Some Extensions of M-Fractions Related to Strong Stieltjes Distributions

The purpose of this paper is to show the symmetric relations that appear between the coefficients of some even and odd extensions of the M-fractions related to a certain kind of symmetric strong Stieltjes distribution.

Virtual states of light non-Borromean halo nuclei

It is shown that three-body non-Borromean halo nuclei like 12Be, 18C, 20C, considered as neutron-neutron-core systems, have p-wave virtual states with energy of about 1.7 times the corresponding neutron-core binding energy. We use a renormalizable model that guarantees the general validity of our results in the context of short range interactions.

On computing discriminants of subfields of ℚ (ζp r)

The conductor-discriminant formula, namely, the Hasse Theorem, states that if a number field K is fixed by a subgroup H of Gal(ℚ(ζn)/ℚ), the discriminant of K can be obtained from H by computing the product of the conductors of all characters defined modulo n which are associated to K. By calculating these conductors explicitly, we derive a formula to compute the discriminant of any subfield of ℚ(ζpr), where p is an odd rime and r is a positive integer. © 2002 Elsevier Science USA.

Magnetic domain states in nano-sized Co nuclei electrodeposited onto monocrystalline silicon

In the present work, nano-sized magnetic nuclei of Co have been electrodeposited onto p-Si (111). The deposition follows a mechanism of progressive nucleation and growth controlled by diffusion. MFM studies showed that the transition between magnetic domain states is strongly dependent on the size and shape of the nuclei. A critical height h0 is defined below which the nuclei presented always a single-domain configuration. The limiting lower boundary for the single-domain state calculated from the theory is quantitatively coincident with the experimental results. © 2004 Elsevier B.V. All rights reserved.

Neutron-neutron correlations in light exotic nuclei

For light exotic nuclei modeled as two neutrons n and a core A, we report results for the two-neutron correlation functions and also for the mean-square radii, considering a universal scaling function. The results of our calculations for the neutron-neutron correlation functions are qualitatively consistent with recent data obtained for 11Li and 14Be nuclei. The root-mean-square distance in the halo of such nuclei are also consistent with data, which means that the neutrons of the halo have a large probability to be found outside the interaction range. Therefore the low-energy properties of these halo neutrons are, to a large extend, model independent as long as few physical input scales are fixed. The model is restricted to s-wave subsystems, with small energies for the bound or virtual states. For the radii we are also shown results for the 6He and 20C. All the interaction effects, as higher partial wave in the interaction and/or Pauli blocking effect are, to some extend, included in our model, as long as the three-body binding energy is supplied. © 2005 American Institute of Physics.

Mapping deformed hyperbolic potentials into nondeformed ones

In this work we introduce a mapping between the so-called deformed hyperbolic potentials, which are presenting a continuous interest in the last few years, and the corresponding nondeformed ones. As a consequence, we conclude that these deformed potentials do not pertain to a new class of exactly solvable potentials, but to the same one of the corresponding nondeformed ones. Notwithstanding, we can reinterpret this type of deformation as a kind of symmetry of the nondeformed potentials. © 2005 Elsevier B.V. All rights reserved.

Role of transitional levels in Np237 (γ,f): Perspectives for studying highly deformed systems

The transition levels at the top of the two Np237 fission barriers were obtained for the first time by means of the so-called semimicroscopic combined method, which we have developed and implemented. To overcome the difficulties in dealing with large nuclear deformations, we used our developed BARRIER code, which calculates single-particle spectra in a deformed Woods-Saxon potential using a coordinate system based on Cassini ovaloids as nuclear shape parametrization. The results enabled us to describe the experimentally observed near-barrier photofission cross-section structures for Np237, as well as a subbarrier shelf, the latter being consistently interpreted in terms of the accumulation of levels at the top of the inner and outer double fission barrier of Np237. © 2006 The American Physical Society.

