Third harmonic of the dynamic magnetic susceptibility of a concentrated ferrofluid: Numerical calculation and simple approximation formula.

Information about the nonlinear magnetic response of dispersions of magnetic particles is the basis for biomedical applications. In this paper, using analytical and numerical methods, the third harmonic of the dynamic susceptibility of an ensemble of moving magnetic particles in an ac magnetic field with an arbitrary amplitude is studied, taking into account interparticle interactions. A simple approximation formula is proposed to predict the third harmonic as a function of two parameters: the Langevin susceptibility χ_{L}, which is used to estimate the particle dipole-dipole interactions, and the Langevin parameter ξ, which represents the ratio of the energy of the magnetic moment interacting with the magnetic field to the thermal energy.

Pair correlations of the easy magnetisation axes of superparamagnetic nanoparticles in a ferrofluid/ferrocomposite.

The widespread use of magnetic nanoparticles in modern technologies and medical applications highlights the need for reliable theoretical models that can predict their physical properties. The pair correlation function of two randomly selected superparamagnetic nanoparticles in a ferrofluid/ferrocomposite is studied to depict the joint probability density of the easy magnetisation axes across the planes of parameters of major importance; these are the interaction of ferroparticles with an external magnetic field, the energy of magnetic anisotropy inside the superparamagnetic nanoparticle, and the interparticle magnetic dipole-dipole interaction. Assuming the rotational symmetry of the system, we come to the conclusion that the pair correlations of interest are dependent only on the polar angles, determining the inclinations of the ferroparticle easy axes from the direction of an external magnetic field.

Influence of a bias dc field and an ac field amplitude on the dynamic susceptibility of a moderately concentrated ferrofluid.

In this paper, we study the effect of a bias dc field on the dynamic response of a moderately concentrated ferrofluid to an ac magnetic field of arbitrary amplitude. The ferrofluid is modeled by an ensemble of interacting moving magnetic particles; the reaction of particle magnetic moments to ac and dc magnetic fields occurs according to the Brownian mechanism; and the ac and dc magnetic fields are parallel. Based on a numerical solution of the Fokker-Planck equation for the probability density of the orientation of the magnetic moment of a random magnetic particle, dynamic magnetization and susceptibility are determined and analyzed for various values of the ac field amplitude, the dc field strength, and the intensity of dipole-dipole interactions.

Effect of Polydispersity on the Structural and Magnetic Properties of a Magnetopolymer Composite.

When using magnetopolymer composites in high-precision industrial and biomedical technologies, the problem of predicting their properties in an external magnetic field arises. In this work, we study theoretically the influence of the polydispersity of a magnetic filler on a composite's equilibrium magnetization and on the orientational texturing of magnetic particles formed during polymerization. The results are obtained using rigorous methods of statistical mechanics and Monte Carlo computer simulations in the framework the bidisperse approximation.

[Obstructive sleep apnea syndrome and cardiovascular risk factors in the antihypertensive therapy "escape" phenomenon].

Aim: To assess the role of obstructive sleep apnea and other cardiovascular (CV) risk factors in the development of the antihypertensive therapy (AHT) efficacy "escape" phenomenon in patients with arterial hypertension (AH).

Materials And Methods: The data of 75 patients with AH stage I-II, grades 1-3 were proceeded. All patients included in the study underwent night respiratory monitoring.

Influence of field amplitude and dipolar interactions on the dynamic response of immobilized magnetic nanoparticles: Perpendicular mutual alignment of an alternating magnetic field and the easy axes.

In this paper, the dynamic magnetic properties of an ensemble of interacting immobilized magnetic nanoparticles with aligned easy axes in an applied ac magnetic field directed perpendicular to the easy axes are considered. The system models soft, magnetically sensitive composites synthesized from liquid dispersions of the magnetic nanoparticles in a strong static magnetic field, followed by the carrier liquid's polymerization. After polymerization, the nanoparticles lose translational degrees of freedom; they react to an ac magnetic field via Néel rotation, when the particle's magnetic moment deviates from the easy axis inside the particle body.

[Russian Medical Society for Arterial Hypertension expert consensus. Resistant hypertension: detection and management].

The diagnosis of resistant arterial hypertension allows us to single out a separate group of patients in whom it is necessary to use special diagnostic methods and approaches to treatment. Elimination of reversible factors leading to the development of resistant arterial hypertension, such as non-adherence to therapy, inappropriate therapy, secondary forms of arterial hypertension, leads to an improvement in the patient's prognosis. Most patients with resistant hypertension should be evaluated to rule out primary aldosteronism, renal artery stenosis, chronic kidney disease, and obstructive sleep apnea.

