225 research outputs found
Photometric observations of the supernova 2009nr
We present the results of our UBVRI CCD photometry for the second brightest
supernova of 2009, SN 2009nr, discovered during a sky survey with the
telescopes of the MASTER robotic network. Its light and color curves and
bolometric light curves have been constructed. The light-curve parameters and
the maximum luminosity have been determined. SN 2009nr is shown to be similar
in light-curve shape and maximum luminosity to SN 1991T, which is the prototype
of the class of supernovae Ia with an enhanced luminosity. SN 2009nr exploded
far from the center of the spiral galaxy UGC 8255 and most likely belongs to
its old halo population. We hypothesize that this explosion is a consequence of
the merger of white dwarfs
Optical polarization observations with the MASTER robotic net
We present results of optical polarization observations performed with the
MASTER robotic net for three types of objects: gamma-ray bursts, supernovae,
and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A,
polarization observations were obtained during very early stages of optical
emission. For GRB100906A it was the first prompt optical polarization
observation in the world. Photometry in polarizers is presented for Type Ia
Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the
linear polarization of SN 2012bh at the early stage of the envelope expansion
was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3,
QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer
the degree of the linear polarization and polarization angle. The blazars OC
457 and 3C 454.3 were observed during their periods of activity. The results
show that MASTER is able to measure substantially polarized light; at the same
time it is not suitable for determining weak polarization (less than 5%) of dim
objects (fainter than 16). Polarimetric observations of the optical
emission from gamma-ray bursts and supernovae are necessary to investigate the
nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been
correcte
Comparative characterization of Leporipoxvirus members’ reproduction in continuous cell culture
Examination of the virus-cell interactions is of both scientific and practical importance. Our study was aimed at comparative characterization of rabbit myxoma virus and Shope fibroma virus biological properties that manifested during the virus reproduction in RK-13/2-03 clonal continuous rabbit kidney cell culture. It was demonstrated that the viruses varied in infection development and cytopathic effect duration in RK-13/2-03 cell culture. Apparent lesions in cell monolayers infected by myxoma virus and fibroma virus at similar multiplicity of infection and cultivation temperature were observed on day 2 and day 3 of cultivation, respec- tively, as well as maximum cell lesions with evident degeneration were observed on day 3 and day 6 of cultivation, respectively. Myxoma virus was accumulated at titre of 6.25–6.50 lg TCID50/0,2 cm3, and Shope fibroma virusа was accumulated at titre of 5.50−5.75 lg TCID50/0.2 cm3. Shope fibroma virus demonstrated such infectivity during three passages and myxoma virus demonstrated such infectivity during twenty passages. Prepared cultures were identified as myxoma virus and Shope fibroma virus with molecular genetic analysis. Tests of the viruses for their antigenic relatedness showed that antibodies against myxoma virus were able to neutralize Shope fibroma virus also. NT titres of antibodies against both viruses were similar (1:8). RK-13/2-03 cell culture was found to be highly permissive to Shope fibroma virus that had been isolated from the diseased rabbit and not been an attenuated variant
Single-Dose Bioequivalence Study of Rivaroxaban-Containing Medicinal Products in Healthy Volunteers
Therapeutically, new oral anticoagulants (NOACs) are considered to be non-inferior or superior to vitamin K antagonists (warfarin). NOACs are included in current guidelines for the treatment of various cardiovascular diseases. Rivaroxaban medicinal products have been shown to effectively fight thrombotic complications of the new coronavirus infection, COVID-19. The wide clinical use of rivaroxaban products motivates the development of generics.The aim of the study was to compare the pharmacokinetics and safety of rivaroxaban medicinal products in a single-dose bioequivalence study in healthy volunteers under fasting conditions.Materials and methods: the bioequivalence study compared single-dose oral administration of Rivaroxaban, 10 mg film-coated tablets (NovaMedica Innotech LLC, Russia), and the reference product Xarelto®, 10 mg filmcoated tablets (Bayer AG, Germany), in healthy volunteers under fasting conditions. The open, randomised, crossover trial included 46 healthy volunteers. Each of the medicinal products (the test product and the reference product) was administered once; blood samples were collected during the 48 h after the administration. The washout between the study periods lasted 7 days. Rivaroxaban was quantified in plasma samples of the volunteers by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS).Results: no adverse events or serious adverse events were reported for the test and reference products during the study. The following pharmacokinetic parameters were obtained for Rivaroxaban and Xarelto®, respectively: Cmax of 134.6 ± 58.0 ng/mL and 139.9 ± 49.3 ng/mL, AUC0–48 of 949.7 ± 354.5 ng×h/mL and 967.6 ± 319.9 ng×h/mL, AUC 0–∞ of 986.9 ± 379.7 ng×h/mL and 1003.6 ± 320.4 ng×h/mL, T1/2 of 8.2 ± 3.2 h and 7.8 ± 3.3 h. The 90% confidence intervals for the ratios of Cmax, AUC0–48, and AUC0–∞ geometric means were 88.04–108.67%, 89.42–104.92% and 89.44–104.81%, respectively.Conclusions: the test product Rivaroxaban and the reference product Xarelto® were found to have similar rivaroxaban pharmacokinetics and safety profiles. The study demonstrated bioequivalence of the medicinal products
Nonlinear effects in microwave photoconductivity of two-dimensional electron systems
We present a model for microwave photoconductivity of two-dimensional
electron systems in a magnetic field which describes the effects of strong
microwave and steady-state electric fields. Using this model, we derive an
analytical formula for the photoconductivity associated with photon- and
multi-photon-assisted impurity scattering as a function of the frequency and
power of microwave radiation. According to the developed model, the microwave
conductivity is an oscillatory function of the frequency of microwave radiation
and the cyclotron frequency which turns zero at the cyclotron resonance and its
harmonics. It exhibits maxima and minima (with absolute negative conductivity)
at the microwave frequencies somewhat different from the resonant frequencies.
