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High resolution CO observations of S88-B
CO J = 2-1 and 13CO J = 2-1 and 1-0 observations have been made of the H II region S88-B, using the 15-m James Clerk Maxwell telescope in Hawaii and the 20-m telescope at Onsala. The core of the cloud is resolved into a horseshoelike structure which surrounds a diffuse reflection nebula. The central core has a mass of â„ 1000 Mâ, with 400 Mâ in the horseshoe structure. The gas in the horse in the horseshoe appears highly fragmented, and has a kinetic temperature of â 60 K, suggesting it is closely coupled to the dust temperature. A recently formed high mass star appears to be in the process of evacuating a cavity, possibly through a large molecular outflow that is found to show an accelerated component in its blue-shifted lobe. A velocity gradient across the horseshoe structure suggest ordered motion, and could represent rotation in the parental cloud
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High signal/noise <sup>13</sup>CO observations of the bipolar outflow in L1551
New high-signal/noise 13CO observations of the bipolar outflow in the molecular cloud L1551 are reported. Contrary to earlier observations of CO J = 1-0 and 2-1, no strong spatial dependence is found for the velocity profile of these spectra. The implications of these observations are such that the model of an empty shell for this source is less likely, and a model consisting of a shell which contains significant amounts of outflowing molecular gas inside the swept-up cavity walls is suggested
Experimental study of vibro-acoustic response of stiffened cylindrical shells
Vibrational response of stiffened cylindrical shell to reverberant acoustic field
Energy-efficient data acquisition for accurate signal estimation in wireless sensor networks
Long-term monitoring of an environment is a fundamental requirement for most wireless sensor networks. Owing to the fact that the sensor nodes have limited energy budget, prolonging their lifetime is essential in order to permit long-term monitoring. Furthermore, many applications require sensor nodes to obtain an accurate estimation of a point-source signal (for example, an animal call or seismic activity). Commonly, multiple sensor nodes simultaneously sample and then cooperate to estimate the event signal. The selection of cooperation nodes is important to reduce the estimation error while conserving the networkâs energy. In this paper, we present a novel method for sensor data acquisition and signal estimation, which considers estimation accuracy, energy conservation, and energy balance. The method, using a concept of âvirtual clusters,â forms groups of sensor nodes with the same spatial and temporal properties. Two algorithms are used to provide functionality. The âdistributed formationâ algorithm automatically forms and classifies the virtual clusters. The âround robin sample schemeâ schedules the virtual clusters to sample the event signals in turn. The estimation error and the energy consumption of the method, when used with a generalized sensing model, are evaluated through analysis and simulation. The results show that this method can achieve an improved signal estimation while reducing and balancing energy consumption
A Corona Australis cloud filament seen in NIR scattered light. III. Modelling and comparison with Herschel sub-millimetre data
With recent Herschel observations, the northern filament of the Corona
Australis cloud has now been mapped in a number of bands from 1.2um to 870um.
The data set provides a good starting point for the study of the cloud over
several orders of magnitude in density. We wish to examine the differences of
the column density distributions derived from dust extinction, scattering, and
emission, and to determine to what extent the observations are consistent with
the standard dust models. From Herschel data, we calculate the column density
distribution that is compared to the corresponding data derived in the
near-infrared regime from the reddening of the background stars, and from the
surface brightness attributed to light scattering. We construct
three-dimensional radiative transfer models to describe the emission and the
scattering. The scattered light traces low column densities of A_V~1mag better
than the dust emission, remaining useful to A_V ~ 10-15 mag. Based on the
models, the extinction and the level of dust emission are surprisingly
consistent with a sub-millimetre dust emissivity typical of diffuse medium.
However, the intensity of the scattered light is very low at the centre of the
densest clump and this cannot be explained without a very low grain albedo.