Low-cost PWM speed controller for an electric mini-baja type vehicle

This paperwork presents a Pulse Width Modulation (PWM) speed controller for an electric mini-baja-type car. A battery-fed 1-kW three-phase induction motor provides the electric vehicle traction. The open-loop speed control is implemented with an equal voltage/frequency ratio, in order to maintain a constant amount of torque on all velocities. The PWM is implemented by a low-cost 8-bit microcontroller provided with optimized ROM charts for distinct speed value implementations, synchronized transition between different charts and reduced odd harmonics generation. This technique was implemented using a single passenger mini-baja vehicle, and the essays have shown that its application resulted on reduced current consumption, besides eliminating mechanical parts. Copyright © 2007 by ABCM.

The surface geometry of exotic nuclei

We analyze the surface geometry of the spherical even-even Ca, Ni, Sn and Pb nuclei using two approaches: The relativistic Dirac-Hartree-Bogoliubov one with several parameter sets and the non-relativistic Hartree-Fock-Bogoliubov one with the Gogny force. The proton and neutron density distributions are fitted to two-parameter Fermi density distributions to obtain the half-density radii and diffuseness parameters. Those parameters allow us to determine the nature of the neutron skins predicted by the models. The calculations are compared with existing experimental data. © 2007 American Institute of Physics.

Spatial characteristics of borromean, tango, samba and all-bound halo nuclei

We report a renormalized zero-range interaction approach to estimate the size of generic weakly bound three-body systems where two particles are identical. We present results for the neutron-neutron root-mean-square distances of the halo nuclei 6He, 11Li, 14Be and 20C, where the systems are taken as two halo neutrons with an inert point-like core. We also report an approach to obtain the neutron-neutron correlation function in halo nuclei. In this case, our results suggest a review of the corresponding experimental data analysis. © 2007 American Institute of Physics.

Exotic neutron-rich nuclei in a three-body model

We present results for spatial distributions of weakly-bound three-body systems, derived from a universal scaling function that depends on the mass ratio of the particles, as well as on the nature of the subsystems. © 2007 American Institute of Physics.

Universalities in halo nuclei

In this contribution I provide an overview of our group papers involving universalities in light exotic nuclei. It is also made a connection of these systems with some weakly bound ultracold molecules. © 2010 American Institute of Physics.

Halo nuclei in a three-body model and universal characteristics of low-energy few-body systems

Within general characteristics of low-energy few-body systems, we revise some well-known correlations found in nuclear physics, and the properties of low-mass halo nuclei in a three-body neutron-neutron-core model. In this context, near the critical conditions for the occurrence of an Efimov state, we report some results obtained for the neutron- 19C elastic scattering. © 2010 American Institute of Physics.

Cellular decomposition of quaternionic spherical space forms

We obtain an explicit cellular decomposition of the quaternionic spherical space forms, manifolds of positive constant curvature that are factors of an odd sphere by a free orthogonal action of a generalized quaternionic group. The cellular structure gives and explicit description of the associated cellular chain complex of modules over the integral group ring of the fundamental group. As an application we compute the Whitehead torsion of these spaces for any representation of the fundamental group. © 2012 Springer Science+Business Media B.V.

Unsupervised segmentation method for cuboidal cell nuclei in histological prostate images based on minimum cross entropy

This paper presents a novel segmentation method for cuboidal cell nuclei in images of prostate tissue stained with hematoxylin and eosin. The proposed method allows segmenting normal, hyperplastic and cancerous prostate images in three steps: pre-processing, segmentation of cuboidal cell nuclei and post-processing. The pre-processing step consists of applying contrast stretching to the red (R) channel to highlight the contrast of cuboidal cell nuclei. The aim of the second step is to apply global thresholding based on minimum cross entropy to generate a binary image with candidate regions for cuboidal cell nuclei. In the post-processing step, false positives are removed using the connected component method. The proposed segmentation method was applied to an image bank with 105 samples and measures of sensitivity, specificity and accuracy were compared with those provided by other segmentation approaches available in the specialized literature. The results are promising and demonstrate that the proposed method allows the segmentation of cuboidal cell nuclei with a mean accuracy of 97%. © 2013 Elsevier Ltd. All rights reserved.