50175 research outputs found
Sort by
Solvent dependent morphology and Co-59 internal field NMR study of Co-aggregates synthesized by a wet chemical method
No full textDifferent shapes of Co-aggregates were synthesized via reduction of a Co salt (CoCl2<bold></bold>6H(2)O) by chemical precipitation using glycerol, ethylene glycol and ethanol as solvents. The effect of solvent on the morphology, fcc or hcp phase-content and the magnetic properties of the synthesized samples were investigated. The Co-aggregates synthesized using glycerol have a dense spherical shape and high saturation magnetization (M-S), whereas ethylene glycol leads to formation of flower-shaped spherical aggregates through loose packing of smaller plate-like particles which have a moderate M-S value. When ethanol was used as a solvent, a dendritic (leaf like)-shape of the aggregates with the lowest M-S value was obtained. The formation of the obtained morphology of the aggregates was explained based on the size of the solvent molecule, the viscosity of the solvent and the number of polar groups (-OH) present in the solvent molecules. The magnetic domain state and domain wall dynamics of all the Co-samples were investigated using Co-59 Internal Field Nuclear Magnetic Resonance (IFNMR) spectroscopy at RT and at 77 K. Through the IFNMR spectroscopy, the presence of gain boundaries, single domain particles and multi-domain particles/aggregates with domain walls associated with fcc and hcp phases were identified and quantified. We observed that the use of ethanol facilitates formation of a higher amount of hcp phase in the sample than the use of glycerol or ethylene glycol
N-Heterocyclic Carbene-Catalyzed Synthesis of alpha-Trifluoromethyl Esters
No full textThe N-heterocyclic carbene (NHC)-catalyzed trifluoromethylation of alpha-chloro aldehydes was developed, allowing straightforward access to valuable alpha-trifluoromethyl ester derivatives. The unique combination of an electrophilic trifluoromethylation reagent with NHC catalysis was the key for the functionalization of a broad range of alpha-chloro aldehydes, and the products are formed in moderate to good yields. Investigations of the enantioselective version of this reaction afforded the enantioenriched products in moderate yields with good ee values
Proteome and Structural Organization of the Knob Complex on the Surface of the Plasmodium Infected Red Blood Cell
No full textPurposeThe cell membrane of the erythrocytes infected with the malaria parasite Plasmodium falciparum undergoes several changes during the course of parasite life cycle and forms protrusions known as knobs' on its surface during the mature trophozoite and schizont stages. The structural organization of knob components especially PfEMP1 on the iRBC surface is the main determinant for the cytoadhesive and rosetting capacity of the iRBC by binding to various host receptors as well as for the variable antigenicity, which is crucial for immunoevasion. Although several studies report individual interactions among knob constituents, a comprehensive identification of the knob proteome is lacking. Experimental designThe detergent-resistant membrane (DRM) rafts are isolated from the infected erythrocyte membrane and knob (KAHRP) positive fractions are subjected to proteomics analysis. In addition, structures of various knob components are modeled and assembled ab initio based on experimentally established protein interactions. ResultsProteins of various functional classes are found to be present in the knobs including the newly identified knob constituents which include host Hsp70, elongation factor 1A, acyl CoA synthetase, and some hypothetical proteins. Ab initio structural prediction of PfEMP1, KHARP, PfEMP2, PfEMP3, and PHIST shows that these proteins are intrinsically disordered and can have varying number of protein-protein interactions depending on their lowest energy structure. Further in silico mathematical modeling of a single repeat unit of PfEMP1-PHIST is present 63-112 times along the periphery of a single knob. Conclusions and clinical relevanceThis study provides structural insight into the organization of the core knob components and uncovers novel proteins as knob components. This structural information can be used for the development of better vaccine design strategies or drug design to destabilize the knob structure, which is a major virulence determinant in P. falciparum malaria
Evolution of texture and asymmetry and its impact on the fatigue behaviour of an in-situ magnesium nanocomposite
No full textA novel in-situ synthesis technique has previously been proposed for the synthesis of magnesium based nano composites, by exploiting the thermodynamic reactions, to fabricate nanoparticles in-situ during the melt processing. Although the microstructural aspects of formation of such nanocomposites have been dealt with previously, the implications of the same on the texture and hence on mechanical properties are not certain. In the present work, the evolution of crystallographic texture and its influence on tension-compression asymmetry (Tensile yield strength divided by Compressive yield strength) and thereby, the impact on fatigue failure mechanisms is studied by comparing the behaviour of Mg-1.8Y/1.53ZnO nanocomposite and its monolithic alloy, Mg-1.8Y. The Mg-1.8Y/1.53ZnO nanocomposite revealed a very strong two component texture, not akin to the weak texture of Mg-1.8Y alloy. The texture was attributed to the loss of Y in the matrix and consumption of Y in formation of Y2O3 nanoparticles in-situ and the formation of the beta(1)' (Mg-Zn') rods during extrusion. Further, this texture exhibited by the nanocomposite favoured high twinning activity under compression, thereby causing strong asymmetry in the tensile and compressive yield strengths. The fatigue tests indicated a superior performance of the nanocomposite as compared to the alloy. The deformation and damage mechanisms, when studied in correlation with the asymmetry revealed that the asymmetric materials exhibit steeper S-N curves as compared to the symmetric materials
Round-table negotiation for fast restoration of connectivity in partitioned wireless sensor networks
No full textThis paper addresses the problem of restoration of connectivity in wireless sensor networks after multiple simultaneous node failures. Such failures of multiple nodes may split the network into several clusters. These clusters are unaware of their own size, surviving nodes and links as well as size and location of other survivor clusters. A distributed and autonomous approach of reconnecting disjoint clusters in a short time is proposed, in which each survivor cluster undergoes a self-discovery process where it compiles information of connected survivors and then sends a negotiator to participate in a round table negotiation and decision-making process. All such negotiators exchange information and decide upon reconnection paths between clusters through known dead node locations and then assign nodes to be deployed on those paths, using available nodes. The negotiators then return to their respective clusters, convey the decision and the reconnection process is carried out. Analytical results of the self-discovery process have been obtained and simulation results on a large network are presented to illustrate the process. It is shown through a detailed comparison with existing methods that the proposed approach achieves reconnection in significantly lower time and compares favorably with respect to other performance metrics as well. (C) 2018 Elsevier B.V. All rights reserved
Supramolecular Switching of Ion-Transport in Nanochannels
No full textNoncovalent approaches to achieve smart ion-transport regulation in artificial nanochannels have garnered significant interest in the recent years because of their advantages over conventional covalent routes. Herein, we demonstrate a simple and generic approach to control the surface charge in mesoporous silica nanochannels by employing pi-electron-rich charged motifs (pyranine-based donors) to interact with the surface of mesoporous silica modified with pi-electron-deficient motifs (viologen-based acceptors) through a range of noncovalent forces, namely, charge-transfer, electrostatic, and hydrophobic interactions. The extent of each of these interactions was independently controlled by molecular design and pH, while employing them in a synergistic or antagonistic fashion to modulate the binding affinity of the charged motifs. This enabled the precise control of the surface charge of the nanochannels to achieve multiple ion-transport states
Spark plasma sintered HA-ZnO ultrafine composite: Mechanical, bactericidal, and cytocompatibility properties
No full textCalcium-phosphate based hydroxyapatite (HA) biomaterials are widely being investigated due to their osseointegration property, but those inherently lack antibacterial property. In the present work, wet-chemically synthesized rod-shaped zinc oxide (ZnO) is embedded in HA and its role as antibacterial agent without compromising cytocompatability property is established. In particular, HA-xZnO (x=0, 5, 10 wt.%) composites were consolidated by spark plasma sintering at 950 degrees C in vacuum. A host of the spectroscopy and microscopy techniques were utilized to analyze the nature of distribution of ZnO as well as surface chemical characteristics. While the bactericidal property is expectedly induced, the elastic modulus as well as cell adhesion property remains uncompromised
Smart Textiles Coated with Eco-Friendly UV-Blocking Nanoparticles Derived from Natural Resources
No full textHerein, eco-friendly iron titanate nanoparticles, FeTiO3 (FT), derived from natural resources (like ilmenite sand) were coated onto cotton fabrics (CF) to develop smart textile with enhanced UV-shielding property. The FT nanoparticles were dispersed in a polyurethane (PU) matrix, and the resulting nanocomposite was coated on CF. In addition, few sandwich architectures were designed by rationally stacking CF coated with PU and FT nanoparticles. The resulting sandwich structures blocked UV rays mainly by absorption. FT nanoparticles were comprehensively characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis, vibrating sample magnetometer, and thermogravimetric analysis. FT was suitably surface-functionalized to enhance the quality of dispersion in PU, thereby facilitating effective coating on CF. The latter was systematically evaluated by microscopic and spectroscopic techniques. In addition, flammability of the coated CF was evaluated and the char was assessed to gain insight into the fire-retardant properties. Interestingly, CF coated with FT exhibited a strong UV-shielding ability in sharp contrast to CF coated with PU. Further, the sandwich architecture consisting of CF with FT and PU resulted in an increase in the ultraviolet-protecting factor value to >50 compared to only PU-coated CF. Our results indicate that the sandwich structure holds excellent promise in the quest of designing smart textiles with enhanced UV shielding
Defluoridation of reject water from a reverse osmosis unit and synthetic water using adsorption
No full textMany parts of the world have excess fluoride in drinking water. At some locations, nitrate is also in excess. Hence, reverse osmosis (RO) units have been installed M several villages in India. Reverse osmosis is a good technique, but it has the disadvantage of discarding a considerable amount of the inlet water as a reject stream. This is an unsustainable way of using water. Two adsorbents, namely, a hybrid anion exchange resin embedded with zirconium oxide nanoparticles (HAIX-Zr), and activated alumina (AA) were used in column experiments. For water containing only F-, HAIX-Zr had a better capacity than AA. The same trend was observed with synthetic water samples containing other ions in addition to F-.(-) However, for RO reject, the converse was true, and the capacities of AA and HAIX-Zr decreased significantly. For AA, the presence of a small concentration of HCO3- increased the uptake of F- by 100% compared to water containing only F-. For HAIX-Zr, the adsorption capacity decreased as the concentration of co-ions increased. The cost of treated water varied from (sic) 0.1-1.5/L (US 0.004-0.23/L) for HAIX-Zr
Green and sustainable anticorrosive coating derived from waterborne linseed alkyd using organic-inorganic hybrid cross linker
No full textIn near future, bio-based polymer coatings are expected to gradually replace the fossil oil based coating materials. However, extensive application of bio-based polymer is still a challenge because of its several limitations. The use of organic-inorganic hybrid cross linker is one of the interesting strategies used for the processing of highly crosslinked polymer coatings with improved mechanical and anticorrosive performance. Thus present work reports the preparation of organic-inorganic hybrid (OIH) cross linker using melamine formaldehyde (MF) and 3 isocynatopropyl triethoxy silane (IPTES). The structural characterization was carried out using various spectroscopic techniques, which provide ample evidence in favor of MF/IPTES cured alkyd formation. The impact of OIH cross linker on various properties like physico-mechanical, adhesion, thermal stability and anticorrosive properties was investigated systematically. The enhancement in aforementioned properties could be explained in terms of synergistic effect of s-triazine ring of melamine formaldehyde and IPTES