ALBERT

Description: Polysaccharides are the most important components of herbal biomass with a high application potential. Their thermochemical characteristics, however, have been little studied. In the present paper, an effective thermodynamic analysis was carried out with the aim of setting a method for reasonably estimating the thermochemical properties of polysaccharides such as cellulose. The properties of formation and heat capacities were estimated by general thermodynamic methods like group contribution methods as well as methods followed from synthetic polymer studies. The results were compared with those obtained by empirical correlations derived from the data for short chain carbohydrates, the only literature data available for validation. The properties were determined depending on the degree of polymerization and temperature. Convenient thermodynamic methods for the estimation of thermochemical properties were analyzed with the objective of specifying those that could provide reasonable values for the homologous series of carbohydrates. The properties were determined as a function of temperature and carbo-hydrate chain length. These allow the prediction of formation properties of polysaccharides such as cellulose.

Description: The physical as well as the chemical solubility of carbon dioxide in several ionic liquids were predicted with quantum chemical a priori methods. The physical solubility was described with the model COSMO-RS. The results were compared to experimental data. Both a qualitative and – based on the concept of relative solubility – quantitative benchmark for the solvents were possible. For the part of chemical absorption, the free reaction enthalpy, Δ R g , and reaction enthalpy, Δ R h , were determined with DFT calculations on the B3LYP/def2-TZVPP level. By combining reaction and phase equilibrium, the CO 2 loading of the reactive solvents were predicted. The results were validated with literature data. An approach was developed for a quantitative a priori description of both physical and chemical solvation of CO 2 . A new approach is presented for the a priori screening of physical and reacting absorbents for CO 2 . Predictions of physical solubility are made using COSMO-RS. For the description of the chemical reaction, the chemical and phase equilibrium are simultaneously solved by combining quantum chemical calculations on the DFT level with a model for the phase equilibrium.

Description: Biomass holds great promise as a renewable source of hydrogen and thus as a zero-emission, carbon-neutral, and nearly inexhaustible energy resource. Thermodynamic analysis of biomass hydration is carried out to study the reaction properties considering a series of saccharides as a model. Equilibrium constants and composition are estimated in dependence on the saccharide chain length and temperature. The latter is also studied as a function of the reactant ratios and in the presence of nonreacting additives. Being highly endothermic, the reaction is thermodynamically favorable due to a high entropic contribution. Increase in the saccharide chain length affects the conversion only slightly, so the results for low-molecular-weight saccharides can be transferred to long-chain ones. The hydration of oligosaccharides to hydrogen is evaluated from the equilibrium thermodynamics viewpoint. The reaction is thermodynamically favorable even at mild conditions and is entropically driven. With increasing oligosaccharide chain length, the conversion remains nearly constant. Therefore, results for short chain saccharides can also be applied to long chain sugars such as cellulose.

Description: Biomass holds great promise as a renewable source of hydrogen and thus as a zero-emission, carbon-neutral, and nearly inexhaustible energy resource. Thermodynamic analysis of biomass hydration is carried out to study the reaction properties considering a series of saccharides as a model. Equilibrium constants and composition are estimated in dependence on the saccharide chain length and temperature. The latter is also studied as a function of the reactant ratios and in the presence of nonreacting additives. Being highly endothermic, the reaction is thermodynamically favorable due to a high entropic contribution. Increase in the saccharide chain length affects the conversion only slightly, so the results for low-molecular-weight saccharides can be transferred to long-chain ones. The hydration of oligosaccharides to hydrogen is evaluated from the equilibrium thermodynamics viewpoint. The reaction is thermodynamically favorable even at mild conditions and is entropically driven. With increasing oligosaccharide chain length, the conversion remains nearly constant. Therefore, results for short chain saccharides can also be applied to long chain sugars such as cellulose.

Description: Basal melting of ice shelves around Antarctica contributes to formation of Antarctic Bottom Water and can affect global sea level by altering the offshore flow of grounded ice streams and glaciers. Tides influence ice shelf basal melt rate (wb) by contributing to ocean mixing and mean circulation as well as thermohaline exchanges with the ice shelf. We use a three-dimensional ocean model, thermodynamically coupled to a nonevolving ice shelf, to investigate the relationship between topography, tides, and wb for Larsen C Ice Shelf (LCIS) in the northwestern Weddell Sea, Antarctica. Using our best estimates of ice shelf thickness and seabed topography, we find that the largest modeled LCIS melt rates occur in the northeast, where our model predicts strong diurnal tidal currents (∼0.4 m s−1). This distribution is significantly different from models with no tidal forcing, which predict largest melt rates along the deep grounding lines. We compare several model runs to explore melt rate sensitivity to geometry, initial ocean potential temperature (θ0), thermodynamic parameterizations of heat and freshwater ice-ocean exchange, and tidal forcing. The resulting range of LCIS-averaged wb is ∼0.11–0.44 m a−1. The spatial distribution of wb is very sensitive to model geometry and thermodynamic parameterization while the overall magnitude of wb is influenced by θ0. These sensitivities in wb predictions reinforce a need for high-resolution maps of ice draft and sub-ice-shelf seabed topography together with ocean temperature measurements at the ice shelf front to improve representation of ice shelves in coupled climate system models.

