Density operator of a system pumped with polaritons: A Jaynes-Cummings like approach

We investigate the effects of considering two different incoherent pumpings over a microcavity-quantum dot system modelled using the Jaynes-Cummings Hamiltonian. When the system is incoherently pumped with polaritons it is able to sustain a large number of photons inside the cavity with Poisson-like statistics in the stationary limit, and also leads to a separable exciton-photon state. We also investigate the effects of both types of pumpings (Excitonic and Polaritonic) in the emission spectrum of the cavity. We show that the polaritonic pumping as considered here is unable to modify the dynamical regimes of the system as the excitonics pumping does. Finally, we obtain a closed form expression for the negativity of the density matrices that the quantum master equation considered here generates.Comment: 16 pages, 4 figure

Periocular Myxoma in a Child

Myxomas are locally invasive, benign mesenchymal neoplasms with odontogenic, osteogenic, or soft tissue origin. Facial myxomas probably account for less than 0.5% of all paranasal sinus and nasal tumors. We report a case of a left painless periocular mass in a 11-month-old girl. The lesion was resected with a clinical diagnosis of lacrimal sac tumor. Histopathology and immunohistochemistry proved the tumor to be a myxoma. There has been no recurrence after 4 years of followup. Midfacial myxomas should be differentiated from other benign and malignant tumors such as dermoid, hamartoma, neurofibroma, nasolacrimal duct cyst, and sarcomas in particular embryonal rhabdomyosarcoma. Because of the infiltrative nature of these tumors, a wide surgery is required to achieve clear resection margins and avoid recurrence

Innovación y mejora docente en el ámbito de la enseñanza de estructuras metálicas.

La asignatura “Estructuras Metálicas” está orientada a completar los conocimientos del análisis de estructuras del futuro ingeniero industrial con su aplicación práctica al diseño de estructuras metálicas. La organización y programación de la asignatura está pensada para transmitir los conocimientos necesarios para el cálculo de elementos estructurales simples, de manera que el alumno posea una perspectiva amplia de la problemática asociada al diseño de estructuras metálicas complejas. Ello se lleva a cabo mediante clases teóricas, clases de problemas, clases prácticas de estructuras por ordenador, prácticas de laboratorio, y trabajos prácticos. Este trabajo presenta nuevas metodologías docentes, de acuerdo con las líneas prioritarias del Plan Propio de la Universidad de Sevilla, para mejorar los diferentes frentes de docencia que la asignatura posee. Para ello se profundiza en el estudio y experimentación de nuevas metodologías didácticas como la enseñanza virtual, usando plataformas virtuales tipo WebCT, la elaboración de clases por transparencias PowerPoint y animaciones numéricas realizadas mediante elementos finitos, todo ello basadas en la normativa vigente actual y bibliografía referente actualizada. Además se fomenta el trabajo en equipo mediante la realización de prácticas de campo y un proyecto en grupo, y se desarrollan nuevas prácticas de laboratorio y actividades de manera que el alumno contemple la visión práctica de los conocimientos adquiridos

Comparison between the methods of the norm L1, L2, hilbert transform and phase analysis to obtain the time of flight of ultrasonic signals

Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.60.Bf.Some techniques to estimate the time of flight (TOF) allow getting a larger resolution, more than a sampling period. Therefore, it is possible to obtain a greater accuracy in the measurement of acoustic parameters using the TOF.In this work a comparison between the mentioned methods is carried out; analyzing the standard deviation of the time of flight in relation to the sign to noise ratio (SNR) between 5 dB to 40 dB and a bandwidth of 4 MHz, 5 MHz and 6 MHz to -6 dB of simulated ultrasound signals, with the purpose of analyzing the performance of each method.The results demonstrate that the method of the phase estimation presents the bigger values of standard deviation. For high-SNRs the methods of the L1 and L2 norm present similar values; furthermore, they exhibit the lowest values of standard deviation of the TOF estimation of the four methods. Finally, it was observed that for low SNR the method of Hilbert transform allows to obtain values of standard deviation similar to the methods of the norm L1 and L2 with a smaller time of processing of the signal.Peer reviewe

