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Bayesian network structure learning is an NP-hard problem that has been faced by a number of traditional approaches in recent decades. Currently, quantum technologies offer a wide range of advantages that can be exploited to solve optimization tasks that cannot be addressed in an efficient way when utilizing classic computing approaches. In this work, a specific type of variational quantum algorithm, the quantum approximate optimization algorithm, was used to solve the Bayesian network structure learning problem, by employing $3n(n-1)/2$ qubits, where $n$ is the number of nodes in the Bayesian network to be learned. Our results showed that the quantum approximate optimization algorithm approach offers competitive results with state-of-the-art methods and quantitative resilience to quantum noise. The approach was applied to a cancer benchmark problem, and the results justified the use of variational quantum algorithms for solving the Bayesian network structure learning problem.

The generation of surface plasmon resonances (SPR) in laser-induced periodic surface structures (LIPSS) allows their application in the field of optical sensing, such as the detection of refractive index variations in gases and liquids. We have fabricated gold-coated LIPSS nanostructures on stainless steel substrates by using femtosecond laser nano-ablation. This technique is a low-cost and high-throughput fabrication method applicable to fast and large-scale manufacturing. The depth profile of the fabricated LIPSS shows a central dip at the top of each ripple that split the geometry. The actual topography is modeled and included in a computational electromagnetism package to obtain the expected optical response under the experimental conditions. The measured and simulated spectral reflectances are compared, and the differences are explained by the departure of the fabricated LIPSS from the ideal topography. The experiments and simulations showed excellent agreement for the main spectral characteristics, like the Fano-like lineshapes of the spectral reflectance. This fitting provides the values used to determine the refractometric performance of the fabricated device, that shows a sensitivity of 518 nm/RIU and a figure of merit of 32 RIU−1 for an aqueous analyte. Our experimental results show that the fabricated devices are competitive in terms of cost and simplicity when compared to existing devices with similar performance.

According to the current legal regulations, the flags of 8 of the 19 autonomous communities and cities in Spain have only qualitative specifications of their colors. We have performed quantitative color measurements under fixed experimental conditions (e.g. illuminant D65, CIE 1964 standard colorimetric observer) for 3 collections of the 19 mentioned flags: One acquired by internet and two existing in high institutions of the Spanish State in Madrid (Supreme Court and Constitutional Court). The 52 main colors of the flags of the Supreme Court and Constitutional Court are relatively similar (average color difference of 6.2 CIELAB units). Therefore, we propose their average colors (with the exception of the blue color of the diagonal stripe of the flag of Galicia and the red and green stripes of the flag of La Rioja), with a tolerance of 10 CIELAB units, as a reference for future studies and standardization. The average color difference between our proposal and the colors of the purchased flags or those specified in current legislation is very high (about 20 CIELAB units). Most colors of the flags in the Supreme Court and Constitutional Court are located in 6 regions of the CIELAB color space we can name as white, black, red, yellow, green and blue. In all our color comparisons of flags from different collections, hue difference was the smallest component (, Según la normativa legal vigente, las banderas de 8 de las 19 comunidades y ciudades autónomas existentes en España tienen sólo especificaciones cualitativas de sus colores. Hemos realizado medidas cuantitativas de color bajo unas mismas condiciones experimentales (e.g. iluminante D65, observador patrón CIE 1964) para 3 colecciones de estas 19 banderas: Una adquirida por internet y dos existentes en altas instituciones del Estado en Madrid (Tribunal Supremo y Tribunal Constitucional). Los 52 colores principales de las banderas del Tribunal Supremo y Tribunal Constitucional son relativamente similares (diferencia de color promedio de 6.2 unidades CIELAB). Por tanto, proponemos su color promedio (con la excepción del color azul de la franja diagonal de la bandera de Galicia y las franjas roja y verde de la bandera de La Rioja), con una tolerancia de 10 unidades CIELAB, como referencia cuantitativa para futuros estudios y estandarización. La diferencia de color promedio entre nuestra propuesta y los colores de las banderas compradas o los especificados en la legislación vigente es muy alta (del orden de 20 unidades CIELAB). La mayor parte de los colores de las banderas del Tribunal Supremo y Tribunal Constitucional se agrupan en 6 regiones del espacio CIELAB, que podemos denominar blanco, negro, rojo, amarillo, verde y azul. La diferencia de tono es la componente más pequeña (

Producción Científica, Herein, we report molecular tweezers for fullerene recognition based on 2,2′-bipyridine-bearing corannulene motifs. The syn or anti confirmation can be selected simply by Cu(I) coordination/decoordination, thus controlling the fullerene recognition capability of the system on demand and leading to the formation of effective metal-triggered ON/OFF molecular tweezers., We thank the Spanish Ministry of Science, Innovation and Universities (MCIU) for funding (project numbers PGC2018096880-A-I00, MCIU/AEI/FEDER, UE, PGC2018-099470-B-I00, and MCIU/AEI/FEDER, UE). R. G.-R. acknowledges the Spanish MINECO/AEI and the European Union (ESF) for a Ramón y Cajal contract (RYC-2015-19035). H. B. acknowledges the Alfonso Martín Escudero Foundation for a postdoctoral fellowship

This manuscript presents the development of a low-pressure extrinsic Fabry-Perot fiber optic sensor based on a thin polyester film, using a phase signal analysis. The proposed interferometer is controlled by the simple contact interaction between the polymer membrane and a multimode fiber optic tip. The created cavity was uniformly stressed by applying a pressure varying from 0 to 2 psi. A finite element analysis was performed for these parameters. The stress applied to the membrane was below the yielding point. Thus, a linear study could be performed. The wavelength spectra exhibited a blue shift with a sensitivity of around 10.5 nm/psi. Although the interference spectra presented crosstalk measurements and required an initial set-point calibration, these effects were overcome by examining the spatial frequency components’ phase analysis. The sensors offered a high sensitivity, close to 3.5 rad/psi. Ultimately, this sensor is a high sensitivity and versatile alternative for low-pressure detection.

Resumen En radioterapia, el espectro de energía de electrones es la característica más importante para modelar la fuente de radiación cuando el propósito es el cálculo exacto de la dosis. Usualmente, se exploran tres métodos para obtener el espectro: (i) simulación de la fuente vía Monte Carlo; (ii) medición directa vía un espectrómetro magnetico y (iii) reconstrucción inversa. Entre ellos, este último es considerado como el mías apropiado por su simplicidad, rapidez y eficacia, a pesar de no ser el más exacto. La reconstrucción inversa tiene por objeto extraer el espectro de energía a partir de la distribución de dosis en profundidad a través de la resolución de un problema mal definido, vía el metodo de regularización de Tikhonov. La idoneidad de la reconstrucción es evaluada usando el índice gamma. Los resultados muestran que la regularización de Tikhonov es capaz de reconstruir el espectro de energía de un haz de electrones dentro del criterio clínico de aceptación del índice gamma en que más del 95 % de los puntos de las distancias entre las dos distribuciones de dosis están dentro de una precisión de 1 %/1 mm. Abstract In radiotherapy, the electron energy spectrum is the most important characteristic for modelling the radiation source whose purpose is an accurate dose calculation. There are mainly three approaches to obtain the energy spectrum: (i) simulation of the source via Monte Carlo; (ii) direct measurement via a magnetic spectrometer and (iii) inverse reconstruction using an appropriate mathematical model. Among them, inverse reconstruction is considered the most appropriate for its simplicity, efficiency and speed despite not being the most accurate. Since inverse reconstruction is an ill-posed problem the Tikhonov regularization is used to overcome this problem and thereby obtain the spectrum. The reconstruction success is evaluated using the gamma index. Results show Tikhonov regularization is able of reconstructing the energy spectrum of a clinical electron beam within gamma index clinical acceptance criterion of > 95% within 1 %/1 mm.

