Iron environment non-equivalence in both octahedral and tetrahedral sites in NiFe2O4 nanoparticles: study using Mössbauer spectroscopy with a high velocity resolution

Mössbauer spectrum of NiFe2O4 nanoparticles was measured at room temperature in 4096 channels. This spectrum was fitted using various models, consisting of different numbers of magnetic sextets from two to twelve. Non-equivalence of the 57Fe microenvironments due to various probabilities of different Ni2+ numbers surrounding the octahedral and tetrahedral sites was evaluated and at least 5 different microenvironments were shown for both sites. The fit of the Mössbauer spectrum of NiFe 2O4 nanoparticles using ten sextets showed some similarities in the histograms of relative areas of sextets and calculated probabilities of different Ni2+ numbers in local microenvironments. © 2012 American Institute of Physics

Orbitally induced hierarchy of exchange interactions in zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6

We report the revised crystal structure, static and dynamic magnetic properties of quasi-two dimensional honeycomb-lattice silver delafossite Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic long range order at low temperatures with N\'eel temperature TN ~ 21.2 K. In addition, the magnetization curves revealed a field-induced (spin-flop type) transition below TN in moderate magnetic fields. The GGA+U calculations show the importance of the orbital degrees of freedom, which maintain a hierarchy of exchange interaction in the system. The strongest antiferromagnetic exchange coupling was found in the shortest Co-Co pairs and is due to direct and superexchange interactions between the half-filled xz+yz orbitals pointing directly to each other. The other four out of six nearest neighbor exchanges within the cobalt hexagon are suppressed, since for these bonds active half-filled orbitals turned out to be parallel and do not overlap. The electron spin resonance (ESR) spectra reveal a Gaussian shape line attributed to Co2+ ion in octahedral coordination with average effective g-factor g=2.3+/-0.1 at room temperature and shows strong divergence of ESR parameters below 120 K, which imply an extended region of short-range correlations. Based on the results of magnetic and thermodynamic studies in applied fields, we propose the magnetic phase diagram for the new honeycomb-lattice delafossite

Novel electronic states close to Mott transition in low-dimensional and frustrated systems

Recent studies demonstrated that there may appear different novel states in correlated systems close to localized-itinerant crossover. Especially favourable conditions for that are met in low-dimensional and in frustrated systems. In this paper I discuss on concrete examples some of such novel states. In particular, for some spinels and triangular systems there appears a "partial Mott transition", in which first some finite clusters (dimers, trimes, tetramers, heptamers) go over to the itinerant regime, and the real bulk Mott transition occurs only later. Also some other specific possibilities in this crossover regime are shortly discussed, such as spin-Peierls-Peierls transition in TiOCl, spontaneous charge disproportionation in some cases, etc.Comment: To be published in Journal of Physics - Condensed Matter, conference serie

Design of Pre-Dumping Ring Spin Rotator with a Possibility of Helicity Switching for Polarized Positrons at the ILC

The use of polarized beams enhance the possibility of the precision measurements at the International Linear Collider (ILC). In order to preserve the degree of polarization during beam transport spin rotators are included in the current TDR ILC Lattice. In this report some advantages of using a combined spin rotator/spin flipper are discussed. A few possible lattice designs of spin flipper developed at DESY in 2012 are presented.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201

Complex therapy of chronic pancreatitis complicated by anxio-depressive disorders in railroad workers

The authors have found out negative impact of anxio-depressive disorders on the course of chronic pancreatitis with the development of stable pain syndrome, gastro-intestinal disorders, resistance to the performed pharmacotherapy, and decrease of reaction rate to presented stimul

ОБ ИНФОРМАЦИОННО-АНАЛИТИЧЕСКОЙ СИСТЕМЕ ОЦЕНКИ (SCIENCE INDEX) ИННОВАЦИОННОЙ АКТИВНОСТИ РОССИЙСКИХ ОРГАНИЗАЦИЙ В СФЕРЕ РАДИАЦИОННОЙ ГИГИЕНЫ И МЕДИЦИНЫ