The calculated power dependence of the amplitude of the microwave
photoconductivity oscillations exhibits pronounced sublinear behavior similar
to a logarithmic function. The height of the microwave photoconductivity maxima
and the depth of its minima are nonmonotonic functions of the electric field.
It is pointed to the possibility of a strong widening of the maxima and minima
due to a strong sensitivity of their parameters on the electric field and the
presence of strong long-range electric-field fluctuations. The obtained
dependences are consistent with the results of the experimental observations.Comment: 9 pages, 6 figures Labeling of the curves in Fig.3 correcte
The optical identifcation of events with poorly defined locations: The case of the Fermi GBM GRB140801A
We report the early discovery of the optical afterglow of gamma-ray burst
(GRB) 140801A in the 137 deg 3- error-box of the Fermi Gamma-ray
Burst Monitor (GBM). MASTER is the only observatory that automatically react to
all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart
was discovered solely from its GBM localization. The optical afterglow of GRB
140801A was found by MASTER Global Robotic Net 53 sec after receiving the
alert, making it the fastest optical detection of a GRB from a GBM error-box.
Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m BTA
of SAO RAS reveals a redshift of . We performed optical and
near-infrared photometry of GRB 140801A using different telescopes with
apertures ranging from 0.4-m to 10.4-m. GRB 140801A is a typical burst in many
ways. The rest-frame bolometric isotropic energy release and peak energy of the
burst is erg and
keV, respectively, which is consistent with the
Amati relation. The absence of a jet break in the optical light curve provides
a lower limit on the half-opening angle of the jet deg. The
observed is consistent with the limit derived from the
Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis shows that GRB
140801A could belong to the class of intermediate duration. The rapid detection
of the optical counterpart of GRB 140801A is especially important regarding the
upcoming experiments with large coordinate error-box areas.Comment: in press MNRAS, 201
Prompt, early, and afterglow optical observations of five gamma-ray bursts (GRBs 100901A, 100902A, 100905A, 100906A, and 101020A)
We present results of the prompt, early, and afterglow optical observations
of five gamma-ray bursts, GRBs 100901A, 100902A, 100905A, 100906A, and 101020A,
made with the Mobile Astronomical System of TElescope-Robots in Russia
(MASTER-II net), the 1.5-m telescope of Sierra-Nevada Observatory, and the
2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A,
we detected optical counterparts and obtained light curves starting before
cessation of gamma-ray emission, at 113 s and 48 s after the trigger,
respectively. Observations of GRB 100906A were conducted with two polarizing
filters. Observations of the other three bursts gave the upper limits on the
optical flux; their properties are briefly discussed. More detailed analysis of
GRB 100901A and GRB 100906A supplemented by Swift data provides the following
results and indicates different origins of the prompt optical radiation in the
two bursts. The light curves patterns and spectral distributions suggest a
common production site of the prompt optical and high-energy emission in GRB
100901A. Results of spectral fits for GRB 100901A in the range from the optical
to X-rays favor power-law energy distributions with similar values of the
optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking
optical light curve suggesting that the prompt optical radiation in this GRB
originated in a front shock. This is supported by a spectral analysis. We have
found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. An
upper limit on the value of the optical extinction on the host of GRB 100906A
is obtained.Comment: 18 pages, 14 figures, 14 tables, 5 machine readable tables; accepted
for publication in MNRA
The MASTER-II network of robotic optical telescopes. First results
The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered. © 2013 Pleiades Publishing, Ltd
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