615 research outputs found
A Parallactic Distance of 389 +24/-21 parsecs to the Orion Nebula Cluster from Very Long Baseline Array Observations
We determine the parallax and proper motion of the flaring, non-thermal radio
star GMR A, a member of the Orion Nebula Cluster, using Very Long Baseline
Array observations. Based on the parallax, we measure a distance of 389 +24/-21
parsecs to the source. Our measurement places the Orion Nebula Cluster
considerably closer than the canonical distance of 480 +/- 80 parsecs
determined by Genzel et al. (1981). A change of this magnitude in distance
lowers the luminosities of the stars in the cluster by a factor of ~ 1.5. We
briefly discuss two effects of this change--an increase in the age spread of
the pre-main sequence stars and better agreement between the zero-age
main-sequence and the temperatures and luminosities of massive stars.Comment: 10 pages, 4 figures, emulateapj, accepted to Ap
Simulation sample sizes for Monte Carlo partial EVPI calculations
Partial expected value of perfect information (EVPI) quantifies the value of removing uncertainty about unknown parameters in a decision model. EVPIs can be computed via Monte Carlo methods. An outer loop samples values of the parameters of interest, and an inner loop samples the remaining parameters from their conditional distribution. This nested Monte Carlo approach can result in biased estimates if small numbers of inner samples are used and can require a large number of model runs for accurate partial EVPI estimates. We present a simple algorithm to estimate the EVPI bias and confidence interval width for a specified number of inner and outer samples. The algorithm uses a relatively small number of model runs (we suggest approximately 600), is quick to compute, and can help determine how many outer and inner iterations are needed for a desired level of accuracy. We test our algorithm using three case studies. (C) 2010 Elsevier B.V. All rights reserved
Surgical Models of Liver Regeneration in Pigs. A Practical Review of the Literature for Researchers
The remarkable capacity of regeneration of the liver is well known, although the involved mechanisms are far from being understood. Furthermore, limits concerning the residual functional mass of the liver remain critical in both fields of hepatic resection and transplantation. The aim of the present study was to review the surgical experiments regarding liver regeneration in pigs to promote experimental methodological standardization. The Pubmed, Medline, Scopus, and Cochrane Library databases were searched. Studies evaluating liver regeneration through surgical experiments performed on pigs were included. A total of 139 titles were screened, and 41 articles were included in the study, with 689 pigs in total. A total of 29 studies (71% of all) had a survival design, with an average study duration of 13 days. Overall, 36 studies (88%) considered partial hepatectomy, of which four were an associating liver partition and portal vein ligation for staged hepatectomy (ALPPS). Remnant liver volume ranged from 10% to 60%. Only 2 studies considered a hepatotoxic pre-treatment, while 25 studies evaluated additional liver procedures, such as stem cell application, ischemia/reperfusion injury, portal vein modulation, liver scaffold application, bio-artificial, and pharmacological liver treatment. Only nine authors analysed how cytokines and growth factors changed in response to liver resection. The most used imaging system to evaluate liver volume was CT-scan volumetry, even if performed only by nine authors. The pig represents one of the best animal models for the study of liver regeneration. However, it remains a mostly unexplored field due to the lack of experiments reproducing the chronic pathological aspects of the liver and the heterogeneity of existing studies
Rethinking project selection at the Monterey Bay Aquarium
The article of record as published may be found at https://www.jstor.org/stable/25062652In 1995, the Monterey Bay Aquarium started an experimental business unit called Electronic Outreach. Electronic Outreach's mission was to employ emerging technologies to deliver the aquarium's messages of ocean stewardship to diverse and scattered audiences. Faced with many projects from which to choose, the Electronic Outreach team wanted to determine which projects were most likely to succeed before they actually had to dedicate resources to development. We constructed two models to help them accomplish this: a multiattribute-value model to quantify a project's alignment with the aquarium's mission and a discounted-cash-flow model to quantify a project's viability as a business venture. We then combined the outputs of these two models into a two-dimensional frame work to allow the Electronic Outreach team members to focus on monetary-nonmonetary trade-offs when evaluating potential projects
Uso de lodos de depuradora sobre suelos de baja productividad en Santa Fe (Argentina)
Se evaluó el efecto de lodos de depuradora sobre la capacidad productiva de los suelos de baja aptitud del centro-norte de Santa Fe, y sobre la producción de sorgo y avena. Se evaluaron dosis entre 0 y 38,5 y entre 0 y 109 Mg de materia seca de lodo/ha, para sorgo y avena respectivamente, aplicadas previo a la siembra sobre un Natracualf típico. Se midió la respuesta en rendimiento y propiedades físicas y químicas del horizonte superficial. En ambos cultivos se observó respuesta positiva en comparación con el testigo. La salinidad moderada del lodo no afectó a los cultivos ya que se lavó con las precipitaciones. Se observó efectopositivo sobre las propiedades químicas y físicas del horizonte superficial, destacándose fósforo extraíble, calcio y magnesio intercambiable, nitrógeno total y carbono orgánico, estabilidad de agregados, e intervalo hídrico óptimo. El pH del suelo sólo tiende a mejorar con altas dosis.Using sewage sludge on soils with low productivity in Santa Fe (Argentina) The effect of sewage sludge on productive capacity of low aptitude soils (class IV or higher) from the center and north of Santa Fe, and on forage production of sorghum and oats was assessed. Before sowing of sorghum and oats, 0 to 38,5 and 0 to 109 Mg of dry matter/ha of sludge was applied respectively, on a Typic Natracualf. Afterwards, along with forage yield, several chemical and physical soil properties were measured. For both crops, forage production was increased in response to the application of sludge. Moderate salinity levels of sludge has no effect on crop production because salts were washed quickly by rainfall. The amount of sludge applied was related positively to extractable phosphorus, exchangeable calcium and magnesium, total nitrogen, organic carbon, aggregate stability and least limiting water range. Soil pH was improved only at higher doses of sludge.Fil: Pilatti, M. A.. Universidad Nacional del Litoral. Facultad de Cs.agrarias. Catedra de Edafologia; ArgentinaFil: Alesso, Carlos Agustín. Universidad Nacional del Litoral. Facultad de Cs.agrarias. Departamento de Biologia Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Agrobiotecnologia del Litoral; ArgentinaFil: Felli, O.. Universidad Nacional del Litoral. Facultad de Cs.agrarias. Catedra de Edafologia; ArgentinaFil: Gasparotti, E.. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias; Argentin
