European glacial relict snails and plants: environmental context of their modern refugial occurrence in southern Siberia

Knowledge of present‐day communities and ecosystems resembling those reconstructed from the fossil record can help improve our understanding of historical distribution patterns and species composition of past communities. Here, we use a unique data set of 570 plots explored for vascular plant and 315 for land‐snail assemblages located along a 650‐km‐long transect running across a steep climatic gradient in the Russian Altai Mountains and their foothills in southern Siberia. We analysed climatic and habitat requirements of modern populations for eight land‐snail and 16 vascular plant species that are considered characteristic of the full‐glacial environment of central Europe based on (i) fossil evidence from loess deposits (snails) or (ii) refugial patterns of their modern distributions (plants). The analysis yielded consistent predictions of the full‐glacial central European climate derived from both snail and plant populations. We found that the distribution of these 24 species was limited to the areas with mean annual temperature varying from ?6.7 to 3.4 °C (median ?2.5 °C) and with total annual precipitation varying from 137 to 593 mm (median 283 mm). In both groups there were species limited to areas with colder and drier macroclimates (e.g. snails Columella columella and Pupilla loessica, and plants Kobresia myosuroides and Krascheninnikovia ceratoides), whereas other species preferred areas with relatively warmer and/or moister macroclimates (e.g. snails Pupilla turcmenica and P. alpicola, and plants Artemisia laciniata and Carex capillaris). Analysis of climatic conditions also indicated that distributional shifts of the studied species during the Pleistocene/Holocene transition were closely related to their climatic tolerances. Our results suggest that the habitat requirements of southern Siberian populations can provide realistic insights into the reconstruction of Eurasian, especially central European, glacial environments. Data obtained from modern populations also highlight the importance of wet habitats as refugia in the generally dry full‐glacial landscape.     

Heat risk assessment based on mobile phone data: case study of Bratislava,Slovakia

The aim of this interdisciplinary study is to assess the heat risk for Bratislava. The following layers were created to compute the risk index: the hazard layer of air temperature, a mitigation layer of tree vegetation, an exposure layer of population and a vulnerability layer of individuals over 65 years of age. The MUKLIMO_3 model was used to evaluate the field of mean surface air temperature at 9 PM during selected days of the summer heat wave in August 2018. The tree vegetation layer, in the form of percentage per grid cell, was derived from Sentinel-2 satellite data. Population density data are based on mobile positioning data, and elderly population data are based on a gridded database from the statistical census. Input layers were unified into a resolution of 500 × 500 m, and the heat risk index was calculated by summation of the weighted input layers. The results reflect the variability of the population and the elderly population within the city, as well as the variability of the temperature field, which is caused by the joint effect of an urban heat island and topography. The highest values of risk index occur within the broader city centre, with specific hot spots at several places.

     

南极冰层钻进铠装钻具升降运动特性分析与试验

极地冰层取心钻具的升降运动特性对提高钻进效率、减少孔内事故具有重要影响。在总结极地冰钻特点的基础上,分析了钻孔直径、钻具质量和钻井液的流变特性对钻具在升降过程中的影响,钻具在钻孔过程中运动的两阶段特性、滞流层的存在与影响因素,确定了因钻具的运动所引起的流体扰动量与扰动范围。研制了用于测试铠装电缆悬挂式钻具升降测试试验台和测试的方法,通过对3个不同直径与3个不同质量的钻具在其下落过程的实际测试,得出了钻具下落速度与直径呈二次方关系,与钻具的质量成线性关系的结论。     

The upper Viséan–Serpukhovian in the type area for the Serpukhovian Stage (Moscow Basin,Russia): Part 2. bulk geochemistry and magnetic susceptibility

This study is the summary analysis of bulk XRF geochemistry (233 samples from three sections) of the Oka and Zaborie groups of the type Serpukhovian succession in the Moscow Basin. The siliciclastic wedges in the limestone‐dominated Oka Group are two to three times enriched in Fe, Ti, and Zr compared to Clarke values. Bulk iron strongly correlates with magnetic susceptibility. Iron tends to form ferruginized horizons (original siderites) in finer grained siliciclastic beds associated with coal seams. These beds also tend to be enriched in Cu, Ni, Pb, Zn, and other trace metals (metal enrichment horizons or MEHs). MEHs formed in ponded conditions of coastal low‐pH marshlands vegetated by mangrove‐like lycopsid bushes. Well‐drained environments of palaeokarst formation and alkaline everglades (Akulshino palustrine event) on the other hand did not accumulate Fe and trace metals. The thin shale seam (found close to the Viséan–Serpukhovian boundary in Polotnyanyi Zavod) has unusually high Rb and Sr values, which may contain volcanigenic material useful for absolute dating. The Gurovo Formation (Steshevian Substage of the Serpukhovian) is less enriched in Fe and Ti. In the Gurovo Formation, the transition from the lower montmorillonitic shale (Glazechnya Member) to the upper palygorskitic shale (Dashkovka Member) is expressed by a five‐fold increase in background MgO values, which indicates progressive shoaling and climatic aridization. Phosphorus remains close to 0% in the Oka Group and tends to increase in the Zaborie Group, in agreement with a dramatic increase of conodont numbers and other signatures of a lower Serpukhovian marine transgression. The lower half of the Glazechnya Member exhibits fluctuating enrichment in Fe, Cu, Ni, Pb, Zn, V, Cr, and Co. These fluctuations are mostly inverse to fluctuations of Mn. This pattern has been interpreted as a signature of seafloor oxygen deficiency, where Mn‐rich samples record oxygen‐poor environments (redox barrier level with the sediment surface) and Mn‐poor samples enriched in Fe and trace metals record transitions to anoxic setting. This interval is interpreted as the Lower Serpukhovian highstand. Enrichment in Fe, Ti, and Zr of Oka siliciclastic units of Polotnyanyi Zavod indicates provenance from the ore‐rich Voronezh Land, south of the Moscow Basin. The westerly flux regarded as a possible provenance in previous palaeogeographic reconstructions is discarded for the studied sections. The Gurovo Shale is also linked to the Voronezh province, although Fe, Ti, and Zr concentrations are lower than in the Oka shales. Copyright © 2014 John Wiley & Sons, Ltd.     

Gas removal and the initial mass function of star clusters

We explore how the expulsion of gas from star-forming cores due to supernova explosions affects the shape of the initial cluster mass function, that is, the mass function of star clusters when cluster infant weight-loss triggered by gas expulsion is over. We demonstrate that if the radii of cluster-forming gas ‘cores’ are roughly constant over the core mass range, as supported by observations, then more massive cores undergo slower gas expulsion. Therefore, for a given star-formation efficiency, more massive cores retain a larger fraction of stars after gas expulsion. The initial cluster mass function may thus substantially differ from the core mass function, with the final shape depending on the star-formation efficiency. A mass-independent star-formation efficiency of about 20% turns a power-law core mass function into a bell-shaped initial cluster mass function, while mass-independent efficiencies of order 40% preserve the shape of the core mass function.