346 research outputs found
Competition of multiband superconducting and magnetic order in ErNi2B2C observed by Andreev reflection
Point contacts (PC) Andreev reflection dV/dI spectra for the
antiferromagnetic (T_N =6K) superconductor (Tc=11K) ErNi2B2C have been measured
for the two main crystallographic directions. Observed retention of the Andreev
reflection minima in dV/dI up to Tc directly points to unusual superconducting
order parameter (OP) vanishing at Tc. Temperature dependence of OP was obtained
from dV/dI using recent theory of Andreev reflection including pair-breaking
effect. For the first time existence of a two superconducting OPs in ErNi2B2C
is shown. A distinct decrease of both OPs as temperature is lowered below T_N
is observed.Comment: 5 pages, 5 figs, to be published in Europhys. Let
Probe microscopy in the study of the surface of aluminum alloys
The work was supported by the Grant of the RNF 14-19-01033-P (study of topography and elemental composition of the surface) and the State Task (№ State registration AAAA-A17-117021310379-5 - study of electrical properties of the surface). The authors are grateful to N.A. Belov (MISiS) for providing samples
On the Specific Features of Temperature Evolution in Ultracold Plasmas
A theoretical interpretation of the recent experimental studies of
temperature evolution in the course of time in the freely-expanding ultracold
plasma bunches, released from a magneto-optical trap, is discussed. The most
interesting result is finding the asymptotics of the form T_e ~ t^{-(1.2 +/-
0.1)} instead of t^{-2}, which was expected for the rarefied monatomic gas
during inertial expansion. As follows from our consideration, the substantially
decelerated decay of the temperature can be well explained by the specific
features of the equation of state for the ultracold plasmas with strong
Coulomb's coupling, whereas a heat release due to inelastic processes (in
particular, three-body recombination) does not play an appreciable role in the
first approximation. This conclusion is confirmed both by approximate
analytical estimates, based on the model of "virialization" of the
charged-particle energies, and by the results of "ab initio" numerical
simulation. Moreover, the simulation shows that the above-mentioned law of
temperature evolution is approached very quickly--when the virial criterion is
satisfied only within a factor on the order of unity.Comment: LaTeX + 3 eps figures, 16 pages. Plasma Physics Reports, v.37, in
press (2011
Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films
Point-contact (PC) Andreev-reflection (AR) measurements of the
superconducting gap in iron-oxipnictide ReFeAsO_{1-x}F_x (Re=La, Sm) films have
been carried out. The value of the gap is distributed in the range 2\Delta
\simeq 5-10 meV (for Re=Sm) with a maximum in the distribution around 6 meV.
Temperature dependence of the gap \Delta(T) can be fitted well by BCS curve
giving reduced gap ratio 2\Delta /kT_c^*\simeq 3.5 (here T_c^* is the critical
temperature from the BCS fit). At the same time, an expected second larger gap
feature was difficult to resolve distinctly on the AR spectra making
determination reliability of the second gap detection questionable. Possible
reasons for this and the origin of other features like clear-cut asymmetry in
the AR spectra and current regime in PCs are discussed.Comment: 6 two-column pages, 6 figs., 26 Refs., to be published in
Superconductor Science and Technolog
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
Measurement of B(J/psi->eta_c gamma) at KEDR
We present a study of the inclusive photon spectrum from 6.3 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of the radiative decay J/psi -> eta_c gamma,
eta_c width and mass. Taking into account an asymmetric photon line shape we
obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4
+- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th
International Workshop on Charm Physics (Charm2010), October 21-24, 2010,
IHEP, Beijin
Pathomorphological picture of diabetic nephropathy in experimental diabetes mellitus
Aim. To conduct a morphological study of the renal glomerulus in experimental diabetes mellitus and to study the pathomorphological features of the development of diabetic nephropathy.
Methods. The study was carried out on 25 male Wistar rats. Modeling of diabetes mellitus was carried out by intraperitoneal injection of streptozotocin at a dose of 65 mg/kg. For more selective modeling of type 2 diabetes, the rats of the control group were intraperitoneally administered a solution of cytoflavin, calculated by the dosage of nicotinamide 115 mg/kg. In the comparison group 1 ml of physiological solution was administered in a similar manner. On day 28 of the experiment, the animals were euthanized under ether anesthesia, the kidneys were extracted, purified and washed with physiological saline. The material was fixed in a 10% neutral formalin solution. Using the morphometric method, the area of the renal glomeruli and the area of the capillary lumens were measured, and after special computer processing of digital photographs, the total area of the vascular bed in the glomerulus and the area of mesangium in the renal glomerulus were estimated.
Results. After four weeks of experiment on rats with diabetes mellitus, some characteristic changes in the morphofunctional state of renal tissues developed: an increase of the area of renal glomeruli, thickening of the basement membrane of glomerular capillaries, an increase in the size of podocytes with a decrease of their number, and foci of nephrosclerosis.
Conclusion. Based on the results of the study, characteristic pathomorphological phenomena in the kidneys of rats with experimental diabetes mellitus were recorded, which indicate the development of diabetic nephropathy
Measurement of J/psi to eta_c gamma at KEDR
We present a study of the inclusive photon spectra from 5.9 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c
width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV,
G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
Phonon structure in I-V characteristic of MgB point-contacts
The search of the phonon structure at the above-gap energies was carried out
for spectra of MgB point contacts with a normal metal.
The two-band model is assumed not only for the gap structure in
-characteristics, but also for phonons in
point-contact spectra, with up to the maximum lattice vibration energy. Since
the current is carried mostly by charges of 3D-band, whereas the strong
electron-phonon interaction occurs in 2D-band, we observe the phonon
peculiarities due to ''proximity'' effect in {\it k}-space, which depends on
the variation of interband coupling through the elastic scattering.Comment: 6 pages, 4 figures, revtex4, reported in International Conference
"Modern Problems in Superconductivity", 9-13 September, Yalta, Ukrain
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