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search.filters.applied.f.access: openAccess × End date: 2023 × Start date: 2020 × Has files: Yes × Type: Text × Type: article ×

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    Measuring and evaluating colorimetric properties of samples from loess-paleosol sequences
    (Amsterdam [u.a.] : Elsevier, 2023) Laag, Christian; Lagroix, France; Kreutzer, Sebastian; Chapkanski, Stoil; Zeeden, Christian; Guyodo, Yohan
    Colorimetric measurements are valuable in studying paleoenvironmental changes in sediment archives such as loess-paleosol sequences. These measurements allow for the identification of climate-sensitive minerals such as hematite, goethite, and secondary carbonates, as well as the observation of stratigraphic changes influenced by paleoclimate variations. Herein, a detailed workflow protocol emphasizing mineral abundance extraction by determining true band amplitudes is presented. Moreover, we present a protocol for colorimetric measurements that eliminates container bias, allowing the analysis and re-analysis of stored sediment quickly and inexpensively. Finally, we introduce a new R-package ('LESLIE') for graphical data display and enhancement. The protocol and its validation are demonstrated on the Suhia Kladenetz loess-paleosol sequence of northern Bulgaria. • A detailed workflow protocol eliminating container bias in colorimetric measurements and extracting mineral abundances is presented. • The protocol is independently validated with aid of Attenuated Total Reflectance Fourier Transform mid-infrared (ATR-FTIR) spectroscopic experiments. • Stratigraphic color enhancement using the R-package 'LESLIE' is facilitated by a user-friendly R-shiny application.
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    Graphical Rainflow Counting - Complete Algorithm for single courses (SCRF)
    (2023-04) Füser, Sven
    Rainflow counting can be considered the most important method in counting random stress- or strain histories with respect to time in the field of fatigue strength. The method is often explained by rules of a rain flow which gave the name to the method. The algorithmic implementation nevertheless is usually done in three-point or four-point algorithms which work by comparing the differences between the adjacent reversals and then delete the points of the identified intermediate cycle from the time history. The SCRF-algorithm presented in this contribution determines the courses of the rain flow in terms of their start und stop classes as half-cycles. In a subsequent step the half-cycles are matched together to form a closed loop resp. kept as a residue if the counter-course is missing. The algorithm is explained in general und by means of an example. For verification the SCRF-algorithm is compared to a three-point and a four-point algorithm. For periodic signals, there is complete agreement between the three methods. For non-periodic signals, there are small differences: The SCRF can combine some more half-cycles into closed cycles which remain as residues in the other methods. Furthermore the sense of direction of the hysteresis loops is captured more precisely with the SCRF due to its chronological approach.
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    Intestinal flow rates, absorption of felodipine from the small intestine and attributes of chyme collected at midgut from Labradors
    (Tübingen : Universitätsbibliothek Tübingen, 2023) Diebold, Steffen M.
    The objectives of the present study were (1) to investigate gastrointestinal hydrodynamics of Labradors as a model for human midgut (2) to examine various attributes of intestinal fluids in vivo and (3) to study the influence of hydrodynamics on the dissolution and absorption of a poorly soluble drug from various suspensions. Gastrointestinal flow rates were determined volumetrically using an aspiration method. Isotonic saline and 20 % glucose solutions were used to alter gastrointestinal hydrodynamics. Felodipine, a BCS class II substance, was suspended in these fluids. Osmolality, pH, bile acid concentration and drug solubility in various chyme samples were determined. Blood plasma levels of felodipine were recorded while gastrointestinal dissolution was ongoing. Fluid recovery at midgut fistula was significantly higher (>100 %) for glucose 20 % than for isotonic saline solutions (70 %). After administration of 200 ml glucose 20 % the (overall) grand median of differential gastrointestinal flow rates (DFR) was 8.3 ml/min.. Individual spike flow ranged from 20 up to 60 ml/min. Corresponding flow rates after administration of 200 ml isotonic saline were 35.0 ml/min. for the grand median including individual spike flows beyond 100 ml/min.. Within and between-dog variability in flow rate data was similar. In general, glucose solutions released more evenly. Following oral administration of glucose solution 20 % osmolality of intestinal fluids decreased within 40 min. from about 1000 mOsm. towards more physiological values of about 350 mOsm.. Saturation solubility of felodipine (Cs) in jejunal chyme after administration of either solution (saline or glucose) was determined to be about 10 (µg/ml) on average (median), exposing high variability with time! The intestinal solubility varied greatly within the course of an experiment. However, a strong correlation was observed between the aspirated fluid volume and the dissolved amount of felodipine confirming the well known relationship of Noyes, Whitney, Nernst and Brunner in-vivo. Grand median of pH in jejunal chyme of labradors was determined to be 6.68. Median values range from 4.38-7.62. The pharmacokinetic data showed a slight trend to differences based on particle size and on fluid administered.