Theoretical study of the electric field effect on ion-molecule reactions in diluted gases and solutions

In diluted gases the rate coefficients of ion-molecule reactions in an electric field depend on the characteristic ratio $\text{E}{}_{\mathrm{<mtext>P</mtext>}}\text{k}{}_{\mathrm{<mtext>B</mtext>}}\text{Θ}$ where E_P represents the energetic threshold for the reaction and k_BΘ is the mean kinetic energy summarizing both electric field effects and collision processes within a two-temperature model. Using the Lorentz-gas concept the model can be precised from a microscopic point of view by solving a kinetic equation for the ionic component.In diluted solutions like in gases the field effect on ion-molecule reactions depends on the energy gain of the ions by the electric field. However, the field effect is considerably reduced here because of the small magnitude of the mean free path in liquids. In addition the rate constant modification by the field depends on the ratio of the ion diffusion coefficient to the sum of the diffusion coefficients of both the reactants.     

The differentiation and identification of pathogenic bacteria using FT-IR and multivariate statistical analysis

Correspondence analysis was used to classify the pattern-like FT-IR spectra of intact bacteria. The analysis was performed on a data set of approximately 80 normalized spectral derivatives of a selection of pathogenic bacteria. The correspondence analysis proved that the various different bacterial species were clustering in distinct regions of the correspondence maps suggesting that there do exist correlations between spectral data and biochemical/microbiological classification.     

A new multi-sample ATR-accessory for the analysis of very similar complex biological and technical materials

Measurements on complex materials are often hampered by the difficulties arising from the prerequisites to control sample uniformity. A new single- and multi-reflection ATR-accessory has been designed for the rapid analysis of many samples under extremely similar experimental conditions. This is performed by passing the ATR-unit, a horizontally mounted ZnSe-prism, by the IR-beam. It includes a gas-tight sample region. Thus, toxic material and even pathogenic bacteria may be measured under controlled conditions.     

A model requiring constant negative muon Coulomb capture ratios for simple ionic crystals

A model is developed which suggests slow muon flux spectra of similar shapes in all alkali halides. The model is based on experimental values of muonic Lyman series intensities and Coulomb capture ratios. It is in good agreement with all the experimental information available at present.     

Coverage-dependent kinetics and thermodynamics of carbon monoxide adsorption on a ternary copper catalyst derived from static adsorption microcalorimetry

A reliable method for adsorption systems in equilibrium is established to derive coverage-dependent kinetics and thermodynamics from the volumetric data obtained during the static microcalorimetric measurement of heats of adsorption. The Wigner-Polanyi equation is applied to analyze the pressure change as a function of time during stepwise dosing of the adsorptive until thermodynamic adsorption-desorption equilibrium is established. For carbon monoxide adsorption on a hydrogen-reduced Cu/ZnO/Al2O3 catalyst, the adsorption rate constant (ka) is found to be in the range from 10(-6) to 10(-4) Pa(-1) s(-1), and the desorption rate constant (kd) from 10(-4) to 10(-2) s(-1), both increasing with fractional coverage theta. The kinetically derived equilibrium constant Ktheta is in good agreement with Ktheta obtained from the adsorption isotherm. RT ln(Kp0) and the differential heat of adsorption (qdiff) were found to decrease in parallel, reflecting a normal Temkin-type heterogeneity.     

Study of spectator tagging in the reaction np → ppπwith a deuteron beam

The reaction has been studied in a kinematically complete experiment at a single beam momentum GeV/c (T = 759MeV). All four ejectiles have been detected in the large-acceptance time-of-flight spectrometer COSY-TOF. We analyzed the data along the lines of the spectator model as a means to isolate the quasi-free reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations of the deuteron wave function. Up to a Fermi momentum of roughly 150MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude that the deuteron can indeed be taken as a valid substitute for the neutron.     

Defect corrected averaging for parabolic PDEs

We consider parabolic partial differential equations with highly oscillatory source terms. The timescale of the problem is assumed to be much larger than the timescale of the oscillation. Resolution of the smallest timescale constitutes a strong restriction on the stepsize of time integration method. Averaging techniques like stroboscopic averaging have been developed to overcome this restriction. In case of parabolic equations these techniques are of limited advantage. We have developed defect corrected averaging techniques that allow timesteps taylored to the timescale of diffusion. They are based on Krylov subspace iterations for the abstract solution operator of the system. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)