Is there a direct relationship between oral astringency and human salivary protein binding?

For decades, it is believed that astringency is due to the polyphenol-induced complexation of proline-rich salivary proteins in the oral cavity. In order to compare for the first time the human sensory threshold concentrations and the salivary protein binding activity of a series of astringent stimuli, human saliva protein was incubated for 5 min at 37 °C in the presence of astringent food-derived compounds and, after micro-centrifugation, the amount of the target molecules in the supernatant was quantitatively determined by HPLC-UV/Vis. Significant protein binding was observed for (−)-epigallocatechin-3-gallate, (−)-gallocatechin-3-gallate, (+)-gallocatechin, and (−)-catechin-3-gallate, all of which containing at least one galloyl moiety in the molecule and exhibiting rather high sensory thresholds of more than 200 μmol/L. In comparison, (+)-catechin and procyanidin B2, both lacking in any galloyl function, showed only comparatively low binding activity and, most interestingly, quercetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside and 3-carboxymethyl-indole-1-N-β-d-glucopyranoside did not show any protein binding at all, although the later N- and O-glycosides exhibited extraordinarily low sensory threshold concentrations of less than 0.001 and 0.0003 μmol/L, respectively. The data give some first evidence that the quantity of the non-bound, “free” astringent stimulus in the saliva liquid might be more closely related to the sensory perception of astringency than the amount complexed or precipitated by proteins. It is therefore questionable as to whether oral perception of astringency is related to the complexation and/or precipitation of salivary proteins.     

Effective modelling of percolation at the landscape scale using data-based approaches

Process-based models have been extensively applied to assess the impact of landuse change on water quantity and quality at landscape scales. However, the routine application of those models suffers from large computational efforts, lack of transparency and the requirement of many input parameters. Data-based models such as Feed-Forward Multilayer Perceptrons (MLP) and Classification and Regression Trees (CART) may be used as effective models, i.e. simple approximations of complex process-based models. These data-based approaches can subsequently be applied for scenario analysis and as a transparent management tool provided climatic boundary conditions and the basic model assumptions of the process-based models do not change dramatically. In this study, we apply MLP, CART and Multiple Linear Regression (LR) to model the spatially distributed and spatially aggregated percolation in soils using weather, groundwater and soil data. The percolation data is obtained via numerical experiments with Hydrus1D. Thus, the complex process-based model is approximated using simpler data-based approaches. The MLP model explains most of the percolation variance in time and space without using any soil information. This reflects the effective dimensionality of the process-based model and suggests that percolation in the study area may be modelled much simpler than using Hydrus1D. The CART model shows that soil properties play a negligible role for percolation under wet climatic conditions. However, they become more important if the conditions turn drier. The LR method does not yield satisfactory predictions for the spatially distributed percolation however the spatially aggregated percolation is well approximated. This may indicate that the soils behave simpler (i.e. more linear) when percolation dynamics are upscaled.     

Quasi-optical measurement of complex dielectric constant at 300 GHz

A two beam interferometer in the Martin-Puplett configuration is used to determine the complex dielectric constant at 300 GHz of teflon, TPX-plastics, SPECTRALON and paraffin waxes with melting temperatures of 48° C and 72° C, respectively. The design of the quasi-optical system leads to a constant beam diameter at the power detector independent of path delay and frequency. The power detector signal is recorded not only along one period but over about 50 periods. A spectrum estimation routine allows to determine more exactly amplitude and phase angle of the signal. A basic problem is noticed: imperfect detector and source match cause harmonic distortion of the power detector signal. The effects on processing the loss tangent and the invalidation are shown. Finally loss tangent and dielectric constant are determined indirectly by optimizing an equivalent microwave circuit using a commercial available microwave design system to take multiple reflections and losses in consideration.     

