Investigations of flocculation possibilities of the water alumina suspension in the presence of nonionic polymer

The effect of solution pH and molecular weight of polyethylene glycol (PEG) and polyethylene oxide (PEO) on their adsorption as well as stability of the colloidal Al₂O₃ water suspension was studied. The following methods were applied: turbidimetry, spectrophotometry, viscosimetry, potentiometric titration and microelectrophoresis.It was shown that the increasing solution pH affects conformation of the adsorbed macromolecules which affects the stability properties of such systems. The polymer adsorption causes deterioration of the stability conditions of the investigated alumina systems in comparison to those without polymer at all investigated pH values. At pH 3 and 6 the effect of the suspension destabilization is significantly smaller than at pH 9. The most effective flocculent of Al₂O₃ water suspension is PEO of the molecular weight 218,000 at pH 9.     

Effect of a Static Magnetic Fields and Fluoride Ions on the Antioxidant Defense System of Mice Fibroblasts

The results of studies on the biological influence of magnetic fields are controversial and do not provide clear answers regarding their impact on cell functioning. Fluoride compounds are substances that influence free radical processes, which occur when the reactive forms of oxygen are present. It is not known whether static magnetic fields (SMF) cause any changes in fluoride assimilation or activity. Therefore, the aim of this work was to determine the potential relationship between magnetic field exposure to, and the antioxidant system of, fibroblasts cultured with fluoride ions. Three chambers with static magnetic fields of different intensities (0.4, 0.6, and 0.7 T) were used in this work. Fluoride ions were added at a concentration of 0.12 mM, which did not cause the precipitation of calcium or magnesium. The results of this study show that static magnetic fields reduce the oxidative stress caused by fluoride ions and normalize the activities of antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). Static magnetic fields modify the energy state of fibroblasts, causing an increase in the ATP concentration and a decrease in the MDA concentration. These results suggest that exposure to fluoride and an SMF improves the tolerance of cells to the oxidative stress induced by fluoride ions.     

Kinetic Studies of n-Butylparaben Degradation in H2O2/UV System

This work reports the experimental results of kinetics study of n-butylparaben (BP) degradation in H₂O₂/UV systems. A pseudo–steady-state and competition kinetic approaches were used to determine the reaction rate constants between the BP and ^?OH. In competition kinetics atrazine (2.30?×?10⁹ M^?1?s^?1) was used as a reference compound. The measured rate constants for ^?OH reaction with BP ranged from (3.84 ± 0.12)?×?10⁹ M^?1?s^?1 to (8.56 ± 0.90)?×?10⁹ M^?1?s^?1 depending on solution pH and temperature. Values of the rate constant obtained using different methods were in good agreement. The calculated activation energy was equal to 19.01 ± 1.02 kJ mol^?1.     

Use of farinograph measurements for predicting extensograph traits of bread dough enriched with carob fibre and oat wholemeal

Farinograph and extensograph tests were applied to determine the effect of carob fibre and oat wholemeal on the rheological properties of wheat flour dough, and characterisation of relationships between the results of the tests was performed. The applied additions of carob fibre (1-5%) and oat wholemeal (5-25%) increased the water absorption of the dough within nearly identical ranges (56-59%). Enrichment with carob fibre made the dough more rheologically stable during mixing compared to dough with oat wholemeal. In the extension test, dough with an admixture of carob fibre was more resistant, but it was less extensible than dough with oat wholemeal.Analysis of relationships of the extensograph traits to the farinograph ones revealed that longer periods of development of dough enriched with the additions under examination involved the formation of a looser dough structure, as a result of which its resistance to extension, ratio number and energy decreased and the dough extensibility increased. Opposite effects were caused by increasing farinograph elasticity and its loss. The degree of softening, negatively correlating with resistance, ratio number and energy, coupled with water absorption or with loss of elasticity, permitted their more accurate prediction. In turn, combining in a regression model of water absorption with development time or with elasticity was the most suitable for predicting dough extensibility.     

