Sex hormones in female residents of Yamal-Nenets autonomous district depending on the fertility status

Severe climatic conditions adversely affect the human reproductive function; there is evidence of earlier aging of the endocrine system in residents of the northern territories. However, there is insufficient data on the content of androgens and estrogens in postmenopausal women of the North. This determined the aim of the work - to study the characteristics of the content of sex hormones in fertile and postmenopausal women in the Arctic zone of the Russian Federation. Material and methods. In the period of increasing daylight hours, there were examined 60 residents of the Yamal-Nenets Autonomous District of the reproductive (n = 33) and postmenopausal (n = 27) periods. The serum luteinizing, follicle-stimulating hormones, progesterone, dehydroepiandrosterone sulfate, dihydrotestosterone, androstenedione, total and free fractions of testosterone, estrogen, estrone, sex-hormone-binding globulin were determined by immunoassay analysis using sets of «Khema-Medica» (Russia), Alkor-Bio (Russia), DRG (Germany). The research results were statistically processed using application software package STATISTIC 10.0. Results. There were shown high median values of progesterone (2.41 nmol/L) and dihydrotestosterone (191.02 pg/ml) in postmenopausal women, as well as increased concentrations of sex-hormone-binding globulin in both fertile (170.66 nmol/L) and postmenopausal (154.84 nmol/L) women. At the same time, free testosterone levels are slightly reduced, especially in postmenopausal women (0.50 pg/ml). Conclusion. The revealed features of the hormonal profile of women living in high latitudes may be an unfavorable factor for the development of various metabolic disorders

Interparticle correlations in the simple cubic lattice of ferroparticles: Theory and computer simulations

Anisotropic interparticle correlations in the simple cubic lattice of single-domain ferroparticles (SCLF) are studied using both theory and computer simulation. The theory is based on the Helmholtz free energy expansion like classical virial series up to the second virial coefficient. The analytical formula for the Helmholtz free energy is incorporated in a logarithmic form to minimize the effects of series truncation. The new theoretical approach, including discrete summation over lattice nodes coordinates, is compared critically against the classical virial expansion of the Helmholtz free energy for the dipolar hard sphere fluid; the main differences between the Helmholtz free energy of SCLF and dipolar hard sphere fluid are discussed. The theoretical results for the Helmholtz free energy, the magnetization, and the initial magnetic susceptibility of the SCLF are compared against Molecular Dynamic simulation data. In all cases, theoretical predictions using logarithmic form of the Helmholtz free energy are seen to be superior, but they only have an applicability range of the effective dipolar coupling constant λe<1.5. For highest values of λe, the structural transition of the magnetic dipoles in SCLF is observed in Molecular Dynamic simulation. It has been shown that for λe≳2, an antiferromagnetic order appears in the system. © 2020The reported study was funded by RFBR , project number 20-02-00358 . AYS and EAE acknowledged Prof. Philip Camp for his advice and useful discussions

The influence of interparticle correlations and self-assembly on the dynamic initial magnetic susceptibility spectra of ferrofluids

Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial magnetic susceptibility of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The susceptibility spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit. © 2016 Elsevier B.V

Computer Simulations of Dynamic Response of Ferrofluids on an Alternating Magnetic Field with High Amplitude

The response of ferrofluids to a high-amplitude AC magnetic field is important for several applications including magnetic hyperthermia and biodetection. In computer simulations of the dynamic susceptibility of a ferrofluid outside the linear response region, there are several problems associated with the fact that an increase in the frequency of the AC field leads to the appearance of additional computational errors, which can even lead to unphysical results. In this article, we study the dependence of the computational error arising in the computer simulation of the dynamic susceptibility on the input parameters of the numerical algorithm: the length of the time step, the total number of computer simulation periods, and averaging period. Computer simulation is carried out using the Langevin dynamics method and takes Brownian rotational relaxation of magnetic particles and interparticle interactions into account. The reference theory [Yoshida T.; Enpuku K. Jap. J. Ap. Phys. 2009] is used to estimate computational error. As a result, we give practical recommendations for choosing the optimal input parameters of the numerical algorithm, which make it possible to obtain reliable results of the dynamic susceptibility of a ferrofluid in a high-amplitude AC field in a wide frequency range. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Ministry of Science and Higher Education of the Russian Federation (Ural Mathematical Center project No. 075-02-2021-1387)

