2,828 research outputs found
mTORC2 regulates auditory hair cell structure and function
mTOR broadly controls cell growth, but little is known about the role of mTOR complex 2 (mTORC2) in the inner ear. To investigate the role of mTORC2 in sensory hair cells (HCs), we generated HC-specific; Rictor; knockout (HC-RicKO) mice. HC-RicKO mice exhibited early-onset, progressive, and profound hearing loss. Increased DPOAE thresholds indicated outer HC dysfunction. HCs are lost, but this occurs after hearing loss. Ultrastructural analysis revealed stunted and absent stereocilia in outer HCs. In inner HCs, the number of synapses was significantly decreased and the remaining synapses displayed a disrupted actin cytoskeleton and disorganized Ca; 2+; channels. Thus, the mTORC2 signaling pathway plays an important role in regulating auditory HC structure and function via regulation of the actin cytoskeleton. These results provide molecular insights on a central regulator of cochlear HCs and thus hearing
Generalized Fock spaces and the Stirling numbers
The Bargmann-Fock-Segal space plays an important role in mathematical
physics, and has been extended into a number of directions. In the present
paper we imbed this space into a Gelfand triple. The spaces forming the
Fr\'echet part (i.e. the space of test functions) of the triple are
characterized both in a geometric way and in terms of the adjoint of
multiplication by the complex variable, using the Stirling numbers of the
second kind. The dual of the space of test functions has a topological algebra
structure, of the kind introduced and studied by the first named author and G.
Salomon.Comment: revised versio
X-ray Insights Into Interpreting CIV Blueshifts and Optical/UV Continua
We present 0.5-8.0 keV Chandra observations of six bright quasars that
represent extrema in quasar emission-line properties -- three quasars each with
small and large blueshifts of the CIV emission line with respect to the
systemic redshift of the quasars. Supplemented with seven archival Chandra
observations of quasars that met our selection criteria, we investigate the
origin of this emission-line phenomenon in the general context of the structure
of quasars. We find that the quasars with the largest CIV blueshifts show
evidence, from joint-spectral fitting, for intrinsic X-ray absorption (N_H ~
10^22 cm^-2). Given the lack of accompanying CIV absorption, this gas is likely
to be highly ionized, and may be identified with the shielding gas in the
disk-wind paradigm. Furthermore, we find evidence for a correlation of
alpha_uv, the ultraviolet spectral index, with the hardness of the X-ray
continuum; an analysis of independent Bright Quasar Survey data from the
literature supports this conclusion. This result points to intrinsically red
quasars having systematically flatter hard X-ray continua without evidence for
X-ray absorption. We speculate on the origins of these correlations of X-ray
properties with both CIV blueshift and alpha_uv and discuss the implications
for models of quasar structure.Comment: 9 figs, 25 pages, AASTeX; accepted for publication in A
Identification of stingless bees (Hymenoptera: Apidae) in Kenya using Morphometrics and DNA barcoding
Stingless bees are important pollinators of wild plants and crops. The identity of stingless bee species in Africa has not been fully documented. The present study explored the utility of morphometrics and DNA barcoding for identification of African stingless bee populations, and to further employ these tools to identify potential cryptic variation within species. Stingless bee samples were collected from three ecological zones, namely Kakamega Forest, Mwingi and Arabuko-Sokoke Forest, which are geographically distant and cover high, medium and low altitudes, respectively. Forewing and hind leg morphometric characters were measured to determine the extent of morphological variation between the populations. DNA barcodes were generated from the mitochondrial cytochrome c-oxidase I (COI) gene. Principal Component Analysis (PCA) on the morphometric measurements separated the bee samples into three clusters: (1) Meliponula bocandei; (2) Meliponula lendliana + Plebeina hildebrandti; (3) Dactylurina schmidti + Meliponula ferruginea black + Meliponula ferruginea reddish brown, but Canonical Variate Analysis (CVA) separated all the species except the two morphospecies (M. ferruginea reddish brown and black). The analysis of the COI sequences showed that DNA barcoding can be used to identify all the species studied and revealed remarkable genetic distance (7.3%) between the two M. ferruginea morphs. This is the first genetic evidence that M. ferruginea black and M. ferruginea reddish brown are separate species
The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
We explore the variability of quasars in the MgII and Hbeta broad emission
lines and UV/optical continuum emission using the Sloan Digital Sky Survey
Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic
study of quasar variability to date: our study includes 29 spectroscopic epochs
from SDSS-RM over months, containing 357 quasars with MgII and 41 quasars
with Hbeta . On longer timescales, the study is also supplemented with
two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional
quasars with MgII and 572 quasars with Hbeta. The MgII emission line is
significantly variable ( 10% on 100-day timescales), a necessary
prerequisite for its use for reverberation mapping studies. The data also
confirm that continuum variability increases with timescale and decreases with
luminosity, and the continuum light curves are consistent with a damped
random-walk model on rest-frame timescales of days. We compare the
emission-line and continuum variability to investigate the structure of the
broad-line region. Broad-line variability shows a shallower increase with
timescale compared to the continuum emission, demonstrating that the broad-line
transfer function is not a -function. Hbeta is more variable than MgII
(roughly by a factor of ), suggesting different excitation mechanisms,
optical depths and/or geometrical configuration for each emission line. The
ensemble spectroscopic variability measurements enabled by the SDSS-RM project
have important consequences for future studies of reverberation mapping and
black hole mass estimation of quasars.Comment: 20 pages, 25 figures. ApJ accepted: minor revisions following referee
repor
Chandra Observations of SDSS J1004+4112: Constraints on the Lensing Cluster and Anomalous X-Ray Flux Ratios of the Quadruply Imaged Quasar
We present results from Chandra observations of SDSS J1004+4112, a strongly
lensed quasar system with a maximum image separation of 15". All four bright
images of the quasar, as well as resolved X-ray emission originating from the
lensing cluster, are clearly detected. The emission from the lensing cluster
extends out to approximately 1.5 arcmin. We measure the bolometric X-ray
luminosity and temperature of the lensing cluster to be 4.7e44 erg s^-1 and 6.4
keV, consistent with the luminosity-temperature relation for distant clusters.
