1,287 research outputs found
A phenomenological model of the superconducting state of the Bechgaard salts
We present a group theoretical analysis of the superconducting state of the
Bechgaard salts, e.g., (TMTSF)_2PF_6 or (TMTSF)_2ClO_6. We show that there are
eight symmetry distinct superconducting states. Of these only the (fully
gapped, even frequency, p-wave, triplet) 'polar state' is consistent with the
full range of the experiments on the Bechgaard salts. The gap of the polar
state is d(k) (psi_uk,0,0), where psi_uk may be any odd parity function that is
translationally invariant.Comment: 4 pages, no figure
Energy deposition by heavy ions: Additivity of kinetic and potential energy contributions in hillock formation on CaF2
The formation of nano-hillocks on CaF2 crystal surfaces by individual ion
impact has been studied using medium energy (3 and 5 MeV) highly charged ions
(Xe19+ to Xe30+) as well as swift (kinetic energies between 12 and 58 MeV)
heavy ions. For very slow highly charged ions the appearance of hillocks is
known to be linked to a threshold in potential energy while for swift heavy
ions a minimum electronic energy loss is necessary. With our results we bridge
the gap between these two extreme cases and demonstrate, that with increasing
energy deposition via electronic energy loss the potential energy threshold for
hillock production can be substantially lowered. Surprisingly, both mechanisms
of energy deposition in the target surface seem to contribute in an additive
way, as demonstrated when plotting the results in a phase diagram. We show that
the inelastic thermal spike model, originally developed to describe such
material modifications for swift heavy ions, can be extended to case where
kinetic and potential energies are deposited into the surface.Comment: 12 pages, 4 figure
Possible Triplet Electron Pairing and an Anisotropic Spin Susceptibility in Organic Superconductors (TMTSF)_2 X
We argue that (TMTSF)_2 PF_6 compound under pressure is likely a triplet
superconductor with a vector order parameter d(k) \equiv (d_a(k) \neq 0, d_c(k)
= ?, d_{b'}(k) = 0); |d_a(k)| > |d_c(k)|. It corresponds to an anisotropic spin
susceptibility at T=0: \chi_{b'} = \chi_0, \chi_a \ll \chi_0, where \chi_0 is
its value in a metallic phase. [The spin quantization axis, z, is parallel to a
so-called b'-axis]. We show that the suggested order parameter explains why the
upper critical field along the b'-axis exceeds all paramagnetic limiting
fields, including that for a nonuniform superconducting state, whereas the
upper critical field along the a-axis (a \perp b') is limited by the Pauli
paramagnetic effects [I. J. Lee, M. J. Naughton, G. M. Danner and P. M.
Chaikin, Phys. Rev. Lett. 78, 3555 (1997)]. The triplet order parameter is in
agreement with the recent Knight shift measurements by I. J. Lee et al. as well
as with the early results on a destruction of superconductivity by nonmagnetic
impurities and on the absence of the Hebel-Slichter peak in the NMR relaxation
rate.Comment: 4 pages, 1 eps figur
Thermal lag correction on Slocum CTD glider data
Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 28 (2011): 1065–1071, doi:10.1175/JTECH-D-10-05030.1.In this work a new methodology is proposed to correct the thermal lag error in data from unpumped CTD sensors installed on Slocum gliders. The advantage of the new approach is twofold: first, it takes into account the variable speed of the glider; and second, it can be applied to CTD profiles from an autonomous platform either with or without a reference cast. The proposed methodology finds values for four correction parameters that minimize the area between two temperature–salinity curves given by two CTD profiles. A field experiment with a Slocum glider and a standard CTD was conducted to test the method. Thermal lag–induced salinity error of about 0.3 psu was found and successfully corrected.This work is part of the SINOCOP
and GliderBal projects funded by CSIC and Govern
Balear, respectively
Creation of multiple nanodots by single ions
In the challenging search for tools that are able to modify surfaces on the
nanometer scale, heavy ions with energies of several 10 MeV are becoming more
and more attractive. In contrast to slow ions where nuclear stopping is
important and the energy is dissipated into a large volume in the crystal, in
the high energy regime the stopping is due to electronic excitations only.
Because of the extremely local (< 1 nm) energy deposition with densities of up
to 10E19 W/cm^2, nanoscaled hillocks can be created under normal incidence.
