1,168 research outputs found
Structural compliance, misfit strain and stripe nanostructures in cuprate superconductors
Structural compliance is the ability of a crystal structure to accommodate
variations in local atomic bond-lengths without incurring large strain
energies. We show that the structural compliance of cuprates is relatively
small, so that short, highly doped, Cu-O-Cu bonds in stripes are subject to a
tensile misfit strain. We develop a model to describe the effect of misfit
strain on charge ordering in the copper oxygen planes of oxide materials and
illustrate some of the low energy stripe nanostructures that can result.Comment: 4 pages 5 figure
Inverse spectral problems for Sturm--Liouville operators with matrix-valued potentials
We give a complete description of the set of spectral data (eigenvalues and
specially introduced norming constants) for Sturm--Liouville operators on the
interval with matrix-valued potentials in the Sobolev space
and suggest an algorithm reconstructing the potential from the spectral data
that is based on Krein's accelerant method.Comment: 39 pages, uses iopart.cls, iopams.sty and setstack.sty by IO
Bunching Transitions on Vicinal Surfaces and Quantum N-mers
We study vicinal crystal surfaces with the terrace-step-kink model on a
discrete lattice. Including both a short-ranged attractive interaction and a
long-ranged repulsive interaction arising from elastic forces, we discover a
series of phases in which steps coalesce into bunches of n steps each. The
value of n varies with temperature and the ratio of short to long range
interaction strengths. We propose that the bunch phases have been observed in
very recent experiments on Si surfaces. Within the context of a mapping of the
model to a system of bosons on a 1D lattice, the bunch phases appear as quantum
n-mers.Comment: 5 pages, RevTex; to appear in Phys. Rev. Let
The production of short-lived radionuclides by new non-rotating and rotating Wolf-Rayet model stars
It has been speculated that WR winds may have contaminated the forming solar
system, in particular with short-lived radionuclides (half-lives in the
approximate 10^5 - 10^8 y range) that are responsible for a class of isotopic
anomalies found in some meteoritic materials. We revisit the capability of the
WR winds to eject these radionuclides using new models of single non-exploding
WR stars with metallicity Z = 0.02. The earlier predictions for non-rotating WR
stars are updated, and models for rotating such stars are used for the first
time in this context. We find that (1) rotation has no significant influence on
the short-lived radionuclide production by neutron capture during the core
He-burning phase, and (2) 26Al, 36Cl, 41Ca, and 107Pd can be wind-ejected by a
variety of WR stars at relative levels that are compatible with the meteoritic
analyses for a period of free decay of around 10^5 y between production and
incorporation into the forming solar system solid bodies. We confirm the
previously published conclusions that the winds of WR stars have a radionuclide
composition that can meet the necessary condition for them to be a possible
contaminating agent of the forming solar system. Still, it remains to be
demonstrated from detailed models that this is a sufficient condition for these
winds to have provided a level of pollution that is compatible with the
observations.Comment: 8 pages, 8 figure
Solar Spectral Irradiance Variability in Cycle 24: Model Predictions and OMI Observations
Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI), we characterize both short-term (solar rotation) and long-term (solar cycle) changes of the solar spectral irradiance (SSI) between 265-500 nanometers during the ongoing Cycle 24. We supplement the OMI data with concurrent observations from the GOME-2 (Global Ozone Monitoring Experiment - 2) and SORCE (Solar Radiation and Climate Experiment) instruments and find fair-to-excellent agreement between the observations and predictions of the NRLSSI2 (Naval Research Laboratory Solar Spectral Irradiance - post SORCE) and SATIRE-S (the Naval Research Laboratory's Spectral And Total Irradiance REconstruction for the Satellite era) models
Biomechanics aspects of technique of high jump
