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Influence of pre-strain on the gaseous hydrogen embrittlement resistance of a high-entropy alloy
No full textThe effect of pre-strain on the resistance to gaseous hydrogen embrittlement of CoCrFeMnNi high-entropy alloy (HEA) was investigated through mechanical testing and thermal desorption analysis. The results reveal that prior plastic deformation does not affect either the hydrogen contents or the excellent hydrogen embrittlement resistance of the HEA
A remote temperature sensor for an ultrasound hyperthermia system using the acoustic signal derived from the heating signals
No full textWe demonstrate a non-invasive technique, based on the modal frequency shift of a region insonified by a dual-beam ultrasound (US) transducer (region of interest, ROI), to remotely assess the temperature of the region in a tissue-mimicking object. The application is in ultrasound hyperthermia systems for controlled maintenance of tumour temperature during chemotherapy. Towards this, we have characterised the variation of the storage modulus with the temperature of two tissue-mimicking visco-elastic materials. Due to this variation in tissue storage modulus (and viscosity), we have observed a shift in the resonant modes of the ROI, vibrated remotely with a dual-beam focussed ultrasound transducer. A modal analysis of the vibrating ROI is done to identify the modes captured by the detector. A variation in this modal frequency with temperature is computed and matches reasonably well with the experimental measurements. Through this, we demonstrate that an ultrasound hyperthermia system can have a remote temperature sensor without using an additional imaging modality
Synthesis, Theory and In Vitro Photodynamic Activities of New Copper(II)-Histidinito Complexes
No full textThe photo-dynamic effect of four new copper(II)-histidinito complexes with phenanthroline-based ligands were studied in details. All the complexes were tested against HeLa (Human Cervical Carcinoma) and 3T3 (normal fibroblast) cells both in dark and in visible light. Although the complexes were toxic to HeLa cells (IC50 approximate to 10M), visible light (400-700nm) remarkably enhanced the cytotoxicity of the complexes to the extent of sub-micromolar level. Several photo-physical measurements along with the Time-dependent density functional theory (TD-DFT) calculations rationalize the level of photodynamic therapy (PDT) effect of the complexes, which is related to the generation of singlet oxygen (O-1(2)) on photo-activation. Presence of low lying, long-lived triplet excited states facilitating the effective intersystem crossing was responsible for generation of higher level of singlet oxygen in pyrenyl complex. High level of reactive oxygen species (ROS) on photo-activation is primarily responsible for apoptotic photo-cytotoxicity. Fluorescence microscopy revealed the cytosolic localization of the complex.Overall results are of paramount importance towards designing of next generation metal-based PDT agents as the viable alternatives of porphyrins
2-Deoxyglycosyl 3-benzoylpropionates as novel donors for the direct and stereoselective synthesis of 2-deoxy-glycosides
No full textLewis acid mediated stereoselective synthesis of 2-deoxy-O-glycosides has been demonstrated using 2-deoxyglycosyl 3-benzoylpropionates as novel glycosyl donors. These newly developed donors are easily synthesized from simple glycals, are stable at room temperature and react with ease to provide products with high stereoselectivity. These donors can be successfully utilized with all types of acceptors (primary, secondary and tertiary alcohols) for the synthesis of 2-deoxy-glycosides. Additionally, these newly developed glycosyl donors are also efficient for the synthesis of trisaccharides
Novel patterning of CdS/CdTe thin film with back contacts for photovoltaic application
No full textThe heterostructure of patterned CdS/CdTe thin films with back contact have been devised with electron beam lithography and fabricated using sputter deposition technique. The metallic contacts for n-CdS and p-CdTe are patterned such that both are placed at the bottom of the cell. This avoids losses due to contact shading and increases absorption in the window layer. Patterning of the device surface helps in increasing the junction area which can modulate the absorption of more number of photons due to total internal reflection. Computing the surface area between a planar and a patterned device has revealed 133% increase in the junction area. The physical and optical properties of the sputter-deposited CdS/CdTe layers are also presented. J-V characteristics of the solar cell showed the fill factor to be 25.9%, open circuit voltage to be 17 mV and short-circuit current density to be 113.68 A/m(2). The increase in surface area is directly related to the increase in the short circuit current of the photovoltaic cell, which is observed from the results of simulated model in Atlas/Silvaco
Origami-Inspired 3D Interconnected Molybdenum Carbide Nanoflakes
No full textHigh-temperature stable transition metal carbides are one of the promising classes of materials for next-generation energy applications such as water splitting catalysis and electrodes for energy storage devices. Herein, origami-like molybdenum carbide flakes with interfacially connected structures in various orientations using an easily scalable chemical vapor deposition method are synthesized. Interestingly, each individual flake of similar orientation is interconnected across different planes. The interconnected architectures are found to be highly elastic and behave in a sponge-like manner. In addition, the surface energy of each plane is calculated using the first-principle density functional theory. The molybdenum carbide shows excellent activity for the hydrogen evolution reaction, with the onset over potential occurring around -16 to -25 mV with high stability. The material is used as an electrode for supercapacitors as a second demonstration. The supercapacitor constructed with polypyrrole reaches the specific capacitance of approximate to 279 F g(-1) at a current density of 0.5 A g(-1)