Immobilization of inert TRISO-coated fuel in glass for geological disposal

Vitrification of TRISO-coated gas reactor fuel particles was achieved via two methods: glass melting and sintering. Inert TRISO-coated fuel particles and a borosilicate glass were used. With glass melting at 1200-1300 °C floatation and decomposition of carbon and silicon carbide occurred. Thermal pre-treatment of the particles for oxidation of pyrocarbon did not improve the coating properties of the glass. During cooling most of the particles floated and sorbed on the crucible or mold walls. The sintered glass at 700 °C showed better coating properties of the TRISO-coated fuel particles despite higher porosity compared to glass made by melting. Aqueous leaching properties of glass with particles are similar regardless the mode of fabrication, indicating the good chemical durability of the sintered glass. Sintered glasses may constitute a good technique for TRISO-coated fuel particles immobilization for an eventual deep geological disposal.     

Dreidimensionale,turbulente Strömungs-und Mischungsgradberechnung mit dem PISO-Algorithmus

Zusammenfassung Die numerische Berechnung von turbulenten Str?mungen, sei es isotherm oder mit chemischer Reaktion und W?rmefreisetzung, kann infolge der st?ndigen Fortschritte auf Seiten der Hardware-Entwicklung, auf immer weiteren Anwendungsgebieten eingesetzt werden. Im vorliegenden Fall handelt es sich um ein Programmpaket (COMPAC-3D), welches für die dreidimensionale Simulation der Str?mung und W?rmefreisetzung in Dampferzeugerfeuerungen konzipiert wurde. Hierbei kommt ein neuer Gleichungsl?sungs-und Bilanzierungsalgorithmus zum Einsatz, welcher es gestattet, Parameterstudient mit wesentlich geringerem Rechenzeitaufwand durchzuführen. Dieser Algorithmus wird im folgenden beschrieben. Anhand eines klassischen Testbeispiels, n?mlich der horizontalen Eindüsung in eine vertikale Hauptstr?mung, werden die Simulationsergebnisse mit Me?werten und Ergebnissen aus Rechenl?ufen mit dem Programmpaket PHOENICS verglichen.     

Nickel and chromium cycles: Stocks and flows project part IV

Nickel and chromium are essential ingredients in alloys increasingly important for energy-efficient, environmentally friendly modern technology. Quantitative assessment of the flows of these metals through the world economy from resource extraction to final disposal informs resource policy, energy planning, environmental science, and waste management. This article summarizes the worldwide technological cycles of nickel and chromium in 2000. Stainless steel is the major use of these metals, but they serve numerous other special needs, as in superalloys for high-temperature service, as plating materials, and in coinage. Because they are used primarily in alloys, novel recycling issues arise as their use becomes more widespread. “... the great New York and St. Louis double track, nickel plated railroad...” — Norwalk, Ohio, Chronicle 10 March 1881 announces arrival of surveyors for the future Nickel Plate Railway “Later [1911] I formed an alloy of Iron and Chromium, which showed remarkable resistance to rust and tarnish ... [It was] rediscovered by an Englishman named Brearley, in 1914.” —Elwood Haynes to Stephen F. Roberts, 17 January 1925     

Formation of compounds by high-flux nitrogen ion implantation in titanium

Polycrystalline titanium was implanted with nitrogen ions at energies from 30 to 60 keV and with doses from 1 × 10¹⁶ to 1.5 × 10¹⁸ N⁺-ions cm^–2 at room temperature. The implanted titanium layers were investigated by high-voltage electron microscopy and transmission high-energy electron diffraction. The formation of titanium nitride, titanium carbonitride and titanium carbide phases were considered in relation to their dependence on nitrogen ion implantation dose. In the dose range from 1 × 10¹⁶ up to 1.5 × 10¹⁸ N⁺-ions cm^–2 the cubic phase -TiN _x was formed. In the dose range between 1 to 2.5 × 10¹⁷ and 1.5 × 10¹⁸N⁺-ions cm^–2 the tetragonal phase -Ti₂N was found in addition to the -TiN _x phase. The lattice structure of these titanium nitride phases is a function of the nitrogen ion implantation dose. Additionally, the presence of titanium carbonitrido TiC _y O _x and titanium carbide TiC _y phases can be proved. The analysed titanium nitride, titanium carbUnitride and titanium carbide phases are represented in a state diagram as a function of implantation dose.     

Untersuchung des einflusses molekularer parameter auf morphologie und eigenschaften von polyethylenen niedriger dichte

Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?_w = 1.2 ? 390·10⁴ g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?_w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?_n, M?_w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?_w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties.