15,477 research outputs found
Suppression of low-energy Andreev states by a supercurrent in YBa_2Cu_3O_7-delta
We report a coherence-length scale phenomenon related to how the high-Tc
order parameter (OP) evolves under a directly-applied supercurrent. Scanning
tunneling spectroscopy was performed on current-carrying YBa_2Cu_3O_7-delta
thin-film strips at 4.2K. At current levels well below the theoretical
depairing limit, the low-energy Andreev states are suppressed by the
supercurrent, while the gap-like structures remain unchanged. We rule out the
likelihood of various extrinsic effects, and propose instead a model based on
phase fluctuations in the d-wave BTK formalism to explain the suppression. Our
results suggest that a supercurrent could weaken the local phase coherence
while preserving the pairing amplitude. Other possible scenarios which may
cause the observed phenomenon are also discussed.Comment: 6 pages, 4 figures, to appear in Physical Review
Nicotine Dependence as a Mediator of Project EX's Effects to Reduce Tobacco Use in Scholars.
In Spain, 44% of 14-18-year-olds have smoked, and 12.5% have smoked cigarettes in the last 30 days. Nicotine is one of the most addictive substances, and can lead to serious addiction in adulthood with adverse consequences to one's health. School plays a relevant role in health promotion and preventing risk behaviors such as tobacco consumption. Despite the fact that some school-based tobacco cessation and prevention interventions prove to be effective for their purposes, there is a lack of understanding as to why these programs succeed or fail. This longitudinal study aims to test the nicotine dependence (ND) as a mediator of Project EX's effect - a tobacco-use cessation program developed for high school youth to reduce tobacco consumption in scholars. Six high schools located in the Mediterranean coast were randomized for the participation of the program (Spanish version of Project EX) or a waiting-list group with baseline, immediate-posttest, and 12-month follow-up assessments. At baseline, 1,546 adolescents aged 14-21 years old (mean age: 15.28; SD = 1.20; 46% were women) were evaluated by self-administered tests on tobacco consumption and ND. A biomarker of smoke inhalation - a measurement of exhaled carbon monoxide (ECM) - was used. Participants who were smokers (N = 501; 32%) were selected for this study. Mediation analyses were conducted using the PROCESS v2.12 macro for Windows. The significant criterion was p ≤ 0.05, and 5,000 samples were used for bias-corrected bootstrap confidence intervals. Results indicated that Project EX indirectly decreased the number of cigarettes smoked in the last month, the number of cigarettes smoked within the last 7 days, the number of daily cigarettes, and ECM level at 12-month follow up through decreasing the level of ND in the short-term. This is the first Spanish study that explores ND as a mediator of the long-term efficacy of Project EX to reduce tobacco consumption in adolescents. Results suggest that interventions that reduce ND at short-term are more likely to be successful to decrease tobacco use at long-term
Photometric Variability in the Faint Sky Variability Survey
The Faint Sky Variability Survey (FSVS) is aimed at finding photometric
and/or astrometric variable objects between 16th and 24th mag on time-scales
between tens of minutes and years with photometric precisions ranging from 3
millimag to 0.2 mag. An area of 23 deg, located at mid and high Galactic
latitudes, was covered using the Wide Field Camera (WFC) on the 2.5-m Isaac
Newton Telescope (INT) on La Palma. Here we present some preliminary results on
the variability of sources in the FSVS.Comment: 4 pages, 3 figures, to appear in 14th European Workshop on White
Dwarfs, ASP Conference Series, eds. D. Koester, S. Moehle
Spin dependent D-brane interactions and scattering amplitudes in matrix theory
Spin interactions beteween two moving Dp-branes are analyzed using the
Green-Schwarz formalism of boundary states. This approach turns out to be
extremely efficient to compute all the spin effects related by supersymmetry to
the leading v^4/r^7-p term. All these terms are shown to be scale invariant,
supporting a matrix model description of supergravity interactions. By
employing the LSZ reduction formula for matrix theory and the mentioned
supersymmetric effective potential for D0-branes, we compute the t-pole of
graviton-graviton and three form-three form scattering in matrix theory. The
results are found to be in complete agreement with tree level supergravity in
the corresponding kinematical regime and provide, moreover, an explicit map
between these degrees of freedom in both theories.Comment: 8 pages, no figures, talk presented at the conference "Quantum
aspects of gauge theories, supergravity and unification", Corfu, Greece, to
appear in the proceeding
Study of the stress intensity factors in the bulk of the material with synchrotron diffraction
ArtĂculo de Proceedings de Congreso Internacional Fatigue2017In this work we present the results of a hybrid experimental and
analytical approach for estimating the stress intensity factor. It uses the
elastic strains within the bulk obtained by synchrotron X-ray diffraction
data. The stress intensity factor is calculated using a multi-point overdeterministic
method where the number of experimental data points is
higher than the number of unknowns describing the elastic field
surrounding the crack-tip. The tool is tested on X-ray strain
measurements collected on a bainitic steel. In contrast to surface
techniques the approach provides insights into the crack tip mechanics
deep within the sample.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech. The authors are grateful to the ESRF for ID15 beamtime awarded under MA-1483. Financial
support of Universidad de Malaga through Plan Propio, Junta de AndalucĂa through Proyectos de
Excelencia grant reference TEP-3244, Campus de Excelencia Internacional del Mar (CEIMAR)
and Ministerio de Economia y Competitividad through grant reference MAT2016-76951-C2-2-P is
also acknowledged. PJW acknowledges an ERC advanced grant
Graded Orbital Occupation near Interfaces in a La2NiO4 - La2CuO4 Superlattice
X-ray absorption spectroscopy and resonant soft x-ray reflectivity show a
non-uniform distribution of oxygen holes in a La2NiO4 - La2CuO4 (LNO-LCO)
superlattice, with excess holes concentrated in the LNO layers. Weak
ferromagnetism with Tc = 160 K suggests a coordinated tilting of NiO6
octahedra, similar to that of bulk LNO. Ni d3z2-r2 orbitals within the LNO
layers have a spatially variable occupation. This variation of the Ni valence
near LNO-LCO interfaces is observed with resonant soft x-ray reflectivity at
the Ni L edge, at a reflection suppressed by the symmetry of the structure, and
is possible through graded doping with holes, due to oxygen interstitials taken
up preferentially by inner LNO layers. Since the density of oxygen atoms in the
structure can be smoothly varied with standard procedures, this orbital
occupation, robust up to at least 280 K, is tunable.Comment: 11 pages, 8 figure
Microstructural and morphological properties of homoepitaxial (001)ZnTe layers investigated by x-ray diffuse scattering
The microstructural and morphological properties of homoepitaxial (001)ZnTe
layers are investigated by x-ray diffuse scattering. High resolution reciprocal
space maps recorded close to the ZnTe (004) Bragg peak show different diffuse
scattering features. One kind of cross-shaped diffuse scattering streaks along
directions can be attributed to stacking faults within the epilayers.
Another kind of cross-shaped streaks inclined at an angle of about 80deg with
respect to the in-plane direction arises from the morphology of the
epilayers. (abridged version
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