553 research outputs found
Intrinsic Josephson Effects in the Magnetic Superconductor RuSr2GdCu2O8
We have measured interlayer current transport in small sized RuSr2GdCu2O8
single crystals. We find a clear intrinsic Josephson effect showing that the
material acts as a natural
superconductor-insulator-ferromagnet-insulator-superconductor superlattice. So
far, we detected no unconventional behavior due to the magnetism of the RuO2
layers.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let
Quantum Quasi-Monte Carlo algorithm for out-of-equilibrium Green functions at long times
We extend the recently developed Quantum Quasi-Monte Carlo (QQMC) approach to
obtain the full frequency dependence of Green functions in a single
calculation. QQMC is a general approach for calculating high-order perturbative
expansions in power of the electron-electron interaction strength. In contrast
to conventional Markov chain Monte Carlo sampling, QQMC uses low-discrepancy
sequences for a more uniform sampling of the multi-dimensional integrals
involved and can potentially outperform Monte Carlo by several orders of
magnitudes. A core concept of QQMC is the a priori construction of a "model
function" that approximates the integrand and is used to optimize the sampling
distribution. In this paper, we show that the model function concept extends to
a kernel approach for the computation of Green functions. We illustrate the
approach on the Anderson impurity model and show that the scaling of the error
with the number of integrand evaluations is in the best
cases, and comparable to Monte Carlo scaling in the worst
cases. We find a systematic improvement over Monte Carlo sampling by at least
two orders of magnitude while using a basic form of model function. Finally, we
compare QQMC results with calculations performed with the Fork Tensor Product
State (FTPS) method, a recently developed tensor network approach for solving
impurity problems. Applying a simple Pad\'e approximant for the series
resummation, we find that QQMC matches the FTPS results beyond the perturbative
regime.Comment: 18 pages, 11 figure
Direct determination of spin orbit interaction coefficients and realization of the persistent spin helix symmetry
The spin orbit interaction plays a crucial role in diverse fields of
condensed matter, including the investigation of Majorana fermions, topological
insulators, quantum information and spintronics. In III V zinc blende
semiconductor heterostructures, two types of spin orbit interaction, Rashba and
Dresselhaus act on the electron spin as effective magnetic fields with
different directions. They are characterized by coefficients alpha and beta,
respectively. When alpha is equal to beta, the so called persistent spin helix
symmetry is realized. In this condition, invariance with respect to spin
rotations is achieved even in the presence of the spin orbit interaction,
implying strongly enhanced spin lifetimes for spatially periodic spin modes.
Existing methods to evaluate alpha/beta require fitting analyses that often
include ambiguity in the parameters used. Here, we experimentally demonstrate a
simple and fitting parameter free technique to determine alpha/beta and to
deduce the absolute values of alpha and beta. The method is based on the
detection of the effective magnetic field direction and the strength induced by
the two spin orbit interactions. Moreover, we observe the persistent spin helix
symmetry by gate tuning.Comment: 34 pages with 7 figures including supplementary information. appears
in Nature Nanotechnology (2014) Published online 13 July 201
Out-of-Plane Magnetic Anisotropy in Ordered Ensembles of FeN Nanocrystals Embedded in GaN
Phase-separated semiconductors containing magnetic nanostructures are
relevant systems for the realization of high-density recording media. Here, the
controlled strain engineering of GaFeN layers with FeN embedded
nanocrystals (NCs) \textit{via} AlGaN buffers with different Al
concentration \% is presented. Through the addition of Al
to the buffer, the formation of predominantly prolate-shaped
-FeN NCs takes place. Already at an Al concentration
\,\,5\% the structural properties---phase, shape,
orientation---as well as the spatial distribution of the embedded NCs are
modified in comparison to those grown on a GaN buffer. Although the magnetic
easy axis of the cubic '-GaFeN nanocrystals in the layer on
the buffer lies in-plane, the easy axis of the
-FeN NCs in all samples with AlGaN buffers
coincides with the growth direction, leading to a sizeable
out-of-plane magnetic anisotropy and opening wide perspectives for
perpendicular recording based on nitride-based magnetic nanocrystals.Comment: 29 pages, 10 figures, submitte
Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry
For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported
in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6
(Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in
the same temperature regime. Based on measurements performed on both bulk and
powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the
observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities.
