Recent immigration to Italy: Character,causes and consequences

During the 1970s Italy changed from being a country of mass emigration to one of mass immigration, taking over from Germany the role of Europe's main recipient of immigrants from less developed countries. By 1991 the officially registered foreign population in Italy stood at 860,000; however, clandestine migrants push the real figure above 1 million. Italy was generally unprepared for this immigration and policy has been slow to evolve. Analysis of residence permit data show that the immigrants come increasingly from Third World, especially African, countries, and that there is a relative concentration in the north of Italy. One third of the immigrants are Moslem. Employment data are scarce but indicate that around two–thirds are involved in low-grade service sector activities (street-trading, domestic service, hotel work etc.). There is a high degree of occupational specialisation amongst certain national groups (Senegalese street-hawkers, Tunisian fishermen, Filipino domestics etc.). The immaturity of the immigration is also revealed by marked gender and age assymetry. Five main causes are suggested as being behind the immigration: ease of entry; Italy's increasing prosperity; segmentation of the Italian labour market, opening up specific niches for immigrant employment; dominance of push factors from the countries of origin; and the demographic collapse in Italy. Within Italy, the reaction to immigration has not been very favourable. Opinion polls indicate that Italians have mainly negative and stereotyped views of immigrants and there is disturbing evidence of growing racism. Further inflows of immigrants are likely, whatever policies Italy attempts to put in place.     

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.     

Recent trends in human migrations: the case of the Venezuelan Andes

Changes in world capitalism caused prices of traditional raw materials to fall and new energy demands to arise at the end of the 19th and beginning of the 20th century. The Andean countries witnessed the fall in the value of their exports and began to receive large flows of foreign investment in mining and industry. Consequently, urban economies were strengthened and demographic patterns were changed. This led to the internal migrations and to a process of social change. These consequences are summarized from relevant studies focusing on Ecuador, Colombia, and Venezuela. Since the 1960s a compendium of information has become available which highlights the causes of the migration, migration patterns, the composition of migratory movements, and the mechanisms that the migrant uses to establish himself/herself in the city. Preston (1969) distinguished 2 migratory patterns in Ecuador: rural to urban, with migratory flows from the rural areas to urban centers and new industrial cities that experienced development and high demand for unskilled labor at comparatively high wages: and rural to rural, based on the movement of population from depressed rural areas to other areas in which programs for colonization or commercial agriculture have been promoted. In a study of Colombia, McGreevey (1968) identifies the lack of cultivatable land, rural violence in certain departments, and other economic and family causes as the principal factors that induced migrations to the cities. The study emphasizes that the predominant model of movement relates to "fill in" migration. The spatial mobility of the Venezuelan Andean population was initially outlined in a voluminous report on economic and social problems of the region (1954). The study indicates that during the intercensal period 1941-50 cities grew much more rapidly than rural "municipos" and that the drive to find employment and earn a living were the most important motives in the movement of peasants to the cities. All of the studies identified that use demographic, economic, or phychosocial approaches have provided partial explanations of the current status of Andean migrations. The explanations they offer, by not transcending the current reality of the migrants, overlook the historical traits of internal migration. Migratory flows do not spring up suddenly. They result from specific socio-political circumstances which, when closely linked to demographic evidence, serve as a basis for understanding the process. Review of studies on internal migration in the Northern Andes, as presented here, reveals a series of distinguishing characteristics: there are 5 migratory patterns--rural to rural, rural to urban, urban to urban, seasonal worker migration, and return migration, and the predominant pattern has been rural to urban; the demographic data show the importance of rural migrants to urban growth in the region and a complementary loss of population in the rural areas; depopulation of the countryside has been selective; and there is a marked disparity in employment remuneration between rural and urban areas.     

垂线偏差-大地水准面与逆范宁-梅尼兹公式的应用——联合多种卫星测高数据求解全球海平面与海洋重力异常

卫星测高开辟了地球科学研究的新纪元。平均海面高(MSSH)和海洋重力异常是卫星测高在大地测量和地球物理应用领域的重要成果。平均海面高对于建立全球潮汐模型、海平面变化研究以及海洋测深等方面有重要意义。关于海洋重力异常的应用,Sandweel与Smith(1997)已进行了说明。根据卫星测高数据计算垂线偏差(DOV)是恢复重力异常的一个新途径。对利用改进的卫星测高数据进一步提高全球平均海面高和重力异     

对欧洲中心500hPa高度场预报能力的检验分析

本文对欧洲中心预报青海省重要天气系统的移速、位置、强度等方面进行了天气学、统计学方法的检验。经检验得出高度场形势预报相似率较高，达99．5％，中高纬度的预报准确率比中低纬度高，西部系统的预报比实况超前，中小尺度的预报效果差。     

