Spectrum of the Relativistic Particles in Various Potentials

We extend the notion of Dirac oscillator in two dimensions, to construct a set of potentials. These potentials becomes exactly and quasi-exactly solvable potentials of non-relativistic quantum mechanics when they are transformed into a Schr\"{o}dinger-like equation. For the exactly solvable potentials, eigenvalues are calculated and eigenfunctions are given by confluent hypergeometric functions. It is shown that, our formulation also leads to the study of those potentials in the framework of the supersymmetric quantum mechanics

Calculation of the energy spectrum of a two-electron spherical quantum dot

We study the energy spectrum of the two-electron spherical parabolic quantum dot using the exact Schroedinger, the Hartree-Fock, and the Kohn-Sham equations. The results obtained by applying the shifted-1/N method are compared with those obtained by using an accurate numerical technique, showing that the relative error is reasonably small, although the first method consistently underestimates the correct values. The approximate ground-state Hartree-Fock and local-density Kohn-Sham energies, estimated using the shifted-1/N method, are compared with accurate numerical self-consistent solutions. We make some perturbative analyses of the exact energy in terms of the confinement strength, and we propose some interpolation formulae. Similar analysis is made for both mean-field approximations and interpolation formulae are also proposed for these exchange-only ground-state cases.Comment: 18 pages, LaTeX, 2 figures-ep

Exact solution of the two-dimensional Dirac oscillator

In the present article we have found the complete energy spectrum and the corresponding eigenfunctions of the Dirac oscillator in two spatial dimensions. We show that the energy spectrum depends on the spin of the Dirac particle.Comment: revtex, 6pp. IVIC-CFLE 93/0

Tunneling and transmission resonances of a Dirac particle by a double barrier

We calculate the tunneling process of a Dirac particle across two square barriers separated a distance $d$, as well as the scattering by a double cusp barrier where the centers of the cusps are separated a distance larger than their screening lengths. Using the scattering matrix formalism, we obtain the transmission and reflection amplitudes for the scattering processes of both configurations. We show that, the presence of transmission resonances modifies the Lorentizian shape of the energy resonances and induces the appearance of additional maxima in the transmission coefficient in the range of energies where transmission resonances occur. We calculate the Wigner time-delay and show how their maxima depend on the position of the transmission resonance.Comment: To appear in Physica Script

Bound states of scalar particles in the presence of a short range potential

We analyze the behavior of the energy spectrum of the Klein-Gordon equation in the presence of a truncated hyperbolic tangent potential. From our analysis we obtain that, for some values of the potential there is embedding of the bound states into the negative energy continuum, showing that, in opposition to the general belief, relativistic scalar particles in one-dimensional short range potentials can exhibit resonant behavior and not only the Schiff-Snyder effect.Comment: To appear in Modern Physics Letters

Computation of inflationary cosmological perturbations in chaotic inflationary scenarios using the phase-integral method

The phase-integral approximation devised by Fr\"oman and Fr\"oman, is used for computing cosmological perturbations in the quadratic chaotic inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to fifth order of the phase-integral approximation. We show that, the phase integral gives a very good approximation for the shape of the power spectra associated with scalar and tensor perturbations as well as the spectral indices. We find that the accuracy of the phase-integral approximation compares favorably with the numerical results and those obtained using the slow-roll and uniform approximation methods.Comment: 21 pages, RevTex, to appear in Phys. Rev

Scattering of a Klein-Gordon particle by a Woods-Saxon potential

We solve the Klein-Gordon equation in the presence of a spatially one-dimensional Woods-Saxon potential. The scattering solutions are obtained in terms of hypergeometric functions and the condition for the existence of transmission resonances is derived. It is shown how the zero-reflection condition depends on the shape of the potential.Comment: 10 pages, Revtex. To appear in Phys. Rev.

Component-resolved diagnosis of pollen allergy based on skin testing with profilin, polcalcin and lipid transfer protein pan-allergens

BACKGROUND Allergy diagnosis needs to be improved in patients suffering from pollen polysensitization due to the existence of possible confounding factors in this type of patients. OBJECTIVE To evaluate new diagnostic strategies by comparing skin responses to pan-allergens and conventional allergenic extracts with specific IgE (sIgE) to purified allergen molecules. METHODS One thousand three hundred and twenty-nine pollen-allergic patients were diagnosed by a combination of an in vitro method with a panel of 13 purified allergens, including major allergens and pan-allergens, using a high-capacity screening technology (ADVIA-Centaur®) and skin prick test (SPT) to pan-allergens and conventional extracts. RESULTS There was a high concordance (κ index) between in vitro (sIgE to major allergens) and in vivo (SPT to conventional extracts) methods in patients who were not sensitized to pan-allergens, but SPT with conventional extracts failed to diagnose patients with sensitization to pan-allergens. In patients who were simultaneously sensitized to polcalcins and profilins, there was a duplication both in the number of sensitizations to major allergens and in the years of disease evolution. There was a statistical association between sensitization to profilins and/or lipid transfer proteins and food allergy (P<0.0001). CONCLUSION The novel diagnostic strategy has proven to be a valuable tool in daily clinical practice. Introduction of routine SPT to pan-allergens is a simple and feasible way of improving diagnostic efficacy. Patients sensitized to pan-allergens should be tested by an adequate panel of allergenic molecules in order to identify the allergens that are responsible for the allergic disease

Estimación de la digestibilidad del pasto a partir de la materia seca indigestible a lo largo de la estación de pastoreo

4 páginas, 3 tablas.-- Ponencia presentada a las XIX Jornadas Científicas de la Sociedad Española de Ovinotecnia y Caprinotecnia (Burgos, España, 1994).La determinación de la digestibilidad de los alimentos es el parámetro más utilizado como indicador de su valor nutritivo. Además, en el caso de los rumiantes en pastoreo, es una medida necesaria para estimar la ingestión, a partir de la excreción fecal. Uno de los métodos que se está desarrollando para la determinación de la digestibilidad de los alimentos en los rumiantes, es la utilización de la Materia Seca Indigestible (MSI) como marcador interno. En el presente trabajo se determinó la digestibilidad de un pasto a partir de la MSI presente en heces y extrusa, en 5 momentos durante la época estival: 29 junio al 3 julio (Pl), 20 julio al 24 julio (P2), 24-28 agosto (P3), 21-25 septiembre (P4), 19-23 octubre (P5). Las muestras de heces y extrusa se obtuvieron en un experimento en pastoreo, en el que se utilizaron 4 ovejas merinas provistas de arneses para la recogida de heces, y 3 ovejas, de la misma raza, provistas de una fístula esofágica. Para la determinación de la MSI de las heces y extrusas, las muestras se incubaron, en el rumen de 3 ovejas merinas provistas de una cánula ruminal, utilizando la técnica de las Bolsas de Nylon, durante 192h. Los coeficientes de digestibilidad obtenidos fueron diferentes en los distintos períodos estudiados (P<0.001). Los valores encontrados fueron de 56.4%, 70.5%, 78.4%, 68.1%, 63.4%, en los períodos Pl, P2, P3, P4, P5 respectivamente. El % de MSI, en las heces obtenidas en los períodos estudiados, no presentó diferencias estadísticamente significativas, mientras que este efecto tuvo una marcada influencia sobre el % de MSI presente en las extrusas.Peer reviewe