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We theoretically investigate the electron and hole states in a semiconductor quantum dot-quantum ring coupled structure, inspired by the recent experimental report by Elborg and collaborators (2017). The finite element method constitutes the numerical technique used to solve the three-dimensional effective mass equation within the parabolic band approximation, including the effects of externally applied electric and magnetic fields. Initially, the features of conduction electron states in the proposed system appear discussed in detail, under different geometrical configurations and values of the intensity of the aforementioned electromagnetic probes. In the second part, the properties of an electron-hole pair confined within the very kind of structure reported in the reference above are investigated via a model that tries to reproduce as close as possible the developed profile. In accordance, we report on the energies of confined electron and hole, affected by the influence of an external electric field, revealing the possibility of field-induced separate spatial localization, which may result in an indirect exciton configuration. In relation with this fact, we present a preliminary analysis of such phenomenon via the calculation of the Coulomb integral.

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We have theoretically investigated the electronic states in a core/shell pyramidal quantum dot with GaAs core embedded in AlGaAs matrix. This system has a quite similar recent experimental realization through a cone/shell structure [Phys. Status Solidi-RRL 13, 1800245 (2018)]. The research has been performed within the effective mass approximation taking into account position-dependent effective masses and the presence of external electric and magnetic fields. For the numerical solution of the resulting three-dimensional partial differential equation we have used a finite element method. A detailed study of the conduction band states wave functions and their associated energy levels is presented, with the analysis of the effect of the geometry and the external probes. The calculation of the non-permanent electric polarization via the off-diagonal intraband dipole moment matrix elements allows to consider the related optical response by evaluating the coefficients of light absorption and relative refractive index changes, under different applied magnetic field configurations.

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The properties of the conduction band energy states of an electron interacting with a donor impurity center in spherical sector-shaped GaAs-Al0.3Ga0.7As quantum dots are theoretically investigated. The study is performed within the framework of the effective mass approximation through the numerical solution of the 3D Schrödinger equation for the envelope function via the finite element method. The modifications undergone by the spectrum due to the changes in the conical structure geometry (radius and apical angle) as well as in the position of the donor atom are discussed. With the information regarding electron states the linear optical absorption coefficient associated with transition between confined energy levels is evaluated and its features are discussed. The comparison of results obtained within the considered model with available experimental data in GaAs truncated-whisker-like quantum dots shows very good agreement. Besides, our simulation leads to identify the lowest energy photoluminescence peak as donor-related, instead of being associated to acceptor atoms, as claimed after experimental measurement (Hiruma et al. (1995) [14]). Also, a checking of our numerical approach is performed by comparing with analytical solutions to the problem of a spherical cone-shaped GaN with infinite confinement and donor impurity located at the cone apex. Coincidence is found to be remarkable.

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The features of the electron energy spectrum in eccentric two-dimensional GaAs-AlGaAs quantum rings of circular shape are theoretically investigated taking into account the effect of externally applied magnetic and intense laser fields. Analytical expressions for the laser-dressed confining potential in this kind of quantum ring geometry are reported for the first time. Finite element method is used to solve the resulting single-particle effective mass two-dimensional partial differential equation. It is shown that the allowed level spectrum is greatly influence by the external probe as well as by the breaking of geometric symmetry related to the changes in eccentricity. In presence of an intense laser field, the conduction band confining profile suffers strong modifications along the structure, with an additional contribution to symmetry breaking. These modifications of electronic quantum states reflect in the intraband optical absorption. Accordingly, the features of the intraband transitions are discussed in detail, revealing the significant influence of the magnetic field strength and laser field intensity and polarization, together with eccentricity, in the allowing of ground-to-excited states transitions and their corresponding intensities.

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The electronic states in GaAs-AlxGa1-xAs elliptically-shaped quantum rings are theoretically investigated through the numerical solution of the effective mass band equation via the finite element method. The results are obtained for different sizes and geometries, including the possibility of a number of hill-shaped deformations that play the role of either connected or isolated quantum dots (hills), depending on the configuration chosen. The quantum ring transversal section is assumed to exhibit three different geometrical symmetries - squared, triangular and parabolic. The behavior of the allowed confined states as functions of the cross-section shape, the ring dimensions, and the number of hills-like structures are discussed in detail. The effective energy bandgap (photoluminescence peak with electron-hole correlation) is reported as well, as a function of the Al molar fraction.

