Growth and characterization of micro and nanostructures of lead telluride (PbTe) by thermal evaporation method

Lead telluride micro and nanostructures have been grown on silicon and glass substrates by a simple thermal evaporation of PbTe in high vacuum of 3 x 10(-5) mbar. Growth was carried out for two different distances between the evaporation source and the substrates. Synthesized products consist of nanorods and micro towers for 2.4 cm and 3.4 cm of distance between the evaporation source and the substrates respectively. X-ray diffraction and transmission electron microscopy studies confirmed crystalline nature of the nanorods and micro towers. Nanorods were grown by vapor solid mechanism. Each micro tower consists of nano platelets and is capped with spherical catalyst particle at their end, suggesting that the growth proceeds via vapor-liquid-solid (VLS) mechanism. EDS spectrum recorded on the tip of the micro tower has shown the presence of Pb and Te confirming the self catalytic VLS growth of the micro towers. These results open up novel synthesis methods for PbTe nano and microstructures for various applications.

Fine scale characterization of surface/subsurface and nanosized debris particles on worn Cu-10 % Pb nanocomposites

The identification of the damage mechanisms involved in the wear process demands the finer scale characterization of the surface, as well as the subsurface region of the wear scar region, and to this end, this article discusses the results obtained with Cu-10 wt% Pb-based metallic nanocomposites using a host of characterization techniques, including transmission electron microscopy and ion milling microscopy. Apart from finer scale characterization to understand deformation and cracking during the wear process, X-ray photoelectron spectroscopy analysis of wear debris confirms the occurrence of oxidation of Pb phase to Pb3O4. In order to understand the role of oxides on friction and wear, sliding wear tests in argon were also carried out and such tests did not result in the formation of any tribo-oxides, as confirmed using electron probe microanalysis. Conclusively, oxidative wear is attributed as the dominant wear mechanism in ambient conditions for Cu-10 wt% Pb composite.

Synthesis and characterization of porous flowerlike alpha-Fe2O3 nanostructures for supercapacitor application

Porous flower-like alpha-Fe2O3 nanostructures synthesized by an ethylene glycol mediated self-assembly process are crystalline and porous with BET surface area of 64.6 m(2) g(-1). The discharge capacitance is 127 F g(-1) when the electrodes are cycled in 0.5 M Na2SO3 at a current density of 1 A g(-1). Capacitance retention after 1000 cycles is about 80% of the initial capacitance. The high discharge capacitance and its retention are attributed to high surface area and porosity of the iron oxide. As the iron oxides are inexpensive, the nano alpha-Fe2O3 is expected to be of potential use for supercapacitor application.

Characterization and microhardness of Co-W coatings electrodeposited at different pH using gluconate bath: a comparative study

Electrodeposition of Co-W alloy coatings has been carried out with DC and PC using gluconate bath at different pH. These coatings are characterized for their structure, morphology and chemical composition by X-ray diffraction, field emission scanning electron microscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy (XPS). Alloy coatings plated at pH8 are crystalline, whereas coatings electrodeposited at pH5 are nanocrystalline in nature. XPS studies have demonstrated that as-deposited alloy plated at pH8 with DC contain only Co2+ and W6+ species, whereas that alloy plated at pH5 has significant amount of Co-0 and W-0 along with Co2+ and W6+ species. Again, Co2+ and W6+ are main species in all as-deposited PC plated alloys in both pH. Co-0 concentration increases upon successive sputtering of all alloy coatings. In contrast, mainly W6+ species is detected in the following layers of all alloys plated with PC. Alloys plated at pH5 show higher microhardness compared to their pH8 counterparts.

Biochemical characterization of C4 protein of cotton leaf curl Kokhran virus-Dabawali