Redox‐Responsive Nanobiomaterials‐Based Therapeutics for Neurodegenerative Diseases
Redox regulation has recently been proposed as a critical intracellular mechanism affecting cell survival, proliferation, and differentiation. Redox homeostasis has also been implicated in a variety of degenerative neurological disorders such as Parkinson's and Alzheimer's disease. In fact, it is hypothesized that markers of oxidative stress precede pathologic lesions in Alzheimer's disease and other neurodegenerative diseases. Several therapeutic approaches have been suggested so far to improve the endogenous defense against oxidative stress and its harmful effects. Among such approaches, the use of artificial antioxidant systems has gained increased popularity as an effective strategy. Nanoscale drug delivery systems loaded with enzymes, bioinspired catalytic nanoparticles and other nanomaterials have emerged as promising candidates. The development of degradable hydrogels scaffolds with antioxidant effects could also enable scientists to positively influence cell fate. This current review summarizes nanobiomaterial‐based approaches for redox regulation and their potential applications as central nervous system neurodegenerative disease treatments
Compact Radio Sources in Orion: New Detections, Time Variability, and Objects in OMC-1S
We present the analysis of four 3.6 cm radio continuum archival observations
of Orion obtained using the Very Large Array in its A-configuration, with
angular resolution. The observations were made during the period
1994-1997. In a region of , we detect a total of 77 compact radio
sources. Of the total of detected sources, 54 are detected in one or more of
the individual observations and 36 of these show time variability (by more than
30%) between the observed epochs. A deep image made from averaging all data
shows an additional 23 faint sources, in the range of 0.1 to 0.3 mJy. Of the
total of 77 sources, 39 are new centimeter detections. However, only 9 of the
77 sources do not have a previously reported counterpart at near-infrared,
optical, or X-ray wavelengths. In particular, we detect three faint sources in
the OMC-1S region that may be related to the sources that power the multiple
outflows that emanate from this part of the Orion nebula. %We discuss the
nature of these sources and its relation with the %near-infrared, optical, and
X-ray objects in the region.Comment: 29 pages, 9 figure
Endoplasmic Reticulum and Mitochondria Contacts Correlate with the Presence and Severity of NASH in Humans
The interaction between the mitochondria and the endoplasmic reticulum (ER) is essential for hepatocyte function. An increase in ER-mitochondria contacts (ERMCs) is associated with various metabolic diseases. Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and type 2 diabetes, and its progressive form non-alcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma. However, the role of ERMCs in the progression of NAFL to NASH is still unclear. We assessed whether ERMCs could correlate with NAFLD severity. We used a proximity ligation assay to measure the abundance of ERMCs in liver biopsies from patients with biopsy-proven NAFLD (n = 48) and correlated the results with histological and metabolic syndrome (MetS) features. NAFLD patients were included according to inclusion and exclusion criteria, and then assigned to NAFL (n = 9) and NASH (n = 39) groups. ERMCs density could discriminate NASH from NAFL (sensitivity 61.5%, specificity 100%). ERMCs abundance correlated with hepatocellular ballooning. Moreover, the density of ERMCs increased with an increase in the number of MetS features. In conclusion, ERMCs increased from NAFL to NASH, in parallel with the number of MetS features, supporting a role for this interaction in the pathophysiology of NASH
Low Velocity Ionized Winds from Regions Around Young O Stars
We have observed seven ultracompact HII regions in hydrogen recombination
lines in the millimeter band. Toward four of these regions, there is a high
velocity (full width to half maximum 60-80 km/s) component in the line
profiles. The high velocity gas accounts for 35-70% of the emission measure
within the beam. We compare these objects to an additional seven similar
sources we have found in the literature. The broad recombination line objects
(BRLOs) make up about 30% of all sources in complexes containing ultracompact
HII regions. Comparison of spectral line and continuum data implies that the
BRLOs coincide with sources with rising spectral indices, >=0.4 up to 100 GHz.
Both the number of BRLOs and their frequency of occurrence within HII region
complexes, when coupled with their small size and large internal motions, mean
that the apparent contradiction between the dynamical and population lifetimes
for BRLOs is even more severe than for ultracompact HII regions. We evaluate a
number of models for the origin of the broad recombination line emission. The
lifetime, morphology, and rising spectral index of the sources argue for photo-
evaporated disks as the cause for BRLOs. Existing models for such regions,
however, do not account for the large amounts of gas observed at supersonic
velocities.Comment: 36 pages, 8 figure
A compactness theorem for scalar-flat metrics on manifolds with boundary
Let (M,g) be a compact Riemannian manifold with boundary. This paper is
concerned with the set of scalar-flat metrics which are in the conformal class
of g and have the boundary as a constant mean curvature hypersurface. We prove
that this set is compact for dimensions greater than or equal to 7 under the
generic condition that the trace-free 2nd fundamental form of the boundary is
nonzero everywhere.Comment: 49 pages. Final version, to appear in Calc. Var. Partial Differential
Equation
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