Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications

Liquid Crystal on Silicon (LCoS) has become one of the most widespread technologies for spatial light modulation in optics and photonics applications. These reflective microdisplays are composed of a high-performance silicon complementary metal oxide semiconductor (CMOS) backplane, which controls the light-modulating properties of the liquid crystal layer. State-of-the-art LCoS microdisplays may exhibit a very small pixel pitch (below 4 ?m), a very large number of pixels (resolutions larger than 4K), and high fill factors (larger than 90%). They modulate illumination sources covering the UV, visible, and far IR. LCoS are used not only as displays but also as polarization, amplitude, and phase-only spatial light modulators, where they achieve full phase modulation. Due to their excellent modulating properties and high degree of flexibility, they are found in all sorts of spatial light modulation applications, such as in LCOS-based display systems for augmented and virtual reality, true holographic displays, digital holography, diffractive optical elements, superresolution optical systems, beam-steering devices, holographic optical traps, and quantum optical computing. In order to fulfil the requirements in this extensive range of applications, specific models and characterization techniques are proposed. These devices may exhibit a number of degradation effects such as interpixel cross-talk and fringing field, and time flicker, which may also depend on the analog or digital backplane of the corresponding LCoS device. The use of appropriate characterization and compensation techniques is then necessary

Dehouve Danièle et Richard Prost, Les Dangers du pouvoir, Tonaltepec Production / Coproduction Les films du village, Cannes TV, CNRS Images France, 2005, 54’ [images : Richard Prost, son : Demetrio, montage : Jean Baptiste Delpios]

Le pouvoir politique a cette particularité de rendre vulnérable celui qui prétend le détenir. L’ambition, la vantardise et la crainte conspirent contre son destin personnel et, de façon inéluctable, également contre le destin collectif. Pour réussir dans la gestion politique il faut donc veiller à soi. Néanmoins, comment conjurer les dangers du pouvoir ? À travers ce film, Danièle Dehouve approfondit cette question en terre tlapanèque, au sud-ouest du Mexique dans la montagne de Guerrero. Au ..

Special Issue on Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications

This special issue provides a collection of papers demonstrating the impact of LCoS microdisplays in current and future spatial light modulation applications. State-of-the-art in LCoS device technology, LC materials, modeling and characterization techniques are presented

Optimization and performance criteria of a Stokes polarimeter based on two variable retarders

In this paper we present the analysis, optimization and implementation of several Stokes polarimeter configurations based on a setup including two variable retarders. The polarimeter analysis is based on the Mueller-Stokes formalism, and as a consequence, it is suitable to deal with depolarized light. Complete Stokes polarimeters are optimized by minimizing the amplification of simulated errors into the final solution. Different indicators useful to achieve this aim, as the condition number or the equally weighted variance, are compared in this paper. Moreover, some of the optimized polarimeters are experimentally implemented and it is studied the influence of small deviations from the theoretical ones on the amplification of the Stokes component error. In addition, the benefit of using incomplete polarimeters, when detecting specific ranges of states of polarization, is discussedFil: Peinado, Alba. Universitat Autonoma de Barcelona; EspañaFil: Lizana, Ángel. Universitat Autonoma de Barcelona; EspañaFil: Vidal, Josep. Universitat Autonoma de Barcelona; España. ALBA Synchrotron Light Source Facility; EspañaFil: Iemmi, Claudio Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campos, Juan. Universitat Autonoma de Barcelona; Españ

Zn-Promoted Selective Gas-Phase Hydrogenation of Tertiary and Secondary C4 Alkynols over Supported Pd

We have investigated the gas-phase (P = 1 atm; T = 373 K) hydrogenation of (tertiary alkynol) 2-methyl-3-butyn-2-ol (MBY) and (secondary) 3-butyn-2-ol (BY) over a series of carbon (C), non-reducible (Al2O3 and MgO), and reducible (CeO2 and ZnO) supported monometallic [Pd (0.6–1.2% wt) and Zn (1% wt)] and bimetallic Pd–Zn (Pd:Zn mol ratio = 95:5, 70:30, and 30:70) catalysts synthesized by deposition–precipitation and colloidal deposition. The catalysts have been characterized by H2 chemisorption, hydrogen temperature-programmed desorption (H2-TPD), specific surface area (SSA), X-ray photoelectron spectroscopy (XPS), and transmission (TEM) and scanning transmission electron microscopy (STEM) analyses. Reaction over these catalysts generated the target alkenol [2-methyl-3-buten-2-ol (MBE) and 3-buten-2-ol (BE)] through partial hydrogenation and alkanol [2-methyl-butan-2-ol (MBA) and 2-butanol (BA)]/ketone [2-butanone (BONE)] as a result of full hydrogenation and double-bond migration. The catalysts exhibit a similar Pd nanoparticle size (2.7 ± 0.3 nm) but a modified electronic character (based on XPS). Hydrogenation activity is linked to surface hydrogen (from H2 chemisorption and H2-TPD). An increase in H2:alkynol (from 1 → 10) results in enhanced alkynol consumption with a greater rate in the transformation of MBY (vs BY); H2:alkynol had negligible effect on product distribution. Reaction selectivity is insensitive to the Pd site electron density with a similar response (SMBE = 65 ± 9% and SBE = 70 ± 8%) over Pdδ− (on Al2O3 and MgO) and Pdδ+ (on C and CeO2). A Pd/ZnO catalyst delivered enhanced alkenol selectivity (SMBE = 90% and SBE = 96%) attributed to PdZn alloy phase formation (proved by XRD and XPS) but low activity, ascribed to metal encapsulation. A two-fold increase in the consumption rate was recorded for Pd–Zn/Al2O3 (30:70) versus Pd/ZnO with a similar alloy content (32 ± 4% from XPS), ascribed to a contribution due to spillover hydrogen (from H2-TPD) where high alkenol selectivity was maintained.This research was funded by the Engineering and Physical Sciences Research Council (EPRSC; grant number EP/L016419/1; Ph.D. studentship to A.G.-F., CRITICAT program), the Spanish Ministerio de Ciencia Innovación y Universidades, Generalitat Valenciana and FEDER (RTI2018-095291-B-I00, MAT2017-87579-R MINECO/FEDER and PROMETEO/2018/076)

