762 research outputs found
Computer-aided diagnosis of pancreatic and lung cancer
When we talk about cancer diagnosis the most
important thing is early diagnosis to prevent cancer cells from
spreading. We may also consider the high cost of diagnostic
tests. Our approach seeks to address both problems. It uses a
software based on Bayesian networks that simulates the causeeffect relationships and gets the chance of suffering a
pancreatic cancer or lung cancer. This software would support
doctors and save a lot of time and resources
Convection and cracking stability of spheres in General Relativity
In the present paper we consider convection and cracking instabilities as
well as their interplay. We develop a simple criterion to identify equations of
state unstable to convection, and explore the influence of buoyancy on cracking
(or overturning) for isotropic and anisotropic relativistic spheres. We show
that a density profile , monotonous, decreasing and concave , i.e.
and , will be stable against convection, if the radial
sound velocity monotonically decreases outward. We also studied the cracking
instability scenarios and found that isotropic models can be unstable, when the
reaction of the pressure gradient is neglected, i.e. ; but if it is considered, the instabilities may vanish and this result is
valid, for both isotropic and anisotropic matter distributions.Comment: 16 pages, 5 figure
Acceptability Conditions and Relativistic Barotropic Equations of State
We sketch an algorithm to generate exact anisotropic solutions starting from
a barotropic EoS and setting an ansatz on the metric functions. To illustrate
the method, we use a generalization of the polytropic equation of state
consisting of a combination of a polytrope plus a linear term. Based on this
generalization, we develop two models which are not deprived of physical
meaning as well as fulfilling the stringent criteria of physical acceptability
conditions. We also show that some relativistic anisotropic polytropic models
may have singular tangential sound velocity for polytropic indexes greater than
one. This happens in anisotropic matter configurations when the polytropic
equation of state is implemented together with an ansatz on the metric
functions. The generalized polytropic equation of state is free from this
pathology in the tangential sound velocity.Comment: 25 pages, 7 figure
Enhanced quench propagation in 2G-HTS coils co-wound with stainless steel or anodised aluminium tapes
Early quench detection and thermal stability of superconducting coils are of great relevance for practical applications. Magnets made with second generation high temperature superconducting (2G-HTS) tapes present low quench propagation velocities and therefore slow voltage development and high local temperature rises, which may cause irreversible damage. Since quench propagation depends on the anisotropy of the thermal conductivity, this may be used to achieve an improvement of the thermal stability and robustness of 2G-HTS coils. On pancake type coils, the thermal conductivity along the tapes (coil's azimuthal direction) is mostly fixed by the 2G-HTS tape characteristics, so that the reduction of anisotropy relies on the improvement of the radial thermal conductivity, which depends on the used materials between superconducting tapes, as well as on the winding and impregnation processes. In this contribution, we have explored two possibilities for such anisotropy reduction: by using anodised aluminium or stainless steel tapes co-wound with the 2G-HTS tapes. For all the analysed coils, critical current distribution, minimum quench energy values and both tangential and radial quench propagation velocities at different temperatures and currents are reported and compared with the results of similar coils co-wound with polyimide (KaptonÂź) tapes.This work was supported by the Spanish Ministerio de EconomĂa y Competitividad and the European FEDER Program (Projects MAT2011-22719 and ENE-2014-52105-R), and by the Gobierno de AragĂłn (research group T12).Peer reviewe
The physical acceptability conditions and the strategies to obtain anisotropic compact objects
We studied five methods to include anisotropy, or unequal stress
distributions, in general relativistic matter configurations. We used nine
acceptability conditions that the metric and physical variables must meet to
determine if our models were astrophysically viable. Our analysis found the
most effective way to introduce anisotropy while keeping a simple density
profile. We also found a practical "rule of thumb" that relates the density at
the boundary to the density at the centre of relativistic matter distributions.
Additionally, we calculated the configuration radius and encountered that
values observed by NICER for PSR J0740+6620 are consistent with several
acceptable matter configurations, both isotropic and anisotropic.Comment: 20 pages, 3 figures. Typo correctio
- âŠ