Structure and magnetization of a magnetoactive ferrocomposite.

This work is devoted to the theoretical study of the structural and magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles immobilized in a non-magnetic medium. This model is typical for describing magnetically active soft materials, "smart" polymer ferrocomposites, which have been applied in science-intensive industrial and biomedical technologies. It is assumed that the ferrocomposite is obtained by solidification of the carrier medium in a ferrofluid under an external magnetic field, the intensity of which is determined by the Langevin parameter ; after the solidification of the carrier liquid, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes.

Magnetic properties of textured ferrocomposite consisting of immobilized superparamagnetic nanoparticles.

Wide use of magnetic nanoparticles in modern technologies and biomedical applications requires reliable theoretical models capable of predicting physical properties. Solidification of a ferroparticle suspension under the action of permanent magnetic field allows us to obtain a ferrocomposite, characterized by some orientational texture of the nanoparticle easy magnetization axes. The static magnetic response of this ferrocomposite differs from that of the parent magnetic suspension due to "freezing" of nanoparticle translational and rotational degrees of freedom.

Theory of static magnetization of magnetopolymer composites: The second virial approximation.

This paper deals with a theoretical study of the static magnetization of a composite, consisting of nanodisperse single-domain ferromagnetic particles immobilized in a nonmagnetic medium. This situation is typical for magnetopolymer systems-smart materials, which found applications in high industrial and biomedical applications. It is supposed that the composite was polymerized without an external magnetic field; after curing the particles retain the spatial distribution and orientation of their axes of easy magnetization that they had before the host medium polymerization.

Dynamic magnetic susceptibility of a ferrofluid: The influence of interparticle interactions and ac field amplitude.

Based on numerical results of dynamic susceptibility, a simple theory of the dynamic response of a ferrofluid to an ac magnetic field is obtained that includes both the effects of interparticle dipole-dipole interactions and the dependence on field amplitude. Interparticle interactions are incorporated in the theory using the so-called modified mean-field approach. The new theory has the following important characteristics: in the noninteracting regime at a weak ac field, it gives the correct single-particle Debye theory results; it expands the applicability of known theories valid for high concentrations [Ivanov, Zverev, and Kantorovich, Soft Matter 12, 3507 (2016)10.

[Adherence and efficacy of long-term PAP therapy in patients with sleep-related breathing disorders associated with cardiac conduction disorders].

Aim: To study the effectiveness of prolonged use of PAP therapy (positive airway pressure therapy) in eliminating sleep respiratory disorders and associated cardiac conduction disturbances.

Materials And Methods: We included 21 patients who were examined at the Myasnikov Institute of Clinical Cardiology, National Medical Research Center of Cardiology, regarding cardiac rhythm and conduction disturbances, as well as obstructive sleep apnea and who have been on PAP therapy for more than 12 months. The average age was 66.

[Clinical profile of patients with obstructive sleep apnea syndrome in a cardiology hospital].

Relevance: Obstructive sleep apnea syndrome (OSAS) is an important medical and social problem due to its high prevalence and impact on quality of life. The relationship between OSAS and cardiovascular pathology has been proven by many studies, which confirms the necessity for early diagnosis of OSAS and its treatment for the prevention of fatal and non-fatal events.

Aim: to study epidemiological and clinical profile of the patients referred by a cardiologist to a specialized sleep laboratory to verify the diagnosis of OSAS.

Static magnetization of immobilized, weakly interacting, superparamagnetic nanoparticles.

The magnetization curve and initial susceptibility of immobilized superparamagnetic nanoparticles are studied using statistical-mechanical theory and Monte Carlo computer simulations. The nanoparticles are considered to be distributed randomly within an implicit solid matrix, but with the easy axes distributed according to particular textures: these are aligned parallel or perpendicular to an external magnetic field, or randomly distributed. The magnetic properties are calculated as functions of the magnetic crystallographic anisotropy barrier (measured with respect to the thermal energy by a parameter σ), and the Langevin susceptibility (related to the dipolar coupling constant and the volume fraction).

Interrelation of erectile dysfunction with obesity in patients with arterial hypertension.

Aim: To study the relationship between the severity of erectile dysfunction and the anthropometric parameters of obesity in patients with arterial hypertension.

Materials And Methods: The study included 71 patients with different severity of erectile dysfunction, overweight and grade 1obesity and arterial hypertension. The anthropometric parameters were analyzed, the degree and characteristics of obesity were assessed according to data of multispiral computed tomography (MSCT), a preliminary assessment of erectile function was performed using the IIEF-5 questionnaire.

