156 research outputs found
Diurnal variations in helium emission
Graphic method for reducing spectrophotoelectric data of twilight helium emissio
An examination of the space-time properties of hydroxyl emission
Spectrometric analysis on space-time properties of hydroxyl emission in various regions of sk
SOX2 is a dose-dependent regulator of retinal neural progenitor competence
Approximately 10% of humans with anophthalmia (absent eye) or severe microphthalmia (small eye) show haploid insufficiency due to mutations in SOX2, a SOXB1-HMG box transcription factor. However, at present, the molecular or cellular mechanisms responsible for these conditions are poorly understood. Here, we directly assessed the requirement for SOX2 during eye development by generating a gene-dosage allelic series of Sox2 mutations in the mouse. The Sox2 mutant mice display a range of eye phenotypes consistent with human syndromes and the severity of these phenotypes directly relates to the levels of SOX2 expression found in progenitor cells of the neural retina. Retinal progenitor cells with conditionally ablated Sox2 lose competence to both proliferate and terminally differentiate. In contrast, in Sox2 hypomorphic/null mice, a reduction of SOX2 expression to <40% of normal causes variable microphthalmia as a result of aberrant neural progenitor differentiation. Furthermore, we provide genetic and molecular evidence that SOX2 activity, in a concentration-dependent manner, plays a key role in the regulation of the NOTCH1 signaling pathway in retinal progenitor cells. Collectively, these results show that precise regulation of SOX2 dosage is critical for temporal and spatial regulation of retinal progenitor cell differentiation and provide a cellular and molecular model for understanding how hypomorphic levels of SOX2 cause retinal defects in humans
Reverberation measurement of the inner radius of the dust torus in NGC 4151 during 2008-2013
We investigate the correlation between infrared (JHKL) and optical (B) fluxes
of the variable nucleus of the Seyfert galaxy NGC 4151 using partially
published data for the last 6 years (2008-2013.). Here we are using the same
data as in Oknyansky et al. (2014), but include also optical (B) data from Guo
et al. We find that the lag of flux in all the infrared bands is the same, 40
+- 6 days, to within the measurement accuracy. Variability in the J and K bands
is not quite simultaneous, perhaps due to the differing contributions of the
accretion disk in these bands. The lag found for the K band compared with the B
band is not significantly different from earlier values obtained for the period
2000-2007. However, finding approximately the same lags in all IR bands for
2008-2013 differs from previous results at earlier epochs when the lag
increased with increasing wavelength. Examples of almost the same lag in
different IR bands are known for some other active nuclei. In the case of NGC
4151 it appears that the relative lags between the IR bands may be different in
different years. The available data, unfortunately, do not allow us to
investigate a possible change in the lags during the test interval. We discuss
our results in the framework of the standard model where the variable infrared
radiation is mainly due to thermal re-emission from the part of the dusty torus
closest to the central source. There is also a contribution of some IR emission
from the accretion disk, and this contribution increases with decreasing
wavelength. Some cosmological applications of obtained results are discussed.Comment: 3 pages, 2 figures, 14-th Odessa International Astronomical Gamow
Conference-School Astronomy and beyond: Astrophysics, Cosmology and
Gravitation, Cosmomicrophysics, Radio-astronomy and Astrobiolog
State regulation features of university integration into national innovative system in the light of "triple helix" modern concept
The study is devoted to state regulation features research of university integration of into national innovative system in the light of “triple helix” modern concept developed by it’s kovit’s leidesdorf describing development of innovative systems through dynamics of state, business and universitiesyesBelgorod State Universit
Diffraction-limited near-IR imaging at Keck reveals asymmetric, time-variable nebula around carbon star CIT 6
We present multi-epoch, diffraction-limited images of the nebula around the
carbon star CIT 6 at 2.2 microns and 3.1 microns from aperture masking on the
Keck-I telescope. The near-IR nebula is resolved into two main components, an
elongated, bright feature showing time-variable asymmetry and a fainter
component about 60 milliarcseconds away with a cooler color temperature. These
images were precisely registered (~35 milliarcseconds) with respect to recent
visible images from the Hubble Space Telescope (Trammell et al. 2000), which
showed a bipolar structure in scattered light. The dominant near-IR feature is
associated with the northern lobe of this scattering nebula, and the
multi-wavelength dataset can be understood in terms of a bipolar dust shell
around CIT 6. Variability of the near-IR morphology is qualitatively consistent
with previously observed changes in red polarization, caused by varying
illumination geometry due to non-uniform dust production. The blue emission
morphology and polarization properties can not be explained by the above model
alone, but require the presence of a wide binary companion in the vicinity of
the southern polar lobe. The physical mechanisms responsible for the breaking
of spherical symmetry around extreme carbon stars, such as CIT 6 and IRC+10216,
remain uncertain.Comment: 18 pages, 5 figures (one in color), to appear in the Astrophysical
Journa
Social levelling factorsin european languagesof Sub-Saharian Africa: class, gender, migration and language
The article deals with the social levelling in European languages of Sub-Saharian Africa. The authors glance on such social levelling factors as class, gender, migration and language. The aim of the article is to show the impact of these factors on the language variation in African societies. The actual material is based on various works of French-, English-, Spanish-, Portuguese- and Russian-speaking scientists from all over the worldThe article deals with the social levelling in European languages of Sub-Saharian Africa. The authors glance on such social levelling factors as class, gender, migration and language. The aim of the article is to show the impact of these factors on the language variation in African societies. The actual material is based on various works of French-, English-, Spanish-, Portuguese- and Russian-speaking scientists from all over the worl
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