Early studies on the biological effects of high-intensity magnetic fields

In 1892, Frederick Peterson described the experiences of humans exposed to magnetic fields of strength comparable to those currently used in magnetic resonance imaging. These investigations were conducted in the Edison Laboratory. None of the subjects exposed to constant and to time-variable magnetic fields suffered any ill effects. Peterson concluded that the human organism was in no way appreciably affected by the most powerful magnets known to nineteenth-century science. Peterson can be credited with the first truly scientific assessment of the biological effects of high-intensity magnetic fields. His experiments on humans, done one century ago with great cogency and skill, provide a source of inspiration to modern studies on magnetic resonance imaging.     

试论华侨华人学科的形成与定位

华侨华人研究具有确定的研究对象、专门的术语 ,开始形成有特色的研究方法和学术规范。理论体系虽处于不够成熟的阶段 ,但在学科建设的过程中 ,将日趋完善。华侨华人学是一门正在兴起的交叉学科 ,具有跨学科性和多学科性。它既承袭和借用了大量老学科的理论、概念、方法和学术规范 ,同时逐步创造出不依附其他学科的相对独立的学科体系     

The widespread occurrence of Celtic field systems in the central part of the Netherlands

The detailed elevation model based on airborne laser altimetry (AHN) proved to be a reliable tool to detect well-developed Celtic field systems, characteristic arable plots of the Iron Age. They were detected in the central part of the Netherlands, where only a limited number of Celtic field systems have been recognized in the past. Most of these previously detected systems were identified in the northern part of the Netherlands or in the southern part, but not in this zone. About 1200 ha of well-developed systems could be identified by AHN in the central part of the Netherlands, of which only 136 ha were registered as an archaeological monument. Another 335 ha of archaeologically identified Celtic field systems were not accepted or recognized by AHN, because they were morphologically less well-developed. Most of the around 1050 ha new discoveries occur in rough vegetations and forested areas, and can hardly be identified with previously used geodetic methods and aerial photography. Less well-developed or preserved systems were even more extensive and remnants were traced as fossil arable layers below plaggen soils or on lower slopes incorporated in mediaeval reclamations. The newly identified Celtic field systems, therefore, can be considered as remnants of much larger areas once covered with these arable plots. In the central part of the Netherlands, the estimated area once covered was at least around 4500 ha, more than enough to supply 10,000 people with cereals. Well-developed Celtic field systems started to develop in the late Iron Age with formation intensifying during the early Roman Period. The central part of the Netherlands is situated just north of the river Rhine, the former boundary of the Roman Empire, the Limes. The newly discovered extent of Celtic field systems will have influenced the interaction between different cultures on the border of the Roman Empire in the early Roman Period, about which very little is known. This perspective underscores the need for an integrated conservation policy and in-depth research through excavations in the near future.     

Restructuring Beijing's Social Space: Observations on the Olympic Games in 2008

Two American geographers comment on the preceding analysis of restructuring of Beijing's social space (Feng et al., 2007) by presenting observations on the city's Olympic Games, forthcoming in the summer of 2008. The authors focus on some of the more salient geographical impacts stemming from construction, relocation, and related measures undertaken by the authorities to accommodate the event. Included in the paper are sections on environmental concerns (particularly air pollution), infrastructure (water supply, automobile traffic, and mass transit), and relocation and displacement of residents (particularly of migrants and other disadvantaged segments of the population). Journal of Economic Literature, Classification Numbers: I31, O15, O18, P20. 2 figures, 2 tables, 44 references.     

Small-scale fluctuations of magnetic and electric components of the ELF and VLF wave fields in the sub-auroral topside ionosphere : stochastic characteristics of the wave field

When the Interkosmos-14 and Interkosmos-19 satellites crossed the region of spatially varying electron concentration in the topside ionosphere adjacent to the high-latitude boundary of the main ionospheric trough, it was discovered that there were simultaneous fluctuations of plasma density, temperature and the amplitudes (H_x and E_y) of the ELF and VLF radio/plasma emissions. The probability characteristics of the naturally perpendicular H_x and E_y fluctuations are analysed. The correlation coefficient R(_H, E_y) turned out to be less than 0.6 at frequencies of F ⩽ 4.65 kHz, while at higher frequencies R increases, up to 0.9 at 15 kHz. The following interpretations are proposed:

1. 1.1. While measuring noise emissions, as a rule a mixture of numerous elementary waves is recorded.
2. 2.2. At frequencies exceeding the local lower hybrid resonance frequency (in our case f_LHR ≈ 5 kHz), a mixture of electromagnetic waves experiencing the influence of the inhomogeneous electron concentration N_e is registered.
3. 3.3. At frequencies which are lower than the local value f_LHR the mixture mainly consists of ELF waves. The wave field has a complicated structure, and the dynamical coherence between electric and magnetic field components is not as simple as at VLF frequencies (f ≈ 15 kHz).
4. 4.4. It is shown that the wave components for a mixture of electromagnetic and electrostatic waves (for instance a mixture of VLF and lower hybrid frequency waves) have a lower correlation coefficient because the electrostatic waves are unrelated to the electromagnetic waves.
5. 5.5. The correlation analysis offers an opportunity to detect the presence of waves of various types in the wave mixture.

     

溯古述今志苑精品--读《洪泽湖志》

我读到《洪泽湖志》,喜不自禁,这是我早就期盼能够读到的志书! 我对名山大川志有一种偏爱,想读的自然首先是家乡的山水志.离我家最近的名山是云台山,最近的名水是洪泽湖.但在旧志书中,只有《云台山志》《云台新志》,洪泽湖没有志,这使我感到十分遗憾.在再度兴起的新中国首轮修志接近尾声、第二轮修志工作陆续展开之际,淮安市地方志办公室终于填补了志林中这一空白,推出了第一部《洪泽湖志》.拜读了荀德麟主编的洋洋137万多字的《洪泽湖志》之后,我为志苑中又增添一部精品力作兴奋不已,对《洪泽湖志》取得的成功表示由衷的祝贺! 下面我谈点读后感想.     

Observations on the Development of Small Private Enterprises in Russia

A prominent Western specialist on the Russian economy presents an up-to-date overview of the country's small private business enterprises, here defined as registered enterprises employing up to 200 workers. Navigating through the inadequacies of the statistical evidence, the author presents and analyzes new data on size, employment, branch structure, geographical distribution, and related economic indices covering developments through the end of 1996. The paper highlights a number of factors that repress and impede development of small private enterprises, identifying among the principal obstacles arbitrary government regulation and punitive inspections involving extortion. Remedial measures in taxation and crime prevention as well as other forms of assistance are proposed and discussed. Journal of Economic Literature, Classification Numbers: Ml3, P31, P42. 2 tables, 31 references.     

Development of the Internet in Russia: Preliminary Observations on Its Spatial and Institutional Characteristics

A geographer specializing in the emerging information-technology sector of the Russian economy presents an exploratory overview of the "widening" and "deepening" of Internet use in Russia during the 1990s and early years of the 21st century. Separate sections of the paper examine the main stages of Internet development in the country to date, explore regional differences in Internet access and use, and outline progress in the installation of surface telecommunications (including fiber optic) trunklines and intra-city networks. Journal of Economic Literature, Classification Numbers: L86, L96, O32. 3 tables, 17 references.