Bright solitons from defocusing nonlinearities

We report that defocusing cubic media with spatially inhomogeneous nonlinearity, whose strength increases rapidly enough toward the periphery, can support stable bright localized modes. Such nonlinearity landscapes give rise to a variety of stable solitons in all three dimensions, including 1D fundamental and multihump states, 2D vortex solitons with arbitrarily high topological charges, and fundamental solitons in 3D. Solitons maintain their coherence in the state of motion, oscillating in the nonlinear potential as robust quasi-particles and colliding elastically. In addition to numerically found soliton families, particular solutions are found in an exact analytical form, and accurate approximations are developed for the entire families, including moving solitons.Comment: 13 pages, 6 figures, to appear in Physical Review

TMOKE as efficient tool for the magneto-optic analysis of ultra-thin magnetic films

Ultra-thin magnetic dielectric films are of prime importance due to their applications for nanophotonics and spintronics. Here, we propose an efficient method for the magneto-optical investigation of ultra-thin magnetic films which allows one to access their state of magnetization and magneto-optical properties. It is based on the surface-plasmon-polariton-assisted transverse magneto-optical Kerr effect (TMOKE). In our experiments, sub-100 nm-thick bismuth-substituted lutetium iron-garnet films covered with a plasmonic gold grating have been analyzed. The excitation of surface plasmon-polaritons provides resonance enhancement of TMOKE up to 0.04 and makes it easily detectable in the experiment. For films thicker than 40 nm, the TMOKE marginally depends on the film thickness. A further decrease in the film thickness diminishes TMOKE since for such thicknesses the surface plasmon-polariton field partly penetrates inside the non-magnetic substrate. Nevertheless, the TMOKE remains measurable even for few-nm-thick films, which makes this technique unique for the magneto-optical study of ultra-thin films. Particularly, the proposed method reveals that the off-diagonal components of the magnetic film permittivity tensor grow slightly with the reduction of the film thickness.Comment: 5 page

Current status of the problem of cardiovascular diseases in the Nizhny Novgorod region: possible ways to reduce mortality

The article considers the urgent problem of combating cardiovascular diseases (CVDs) in the Nizhny Novgorod region, including the high prevalence of CVDs and the timely identification of risk factors. The changes in mortality from all and individual causes was analyzed. Attention was paid to the negative impact of the coronavirus disease 2019 (COVID-19) pandemic on the health of people suffering from noncommunicable diseases. We also described the necessity to improve healthcare efficiency for CVD patients by improving the complex of managerial and preventive measures

Catalytic sulfation of betulin with sulfamic acid : experiment and DFT calculation

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst(®)15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835–841 cm(−1); in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K(1) and K(2) of a solution of the betulin disulfate H(+) form has been found to be 3.86 × 10(–6) ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data

On strong causal binomial approximation for stochastic processes

This paper considers binomial approximation of continuous time stochastic processes. It is shown that, under some mild integrability conditions, a process can be approximated in mean square sense and in other strong metrics by binomial processes, i.e., by processes with fixed size binary increments at sampling points. Moreover, this approximation can be causal, i.e., at every time it requires only past historical values of the underlying process. In addition, possibility of approximation of solutions of stochastic differential equations by solutions of ordinary equations with binary noise is established. Some consequences for the financial modelling and options pricing models are discussed

