The effect of Aharanov-Bohm phase on the magnetic-field dependence of two-pulse echos in glasses at low temperatures

The anomalous response of glasses in the echo amplitude experiment is explained in the presence of a magnetic field. We have considered the low energy excitations in terms of an effective two level system. The effective model is constructed on the flip-flop configuration of two interacting two level systems. The magnetic field affects the tunneling amplitude through the Aharanov-Bohm effect. The effective model has a lower scale of energy in addition to the new distribution of tunneling parameters which depend on the interaction. We are able to explain some features of echo amplitude versus a magnetic field, namely, the dephasing effect at low magnetic fields, dependence on the strength of the electric field, pulse separation effect and the influence of temperature. However this model fails to explain the isotope effects which essentially can be explained by the nuclear quadrupole moment. We will finally discuss the features of our results.Comment: 8 pages, 7 figure

Effect of nuclear quadrupole interactions on the dynamics of two-level systems in glasses

The standard tunneling model describes quite satisfactorily the thermal properties of amorphous solids at temperatures $T<1K$ in terms of an ensemble of two-level systems possessing logarithmically uniform distribution over their tunneling amplitudes and uniform distribution over their asymmetry energies. In particular, this distribution explains the observable logarithmic temperature dependence of the dielectric constant. Yet, experiments have shown that at ultralow temperatures $T<5mK$ such a temperature behavior breaks down and the dielectric constant becomes temperature independent (plateau effect). In this letter we suggest an explanation of this behavior exploiting the effect of the nuclear quadrupole interaction on tunneling. We show that below a temperature corresponding to the characteristic energy of the nuclear quadrupole interaction the effective tunneling amplitude is reduced by a small overlap factor of the nuclear quadrupole ground states in the left and right potential wells of the tunneling system. It is just this reduction that explains the plateau effect . We predict that the application of a sufficiently large magnetic field $B>10T$ should restore the logarithmic dependence because of the suppression of the nuclear quadrupole interaction.Comment: To appear in the Physical Review Letter

On the theory of resonant susceptibility of dielectric glasses in magnetic field

The anomalous magnetic field dependence of dielectric properties of insulating glasses in the temperature interval $10mK<T<50mK$ is considered. In this temperature range, the dielectric permittivity is defined by the resonant contribution of tunneling systems. The external magnetic field regulates nuclear spins of tunneling atoms. This regulation suppresses a nuclear quadrupole interaction of these spins with lattice and, thus, affects the dielectric response of tunneling systems. It is demonstrated that in the absence of an external magnetic field the nuclear quadrupole interaction $b$ results in the correction to the permittivity $\delta\chi\sim| b| /T$ in the temperature range of interest. An application of a magnetic field results in a sharp increase of this correction approximately by a factor of two when the Zeeman splitting $m$ approaches the order of $| b|$. Further increase of the magnetic field results in a relatively smooth decrease in the correction until the Zeeman splitting approaches the temperature. This smooth dependence results from tunneling accompanied by a change of the nuclear spin projection. As the magnetic field surpasses the temperature, the correction vanishes. The results obtained in this paper are compared with experiment. A new mechanism of the low temperature nuclear spin-lattice relaxation in glasses is considered.Comment: 9 Pages, 5 Figures, To be submitted to the Physical Review B, please send comment

In vitro rhizogenesis of sugar beet microclones

The features of rhizogenesis of male-sterile simple hybrids, maternal components of sugar beet heterozosis hybrid and O-types of Darinka variety grown from seeds were investigated. The paper presents the results of studying the main basic nutrient media (B5–A1, B5–A2, B5–A3, B5–A4, B5–A5 and B5–A6) for rhizogenesis, in which the content of macro- and microelements has been reduced by three times, the content of sucrose is reduced by almost 6 times, the amount of agar is reduced by almost five times, while the vitamin РР content is increased by 1.6 times, and the BAP is completely removed. The largest number of rooted microclones was obtained with NAAs by the high indexes of average number of roots and medium indexes of average roots length. To the second, by the number of rooted microclones is assigned, media of 2,4–D, 2,4–DB containing, potassium salt of NAA and IBA were classified, while IAA was characterized by a lower efficiency. The possibilities of regulation of growth and development processes of sugar beet in vitro explants in favor of undifferentiated growth at the stage of proliferation or organogenesis (hemo- and rhizogenesis) have been determined. To improve the quality of rooting of sugar beet plants-regenerants, we have developed the method for dimming agarized nutrient medium with methylene blue at a 0.05% concentration, which made it possible to reduce the inhibitory effect of light on the development of lateral roots. The average index of micro-roots rooting for MS-forms was 81.5 %. The technology of adaptation of micro-roots rooting was developed, in which the plant material at the initial stage of growth had slight morphological changes in the puffer apparatus and stem, but by the end of the vegetation, the plants acquired the appearance characteristic of the donor plants of explants. The clone’s resiliency is reached about 100% in the soil. According to the variability of morphological characteristics in reproduced in vitro sugar beet plants of the MS-forms of the Darynka hybrid, all the plants grown from the regenerants were more, than seed progeny from seed sowing of the same component obtained as a result of the attachment of sterility to the corresponding O-type. It has been found that in vitro cultivation has not weakened, and in some cases even increased the mitotic index of meristem cells of young roots of sugar beet. Most genotypes have reduced the number of pathological mitoses, apparently due to the activation of reparative systems, but did not extend the duration of individual phases of mitosis; without increasing the number of anaphase with bridges and fragments, but changed the number of anaphases with other chromosomal abnormalities. In all variants of the experiment, where activation of growth processes has been observed, the lowest variability of the signs is observed, that is, under the influence of stimulants, which are part of nutrient media, obviously there is unification of cell populations

