Pulse plating effect on microstructure and corrosion properties of Zn–Ni alloy coatings

The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn₂₁Ni₅ phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity of grain distribution were established to be the main factors determining corrosion behaviour of the coating. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005     

Estimation scheme for level-dependent uncertainty of analytical result: application for determination of 1-hydroxypyrene in urine

The estimation scheme of uncertainty of determination of 1-hydroxypyrene (1-OHP) in urine was developed analysing the main stages of the analytical procedure: (1) preparation of 1-OHP standards, (2) creation of the calibration curve for the high performance liquid chromatography (HPLC) analysis method with the evaluation of recovery, (3) measuring procedure of aliquot of urine, (4) adjusting the pH of aliquot and hydrolysis with enzyme, (5) solid phase extraction, (6) concentration of the extract, (7) injection of the extract to chromatograph and analysing by the HPLC method, (8) calculation of 1-OHP mass from the calibration curve, (9) calculation of 1-OHP concentration in urine. The evaluation of the uncertainty is based on quantification of individual components. Combined uncertainty was calculated using the law of propagation of uncertainties according to the EURACHEM/CITAC guidelines. Level dependence of the uncertainty arises from the calibration curve. The limits of detection and quantification were found to be equal to 0.03 and 0.1 ng/mL, respectively. The calculated expanded level-dependent uncertainty covers 47–27–25% within the concentration range 0.03–0.1–0.4 ng/mL with the materials and equipment used. These parameters could easily be recalculated according to the proposed scheme if there are some changes in the analysis procedure.     

Sonochemical effectiveness factor (eUS) in the reactors for wastewater treatment by sono-Fenton oxidation: Novel considerations

A comprehensive algorithm was recently proposed for calculation of the sonochemical effectiveness factor and wastewater treatment modeling. The presented approach implies that ultrasound is an auxiliary source of free radicals in Fenton type reactions; introduction of ultrasound represents an enhancement of pollutant degradation rates. The sonochemical effectiveness factor was introduced in kinetic models as the e_US factor (Gr?i? et al., 2012 [1]). As a substantial follow-up, this study presents novel considerations. The e_US factor was modeled as a function of employed frequency, actual cavitation-related power intensity of ultrasound and a portion of the cavitationally active zone, i.e. dimensionless active volume. The effect of temperature was disregarded in the present model considerations. Cavitationally active zone in reactors was determined based on the erosion of aluminum foil, resulting in cone-shaped space arising from transducer.In the present study, sonochemical treatment of industrial wastewater containing HCOONa as organic pollutant was performed using different equipment: ultrasonic baths (UB1, UB2 and UB3), cylindrical reactor with homogenizer (HCR) and three-frequency hexagonal cell, i.e. ultrasonic pilot reactor prototype (PP). Explored frequency range was from 20 to 120 kHz. Homogeneous and heterogeneous Fenton-type sonochemical processes, US/Fe(II)(FeSO₄,aq.)/H₂O₂ and US/Fe(II)(steel-plate)/H₂O₂, respectively, applied to industrial wastewater were investigated in terms of mineralization kinetics. Newly modeled e_US factor was introduced in corresponding kinetic models and the overall model was validated. Kinetic parameters of Fenton process were treated as independent of ultrasound, since e_US factor consists of cavitation-related phenomena responsible for the mineralization rate enhancement. In average, a 21% increase of mineralization efficiency was achieved using a single frequency, while more than 70% increase can be achieved by combining 20, 68 and 120 kHz in PP.     

Decidability of Some Classes of Modal Logic

We describe a modal sequential calculus some modal rules of which do not contain duplications of the main formula. We also prove its equivalence to the modal calculus S4 and the decidability of some classes of formulas containing only oneplace predicate variables.     

Bidegree (2,1) parametrizable surfaces in projective 3-space

The main purpose of this paper is to study projective classes of bidegree (2,1) parametrizable surfaces in a real projective 3-space. It turns out that the implicit degree of such surfaces is two, three, or four, and singular curves have degree three. We describe all possibilities for singular curves and pinch points on such surfaces. The presentation has been made from the point of view of analytic geometry and does not presume a deep knowledge of algebraic geometry. Partially supported by the Lithuanian State Science and Studies Foundation. Vilnius University, Naugarduko 24, 2006 Vilnius, Lithuania. Published in Lietuvos Matematikos Rinkinys, Vol. 38, No. 3, pp. 379–402, July–September, 1998.     

NEW SEMISYNTHETIC CEPHALOSPORINS WITH ANTIBACTERIAL,ANTIVIRAL AND ANTIFUNGAL ACTIVITY

Abstract

The synthesis of new derivatives of thiazolidine 2-alkylidene-4-on-5-acetamidocephalosporanic acids or thiazolidine 2-arylidenazino-4-on-5-acetamidocephalosporanic acids and their salts of general formula (I) has been achieved.