Sub-lattice of Jahn-Teller centers in hexaferrite crystal.

A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe12O19. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe3+ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe2+ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect. The arranged JT complexes, Fe2+O4, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.

Experimental Approach to Search for Free Neutron-Antineutron Oscillations Based on Coherent Neutron and Antineutron Mirror Reflection.

An observation of neutron-antineutron oscillations (n-n[over ¯]), which violate both B and B-L conservation, would constitute a scientific discovery of fundamental importance to physics and cosmology. A stringent upper bound on its transition rate would make an important contribution to our understanding of the baryon asymmetry of the Universe by eliminating the postsphaleron baryogenesis scenario in the light quark sector. We show that one can design an experiment using slow neutrons that in principle can reach the required sensitivity of τ_{n-n[over ¯]}∼10^{10} s in the oscillation time, an improvement of ∼10^{4} in the oscillation probability relative to the existing limit for free neutrons. The improved statistical accuracy needed to reach this sensitivity can be achieved by allowing both the neutron and antineutron components of the developing superposition state to coherently reflect from mirrors. We present a quantitative analysis of this scenario and show that, for sufficiently small transverse momenta of n/n[over ¯] and for certain choices of nuclei for the n/n[over ¯] guide material, the relative phase shift of the n and n[over ¯] components upon reflection and the n[over ¯] annihilation rate can be small enough to maintain sufficient coherence to benefit from the greater phase space acceptance the mirror provides.

Ultrasonic evaluation of the Jahn-Teller effect parameters. Application to ZnSe:Cr2+.

A method is constructed that uses ultrasonic experiments to evaluate the parameters of the Jahn-Teller (JT) effect in impurity centers in crystals. The method is based on measurements of temperature dependent attenuation and phase velocity and does not require assumptions about mechanisms of relaxation. The results are illustrated by measurements performed on the impurity system ZnSe:Cr(2+), in which the Cr(2+) ion has a threefold degenerate T term in the ground state, subject to the [Formula: see text] JT problem. Ultrasound propagation anomalies show that the main JT distortions of the tetrahedral environment of the Cr(2+) ion are of tetragonal E type and hence the lowest branch of the adiabatic potential energy surface (APES) is formed in accordance with the [Formula: see text] problem. With dopant concentration 3.8 × 10(18) cm(-3) the modulus of the constant of linear vibronic coupling to tetragonal E type vibrations is determined by two independent experiments: |F(E)| = 5.49 × 10(-5) dyn revealed from attenuation measurements, while a slightly different value |F(E)| = 5.57 × 10(-5) dyn emerges from phase velocity measurements. Contributions of other active vibronic modes to the elastic modulus C(l) = (C(11) + C(12) + 2C(44))/2 are analyzed and it is shown that the influence of the totally symmetric mode is negligible. Using additional information about this system obtained from independent sources, we also estimated the primary force constant in the E direction (K(E)≈(1.4-4.2) × 10(4) dyn cm(-1)) and orthorhombic and trigonal saddle points of the APES in the five-dimensional space of the tetragonal and trigonal coordinates, their stabilization energies being E(JT)(O)≈81-450 cm(-1) and E(JT)(T)≈48-417 cm(-1), respectively (the variations of the K(E), E(JT)(O) and E(JT)(T) values are due to different literature data for E(JT)(E)). With these data the APES of the JT linear [Formula: see text] problem for the Cr(2+) ion in the ZnSe:Cr(2+) system is revealed.

Community detection in complex networks by dynamical simplex evolution.

We benchmark the dynamical simplex evolution (DSE) method with several of the currently available algorithms to detect communities in complex networks by comparing correctly identified nodes for different levels of "fuzziness" of random networks composed of well-defined communities. The potential benefits of the DSE method to detect hierarchical substructures in complex networks are discussed.

Doppler-shifted cyclotron, doppleron-phonon, and pseudo-doppleron-phonon resonances in indium.

Ultrasonic investigations have been carried out in geometry of the experiment corresponding to acoustic analogy of the Faraday effect with the use of a super pure crystal like indium. Lowering the temperature from 4.2 K to 1.28 K has revealed new peculiarities of in the magnetic field dependences of absorption and phase velocity of circularly polarized ultrasonic waves. The peculiarities have been interpreted as manifestation of multiple doppleron-phonon and Doppler-shifted cyclotron resonances. The discovery of these resonances has changed interpretation of some anomalies observed in the previous experiments.

