10,064 research outputs found
Numerical Modelling of Industrial Induction
Induction heating is a physical process extensively used in the metallurgical industry for different applications involving metal melting. The main components of an induction heating
system are an induction coil connected to a power-supply providing an alternating electric
current and a conductive workpiece to be heated, placed inside the coil. The alternating
current traversing the coil generates eddy currents in the workpiece and by means of ohmic
losses the workpiece is heate
Statistics of Core Lifetimes in Numerical Simulations of Turbulent, Magnetically Supercritical Molecular Clouds
We present measurements of the mean dense core lifetimes in numerical
simulations of magnetically supercritical, turbulent, isothermal molecular
clouds, in order to compare with observational determinations. "Prestellar"
lifetimes (given as a function of the mean density within the cores, which in
turn is determined by the density threshold n_thr used to define them) are
consistent with observationally reported values, ranging from a few to several
free-fall times. We also present estimates of the fraction of cores in the
"prestellar", "stellar'', and "failed" (those cores that redisperse back into
the environment) stages as a function of n_thr. The number ratios are measured
indirectly in the simulations due to their resolution limitations. Our approach
contains one free parameter, the lifetime of a protostellar object t_yso (Class
0 + Class I stages), which is outside the realm of the simulations. Assuming a
value t_yso = 0.46 Myr, we obtain number ratios of starless to stellar cores
ranging from 4-5 at n_thr = 1.5 x 10^4 cm^-3 to 1 at n_thr = 1.2 x 10^5 cm^-3,
again in good agreement with observational determinations. We also find that
the mass in the failed cores is comparable to that in stellar cores at n_thr =
1.5 x 10^4 cm^-3, but becomes negligible at n_thr = 1.2 x 10^5 cm^-3, in
agreement with recent observational suggestions that at the latter densities
the cores are in general gravitationally dominated. We conclude by noting that
the timescale for core contraction and collapse is virtually the same in the
subcritical, ambipolar diffusion-mediated model of star formation, in the model
of star formation in turbulent supercritical clouds, and in a model
intermediate between the previous two, for currently accepted values of the
clouds' magnetic criticality.Comment: 25 pages, 8 figures, ApJ accepted. Fig.1 animation is at
http://www.astrosmo.unam.mx/~e.vazquez/turbulence/movies/Galvan_etal07/Galvan_etal07.htm
Novel Microscopic Mechanism of Intermixing during Growth on Soft Metallic Substrates
Generic computer simulations using empiric interatomic potentials suggest a new, collective mechanism that could be responsible for mixing at heteroepitaxial interfaces. Even if single adsorbate atoms diffuse by hopping on the substrate surface and do not mix at the terraces, two-dimensional islands formed by nucleation may become unstable above a certain critical size and explode upwards forming clusters of several atomic layers. This process is accompanied by strong distortions of the underlying atomic layers, and on soft materials it can result in surface etching and incorporation of substrate atoms into the islands.Fil: Gomez, Liliana Maria. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, IngenierĂa y Agrimensura; ArgentinaFil: Slutzky, Claudia Marcela. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Santa Fe. Instituto de Desarrollo TecnolĂłgico para la Industria QuĂmica. Universidad Nacional del Litoral. Instituto de Desarrollo TecnolĂłgico para la Industria QuĂmica; ArgentinaFil: Ferron, Julio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Santa Fe. Instituto de Desarrollo TecnolĂłgico para la Industria QuĂmica. Universidad Nacional del Litoral. Instituto de Desarrollo TecnolĂłgico para la Industria QuĂmica; ArgentinaFil: de la Figuera, J.. Sandia National Laboratories; Estados UnidosFil: Camarero, J.. Universidad AutĂłnoma de Madrid; EspañaFil: Vazquez de Parga, A.. Universidad AutĂłnoma de Madrid; EspañaFil: de Miguel, J.J.. Universidad AutĂłnoma de Madrid; EspañaFil: Miranda, R.. Universidad AutĂłnoma de Madrid; Españ
Formation and Collapse of Quiescent Cloud Cores Induced by Dynamic Compressions
(Abridged) We present numerical hydrodynamical simulations of the formation,
evolution and gravitational collapse of isothermal molecular cloud cores. A
compressive wave is set up in a constant sub-Jeans density distribution of
radius r = 1 pc. As the wave travels through the simulation grid, a
shock-bounded spherical shell is formed. The inner shock of this shell reaches
and bounces off the center, leaving behind a central core with an initially
almost uniform density distribution, surrounded by an envelope consisting of
the material in the shock-bounded shell, with a power-law density profile that
at late times approaches a logarithmic slope of -2 even in non-collapsing
cases. The resulting density structure resembles a quiescent core of radius <
0.1 pc, with a Bonnor-Ebert-like (BE-like) profile, although it has significant
dynamical differences: it is initially non-self-gravitating and confined by the
ram pressure of the infalling material, and consequently, growing continuously
in mass and size. With the appropriate parameters, the core mass eventually
reaches an effective Jeans mass, at which time the core begins to collapse.
