Quantum optical signals in telecommunication networks

Introducción a una red óptica metropolitana cuántica donde señales cuánticas y convencionales son multiplexadas en longitud de onda utilizando bandas separadas del espectro óptico. El enrutado se realiza con componentes pasivos para no perturbar los qubits. Se estudian dos redes: red de acceso WDM-PON y red metropolitana completa con backbone DWDM y redes de acceso WDM-PON

Relationship between enamel fluorosis severity and fluoride content

OBJECTIVES: Enamel fluorosis is a hypomineralization caused by chronic exposure to high levels of fluoride during tooth development. Previous research on the relationship between enamel fluoride content and fluorosis severity has been equivocal. The current study aimed at comparing visually and histologically assessed fluorosis severity with enamel fluoride content. METHODS: Extracted teeth (n=112) were visually examined using the Thylstrup and Fejerskov Index for fluorosis. Eruption status of each tooth was noted. Teeth were cut into 100 μm slices to assess histological changes with polarized light microscopy. Teeth were categorized as sound, mild, moderate, or severe fluorosis, visually and histologically. They were cut into squares (2 × 2 mm) for the determination of fluoride content (microbiopsy) at depths of 30, 60 and 90 μm from the external surface. RESULTS: Erupted teeth with severe fluorosis had significantly greater mean fluoride content at 30, 60 and 90 μm than sound teeth. Unerupted teeth with mild, moderate and severe fluorosis had significantly greater mean fluoride content than sound teeth at 30 μm; unerupted teeth with mild and severe fluorosis had significantly greater mean fluoride content than sound teeth at 60 μm, while only unerupted teeth severe fluorosis had significantly greater mean fluoride content than sound teeth at 90 μm. CONCLUSIONS: Both erupted and unerupted severely fluorosed teeth presented higher mean enamel fluoride content than sound teeth. CLINICAL SIGNIFICANCE: Data on fluoride content in enamel will further our understanding of its biological characteristics which play a role in the management of hard tissue diseases and conditions

Four-port coupled channel-guide device based on 2D photonic crystal structure

We have fabricated and measured a four-port coupled channel-waveguide device using W1 channel waveguides oriented along ΓK directions in a two-dimensional (2D) hole-based planar photonic crystal (PhC) based on silicon-on-insulator (SOI) waveguide material, at operation wavelengths around 1550 nm. 2D FDTD simulations and experimental results are shown and compared. The structure has been designed using a mode conversion approach, combined with coupled-mode concepts. The overall length of the photonic crystal structure is typically about 39 μm and the structure has been fabricated using a combination of direct-write electron-beam lithography (EBL) and dry-etch processing. Devices were measured using a tunable laser with end-fire coupling into the planar structure

3-Dimensional Kinematics in low foreground extinction windows of the Galactic Bulge: Radial Velocities for 6 bulge fields

The detailed structure of the Galactic bulge still remain uncertain. The strong difficulties of obtaining observations of stars in the Galactic bulge have hindered the acquisition of a kinematic representation for the inner kpc of the Milky Way. The observation of the 3-d kinematics in several low foreground extinction windows can solve this problem. We have developed a new technique, which combines precise stellar HST positions and proper motions with integral field spectroscopy, in order to obtain reliable 3-d stellar kinematics in crowded fields of the Galactic center. In addition, we present results using the new techniques for six fields in our project. A significant vertex deviation has been found in some of the fields in agreement with previous determinations. This result confirms the presence of a stellar bar in the Galactic bulge.Comment: 14 pages, 15 figures, Accepted for publication in A&

The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees

The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey has observed 8 different regions of the sky, including sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous ~ $300\AA$ filters covering the optical range, combining them with deep $JHKs$ imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq. deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to ~700hrs on-target science images. The photometric system was designed to maximize the effective depth of the survey in terms of accurate spectral-type and photo-zs estimation along with the capability of identification of relatively faint emission lines. Here we present multicolor photometry and photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down to I~24.5 AB, taking into account realistic noise estimates, and correcting by PSF and aperture effects with the ColorPro software. The photometric ZP have been calibrated using stellar transformation equations and refined internally, using a new technique based on the highly robust photometric redshifts measured for emission line galaxies. We calculate photometric redshifts with the BPZ2 code, which includes new empirically calibrated templates and priors. Our photo-zs have a precision of $dz/(1+z_s)=1$ for I<22.5 and 1.4% for 22.5<I<24.5. Precisions of less than 0.5% are reached for the brighter spectroscopic sample, showing the potential of medium-band photometric surveys. The global $P(z)$ shows a mean redshift =0.56 for I=0.86 for I<24.5 AB. The data presented here covers an effective area of 2.79 sq. deg, split into 14 strips of 58.5'x15.5' and represents ~32 hrs of on-target.Comment: The catalog data and a full resolution version of this paper is available at https://cloud.iaa.csic.es/alhambra