Temperature dependences of relaxation time, adiabatic and isothermal elastic moduli in ZnSe:Ni and ZnSe:Cr crystals obtained in an ultrasonic experiment.

Theory of ultrasonic absorption and dispersion, based on the Zener equation, was used for constructing the equations, those made it possible to restore the temperature dependences of relaxation time, adiabatic and isothermal elastic moduli on the basis of experimental data on the temperature dependences of ultrasound absorption and phase velocity. This method was used for processing the experimental results obtained in single crystals of ZnSe:Ni and ZnSe:Cr.

Radiative Corrections for Neutron Decay and Search for New Physics.

The expected increased accuracy of neutron ß-decay experiments at the new Spallation Neutron Source could result in more stringent tests of the Standard Model. For an unambiguous search for new physics in neutron decay experiments and for a precise determination of fundamental constants, it is necessarily to understand and evaluate all corrections for neutron decay with higher accuracy than the expected experimental precision. We discuss the possibility to estimate the accuracy of radiative corrections. New results based on the applications of effective field theory for neutron decay is presented.

Measurement of Neutron Decay Parameters-The abBA Experiment.

We are developing an experiment to measure the correlations a, A, and B, and the Fierz interference term b in neutron decay, with a precision of approximately 10(-4). The experiment uses an electromagnetic spectrometer in combination with two large-area segmented silicon detectors to detect the proton and electron from the decay in coincidence, with 4π acceptance for both particles. For the neutron-polarization-dependent observables A and B, precision neutron polarimetry is achieved through the combination of a pulsed neutron beam, under construction at the SNS, and a polarized (3)He neutron polarizer. Measuring a and A in the same apparatus provides a redundant determination of λ = gA/gV . Uncertainty in λ dominates the uncertainty of CKM unitarity tests.

Dispersion of doppleron-phonon modes in strong coupling regime.

The dispersion equation for doppleron-phonon modes was constructed and solved analytically in the strong coupling regime. The Fermi surface model proposed previously for calculating the doppleron spectrum in an indium crystal was used. It was shown that in the vicinity of doppleron-phonon resonance, the dispersion curves of coupled modes form a gap qualitatively different from the one observed under helicon-phonon resonance: there is a frequency interval forbidden for existence of waves of definite circular polarization depending upon direction of the external DC magnetic field. The physical reason for it is interaction of the waves which have oppositely directed group velocities.

[Active aluminum oxide--a new adsorbent for concentrating intestinal viruses from water]. / Aktivnyi oksid aliuminiia--novyi adsorbent dlia kontsentrirovaniia kishechnykh virusov iz vody.

Concentrating properties of a new adsorbent, active aluminum oxide, towards poliomyelitis virus type III and simian rotavirus are studied using virus contamination of sewage and drinking water. Optimal concentrations of the adsorbent for effective adsorption of both rota- and polioviruses are established (1.5 and 1 g/liter, respectively) at pH typical of sewage and drinking water (7.0-8.5), as well as the optimal time of virus contact with the adsorbent (30 min). Elution conditions are determined: 3% elution agent beef extract and pH 8.5-9.5 are optimal for both viruses. Active aluminum oxide is recommended as an adsorbent for elimination of enteroviruses from water objects.

[Microsurgical anatomy of a large size tumor of vestibulo-cochlear nerve]. / Mikrokhirurgicheskaia anatomiia opukholi preddverno-ulitkovogo nerva bol'shogo razmera.

The microsurgical anatomy peculiarities of a large size tumor of n. vestibulocochlearis (NVC) were studied, basing on intraoperative (in 380 patients) and sectional (30) observations data. The distinguishing of three main anatomic-topographical variants of a large size NVC tumor growth has great significance for elaboration of the microsurgical tumoral excision method.

[Microsurgical anatomy of cholesteatoma of posterior cranial fossa]. / Mikrokhirurgicheskaia anatomiia kholesteatomy zadnei cherepnoi iamki.

