685 research outputs found
Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk
Using the Hubble Space Telescope, the 4 m Blanco telescope at the Cerro
Tololo Inter-American Observatory, and the Spitzer Space Telescope, we have
performed deep imaging from 0.8 to 8 um of the southern subcluster in the
Chamaeleon I star-forming region. In these data, we have discovered an object,
Cha 110913-773444, whose colors and magnitudes are indicative of a very
low-mass brown dwarf with a circumstellar disk. In a near-infrared spectrum of
this source obtained with the Gemini Near-Infrared Spectrograph, the presence
of strong steam absorption confirms its late-type nature (>=M9.5) while the
shapes of the H- and K-band continua and the strengths of the Na I and K I
lines demonstrate that it is a young, pre-main-sequence object rather than a
field dwarf. A comparison of the bolometric luminosity of Cha 110913-773444 to
the luminosities predicted by the evolutionary models of Chabrier and Baraffe
and Burrows and coworkers indicates a mass of 8+7/-3 M_Jup, placing it fully
within the mass range observed for extrasolar planetary companions (M<=15
M_Jup). The spectral energy distribution of this object exhibits mid-infrared
excess emission at >5 um, which we have successfully modeled in terms of an
irradiated viscous accretion disk with M'<=10e-12 M_sun/year. Cha 110913-773444
is now the least massive brown dwarf observed to have a circumstellar disk, and
indeed is one of the least massive free-floating objects found to date. These
results demonstrate that the raw materials for planet formation exist around
free-floating planetary-mass bodies.Comment: 5 pages, accepted to Astrophysical Journal Letter
Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf
We present observations of a circumstellar disk that is inclined close to
edge-on around a young brown dwarf in the Taurus star-forming region. Using
data obtained with SpeX at the NASA Infrared Telescope Facility, we find that
the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399
cannot be reproduced with a photosphere reddened by normal extinction. Instead,
the slope is consistent with scattered light, indicating that circumstellar
material is occulting the brown dwarf. By combining the SpeX data with mid-IR
photometry and spectroscopy from the Spitzer Space Telescope and previously
published millimeter data from Scholz and coworkers, we construct the spectral
energy distribution for 2MASS J04381486+2611399 and model it in terms of a
young brown dwarf surrounded by an irradiated accretion disk. The presence of
both silicate absorption at 10 um and silicate emission at 11 um constrains the
inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional
evidence of the high inclination of this disk is provided by our detection of
asymmetric bipolar extended emission surrounding 2MASS J04381486+2611399 in
high-resolution optical images obtained with the Hubble Space Telescope.
According to our modeling for the SED and images of this system, the disk
contains a large inner hole that is indicative of a transition disk (R_in~58
R_star~0.275 AU) and is somewhat larger than expected from embryo ejection
models (R_out=20-40 AU vs. R_out<10-20 AU).Comment: The Astrophysical Journal, in pres
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Corticotropinoma as a Component of Carney Complex.
Known germline gene abnormalities cause one-fifth of the pituitary adenomas in children and adolescents, but, in contrast with other pituitary tumor types, the genetic causes of corticotropinomas are largely unknown. In this study, we report a case of Cushing disease (CD) due to a loss-of-function mutation in PRKAR1A, providing evidence for association of this gene with a corticotropinoma. A 15-year-old male presenting with hypercortisolemia was diagnosed with CD. Remission was achieved after surgical resection of a corticotropin (ACTH)-producing pituitary microadenoma, but recurrence 3 years later prompted reoperation and radiotherapy. Five years after the original diagnosis, the patient developed ACTH-independent Cushing syndrome, and a diagnosis of primary pigmented nodular adrenocortical disease was confirmed. A PRKAR1A mutation (c.671delG, p.G225Afs*16) was detected in a germline DNA sample from the patient, which displayed loss of heterozygosity in the corticotropinoma. No other germline or somatic mutations of interest were found. As corticotropinomas are not a known component of Carney complex (CNC), we performed loss of heterozygosity and messenger RNA stability studies in the patient's tissues, and analyzed the effect of Prkar1a silencing on AtT-20/D16v-F2 mouse corticotropinoma cells. No PRKAR1A defects were found among 97 other pediatric CD patients studied. Our clinical case and experimental data support a role for PRKAR1A in the pathogenesis of a corticotroph cell tumor. This is a molecularly confirmed report of a corticotropinoma presenting in association with CNC. We conclude that germline PRKAR1A mutations are a novel, albeit apparently infrequent, cause of CD
Influencia de nuevas técnicas de desinfección de suelos sobre la precocidad y productividad del fresón ecológico.
