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111.
Fadila Balegroune Pierre Braunstein Laurent Douce Yves Dusausoy Daniel Grandjean Michael Knorr Martin Strampfer 《Journal of Cluster Science》1992,3(3):275-296
The reactions of K[Fe{Si(OMe)3}(CO)3(PY)][PY=Ph2PCH2C(O)Ph, Ph2PCH2C(O)[(-C5H4)FeCp] (Cp=5-C5H5), Ph2P(CH2)2CN] with CdCl2·2.5H2O, ZnX
2 (X=Cl, I) or InCl3 afforded Fe-Cd-Fe or Fe-M(-X)2
M-Fe (M=Cd, Zn, In;X=Cl, I) and Fe-InCl2 complexes. Some of them contain an unusual and labile -2-SiO alkoxysilyl bridge which may be associated with a bridging mode for the ketophosphine ligand (first such example structurally established), thus providing original results in bimetallic chemistry on the intramolecular coordination of oxygendonor functions ofchemically different hemilabile ligands firmly attached to a neighboring metal center. The structures of the trinuclear complex (3), of the chlorobenzene solvate of the tetranuclear complex (4a·C6H5Cl) and of [mer-(OC)3{(EtO)3Si} (4e) have been determined by X-ray diffraction. Crystals of 3 are orthorhombic, space groupPbcn, witha=19.010(4),b=11.766(5),c=26.998(7)Å, andZ=4. Crystals of4a·C6H5Cl are monoclinic, space groupC2/c witha=22.455(3),b=17.680(2),c=16.627(4)Å, =90.80(4)°, andZ=4. Crystals of4e are monoclinic, space groupC2/c witha=25.392(5),b=18.554(6),c=16.28(1)Å, =120.73(3)°, andZ=4. The structures were solved using direct methods and Fourier difference techniques and refined by blocked full-matrix least squares toR=0.035 (R
w
=0.049) for 2719 observed reflections, toR=0.042 (R
w
=0.056) for 3082 observed reflections, and toR=0.057 (R
w
=0.075) for 1850 observed reflections for3, 4a·C6H5Cl and4e, respectively. The Fe-Zn complexes (9a), (9b) and (9c) were prepared and characterized by spectroscopic methods.Part 21 in the Series: Complexes with Functional Phosphines. Part 20: P. Braunstein, S. Coco Cea, A. DeCian, and J. Fischer (1992).Inorg. Chem.
31, 4203. 相似文献
112.
Thierry Boulanger Daniel P. Vercauteren Guy Evrard François Durant 《Journal of chemical crystallography》1987,17(5):561-573
The crystal structure of 2-(carboxy-3-propyl)-3-amino-6-cyclohexylpyridazinium bromide has been determined by single-crystal X-ray diffraction techniques and refined by full-matrix least squares. The compound crystallized in the tri-clinic space groupP ¯1 witha=10.275(1),b=11.215(1),c=7.082(1) Å,=91.84(1),=102.21(1), =106.77(1)°, andZ=2. FinalR-factor is 0.045. The main structural results are very similar to the ones observed for the 6-phenyl analog. These two compounds are GABA-A antagonists.Ab initio molecular orbital calculations, with STO-3G and 4-31G basis sets, suggest that the exocyclic nitrogen accurately mimics the nitrogen atom of GABA. 相似文献
113.
A simple metric property satisfied by bases of (finite, not necessarily reduced) root systems is used to define sets in Euclidean space that provide models for Dynkin diagrams and their positive semidefinite one-vertex extensions. The theory of root systems can be founded on the study of these Dynkin sets, and conversely the Dynkin sets representing connected diagrams can be characterized as the bases and extended bases of root systems. (By an extended base, we mean a base together with the lowest root of a given length.) In this correspondence the role of nonreduced root systems is natural and important. 相似文献
114.
Hydrodynamic properties for a class of nondiffusive particle systems are investigated. The method allows one to study local equilibria for a class of asymmetric zero-range processes, and applies as well to other models, such as asymmetric simple exclusion and misanthropes. Attractiveness is an essential ingredient. The hydrodynamic equations present shock wave phenomena. Preservation of local equilibrium is proven to hold away from the shocks. The problem of breakdown of local ergodicity at the shocks, which was investigated by D. Wick in a particular model, remains open in this more general setup. 相似文献
115.
116.
