Zur chemischen Variabilität regionalmetamorph gebildeter Plagioklase,Epidote und Granate

Plagioclases, Fe-rich epidotes and garnets coexisting in metamorphic rocks of basaltoid and granitoid substrata have been analyzed by standard microprobe techniques. The results presented are based on 34000 data on plagioclases, nearly 24400 on coexisting epidotes as well as of 5000 garnet data. The chemical variations within the singular plagioclase grain and in the range of a thin section are very comprehensive. Adjoining microfields (10–20 μm distance) exhibit differences in the An-contents between 30 and 80% rel. These observations are valid for nearly 78% of the examined plagioclases. Only in the higher amphibolite facies the An-variations are reduced to an average value of 32% rel. Merely the high temperature plagioclases with a compositional range of An 68-An 79 coexisting with clinopyroxene are largely homogeneous. Their variation is amounting to 6,5% An rel. The epidote chemisms reveal a dependance on both of the different substrata and their oxidation status. The maximum value of the Fe (III) substitution on the M₁ position in the epidote structure is reaching 97 molar per cent at the higher oxidized meta-granitoids and merely 87% at the metabasaltoids. The variations of the Fe/Al-proportions in the microfields are amounting to 5–20% as to the granitoid substrata and to 5–47% rel. as to the basaltoid substrata. In both of the substrata the garnets are very rich of almandine (40–70%). Besides variable amounts of grossularite and pyrope components they also contain 10–20% (basaltoids) and 1–20% (granitoids) spessartine. The most significant element variations are observed for the element Mn in garnets of granitoid origin. These variations attain 46% within the garnet grains. Only for the garnets of the basic substrata from the amphibolite facies one can state a homogenization. The reaction inertia in achieving metamorphic equilibrium is demonstrated by a selected metabasite sample of the amphibolite facies. It seems that only at temperature >600°C a homogenization of the plagioclases and garnets is initiated so that at low temperature a thermometry by means of An-contents in the plagioclases or Mn/Fe-relations in the garnets is not possible.     

Considerations on the European Standard EN 14157 Test Methods: Abrasion Resistance of Natural Stones Used for Flooring in Buildings

In Europe, the Wide Wheel abrasion (WWA) test and the B?hme abrasion (BA) test are among the most widely used standard test methods for determining abrasion resistance of natural stones, the former being the reference test method in EN 14157 Standard. However, it is stated in the Annex-A (Informative) of EN 14157 Standard that very limited data are available to provide correlations between these two test methods. To be able to fill this gap, in this study, 25 different natural stones belonging to sedimentary, metamorphic and igneous groups were tested for their abrasion resistance as well as physico-mechanical properties. Also, for a better interpretation of abrasion resistance characteristics of the tested stone materials, relationships between abrasion resistance and physico-mechanical properties were statistically examined. A statistically significant linear correlation (R ² = 0.85; P value = 0.000) was established between the WWA test and the BA test, which could be used in practice for converting the measured abrasion resistance values from one testing method to another. It was also found that the correlation between these two test methods improved significantly (R ² = 0.93; P value = 0.001) when relatively high-porosity stone materials (porosity ≥1%) were separately evaluated. Both methods of abrasion resistance employed in the present study showed statistically significant linear correlations with uniaxial compressive strength and Brazilian tensile strength, the former proving to be a more influencing parameter on resistance to abrasion. Also, from the point view of representing actual abrasion mechanism of stone materials in practice, the necessity of simulating multi-directional foot traffic in abrasion testing methods was discussed. In this respect, the reference test method in the EN 14157 Standard was criticized for not fully meeting this requirement. It was also pointed out that the reference method could have some drawbacks when applied to coarse-grained granitic rocks having cleavable minerals such as plagioclase and orthoclase feldspars.     

