544 research outputs found
Hysteresis of Finite Arrays of Magnetic nano Dots
Hysteresis curves for finite arrays of ferromagnetic nano dots
subject to the dipole-dipole interaction are investigated for . Spin
arrangements up to N=6 are presented, which indicate the onset of bulk-like
behavior associated with odd (N=5) and even (N=6) systems. The effect of field
misalignment on the hysteresis loops is also studied for . The area
of the hysteresis loop is studied as a function of . We find that
approximately scales as for odd and as
for even.Comment: 6 pages, 8 figures, Submitted to PR
Anisotropic Transport Properties of Ferromagnetic-Superconducting Bilayers
We study the transport properties of vortex matter in a superconducting thin
film separated by a thin insulator layer from a ferromagnetic layer. We assume
an alternating stripe structure for both FM and SC layers as found in [7]. We
calculate the periodic pinning force in the stripe structure resulting from a
highly inhomogeneous distribution of the vortices and antivortices. We show
that the transport properties in FM-SC bilayer are highly anisotropic. In the
absence of random pinning it displays a finite resistance for the current
perpendicular to stripes and is superconducting for the current parallel to
stripes. The average vortex velocity, electric field due to the vortex motion,
Josephson frequency and higher harmonics of the vortex oscillatory motion are
calculated.Comment: 4 pages, 2figures, Submitted to PR
Ferromagnetic Annulus And Superconducting Vortices
The screening currents induced in a superconducting film by a magnetic
annulus whose magnetization is perpendicular to the superconductor are
calculated. We show that close to the superconductor transition temperature
particular values of the magnetization and radii of the annulus make the
creation of superconducting vortices energy favorable. We also show that the
magnetic annulus offers an alternative tool for vortex pinning in the
superconductor. Statistical mechanical properties of this system are discussed.Comment: 4 pages, 2 figures, submitted to PR
Superconducting Vortices and Elliptical Ferromagnetic Textures
In this article an analytical and numerical study of superconducting thin
film with ferromagnetic textures of elliptical geometries in close proximity is
presented. The screening currents induced in the superconductor due to the
magnetic texture are calculated. Close to the superconducting transition
temperature the spontaneous creation of superconducting vortices becomes
energy favorable depending on the value of the magnetization and the
geometrical quantities of the magnetic texture. The creation of vortices by
elliptic dots is more energy favorable than those created by circular ones. The
superconductor covered by elliptic dots array exhibits anisotropic transport
properties.Comment: 4 pages, 5figure
Dissipation and coherent effects in narrow superconducting channels
We apply the time dependent Ginzburg-Landau equations (TDGL) to study small
ac currents of frequency in superconducting channels narrow on the
scale of London penetration depth. We show that TDGL have -dependent and
spatially uniform solutions that describe the order parameter with an
oscillating part of the double frequency coexisting with an ac electric field.
We evaluate the Ohmic losses (related neither to the flux flow nor to the phase
slips) and show that the resistivity reduction on cooling through the critical
temperature should behave as . If the channel is cut
out of an anisotropic material in a direction other than the principal axes,
the transverse phase difference and the Josephson voltage between the channel
sides are generated.Comment: 5 pages, 1 figures, Accepted for publication in Phys. Rev.
Theory of pinning in a Superconducting Thin Film Pierced by a Ferromagnetic Columnar Defect
This is an analytical study of pinning and spontaneous vortex phase is a
system consisting of a superconducting thin film pierced by a long
ferromagnetic columnar defect of finite radius . The magnetic fields,
screening currents, energy and pinning forces for this system are calculated.
The interaction between the magnetic field of vortices and the magnetization
outside the plane of the film and its close proximity enhances vortex pinning
significantly. Spontaneous vortex phase appears when the magnetization of the
columnar defect is increased above a critical value. Transitions between phases
characterized by different number of flux quanta are also studied. These
results are generalized to the case when the superconductor is pierced by an
array of columnar defects.Comment: 6 pages, 4 figures, Accepted for publication in Phys. Rev.
The impact of demographic, anthropometric and athletic characteristics on left atrial size in athletes.
