Measurement of surface diffusivities in mesoporous Vycor glass membranes using a modified Wicke–Kallenbach cell with variable cell volume

The purpose of this paper is to suggest a new experimental method for the measurement of surface diffusivities in porous membranes and to demonstrate its applicability in a case study. So far only indirect methods are applied. Hereby the flux contributions due to surface diffusion are extracted from the total fluxes by subtracting calculated gas phase contributions. Since gas and adsorbed phases are coupled by adsorption equilibrium, surface diffusivities cannot be extracted from surface diffusion fluxes without knowing sorption isotherms. Thus, the quality of surface diffusivity data then depends on the quality of the adsorption data. Therefore, it might be worthwhile to look for another method, which allows the direct measurement of surface diffusivities without knowing the adsorption isotherm. We propose to use a modified Wicke–Kallenbach cell (WKC) with a variable chamber volume and to run pressure response experiments with one inert gas and the counter-diffusing adsorbable gas, for which one wants to determine the surface diffusivity.     

An optimization method with experimental validation for the design of extrusion wire coating dies for a range of different materials and operating conditions

The objective of this article is to determine a wire coating‐hanger melt distributor geometry to ensure a homogenous exit velocity distribution that will best accommodate a wide material range and multiple operating conditions (i.e., die wall temperature and flow rate change). The computational approach incorporates finite element (FE) analysis to evaluate the performance of a die design and includes a nonlinear constrained optimization algorithm based on the Kriging interpolation and sequential quadratic programming algorithm to update the die geometry. Two optimization problems are then solved, and the best solution is taken into account to manufacture the optimal distributor. The Taguchi method is used to investigate the effect of the operating conditions, i.e., melt and die wall temperature, flow rate and material change, on the velocity distribution for the optimal die. In the example chosen, the wire coating die geometry is optimized by taking into account the geometrical limitations imposed by the tool geometry. Finally, the FE analysis and optimization results are validated by comparison with the experimental data obtained with the optimal die. The purpose of the experiments described below is to investigate the effect of material change. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Electron Beam Induced Reduction of V2O5 Studied by Analytical Electron Microscopy

The reduction of V₂O₅ under electron irradiation was studied by means of electron energy-loss spectroscopy, electron diffraction, and high-resolution imaging. The decrease of spectral intensity of O 1s excitations indicates a preferential removal of oxygen. The observed chemical shifts of the V 2p_3/2 and V 2p_1/2 peaks reveal that V⁵⁺ is reduced to V²⁺. Electron diffraction and high-resolution imaging show a structural change from the orthorhombic V₂O₅ to cubic VO. The beam induced reduction is compared with thermal decomposition of V₂O₅.     

Studies on the current 137Cs body burden of children in Belarus--can the dose be further reduced?

After the Chernobyl reactor accident wide areas of Belarus were contaminated with radioactive fallout. The verification and documentation of the long-term development of radiation doses is still going on. A population group of special concern are the children living in contaminated regions. The annual dose limit of 1 mSv is still exceeded in some cases, essentially due to high body burdens of (137)Cs as indicated by screening measurements with portable incorporation monitors. In this situation the evaluation of possible dose reduction measures in addition to the control of food contamination is being investigated. Special attention is given to the therapeutic application of a pectin preparation (Vitapect), for which a dose-lowering effect is presumed by Belarusian scientists. In a placebo-controlled double-blind study, several groups of contaminated children received a pectin compound named Vitapect for a two-week period during their stay in a sanatorium. For comparison the same number of control groups were given a placebo preparation. The (137)Cs body burden of the children was measured at the beginning and the end. The mean relative reduction of the specific activity within the Vitapect groups was found to be approximately 33%, whereas the specific activity of the children who received a placebo decreased only by approximately 14%, due to clean food supply. It is known that pectins chemically bind cations like caesium in the gastrointestinal tract and thereby increase faecal excretion. Theoretical calculations based on this assumption and considering metabolism processes are qualitatively consistent with the experimentally found retention of radiocaesium in the human body after pectin treatment.     

Pressure dependence of superconductivity in Ba4C60

In Ba_xC₆₀ superconductivity (sc) at T_c=(6.8±0.2) K is associated with the x=4 phase. Here we present pressure studies of T_c of a Ba_xC₆₀ sample (dT_c/dp= –1.9 K/GPa) which exhibits a large volume fraction of the x=4 phase. In the alkali-fullerides K₆₀C₆₀ and Rb₃C₆₀ T_c is governed by the electronic density of states N(E_F) (T_c exp{–1/N(E_F)V}). The dependence of N(E_F) on volume can be approximated by N(E_F)=N₀ d _eff ³, where d_eff is the surface to surface distance of neighboured C₆₀-molecules. This relationship is corroborated by (T_C,d)-data of various compounds of the form A_3–xB_xC₆₀ (A: K, Rb; B: K, Rb, Cs; x2). Strong deviation from this behavior is found for the alkaline-fulleride superconductor Ba₄C₆₀. This deviation is attributed to the hybridization of alkaline-metal s-, d-states and C₆₀ -states.     

Lächerliche Erkenntnisse?! Kann man Geschlechterforschung wirklich ernstnehmen?

Speaking about gender and sexuality often results in giggles, laughter, and sometimes ripples of jocularity from the audience. In my paper I try to follow the traces of these emotional reactions, not in order to educate the audience but to examine their sources. The sources of these affects offer opportunities to discover 'situated emotions' as an attitude toward research in feminist science studies.     

Performance assessment of onboard and scene-based methods for Airborne Prism Experiment spectral characterization

Accurate spectral calibration of airborne and spaceborne imaging spectrometers is essential for proper preprocessing and scientific exploitation of high spectral resolution measurements of the land and atmosphere. A systematic performance assessment of onboard and scene-based methods for in-flight monitoring of instrument spectral calibration is presented for the first time in this paper. Onboard and ground imaging data were collected at several flight altitudes using the Airborne Prism Experiment (APEX) imaging spectrometer. APEX is equipped with an in-flight characterization (IFC) facility allowing the evaluation of radiometric, spectral, and geometric system properties, both in-flight and on-ground for the full field of view. Atmospheric and onboard filter spectral features present in at-sensor radiances are compared with the same features in reference transmittances convolved to varying instrument spectral configurations. A spectrum-matching algorithm, taking advantage of the high sensitivity of measurements around sharp spectral features toward spectrometer spectral performance, is used to retrieve channel center wavelength and bandwidth parameters. Results showed good agreement between spectral parameters estimated using onboard IFC and ground imaging data. The average difference between estimates obtained using the O(2) and H(2)O features and those obtained using the corresponding filter features amounted to about 0.3 nm (0.05 of a spectral pixel). A deviation from the nominal laboratory instrument spectral calibration and an altitude-dependent performance was additionally identified. The relatively good agreement between estimates obtained by the two approaches in similar spectral windows suggests they can be used in a complementary fashion: while the method relying on atmospheric features can be applied without the need for dedicated calibration acquisitions, the IFC allows assessment at user-selectable wavelength positions by custom filters as well as for the system on-ground.