General integral relations for the description of scattering states using the hyperspherical adiabatic basis

In this work we investigate 1+2 reactions within the framework of the hyperspherical adiabatic expansion method. To this aim two integral relations, derived from the Kohn variational principle, are used. A detailed derivation of these relations is shown. The expressions derived are general, not restricted to relative $s$ partial waves, and with applicability in multichannel reactions. The convergence of the ${\cal K}$-matrix in terms of the adiabatic potentials is investigated. Together with a simple model case used as a test for the method, we show results for the collision of a $^4$He atom on a \dimer dimer (only the elastic channel open), and for collisions involving a $^6$Li and two $^4$He atoms (two channels open).Comment: Accepted for publication in Physical Review

Variational description of continuum states in terms of integral relations

Two integral relations derived from the Kohn Variational Principle (KVP) are used for describing scattering states. In usual applications the KVP requires the explicit form of the asymptotic behavior of the scattering wave function. This is not the case when the integral relations are applied since, due to their short range nature, the only condition for the scattering wave function $\Psi$ is that it be the solution of $(H-E)\Psi=0$ in the internal region. Several examples are analyzed for the computation of phase-shifts from bound state type wave functions or, in the case of the scattering of charged particles, it is possible to obtain phase-shifts using free asymptotic conditions. As a final example we discuss the use of the integral relations in the case of the Hyperspherical Adiabatic method.Comment: 34 pages, 7 figures, accepted in Phys. Rev.

Protocolo de actuación ante hemangiomas y/o malformaciones vasculares

When facing any vascular lesion present in the first moments of life, it is necessary to determine whether one is dealing with a tumour or a vascular malformation, given the different evolution of both processes and, hence, the different treatments they require. Diagnosis is basically clinical, based on a correct anamnesis and a detailed physical exploration. The first thing is to establish whether the lesion was present at birth and has changed size significantly, which would lead one to think of a haemangioma or, on the contrary, whether it is congenital and of very slow growth, such as vascular malformations. Facing dubious lesions, it is recommendable to carry out a biopsy with immunohistochemistry for the GLUT-1 antibody, specific to haemangiomas. Amongst the image tests, the first choice is usually ecography-Doppler, which makes it possible to determine whether the lesion is of high or low flow and to distinguish whether one is dealing with a haemangioma or a vascular malformation. Depending on the type of lesion, its localisation and degree of affectation it might be necessary to carry out radiography, magnetic resonance, phlebography, angio-resonance, arteriography or lymphoscintigraphy to complete the study. In more particular cases, such as multiple haemangiomatosis, it is necessary to carry out an hepatic echography, blood concealed in faeces, gastroscopy and colonoscopy, as well a determination of thyroid hormones; and in venous or combined extensive malformations, a haemogram and coagulation tests. On the other hand, the possible repercussions on other organs make a multidisciplinary approach essential, with the participation of different specialists. Due to the wide spectrum covered by vascular anomalies, treatment must be individualised

An experimental model of mixing processes generated by an array of top-heavy turbulent plumes

The mixing process of two fluids of unequal density generated by the evolution of an array of forced turbulent plumes is studied in the laboratory. The corresponding qualitative conclusions and the quantitative results based on measures of the density field and of the height of the fluid layers are described. The partial mixing process is characterized and analyzed, and the conclusions of this analysis are related to the mixing efficiency and the volume of the final mixed layer as functions of the Atwood number, which ranges from 0.010 to 0.134. An exponential fit is used to evaluate the mixing efficiency versus the Atwood showing the role of initial conditions on mixing efficiency variability

Induced structures under seasonal flow conditions in the Ebro delta shelf. Laboratory and numerical models

The characteristic induced length scale produced by a river flow in its outlet is studied. Two experimental methods are compared: a) Physical modeling in laboratory and b) numerical mesoscale diffusion model; under low tidal and realistic seasonal flow conditions from Spring, Summer, Fall and Winter field data from the Ebro delta shelf. The physical laboratory experiences were performed on a five-meter diameter turntable, using the Froude-Rossby similarity. This paper shows complementary results from both methods investigating the vortex characteristic and the dynamics of the flow. The experimental results under rotating conditions show coherent vortex dynamics in the large-meso scale coastal boundary. The numerical model, on the other hand, lacks the mesoscale vortex dynamics and its induced diffusion but gives reasonable flow conditions in the close region (15–20 km) around the river mouth. Both the experiments and numerical simulations show river plume diffusion smaller than D2 ∝ t3

Particle dispersion processes in two-dimensional turbulence: a comparison with 2-D kinematic simulation.

International audienceWe study numerically the comparison between Lagrangian experiments on turbulent particle dispersion in 2-D turbulent flows performed, on the one hand, on the basis of direct numerical simulations (DNS) and, on the other hand, using kinematic simulations (KS). Eulerian space-time structure of both DNS and KS dynamics are not comparable, mostly due to the absence of strong coherent vortices and advection processes in the KS fields. The comparison allows to refine past studies about the contribution of non-homogeneous space-time 2-D Eulerian structure on the turbulent absolute and relative particle dispersion processes. We particularly focus our discussion on the Richardson's regime for relative dispersion

Predicting the spread of epidemiological diseases by using a multi-objective algorithm

The epidemiological models are able to predict the spread of diseases, but a previous work on calibrating some involved parameters must be done. In this work, we propose a methodology to adjust those parameters based on solving a multi-objective optimization problem whose objective functions measure the accuracy of the model. More precisely, we have considered the Between-Countries Disease Spread model because it involves a set of countries taking into account the migratory movements among them. As a result, using some real data about the number of detected cases and the number of deaths for the Ebola virus disease, we have shown that the methodology is able to find a set of values for the parameters so that the model fits the outbreak spread for a set of countries

Integral relations for three-body continuum states with the adiabatic expansion

Application of the Hyperspherical Adiabatic expansion to describe three-body scattering states suffers the problem of a very slow convergence. Contrary to what happens for bound states, a huge number of hyperradial equations has to be solved, and even if done, the extraction of the scattering amplitude is problematic. In this paper we show how to obtain accurate scattering phase shifts using the Hyperspherical Adiabatic expansion. To this aim two integral relations, derived from the Kohn Variational Principle, are used. The convergence of this procedure is as fast as for bound states.Comment: 4 pages, 1 figur

Application of Resonance Perturbation Theory to Dynamics of Magnetization in Spin Systems Interacting with Local and Collective Bosonic Reservoirs

We apply our recently developed resonance perturbation theory to describe the dynamics of magnetization in paramagnetic spin systems interacting simultaneously with local and collective bosonic environments. We derive explicit expressions for the evolution of the reduced density matrix elements. This allows us to calculate explicitly the dynamics of the macroscopic magnetization, including characteristic relaxation and dephasing time-scales. We demonstrate that collective effects (i) do not influence the character of the relaxation processes but merely renormalize the relaxation times, and (ii) significantly modify the dephasing times, leading in some cases to a complicated (time inhomogeneous) dynamics of the transverse magnetization, governed by an effective time-dependent magnetic field