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    Tytuł:
    Palaeoenvironmental and palaeoclimatic inferences based on X-ray computer tomography: a case study of alkaline lake deposits in Hungary
    Autorzy:
    Alzoubi, Nour N.
    Gulyas, Sandor
    Geiger, Janos
    Powiązania:
    https://bibliotekanauki.pl/articles/2204374.pdf
    Data publikacji:
    2023
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    freshwater carbonates
    CT analysis
    statistical properties
    palaeoenvironment
    Holocene
    słodka woda
    tomografia komputerowa
    właściwości statystyczne
    paleośrodowisko
    Holocen
    Opis:
    Widely distributed freshwater carbonate sediments, i.e., limestone, dolomitic limestone and dolomite, developed in inter-dune alkaline ponds of the Danube-Tisza Interfluve in the centre of the Carpathian Basin during the Holocene. The key parameters that determine the formation of any given type of carbonate mineral (calcite, dolomite) are temperature, evaporation rate, pH and ion concentrations, in addition to CO2 absorption by aquatic plants. CT analysis is capable of recording small-scale density variations attributable to compositional differences of sedimentary rocks. As the type and proportion of rock-forming minerals and other components is an artifact of past environmental and climatic conditions, CT values may act as potential palaeoenvironmental proxies. The present study compares variations in rock-forming components obtained for freshwater carbonates utilizing the CT method with already available geochemical and palaeoecological proxy data. Variations in molluscan ecology and isotope geochemistry, sedimentation times and CT-based rock density values all indicate the relevance of millennial-scale, climate-driven changes in carbonate formation. As previously observed, the emergence of colder conditions in the North Atlantic, which resulted in increased cyclonic activity and heavier rainfall in western Europe and the Danube watershed area between 10.3 and 9.3 kyr cal BP, resulted in the emergence of humid conditions favouring a rise in the groundwater table at our site and precipitation of calcite from pore waters as opposed to high-magnesium calcite. This is clearly reflected in a negative shift in CT density values in our dated rock samples.
    Źródło:
    Geologos; 2023, 29, 1; 33-49
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessing the representative elementary volume of rock types by X-ray computed tomography (CT) – a simple approach to demonstrate the heterogeneity of the Boda Claystone Formation in Hungary
    Autorzy:
    Abutaha, Saja M.
    Geiger, János
    Gulyás, Sándor
    Fedor, Ferenc
    Powiązania:
    https://bibliotekanauki.pl/articles/2204358.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    Hounsfield Unit
    HU
    autoregressive integrated moving average
    ARIMA
    Statistical Process Control
    SPC technique
    skala Hounsfielda
    model ARIMA
    statystyczna kontrola procesu
    SPC
    Opis:
    X-ray computed tomography (CT) can reveal internal, three-dimensional details of objects in a non-destructive way and provide high-resolution, quantitative data in the form of CT numbers. The sensitivity of the CT number to changes in material density means that it may be used to identify lithology changes within cores of sedimentary rocks. The present pilot study confirms the use of Representative Elementary Volume (REV) to quantify inhomogeneity of CT densities of rock constituents of the Boda Claystone Formation. Thirty-two layers, 2 m core length, of this formation were studied. Based on the dominant rock-forming constituent, two rock types could be defined, i.e., clayey siltstone (20 layers) and fine siltstone (12 layers). Eleven of these layers (clayey siltstone and fine siltstone) showed sedimentary features such as, convolute laminations, desiccation cracks, cross-laminations and cracks. The application of the Autoregressive Integrated Moving Averages, Statistical Process Control (ARIMA SPC) method to define Representative Elementary Volume (REV) of CT densities (Hounsfield unit values) affirmed the following results: i) the highest REV values corresponded to the presence of sedimentary structures or high ratios of siltstone constituents (> 60%). ii) the REV average of the clayey siltstone was (5.86 cm3) and (6.54 cm3) of the fine siltstone. iii) normalised REV percentages of the clayey siltstone and fine siltstone, on the scale of the core volume studied were 19.88% and 22.84%; respectively. iv) whenever the corresponding layer did not reveal any sedimentary structure, the normalised REV values would be below 10%. The internal void space in layers with sedimentary features might explain the marked textural heterogeneity and elevated REV values. The drying process of the core sample might also have played a significant role in increasing erroneous pore proportions by volume reducation of clay minerals, particularly within sedimentary structures, where authigenic clay and carbonate cement were presumed to be dominant.
