Moscow State University

About: Moscow State University is a education organization based out in Moscow, Russia. It is known for research contribution in the topics: Laser & Population. The organization has 66747 authors who have published 123358 publications receiving 1753995 citations. The organization is also known as: MSU & Lomonosov Moscow State University.

The Changing Face of Arctic Snow Cover: A Synthesis of Observed and Projected Changes

Abstract: Analysis of in situ and satellite data shows evidence of different regional snow cover responses to the widespread warming and increasing winter precipitation that has characterized the Arctic climate for the past 40–50 years. The largest and most rapid decreases in snow water equivalent (SWE) and snow cover duration (SCD) are observed over maritime regions of the Arctic with the highest precipitation amounts. There is also evidence of marked differences in the response of snow cover between the North American and Eurasian sectors of the Arctic, with the North American sector exhibiting decreases in snow cover and snow depth over the entire period of available in situ observations from around 1950, while widespread decreases in snow cover are not apparent over Eurasia until after around 1980. However, snow depths are increasing in many regions of Eurasia. Warming and more frequent winter thaws are contributing to changes in snow pack structure with important implications for land use and provision of ecosystem services. Projected changes in snow cover from Global Climate Models for the 2050 period indicate increases in maximum SWE of up to 15% over much of the Arctic, with the largest increases (15–30%) over the Siberian sector. In contrast, SCD is projected to decrease by about 10–20% over much of the Arctic, with the smallest decreases over Siberia (<10%) and the largest decreases over Alaska and northern Scandinavia (30–40%) by 2050. These projected changes will have far-reaching consequences for the climate system, human activities, hydrology, and ecology.

Mitochondria-targeted plastoquinone derivatives as tools to interrupt execution of the aging program. 1. Cationic plastoquinone derivatives: Synthesis and in vitro studies

Abstract: Synthesis of cationic plastoquinone derivatives (SkQs) containing positively charged phosphonium or rhodamine moieties connected to plastoquinone by decane or pentane linkers is described. It is shown that SkQs (i) easily penetrate through planar, mitochondrial, and outer cell membranes, (ii) at low (nanomolar) concentrations, posses strong antioxidant activity in aqueous solution, BLM, lipid micelles, liposomes, isolated mitochondria, and cells, (iii) at higher (micromolar) concentrations, show pronounced prooxidant activity, the “window” between anti- and prooxidant concentrations being very much larger than for MitoQ, a cationic ubiquinone derivative showing very much lower antioxidant activity and higher prooxidant activity, (iv) are reduced by the respiratory chain to SkQH2, the rate of oxidation of SkQH2 being lower than the rate of SkQ reduction, and (v) prevent oxidation of mitochondrial cardiolipin by OH·. In HeLa cells and human fibroblasts, SkQs operate as powerful inhibitors of the ROS-induced apoptosis and necrosis. For the two most active SkQs, namely SkQ1 and SkQR1, C 1/2 values for inhibition of the H2O2-induced apoptosis in fibroblasts appear to be as low as 1·10−11 and 8·10−13 M, respectively. SkQR1, a fluorescent representative of the SkQ family, specifically stains a single type of organelles in the living cell, i.e. energized mitochondria. Such specificity is explained by the fact that it is the mitochondrial matrix that is the only negatively-charged compartment inside the cell. Assuming that the Δψ values on the outer cell and inner mitochondrial membranes are about 60 and 180 mV, respectively, and taking into account distribution coefficient of SkQ1 between lipid and water (about 13,000: 1), the SkQ1 concentration in the inner leaflet of the inner mitochondrial membrane should be 1.3·108 times higher than in the extracellular space. This explains the very high efficiency of such compounds in experiments on cell cultures. It is concluded that SkQs are rechargeable, mitochondria-targeted antioxidants of very high efficiency and specificity. Therefore, they might be used to effectively prevent ROS-induced oxidation of lipids and proteins in the inner mitochondrial membrane in vivo.

Collisionless Reconnection and High-Energy Particle Acceleration in Solar Flares

Abstract: Observations with the Hard X-Ray Telescope (HXT) and the Soft X-Ray Telescope (SXT) on board Yohkoh show that the reconnection process is common to impulsive and gradual Nares. We apply the collisionless reconnection theoryEmore exactly, the model of a high-temperature turbulent-current sheet (HTTCS)Eto the coronal conditions derived from the Yohkoh data on the site and mechanism of mag- netic energy transformation into kinetic and thermal energies of "" superhot II plasma and accelerated par- ticles. We consider the reconnecting current sheet as the source of Nare energy and the -rst-step mechanism in a two-step acceleration of electrons and ions to high energies. According to our model, reconnected -eld lines rapidly move out of the HTTCS, being frozen into superhot plasma, and form magnetic loops on the upstream side of a fast oblique collisionless shock (FOCS) situated above the soft X-rayEemitting loops of a strong magnetic -eld. The electrons and ions energized and preaccelerated by the HTTCS are trapped in magnetic loops. The top of each loop moves with a high speed toward the FOCS, while its feet penetrate through the shock front. For these reasons, two mechanismsEthe adiabatic heating inside the collapsing trap and acceleration by the shock front at the two feet of the trapEefficiently increase the particle energy. The lifetime of an individual collapsing trap can be identi-ed with the observed few-second delay to higher energies of hard X-ray and gamma-ray emission. The trap of accelerated electrons can be seen as the coronal hard X-ray "" above-the-loop-top source.II Precipitation of accelerated electrons from the trap through the FOCS into the chromosphere is responsible for the hard X-ray "" footpoint sources.II The model explains timing, location, and motion of the hard X-ray sources in solar Nares as well as the observed relative intensity of the coronal and chromospheric hard X-ray sources and other physical properties.

Optic disc and cup segmentation methods for glaucoma detection with modification of U-Net convolutional neural network

Abstract: Glaucoma is the second leading cause of blindness all over the world, with approximately 60 million cases reported worldwide in 2010. If undiagnosed in time, glaucoma causes irreversible damage to the optic nerve leading to blindness. The optic nerve head examination, which involves measurement of cup-todisc ratio, is considered one of the most valuable methods of structural diagnosis of the disease. Estimation of cup-to-disc ratio requires segmentation of optic disc and optic cup on eye fundus images and can be performed by modern computer vision algorithms. This work presents universal approach for automatic optic disc and cup segmentation, which is based on deep learning, namely, modification of U-Net convolutional neural network. Our experiments include comparison with the best known methods on publicly available databases DRIONS-DB, RIM-ONE v.3, DRISHTI-GS. For both optic disc and cup segmentation, our method achieves quality comparable to current state-of-the-art methods, outperforming them in terms of the prediction time.

Specific interaction of eukaryotic translation initiation factor 3 with the 5' nontranslated regions of hepatitis C virus and classical swine fever virus RNAs.

Abstract: Translation of hepatitis C virus (HCV) and classical swine fever virus (CSFV) RNAs is initiated by cap-independent attachment (internal entry) of ribosomes to the approximately 350-nucleotide internal ribosomal entry segment (IRES) at the 5' end of both RNAs. Eukaryotic initiation factor 3 (eIF3) binds specifically to HCV and CSFV IRESs and plays an essential role in the initiation process on them. Here we report the results of chemical and enzymatic footprinting analyses of binary eIF3-IRES complexes, which have been used to identify the eIF3 binding sites on HCV and CSFV IRESs. eIF3 protected an internal bulge in the apical stem IIIb of domain III of the CSFV IRES from chemical modification and protected bonds in and adjacent to this bulge from cleavage by RNases ONE and V1. eIF3 protected an analagous region in domain III of the HCV IRES from cleavage by these enzymes. These results are consistent with the results of primer extension analyses and were supported by observations that deletion of stem-loop IIIb or of the adjacent hairpin IIIc from the HCV IRES abrogated the binding of eIF3 to this RNA. This is the first report that eIF3 is able to bind a eukaryotic mRNA in a sequence- or structure-specific manner. UV cross-linking of eIF3 to [32P]UTP-labelled HCV and CSFV IRES elements resulted in strong labelling of 4 (p170, p116, p66, and p47) of the 10 subunits of eIF3, 1 or more of which are likely to be determinants of these interactions. In the cytoplasm, eIF3 is stoichiometrically associated with free 40S ribosomal subunits. The results presented here are consistent with a model in which binding of these two translation components to separate, specific sites on both HCV and CSFV IRESs enhances the efficiency and accuracy of binding of these RNAs to 40S subunits in an orientation that promotes entry of the initiation codon into the ribosomal P site.