2,099 research outputs found

    Binder jetting additive manufacturing of biodegradable Zn

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    Biodegradable materials avoid second surgeries and long-term associated risks of conventional inert implants. Zn arose as a potential candidate for bioresorbable implants due to its proper degradation behaviour and biocompatibility [1]. However, its low melting point induces uncontrolled porosity in LPBF, promoting the future cracking of the implant. Therefore, new fabrication techniques need to be explored. In this work, binder jetting 3d printing (BJ3P) was studied for Zn powders. The samples were printed and sintered under different conditions. It is concluded that, the increase the temperature almost up to melting point leads to higher densification, at the same time, the rise of temperature provokes the formation and growth of oxidized layer on the surface of the powders

    Influence of the metal chips disintegration method on the physical and mechanical properties of metal powders obtained

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    This paper presents the results obtained in comparative grinding studies of alloy metal chips using a ball mill and a vibrating mill. A comparison of the effective viscosity, bulk and tapped density in narrow size classes demonstrated higher rheological properties of the vibration grinding product and significant differences in the distribution of indicators by the size classes, depending on the grinding method. The specific yield and energy consumption indicators were established, which confirmed the superiority of vibration grinding over ball mill grinding. A visual assessment of the shape and surface condition of the ground particles is presented, conducted using a scanning electron microscope

    Modern Approaches to the Study of Medicines Used in the Treatment of Patients Diagnosed with Covid-19

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    The new coronavirus (COVID-19) was first detected in the city of Wuhan in China in December 2019. Most patients infected with COVID-19 had clinical manifestations of dry cough, fever, shortness of breath, chest pain, fatigue and malaise, pneumonia, and bilateral chest CT infiltration. Soon COVID-19 spread around the world and turned into a pandemic. Now this disease affects many patients around the world. Patients with concomitant diseases have a high risk of COVID-19 infection, the infection is quite severe, leading to organ dysfunction, which is acute respiratory distress syndrome, acute kidney damage, septic shock, pneumonia and death. Currently, the coronavirus disease (COVID-19) is an imminent threat to global public health. Experts around the world are now actively searching for medicines that can stop the infection. Despite the fact that some modern therapeutic drugs have demonstrated quite high capabilities in the field of prevention or treatment of patients with COVID-19, various side effects have occurred during their use. Therefore, a comprehensive assessment of the safety profile of therapeutic agents against COVID-19 is highly relevant

    ОСОБЕННОСТИ ХЕМИЛЮМИНЕСЦЕНТНОЙ АКТИВНОСТИ ТРОМБОЦИТОВ В НОРМЕ И ПРИ ИШЕМИЧЕСКОЙ БОЛЕЗНИ СЕРДЦА

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    The aim of the study was to study the characteristics of the chemiluminescent activity of platelets in normal and coronary heart disease. The study involved 35 patients with coronary artery disease and 16 relatively healthy people. The object of study is peripheral blood. The result was significant differences in the intensity of luminescence of platelets. Patients have increased luminescence, and therefore increased production of reactive oxygen species. This feature of chemiluminescence is associated with a change in the functional activity of cells in CHD.Целью исследования явилось изучение особенностей хемилюминесцентной активности тромбоцитов в норме и при ишемической болезни сердца. В исследование приняли участие 35 больных ИБС и 16 относительно здоровых людей. Объект изучения – периферическая кровь. Результатом стали достоверные различия в интенсивности свечения тромбоцитов. У больных наблюдается повышенное свечение, а значит и увеличенное продукция активных форм кислорода. Данную особенность хемилюминесценции связываем с изменением функциональной активности клеток при ИБС

    Influence of ECAP process on mechanical, corrosion and bacterial properties of Zn-2Ag alloy for wound closure devices

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    Actual polymeric wound closure devices are not optimal for load-bearing applications due to the low mechanical properties and the risk of inflammation and bacterial infection mainly produced by multifilament and braided configurations. Biodegradable metallic Zn alloys are promising materials candidates; however, mechanical performance, corrosion behaviour, and biological response should be controlled in order to inhibit the risk of inflammation and bacterial infection. To this end, a Zn-2Ag (2 wt% Ag) alloy was processed by ECAP to evaluate the concurrent combined effect of grain refinement and Ag alloying on biodegradation and antibacterial activity. Two ECAP cycles were successfully applied to a Zn-2Ag alloy obtaining a homogeneous ultra-fine-grained structure in which nanoindentation maps suggested isotropic mechanical properties. Lower UTS and YS with higher elongation was reported after ECAP with similar corrosion rates as before processing. ECAP processed samples showed a homogeneous Ag+ release below the minimum inhibitory concentration for S. Aureus and no antibacterial effect was observed by diffusion. As expected, the presence of Ag in Zn-Ag alloys reduced bacterial attachment. Nevertheless, ECAP processed Zn-2Ag provided an excellent antibacterial activity after 3 h probably caused by the uniformly degraded and thus, non– stable, surface observed after bacterial adhesion.Peer ReviewedPostprint (published version

    Novel hydrogen clathrate hydrate

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    We report a new hydrogen clathrate hydrate synthesized at 1.2 GPa and 298 K documented by single-crystal X-ray diffraction, Raman spectroscopy, and first-principles calculations. The oxygen sublattice of the new clathrate hydrate matches that of ice II, while hydrogen molecules are in the ring cavities, which results in the trigonal R3c or R-3c space group (proton ordered or disordered, respectively) and the composition of (H2O)6H2. Raman spectroscopy and theoretical calculations reveal a hydrogen disordered nature of the new phase C1', distinct from the well-known ordered C1 clathrate, to which this new structure transforms upon compression and/or cooling. This new clathrate phase can be viewed as a realization of a disordered ice II, unobserved before, in contrast to all other ordered ice structures.Comment: 9 pages, 4 figures, 1 table; Supplementary materials: Materials and Methods, Supplementary Figures S1-S8, Tables S1-S3, and Bibliography with 18 Reference

    Non-Fermi-Liquid Behavior of Superconducting SnH4_4

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    We studied chemical interaction of Sn with H2_2 by X-ray diffraction methods at pressures of 180-210 GPa. A previously unknown tetrahydride SnH4_4 with a cubic structure (fcc{fcc}) exhibiting superconducting properties below T{T}C_C = 72 K was obtained; the formation of a high molecular C2/m{C2/m}-SnH14_{14} superhydride and several lower hydrides, fcc{fcc} SnH2_2 and C2{C2}-Sn12_{12}H18_{18}, was also detected. The temperature dependence of critical current density J{J}C_C(T) in SnH4_4 yields the superconducting gap 2Δ\Delta(0) = 20-22 meV at 180 GPa. The SnH4_4 superconductor has unusual behavior in strong magnetic fields: linear temperature dependences of magnetoresistance and the upper critical magnetic field B{B}C2_{C2}(T) \propto (T{T}C_C - T{T}). The latter contradicts the Wertheimer-Helfand-Hohenberg model developed for conventional superconductors. Along with this, the temperature dependence of electrical resistance of fcc{fcc} SnH4_4 in normal resistivity state exhibits a deviation from what is expected for phonon-mediated scattering described by the Bloch-Gr\"uneisen model, and is beyond the framework of the Fermi liquid theory. Such anomalies occur for many superhydrides, making them much closer to cuprates than previously believed
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