Ohm's Law for Plasma in General Relativity and Cowling's Theorem

The general-relativistic Ohm's law for a two-component plasma which includes the gravitomagnetic force terms even in the case of quasi-neutrality has been derived. The equations that describe the electromagnetic processes in a plasma surrounding a neutron star are obtained by using the general relativistic form of Maxwell equations in a geometry of slow rotating gravitational object. In addition to the general-relativistic effect first discussed by Khanna \& Camenzind (1996) we predict a mechanism of the generation of azimuthal current under the general relativistic effect of dragging of inertial frames on radial current in a plasma around neutron star. The azimuthal current being proportional to the angular velocity $\omega$ of the dragging of inertial frames can give valuable contribution on the evolution of the stellar magnetic field if $\omega$ exceeds $2.7\times 10^{17} (n/\sigma) \textrm{s}^{-1}$ ($n$ is the number density of the charged particles, $\sigma$ is the conductivity of plasma). Thus in general relativity a rotating neutron star, embedded in plasma, can in principle generate axial-symmetric magnetic fields even in axisymmetry. However, classical Cowling's antidynamo theorem, according to which a stationary axial-symmetric magnetic field can not be sustained against ohmic diffusion, has to be hold in the general-relativistic case for the typical plasma being responsible for the rotating neutron star.Comment: Accepted for publication in Astrophysics & Space Scienc

Розширення функціональних можливостей резонаторних апертурних датчиків для НВЧ діагностики малорозмірних об'єктів

У роботі розглядаються основні принципи функціонування резонаторних датчиків з рухомим зондоутворюючим центральним провідником і підходи, спрямовані на оптимізацію їх вимірювальних характеристик. Показано внесок втрат, пов'язаних із виникненням хвильового поля, неузгодженістю умов поширення в обсязі резонансного вимірювального перетворювача (РВП), а також прийоми, спрямовані на виключення їх впливу. Представлені кількісні дані, що характеризують роботу сенсору, що перебудовується, в межах кожного з двох розглянутих режимів функціонування, а також переконують у необхідності оптимізації геометрії конструктиву резонаторного зонда (РЗ). Наведено порівняльний аналіз використання як РВП зондів конусного та циліндричного типів. Показано, що екранування зразків має набагато більший сенс для використання циліндричного конструктиву при діагностиці об'єктів з низьким тангенсом кута втрат. Отримана інваріантність гібридного сигналу (δQ/Q)/(δf/f) до впливу заважаючих факторів, обумовлених зміною геометрії апертурного вузла сенсора при переміщенні вістря зонда, та ступеня включення об'єкта в електромагнітне поле резонатора.The paper discusses the basic principles of functioning of resonator sensors with a movable probeforming central conductor and approaches aimed at optimizing their measuring characteristics. The effectiveness of changing the coefficient of inclusion of an object in the electromagnetic field of the resonator is shown by introducing a mechanism into the sensor design that provides axial movement of the central conductor of the coaxial. This design allows the probing tip to be positioned both coplanar with the end aperture and displaced inside or outside the coaxial. It is shown that in order to diagnose objects with low dielectric losses, the probing tip must be pulled out of the coaxial, thereby transferring the probe to the mode of a monopole antenna. When the object has high dielectric losses, the required sensitivity of the sensor is achieved by shifting the probing tip into the inside of the coaxial, and the shortened capacitance mode is implemented. Quantitative data are presented that characterize the operation of the tunable sensor within each of the two modes of operation considered, as well as convincing of the need to optimize the geometry of the resonator probe (RP) construct. The contribution of losses associated with the appearance of a wave field, the mismatch of propagation conditions in the volume of a resonant measuring transducer (RMT), as well as techniques aimed at eliminating their influence is shown. A comparative analysis of the use of conical and cylindrical probes as RMT is presented. It is shown that the shielding of samples makes much more sense for the use of a cylindrical construct in the diagnostics of objects with a low loss tangent. It is shown that it is possible to significantly reduce the influence of interfering factors caused by a change in the geometry of the sensor aperture assembly when the probe tip is moved, by using a hybrid signal (δQ/Q)/(δf/f)

Microbiological study of the efficiency of root canal treatment with er:yag laser

Mechanical and drug treatment of the root canal are the most important components of the success of endodontic treatment. This work presents the results on the effectiveness of the root canal disinfection using an erbium laser in combination with a 17% solution of ethylenediaminetetraacetic acid (EDTA) in vitro and in clinical studies. An in vitro study was carried out on removed intact teeth infected with strains of Enterococcus faecalis, Streptococcus sanguinis, and Candida albicans. An experimental group of teeth was treated medically according to a standard protocol using 3% solution of sodium hypochlorite and 17% solution of EDTA followed by irradiation with erbium laser. The control group was treated similarly but without laser irradiation. The treatment effectiveness was evaluated by the reduction of CFU. After the treatment, in the control group after the mechanical and drug treatment, the CFU amount lowered by 4 times, while the complete sterilization was observed in the experimental group. The clinical studies included two groups of 35 patients each diagnosed with chronic periodontitis. In the experimental group of patients, at the final stage, treatment with erbium laser for 1 min using endodontic piece (40 mJ power, 2940 nm wavelength, 10 Hz pulse rate) and a 17% EDTA solution was performed before filling. Periodontitis treatment in the control group was carried out without the laser treatment. The control group of patients saw the reduction on CFU after the mechanical and drug treatment by 3 6 times, while the experimental group achieved the complete sterilization of the root canals. The obtained results prove that the modification of the root canal treatment by the inclusion of erbium laser irradiation is a promising direction in endodontics. © 2019 Russian Photodynamic Association. All rights reserved