Description: In situ Microscopy (ISM) is an optical analysis method that allows non-invasive monitoring of processes in real-time. In this article online monitoring of enzyme carriers and the determination of their mechanical stability are presented as new application areas for ISM. As proof of principle the fragmentation of Lewatit VP OC 1600 particles in a stirred tank reactor is tracked. The image algorithm that was used to analyze the acquired image data is described and the results of the stability study are shown. Additional application possibilities of ISM in the area of two-phase systems are demonstrated. In situ microscopy (ISM) is an optical analysis method that allows noninvasive acquisition of image information from running processes. It is demonstrated how this analysis technique can be used to determine the mechanical stability of enzyme carriers. Furthermore, application possibilities of ISM for the characterization of two-phase systems are presented.

Description: The accuracy of state-of-the-art global barotropic tide models is assessed using bottom-pressure data, coastal tide gauges, satellite altimetry, various geodetic data on Antarctic ice shelves, and independent tracked satellite orbit perturbations. Tidemodels under review include empirical, purely hydrodynamic (“forward”), and assimilative dynamical, i.e., constrained by observations. Ten dominant tidal constituents in the diurnal, semidiurnal, and quarter-diurnal bands are considered. Since the last major model-comparison project in 1997, models have improved markedly, especially in shallow-water regions but also in the deep ocean. The root-sum-square differences between tide observations and the best models for 8 major constituentsis approximately 0.9, 5.0, and 6.5 cm for pelagic, shelf, and coastal conditions, respectively. Large inter-model discrepancies occur in high latitudes, but testing in those regions is impeded by the paucity of high-quality in-situ tide records. Long-wavelength components of models tested by analyzing satellite laser ranging measurements suggest several models are comparably accurate for use in precise orbit determination, but analyses of GRACE inter-satellite ranging data show that all models are still imperfect on basin and sub-basin scales, especially near Antarctica. For the M 2 constituent, errors in purely hydrodynamic models are now almost comparable to the 1980-era Schwiderski empirical solution, indicating marked advancement in dynamical modeling. Assessing model accuracy using tidal currents remains problematic owing to uncertainties in in-situ current-meter estimates and the inability to isolate the barotropic mode. Velocity tests against both acoustic tomography and current meters do confirm that assimilative models perform better than purely hydrodynamic models.

Description: ABSTRACT The strongest Czech windstorms from 1961 to 2010 were evaluated using a weather extremity index. The index combines the return periods of station wind gusts and the size of the affected area allowing determination of the duration of individual events. Of 50 extreme wind events (EWEs), most were synoptic-scale windstorms that occurred between the end of October and the beginning of March. However, six EWEs were categorized as the convective-scale windstorms. Four of the strongest Czech and European windstorms were related to one other (Kyrill, the November 1984 storm, Vivian and Wiebke, and Jeanette). Approximately 90% of the synoptic-scale windstorms were characterized by strong westerly or northwesterly flow at the 850 hPa level and a north–south temperature gradient at the 500 hPa level. The remaining (rather weaker) synoptic-scale events were characterized by southerly flow and a west–east temperature gradient at the 850 and 500 hPa levels, respectively. To determine the abnormality of windstorms by season, a weather abnormality index was used to evaluate 50 abnormal wind events (AWEs). Throughout the summer, as well as in half of May and September, AWEs were categorized as the convective-scale windstorms accompanied by weak 850 hPa winds. Apart from two events with easterly winds, the remaining AWEs were accompanied by winds from the southwest and a strong west–east temperature gradient at the 850 hPa level. Ten of the latter events occurred in the last two ten-day periods of July and first two ten-day periods of August. All of the events followed hot episodes, and seven of them followed one of the 25 extreme high-temperature events. A less pronounced relationship between wind and temperature anomalies was present in the colder half of the year from October to March: three of the strongest Czech EWEs were associated with abnormal high-temperature events (AHEs).