Comparison of Hexane Vapour Permeation in Two Different Polymeric Membranes via an Innovative In-line FID Detection Method

This manuscript presents a novel method for the analysis of vapour permeation through polymeric membranes based on in-line analysis of the permeate with an FID detector. The hexane vapour permeation was studied for two commercially available membranes, namely low-density polyethylene (LDPE) and thin-film-composite polyamide (PA) membrane. The hexane permeation was studied at temperatures of 25–45 °C, hexane vapour activity in the range of 0.2–0.8 and trans-membrane pressures of 5–50 kPa. Two fundamentally different membranes were chosen to demonstrate the potential and sensitivity of the permeation apparatus. Upon increasing the temperature from 25 to 45 °C, the flux in LDPE was found to increase almost fourfold over the whole activity range. The nonlinear increase of the flux with activity indicates plasticization of the polymer by hexane. Contrarily, the flux in the PA membrane increases almost linearly with activity, with only a minor upward curvature. Since the PA is far away from any phase transition, it is less temperature-dependent than LDPE. The activation energy for permeation demonstrates that the temperature dependence in the LDPE membrane is dominated by changes in diffusion, whereas it is dominated by changes in solubility in the PA membrane. This work is licensed under a Creative Commons Attribution 4.0 International License

Interdependencies between Leverage and Capital Ratios in the Banking Sector of the Czech Republic

In this paper we discuss the implications of the Basel III requirements on the leverage ratio for the banking sector in the Czech Republic. We identify the potential binding constraints from regulatory limits and analyze the interactions among leverage and capital ratios over the country’s economic cycle (during the period 2007-2014). The historical data confirm stronger capital ratios of the banks and an overall solid leverage level with only 5% of the total historical observations being lower than the regulatory recommendations. By analyzing the components of ratios, we conclude that the banks are focusing more on the optimization of risk weighted assets. Strong co-movement patterns between leverage and assets point to the active management of leverage as a means of expanding and contracting the size of balance sheets and maximizing the utility of the capital. The analysis of correlation patterns among the variables indicates that the total assets (and exposure) in contrast to Tier 1 capital are the main contributors to the cyclical movements in the leverage. The leverage and the total assets also demonstrate a weak correlation with GDP, but a strong co-movement with loans to the private sector

A Mixed-signal Neural Network for Auditory Attention

This paper describes a 1MHz CMOS implementation of a neural network used for auditory attention. Signals are coded into binary spikes modelling the biology. A uniform model of pulse propagating cell is used in different performing stages. The signal processing is distributed to neurons and synapses realized as analog circuits. 1 Introduction The concept of attention in an acoustical environment is mainly concerned with the solution of the objectbackground problem (Cocktail-Party Effect). Our spike propagating network approaches this task by reassembling the functionality of the timing pathway in vertebrates. Based on the evaluation of interaural time delay of arrival we separate the sound sources in an acoustical scene by their azimuthal location relative to the 25 cm microphone base. A knowledge guided selection principle 14 is employed to extract the most attractive sound source in terms of recent appearance and correspondence with other sensoric systems of the multi sensoric robot ..

Nafion membranes modified by cationic cyclodextrin derivatives for enantioselective separation

Nafion117® membranes modified by three cationic cyclodextrin (CD) derivatives have been prepared by strong ionic bonding. All CD derivatives contained bis(methylimidazolium) (MIM2) cationic anchor covalently bound to the CD unit, either using no spacer or using diethylene glycol (DEG) or tetraethylene glycol (TEEG) spacers. The modified membranes were tested in chiral separation of a model racemic mixture (d/l-tryptophan) from water. Different experimental set-ups for characterising membranes in enantioselective separation – pertraction, two kinds of sorption, and pressure-driven membrane separation – have been described and rigorously compared. The membranes CD-MIM2, CD-DEG-MIM2 have reached the highest enantiomeric excess, 14 and 44% respectively, in 280 days. The lowest performance of the CD-TEEG-MIM2 membrane, with the long spacer, has been visibly ameliorated by applying pertraction; enantiomeric excess rose from 2 to 27% in 80 days. Even though sorption played the main role in pertraction, this process substantially enhanced the separation of racemic mixtures. The pressure-driven approach has allowed the operation to be continuous and faster, which has the potential for continuous large-scale production of enantiopure compounds and could pave the way for many more commercial applications, satisfying the considerable demand for large-scale chiral separation techniques