Prediction of partition coefficients using COSMO-RS: Solvent screening for maximum conversion in biocatalytic two-phase reaction systems

Many biocatalytic reaction systems are biphasic with a reactive and an immiscible non-reactive phase. The reactive, mostly aqueous phase provides a natural enzyme environment and the non-reactive phase serves for delivery of dissolved substrates at high concentrations and for extraction of products. The proper choice of the non-reactive phase will have manifold influence on the catalytic parameters, such as activity, selectivity, and stability, but also on the maximum obtainable conversion or yield.

Conversion or yield constitutes a concise target of practical relevance for rational solvent screening which requires thermodynamic information on coupled reaction and phase equilibria as input information. As long as the reactive phase is kept constant, only the partition equilibrium of each solute in any solvent combination has to be determined. The experimental determination of these data requires a considerable laboratory effort. Therefore, an in-silico screening of solvents for maximal conversion of alcohol dehydrogenase-catalysed oxidoreductions of prochiral ketones was evaluated. COSMO-RS was used for the prediction of solute partitioning between organic solvents and aqueous reaction medium.

Although significant absolute deviations were found, COSMO-RS still predicted the correct trends for the partition coefficients of solutes in different solvents. The calculated overall reaction equilibrium using these partition coefficients again resulted in the prediction of the correct best solvent regarding conversion.     

Impact of tributyltin on immune response and life history traits of Chironomus riparius: single and multigeneration effects and recovery from pollution

Chironomids play an important role in the detritus cycle and as a component in brackish- and freshwater benthic and terrestrial food webs. If TBT is present in their environment, then they may accumulate tributyltin (TBT) during their juvenile period, which negatively affects many of their life history characteristics. The aim of this experiment is to test the effects of three TBT sediment concentrations (nominal 30, 90, and 180 μg/kg) on life history traits (development time, survival, fecundity, and weight) and immune response (number of hemocytes and phenoloxidase activity) of the nonbiting midge, Chironomus riparius. These responses were recorded immediately after one generation of TBT exposure, and in the long run during five consecutive generations. We also assessed recovery from pollution after four generations of TBT exposure. In a single generation, TBT affected all measured parameters, except phenoloxidase activity, when compared to the control. Long-term-effects of TBT lead to extinction of all treatments after the fifth generation. Again, all measured variables significantly differ from the control, although TBT had varying effects on the measured variables. Most of the effects of TBT on population viability were not evident during recovery, once TBT was removed from the sediment. The effect of previous TBT contamination was observed only in delayed larval development, suggesting that TBT has only limited maternal/epigenetic effects on individual condition. However, altered schedules in the life-cycle can have unexpected ecological impacts. TBT decreases the viability of Chironomus riparius and the effect will become stronger if exposure to TBT continues for many generations. Yet, the harmful effect of TBT disappears quickly as the TBT is removed from the environment.     

Efficient Management of Fines in the Stock Flow prior to Headbox in Paper, Board, and Tissue Production

Fines represent a significant volume of biobased wood material and filler, which is of significant importance to sheet quality. New imaging technology reveals the true nature of the behavior of fines in the retention process. This study illustrates new chemical mixing systems, novel and efficient flash mixing methods, and active measurement and automation systems pertaining to efficient management of fines in the stock flow prior to headbox in paper, board, and tissue production, which can reduce additive, fresh water, energy consumption, and the carbon footprint of production to improve sustainability and provide novel opportunities for fines and filler management.     

