Coherent Time Evolution and Boundary Conditions of Two-Photon Quantum Walks

Multi-photon quantum walks in integrated optics are an attractive controlled quantum system, that can mimic less readily accessible quantum systems and exhibit behavior that cannot in general be accurately replicated by classical light without an exponential overhead in resources. The ability to observe time evolution of such systems is important for characterising multi-particle quantum dynamics---notably this includes the effects of boundary conditions for walks in spaces of finite size. Here we demonstrate the coherent evolution of quantum walks of two indistinguishable photons using planar arrays of 21 evanescently coupled waveguides fabricated in silicon oxynitride technology. We compare three time evolutions, that follow closely a model assuming unitary evolution, corresponding to three different lengths of the array---in each case we observe quantum interference features that violate classical predictions. The longest array includes reflecting boundary conditions.Comment: 7 pages,7 figure

Increased Mortality for Elective Surgery during Summer Vacation: a Longitudinal Analysis of Nationwide Data

Surgical safety during vacation periods may be influenced by the interplay of several factors, including workers' leave, hospital activity, climate, and the variety of patient cases. This study aimed to highlight an annually recurring peak of surgical mortality during summer in France and explore its main predictors. We selected all elective of open surgical procedures performed in French hospitals between 2007 and 2012. Surgical mortality variation was analyzed over time in relation to workers leaving on vacation, the volume of procedures performed by hospitals, and temperature changes. We ran a multilevel logistic regression for exploring the determinants of surgical mortality, taking into account the clustering of patients within hospitals and adjusting for patient and hospital characteristics. A total of 609 French hospitals had 8,926,120 discharges related to open elective surgery. During 6 years, we found a recurring mortality peak of 1.15% (95% CI 1.09-1.20) in August compared with 0.81% (0.79-0.82, p<.001) in other months. The incidence of worker vacation was 43.0% (38.9-47.2) in August compared with 7.3% (4.6-10.1, p<.001) in other months. Hospital activity decreased substantially in August (78,126 inpatient stays, 75,298-80,954) in relation to other months (128,142, 125,697–130,586, p<.001). After adjusting for all covariates, we found an "August effect" reflecting a higher risk to patients undergoing operations at this time (OR 1.16, 95% CI 1.12-1.19, p<.001). The main study limitation was the absence of data linkage between surgical staffing and mortality at the hospital level. The observed, recurring mortality peak in August raises questions about how to maintain hospital activity and optimal staffing through better regulation of human activities

Near-field scanning optical microscopy to study nanometric structural details of LiNbO3 Zn-diffused channel waveguides

A near-field scanning optical microscope (NSOM) is used to perform structural and optical characterization of the surface layer after Zn diffusion in a channel waveguide fabricated on lithium niobate. A theoretical approach has been developed in order to extract refractive index contrast from NSOM optical transmission measurements (illumination configuration). As a result, different solid phases present on the sample surface can be identified, such as ZnO and ZnNb2O6. They appear like submicrometric crystallites aligned along the domain wall direction, whose origin can be ascribed to some strain relaxation mechanism during the annealing process after Zn [email protected]

SNOM characterization of a potential low cost thin gold coated micro-structured grating using a commercial CD substrate

In this work near-field optical measurements of a corrugated grating coated with a 30 nm thick gold film are presented. The grating was made using the polycarbonate corrugated substrate of a commercially available recordable CD as template. This has been proved to be a versatile and low cost technique in producing large 1.6 μm period gratings. The study was carried out using a Scanning Near-Field Optical Microscope (SNOM) working in both collection and reflection modes at two different wavelengths, 532 nm and 633 nm. The results illustrate that the intensity patterns of near-field images are strongly polarization-dependent, even showing different periodicity of the localized fields for orthogonal polarization states. When electric field of the light is polarized parallel to the grooves, the periodicity of the SNOM images is coincident with the grating period, whereas when the light is polarized perpendicular to the grooves the SNOM pattern shows a periodicity twice that of the corresponding topography of the grating. Numerical simulations of the SNOM data based on a two-dimensional Finite Difference Time-Domain (2D-FDTD) model have been realized. The results of the simulations are in good agreement with the experimental data, emphasizing the need of performing numerical simulation for the correct interpretation of SNOM data

Phylogenetic, Cytogenetic and Morphological Evidences are Critical for Recognizing a New Genus: Valdesiana, an Iberian Intergeneric Allopolyploid Between Schenkia and Exaculum

