Standing Alfvén waves with m ? 1 in an axisymmetric magnetosphere excited by a non-stationary source

International audienceAs a continuation of our earlier paper, we consider here the case of the excitation of standing Alfvén waves by a source of the type of sudden impulse. It is shown that, following excitation by such a source, a given magnetic shell will exhibit oscillations with a variable frequency which increases from the shell's poloidal to toroidal frequency. Simultaneously, the oscillations will also switch over from poloidally (radially) to toroidally (azimuthally) polarized. With a reasonably large attenuation, only the start of this process, the stage of poloidal oscillations, will be observed in the ionosphere

Standing Alfvén waves with m ? 1 in an axisymmetric magnetosphere excited by a stochastic source

International audienceIn the framework of an axisymmetric magnetospheric model, we have constructed a theory for broad-band standing Alfvén waves with large azimuthal wave number m » 1 excited by a stochastic source. External currents in the ionosphere are taken as the oscillation source. The source with statistical properties of "white noise" is considered at length. It is shown that such a source drives oscillations which also have the "white noise" properties. The spectrum of such oscillations for each harmonic of standing Alfvén waves has two maxima: near the poloidal and toroidal eigenfrequencies of the magnetic shell of the observation. In the case of a small attenuation in the ionosphere the maximum near the toroidal frequency is dominated, and the oscillations are nearly toroidally polarized. With a large attenuation, a maximum is dominant near the poloidal frequency, and the oscillations are nearly poloidally polarized

A Quantum Mechanical Model of the Reissner-Nordstrom Black Hole

We consider a Hamiltonian quantum theory of spherically symmetric, asymptotically flat electrovacuum spacetimes. The physical phase space of such spacetimes is spanned by the mass and the charge parameters $M$ and $Q$ of the Reissner-Nordstr\"{o}m black hole, together with the corresponding canonical momenta. In this four-dimensional phase space, we perform a canonical transformation such that the resulting configuration variables describe the dynamical properties of Reissner-Nordstr\"{o}m black holes in a natural manner. The classical Hamiltonian written in terms of these variables and their conjugate momenta is replaced by the corresponding self-adjoint Hamiltonian operator, and an eigenvalue equation for the ADM mass of the hole, from the point of view of a distant observer at rest, is obtained. Our eigenvalue equation implies that the ADM mass and the electric charge spectra of the hole are discrete, and the mass spectrum is bounded below. Moreover, the spectrum of the quantity $M^2-Q^2$ is strictly positive when an appropriate self-adjoint extension is chosen. The WKB analysis yields the result that the large eigenvalues of the quantity $\sqrt{M^2-Q^2}$ are of the form $\sqrt{2n}$, where $n$ is an integer. It turns out that this result is closely related to Bekenstein's proposal on the discrete horizon area spectrum of black holes.Comment: 37 pages, Plain TeX, no figure

Efficiency of the Left Atrial Appendage Thrombus Dissolution in Patients with Persistent Nonvalvular Atrial Fibrillation with Warfarin or Direct Oral Anticoagulants Therapy

Aim. Compare the incidence of the left atrial appendage (LAA) thrombus dissolution in patients with persistent nonvalvular atrial fibrillation receiving warfarin and direct oral anticoagulants (DOAC).Materials and methods. 68 patients with persistent nonvalvular atrial fibrillation were included in a retrospective study (age was 59.7±9.8 years, 60.3% men), in whom at least one repeated transesophageal echocardiographic examination was performed after detecting a thrombus. After detecting a thrombus in the LAA, 37 (54.4%) patients started or continued taking warfarin in doses that ensure the INR maintenance at the level of 2-3, 14 (20.6%) started or continued taking dabigatran at a dose of 150 mg 2 times/day, 14 (20.6%) started or continued taking rivaroxaban 20 mg 1 time/day and 3 (4.4%) started or continued taking apixaban 5 mg 2 times/day. Repeated transesophageal echocardiographic examination was performed on average 33.3±14.2 days after the first one.Results. Dissolution of a previously identified thrombus was found in 26 (83.9%) of 31 patients receiving DOAC and in 19 (51.4%) of 37 patients receiving warfarin (p=0.011). The logistic regression analysis showed that the chances of a thrombus dissolution in LAA while taking DOAC are 14.8 times (95% confidence interval [CI] was 2.469-88.72) higher than while taking warfarin. The size and the rate at which blood is expelled from the LAA also have an independent influence on the chances of thrombus dissolution. An increase in the size of a thrombus by 1 mm reduces the chances of a thrombus dissolution by 1.136 (95% CI was 1.040-1.244) times, and an increase in the rate of blood expulsion from the LAA by 1 cm/sec increases these chances by 1.105 (95% CI was 1.003-1.219) times.Conclusion. In the present study, the incidence of the LAA thrombus dissolution in patients with persistent nonvalvular atrial fibrillation while receiving DOAC was higher than while receiving warfarin

Development of a model of cyber security management for automated systems

A model of a system of managing information security of automated data processing systems of critical application is offered in the article. The model allows to evaluate the level of risk for the information security and provides support of decision-making on the counteraction to the unauthorized access to the information circulating in the information systems

