24 research outputs found
Coexisting conical bipolar and equatorial outflows from a high-mass protostar
The BN/KL region in the Orion molecular cloud is an archetype in the study of
the formation of stars much more massive than the Sun. This region contains
luminous young stars and protostars, but it is difficult to study because of
overlying dust and gas. Our basic expectations are shaped to some extent by the
present theoretical picture of star formation, the cornerstone of which is that
protostars acrete gas from rotating equatorial disks, and shed angular momentum
by ejecting gas in bipolar outflows. The main source of the outflow in the
BN/KL region may be an object known as radio source I, which is commonly
believed to be surrounded by a rotating disk of molecular material. Here we
report high-resolution observations of silicon monoxide (SiO) and water maser
emission from the gas surrounding source I; we show that within 60 AU (about
the size of the Solar System), the region is dominated by a conical bipolar
outflow, rather than the expected disk. A slower outflow, close to the
equatorial plane of the protostellar system, extends to radii of 1,000 AU.Comment: 10 pages, 2 figures. Accepted by Nature. To appear December 199
The 492 GHz emission of Sgr A* constrained by ALMA
We report linearly polarized continuum emission properties of Sgr A* at 492 GHz, based on the Atacama Large Millimeter Array (ALMA) observations. We used the observations of the likely unpolarized continuum emission of Titan, and the observations of C\textsc{i} line emission, to gauge the degree of spurious polarization. The Stokes I flux of 3.60.72 Jy during our run is consistent with extrapolations from the previous, lower frequency observations. We found that the continuum emission of Sgr A* at 492 GHz shows large amplitude differences between the XX and the YY correlations. The observed intensity ratio between the XX and YY correlations as a function of parallactic angle may be explained by a constant polarization position angle of 1583. The fitted polarization percentage of Sgr A* during our observational period is 14\%1.2\%. The calibrator quasar J1744-3116 we observed at the same night can be fitted to Stokes I = 252 mJy, with 7.9\%0.9\% polarization in position angle P.A. = 4.14.2. The observed polarization percentage and polarization position angle in the present work appear consistent with those expected from longer wavelength observations in the period of 1999-2005. In particular, the polarization position angle at 492 GHz, expected from the previously fitted 1677 intrinsic polarization position angle and (-5.60.7)10 rotation measure, is 155, which is consistent with our new measurement of polarization position angle within 1. The polarization percentage and the polarization position angle may be varying over the period of our ALMA 12m Array observations, which demands further investigation with future polarization observations
Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
Most galactic nuclei are now believed to harbour supermassive black holes.
Studies of stellar motions in the central few light-years of our Milky Way
Galaxy indicate the presence of a dark object with a mass of about 2.6 million
solar masses. This object is spatially coincident with Sagittarius A* (Sgr A*),
the unique compact radio source located at the dynamical centre of our Galaxy.
By analogy with distant quasars and nearby active galactic nuclei (AGN), Sgr A*
is thought to be powered by the gravitational potential energy released by
matter as it accretes onto a supermassive black hole. However, Sgr A* is much
fainter than expected in all wavebands, especially in X-rays, casting some
doubt on this model. Recently, we reported the first strong evidence of X-ray
emission from Sgr A*. Here we report the discovery of rapid X-ray flaring from
the direction of Sgr A*. These data provide compelling evidence that the X-ray
emission is coming from accretion onto a supermassive black hole at the
Galactic Centre, and the nature of the variations provides strong constraints
on the astrophysical processes near the event horizon of the black hole.Comment: 4 pages, 3 figures (Figs 1 and 3 in color), LaTe
Product–process matrix and complementarity approach
The relationship between different types of innovation is analysed from three different approaches. On the one hand, the distinctive view assumes that the determinants of each type of innovation are different and therefore there is no relationship between them. On the other hand, the integrative view considers that the different types of innovation are complementary. Finally, the product–process matrix framework suggests that the relationship between product innovation and process innovation is substitutive. Using data from Spain belonging to the Technological Innovation Panel (PITEC) for the years 2008, 2009, 2010, 2011 and 2012, we tested which of the three approaches is predominant. To perform the hypothesis test, we used the so-called complementarity approach. We find that there is no unique relation. The nature of the relationship depends on the types of innovation that interact. Our most significant finding is that the relationship between product innovation and process innovation is complementary. This finding contradicts the proposal of the product–process matrix framework. Consequently, the joint implementation of both types of innovation generates a greater impact on the performance of a company than the sum of their separate implementation
Pharmacological differentiation of opioid receptor antagonists by molecular and functional imaging of target occupancy and food reward-related brain activation in humans
Opioid neurotransmission has a key role in mediating reward-related behaviours. Opioid receptor (OR) antagonists, such as naltrexone (NTX), can attenuate the behaviour-reinforcing effects of primary (food) and secondary rewards. GSK1521498 is a novel OR ligand, which behaves as an inverse agonist at the μ-OR sub-type. In a sample of healthy volunteers, we used [11C]-carfentanil positron emission tomography to measure the OR occupancy and functional magnetic resonance imaging (fMRI) to measure activation of brain reward centres by palatable food stimuli before and after single oral doses of GSK1521498 (range, 0.4–100 mg) or NTX (range, 2–50 mg). GSK1521498 had high affinity for human brain ORs (GSK1521498 effective concentration 50=7.10 ng ml−1) and there was a direct relationship between receptor occupancy (RO) and plasma concentrations of GSK1521498. However, for both NTX and its principal active metabolite in humans, 6-β-NTX, this relationship was indirect. GSK1521498, but not NTX, significantly attenuated the fMRI activation of the amygdala by a palatable food stimulus. We thus have shown how the pharmacological properties of OR antagonists can be characterised directly in humans by a novel integration of molecular and functional neuroimaging techniques. GSK1521498 was differentiated from NTX in terms of its pharmacokinetics, target affinity, plasma concentration–RO relationships and pharmacodynamic effects on food reward processing in the brain. Pharmacological differentiation of these molecules suggests that they may have different therapeutic profiles for treatment of overeating and other disorders of compulsive consumption
Photometry of the Hotspots of Cygnus A
We have observed the hotspots of Cygnus A with the JCMT1 at 1100 and 800μm. We find that the spectra of both hotspots are power laws from ~ 1 GHz to ~ 370 GHz