Voltage stability : some reflections on Q-V characteristics of loads

Considering voltage stability as a static viability problem, this paper takes a particular concern of Q-V characteristics and reflects on certain notions that do not seem to have been explicitly mentioned or derived in the existing documented literature. The equations of Q-V characteristics are rederived in exactness, some salient points on the curve are discovered and analysed. The results of the analysis are illustrated through a case study

Solvent effect on the fluorescence quenching of biologically active carboxamide by aniline and carbon tetrachloride in different solvents using S-V plots

The fluorescence quenching studies of carboxamide namely (E)-N-(3-Chlorophenyl)-2-(3,4,5-trimethoxybenzylideneamino)-4,5,6,7 tetrahydrobenzob]thiophene-3-carboxamide ENCTTTC] by aniline and carbon tetrachloride in six different solvents namely toluene, cyclohexane, n-hexane, n-heptane, n-decane and n-pentane have been carried out at room temperature with a view to understand the quenching mechanisms. The Stern-Volmer (S-V) plots have been found to be nonlinear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R' and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R' and D with the values of the encounter distance R and the mutual coefficient D determined using the Edward's empirical relation and Stokes Einstein relation. (C) 2011 Elsevier B.V. All rights reserved.

Diffusion mechanism in XSi2 and X5Si3 (X= Nb, Mo, V) phases

In view of the importance of the suicides in the high temperature applications, the diffusion behaviour is compared in different systems for two types of silicides, XSi2 and X5Si3 (X=Nb, Mo, V). Atomic mechanism of diffusion and defects present in the structure are discussed. In both the phases, Si has faster diffusion rate than the metal species. This is expected from the nearest neighbour (NN) bonds present in the XSi2 phase but rather unusual in the X5Si3 phase. Relative mobilities of the species calculated indicate the presence of high concentration of Si antisites. Moreover, the concentration of the defects is different in different systems to find different diffusion rates.

Synthesis of zero valent iron nanoparticles and application to removal of arsenic(III) and arsenic(V) from water

Recently nano scale zero valent iron particles (nZVI) have been considered as smart adsorbent for environmental and groundwater remediation. Although several synthetic methods are available for the preparation of nZVI, air stable nZVI are not available for remediation works. Further, challenges demand synthesis of nZVI without stabilizers and capping agents. A modified methodology for the synthesis of air stable nZVI has been developed without any capping agents and characterized by powder X-Ray Diffraction (XRD), Scanning Electron Microscopy Energy-dispersive X-Ray (SEM-EDS), Transmission Electron Microscopy (TEM) and X-Ray Photoelectron Spectroscopy (XPS). The results of the present study suggest that the synthetic nZVI are air-stable over a period of one year and consists of particles of 30-40 nm in diameter. Although a layer of less than 3 am thick oxide/hydroxide is observed by TEM and XPS, it appears to be due to oxidation of outer surface during analysis. Adsorption study has shown that the synthetic nZVI are more effective adsorbent than the commercial nZVI and can remove simultaneously arsenite As-III] and arsenate As-V] from water without prior reduction of As-V to As-III. The removal process is adsorptive rather than precipitative and the removal of As-III is greater than that of As-V.

A 12 V Substrate-Integrated PbO2-Activated Carbon Asymmetric Hybrid Ultracapacitor with Silica-Gel-Based Inorganic-Polymer Electrolyte

A 12 V Substrate-Integrated PbO2-Activated Carbon hybrid ultracapacitor (SI-PbO2-AC HUCs) with silica-gel sulfuric acid electrolyte is developed and performance tested. The performance of the silica-gel based hybrid ultracapacitor is compared with flooded and AGM-based HUCs. These HUCs comprise substrate-integrated PbO2 (SI-PbO2) as positive electrodes and high surface-area activated carbon with dense graphite-sheet substrate as negative electrodes. 12 V SI-PbO2-AC HUCs with flooded, AGM and gel electrolytes are found to have capacitance values of 308 F, 184 F, and 269 F at C-rate and can be pulse charged and discharged for 100,000 cycles with only a nominal decrease in their capacitance values. The best performance is exhibited by gel-electrolyte HUCs.