    Źródło:
    Geologos; 2021, 27, 3; 157--172
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Environmental history of the Csorna Plain (Western Danube Plain, NW Hungary) from the Late Glacial to the Late Holocene as seen from data of multiproxy geoarchaeological investigations
    Autorzy:
    Törőcsik, Tünde
    Gulyás, Sándor
    Sümegi, Pál
    Sümegi, Balázs
    Molnár, Dávid
    Benyó-Korcsmáros, Réka
    Powiązania:
    https://bibliotekanauki.pl/articles/2025095.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    fluvial geoarchaeology
    environmental history
    flood cycles
    Danube Plain
    NW Hungary
    Nauki o Ziemi
    Opis:
    This study presents the results of a comprehensive geoarchaeological study implemented at an archeological site covering ca. 5 ha near the city of Csorna on the NW part of the Danube Plain, NW Hungary. The site itself exposed a complex fluvial system of an ice age creek with near bank and overbank areas (levee, point bar, back swamp). Spatial distribution of archeological features allowed for the interpretation of differential use of the fluvial landscape by different cultures. According to our data, the referred fluvial system must have emerged during the Late Glacial. At this time, creeks originating from hills to the SE followed a uniform NW trajectory. From the Holocene, small creeks were beheaded turning into inactive flood channels. It was the time when the gradual infilling of the floodplain started. Alternating layers of floodwater coarses and floodplain fines mark recurring floods at our site. These could have been correlated with cooler, wetter climatic phases of the North Atlantic, Western Europe and high stands in Central European lakes. Highest floods are recorded during the Late Bronze and Iron Ages besides the Neolithic. Pollen data enabled us to make inferences on the vegetation as well.
    Źródło:
    Studia Quaternaria; 2019, 36; 19-43
    1641-5558
    2300-0384
    Pojawia się w:
    Studia Quaternaria
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Methodological add-ons to a non-destructive, micro-CT-based taxonomic/morphometric analysis of characean remains
    Autorzy:
    Benyó-Korcsmáros, Réka
    Gulyás, Sándor
    Sebők, Dániel
    Benyó, Dániel
    Cseh, Péter
    Sümegi, Pál
    Powiązania:
    https://bibliotekanauki.pl/articles/24201075.pdf
    Data publikacji:
    2023
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    characeae
    computer tomography
    gyrogonite
    tomografia komputerowa
    gyrogonit
    Opis:
    Ever since its introduction, computed tomography has come a long way. No longer is it merely a method that is used in clinical diagnostics, but it is becoming more and more popular among palaeontologists because it can be used to analyse both external and internal structures of fossil remains, such as small insects, snail shells and plant remains. The present study describes non-destructive analyses of Late Cretaceous and early Holocene charophyte gyrogonites by using the micro-CT technique, from sample preparation (embedding, fixing) to visualisation and assessment of images obtained. In addition to this non-destructive examination, we wished to test whether or not computed tomography could be used to examine the gyrogonites. Our preliminary results have made it clear that the micro-CT technique is worth employing for further research. It has proved possible to visualise the samples in 3D, rotate them, and observe them from different directions. By using the appropriate parameters, we have also been able to observe density differences between parts of characean remains and to study several important defining features of these.
    Źródło:
    Geologos; 2023, 29, 2; 69--75
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of sonication and stirring on ultrafiltration of fermentation broth
    Autorzy:
    Lemmer, Balázs
    Jákói, Zoltán
    Gulyás, Nikolett
    Kertész, Szabolcs
    Beszédes, Sándor
    László, Zsuzsanna
    Hodúr, Cecilia
    Powiązania:
    https://bibliotekanauki.pl/articles/207543.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    sonication
    fermentation broth
    membrane separation
    sonifikacja
    brzeczka fermentacyjna
    separacja membranowa
    Opis:
    Membrane separation is a widely used technique whose main obstacle is membrane fouling, during which a solution or particles accumulate on the membrane surface or inside its pores. This phenomenon causes both reversible and irreversible flow resistances that can be minimized with complementary techniques such as sonication and/or stirring. The application of ultrasonic energy can increase the flux by breaking the concentration polarization and cake layer on the membrane surface without affecting the intrinsic permeability of the membrane. Our work focused on cellulase and β-glucosidase enzyme recovery through sonicated/stirred ultrafiltration from the real fermentation broth, at which the fermentation liquid was produced from tobacco plants. Membrane filtrations were carried out in a laboratory-grade batch ultrafiltration cell, extended with stirrer and ultrasound processor. The effects of stirring speed and ultrasound treatment were investigated on the membrane’s permeate flux efficiency and on the quality of recycled enzymes. Resistance values were calculated by the resistance-in-series model, as well as by Hermia’s analysis, to reveal deeper, process-related information. Our results revealed that enzymes could be efficiently separated from real fermentation broth. Furthermore, the enzyme activity test showed that neither stirred nor sonicated processes were detrimental to the enzyme activity.
    Źródło:
    Environment Protection Engineering; 2020, 46, 1; 49-62
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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