Fuel-Rich Combustion Synthesized Co/Al2O3 Catalysts for Wax and Liquid Fuel Production via Fischer-Tropsch Reaction
No full textAlumina supported cobalt catalysts were synthesized for Fischer-Tropsch (FT) reaction using combustion synthesis (CS) method via the redox reaction of hexamethylenetetramine and cobalt nitrate with equivalence ratios (phi) of 1, 1.2, and 1.5. Higher equivalence ratios (phi > 1.0) were selected to increase the synthesis temperature and thereby decrease the formation of cobalt aluminates. Chemisorption and XPS studies of CS(phi = 1.2) and CS(phi = 1.5) catalysts showed high degree of reduction, high metal dispersion, and decreased formation of cobalt aluminates compared to CS(phi = 1) catalysts. Higher FT activity was observed for catalysts synthesized with equivalence ratios of 1.2 and 1.5 compared to the catalysts synthesized with phi = 1. Simultaneously, the hydrocarbon product spectrum shifted from predominantly waxes (C24+) for CS(phi = 1) catalysts to mixed fractions of liquid fuel (C-6-C-24) and waxes for CS(phi = 1.2) and CS(phi = 1.5) catalysts. This work investigates the impact of CS stoichiometry on catalyst properties, in particular the metal support interaction, and its outcome on FT activity and selectivity
Wireless Bidirectional Relaying using Physical Layer Network Coding with Heterogeneous PSK Modulation
No full textIn bidirectional relaying using Physical Layer Network Coding (PLNC), it is generally assumed that users employ same modulation schemes in the Multiple Access phase. However, as observed by Zhang et al., it may not be desirable for the nodes to always use the same modulation schemes, particularly when node-relay channels are not equally strong. Such a scheme is called Heterogeneous PLNC. However, the above approach uses the computationally intensive Closest Neighbour Clustering algorithm to find the network coding maps to be applied at the relay. Also, the treatment is specific to certain cases of heterogeneous modulations. In this paper, we show that, when users employ heterogeneous symmetric-PSK modulations, the network coding maps and the mapping regions in the fade state plane can be obtained analytically. Performance results are provided in terms of relay error rate and bit error rate
Rayleigh analysis of domain dynamics across temperature induced polymorphic phase transitions in lead-free piezoceramics (1-&ITx&IT)(BaTi0.88Sn0.12)-&ITx&IT(Ba0.7Ca0.3)TiO3
No full textWe carried out a Rayleigh analysis of the dielectric permittivity of a lead-free piezoceramic system (1-x)(BaTi0.88Sn0.12)-x(Ba0.7Ca0.3)TiO3 across the composition and temperature induced polymorphic phase transformations to determine the trend in the reversible and irreversible domain wall motion across the composition and temperature induced structural changes. Experiments were carried out on three representative compositions x = 0.10, 0.2, and 0.25 exhibiting rhombohedral, orthorhombic, and tetragonal phases at room temperature. While confirming that the irreversible Rayleigh parameter is large in the orthorhombic phase, we discuss a correspondence between the reduction in the coercive field and the corresponding increase in the irreversible Rayleigh parameter. We also show how the proximity of the Curie point to the polymorphic phase boundary greatly undermines this correspondence
Effects of Arctic geoengineering on precipitation in the tropical monsoon regions
No full textArctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modeling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless offset by comparable geoengineering in the Southern Hemisphere. In this study, we investigate and quantify the implications of this ITCZ shift due to Arctic geoengineering for the global monsoon regions using the Community Atmosphere Model version 4 coupled to a slab ocean model. A doubling of CO2 from pre-industrial levels leads to a warming of similar to 6 K in the Arctic region and precipitation in the monsoon regions increases by up to similar to 15%. In our Arctic geoengineering simulation which illustrates a plausible latitudinal distribution of the reduction in sunlight, an addition of sulfate aerosols (11 Mt) in the Arctic stratosphere nearly offsets the Arctic warming due to CO2 doubling but this shifts the ITCZ southward by similar to 1.5A degrees relative to the pre-industrial climate. The combined effect from this shift and the residual CO2-induced climate change in the tropics is a decrease/increase in annual mean precipitation in the Northern Hemisphere/Southern Hemisphere monsoon regions by up to -12/+17%. Polar geoengineering where sulfate aerosols are prescribed in both the Arctic (10 Mt) and Antarctic (8 Mt) nearly offsets the ITCZ shift due to Arctic geoengineering, but there is still a residual precipitation increase (up to 7%) in most monsoon regions associated with the residual CO2 induced warming in the tropics. The ITCZ shift due to our Global geoengineering simulation, where aerosols (20 Mt) are prescribed uniformly around the globe, is much smaller and the precipitation changes in most monsoon regions are within +/- 2% as the residual CO2-induced warming in the tropics is also much less than in Arctic and Polar geoengineering. Further, global geoengineering nearly offsets the Arctic warming. Based on our results we infer that Arctic geoengineering leads to ITCZ shift and leaves residual CO2 induced warming in the tropics resulting in substantial precipitation decreases (increases) in the Northern (Southern) hemisphere monsoon regions