The generation of photon-pairs with controllable spectral correlations is crucial in quantum photonics. Here we present the design of a photonic crystal fiber to generate widely-spaced four-wave mixing bands with spectral correlations that can be tuned through the thermo-optic effect after being infiltrated with heavy water. We present a theoretical study of the purity of the signal (idler) photon generated as a function of temperature, pump spectral linewidth and the length of the fiber. 511-6/18-8876 CIIC155/2019 APN-624 TEC2016- 76664-C2-1-R PROMETEO/2019/048

Producción Científica, Due to the high number of reachable conductance levels in resistive switching devices, they are good candidates to implement artificial synaptic devices. In this work, we have studied the control of the intermediate conductance levels in HfO2-based MIM capacitors using current pulses. The set transition can be controlled in a linear way using this kind of signal. The potentiation characteristic is not affected by the pulse length due to the filament formation takes place in very short times. This behavior does not allow using identical pulses to obtain the potentiation characteristic. The transient response of the devices when applying current pulses showed the filament formation is characterized by a peak in the voltage transient signal. No depression characteristic can be obtained using current signals due to the abrupt reset transition. However, the depression characteristic can be obtained using voltage pulses, so combining both signals should allow control the synaptic weight in an appropriate way.

Geometrical and material - i.e., external and internal - scaling symmetries are exploited to obtain approximated analytical expressions for the mode effective index, group index, and chromatic dispersion of a scaled fiber. Our results include material refractive index scaling that changes the numerical aperture. First, the analytical expressions are successfully tested with a conventional step index fiber in a broadband range of wavelengths, from 1 to 2 mu m. Then, we establish a procedure to adapt the analytical expressions to photonic crystal fibers (PCFs) and illustrate its application in a triangular PCF with circular holes. These adapted analytical expressions show good agreement with a rigorous numerical solution of the fundamental fiber mode. Finally, we demonstrate how powerful these expressions are for the design of PCFs. In particular, we illustrate our approach designing, in four iterations or less, PCFs with flattened dispersion profile over 300 nm or high dispersion slope over 40 nm, with different chromatic dispersion values. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Resumen Coloides con nanopartículas esféricas de plata fueron obtenidos por la técnica de ablación con láser pulsado en líquidos. Los parámetros del laser para la síntesis fueron: longitud de onda de 1064 nm, duración de pulso laser de 10 ns, energía por pulso de 15.7 mJ, y se aplicaron 2400, 3600 y 4800 pulsos laser. La radiación laser infrarroja fue enfocada por una lente convergente sobre la superficie de un blanco de plata sumergido en agua desionizada. Cada coloide sintetizado (muestra referencia) fue post irradiado con el mismo láser considerado para la síntesis, pero con energía incidente de 8.3 mJ. Para la post irradiación se consideró una razón de repetición de 10 Hz y diferentes números de pulsos. Durante la post irradiación, el rompimiento óptico del coloide se produjo a mitad de altura del mismo. La caracterización de los coloides se realizó con las técnicas de espectroscopia ultravioleta-visible y microscopia electrónica de barrido. Las curvas para el máximo de absorción y la integral del espectro de absorción en el intervalo correspondiente al infrarrojo cercano (desde 600 nm a 800 nm) sugieren que conforme se incrementó el numero de pulsos láser considerados para la post irradiación de una muestra referencia, se presentó: ablación y la fragmentación de nanopartículas hasta un tamaño crítico, agregación, aglomeración y sedimentación de nanopartículas. Se encontró una dependencia entre las propiedades opticas de nanopartículas de plata con las condiciones de síntesis y post irradiación de coloides con laser pulsado y enfocado. Abstract Colloids with silver spherical nanoparticles were obtained by pulsed laser ablation technique in liquids. The laser parameters for the synthesis were: 1064 nm wavelength, 10 ns laser pulse duration, 15.7 mJ energy per pulse, and 2400, 3600 as well as 4800 number of laser pulses. The infrared laser radiation was focused on the surface of a silver target submerged in deionized water. Each synthesized colloid (reference sample) was post-irradiated with the same laser considered for the synthesis, but with an incident energy of 8.3 mJ. The post-irradiation were performed with a repetition rate of 10 Hz and several numbers of pulses. During the post-irradiation, the optical breakdown of the colloid occurred at the half height of it. The characterization of the colloids was carried out with ultraviolet-visible spectroscopy and scanning electron microscopy techniques. The analysis of the maximum absorption, integral of the absorption spectrum in the near infrared interval (from 600 nm to 800 nm), and the post-irradiation number of pulses suggest that as the number of pulses increases, ablation as well as fragmentation of nanoparticles up to a critical size, aggregation, agglomeration, and sedimentation of nanoparticles occur in the colloid. A dependence was found between the optical properties of silver nanoparticles with synthesis conditions and the colloids post-irradiated with a pulsed and focused laser.

Resumen Se describe un sistema de calentamiento escalonado para la medición de la conductividad térmica, el cual mezcla las ventajas de los métodos dinámicos con las propias de los métodos estacionarios, permitiendo la realización de mediciones rápidas y confiables en el rango de temperatura entre 85K y la temperatura ambiente. Este sistema es especialmente apropiado para la mediación de materiales solidos con una relación longitud-espesor mayor que la unidad. A fin de ilustrar las capacidades y la fiabilidad del sistema se presentan mediciones de conductividad térmica en muestras de plomo (99.9%) y material cerámico del tipo La 0.92 Sr 0.08 CoO 3 . Se concluye que este arreglo experimental permite realizar mediciones rápidas y seguras, permitiendo además controlar de manera eficiente las pérdidas por radiación y convección. Abstract We describe a step heating method, which is used for thermal conductivity measurements. This system takes the advantages of both dynamic and steady-state methods. It is especially suitable for solid materials having large length-to-thickness ratio. In order to illustrate the capabilities and reliability of the system we show some measurements of thermal conductivity on pure lead (99.9 %) and La 0.92 Sr 0.08 CoO 3 ceramic samples. This technique provides very good precision and fast measurements in the temperature range between 85K and room temperature, along with an effective control of radiative and convective heat losses.

Resumen En este trabajo se presentan los resultados obtenidos al desarrollar la metodología propuesta en la norma IEC 61267 para la caracterización de las calidades de radiación del haz de rayos x para radiodiagnóstico. Las características fueron analizadas por medio de la medición de los parámetros: filtración inherente, primera capa hemireductora (1oHVL) y coeficiente de homogeneidad, estas mediciones se realizaron solo para la calidad de radiación RQR3. Los materiales utilizados en el trabajo fueron: el tubo de rayos x Balteau NDT modelo XSDBip-LS1 instalado en Laboratorio Secundario de Calibración Dosimétrica (LSCD), cámara de ionización de placas paralelas con un volumen de 75cm3 modelo 39060, filtros de aluminio de diferentes espesores con una pureza del 99.9 % y una cámara monitora PTW tipo 34014. Los resultados obtenidos de filtración inherente nos permitieron comprobar que el tubo puede ser utilizado para la implementación de las demás calidades de radiodiagnóstico, además se determinó que la medición de los restantes parámetros encontrados para RQR3 estóan dentro de los lómites propuestos en la norma. Estos resultados son un aporte fundamental al posterior establecimiento de patrones de referencia a nivel de radiodiagnóostico, mamografóa y tomografóa computarizada que en la actualidad no existen en el país. Abstract This paper presents the results obtained by developing the methodology proposed in the IEC 61267 standard for the characterization of the radiation qualities of the x-ray beam for radiodiagnostic. The characteristics were analyzed by means of the measurement of the parameters: inherent filtration, first hemireductor layer (1oHVL) and homogeneity coefficient, these measurements were made only for the RQR3 radiation quality. The materials used in the work were: the Balteau NDT x-ray tube model XSDBip-LS1 installed in Secondary Calibration Dosimetry Laboratory (LSCD), ionization chamber of parallel plates with a volume of 75cm3 model 39060, aluminum filters of different thicknesses with a purity of 99.9% and a PTW monitor chamber type 34014. The results obtained from inherent filtration allowed us to verify that the tube can be used for the implementation of the other radiodiagnostic qualities, in addition it was determined that the measurement of the remaining parameters found for RQR3 they are within the limits proposed in the standard. These results are a fundamental contribution to the subsequent establishment of reference patterns at the level of radiodiagnostic, mammography and computed tomography that currently do not exist in the country.

Reportamos un estudio de la reflectividad de una interface vidrio-vapor atómico de cesio cerca de la línea de resonancia D2 del cesio para densidades del vapor de cesio desde 0.9x1014hasta 3.2x1014átomos/cm3. Los resultados experimentales se compararon con cálculos basados sobre una teoría en la cual primero se tienen en cuenta solamente las colisiones átomo-átomo y luego tomando en cuenta también las colisiones átomo-pared. También detectamos un desplazamiento dhacia el azul de la frecuencia del pico de la resonancia 4 →5 que depende aproximadamente en forma lineal de la densidad N. We report a study of the reflectivity of a glass-cesium vapor interface near the cesium D2 resonance line for cesium vapor densities from 0.9x1014 up to 3.2x1014atoms/cm3. The experimental results are compared with calculations based on a theory on which are taken into account first only the atom-atom collisions and then also taking into account the atom-wall collisions. We also detect a shift for the blue of the frequency of the peak of the resonance 4 →5 that approximately depends linearly on the density N.

Las películas de AlGaAs fueron depositadas por pulverización catódica asistida por campo magnético sobre sustratos de vidrio y Si (100). Se mantuvo constante la temperatura del substrato y se varió la relación de la potencia de los blancos de Al y GaAs. Para disminuir los efectos del desacople del parámetro de red entre la capa de AlGaAs y los substratos, se depositó una capa buffer de GaAs. Los espectros de difracción de rayos X muestran que las películas son policristalinas con orientación preferencial (111). Los espectros Raman evidencian un comportamiento de dos modos, correspondiente a modos vibracionales TO y LO de GaAs y de AlAs, respectivamente. AlGaAs layers were deposited by RF magnetron sputtering on glass and Si (100) substrates. The substrate temperature was kept constant and the power ratio of the Al and GaAs targets was varied. In order to decrease the effects of decoupling the lattice parameter between the AlGaAs layer and the Si substrate, a GaAs buffer layer was deposited. The X-ray diffraction spectra show that the films are polycrystalline with preferential orientation (111). The Raman spectra show a behavior of two modes, corresponding to TO and LO vibrational modes of GaAs and AlAs, respectively.

Los equipos de IRM en campo magnético ultra bajo (cercano al terrestre) pueden ser un complemento para formar equipos híbridos con los de Medicina Nuclear. Este trabajo presenta el diseño y la construcción de un campo magnético homogéneo, con el fin de mantener las condiciones requeridas para el funcionamiento de un equipo de IRM de campo ultra bajo en ambientes con campos nominales débiles o heterogéneos. Esto facilita su implementación como complemento a un equipo de Medicina Nuclear y así tener un equipo híbrido. La homogenización del campo se logra con un arreglo de bobinas de Maxwell, minimizando el ruido externo en el equipo de resonancia. Por medio de simulaciones en GEANT4 se analiza el efecto del arreglo de bobinas sobre la detección del material radiactivo. Se muestra que la atenuación del sistema homogeneizador de campo magnético tiene una atenuación del orden del 0.5 %, lo que apenas afecta la calidad de la imagen de la PET ya que es del orden del error en estos sistemas de detección. Low field MRI can be used as potential hybrid complement with Nuclear Medicine devices. This paper presents the design and construction of an experimental set up based on Maxwell coils. The coil arrangement will perform a homogeneous magnetic field as condition required for an ultra low field MRI operation. The homogenization minimize the external noise on the MRI device, while keeping the imaging conditions. GEANT4 simulations were performed to analyze the effect of the coils array over the radioactive material detection. A radiation attenuation of ca. 0.5 % is observed due to the coil arrangement, which practically does not affect the PET quality image since it is close to the error estimation for these kinds of detectors.

The implementation of the square root computation in an FPGA device is presented in this work. The calculation is not one of convergence type, so the accuracy is very high and there are no conditions or restrictions for the operation to be fulfilled. It also consumes much less hardware surface than other algorithms for calculating the square root of a number. The number entered is of fixed-point representation, it is parameterizable, that is, two constants N and M can define the size of the number, where N defines the number of bits in the integer part of the number and M defines the number of bits of the fractional part. En este trabajo se presenta la implementación de la raíz cuadrada de un número en un dispositivo FPGA. El algoritmo usado no es un algoritmo de convergencia, por tanto, la exactitud del cálculo es muy alta, además no existen restricciones de ningún tipo para que la operación sea llevada a cabo. El uso de hardware en la FPGA es mucho menor que el usado por otros algoritmos que también calculan la raíz cuadrada de un número. Para representar el número se usa la representación de punto fijo, para ello se usan dos parámetros, N y M, donde N define el número de bits que representan la parte entera y M define el número de bits de la parte fraccional. M y N son definidos en la síntesis del módulo.

19 páginas La correcta interpretación del trazado del monitoreo fetal electrónico es un desafío para la clínica actual. Recientemente se desarrolló una metodología diagnóstica fundamentada en las teorías de probabilidad y la entropía, que logro evaluar de manera objetiva y reproducible el trazado de la monitora fetal diferenciando normalidad de enfermedad y evolución entre estos estados. El objetivo del presente trabajo es aplicar dicha metodología para evaluar el trazado de la monitoria fetal y confirmar su aplicabilidad clínica y reproducibilidad. Para ello se evaluaron 25 monitorias fetales en 20 minutos divididas en dos grupos: 10 normales y 15 con pérdida de bienestar fetal, de acuerdo con la interpretación convencional de la monitoria y la evaluación clínica general. Se tomaron frecuencias cardíacas presentadas en intervalos discretos de tiempo a partir de los trazados, y se evaluó la probabilidad y la relación S/k de la entropía. Las relaciones S/k de la entropía para las monitoría evaluadas diferenciaron normalidad de enfermedad. Se confirmó la aplicabilidad clínica del diagnóstico físico y matemático para la evaluación del trazado de la monitoria fetal. The correct interpretation of the layout of fetal monitoring is a challenge for current clinical; recently a diagnostic methodology based on the theories of probability and entropy, which managed to assess in an objective and reproducible way the layout of differentiating normal fetal monitoring and evolution of disease between these states was developed. The aim of this paper is to apply this methodology to assess fetal monitoring tracing and confirm their clinical applicability and reproducibility. For this 25 fetal monitoring in 20 minutes divided into two groups were evaluated: 10 normal and 15 with loss of fetal well-being, according to the conventional interpretation of the monitoring, and general clinical evaluation. Heart rates presented in discrete time intervals from the paths they took, and the likelihood and the S/k ratio of entropy was evaluated. The S/k relations of entropy for normal differentiated evaluated by monitors disease. The clinical applicability of physical and mathematical diagnostic assessment of fetal monitoring tracing was confirmed.

Se presenta un estudio de la evolución de diferentes posibles progenitores sin materia oscura de la galaxia enana esferoidal Carina, una de las galaxias satélites de la Vía Láctea, mediante simulaciones numéricas Newtonianas de N-Cuerpos. No fue posible reproducir completamente las propiedades observacionales de Carina, y por consiguiente no se pudo determinar un posible progenitor sin materia oscura para la misma; sin embargo, progenitores con masa inicial 1x107 M. y radios de Plummer 0.5 y 0.6 kpc, reprodujeron los valores observacionales de Carina para tres de las cinco variables estudiadas (radio de brillo medio, dispersión de velocidades sobre la visual y distancia galactocéntrica). Por lo tanto estos progenitores podrán ser la base para posteriores trabajos sobre el origen de la galaxia enana Carina. We present a study of the evolution of several different dark matter free possible progenitors of the Carina dSph galaxy, one of the satellites of the Milky Way, using Newtonian numerical N-body simulations. It was not possible to reproduce all the observed properties of Carina, therefore a possible dark matter free progenitor of it was not found; nevertheless, progenitors with initial mass 1x107 M. and Plummer radii 0.5 and 0.6 kpc reproduced the observational values of Carina for three of the five studied variables (half light radius, line-of-sight velocity dispersion and galactocentric distance). Thus, those satellites could be the starting point for further work about the origin of the Carina dwarf galaxy.

