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51.
It is well known that orientational correlations appear in polymer chain models when the subunits are linked by ball-socket joints implemented as rigid constraint conditions. These correlations do not appear when the subunits are connected by springlike potential forces, even in the limit of infinitely stiff springs. In a widely used class of algorithms for Brownian dynamics simulations, inertia effects are ignored. However, in the recently introduced needle chain and nugget chain algorithms, the rigid constraint correlations depend on the mass and moment of inertia. This inconsistency does not appear in the bead-rod (Kramers) polymer chain model, which also has orientational correlations introduced by rigid constraint conditions. Explicit expressions for the correlation functions are given for thermodynamic equilibrium states. Analytical expressions for the associated forces ("metric forces") and simulation results showing how the rigid constraint correlations influence dynamical properties, are also presented. Further we discuss the physical relevance of these correlations and show via simulations that their influence on stationary and dynamical properties depend significantly on chain length. We further show that if the metric forces are removed, algorithms designed with rigid constraint conditions describe a chain of segments connected by infinitely stiff springs. Finally we show that the results presented here for needle chains are relevant also for the bead-rod (Kramers) chain model, making it possible to simulate a bead-spring chain with infinitely stiff springs. 相似文献
52.
Narayan T. Akinchan Douglas X. West Yong Hong Yang Michelle M. Salberg Tracey L. Klein 《Transition Metal Chemistry》1995,20(5):481-484
Summary CuII complexes of 1-salicoyl-4-phenylthiosemicarbazide (SPT) have been synthesized and characterized by means of elemental analysis, magnetic measurements, and i.r. and e.p.r. spectroscopic methods; 1H- and 13C-n.m.r. and mass spectral data on the thiosemicarbazide are also reported. A paramagnetic complex
eff= 1.298 B.M., is formed with copper(II) sulphate; the low magnetic moment and the e.p.r. spectral data suggest a binuclear species. A diamagnetic complex due to a strong Cu-Cu interaction has been isolated with copper(II) chloride. 相似文献
53.
Binary and quasi-binary freezing point data have been obtained to establish the freezing point diagram for the ternary reciprocal salt pair system involving cyclohexylamine stearate, cyclohexylamine palmitate, 2,2'-dipyridylamine stearate, and 2,2'-dipyridylamine palmitate. The compositions and primary freezing points of the ternary peritectic and eutectic mixtures have been determined Apparent anomalies in the heating curves for selected compositions have been explained on the basis of the existence of metastable equilibria. 相似文献
54.
J. H. Griffith C. S. Marvel G. W. Hedrick Frank Magne 《Journal of polymer science. Part A, Polymer chemistry》1966,4(8):1993-2002
The preparation of vinyl 2,2-dimethyl-3-morpholinocarbonylcyclobutaneacetate, vinyl 2,2-dimethyl-3-piperidinocarbonylcyclobutaneacetate, and vinyl 2,2-dimethyl-3-di-n-butylaminocarbonylcyclobutaneacetate has been achieved by selective amination followed by vinyl interchange. Homopolymers and vinyl chloride copolymers containing 25 and 30 wt.-% of the vinyl esteramides were prepared and evaluated as nonrigid plastics. The vinyl esteramides incorporated in vinyl chloride copolymers did impart some plasticization, but their effect was far below the effect of added plasticizer to a vinyl chloride polymer. 相似文献
55.
Roberta C. L. Chow C. S. Marvel Frank C. Magne 《Journal of polymer science. Part A, Polymer chemistry》1970,8(5):1247-1259
Vinyl esters and acrylates of polyesters derived from C10?C18 hydroxyacids have been synthesized and copolymerized with vinyl chloride with the hope of achieving an internally plasticized poly(vinyl chloride). Copolymers containing 10–30% polyester are film-forming materials, and the films cast from THF solutions are generally flexible. A number of these vinyl chloride copolymers with polyesters at approximately 15 and 25% level have been tested for various properties. The internal plasticization is not extensive. 相似文献
56.
Magne O. Sydnes 《Tetrahedron》2007,63(12):2593-2603
Five photoaffinity probes of tautomycin, which possess an aromatic azide with linker attached to the 2-position of tautomycin, were prepared in order to study the binding site of tautomycin with protein phosphatase 1γ. The photoaffinity probes were synthesized by selectively introducing the photolabeling units onto the 2-position of tautomycin by using oxime chemistry. 相似文献
57.
Per Fotland Kjell Magne Askvik 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):22-27
Asphaltene deposition during oil production may lead to expensive and frequent clean-up operations. Knowledge of the interaction between asphaltene particles and deposition is vital in order to predict the magnitude of this problem.Surface energies for asphaltenes precipitated at field conditions are determined from measurements of contact angles of several probe liquids. Using the surface tension component model, the energies are found to be dispersive. Hamaker constants of a simple mixture of pentane and benzene are estimated from the application of Lifshitz theory.The effective Hamaker constants of asphaltenes in a pentane/benzene mixture are calculated. It is shown that increasing amounts of benzene lowers the attractive interaction between asphaltenes. This result is consistent with the definition that asphaltenes are soluble in benzene. 相似文献
58.
Samples were decomposed in HClO4/HF mixture in a Teflon beaker to avoid electrochemical interference from platinum ions. The residue remaining after evaporation to dryness was taken up in nitric acid and examined by anodic stripping voltammetry. Both the hanging mercury drop electrode and the rotating glassy carbon electrode, mercury-plated in situ, were used with success. Copper at 120 ppm and lead at 40 ppm were determined with a relative standard deviation of 6%. The schist was the Nordic reference sample ASK-2. 相似文献
59.
Giruzzi G Artaud JF Dumont RJ Imbeaux F Bibet P Berger-By G Bouquey F Clary J Darbos C Ekedahl A Hoang GT Lennholm M Maget P Magne R Ségui JL Bruschi A Granucci G 《Physical review letters》2004,93(25):255002
Improvement (up to a factor of approximately 4) of the electron-cyclotron (EC) current drive efficiency in plasmas sustained by lower-hybrid (LH) current drive has been demonstrated in stationary conditions on the Tore Supra tokamak. This was made possible by feedback controlled discharges at zero loop voltage, constant plasma current, and constant density. This effect, predicted by kinetic theory, results from a favorable interplay of the velocity space diffusions induced by the two waves: the EC wave pulling low-energy electrons out of the Maxwellian bulk, and the LH wave driving them to high parallel velocities. 相似文献
60.
Two nonoverlapping domain decomposition algorithms are proposed for convection dominated convection–diffusion problems. In
each subdomain, artificial boundary conditions are used on the inflow and outflow boundaries. If the flow is simple, each
subdomain problem only needs to be solved once. If there are closed streamlines, an iterative algorithm is needed and the
convergence is proved. Analysis and numerical tests reveal that the methods are advantageous when the diffusion parameter
ɛ is small. In such cases, the error introduced by the domain decomposition methods is negligible in comparison with the error
in the singular layers, and it allows easy and efficient grid refinement in the singular layers.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献