Thus, there is necessarily a time delay between the appearance of the core and
the onset of its collapse, but this is not due to the dissipation of its
internal turbulence as it is often believed. These results suggest that
pre-stellar cores may approximate Bonnor-Ebert structures which are however of
variable mass and may or may not experience gravitational collapse, in
qualitative agreement with the large observed frequency of cores with BE-like
profiles.Comment: Accepted for publication in ApJ. Associated mpeg files can be found
in http://www.astrosmo.unam.mx/~g.gomez/publica.htm
Observation of a New Excited Ds+ Meson in B0 âd-D+K+Ï-Decays
Using pp collision data corresponding to an integrated luminosity of 5.4 fbâ1 collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B0 â DâDĂŸKĂŸÏâ decay is studied. A new excited DĂŸ s meson is observed decaying into the DĂŸKĂŸÏâ final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be mR ÂŒ 2591 6 7 MeV, ÎR ÂŒ 89 16 12 MeV, and JP ÂŒ 0â, where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as Ds0Ă°2590ĂĂŸ, is a strong candidate to be the DsĂ°21 S0ĂĂŸ state, the radial excitation of the pseudoscalar ground-state DĂŸ s meson
Mental Health Patients' Expectations about the Non-Medical Care They Receive in Primary Care: A Cross-Sectional Descriptive Study
A health system's responsiveness is the result of patient expectations for the non-medical care they receive. The objective of this study was to assess mental patients' responsiveness to the health system in primary care, as related to the domains of dignity, autonomy, confidentiality, and communication. Data were collected from 215 people over the age of 18 with mental disorders, using the Multi-Country Survey Study (MCSS) developed by the World Health Organization. Of them, 95% reported a good experience regarding the dignity, confidentiality, communication, and autonomy domains. Regarding responsiveness, patients valued the dignity domain as the most important one (25.1%). Among the patients who experienced poor confidentiality, five out of seven earned less than 900 euros per month (X-2 = 10.8, p = 0.004). Among those who experienced good autonomy, 85 out of 156 belonged to the working social class (90.4%), and among those who valued it as poor (16.1%), the highest proportion was for middle class people (X-2 = 13.1, p = 0.028). The two students and 87.5% of retirees experienced this dimension as good, and most patients who valued it as poor were unemployed (43.5%) (X-2 = 13.0, p = 0.011). Patients with a household income higher than 900 euros more frequently valued responsiveness as good, regarding those domains related to communication, with OR = 3.84, 95% CI = 1.05-14.09, and confidentiality, with OR = 10.48, 95% CI = 1.94-56.59. To conclude, as regards responsiveness in primary care, the dignity domain always obtained the best scores by people with mental disorders. Low economic income is related to a poor assessment of confidentiality. Working class patients, students, and retirees value autonomy as good
PANIC: the new panoramic NIR camera for Calar Alto
PANIC is a wide-field NIR camera, which is currently under development for
the Calar Alto observatory (CAHA) in Spain. It uses a mosaic of four Hawaii-2RG
detectors and covers the spectral range from 0.8-2.5 micron(z to K-band). The
field-of-view is 30x30 arcmin. This instrument can be used at the 2.2m
telescope (0.45arcsec/pixel, 0.5x0.5 degree FOV) and at the 3.5m telescope
(0.23arcsec/pixel, 0.25x0.25 degree FOV). The operating temperature is about
77K, achieved by liquid Nitrogen cooling. The cryogenic optics has three flat
folding mirrors with diameters up to 282 mm and nine lenses with diameters
between 130 mm and 255 mm. A compact filter unit can carry up to 19 filters
distributed over four filter wheels. Narrow band (1%) filters can be used. The
instrument has a diameter of 1.1 m and it is about 1 m long. The weight limit
of 400 kg at the 2.2m telescope requires a light-weight cryostat design. The
aluminium vacuum vessel and radiation shield have wall thicknesses of only 6 mm
and 3 mm respectively.Comment: This paper has been presented in the SPIE of Astronomical Telescopes
and Instrumentation 2008 in Marseille (France
Observation of Multiplicity Dependent Prompt Ïc1 (3872) and Ï (2S) Production in pp Collisions
The production of Ïc1(3872) and Ï(2S) hadrons is studied as a function of charged particle multiplicity in pp collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2 fbâ1 . For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of Ïc1(3872) to Ï(2S) cross-sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the Ïc1(3872) structure as a compact tetraquark. Implications for the binding energy of the Ïc1(3872) state are discussed
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