Se presenta un estudio magnético acerca de la transformación térmica de hematita dopada con CuO (Fe2O3 + CuO). El tratamiento térmico se realizó a una temperatura de 375 ± 1 ºC, en una atmosfera controlada compuesta por 20% de hidrogeno y 80% de nitrógeno. Las muestras fueron caracterizadas por espectroscopía Mössbauer a temperatura ambiente, magnetización en función de la temperatura y ciclos de histéresis a 10K. Los resultados sugieren que los campos hiperfinos y los anchos de línea A y B permanecen esencialmente constantes con el aumento de la concentración de CuO, mientras que a la vez surge una componente paramagnética, lo cual es indicativo de la aparición de un precipitado o nueva fase de Fe-Cu, i.e. no hay una incorporación efectiva del cobre en la estructura de la magnetita. La magnetización de saturación cae aproximadamente de 87 emu/g a 78 emu/g, consistente con la presencia de dicha fase paramagnética. Se presenta también un aumento de la coerctividad desde ~576 Oe hasta ~621 Oe con el aumento del %CuO desde 2% hasta 20 %. Tal aumento se atribuye también a dicha fase paramagnética actuando como centro de anclaje de las paredes de dominio, sumado al efecto de anclaje de las posibles vacancias inducidas por el tratamiento térmico. Finalmente, se observa una inversión de la magnetización en la temperatura de Verwey. Los datos sugieren que mediante el método de síntesis empleado se obtienen partículas de magnetita Fe3O4 coexistiendo con precipitados de Fe-Cu, lo cual modifica las propiedades magnéticas y genera un efecto interesante en la magnetización a la temperatura de Verwey. A magnetic study about the thermal transformation of hematite doped with CuO (Fe2O3 + CuO) is presented. The heat treatment was carried out at a temperature of 375 ± 1 ºC, in a controlled atmosphere composed by 20% hydrogen and 80% nitrogen. Samples were characterized by Mössbauer spectroscopy at room temperature, magnetization as a function of temperature and hysteresis loops at 10K. Our results suggest that both the hyperfine fields and linewidths of the A and B sites remain essentially constant with increasing the CuO concentration, while at the same time a paramagnetic component arises, which is indicative of the appearance of a precipitate or a new phase of Fe-Cu, i.e. there is not an effective incorporation of the copper into the structure of the magnetite. The saturation magnetization falls from approximately 87 emu/g to 78 emu/g, consistent with such a paramagnetic phase. Also, an increase in the coercivity from ~576 Oe up to ~621 Oe by increasing the percentage of CuO from 2% up to 20% is observed. Such increase is also attributed to the paramagnetic phase acting as pinning center for domain walls, besides also de pinning effect due to vacancies induced by the thermal treatment. Finally, an inversion of the magnetization in the Verwey temperature is observed. The data suggest that by means of the synthesis method employed, it is possible to obtain Fe3O4 magnetite particles coexisting with precipitates of Fe-Cu, giving rise to a modification in the magnetic properties and generatingan interesting effect in the magnetization at the Verwey temperature.

espanolThe aim of this work is to evaluate the response of healthy subjects to the Farnsworth-Munsell 100 Hue color test using colored optical filters and without them under different illuminations. Thirty healthy subjects (range 20-27 years) performed this color test under simulated A, D65 and LED illuminants, without and with three different filters. Results indicate that LED could be a good alternative to perform Farnsworth Munsell 100 Hue color test. Colored filters modify color perception in specific spectral regions, it should be taken into account when a subject wears these filters. EnglishLa finalidad de este trabajo ha sido analizar la variabilidad de los resultados obtenidos al realizar el test de color Farnsworth-Munsell 100 Hue en diferentes condiciones de observacion e iluminacion. El test se realizo a 30 sujetos jovenes (entre 20 y 27 anos de edad) sin alteraciones en la vision cromatica. Se variaron las condiciones de iluminacion utilizando fuentes de luz que simulaban al iluminante A y D65, y con una fuente de luz LED, ademas se utilizaron filtros opticos coloreados. Los resultados indican que la fuente de iluminacion LED podria ser adecuada como alternativa para la realizacion del test de color Farnsworth Munsell 100 Hue. Los filtros coloreados modifican la percepcion de los colores en determinadas regiones del espectro lo que deberia tenerse en cuenta a la hora de su porte.

Se reporta la respuesta fotoacústica de un sensor piezoeléctrico que fue irradiado con pulsos láser de longitudde onda de 1064 nm y distinta energía emitidos por un láser Nd:YAG. La medida de la energía de los pulsoslaser se hizo con un medidor, marca Newport modelo 1936-R con sensor piroeléctrico y las señales fotoacústicascon un osciloscopio Tektronix, modelo DPO3054 de 500 MHz. Experimentalmente se encontró una dependencialineal entre la intensidad de la señal fotoacústica del sensor piezoeléctrico y la energía del pulso laser. La sensibilidadde la respuesta fotoacústica del sensor fue dependiente de la placa protectora. Para placas de aluminio y aluminiopintado de negro fueron (6.52 ± 0.06)mV/mJ y (51.2 ± 1.5)mV/mJ respectivamente. Se concluyó que este tipo de sensor piezoeléctrico es muy sensible a los cambios de energía de láseres pulsados de 1064 nm, su respuesta es directamente proporcional a la energía incidente, es apropiado para mediciones de energía de láseres pulsados en tiempo real y, no se ve afectado por ruidos acústicos ni condiciones de iluminación del laboratorio. We report the photoacoustic response of a piezoelectric sensor that was irradiated with laser pulses of wavelength of 1064 nm and different energy emitted by an Nd:YAG laser. The measurement of laser pulse energy was done with a meter, Newport model 1936-R with pyroelectric sensor and the photoacoustic signals with a Tektronix oscilloscope, model DPO3054 of 500 MHz. Experimentally, we found a linear dependence between the intensity of the photoacoustic signal of the piezoelectric sensor and the energy of the laser pulse. The sensitivity of the photoacoustic response of the sensor was dependent on the protective plate. For aluminum and aluminum plates painted black were (6.52 ± 0.06)mV/mJ and (51.2 ± 1.5)mV/mJ respectively. It was concluded that this type of piezoelectric sensor is very sensitive to the energy changes of 1064 nm pulsed lasers, its response is directly proportional to the incident energy, it is suitable for energy measurements of lasers pulsed in real time and it is not seen affected by acoustic noises or lighting conditions of the laboratory.

Proca's electrodynamics describes a theory of massive photons which is not gauge invariant. In this paper we show that the gauge invariance is recovered if a scalar field is properly incorporated into the theory. We followed the Dirac's technique to perform a detailed analysis of the constraint structure of the theory. Appropriate gauge conditions were derived to eliminate the first class constraints and obtain the Dirac's brackets of the independent dynamical variables. Alternatively, the generalized symplectic formalism method is used to study the gauge invariance Proca's electrodynamics theory. After fixing the gauge, the generalized brackets are calculated and the equivalence with the Dirac's brackets is shown. La electrodinámica de Proca describe una teoría de fotones masivos que no es invariante de gauge. En este trabajo se mostrará que la libertad de gauge es restaurada si un campo escalar es apropiadamente incorporado en la teoría. El método de Dirac es utilizado para realizar un detallado análisis de la estructura de vínculos de la misma. Apropiadas condiciones de gauge fueron derivadas con el fin de eliminar los vínculos de primera clase y obtener los corchetes de Dirac entre las variables dinámicas independientes. De manera alternativa, la formulación simplectica generalizada es utilizada para estudiar la teoría electromagnética de Proca invariante de gauge. Después de fijar el gauge, los corchetes generalizados son calculados y la equivalencia con los corchetes de Dirac es mostrada.

Películas delgadas de aleaciones ternarias de GaSb:Ni fueron preparadas por el método de pulverización catódica (DC magnetrón Co{Sputtering) variando la temperatura de sustrato (Ts). A partir de medidas de transmitancia espectral y difracción de rayos X (XRD) fueron obtenidas las constantes ópticas y las propiedades estructurales del material, respectivamente. Fases predominantes de GaSb y NiSb fueron observadas para todas las variaciones de Ts. A partir de medidas de absorción del material el valor de la banda de energía prohibida o “band gap” fue obtenido,variando entre 0,63 eV y 0,72 eV. Se reporta el coeficiente de extinción en función de la longitud de onda de las películas de GaSb:Ni. GaSb:Ni ternary alloys thin films were deposited via sputtering method (DC magnetron Co{Sputtering) varying the substrate temperature (Ts). From spectra transmittance measurements and X-ray diffraction (XRD) were obtained the optical constants and structural properties of material, respectively. Predominant phases of GaSb and NiSb were observed for all Ts variations. From absorption measurements, the value of energy band forbidden or “band gap” was obtained varying between 0,63 eV and 0,72 eV. The extinction coefficient as a function of wavelength of the GaSb:Ni thin films, was reported.

Se realizaron cálculos de primeros principios para estudiar las propiedades estructurales, electrónicas y magnéticas de la superficie m-GaN dopada con manganeso (Mn). Este dopaje generó un momento magnético total de 4 µB debido a la interacción de los estados 2p-N y 3d-Mn. Se encontró que el dopaje de Mn es responsable del 82 % de la magnetización total de la superficie. Además, el dopaje generó cambios estructurales en la superficie y se evidenciaron en las distancias entre las capas atómicas “d12, d23, d34, d45”. La superficie mostró propiedades de metal y semiconductor simultáneamente, estos materiales son llamados “half-metalic”, dependiendo de la polarización del espín. Se determinó la posición sustitucional del dopaje mas estable energéticamente, así mismo se observó que este dopaje generó menos cambios estructurales como lo muestran los porcentajes de cambio en las distancias entre capas atómicas “∆d12, ∆d23, ∆d34, ∆d45” First principles calculations were performed to study the structural, electronic and magnetic properties of the surface of m-GaN doped with manganese (Mn). This doping generated total magnetic moment 4 µB due to interaction of the 2p-N and Mn 3d-states. It was found that doping of Mn is responsible for 82 % of the total magnetization of the surface. In addition, doping generated structural changes in the surface which were evident in the distances between the atomic layers “d12, d23, d34, d45”. The surface showed metal and semiconductor properties simultaneously. These materials are called “half-metalic” depending on the spin polarization. Substitutional position of the most stable energy doping was determined, and was observed that doping generated less structural changes as that shown by the changes in the distance between atomic layers “∆d12, ∆d23, ∆d34, ∆d45”.

Los equipos y prototipos disponibles en Colombia para la enseñanza de la física a nivel medio y superior, son por norma costosos, imposibles de actualizar y/o adecuar a diferentes necesidades y soportados en otros idiomas diferentes al español entre otras limitantes, razón por la cual se diseña y construye un sistema que cubra las necesidades básicas de un curso de física experimental, que en contraste con los importados sea económico, con hardware y software libre que es fácil de actualizar y/o adecuar a las necesidades puntuales de cualquier curso o profesor. A manera de ejemplo, se comparten los resultados obtenidos con estudiantes de la Universidad del Valle sede Tuluá, en la cual se hizo el experimento llamado “Teorema del trabajo y la energía mecánica”, usando el sistema descrito en este documento. The equipment and prototypes available in Colombia for the teaching of physics at the intermediate and higher level, are normally expensive, impossible to update and/or adapt to different needs and supported in languages other than Spanish among other limitations This is why a new system is designed and constructed that covers the basic needs of an experimental physics course, in contrast to the imported one, with hardware and free software easier to update and/or adapt to the specific needs of any course or teacher. As example, we show the results obtained with students of the Universidad del Valle (Tulu´a), in the experiment called “Mechanical Work Theorem” which was carried out, using the system described in this document.

Utilizando el método de reacción de estado sólido se prepararon muestras policristalinas del compuesto Ca1-xLaxMnO3 (0 ≤ x ≥ 0.15). Sus propiedades de transporte se estudiaron en función de la temperatura y el contenido de lantano, a partir de mediciones de resistividad eléctrica ro(T) y coeficiente Seebeck S(T) en el rango de temperatura entre 100 y 290K. Las propiedades estructurales y morfológicas se estudiaron mediante estudios de difracción de rayos-X (XRD) y microscopia electrónica de barrido (SEM), respectivamente. El coeficiente Seebeck es negativo en todo el rango de temperatura estudiado, indicando una conducción dada por portadores de carga negativos, su magnitud disminuye con el contenido de lantano desde |-261| mV/K hasta |-120| mV/K. La resistividad eléctrica muestra un comportamiento de carácter semiconductor, descrito mediante un mecanismo tipo hopping de pequeños polarones. Las propiedades termoeléctricas de los compuestos obtenidos se evaluaron a través de su factor de potencia termoeléctrico PF, el cual alcanza valores máximos cercanos a 2mW/K2cm, estos valores permiten considerar esta familia de compuestos como posibles materiales útiles en aplicaciones termoeléctricas. By using the solid state reaction method samples of Ca1-xLaxMnO3 (0 ≤ x ≥ 0.15) were prepared. Their transport properties were studied by electrical resistivity rho(T) and Seebeck coefficient S(T) measurements as a function of temperature and lanthanum content, in the temperature range between 100 and 290K. The structural and morphological properties were studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. The Seebeck coefficient is negative throughout the studied temperature range indicating a conduction given by negative charge carriers, its magnitude decreases with the lanthanum content from |-261| mV/K to |-120| mV/K. The electrical resistivity shows a semiconducting behavior, it was interpreted in terms of small polaron hopping model. Thermoelectric properties of the obtained compounds were studied by the thermoelectric power factor PF, which reaches maximum values around 2mW/K2cm, these values become this kind of ceramics promising thermoelectric compound, to be used in technological applications.

Se establece la analogía entre la propagación de electrones en pozos cuánticos, con la propagación de ondas electromagnéticas entre medios dieléctricos. Al ser estudiados los fenómenos de transmisión en medios estratificados; pozos o dieléctricos, se encuentran resultados análogos. En primer lugar, se describe la transmitancia para el caso cuántico como electrodinámico. Luego, las relaciones de dispersión mediante los coeficientes de transmisión en ambos casos (electrones-luz) relacionando estos dos sistemas. Y finalmente se compara esta equivalencia con los resultados experimentales en la zona transparente (baja absorción 800-2500 (nm)) del espectro de transmisión de la película delgada de ZnSe, utilizando el método de la matriz de transferencia (MMT). The analogy between the solutions of Schrödinger equation with Helmholtz equation in a dimension is established, mainly of particle propagation (electrons) on quantum wells, with the propagation of electromagnetic waves (light) among electrical means. When transmission phenomena are studied in layered media, wells or dielectrics, they are found in analogical results. In this work, it is first presented the transmittance for quantum case and electrodynamic case independently. Then, the scattering amplitudes are related in both cases (electrons and waves), describing the connection and representation between these two systems. Finally they are compared with the experimental resultsin the transparent zone (low-absorption 800-2500 (nm)) of ZnSe thin film transmission spectrum, making use of the Transfer Matrix Method (TMM).

El láser de baja potencia se ha implementado dentro del campo médico, como una alternativa segura para influir en el comportamiento de las células del organismo humano. Se ha sugerido que la radiación de baja potencia reduce agentes patógenos, actúa como protector ante radiación ionizante e incrementa la población de plaquetas en sangre. Este trabajo tiene como objetivo analizar la tasa de crecimiento de las plaquetas humanas luego de aplicar radiación láser de baja potencia. The low-power laser has been implemented within the medical field as a safe alternative for influencing the behavior of cells of the human body. It has been suggested that low power radiation reduces pathogens and acts as a shield against ionizing radiation and increases the platelets population in blood. This study aims to analyze the rate of growth of human platelets after applying low power laser radiation.

Colombia es un país con importantes centros de desarrollo tecnológico e industrial a varios metros sobre el nivel del mar, esta condición limita la capacidad de calibración para la presión neumática por debajo de la presión atmosférica. En este trabajo se presentan los primeros resultados de un método de calibración indirecto que permite cubrir el alcance completo de medición de los vacuómetros digitales aun cuando se calibran varios metros sobre el nivel del mar. Colombia is a country with important technological and industrial centers located at different heights over sea level; this condition restrict the calibration procedures for pneumatic pressures below the atmospheric pressure. In this work we show the first results of an indirect calibration method that allows covering the full measurement span of digital vacuometers even when calibrated several meters above sea level.

