25,444 research outputs found
Non-equilibrium structural phase transitions of the vortex lattice in MgB2
We have studied non-equilibrium phase transitions in the vortex lattice in
superconducting MgB2, where metastable states are observed in connection with
an intrinsically continuous rotation transition. Using small-angle neutron
scattering and a stop-motion technique, we investigated the manner in which the
metastable vortex lattice returns to the equilibrium state under the influence
of an ac magnetic field. This shows a qualitative difference between the
supercooled case which undergoes a discontinuous transition, and the
superheated case where the transition to the equilibrium state is continuous.
In both cases the transition may be described by an an activated process, with
an activation barrier that increases as the metastable state is suppressed, as
previously reported for the supercooled vortex lattice [E. R. Louden et al.,
Phys. Rev. B 99, 060502(R) (2019)]. Separate preparations of superheated
metastable vortex lattices with different domain populations showed an
identical transition towards the equilibrium state. This provides further
evidence that the vortex lattice metastability, and the kinetics associated
with the transition to the equilibrium state, is governed by nucleation and
growth of domains and the associated domain boundaries.Comment: 27 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1812.0597
Inelastic X-ray scattering from valence electrons near absorption edges of FeTe and TiSe
We study resonant inelastic x-ray scattering (RIXS) peaks corresponding to
low energy particle-hole excited states of metallic FeTe and semi-metallic
TiSe for photon incident energy tuned near the absorption edge of
Fe and Ti respectively. We show that the cross section amplitudes are well
described within a renormalization group theory where the effect of the core
electrons is captured by effective dielectric functions expressed in terms of
the the atomic scattering parameters of Fe and Ti. This method can be
used to extract the dynamical structure factor from experimental RIXS spectra
in metallic systems.Comment: 6 pages, 4 figure
Pauli Paramagnetic Effects on Vortices in Superconducting TmNi2B2C
The magnetic field distribution around the vortices in TmNi2B2C in the
paramagnetic phase was studied experimentally as well as theoretically. The
vortex form factor, measured by small-angle neutron scattering, is found to be
field independent up to 0.6 Hc2 followed by a sharp decrease at higher fields.
The data are fitted well by solutions to the Eilenberger equations when
paramagnetic effects due to the exchange interaction with the localized 4f Tm
moments are included. The induced paramagnetic moments around the vortex cores
act to maintain the field contrast probed by the form factor.Comment: 4 pages, 4 figure
Bulk, rare earth and other trace elements in Apollo 14 and 15 and Luna 16 samples
The chemical abundances were measured by instrumental and radiochemical neutron activation analysis in a variety of lunar specimens. Apollo 14 soils are characterized by significant enrichments of Al2O3, Na2O and K2O and depletions of TiO2, FeO, MnO and Cr2O3 relative to Apollo 11 and to most of Apollo 12 soils. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within approximately 200 m from the lunar module. Two Luna 16 breccias are similar in composition to Luna 16 soils. Four Apollo 15 soils (LM, STA 4, 9, and 9a) have variable compositions. Interelement correlations between MnO-FeO, Sc-FeO, V-Cr2O3 and K2O-Hf negate the hypothesis that howardite achondrites may be primitive lunar matter, argue against the fission hypothesis for the origin of the moon, and precludes any selective large scale volatilization of alkalies during lunar magmatic events
Jet directions in Seyfert galaxies: B and I imaging data
We present the results of broad-band B and I imaging observations for a
sample of 88 Seyfert galaxies (29 Seyfert 1's and 59 Seyfert 2's), selected
from a mostly isotropic property, the flux at 60m. We also present the B
and I imaging results for an additional sample of 20 Seyfert galaxies (7
Seyfert 1's and 13 Seyfert 2's), selected from the literature and known to have
extended radio emission. The I band images are fitted with ellipses to
determine the position angle and ellipticity of the host galaxy major axis.
This information will be used in a future paper, combined with information from
radio observations, to study the orientation of radio jets relative to the
plane of their host galaxies (Kinney et al. 2000). Here we present surface
brightness profiles and magnitudes in the B and I bands, as well as mean
ellipticities and major axis position angles.Comment: To appear in The Astrophysical Journal Supplement Series, June 2000.
48 pages, 7 tables, 19 gif and 11 postscript figures. Better quality figures
can be obtained with the autho
On the Use of a Test to Exhaustion Specific to Tennis (TEST) with Ball Hitting by Elite Players.
PURPOSE: We aimed to a) introduce a new Test to Exhaustion Specific to Tennis (TEST) and compare performance (test duration) and physiological responses to those obtained during the 20-m multistage shuttle test (MSST), and b) determine to which extent those variables correlate with performance level (tennis competitive ranking) for both test procedures.
METHODS: Twenty-seven junior players (8 males, 19 females) members of the national teams of the French Tennis Federation completed MSST and TEST, including elements of the game (ball hitting, intermittent activity, lateral displacement), in a randomized order. Cardiorespiratory responses were compared at submaximal (respiratory compensation point) and maximal loads between the two tests.
RESULTS: At the respiratory compensation point oxygen uptake (50.1 ± 4.7 vs. 47.5 ± 4.3 mL.min(-1).kg(-1), p = 0.02), but not minute ventilation and heart rate, was higher for TEST compared to MSST. However, load increment and physiological responses at exhaustion did not differ between the two tests. Players' ranking correlated negatively with oxygen uptake measured at submaximal and maximal loads for both TEST (r = -0.41; p = 0.01 and -0.55; p = 0.004) and MSST (r = -0.38; P = 0.05 and -0.51; p = 0.1).
CONCLUSION: Using TEST provides a tennis-specific assessment of aerobic fitness and may be used to prescribe aerobic exercise in a context more appropriate to the game than MSST. Results also indicate that VO2 values both at submaximal and maximal load reached during TEST and MSST are moderate predictors of players competitive ranking
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