84 research outputs found
Optimization of the diffraction efficiency in photorefractive crystals
Get PDFThe aim of this work is to study and to optimize the diffraction efficiency in sillenite BTO crystals. A theoretical analysis, where the effects of coupling beams are significant,is carried on. In addition, non-mobile transmission gratings are considered. The diffraction efficiency is obtained by using the coupled wave equations in on-Bragg regime using Method Runge-Kutta of order 4 in Matlab. Also, the non-uniformity of the gratings in side the crystal sample, the optical activity of the material and the polarization of the recording beams are taken into account.Fil: Villamizar Amado, Astrid Lorena. Universidad de Pamplona; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arias Hernández, Néstor Alonso. Universidad de Pamplona; ColombiaFil: Molina Prado, Martha Lucia. Universidad de Pamplona; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tebaldi, Myriam Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentin
Eficiência de difracção modulada speckle gerado a partir de superfícies de difusão de reflectores
Get PDFEn este trabajo se amplia el estudio de difracción de los registros de patrones de speckle modulados generados por superficies reflecto-difusoras en medios fotorrefractivos, se investiga la influencia de la aplicación de un campo eléctrico externo y la relevancia de la orientación relativa de este campo respecto a la dirección de las redes de índices que modulan los speckle individuales, es decir, la orientación de las pupilas. Además se definen los parámetros a ser seleccionados, en términos de lograr un compromiso que mantenga buenos valores de eficiencia para realizar aplicaciones con este tipo de montaje experimental.In this paper extends the diffraction study of the recording modulated speckle patterns generated by diffusing reflectors surfaces in photorefractive crystals. The diffraction efficiency in terms of the application of an external electric field and the relative orientation of the field with respect a grating of indices which modulated speckle, ie the orientation of the pupils, are studied. Besides the parameters to be selected, in terms of achieving a compromise that maintains good efficiency values for applications of this experimental setup.Neste artigo estende a registos de difracção de estudo modulados salpico padrões gerados por superfícies difusoras reflectores media fotorrefrativos, investigando a influência da aplicação de um campo eléctrico externo e a importância da orientação relativa do campo no que diz respeito os índices de endereço de rede que modulam salpico indivíduo, isto é, a orientação dos alunos. Além de definir os parâmetros a serem selecionados, em termos de obtenção de um compromisso que mantém bons valores de eficiência para aplicações de configuração, tais experimental.Fil: Molina Prado, Martha Lucia. Universidad de Pamplona; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Tebaldi, Myriam Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Bolognini, Nestor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentin
CONSTRUCCIÓN DE UN MICROSCOPIO PERFILOMETRICO POR INTERFEROMETRÍA DE LUZ BLANCA
Get PDFEn este trabajo se presenta el diseño y construcción de un microscopio perfilométrico por interferometría de luz blanca, que permite el levantamiento topográfico de objetos con resolución nanométrica. Por medio de un escaneo axial del objeto, se adquiere un conjunto de imágenes con franjas interferométricas deformadas las cuales dan información de la rugosidad del objeto. El principio del sistema está basado en la localización del pico de coherencia en cada posición Im(i,j) del conjunto de m imágenes adquiridas, en donde la posición z(m) del pico de coherencia cambia de acuerdo a la topografía del objeto. Se presenta una serie de reconstrucciones tridimensionales de varios objetos a resolución nanométrica, obtenidas de manera automática con la ayuda de una interface gráfica elaborada en Matlab, que permite el control de los dispositivos, procesado digital de las imágenes y el cálculo de la topografía del objeto
Análisis de la fuerza transversal en las aproximaciones de Rayleigh y Mie para un rayo de captura TEM00 y TEM*01
Get PDFOptical tweezers use a highly-focused laser beam to capture and manipulate micro- and nanometric objects. These have been demonstrated to be a promising devices for state-of-the-art research in several fields, such as microbiology and biophysics. The prediction of the optical forces that are present in this phenomenon is a current problem in continuous evolution. Additionally, the recent use of vortex beams with exotic properties as the orbital angular momentum, with advantages as the rotational manipulation of the captured microparticles and reduction of the optical damage in biological samples (Opticution), makes the problem even more complex. Mathematical expressions in the Rayleigh and Mie regimes for the radiation force on a dielectric sphere captured by TEM00 and TEM*01 mode beams are presented. Theoretical results are then compared with experimental measurements obtained with a direct force measurement device based on light-momentum detection.Las pinzas ópticas utilizan un rayo láser altamente enfocado para capturar y manipular objetos micro y nanométricos. Se ha demostrado que son un dispositivo prometedor para la investigación de vanguardia en varios campos, como la microbiología y la biofísica. La predicción de las fuerzas ópticas presentes en este fenómeno es un problema actual en continua evolución. Además, el reciente uso de haces de vórtice con propiedades exóticas como el momento angular orbital, con ventajas como la manipulación rotacional de las micropartículas capturadas y la reducción del daño óptico en las muestras biológicas (Opticution), hace que el problema sea aún más complejo. Se presentan expresiones matemáticas en los regímenes de Rayleigh y Mie para la fuerza de radiación sobre una esfera dieléctrica capturada por los haces de los modos TEM00 y TEM*01. A continuación se comparan los resultados teóricos con las mediciones experimentales obtenidas con un dispositivo de medición directa de la fuerza basado en la detección del momento de la luz
Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions
Get PDFWe present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe
Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV
Get PDFTwo-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe
Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV
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Finishing the euchromatic sequence of the human genome
Get PDFThe sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV
Get PDFThe pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe
Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV
Get PDFThe elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe
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