The extensive usage of the modern technologies in the learning of foreign students at histology, cytology and embryology department of Bukovinian state medical university

МЕДИЦИНСКИЕ УЧЕБНЫЕ ЗАВЕДЕНИЯОБРАЗОВАНИЕ МЕДИЦИНСКОЕСТУДЕНТЫ МЕДИЦИНСКИХ УЧЕБНЫХ ЗАВЕДЕНИЙИНОСТРАННЫЕ СТУДЕНТЫГИСТОЛОГИЯ /ОБУЧГИСТОЛОГИЯ (ДИСЦИПЛИНА)ЭМБРИОЛОГИЯ /ОБУЧЭМБРИОЛОГИЯ (ДИСЦИПЛИНА)ЦИТОЛОГИЯ /ОБУЧЦИТОЛОГИЯ (ДИСЦИПЛИНА)МЕТОДИКА ОБУЧЕНИЯМЕТОДИКА ПРЕПОДАВАНИ

Post-Newtonian Theory for Precision Doppler Measurements of Binary Star Orbits

The determination of velocities of stars from precise Doppler measurements is described here using relativistic theory of astronomical reference frames so as to determine the Keplerian and post-Keplerian parameters of binary systems. We apply successive Lorentz transformations and the relativistic equation of light propagation to establish the exact treatment of Doppler effect in binary systems both in special and general relativity theories. As a result, the Doppler shift is a sum of (1) linear in $c^{-1}$ terms, which include the ordinary Doppler effect and its variation due to the secular radial acceleration of the binary with respect to observer; (2) terms proportional to $c^{-2}$, which include the contributions from the quadratic Doppler effect caused by the relative motion of binary star with respect to the Solar system, motion of the particle emitting light and diurnal rotational motion of observer, orbital motion of the star around the binary's barycenter, and orbital motion of the Earth; and (3) terms proportional to $c^{-2}$, which include the contributions from redshifts due to gravitational fields of the star, star's companion, Galaxy, Solar system, and the Earth. After parameterization of the binary's orbit we find that the presence of periodically changing terms in the Doppler schift enables us disentangling different terms and measuring, along with the well known Keplerian parameters of the binary, four additional post-Keplerian parameters, including the inclination angle of the binary's orbit, $i$. We briefly discuss feasibility of practical implementation of these theoretical results, which crucially depends on further progress in the technique of precision Doppler measurements.Comment: Minor changes, 1 Figure included, submitted to Astrophys.

Constraining the properties of delta Scuti stars using spectroscopic eclipsing binary systems

Many stars exhibit stellar pulsations, favoring them for asteroseismic analyses. Interpreting the oscillations requires some knowledge of the oscillation mode geometry (spherical degree, radial and azimuthal orders). The delta Scuti stars (1.5 - 2.5 M_sol) often show just one or few pulsation frequencies. Although this may promise a successful seismological analysis, we may not know enough about either the mode or the star to use the oscillation frequency to improve the determination of the stellar model, or probe the star's structure. For the observed frequencies to be used successfully as seismic probes of these objects, we need to concentrate on stars for which we can reduce the number of free parameters in the problem, such as binary systems or open clusters. We investigate how much our understanding of a delta Scuti star is improved when it is in a detached eclipsing binary system instead of being a single field star. We use singular value decomposition to explore the precision we expect in stellar parameters (mass, age and chemical composition) for both cases. We examine how the parameter uncertainties propagate to the luminosity - effective temperature diagram and determine when the effort of obtaining a new measurement is justified. We show that for the single star, a correct identification of the oscillation mode is necessary to produce strong constraints on the stellar model properties, while for the binary system the observations without the pulsation mode provide the same or better constraints on the stellar parameters. In the latter case, ...Comment: emulateapj 16 pages, accepted Ap

In-the-Gap SU UMa-Type Dwarf Nova, Var73 Dra with a Supercycle of about 60 Days

An intensive photometric-observation campaign of the recently discovered SU UMa-type dwarf nova, Var73 Dra was conducted from 2002 August to 2003 February. We caught three superoutbursts in 2002 October, December and 2003 February. The recurrence cycle of the superoutburst (supercycle) is indicated to be $\sim$60 d, the shortest among the values known so far in SU UMa stars and close to those of ER UMa stars. The superhump periods measured during the first two superoutbursts were 0.104885(93) d, and 0.10623(16) d, respectively. A 0.10424(3)-d periodicity was detected in quiescence. The change rate of the superhump period during the second superoutburst was $1.7\times10^{-3}$, which is an order of magnitude larger than the largest value ever known. Outburst activity has changed from a phase of frequent normal outbursts and infrequent superoutbursts in 2001 to a phase of infrequent normal outbursts and frequent superoutbursts in 2002. Our observations are negative to an idea that this star is an related object to ER UMa stars in terms of the duty cycle of the superoutburst and the recurrence cycle of the normal outburst. However, to trace the superhump evolution throughout a superoutburst, and from quiescence more effectively, may give a fruitful result on this matter.Comment: 9 pages, 8 figures, submitted to A&

Pulsations, Boundary Layers, and Period Bounce in the Cataclysmic Variable RE J1255+266

We report time-series photometry of the quiescent optical counterpart of the EUV transient RE J1255+266. The star appears as a DA white dwarf with bright emission lines and a complex spectrum of periodic signals in its light curve. A signal at 0.0829 d is likely to be the orbital period of the underlying cataclysmic binary (probably a dwarf nova). Characteristic periods of 1344, 1236, and 668 s are seen, and a host of weaker signals. We interpret these noncommensurate signals as (nonradial) pulsation periods of the white dwarf. The donor star is unseen at all wavelengths, and the accretion rate is very low. We estimate a distance of 180+-50 pc, and M_v=14.6+-1.3 for the accretion light. The binary probably represents a very late stage of evolution, with the donor star whittled down to M_2<0.05 M_sol. Such binaries stubbornly resist discovery due to their faintness and reluctance to erupt, but are probably a very common type of cataclysmic variable. If the signal at 0.0829 d is indeed the orbital period, then the binary is an excellent candidate as a "period bouncer". Plausible colleagues in this club include four dwarf novae and the (so far) noneruptive stars GD 552 and 1RXS J105010.3-140431 (hereafter RX 1050). The 1994 EUV eruption implies a soft X-ray/EUV luminosity of 10^(34-35) erg/s, greater than that of any other dwarf nova. We attribute that to a favorable blend of properties: a high-mass white dwarf; a very transparent line of sight (the "Local Chimney"); and a low binary inclination. The first maximizes the expected temperature and luminosity of boundary-layer emission; the other two increase the likelihood that soft X-rays can survive their perilous passage through an accretion-disk wind and the interstellar medium.Comment: PDF, 43 pages, 5 tables, 10 figures, 1 appendix; accepted, in press, to appear May 2005, PASP; more info at http://cba.phys.columbia.edu

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts

Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships