Calculation of stresses initiated by electrical explosion of conductors in a composite thick-walled cylinder

In various fields of engineering, such structural elements are widely used that, from the point of view of their strength calculation, can be referred to thin shells (tanks, reservoirs, cylinders, etc.). When calculating thin-walled shells, a number of hypotheses are adopted to simplify the solution of the problem. The problem is most simply solved within the framework of the momentless theory of shells, according to which only the force normal to the section (the membrane force) is different from zero, and all moments and transverse forces are equal to zero. The paper presents an analysis of dynamic loading of the material carried out by the method of electric explosion of conductors (EEC). A composite cylinder, which is a thick-walled cylinder made of polymethylmethacrylate with an axial hole pressed into an aluminum shell, was chosen as an experimental sample. The sample is loaded by applying an electric voltage to a conductor in the form of a copper wire placed inside the axial opening of the sample. The equation of state at electric explosion of the conductor is obtained; experimental and calculated graphs of dependence of pressure in the air channel on the expansion coefficient of EEC products are constructed. A theoretical model describing the change in the radial stresses arising in the process of loading with regard for the boundary and initial conditions is built. The accuracy of the built model is justified by comparing the obtained results with the experimental data. The circumferential stress, at which the rupture of aluminum shell directly occurs, is estimated

Garcinoxanthones from Garcinia mangostana L. against SARS-CoV-2 infection and cytokine storm pathway inhibition: A viroinformatics study

Context: Mangosteen (Garcinia mangostana L.) is used in traditional medicine as an antibacterial, antioxidant, and anti-inflammatory. Aims: To determine the molecular mechanism and potential of garciniaxanthone derivate compounds from G. mangostana as SARS-CoV-2 antiviral and prevent cytokine storm through in silico approach. Methods: Ligand and protein samples were obtained from databases such as PubChem and Protein Databank, then drug-likeness analysis using Lipinski, Ghose, Veber, Egan, and Muege rules on SwissADME server, prediction of antiviral probability through PASSOnline server. Furthermore, molecular docking simulation with PyRx v1.0 software (Scripps Research, USA) with an academic license, identification of interactions and chemical bond positions of ligands on the target by PoseView server, 3D visualization of PyMOLv.2.5.2 software (Schrödinger, Inc., USA) with an academic license, molecular dynamics simulation for molecular stability prediction by CABS-flex v2.0 server, target prediction of antiviral candidate compounds by SwissTargetPrediction server, pathway analysis through STRING v11.5 database, and toxicity by ProTox-II server were used. Results: Garciniaxanthone C from G. mangostana was found to be a drug-like molecule with low toxicity. This can be a candidate for SARS-Cov-2 antiviral through inhibitor activity on two viral enzymes consisting of Mpro and replicase with a binding affinity value that is more negative than other garciniaxanthone derivates and is stable. Garciniaxanthone C is predicted to bind and inhibit pro-inflammatory proteins that trigger cytokine storms, such as NFKB1 and PTGS2. Conclusions: Garciniaxanthone derivative compounds from G. mangostana may be candidates for SARS-CoV-2 antiviral and preventing cytokine storm through garciniaxanthone C activity

Calculation of stresses initiated by electrical explosion of conductors in a composite thick-walled cylinder

In various fields of engineering, such structural elements are widely used that, from the point of view of their strength calculation, can be referred to thin shells (tanks, reservoirs, cylinders, etc.). When calculating thin-walled shells, a number of hypotheses are adopted to simplify the solution of the problem. The problem is most simply solved within the framework of the momentless theory of shells, according to which only the force normal to the section (the membrane force) is different from zero, and all moments and transverse forces are equal to zero. The paper presents an analysis of dynamic loading of the material carried out by the method of electric explosion of conductors (EEC). A composite cylinder, which is a thick-walled cylinder made of polymethylmethacrylate with an axial hole pressed into an aluminum shell, was chosen as an experimental sample. The sample is loaded by applying an electric voltage to a conductor in the form of a copper wire placed inside the axial opening of the sample. The equation of state at electric explosion of the conductor is obtained; experimental and calculated graphs of dependence of pressure in the air channel on the expansion coefficient of EEC products are constructed. A theoretical model describing the change in the radial stresses arising in the process of loading with regard for the boundary and initial conditions is built. The accuracy of the built model is justified by comparing the obtained results with the experimental data. The circumferential stress, at which the rupture of aluminum shell directly occurs, is estimated