The structural adaptations of the “athlete’s heart” include left atrial (LA) enlargement. A literature search was performed based on PubMed listings up to 2nd November 2019 using "athletes AND left atrium", "athletes AND left atrial", "sports AND left atrium", "sports AND left atrial", “exercise AND left atrium” and “exercise AND left atrial” as the search terms. Eligible studies included those reporting the influence of demographic, anthropometric and athletic characteristics on left atrial size in athletes. A total of 58 studies were included in this review article. Although LA volume has been reported to be greater in males compared to females when indexed for body surface area (BSA), there was no difference between sexes. The positive association between LA size and age in athletes may reflect the increase in body size with maturation in nonadult athletes and the training age of endurance athletic activity in adult athletes. Caucasian and black athletes have been demonstrated to exhibit similar LA enlargement. The positive association of LA size with lean body mass possibly accounts for the relationship of LA size with BSA. LA enlargement has been reported only in endurance-trained, but not in strength-trained athletes. LA size appears to increase with an increase in both the volume and intensity of endurance training. LA size correlates independently with the training age of endurance athletes. The athlete’s characteristics that independently determine LA size include lean body mass, endurance training and training age
The dynamical response to the node defect in thermally activated remagnetization of magnetic dot array
The influence of nonmagnetic central node defect on dynamical properties of
regular square-shaped 5 x 5 segment of magnetic dot array under the thermal
activation is investigated via computer simulations. Using stochastic
Landau-Lifshitz-Gilbert equation we simulate hysteresis and relaxation
processes. The remarkable quantitative and qualitative differences between
magnetic dot arrays with nonmagnetic central node defect and magnetic dot
arrays without defects have been found.Comment: 4 pages,5 figures, submitted to J. Magn. Magn. Matte
Landspotting: Social gaming to collect vast amounts of data for satellite validation
At present there is no single satellite-derived global land cover product that is accurate enough to provide reliable estimates of forest or cropland area to determine, e.g., how much additional land is available to grow biofuels or to tackle problems of food security. The Landspotting Project aims to improve the quality of this land cover information by vastly increasing the amount of in-situ validation data available for calibration and validation of satellite-derived land cover. The Geo-Wiki (Geo-Wiki.org) system currently allows users to compare three satellite derived land cover products and validate them using Google Earth. However, there is presently no incentive for anyone to provide this data so the amount of validation through Geo-Wiki has been limited. However, recent competitions have proven that incentive driven campaigns can rapidly create large amounts of input. The LandSpotting Project is taking a truly innovative approach through the development of the Landspotting game. The game engages users whilst simultaneously collecting a large amount of in-situ land cover information. The development of the game is informed by the current raft of successful social gaming that is available on the internet and as mobile applications, many of which are geo-spatial in nature. Games that are integrated within a social networking site such as Facebook illustrate the power to reach and continually engage a large number of individuals. The number of active Facebook users is estimated to be greater than 400 million, where 100 million are accessing Facebook from mobile devices. The Landspotting Game has similar game mechanics as the famous strategy game "Civilization" (i.e. build, harvest, research, war, diplomacy, etc.). When a player wishes to make a settlement, they must first classify the land cover over the area they wish to settle. As the game is played on the earth surface with Google Maps, we are able to record and store this land cover/land use classification geographically. Every player can play the game for free (i.e. a massive multiplayer online game). Furthermore, it is a social game on Facebook (e.g. invite friends, send friends messages, purchase gifts, help friends, post messages onto the wall, etc). The game is played in a web browser, therefore it runs everywhere (where Flash is supported) without requiring the user to install anything additional. At the same time, the Geo-Wiki system will be modified to use the acquired in-situ validation information to create new outputs: a hybrid land cover map, which takes the best information from each individual product to create a single integrated version; a database of validation points that will be freely available to the land cover user community; and a facility that allows users to create a specific targeted validation area, which will then be provided to the crowdsourcing community for validation. These outputs will turn Geo-Wiki into a valuable system for earth system scientists
Magnetic Pinning of Vortices in a Superconducting Film: The (anti)vortex-magnetic dipole interaction energy in the London approximation
The interaction between a superconducting vortex or antivortex in a
superconducting film and a magnetic dipole with in- or out-of-plane
magnetization is investigated within the London approximation. The dependence
of the interaction energy on the dipole-vortex distance and the film thickness
is studied and analytical results are obtained in limiting cases. We show how
the short range interaction with the magnetic dipole makes the co-existence of
vortices and antivortices possible. Different configurations with vortices and
antivortices are investigated.Comment: 12 pages, 12 figures. Submitted to Phys. Rev.
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