3,470 research outputs found
Electron scattering states at solid surfaces calculated with realistic potentials
Scattering states with LEED asymptotics are calculated for a general
non-muffin tin potential, as e.g. for a pseudopotential with a suitable barrier
and image potential part. The latter applies especially to the case of low
lying conduction bands. The wave function is described with a reciprocal
lattice representation parallel to the surface and a discretization of the real
space perpendicular to the surface. The Schroedinger equation leads to a system
of linear one-dimensional equations. The asymptotic boundary value problem is
confined via the quantum transmitting boundary method to a finite interval. The
solutions are obtained basing on a multigrid technique which yields a fast and
reliable algorithm. The influence of the boundary conditions, the accuracy and
the rate of convergence with several solvers are discussed. The resulting
charge densities are investigated.Comment: 5 pages, 4 figures, copyright and acknowledgment added, typos etc.
correcte
Effects of interaction on an adiabatic quantum electron pump
We study the effects of inter-electron interactions on the charge pumped
through an adiabatic quantum electron pump. The pumping is through a system of
barriers, whose heights are deformed adiabatically. (Weak) interaction effects
are introduced through a renormalisation group flow of the scattering matrices
and the pumped charge is shown to {\it always} approach a quantised value at
low temperatures or long length scales. The maximum value of the pumped charge
is set by the number of barriers and is given by . The
correlation between the transmission and the charge pumped is studied by seeing
how much of the transmission is enclosed by the pumping contour. The (integer)
value of the pumped charge at low temperatures is determined by the number of
transmission maxima enclosed by the pumping contour. The dissipation at finite
temperatures leading to the non-quantised values of the pumped charge scales as
a power law with the temperature (), or with
the system size (), where is a
measure of the interactions and vanishes at . For a double
barrier system, our result agrees with the quantisation of pumped charge seen
in Luttinger liquids.Comment: 9 pages, 9 figures, better quality figures available on request from
author
Heat transfer between a plane surface and a pulsating, perpendicularly impinging air jet
Call number: LD2668 .T4 1959 B8
Deformation and magnetic fabrics in ductile shear zones: A review
The Anisotropy of Magnetic Susceptibility (AMS) is a well-established petrofabric tool for indicating relative strain and microstructural character and has been validated on various rock types and different structural settings. The magnetic susceptibility of a rock (K) depends primarily on the nature and abundance of magnetic minerals. The physical arrangement and lattice-preferred orientation of these magnetic minerals give rise to magnetic anisotropy. The AMS scalar parameters most commonly used to constrain strain include the corrected degree of anisotropy (P'> 1), a proxy for fabric intensity, and the shape factor (- 1 ≤ T≤ + 1), an indicator of the magnetic fabric symmetry (prolate vs. oblate).A number of studies have shown that a positive correlation generally exists between P' and strain. Thus, the AMS shows a great potential as a tool for examining deformation in geologic structures characterized by large strain gradients such as shear zones. However, a number of caveats exist: (i) The increase of P' with strain cannot be solely attributed to deformation because P' also increases with K regardless of deformation; (ii) Strain across shear zones is typically heterogeneous and is often localized in units of different lithology, thus making the separation of the lithological and strain controls on AMS difficult; also, deformation is commonly accompanied by mineral segregation or fluid-rock interaction that induces changes in magnetic mineralogy; (iii) Even if the undeformed lithology was uniform across a shear zone, variations in strain rate or temperature may result in different deformation mechanisms; hence, the relationship between P' and strain depends strongly on both the mineral carriers of AMS and on deformation mechanisms; and (iv) The AMS is unable to resolve composite fabrics, such as those resulting from S-C structures, where minerals on the C and S planes, respectively, contribute to AMS
Chromosome mapping: radiation hybrid data and stochastic spin models
This work approaches human chromosome mapping by developing algorithms for
ordering markers associated with radiation hybrid data. Motivated by recent
work of Boehnke et al. [1], we formulate the ordering problem by developing
stochastic spin models to search for minimum-break marker configurations. As a
particular application, the methods developed are applied to 14 human
chromosome-21 markers tested by Cox et al. [2]. The methods generate
configurations consistent with the best found by others. Additionally, we find
that the set of low-lying configurations is described by a Markov-like ordering
probability distribution. The distribution displays cluster correlations
reflecting closely linked loci.Comment: 26 Pages, uuencoded LaTex, Submitted to Phys. Rev. E,
[email protected], [email protected]
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