Population of isomers in decay of the giant dipole resonance

The value of an isomeric ratio (IR) in N=81 isotones ($^{137}$Ba, $^{139}$Ce, $^{141}$Nd and $^{143}$Sm) is studied by means of the ($\gamma, n)$ reaction. This quantity measures a probability to populate the isomeric state in respect to the ground state population. In ($\gamma, n)$ reactions, the giant dipole resonance (GDR) is excited and after its decay by a neutron emission, the nucleus has an excitation energy of a few MeV. The forthcoming $\gamma$ decay by direct or cascade transitions deexcites the nucleus into an isomeric or ground state. It has been observed experimentally that the IR for $^{137}$Ba and $^{139}$Ce equals about 0.13 while in two heavier isotones it is even less than half the size. To explain this effect, the structure of the excited states in the energy region up to 6.5 MeV has been calculated within the Quasiparticle Phonon Model. Many states are found connected to the ground and isomeric states by $E1$, $E2$ and $M1$ transitions. The single-particle component of the wave function is responsible for the large values of the transitions. The calculated value of the isomeric ratio is in very good agreement with the experimental data for all isotones. A slightly different value of maximum energy with which the nuclei rest after neutron decay of the GDR is responsible for the reported effect of the A-dependence of the IR.Comment: 16 pages, 4 Fig

Building blocks of a black hole

What is the nature of the energy spectrum of a black hole ? The algebraic approach to black hole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand black hole entropy as reflecting degeneracy of the observable states. Here we construct the black hole states by means of a pair of "creation operators" subject to a particular simple algebra, a slight generalization of that for the harmonic oscillator. We then prove rigorously that the n-th area eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole entropy qua logarithm of the number of states for fixed horizon area comes out proportional to that area.Comment: PhysRevTeX, 14 page

Epicardial obesity and atrial fibrillation: emphasis on atrial fat depot

The studies, performed with MRI and CT, showed that the increase of fat, immediately adjacent to the myocardium (epicardial fat) is correlated more strongly with the risk of atrial fibrillation than the general or abdominal obesity. According to some studies, epicardial fat around the left atrium is a strong predictor of the development at atrial fibrillation. Also, the amount of the fat is associated with the effectiveness of cardioversion and the risk of developing thromboembolic stroke in patients with atrial fibrillation. The number of such works is small, since tomographic examinations are not needed if intra-atrial thrombosis is suspected, and transthoracic echocardiograthy does not allow visualization of atrial fat. However, transesophageal echocardiography is widely used in patients with atrial fibrillation and allows to measure the structures that serve as depots of epicardial fat, namely the interatrial septum and left lateral ridge. Accumulation of epicardial fat leads to thickening of these structures. This can be used to study the relationship between epicardial obesity and the risk of thromboembolic complications in patients with atrial fibrillations

Left atrial strain in assessing heart failure with preserved ejection fraction in hypertensive patients

Aim. To compare the results of diagnosing heart failure with preserved ejection fraction (HFpEF) in patients with hypertension (HTN) according left atrial (LA) strain values with the results obtained using the H2FPEF score and diastolic stress testing (DST).Material and methods. The study included 293 patients with previously established HTN who were examined due to complaints of shortness of breath and/or palpitations (men, 97 (33,5%), mean age, 62,0 (55,0; 67,0) years). All patients underwent transthoracic echocardiography with the assessment of LA strain parameters and probability of HFpEF using the H2FPEF score. Eighty five patients with an intermediate probability of HFpEF underwent DST.Results. A low probability of HFpEF according to the H2FPEF score was registered in 35 (11,9%) patients, uncertain — in 206 (70,3%), high — in 52 (17,7%). DST was negative in 43 (50,6%) and positive in 42 (49,4%) patients with an intermediate probability of HFpEF. LA strain in the reservoir phase in patients with a low probability of HFpEF averaged (median and interquartile interval) 28,0 (23,6; 31,5)%, while in patients with an intermediate probability and negative DST — 24,0 (22,0; 26,8)%, with an intermediate probability and positive DST — 20,0 (18,0; 21,0)%, and with a high probability of HFpEF — 19,6 (16,9; 21,8)%. HFpEF was diagnosed in 94 patients, including 52 with a high probability on the H2FPEF score and 42 with an intermediate probability and positive DST. The diagnosis of HFpEF was ruled out in 78 patients, including 35 with a low probability on the H2FPEF score and 43 with an intermediate probability and negative DST. Further, 172 patients with confirmed or excluded HFpEF were randomly divided into two equal cohorts. In the training cohort, HFpEF was diagnosed in 44 (51,2%) patients, in the validation cohort — in 50 (58,1%). ROC analysis performed on the training cohort for the LA strain in reservoir phase showed AUC of 0,920 (95% confidence interval (CI), 0,842-0,968) and cut-off point of 21,5%. In the training cohort, the results of HFpEF diagnosis using the indicated criterion coincided with those using H2FPEF score and DST in 86,1% (95% CI, 77,2-91,8) of cases. The Cohen’s kappa was 0,721 (95% C,I 0,575-0,868). In the validation cohort, agreement was observed in 84,9% (95% CI 75,8-91,0) of cases with Cohen’s kappa of 0,702 (95% CI 0,553-0,851).Conclusion. In hypertensive patients, the diagnosis of HFpEF made on the basis of a decrease in the LA strain in reservoir phase to ≤21,5%, is in good agreement with the diagnosis made using the H2FPEF score and DST