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    The new BELUGA setup for collocated turbulence and radiation measurements using a tethered balloon: First applications in the cloudy Arctic boundary layer
    (Göttingen : Copernicus GmbH, 2019) Egerer, U.; Gottschalk, M.; Siebert, H.; Ehrlich, A.; Wendisch, M.
    The new BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) tethered balloon system is introduced. It combines a set of instruments to measure turbulent and radiative parameters and energy fluxes. BELUGA enables collocated measurements either at a constant altitude or as vertical profiles up to 1.5km in height. In particular, the instrument payload of BELUGA comprises three modular instrument packages for high-resolution meteorological, wind vector and broadband radiation measurements. Collocated data acquisition allows for estimates of the driving parameters in the energy balance at various heights. Heating rates and net irradiances can be related to turbulent fluxes and local turbulence parameters such as dissipation rates. In this paper the technical setup, the instrument performance, and the measurement strategy of BELUGA are explained. Furthermore, the high vertical resolution due to the slow ascent speed is highlighted as a major advantage of tethered balloon-borne observations. Three illustrative case studies of the first application of BELUGA in the Arctic atmospheric boundary layer are presented. As a first example, measurements of a single-layer stratocumulus are discussed. They show a pronounced cloud top radiative cooling of up to 6K h-1. To put this into context, a second case elaborates respective measurements with BELUGA in a cloudless situation. In a third example, a multilayer stratocumulus was probed, revealing reduced turbulence and negligible cloud top radiative cooling for the lower cloud layer. In all three cases the net radiative fluxes are much higher than turbulent fluxes. Altogether, BELUGA has proven its robust performance in cloudy conditions of the Arctic atmospheric boundary layer.
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    Physiological Parameters Relevant to Dissolution Testing - Hydrodynamic Considerations (rev. and suppl. version)
    (Tübingen : Universitätsbibliothek Tübingen, 2023) Diebold, Steffen M.
    The first two sections of the monograph present an introduction into basic hydrodynamics relevant to in vitro dissolution testing including V. G. Levichs convective diffusion theory and the authors combination model. This part is followed by hydrodynamic considerations of in vivo dissolution including hydrodynamic problems inherent to in vivo bioavailability of solid oral dosage forms. Hydrodynamics in the upper GI tract contribute to in vivo dissolution. Our ability to forecast dissolution of poorly soluble drugs in vitro depends on our knowledge of and ability to control hydrodynamics as well as other factors influencing dissolution. Provided suitable conditions (apparatus, hydrodynamics, media) are chosen for the dissolution test, it seems possible to predict dissolution limitations to the oral absorption of drugs and to reflect variations in hydrodynamic conditions in the upper GI tract. The fluid volume available for dissolution in the gut lumen, the contact time of the dissolved compound with the absorptive sites and the particle size have been identified as the main hydrodynamic determinants for the absorption of poorly soluble drugs in vivo. The influence of these factors is usually more pronounced than that of the motility pattern or the gastrointestinal flow rates per se.