212 research outputs found
Mutations in human dynamin block an intermediate stage in coated vesicle formation
The role of human dynamin in receptor-mediated endocytosis was investigated by transient expression of GTP-binding domain mutants in mammalian cells. Using assays which detect intermediates in coated vesicle formation, the dynamin mutants were found to block endocytosis at a stage after the initiation of coat assembly and preceding the sequestration of ligands into deeply invaginated coated pits. Membrane transport from the ER to the Golgi complex was unaffected indicating that dynamin mutants specifically block early events in endocytosis. These results demonstrate that mutations in the GTP-binding domain of dynamin block Tfn-endocytosis in mammalian cells and suggest that a functional dynamin GTPase is required for receptor-mediated endocytosis via clathrin-coated pits
A multifrequency study of the active star forming complex NGC6357. I. Interstellar structures linked to the open cluster Pis24
We investigate the distribution of the gas (ionized, neutral atomic and
molecular), and interstellar dust in the complex star forming region NGC6357
with the goal of studying the interplay between the massive stars in the open
cluster Pis24 and the surrounding interstellar matter. Our study of the
distribution of the ionized gas is based on narrow-band Hhalfa, [SII], and
[OIII] images obtained with the Curtis-Schmidt Camera at CTIO, Chile, and on
radio continuum observations at 1465 MHz taken with the VLA with a synthesized
beam of 40 arcsec. The distribution of the molecular gas is analyzed using
12CO(1-0) data obtained with the Nanten radiotelescope, Chile (angular
resolution = 2.7 arcmin). The interstellar dust distribution was studied using
mid-infrared data from the GLIMPSE survey and far-infrared observations from
IRAS. NGC6357 consists of a large ionized shell and a number of smaller optical
nebulosities. The optical, radio continuum, and near- and mid-IR images
delineate the distributions of the ionized gas and interstellar dust in the HII
regions and in previously unknown wind blown bubbles linked to the massive
stars in Pis24 revealing surrounding photodissociation regions. The CO line
observations allowed us to identify the molecular counterparts of the ionized
structures in the complex and to confirm the presence of photodissociation
regions. The action of the WR star HD157504 on the surrounding gas was also
investigated. The molecular mass in the complex is estimated to be (4+/-2)X10^5
Mo. Mean electron densities derived from the radio data suggest electron
densities > 200 cm^-3, indicating that NGC6357 is a complex formed in a region
of high ambient density. The known massive stars in Pis24 and a number of newly
inferred massive stars are mainly responsible for the excitation and
photodissociation of the parental molecular cloud.Comment: 16 pages, 9 figures. Accepted for publication in MNRA
Direct Confirmation of the Asymmetry of the Cas A Supernova with Light Echoes
We report the first detection of asymmetry in a supernova (SN) photosphere
based on SN light echo (LE) spectra of Cas A from the different perspectives of
dust concentrations on its LE ellipsoid. New LEs are reported based on
difference images, and optical spectra of these LEs are analyzed and compared.
After properly accounting for the effects of finite dust-filament extent and
inclination, we find one field where the He I and H alpha features are
blueshifted by an additional ~4000 km/s relative to other spectra and to the
spectra of the Type IIb SN 1993J. That same direction does not show any shift
relative to other Cas A LE spectra in the Ca II near-infrared triplet feature.
