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Purpose: The purpose of this study was to examine the impact of the first year of COVID-19 pandemic on maternal and neonatal outcomes at a large military treatment facility in Southern California. Study Design and Methods: A retrospective review of maternal and neonatal medical records was conducted between January 1, 2019, and December 31,2020. Outcomes measured included necesstillbirth rate, neonatal intensive care unit admission, neonatal death, cesarean birth, and postpartum hemorrhage. Results: A total of 4,425 records were analyzed. Rates of stillbirth between the years did not vary. The neonatal death rate decreased more than 50% in 2020 (p = .149). Cesarean births rose by 2.7% in 2020 Cp = .046) Rates of postpartum hemorrhage did not vary between years. Clinical Implications: The impact of COVID-19 on maternal and neonatal outcomes at a military treatment facility in the first year of the COVID-19 pandemic provides guidance for optimizing perinatal health care. Vertical transmission of COVID-19 is low and routine testing of asymptomatic neonates of positive mothers may not be necesstillbirth sary. COVID-19 infections should not be an indication for cesarean birth and are not associated with neonatal deaths or NICU admission. [ABSTRACT FROM AUTHOR]

Whether steady-state gaseous microgravity spherical diffusion exist in the presence of radiation heat loss is an important fundamental question and has important implications for spacecraft fire safety. In this work, experiments aboard the International Space Station and a transient numerical model are used to investigate the existence of steady-state microgravity spherical diffusion flames. Gaseous spherical diffusion flames stabilized on a porous spherical burner are employed in normal (i.e., fuel flowing into an ambient oxidizer) and inverse (i.e., oxidizer flowing into an ambient fuel) flame configurations. The fuel is ethylene and the oxidizer oxygen, both diluted with nitrogen. The flow rate of the reactant gas from the burner is held constant. It is found that steady-state gaseous microgravity spherical diffusion flames can exist in the presence of radiation heat loss, provided that the steady-state flame size is less than the flame size for radiative extinction, and the flame develops fast enough that radiation heat loss does not drop the flame temperature below the critical temperature for radiative extinction (1130 K). A simple model is provided that allows for the identification of initial conditions that can lead to steady-state spherical diffusion flames. In the spherical, infinite domain configuration, the characteristic time for the diffusion-controlled system to effectively reach steady-state is found to be on the order of 100,000 s. Despite a narrow range of attainable conditions, flames that exhibit steady-state behavior are observed aboard the ISS for up to 870 s, even with the constraint of a finite boundary. Steady-state flames are simulated using the numerical model for over 100,000 s. [ABSTRACT FROM AUTHOR]

The article discusses the mathematical model of technical condition-based maintenance of weapon systems. The model his developed based on a semi-Markov stochastic process. The diffusion-monotonic (DM) distribution law, which is specific for airfield technical condition-based maintenance of aircraft, is has been used as a failure model, and type I errors are considered. For standard operating conditions, graphs of the dependence of the coefficient of technical use and specific costs per hour of operation in good condition from the basic parameters are shown. The optimal maintenances interval ensuring maximum maintenance coefficient value has been proved. The principal results have been achieved by using multiple calculation method. [ABSTRACT FROM AUTHOR]

A method for monitoring the frequency and amplitude parameters of ventricular fibrillation (VF) during artificial perfusion of the heart is described. The method is based on spectral analysis of VF cardiosignal at 30 frequencies of 0.5 Hz width in the frequency range of 0.5-15 Hz and determining the frequency, amplitude, and relative weight of the 1st-3rd highest amplitude oscillations. The method can be used for monitoring the frequency and amplitude parameters of VF during long-term artificial perfusion of the heart. [ABSTRACT FROM AUTHOR]

Joint kinetics, a new paradigm for chemical kinetics and chemical engineering, is proposed. Its main idea is performing a battery of kinetic experiments from special initial compositions accompanied by the analysis of the information obtained. Within the developed theory, new basic concepts are presented: events and maps of events; new invariances, thermodynamic and non-thermodynamic; perturbed equilibria, conservatively perturbed equilibrium and swapped equilibrium. Joint kinetics can be considered as an efficient tool for revealing the detailed mechanism and determining the kinetic coefficients of complex reactions. [ABSTRACT FROM AUTHOR]

Previous studies have found that the elevation of ambient pressure helps facilitate cool and warm flame formation. In this work, the behavior and chemical kinetics of burner-supported C 2 H 4 microgravity spherical diffusion flames at elevated pressure are examined. Experiments were carried out aboard the International Space Station at pressures of 0.5–3 bar, and thin-filament pyrometry measurements were used to measure peak flame temperature. Flame temperatures at extinction are shown to decrease with increasing pressure, and at a pressure of 3 bar the flame is shown to extend below the critical temperature of 1130 K and into the warm flame regime. Simulations were performed using a transient numerical model with detailed chemistry, transport, and radiation. This model incorporates the San Diego mechanism with 57 species and 270 reactions, including low-temperature chemistry. Species concentrations, temperatures, reaction rates, and heat release rates are examined. When the pressure is increased to 50 bar the flame smoothly transitions into the warm flame regime, and cool flame behavior is observed in the simulations after warm flame radiative extinction. The results for hot, warm, and cool flame combustion at elevated pressure are compared to the results for hot flame burning at atmospheric pressure. The flame is shown to move from stabilizing on the oxidizer side to the fuel side as temperature decreases. The HO 2 radical becomes the dominant radical early in the flame lifetime and is largely responsible for the emergence of low-temperature chemistry. [ABSTRACT FROM AUTHOR]

Abstract: The utility of interpreting flame results in carbon-to-oxygen atom ratio (C/O ratio) space, as opposed to physical space or mixture fraction space, is evaluated. Flame and soot zone structures of counterflow diffusion flames have been studied for C2H4 and C3H8 and interpreted in C/O ratio space as a function of stoichiometric mixture fraction (Z st). The Burke–Schumann results expressed in C/O ratio space demonstrate how a clear and direct understanding of how structure is affected by Z st can be realized in C/O ratio space because, unlike physical or mixture fraction space, the flame location is independent of stoichiometric mixture fraction. Numerical results with detailed chemical kinetics also indicate that C/O ratio space is a fundamental variable in the sense that, for a given fuel, the location of the flame zones and critical reactions is invariant with Z st and strain rate. Two zones are clearly observed, namely the radical pool and the soot precursor zone located on the fuel side of the flame. The onset threshold of soot precursors (C6H5 and C6H6) for the high temperature side of the soot precursor zone is characterized by the depletion of radicals. The role of the hydrogen radical in flame structure and soot inception is demonstrated by studying its production and consumption channels in C/O ratio space. Finally, a modified (C/O)∗ is given to interpret the physical meaning of C/O ratio. The numerical results in this work indicate and explain the advantages of applying C/O ratio space in the analysis of flame structure and soot precursor chemistry. [Copyright &y& Elsevier]

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