Albrecht H Binder U Harder G Lembke-Koppitz I Philipp A Schmidt-Parzefall W Schröder H Schulz HD Wurth R Donker JP Drescher A Matthiesen U Scheck H Spaan B Spengler J Wegener aD Gabriel JC Schubert KR Stiewe J Waldi R Weseler S Brown NN Edwards KW Frisken WR Fukunaga C Gilkinson DJ Gingrich DM Goddard M Kapitza H Kim PC Kutschke R MacFarlane DB McKenna JA McLean KW Nilsson AW Orr RS Padley P Patel PM Prentice JD Seywerd HC Stacey BJ Yoon T Yun JC Ammar R Coppage D Davis R Kanekal S Kwak N 《Physical review letters》1986,56(6):549-552
117.
A density functional theory of diffusion is developed for lattice fluids with molecular flux as a functional of the density distribution. The formalism coincides exactly with the generalized Ono-Kondo density functional theory when there is no gradient of chemical potential, i.e., at equilibrium. Away from equilibrium, it gives Fick's first law in the absence of a potential energy gradient, and it departs from Fickian behavior consistently with the Maxwell-Stefan formulation. The theory is applied to model a nanopore, predicting nonequilibrium phase transitions and the role of surface diffusion in the transport of capillary condensate. 相似文献
118.
Daniel M. Oberlin 《Israel Journal of Mathematics》1986,55(3):305-316
We prove inequalities which give lower bounds for the Lebesgue measures of setsE +K whereK is a certain kind of Cantor set. For example, ifC is the Cantor middle-thirds subset of the circle groupT, then $$m(E)^{1 - log2/log3} \leqq m(E + C)$$ for every BorelE ?T. 相似文献
119.
H. W. Gronert D. M. Herlach A. Schröder R. van den Berg H. von Löhneysen 《Zeitschrift für Physik B Condensed Matter》1986,63(2):173-178
Low-temperature measurements of the thermal conductivity (0.3KT5K) and of the specific heatC (0.07KT3.5K) of splat-cooled amorphous superconducting Zr0.67Ni0.33(T
c
2.7K) after different annealing stages are reported. increases progressively (up to 55%) after annealing. An analysis of with the help of normal-state measurements belowT
c
in an overcritical field shows that the phonon-electron scattering remains unaltered after annealing. Hence the increase in must be entirely attributed to structure-induced (intrinsic) scattering, i.e. by two-level tunneling states (TLS) at low temperatures (T1K). The specific heat shows a small decrease aboveT
c
(by 8%) which is attributed to a small diminution of the electronic density of states at the Fermi level and to a small increase in the Debye temperature. ForTT
c
where TLS dominate, the specific heatC decreases less upon annealing than expected from the increase of in the standard tunneling model. This points to a change in the TLS relaxation time spectrum upon annealing, as observed previously for Zr
x
Cu1–x
glasses. 相似文献
120.
Parameterization of peptide 13C carbonyl chemical shielding anisotropy in molecular dynamics simulations. 总被引:1,自引:0,他引:1
Daniel M Jordan K Maria Mills Ioan Andricioaei Akash Bhattacharya Kim Palmo Erik R P Zuiderweg 《Chemphyschem》2007,8(9):1375-1385
NMR chemical shielding anisotropy (CSA) relaxation is an important tool in the study of dynamical processes in proteins and nucleic acids in solution. Herein, we investigate how dynamical variations in local geometry affect the chemical shielding anisotropy relaxation of the carbonyl carbon nucleus, using the following protocol: 1) Using density functional theory, the carbonyl (13)C' CSA is computed for 103 conformations of the model peptide group N-methylacetamide (NMA). 2) The variations in computed (13)C' CSA parameters are fitted against quadratic hypersurfaces containing cross terms between the variables. 3) The predictive quality of the CSA hypersurfaces is validated by comparing the predicted and de novo calculated (13)C' CSAs for 20 molecular dynamics snapshots. 4) The CSA fluctuations and their autocorrelation and cross correlation functions due to bond-length and bond-angle distortions are predicted for a chemistry Harvard molecular mechanics (CHARMM) molecular dynamics trajectory of Ca(2+)-saturated calmodulin and GB3 from the hypersurfaces, as well as for a molecular dynamics (MD) simulation of an NMA trimer using a quantum mechanically correct forcefield. We find that the fluctuations can be represented by a 0.93 scaling factor of the CSA tensor for both R(1) and R(2) relaxations for residues in helix, coil, and sheet alike. This result is important, as it establishes that (13)C' relaxation is a valid tool for measurement of interesting dynamical events in proteins. 相似文献