Study of the effect of alkali mixture on V-O bond length in Oxyfluoro Vanadate glasses using Raman spectroscopy

Raman spectroscopic study on Oxyfluoro Vanadate glasses containing various proportions of lithium fluoride and rubidium fluoride was carried out to see an effect of mixture of alkali on vanadium-oxygen (V-O) bond length. Glasses with a general formula 40V(2)O(5) - 30BaF(2) - (30 - x) LiF - xRbF (x = 0-30) were prepared. Room temperature Raman spectra of these glass samples were recorded in back scattering geometry. The data presented is in ``reduced Raman intensity'' form with maximum peak scaled to 100. We have used v = Aexp(BR), where A and B are fitting parameters, to correlate the bond length R with Raman scattering frequency v. We observed that variation in bond length and its distribution about a most probable value can be correlated to the alkali environment present in these glasses. We also observed that all rubidium environment around the network forming unit is more homogenous than all lithium environment.

1.5 V battery driven reduced graphene oxide-silver nanostructure coated carbon foam (rGO-Ag-CF) for the purification of drinking water

A porous carbon foam (CF) electrode modified with a reduced graphene oxide-Ag (rGO-Ag) nanocomposite has been fabricated to purify water. It can perform as an antibacterial device by killing pathogenic microbes with the aid of a 1.5 V battery, with very little power consumption. The device is recycled ten times with good performance for long term usage. It is shown that the device may be implemented as a fast water purifier to deactivate the pathogens in drinking water.

Molecular flexibility tuned emission in ``V'' shaped naphthalimides: Hg(II) detection and aggregation-induced emission enhancement (AIEE)

Four ``V'' shaped 1,8-naphthalimides (1-4) have been synthesized and their fluorescence quantum-yields correlated to their molecular flexibility. The correlation was used for detection of Hg(II) via a chemodosimetric approach. 4 was found to be an AIE active molecule with the formation of fluorescent nanoaggregates.

Diffusion pattern in MSi2 and M5Si3 silicides in group VB (M = V, Nb, Ta) and VIB (M = Mo, W) refractory metal-silicon systems

Group VB and VIB M-Si systems are considered to show an interesting pattern in the diffusion of components with the change in atomic number in a particular group (M = V, Nb, Ta or M = Mo, W, respectively). Mainly two phases, MSi2 and M5Si3 are considered for this discussion. Except for Ta-silicides, the activation energy for the integrated diffusion of MSi2 is always lower than M5Si3. In both phases, the relative mobilities measured by the ratio of the tracer diffusion coefficients, , decrease with an increasing atomic number in the given group. If determined at the same homologous temperature, the interdiffusion coefficients increase with the atomic number of the refractory metal in the MSi2 phases and decrease in the M5Si3 ones. This behaviour features the basic changes in the defect concentrations on different sublattices with a change in the atomic number of the refractory components.

Multichannel-Emissive V-Shaped Boryl-BODIPY Dyads: Synthesis, Structure, and Remarkably Diverse Response toward Fluoride

Three new V-shaped boryl-BODIPY dyads (1-3) were synthesized and structurally characterized. Compounds 1-3 are structurally close molecular siblings differing only in the number of methyl substituents on the BODIPY moiety that were found to play a major role in determining their photophysical behavior. The dyads show rare forms of multiple-channel emission characteristics arising from different extents of electronic energy transfer (EET) processes between the two covalently linked fluorescent chromophores (borane and BODIPY units). Insights into the origin and nature of their emission behavior were gained from comparison with closely related model molecular systems and related photophysical investigations. Because of the presence of the Lewis acidic triarylborane moiety, the dyads function as highly selective and sensitive fluoride sensors with vastly different response behaviors. When fluoride binds to the tricoordinate borane center, dyad 1 shows gradual quenching of its BODIPY-dominated emission due to the ceasing of the (borane to BODIPY) EET process. Dyad 2 shows a ratiometric fluorescence response for fluoride ions. Dyad 3 forms fluoride-induced nanoaggregates that result in fast and effective quenching of its fluorescence intensity just for similar to 0.3 ppm of analyte (i.e., 0.1 equiv 0.26 ppm of fluoride). The small structural alterations in these three structurally close dyads (1 - 3) result in exceptionally versatile and unique photophysical behaviors and remarkably diverse responses toward a single analyte, i.e., fluoride ion.

