Relativistic Coulomb excitation of the giant dipole resonance in nuclei: How to calculate transition probabilities without invoking the Liénard-Wiechert relativistic scalar and vector potentials

The conclusions extracted from a recent study of the excitation of giant dipole resonances in nuclei at relativistic bombarding energies open the way for a further simplification of the problem. It consists in the elimination of the relativistic scalar and vector electromagnetic potentials and the familiar numerical difficulties associated with their presence in the calculation scheme. The inherent advantage of a reformulation of the problem of relativistic Coulomb excitation of giant dipole resonances along these lines is discussed.Ministerio de Educación y Ciencia IS2005-01105 FPA2005-0446

Relativistic Coulomb excitation of the giant dipole resonance in nuclei: A straightforward approach

We investigate alternatives to the standard formalism used for the study of relativistic Coulomb excitation of the giant dipole resonance in nuclei. The idea is to obtain reasonable results for the probabilities of excitation and cross sections to the one-phonon and two-phonon levels avoiding the substantial complexity of the treatments exploited so far. This is achieved for the relevant range of partial waves up to bombarding energies of at least 5 GeV per nucleon. The transfer of energy to the center of mass of the excited nuclei is also investigated

Macroscopic pairing vibrational model, self-consistent pairing coupling constant, and the fifth term of von Weizs ̈ acker’s semiempirical formula

The implementation of a number-conserving formalism for pair-addition and pair-removal modes has impaired the possibility of developing an intuitive and self-consistent picture for collective pairing modes. In this paper, we show how a relaxation of this constraint leads to a unified model with true predictive poweFEDER y Ministerio de Educación y Ciencia FIS2005-01105 FPA2005-0446

GEANT4 application for the simulation of the head of a siemens primus linac

The Monte Carlo simulation of the head of a Siemens Primus Linac used at Virgen Macarena Hospital (Sevilla, Spain) has been performed using the code GEANT4 [1-2], version 9.2. In this work, the main features of the application built by our group are presented. They are mainly focused in the optimization of the performance of the simulation. The geometry, including the water phantom, has been entirely wrapped by a shielding volume which discards all the particles escaping far away through its walls. With this, a factor of four in the time spent by the simulation can be saved. An interface to read and write phase-space files in IAEA format has been also developed to save CPU time in our simulations [3-4]. Finally, some calculations of the dose absorption in the water phantom have been done and compared with the results given by EGSnrc [5] and with experimental data obtained for the calibration of the machine

Semiclassical calculation of heavy-ion scattering in the chaotic regime

The semiclassical approach has proven to be a most valuable tool for the construction of the scattering matrix and accurate evaluation of cross sections in a large variety of heavy-ion collision problems. In its familiar implementation, however, its use is restricted to what is now known as the "regular regime", as it makes use of classical reaction functions that must be continuous and interpolable. In this paper we identify what version of the semiclassical formalisms may be especially suitable for extension into the chaotic regime that develops at energies close to the Coulomb barrier. We also show the crucial role of the absorptive part of the ion-ion potential to retain the usefulness of the semiclassical methods under conditions of irregularity.Ministerio de Educación y Ciencia FIS2005-01105 FPA2005-0446

Selective nuclear transparency induced by chaotic scattering

We investigate the effects of nuclear absorption on the population of intrinsic vibrational states in scattering processes involving heavy ions. It is found that at the classical level the removal of flux assumes a qualitatively different form in the regular or chaotic regimes. Specifically, it is shown how certain reaction channels turn out to be—in the latter case—relatively insensitive to the strength of the absorptive potential. This realization has a counterpart at the quantum level where, at the chaotic layer, conditions of selective transparency in the nuclear system are enforced.DFG Bo 1109/1CONYCET Pid. 3233/92EU Network Contract CHRX-CT92-0075Comisión Interministerial de Ciencia y Tecnología PB95-0533-

Oral lichenoid lesions related to contact with dental materials: A literature review