Microtopographical interrelations of the posterior cranial fossa structures in the presence of cholesteatoma were studied up intraoperatively in 36 cases and while the pathomorphological investigation conduction in 6 sectional observations. Cholesteatoma mostly localizes in cerebellopontile angle and more rarely--in the IV ventricle with craniospinal spreading. It is the tumor's capsule texture what causes dense adherence of cholesteatoma with surrounding cranial nerves, vessels, incorporated frequently in her structure together with underlying cerebral substance.

[Causes of disorders of vitally significant functions in surgical treatment of extracerebral parastem tumors of the posterior cranial fossa]. / Prichiny narusheniia zhiznenno vazhnykh funktsii pri khirurgicheskom lechenii vnemozgovoi parastvolovoi opukholi zadnei cherepnoi iamki.

The postoperative period course and an autopsy data of 68 patients operated on for n. vestibulocochlearis neurinoma, parasternal meningioma, cholesteatoma. Principal damaging factors and cerebral stem functional disorders are assigned.

[An improvement in information support in the interests of the epidemiological health welfare of the troops]. / Sovershenstvovanie informatsionnogo obespecheniia v interesakh sanitarno-épidemiologicheskogo blagopoluchiia voisk.

The information acquisition, decision-making and control system must be the basic tool for optimizing the information procedures in the interests of sanitary-epidemiological welfare of troops. It's necessary to make a thorough revision of the existing account and record documentation in order to study its value. Each pattern of record cards must be scientifically substantiated depending on its effectiveness for further decision making. It's necessary to exclude all futile information. Record and account procedures must be automated and computerized throughout all chains of command beginning from a single military unit. Special systems must be developed for this matter. Realization of these goals will completely assure the monitoring of health status indices of servicemen and the environmental situation, as well as monitoring of risk factors influence upon the health of personnel.

[Virus-induced dyslipidemias as possible risk factors in the development of somatic diseases]. / Virusindutsirovannye dislipidemii kak vozmozhnye faktory riska v razvitii somaticheskikh zabolevanii.

Experimental and clinical studies showed a number of virus infections to be accompanied by lipidemic disorders. Experimentally, dyslipidemias were found in tick-borne encephalitis (TBE) in mice, rotavirus infection in rabbits, and amyotrophic leukospongiosis in guinea pigs. The possibility of correcting the virus-induced lipidemic disorders with an antiviral drug, lincomycin, was demonstrated in TBE in mice. Dynamic study of the lipidemic status of patients with virus hepatitis A revealed marked dyslipidemia of the atherogenic type which was stable and persisted up to the time of clinical recovery. The data obtained supplement the current concepts concerning the pathogenesis of virus infections.

[Microsurgical anatomy of meningioma of the posterior cranial fossa]. / Mikrokhirurgicheskaia anatomiia meningiomy zadnei cherepnoi iamki.

On the material of 107 intraoperative and 19 section specimens, a topographic anatomy of meningiomas of the posterior cranial fossa was studied. The groups of tumours were distinguished, depending on location of primary meningioma and direction of its growth. Tumour interrelations with the caudal cranial nerves and surrounding vessels were studied.

[Status of collective immunity to hepatitis A virus in urban residents in Byelorussia]. / Sostoianie kollektivnogo immuniteta k virusnomu gepatitu A u gorodskogonaseleniia Belorussii.

The large immune stratum and intense collective immunity to virus hepatitis A among the urban population of Byelorussia are characteristic of hyperendemic territory. The geometric mean of the antibody titer has been noted to increase with age, which is probably due to repeated infections of persons who have already had the disease. The use of this value for the characterization of collective immunity and epidemiological situation has been proposed.

Adaptation of human rotavirus to cell culture and characterization of the isolated strain.

Human rotavirus strain 649 was isolated from a child with clinical picture of acute intestinal infection in the West European part of the U.S.S.R. This strain was adapted to MA-104 (rhesus monkey kidney) cells. By electrophoresis and haemagglutination it differed from the human rotavirus strain Wa and from the simian strain Sa-11. The productive reproduction of human rotavirus strain 649 may allow its use for the preparation of antigens for diagnostic, immunoprophylaxis, and treatment.