The study of spontaneous domain nucleation in the interelectrode gap of phase modulator based on titanium indiffused waveguides in lithium niobate crystals

The paper presents the analysis of nucleating kinetics and growing of switched domains in the surface layer of monodomain lithium niobate X-cut crystal in the interelectrode gap of integrated optical phase modulators. The work proposes the morphology model of domains growing along the boundary of surface electrodes in X-cut phase modulators. The mechanism of spontaneous needle-like domain growing as a result of the electric field induced by the pyroelectric effect at temperature changing of the crystal was theoretically substantiated. The Comsol Multiphysics cross-platform was used for the numerical estimation of the pyroelectric field in the interelectrode gap. The needle-like domain structures were studied experimentally at industrial samples of integrated optical phase modulators based on Ti:LiNbO3 waveguides. The experimental research of the form and size of domains was performed with the anisotropic etching method by HF solution and followed by visual analysis. For non-destructive testing, the authors used scanning electron microscopy and piezo-response force microscopy. For the first time, the morphology of needle-like domains occurring in the interelectrode gap of phase modulators based on lithium niobate was experimentally studied. The results showed the theoretical and numerical model of domain growing that involves the pyroelectric nature of the electric field. It was demonstrated that along the electrode boundary, the needle-like domains grow up to 20 μm long at normal conditions and achieve 30 μm after the thermal shock by cooling at ΔT = – 125 °С. The discovered switched domains in the interelectrode gap can affect electro-optical characteristics of integrated optical phase modulators with the lithium niobate base and should be taken into account in the future design of electrode topology and modulator usage

Tensiometric estimation of material properties of tissue spheroids

Tissue spheroids have been proposed to use as building blocks in biofabrication and as bioinks in 3D bioprinting technologies. Tissue fusion is an ubiqious phenomenon during embryonic development. Biomimetic tissue spheroid fusion is a fundamental constructional principle of emerging organ printing technology because closely placed tissue spheroids could fuse into tissue and organ-like constructs in fusion permissive bioprintable hydrogel. From physical point of view tissue spheroids could be considered as a visco-elastic-plastic soft matter or complex fluid. We hypothesize that quantitative estimation of material properties of tissue spheroids using tensiometry could predict their tissue spreading and tissue fusion behavior as well as provide a powerful insight about possible speed of post-printed tissue and organ-like constructs compaction and maturation. Tissue spheroids from human fibroblasts, ovine and human chondrocytes and immortalised human keratinocytes have been biofabricated using non-adhesive cell culture plates (Corning, USA). For estimation of material properties of tissue spheroids commercial tensiometer Microsquisher have been emploied (CellScale, Toronto, Canada). Modulus of elasticity of tissue spheroids have been calculated based on peformed tissue compression tests. In order to identify structural determinants of material properties of tissue spheroids standard perturbants of cytoskeleton such as Cytochalasin D (Sigma, USA) for disruption of microfilaments and Nocodazole (Sigma, USA) for disruption of microtubules have been used. Viability of tissue spheroids have been also estimated and their morphology have been analysed using light microscopy, histochemistry, immunohistochemistry, semithin sections stained wih toluidine blue and transmission and scanning electron microscopy. Kinetics of tissue spheroids spreading on electrospun polyurethane matrices have been analysed. Kinetics of two closely placed tissue spheroids fusion have been analysed in hanging drop. Additionally toxic effect of water solution of paramagnetic gadolinium salt (Omniscan®, GE Health Care, USA) on material properties of tissue spheroids have been investigated. It have been demonstrated that material properties of tissue spheroids biofabricated from different cell types have different modulus of elasticity. Even tissue spheroids biofabricated the same cell types but from different species have different material properties. Incubation with Cytochlasin D dramatically reduces estimated material properties of tissue spheroids. Incubation with Nocodazole does not significantly change material properties of tissue spheroids. Material properties of tissue spheroids from chondrocytes (chondrospheres) correlates very well with increasing deposition and accumulation of extracellular matrix (confirmed by expression of collagen type II and glycosoaminoglycans). The incubation with toxic concentration of gadolinium solution dramatically reduces material properties of chondrospheres. There is no any significant correlation between material properties of tissue spheriods and their spreading kinetics. However, there is a certain correction between material properties of tissue spheroids and their tissue fusion kinetics. Our data demonstrate that beside already well established role of cell adhesion receptors such as cadherin and integrins in the realisation of cell cohesion inside tissue spheroids the structural determinants of material properties of tissue spheroids also include components of cytoskeleton such as actin micofilaments and accumulated extracellular matrix. It is possible to predict post-printing tissue fusion behaviour of tissue spheroids based on preliminary estimation of their material properties. Finally, it have been also shown that material properties of tissue spheroids correlate with their viability. Thus, tensiometry is a valuable method for systematic characterization of material properties of tissue spheroids and for prediction of tissue spheroids post-printed tissue fusion behaviour