Incidencia de los estilos de vida para el desarrollo de Diabetes Mellitus tipo II en la población chilena

Tesis (Profesor de Educación Física, Licenciado en Educación)La presente investigación surge con el motivo de analizar la incidencia de los estilos de vida para el desarrollo de la diabetes mellitus tipo II (DM2). En esta obra se analizará a personas con DM2, identificando los estilos de vidas previos al diagnóstico de esta enfermedad, que pueden incidir o ser causantes directos de ella. Para verificar esto, se formuló una encuesta para ser aplicada en la ADICH (asociación de diabéticos de Chile) a personas que padecen DM2. La muestra total de la investigación fue de 100 personas; 50 hombres y 50 mujeres. Con los resultados obtenidos se dará a conocer cómo era la vida de estas personas antes del diagnóstico de la DM2 en cuanto a la cantidad y duración de actividad física, tipo de nutrición, cantidad de alimentos y horarios dispuestos para alimentarse, y finalmente los factores de riesgo cardiovasculares, tanto modificables como no modificables, asociados a la enfermedad en cuestión. De esta manera, se enfatizará lo importante de estas tres características tanto en la génesis de la enfermedad, como en la influencia que cada una de ellas en tendrá en la prevención o retardo de la aparición de esta patología. Los resultados obtenidos se darán a conocer mediante análisis, apoyados por una serie de gráficos y su respectiva explicación. Se podrá ver las diferencias presentadas entre hombres y mujeres previos al diagnóstico de la DM2, obteniendo conclusiones generales y entendiendo como los hábitos de vida pudieron tener relevancia en la génesis de la DM2. Dentro de los resultados relevantes, el escaso tiempo destinado a la práctica de actividad física, junto a la mala conjugación y calidad de los alimentos ingeridos, se ven potenciadas con factores de riesgo asociados. Todo esto finalmente converge en una sinergia de efectos negativos que van en desmedro de la salud, gestando la aparición de la DM2

Study of C, N, P and K Release from Residues of Newly Proposed Cover Crops in a Spanish Olive Grove

Cover crops (CC)s are increasingly employed by farmers in olive groves. Spontaneous soil cover is the most commonly used CC. Its continuous utilization changes ruderal flora. It is necessary to study new CCs. Living CCs provide C and nutrients to soil during decomposition. Information on this issue in olive groves is scarce. A 4-year field study involving grab sampling of Brachypodium distachyon, Sinapis alba and spontaneous CC residues was conducted to study C and nutrient release from cover crop residues. Throughout the decomposition cycles, C, N and P release accounted for 40 to 58% of the C, N and P amounts in the residues after mowing. Most K was released (80–90%). Expressed in kg per hectare, the release of C and N in Brachypodium (C: 4602, N: 181, P: 29, K: 231) and Sinapis (C: 4806, N: 152, P: 18, K: 195) was greater than that in spontaneous CC (C: 3115, N: 138, P: 21, K: 256). The opposite results were observed for K. The Rickman model, employed to estimate the amount of C, N and P in residues, yielded a good match between the simulated and measured values. In comparison to spontaneous CC, the newly proposed CCs have a higher potential to provide soil with C and N

Comparación de sistemas de manejo de suelo en olivar en ensayos de simulación de lluvia

El objetivo de este estudio es comparar la influencia de dos sistemas de manejo de suelo utilizados en olivar, cubierta vegetal y laboreo convencional, en la generación y calidad de las aguas de escorrentía y la erosión asociada a estos fenómenos. Se parte de la convicción de que la cubierta vegetal, al reducir el flujo superficial y la pérdida de suelo, ha de disminuir en principio la contaminación de las aguas superficiales

Misalignment error analysis in polychromatic division of focal plane Stokes polarimeters

Snapshot imaging polarimeters are used in many different areas. Recently, division of focal plane (DoFP) polarimeters have proved useful as snapshot polarimeters for dynamic applications. For an optimal performance of polarimeters, different works dealing with the error analysis of such devices are proposed in literature. In terms of noise amplification from intensity measurements to the final polarization calculations, well-established quality metrics, as in the condition number or the equally weighted variance criteria, are used. Other studies analyze systematic errors due to deviations in the construction parameters. However, something not considered so far is the effect produced by misalignment between the various pixelated masks over the pixelated structure of the camera sensor, always occurring in experimental implementations of DoFPs. In this work, we study the effect of such misalignments in DoFP polarimeters and demonstrate how they lead to polarimetric systems composed of partially depolarized analyzers. We calculate the combined degree of polarization related to different amounts of misalignment and analyze the corresponding system performance. From this study, we show how an imaging polarimeter based on partially polarized analyzers can still lead to a robust and accurate polarimetric performance, and we also provide the misalignment limits in which an acceptable performance is obtained. We evaluate both the monochromatic and the polychromatic cases with special focus on the latter.Ministerio de Economía y Competitividad (MINECO) (FIS2015-66328-C3-1-R, fondos FEDER)