One-dimensional hydrodynamic model of the atom and ion dynamics in a stationary plasma thruster

A one-dimensional hydrodynamic model of the atom, ion, and electron dynamics in the channel of a stationary plasma thruster is developed. The relevant set of integrodifferential equations is derived and investigated both analytically (steady-state solutions) and numerically (dynamic regimes). It is shown that adjusting only one parameter (the channel resistivity) makes it possible to achieve a good agreement between the calculated global parameters and experimental data. The general features of oscillations revealed with the help of the model are also found to agree fairly well with the experiment.     

Diptera in Nests of the Fieldfare <Emphasis Type="Italic">Turdus pilaris</Emphasis> in Moscow City

The composition of dipterans inhabiting fieldfare nests in a big city was studied for the first time, based on material collected soon after chick fledging. Larvae of 21 species belonging to 14 families were found, including saprophages, necrophages, and predators (Scatopsidae, Ceratopogonidae, Phoridae, Chloropidae, Anthomyiidae, etc.), and also Protocalliphora azurea (Fallén, 1816) (Calliphoridae) and Neottiophilum praeustum (Meigen, 1826) (Neottiophilidae) known as bloodsucking ectoparasites of nestlings. Larvae of P. azurea (up to 121 per nest) were found in both early (April–May) and late (May–June) nests. Larvae of N. praeustum (up to 299 per nest) were recorded only in late nests. The two species occurred both separately and jointly in one nest, with N. praeustum dominating numerically. The seasonal differences in the development of these two parasitic species may account for their high abundance in such ephemeral habitats. Larvae of Trypocalliphora braueri (Hendel, 1901), a subcutaneous parasite of nestlings of many bird species, were not found in the fieldfare nests. A key to the larvae of the three fly species parasitizing nestlings in European Russia is given.     

Multifractal Characterization of Butterfly Wings Scales

A lot of insect families have physical structures created by evolution for coloration. These structures are a source of ideas for new bio-inspired materials. The aim of this study was to quantitatively characterize the micromorphology of butterfly wings scales using atomic force microscopy and multifractal analysis. Two types of butterflies, Euploea mulciber (“striped blue crow”) and Morpho didius (“giant blue morpho”), were studied. The three-dimensional (3D) surface texture of the butterfly wings scales was investigated focusing on two areas: where the perceived colors strongly depend on and where they do not depend on the viewing angle. The results highlight a correlation between the surface coloration and 3D surface microtexture of butterfly wings scales.     

MAGO-IX Experiment

The results of the last (in the thermonuclear program “Magnetic compression”) MAGO-IX experiment with a plasma chamber including a third compartment designed to compress plasma with a converging liner are presented. An X-ray pulse consisting of an intense peak of 1-μs duration, followed by a low-intensity tail with a duration of more than 10 μs, was recorded. In the MAGO-IX experiment, the neutrons were generated mainly in the third compartment. A neutron yield of 2 × 10¹² was obtained. The results demonstrate that the expected compression of preheated plasma in chambers similar to MAGO-IX is promising for achieving thermonuclear ignition.     

Cellular accumulation and antioxidant activity of acetoxymethoxycarbonyl pyrrolidine nitroxides

Abstract

Nitroxides are widely used in biology as antioxidants, spin labels, functional spin probes for pH, oxygen and thiol levels, and tissue redox status imaging using electron paramagnetic resonance (EPR); however, biological applications of nitroxides is hindered by fast bioreduction to EPR-silent hydroxylamines and rapid clearance. In this work, we have studied pyrrolidine nitroxides with acetoxymethoxycarbonyl groups which can undergo hydrolysis by cellular esterases to hydrophilic carboxylate derivatives resistant to bioreduction. Nitroxides containing acetoxymethoxycarbonyl groups were rapidly absorbed by cells from the media, 3,4-bis-(acetoxymethoxycarbonyl)-proxyl (DCP-AM2) and 3-(2-(bis(2-(acetoxymethoxy)-2-oxoethyl)amino)acetamido)-proxyl (DCAP-AM2) showing the strongest EPR signal of the cellular fraction. Remarkably, the EPR parameters of 3,4-dicarboxy-proxyl (DCP) and its mono- and di-acetoxymethyl esters are different, and consequent intracellular hydrolysis of acetoxymethoxycarbonyl groups in DCP-AM2 can be followed by EPR. To elucidate intracellular location of the resultant DCP, the mitochondrial fraction has been isolated. EPR measurements showed that mitochondria were the main place where DCP was finally accumulated. TEMPO derivatives showed expectedly much faster decay of EPR signal in the cellular fraction, compared to pyrrolidine nitroxides. It was found that supplementation of endothelial cells with 50?nM of DCP-AM2 completely normalised the mitochondrial superoxide level. Moreover, administration of DCP-AM2 to mice (1.4?mg/kg/day) resulted in substantial nitroxide accumulation in the tissues and significantly reduced hypertension. We found that hydroxylamine derivatives of dicarboxyproxyl nitroxide DCP-AM-H can be used for the detection of superoxide in vivo in angiotensin II model of hypertension. Infusion of DCP-AM-H in mice leads to accumulation of persistent EPR signal of nitroxide in the blood and vascular tissue in angiotensin II-infused wild-type but not in SOD2 overexpressing mice. Our data demonstrate that acetoxymethoxycarbonyl group containing nitroxides accumulate in mitochondria and demonstrate site-specific antioxidant activity.