Influence of grinding on graphite crystallinity from experimental and natural data: implications for graphite thermometry and sample preparation

This paper examines the effects of shear stress on the structuralparameters that define the ‘crystallinity’ of graphite. The results show that highly crystalline graphite samples ground for up to 120 min do not undergo detectable changes in the three-dimensional arrangement of carbon layers but crystallite sizes (Lc and La) decrease consistently with increasing grinding time. Grinding also involves particle-size diminution that results in lower temperatures for the beginning of combustion and exothermic maxima in the differentialthermalanal ysis curves. These changes in the structuraland thermalcharacteristics of graphite upon grinding must be taken into account when such data are used for geothermometric estimations. Tectonic shear stress also induces reduction of the particle size and the Lc and La values of highly crystalline graphite. Thus, the temperature of formation of graphite according to structural as well as thermaldata is underestimated by up to 100ºC in samples that underwent the most intense shear stress. Therefore, application of graphite geothermometry to fluid-deposited veins where graphite is the only mineralfound should take into consideration the effect of tectonic shearing, or the estimated temperatures must be considered as minimum temperatures of formation only

Influence of Selected Mountain Barrier for the Distribution of Precipitation in the Polish Carpathians

Krawędzie gór i wyżyn stanowią istotne bariery dla przepływu mas powietrza wędrujących znad oceanów. Przy znacznej wysokości i szerokości pasm górskich mogą one stanowić zaporę trudną do przebycia albo być strefą podwyższonych opadów, zwłaszcza dla wędrujących cyklonów. Nawet niewysokie progi stanowią barierę, która objawia się w postaci prądów konwekcyjnych. Autorzy omawiają przykłady z różnych części polskich Karpat. Zwarte krawędzie Beskidu Śląskiego, Małego i Żywieckiego do 1 km wysokości wystawione są na opady ośrodków niżowych z kierunków W-NW. Ku wschodowi krawędź rozbita jest na mniejsze grupy górskie Beskidu Wyspowego, co ułatwia wnikanie opadów w głąb gór wysokich. Niekiedy chmura burzowa wędruje wzdłuż wysokiego progu (np. krawędzi Zachodnich Bieszczadów), ale i próg Pogórza wysoki tylko do 200 m sprzyja lokalnym opadom konwekcyjnym.The edges of mountains and uplands constitute significant barriers to the flow of air masses travelling from the oceans. The barriers are particularly difficult to be overcome when the height and width of mountain ranges are large, such settings can be create zones of increased rainfall, especially for roaming cyclones. Even low mountain edges form barriers which induce convectional currents. The authors discuss examples from various parts of the Polish Carpathians. The compact edges of the Silesian, Mały and Żywiecki Beskids up to 1 km high are exposed to precipitation of low-pressure systems from the W-NW directions. To the east, the edge is split into smaller mountain groups of the Beskid Wyspowy, which facilitates the penetration of high rainfall into the mountain interior. Sometimes storm clouds travel along a high edge of the mountains, e.g. along the edge of the Western Bieszczady. The edge of the foothills, only up to 200 m high, favours local convection rainfall

The role of orographic barriers in the origin of extreme rainfalls as exemplified by the front of high Eastern Himalaya and the low northern slope of Carpathians

The paper discusses the role of orographic barriers in generating torrential precipitation in mountainous regions in different climatic zones, the Eastern Himalayas (tropical zone with well-developed monsoon activity) and the northern slope of the Carpathians (temperate zone with transitional climate). Attention has been paid to the different altitudes and courses of the orographic ridges as well as their location relative to the prevailing directions of influx of moist air masses. The cases analysed included torrential rains with monsoon circulation from the S–SW direction at the 2–3 km high edge of the Himalayas, with special consideration to the distance from the margin of the mountains and the exposure of the slopes. They generate frequent flood waves, landslides, debris flows and upbuilding of the alluvial cones in the foreland of the mountain barriers. The impact of the orographic barrier is significantly less marked in the Polish Carpathians. In the western part, the compact edge of the Western Beskids with an altitude of 0.5–1 km and the WSW–NEE course, exposed to moist air masses inflowing from the northern sector, is fragmented eastward into smaller mountain groups, which facilitates the penetration of moist masses of air with occurrence of prolonged precipitation into the mountains. At times, the storm cloud moves along the mountain edge (the margin of the Western Bieszczady Mts.). The marginal scarp of the Foothills has a northern exposure and a height of 150–200 m, and promotes frequent convective precipitation causing local flash floods in small streams. The cases of downpours and high discharges selected for the analysis were those for which there was available a dense network of measuring stations. An insufficient number of stations in constructing precipitation maps based on interpolation would lead to distorting the spatial image. If this were the case, then the role of slope exposure, which has an essential impact on the distribution of precipitation in mountainous regions, would be completely neglected

Controlled rate thermal analysis of sepiolite

CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of a clay mineral such as sepiolite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal changes in the sepiolite as the sepiolite is converted to an anhydride. In the dynamic experiment two dehydration steps are observed over the ~20-170 and 170-350°C temperature range. In the dynamic experiment three dehydroxylation steps are observed over the temperature ranges 201-337, 337-638 and 638-982°C. The CRTA technology enables the separation of the thermal decomposition steps