Oral lichenoid lesions related to contact are defined as oral-cavity eruptions with an identifiable etiology, and are clinically and histologically similar to oral lichen planus. Within this group are found oral lichenoid lesions related to contact with dental materials (OLLC), the most common being those related to silver amalgam. Currently, it remains difficult to diagnose these lesions due to the clinical and histopathological similarity with oral lichen planus and other oral mucosa lesions of lichenoid characteristics. In the present paper, we carry out an updated review of the tests for, and the different characteristics of OLLC, which may aid the diagnosis. For this review, we made searches in the Pubmed® and Cochrane® databases. Among the literature we found several published papers, from which we have used review papers, case papers, cohort studies, case and control studies, and a meta-analysis study. After carrying out this review, we can conclude that the diagnosis of these lesions is still difficult and controversial. However, there are different aspects in the clinical presentation, pathological study and results obtained when replacing suspect materials, which, when taken together, may be useful when establishing the final diagnosis of OLLC

Comment on “Pairing interaction and Galilei invariance”

A recent article by Dussel, Sofia, and Tonina studies the relation between Galilei invariance and dipole energy weighted sum rule (EWSR). The authors find that the pairing interaction, which is neither Galilei nor Lorentz invariant, produces big changes in the EWSR and in effective masses of the nucleons. They argue that these effects of the pairing force could be realistic. In this Comment we stress the validity of Galilei invariance to a very good approximation in this context of low-energy nuclear physics and show that the effective masses and the observed change in the EWSR for the electric dipole operator relative to its classical value are compatible with this symmetry.Dirección General de Investigación Científica y Técnica PB95-0533European Commission CI1*-CT94-007

Chemiluminescence as a screening method in oral cancer

El cáncer oral es un problema de salud con el que nos enfrentamos todos los días en nuestras consultas. Los dentistas formamos la primera línea de defensa ante una patología que no ha presentado una mejora de los índices de mortalidad y morbilidad en las últimas décadas. La principal arma con la que contamos es la del diagnóstico precoz de la enfermedad, y esto es mucho más complicado de lo que parece. Para ayudar a los dentistas en la visualización de lesiones de precáncer o cáncer temprano han aparecido algunas técnicas o dispositivos de screening de cáncer oral basadas en la interacción de los tejidos orales con la luz. La técnica más extendida y estudiada es la basada en la quimioluminiscencia, intentaremos poner en claro algunos aspectos analizando los estudios que hay en la literatura actual.Oral cancer is a health problem with which we face every day in our consultations. Dentists form the first line of defense against a disease that has not produced an improvement in mortality and morbidity in recent decades. The main weapon with which we have is the early diagnosis of the disease, and this is much more complicated than it seems. To assist dentists in the visualization of pre-cancer lesions or early cancer have appeared some techniques and devices for oral cancer screening based on interaction of the oral tissues with light. The most widely used and studied technique is based on the chemiluminescence. Above it has been much talk and try to clarify some aspects of the studies that are analyzing the current literature

Lesiones liquenoides orales asociadas a metales presentes en una prótesis parcial removible tipo esquelético: a propósito de un caso

Las reacciones alérgicas de contacto intraoral se atribuyen con frecuencia a materiales de uso odontológico. Aunque se consideran poco frecuentes, existen muchas publicaciones de reacciones a materiales de restauración, sobre todo a la amalgama. En cambio, resulta muy difícil encontrar referencias en la literatura de este tipo de reacciones a metales presentes en aleaciones metálicas de prótesis dentales. Presentamos el caso de una mujer de 60 años que presenta lesiones de tipo liquenoide en paladar duro y en reborde alveolar, todas las lesiones se hallaban bajo la base de la prótesis. Se realiza una biopsia incisional y el estudio histopatológico mostró cambios compatibles con liquen plano oral. Las pruebas epicutáneas mostraron una sensibilización a cloruro de cobalto, amonio hexacloroplatinato y cloruro de aluminio. Como medidas terapéuticas se recomendó retirar la prótesis y recambiar las obturaciones de amalgama, consiguiendo una mejoría considerable en las lesiones y la sintomatología que presentaba la paciente.Intraoral contact allergy reactions often attributed to dental materials. Although appear to be less frequent, there are many published papers of reactions to dental restorative materials, mercury amalgam being the most common. However, it is very difficult to find references in the literature about these reactions to metals presents in metal alloys of dental prosthesis. We report a clinical case of a 60 year-old woman with oral lichenoid lesions located in hard palate and alveolar ridge, all lesions were located under the base of the prosthesis. Incisional biopsy was made and the histopathological study revealed changes compatible with oral lichen planus. The epicutaneous test showed a sensitivity to chloride of cobalt, ammonium hexacloroplatinato and chloride of aluminium. Treatment consisted of the removal the prosthesis and amalgam fillings, obtaining a considerable improvement in lesions and symptoms of patient