Dynamic sability of rotating shaft under parametric excitation subjected to specified boundary conditions

The dynamic stability behavior of a rotating shaft system under parametric excitation subjected to specified boundary conditions is studied theoretically and theoretical findings with the experimental results. For this theoretical analysis Finite Element Method is applied to derive the governing equation of motion. In this paper, the Ritz finite element procedure and LaGrange’s equation are employed to derive the governing equation of a rotating shaft subjected to axial compressive forces. The effects of gyroscopic moment and the static buckling load parameter on the regions of dynamic instability are studied. Application of Bolotin’s method and under the conditions of constant rotational speed, the boundaries between the regions of stability and instability are constructed. For experimental work the existing experimental setup is redesigned. Suitable End Attachments are designed and fabricated to achieve various conditions of boundary conditions for the rotating shaft

Investigating the Control by Quantum Confinement and Surface Ligand Coating of Photocatalytic Efficiency in Chalcopyrite Copper Indium Diselenide Nanocrystals

In the past few years, there has been immense interest in the preparation of sustainable photocatalysts composed of semiconductor nanocrystals (NCs) as one of their components. We report here, for the first time, the effects of structural parameters of copper indium diselenide (CuInSe2) NCs on visible light-driven photocatalytic degradation of pollutants under homogeneous conditions. Ligand exchange reactions were performed replacing insulating, oleylamine capping with poly(ethylene glycol) thiols to prepare PEG-thiolate-capped, 1.8–5.3 nm diameter CuInSe2 NCs to enhance their solubility in water. This unique solubility property caused inner-sphere electron transfer reactions (O2 to O2•−) to occur at the NC surface, allowing for sustainable photocatalytic reactions. Electrochemical characterization of our dissolved CuInSe2 NCs showed that the thermodynamic driving force (−ΔG) for oxygen reduction, which increased with decreased NC size, was the dominant contributor to the overall process when compared to ..

Family of Single-Micelle-Templated Organosilica Hollow Nanospheres and Nanotubes Synthesized through Adjustment of Organosilica/Surfactant Ratio

A family of hollow organosilica nanospheres and nanotubes was synthesized at appropriately low organosilica-precursor/block-copolymer-surfactant ratios. In Pluronic F127 (EO₁₀₆PO₇₀EO₁₀₆) block copolymer templated synthesis of ethylene-bridged organosilicas in the presence of a swelling agent, the lowering of the organosilica-precursor/surfactant ratio led to a change from highly ordered face-centered cubic structure of spherical mesopores to individual hollow spherical nanoparticles. It was hypothesized that at low ratios of organosilica precursor to PEO-PPO-PEO, the framework precursor is solubilized in the micelles and its concentration on their surface is not sufficient to induce appreciable cross-linking between the resulting nanoobjects and the consolidation into larger particles. The inner pore size of the nanospheres was adjusted by varying the micelle expander, allowing us to obtain pore diameters up to ∼20 nm. By employing low precursor/surfactant ratios, hollow spheres of methylene-, ethenylene-, and phenylene-bridged organosilicas were synthesized. Hollow silica spheres were also obtained through judicious choice of block copolymer. The synthesis strategy involving the adjustment of the framework-precursor/surfactant ratio was further extended on organosilica nanotubes synthesized using Pluronic P123 surfactant and cyclohexane as a swelling agent. One can envision a large number of framework compositions for which hollow nanospheres and nanotubes can be obtained using our synthesis approach

Surfactant-Templated Synthesis of Ordered Silicas with Closed Cylindrical Mesopores

Ordered mesoporous silicas with 2-dimensional hexagonal arrays of closed cylindrical pores were synthesized via templating with block copolymer surfactant followed by calcination at appropriately high temperatures. Precursors to closed-pore silicas, including SBA-15 silicas and organosilicas, were selected based on the existence of narrow passages to the mesopores. The increase in calcination temperature to 800–950 °C led to a dramatic decrease in nitrogen uptake by the materials, indicating the loss of accessible mesopores, whereas small-angle X-ray scattering (SAXS) indicated no major structural changes other than the framework shrinkage. Since SAXS patterns for ordered mesoporous materials are related to periodic arrays of mesopores, the existence of closed mesopores was evident, as additionally confirmed by TEM. The formation of closed-pore silicas was demonstrated for ultralarge-pore SBA-15 and large-pore phenylene-bridged periodic mesoporous organosilicas. The increase in the amount of tetraethyl orthosilicate in standard SBA-15 synthesis also allowed us to observe the thermally induced pore closing. It is hypothesized that the presence of porous plugs in the cylindrical mesopores and/or caps at their ends was responsible for the propensity to the pore closing at sufficiently high temperatures. The observed behavior is likely to be relevant to a variety of silicas and organosilicas with cylindrical mesopores

High-pressure synthesis of mesoporous stishovite. Potential applications in mineral physics

Recently, we have described a successful synthesis route to obtain mesoporous quartz and its high-pressure polymorph coesite by nanocasting at high pressure using periodic mesostructured precursors, such as SBA-16 and FDU-12/carbon composite as starting materials. Periodic mesoporous high-pressure silica polymorphs are of particular interest as they combine transport properties and physical properties such as hardness that potentially enable the industrial use of these materials. In addition, synthesis of mesoporous crystalline silica phases can allow more detailed geology-related studies such as water/mineral interaction, dissolution/crystallization rate and the surface contribution to the associated thermodynamic stability (free energy and enthalpy) of the various polymorphs and their crossover. Here, we present results of synthesis of mesoporous stishovite from cubic large-pore periodic mesoporous silica LP-FDU-12/C composite as precursor with an fcc lattice. We describe the synthesis procedure using multi-anvil apparatus at 9 GPa (about 90,000 atm) and temperature of 500 A degrees C. The synthetic mesoporous stishovite is, then, characterized by wide and small-angle X-ray diffraction, scanning/transmission electron microscopy and gas adsorption. Results show that this new material is characterized by accessible mesopores with wide pore size distribution, surface area of similar to 45 m(2)/g and volume of pores of similar to 0.15 cm(3)/g. Results from gas adsorption indicate that both porosity and permeability are retained at the high pressures of synthesis but with weak periodic order of the pores

Size Tunable Synthesis of Solution Processable Diamond Nanocrystals

Diamond nanocrystals were synthesized catalyst-free from nano-porous carbon at high pressure and high temperature (HPHT). The synthesized nanocrystals have tunable diameters between 50 and 200 nm. The nanocrystals are dispersible in organic solvents such as acetone and are isotropic in nature as seen by dynamic light scattering

Study of Glucose -6-Phosphate Dehydrogenase Deficiency In Neonatal Jaundice

Abstract: The enzyme

Immunotoxic and genotoxic potential of arsenic and its chemical species in goats

The study investigated the immunotoxic and genotoxic effect of arsenic and its different species on goats. It was found that arsenic causes haematological crisis. Histopathological changes in spleen and reduced serum immunoglobulin G level without any changes in formazan production in arsenic-treated animals indicated that arsenic is toxic to the humoral immune system. Increased caspase-3 production and higher number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling)-positive bone marrow cells along with oligonucleosomal DNA fragmentation on agarose gel suggested apoptosis induction by arsenic in the bone marrow cells of goat. Total arsenic concentration in the plasma, bone marrow, and spleen of the exposed group was, respectively, 1.22 ± 0.11, 2.20 ± 0.21, and 3.39 ± 0.14 ppm. Speciation study revealed that arsenite and organoarsenic were the major arsenic species in these samples, suggesting their role in immunotoxic and genotoxic potential in goats