Background: Cotton leaf curl Kokhran Virus-Dabawali (CLCuKV-Dab) is a monopartite begomovirus encoding two proteins V1 and V2 in the virion sense and four proteins Cl, C2, C3 and C4 in the complementary sense. The C4 protein of monopartite begomoviruses has been implicated to play a role in symptom determination and virus movement. The present work aims at the biochemical characterization of this protein. Methods: The C4 protein of CLCuKV-Dab was purified in fusion with GST and tested for the ability to hydrolyze ATP and other phosphate containing compounds. ATPase activity was assayed by using radiolabeled gamma-32P]-ATP and separating the product of reaction by thin layer chromatography. The hydrolysis of other compounds was monitored by the formation of a blue colored phosphomolybdate complex which was estimated by measuring the absorbance at 655 nm. Results: The purified GST-C4 protein exhibited metal ion dependent ATPase and inorganic pyrophosphatase activities. Deletion of a sequence resembling the catalytic motif present in phosphotyrosine phosphatases resulted in 70% reduction in both the activities. Mutational analysis suggested arginine 13 to be catalytically important for the ATPase and cysteine 8 for the pyrophosphatase activity of GST-C4. Interaction of V2 with GST-C4 resulted in an increase in both the enzymatic activities of GST-C4. Conclusions: The residues important for the enzymatic activities of GST-C4 are present in a motif different from the classical Walker motifs and the non-classical ATP binding motifs reported so far. General significance: The C4 protein of CLCuKV-Dab, a putative natively unfolded protein, exhibits enzymatic activities.

Structural characterization and molecular order of rodlike mesogens with three- and four-ring core by XRD and C-13 NMR spectroscopy

Structural characterizations using XRD and C-13 NMR spectroscopy of two rodlike mesogens consisting of (i) three phenyl ring core with a polar cyano terminal and (ii) four phenyl ring core with flexible dodecyl terminal chain are presented. The three-ring-core mesogen with cyano terminal exhibits enantiotropic smectic A phase while the four-ring mesogen reveals polymesomorphism and shows enantiotropic nematic, smectic C, and tilted hexatic phases. The molecular organization in the three-ring mesogen is found to be partial bilayer smectic Ad type, and the interdigitation of the molecules in the neighboring layers is attributed to the presence of the polar terminal group. For the four-ring mesogen, the XRD results confirm the existence of the smectic C and the tilted hexatic mesophases. A thermal variation of the layer spacing across the smectic C phase followed by a discrete jump at the transition to the tilted hexatic phase is also observed. The tilt angles have been estimated to be about 45 degrees in the smectic C phase and about 40 degrees in tilted hexatic phase. C-13 NMR results indicate that in the mesophase the molecules are aligned parallel to the magnetic field. From the C-13-H-1 dipolar couplings determined from the 2D experiments, the overall order parameter for the three-ring mesogen in its smectic A phase has been estimated to be 0.72 while values ranging from 0.88 to 0.44 have been obtained for the four-ring mesogen as it passes from the tilted hexatic to the nematic phase. The orientations of the different rings of the core unit with respect to each other and also with respect to the long axis of the molecule have also been obtained.

Deposition and characterization of pure and Cd doped SnO2 thin films by the nebulizer spray pyrolysis (NSP) technique

Pure and cadmium doped tin oxide thin films were deposited on glass substrates from aqueous solution of cadmium acetate, tin (IV) chloride and sodium hydroxide by the nebulizer spray pyrolysis (NSP) technique. X-ray diffraction reveals that all films have tetragonal crystalline structure with preferential orientation along (200) plane. On application of the Scherrer formula, it is found that the maximum size of grains is 67 nm. Scanning electron microscopy shows that the grains are of rod and spherical in shape. Energy dispersive X-ray analysis reveals the average ratio of the atomic percentage of pure and Cd doped SnO2 films. The electrical resistivity is found to be 10(2) Omega cm at higher temperature (170 degrees C) and 10(3) Omega cm at lower temperature (30 degrees C). Optical band gap energy was determined from transmittance and absorbance data obtained from UV-vis spectra. Optical studies reveal that the band gap energy decreases from 3.90 eV to 3.52 eV due to the addition of Cd as dopant with different concentrations.

C12-Helix development in ()n sequences - spectroscopic characterization of Boc-Aib-4(R)Val]-OMe oligomers

The solution conformations of the -hybrid oligopeptides Boc-Aib-4(R)Val]n-OMe (n = 1-8) in organic solvents have been probed by NMR, IR, and CD spectroscopic methods. In the solid state, this peptide series favors C12-helical conformations, which are backbone-expanded analogues of 310 helices in -peptide sequences. NMR studies of the six- (n = 3) and 16-residue (n = 8) peptides reveal that only two NH protons attached the N-terminus residues Aib(1) and 4(R)Val(2) are solvent-exposed. Sequential NiH-Ni+1H NOEs characteristic of local helical conformations are also observed at the residues. IR studies establish that chain extension leads to a large enhancement in the intensities of the hydrogen-bonded NH stretching bands (3343-3280 cm-1), which suggest elongation of intramolecularly hydrogen-bonded structures. The development of C12-helical structures upon lengthening of the sequence is supported by the NMR and IR observations. The CD spectra of the ()n peptides reveal a negative maximum at ca. 206 nm and a positive maximum at ca. 192 nm, spectral feature that are distinct from those of 310 helices in -peptides.