The present taxonomic status of Schenkia elegans, endemism recently described in the Iberian Peninsula, and its relationship with the sympatric and the nearest morphological species Schenkia spicata and Exaculum pusillum is revaluated. Different kinds of evidence based on plant morphology, ploidy estimation by flow cytometry, karyotype characterisation, and phylogenetic data have been analysed. Two maternally inherited plastid DNA regions (trnL intron and trnL-F spacer) and biparentally inherited nuclear ribosomal DNA sequence region (nrDNA ITS) have been used. Comparative multivariate analyses show an intermediate morphology of the S. elegans plants between the other two species studied. Flow cytometry and karyotype analyses in S. elegans point to an allopolyploid origin, with the latter constituted by a mixture of those of the diploids S. spicata and E. pusillum. Phylogenetic analyses based on plastid and nuclear DNA regions cluster S. elegans in two different clades, those of S. spicata and E. pusillum, suggesting a possible hybrid origin of S. elegans between both species, acting as maternal or paternal progenitors. In consequence, taking in consideration the taxonomic relationships among genera (Exaculum, Schenkia and the closely related genus Zeltnera found in America), a monotypic genus Valdesiana gen. nov. is proposed to accommodate the allopolyploid species, combined as V. elegans, for which immediate conservation measures must be evaluated.Ministerio de Economía y Competitividad CGL2013-45037-Pproject CULTIVAR CENTRO-01-0145-FEDER-00002

Self-frequency-doubling of ultrafast laser inscribed neodymium doped yttrium aluminum borate waveguides

Copyright (2011) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 98 (2011): 181103 and may be found at http://apl.aip.org

Relationship between Retinal Microvasculature, Cardiovascular Risk and Silent Brain Infarction in Hypertensive Patients

Objective: The aims of this study are to analyze the role of artery-vein ratio AVR assessment using VesselMap 2 software (Imedos Systems) and cardiovascular risk evaluation by means of REGICOR in the prediction of silent brain infarction (SBI) in middle-age hypertensive patients from the ISSYS study. Material and Methods: A cross-sectional study with 695 patients with hypertension aged 50 to 70 years who participated in the project Investigating Silent Strokes in HYpertensives: a Magnetic Resonance Imaging Study (ISSYS), was conducted in two Primary Care Centres of Barcelona. Participants agreed to a retinography and an MRI to detect silent brain infarction (SBI). The IMEDOS software was used for the semiautomatic caliber measurement of retinal arteries and veins, and the AVR was considered abnormal when <0.66. The REGICOR score was calculated for all patients. Results: Multivariate logistic regression analysis was used to evaluate the impact of AVR and REGICOR scores on SBI. The OR (odds ratio) for a high REGICOR score and an abnormal AVR were 3.16 and 4.45, respectively. When analysing the interaction of both factors, the OR of an abnormal AVR and moderate REGICOR score was 3.27, whereas with a high REGICOR score it reached 13.07. Conclusions: The measurement of AVR in patients with hypertension and with a high REGICOR score can contribute to the detection of silent brain infarction

Group and call effect in achieving success in a subject: Analyses of the "Biology and Botany" whole life in the E.U.I.T.A. (University of Seville)

La Biología y la Botánica son dos materias fundamentales en la formación de un ingeniero técnico agrícola. Sus contenidos se han ofrecido a veces en asignaturas independientes y, en otras ocasiones como la que nos ocupa, en una sola asignatura. Por otra parte, siempre se ha mirado con interés, e incluso preocupación, el efecto de la variable grupo, de forma independiente o relacionándola con su distribución en turnos de mañana o tarde, así como la importancia de la convocatoria (en los distintos momentos a lo largo del curso académico) en la que el alumno consigue superar la asignatura. Aquí presentamos los resultados en la consecución de objetivos por parte de los alumnos y, por ende, de los profesores y de la Universidad de Sevilla a lo largo de la totalidad de la vida de la asignatura "Biología y Botánica" dentro del plan de estudios 2003/04 para tres titulaciones simultáneas, desde su comienzo en el curso 2003/04 hasta su extinción en el curso 2009/10, de la E.U.I.T.A. (Escuela Universitaria de Ingeniería Técnica Agrícola) de la Universidad de Sevilla. Además se consideran convocatorias pertenecientes al período de extinción añadido. Los análisis toman en cuenta además el éxito en la superación de la asignatura tanto de forma cualitativa (aprobado o suspenso de la evaluación a la que el alumno se ha sometido) como cuantitativa (nota conseguida). Las conclusiones obtenidas permiten mirar los resultados y la consecución de objetivos, así como una potencial toma de decisiones para el futuro, basándose en un marco temporal amplio y objetivo.Biology and Botany are two critical issues in the formation of a technical agricultural engineer. Their topics are sometimes offered in separate subjects and, at other times as here, within a single one. Besides, it has always been considered with interest, and even concern, the effect of the variable group, independently or in relation to their distribution in the morning or afternoon turns, and the importance of the call (at different times during the academic year) at which the student gets to pass the subject. Here we present the results in the achievement of objectives by students, and therefore teachers and the University of Seville, along the entire life of the subject "Biology and Botany" within the teaching 2003/04 plan for three simultaneous academic programs, from its start in the course 2003/04 to its extinction in the course 2009/10, in the E.U.I.T.A. (University School of Technical Agricultural Engineering) of the University of Seville. Calls belonging to the period of extinction are also considered. Analyses are both qualitative, based on having success in passing the subject or not, and quantitative (mark scored). Obtained conclusions let us see the results and the achievement of objectives, as well as a potential decision-making for the future, with a base on a comprehensive and objective frame