The effect is related to the superconductivity of Ru-1212, but it is not an
intrinsic property of this compound. We provide evidence that the observation
of magnetization peaks in the superconducting state of Ru-1212 is due to flux
motion generated by the movement of the sample in an inhomogeneous field,
during the measurement in the SQUID magnetometer. We propose several tests,
that help to decide, whether the features observed in a SQUID magnetization
measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure
Safety and Efficacy of Dronedarone in the Treatment of Atrial Fibrillation/Flutter
Dronedarone is an amiodarone analog but differs structurally from amiodarone in that the iodine moiety was removed and a methane-sulfonyl group was added. These modifications reduced thyroid and other end-organ adverse effects and makes dronedarone less lipophilic, shortening its half-life. Dronedarone has been shown to prevent atrial fibrillation/flutter (AF/AFl) recurrences in several multi-center trials. In addition to its rhythm control properties, dronedarone has rate control properties and slows the ventricular response during AF. Dronedarone is approved in Europe for rhythm and rate control indications. In patients with decompensated heart failure, dronedarone treatment increased mortality and cardiovascular hospitalizations. However, when dronedarone was used in elderly high risk AF/AFl patients excluding such high risk heart failure, cardiovascular hospitalizations were significantly reduced and the drug was approved in the USA for this indication in 2009 by the Food and Drug Administration. Updated guidelines suggest dronedarone as a front-line antiarrhythmic in many patients with AF/Fl but caution that the drug should not be used in patients with advanced heart failure. In addition, the recent results of the PALLAS trial suggest that dronedarone should not be used in the long-term treatment of patients with permanent AF
Josephson Plasma in RuSr2GdCu2O8
Josephson plasma in RuSrGdCuO,
RuSrGdCuO (x = 0.3), and
RuSrEuCeCuO (x = 0.5) compounds is
investigated by the sphere resonance method. The Josephson plasma is observed
in a low-frequency region (around 8.5 cm at T ) for
ferromagnetic RuSrGdCuO, while it increases to 35 cm
for non-ferromagnetic RuSrGdCuO (x = 0.3), which
represents a large reduction in the Josephson coupling at ferromagnetic
RuO block layers. The temperature dependence of the plasma does not shift
to zero frequency ({\it i.e.} = 0) at low temperatures, indicating that
there is no transition from the 0-phase to the -phase in these compounds.
The temperature dependence and the oscillator strength of the peak are
different from those of other non-magnetic cuprates, and the origins of these
anomalies are discussed.Comment: to appear in Phys. Rev.B Rapid Com
Study of the crystal structure, superconducting and magnetic properties of Ru1-xFexSr2GdCu2O8
Samples of the Ru1-xFexSr2GdCu2O8 system with x = 0, 0.025, 0.05, 0.075, 0.1
and 0.2, were prepared and their structural, superconducting and magnetic
properties were studied. Rietveld refinement of the X-ray diffraction patterns
show that the Fe substitution occurs in both Ru and Cu sites. An increase of Fe
concentration produces no significant changes in the bond angle Ru-O(3)-Ru,
which is a measure of the rotation of the RuO6 octahedra around the c-axis, and
also in the bond angle Ru-O(1)-Cu, which is a measure of the canting of the
RuO6 octahedra. On the other hand, the bond angle Cu-O(2)-Cu, which is a
measure of the buckling of the CuO2 layer, has a slight tendency to decrease
with the increase of the Fe content. We found thet both ferromagnetic and
superconducting transition temperatures are reduced with the increase of Fe
concentration. Analisys related to the decay of the superconducting and
ferromagnetic states is presented.Comment: 9 pages, 7 figure
Mapping competencies taught in public health – Experience of the Europubhealth Consortium
International audienceBackground Public health education aims at producing a competent workforce. The WHO-ASPHER framework proposes a set of relevant public health competencies organised in 10 sections (e.g. science practice, leadership, law policies and ethics etc). As part of the Europubhealth consortium (EPHc), eight universities collaborate for the delivery of a 2-year international public health master course. The course includes a first-year, or foundation component (4 options), and a second-year or specialisation component (7 options). Objectives In 2020, EPHc decided to use the framework in order to map the competencies addressed, and the level of proficiency aimed at, by each Y1 and Y2 option of the Master. To that end, component's coordinators answered an 84-item questionnaire covering the whole framework. Answers were summarised by calculating mean proficiency levels for each competency section. Results There were differences in overall proficiency levels between years with, as expected, higher scores in Y2. Options in Y1 reached medium to high proficiency scores for the sections “science practice”, “health promotion” and “communication” with scores of 2.6 to 3 (on a 1 to 4 scale). When compared with Y1 on a heat-map, Y2 options displayed more contrasted profiles, typically focussing (i.e. scores > 3.5) on 3 out of the 10 sections of competencies. Except for the “collaborations and partnership” section, the training pathways offered by the EPHc seem to offer opportunities for a high proficiency level in all domains of competencies. Conclusions The mapping proved a useful exercise to identify strengths and complementarities among the EPHc. The results suggest that the EPHc master course is coherent and offers students opportunities to gain proficiency in most competencies relevant to public health practice. Key messages • Competency-based education is likely to shape the future public health workforce. • The WHO-ASPHER framework proved a useful tool to map public health competencies addressed in the teaching of the Europubhealth international Master
Polyenylpyrrole Derivatives Inhibit NLRP3 Inflammasome Activation and Inflammatory Mediator Expression by Reducing Reactive Oxygen Species Production and Mitogen-Activated Protein Kinase Activation
10.1371/journal.pone.0076754PLoS ONE810-POLN
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