Effect of viscosity and applied potential on oscillations at a Pt-Pt dual-electrode in a ferricyanide system

This paper outlines the effect of viscosity and applied potential on oscillations occurring at two platinum electrodes placed proximal to each other. Potential oscillations taking place on the primary electrode (WE1) under galvanostatic control in the ferricyanide system are affected by the solution viscosity as it modifies the convective feedback mechanism necessary for oscillations. Measured transition times correlate with those calculated using Sand equation thus allowing the estimation of current density windows for periodic oscillation for different solution viscosities for pre-determined transition times. Current oscillations on the secondary working electrode (WE2) - under potentiostatic control and induced by the potential oscillations on WE1 - can be tuned through the applied potential. At higher potentials the reaction is oxidation of [Fe(CN)₆]⁴⁻ and the coupling is primarily through the transfer of [Fe(CN)₆]⁴⁻ from WE1 to WE2 via H₂ evolution whilst at more cathodic potentials the reduction of [Fe(CN)₆]³⁻ takes place at both WE1 and WE2 and the convective feedback from WE1 refreshes the surface of both electrodes simultaneously.     

Burnout of pulverized biomass particles in large scale boiler – Single particle model approach

Burning of coal and biomass particles are studied and compared by measurements in an entrained flow reactor and by modelling. The results are applied to study the burning of pulverized biomass in a large scale utility boiler originally planned for coal. A simplified single particle approach, where the particle combustion model is coupled with one-dimensional equation of motion of the particle, is applied for the calculation of the burnout in the boiler. The particle size of biomass can be much larger than that of coal to reach complete burnout due to lower density and greater reactivity. The burner location and the trajectories of the particles might be optimised to maximise the residence time and burnout.     

Niho type cross-correlation functions via dickson polynomials and Kloosterman sums

Suppose that n=2k is even. We study the cross-correlation function between two m-sequences for Niho type decimations d=(2/sup k/-1)s+1. We develop a new technique to study the value distribution of these cross-correlation functions, which makes use of Dickson polynomials. As a first application, we derive here the distribution of the six-valued cross-correlation function for s=3 and odd k, up to a term which depends on Kloosterman sums. In addition, applying simpler methods, we prove a theorem providing Niho type decimations with four-valued cross-correlation functions and their distribution. We conjecture that the latter result actually covers all such decimations.     

Radiology--an exciting specialty, unsatisfactory training situation?

Despite the medical and technological advances during the last decade, there have been problems in attracting new recruits for radiology specialization in Norway. The increasing number of vacancies is a cause for concern. To address this problem, we held interviews with six residents--three males and three females aged between 30 and 39 years. They had from four months to three years of experience in diagnostic radiology at the time of the study. The data were analyzed according to the principles of Giorgi. The participants found radiology both interesting and challenging, but considered the specialist training inadequate, mainly because there were too many routine tasks and not enough supervision.     

Effect of concentration polarization on the current-voltage characteristics of ion transfer across ities

Current-voltage characteristics of ion transfer across the ITIES was theoretically studied, taking concentration polarization into account through the Nernst-Planck equation in the diffusion boundary layers. In the inner layer transport was modelled using either Butler-Volmer or Nernst-Planck equations. Potential distribution across the ideally polarizable ITIES was calculated from the Poisson-Bolzman equation. The current-voltage curves were of the Butler-Volmer type, but no distinction between the two approaches inside the inner layer could be seen because the permeability of the entire system was determined by the diffusion boundary layers.     

Evaluation of High Step-Up Power Electronics Stages in Thermoelectric Generator Systems

To develop practical thermoelectric generator (TEG) systems, especially radioisotope thermoelectric power supplies for deep-space exploration, a power conditioning stage with high step-up gain is indispensable. This stage is used to step up the low output voltage of thermoelectric generators to the required high level. Furthermore, maximum power point tracking control for TEG modules needs to be implemented into the power electronics stages. In this paper, the temperature-dependent electrical characteristics of a thermoelectric generator are analyzed in depth. Three typical high step-up power converters suitable for TEG applications are discussed: an interleaved boost converter, a boost converter with a coupled inductor, and an interleaved boost converter with an auxiliary transformer. A general comparison of the three high step-up converters is conducted to study the step-up gain, conversion efficiency, and input current ripples. The interleaved boost converter with an auxiliary transformer is found to be the most suitable topology for TEG applications, which is verified by experiments.