Commercial articulated collaborative in situ 3D bioprinter for skin wound healing

In situ bioprinting is one of the most clinically relevant techniques in the emerging bioprinting technology because it could be performed directly on the human body in the operating room and it does not require bioreactors for post-printing tissue maturation. However, commercial in situ bioprinters are still not available on the market. In this study, we demonstrated the benefit of the originally developed first commercial articulated collaborative in situ bioprinter for the treatment of full-thickness wounds in rat and porcine models. We used an articulated and collaborative robotic arm from company KUKA and developed original printhead and correspondence software enabling in situ bioprinting on curve and moving surfaces. The results of in vitro and in vivo experiments show that in situ bioprinting of bioink induces a strong hydrogel adhesion and enables printing on curved surfaces of wet tissues with a high level of fidelity. The in situ bioprinter was convenient to use in the operating room. Additional in vitro experiments (in vitro collagen contraction assay and in vitro 3D angiogenesis assay) and histological analyses demonstrated that in situ bioprinting improves the quality of wound healing in rat and porcine skin wounds. The absence of interference with the normal process of wound healing and even certain improvement in the dynamics of this process strongly suggests that in situ bioprinting could be used as a novel therapeutic modality in wound healing.publishersversionPeer reviewe

Vestibular neuronitis

Vestibular neuronitis occurs as a result of damage to the vestibular nerve and is manifested by a sudden and prolonged attack of vestibular vertigo, accompanied by nausea, vomiting and imbalance. Questions of etiology, pathogenesis, clinical picture, diagnosis and treatment of VN are discussed. The disease is associated with selective inflammation (viral or infectious-allergic genesis) of the vestibular nerve. The role of herpes simplex virus type 1 is confirmed by cases of herpetic encephalitis in VN. In 2020, cases of VN development in patients with COVID-19 are described. VN usually affects the upper branch of the vestibular nerve, which innervates the horizontal and anterior semicircular canals. The duration of vertigo with VN ranges from several hours to several days. The timing of the restoration of vestibular function depends on the degree of damage to the vestibular nerve, the speed of central vestibular compensation and the patient’s performance of vestibular gymnastics. Some patients, months and even years after VN, experience significant instability. The diagnosis of VL is based on the clinical picture of the disease, the results of an otoneurological examination, and the exclusion of other diseases. VN treatment is aimed at reducing dizziness, nausea and vomiting and accelerating vestibular compensation. In our country VN is rarely diagnosed, which is associated with poor awareness of doctors about this disease. The article presents the observation of a 46-year-old patient with VN, who was mistakenly diagnosed with vertebrobasilar insufficiency, which contributed to the patient’s long-term disability. Establishing the correct diagnosis, educational work with the patient, conducting vestibular gymnastics led to an improvement in the condition, regression of instability. The issues of the effectiveness of vestibular gymnastics, the use of betahistine to accelerate the recovery of patients with VN are discussed

The Stability of Sulfide Sorbents Based on Silica in Aqueous Media. Part I. SBA-15 Matrix

Физико-химическими методами исследована химическая и термическая устойчивость сорбентов на основе мезопористого мезоструктурированного силиката SBA-15 с привитыми сульфидными функциональными группами типа R-S-R’. Установлено, что обработка материала в кислой, нейтральной и щелочной средах при температурах кипения приводит к незначительным изменениям структурных, текстурных и сорбционных характеристик, демонстрируя суммарные потери сорбента около 20 % мас. Привитый функциональный слой сохраняется. Полученные сорбенты способны длительное время работать в различных технологических растворах и не уступают известным коммерческим сорбентам с функциональными группамиThe chemical and thermal stability of the sulfide-functionalized (R-S-R’ type) sorbents based on SBA- 15 mesoporous mesostructured silica have been investigated by physico-chemical methods. It has been found that the material treatment in acid, neutral and alkaline conditions at the boiling temperature result in insignificant changes in structural, textural and sorption characteristics, showing sorbent total losses about 20 % mass. The grafted functional layer is saved. The sorbents obtained are able to work over a long period of time in a variety of technological solutions and are not inferior to wellknown commercial sorbents with functional group