The effectiveness of combination antihypertensive therapy in patients with arterial hypertension and additional risk factors: obesity and obstructive sleep apnea syndrome.

Aim: To study the effectiveness of a fixed combination of perindopril and amlodipine, with the subsequent addition of indapamide-retard in male patients with arterial hypertension (AH), obesity and severe sleep apnea (OSAS).

Materials And Methods: The study included 43 male patients in whom antihypertensive therapy titration was performed to achieve target blood pressure values with a fixed combination of calcium antagonist amlodipine (10 mg) and an angiotensin-converting inhibitor perindopril (5-10 mg) and indapamide-retard. At baseline and after 4-6 weeks, the effectiveness of antihypertensive therapy was monitored according to clinical measurements and ambulatory blood pressure monitoring (ABPM).

Modified mean-field theory of the magnetic properties of concentrated, high-susceptibility, polydisperse ferrofluids.

The effects of particle-size polydispersity on the magnetostatic properties of concentrated ferrofluids are studied using theory and computer simulation. The second-order modified mean-field (MMF2) theory of Ivanov and Kuznetsova [Phys. Rev.

[A clinical case of hemangioma of the face and tongue concurrent with severe obstructive sleep apnea syndrome complicated by cardiac arrhythmias and conduction disturbances].

The paper describes a clinical case of a female patient with severe obstructive sleep apnea syndrome in the presence of congenital hemangioma of the face, soft palate, and tongue concurrent with paroxysmal atrial fibrillation and atrial flutter, paroxysmal supraventricular tachycardia, and sinoatrial block (maximally up to 3.9 sec). Continuous positive airway pressure therapy could reduce the number of paroxysms of atrial fibrillation and atrial flutter, supraventricular tachycardia and eliminate sinoatrial block.

The initial magnetic susceptibility of polydisperse ferrofluids: A comparison between experiment and theory over a wide range of concentration.

Temperature dependencies of the static initial magnetic susceptibility for ferrofluids at various concentrations are studied using experiment and statistical-mechanical theories. Magnetic susceptibility measurements are carried out for twelve samples of magnetite-based fluids stabilized with oleic acid over a wide range of temperatures (210 K ≲T ≲ 390 K); all samples have the same granulometric composition but different volume ferroparticle concentrations (0.2 ≲ φ ≲ 0.

Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids.

The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that the constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test the predictions of a recent theory [A. O.

Temperature-dependent dynamic correlations in suspensions of magnetic nanoparticles in a broad range of concentrations: a combined experimental and theoretical study.

The interweave of competing individual relaxations influenced by the presence of temperature and concentration dependent correlations is an intrinsic feature of superparamagnetic nanoparticle suspensions. This unique combination gives rise to multiple applications of such suspensions in medicine, nanotechnology and microfluidics. Here, using theory and experiment, we investigate dynamic magnetic susceptibility in a broad range of temperatures and frequencies.

Sedimentation equilibria in polydisperse ferrofluids: critical comparisons between experiment, theory, and computer simulation.

The sedimentation equilibrium of dipolar particles in a ferrofluid is studied using experiment, theory, and computer simulation. A theory of the particle-concentration profile in a dipolar hard-sphere fluid is developed, based on the local-density approximation and accurate expressions from a recently introduced logarithmic free energy approach. The theory is tested critically against Monte Carlo simulation results for monodisperse and bidisperse dipolar hard-sphere fluids in homogeneous gravitational fields.

[[How to Prevent Emotional Burnout Syndrome in Health Professionals?].].

Working in conditions of physical and psychological overload, occupational hazard makes health workers vulnerable to the development of burnout syndrome. Currently, 67.6% of physicians in Russia suffer from emotional burnout syndrome.

[PSYCHOSOMATIC RELATIONSHIPS DURING GASTROINTESTINAL DISEASE ON THE MODEL OF IRRITABLE BOWEL SYNDROME].

On the model of irritable bowel syndrome basic concept of psychosomatic relationships in diseases of the gastrointestinal tract and main methods of treatment tailored to their specific effects on the gastrointestinal tract are analyzed.

The effects of polydispersity on the initial susceptibilities of ferrofluids.

The effects of particle-size polydispersity on the initial susceptibilities of concentrated ferrofluids are analyzed using a combination of theory and computer simulation. The study is focused on a model ferrofluid with a prescribed magnetic-core diameter distribution, a fixed non-magnetic surface layer (corresponding to a demagnetized layer and adsorbed surfactant) and a combination of dipolar and hard-core interactions. The non-trivial effects of polydispersity are identified by comparing the initial susceptibilities of monodisperse and polydisperse ferrofluids with the same Langevin susceptibility.