Creation of the precision magnetic spectrometer SCAN-3

The new JINR project [1] is aimed at studies of highly excited nuclear matter created in nuclei by a high-energy deuteron beam. The matter is studied through observation of its particular decay products - pairs of energetic particles with a wide opening angle, close to 180°. The new precision hybrid magnetic spectrometer SCAN-3 is to be built for detecting charged (π±, K±, p) and neutral (n) particles produced at the JINR Nuclotron internal target in dA collisions. One of the main and complex tasks is a study of low-energy ηA interaction and a search for η-bound states (η-mesic nuclei). Basic elements of the spectrometer and its characteristics are discussed in the article

A novel operando approach to analyze the structural evolution of metallic materials during friction with application of synchrotron radiation

International audienceIn this study, we describe an experimental setup and a new approach for operando investigation of structural evolution of materials during wear and friction. The setup is particularly suited for testing various friction pairs, including those in which both rubbing bodies are made of metals. The developed device allows circumventing the problems related to significant scattering of X-rays produced by metals and makes it possible using “real samples” in synchrotron beamlines operating in reflection mode. To demonstrate the capabilities of the device and the proposed new approach, an iron-based massive sample was subjected to thousands of friction cycles using a cemented carbide pin. The material was probed with synchrotron X-ray radiation within a few milliseconds after leaving the friction zone. The results of the microstructural and structural analysis, as well as results obtained from diverse mathematical models, allowed us to evaluate several features, including gradual accumulation of defects, microstructural refinement, dislocation density changes, surface layer oxidation, as well as several other phenomena caused by the dry sliding friction process. Mainly, it was possible to conclude that the process of wear occurred due to the cooperative action of oxidation and plastic deformation, which began during the first cycle of frictional interaction and was manifested in increasing the dislocation density, whose type was changed gradually during testing. The number of defects quickly reached a threshold value and subsequently fluctuated around it due to periodically repeated processes of defect accumulation and stress relaxation resulting from material wear. It was also observed that friction led to the quick formation of a mechanically mixed layer, consisting of the sample material and a mixture of two types of iron oxide – hematite and magnetite. The delamination of this layer was probably the primary wear mechanism

Nonwoven polycaprolactone scaffolds for tissue engineering: The choice of the structure and the method of cell seeding

Nonwoven polycaprolactone materials produced by electrospinning are perspective internal prosthetic implants. Seeding these implants with multipotent mesenchymal stromal cells stimulates the replacement of the prosthesis with recipient's own connective tissue. Electrospinning method was used for producing polycaprolactone matrices differing in thickness, pore diameter, fiber size, and biomechanical properties. Labeled cells were seeded on scaffolds in three ways: (1) static, (2) dynamic, and (3) directed flow of the cell suspension generated by capillary action. Cell distribution on the surface and the interior of the scaffolds was studied; the metabolic activity of cells was measured by MTT assay. Static seeding method yielded fully confluence of cells covered the entire scaffold surface, but the cells were located primarily in the upper third of the matrix. Dynamic method proved to be effective only for scaffolds of thickness greater than 500 microns, irrespective of the pore diameter. The third method was effective only for scaffolds with the pore diameter of 20-30 microns, regardless of the material thickness. Resorbable nonwoven polycaprolactone electrospun materials have appropriate biomechanical properties and similar to native tissue matrix structures for internal prosthesis. The choice of the most effective cell seeding method depends on the spatial characteristics - the material thickness, pore diameter, and fibers size, which are determined by the electrospinning conditions

Нетканые материалы на основе поликапролактона для тканевой инженерии: выбор структуры и способа заселения

Nonwoven polycaprolactone materials produced by electrospinning are perspective internal prosthetic implants. Seeding these implants with multipotent mesenchymal stromal cells stimulates the replacement of the prosthesis with recipient's own connective tissue. Electrospinning method was used for producing polycaprolactone matrices differing in thickness, pore diameter, fiber size, and biomechanical properties. Labeled cells were seeded on scaffolds in three ways: (1) static, (2) dynamic, and (3) directed flow of the cell suspension generated by capillary action. Cell distribution on the surface and the interior of the scaffolds was studied; the metabolic activity of cells was measured by MTT assay. Static seeding method yielded fully confluence of cells covered the entire scaffold surface, but the cells were located primarily in the upper third of the matrix. Dynamic method proved to be effective only for scaffolds of thickness greater than 500 microns, irrespective of the pore diameter. The third method was effective only for scaffolds with the pore diameter of 20-30 microns, regardless of the material thickness. Resorbable nonwoven polycaprolactone electrospun materials have appropriate biomechanical properties and similar to native tissue matrix structures for internal prosthesis. The choice of the most effective cell seeding method depends on the spatial characteristics - the material thickness, pore diameter, and fibers size, which are determined by the electrospinning conditions.Нетканые материалы на основе поликапролактона, полученные методом электроформования, являются перспективными имплантатами для эндопротезирования. Заселение таких имплантатов мультипотентными мезенхимальными стромальными клетками способствует замещению протеза собственной соединительной тканью реципиента. Целью настоящего исследования являлось сравнение эффективности трех методов заселения клетками нетканых носителей на основе поликапролактона, обладающих различными пространственными характеристиками. Методом электроформования были получены три образца поликапролактоновых матриц, отличающихся толщиной, диаметром пор и волокон, биомеханическими свойствами. Заселение носителей мечеными мультипотентными мезенхимальными стромальными клетками пупочного канатика проводили тремя способами: статичным, динамическим и методом с использованием капиллярного эффекта. Оценивали распределение клеток по поверхности и толщине образцов, метаболическую активность клеток измеряли с помощью МТТ-теста. Статичный метод позволил получить носители с равномерным покрытием поверхности, однако клетки в основном располагались в верхней трети матрикса. Динамический метод оказался эффективен только для носителей толщиной более 500 мкм, независимо от диаметра пор. Метод заселения с использованием капиллярного эффекта был эффективен только для носителей с диаметром пор 20-30 мкм, независимо от толщины материала. Биорезорбируемые нетканые материалы на основе по-ликапролактона, полученные методом электроформования, обладают подходящими биомеханическими свойствами для выполнения пластики дефектов стенок брюшной полости, имеют сходное с матриксом нативной ткани строение. Выбор наиболее эффективного метода заселения носителей клетками зависит от его пространственных характеристик - толщины материала, диаметра пор и волокон, которые, в свою очередь, определяются условиями электроформования материала