84 research outputs found

    The first light of Mini-MegaTORTORA wide-field monitoring system

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    Here we describe the first light of the novel 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which is being tested now at Special Astrophysical Observatory on Russian Caucasus. The system is able to observe the sky simultaneously in either wide (~900 square degrees) or narrow (~100 square degrees) fields of view, either in clear light or with any combination of color (Johnson B, V or R) polarimetric filters installed, with exposure times ranging from 100 ms to 100 s. The primary goal of the system is the detection of rapid -- with sub-second characteristic time-scales -- optical transients, but it may be also used for studying the variability of the sky objects on longer time scales.Comment: 9 pages, 9 figures, based on the talk presented on "Modern stellar astronomy-2014" (Rostov-on-Don

    Accuracy comparison of several common implicit solvent models and their implementations in the context of protein-ligand binding.

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    In this study several commonly used implicit solvent models are compared with respect to their accuracy of estimating solvation energies of small molecules and proteins, as well as desolvation penalty in protein-ligand binding. The test set consists of 19 small proteins, 104 small molecules, and 15 protein-ligand complexes. We compared predicted hydration energies of small molecules with their experimental values; the results of the solvation and desolvation energy calculations for small molecules, proteins and protein-ligand complexes in water were also compared with Thermodynamic Integration calculations based on TIP3P water model and Amber12 force field. The following implicit solvent (water) models considered here are: PCM (Polarized Continuum Model implemented in DISOLV and MCBHSOLV programs), GB (Generalized Born method implemented in DISOLV program, S-GB, and GBNSR6 stand-alone version), COSMO (COnductor-like Screening Model implemented in the DISOLV program and the MOPAC package) and the Poisson-Boltzmann model (implemented in the APBS program). Different parameterizations of the molecules were examined: we compared MMFF94 force field, Amber12 force field and the quantum-chemical semi-empirical PM7 method implemented in the MOPAC package. For small molecules, all of the implicit solvent models tested here yield high correlation coefficients (0.87-0.93) between the calculated solvation energies and the experimental values of hydration energies. For small molecules high correlation (0.82-0.97) with the explicit solvent energies is seen as well. On the other hand, estimated protein solvation energies and protein-ligand binding desolvation energies show substantial discrepancy (up to 10kcal/mol) with the explicit solvent reference. The correlation of polar protein solvation energies and protein-ligand desolvation energies with the corresponding explicit solvent results is 0.65-0.99 and 0.76-0.96 respectively, though this difference in correlations is caused more by different parameterization and less by methods and indicates the need for further improvement of implicit solvent models parameterization. Within the same parameterization, various implicit methods give practically the same correlation with results obtained in explicit solvent model for ligands and proteins: e.g. correlation values of polar ligand solvation energies and the corresponding energies in the frame of explicit solvent were 0.953-0.966 for the APBS program, the GBNSR6 program and all models used in the DISOLV program. The DISOLV program proved to be on a par with the other used programs in the case of proteins and ligands solvation energy calculation. However, the solution of the Poisson-Boltzmann equation (APBS program) and Generalized Born method (implemented in the GBNSR6 program) proved to be the most accurate in calculating the desolvation energies of complexes

    FAVOR (FAst Variability Optical Registration) -- A Two-telescope Complex for Detection and Investigation of Short Optical Transients

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    An astronomical complex intended to detect optical transients (OTs) in a wide field and follow them up with high time resolution investigation is described.Comment: 4 pages, 3 figures. To be published in "Il Nuovo Cimento", Proceedings of the 4th Rome Workshop on Gamma-Ray Bursts in the Afterglow Era, eds. L. Piro, L. Amati, S. Covino, B. Gendr

    Effect of vasopressin on the expression of genes for key enzymes of interstitial hyaluronan turnover and concentration ability in WAG rat kidneys

