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21.
Kartik Sau 《Ionics》2016,22(12):2379-2385
Molecular dynamics (MD) study of Na+ transport in Na2Ni2TeO6 is performed systematically with varying strength of Na+–Na+ short range repulsions to understand the physical principle governing ion transport mechanism. Na+ diffusion is enhanced by nearly an order of magnitude with reduced Na+–Na+ short range repulsion within the studied range. A similar behavior is also observed in other systems, e.g., AgI and Na2Zn2TeO6, where mobile ions are located closely. The Na+ ion occupancy in Na2Ni2TeO6 shows a significant shift from Na1 to Na2 sites gaining some degree of correlation. The study also emphasizes how mobile ion size influences the ionic diffusion. The fresh insight such as microscopic migration pathways, energy barriers, and jumping mechanism of Na+ are derived from the study. 相似文献
22.
Dr. Kartik Chandra Mondal Dr. Sudipta Roy Priv.‐Doz. Dr. Birger Dittrich Dr. Diego M. Andrada Prof. Dr. Gernot Frenking Prof. Dr. Herbert W. Roesky 《Angewandte Chemie (International ed. in English)》2016,55(9):3158-3161
Reduction of the neutral carbene tetrachlorosilane adduct (cAAC)SiCl4 (cAAC=cyclic alkyl(amino) carbene :C(CMe2)2(CH2)N(2,6‐iPr2C6H3) with potassium graphite produces stable (cAAC)3Si3, a carbene‐stabilized triatomic silicon(0) molecule. The Si?Si bond lengths in (cAAC)3Si3 are 2.399(8), 2.369(8) and 2.398(8) Å, which are in the range of Si?Si single bonds. Each trigonal pyramidal silicon atom of the triangular molecule (cAAC)3Si3 possesses a lone pair of electrons. Its bonding, stability, and electron density distributions were studied by quantum chemical calculations. 相似文献
23.
Recognition of Artificial Nucleobases by E. coli Purine Nucleoside Phosphorylase versus its Ser90Ala Mutant in the Synthesis of Base‐Modified Nucleosides
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Dr. Ilja V. Fateev Maria I. Kharitonova Konstantin V. Antonov Dr. Irina D. Konstantinova Dr. Vasily N. Stepanenko Dr. Roman S. Esipov Prof. Frank Seela Dr. Kartik W. Temburnikar Prof. Katherine L. Seley‐Radtke Vladimir A. Stepchenko Dr. Yuri A. Sokolov Prof. Anatoly I. Miroshnikov Prof. Igor A. Mikhailopulo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13401-13419
A wide range of natural purine analogues was used as probe to assess the mechanism of recognition by the wild‐type (WT) E. coli purine nucleoside phosphorylase (PNP) versus its Ser90Ala mutant. The results were analyzed from viewpoint of the role of the Ser90 residue and the structural features of the bases. It was found that the Ser90 residue of the PNP 1) plays an important role in the binding and activation of 8‐aza‐7‐deazapurines in the synthesis of their nucleosides, 2) participates in the binding of α‐D ‐pentofuranose‐1‐phosphates at the catalytic site of the PNP, and 3) catalyzes the dephosphorylation of intermediary formed 2‐deoxy‐α‐D ‐ribofuranose‐1‐phosphate in the trans‐2‐deoxyribosylation reaction. 5‐Aza‐7‐deazaguanine manifested excellent substrate activity for both enzymes, 8‐amino‐7‐thiaguanine and 2‐aminobenzothiazole showed no substrate activity for both enzymes. On the contrary, the 2‐amino derivatives of benzimidazole and benzoxazole are substrates and are converted into the N1‐ and unusual N2‐glycosides, respectively. 9‐Deaza‐5‐iodoxanthine showed moderate inhibitory activity of the WT E. coli PNP, whereas 9‐deazaxanthine and its 2′‐deoxyriboside are weak inhibitors. 相似文献
24.
