Selective catalytic reduction of NO by alcohols on Co- and Fe-Siβ catalysts

Co–Siβ and Fe–Siβ catalysts prepared by a two-step post-synthesis method were characterised by EPR, diffuse reflectance UV–vis, XRD and N₂-physisorption. Iron and cobalt ions are present as isolated lattice tetrahedral Co^II and Fe^III species for low metal contents (0.7 and 0.9 wt.%, respectively). For higher iron content, FeO_x oligomers appear. Zeolites with isolated Co^II and Fe^III species are active in selective catalytic reduction of NO with ethanol. On FeO_x oligomers the oxidation of NO to NO₂ starts to dominate in the selective catalytic reduction of NO with ethanol at the temperatures higher than 700 K.     

Yield and maintenance coefficients in S. cerevisiae cultures

Precise determination of yields deduced from measurements of metabolic rates needs an understanding of the physiology and energetics of growth of microorganisms. The linear growth equation derived from the simplified picture of microbial metabolism is generally accepted. However, the significance of the yields it gives is less well understood. The analysis of the theoretical and real observed and true yield coefficients for partly aerobic and anaerobic growth of S. cerevisiae is presented in this study. In the calculations of yields and maintenance coefficients, the pseudoconstants Y, P/O were used. A set of limitations imposed on true yields in the linear growth equation is established and the significance of the yields is also discussed. The experimental runs were performed in a laboratory-scale bioreactor (1·5 dm³ of operating capacity). The yeast Saccharomyces cerevisiae hybrid G-67 was cultured in synthetic Reader medium containing sucrose as the main carbon and energy source. The comparison between experimentally obtained yield coefficients relative to cell growth and ethanol formation and the real theoretical values is presented. The maintenance coefficients calculated for anaerobic and respiro-fermentative processes are 0·14 C-mole ATP (C-mole DM h)⁻¹. © 1998 SCI     

Thiomethylstilbenes as inhibitors of CYP1A1, CYP1A2 and CYP1B1 activities

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural stilbene derivative occurring in grapes, peanuts and red wine. Its chemopreventive action has been established in studies on animal models. Recently, numerous classes of compounds with stilbene backbone have been investigated for their biological activity concerning cancer prevention; e. g. resveratrol methyl ethers appeared to be specific and potent inhibitors of cytochromes P450 (CYP) family 1 involved in the activation of procarcinogens. Since the replacement of the 4'-hydroxyl with a thiomethyl group is supposed to reduce toxicity of stilbene derivatives, the purpose of this study was the synthesis and evaluation of a series of 4-thiomethyl-trans-stilbene derivatives differing in a number and position of additional methoxy groups. Their inhibitory potency toward human recombinant CYPs: CYP1A1, CYP1A2 and CYP1B1 have been studied and compared with the effect of resveratrol and its analogues. Among compounds tested, 2-methoxy-4'-thiomethyl-trans-stilbene and 3-methoxy-4'-thiomethyl-trans-stilbene demonstrated the most potent and selective inhibitory effect on CYP1A1 and CYP1B1 activities. The results of our study indicate that modification of stilbene derivatives with thiomethyl group may influence the selectivity and inhibitory potency of these compounds toward P450 isozymes. Thus, it should be considered in developing new chemopreventive agents based on their mechanism of action.     

Advanced Oxidation of Textile Wastewaters

Model dyeing and laundering wastewaters produced during two basic technological operations of the textile industry were subjected to treatment by advanced oxidation processes (AOPs). The following agents were used: ozone (O₃), hydrogen peroxide (H₂O₂) and UV radiation. They were applied separately and in all possible combinations: O₃ + UV, O₃ + H₂O₂, UV + H₂O₂, as well as all three at the same time: O₃ + UV + H₂O₂. Effluents before and after the treatment were analyzed according to requirements of the Polish Standards that included pH, color threshold, COD and concentration of anionic and non-ionic surfactants. Ozonation was carried out in a lab-scale bubble column reactor with a centrally located UV burner. The most effective version of AOPs proved to be the simultaneous use of all three agents. In the case of such treatment of dyeing wastewaters nearly complete discoloration and full decomposition of surface-active substances were obtained at 80% reduction of COD. A similar tendency was observed in the case of laundering wastewater, though in that case the results were slightly worse, which may be explained by much higher initial concentrations of the pollutants. Good treatment effects have also been obtained in combined treatment by simultaneous use of hydrogen peroxide and ozone.     