Multiple catastrophic fault diagnosis of analog circuits considering the component tolerances

This paper deals with the diagnosis of multiple catastrophic faults, being cuts (open‐circuits) of some connecting paths and/or short‐circuits of some pairs of points in analog circuits. A method enabling us to detect and identify the faults, taking into account the deviations of the circuit parameters within their tolerance ranges, is developed. The method exploits an appropriate fault dictionary. The fault dictionary is used only for preliminary identification of the faults, because it is based on the analysis of the circuits with nominal parameters. The crucial point of the method is a verification procedure, proposed in this paper, based on the linear programming approach. It leads to the results considering the component variations within their tolerance ranges. In addition, a procedure for selecting appropriate test points, employing some evolutionary techniques, is developed. Although the approach presented in this paper is described in detail for linear circuits, it can be directly generalized to nonlinear circuits. Three numerical examples, including two linear and one nonlinear circuits, illustrate the proposed method and show its efficiency. Copyright © 2011 John Wiley & Sons, Ltd.     

Multiple Soft Fault Diagnosis of Nonlinear Circuits Using the Continuation Method

This paper offers a method for multiple soft fault diagnosis of nonlinear static circuits. The method enables us to locate the faulty elements and evaluate their parameters. It exploits a set of n nonlinear algebraic type diagnostic equations in n unknown variables and is oriented on finding multiple solutions of these equations. As a result, the method is capable of finding, in systematic manner, different sets of the parameters which satisfy the diagnostic test, rather than one specific set. For this purpose the continuation (homotopy) approach is applied and an efficient procedure for tracing a homotopy path is developed. The proposed method is especially useful at the pre-production stage, where corrections of the technological process are possible and the diagnostic time is not crucial. To illustrate the proposed approach two numerical examples are given.     

Evaluation of hydrogen and methanol fuel cell performance of sulfonated diels alder poly(phenylene) membranes

Hydrogen fuel cell performance of sulfonated diels alder poly(phenylene) (SDAPP) with IECs ≥ 1.8 meq g⁻¹ is comparable to Nafion 212 under fully humidified conditions at 80 °C. However, as relative humidity is reduced, performance loss is substantial for SDAPP when compared to Nafion 212. This loss can be attributed to the large drop in proton conductivity in SDAPP as relative humidity is reduced; the proton conductivity of SDAPP with an IEC of 2.3 meq g⁻¹ dropped from 0.117 S cm⁻¹ to 0.001 S cm⁻¹ as the relative humidity was reduced from 100% to 25% at 80 °C. Methanol fuel cell experiments using 3 M methanol result in a 60 mV performance improvement at 25 mA cm⁻² when using SDAPP with an IEC of 1.2 meq g⁻¹ instead of Nafion 212. This improvement is due to lower methanol permeability of SDAPP (1.4 meq g⁻¹) over Nafion 212, with SDAPP films having methanol permeabilities less than 25% of Nafion 212.     

Four-quadrant analog multiplier based on CMOS inverters

In the article a new implementation of four-quadrant analog multiplier in CMOS technology is proposed. The circuit is based exclusively on CMOS inverters (or similar two-transistor blocks) and operates using quarter square technique. The outstanding feature of the circuit is an extreme suitability for low voltage operation and full compatibility with digital CMOS, since there are only two transistors stacked-up between supply rails. Thus the supplying voltage of this circuit class is the lowest possible one for any particular CMOS technology. The operation principle based on symbolic analysis with simple square model has been fully confirmed by simulations with BSIM3v3 models provided by different silicon foundries and verified experimentally using one of them.     

Plane contact problems with frictional heating for a vertically layered half-space

The paper deals with a contact problem of a moving infinitely long punch on the boundary plane of vertically laminated half-space. The problem is solved within the homogenized model with microlocal parameters and under some physical assumptions. By using Fourier transforms the problem is reduced to a integral equation, which is solved numerically. The analysis of temperature and stress distributions and Barber’s contact parameter is presented.