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41.
Jürgen-Hinrich Fuhrhop Joachim Mathieu 《Angewandte Chemie (International ed. in English)》1984,23(2):100-113
Fixation of reaction partners at appropriate distances from one another is a structural prerequisite for vectorial reactions and reaction sequences. In biological systems (e.g. the photosynthetically active thylakoid membrane or membrane receptors) the positions of the reaction centers are fixed by membrane-protein complexes, but little is known about the structure of these complexes. Ordered reactive systems in synthetic vesicle membranes were first obtained by employing amphiphiles with reactive head groups as building units, by regioselective incorporation of foreign molecules into the membrane, by alignment of bolaamphiphiles with two head groups of differing solubility or size, and by the formation of domains. Chiral superstructures have also been observed in membranes, and the first stereoselective reactions have been performed in vesicle membranes. The report concludes with a brief discussion of membranes constructed from non-amphiphilic building blocks and problems which still have to be solved. 相似文献
42.
R. Eichele W. Kern R. P. Huebener 《Applied Physics A: Materials Science & Processing》1981,25(2):95-103
We have studied the influence of oxygen on the superconducting properties of thin films of lead, indium and tin deposited
on glass or sapphire substrates. In addition, the morphological microstructure was investigated by scanning electron microscopy.
The film thickness was 1.0 μm, and the partial pressure of O2 during the film deposition was raised up to 1×10−4 Torr. In all three materials the development of a granular structure and a strong increase in the residual electric resistivity
was observed due to the O2-treatment. Whereas in the Pb films no change of the critical temperature was found, the In films deposited on glass substrates
showed a slight increase ofT
c due to the oxygen. The strongest increase ofT
c (up to 8%) was observed in the O2-treated Sn films. These results are discussed in terms of the McMillan theory. From our measurements of the critical current
densityj
c we conclude that edge pinning is dominant in the undoped films. All three materials showed a strong increase ofj
c due to the O2-treatment which must be interpreted in terms of bulk pinning. 相似文献
43.
Sergei Yu. Davydov 《Applied Surface Science》2010,257(5):1506-1510
Within the scope of the Anderson-Newns model of adsorption the Na, K, and Cs submonolayer films on graphite are considered. The adatoms dipole-dipole repulsion is taken into account with the use of the Muscat approach. The calculated work function variations are in a reasonable agreement with the experimental data. We have found that the charges of K, Na, and Cs adatoms are Z0 = 0.22, 0.38, and 0.41 for the zero coverage limit and ZML = 0.09, 0.15, and 0.16 for the monolayer coverage correspondingly. The crude estimations of the single adatom binding energies got Eb = 0.76, 0.67, and 0.37 eV for Na, K, and Cs accordingly. 相似文献
44.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):85-90
A compartmentalized surface model of Nambu and Goto is studied on triangulated spherical surfaces by using the canonical Monte
Carlo simulation technique. One-dimensional bending energy is defined on the skeletons and at the junctions, and the mechanical
strength of the surface is supplied by the one-dimensional bending energy defined on the skeletons and junctions. The compartment
size is characterized by the total number L′ of bonds between the two-neighboring junctions and is assumed to have values in the range from L′ = 2 to L′ = 8 in the simulations, while that of the previously reported model is characterized by L′ = 1, where all vertices of the triangulated surface are the junctions. Therefore, the model in this paper is considered to
be an extension of the previous model in the sense that the previous model is obtained from the model in this paper in the
limit of L′↦1. The model in this paper is identical to the Nambu-Goto surface model without curvature energies in the limit of L′↦∞ and hence is expected to be ill-defined at sufficiently large L′. One remarkable result obtained in this paper is that the model has a well-defined smooth phase even at relatively large
L′ just as the previous model of L′↦ 1. It is also remarkable that the fluctuations of surface in the smooth phase are crucially dependent on L′; we can see no surface fluctuation when L′≤ 2, while relatively large fluctuations are seen when L′≥ 3. 相似文献
45.
Debye-Hückel theory of mixed charged-zwitterionic lipid layers 总被引:1,自引:0,他引:1
46.
Finken R Lamura A Seifert U Gompper G 《The European physical journal. E, Soft matter》2008,27(3):309-321
The stochastic motion of a two-dimensional vesicle in linear shear flow is studied at finite temperature. In the limit of
small deformations from a circle, Langevin-type equations of motion are derived, which are highly nonlinear due to the constraint
of constant perimeter length. These equations are solved in the low-temperature limit and using a mean-field approach, in
which the length constraint is satisfied only on average. The constraint imposes non-trivial correlations between the lowest
deformation modes at low temperature. We also simulate a vesicle in a hydrodynamic solvent by using the multi-particle collision
dynamics technique, both in the quasi-circular regime and for larger deformations, and compare the stationary deformation
correlation functions and the time autocorrelation functions with theoretical predictions. Good agreement between theory and
simulations is obtained. 相似文献
47.
Sakuma Y Imai M Yanagisawa M Komura S 《The European physical journal. E, Soft matter》2008,25(4):403-413
We report the adhesion of binary giant vesicles composed of two types of phospholipids, one has negative spontaneous curvature which tends to bend toward the head group and the other has zero spontaneous curvature. In a homogeneous one-phase region, the giant vesicles do not adhere to each other, whereas in a coexisting two-phase region, the giant vesicles show adhesion. A fluorescence microscope observation reveals that the adhesion takes place through the domains rich in phospholipids having negative spontaneous curvature. We propose a phase separation induced hemifusion model where two apposed monolayers of adjacent vesicles are hemifused in order to reduce the bending energy of monolayers with negative spontaneous curvature and the boundary energy between the domains and matrix. We provide a strong evidence for the hemifusion model by lipid transfer experiments. 相似文献
48.
49.
In this Letter, using the first-principles full-potential linearized augmented plane-wave (FP-LAPW) method, we extend the electronic structure and magnetism studies on zinc-blende structure of II-V compounds MX (M=Ca,Sr,Ba; X=N,P,As) [M. Sieberer, J. Redinger, S. Khmelevskyi, P. Mohn, Phys. Rev. B 73 (2006) 024404] to the rock-salt structure. It is found that, in the nine rock-salt compounds, only alkaline-earth nitrides CaN, SrN and BaN exhibit ferromagnetic half-metallic character with a magnetic moment of per formula unit. Furthermore, compared with the zinc-blende structure of CaN, SrN and BaN, the rock-salt structure has lower energy, which makes them more promising candidates of possible growth of half-metallic films on suitable substrates. 相似文献
50.
The mixed spin-1/2 and spin-1 Ising chain with both longitude and transverse single-ion anisotropies Dz and Dx is solved exactly by means of a mapping to the spin-1/2 Ising chain with the alternating transverse fields and the Jordan-Wigner transformation. The analytical expressions of the quasi-particles' spectra Λk, the minimal energy gap Δ0 for exciting a fermion quasi-particle, the minimal energy gap Δh for exciting a hole, and the ground state energy are obtained. The phase diagram of the ground state is also given. The results show that when Dz?0 for any finite value of Dx, there is no quantum critical point and the ground state is always in a spin ordered phase disregard of the boundary condition in the present system. 相似文献