6,590 research outputs found
A systematic search for massive young stars in the Galaxy - the RMS survey
We have selected red MSX sources (RMS) that have the colours of massive young
stellar objects (MYSOs). Our aim is to generate a large, systematically
selected sample to address questions such as their luminosity function,
lifetimes, clustering and triggering. Other objects such as UCHIIs, PN, PPN and
AGB stars have similar IR colours and a large programme of ground-based
follow-up observations is underway to identify and eliminate these from the
sample of the red MSX sources. These include radio continuum observations,
kinematic distances, ground-based mid-IR imaging, near-IR imaging and
spectroscopy to distinguish. We report the progress of these campaigns on the
3000 candidates, with initial indications showing that a substantial fraction
are indeed massive YSOs.Comment: 3 pages, 4 figures Talk in conference: Milky Way surveys, the
structure and evolution of our Galaxy, Boston 200
Classical theta constants vs. lattice theta series, and super string partition functions
Recently, various possible expressions for the vacuum-to-vacuum superstring
amplitudes has been proposed at genus . To compare the different
proposals, here we will present a careful analysis of the comparison between
the two main technical tools adopted to realize the proposals: the classical
theta constants and the lattice theta series. We compute the relevant Fourier
coefficients in order to relate the two spaces. We will prove the equivalence
up to genus 4. In genus five we will show that the solutions are equivalent
modulo the Schottky form and coincide if we impose the vanishing of the
cosmological constant.Comment: 21 page
A distance-limited sample of massive molecular outflows
We have observed 99 mid-infrared-bright, massive young stellar objects and compact H ii regions drawn from the Red MSX source survey in the J = 3−2 transition of 12CO and 13CO, using the James Clerk Maxwell Telescope. 89 targets are within 6 kpc of the Sun, covering a representative range of luminosities and core masses. These constitute a relatively unbiased sample of bipolar molecular outflows associated with massive star formation. Of these, 59, 17 and 13 sources (66, 19 and 15 per cent) are found to have outflows, show some evidence of outflow, and have no evidence of outflow, respectively. The time-dependent parameters of the high-velocity molecular flows are calculated using a spatially variable dynamic time-scale. The canonical correlations between the outflow parameters and source luminosity are recovered and shown to scale with those of low-mass sources. For coeval star formation, we find the scaling is consistent with all the protostars in an embedded cluster providing the outflow force, with massive stars up to ∼30 M⊙ generating outflows. Taken at face value, the results support the model of a scaled-up version of the accretion-related outflow-generation mechanism associated with discs and jets in low-mass objects with time-averaged accretion rates of ∼10−3 M⊙ yr−1 on to the cores. However, we also suggest an alternative model, in which the molecular outflow dynamics are dominated by the entrained mass and are unrelated to the details of the acceleration mechanism. We find no evidence that outflows contribute significantly to the turbulent kinetic energy of the surrounding dense cores
The Sphaleron Rate in SU(N) Gauge Theory
The sphaleron rate is defined as the diffusion constant for topological
number NCS = int g^2 F Fdual/32 pi^2. It establishes the rate of equilibration
of axial light quark number in QCD and is of interest both in electroweak
baryogenesis and possibly in heavy ion collisions. We calculate the
weak-coupling behavior of the SU(3) sphaleron rate, as well as making the most
sensible extrapolation towards intermediate coupling which we can. We also
study the behavior of the sphaleron rate at weak coupling at large Nc.Comment: 18 pages with 3 figure
A biomimetic vocalisation system for MiRo
There is increasing interest in the use of animal-like robots in applications such as companionship and pet therapy. However, in the majority of cases it is only the robot's physical appearance that mimics a given animal. In contrast, MiRo is the first commercial biomimetic robot to be based on a hardware and software architecture that is modelled on the biological brain. This paper describes how MiRo's vocalisation system was designed, not using pre-recorded animal sounds, but based on the implementation of a real-time parametric general-purpose mammalian vocal synthesiser tailored to the specific physical characteristics of the robot. The novel outcome has been the creation of an 'appropriate' voice for MiRo that is perfectly aligned to the physical and behavioural affordances of the robot, thereby avoiding the 'uncanny valley' effect and contributing strongly to the effectiveness of MiRo as an interactive device
Access to recreational physical activities by car and bus : an assessment of socio-spatial inequalities in mainland Scotland
Obesity and other chronic conditions linked with low levels of physical activity (PA) are associated with deprivation. One reason for this could be that it is more difficult for low-income groups to access recreational PA facilities such as swimming pools and sports centres than high-income groups. In this paper, we explore the distribution of access to PA facilities by car and bus across mainland Scotland by income deprivation at datazone level. GIS car and bus networks were created to determine the number of PA facilities accessible within travel times of 10, 20 and 30 minutes. Multilevel negative binomial regression models were then used to investigate the distribution of the number of accessible facilities, adjusting for datazone population size and local authority. Access to PA facilities by car was significantly (p<0.01) higher for the most affluent quintile of area-based income deprivation than for most other quintiles in small towns and all other quintiles in rural areas. Accessibility by bus was significantly lower for the most affluent quintile than for other quintiles in urban areas and small towns, but not in rural areas. Overall, we found that the most disadvantaged groups were those without access to a car and living in the most affluent areas or in rural areas
Current noise in the vicinity of the 2D superconductor-insulator quantum critical point
Systems near to quantum critical points show universal scaling in response to external probes. We consider whether this scaling is reflected in their out-of-equilibrium fluctuations. We study current noise in the metallic state at the z=1 quantum critical point between a superconductor and an insulator in two dimensions. Using a Boltzmann-Langevin approach within a 1/N expansion, we show that the current noise obeys a universal scaling form S-j=T Phi[T/T-eff(E)], with T-eff proportional to root E. This treatment recovers Johnson noise in thermal equilibrium and S-j proportional to root E at strong electric fields. The latter differs significantly from both the shot noise in conventional metals (diffusive Fermi liquids) and the free carrier result, due to strong correlations between the critical bosonic excitations. Current-noise measurements could therefore help clarify the physics of the destruction of superconductivity in thin film superconductors
Chest computed tomography of a patient revealing severe hypoxia due to amniotic fluid embolism: a case report
<p>Abstract</p> <p>Introduction</p> <p>Amniotic fluid embolism is one of the most severe complications in the peripartum period. Because its onset is abrupt and fulminant, it is unlikely that there will be time to examine the condition using thoracic computed tomography (CT). We report a case of life-threatening amniotic fluid embolism, where chest CT in the acute phase was obtained.</p> <p>Case presentation</p> <p>A 22-year-old Asian Japanese primiparous woman was suspected of having an amniotic fluid embolism. After a Cesarean section for cephalopelvic disproportion, her respiratory condition deteriorated. Her chest CT images were examined. CT findings revealed diffuse homogeneous ground-glass shadow in her bilateral peripheral lung fields. She was therefore transferred to our hospital. On admission to our hospital's intensive care unit, she was found to have severe hypoxemia, with SpO<sub>2 </sub>of 50% with a reservoir mask of 15 L/min oxygen. She was intubated with the support of noninvasive positive pressure ventilation. She was successfully extubated on the sixth day, and discharged from the hospital on the twentieth day.</p> <p>Conclusion</p> <p>This is the first case report describing amniotic fluid embolism in which CT revealed an acute respiratory distress syndrome-like shadow.</p
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