368 research outputs found
Prospects for the joint development of oil and coal deposits in previsean depressions of Volga-Ural oil and gas province
The article deals with the conditions and patterns bedding oil and coal beds in the Visean sediments that fill local depressions on the surface of paleorelief Tournaisian carbonate strata. The proximity of coal and oil-saturated seams can be used for the joint development of oil and coal deposits
Muon-spin rotation measurements of the penetration depth of the Mo_3Sb_7 superconductor
Measurements of the magnetic field penetration depth \lambda in
superconductor Mo_3Sb_7 (T_c~2.1 K) were carried out by means of
muon-spin-rotation. The absolute values of \lambda, the Ginzburg-Landau
parameter \kappa, the first H_{c1} and the second H_{c2} critical fields at T=0
are \lambda(0)=720(100)nm, \kappa(0)=55(9), \mu_0H_{c1}(0)=1.8(3)mT, and
\mu_0H_{c2}(0)=1.9(2)T. The zero temperature value of the superconducting
energy gap \Delta(0) was found to be 0.35(1)meV corresponding to the ratio
2\Delta(0)/k_BT_c=3.83(10). At low temperatures \lambda^{-2}(T) saturates and
becomes constant below T~0.3T_c, in agreement with what is expected for s-wave
BCS superconductors. Our results suggest that Mo_3Sb_7 is a BCS superconductor
with the isotropic energy gapComment: 5 pages, 4 figure
Muon-spin-rotation measurements of the penetration depth in Li_2Pd_3B
Measurements of the magnetic field penetration depth in the ternary
boride superconductor LiPdB ( K) have been carried out by
means of muon-spin rotation (SR). The absolute values of , the
Ginzburg-Landau parameter , and the first and the second
critical fields at T=0 obtained from SR were found to be
nm, , mT, and
T, respectively. The zero-temperature value of the
superconducting gap 1.31(3) meV was found, corresponding to the
ratio . At low temperatures saturates and
becomes constant below , in agreement with what is expected for
s-wave BCS superconductors. Our results suggest that LiPdB is a s-wave
BCS superconductor with the only one isotropic energy gap.Comment: 6 pages, 7 figure
Geological bases of the coal deposits prediction in the Volga-Ural oil and gas province in connection with depletion of oil resources
Volga-Ural oil and gas province is one of the oldest on the territory of Russia and is characterized by the depletion of proven reserves. An alternative source of hydrocarbons that can replace conventional oil is coal. Within the Volga-Ural oil and gas province in the territory of Tatarstan in the Lower Carboniferous deposits by now identified and evaluated 95 deposits with resources of about 3.5 billion tons. Patterns of distribution of Visean coal deposits in the region are controlling by paleotectonic, palaeogeomorphology and facies factors. Evaluation of prognostic resources of Visean coals with considering to the conditions of their formation and involvement to erosional incision significantly increases the accuracy of the prediction. Coal resources comparable with oil and may have industrial importance as a source of coalbed methane. Researches indicate that the increasing of gassing from the formation is possible by thermal effects on the coal substance. Thermal effects on the formation may increase the efficiency of coal deposits mining by method of gas field
Pressure effect on the in-plane magnetic penetration depth in YBa_2Cu_4O_8
We report a study of the pressure effect (PE) on the in-plane magnetic field
penetration depth lambda_{ab} in YBa_2Cu_4O_8 by means of Meissner fraction
measurements. A pronounced PE on lambda_{ab}^{-2}(0) was observed with a
maximum relative shift of \Delta\lambda^{-2}_{ab}/\lambda^{-2}_{ab}= 44(3)% at
a pressure of 10.2 kbar. It arises from the pressure dependence of the
effective in-plane charge carrier mass and pressure induced charge carrier
transfer from the CuO chains to the superconducting CuO_2 planes. The present
results imply that the charge carriers in YBa_2Cu_4O_8 are coupled to the
lattice.Comment: 4pages 3 figure
Comment on ``Muon-spin rotation studies of the superconducting properties of Mo_3Sb_7'', Phys.Rev.B 78, 172505 (2008)
In a recent article Tran et al. [Phys. Rev.B 78, 172505 (2008)] report on the
result of the muon-spin rotation (\muSR) measurements of Mo_3Sb_7
superconductor. Based on the analysis of the temperature and the magnetic field
dependence of the Gaussian relaxation rate \sigma_{sc} they suggest that
Mo_3Sb_7 is the superconductor with two isotropic s-wave like gaps. An
additional confirmation was obtained from the specific heat data published
earlier by partly the same group of authors in [Acta Mater. 56, 5694 (2008)].
The purpose of this Comment is to point out that from the analysis made by Tran
et al. the presence of two superconducting energy gaps in Mo_3Sb_7 can not be
justified. The analysis of \muSR data does not account for the reduction of
\sigma_{sc} with increasing temperature, and, hence, yields inaccurate
information on the magnetic penetration depth. The specific heat data can be
satisfactory described within the framework of the one-gap model with the small
residual specific heat component. The experimental data of Tran et al., as well
as our earlier published \muSR data [Phys. Rev. B 78, 014502 (2008)] all seem
to be consistent with is the presence of single isotropic superconducting
energy gap in Mo_3Sb_7.Comment: Comment on Phys.Rev.B 78, 172505 (2008
Mutual independence of critical temperature and superfluid density under pressure in optimally electron-doped superconducting LaFeAsOF
The superconducting properties of LaFeAsOF in conditions of
optimal electron-doping are investigated upon the application of external
pressure up to kbar. Measurements of muon-spin spectroscopy and dc
magnetometry evidence a clear mutual independence between the critical
temperature and the low-temperature saturation value for the ratio
(superfluid density over effective band mass of Cooper pairs).
Remarkably, a dramatic increase of % is reported for at
the maximum pressure value while is substantially unaffected in the
whole accessed experimental window. We argue and demonstrate that the
explanation for the observed results must take the effect of non-magnetic
impurities on multi-band superconductivity into account. In particular, the
unique possibility to modify the ratio between intra-band and inter-bands
scattering rates by acting on structural parameters while keeping the amount of
chemical disorder constant is a striking result of our proposed model.Comment: 8 pages (Main text: 5 pages. Paper merged with supplemental
information), 5 figure
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