En esta presentación se describen los imanes que componen los denominados tripletes que hacen parte del acelerador LHC y se discute cómo todos los errores magnéticos en dos tripletes se resumen en cierta combinación. El LHC es el acelerador, ubicado en el Laboratorio Europeo para la Física de Partículas del CERN, construido para operar a altas energías, de hasta 14 TeV para colisiones protón-protón. En la primera parte de esta presentación, se resumen los diseños, materiales y dimensiones presentes en la bibliografía para los imanes que componen un triplete del LHC, estos son principalmente cuadrupolos que están localizados cerca del punto de colisión (IP). En el LHC para las regiones de interacción (IR) alrededor de los IP 5 y 1 se tienen dos tripletes, uno a cada lado del IP. Para obtener un haz más fino se hacen correcciones de los errores magnéticos presentes, por ejemplo usando el método de Acción y Fase, y en este proceso no es conveniente mover todos los imanes. Por esto hemos estudiado cuál es la combinación de imanes que mejor sustituye todos los errores magnéticos, al menos a nivel lineal, usando únicamente dos correctores de cuadrupolo normal (B1) y un corrector cuadrupolo normal rotado (A1) con el método de Acción y Fase. Este estudio es desarrollado usando el simulador del LHC en MAD-X. Los resultados principales que muestran la efectividad de las correcciones son explicados en la segunda parte de esta presentación. A description of the magnets which compose the arrangements called triplets in the LHC is presented and it is discussed how the magnetic errors from two triplets can be summarize in certain combination. The LHC is the accelerator located at the European Laboratory for the Particle Physics at CERN, it is builded to operate at high energies, up to 14 TeV for proton-proton collisions. In the first part of this presentation, a summary, from the bibliography, of the design, materials and dimensions of the triplet magnets, is given; these are mainly quadrupoles which are located close to the collision point (IP). In the LHC for the Insertion Regions (IR) around IPs 5 and 1, there are two triplets, one at each IP side. To obtain a more fine beam, magnetic error corrections are done, for instance using the Action and Phase method, and in this process is not convenient to move all magnets. Because of this last we studied what is the combination of magnets which account best for all the magnetic errors, at least to a linear level, using just two normal quadrupole correctors (B1) and one skew quadrupole corrector (A1) with the Action and Phase Jump Method. This study is developed using the LHC simulator in MAD-X. The main results which shows the effectivity of the corrections are explained in the second part of this presentation.

In this work we report, for the first time at room temperature, experimental results that prove, simultaneously in the same device, the two main physical principles involved in the operation of intermediate band solar cells: (1) the production of sub-bandgap photocurrent by two optical transitions through the intermediate band; (2) the generation of an output voltage which is not limited by the photon energy absorption threshold. These principles, which had always required cryogenic temperatures to be evidenced all together, are now demonstrated at room temperature on an intermediate band solar cell based on InAs quantum dots with Al0.3Ga0.7As barriers.

Silicon wafers comprise approximately 40% of crystalline silicon module cost, and represent an area of great technological innovation potential. Paradoxically, unconventional wafer-growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect-management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled to effective control of fast-diffusing species during cell processing, is critical to enable high cell efficiencies. To accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection-dependent lifetime measurements.

Here we derive a completely quantum mechanical expression for linear susceptibility using a density matrix formalism where the electromagnetic field is also quantized. A zeroth order susceptibility emerges naturally from the treatment. By studying the dependence of susceptibility on material asymmetry and on the quantum state of light, we predict new and intriguing phenomena such as photon number dependent refraction index. Resumen En este trabajo derivamos una expresión completamente cuántica para la susceptibilidad eléctrica lineal usando un formalismo de matriz densidad donde el campo electromagnético también esta cuantizado. Del tratamiento se deduce de manera natural una susceptibilidad de orden cero. Mediante el estudio de la dependencia de la susceptibilidad con la asimetría de la materia y el estado cuántico de la luz, predecimos fenómenos nuevos e intrigantes como el índice de refracción dependiente del número de fotones.

Hemos usado las técnicas de calorimetría de barrido diferencial (DSC), análisis termogravimétrico (TGA) y espectroscopia de impedancias (IS) para estudiar el comportamiento de las fases del sistema NaH2PO4.H2O a temperaturas por encima de la temperatura ambiente. Los resultados de DSC muestran cinco anomalías endotérmicas con picos alrededor de 70 oC, 120 oC, 210 oC, 325 oC y 350 oC, durante el primer barrido de calentamiento, pero ninguna anomalía aparece en el siguiente barrido de enfriamiento.Los resultados de TGA revelan que la muestra fresca de NaH2PO4.H2O pierde peso cuando es calentada por primera vez a través de las diferentes temperaturas. La resistencia eléctrica de la muestra fresca de NaH2PO4.H2O también exhibe fuertes variaciones a través de las anomalías ubicadas alrededor de 70oC y 120oC, indicando que el transporte iónico es favorecido entre 55 oC y 108 oC y entre 120 oC y 150 oC. Nosotros discutimos y atribuimos el comportamiento observado en el NaH2PO4.H2O a lo largo de todas las temperaturas donde se observan las anomalías, como una consecuencia de procesos de deshidratación de la muestra. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Impedance Spectroscopy (IS) were used to study the phase behavior of the system, NaH2PO4.H2O above room temperature. The DSC results show five endothermic anomalies with picks around 70 oC, 120 oC, 210 oC, 325 oC and $350 oC, during the first heating run, but any anomaly is show on the subsequent cooling run. The TGA results show that fresh powder of NaH2PO4.H2O loss weight when the sample is first heated across the different temperatures. The electrical resistance of fresh sample NaH2PO4.H2O also shows strong variation at 70 oC and 120 oC anomalies, indicating that the ionic transport is enhanced between 50 oC and 108 oC, and between 120 oC and 150 oC. We discuss and attributed the observed behavior in NaH2PO4.H2O throw the different temperatures, where observed the anomalies, as a consequence of a dehydration process of the sample.

Resumen Se depositaron películas delgadas de ZnMnO por el método de Deposición por Laser Pulsado (PLD, por sus siglas en inglés) sobre sustratos de Silicio, variando la concentración de Mn en el rango entre 1 y 20 wt.%, manteniendo la presión del gas de trabajo y la temperatura del substrato constantes, en 46 mTorr y temperatura ambiente respectivamente. Para observar el efecto de la concentración de Mn en las muestras crecidas se usaron las técnicas de difracción de rayos-X (DRX) y espectroscopia Raman. Del estudio de DRX se observa que todas las muestras preparadas en este trabajo tienen una estructura wurzita hexagonal y se presenta una ligera variación de los parámetros de red, entre 3.170 Å a 3.192 Å y 5.176 Å a 5.213 Å para las constantes a y c respectivamente. El análisis Raman corrobora la estructura wurzita de las muestras al observarse en todas ellas el modo óptico E2 (High) tópico de la estructura del ZnO. En general se observaron bandas localizadas en 100 cm-1, 434 cm-1 y 570 cm-1 asociados con los modos de vibración E2 (Low), E2 (High) y E1 (LO) respectivamente. El estudio estructural de las muestras permite establecer que no hubo cambio de fase respecto al ZnO debido a la incorporación del Mn. Abstract ZnO thin films were deposited by the method of pulsed laser deposition (PLD, for its acronym in English) on silicon substrates, varying the concentration of Mn in the range of 1 to 20 wt.%. The gas pressure work and substrate temperature were keeping constant, at 46 mTorr and room temperature respectively. In order to observe the effect of the Mn concentration in the grown samples, X-ray diffraction (XRD) and Raman spectroscopy techniques were used. The XRD study shows that all samples prepared in this work have a hexagonal wurtzite structure with slight variation of the lattice parameters between 3.170 Å to 3.192 Å and 5.176 Å to 5.213 Å for the constants a and c respectively. All the samples diplay the optical mode E2 (High) typical of the structure of ZnO, which supports the existence of the wurtzite structure. Generally bands located at 100 cm-1, 434 cm-1 and 570 cm-1 associated with the vibration modes E2 (Low), E2 (High) and E1 (LO) were observed respectively. There is no chance of phase relative to ZnO due to the incorporation of Mn as determined from structural study of samples.

Medical cyclotrons are now commonly used for the production of PET nuclides by the (pn) reaction. These devices are typically capable of delivering 10-15 MeV protons beams at sufficiently high intensity for timely production of β+ decaying nuclides. Non-conventional PET nuclides have emerged recently and offers new opportunities for diagnostic and therapy drug discovery. In this paper, we will review the production capabilities for such nuclides at Washington University Medical School in St. Louis and present their production. Finally, challenges for imaging imposed by the specific of the decay characteristics will be discussed. Los ciclotrones médicos son usados actualmente para la producción de Nucleidos de PET. Esos dispositivos son capaces de producir haces de protones de 10-15 MeV con suficiente intensidad para la producción de radionúcleos con decaimiento β+. Los nucleidos no convencionales de PET han surgido recientemente y ofrecen nuevas oportunidades para diagnóstico y farmacoterapia. En este artículo se hará mención de la capacidad de producción de tales nucleidos en la Washington University Medical School. Serán discutidos los retos en imagenología impuestos por las características del decaimiento.

Ternary Cu(Sb,Bi)S2 semiconductors are a group of materials with a wide variety of applications, especially photovoltaic. An analysis of the structural, electronic, and optical properties obtained from first-principles is presented. The microscopic justification of the high absorption coefficients is carried out by splitting the optical properties on chemical species contributions according to the symmetry. Focusing on photovoltaic applications, and from first-principles results, the efficiencies for several solar spectra are obtained as a function of the device thickness. This study indicates the great potential of these materials for photovoltaic and other optical devices.

7 págs.; 5 figs., In this work, we analyze the effect of temperature drifts in a spatial heterodyne Fourier-transform micro-spectrometer fabricated in a Silicon-on-insulator chip. The device comprises an array of 32 Mach-Zehnder interferometers implemented with microphotonic spirals of linearly increasing length. This configuration provides a resolution of 42 pm in a footprint under 12 mm. However, this resolution enhancement implies a greater sensitivity to environmental variations during the spectrometer operation. In this work, the effect of temperature drifts in the spectral retrieval algorithm is studied, and compensation techniques based on multiple calibration matrices is presented. © Sociedad Española de Óptica, Este trabajo ha sido apoyado económicamente por el Ministerio de Economía de España a través de los proyectos TEC2012-37958-C02-02 y TEC2012-37958-C02-01, la Comunidad de Madrid a través de S2013/MIT-2790, y EURAMET a través del proyecto JRP-i22 14IND13 Photind.

[ES] Esta publicación resume los resultados de la tesis doctoral: Diseño, Fabricación y Control de Calidad de Lentes Intraoculares Multifocales, presentada por L. Remón en la Universitat Politècnica de València (Octubre de 2012) y dirigida por los profesores J.A Monsoriu y W.D. Furlan [1]. Las lentes multifocales (LIOMs) suponen una alternativa prometedora en pacientes de más de 50 años para la compensación de la presbicia. En el mercado existen gran disparidad de diseños multifocales, cada uno con sus ventajas e inconvenientes, lo que evidencia que la LIOM que ofrece las mejores prestaciones todavía no ha sido diseñada. En este trabajo se presentan resultados de diseño, fabricación y evaluación de la calidad óptica de un nuevo tipo de LIOMs, con geometría fractal, que presenta una mayor profundidad de foco y una menor aberración cromática con respecto a las que actualmente se encuentran en el mercado. Para la evaluación de la calidad óptica de las LIOMs propuestas se han desarrollado expresamente dos dispositivos experimentales basados en las especificaciones de la Norma UNE ISO 11979-2., [EN] This paper is a summary of the results of the PhD entitled: Design, Fabrication and Quality Control of the Multifocal Intraocular Lenses presented and defended by L. Remon at Universitat Politecnica de Valencia (October 2012) and supervised by Prof. J.A Monsoriu and Prof. W.D. Furlan [1]. Multifocal IOLs (MIOLs) are a promising alternative to presbyopic patients (suffering from cataracts). There exist several commercially available models and designs of MIOLs, each one with its own drawbacks and advantages, evidencing that the optimum MIOL has not yet designed. This work presents the design, and quality control of a new design of MIOL with a fractal profile. This type of lenses provides an extended depth of field and a reduced chromatic aberration compared to other commercially available designs. Additionally, to assess the optical quality of MIOLs, two different experimental setups were designed "ad-hoc"; according to the requirements of the UNE ISO 11979-2 standard., Este trabajo ha sido financiado por el Ministerio de Economía y Competitividad a través del Proyecto FIS2011-23175 y por la Generalitat Valenciana a través de los Proyectos PROMETEOII/2014/072 y ACOMP/2014/180. L. Remón agradece el apoyo de todos los miembros del grupo DiOG (UV-UPV), a la empresa AJL Ophthalmic S.A. por la fabricación de las lentes intraoculares que se han caracterizado en este trabajo y a la Fundación CajaMurcia por la concesión de una beca pre-doctoral.

This paper summarizes the contributions of a PhD focused on developing a set of numerical methods for the analysis of periodic diffractive optical devices such as holographic diffractive devices, thin film filters or diffraction gratings. For the rigorous and comprehensive analysis of these devices in optical wavelengths the finite difference time domain (DFDT) method was considered being compared to classical theories. Application of DFDT in optical wavelengths implies a considerable computational cost. Therefore, this method was accelerated for the most common computing platforms: CPU (Central Processing Unit) and GPU (Graphic Processing Unit). En este artículo se hace una revisión de las aportaciones de la Tesis Doctoral en la que se ha desarrollado una serie de métodos numéricos para el análisis de dispositivos ópticos difractivos periódicos como pueden ser Redes de Difracción Holográficas (RDH), filtros de capa delgada o redes de apertura. Para el análisis riguroso y completo de estos medios en longitudes de onda ópticas se ha recurrido al método de las diferencias finitas en el dominio del tiempo (DFDT), siendo contrastado mediante teorías clásicas. La aplicación del método de las DFDT en longitudes de onda ópticas implica un coste computacional considerable. Por ello, este método se ha acelerado en las plataformas de cálculo más comunes en la actualidad: CPU (Central Processing Unit) y GPU (Graphic Processing Unit). Este trabajo ha sido parcialmente financiado por el Ministerio de Economía y Competitividad de España a través del proyectos FIS2011-29803-C02-01, por la Universidad de Alicante a través del proyecto GRE12-14 y por la Generalitat Valenciana a través del proyecto GV/2014/076.

Thermography for scientific research and practical purposes requires a series of procedures to obtain images that should be standardized; one of the most important is the time required for acclimatization in the controlled environment. Thus, the objective of this study was to identify the appropriate acclimatization time in rest to reach a thermal balance on young people skin. Forty-four subjects participated in the study, 18 men (22.3 ± 3.1 years) and 26 women (21.7 ± 2.5 years). Thermographic images were collected using a thermal imager (Fluke ®), totaling 44 images over a period of 20 minutes. The skin temperature (TSK) was measured at the point of examination which included the 0 minute, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20. The body regions of interest (ROI) analyzed included the hands, forearms, arms, thighs, legs, chest and abdomen. We used the Friedman test with post hoc Dunn?s in order to establish the time at rest required to obtain a TSK balance and the Mann-Whitney test was used to compare age, BMI, body fat percentage and temperature variations between men and women, considering always a significance level of pmenor que0.05. Results showed that women had significantly higher temperature variations than men (pmenor que0.01) along the time. In men, only the body region of the abdomen obtained a significant variance (pmenor que0.05) on the analyzed period, both in the anterior and posterior part. In women, the anterior abdomen and thighs, and the posterior part of the hands, forearms and abdomen showed significant differences (pmenor que0.05). Based on our results, it can be concluded that the time in rest condition required reaching a TSK balance in young men and women is variable, but for whole body analysis it is recommended at least 10 minutes for both sexes.

