Dispersion of resistivity anomalies in critical binary liquid systems

The critical resistivity in the binary liquid systems n-C7H16 + CH3OH and CS2 + CH3NO2 is measured from 10 Hz to 100 kHz. There is no noticeable effect of the frequency on the resistivity singularities. Thus any contribution from dielectric dispersion is not appreciable.

Autophosphorylation of Ser(428) of EhC2PK Plays a Critical Role in Regulating Erythrophagocytosis in the Parasite Entamoeba histolytica

The protozoan parasite Entamoeba histolytica can invade both intestinal and extra intestinal tissues resulting in amoebiasis. During the process of invasion E. histolytica ingests red blood and host cells using phagocytic processes. Though phagocytosis is considered to be a key virulence determinant, the mechanism is not very well understood in E. histolytica. We have recently demonstrated that a novel C2 domain-containing protein kinase, EhC2PK is involved in the initiation of erythrophagocytosis. Because cells overexpressing the kinase-dead mutant of EhC2PK displayed a reduction in erythrophagocytosis, it appears that kinase activity is necessary for initiation. Biochemical analysis showed that EhC2PK is an unusual Mn2+-dependent serine kinase. It has a trans-autophosphorylated site at Ser(428) as revealed by mass spectrometric and biochemical analysis. The autophosphorylation defective mutants (S428A, KD Delta C) showed a reduction in auto and substrate phosphorylation. Time kinetics of in vitro kinase activity suggested two phases, an initial short slow phase followed by a rapid phase for wild type protein, whereas mutations in the autophosphorylation sites that cause defect (S428A) or conferred phosphomimetic property (S428E) displayed no distinct phases, suggesting that autophosphorylation may be controlling kinase activity through an autocatalytic mechanism. A reduction and delay in erythrophagocytosis was observed in E. histolytica cells overexpressing S428A and KD Delta C proteins. These results indicate that enrichment of EhC2PK at the site of phagocytosis enhances the rate of trans-autophosphorylation, thereby increasing kinase activity and regulating the initiation of erythrophagocytosis in E. histolytica.

A trade-off between maxima in efficiency and specific work output of super- and trans-critical CO2 Brayton cycles

Several operational aspects for thermal power plants in general are non-intuitive and involve simultaneous optimization of a number of operational parameters. In the case of solar operated power plants, it is even more difficult due to varying heat source temperatures induced by variability in insolation levels. This paper introduces a quantitative methodology for load regulation of a CO2 based Brayton cycle power plant using the `thermal efficiency and specific work output' coordinate system. The analysis shows that a transcritical CO2 cycle offers more flexibility under part load performance than the supercritical cycle in case of non-solar power plants. However, for concentrated solar power, where efficiency is important, supercritical CO2 cycle fares better than transcritical CO2 cycle. A number of empirical equations relating heat source temperature, high side pressure with efficiency and specific work output are proposed which could assist in generating control algorithms. (C) 2015 Elsevier B.V. All rights reserved.