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Start Over Subject Geologie. Meteorologie. Klimatologie

441. Pokus o rekonstrukci teplotních poměrů během stalingradské operace :

Creator:
Štekl, Josef,
Type:
text and studie
Subject:
Geologie. Meteorologie. Klimatologie, Dějiny zemí východní Evropy, klima, bitva u Stalingradu (1942-1943), klimatologie, mrazy, válka druhá světová (1939-1945), SSSR, světové dějiny 1939-1945, vědy o neživé přírodě, přírodní prostředí, astronomie, and vojenské operace, války, bitvy
Language:
Czech
Description:
An attemp on reconstruction of temperature conditions during the Stalingrad operation (November 1942–January 1943).
Rights:
unknown

442. Polycyclic aromatic hydrocarbons and other organic compounds in ashes from biomass combustion

Creator:
Pavel Straka and Havelcová, Martina
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, popely, ashes, biomass combustion, PAHs, unburned carbon, 7, and 551
Language:
English
Description:
Power generation from biomass is a substantial source of ashes, the extent of which depends on the type of biomass fuel and technology of combustion being used. The current study focuses on comparison of ashes with a special emphasis on hazardous organic compounds, particularly the polycyclic aromatic hydrocarbons (PAHs) fraction, present in ash. The reason is that ashes from combustion of wood or straw are considered as fertilizers in agricultural soils. Ash samples were therefore collected from power plants in the Czech Republic coming from combustion of wood chips, sawdust, bark and straw. The organic fraction was separated by extraction, the final determination of PAHs was performed by GC-UV. The total concentration of PAHs was found to be in the range 15-733 μ g/kg. These compounds are formed during the pyrolysis stage of the combustion process by the secondary ar omatization reactions in char at temperatures above 400 °C. The created PAHs are bound in the porous unburned carbon. For a more detailed qualitative analysis of other organic compounds the GC-MS was used. Higher and branched aliphatic hydrocarbons, ketones, amides and phthalates in the sample with the highest unburned carbon content were found., Pavel Straka and Martina Havelcová., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

443. Porosity changes induced by salt weathering of sandstones, Bohemian Cretaceous Basin, Czech Republic

Creator:
Jiří Adamovič, Mikuláš, Radek, Böhmová, Vlasta, and Jana Schweigstillová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, pórovitost, pískovce, porosity, sandstones, honeycombs, rock crust, salt weathering, case hardening, 7, and 551
Language:
English
Description:
Different types of rock crusts and the underlying unweathered sandstone were sampled in the Bohemian Cretaceous Basin, Czech Republic. Structure and mineral composition of the samples were studied using optical microscopy, scanning electron microscopy with EDAX, and X-ray diffraction. Pore parameters were determined using mercury intrusion porosimetry/ helium pycnometry. Principal salts identified in the rock crusts and in the efflorescences are gypsum and alums. Two types of rock crusts were distinguished on morphological basis: 1. patterned rock crusts with a variety of weathering forms (honeycombs, wandkarren), and 2. armoured rock crusts with a relatively smooth, hardened layer. Patterned rock crusts on medium- to coarse-grained quartzose sandstones show an increase in the size of macropores relative to unweathered sandstone, which mostly implies an increase in total effective porosity. This is explained by the subflorescent growth of salt crystals, the force of which leads to the loss of contact among grains, pore widening, and granular disintegration. Armoured rock crusts on fine-grained clayey sandstone show a reduced volume and size of macropores, as these are filled with clay mineral aggregates and gypsum crystals. A prominent increase in the volume of micropores is due to secondary porosity in kaolinite and corrosion of feldspar grains. Insufficient passability of macropores in the armoured layer for pore waters shifts the evaporation front deeper into the rock. This results in contour scaling as the main process of rock-surface degradation, as opposed to granular disintegration on patterned rock crusts., Jiří Adamovič, Radek Mikuláš, Jana Schweigstillová and Vlasta Böhmová., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

444. Possibilities of cyclization of side alkyl chains of n-alkylphenols and n-alkylbenzenes in the environment of a stationary phase

Creator:
Pavel Straka, Petr Buryan, and Jana Tomanová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, geochemie, alkylphenols, alkylbenzenes, non-covalent interactions, van der Waals forces, retention times, 7, and 551
Language:
English
Description:
During separations in both polar and nonpolar stationary phases of gas chromatographic columns, side alkylchains of n-alkylphenols and n-alkylbenzenes become cyclized. In the aromatic-quasi-alicyclic molecules that are thereby formed, the effect of van der Waals forces is thus increased. The increase involves not only intramolecularly but also intermolecularly acting effects and becomes significantly evident when propyl and higher substituents as butyl, pentyl and hexyl constitute the side alkyl chains. As a result, boiling points considerably increase (non-linearly) in the case of n-alkylphenols and n-alkylbenzenes with total number of carbons in the molecule higher than 9. This leads to divergence in the retention characteristics of the above-mentioned compounds, which can be observed in the dependence of relative retention times on the number of carbons. Cyclization of side alkyl chains in a stationary phase is a quite new phenomenon., Pavel Straka, Petr Buryan and Jana Náhunková., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

445. Potential of precise point positioning using 1 Hz GPS data for detection of seismic-related displacements

Creator:
Ján Hefty and Ľubomíra Gerhátová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, seizmicita, zemětřesení, seismicity, earthquake, high-rate GPS, GPS seismology, precise point positioning, arthquake re lated displacements, 7, and 551
Language:
English
Description:
The Precise Point Positioning (PPP) analysis technique adapted for monitoring of moderate high-rate coordinate variations from GPS observations is applied for measuring actual displacements related to earthquakes. Two approaches are examined: kinematic PPP which is suitable for larger displacements and analysis of residuals from quasi-static PPP which is suitable for detection of minor displacements. Results from simulated horizontal movements of GPS antenna as well as analyses of 1 Hz GPS data from M 9.0 Sendai earthquake, M 6.3 L’Aquila earthquake and M 4.3 Tatabanya earthquake are shown. Our experiments proved the ability to measure dynamic seismic-related short-term coordinate variations at sub-centimetre level with PPP and to detect both strong and weak seismic signals using GPS satellites observations., Ján Hefty and Ľubomíra Gerhátová., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

450. Pre-portland cements and geopolymers

Creator:
Tomáš Hanzlíček, Perná, Ivana, Ertl, Zdenek, and Miller, Sean M.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, cement, caementum, cementitious, calcareous cement, hydraulic cement, Roman cement, English cement, cement of Boulogne pebbles, Pouilly cement, Russian cement, cement of Baye, aqua-fortis cement, plastic cement, Parker’s cement, common cement, Portland cement, 7, and 551
Language:
English
Description:
This paper presents the historical background of the 20th-century technology of geopolymers in light of a literature research of the 15th to 19th centuries and offers a hypothesis on why this historical knowledge was forgotten when Portland cement appeared. The recapitulation of the different cementitious calcareous matters returns all the way to the Bible builders; Ancient Vitruvius Pollio’s work "Ten Books of Architecture". These books were not only read but practically proven in pre-Portland times and especially at the beginning of 19th century. The long-term stability of Roman mortars and constructions was studied from the perspective of the cementitious materials, and the cited literature demonstrates the historical evolution of calcareous cements, then the reasons for the interruption of progress and return to the historical experience in the 1980s., Tomáš Hanzlíček, Ivana Perná, Zdenek Ertl and Sean M. Miller., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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