ЭНЦЕФАЛОПАТИЯ И ГИПЕРЛАКТАТЕМИЯ В-ТИПА КАК ОСЛОЖНЕНИЕ ЛЕЧЕНИЯ 5-ФТОРУРАЦИЛОМ

Background. There is a wide spectrum of metabolic and toxic disorders that can cause acute encephalopathy in cancer patients. In routine clinical practice, hypoglycemia, vitamin B1 (thiamine) deficit, fulminant liver failure, uremia, severe hypoand hypernatremia should be primarily excluded. Central neurotoxicity associated with hyperammonemia in patients receiving 5-fluorouracil (5-FU) and oral fluoropyrimidines should be considered in differential diagnosis. In this case, the analysis of the blood acid-base status and the detection of B-type hyperlactatemia can facilitate the diagnosis of the cause of encephalopathy.Case description. We present two cases of hyperlactatemia and encephalopathy in stage IV cancer patients with continuous infusion of 5-FU via a portable infusion pump.Conclusion. Diagnosis of the frequent fluoropyrimidin-related adverse effects, such as myelosuppression, anorexia, diarrhea, mucositis, and palm-plantar syndrome, are routine and mastered by an oncologist at the very beginning of his/her professional activity. Specific fluoropyrimidinerelated encephalopathy or hyperlactatemia are difficult to suspect and recognize. We hope our description will be useful to prevent possible diagnostic errors.Актуальность. Спектр метаболических и токсических расстройств, провоцирующих развитие острой энцефалопатии в онкологии, довольно широк. В первую очередь следует исключать гипогликемию, недостаток витамина B1 (тиамина), фульминантную печеночную недостаточность, уремию, тяжелую гипои гипернатриемию. У пациентов, получающих 5-фторурацил (5-ФУ) и фторпиримидины для приема внутрь, при дифференциальной диагностике следует учитывать и возможную центральную нейротоксичность этого класса противоопухолевых препаратов, связанную с гипераммониемией. В этом случае диагностике энцефалопатии может способствовать анализ кислотно-основного состояния крови и выявление гиперлактатемии B-типа.Описание случаев. Представлено два клинических случая энцефалопатии и гиперлактатемии у больных раком желудка и прямой кишки IV стадии, получавших 5-ФУ в виде длительной инфузии.Заключение. Диагностика частых побочных эффектов противоопухолевого лечения (в случае фторпиримидинов – миелосупрессия, анорексия, диарея, мукозит и ладонно-подошвенный синдром) является рутинной и осваивается онкологом на самых ранних этапах профессиональной деятельности; лечение этих осложнений и дальнейшая коррекция противоопухолевой терапии подробно освещены в руководствах. Специфические фторпиримидин-обусловленные энцефалопатию и гистотоксическую гиперлактатемию распознать довольно сложно. Надеемся, что наше описание поможет практическим врачам предотвратить возможные ошибки диагностики

Hyperbaric Oxygen Therapy in Patients with COVID-19

The aim of the study is to evaluate the efficacy of hyperbaric oxygen therapy and its effect on oxidative stress and apoptosis in patients with new coronavirus infection COVID-19.Materials and methods. 90 patients diagnosed with new coronavirus infection caused by SARS-CoV-2 virus were examined. Hyperbaric oxygen therapy sessions were conducted in 57 patients (38 in severe condition (CT 3-4), 19 in moderate condition (CT 1-2)). The procedures were performed in 1.4-1.6 ATA mode for 40 minutes, 247 sessions in total were performed. The effect of hyperbaric oxygenation was assessed by measuring the level of oxygen saturation, the severity of oxidative stress and apoptosis of blood lymphocytes.Results. In all examined patients with new coronavirus infection caused by SARS-CoV-2, positive changes such as dyspnea reduction and improvement of general well-being were registered after hyperbaric oxygen therapy sessions. The level of oxygen saturation after the end of the hyperbaric oxygen therapy course was 95.0±1.6% (before the course — 91.3±5.9%), which allowed to return almost all patients to spontaneous respiration without the need for further oxygenation therapy. Hyperbaric oxygen therapy did not reduce the total antioxidant activity, however, it was associated with a decrease in the blood malone dialdehyde from 4.34±0.52 pmol/l to 3.98±0.48 pmol/l and a decrease in open circuit potential of platinum electrode from -22.78±24.58 mV to -37.69±17.4 mV. Besides, the positive effect of hyperbaric oxygen therapy was manifested in normalization of blood cell apoptosis.Conclusion. Hyperbaric oxygen therapy in patients with new coronavirus infection caused by the SARS-CoV-2 virus is an effective treatment method with multiple effects resulting in improvement of subjective indicators of the patients' condition, increase of hemoglobin oxygen saturation, decrease of lipid peroxidation intensity, activation of antioxidant system, restoration of pro- and antioxidant balance and apoptosis normalization