Both the scattered light and dust emission indicate an anisotropic radiation
field. The modelling of the dust emission suggests that the radiation field
intensity is at least three times the value of the normal interstellar
radiation field. The inter-comparison between the extinction, light scattering,
and dust emission provides very stringent constraints on the cloud structure,
the illuminating radiation field, and the grain properties.Comment: 13 pages, 16 figures, accepted to A&
An Instrumented Crutch for Monitoring Patients' Weight Distribution during Orthopaedic Rehabilitation
This paper discusses an instrumented forearm crutch that has been developed to monitor a patientâs weight bearing over the full period of their recovery, and that can potentially be used in a home environment. The crutch measures the applied weight, crutch tilt, and hand position on the grip. Data are transmitted wirelessly to a remote computer, where they are processed and visualized in LabVIEW. The results obtained from a successful pilot study highlight both the need for such an instrumented crutch and its ability to measure the weight being applied through a patientâs lower limb
First principle computation of stripes in cuprates
We present a first principle computation of vertical stripes in
within the LDA+U method. We find that Cu centered
stripes are unstable toward O centered stripes. The metallic core of the stripe
is quite wide and shows reduced magnetic moments with suppressed
antiferromagnetic (AF) interactions. The system can be pictured as alternating
metallic and AF two-leg ladders the latter with strong AF interaction and a
large spin gap. The Fermi surface shows warping due to interstripe
hybridization. The periodicity and amplitude of the warping is in good
agreement with angle resolved photoemission experiment. We discuss the
connection with low-energy theories of the cuprates.Comment: 5 pages,4 figure
The phase-space structure of cold dark-matter halos: Insights into the Galactic halo
We study the formation of the Milky Way's halo in a CDM cosmology by
scaling down a high resolution simulation of the formation of a cluster of
galaxies. We determine how much phase-space substructure is left over from the
objects that merge to build up the present galaxy. We study the debris streams
originating from such objects and find that their evolution can be explained
simply in terms of the conservation of phase-space density. Analysing the mass
growth history of our halo we find that its inner regions have been in place
for more than 10 Gyr, but that the growth of the halo as a whole is more
gradual, in agreement with other high resolution simulations of dark-matter
halos. Recent accretion contributes to the inner 10 kpc of the halo only at the
10 level. Finally we determine the number of dark-matter streams as a
function of distance from the centre of the halo. In the equivalent of the
``Solar vicinity'', we find that the dark-matter is smoothly distributed in
space, and that the velocity ellipsoid is formed by hundreds of thousands of
streams, most of which have velocity dispersions of the order of 1 km/s or
less.Comment: 16 pages, 21 figures, MNRAS in press. Postscript version with high
resolution figures available from
http://www.mpa-garching.mpg.de/~ahelmi/research/lcdm_cl.html. Minor change
Spin transfer torque in continuous textures: semiclassical Boltzmann approach
We consider a microscopic model of itinerant electrons coupled via
ferromagnetic exchange to a local magnetization whose direction vector n(r,t)
varies in space and time. We assume that to first order in the spatial gradient
and time derivative of n(r,t) the magnetization distribution function f(p,r,t)
of itinerant electrons has the Ansatz form: f(p,r,t)=f_{parallel}(p)n(r,t)+
f_{1 r}(p) n ^ nabla_{r} n+f_{2 r}(p) nabla_{r} n+ f_{1 t}(p) n ^ partial_t
n+f_{2 t}(p) partial_t n. Using then the Landau-Sillin equations of motion
approach we derive explicit forms for the components f_{parallel}(p), f_{1
r}(p), f_{2 r}(p), f_{1 t}(p) and f_{2 t}(p) in "equilibrum" and in out of
equilibrum situations for: (i) no scattering by impurities, (ii) spin
conserving scattering and (iii) spin non-conserving scattering. The back action
on the localized electron magnetization from the out of equilibrum part of the
two components f_{1 r}, f_{2 r} constitutes the two spin transfer torque terms.Comment: Revised version accepted for publication, 12 pages, one figur
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