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101.
Hatchootah Ashish 《Molecular physics》2013,111(1):175-185
This work aims to study the trans and cis conformers of furfural, thiofurfural and selenofurfural in the gas and solution phases. Assuming that there is equilibrium between these conformers, the transition state has also been investigated. All computations have been done using density functional theory method with B3LYP as the functional and 6-311++G(d,p) as the basis sets. The optimized molecular structures and related parameters of these conformers are reported. The infrared wavenumbers and Raman activities of these conformers are also reported with appropriate assignments. The energy differences between the trans and cis conformers, associated barriers and thermodynamical parameters have been derived from the computations. It is found that the structural parameters are not much different in the gas and solution phases. However, in the gas phase, the trans conformer is always more stable, but increasing the polarity of the solvent leads to the cis conformer becoming more stable. The rotational barrier is always larger than the energy difference and both of them increase when the solvent becomes more polar. Some of the results for furfural compare satisfactorily with literature and therefore the data from this work will be useful for thiofurfuraldehyde and selenofurfuraldehyde, as their literature is limited. 相似文献
102.
Ashish A. Rokade Maheshkumar P. Patil Seong Il Yoo Won Ki Lee 《Green Chemistry Letters and Reviews》2016,9(4):216-222
In this study, a green chemistry method is reported for the synthesis of Ag2O nanoparticles with the utilization of starch molecules as a stabilizing agent. In particular, by simply adjusting the concentration of starch in the reaction media, the structure of A2O nanoparticles can be engineered in disc and faceted shapes, which has been analyzed by transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction technique. In addition, antibacterial activity of the prepared Ag2O nanoparticles had been evaluated against food poisoning and pathogenic bacteria. 相似文献
103.
Somdutta Mukherjee Vishal Ranjan Rajeev Gupta Ashish Garg 《Solid State Communications》2012,152(13):1181-1185
We show the effect of composition on the structure, polyhedral distortion and magnetic characteristics of pure phase polycrystalline Ga2?xFexO3 (GFO) for compositions between 0.8≤x≤1.3. X-ray analysis reveals that lattice parameters of GFO exhibit a linear dependence on Fe content in single phase region indicating manifestation of Vegard's law. Upon changing the composition, a rather small change in the overall unit cell volume (~1%) appears to be an outcome of a competition between changing trends of various polyhedra. Increasing Fe content of the samples also leads to stretching of the bonds as indicated by the Raman peak shifts. Further, low temperature magnetic measurements show that the coercivity of the samples is maximum for Ga:Fe ratio of 1:1 driven by a competition between decreasing crystallite size and increasing magnetic anisotropy. 相似文献
104.
An improved, highly scalable methodology for the multigram-scale preparation of an important synthon, 17-β-(2-carboxyethyl)-1,3,5(10)-estratriene, is described. Previous approaches have failed to provide useful quantities of the analytically pure product because of facile retro-Michael breakdown of the β-alkoxy carbonyl precursors during workup and isolation operations. The synthetic approach described herein has been designed specifically to sidestep this problematic breakdown process. This new scalable method of preparation overcomes a major hurdle in the exploration of structure–activity relationships centered around novel estradiol derivatives with bone-targeting properties and also provides a scalable process for subsequent developmental work. 相似文献
105.
Ashish Kumar Singha Deb B. N. Mohanty P. Ilaiyaraja K. Sivasubramanian B. Venkatraman 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1161-1169
Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g?1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol?1, 0.093 kJ mol?1 K?1 and -18.521 kJ mol?1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs. 相似文献
106.
Vaibhav Sinha Ashish V. Avachat Hyoung K. Lee 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):799-806
A new method for non-destructive analysis has been developed using a combined neutron/X-ray imaging system at the Missouri Science & Technology Reactor (MSTR). The interactions of neutrons and X-ray photons with matter produce differing characteristic information, resulting in distinctly different visual images. In order to obtain a more comprehensive picture of the structural and compositional data for a desired object, a prototype imaging system has been designed which utilizes neutron and X-ray imaging simultaneously without obstructing the beam geometry for each imaging mechanism. The current system is optimized for the imaging of small to medium sized objects of 0.5–50 mm. This new imaging capability in place at the MSTR promises great advances in the field of non-destructive testing, especially for nuclear engineering, nuclear medical science, and material science research. In an imaging object, a range of atomic number values and thermal cross-sections may be present. Where multiple materials having similar atomic number and differing thermal cross-section or vice versa may be present, exclusive neutron or X-ray analysis may exhibit shortcomings in distinguishing interfaces. However, fusing the neutron image and X-ray image into a combined image offers the strengths of both and may provide a superior method of analysis. In this paper, a novel combined X-ray and neutron imaging system will be introduced for superior analysis of certain imaging objects. Design details of experimental set-up and examples of preliminary imaging tests from individual modality will be detailed. 相似文献
107.