Usually, each nanodot is due to the impact of a single ion and the dots are
randomly distributed. We demonstrate that multiple periodically spaced dots
separated by a few 10 nanometers can be created by a single ion if the sample
is irradiated under grazing angles of incidence. By varying this angle the
number of dots can be controlled.Comment: 12 pages, 6 figure
Midgap edge states and pairing symmetry of quasi-one-dimensional organic superconductors
The singlet s-, d- and triplet p-wave pairing symmetries in
quasi-one-dimensional organic superconductors can be experimentally
discriminated by probing the Andreev bound states at the sample edges. These
states have the energy in the middle of the superconducting gap and manifest
themselves as a zero-bias peak in tunneling conductance into the corresponding
edge. Their existence is related to the sign change of the pairing potential
around the Fermi surface. We present an exact self-consistent solution of the
edge problem showing the presence of the midgap states for p_x-wave
superconductivity. The spins of the edge state respond paramagnetically to a
magnetic field parallel to the vector d that characterizes triplet pairing.Comment: 6 pages, 4 figures. V.2: New section on spin response is added and
references are updated. V.3: Final version accepted to PRB. Typos are
corrected and important note is added in proof
Stretching of the Back Improves Gait, Mechanical Sensitivity and Connective Tissue Inflammation in a Rodent Model
Abstract The role played by nonspecialized connective tissues in chronic non-specific low back pain is not well understood. In a recent ultrasound study, human subjects with chronic low back pain had altered connective tissue structure compared to human subjects without low back pain, suggesting the presence of inflammation and/or fibrosis in the low back pain subjects. Mechanical input in the form of static tissue stretch has been shown in vitro and in vivo to have anti-inflammatory and anti-fibrotic effects. To better understand the pathophysiology of lumbar nonspecialized connective tissue as well as potential mechanisms underlying therapeutic effects of tissue stretch, we developed a carrageenan-induced inflammation model in the low back of a rodent. Induction of inflammation in the lumbar connective tissues resulted in altered gait, increased mechanical sensitivity of the tissues of the low back, and local macrophage infiltration. Mechanical input was then applied to this model as in vivo tissue stretch for 10 minutes twice a day for 12 days. In vivo tissue stretch mitigated the inflammation-induced changes leading to restored stride length and intrastep distance, decreased mechanical sensitivity of the back and reduced macrophage expression in the nonspecialized connective tissues of the low back. This study highlights the need for further investigation into the contribution of connective tissue to low back pain and the need for a better understanding of how interventions involving mechanical stretch could provide maximal therapeutic benefit. This tissue stretch research is relevant to body-based treatments such as yoga or massage, and to some stretch techniques used with physical therapy
Defect-unbinding and the Bose-glass transition in layered superconductors
The low-field Bose-glass transition temperature in heavy-ion irradiated
Bi_2Sr_2CaCu_2O_8+d increases progressively with increasing density of
irradiation-induced columnar defects, but saturates for densities in excess of
1.5 x10^9 cm^-2. The maximum Bose-glass temperature corresponds to that above
which diffusion of two-dimensional pancake vortices between different vortex
lines becomes possible, and above which the ``line-like'' character of vortices
is lost. We develop a description of the Bose-glass line that is in excellent
quantitative agreement with the experimental line obtained for widely different
values of track density and material parameters.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Software countermeasures for control flow integrity of smart card C codes
International audienceFault attacks can target smart card programs in order to disrupt an execution and gain an advantage over the data or the embedded functionalities. Among all possible attacks, control flow attacks aim at disrupting the normal execution flow. Identifying harmful control flow attacks as well as designing countermeasures at software level are tedious and tricky for developers. In this paper, we propose a methodology to detect harmful intra-procedural jump attacks at source code level and to automatically inject formally-proven countermeasures. The proposed software countermeasures defeat 100% of attacks that jump over at least two C source code statements or beyond. Experiments show that the resulting code is also hardened against unexpected function calls and jump attacks at assembly level
A new daily quarter degree sea level anomaly product from CryoSat-2 for ocean science and applications
The European Space Agency launched CryoSat-2 as the first European ice mission in 2010. Its advanced altimeter met primary objectives concerned with sea ice thickness and ice sheets. The value of Cryosat-2 data over global oceans was recognised, and operational products were developed via the CryoSat Ocean Processor (COP). The novel orbit of CryoSat-2 results in a denser coverage of sample points compared to other satellite altimeters. The National Oceanography Centre Sea Level Anomaly (NOCSLA) gridded product is based on interpolating Geophysical Ocean Products (GOP) using weights in space and time. GOP represents the highest quality operational ocean data. NOCSLA is a daily, ¼° sea level anomaly product covering non-coastal oceans between [60°N 60°S] and January 2011 to October 2020. The paper presents the methodology and scientific applications of NOCSLA. Oceanographic features observed are compared against products from other missions, including Rossby waves and El Niño signals. Results show good agreement with other products, confirming the value of Cryosat-2 data for ocean science and applications
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