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排序方式: 共有1510条查询结果,搜索用时 62 毫秒
941.
Guanghui Zhu Christopher D. Hoffman Yang Liu Souryadeep Bhattacharyya Dr. Uma Tumuluri Melinda L. Jue Dr. Zili Wu Dr. David S. Sholl Dr. Sankar Nair Dr. Christopher W. Jones Dr. Ryan P. Lively 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10743-10747
Both known and new CC3‐based porous organic cages are prepared and exposed to acidic SO2 in vapor and liquid conditions. Distinct differences in the stability of the CC3 cages exist depending on the chirality of the diamine linkers used. The acid catalyzed CC3 degradation mechanism is probed via in situ IR and a degradation pathway is proposed and supported with computational results. CC3 crystals synthesized with racemic mixtures of diaminocyclohexane exhibited enhanced stability compared to CC3‐R and CC3‐S. Confocal fluorescent microscope images reveal that the stability difference in CC3 species originates from an abundance of mesoporous grain boundaries in CC3‐R and CC3‐S, allowing facile access of aqueous SO2 throughout the crystal, promoting decomposition. These grain boundaries are absent from CC3 crystals made with racemic linkers. 相似文献
942.
Syntheses of tri- and tetrahydroxylated 1-amino-heptanes from α-D-glucose are described. 相似文献
943.
Harshad Pathak Alexander Späh Katrin Amann-Winkel Fivos Perakis Kyung Kyung Hwan Kim 《Molecular physics》2019,117(22):3232-3240
Here we report on the temperature dependence of the anomalous behaviour of water in terms of (i) its growth in tetrahedral structures, (ii) instantaneous spatial correlations from small angle x-ray scattering (SAXS) data, (iii) estimates of thermodynamic response functions of isothermal compressibility and (iv) thermal expansion coefficient. Water’s thermal expansion coefficient is estimated for the first time at supercooled conditions from liquid water’s structure factor. We used previously published data from classical force-fields of TIP4P/2005 and iAMOEBA to compare experimental data with molecular dynamics simulations and observe that these force-fields underestimate water’s anomalous behaviour but perform better upon increasing pressure. We demonstrate that the molecular dynamics simulations can describe better the temperature dependent anomalous behaviour of ambient pressure water if simulated at 1?kbar. The deviation in anomalous fluctuations in the simulations is not restricted to ≈228?K but extends all the way to ambient temperatures. 相似文献
944.
Siddhartha Laghuvarapu Yashaswi Pathak U. Deva Priyakumar 《Journal of computational chemistry》2020,41(8):790-799
Recent advances in artificial intelligence along with the development of large data sets of energies calculated using quantum mechanical (QM)/density functional theory (DFT) methods have enabled prediction of accurate molecular energies at reasonably low computational cost. However, machine learning models that have been reported so far require the atomic positions obtained from geometry optimizations using high-level QM/DFT methods as input in order to predict the energies and do not allow for geometry optimization. In this study, a transferable and molecule size-independent machine learning model bonds (B), angles (A), nonbonded (N) interactions, and dihedrals (D) neural network (BAND NN) based on a chemically intuitive representation inspired by molecular mechanics force fields is presented. The model predicts the atomization energies of equilibrium and nonequilibrium structures as sum of energy contributions from bonds (B), angles (A), nonbonds (N), and dihedrals (D) at remarkable accuracy. The robustness of the proposed model is further validated by calculations that span over the conformational, configurational, and reaction space. The transferability of this model on systems larger than the ones in the data set is demonstrated by performing calculations on selected large molecules. Importantly, employing the BAND NN model, it is possible to perform geometry optimizations starting from nonequilibrium structures along with predicting their energies. © 2019 Wiley Periodicals, Inc. 相似文献
945.
Research on Chemical Intermediates - Iron nanoparticles immobilized on reduced graphene oxide (rGO), nanocomposite Fe(0)@rGO 1, were prepared in situ by reduction of GO and FeCl3·6H2O using... 相似文献
946.
Debnath Chatterjee Tanmoy Halder Navendu P. Pathak Abhijit Paul Somnath Yadav 《Tetrahedron letters》2017,58(20):1943-1946
Anomeric sugar lactones are important intermediates for the synthesis of C-glycosides, carbasugars and iminosugars. Herein we present a facile synthesis of anomeric sugar lactones via the DAIB/TEMPO oxidation of anomeric hydroxides. The reactions are very efficient providing the lactones in 2–4 h in almost quantitative yields. The reaction conditions tolerate several common protecting groups used in carbohydrate synthesis. The advantages of the present methodology over previously reported non-metal based methods have also been demonstrated through head to head comparisons. Finally, we have applied the reaction for the sequential conversion of anomeric thioglycosides to the lactones through sequential reactions with NBS followed by the oxidation with DAIB/TEMPO. 相似文献
947.
Benjamin A. Griffin Venkataraman Chandrasekaran Matthew D. Williams Bhavani V. Sankar Mark Sheplak 《International Journal of Solids and Structures》2011,48(10):1466-1473
This paper presents a reduced analytical modeling method for the initial optimal design of thermoelastic micromachined actuators. The key aspects of the model are a Green’s function formulation of the axisymmetric heat conduction equation that incorporates an internal heat source and the solution of the thermoelastically forced bending wave equation. Model results of a representative thermoelastic structure include transient temperature and sinusoidal steady state transverse displacement. Comparison with finite element analysis shows excellent agreement with favorable computational costs. Model constraints at low frequencies are identified and discussed. The computational efficiency of the analytical model makes it a more viable modeling method for design optimization. 相似文献
948.
949.
Gemma L. Brett Qian He Ceri Hammond Peter J. Miedziak Nikolaos Dimitratos Meenakshisundaram Sankar Andrew A. Herzing Marco Conte Jose Antonio Lopez‐Sanchez Christopher J. Kiely David W. Knight Stuart H. Taylor Graham J. Hutchings 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2011,123(43):10318-10321
950.
Pooja Soni Gitanjali Pagare Sankar P. Sanyal 《Journal of Physics and Chemistry of Solids》2011,72(6):810-816
The structural, elastic and thermal properties of four transition metal monocarbides ScC, YC (group III), VC and NbC (group V) have been investigated using full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) both at ambient and high pressure. We predict a B1 to B2 structural phase transition at 127.8 and 80.4 GPa for ScC and YC along with the volume collapse percentage of 7.6 and 8.4%, respectively. No phase transition is observed in case of VC and NbC up to pressure 400 and 360 GPa, respectively. The ground state properties such as equilibrium lattice constant (a0), bulk modulus (B) and its pressure derivative (B′) are determined and compared with available data. We have computed the elastic moduli and Debye temperature and report their variation as a function of pressure. 相似文献