Calculation of tractive nozzle characteristics with altitude compensation

The numerical calculations of flows in conical and contoured nozzles with slots in the supersonic part that operate under overexpansion conditions are presented. The calculations were made with the aid of the authors’ algorithm and program of simulating turbulent two-dimensional (axisymmetric) flows of a viscous heat-conducting gas. The results of computational investigations of tractive slot nozzle characteristics and the amount of combustion product leakage from an annular slot depending on the flight altitude are given. It is shown that the flight altitude at which the gas flow through the annular slot is “chocked” depends on its size and location in the supersonic nozzle part.     

Electric currents from thunderstorms to the ionosphere during a solar cycle: Quasi-static modeling of the coupling mechanism

Conduction and displacement currents, and their sum the Maxwell current, generated over a thunderstorm (TS) with recurrent lightning discharges are investigated theoretically. The aim is to study better the influence of different factors on these currents, which form the link between thunderstorms and the ionosphere in the global atmospheric electrical circuit. The factors studied concern the thunderstorm characteristics (the charge separation current, and the lightning discharge parameters), as well as the atmospheric and cloud conductivity. Some of these factors may show long-term changes with the 11-year solar cycle, possibly realized through an inverse dependence of the cosmic ray flux on solar activity. Earlier investigations have suggested that the lightning-related charge redistribution and subsequent relaxation, rather than the high intensity current, is mainly the source of the energy coupled to the ionosphere. With respect to this, a quasi-electrostatic analytical model is proposed, based on Maxwell’s equations. The currents are generated by a TS modeled as a positive vertical dipole with charges which are first accumulated and then destroyed by lightning. Our computations show that the mean and peak values of the conduction and total Maxwell currents to the ionosphere depend significantly on the charge moment change. The mean currents are also sensitive to the reduction of the conductivity in thunderclouds. Small variations of the stratospheric conductivity (20% at geomagnetic latitude 40° and 40–50% at 55°) with the solar activity do not influence the currents to the ionosphere very much.     

Analytical approach to cosmic ray ionization by nuclei with charge Z in the middle atmosphere – Distribution of galactic CR effects

The effects of galactic and solar cosmic rays (CR) in the middle atmosphere are considered in this work. A new analytical approach for CR ionization by protons and nuclei with charge Z in the lower ionosphere and middle atmosphere is developed in this paper. For this purpose the ionization losses (dE/dh) according to the Bohr–Bethe–Bloch formula for the energetic charged particles are approximated in three different energy intervals. More accurate expressions for energy decrease E(h) and electron production rate profiles q(h) are derived. The obtained formulas allow comparatively easy computer programming. The integrand in q(h) gives the possibility for application of adequate numerical methods – such as Romberg method or Gauss quadrature, for the solution of the mathematical problem. On this way the process of interaction of cosmic ray particles with the upper, middle and lower atmosphere will be described much more realistically. Computations for cosmic ray ionization in the middle atmosphere are made. The full CR composition is taken into account: protons, Helium (α-particles), light L, medium M, heavy H and very heavy VH group of nuclei.     

Host–parasite interactions in closed and open microbial cultivation system

The study addresses interaction of bacteria and phages in the host–parasite system in batch and continuous cultures. The study system consists of the auxotrophic strain of Brevibacterium – Brevibacterium sp. 22L – and the bacteriophage of Brevibacterium sp., isolated from the soil by the enrichment method.

1.

Closed system. In the investigation of the relationship between the time of bacterial lysis and multiplicity of phage infection it has been found that at a lower phage amount per cell it takes a longer time for the lysis of the culture to become discernible. Another important factor determining cytolysis in liquid medium is the physiological state of bacterial population. Specific growth rate of bacteria at the moment of phage infection has been chosen as an indicator of the physiological state of bacteria. It has been shown that the shortest latent period and the largest output of the phage are observed during the logarithmic growth phase of bacteria grown under favorable nutrient conditions. In the stationary phase, bacterial cells become “a bad host” for the phage, whose reproduction rate decreases, and the lysis either slows down significantly or does not occur at all.     