Characterization and magnetic response of multiwall carbon nanotubes filled with iron nanoparticles of different aspect ratios

Three samples of multiwall carbon nanotubes (MWCNT) TF200, TF150 and TF100, where T and F stand for toluene and ferrocene respectively, and numeral denotes the amount (mg) of ferrocene] filled with iron-nanoparticles (Fe-NPs) of different aspect ratios are grown by chemical vapor deposition of toluene-ferrocene mixture. Energy dispersive X-ray analysis shows a systematic variation in the intensities of peak corresponding to Fe, indicating that Fe is present in different amounts in the three MWCNT samples. The lengths of Fe-NPs lie in the range of 200-250; 80-120; and 30-40 nm for TF200, TF150 and TF100, respectively, as estimated statistically from transmission electron microscopy micrographs. However, the diameter of the encapsulated Fe-NPs does not vary significantly for different samples and is 20-30 nm for all samples. Hysteresis loop measurements on these MWCNT samples were done at 10, 150 and 300 K up to an applied field of 1.5 T. At 10 K, values of coercivity are 2584, 2315, and 2251 Oe for TF200, TF150 and TF100 respectively. This is attributed to the strong shape anisotropy of the Fe-NPs and significant dipolar interactions between them. Further, M-H loops reveal that saturation magnetization of TF200 is almost four times that of TF100 at all temperatures.

Hydrothermal synthesis and characterization of bis(4,4 `-bipyridinium) dodecatungstosilicate dihydrate

Hydrothermal synthesis and structural characterization of a new organic polyoxometalate, namely, bis(4,4'-bipyridinium) dodecatungstosilicate dihydrate, 4,4'-bipyH(2)](2)SiW12O40]center dot 2H(2)O (1) is reported. The crystal structure of (1) consists of a SiW12O40](4-) Keggin anion situated on a two-fold axis, two unique 4,4'-bipyridinium cations, one of which is situated on a two-fold axis, and two independent lattice water molecules. The cations and anions are linked by H-bonding.

Characterization of Birkhoff-James orthogonality

The Birkhoff-James orthogonality is a generalization of Hilbert space orthogonality to Banach spaces. We investigate this notion of orthogonality when the Banach space has more structures. We start by doing so for the Banach space of square matrices moving gradually to all bounded operators on any Hilbert space, then to an arbitrary C*-algebra and finally a Hilbert C*-module.

Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India

Hydrogeological and climatic effect on chemical behavior of groundwater along a climatic gradient is studied along a river basin. `Semi-arid' (500-800 mm of mean annual rainfall), `sub-humid' (800-1,200 mm/year) and `humid' (1,200-1,500 mm/year) are the climatic zones chosen along the granito-gneissic plains of Kabini basin in South India for the present analysis. Data on groundwater chemistry is initially checked for its quality using NICB ratio (<+/- 5 %), EC versus TZ+ (similar to 0.85 correlation), EC versus TDS and EC versus TH analysis. Groundwater in the three climatic zones is `hard' to `very hard' in terms of Ca-Mg hardness. Polluted wells are identified (> 40 % of pollution) and eliminated for the characterization. Piper's diagram with mean concentrations indicates the evolution of CaNaHCO3 (semi-arid) from CaHCO3 (humid zone) along the climatic gradient. Carbonates dominate other anions and strong acids exceeded weak acids in the region. Mule Hole SEW, an experimental watershed in sub-humid zone, is characterized initially using hydrogeochemistry and is observed to be a replica of entire sub-humid zone (with 25 wells). Extension of the studies for the entire basin (120 wells) showed a chemical gradient along the climatic gradient with sub-humid zone bridging semi-arid and humid zones. Ca/Na molar ratio varies by more than 100 times from semi-arid to humid zones. Semi-arid zone is more silicaceous than sub-humid while humid zone is more carbonaceous (Ca/Cl similar to 14). Along the climatic gradient, groundwater is undersaturated (humid), saturated (sub-humid) and slightly supersaturated (semi-arid) with calcite and dolomite. Concentration-depth profiles are in support of the geological stratification i.e., not approximate to 18 m of saprolite and similar to 25 m of fracture rock with parent gneiss beneath. All the wells are classified into four groups based on groundwater fluctuations and further into `deep' and `shallow' based on the depth to groundwater. Higher the fluctuations, larger is its impact on groundwater chemistry. Actual seasonal patterns are identified using `recharge-discharge' concept based on rainfall intensity instead of traditional monsoon-non-monsoon concept. Non-pumped wells have low Na/Cl and Ca/Cl ratios in recharge period than in discharge period (Dilution). Few other wells, which are subjected to pumping, still exhibit dilution chemistry though water level fluctuations are high due to annual recharge. Other wells which do not receive sufficient rainfall and are constantly pumped showed high concentrations in recharge period rather than in discharge period (Anti-dilution). In summary, recharge-discharge concept demarcates the pumped wells from natural deep wells thus, characterizing the basin.

