Heat transfer in porous metal hydride (MH) beds is the major bottleneck in scaling up of the metal hydride technology, while a role of mass transfer limitations in operation is generally overlooked ...in lab-scale experiments with relatively small beds. We present relations for gas permeability within the Kozeny-Carman approach and a dimensionless parameter to compare heat and mass transfer limitations in metal hydride devices. From experiments on hydrogen absorption and desorption in a flow-through reactor containing 1 kg of La0.9Ce0.1Ni5 alloy we experimentally determined an apparent permeability and showed, that the “breathing’ of the bed can lead to appearance of dual porosity due to fracturing of the bed, which leads to increased permeability at absorption of hydrogen (∼20 μm2) comparing with desorption (∼0.3 μm2). Particle swelling leads to decrease of porosity both due to decrease of pores and due to closure of fractures, thus deformation of the metal hydride bed leads to decrease of permeability during absorption. The effect can be important for flow-through reactors with thick layers of metal hydride.
•Gas permeability of metal hydride beds investigated.•History of absorption/desorption cycles have influence on permeability.•“Breathing’ of the MH bed can lead to appearance of dual porosity.•Fractures appear due to swelling and shrinking of MH particles.•Fractured bed has much higher permeability than predicted by the Kozeny-Carman equation.
The structure of the surface layer in high-nitrogen 05Kh22AG15N8M2F steel workpieces subjected to face turning is studied by electron microscopy. It is found that improved machinability by VK8 alloy ...cutting tools is achieved at a cutting depth of 0.25 mm and that the cutting-tool life decreases sharply when the cutting depth increases to 1 mm. A nanocrystalline structure with nanocrystal sizes from several to several tens of nanometers forms in the surface layer upon face turning in the as-cast, hot-rolled, and thermally deformed states. The structure of the surface layer is characterized by a high dislocation density and large austenite fragments with broad subgrains and deformation twins.
Data on optimization of a laboratory method for determining the level of
L
-asparaginase in blood serum are presented. It is shown that the method allows quantification of
L
-asparaginase activity in ...patient blood serum in the range of enzyme activity 19.531 – 1250 U/L using the same calibration curve for high (>78.125 U/L) and low values of enzyme activity (19.531 – 78.125 U/L), which leads to significant acceleration of the analysis procedure at almost the same measurement accuracy. Validation of the conformity of measurements between the modified and original method using a comparative analysis of calibration curves built under the conditions of the corresponding protocols showed that the quantitative determinations had comparable accuracy. The results can be successfully used for drug monitoring in oncological and oncohematological practice.
Aim: to evaluate the ability of serum biochemical markers in pregnant woman - PAPP-A (pregnancy-associated plasma protein-A) and β-hCG (the в-subunit of human chorionic gonadotropin) studied in the ...first trimester (11+0-13+6) during combined prenatal screening to predict adverse perinatal outcomes of multiple pregnancy that occurred spontaneously and as a result of in vitro fertilization (IVF).Materials and methods. The main group consisted from 65 women with pregnancy occurred as a result of IVF; comparison group included 56 women with spontaneous pregnancy. All pregnancies were multiple and their outcomes were known. Serum PAPP-A and β-hCG levels were measured in the first trimester. The results were expressed in absolute values and in MoM (multiples of median). Subgroups were compared with mono- and dichorionic pregnancies, complicated and uncomplicated pregnancies, distributed according to MoM index: within the reference values (0.5-2.0), below or above the reference values.Results. PAPP-A MoM values in the spontaneous pregnancy group were 1.12 0.8; 1.57, in the IVF group - 1.35 1.11; 1.72 (p = 0.01). In subgroup of low PAPP-A MoM antenatal fetal death occurred in 50 %, in subgroup of normal PAPP-A MoM - in 14.58 %, in subgroup of high PAPP-A MoM - in 5.88 % (p = 0.011). In addition, a positive correlation was found between serum PAPP-A level and time of fetal death (rs = 0.564; p = 0.036). Low PAPP-A MoM values were associated with 50 % fetal mortality, 75 % of them were attributable to pregnancy as a result of IVF.Conclusion. Identification of adverse outcomes in multiple pregnancies is still a difficult task, but evaluation of serum biochemical markers during the first trimester screening can help in early diagnosis of necessity and extent of timely prophylaxis.