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PURPOSE AND METHODS: Although lumbar spinal stenosis syndrome is extremely common, considerable controversy continues to surround its classification, diagnosis, and treatment. We retrospectively reviewed the medical charts of 62 patients admitted for lumbar spinal stenosis syndrome, and we compared our findings to those in the literature. There were 31 women and 31 men. Mean age was 71.8 years. The most common symptoms were positional radiculopathy (92%) and low back pain (95%). The more suggestive sign of pseudoclaudication was observed in only 75% of cases, in keeping with earlier studies. Neurologic symptoms consisting primarily in mild motor loss were present in 15 patients. RESULTS: The most common physical finding was pain during spinal extension (70%). Adopting a bent forward position during walking, a very suggestive manifestation, was seen in 15 patients. Imaging study findings included extensive changes in the discs and facet joints, disc protrusion, scoliosis, and degenerative spondylolisthesis. Myelography was rarely needed. There are no criteria sets for lumbar spinal stenosis syndrome. The diagnosis rests on clinical grounds, and extensive imaging studies are usually unnecessary. Our patients were treated with repeated corticosteroid injections into the thecal sac or epidural space and/or into the facet joints. Only eight patients required surgery. CONCLUSION: Our study supports the view that most cases of lumbar spinal stenosis can be managed conservatively.

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The detection of antineutrophil cytoplasmic antibodies is a very important tool for the diagnosis of systemic vasculitis. The specificity and sensitivity of these antibodies depends on the assay utilized for their detection. Therefore we have compared the immunofluorescence test (IF) with the ELISA using two different antigens: total neutrophil extract and isolated primary granules. Two patterns of fluorescence were detected by IF: the classic pattern was highly specific for Wegener's granulomatosis. In contrast the perinuclear staining correlated with renal vasculitis but was also observed in other diseases. However the IF test was unable to differentiate low-positive from atypical patterns. Such distinction could be achieved by ELISA. The use of ELISA with isolated primary granules is a good alternative for if since it has a good specificity, sensitivity and reproducibility, moreover it is a quantitative method.

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The term systemic vasculitis concerns a group of diseases characterized by inflammation of vessels. The diagnosis and follow-up of these conditions is a serious challenge since their classification is difficult and the therapy is usually empiric. Perhaps the greatest breakthrough in the management of these diseases is the recent discovery of serological markers for some vasculitic syndromes. Wishing to determine how far the tests for detection of these antibodies are specific, sera from 63 patients with systemic vasculitides were tested by immunofluorescence of ethanol fixed neutrophils. Two different staining patterns were observed. The cytoplasmic staining (classic pattern) was very specific for Wegener's granulomatosis. In contrast, the perinuclear staining was also present in many vasculitic syndromes such as microscopic polyarteritis and poliarteritis nodosa. In addition, the sera were tested by ELISA, using whole neutrophil cell extract. Although the assay was less specific than the immunofluorescence, the test was helpful in discriminating between true ANCA and atypical fluorescence patterns. Moreover, high levels of antimieloperoxidase antibodies detected by ELISA in a limited number of patients were exclusively associated with the diagnosis of microscopic polyarteritis or Wegener's granulomatosis with renal involvement. Our data confirm the remarkable association of antineutrophil cytoplasmic antibodies with vasculitic syndromes.(ABSTRACT TRUNCATED AT 250 WORDS)

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The authors revised the published data on coagulation abnormalities observed in patients suffering from primary vascular diseases or vasculitides associated with systemic diseases of the connective tissue. These patients present a tendency toward thrombosis as a result from platelet activation and endothelial cell injury, together with altered fibrinolytic activity. The proliferative events secondary to platelet activation and endothelial injury remain present after cessation of the inflammatory process and may play a role at the end stage obstruction of the vascular lumen always seen in these diseases.

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