Split structures in general relativity and the Kaluza-Klein theories

We construct a general approach to decomposition of the tangent bundle of pseudo-Riemannian manifolds into direct sums of subbundles, and the associated decomposition of geometric objects. An invariant structure {\cal H}^r defined as a set of r projection operators is used to induce decomposition of the geometric objects into those of the corresponding subbundles. We define the main geometric objects characterizing decomposition. Invariant non-holonomic generalizations of the Gauss-Codazzi-Ricci's relations have been obtained. All the known types of decomposition (used in the theory of frames of reference, in the Hamiltonian formulation for gravity, in the Cauchy problem, in the theory of stationary spaces, and so on) follow from the present work as special cases when fixing a basis and dimensions of subbundles, and parameterization of a basis of decomposition. Various methods of decomposition have been applied here for the Unified Multidimensional Kaluza-Klein Theory and for relativistic configurations of a perfect fluid. Discussing an invariant form of the equations of motion we have found the invariant equilibrium conditions and their 3+1 decomposed form. The formulation of the conservation law for the curl has been obtained in the invariant form.Comment: 30 pages, RevTeX, aps.sty, some additions and corrections, new references adde

Microbiological monitoring as a component of efficient prevention and treatment of purulent-septic infections in an orthopedics and traumatology department

Efficient monitoring of circulating purulent-septic infectious agents in a clinical setting and a study on antibiotic susceptibility of isolated strains of microorganisms allows identifying changes in the pathogen structure and trends in antibiotic resistance development, which helps to determine the tactics of antibacterial therapy and elaborate appropriate measures. The aim of the study. Retrospective analysis of the results of microbiological monitoring of purulent-septic infectious (PSI) agents in the Orthopedics and Traumatology Department (OTD) of the Zaporizhzhia Central Ambulance and Emergency Care Hospital over the period 2017–2020 to determine the main antibacterial drugs for empirical therapy. Materials and methods. We analyzed the bacteriological test results of 664 clinical material samples obtained from OTD patients using bacteriological examination statistical reporting and analytical data of the WHONET 5.6 software. Results. The main PSI pathogens in the OTD were from the ESKAPE group: E. coli, S. aureus, K. pneumoniae, A. baumannii, E. faecalis, P. aeruginosa and S. epidermidis, P. mirabilis, C. amycolatum. Isolates of E. faecalis were sensitive to vancomycin, linezolid, S. aureus – to linezolid, tigecycline, netilmicin, A. baumannii – to tigecycline. All P. aeruginosa strains were resistant to ticarcillin/clavulanate, cefepime, chloramphenicol, imipenem, meropenem, aztreonam, ciprofloxacin. E. coli and K. pneumoniae were resistant to ampicillin, ticarcillin/clavulanate, aztreonam, ceftriaxone, cefepime. The number of isolates sensitive to piperacillin/tazobactam, carbapenems, levofloxacin, gentamicin, amikacin, chloramphenicol ranged from 37 % to 65 %. Conclusions. E. coli, S. aureus, K. pneumoniae, A. baumannii, E. faecalis, P. aeruginosa, S. epidermidis, P. mirabilis, C. amycolatum play an important role in the structure of PSI pathogens in the Orthopedics and Traumatology Department of Zaporizhzhia Central Ambulance and Emergency Care Hospital. The antibiotics of choice as the antibacterial empirical therapy for enterococcal infections are vancomycin, linezolid, for staphylococcal infections – vancomycin, linezolid, tigecycline, netilmicin. PSI pathogens continually evolve developing antibiotic resistance, and it is of particular importance to monitor antibiotic susceptibility of microorganisms within the OTD

Low temperature breakdown of coherent tunneling in amorphous solids induced by the nuclear quadrupole interaction

We consider the effect of the internal nuclear quadrupole interaction on quantum tunneling in complex multi-atomic two-level systems. Two distinct regimes of strong and weak interactions are found. The regimes depend on the relationship between a characteristic energy of the nuclear quadrupole interaction $\lambda_{\ast}$ and a bare tunneling coupling strength $\Delta_{0}$. When $\Delta_{0}>\lambda_{\ast}$, the internal interaction is negligible and tunneling remains coherent determined by $\Delta_{0}$. When $\Delta_{0}<\lambda_{\ast}$, coherent tunneling breaks down and an effective tunneling amplitude decreases by an exponentially small overlap factor $\eta^{\ast}\ll1$ between internal ground states of left and right wells of a tunneling system. This affects thermal and kinetic properties of tunneling systems at low temperatures $T<\lambda_{*}$. The theory is applied for interpreting the anomalous behavior of the resonant dielectric susceptibility in amorphous solids at low temperatures $T\leq 5$mK where the nuclear quadrupole interaction breaks down coherent tunneling. We suggest the experiments with external magnetic fields to test our predictions and to clarify the internal structure of tunneling systems in amorphous solids.Comment: To appear in the Physical Review

Magnetic Gaps related to Spin Glass Order in Fermionic Systems

We provide evidence for spin glass related magnetic gaps in the fermionic density of states below the freezing temperature. Model calculations are presented and proposed to be relevant for explaining resistivity measurements which observe a crossover from variable-range- to activated behavior. The magnetic field dependence of a hardgap and the low temperature decay of the density of states are given. In models with fermion transport a new metal-insulator transition is predicted to occur due to the spin-glass gap, anteceding the spin glass to quantum paramagnet transition at smaller spin density. Important fluctuation effects due to finite range frustrated interactions are estimated and discussed.Comment: 4 pages, 1 Postscript figure, revised version accepted for publication in Physical Review Letter