2,168 research outputs found
Estimate of convection-diffusion coefficients from modulated perturbative experiments as an inverse problem
The estimate of coefficients of the Convection-Diffusion Equation (CDE) from
experimental measurements belongs in the category of inverse problems, which
are known to come with issues of ill-conditioning or singularity. Here we
concentrate on a particular class that can be reduced to a linear algebraic
problem, with explicit solution. Ill-conditioning of the problem corresponds to
the vanishing of one eigenvalue of the matrix to be inverted. The comparison
with algorithms based upon matching experimental data against numerical
integration of the CDE sheds light on the accuracy of the parameter estimation
procedures, and suggests a path for a more precise assessment of the profiles
and of the related uncertainty. Several instances of the implementation of the
algorithm to real data are presented.Comment: Extended version of an invited talk presented at the 2012 EPS
Conference. To appear in Plasma Physics and Controlled Fusio
The role of dissipation in biasing the vacuum selection in quantum field theory at finite temperature
We study the symmetry breaking pattern of an O(4) symmetric model of scalar
fields, with both charged and neutral fields, interacting with a photon bath.
Nagasawa and Brandenberger argued that in favourable circumstances the vacuum
manifold would be reduced from S^3 to S^1. Here it is shown that a selective
condensation of the neutral fields, that are not directly coupled to photons,
can be achieved in the presence of a minimal ``external'' dissipation, i.e. not
related to interactions with a bath. This should be relevant in the early
universe or in heavy-ion collisions where dissipation occurs due to expansion.Comment: Final version to appear in Phys. Rev. D, 2 figures added, 2 new
sub-section
EuroSpine Task Force on Research: support for spine researchers
In recognition of the value of research to the practice of spine care, Federico Balagué and Ferran Pellisé, at the time President and Secretary for EuroSpine, asked Margareta Nordin to set up a Task Force on Research (TFR) for EuroSpine during summer 2011. The concept was to stimulate and facilitate a research community within the society, through two main functions: (1) distribution of EuroSpine funds to researchers; (2) develop and deliver research training/education courses. What has the EuroSpine TFR accomplished since its inception
Detection and count of Salmonella enterica in pork meat products
A direct plating technique for the enumeration S. enterica in 90 pig meat samples was evaluated in comparison with a three tube-MPN procedure. For the detection of S. enterica the ISO 6597:2002 method was employed. Pork samples were collected at retail level in northern Italy. A total of 15 (16.7%) Salmonella positive samples were detected. By the use of the MPN method, S. enterica was countable m 12 (80.0%) samples, while the direct count gave positive results in two (13.3%) samples only The ISO 6597.2002 method identified 12 (80 %) contaminated samples out of 15. The enumeration levels of S. enterica ranged from 0.03 MPN/g to \u3e 110 MPN/g by the MPN method, and from 10 CFU/g to 180 CFU/g by direct plating. Seven Salmonella serovars were detected. S. Typhimurium, S. Derby, S. Give, S. Rissen, S. Livingstone, S. Brandenburg and S. London, with S. Typhimurium and S. Derby as the predominant ones
Abrasive fluidized bed finishing to improve the fatigue behaviour of Ti6Al4V parts fabricated by electron beam melting
A study of the abrasive fluidized bed (AFB) finishing process was conducted to quantify the obtainable improvement of the fatigue behaviour of Ti6Al4V parts produced by electron beam melting (EBM). Axial-symmetric EBM samples were rotated at high speed inside a fluidized bed of stainless-steel media. The effects of the treatment time and the rotational speed on morphological features and fatigue life of the EBM samples were investigated. Outcomes showed that the improvement in surface properties induced by the AFB finishing process determined an increase up to 50% in fatigue life and a shift of the S-N curve
Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars
We computed accurate atmosphere models of rotation-powered millisecond
pulsars in which the polar caps of a neutron star (NS) are externally heated by
magnetospheric return currents. The external ram pressure, energy losses, and
stopping depth of the penetrating charged particles were computed
self-consistently with the atmosphere model, instead of assuming a simplified
deep-heated atmosphere in radiative equilibrium. We used exact Compton
scattering formalism to model the properties of the emergent X-ray radiation.
The deep-heating approximation was found to be valid only if most of the heat
originates from ultra-relativistic bombarding particles with Lorentz factors of
. In the opposite regime, the atmosphere attains a distinct
two-layer structure with an overheated optically thin skin on top of an
optically thick cool plasma. The overheated skin strongly modifies the emergent
radiation: it produces a Compton-upscattered high-energy tail in the spectrum
and alters the radiation beaming pattern from limb darkening to limb
brightening for emitted hard X-rays. This kind of drastic change in the
emission properties can have a significant impact on the inferred NS pulse
profile parameters as performed, for example, by Neutron star Interior
Composition ExploreR. Finally, the connection between the energy distribution
of the return current particles and the atmosphere emission properties offers a
new tool to probe the exact physics of pulsar magnetospheres.Comment: 13 pages, 10 figures, published in A&
SPh functionalized bridging-vinyliminium diiron and diruthenium complexes
The SPh functionalized vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(SPh)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R′ = Me, 2a; R = Me, R′ = Me, 2b; R = 4-C6H4OMe, R′ = Me, 2c; R = Xyl, R′ = CH2OH, 2d; R = Me, R′ = CH2OH, 2e; Xyl = 2,6-Me2C6H3] are generated in high yields by treatment of the corresponding vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(H)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (1a–e) with NaH in the presence of PhSSPh. Likewise, the diruthenium complex [Ru2{μ-η1:η3-Cγ(Me)Cβ(SPh)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (2f) was obtained from the corresponding vinyliminium complex [Ru2{μ-η1:η3-Cγ(Me)Cβ(H)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (1f). The synthesis of 2c is accompanied by the formation, in comparable amounts, of the aminocarbyne complex [Fe2{μ-CN(Me)(4-C6H4OMe)}(SPh)(μ-CO)(CO)(Cp)2] (3). The molecular structures of 2d, 2e and 3 have been determined by X-ray diffraction studies
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