Adsorption Properties of Thiol-Functionalized Mesoporous Silica

Работа посвящена синтезу и исследованию физико-химических характеристик функциональных сорбентов на основе мезопористых мезоструктурированных силикатов типа МСМ-41 и SBA- 15 с привитыми тиольными группами. Изучены сорбционные свойства полученных материалов по отношению к ионам благородных металлов, в частности палладия(II), из солянокислых растворов. Полученные материалы охарактеризованы комплексом физико-химических методов до и после функционализации. Проведена оценка сорбционной способности полученных материалов по отношению к ионам Pd(II). Экспериментальные результаты свидетельствуют о высокой сорбционной активности функционализированных мезопористых силикатовThe synthesis and physico-chemical characteristics of thiol-functionalized mesoporous silicates MCM-41 and SBA-15 are described. The sorption properties of the materials with respect to noble metal ions, in particular palladium(II) from hydrochloric acid solutions have been studied. The materials obtained have been characterized using a complex of physical and chemical methods before and after functionalization. The evaluation of the sorption capacity of the obtained sorbents with respect to Pd(II) ions has been performed. Experimental results show high sorption activity of thiol-functionalized mesoporous silic

Antyhypertensive therapy-based secondary prevention of ischemic stroke

The paper reviews the data available in the literature on the prevention of ischemic stroke by using antihypertensive therapy. It gives international guidelines and the results of randomized placebo-controlled trials of the use of different antihypertensive drugs in patients with prior stroke or transient ischemic attack. The possible neuroprotective effects of angiotensin II receptor blockers are discussed when analyzing the advantages of eprosartan over nitrendipine in the secondary prevention of stroke. The realities and optimization of secondary prevention of stroke in outpatient practice are analyzed

Hydrothermal Stability of Mesostructured Silicate MCM-41 in Connection with Pathways Synthesis

Проведено исследование изменения мезоструктуры силикатного материала МСМ-41 на основных стадиях синтеза в зависимости от изменяемых условий. Для фиксации параметров мезоструктурного состояния применена рентгеновская дифракция в сочетании с методом непрерывной электронной плотности. Рентгеноструктурные данные дополнены адсорбционными измерениями. Рассмотрены вариации условий синтеза, влияющие на гидротермальную устойчивость, в частности создание основности реакционного раствора с применением аммиака и щелочи, замена реакционного раствора при гидротермальной обработке на воду и солевой раствор. Показано, что поликонденсация силиката в плотно упакованных цилиндрических органосиликатных мицеллах развивается в условиях химических и стерических факторов. Процесс поликонденсации имеет анизотропный характер и приводит к множеству траекторий формирования конечного твердого продукта, выражающихся в разнообразии мезоструктурных форм. Установлено, что рост диаметра поры, как правило, вызван осмотическим давлением воды. Причем если поликонденсация кремнезема замедлена, либо стерически затруднена, то поры приобретают гексагональную форму, а в условиях, способствующих поликонденсации, поры имеют цилиндрическую форму. Стенка поры представляет собой двухслойный молекулярный пакет кремнезема с толщиной 0,8-1,0 нм. Наращивание стенки с использованием тетраэтоксисилана заканчивается зарастанием пор кремнеземом и потерей удельного внутреннего объема и поверхности. Обработка материала раствором силиката натрия приводит к эффекту «залечивания» поверхности и повышению гидротермальной стабильности. Применение аммиака как фактора основности среды обеспечивает наибольшую скорость поликонденсации кремнезема и высокую гидротермальную стабильность продукта.The changes of the MCM-41 silicate material mesostructure during the main synthesis stages depending on the modified conditions have been investigated. To estimate the parameters of the mesostructured state the X-ray powder diffraction has been applied in combination with the continuous electron density approach. The X-ray data are supplemented by adsorption measurements. Consideration has been given to the variations of the synthesis conditions affecting the hydrothermal stability, in particular the creation of the basicity of the synthesis solution using ammonia and alkali and the substitution of the synthesis solution with water and a salt solution at hydrothermal treatment. It has been shown that polycondensation of the silicate in closely-packed cylindrical organosilicate micelles occurs under the conditions of chemical and steric factors. The polycondensation process is anisotropic and results in numerous pathways of the final solid product formation, showing the variety of mesostructured forms. It has been established that increasing the pore diameter, as a rule, is due to the osmotic pressure of water. Moreover, if the silica polycondensation is slowed down or sterically difficult, the pores acquire the hexagonal shape, and under the conditions favourable for the polycondensation, they are cylindrical. The pore wall is a two-layer molecular pack of silica 0.8-1.0 nm in thickness. The wall growth using tetraethoxysilan ends by the pore healing with silica and the loss of the specific inner volume and surface. The material treatment by a sodium silicate solution results in the effect of the surface «healing» and increased hydrothermal stability. Using ammonia as the medium basicity factor provides the highest rate of the silica polycondensation and high hydrothermal stability of the product