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    In mammals, arginine-vasopressin (AVP) is a major¬†hormone involved in the regulation of renal water¬†reabsorption, acting via an increase in the osmotic¬†permeability of the collecting duct epithelium.¬†The AVP-induced intracellular events include, as¬†an essential step, the trafficking of the vesicles¬†containing the water channels, aquaporin-2,¬†to the apical plasma membrane of the collecting¬†duct principal cells. The interstitium of the renal inner¬†medulla contains abundant linear negatively charged¬†glycosaminoglycan hyaluronan (HA), which affects¬†the water flow depending on their polymeric state.¬†Using real-time RT-PCR, we tested the assumption that¬†the renal hyaluronan may be involved in the longterm¬†vasopressin effect on water reabsorption.¬†The expression of the genes encoding hyaluronan¬†synthase-2 (Has2) and hyaluronidase-1, 2 (Hyal1,¬†Hyal2) in the kidneys of Wistar Albino Glaxo (WAG)¬†was studied. Has2 mRNA content was the highest¬†in the kidney papilla of the hydrated rats. The V2 receptor-selective vasopressin analog dDAVP (100 őľg/kg bw,¬†ip, twice a day for 2 days) induced a considerable¬†decrease in Has2 mRNA content in the papilla with less¬†pronounced changes in the cortex. In contrast to Has2,¬†dDAVP treatment caused a significant increase in Hyal1¬†and Hyal2 mRNA content in the renal papilla. There¬†was a good fit between Hyal1 and Hyal2 transcriptional¬†level and changes in hyaluronidase activity in the renal¬†tissue. It was suggested that vasopressin is able to¬†inhibit the synthesis of hyaluronan and concomitantly promotes its degradation in the renal papilla interstitium, thereby facilitating water flow between elements of the renal countercurrent system. The implications for this effect are discussed in the context of the literature data

    Wide-field subsecond temporal resolution optical monitoring systems for the detection and study of cosmic hazards

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    The possibility of using multi-objective optical telescopes equipped with detectors with high time resolution is studied. Two types of instruments with six and nine channels are considered here, which include the standard high-aperture objectives with small diameters, panoramic detectors with high time resolution, and equatorial mounts. The instruments function in two regimes, the monitoring mode and the follow-up mode in which all objectives observe one field with a rapidly moving celestial object detected by monitoring. Using the FAVOR and TORTORA cameras moving satellites and meteors of 9-10 stellar magnitudes in brightness were registered. The positive experience acquired from the exploitation of the FAVOR and TORTORA systems led to awareness of the need to further develop the wide-field technique to search for fast optical transients. The main result of the realization of the project will be the construction of a new type of instrument to discover and study rapidly variable optical sources with a priori unknown location

    Mini-MegaTORTORA-multichannel system for wide-field optical monitoring with high temporal resolution

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    We report on a multi-objective and transforming 9-channel monitoring system, the Mini-MegaTORTORA (MMT-9). This system combines a wide field of view with a subsecond temporal resolution in the monitoring regime, and is able to recofingure itself, in fractions of a second, to a follow up mode which has better sensitivity and provides us with multi-color and polarimetric information on detected transients simultaneously

    Observations of transient events with Mini-MegaTORTORA wide-field monitoring system with sub-second temporal resolution

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    Here we present the summary of first years of operation and the first results of a novel 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA (MMT-9), which is in operation now at Special Astrophysical Observatory on Russian Caucasus. The system is able to observe the sky simultaneously in either wide (900 square degrees) or narrow (100 square degrees) fields of view, either in clear light or with any combination of color (Johnson-Cousins B, V or R) and p olarimetric filters installed, with exposure times ranging from 0.1 s to hundreds of seconds. The real-time system data analysis pipeline performs automatic detection of rapid transient events, both near-Earth and extragalactic. The objects routinely detected by MMT also include faint meteors and artificial satellites

    Wide-field optical monitoring with Mini-MegaTORTORA (MMT-9) multichannel high temporal resolution telescope

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    ¬© 2017, Pleiades Publishing, Ltd.We describe the properties of Mini-MegaTORTORA (MMT-9) nine-channel wide-field optical sky monitoring system with subsecond temporal resolution. This instrument can observe sky areas as large as 900 deg2, perform photometry in three filters close to Johnson BV R system and polarimetry of selected objects or areas with 100‚Äď300 deg2 sizes. The limiting magnitude of the system is up to V = 11m for 0.1 s temporal resolution, and reaches V = 15m in minute-long exposures. The system is equipped with a powerful computing facility and dedicated software pipeline allowing it to perform automatic detection, real-time classification, and investigation of transient events of different nature located both in the near- Earth space and at extragalactic distances. The objects routinely detected by MMT-9 include faint meteors and artificial Earth satellites.We discuss astronomical tasks that can be solved using MMT-9, and present the results of the first two years of its operation. In particular, we report the parameters of the optical flare detected on June 25, 2016, which accompanied the gamma-ray burst GRB160625B

    Mini-megatortora status update

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    Here we give a status report on the next generation, multi-objective and transforming monitoring system, MiniMegaTORTORA, with two variants (MMT-6 based on image intensifiers with fast CCDs and MMT-9 equipped with Andor Neo sCMOSes) now under construction and commissioning at SAO RAS. This system combines a wide field of view with subsecond temporal resolution in monitoring regime, and is able to reconfigure itself, in a fractions of second, to follow-up mode which has better sensitifity and provides us with multi-color and polarimetric information on detected transients simultaneously. Hardware and software solutions used for the systems, as well as perspectives of its operation, are also discussed
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