Collective oscillations in quantum rings: a broken symmetry case

We present calculations within density functional theory of the ground state and collective electronic oscillations in small two-dimensional quantum rings. No spatial symmetries are imposed to the solutions and, as in a recent contribution, a transition to a broken symmetry solution in the intrinsic reference frame for an increasingly narrow ring is found. The oscillations are addressed by using real-time simulation. Conspicuous effects of the broken symmetry solution on the spectra are pointed out.Comment: ReVTeX, 5 embedded eps, two gifs. Accepted in EPJ

Electron spin precession in semiconductor quantum wires with Rashba spin-orbit coupling

The influence of the Rashba spin-orbit coupling on the electron spin dynamics is investigated for a ballistic semiconductor quantum wire with a finite width. We monitor the spin evolution using the time-dependent Schr\"odinger equation. The pure spin precession characteristic of the 1D limit is lost in a 2D wire with a finite lateral width. In general, the time evolution in the latter case is characterized by several frequencies and a nonrigid spin motion.Comment: 7 pages, 9 figure

Characterization of Bernstein modes in quantum dots

The dipole modes of non-parabolic quantum dots are studied by means of their current and density patterns as well as with their local absorption distribution. The anticrossing of the so-called Bernstein modes originates from the coupling with electron-hole excitations of the two Landau bands which are occupied at the corresponding magnetic fields. Non-quadratic terms in the potential cause an energy separation between bulk and edge current modes in the anticrossing region. On a local scale the fragmented peaks absorb energy in complementary spatial regions which evolve with the magnetic field.Comment: 6 pages; embedded figs. 1-3; figs. 4, 5 separate files; accepted in EPJ-

Chaotic spin-dependent electron dynamics in a field-driven double dot potential

We study the nonlinear classical dynamics of an electron confined in a double dot potential and subjected to a spin-orbit coupling and a constant external magnetic field. It is shown that due to the spin orbit coupling, the energy can be transferred from the spin to the orbital motion. This naturally heats up the orbital motion which, due to the presence of the separatrix line in the phase space of the system, results in a motion of the electron between the dots. It is shown that depending on the strength of the spin orbit coupling and the energy of the system, the electronic orbital motion undergoes a transition from the regular to the chaotic regime.Comment: 15 pages, 5 figure

Resultados del tratamiento antituberculoso en España por grupos de edad. Factores de riesgo para los resultados potencialmente insatisfactorios

[ES] En este trabajo se analizaron los factores que influyen en los resultados potencialmente insatisfactorios (RPI) del tratamiento antituberculoso por grupos de edad a partir de los casos de tuberculosis declarados a la Red Nacional de Vigilancia Epidemiológica (RENAVE) en 2012. Se consideraron RPI a los fracasos terapéuticos, traslados, defunciones, abandonos, tratamientos prolongados y desconocidos; y satisfactorios (RS) a la curación y tratamiento completo. Los casos se clasificaron en cuatro grupos de edad (0-14 años, 15-44, 45-64 y mayores de 65). Se analizó la asociación del RPI vs. RS con las variables de la declaración en cada uno de los grupos de edad, calculándose las OR crudas (ORc) y ajustadas (ORa) mediante un análisis bivariado y por regresión logística. De los 5.880 casos incluidos en el estudio el 80% tenían un RS. Por grupos de edad, los RS fueron 90, 83, 80 y 70% en los grupos de 0-14, 15-44, 45-64 y > 65 respectivamente. En adultos de 45 a 64 años los principales riesgos de RPI (p < 0,05) fueron ser hombre (ORc=1,47, ORa=1,39), tener un tratamiento previo (ORc=2,29, ORa=1,94) y ser VIH positivo (ORc=1,99, ORa=1,98), y en adultos jóvenes (15-44 años), además de los anteriores, el ser de origen extranjero (ORc=1,84, ORa=1,84). El 19% de los casos mayores de 65 años fallecieron durante el tratamiento. Es necesario mejorar el manejo de los casos VIH positivos y tratados previamente, así como el seguimiento de los casos en extranjeros. [EN] In this article the risk factors for unsuccessful completion of treatment by age group are analyzed. The source of data is tuberculosis (TB) cases reported to the Spanish Surveillance Epidemiological Network in 2012. Outcomes were classified as: successful (S: cured and treatment completed) and potentially unsuccessful (PU: failed, transferred, deaths, defaulted, still on treatment and unknown). Age groups used for the analysis were: 0-14, 15-44, 45-64 and >65 years. Bivariate (crude Odds Ratio, cOR) and multivariate analysis (adjusted Odds Ratio, aOR) by logistic regression was used to explore the association between epidemiological and clinical factors with PU as outcome variable. The study included 5,880 TB cases. Successful outcome was 80% for the total and 90, 83, 80 and 70% in 0-14, 15-44, 45-64 and >65 age groups respectively. Risk factors (

Tuberculosis treatment outcome by age group in Spain. Risk factors for potentially unsuccessful results