Copper nanoparticles (Cu NPs) supported on diamond nanoparticles (D NPs) previously purified by Fenton treatment (Cu/D) followed by annealing with hydrogen (Cu/DH) are highly efficient and reusable heterogeneous catalysts for hydrogenation of styrene to ethylbenzene with the minimum productivity value of 30617 cycles., Financial support from the Spanish Ministry of Science and Education (Consolider MULTICAT, CTQ-2012-32316) is gratefully acknowledged.

CaO:Eu3+, M+ (Li+ or Na+ or K+ ), SrO:Eu3+and CaSrO2:Eu3+ powders were prepared by combustion synthesis method and the samples were further heated to 1000 C to improve the crystallinity of the materials. The structure and morphology of materials were examined by X-ray diffraction and scanning electron microscopy. The morphology of CaO:Eu3+ and co-doped with alkali metal ions powders was very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. The surface morphology of SrO and CaSrO2 materials was not smooth and coagulated particles of irregular shapes with different sizes were observed. The characteristic emissions of Eu3+ had strong emission at 614 and 620 nm for 5 D0 ? 7 F2 with other weak transitions observed at 580, 592, 654, 705 nm for 5 D0 ? 7 Fn transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity followed the order as in CaO > CaSrO2 > SrO lattices. A remarkable increase of photoluminescence intensity was observed by the co-doping of alkali metal ions particularly K+ ions in CaO:Eu3+., This work was supported by Spanish Government through MCINN Grant MAT2009-14625-C03-03. K.C. Singh acknowledges MEC for financial support (SAB2010-0019).

We report results of molecular dynamics simulations on the transient and equilibrium surface adsorption of methane in a model Si-LTA zeolite structure with explicit silanol terminal groups. Using probability occupancy maps, 2D occupational densities, and free energy pro¿les, we extract a microscopic picture of the adsorption process, showing surface preferential zones of interaction around the partially exposed oxygen atoms of the surface silanol groups due to attractive silanol guest attractions. The global e¿ect of the loading on the uptake process is observed as a decrease in the free energy barrier as the loading increases and an increase in the surface permeability, calculated either from the initial uptake transient process or from equilibrated trajectories. The order of magnitude of the obtained surface permeability suggests a barrier that becomes relevant to the overall mass transfer for crystal sizes in the range of a few unit cells. Our results support experimental evidence that ascribe surface resistances to severe crystal structure deviations, causing an almost complete blockage of the surface available entering windows., Funding through Ministerio de Ciencia e Innovacion (project MAT2007-64682) and computing time from Red Espanola de Supercomputacion are gratefully acknowledged. A.F.C. acknowledges a research fellowship provided by the Instituto de Tecnologia Quimica UPV-CSIC. We thank an anonymous reviewer for very insightful comments.

In conjunction with quenching metal ions, silica nanoparticles carrying terpyridine coordination sites and sulforhodamine B signalling units were employed for the differential fluorometric recognition of anions. © 2011 The Royal Society of Chemistry.

In this work, CuInSe 2 based flexible photovoltaic cells have been fabricated completely using non-vacuum low-cost techniques. Thin films were deposited on molybdenum thin foil substrates by electrodeposition using a buffered aqueous electrolyte with the deposition of subsequent layers performed by spray pyrolysis. In addition, the buffer layer CdS was replaced with a wider bandgap ZnS (3.7 eV) and analysis undertaken of the fabrication pathway, morphological and compositional changes resulting from the different precursor route. The deposited films were annealed in a Se atmosphere at 450 °C. The influence of annealing temperature and time on the properties of the films are briefly discussed. Characterisation of thin films was performed using aqueous electrolyte contacts. Capacitance measurements were made as a function of applied bias on thin films deposited on metal substrates with blocking electrolyte contacts where analysis of the impedance gave values of the space charge capacitance from which the doping density and flat band potential were derived. The structural characterisation was carried out using X-ray diffraction and Raman spectroscopy. The structure and device properties of Mo (SS)/CuInSe 2/ZnS/n +-ZnO/Ni were characterized using current-voltage technique and photocurrent spectroscopy. © 2011 Elsevier B.V., This work was supported by the Spanish Government through MEC grant MAT2009-14625-C03-03 and the Fundacao para a Ciencia e a Tecnologia (FCT) in Portugal.

The characteristic temperatures of the threshold current density, T0, and external differential quantum efficiency, T1, of a series of (Ga,In)(N,As)/GaAs quantum well (QW) laser diodes are measured in the wavelength range from 1 to 1.5 µm. It is found that both T0 and T1 strongly decrease with increasing lasing wavelength. The origin of this degradation is shown to be, in the case of T0, mostly dominated by a decrease in the transparency current density characteristic temperature, an increase in the optical losses and a decrease in the modal gain. The degradation of T1 is mainly due to the increase in the optical losses. The effective carrier recombination lifetime in the QW is shown to decrease from 1.2 to 0.2 ns with N content up to 2%, in good agreement with previous reports that link this low lifetime to non-radiative monomolecular recombination through defects in the QW. Carrier leakage is ruled out as the dominant process degrading T0 and T1 on the basis of the temperature dependence of the effective carrier recombination lifetime.

Crystalline silicon photovoltaic (PV) modules are often stated as being the most reliable element in PV systems. This presumable high reliability is reflected by their long power warranty periods. In agreement with these long warranty times, PV modules have a very low total number of returns, the exceptions usually being the result of catastrophic failures. Up to now, failures resulting from degradation are not typically taken into consideration because of the difficulties in measuring the power of an individual module in a system. However, lasting recent years PV systems are changing from small isolated systems to large grid-connected power stations. In this new scenario, customers will become more sensitive to power losses and the need for a reliability model based on degradation may become of utmost importance. In this paper, a PV module reliability model based on degradation studies is presented. The main analytical functions of reliability engineering are evaluated using this model and applied to a practical case, based on state-of-the-art parameters of crystalline silicon PV technology. Relevant and defensible power warranties and other reliability data are obtained with this model based on measured degradation rates and time-dependent power variability. In the derivation of the model some assumptions are made about the future behaviour of the products—i.e. linear degradation rates—although the approach can be used for other assumed functional profiles as well. The method documented in this paper explicitly shows manufacturers how to make reasonable and sensible warranty projections. Copyright © 2008 John Wiley & Sons, Ltd.

Structural refinement of the ternary chalcogenide compoundCu2GeTe3 by X-ray powder diffraction Delgado, Gerzon E.; Mora, Asiloé J.; Pirela, María, Velásquez-Velásquez, Ana, Villarreal, Manuel; Fernández, Braulio J. Abstract The Cu2GeTe3 compound crystallizes in the Imm2 (N° 44) space group, Z = 2, with a = 12.641(1) Å, b = 4.2115(2) Å, c = 5.9261(2) Å, V = 315.49(3) Å3. Its structure was refined from X-ray powder diffraction data using the Rietveld method. The refinement of 23 instrumental and structural variables led to Rp = 8.2%, Rwp = 11.6%, Rexp = 6.8%, RB = 11.2 % and S = 1.7, for 5501 step intensities and 253 independent reflections. This compound is isostructural with Cu2GeSe3, and consists of a three-dimensional arrangement of slightly distorted CuTe4 and GeTe4 tetrahedra connected by common corners.. gerzon@ula.ve mavu@ula.ve mpireira@ula.ve anita@ula.ve asiloe@ula.ve braulio@ula.ve Nivel monográfico

The contribution of charge balance and optical microcavity effects in solution processed OLEDs cannot be easily quantified due to the absence of a well defined location for the emission zone. In this paper, we study the device efficiency of a solution processed blue electrophosphorescent OLED where the relative electron–hole balance is varied by means of molecular doping with an electron transport material. Changes in the electroluminescent spectra for the device series indicate the presence of optical microcavity effects, which we quantify by means of optical simulation. Furthermore, this enables us to factor out the contribution of microcavity effects on device efficiency enabling the quantification of the charge balance effect on device performance.