玻色-爱因斯坦凝聚和重力测量——2001年诺贝尔物理学奖评介

介绍了2001年诺贝尔物理学奖获得者康奈尔，韦曼，克特勒的科学研究成果，实验玻色－爱因斯坦凝聚（BEC）及其在理论上的意义和应用前景，讨论了BEC在研制高精度重力仪方面的应用问题，为此回顾了重力测量现状，朱棣文等研制的原子干涉重力仪和ClauserJ提出的物质波干涉重力仪，分析表明，如果利用BEC，则重力仪的测量精度在朱棣文等工作基础上将会有很大的提高。     

Observational study of the seasonality of the submonthly and intraseasonal signal over the tropics

Summary Atmospheric variability in outgoing long-wave radiation (OLR) and tropospheric relative vorticity (VOR) over the South American region was studied from 1979 to 1996 using the complex Morlet wavelet function. The analyses focus on spatial variation in intraseasonal and submonthly scales. Scalograms were used to measure submonthly intraseasonal oscillations in convection, which were found to be predominant in the tropical regions. However, 7-day and 15-day oscillations were observed at tropical and extratropical latitudes in spring and winter, indicating that transient disturbances play a more prominent role. Regarding VOR, tropical energy intensities were highest in the spring and summer, whereas subtropical and extratropical energy intensities were highest in the autumn and winter. The dynamics of the 25-day and 45-day VOR oscillations indicates a possible correlation with Rossby waves over the eastern tropical Pacific Ocean, mainly during the summer. During winter, the 7-day and 15-day VOR oscillations are more frequent at higher latitudes and are enhanced along storm tracks. It was also observed that convection amplitudes in the regions of maximum intensity change appreciably from year to year and from season to season, showing that the behavior of the submonthly and intraseasonal oscillations is nonperiodic and correlates strongly with El Ni?o/Southern Oscillation years. These results confirm the efficiency of wavelet analysis for time-scale studies of atmospheric variability.     

Late variscan tectonic evolution by thinning of earlier thickened crust. An Ar---Ar study of the Montagne Noire, southern Massif Central, France

⁴⁰Ar---³⁹Ar age determinations on samples selected on deformational criteria form the basis of a proposal of a new detailed tectonometamorphic history of the Montagne Noire (the southern part of the Massif Central, France).

This range is classically divided into a cover and an axial gneissic and migmatitic core which was metamorphosed under high T/medium P conditions. The basement is structurally overlain by epimetamorphic Paleozoic sediments in the north. In the south, equivalent rocks form a well-known pile of recumbent nappes. The Variscan history of this area comprises early shortening and thickening of the continental crust. The climax of this event took place around 320 Ma ago, as is shown by previous Rb---Sr data and by ⁴⁰Ar---³⁹Ar measurements. New developments in structural analyses have led to a better understanding of the late evolution of the area in terms of diapiric uplift of the core. South-southwestwards verging recumbent nappes have been emplaced and were weakly metamorphosed in their lower parts. This movement was accompanied and followed by dextral extensional wrenching of the Paleozoic cover along the northern and southern margins of the axial zone. Attendantly, ductile shear zones were formed.

In order to decipher the complex history, three structural levels have been dated with the ⁴⁰Ar---³⁹Ar method. These levels are: (1) The migmatitic and gneissic series in the axial core, where micas yield ages of c. 315 Ma; (2) Mylonites from the northern and southern shear zones where biotites and muscovites yield ages of c. 310 Ma; (3) Muscovites and biotites from the epimetamorphic nappe structures yielding ages of c. 297 Ma. The later ages may represent a younger thermal pulse. These data are compared and discussed in the light of previous radiometric studies of the area and precise biostratigraphic constraints. A detailed geodynamic evolution of the studied segment is proposed.     

时间延迟对劈裂试验条件下岩石凯塞效应的影响

验证了粗晶花岗岩在劈裂试验条件下凯塞效应的存在性。进行了循环加卸载时间间隔分别为2、15d和45d时岩石的声发射试验,讨论了时间延迟对花岗岩凯塞效应的影响。研究结果表明,前期荷载越接近极限强度,岩石的凯塞效应越不明显;凯塞效应随再次加载时间延迟的增加而削弱,在对花岗岩的声发射试验中观察到15d以后岩石的凯塞效应仍然很显著,45d后凯塞效应基本消失。文中同时对试件与加载设备之间的接触状态对声发射试验结果的影响作了初步的定性分析。     

A ‘mathematical’ spider living on gravel plains of the Namib Desert

In certain areas of the Namib gravel plains a new Ariadna sp. was discovered. It rims its vertical burrow with a stone circle, made on average of seven quartz stones. Some mathematical relationships between hole diameter, stone sizes and weight, and animal size were studied. A correlation was found, and stone selection by this spider postulated. Different hypotheses on the adaptive value of stone circle are suggested.     

Urban forest loss using a GIS-based approach and instruments for integrated urban planning:A case study of Jo(a)o Pessoa,Brazil

Urban forests play an important role in the thermal comfort and overall life of local populations in large-and medium-sized cities.This study analyzes urban forest loss and maps land use and land cover (LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in Jo～o Pessoa,Brazil.For this purpose,satellite-derived LULC images from 1991,2006,2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used.In addi-tion,this paper also discusses the instruments used for integrated urban planning,which are(a) the legal sector,responsibility and nature;(b) the urban expansion process;and (c) the elements of urban infrastructure.The results show a clear shift in land use in the study area.The major changes in LULC classes occurred in urban areas and herbaceous vegetation,while the greatest loss was in arboreal/shrub vegetation.Thus,an increase in the pressure to occupy zones intended for environmental preservation could be estimated.Our results showed similar accuracies with other studies and more spatial details.The characteristics of the patterns,traces,and hotspots of urban expansion and forest cover loss were explored.We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of ur-ban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches.     

Analyzing the spatial interactions between rainfall levels and flooding prediction in São Paulo

Rainfall is one of the primary triggers for many geological and hydrological natural disasters. While the geological events are related to mass movements in land collapse due to waterlogging, the hydrological ones are usually assigned to runoff or flooding. Studies in the literature propose predicting mass movement events as a function of accumulated rainfall levels recorded at distinct periods. According to these approaches, a two-dimensional rainfall levels feature space is segmented into the occurrence and non-occurrence decision regions by an empirical critical curve (CC). Although this scheme may easily be extended to other purposes and applications, studies in the literature need to discuss its use for flooding prediction. In light of this motivation, the present study is unfolded in (1) verifying that defining CCs in the rainfall levels feature space is a practical approach for flooding prediction and (2) analyzing how geospatial components interact with rainfall levels and flooding prediction. A database containing the rainfall levels recorded for flooding and non-flooding events in São Paulo city, Brazil, regarding the period 2015–2016, was considered in this study. The results indicate good accuracy for flooding prediction using only partial rain, which can be improved by adding physical characteristics of the flooding locations, demonstrating a direct correlation with spatial interactions, and rainfall levels.