Sai Manoj N. V. T. Gorantla Dr. Sudip Pan Prof. Dr. Kartik Chandra Mondal Prof. Dr. Gernot Frenking 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(62):14211-14220
Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L-C3-L with L=PPh3 ( 1 ), NHCMe ( 2 , NHC=N-heterocyclic carbene), and cAACMe ( 3 , cAAC=cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C3 moiety. The phosphine adduct 1 has a synclinal (gauche) conformation whereas 2 exhibits a trans conformation of the ligands. In contrast, the compound 3 possesses a nearly linear arrangement of the carbene ligands at the C3 fragment. The bond dissociation energies of the ligands have the order 1 < 2 < 3 . The bonding analysis using charge and energy decomposition methods suggests that 3 is best described as a cumulene with electron-sharing double bonds between neutral fragments (cAACMe)2 and C3 in the respective electronic quintet state yielding (cAACMe)=C3=(cAACMe). In contrast, 1 and 2 possess electron-sharing and dative bonds between positively charged ligands [(PPh3)2]+ or [(NHCMe)2]+ and negatively charged [C3]− fragments in the respective doublet state. 相似文献
25.
We have investigated the magnetic behavior of ball-milled fine particles of well-known Kondo lattices, CeAu2Si2, CePd2Si2 and CeAl2, by magnetization and heat-capacity studies in order to understand the magnetic behavior when the particle size is reduced. These compounds have been known to order antiferromagnetically in the bulk form near () 10, 10 and 3.8 K respectively. We find that the features due to magnetic ordering get suppressed to temperatures below 1.8 K in the case of fine particles of ternary alloys, though trivalence of Ce as inferred from the effective moment remains unchanged. In contrast to this, in CeAl2, there appears to be a marginal enhancement of , when the particle size is reduced to less than a micron. These results can be consistently understood by proposing that these compounds move toward left in the Doniach magnetic phase-diagram, for instance, due to relatively more 4f-localization, as the particle size is reduced. 相似文献
26.
We report on the physical properties of the series Ce(1-x)La(x)Ir(2)B(2) (x = 0-0.9), obtained by means of magnetization, heat capacity and electrical resistivity measurements as a function of temperature (down to 0.7 K for the latter two measurements). The Curie temperature of CeIr(2)B(2) (~5 K) is lowered due to La substitution, as expected. However, no quantum critical point or 'non-Fermi liquid' behavior was observed even in the dilute limit of x = 0.9. Interestingly, ferromagnetic ordering persists even for Ce(0.1)La(0.9)Ir(2)B(2), below 0.8 K. Among the Ce systems, CeIr(2)B(2) is one of the compounds in which direct 4f-4f interaction does not appear to play any role in the magnetism, which is controlled by the indirect exchange interaction alone. In this compound, the Kondo effect persists in the ferromagnetic ordered state, as inferred from the entropy data. 相似文献
27.
David H. Frakes Kerem Pekkan Lakshmi P. Dasi Hiroumi D. Kitajima Diane de Zelicourt Hwa Liang Leo Josie Carberry Kartik Sundareswaran Helene Simon Ajit P. Yoganathan 《Experiments in fluids》2008,45(6):987-997
Complex applications in fluid dynamics research often require more highly resolved velocity data than direct measurements
or simulations provide. The advent of stereo PIV and PCMR techniques has advanced the state-of-the-art in flow velocity measurement,
but 3D spatial resolution remains limited. Here a new technique is proposed for velocity data interpolation to address this
problem. The new method performs with higher quality than competing solutions from the literature in terms of accurately interpolating
velocities, maintaining fluid structure and domain boundaries, and preserving coherent structures. 相似文献
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29.
YN molecules were produced in a free jet molecular beam apparatus by a laser vaporizing yttrium metal in the presence of He doped with NH3. Laser excitation spectra were observed in the range 18 250-19 850 cm−1. The ground state was confirmed to have 1Σ+ symmetry. The fundamental vibration in the ground state was measured to be 650.6(1) cm−1. Three new electronic states, B1, C1, and D1, were observed at 18 974.7(1), 19 023.3(1), and 19 824.0(1) cm−1, respectively. The fundamental vibrations and equilibrium internuclear distances were found to be 718.3(1) cm−1 and 1.939(8) for the B1 state and 723.5(1) cm−1 and 1.9194(3) for the C1 state. Two additional electronic states were identified with the help of a deperturbation procedure, one of which is either the 1Σ+ or the 3Σ0− state. The newly observed electronic states cannot be accounted for based on the existing ab initio results. We expect that these states correlate with the excited asymptote Y(4d15s22D)+N(2D). 相似文献
30.