Power Factor Correction Using Bridgeless Boost Topology

Power quality is becoming a major concern for many electrical users. The high power non linear loads (such as adjustable speed drives, arc furnace, static power converter etc) and low power loads (such as computer, fax machine etc) produce voltage fluctuations, harmonic currents and an inequality in network system which results into low power factor operation of the power system. The devices commonly used in industrial, commercial and residential applications need to go through rectification for their proper functioning and operation. Due to the increasing demand of these devices, the line current harmonics create a major problem by degrading the power factor of the system thus affecting the performance of the devices. Hence there is a need to reduce the input line current harmonics so as to improve the power factor of the system. This has led to designing of Power Factor Correction circuits. Power Factor Correction (PFC) involves two techniques, Active PFC and Passive PFC. An active power factor circuit using Boost Converter is used for improving the power factor. This thesis work analyzes the procedural approach and benefits of applying Bridgeless Boost Topology for improving the power factor over Boost Converter Topology. A traditional design methodology Boost Converter Topology is initially analyzed and compared with the Bridgeless Boost topology and the overall Power Factor (PF) can be improved to the expectation. Method of re-shaping the input current waveform to be similar pattern as the sinusoidal input voltage is done by the Boost converter and the related controls that act as a Power Factor Correction (PFC) circuit. Higher efficiency can be achieved by using the Bridgeless Boost Topology. In this paper simulation of Boost Converter topology and Bridgeless PFC boost Converter is presented. Performance comparisons between the conventional PFC boost Converter and the Bridgeless PFC Boost Converter is done

Assessment of surface water quality using hierarchical cluster analysis

This study was carried out to assess the physicochemical quality river Varuna inVaranasi,India. Water samples were collected from 10 sites during January-June 2015. Pearson correlation analysis was used to assess the direction and strength of relationship between physicochemical parameters. Hierarchical Cluster analysis was also performed to determine the sources of pollution in the river Varuna. The result showed quite high value of DO, Nitrate, BOD, COD and Total Alkalinity, above the BIS permissible limit. The results of correlation analysis identified key water parameters as pH, electrical conductivity, total alkalinity and nitrate, which influence the concentration of other water parameters. Cluster analysis identified three major clusters of sampling sites out of total 10 sites, according to the similarity in water quality. This study illustrated the usefulness of correlation and cluster analysis for getting better information about the river water quality.International Journal of Environment Vol. 5 (1) 2016,  pp: 32-44</p

Cerebrospinal fluid cytokines and matrix metalloproteinases in human immunodeficiency seropositive and seronegative patients of tuberculous meningitis

Background: Some important clinical differences exist between human immunodeficiency virus (HIV)-seropositive and HIV-seronegative patients. Alterations in the cerebrospinal fluid (CSF) cytokines and matrix metalloproteinase have been noted in tuberculous meningitis. In HIV-infected patients, the immunopathogenesis is expected to be different. Materials and Methods: In this study, 64 patients of tuberculous meningitis (28 HIV seropositive and 36 seronegative) were included. The patients were followed up for six months. Cerebrospinal fluid (CSF) samples of tuberculous meningitis patients and 20 controls were subjected to tissue necrosis factor (TNF)-α, interleukin (IL)-1β, interferon (IFN)-γ, IL-10, matrix metalloproteinase (MMP)-2, and MMP-9 estimations. The levels were correlated with the patients′ baseline clinical characteristics, CSF parameters, neuroimaging findings, and the outcome. The outcome was assessed and modified with the Barthel index. Results: The CSF cytokines and MMP levels were significantly elevated in tuberculous meningitis when compared with the controls. There was no significant difference seen between HIV seropositive and seronegative tuberculous meningitis, except for the IL-1β level, which was significantly lower in the HIV-infected patients. The cytokine and MMP levels did not correlate with the baseline clinical characteristics, disease severity, cerebrospinal fluid characteristics, neuroimaging findings, and outcome. Conclusion: In conclusion, HIV infection did not affect a majority of the CSF cytokines and MMP levels in tuberculous meningitis except for IL-1β level. None of the estimated inflammatory parameters correlated with the outcome

Function and Structure of MalA/MalA′, Iterative Halogenases for Late-Stage C–H Functionalization of Indole Alkaloids

Malbrancheamide is a dichlorinated fungal indole alkaloid isolated from both <i>Malbranchea aurantiaca</i> and <i>Malbranchea graminicola</i> that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]­diazaoctane core. The introduction of chlorine atoms on the indole ring of malbrancheamide differentiates it from other members of this family and contributes significantly to its biological activity. In this study, we characterized the two flavin-dependent halogenases involved in the late-stage halogenation of malbrancheamide in two different fungal strains. MalA and MalA′ catalyze the iterative dichlorination and monobromination of the free substrate premalbrancheamide as the final steps in the malbrancheamide biosynthetic pathway. Two unnatural bromo-chloro-malbrancheamide analogues were generated through MalA-mediated chemoenzymatic synthesis. Structural analysis and computational studies of MalA′ in complex with three substrates revealed that the enzyme represents a new class of zinc-binding flavin-dependent halogenases and provides new insights into a potentially unique reaction mechanism