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- Author or Editor: L. Marta x
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Abstract
This work reports the study of Bi4V2–xBaxO11–1.5x (0.02≤x≤0.50) series, which is a potential source of solid electrolytes to apply in oxygen sensors. X-ray powder diffraction was used to point out the formation of major ionic conductive phases and minor ones. The modifications of vanadate substructure were probed, at short range, by Fourier-transform infrared spectroscopy. Differential scanning calorimetry evidenced the formation of tetragonal γ phase, which can be ionic conductive, for x=0.14.
Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin- (Rif) and ampicillin- (Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rif r mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.
Thermal and structural investigation of some oxalato-niobium complexes
III. Strontium tris(oxalato)oxoniobate
Abstract
The paper presents a new, nonconventional method, based upon coprecipitation, for the synthesis of niobium oxidic compounds. The coprecipitation product of niobic acid with calcium oxalate was used as precursor. Calcium metaniobate was obtained by appropriate thermal treatment of the coprecipitate. The coprecipitation mechanism was studied and the optimal conditions for quantitative precipitation of niobium and calcium were established. The mechanism of thermal decomposition of the coprecipitate was investigated by means of differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, calcium metaniobate, is formed at 730°C.
Abstract
The paper reports a new, nonconventional method for the preparation of oxygen-containing niobium compounds, based upon coprecipitation. The coprecipitation product of niobic acid with lead oxalate was used as precursor. Lead metaniobate was obtained by proper thermal treatment of the coprecipitate. The coprecipitate mechanism was studied and the optimal conditions for quantitative precipitation of niobium and lead were established. The mechanism of thermal decomposition of the coprecipitate was investigated by differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, lead metaniobate, is formed at 850C.
In our present study we aimed to recognize the temporal and spatial patterns of Noctuinae communities (Lep.Noctuidae)of four differently managed apple orchards laying in different localities of Hungary.Data were obtained by light trap collection. The quantitative data resulting from our investigations were analyzed by multivariate methods and were also analyzed by their diversity characteristics.As a result connections were found regarding the diversities of species and individuals,the patterns of occurrence and phenological properties.The studies were based on 8497 individuals of 39 species.
The knowledge of the population dynamical characteristics of the pests fundamentally determines the success of the plant protection prognosis. In this paper we examine the possibilities of the utilization of the information about the population dynamical stability that we get from field examination data. We take into account neighbouring data pairs from data series regarding the change of insect density counted at stated intervals. Using these pairs of values – from the tendency of the absolute and relative changes – we can draw conclusion on the stability of the individual density values or on the stability of the whole dynamical pattern.
The paper presents a new, non-traditional method for the synthesis of barium metaniobate, BaNb2O6, and of a mixed barium-strontium metaniobate, Ba0.29Sr0.71Nb2O6, through the thermal decomposition of coprecipitation products. The conditions of quantitative precipitation of the metals as niobic acid and barium or barium-strontium oxalate were established. The mechanism of thermal decomposition of the coprecipitate was deduced from differential thermal analysis and X-ray diffraction date. Barium metaniobate forms at 470°C, below the temperature required in the synthesis based upon the solid-state reaction between Nb2O5 and BaCO3 (1100°C). The mixed barium-strontium compound is formed at 700°C, below the 1100°C used in the reaction between Nb2O5, BaCO3 and SrCO3.
Thermal and kinetic study of statins
Simvastatin and lovastatin
Abstract
Statins are a group of lipoproteins that are used in medicine to treat the high cholesterol level. The effectiveness of statins in reducing the cholesterol level is significant and in long time scale the reduction of the cholesterol level helps to avoid the incidence of degenerative diseases. Simvastatin and lovastatin are belonging to the ‘statins’ family, one of the pharmacologic groups used in the control of dislipidemy. The objective of this work is the thermal stability and kinetic study of the active forms of simvastatin and lovastatin. Thermal data indicated that lovastatin and simvastatin are stable up to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively. For melting temperatures DSC curves showed good correlation with the literature data. Comparing the activation energies of the statins at heating rate of 10°C min–1, lovastatin is more stable than simvastatin under the applied experimental conditions.