珠江流域1961-2007年气候变化及2011-2060年预估分析

 根据珠江流域1961-2007年气温、降水量观测资料和ECHAM5/MPI-OM模式2011-2060年预估结果,分析了流域过去47 a的气温和降水量变化,并预估未来50 a变化趋势。结果表明,在全球变暖的背景下,过去47 a温度呈上升趋势,约升高1.8℃。冬季增温最明显,夏季最弱。未来50 a流域温度仍呈上升趋势,A1B情景下升幅约1.9℃,并且年际变化增强。A2和B1两种排放情景下秋季升温最显著,冬季最弱,A1B排放情景与此相反。过去47 a秋季降水量呈减少趋势;春、夏、冬季和年降水量均呈增加趋势。未来50 a降水总体呈增加趋势,A1B排放情景降水增加最多,约为230 mm。A2、A1B和B1情景下降水季节分配未发生显著变化。年降水和冬季降水的年际变率增强,秋季减弱。     

Atmospheric effects from post-nuclear fires

During a large nuclear war, the atmosphere would be loaded with huge quantities of pollutants, which are produced by fires in urban and industrial centers, cultivated lands, forests and grasslands. Especially detrimental are the effects of light absorbing airborne particles. An analysis of the amounts of the various types of fuels which could burn in a nuclear war indicates that more than 10¹⁴ g of black smoke could be produced by fires started by the nuclear explosions. Due to this, the penetration of sunlight to the earth's surface would be reduced greatly over extended areas of the northern hemisphere, maybe even globally. This could temporarily cause extreme darkness in large areas in midlatitudes and reduce crop growth and biospheric productivity.This situation would last for several weeks and cause very anomalous meteorological conditions. Much solar radiation would be absorbed in the atmosphere instead of at the earth's surface. The land areas and lower atmosphere would, therefore, cool and the overlying atmosphere warm, creating strong vertical thermal stability in a highly polluted atmosphere. For extended periods and in large parts of the world, weather conditions would be abnormal. The resulting cold, probably freezing, temperatures at the ground would interfere severely with crop production during the growing season and cause extreme conditions for large sections of the biosphere. The combination of lack of sunlight, frost and other adverse meteorological conditions would add enormously to the already huge problems of the survivors.     

基于CERES观测数据的全球行星反照率时空变化特征分析

为了理解行星反照率时空变化规律及成因,基于CERES数据对全球行星反照率的大气(主要为云与气溶胶等)和地表贡献进行了分解,通过Theil-Sen+Mann-Kendall方法得到了2001～2018年全球行星反照率及其大气和地表贡献的时空变化趋势,并基于回归分析方法对典型区域的变化趋势进行了初步解释.研究结果表明:1)...     

Evolutionary approach to the missing mass problem of clusters of galaxies

In a gravitationally bound and stable cluster of galaxies the amount and distribution of matter determine both the velocity dispersion of the members and the type of evolution of the system. The use of the first of these physical connections — the application of virial theorem — led to the idea of missing mass in clusters, that of the second one seems to support this idea by an independent “rediscovery” and “redistribution” of missing mass. On the basis of this “evolutionary approach” to the missing mass problem — that is free from the uncertainties of measuring and interpreting red shifts — evidences are obtained for the existence of large amounts of discretely distributed dark circumgalactic or intragalactic matter in rich clusters of galaxies.     

Exploring the spatial distribution patterns of South African Cape hakes using generalised additive models

We developed delta generalised additive models (GAMs) to predict the spatial distribution of different size classes of South African hakes, Merluccius capensis and M. paradoxus, using demersal trawl survey data and geographical (latitude and longitude) and environmental features (depth, temperature, bottom dissolved oxygen and sediment type). Our approach consists of fitting, for each hake size class, two independent models, a binomial GAM and a quasi-Poisson GAM, whose predictions are then combined using the delta method. Delta GAMs were validated using an iterative cross-validation procedure, and their predictions were then employed to produce distribution maps for the southern Benguela. Delta GAM predictions confirmed existing knowledge about the spatial distribution patterns of South African hakes, and brought new insights into the factors influencing the presence/absence and abundance of these species. Our GAM approach can be used to produce distribution maps for spatially explicit ecosystem models of the southern Benguela in a rigorous and objective way. Ecosystem models are critical features of the ecosystem approach to fisheries, and distribution maps constructed using our GAM approach will enable a reliable allocation of species biomasses in spatially explicit ecosystem models, which will increase trust in the spatial overlaps and, therefore, the trophic interactions predicted by these models.     

On the distinction of tectonic and nontectonic faulting in palaeoseismological research: a case study from the southern Marmara region of Turkey

International Journal of Earth Sciences - This study reports on spectacular deformation structures, including arrays of striated thrusts, discovered by excavation work in Holocene deposits in...