The purpose of work consists in the theoretical ground of optimum biomechanics descriptions in high jumps. A mathematical model is developed for determination of influence on the height of jump: speed and corner of flight of centre-of-mass during pushing away, positions of centre-of-mass body of sportsman in the phases of pushing away and transition through a slat, forces of resistance of air environment, influences of moment of inertia of body. The basic technical run-time errors of sportsman are selected exercises. To biomechanics descriptions, to the step-up effectiveness of high jumps belong: speed of flight of centre-of-mass sportsman (4.2-5.8 meters in a second), corner of flight of centre-of-mass body (50-58 degrees), height of flight of centre-of mass body (0.85-1.15 meter). Directions of choice of necessary biomechanics descriptions which a sportsman can realize are shown. Offered recommendation on the increase of effectiveness of high jumps
Biomechanics aspects of technique of high jump
The purpose of work consists in the theoretical ground of optimum biomechanics descriptions in high jumps. A mathematical model is developed for determination of influence on the height of jump: speed and corner of flight of centre-of-mass during pushing away, positions of centre-of-mass body of sportsman in the phases of pushing away and transition through a slat, forces of resistance of air environment, influences of moment of inertia of body. The basic technical run-time errors of sportsman are selected exercises. To biomechanics descriptions, to the step-up effectiveness of high jumps belong: speed of flight of centre-of-mass sportsman (4.2-5.8 meters in a second), corner of flight of centre-of-mass body (50-58 degrees), height of flight of centre-of mass body (0.85-1.15 meter). Directions of choice of necessary biomechanics descriptions which a sportsman can realize are shown. Offered recommendation on the increase of effectiveness of high jumps
Qualitative features of periodic solutions of KdV
In this paper we prove new qualitative features of solutions of KdV on the
circle. The first result says that the Fourier coefficients of a solution of
KdV in Sobolev space , admit a WKB type expansion up to first
order with strongly oscillating phase factors defined in terms of the KdV
frequencies. The second result provides estimates for the approximation of such
a solution by trigonometric polynomials of sufficiently large degree
Electric-field induced capillary interaction of charged particles at a polar interface
We study the electric-field induced capillary interaction of charged
particles at a polar interface. The algebraic tails of the electrostatic
pressure of each charge results in a deformation of the interface . The resulting capillary interaction is repulsive and varies as with the particle distance. As a consequence, electric-field induced
capillary forces cannot be at the origin of the secondary minimum observed
recently for charged PMMA particles at on oil-water interface.Comment: June 200
Absence of the Transition into Abrikosov Vortex State of Two-Dimensional Type-II Superconductor with Weak Pinning
The resistive properties of thin amorphous NbO_{x} films with weak pinning
were investigated experimentally above and below the second critical field
H_{c2}. As opposed to bulk type II superconductors with weak pinning where a
sharp change of resistive properties at the transition into the Abrikosov state
is observed at H_{c4}, some percent below H_{c2} (V.A.Marchenko and
A.V.Nikulov, 1981), no qualitative change of resistive properties is observed
down to a very low magnetic field, H_{c4} < 0.006 H_{c2}, in thin films with
weak pinning. The smooth dependencies of the resistivity observed in these
films can be described by paraconductivity theory both above and below H_{c2}.
This means that the fluctuation superconducting state without phase coherence
remains appreciably below H_{c2} in the two-dimensional superconductor with
weak pinning. The difference the H_{c4}/H_{c2} values, i.e. position of the
transition into the Abrikosov state, in three- and two-dimensional
superconductors conforms to the Maki-Takayama result 1971 year according to
which the Abrikosov solution 1957 year is valid only for a superconductor with
finite dimensions. Because of the fluctuation this solution obtained in the
mean field approximation is not valid in a relatively narrow region below
H_{c2} for bulk superconductors with real dimensions and much below H_{c2} for
thin films with real dimensions. The superconducting state without phase
coherence should not be identified with the mythical vortex liquid because the
vortex, as a singularity in superconducting state with phase coherence, can not
exist without phase coherence.Comment: 4 pages, 4 figure
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