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151.
152.
X.W. Zhang Y.H. Zhu J.B. Xia 《Physica E: Low-dimensional Systems and Nanostructures》2006,33(2):376-380
The Hamiltonian of the zinc-blende quantum rods in the framework of eight-band effective-mass approximation in the presence of external homogeneous magnetic field is given. The electronic structure, optical properties and electron g factors of GaAs quantum rods are investigated. We found that the electron g factors are very sensitively dependent on the dimensions of the quantum rods. As some of the three dimensions increase, the electron g factors decrease. The more the dimensions increase, the more the electron g factors decrease. The dimensions perpendicular to the direction of the magnetic field affect the electron g factors more than the other dimension. 相似文献
153.
J. S. Gutmann P. Müller-Buschbaum D. W. Schubert N. Stribeck M. Stamm 《Journal of Macromolecular Science: Physics》2013,52(5-6):563-576
Thin films of incompatible polymer blends can form a variety of structures on preparation. For the polymer blend system consisting of two poly(styrene-co-para-bromo-styrene)s at different degrees of bromination, PBrxS/PBryS, the compatibility can be tuned through a variation of the difference in the degree of bromination. Within this blend system, two series of samples with different compatibilities were investigated at various blend compositions. The surface morphology of the thin films was investigated by atomic force microscopy (AFM) measurements, while diffuse X-ray scattering provided additional depth sensitivity at a comparable lateral resolution. The results are indicative for phase separation lateral, as well as perpendicular, to the sample surface. 相似文献
154.
Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics results in a structure in which dopant ions intercalate as a sandwich between thiophene rings on adjacent polymer chains. The ions occupy sites in channels parallel to the polymer main chain, which retains a high degree of planarity in contrast to the pristine (undoped) polymer. Even when lattice imperfections are created by expanding the cell, Coulomb forces ensure that the intercalation features containing the dopant channels are largely retained. On applying electric fields in the principal directions of the 'perfect lattice' it is found that the ions migrate most readily along the ion-channel directions (the lattice c axis), leaving the lattice undisturbed. Although higher electric fields cause dopant migration to occur perpendicular to the channel directions they destroy the intercalated lattice. In the reduced-order lattice regions substantial motion of the ions are predicted at a critical value of the lattice parameter. 相似文献
155.
The ion irradiation of polymeric solids induces numerous modifications in the polymer properties thus increasing their applicability in various fields. The present work looks into the aspect of thermal modifications induced in the irradiated polymers. The kinetics of thermal decomposition of polymers is investigated by using the thermogravimetric (TG) technique. It has been observed that the degradation of polymers is a multi-step process that involves sequential and competing processes, and obeys the Arrhenius kinetics which allows us to connect the rate constant with the absolute temperature and the activation energy. The activation energy of thermal decomposition has been calculated from the TG curves, and its variation with different irradiation doses has been derived. 相似文献
156.
In this paper we propose a new definition of prime ends for domains in metric spaces under rather general assumptions. We compare our prime ends to those of Carathéodory and Näkki. Modulus ends and prime ends, defined by means of the p-modulus of curve families, are also discussed and related to the prime ends. We provide characterizations of singleton prime ends and relate them to the notion of accessibility of boundary points, and introduce a topology on the prime end boundary. We also study relations between the prime end boundary and the Mazurkiewicz boundary. Generalizing the notion of John domains, we introduce almost John domains, and we investigate prime ends in the settings of John domains, almost John domains and domains which are finitely connected at the boundary. 相似文献
157.
Basu A Joanny JF Jülicher F Prost J 《The European physical journal. E, Soft matter》2008,27(2):149-160
We discuss general features of noise and fluctuations in active polar gels close to and away from equilibrium. We use the
single-component hydrodynamic theory of active polar gels built by Kruse and coworkers to describe the cytoskeleton in cells.
Close to equilibrium, we calculate the response function of the gel to external fields and introduce Langevin forces in the
constitutive equations with correlation functions respecting the fluctuation-dissipation theorem. We then discuss the breakage
of the fluctuation-dissipation theorem due to an external field such as the activity of the motors. Active gels away from
equilibrium are considered at the scaling level. As an example of application of the theory, we calculate the density correlation
function (the dynamic structure factor) of a compressible active polar gel and discuss possible instabilities. 相似文献
158.
Gravimetry experiments in a well-controlled environment have been performed to investigate aging for a glassy PMMA/toluene
film. The temperature is constant and the control parameter is the solvent vapor pressure above the film (i.e. the activity). Several experimental protocols have been used, starting from a high activity where the film is swollen and
rubbery and then aging the film at different activities below the glass transition. Desorption and resorption curves have
been compared for the different protocols, in particular in terms of the softening time, i.e. the time needed by the sample
to recover an equilibrium state at high activity. Non-trivial behaviors have been observed, especially at small activities
(deep quench). A model is proposed, extending the Leibler-Sekimoto approach to take into account the structural relaxation
in the glassy state, using the Tool formalism. This model well captures some of the observed phenomena, but fails in describing
the specific kinetics observed when aging is followed by a short but deep quench. 相似文献
159.
O. Werzer B. Stadlober A. Haase M. Oehzelt R. Resel 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):455-459
Pentacene thin films with thicknesses ranging from 10 nm to
180 nm are investigated by specular X-ray diffraction in the
reflectivity regime and in the wide angular regime. The results of
the reflectivity measurements show a clear shift of the 001
reflection of the thin film phase depending on the layer thickness.
It is shown that this shift can be explained by the dynamical
scattering theory. The wide angular regime measurements show the 00L
of the thin film phase. Williams-Hall plots are used to extract
information on the crystallite size and mean micro strain of the
thin film phase. The crystallite size is in good agreement with the
results obtained by the reflectivity measurements. From this it can
be concluded that the thin film phase crystallites are extended over
the entire film thickness down to the substrate. Additionally an
increase of the micro strain with increasing film thickness is
observed. 相似文献
160.
Shape transformation of thin two-dimensional sheets into three-dimensional structures using light is of great interest for remotely controlled fabrication, surface modulation, and actuation. Over the last few decades, significant efforts have been made to develop material systems incorporating photochemical or photothermal elements to drive deformation in response to illumination. However, the full extent of the interplay between chemistry, optics, and mechanics in these materials is poorly understood. In this review, we introduce principles of shape morphing in these systems by considering the underlying physics of photoinduced stresses and how these have been used in recent literature. In addition, we provide a critical overview of the important design characteristics of both photochemical and photothermal system and offer our view on the open opportunities and challenges in this rapidly growing field. 相似文献