Behavior of Bulky Ferrofluids in the Diluted Low-Coupling Regime: Theory and Simulation

A theoretical formalism to predict the structure factors observed in dipolar soft-sphere fluids based on a virial expansion of the radial distribution function is presented. The theory is able to account for cases with and without externally applied magnetic fields. A thorough comparison of the theoretical results to molecular-dynamics simulations shows a good agreement between theory and numerical simulations when the fraction of particles involved in clustering is low; i.e., the dipolar coupling parameter is λ 2, and the volume fraction is φ 0.25. When magnetic fields are applied to the system, special attention is paid to the study of the anisotropy of the structure factor. The theory reasonably accounts for the structure factors when the Langevin parameter is smaller than 5. © 2010 The American Physical Society.This research has been carried out within the financial support of RFBR Grant No. 08-02-00647 and DFG-RFBR Joint Grants No. HO 1108/12-1 and No. 06-02-04019

Changes of metabolic parameters in patients with primary hyperparathyroidism of different age groups

BACKGROUND: Studies have shown a high incidence of metabolic disorders and cardiovascular diseases in patients with primary hyperparathyroidism (PHPT). PHPT is usually diagnosed in people of age over 50 years and therefore age-associated changes of metabolism should be excluded. Researching predictors of cardiovascular pathology contributes to choosing optimal approaches to personalized patient management.AIM: To determine the features of metabolic disorders in patients of various age groups with confirmed active stage of PHPT.MATERIALS AND METHODS: A single-center observational retrospective comparative study of patients with active PHPT at the age of 18-49 years (Group 1, n=66) and over 50 years (Group 2, n=290) was carried out. The exclusion criteria for both groups were: persistent PHPT or recurrence after surgical treatment of the disease in history; clinical/genetically confirmed multiple endocrine neoplasia syndrome; for Group 1 — pregnancy, lactation. The assessment of laboratory parameters of mineral, carbohydrate, fat and purine metabolism obtained during a hospital examination was carried out, the frequencies of various metabolic disorders were determined and compared between age groups.RESULTS: There were no significant differences in parathyroid hormone and serum calcium levels between age groups, however, there were more severe hypercalciuria, a tendency to active bone metabolism and lower vitamin D level in Group 1. Patients of Group 2 had statistically significantly lower glomerular filtration rate and a higher frequency of bone complications. In the same group glycaemia and triglycerides levels were higher (the latter difference has the level of a statistical tendency). These patients also had a higher body mass index and, as a result, a higher incidence of obesity (37% vs 20%, p=0.006) and diabetes mellitus type 2 (12.5% vs 3%, p=0.013). At the same time, patients did not significantly differ in the rates of hypercholesterolemia (62% in Group 1 vs 70% in Group 2, p=0.228), hypertriglyceridemia (27% vs 32%, p=0.433) and hyperuricemia (42% vs 50%, p=0.302), significantly exceeding similar indicators in the general Russian population.CONCLUSION: Carbohydrate disorders are more often observed in patients older than 50 years, providing an increased prevalence of diabetes mellitus type 2 among patients with PHPT compared with the general population. The high incidence of various types of dyslipidemia and hyperuricemia in the primary parathyroid pathology has no age specific features. Thereby these disorders are significant risk factors of cardiovascular diseases, even in young people with PHPT

Soluble endoglin as a perspective marker of endothelial dysfunction in patients with primary hyperparathyroidism: a pilot study

