Self-Consistent Schrödinger-Poisson Study of Electronic Properties of GaAs Quantum Well Wires with Various Cross-Sectional Shapes.

Quantum wires continue to be a subject of novel applications in the fields of electronics and optoelectronics. In this work, we revisit the problem of determining the electron states in semiconductor quantum wires in a self-consistent way. For that purpose, we numerically solve the 2D system of coupled Schrödinger and Poisson equations within the envelope function and effective mass approximations. The calculation method uses the finite-element approach. Circle, square, triangle and pentagon geometries are considered for the wire cross-sectional shape. The features of self-consistent band profiles and confined electron state spectra are discussed, in the latter case, as functions of the transverse wire size and temperature. Particular attention is paid to elucidate the origin of Friedel-like oscillations in the density of carriers at low temperatures.

Shallow Donor Impurity States with Excitonic Contribution in GaAs/AlGaAs and CdTe/CdSe Truncated Conical Quantum Dots under Applied Magnetic Field.

Using the effective mass approximation in a parabolic two-band model, we studied the effects of the geometrical parameters, on the electron and hole states, in two truncated conical quantum dots: (i) GaAs-(Ga,Al)As in the presence of a shallow donor impurity and under an applied magnetic field and (ii) CdSe-CdTe core-shell type-II quantum dot. For the first system, the impurity position and the applied magnetic field direction were chosen to preserve the system's azimuthal symmetry. The finite element method obtains the solution of the Schrödinger equations for electron or hole with or without impurity with an adaptive discretization of a triangular mesh. The interaction of the electron and hole states is calculated in a first-order perturbative approximation. This study shows that the magnetic field and donor impurities are relevant factors in the optoelectronic properties of conical quantum dots. Additionally, for the CdSe-CdTe quantum dot, where, again, the axial symmetry is preserved, a switch between direct and indirect exciton is possible to be controlled through geometry.

Escoliosis desarrollo temprano. Curso de instrucción / Early onset scoliosis. Instructional course

Introducción Escoliosis de desarrollo temprano, es aquella escoliosis que se presenta antes de los 10 años de edad secundaria a anomalías estructurales congénitas de la columna, enfermedades neuromusculares, síndromes, o idiopáticamente. Materiales & Métodos Revisión literaria narrativa de todo lo publicado sobre escoliosis de desarrollo temprano durante 2003 al 2018. Resultados Esta deformidad de la columna a temprana edad limitara el crecimiento pulmonar e incapacitara la función respiratoria apropiada, provocando el síndrome de insuficiencia torácica. Históricamente, la historia natural de esta condición puede ser letal y el daño ocasionado por la escoliosis de desarrollo temprano suele ser permanente a pesar de su restauración. Actualmente, la escoliosis de desarrollo temprano se clasifica utilizando la combinación de las variables: edad, etiología, magnitud de la escoliosis y cifosis. Los métodos de tratamiento más utilizados son: enyesado en serie, implantes de distracción costal longitudinal en aleación de titanio, barras de crecimiento dobles, técnica de Shilla™, y barras de crecimiento electromagnéticas. Discusión Indudablemente, es imperativo conocer sus manifestaciones y peculiaridades para poder clasificar, monitorear la severidad, personalizar el tratamiento, detener el deterioro de la columna lo más pronto posible, y prevenir la insuficiencia respiratoria Nivel de evidencia IV

Background Early onset scoliosis presents before the age of 10 years old due to congenital structural anomalies of the thorax, neuromuscular diseases, and syndromes, or is idiopathic. Methods A review of the literature from 2003 to 2018 on the early onset scoliosis. Result A deformity of the spine at an early age limits lung development and proper respiratory function, thereby provoking the onset of a thoracic insufficiency syndrome. Historically, the natural path of this condition can be lethal, and the damage caused by the early onset scoliosis tends to be permanent, regardless of its restoration after the age of 10. The early onset scoliosis classification is currently based on the age, aetiology, and the extent of the deformity. The treatment modalities most often used are: serial casts, vertical expandable prosthetic titanium ribs, double traditional growing rods, Shilla™ growing rods, and magnetically controlled growing rods. Discussion Undoubtedly, it is imperative to know its manifestations and peculiarities in order to classify the disease, as well as to monitor the disease. Treatment should be personalised, and the deterioration of the spine halted as soon as possible, as well as to prevent respiratory insufficiency Level of evidence IV

Donor impurity-related linear and nonlinear intraband optical absorption coefficients in quantum ring: effects of applied electric field and hydrostatic pressure.

: The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum.