97 research outputs found
Method to determine defect positions below a metal surface by STM
The oscillatory voltage dependence of the conductance of a quantum point
contact in the presence of a single point-like defect has been analyzed
theoretically. Such signals are detectable and may be exploited to obtain
information on defect positions below a metal surface. Both tunnel junctions
and ballistic contacts of adiabatic shape have been considered. The effect of
quantum interference has been taking into account between the principal wave
that is directly transmitted through the contact and the partial wave that is
scattered by the contact and the defect. This effect leads to oscillations of
the conductance as a function of applied voltage. We obtain the dependence of
the period and amplitude of the conductance oscillations on the position of the
defect inside the metal.Comment: 16 pages, 7 figure
Temperature-dependent quantum electron transport in 2D point contact
We consider a transmission of electrons through a two-dimensional ballistic
point contact in the low-conductance regime below the 0.7-anomaly. The
scattering of electrons by Friedel oscillations of charge density results in a
contribution to the conductance proportional to the temperature. The sign of
this linear term depends on the range of the electron-electron interaction and
appears to be negative for the relevant experimental parameters.Comment: 10 pages, 5 figure
Secreted hydrolases from streptomycin-resistant strains of Bacillus intermedius
Alkaline phosphatase and serine proteinase have been isolated from streptomycin-resistant strains of Bacillus intermedius using ion-exchange, affinity and FPLC chromatography. Substrate blotting analysis and electrophoresis revealed two phosphatase forms with molecular weight of 40 and 50 kDa. The pH and temperature optima of phosphatase were at pH 9.5 and 50°C. The enzyme showed a broad substrate specificity. It was suggested that the two forms of phosphatase are the products of processing, in which serine proteinase is the participant. Two proteinase peaks with molecular weights of 29 and 33 kDa were isolated from B. intermedius S7, the first peak having only 5% of the activity of the second peak. The major peak was identical to serine proteinase described earlier. The minor peak was distinct from the major one by the pH-optima. Analysis of inhibitors' effects revealed that the minor peak also corresponded to serine proteinase
К 100-ЛЕТНЕМУ ЮБИЛЕЮ ПЕРВОЙ В МИРЕ КАФЕДРЫ РЕНТГЕНОЛОГИИ
The article reflects the stages of development of the first in the world department of radiology throughout the century. During the existence of the department, it was headed by eminent scientists. Under their leadership, the department staff made an invaluable contribution not only to the development of radiology as a science, but also to the development of teaching this specialty in the USSR. The traditions of innovation and teaching excellence laid down by the founders of the department are preserved and developed at the present stage.В статье отражены этапы развития первой в мире кафедры рентгенологии на протяжении века. За время существования кафедры ею руководили выдающиеся ученые. Под их руководством сотрудники кафедры внесли неоценимый вклад не только в развитие рентгенологии как науки, но и в становление преподавания этой специальности в СССР. Традиции новаторства и мастерства преподавания, заложенные основоположниками кафедры, сохраняются и развиваются на современном этапе
Secreted hydrolases from streptomycin-resistant strains of Bacillus intermedius
Alkaline phosphatases and serine proteinases have been isolated from the culture liquid of streptomycin-resistant strains of Bacillus intermedius using ion-exchange and affinity chromatography and FPLC. Substrate blotting and electrophoresis revealed two phosphatase forms with molecular masses of 40 and 50 kD. The enzyme had maximal activity at pH 9.5 and 50°C and could cleave the phosphate moiety from a range of substrates. It is suggested that both forms of the phosphatase are products of processing that involves a serine proteinase. Two proteinases, with molecular masses of 29 and 33 kD, were purified to homogeneity from the culture liquid of A. intermedius S7. The protein from the major peak was identical in its properties to an earlier described serine proteinase. The minor peak was 5% of the major one. These enzymes had different pH optima. Inhibitor analysis indicated that the minor peak is also a serine proteinase
Classification of human coronary atherosclerotic plaques with T1, T2 and Ultrashort TE MRI
Multicontrast MRI with T1, T2 and Ultrashort TE (UTE) sequences is used to image atherosclerotic plaque in human coronary arteries. MRI classification of the plaques is compared with their histological classification and found to correlate extremely well. The addition of UTE MRI adds significant value to the imaging of human coronary artery plaque by MRI
Comparative efficacy of a combination of undenatured type II collagen, Boswellic acids, methylsulfonylmethane, vitamins C and D<sub>3</sub> and a combination of chondroitin sulfate and glucosamine hydrochloride in the treatment of primary osteoarthritis of the knee joint
Aim. To evaluate the efficacy of Artneo (AN) in comparison with a combination of glucosamine hydrochloride and chondroitin sulfate (GC) in patients with osteoarthritis (OA) of the knee joint (KJ).
Materials and methods. 70 patients with stages I–III of primary knee OA were randomized into 2 groups. Participants in the 1st (n=35) took AN 1 caps/day, in the 2nd (n=35) GC according to the standard regimen. After 7, 30, 90, 180 days, the Lequesne index (severity of OA), pain when moving according to VAS, WOMAC score were assessed, after 1, 3, 6 months – quality of life SF-36 and morning stiffness, after 6 months – MRI with T2 mapping, laboratory safety indicators.
Results. Over the course of 6 months of use, an improvement in the WOMAC index and a decrease in pain were observed without intergroup differences, and a greater decrease in stiffness in the AN group. After 3 months, the severity of OA decreased from moderate to mild in the AN group and was significantly lower compared to the GC group; quality of life (physical component of SF-36) was higher in the AN group. After 6 months, there was an improvement in cartilage ultrastructure (T2 relaxation time) in both groups and a more pronounced reduction of the synovitis area (MRI) in the AN group (2.95 and 1.37 times in the AN and GC group, respectively). There were no clinically significant adverse reactions observed in both groups.
Conclusion. The use of AN in patients with stage I–III primary knee OA was not inferior in efficacy to the combination of GC. Further studies with greater statistical power (sample size) and follow-up period are warranted including in real clinical practice
Enzymatic properties of thiol-dependent serine proteinase of Bacillus intermedius 3-19
Effects of a thiol-dependent serine proteinase of Bacillus intermedius on peptide substrates and insulin B-chain were studied. The enzyme preferably splits peptide bonds formed by carboxyl groups of hydrophobic amino acids. Ca2+ increases the thermal stability of the proteinase significantly. The kinetic characteristics of hydrolysis of Z-Ala-Ala-Leu-pNA by this enzyme was determined as Km = 1.25 mM and kcat = 0.15 sec-1. The enzyme has high stability to DMFA and isopropanol, and is able to catalyze peptide bond synthesis
Resonant multiple Andreev reflections in mesoscopic superconducting junctions
We investigate the properties of subharmonic gap structure (SGS) in
superconducting quantum contacts with normal-electron resonances. We find two
distinct new features of the SGS in resonant junctions which distinguish them
from non-resonant point contacts: (i) The odd-order structures on the
current-voltage characteristics of resonant junctions are strongly enhanced and
have pronounced peaks, while the even-order structures are suppressed, in the
case of a normal electron resonance being close to the Fermi level. (ii)
Tremendous current peaks develop at where indicates a
distance of the resonance to the Fermi level. These properties are determined
by the effect of narrowing of the resonance during multiple Andreev reflections
and by overlap of electron and hole resonances.Comment: 13 pages, 10 figure
Andreev reflection and order parameter symmetry in heavy-fermion superconductors: the case of CeCoIn
We review the current status of Andreev reflection spectroscopy on the heavy
fermions, mostly focusing on the case of CeCoIn, a heavy-fermion
superconductor with a critical temperature of 2.3 K. This is a well-established
technique to investigate superconducting order parameters via measurements of
the differential conductance from nanoscale metallic junctions. Andreev
reflection is clearly observed in CeCoIn as in other heavy-fermion
superconductors. The measured Andreev signal is highly reduced to the order of
maximum 13% compared to the theoretically predicted value (100%).
Analysis of the conductance spectra using the extended BTK model provides a
qualitative measure for the superconducting order parameter symmetry, which is
determined to be -wave in CeCoIn. A phenomenological model is
proposed employing a Fano interference effect between two conductance channels
in order to explain both the conductance asymmetry and the reduced Andreev
signal. This model appears plausible not only because it provides good fits to
the data but also because it is highly likely that the electrical conduction
occurs via two channels, one into the heavy electron liquid and the other into
the conduction electron continuum. Further experimental and theoretical
investigations will shed new light on the mechanism of how the coherent
heavy-electron liquid emerges out of the Kondo lattice, a prototypical strongly
correlated electron system. Unresolved issues and future directions are also
discussed.Comment: Topical Review published in JPCM (see below), 28 pages, 9 figure
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