127 research outputs found
Role of Color Perimetry and Visocontrastometry in Diagnosis of Optical Neuritis
The most sensitive method for assessing changes in visual functions in patients with optical neuritis is chromatic computer perimetry with a red mark on a green background.Aim. To evaluate the effectiveness of clinical and functional diagnostic methods for optical neuritis. Material and methods. A cross-sectional, non-randomized, comprehensive examination of 53 patients aged 19â48 years (31.65 ± 4.88), the ratio M : W = 1 : 1.2 with optic neuritis was performed. Of these, 43 cases are patients with multiple sclerosis. The control group consisted of 37 people with high visual acuity, somatically healthy, corresponding to the clinical group by sex and age.Results. Retinal sensitivity in patients with optic neuritis according color contrast perimetry was below the norm by 21.96 %. The depth of blindspots at optical neuritis, differed in significant variability and was in the range from to 2.6 to â19.64 dB. The level of visual field defects depended on the severity of the inflammatory process and, on average, exceeded the indices of the control group by 4.64 times. The area of scotoma in optical neuritis exceeded the values of the control group by 1.81 times.Conclusion. The most sensitive method for assessing changes in visual functions in patients with optical neuritis is chromatic perimetry with a red mark on a green background. Chromatic and achromatic visocontrastometry makes it possible to reveal a significant decrease in indices only in the high frequency range, which characterizes the state of the macular area, which generally indicates the predominant involvement of the retinal ganglion cells in the pathological process.The most sensitive method for assessing changes in visual functions in patients with optical neuritis is chromatic perimetry with a red mark on a green background
Pushing the limit of instrument capabilities
Chemically Peculiar (CP) stars have been the subject of systematic research for more than 50 years. With the discovery of pulsation of some of the cool CP stars, and the availability of advanced spectropolarimetric instrumentation and high signal-to-noise, high resolution spectroscopy, a new era of CP star research emerged about 20 years ago. Together with the success in ground-based observations, new space projects are developed that will greatly benefit future investigations of these unique objects. In this contribution we will give an overview of some interesting results obtained recently from ground-based observations and discuss the future outstanding Gaia space mission and its impact on CP star researc
Variability of Properties Characterizing Persistent Potential of Cholera Vibrio in Biofilm Communities
Represented are the results of studies on variability of properties characterizing persistent potential of
V. cholerae in biofilm communities under the long-term cultivation in river water. Demonstrated is the fact that in the cold water epidemically significant cholera vibrios form thin biofilms and do not survive for the most part. But atoxigenic strains, isolated from the water, can survive in the environment both in the cold and warm time of the year due to formation of thick biofilm and realization of the persistent activity. Expressiveness of the properties studied, except antilysozyme activity (ALA), directly correlate with biofilm formation intensity. In case of ALA one observes inverse correlation
Pushing the limit of instrument capabilities
Chemically Peculiar (CP) stars have been subject of systematic research since
more than 50 years. With the discovery of pulsation of some of the cool CP
stars, the availability of advanced spectropolarimetric instrumentation and
high signal- to-noise, high resolution spectroscopy, a new era of CP star
research emerged about 20 years ago. Together with the success in ground-based
observations, new space projects are developed that will greatly benefit for
future investigations of these unique objects. In this contribution we will
give an overview of some interesting results obtained recently from
ground-based observations and discuss on future outstanding Gaia space mission
and its impact on CP star research.Comment: Joint Discussion 04, Secsion 1, To appear in Highlights of Astronomy,
Proc. of the XXVIIth IAU General Assembly, Rio de Janeiro, Brazil, August
2009, 9 page
Doppler confirmation of TESS planet candidate TOI1408.01: grazing transit and likely eccentric orbit
We report an independent Doppler confirmation of the TESS planet candidate
orbiting an F-type main sequence star TOI-1408 located 140 pc away. We present
a set of radial velocities obtained with a high-resolution fiber-optic
spectrograph FFOREST mounted at the SAO RAS 6-m telescope (BTA-6). Our
self-consistent analysis of these Doppler data and TESS photometry suggests a
grazing transit such that the planet obscures its host star by only a portion
of the visible disc. Because of this degeneracy, the radius of TOI-1408.01
appears ill-determined with lower limit about 1 R,
significantly larger than in the current TESS solution. We also derive the
planet mass of ~ and the orbital period
days, thus making this object a typical hot Jupiter, but with a significant
orbital eccentricity of . Our solution may suggest the planet is
likely to experience a high tidal eccentricity migration at the stage of
intense orbital rounding, or may indicate possible presence of other unseen
companions in the system, yet to be detected.Comment: 5 pages, 3 figure
Eight exoplanet candidates in SAO survey
Here we present eight new candidates for exoplanets detected by the transit
method at the Special Astrophysical Observatory of the Russian Academy of
Sciences. Photometric observations were performed with a 50-cm robotic
telescope during the second half of 2020. We detected transits with depths of
and periods in the light curves
of stars with magnitudes of . All considered stars are
classified as dwarfs with radii of (with the
uncertainty for one star up to ). We estimated the candidate radii
(all are greater than 1.4 times the Jovian radius), semi-major axes of their
orbits (), and other orbital parameters by modelling. We report
the light curves with transits for two stars obtained in 2022 based on
individual observations.Comment: 16 pages, 14 figures, 3 table
Longâterm population dynamics of dreissenid mussels (Dreissena polymorpha and D. rostriformis): a crossâsystem analysis