BACKGROUND: Primary hyperparathyroidism  (PHPT), one of the most common endocrine pathologies, is associated with a higher incidence of cardiovascular diseases, in particular, those caused by endothelial dysfunction. Evaluation of endothelial dysfunction in patients with PHPT will predict the development of cardiovascular pathology and determine the optimal tactics for PHPT management.AIM: To evaluate the concentration  of soluble endoglin  and photoplethysmographic parameters as potential markers of endothelial dysfunction in patients with PHPT.MATERIALS AND METHODS:  A single-center interventional single-stage study was carried out. 2 groups were formed. The first group included 50 patients with verified PHPT who did not have cardiovascular or other concomitant somatic pathologies in anamnesis. The comparison group included 21 healthy volunteers comparable in sex and age. All participants underwent a biochemical blood test (total calcium, ionized, albumin, lipidogram, urea, uricacid, glucose, creatinine, alkaline phosphatase), parathyroid hormone, 25 (OH) D and endoglin concentrations were evaluated. In addition, echocardiography, ultrasound of the brachiocephalic arteries and arteries of the lower extremities, as well as photoplethysmography were performed.RESULTS: The groups differed in mineral parameters associated with PHPT; no differences were found in parameters of lipid, uric acid and carbohydrate metabolism. Serum levels of endoglin  were lower in PHPT patients (p=0.002). We found a negative correlation between the concentration of albumin-corrected calcium and PTH with endoglin (r1=-0.370, p1=0.003 and r2=-0.475, p2<0.001, respectively) and a positive correlation between the concentration of endoglin  and phosphorus (r=0.363, p=0.003). These associations s were accompanied by changes in photoplethysmographic parameters that indicate an increase in the vascular wall stiffness.CONCLUSION: The serum level of soluble endoglin  is lower in patients with PHPT than in healthy volunteers, negatively correlates with calcium and PTH concentrations and positively with serum phosphorus concentrations. Further studies will make it possible to establish the pathogenetic mechanism of the identified relationships and evaluate the role of endoglin as a potential predictor of cardiovascular pathology in PHPT population

The Dynamic Magnetic Susceptibility of a Ferrofluid: the Influence of Interparticle Interactions and Ac Field Amplitude

Целью данной работы является описание одновременного влияния как диполь-дипольных взаимодействий, так и амплитуды поля на динамическую восприимчивость и релаксационные процессы в феррожидкостях. Для этого будут построены формулы, отражающие зависимость диполь­дипольных и поле-дипольных взаимодействий. Акцент ставится на изучение области высоких амплитуд магнитного поля и восприимчивости Ланжевена. Полученные приближенные формулы для динамической восприимчивости комплексно предсказываю динамический отклик феррожидкостей, одновременно учитывая влияние амплитуды переменного поля и диполь-дипольных взаимодействий.This work describes the influence of dipole-dipole interactions and the field amplitude on the dynamic susceptibility and relaxation processes in ferrofluids. For this purpose, we will construct formulas reflecting the dipole-dipole and field-dipole interactions dependence. The main direction is the study of the region of high amplitudes of the magnetic field and the Langevin susceptibility. Approximate formulas for the dynamic susceptibility complexly predict the dynamic response of ferrofluids. At the same time, the influence of the amplitude of the alternating field and dipole-dipole interactions are considered

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. The theory is based on a correction to the second-order modified mean-field theory arising from a formal Mayer-type cluster expansion; this correction is dependent on a parameter similar to the normal dipolar coupling constant, except that it contains a complicated double average over the particle-size distribution, which means that the initial susceptibility should depend significantly on polydispersity. Specifically, the theory predicts that the initial susceptibility is enhanced significantly by polydispersity. This prediction is tested rigorously against results from Monte Carlo simulations and is found to be robust. The qualitative agreement between theory and simulation is already satisfactory, but the quantitative agreement could be improved by a systematic extension of the cluster expansion. The overall conclusion is that polydispersity should be accounted for carefully in magnetogranulometric analyses of real ferrofluids. © 2014 IOP Publishing Ltd

Mathematical Modeling of Magnetic Properties of Composites

Работа посвящена теоретическому исследованию свойств ансамбля обездвиженных магнитных частиц с анизотропной ориентационной структурой. Главный акцент в работе сделан на учете межчастичных диполь­дипольных взаимодействий. Получено аналитическое выражение, позволяющее прогнозировать намагниченность системы в зависимости от ее внутренней ориентационной структуры.The work is devoted to a theoretical study of the properties of an ensemble of immobilized magnetic particles with an anisotropic orientational structure. In this work the main emphasis is on considering interparticle dipole-dipole interactions. An analytical expression is obtained that makes it possible to predict the magnetization of the system depending on its internal orientational structure