We compare the perspectives of the Cas A LE dust concentrations with recent
three-dimensional modeling of the SN remnant (SNR) and note that the location
having the blueshifted He I and H alpha features is roughly in the direction of
an Fe-rich outflow and in the opposite direction of the motion of the compact
object at the center of the SNR. We conclude that Cas A was an intrinsically
asymmetric SN. Future LE spectroscopy of this object, and of other historical
SNe, will provide additional insight into the connection of explosion mechanism
to SN to SNR, as well as give crucial observational evidence regarding how
stars explode.Comment: 13 pages, 7 figures, accepted for publication in Ap
Meta-analysis identifies pleiotropic loci controlling phenotypic trade-offs in sorghum
Community association populations are composed of phenotypically and genetically diverse accessions. Once these populations are genotyped, the resulting marker data can be reused by different groups investigating the genetic basis of different traits. Because the same genotypes are observed and scored for a wide range of traits in different environments, these populations represent a unique resource to investigate pleiotropy. Here, we assembled a set of 234 separate trait datasets for the Sorghum Association Panel, a group of 406 sorghum genotypes widely employed by the sorghum genetics community. Comparison of genome-wide association studies (GWAS) conducted with two independently generated marker sets for this population demonstrate that existing genetic marker sets do not saturate the genome and likely capture only 35â43% of potentially detectable loci controlling variation for traits scored in this population. While limited evidence for pleiotropy was apparent in cross-GWAS comparisons, a multivariate adaptive shrinkage approach recovered both known pleiotropic effects of existing loci and new pleiotropic effects, particularly significant impacts of known dwarfing genes on root architecture. In addition, we identified new loci with pleiotropic effects consistent with known trade-offs in sorghum development. These results demonstrate the potential for mining existing trait datasets from widely used community association populations to enable new discoveries from existing trait datasets as new, denser genetic marker datasets are generated for existing community association populations
Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project
The dynamics of the core of the Sagittarius (Sgr) dwarf spheroidal (dSph)
galaxy are explored using high-resolution (R~22,500), H-band, near-infrared
spectra of over 1,000 giant stars in the central 3 deg^2 of the system, of
which 328 are identified as Sgr members. These data, among some of the earliest
observations from the SDSS-III/Apache Point Observatory Galactic Evolution
Experiment (APOGEE) and the largest published sample of high resolution Sgr
dSph spectra to date, reveal a distinct gradient in the velocity dispersion of
Sgr from 11-14 km/s for radii >0.8 degrees from center to a dynamical cold
point of 8 km/s in the Sgr center --- a trend differing from that found in
previous kinematical analyses of Sgr over larger scales that suggest a more or
less flat dispersion profile at these radii. Well-fitting mass models with
either cored and cusped dark matter distributions can be found to match the
kinematical results, although the cored profile succeeds with significantly
more isotropic stellar orbits than required for a cusped profile. It is
unlikely that the cold point reflects an unusual mass distribution. The
dispersion gradient may arise from variations in the mixture of populations
with distinct kinematics within the dSph; this explanation is suggested (e.g.,
by detection of a metallicity gradient across similar radii), but not
confirmed, by the present data. Despite these remaining uncertainties about
their interpretation, these early test data (including some from instrument
commissioning) demonstrate APOGEE's usefulness for precision dynamical studies,
even for fields observed at extreme airmasses.Comment: 15 pages, 3 figure
Deep Learning assessment of galaxy morphology in S-PLUS Data Release 1
The morphological diversity of galaxies is a relevant probe of galaxy evolution and cosmological structure formation, but the classification of galaxies in large sky surveys is becoming a significant challenge. We use data from the Stripe-82 area observed by the Southern Photometric Local Universe Survey (S-PLUS) in 12 optical bands, and present a catalogue of the morphologies of galaxies brighter than r = 17 mag determined both using a novel multiband morphometric fitting technique and Convolutional Neural Networks (CNNs) for computer vision. Using the CNNs, we find that, compared to our baseline results with three bands, the performance increases when using 5 broad and 3 narrow bands, but is poorer when using the full 12 band S-PLUS image set. However, the best result is still achieved with just three optical bands when using pre-trained network weights from an ImageNet data set. These