Field emission characteristics of gold dust grains

The space plasma environment usually contains charged dust grains. The grain charge is an important parameter determining its migration through the space, coagulation, formation of dust clouds and so on. The knowledge of its charge is thus one of the basic information we want to know. There are several emission processes leading to both positive and negative charges, among others photoemission, all kinds of secondary emissions, field emissions, etc. The present study is focused on a laboratory simulation of emissions caused by impacts by energetic ions. Our experiment is based on the Paul trap which gives us an opportunity to catch a single dust grain for several days inside the vacuum vessel and exposed it by electron/ion beams. This experimental approach allows us to separate an individual charging process. We have chosen spherically shaped gold grains and discussed the processes leading to the limitation of the grain charge. We suggested that the implantation of charging ions leads to deformations of the grain surface. The deformations enhance the local electric field strength that becomes sufficient for the field ionization.     

Which solar EUV indices are best for reconstructing the solar EUV irradiance?

The solar EUV irradiance is of key importance for space weather. Most of the time, however, surrogate quantities such as EUV indices have to be used by lack of continuous and spectrally resolved measurements of the irradiance. The ability of such proxies to reproduce the irradiance from different solar atmospheric layers is usually investigated by comparing patterns of temporal correlations. We consider instead a statistical approach. The TIMED/SEE experiment, which has been continuously operating since February 2002, allows for the first time to compare in a statistical manner the EUV spectral irradiance to five EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices, and the He I equivalent width.     

Current status of X-ray spectrometer development in the SELENE project

The X-ray spectrometer (XRS) on the SELENE (SELenological and ENgineering Explorer) spacecraft, XRS, will observe fluorescent X-rays from the lunar surface. The energy of the fluorescent X-ray depends on the elements of which the lunar soil consists, therefore we can determine elemental composition of the upper most lunar surface. The XRS consists of three components: XRF-A, SOL-B, and SOL-C. XRF-A is the main sensor to observe X-rays from the lunar surface. SOL-B is direct monitor of Solar X-ray using Si-PIN photodiode. SOL-C is another Solar X-ray monitor but observes the X-rays from the standard sample attached on the base plate. This enables us to analyze by a comparative method similar to typical laboratory XRF methods. XRF-A and SOL-C adopt charge coupled device as an X-ray detector which depletion layer is deep enough to detect X-rays. The X-ray spectra were obtained by the flight model of XRS components, and all components has been worked well to analyze fluorescent X-rays. Currently, development of the hardware and software of the XRS has been finished and we are preparing for system integration test for the launch.     

Presynaptic transporter-mediated release of glutamate evoked by the protonophore FCCP increases under altered gravity conditions

High-affinity Na⁺-dependent glutamate transporters of the plasma membrane mediate the glutamate uptake into neurons, and thus maintain low levels of extracellular glutamate in the synaptic cleft. The study focused on the release of glutamate by reversal of Na⁺-dependent glutamate transporters from rat brain nerve terminals (synaptosomes) under conditions of centrifuge-induced hypergravity. Flow cytometric analysis revealed similarity in the size and cytoplasmic granularity between synaptosomal preparations obtained from control and G-loaded animals (10 G, 1 h). The release of cytosolic l-[¹⁴C]glutamate from synaptosomes was evaluated using the protonophore FCCP, which dissipated synaptic vesicle proton gradient, thus synaptic vesicles were not able to keep glutamate inside and the latter enriched cytosol. FCCP per se induced the greater release of l-[¹⁴C]glutamate in hypergravity as compared to control (4.8 ± 1.0% and 8.0 ± 1.0% of total label). Exocytotic release of l-[¹⁴C]glutamate evoked by depolarization was reduced down to zero after FCCP application under both conditions studied. Depolarization stimulated release of cytosolic l-[¹⁴C]glutamate from synaptosomes preliminary treated with FCCP was considerably increased from 27.0 ± 2.2% of total label in control to 35.0 ± 2.3% in hypergravity. Non-transportable inhibitor of glutamate transporter dl-threo-β-benzyloxyaspartate was found to significantly inhibit high-KCl and FCCP-stimulated release of l-[¹⁴C]glutamate, confirming the release by reversal of glutamate transporters. The enhancement of transporter-mediated release of glutamate in hypergravity was found to result at least partially from the inhibition of the activity of Na/K-ATPase in the plasma membrane of synaptosomes. We suggested that hypergravity-induced alteration in transporter-mediated release of glutamate indicated hypoxic injury of neurons.     

Relation between galactic and solar cosmic radiation at aviation altitude

Cosmic radiation bombards us at high altitude with ionizing particles; the radiation has a galactic component, which is normally dominant, and a component of solar origin. Cosmic ray particles are the primary source of ionization in the atmosphere above 1 km; below 1 km radon is a dominant source of ionization in many areas.