Charging and discharging phenomena in electrostatically-driven single-crystal-silicon MEM resonators: DC bias dependence and influence on the series resonance frequency

This paper presents a first study concerned with charging and discharging phenomena in single crystal silicon MEM resonators. It is shown that the DC voltage required for the device operation induces a residual voltage between the resonator and its driving electrode, which is attributed to dielectric charging. The residual voltage can affect the device series resonance frequency and is determined from the measurements. The residual voltage maximum amplitude and the charging rate depend not only on the stressing voltage amplitude but also on the polarization.     

Robust output feedback stabilization of uncertain dynamic systems with bounded controllers

We propose a new class of infinitely many bounded output feedback controllers for uncertain dynamic systems with bounded uncertainties. No statistical information about the uncertainties is assumed. A variable structure systems approach is employed in the synthesis of the proposed output feedback controllers. The role of the system zeros in the output feedback stabilization using the variable structure approach is discussed. We show that the proposed controllers guarantee the practical stability of the closed-loop system and give estimates of the regions of practical stability.     

Technique for measurement of powerline impedances in the frequencyrange from 500 kHz to 500 MHz

A method for measuring power line impedances using two current probes is examined. This method is characterized by good isolation of the measurement equipment from the power line voltage and by the capability of measuring power line impedances between any pair of power-plug terminals. The use of this two-current probe method with the model described is effective in measuring power line impedances from 0.5 MHz to 100 MHz. Using purely resistive loads for calibration, the error is less than 5% for frequencies below 100 MHz, and less than 20% for frequencies between 100 MHz and 500 MHz. The error in an impedance measurement increases with the magnitude of the load impedance     

Thermodynamic studies of zinc chloride in mixed aqueous solvents from electromotive force measurements—II. Dioxan,acetone and acetic acid mixtures with water

From the emf measurements of the cell Pt/Zn(Hg)/ZnCl₂, H₂O, organic co-solvent/AgCl/Ag the standard emf of the cell have been determined for dioxan (10,20 and 30 wt%), acetone (10, 20 and 30 wt%) and acetic acid (10, 20, 30, 50, 70 and 90 wt%) mixtures with water at 298 K. These data were used in calculations of: (a) the mean activity coefficients of zinc chloride (b) the primary medium effect (c) the standard Gibbs energies of transfer of zinc chloride from water to mixed solvents. The standard Gibbs energies for the transfer process have been interpreted in regard to the acid-base (in Lewis meaning) properties of the water molecules in mixed solvents.     

An international comparison of energy use in industry: United Kingdom,West Germany,and Italy

The paper presents an investigation on the relation between energy use and economic activity in eight industrial sectors in the United Kingdom, West Germany, and Italy. The approach relies on the analysis of time-series data. In the first section, we point to the role of energy in its interrelationship with the structural characteristics of the national economies. Subsequently, having observed that unit energy requirements vary in the same sector across the three countries, the analysis focuses on possible explanations. The different unit energy consumption pattern, as exhibited by most of the Italian sectors when compared with both the British and the West German ones, is not related to different unit labour and unit capital utilisation patterns. The lack, in the Italian sectors, of a large coal consumption share in the first post-war decade provides an intuitively plausible explanation for the observed unit energy consumption. We test the hypothesis that interfuel substitution alone can account for increased energy productivity. From the results obtained, we deduce that, for a small subset of our sectors, the tested hypothesis turns out to be a meaningful one. In a subsequent section, we analyse and compare the substitution characteristics and the price elasticities of consumption for four fuels. We also take account of the price of labour. Our results support the conclusion that electricity tends to be used as a complement to the other fuels, while the fossil fuels substitute for each other.