Una pérdida del equilibrio del suelo puede presentar peligrosidad para el cultivo por la
presencia de hongos patógenos, nemátodos parásitos, ácaros,…En agricultura
ecológica se hace necesaria una rotación de cultivos para controlar la presión de los
patógenos, que puede verse complementado con los tratamientos de biofumigación y
solarización. Con este trabajo se pretende estudiar la influencia de nuevas técnicas de
desinfección de suelos, como son la biofumigación y la solarización, en la precocidad
y productividad en el cultivo ecológico de fresón. El ensayo se desarrolló durante las
campañas 2003/04 y 2004/05 en una explotación comercial ecológica certificada de
Almonte (Huelva). Para ello se diseñó un experimento en bloques al azar, con tres
repeticiones en el que se dispusieron tres tratamientos: control (C), biofumigación (BF)
y biofumigación+solarización (BF+S). Durante la campaña 2003-04 los resultados
mostraron diferencias significativas en la producción de fresón de primera categoría
comercial entre los tratamientos biofumigados y el tratamiento control, alcanzándose
valores máximos de producción de 623,5 g planta-1 en el tratamiento biofumigación. La
precocidad durante la primera campaña mostró diferencias significativas entre el
tratamiento biofumigación+solarización y el tratamiento control. En la campaña
2004/05 la influencia de las heladas sobre el cultivo del fresón pudo ser la causa que
provocó la ausencia de diferencias significativas entre los tratamientos, a pesar de ello
se siguieron obteniendo las mayores producciones con los tratamientos biofumigados
D3.1. Architecture and design of the platform
This document aims to establish the requirements and the technological basis and design of the PANACEA platform. These are the main goals of the document: - Survey the different technological approaches that can be used in PANACEA. - Specify some guidelines for the metadata. - Establish the requirements for the platform. - Make a Common Interface proposal for the tools. - Propose a format for the data to be exchanged by the tools (Travelling Object). - Choose the technologies that will be used to develop the platform. - Propose a workplan
The CIDA Variability Survey of Orion OB1. I: the low-mass population of Ori OB 1a and 1b
We present results of a large scale, multi-epoch optical survey of the Ori
OB1 association, carried out with the QuEST camera at the Venezuela National
Astronomical Observatory. We identify for the first time the widely spread
low-mass, young population in the Orion OB1a and OB1b sub-associations.
Candidate members were picked up by their variability in the V-band and
position in color-magnitude diagrams. We obtained spectra to confirm
membership. In a region spanning ~ 68 deg^2 we found 197 new young stars; of
these, 56 are located in the Ori OB1a subassociation and 142 in Ori OB1b.
Comparison with the spatial extent of molecular gas and extinction maps
indicates that the subassociation Ori 1b is concentrated within a ring-like
structure of radius ~2 deg (~15 pc at 440 pc), centered roughly on the star
epsilon Ori in the Orion belt. The ring is apparent in 13CO and corresponds to
a region with an extinction Av>=1. The stars exhibiting strong Ha emission, an
indicator of active accretion, are found along this ring, while the center is
populated with weak Ha emitting stars. In contrast, Ori OB1a is located in a
region devoid of gas and dust. We identify a grouping of stars within a ~3
deg^2 area located in 1a, roughly clustered around the B2 star 25 Ori. The
Herbig Ae/Be star V346 Ori is also associated with this grouping, which could
be an older analog of sigma Ori. Using using several sets of evolutionary
tracks we find an age of 7 - 10 Myr for Ori 1a and of ~4 - 6 Myr for Ori OB1b,
consistent with previous estimates from OB stars. Indicators such as the
equivalent width of Ha and near-IR excesses show that while a substantial
fraction of accreting disks remain at ages ~5 Myr, inner disks are essentially
dissipated by 10 Myr.Comment: 44 pages, 12 figures, to appear in the Astronomical Journal.
(Abridged abstract - to fit length limit in astroph) Full resolution figures
in http://www.cida.ve/~briceno/publications
Probing Dynamical Processes in the Planet-forming Region with Dust Mineralogy
We present Herschel Space Observatory PACS spectra of GQ Lup, a protoplanetary disk in the Lupus star-forming region. Through spectral energy distribution fitting from 0.3 μm to 1.3 mm, we construct a self-consistent model of this system's temperature and density structures, finding that although it is 3 Myr old, its dust has not settled to the midplane substantially. The disk has a radial gradient in both the silicate dust composition and grain size, with large amorphous grains in the upper layers of the inner disk and an enhancement of submicron, crystalline grains in the outer disk. We detect an excess of emission in the Herschel PACS B2A band near 63 μm and model it with a combination of ~15-70 μm crystalline water ice grains with a size distribution consistent with ice recondensation-enhanced grain growth and a mass fraction half of that of our solar system. The combination of crystalline water ice and silicates in the outer disk is suggestive of disk-wide heating events or planetesimal collisions. If confirmed, this would be the first detection of water ice by Herschel .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98541/1/2041-8205_759_1_L10.pd
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Loss-of-function mutations in the CABLES1 gene are a novel cause of Cushing's disease.
The CABLES1 cell cycle regulator participates in the adrenal-pituitary negative feedback, and its expression is reduced in corticotropinomas, pituitary tumors with a largely unexplained genetic basis. We investigated the presence of CABLES1 mutations/copy number variations (CNVs) and their associated clinical, histopathological and molecular features in patients with Cushing's disease (CD). Samples from 146 pediatric (118 germline DNA only/28 germline and tumor DNA) and 35 adult (tumor DNA) CD patients were screened for CABLES1 mutations. CNVs were assessed in 116 pediatric CD patients (87 germline DNA only/29 germline and tumor DNA). Four potentially pathogenic missense variants in CABLES1 were identified, two in young adults (c.532G > A, p.E178K and c.718C > T, p.L240F) and two in children (c.935G > A, p.G312D and c.1388A > G, and p.D463G) with CD; no CNVs were found. The four variants affected residues within or close to the predicted cyclin-dependent kinase-3 (CDK3)-binding region of the CABLES1 protein and impaired its ability to block cell growth in a mouse corticotropinoma cell line (AtT20/D16v-F2). The four patients had macroadenomas. We provide evidence for a role of CABLES1 as a novel pituitary tumor-predisposing gene. Its function might link two of the main molecular mechanisms altered in corticotropinomas: the cyclin-dependent kinase/cyclin group of cell cycle regulators and the epidermal growth factor receptor signaling pathway. Further studies are needed to assess the prevalence of CABLES1 mutations among patients with other types of pituitary adenomas and to elucidate the pituitary-specific functions of this gene
Stroke risk and NSAIDs: A systematic review of observational studies
Aims: To perform a quantitative systematic review of observational studies on the risk of stroke associated with the use of individual NSAIDs. Methods and results: Searches were conducted using the Medline database within PubMed (1990-2008). Observational cohort or case-control studies were eligible if reported on the risk of cardiovascular events associated with individual NSAIDs versus the nonuse of NSAIDs. We found 3193 articles, in which 75 were eligible for review and abstraction. Of the 75 articles, 6 reported relative risk (RR) of stroke. Data were abstracted into a database using a standardized entry form. Two authors assessed study quality, and discrepancies were resolved by consensus. The pooled RR of all subtypes of incident stroke was increased with the current use of rofecoxib (RR=1.64, 95% CI=1.15-2.33) and diclofenac (RR=1.27, 95% CI=1.08-1.48). The pooled estimates for naproxen, ibuprofen, and celecoxib were close to unity. The risk of ischemic stroke was also increased with rofecoxib (RR=1.82, 95% CI=1.09-3.04) and diclofenac (RR=1.20, 95% CI=0.99-1.45). Data were inadequate to estimate the pooled RR by dose and duration, for other individual NSAIDs or nonischemic stroke subtypes. Conclusion: This meta-analysis supports an increased risk of ischemic stroke with the current use of rofecoxib and diclofenac. Additional studies are required to evaluate most individual NSAIDS, the effect of dose and duration, and the subtypes of stroke
Description of the annual reproductive cycle of wreckfish; Polyprion americanus, in captivity
Successful spontaneous reproduction and the production of viable offspring of wild fish in captivity can take some years of adaptation, and may also involve different environmental conditions, sex ratios and densities compared to natural populations. We followed the reproductive cycle of wreckfish Polyprion americanus—a late maturing, deep-sea benthic species—in captivity in three different broodstocks in Spain under natural photoperiod and temperature, and one broodstock in Greece under a constant temperature of 16 °C for two consecutive years, to describe the reproductive cycle of the species and the associated sex steroid hormone profiles. Oogenesis begun in the fall and post-vitellogenic oocytes of 1250 μm were present between March and June. Males were in spermiation condition and produced good-quality sperm throughout the year, regardless of the temperature profile to which they were exposed. Some females completed oogenesis, underwent oocyte maturation, and spawned spontaneously under both constant and fluctuating temperatures. The sex steroid hormones of both males and females followed the already-known profiles during fish gametogenesis, except for 17,20β-dihydroxy-progesterone, which did not seem to be related to either female or male maturation. The female reproductive dysfunctions that were identified included (a) the arrest of oogenesis at the cortical alveoli stage in certain females; (b) the failure to undergo oocyte maturation in others; and (c) the production of large percentages of unfertilized eggs from the females that spawned spontaneously. Our study suggests that reproduction in captivity is possible in wreckfish maintained under typical marine aquaculture conditions, but that reliable spawning and production of high-quality eggs may require some years of adaptation to captivity, before the reproductive dysfunctions will be overcome.Versión del edito
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