Growth and characterization of L-histidinium 2-nitrobenzoate single crystals: A new NLO material

Crystals of a new nonlinear optical (NLO) material, viz., L-histidinium 2-nitrobenzoate (LHNB) (1) were grown by slow evaporation of an aqueous solution containing equimolar concentrations of L-histidine and 2-nitrobenzoic acid. The structure of the title compound which crystallizes in the non-centrosymmetric monoclinic space group P2(1) was elucidated using single crystal X-ray intensity data. The UV-Vis-NIR spectrum of 1 reveals its transparent nature while the vibrational spectra confirm the presence of the functional groups in 1. The thermal stability and second harmonic generation (SHG) conversion efficiency of 1 were also investigated. (C) 2012 Elsevier GmbH. All rights reserved.

In vitro and in vivo characterization of designed immunogens derived from the CD-helix of the stem of influenza hemagglutinin

The conserved stem domain of influenza virus hemagglutinin (HA) is a target for broadly neutralizing antibodies and a potential vaccine antigen for induction of hetero-subtypic protection. The epitope of 12D1, a previously reported bnAb neutralizing several H3 subtype influenza strains, was putatively mapped to residues 76-106 of the CD-helix, also referred to as long alpha helix (LAH) of the HA stem. A peptide derivative consisting of wt-LAH residues 76-130 conjugated to keyhole limpet hemocyanin was previously shown to confer robust protection in mice against challenge with influenza strains of subtypes H3, H1, and H5 which motivated the present study. We report the design of multiple peptide derivatives of LAH with or without heterologous trimerization sequences and show that several of these are better folded than wt-LAH. However, in contrast to the previous study immunization of mice with wt-LAH resulted in negligible protection against a lethal homologous virus challenge, while some of the newly designed immunogens could confer weak protection. Combined with structural analysis of HA, our data suggest that in addition to LAH, other regions of HA are likely to significantly contribute to the epitope for 12D1 and will be required to elicit robust protection. In addition, a dynamic, flexible conformation of isolated LAH peptide may be required for eliciting a functional anti-viral response. Proteins 2013; 81:1759-1775. (c) 2013 Wiley Periodicals, Inc.

Identification and characterization of starvation induced msdgc-1 promoter involved in the c-di-GMP turnover

C-di-GMP Bis-(3'-5')-cyclic-dimeric-guanosine monophosphate], a second messenger is involved in intracellular communication in the bacterial species. As a result several multi-cellular behaviors in both Gram-positive and Gram-negative bacteria are directly linked to the intracellular level of c-di-GMP. The cellular concentration of c-di-GMP is maintained by two opposing activities, diguanylate cyclase (DGC) and phosphodiesterase (PDE-A). In Mycobacterium smegmatis, a single bifunctional protein MSDGC-1 is responsible for the cellular concentration of c-di-GMP. A better understanding of the regulation of c-di-GMP at the genetic level is necessary to control the function of above two activities. In this work, we have characterized the promoter element present in msdgc-1 along with the + 1 transcription start site and identified the sigma factors that regulate the transcription of msdgc-1. Interestingly, msdgc-1 utilizes SigA during the initial phase of growth, whereas near the stationary phase SigB containing RNA polymerase takes over the expression of msdgc-1. We report here that the promoter activity of msdgc-1 increases during starvation or depletion of carbon source like glucose or glycerol. When msdgc-1 is deleted, the numbers of viable cells are similar to 10 times higher in the stationary phase in comparison to that of the wild type. We propose here that msdgc-1 is involved in the regulation of cell population density. (C) 2013 Elsevier B.V. All rights reserved.