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861.
The neural network (NN) procedure to interpolate ab initio data for the purpose of molecular dynamics (MD) simulations has been tested on the SiO(2) system. Unlike other similar NN studies, here, we studied the dissociation of SiO(2) without the initial use of any empirical potential. During the dissociation of SiO(2) into Si+O or Si+O(2), the spin multiplicity of the system changes from singlet to triplet in the first reaction and from singlet to pentet in the second. This paper employs four potential surfaces. The first is a NN fit [NN(STP)] to a database comprising the lowest of the singlet, triplet, and pentet energies obtained from density functional calculations in 6673 nuclear configurations. The other three potential surfaces are obtained from NN fits to the singlet, triplet, and pentet-state energies. The dissociation dynamics on the singlet-state and NN(STP) surfaces are reported. The results obtained using the singlet surface correspond to those expected if the reaction were to occur adiabatically. The dynamics on the NN(STP) surface represent those expected if the reaction follows a minimum-energy pathway. This study on a small system demonstrates the application of NNs for MD studies using ab initio data when the spin multiplicity of the system changes during the dissociation process. 相似文献
862.
Jyothi C. Abbar Shweta J. Malode Sharanappa T. Nandibewoor 《Journal of molecular catalysis. A, Chemical》2009,313(1-2):88-99
The oxidation of dl-ornithine monohydrochloride (OMH) by diperiodatocuprate(III) (DPC) has been investigated both in the absence and presence of ruthenium(III) catalyst in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm−3 spectrophotometrically. The stiochiometry was same in both the cases, i.e., [OMH]/[DPC] = 1:4. In both the catalyzed and uncatalyzed reactions, the order of the reaction with respect to [DPC] was unity while the order with respect to [OMH] was < 1 over the concentration range studied. The rate increased with an increase in [OH−] and decreased with an increase in [IO4−] in both cases. The order with respect to [Ru(III)] was unity. The reaction rates revealed that Ru(III) catalyzed reaction was about eight-fold faster than the uncatalyzed reaction. The oxidation products were identified by spectral analysis. Suitable mechanisms were proposed. The reaction constants involved in the different steps of the reaction mechanisms were calculated for both cases. The catalytic constant (KC) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of the mechanism and also the thermodynamic quantities were determined. Kinetic experiments suggest that [Cu(H2IO6)(H2O)2] is the reactive copper(III) species and [Ru(H2O)5OH]2+ is the reactive Ru(III) species. 相似文献
863.
We revisit the problem of the optimization of a silicon-nanocrystal (Si-NC) waveguide, aiming to attain the maximum field confinement inside its nonlinear core and to ensure optimal waveguide performance for a given mode power. Using a Si-NC/SiO2 slot waveguide as an example, we show that the common definition of the effective mode area may lead to significant errors in estimation of optical intensity governing the nonlinear optical response and, as a result, to poor strength evaluation of the associated nonlinear effects. A simple and physically meaningful definition of the effective mode area is given to relate the total mode power to the average field intensity inside the nonlinear region and is employed to study the optimal parameters of Si-NC slot waveguides. 相似文献
864.
The present paper deals with ion transport studies on a new proton conducting composite polymer electrolyte — (PVAx:NH4SCN)y:PVAc system. Complexation and morphology of the composite electrolyte films are discussed on the basis of X-ray diffraction
and differential scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge transport
through protons. The maximum ion conductivity was found to be 7.4·10−4 S·cm−1 for the composition: x=0.15, y=0.12. The observed conductivity behaviour is correlated to the morphology of the films. The
temperature dependence of the electrical conductivity exhibits Arrhenius characteristics in two different temperature ranges
separated by a plateau region related to morphological changes occurring in the electrolyte. 相似文献
865.
We investigate the possibility of forming spatiotemporal solitons (optical bullets) in inhomogeneous, dispersive nonlinear media using a graded-index Kerr medium as an example. We use a variational approach to solve the multidimensional, inhomogeneous, nonlinear Schrödinger equation and show that spatiotemporal solitons can be stabilized under certain conditions. We verify their existence by means of a full numerical analysis and show that such solitons should be observable experimentally. 相似文献
866.
867.
Richa Agrawal N. S. Saxena M. S. Sreekala S. Thomas 《Journal of Polymer Science.Polymer Physics》2000,38(7):916-921
The thermal conductivity and thermal diffusivity of oil‐palm‐fiber‐reinforced untreated (Sample 1) and differently treated composites were measured with the transient plane source technique at room temperature and under normal pressure. All the composites were 40% oil‐palm fiber by weight. The fibers were treated with alkali (Composite 2), silane (Composite 3), and acetic acid (Composite 4) and reinforced in a phenolformaldehyde matrix. The thermal conductivity and thermal diffusivity of the composites increased after treatment to different extents. The thermal conductivity of the treated fibers as well as of the untreated fibers was calculated theoretically. The model results show that the thermal conductivity of the untreated fiber was smaller than the thermal conductivity of the treated fibers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 916–921, 2000 相似文献
868.
Shweta D. Dabhi Swati Gahlot Sheefa Mirza Medha Pandya Rakesh Rawal Vaibhav Kulshrestha Prafulla K. Jha 《Macromolecular Symposia》2024,413(1):2300086
Graphene and graphene oxide (GO) have garnered significant attention due to their exceptional properties. GO, enriched with various functional groups such as epoxy, hydroxyl, and carboxylic groups, has exhibited remarkable potential in biomedical applications. The combination of GO with metals has proven to be a promising platform for cellular imaging, with this study focusing on the preparation of diverse hybrids of GO with metal oxides (GO/MO) and their potential as anticancer agents. In this research, GO is functionalized with MOs like TiO2, Fe3O4, and Cu2O using specific chemical methods and investigated for the anticancer activity for the application as cancer therapeutic agent. The resulting GO/MO hybrids exhibits favorable thermal and mechanical properties. Moreover, their cytotoxicity against human lung cancer cells is assessed in vitro, revealing the promising anticancer activity of GO/MO hybrids. Notably, the GO/Cu2O hybrid demonstrates particularly high cytotoxicity in human lung cancer cells. 相似文献
869.
Heterocyclic systems are now considered to be an integral part of material chemistry. Thiophene, selenophene, furan, pyrrole, carbazole, triazine and others are some such examples worth mentioning. 2,4,6-Tri(thiophen-2-yl)-1,3,5-triazine is a C3h-symmetric system with thiophene as the donor unit and s-triazine as the acceptor unit. This review gives an insight into the advances made in the thienyl-triazine chemistry over the past two to three decades. The synthetic pathways for arriving at this system and all its important derivatives are provided. The major focus is on the materials synthesized using the thienyl-triazine system, including star molecules, linear and hyperbranched polymers, porous materials and their diverse applications. This review will play a catalytic role for new dimensions to be explored in thienyl-triazine chemistry. 相似文献
870.
Dr. Chenikkayala Siva Sankara Dr. Shweta Bhagat Dr. Ajeet Chandra Prof. Dr. Irishi N. N. Namboothiri 《European journal of organic chemistry》2023,26(15):e202300069
An enantioselective desymmetrization of curcumins with 3-olefinic oxindoles involving a cascade double-Michael addition strategy provides direct access to spirocyclohexanone-oxindoles with complete regio- and diastereoselectivities and excellent enantioselectivities, besides good to excellent yields. The products possess three contiguous chiral centers and multiple reactive functionalities. The observed selectivities were rationalized by transitions state energy calculations at B3LYP//6-31g(d) level of DFT. 相似文献