Technical condition of welded load-bearing metal structures of operated agricultural hoisting cranes

The paper considers the methodology for assessing the technical condition of welded load-bearing metal structures of operated agricultural hoisting cranes. In the course of the study, the relationship between structural, mechanical and magnetic parameters was established during cyclic elastic-plastic deformation of low-carbon and low alloy steels. Based on the analysis, it was concluded that the dependence of the minimum values of the magnetic parameter on the acting stresses Нр(σ) is influenced by the metal structure and its chemical composition. It has been established that the coarser-grained structure of the studied steels under elastic-plastic deformation contributes to a shift in the minimum values of Нр towards lower acting stresses; an increase in the strength characteristics of steels shifts the minimum of Нр toward large values of s, which must be taken into account when conducting technical diagnostics of the elements of the operating metal structures of hoisting cranes. Based on the results of the study, a method for determining the acting stresses in the elements of the metal structures of hoisting cranes was developed, which, by the nature and magnitude of the change in the residual magnetization of the scattering field during their stepwise loading (unloading), allows judging the magnitude of the acting stresses. The work also presents a methodology for assessing the technical condition of welded load-bearing metal structures of hoisting cranes based on the integrated use of passive flux-gate and other control methods, which allows determining the acting stresses used in strength calculations in the identified hazardous zones of concentration of stresses in the elements of metal structures

ACCUMULATION OF MACRO- AND MICROELEMENTS BY DUCKWEED (LEMNA MINOR) IN CONDITIONS OF LOW AND SIGNIFICANT ANTHROPOGENIC LOADING

Wide utilization of duckweed in phytoremediation of industrial and municipal wastewater supposes its significant role in maintaining ecological balance in polluted water bodies. Using ICP-MS method, peculiarities of macro- and microelements accumulation by Lemna minor L. in abundant flooded quarry near phosphorgypsum (PG) storage site and in unpolluted lake of Yoshkar-Ola was investigated. Duckweed biological accumulator factor (BAF) of macro-elements in conditions of elevated pollution was significantly lower than in unpolluted area. The same phenomenon was revealed for As, Sr, Cu and Ni contrary to Cr, Pb, V, Cd and Al with higher BAF values in conditions of increased pollution. The highest value of BAF (more than a million) was shown for Mn in unpolluted. During summer concentrations of P, Zn, Co, Cr. Cd, Ni, Al, Mn, Si, Cu and As in water flooded quarry decreased 13.25, 8, 4.2, 2.27, 2.0, 1.75, 1.75, 1.6, 1.44 and 1.41 times accordingly. Concentration of all microelements and heavy metals except Sr, Mn, Se and B also decreased. The period of intensive duckweed growth (summer) was accompanied by significant changes in BAF values: increase of macro-elements BAF; for Cr, Al, Pb, and V- intensive decrease of BAF values and among microelements intensive BAF increase only for Zn and Mn

Phosphorus Feast and Famine in Cyanobacteria: Is Luxury Uptake of the Nutrient Just a Consequence of Acclimation to Its Shortage?

To cope with fluctuating phosphorus (P) availability, cyanobacteria developed diverse acclimations, including luxury P uptake (LPU)—taking up P in excess of the current metabolic demand. LPU is underexplored, despite its importance for nutrient-driven rearrangements in aquatic ecosystems. We studied the LPU after the refeeding of P-deprived cyanobacterium Nostoc sp. PCC 7118 with inorganic phosphate (Pi), including the kinetics of Pi uptake, turnover of polyphosphate, cell ultrastructure, and gene expression. The P-deprived cells deployed acclimations to P shortage (reduction of photosynthetic apparatus and mobilization of cell P reserves). The P-starved cells capable of LPU exhibited a biphasic kinetic of the Pi uptake and polyphosphate formation. The first (fast) phase (1–2 h after Pi refeeding) occurred independently of light and temperature. It was accompanied by a transient accumulation of polyphosphate, still upregulated genes encoding high-affinity Pi transporters, and an ATP-dependent polyphosphate kinase. During the second (slow) phase, recovery from P starvation was accompanied by the downregulation of these genes. Our study revealed no specific acclimation to ample P conditions in Nostoc sp. PCC 7118. We conclude that the observed LPU phenomenon does not likely result from the activation of a mechanism specific for ample P conditions. On the contrary, it stems from slow disengagement of the low-P responses after the abrupt transition from low-P to ample P conditions