Novel Rearrangements in the Staphylococcal Cassette Chromosome Mec Type V Elements of Indian ST772 and ST672 Methicillin Resistant Staphylococcus aureus Strains

Staphylococcus aureus is a commensal gram positive bacteria which causes severe and non severe infections in humans and livestock. In India, ST772 is a dominant and ST672 is an emerging clone of Staphylococcus aureus. Both cause serious human diseases, and carry type V SCCmec elements. The objective of this study was to characterize SCCmec type V elements of ST772 and ST672 because the usual PCR methods did not amplify all primers specific to the type. Whole genome sequencing analysis of seven ST772 and one ST672 S. aureus isolates revealed that the SCCmec elements of six of the ST772 isolates were the smallest of the extant type V elements and in addition have several other novel features. Only one ST772 isolate and the ST672 isolate carried bigger SCCmec cassettes which were composites carrying multiple ccrC genes. These cassettes had some similarities to type V SCCmec element from M013 isolate (ST59) from Taiwan in certain aspects. SCCmec elements of all Indian isolates had an inversion of the mec complex, similar to the bovine SCCmec type X. This study reveals that six out of seven ST772 S. aureus isolates have a novel type V (5C2) SCCmec element while one each of ST772 and ST672 isolates have a composite SCCmec type V element (5C2&5) formed by the integration of type V SCCmec into a MSSA carrying a SCC element, in addition to the mec gene complex inversions and extensive recombinations.

Syntheses and structural investigation of some alkali metal ion-mediated (LVO2-)-O-V (L2- = tridentate ONO ligands) species: DNA binding, photoinduced DNA cleavage and cytotoxic activities

Eight alkali metal ion-mediated dioxidovanadium(V), {(VO2L1-6)-O-V} A(H2O)n]proportional to, complexes for A = Li+, Na+, K+ and Cs+, containing tridentate aroylhydrazonate ligands coordinating via ONO donor atoms, are described. All the synthesised ligands and the metal complexes were successfully characterised by elemental analysis, IR, UV-Vis and NMR spectroscopy. X-ray crystallographic investigation of 3, 5-7 shows the presence of distorted NO4 coordination geometries for LVO2- in each case, and varying mu-oxido and/ or mu-aqua bridging with interesting variations correlated with the size of the alkali metal ions: with small Li+, no bridging-O is found but four ion aggregates are found with Na+, chains for K+ and finally, layers for Cs+. Two (5) or three-dimensional (3, 6 and 7) architectures are consolidated by hydrogen bonding. The dioxidovanadium(V) complexes were found to exhibit DNA binding activity due to their interaction with CT-DNA by the groove binding mode, with binding constants ranging from 10(3) to 10(4) M-1. Complexes 1-8 were also tested for DNA nuclease activity against pUC19 plasmid DNA which showed that 6 and 7 had the best DNA binding and photonuclease activity; these results support their good protein binding and cleavage activity with binding constants ranging from 104 to 105 M-1. Finally, the in vitro antiproliferative activity of all complexes was assayed against the HeLa cell line. Some of the complexes (2, 5, 6 and 7) show considerable activity compared to commonly used chemotherapeutic drugs. The variation in cytotoxicity of the complexes is influenced by the various functional groups attached to the aroylhydrazone derivative.