The mass estimated from the X-ray observation shows excellent agreement with
the mass derived from gravitational lensing. The X-ray flux ratios of the
quasar images differ markedly from the optical flux ratios, and the combined
X-ray spectrum of the images possesses an unusually strong Fe Kalpha emission
line, both of which are indicative of microlensing.Comment: 9 pages, 5 figures. Accepted for publication in ApJ. Version with
high-quality color figures at
http://cosmic.riken.jp/ota/publications/index.htm
The Minimal Supersymmetric Fat Higgs Model
We present a calculable supersymmetric theory of a composite ``fat'' Higgs
boson. Electroweak symmetry is broken dynamically through a new gauge
interaction that becomes strong at an intermediate scale. The Higgs mass can
easily be 200-450 GeV along with the superpartner masses, solving the
supersymmetric little hierarchy problem. We explicitly verify that the model is
consistent with precision electroweak data without fine-tuning. Gauge coupling
unification can be maintained despite the inherently strong dynamics involved
in electroweak symmetry breaking. Supersymmetrizing the Standard Model
therefore does not imply a light Higgs mass, contrary to the lore in the
literature. The Higgs sector of the minimal Fat Higgs model has a mass spectrum
that is distinctly different from the Minimal Supersymmetric Standard Model.Comment: 13 pages, 5 figures, REVTe
Recommended from our members
Freshwater monitoring by nanopore sequencing.
While traditional microbiological freshwater tests focus on the detection of specific bacterial indicator species, including pathogens, direct tracing of all aquatic DNA through metagenomics poses a profound alternative. Yet, in situ metagenomic water surveys face substantial challenges in cost and logistics. Here, we present a simple, fast, cost-effective and remotely accessible freshwater diagnostics workflow centred around the portable nanopore sequencing technology. Using defined compositions and spatiotemporal microbiota from surface water of an example river in Cambridge (UK), we provide optimised experimental and bioinformatics guidelines, including a benchmark with twelve taxonomic classification tools for nanopore sequences. We find that nanopore metagenomics can depict the hydrological core microbiome and fine temporal gradients in line with complementary physicochemical measurements. In a public health context, these data feature relevant sewage signals and pathogen maps at species level resolution. We anticipate that this framework will gather momentum for new environmental monitoring initiatives using portable devices
A Large, Uniform Sample of X-ray Emitting AGN from the ROSAT All-Sky and Sloan Digital Sky Surveys: the Data Release 5 Sample
We describe further results of a program aimed to yield ~10^4 fully
characterized optical identifications of ROSAT X-ray sources. Our program
employs X-ray data from the ROSAT All-Sky Survey (RASS), and both optical
imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS).
RASS/SDSS data from 5740 deg^2 of sky spectroscopically covered in SDSS Data
Release 5 (DR5) provide an expanded catalog of 7000 confirmed quasars and other
AGN that are probable RASS identifications. Again in our expanded catalog, the
identifications as X-ray sources are statistically secure, with only a few
percent of the SDSS AGN likely to be randomly superposed on unrelated RASS
X-ray sources. Most identifications continue to be quasars and Seyfert 1s with
15<m<21 and 0.01<z<4; but the total sample size has grown to include very
substantial numbers of even quite rare AGN, e.g., now including several
hundreds of candidate X-ray emitting BL Lacs and narrow-line Seyfert 1
galaxies. In addition to exploring rare subpopulations, such a large total
sample may be useful when considering correlations between the X-ray and the
optical, and may also serve as a resource list from which to select the "best"
object (e.g., X-ray brightest AGN of a certain subclass, at a preferred
redshift or luminosity) for follow-on X-ray spectral or alternate detailed
studies.Comment: Accepted for publication in AJ; 32 pages, including 11 figures, and 6
example table
- …