1990年代期间b值和地壳形变的相关变化能够确定1999年8月17日伊兹米特M_W=7.4级地震的破裂起始

在30.1°E和30.8°E之间的北安纳托利亚断层系,从平直段到释放弯曲段,其b值从1.1上升到1.7。GPS资料对这个弯曲段的扩张特性给予了证实,观测到的扩张速率为0.3μ应变/a。在该区域断层面解从大量右旋走滑变为弯曲段中部的带法向分量的斜向滑动,这与拉张盆地构造相吻合。我们认为,由于切向和法向断层运动的叠加,地壳体高度破碎,相当于一个短的平均裂纹长度。由于现存裂纹上的低正应力,摩擦滑动被认为是地震活动产生的主要机制,引起b值升高。研究区中的最低b值(b～0.8)是在断层弯曲段和毗连段之间的交汇处发现的,这个地段恰好穿过1999年伊兹米特地震的震中。沿几何障碍体的地震活动数值模拟预示着,在这个交汇处有局部应力集中。因此,b值最低的场地被认为是大地震最容易发生的地方,这个结论被伊兹米特地震所证实,震中离预测位置约13km。在1992年年初,沿断层弯曲段的中部和西北部空间平均b值开始上升,并且对应一个强烈的水平拉张期。由于1992年没有记录到任何大地震,因此假定这种异常拉张和应力的相关变化是由无震断层滑动引起的。根据可使用的地震构造信息,计算出了因深处缓慢位错而造成的地表位移。GPS资料通过深度为10km、等效震级M_W=5.9的正断层震源而得到很好的解释。不同孕震深度的应力变化也计算了出来,基于的假设是偏应力和平均应力下降而库伦应力变化为正的地段最容易观测到b值上升,也就是说,断层已接近破裂。对于右旋走滑断层,满足这种应力条件的地点是b值上升最大的地方。伊兹米特地震的地表破裂仅同研究区西部和东部的已知断层迹线有关。沿断层弯曲部分,地表破裂从地图上标示出的断层迹线脱离出来,贯穿推测的1992年慢地震引起的正库伦应力变化区域。最大地表滑动(5m)是在最大库伦应力变化(～3bar)场地附近观测到的,这表明1992年的慢地震可能已部分地松开了其后发生的伊兹米特地震的破裂面。我们认为,沿复杂断层弯曲部分观测到b值的明显变化可用来描述构造形变在时空上的不同状态。     

FORMATION OF THE SINO-U.S. CENTERS FOR SOIL AND WATER CONSERVATION AND ENVIRONMENTAL PROTECTION

1 NEED The ability to achieve and sustain a healthy and functional environment fortifies a country抯 economy and social structure and its ability to share experience and wealth for worldwide benefit. Inadequate attention to environmental conditions and poor or deficient application of land- and water-management technologies, coupled with increasing demands to occupy, use, and reshape the land, produce food, and manage water resources are barriers to using and sustaining natural resources. …     

RATIONAL BASIS FOR SUSPENDED SEDIMENT MODELING

This paper presents a rational basis to model the transport of suspended sediment. The loose-boundary condition for 3D models and the adjustment coefficients for both the depth-integrated 2D and laterally integrated 1D models are treated comprehensively. A combination of Dirichlet and Neumann conditions is proposed as the loose-boundary condition. The adjustment coefficient for 2D models is obtained on the basis of the proposed boundary condition and analytical solutions developed for some simple cases of non-equilibrium transport of sediment in uniform flows. The adjustment coefficient for 1D models for natural rivers is further obtained from lateral integration. Comparisons with analytical solutions and a considerable amount of laboratory and prototype data show that mathematical models developed along the proposed line of attack would well simulate the transport of suspended sediment in practical problems.     

Analysis Method for Predicting Strain in Interior Beds and Sub-Resolution Faults from Area Balance Theory in Extensional Basins

Extensional basins include mainly grabens and half grabens displaced along a lower detachment. Based on area balance theory, there is a linear relationship between a height of regional and the lower detachment h on the outside of the basin and “lost area S“ from the regional in the basin. The pre-growth beds above lower detachment are of the same extensional displacement so that an “S-h diagram“ can be used to determine the depth to lower detachment and to calculate the total extensional displacement of the beds above the lower detachment. The extensional displacement is dominated by the heave of various scale normal faults. The displacement of obvious faults can be immediately figured out from the measured bed-length. The requisite extension calculated by area balance is the layer-parallel strain, which could be accommodated by displacement on sub-resolution faults. Accordingly, the layer-parallel strain can help us predict the magnitude and distribution of sub-resolution faults on the basis of analysis of the structural style and rheological behavior.