426 research outputs found
GABAA Receptor β3 Subunit Expression Regulates Tonic Current in Developing Striatopallidal Medium Spiny Neurons
The striatum is a key structure for movement control, but the mechanisms that dictate the output of distinct subpopulations of medium spiny projection neurons (MSNs), striatonigral projecting and dopamine D1 receptor- (D1+) or striatopallidal projecting and dopamine D2 receptor- (D2+) expressing neurons, remains poorly understood. GABA-mediated tonic inhibition largely controls neuronal excitability and action potential firing rates, and we previously suggested with pharmacological analysis that the GABAA receptor β3 subunit plays a large role in the basal tonic current seen in D2+ MSNs from young mice (Ade et al., 2008; Janssen et al., 2009). In this study, we demonstrated the essential role of the β3 GABAA receptor subunit in mediating MSN tonic currents using conditional β3 subunit knock-out (β3f/fDrd2) mice. Cre-lox genetics were used to generate mice where Cre recombinase was expressed under the D2 receptor (Drd2) promoter. We show that while the wild-type MSN tonic current pattern demonstrates a high degree of variability, tonic current patterns from β3f/fDrd2 mice are narrow, suggesting that the β3 subunit is essential to striatal MSN GABA-mediated tonic current. Our data also suggest that a distinct population of synaptic receptors upregulate due to β3 subunit removal. Further, deletion of this subunit significantly decreases the D2+ MSN excitability. These results offer insight for target mechanisms in Parkinson’s disease, where symptoms arise due to the imbalance in striatal D1+ and D2+ MSN excitability and output
A Catalogue of Morphologically Classified Galaxies from the Sloan Digital Sky Survey: North Equatorial Region
We present a catalogue of morphologically classified bright galaxies in the
north equatorial stripe (230 deg) derived from the Third Data Release of
the Sloan Digital Sky Survey (SDSS). Morphological classification is performed
by visual inspection of images in the band. The catalogue contains 2253
galaxies complete to a magnitude limit of after Galactic extinction
correction, selected from 2658 objects that are judged as extended in the
photometric catalogue in the same magnitude limit. 1866 galaxies in our
catalogue have spectroscopic information. A brief statistical analysis is
presented for the frequency of morphological types and mean colours in the
catalogue. A visual inspection of the images reveals that the rate of
interacting galaxies in the local Universe is approximately 1.5% in the
sample. A verification is made for the photometric catalogue generated
by the SDSS, especially as to its bright end completeness.Comment: Accepted for publication in Astronomical Journal. Table 2 available
at http://www.icrr.u-tokyo.ac.jp/~fukugita/MCGpaper/table2.tx
The Blue Tip of the Stellar Locus: Measuring Reddening with the SDSS
We present measurements of reddening due to dust using the colors of stars in
the Sloan Digital Sky Survey (SDSS). We measure the color of main sequence
turn-off stars by finding the "blue tip" of the stellar locus: the prominent
blue edge in the distribution of stellar colors. The method is sensitive to
color changes of order 18, 12, 7, and 8 mmag of reddening in the colors u-g,
g-r, r-i, and i-z, respectively, in regions measuring 90' by 14'. We present
maps of the blue tip colors in each of these bands over the entire SDSS
footprint, including the new dusty southern Galactic cap data provided by the
SDSS-III. The results disfavor the best fit O'Donnell (1994) and Cardelli et
al. (1989) reddening laws, but are well described by a Fitzpatrick (1999)
reddening law with R_V = 3.1. The SFD dust map is found to trace the dust well,
but overestimates reddening by factors of 1.4, 1.0, 1.2, and 1.4 in u-g, g-r,
r-i, and i-z, largely due to the adopted reddening law. In select dusty regions
of the sky, we find evidence for problems in the SFD temperature correction. A
dust map normalization difference of 15% between the Galactic north and south
sky may be due to these dust temperature errors.Comment: 18 pages, 22 figure
Spatial Variations of Galaxy Number Counts in the SDSS I.: Extinction, Large-Scale Structure and Photometric Homogeneity
We study the spatial variation of galaxy number counts using five band
photometric images from the Sloan Digital Sky Survey. The spatial variation of
this sample of 46 million galaxies collected from 2200 sq. degrees can be