Effect of cooling rate during solidification on the hard phases of M23C6-type of cast CoCrMo alloy

Microstructural morphology of CoCrMo alloy by control of the cooling rate during the solidification was investigated. Samples were obtained using both an induction furnace for slow cooling rate and electric arc furnace for fast cooling rate. Microstructural characterizations were performed with metallographic techniques. It was found that the difference between the formation temperature of hard secondary phases of M23C6-type carbides determine the reduction of carbide size by increasing the cooling rate

Effect of cooling rate during solidification on the hard phases of M23C6-type of cast CoCrMo alloy

Microstructural morphology of CoCrMo alloy by control of the cooling rate during the solidification was investigated. Samples were obtained using both an induction furnace for slow cooling rate and electric arc furnace for fast cooling rate. Microstructural characterizations were performed with metallographic techniques. It was found that the difference between the formation temperature of hard secondary phases of M23C6-type carbides determine the reduction of carbide size by increasing the cooling rate

Structural effects of Sc doping on the multiferroic TbMnO3

9 páginas, 8 figuras, 4 tablas.-- PACS number(s): 75.85.+t, 61.05.cp, 61.05.fm, 61.05.cjThe new TbMn1−xScxO3 series has been synthesized and the structural properties have been characterized by x-ray diffraction, neutron diffraction, and x-ray absorption spectroscopy. The whole series belongs to the family of ABO3 perovskites. All of the samples are isostructural to the parent compound TbMnO3, crystallizing in an orthorhombic cell with space-group Pbnm symmetry. The homovalent substitution of Mn3+ with the larger Sc3+ ion leads to an increase in both the unit-cell volume and the BO6 octahedra tilting. The analysis of neutron and x-ray diffraction patterns suggest a continuous evolution from a Jahn-Teller distorted BO6 octahedron in TbMnO3 into a nearly regular one in TbScO3. However, x-ray absorption measurements at the Mn K edge reveal that the local geometry around the Mn3+ cation remains distorted in the series even for high values of x. This result is in opposition to previous findings in similar compounds such as LaMn1−x(Ga/Sc)xO3 and suggests that the strong orthorhombic distortion of the unit cell due to the small Tb3+ cation size favors the stability of the distorted MnO6 octahedron in diluted systems. Long-range magnetic ordering is not found for x≥0.3 samples and there is not sign of ferromagnetism for x=0.5 in opposite to the behavior observed in the La-based compounds. Since Sc substitution induces a minor perturbation on the local structure of the Mn sublattice but magnetic ordering of both Mn and Tb sublattices disappear for a small degree of substitution, we conclude that the involved magnetic interactions should have a strong directional anisotropy and the Tb magnetic ordering strongly depends on the existence of a long-range coherent Mn ordering.Financially supported by the Spanish MICINN (Projects No. FIS08-03951 and No. MAT2007-61621) and DGA (Camrads).Peer reviewe

Sistemas caóticos y su aplicación a la encriptación de señales

La sincronización y control de señales caóticas es una activa área de investigación por sus posibles aplicaciones en telecomunicaciones y transmisión de señales [1, 2, 3, 4]. En el presente trabajo se estudia un sistema de comunicación basado en la sincronización de dos sistemas no lineales caóticos, cada uno modelado a partir de las ecuaciones de movimiento de un péndulo forzado amortiguado y que se encuentran en el mismo punto de operación del espacio de parámetros. Synchronization and control of chaotic signals is an active research area because of its applications in telecommunications and secure signal transmission [1,2,3,4]. In this work a communication system based in the synchronization of two chaotic nonlinear systems, each one being modeled by the motion equations of a driven damped pendulum and operated in the same parameter space region is shown. Two communication channels were used: the first one for the synchronizing signal and the second one for the sent message. By using two channels the initial conditions sensibility problem is solved. In the receiver system a feedback loop as a proportional controller is used in order to drive quickly the error between the decoder and encoder states to zero. The last two facts make the system to be robust to external pertubative signals such as noise in the communication channels