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821.
By means of molecular dynamics simulations we investigated the shear viscosity of the Gaussian Core Model fluid. We observed anomalous viscous behaviour for dimensionless densities greater than 0.3 and dimensionless temperatures below 0.04. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
822.
T. Mančal V. May 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):633-643
Non-Markovian dynamics in open quantum systems is characterized by a time-non-locality in the equation of motion valid for
the reduced density operator. An expansion of this density matrix equation with respect to Laguerre polynomials is used to
tackle the time-non-locality. The applicability and the numerical limitations of the method are discussed in detail. In order
to illuminate the characteristics of non-Markovian dynamics the reference example is studied of a single quantum degree of
freedom moving in a harmonic potential and being embedded in a heat bath. If interpreted as the photoinduced dynamics of nuclear
motion in polyatomic molecules we can suggest two clear signatures of non-Markovian dynamics observable in ultrafast optical
experiments, firstly a pronounced and somewhat irregular oscillatory behavior of the vibrational level populations, and secondly
a separation of the vibrational wavepacket into a double-structure.
Received 12 April 2000 and Received in final form 2 September 2000 相似文献
823.
824.
Zhang H Tumarkin E Peerani R Nie Z Sullan RM Walker GC Kumacheva E 《Journal of the American Chemical Society》2006,128(37):12205-12210
We report a microfluidic approach to generating capsules of biopolymer hydrogels. Droplets of an aqueous solution of a biopolymer were emulsified in an organic phase comprising a cross-linking agent. Polymer gelation was achieved in situ (on a microfluidic chip) by diffusion-controlled ionic cross-linking of the biopolymer, following the transfer of the cross-linking agent from the continuous phase to the droplets. Gelation was quenched by collecting particles in a large pool of cross-linking agent-free liquid. The structure of microgels (from capsules to gradient microgels to particles with a uniform structure) was controlled by varying the time of residence of droplets on the microfluidic chip and the concentration of the cross-linking agent in the continuous phase. We demonstrated the encapsulation of a controlled number of polystyrene beads in the microgel capsules. The described approach was applied to the preparation of capsules of several polysaccharides such as alginate, kappa-carrageenan, and carboxymethylcellulose. 相似文献
825.
Four new isostructural one-dimensional dodecaniobate Keggin materials, Na12[Ti2O2][TNb12O40] x xH2O and Na10[Nb2O2][TNb12O40] x xH2O with T = (Si or Ge), have been synthesized hydrothermally using a Lindqvist-ion salt, Na7[Nb6O19H] x 15H2O, as the precursor. Their structure, consisting of chains of Keggin ions [TNb12O40]16- linked by [Ti2O2]4+ or [Nb2O2]6+ bridges, was solved ab initio from powder diffraction data. The location of the charge-balancing sodium atoms and the water molecules was further investigated by molecular simulations. These compounds were also characterized by IR and solid-state 1H, 29Si, and 23Na MAS NMR spectroscopies. The structural relationships between these and related phases based on similar Keggin ion building units are discussed. 相似文献
826.
Copsey MC Gallon SB Grocott SK Jeffery JC Russell CA Slattery JM 《Inorganic chemistry》2005,44(15):5495-5500
High-yielding syntheses of complexes based around the cyclodistibazane (Sb(2)N(2)) core are described from the reaction of organoantimony(V) chlorides with varying stoichiometric amounts of lithiated primary amines, LiN(H)R. Thus, mixing Ph(3)SbCl(2) with 2 equiv of LiN(H)R (R = CH(2)Ph) produces Ph(3)Sb(mu-NR)(2)SbPh(3) (1). Mixed amido/imido complexes of formula {R(H)N}Ph(2)Sb(mu-NR)(2)SbPh(2){N(H)R} (2) (R = CH(2)Ph, 2-OMe-5-(t)()Bu-C(6)H(3), and Cy) are made from the corresponding 3:1 molar ratio combination of LiN(H)R with Ph(2)SbCl(3). A similar reaction employing only 2 equiv of LiN(H)R (R = CH(2)Ph) with 1 equiv of Ph(2)SbCl(3) yields ClPh(2)Sb(mu-NR)(2)SbPh(2)Cl (3). Compounds 2a-c and 3 possess reactive functionality which may make them useful synthetic reagents in the preparation of more complex main group imido architectures. All of the complexes have been characterized by (1)H NMR spectroscopy, elemental analysis (CHN), and X-ray crystallography. An investigation of all known crystallographically characterized Sb-N fragments from the Cambridge Structural Database highlights a series of parameters that appear to influence the observed Sb-N bond lengths. 相似文献
827.
828.
Macroion adsorption on a mixed, fluid, lipid membrane containing oppositely charged lipids induces local changes in lipid composition at the interaction zones, and gradients at their boundaries. Including these effects in the free energy of the macroion-dressed membrane we derive its spinodal equation, and show that nonideal lipid mixing can lead to (lipid-mediated) attraction between macroions and lateral phase separation in the composite membrane. The critical nonideality for this transition is substantially smaller than that of the bare lipid membrane, decreasing with macroion size and charge. That is, the lipid membrane is destabilized by macroion adsorption. 相似文献
829.
S.J. May 《Applied Surface Science》2006,252(10):3509-3513
Variable-temperature magnetic force microscopy (MFM) has been performed over the temperature range of 298-348 K on ferromagnetic (In,Mn)As thin films deposited by metal-organic vapor phase epitaxy (MOVPE). Ferromagnetic domains were observed with submicron resolution in both single and two phase (In,Mn)As films, persisting up to 328 K. Isolated cylindrical domains ranging from 100 to 350 nm in diameter with densities of 2-5 × 108 cm−2 were observed in phase pure films. Longer range magnetic order, in the form of ribbon-like domains up to 1 μm in length, are present in the regions between the cylindrical domains. Two phase (In,Mn)As films produced a well-resolved complex domain structure consisting of 180° parallel and antiparallel domains. Excellent agreement between the temperature dependence of the relative magnetization obtained by MFM and superconducting quantum interference device measurements was observed. 相似文献