Open Access
Access granted
Subscription Access
Vol 44, No 3 (2017)
- Year: 2017
- Articles: 7
- URL: https://journal-vniispk.ru/1068-3356/issue/view/14095
Article
53-55
Quantification of cerebral aspartate concentration in vivo using proton magnetic resonance spectroscopy
Abstract
The 1Н MRS is a unique method allowing in vivo observation of concentrations of proton-containing chemical compounds in human tissues and organs. The main problem of this technique is the signal overlap caused by the similarity of structural fragments of variousmetabolites. To separate overlapped signals, the J-modulation technique for editing spectra, based on the spin–spin interaction can be used. In this study, a method of direct observation of the lifetime aspartate concentration in local regions of the human brain, based on the MEGA-PRESS pulse sequence, is developed for the first time.
56-60
Current-carrying capability of GdBa2Cu3O7−x HTSC tapes in magnetic fields in the temperatute range of 2–100 K
Abstract
The current-carrying capability of the second-generation HTSC tapes based on GdBa2Cu3O7−x (GdBCO), produced by the SuperOx Company by the pulsed laser deposition method is studied. Critical currents inmagnetic fields aremeasured by resistive andmagnetic (using a SQUID magnetometer) methods. The results obtained are compared with characteristics of an YBCO tape grown by chemical deposition (SuperPower, USA).
61-65
Josephson Fourier spectrometer based on HTSC: Construction and the problem of physical implementation of a quantum computer
Abstract
The possibility of developing the broadband Fourier spectrometer based on the unsteady Josephson effect in HTSC, with a frequency range including the terahertz region, is considered. A simple design of a precisely tuned point Josephson junction is developed, which allows “fitting” of its parameters immediately under cryogenic conditions. A modification of such a spectrometer for solving the problems of factorizing multidigit numbers is proposed, which is currently one of the best known motivations of works on the quantum computer development.
66-71
Resonant tunneling GaAs/AlGaAs quantum well structures for p-i-n photovoltaic cells
Abstract
This study is devoted to the development of resonant-tunneling structures of quantum wells implementing resonant matching of lower subbands of size quantization in an electric field of the p-i-n junction of photovoltaic elements. The method for controlling the lower subband position in quantum wells by introducing a series of the tunnel-transparent barriers into a quantum well is proposed. The possibility of varying the level position in deep quantum wells in a wide range up to the continuous spectrum is demonstrated on a grown model structure; in this case, agreement between calculated and experimental subband positions is achieved.
72-76
Numerical study of the rutile band structure by the Hartree–Fock–Roothaan method in the CO LCAO approximation using the cyclic cluster model
Abstract
The technique for calculatingmaterial characteristicswith the aid of theHartree–Fock–Roothaan method in the CO LCAO approximation using the cyclic clustermodel is considered. The results of the numerical study are verified for the TiO2 system. The band gap minimum (2.9 eV) is calculated for the system under consideration.
77-80
On the energy transport velocity in a dissipative medium
Abstract
An exact definition of the group velocity vg is proposed for a wave process with arbitrary dispersion relation ω = ω′(k) + iω″(k). For the monochromatic approximation, a limit expression vg(k) is obtained. A condition under which vg(k) takes the form of the Kuzelev–Rukhadze expression [1] dω′(k)/dk is found. In the general case, it appears that vg(k) is defined not only by the dispersion relation ω(k), but also by other elements of the initial problem. As applied to the dissipative medium, it is shown that vg(k) defines the field energy transfer velocity, and this velocity does not exceed thee light speed in vacuum. An expression for the energy transfer velocity is also obtained for the case where the dispersion relation is given in the form k = k′(ω) + ik″(ω) which corresponds to the boundary problem.
81-88