understood as the combination of Galactic extinction and large-scale
clustering. With the use of the reddening map of Schlegel, Finkbeiner & Davis
(1998), the standard extinction law is verified for the colour bands from u to
z within 5% in the region of small extinction values, E(B-V)<0.15. The residual
spatial variations of the number counts suggests that the error of global
calibration for SDSS photometry is smaller than 0.02 mag.Comment: Submitted to Astronomical Journa
Real and complex random neutrino mass matrices and theta13
Recently it has been shown that one of the basic parameters of the neutrino
sector, so called theta13 angle is very small, but quite probably non-zero. We
argue that the small value of theta13 can still be reproduced easily by a wide
spectrum of randomly generated models of neutrino masses. For that we consider
real and complex neutrino mass matrices, also including sterile neutrinos. A
qualitative difference between results for real and complex mass matrices in
the region of small theta13 values is observed. We show that statistically the
present experimental data prefers random models of neutrino masses with sterile
neutrinos.Comment: v3: Discussion about 3+1 scenario extended, fig 5,6 adde
Type II-P Supernovae from the SDSS-II Supernova Survey and the Standardized Candle Method
We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae
(SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity
during the plateau, to 15 SNe II-P discovered over the three season run of the
Sloan Digital Sky Survey - II Supernova Survey. The redshifts of these SNe -
0.027 < z < 0.144 - cover a range hitherto sparsely sampled in the literature;
in particular, our SNe II-P sample contains nearly as many SNe in the Hubble
flow (z > 0.01) as all of the current literature on the SCM combined. We find
that the SDSS SNe have a very small intrinsic I-band dispersion (0.22 mag),
which can be attributed to selection effects. When the SCM is applied to the
combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29
mag, larger than the scatter for either set of SNe separately. We show that the
standardization cannot be further improved by eliminating SNe with positive
plateau decline rates, as proposed in Poznanski et al. (2009). We thoroughly
examine all potential systematic effects and conclude that for the SCM to be
useful for cosmology, the methods currently used to determine the Fe II
velocity at day 50 must be improved, and spectral templates able to encompass
the intrinsic variations of Type II-P SNe will be needed.Comment: Accepted for publication by ApJ; data used in this paper can be
downloaded from http://sdssdp47.fnal.gov/sdsssn/photometry/SNIIp.tgz;
citation errors correcte
Type Ia Supernova Properties as a Function of the Distance to the Host Galaxy in the SDSS-II SN Survey
We use type-Ia supernovae (SNe Ia) discovered by the SDSS-II SN Survey to
search for dependencies between SN Ia properties and the projected distance to
the host galaxy center, using the distance as a proxy for local galaxy
properties (local star-formation rate, local metallicity, etc.). The sample
consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at
redshifts below 0.25. The sample is split into two groups depending on the
morphology of the host galaxy. We fit light-curves using both MLCS2k2 and
SALT2, and determine color (AV, c) and light-curve shape (delta, x1) parameters
for each SN Ia, as well as its residual in the Hubble diagram. We then
correlate these parameters with both the physical and the normalized distances
to the center of the host galaxy and look for trends in the mean values and
scatters of these parameters with increasing distance. The most significant (at
the 4-sigma level) finding is that the average fitted AV from MLCS2k2 and c
from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies.
We also find indications that SNe in elliptical galaxies tend to have narrower
light-curves if they explode at larger distances, although this may be due to
selection effects in our sample. We do not find strong correlations between the
residuals of the distance moduli with respect to the Hubble flow and the
galactocentric distances, which indicates a limited correlation between SN
magnitudes after standardization and local host metallicity.Comment: Accepted for publication in The Astrophysical Journal (33 pages, 5
figures, 8 tables
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