Dreissenid mussels (including the zebra mussel Dreissena polymorpha and the quagga mussel D. rostriformis) are among the world's most notorious invasive species, with large and widespread ecological and economic effects. However, their longâterm population dynamics are poorly known, even though these dynamics are critical to determining impacts and effective management. We gathered and analyzed 67 longâterm (>10 yr) data sets on dreissenid populations from lakes and rivers across Europe and North America. We addressed five questions: (1) How do Dreissena populations change through time? (2) Specifically, do Dreissena populations decline substantially after an initial outbreak phase? (3) Do different measures of population performance (biomass or density of settled animals, veliger density, recruitment of young) follow the same patterns through time? (4) How do the numbers or biomass of zebra mussels or of both species combined change after the quagga mussel arrives? (5) How does body size change over time? We also considered whether current data on longâterm dynamics of Dreissena populations are adequate for science and management. Individual Dreissena populations showed a wide range of temporal dynamics, but we could detect only two general patterns that applied across many populations: (1) Populations of both species increased rapidly in the first 1â2 yr after appearance, and (2) quagga mussels appeared later than zebra mussels and usually quickly caused large declines in zebra mussel populations. We found little evidence that combined Dreissena populations declined over the long term. Different measures of population performance were not congruent; the temporal dynamics of one life stage or population attribute cannot generally be accurately inferred from the dynamics of another. We found no consistent patterns in the longâterm dynamics of body size. The longâterm dynamics of Dreissena populations probably are driven by the ecological characteristics (e.g., predation, nutrient inputs, water temperature) and their temporal changes at individual sites rather than following a generalized time course that applies across many sites. Existing longâterm data sets on dreissenid populations, although clearly valuable, are inadequate to meet research and management needs. Data sets could be improved by standardizing sampling designs and methods, routinely collecting more variables, and increasing support
Statistics of Magnetic Fields for OB Stars
Based on an analysis of the catalog of magnetic fields, we have investigated
the statistical properties of the mean magnetic fields for OB stars. We show
that the mean effective magnetic field of a star can be used as a
statistically significant characteristic of its magnetic field. No correlation
has been found between the mean magnetic field strength and
projected rotational velocity of OB stars, which is consistent with the
hypothesis about a fossil origin of the magnetic field. We have constructed the
magnetic field distribution function for B stars, , that has a
power-law dependence on with an exponent of . We have
found a sharp decrease in the function F for {\cal B}\lem 400 G
that may be related to rapid dissipation of weak stellar surface magnetic
fields.Comment: 22 pages, 7 figures, accepted Astronomy Letters, 2010, vol.36, No.5,
pp.370-379, contact E-mail: [email protected]
Complete mitochondrial genomes of the freshwater mussels Amblema plicata (Say, 1817), Pleurobema oviforme (Conrad, 1834), and Popenaias popeii (Lea, 1857) (Bivalvia: Unionidae: Ambleminae)
Freshwater mussels are a critically imperiled group of mollusks that play key ecological roles and provide important services to humans. The Ambleminae is the only subfamily of these mussels, endemic to North America. Complete mitogenomes have only been sequenced for two of five tribes of the subfamily. Pleurobema oviforme, Amblema plicata, and Popenaias popeii each belong to tribes Pleurobemini, Amblemini, and Popenaidini, respectively, and have not had published mitogenomes. Thus, this study aims to present the complete mitogenomes for these species, to provide a phylogeny of the Ambleminae and confirm the gene arrangements with representation from each of its tribes. The newly sequenced mitogenomes range from 15,852 to 15,993 nucleotides, are composed of 13 PCGs, 22 tRNAs, and two rRNAs and all share the same (UF1) gene order.This work was supported by Portuguese Foundation for Science and
Technology (FCT) [grant number ConBioMics/BI-Lic/2019-037 (JTT), grant
number SFRH/BD/137935/2018 (AGS)]; COMPETE 2020, Portugal 2020
and the European Union through the ERDF, and by Portuguese
Foundation for Science and Technology (FCT) through national funds
[UID/Multi/04423/2019] under project ConBiomics: the missing approach
for the Conservation of Bivalves Project, and [project number NORTE-01-
0145-FEDER-030286]. Fieldwork in Texas was funded by the U.S. Fish and Wildlife Service, and Texas Parks and Wildlife Department (TPWD) as a Joint Traditional Section 6 Project 407348.info:eu-repo/semantics/publishedVersio
Detection of regular low-amplitude photometric variability of the magnetic dwarf WD0009+501. On the possibility of photometric investigation of exoplanets on the basis of 1-meter class telescopes of the special and crimean astrophysical observatories
© 2015, Pleiades Publishing, Ltd. We present the results of photometric observations of the weak magnetic white dwarf WD0009+501. The observations were carried out for two years with the 1-m telescopes of the Special and Crimean Astrophysical Observatories. As a result of these observations, we detected regular V -band luminosity variations with a period of P â 8 hours. The amplitude of the variability is stable on timescales greater than two years and amounts to 11 ± 1 mmag. The difference in the variability amplitude from observations with different telescopes is 1â3 mmag. The result is interpreted within the concept of a rotation-modulated variability of magnetic properties of the starâs atmosphere. We also discuss a possible variability due to the presence of planetary companions around stars of this type. The results of monitoring were used to explore the capabilities of the telescopes for exoplanet investigation. We studied the dependences between the characteristic times of exposures, magnitudes of the objects, and a threshold level of the expected variability amplitudes for all the telescopes involved in our program. A program of exoplanet monitoring with the mentioned telescopes was drawn up for the next few years based on the results of the study
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