sediments, and inclined reflectors partly caused by progradation and accumulation of beach sand and gravel. Quasi-continuous, hummocky and chaotic reflectors from the shoal of Nangang village correspond to mixed accumula  相似文献   

泥盆纪最早期牙形刺带化石在蒙古南戈壁幕使盖(Mushgai)地区"尕屋(Gavuu)"段的首次发现     

王成源  Ziegler W  Minjin Ch  Sersmaa G  Munchtsetseg J  Gereltsetseg L  Nadya I 《世界地质》2003,22(1):15-20

在蒙古南戈壁的Bayan—Khoshuu Ruins剖面原归入到志留系Mandalovoo组尕屋(Gavuu)段的地层中发现了牙形刺Caudicriodus woschimidti woschmidti，这是泥盆纪最早期牙形刺带化石在蒙古的首次发现。尕屋(Gavuu)段的下部属志留系，但其上部，即采集牙形刺样品M-9～M-12的层位肯定属下泥盆统(下洛霍考夫阶)，而不是下志留统。Mandalovoo组应当改为Mandalovoo群，它的三个段应提升为三个组。  相似文献   

Amplitude—Phase Characteristics of the Annual Cycle of Surface Air Temperature in the Northern Hemisphere   总被引：2，自引：0，他引：2  

Alexey V.ELISEEV  Igor I. MOKHOV 《大气科学进展》2003,20(1):1-16

The amplitude-phase characteristics(APC)of surface air temperature(SAT)annual cycle(AC)in the Northern Hemisphere are analyzed.From meteorological observations for the 20th century and meteorological reanalyses for its second half,it is found that over land negative correlation of SAT ACamplitude with annual mean SAT dominates.Nevertheless,some exceptions exist.The positive correlationbetween these two variables is found over the two desert regions:in northern Africa and in Central America.Areas of positive correlations are also found for the northern Pacific and for the tropical Indian and PacificOceans.Southward of the characteristic annual mean snow-ice boundary (SIB) position,the shape ofthe SAT AC becomes more sinusoidal under climate warming.In contrast,northward of it,this shapebecomes less sinusoidal.The latter iS also found for the above-mentioned two desert regions.In theFar East(southward of about 50°N),the SAT AC shifts as a whole:here its spring and autumn phasesoccur earlier if the annual  相似文献   

Impact of Aircraft NOx Emission on NOx and Ozone over China   总被引：2，自引：1，他引：2  

刘煜 I.S.A.ISAKSEN J.K.SUNDET周秀骥  马建中 《大气科学进展》2003,20(4):565-574

A three-dimensional global chemistry transport model (OSLO CTM2) is used to investigate the impact of subsonic aircraft NOx emission on NOz and ozone over China in terms of a year 2000 scenario of subsonic aircraft NOx emission. The results show that subsonic aircraft NOx emission significantly affects northern China, which makes NOx at 250 hPa increase by about 50 pptv with the highest percentage of 60% in January, and leading to an ozone increase of 8 ppbv with 5% relative change in April. The NOx increase is mainly attributed to the transport process, but ozone increase is produced by the chemical process. The NOx increases by less than 10 pptv by virtue of subsonic aircraft NOx emission over China,and ozone changes less than 0.4 ppbv. When subsonic aircraft NOx emission over China is doubled, its influence is still relatively small.  相似文献