R. Pankajavalli Ashish Jain R. Babu S. Anthonysamy K. Ananthasivan V. Ganesan K. Nagarajan 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1609-1614
The standard Gibbs energy of formation of Pr2TeO6 $ (\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)) $ was derived from its vapour pressure in the temperature range of 1,400–1,480 K. The vapour pressure of TeO2 (g) was measured by employing a thermogravimetry-based transpiration method. The temperature dependence of the vapour pressure of TeO2 over the mixture Pr2TeO6 (s) + Pr2O3 (s) generated by the incongruent vapourization reaction, Pr2TeO6 (s) = Pr2O3 (s) + TeO2 (g) + ½ O2 (g) could be represented as: $ { \log }\left\{ {{{p\left( {{\text{TeO}}_{ 2} ,\;{\text{g}}} \right)} \mathord{\left/ {\vphantom {{p\left( {{\text{TeO}}_{ 2} ,\;{\text{g}}} \right)} {{\text{Pa}} \pm 0.0 4}}} \right. \kern-0em} {{\text{Pa}} \pm 0.0 4}}} \right\} = 19. 12- 27132\; \left({\rm{{{\text{K}}}}/T} \right) $ . The $ \Updelta_{\text{f}} G^{^\circ } \;\left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} } \right) $ could be represented by the relation $ \left\{ {{{\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)} \mathord{\left/ {\vphantom {{\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}}} \right. \kern-0em} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}} \pm 5.0} \right\} = - 2 4 1 5. 1+ 0. 5 7 9 3\;\left(T/{\text{K}}\right) .$ Enthalpy increments of Pr2TeO6 were measured by drop calorimetry in the temperature range of 573–1,273 K and heat capacity, entropy and Gibbs energy functions were derived. The $ \Updelta_{\text{f}} H_{{298\;{\text{K}}}}^{^\circ } \;\left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} } \right) $ was found to be $ {{ - 2, 40 7. 8 \pm 2.0} \mathord{\left/ {\vphantom {{ - 2, 40 7. 8 \pm 2.0} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}}} \right. \kern-0em} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}} $ . 相似文献
108.
Ashish Jain R. Pankajavalli R. Babu S. Anthonysamy V. Ganesan 《Journal of Thermal Analysis and Calorimetry》2013,112(1):109-116
The standard Gibbs energy of formation of tin tellurate, SnTe3O8(s) was determined from its vapour pressure measurements over the temperature range 973–1,158 K by employing thermogravimetry-based transpiration method. The temperature dependence of vapour pressure of TeO2 over the mixture SnTe3O8(s) + SnO2(s) generated by the incongruent vapourisation reaction, SnTe3O8(s) → SnO2(s) + 3 TeO2(g) could be represented as: log (p (TeO2, g)/Pa ± 0.03) = 13.943–14,181 (K/T) (973–1,158 K). The standard Gibbs energy of formation of SnTe3O8(s) was also determined by measuring the oxygen potential of SnO2(s)–Te(s)–SnTe3O8(s) phase mixture by the electromotive force method. Enthalpy increments of SnTe3O8(s) were determined by inverse drop calorimetric method in the temperature range 523–973 K. The thermodynamic functions, viz., heat capacity, entropy and free energy functions were derived from the measured values of enthalpy increments. A mean value of ?1,642 ± 2.0 kJ mol?1 was obtained for $ \Updelta_{\text{f}} H_{298}^{\circ } $ (SnTe3O8, s) by combining the value of Δf $ G^{\circ } $ (SnTe3O8, s) derived from vapour pressure data and the free energy functions derived from the drop calorimetric data. 相似文献
109.
110.
A. S. Singha Ashish Guleria Raj K. Rana Ashvinder K. Rana 《International Journal of Polymer Analysis and Characterization》2013,18(5):377-389
A novel redox system, ascorbic acid-hydrogen peroxide, was employed to initiate graft copolymerization of ethyl acrylate and methyl methacrylate binary monomer mixtures onto Abelmoschus esculentus fibers at a temperature of 45°C for 90 min in an aqueous medium. Factors affecting grafting such as feed molarity and comonomer composition were investigated. Contrary to the lower affinity of methyl methacrylate for grafting on Abelmoschus fibers, a synergistic effect of ethyl acrylate on methyl methacrylate was observed when graft copolymers were prepared using different feed compositions (fMMA). The percentage of grafting increased from 40.2% to 89.74% at 0.4 mole fraction of fMMA. The graft copolymers were characterized by FT-IR, TGA, and SEM techniques. 相似文献