X-ray diffraction is used to investigate the effect of the tensile strain on the phase composition, texture, and stress state of the α and γ phases in VNS9-Sh alloy. The α phase content increases ...from 75 to 91% at the surface and from 45–50% to approximately 70% in the subsurface layers during testing until failure. The relative amount of decomposed austenite at different stages of tensile deformation, which reflects the metastability of austenite, is proposed as a parameter to measure the tendency of two-phase steels to the TRIP effect. Compressive stresses up to –1000 MPa form in austenite at the surface in a 0.3-mm-thick initial steel strip due to the positive volume effect of the γ → α transformation. In contrast, tensile stresses are observed in martensite. Heating the metal creates the compressive stresses, but the subsequent cooling causes tensile stresses in martensite because of its lower linear thermal expansion coefficient (LTEC) as compared to austenite.
A method of measurement of the energy of electrons extracted from the VEPP-4M accelerator is described. The method was verified experimentally. The results obtained are in good agreement with ...simulation. The energy resolution is 1.8% for electron energy of 1000 MeV and improves to 0.7% for electron energy of 3500 MeV.
Rhabdophane
(Ce0.34−0.43Nd0.13−0.14Ca0.06−0.29La0.08−0.11Y0.05−0.12Pr0.03−0.05Sm0.02−0.05Gd0.02−0.05Fe0−0.04Dy0.00-0.01)0.97-1.01((P0.69−0.96S0.04−0.31)1.00O4)⚫H2O is found in a Fe3+-oxyhydroxide ...nodule (brown iron ore)
collected from the upper part of the oxidation profile of the Babaryk
massive sulfide occurrence (South Urals, Russia) at a 1.6 m depth. The
structural and microtextural features of rhabdophane are revealed by
electron backscattered diffraction (EBSD); the chemical composition and
distribution of the main components are determined on a scanning electron
microscope (SEM) equipped with an energy-dispersive analyzer (EDA); the bulk
contents of rare earth elements (REEs) and other elements in rock samples are analyzed using
inductively coupled plasma mass spectrometry (ICP-MS). Rhabdophane forms
spherulitic aggregates up to 35 µm in size with a fine-grained core
and radial radiant rims composed of prismatic crystals. The chaotically
oriented aggregates of its particles of various sizes including prismatic
crystals and spherulitic intergrowths also fill fractures up to 200 µm long and 20–30 µm thick in goethite. The zonal radial radiant
structure of the rhabdophane aggregates and their occurrence in fractures of
goethite unambiguously indicate the authigenic origin of rhabdophane. The
chemically heterogeneous rhabdophane grains always contain Y, Ca and S and
rarely Fe and Sr and are Th- or U-free. Contrasting zonation of Ca, S and Y
contents is characteristic of spherulites. The band contrast of the EBSD
patterns shows a good crystallinity of prismatic crystals regardless of the
chemical composition even for Ca–S-rich zones. On the other hand, the Ca-
and S-rich fine-grained centers of the spherulites do not yield any
distinguishable diffraction patterns. There is a strong negative correlation
in pairs (Ca+Sr)–P and (REEs+Y)–S and a positive correlation in
pairs (Ca+Sr)–S and (REEs+Y)–P, which indicates the isomorphism
according to the scheme (REEs+Y)3+ + (PO4)3−
↔ (Ca+Sr)2+ + (SO4)2−. Thus, the chemical
composition of rhabdophane does not completely correspond to the
rhabdophane–tristramite/brockite series because of the absence of
tetravalent U or Th. In contrast to similar samples from the deeper part of
the oxidation zone, the brown iron ore with rhabdophane is enriched in light rare earth elements (LREEs)
and P. The REEs were probably sourced from ore-bearing volcanomictic rocks,
while P could also have been derived from the soil. The enrichment in REEs and P
and the formation of rhabdophane are related to the alternation of dry and wet
periods, the P input, and sorption–desorption of REEs from
Fe3+ oxyhydroxides and/or clay minerals due to pH changes and variable
composition of pore water.