Science Index system for information analysis is one of effective modern indexes of innovative activity of Russian research and educational personnel, research and educational institutions. However, it should be noted that this assessment system does not yet include such important parameters as data on patent analysis and dissertation research. The article describes information search and preliminary bibliometric assessment of publication activity of the authors and some research institutions and periodicals in the field of radiation hygiene and medicine.Информационно-аналитическая система Scienсe Index является одним из эффективных современных показателей оценки инновационной активности российских научно-педагогических кадров,научных и образовательных учреждений. Вместе с тем, следует отметить, что эта система оценки пока еще не содержит такие важные показатели, как данные патентного анализа и диссертационных исследований. В статье представлены информационный поиск и предварительная библиометрическая оценка публикационной активности авторов и некоторых научных учреждений и журналов сферы радиационной гигиены и медицины

Study of NiFe2O4 nanoparticles using Mössbauer spectroscopy with a high velocity resolution

The nanocrystalline NiFe2O4 particles prepared by solution combustion synthesis technique using different fuels such as ethylene-diamine-tetra-acetic acid (NA sample) and urea (NB sample) were studied using magnetic measurement and 57Fe Mössbauer spectroscopy with a high velocity resolution. The temperature dependence of magnetization is different for the two samples. Mössbauer spectra demonstrate the necessity to use more than two magnetic sextets, usually used to fit the NiFe2O4 nanoparticles spectra. Evaluation of the different local microenvironments for Fe in both tetrahedral (A) and octahedral (B) sites, caused by different Ni2 + occupation of octahedral sites, demonstrates at least five different local microenvironments for both A and B sites. Therefore, the Mössbauer spectra were fitted by using ten magnetic sextets which are related to the spread 57Fe location in octahedral and tetrahedral sites. © 2012 Springer Science+Business Media Dordrecht

Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions

The differential production cross sections of K^+ and K^- mesons have been measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A detailed comparison of these data with the results of calculations within an appropriate folding model for incoherent primary proton-nucleon, secondary pion-nucleon kaon and antikaon production processes and processes associated with the creation of antikaons via the decay of intermediate phi mesons is given. We show that the strangeness exchange process YN->NNK^- gives a small contribution to the antikaon yield in the kinematics of the performed experiment. We argue that in the case when antikaon production processes are dominated by the channels with KK^- in the final state, the cross sections of the corresponding reactions are weakly influenced by the in-medium kaon and antikaon mean fields.Comment: 24 pages. accepted for publication at J.Phys.

Improving the energy efficiency of wind turbines for charging batteries

The article describes the method for determining the optimal angular velocity and the number of turns of the generator winding on permanent magnets powered by a wind turbine operating in specific operating conditions according to the wind speed regime. The optimization criterion is the maximum potential of energy that can be used to charge the battery. The permissible power of the generator and wind turbine, current and battery charging voltage are accepted as limiting factors. The restriction is provided by connecting a ballast resistor to the generator output. The power developed by the turbine is determined taking into account the wind energy utilization factor, which depends on the angular velocity of its shaft and wind speed. Two variants of power limitation are compared: by limiting the angular velocity by aerodynamic means and by stopping the wind turbine. The return of energy to charging in both cases is determined taking into account the distribution of wind speeds, obeying the Weibull probability distribution law. As an example, the calculation of the possible annual power generation for charging a battery with a capacity of 200 A∙h with a voltage of 24 volts from a synchron generator with a number of poles of 48 driven by a wind turbine with a radius of 2 meters, operating in an area with an average wind speed of 5 m/s. The calculation shows that for the parameters and operating conditions of the electrical installation used in the example, the maximum annual energy output (3.3 × 103 kWh) is observed at optimal 11 turns of the winding at each of the poles of the generator. The deviation of the number of turns from the optimal one in both directions by 2 times leads, with the same dimensions of the wind turbine, to a decrease in annual energy output by 3...5 times, which is a clear proof of the need to carry out such a calculation for each specific wind turbine

Electrostriction measurements in gadolinium doped cerium oxide

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The research was made possible with the financial support of Russian Foundation for Basic Research grant (15-52-06006-MNTI_a)