results demonstrate the importance of using prior knowledge about neural network weights based on training in unrelated, extensive data sets, when available. Our catalogue contains 3274 galaxies in Stripe-82 that are not present in Galaxy Zoo 1 (GZ1), and we also provide our classifications for 4686 galaxies that were considered ambiguous in GZ1. Finally, we present a prospect of a novel way to take advantage of 12 band information for morphological classification using morphometric features, and we release a model that has been pre-trained on several bands that could be adapted for classifications using data from other surveys. The morphological catalogues are publicly available.Fil: Bom, C. R.. Centro Brasileiro de Pesquisa Fisicas; BrasilFil: Cortesi, A.. Valongo Observatory; BrasilFil: Lucatelli, G.. Universidade do Sao Paulo. Instituto de Astronomia, GeofĂsica e CiĂȘncias AtmosfĂ©ricas; BrasilFil: Dias, L. O.. Centro Brasileiro de Pesquisa Fisicas; BrasilFil: Schubert, P.. Centro Brasileiro de Pesquisa Fisicas; BrasilFil: Oliveira Schwarz, G. B.. Universidade Presbiteriana Mackenzie; BrasilFil: Cardoso, N. M.. Universidade de Sao Paulo; BrasilFil: Lima, E. V. R.. Universidade do Sao Paulo. Instituto de Astronomia, GeofĂsica e CiĂȘncias AtmosfĂ©ricas; BrasilFil: Mendes de Oliveira, C.. Universidade do Sao Paulo. Instituto de Astronomia, GeofĂsica e CiĂȘncias AtmosfĂ©ricas; BrasilFil: Sodre, L.. Universidade do Sao Paulo. Instituto de Astronomia, GeofĂsica e CiĂȘncias AtmosfĂ©ricas; BrasilFil: Smith Castelli, Analia Viviana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Ferrari, F.. Universidade Federal Do Rio Grande.; BrasilFil: Damke, G.. Universidad de La Serena; ChileFil: Overzier, R.. MinistĂ©rio de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; BrasilFil: Kanaan, A.. Universidade Federal Da Santa Catarina. Cent.de Cs FĂsicas E MatemĂĄticas. Departamento de FĂsica; BrasilFil: Ribeiro, T.. Universidade Federal do Rio Grande do Sul; BrasilFil: Schoenell, W.. Noao; Estados Unido
Fission of Tubular Endosomes Triggers Endosomal Acidification and Movement
The early endosome acts as a sorting station for internalized molecules destined for recycling or degradation. While recycled molecules are sorted and delivered to tubular endosomes, residual compartments containing molecules to be degraded undergo âmaturationâ before final degradation in the lysosome. This maturation involves acidification, microtubule-dependent motility, and perinuclear localization. It is currently unknown how sorting and the processes of maturation cooperate with each other. Here, we show that fission of a tubular endosome triggers the maturation of the residual endosome, leading to degradation. Use of the dynamin inhibitor dynasore to block tubular endosome fission inhibited acidification, endosomal motility along microtubules, perinuclear localization, and degradation. However, tubular endosome fission was not affected by inhibiting endosomal acidification or by depolymerizing the microtubules. These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome. We believe this to be the first evidence of a cascade from sorting to degradation
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
We describe the design and performance of the near-infrared (1.51--1.70
micron), fiber-fed, multi-object (300 fibers), high resolution (R =
lambda/delta lambda ~ 22,500) spectrograph built for the Apache Point
Observatory Galactic Evolution Experiment (APOGEE). APOGEE is a survey of ~
10^5 red giant stars that systematically sampled all Milky Way populations
(bulge, disk, and halo) to study the Galaxy's chemical and kinematical history.
It was part of the Sloan Digital Sky Survey III (SDSS-III) from 2011 -- 2014
using the 2.5 m Sloan Foundation Telescope at Apache Point Observatory, New
Mexico. The APOGEE-2 survey is now using the spectrograph as part of SDSS-IV,
as well as a second spectrograph, a close copy of the first, operating at the
2.5 m du Pont Telescope at Las Campanas Observatory in Chile. Although several
fiber-fed, multi-object, high resolution spectrographs have been built for
visual wavelength spectroscopy, the APOGEE spectrograph is one of the first
such instruments built for observations in the near-infrared. The instrument's
successful development was enabled by several key innovations, including a
"gang connector" to allow simultaneous connections of 300 fibers; hermetically
sealed feedthroughs to allow fibers to pass through the cryostat wall
continuously; the first cryogenically deployed mosaic volume phase holographic
grating; and a large refractive camera that includes mono-crystalline silicon
and fused silica elements with diameters as large as ~ 400 mm. This paper
contains a comprehensive description of all aspects of the instrument including
the fiber system, optics and opto-mechanics, detector arrays, mechanics and
cryogenics, instrument control, calibration system, optical performance and
stability, lessons learned, and design changes for the second instrument.Comment: 81 pages, 67 figures, PASP, accepte
- âŠ