Antithrombotic therapy in COVID-19 patients Slukhanchuk, E. V.; Bitsadze, V. O.; Khizroeva, J. Kh ...
Акушерство, гинекология и репродукция,
01/2023, Letnik:
16, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Recently, there have been published the data of large randomized trials on the use of antithrombotic agents for reducing a risk of thromboembolic complications, multiple organ failure and mortality ...in COVID-19 patients. However, principles of selecting optimal therapy remain open. Strategies for the use of antithrombotic drugs in outpatient and inpatient settings, thromboprophylaxis in specific patient populations, and treatment of acute thrombosis in hospitalized COVID-19 patients are being developed. In October 2021, the International Society on Thrombosis and Hemostasis (ISTH) formed an interdisciplinary international panel of experts to develop recommendations for use of anticoagulants and antiplatelet agents in COVID-19 patients. Expert opinions are published. Here, we summarize all the publications available globally at the present time on this issue, obtained by using the principles of evidence-based medicine.
More than two year-experience in monitoring patients with severe novel coronavirus disease revealed an increased risk of macroand microcirculatory thrombosis, clinically manifested by heart attack, ...stroke, thromboses of rare localizations (thrombosis of the hepatic veins, mesenteric veins, cerebral sinuses, portal vein), being the main cause of adverse outcomes. Thromboembolic complications, expressed as sepsis-induced coagulopathy, disseminated intravascular coagulation, venous and arterial thromboembolism, pulmonary embolism, microthrombosis, and thrombotic microangiopathy were noted to affect various organs such as the lungs, heart, kidneys, and brain. Earlier, we showed that hypercoagulability is closely related to inflammatory diseases and hemostasis dysregulation. Endothelial injury and dysfunction have been identified as critical pathways to thrombosis, and other mechanisms occurring in the microvasculature were described such as endothelial activation, cytokine storm, and formation of neutrophil extracellular traps (NETs). However, a role of platelets in severe COVID-19 has not been examined. Platelets are small non-nucleated cells most known as the central mediators of hemostasis. However, upon activation, platelets release a variety of immunomodulatory cytokines and chemokines involved in regulating immune response. Because platelets are involved in both immunity and coagulation, they play a central role in immunothrombosis, a physiological process wherein immune cells induce microthrombogenesis both to prevent spread of pathogens and facilitate their clearance. Moreover, platelets can directly interact with viral receptors including those related to SARS-CoV-2. Platelet dysfunction includes both thrombocytopenia and platelet hyperactivation. It should be noted that persistent thrombocytopenia is usually correlated with mortality being associated with thrombosis of the cerebral sinuses, splanchnic system, autoimmune reactions, as well as with administered heparin and vaccines. Therefore, here we review a role of platelets in the pathogenesis of COVID-19.
The effect of the rolling temperature and strain on the structure and the properties of corrosionresistant austenitic–martensitic 14Kh15AN4M steel is studied. The steel is shown to exhibit high ...ductility: upon rolling in the temperature range 700–1100°C at a reduction per pass up to 80%, wedge steel specimens are uniformly deformed along and across the rolling direction without cracking and other surface defects. Subsequent cold treatment and low-temperature tempering ensure a high hardness of the steel (50–56
HRC
). Austenite mainly contributes to the hardening upon rolling in the temperature range 700–800°C at a reduction of 50–70%, and martensite makes the main contribution at higher temperatures and lower strains. Texture does not form under the chosen deformation conditions, which indicates dynamic recrystallization with the nucleation and growth of grains having no preferential orientation.
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