[ES] En este trabajo se analizaron los factores que influyen en los resultados potencialmente insatisfactorios (RPI) del tratamiento antituberculoso por grupos de edad a partir de los casos de tuberculosis declarados a la Red Nacional de Vigilancia Epidemiológica (RENAVE) en 2012. Se consideraron RPI a los fracasos terapéuticos, traslados, defunciones, abandonos, tratamientos prolongados y desconocidos; y satisfactorios (RS) a la curación y tratamiento completo. Los casos se clasificaron en cuatro grupos de edad (0-14 años, 15-44, 45-64 y mayores de 65). Se analizó la asociación del RPI vs. RS con las variables de la declaración en cada uno de los grupos de edad, calculándose las OR crudas (ORc) y ajustadas (ORa) mediante un análisis bivariado y por regresión logística. De los 5.880 casos incluidos en el estudio el 80% tenían un RS. Por grupos de edad, los RS fueron 90, 83, 80 y 70% en los grupos de 0-14, 15-44, 45-64 y >65 respectivamente. En adultos de 45 a 64 años los principales riesgos de RPI (p<0,05) fueron ser hombre (ORc=1,47, ORa=1,39), tener un tratamiento previo (ORc=2,29, ORa=1,94) y ser VIH positivo (ORc=1,99, ORa=1,98), y en adultos jóvenes (15-44 años), además de los anteriores, el ser de origen extranjero (ORc=1,84, ORa=1,84). El 19% de los casos mayores de 65 años fallecieron durante el tratamiento. Es necesario mejorar el manejo de los casos VIH positivos y tratados previamente, así como el seguimiento de los casos en extranjeros. [EN] In this article the risk factors for unsuccessful completion of treatment by age group are analyzed. The source of data is tuberculosis (TB) cases reported to the Spanish Surveillance Epidemiological Network in 2012. Outcomes were classified as: successful (S: cured and treatment completed) and potentially unsuccessful (PU: failed, transferred, deaths, defaulted, still on treatment and unknown). Age groups used for the analysis were: 0-14, 15-44, 45-64 and >65 years. Bivariate (crude Odds Ratio, cOR) and multivariate analysis (adjusted Odds Ratio, aOR) by logistic regression was used to explore the association between epidemiological and clinical factors with PU as outcome variable. The study included 5,880 TB cases. Successful outcome was 80% for the total and 90, 83, 80 and 70% in 0-14, 15-44, 45-64 and >65 age groups respectively. Risk factors (p<0.05) for PU in 45-64 age group were: male sex (cOR=1.47, aOR=1.39), previous treatment (cOR=2.29, aOR=1.94), HIV coinfection (cOR=1.99, aOR=1.98) and additionally foreign origin in 15-44 age group (cOR=1.84, aOR=1.84). Mortality rate in over 65 group was 19%. Improvements in the management of HIV co-infected and previously treated cases and better follow-up in foreigners are needed in Spain.N

Supersymmetry approach to nuclear-spin-polarization-induced quantum dot structure calculations

In nuclear-spin-polarization-induced quantum dots the electrons are confined through local nuclear spin polarization. The model electron confinement potential is time-dependent due to the nuclear spin diffusion and relaxation processes. It can be well-approximated by a Gaussian curve which is not an exactly solvable potential. We demonstrate that it can also be approximated by multisoliton potentials for the zero value of the angular momentum and by their singular analogues for other values of momentum without any loss of calculational accuracy. We obtain these potentials by supersymmetric (or equivalently Darboux) transformations from the zero potential. The main advantage of such potentials is that they are exactly solvable. Time-dependence of the nuclear-spin-polarization-induced quantum dot energy levels is found.Comment: Physica E (in press) (2005

Epidemiology of childhood tuberculosis in Spain: 2005-2009

BACKGROUND: European recent data about paediatric tuberculosis point out the importance of evaluate the trends of the disease to study the recent transmission, as well as the necessity of improving the microbiological diagnosis in paediatric cases. The aim of this paper is to study the epidemiology and trend evolution of paediatric tuberculosis in Spain during the period 2005-2009 and to establish the epidemiological differences between adult and paediatric tuberculosis. METHODS: Data reported to the National Surveillance Net (Red Nacional de Vigilancia Epidemiológica) in Spain was checked. Lineal regression was developed to establish the trend of the disease in all, adult and paediatric cases. Bivariate and multivariate logistic regression was used to compare paediatric and adult cases reported in 2009 and estimate the influence of different factors in the development of the disease. RESULTS: A total 39775, 2690 paediatrics (6.76%) cases of tuberculosis were reported during 2005-2009 period. Paediatric tuberculosis rates showed a slight increasing tendency (y=0.15x+7.8), while adult rates decrease during the period (y=-0.28x+20.2). In 2009, rates were 8.1 and 18.3 cases/100,000 inhab. for children and adults respectively. Paediatric cases presented higher proportion of pulmonary locations (84% vs. 76% in adults) and lower percentages of cases confirmed by culture (51% vs. 82% in adults) and of cases in non-Spanish population (25% vs. 34%). CONCLUSIONS: Paediatric tuberculosis rates showed a slight increasing tendency, while global and adult rates decrease slightly during the period. Tuberculosis disease shows different epidemiology in children and adults, what it is important to take into account to design public heh interventions

Quantum dot with spin-orbit interaction in noncommutative phase space and analog Landau levels

We have studied a quantum dot with Rashba spin orbit interaction on a plane where the position and momentum coordinates are considered to be noncommutative. The energy spectrum of the system is found to be equivalent to that of a quantum dot with Rashba spin-orbit interaction in a magnetic field under certain conditions.Comment: 12 page