A Uniform Analysis of the Ly-alpha forest at z = 0 - 5: II. Measuring the mean intensity of the extragalactic ionizing background using the proximity effect

A homogeneous sample of 99 moderate resolution QSO spectra at z > 1.7 were presented in Paper I, including 39 previously unpublished spectra from the Multiple Mirror Telescope. The statistics of the Lyman alpha forest were discussed. In this analysis, we demonstrate that a proximity effect is present in the data, ie. there exists a significant (5.5$\sigma$) deficit of lines at $z_{abs} \approx z_{em}$. Within 1.5 $h^{-1}$ Mpc of the QSO emission redshift, the significance does depend on QSO luminosity, in accordance with the theory that this effect is caused by enhanced ionization of hydrogen in the vicinity of the QSO from UV photons from the QSO itself. The photoionization model of Bajtlik, Duncan, and Ostriker (1988) permits an estimate of the mean intensity of the extragalactic background radiation at the Lyman limit. We compare the results of this standard analysis with those obtained using a maximum likelihood technique. The best fit value for $J(\nu_{0})$ is 7.0$^{+3.4}_{-4.4}$ x 10$^{-22}$ ergs/s/cm$^{2}$/Hz/sr, over the redshift range 1.7 < z < 3.8, using QSO redshifts based on narrow emission lines. The best fit value for the HI ionization rate is 1.9$^{+1.2}_{-1.0}$ x 10$^{-12}$ s$^{-1}$, in good agreement with models of the background which incorporate QSOs only. This large absorption line sample and these techniques for measuring the background and understanding the systematics involved allow us to place what we believe are are the firmest limits on the background at these redshifts.Comment: revised figures 13 and 14, and other minor corrections, 42 Latex pages, 23 encapsulated Postscript figures, uses emulateapj.sty, To appear in the Sept. 2000 ApJ

3D kinematics through the X-shaped Milky Way bulge

Context. It has recently been discovered that the Galactic bulge is X-shaped, with the two southern arms of the X both crossing the lines of sight at l = 0 and | b| > 4, hence producing a double red clump in the bulge color magnitude diagram. Dynamical models predict the formation of X-shaped bulges as extreme cases of boxy-peanut bulges. However, since X-shaped bulges were known to be present only in external galaxies, models have never been compared to 3D kinematical data for individual stars. Aims. We study the orbital motion of Galactic bulge stars in the two arms (overdensities) of the X in the southern hemisphere. The goal is to provide observational constraints to bulge formation models that predict the formation of X-shapes through bar dynamical instabilities. Methods. Radial velocities have been obtained for a sample of 454 bulge giants, roughly equally distributed between the bright and the faint red clump, in a field at (l,b) = (0, −6). Proper motions were derived for all red clump stars in the same field by combining images from two epochs, which were obtained 11 years apart, with WFI at the 2.2 m at La Silla. The observed field contains the globular cluster NGC 6558, whose member stars were used to assess the accuracy of the proper motion measurement. At the same time, as a by-product, we provide the first proper motion measurement of NGC 6558. The proper motions for the spectroscopic subsample are analyzed for a subsample of 352 stars, taking into account the radial velocities and metallicities measured from near-infrared calcium triplet lines. Results. The radial velocity distribution of stars in the bright red clump, which traces the closer overdensity of bulge stars, shows an excess of stars moving towards the Sun. Similarly, an excess of stars receding from the Sun is seen in the far overdensity, which is traced by faint red clump stars. This is explained by the presence of stars on elongated orbits, which are most likely streaming along the arms of the X-shaped bulge. Proper motions for these stars are consistent with qualitative predictions of dynamical models of peanut-shaped bulges. Surprisingly, stars on elongated orbits have preferentially metal-poor (subsolar) metallicities, while the metal rich ones, in both overdensities, are preferentially found in more axisymmetric orbits. The observed proper motion of NGC 6558 has been measured as (μlcos   (b),μb) = (0.30   ±   0.14, −0.43 ± 0.13), with a velocity dispersion of (σlcos(b),σb) = (1.8,1.7) mas/yr. This is the first proper motion measurement for this cluster

Geochemical characteristics of surface sediments from the marine-coastal region north and south of the paria peninsula, Venezuela

[eng] Environmental characteristics of the Northern Platform of the Paria Peninsula (PP) and the Paria Gulf (GP)are caused by water flow and sediment of the Orinoco river, the ocean currents that move along the eastern coast of SouthAmerica transporting a large quantity of sediment from the Amazon river, the tidal action, waves and the current regime ofthe continental shelf including coastal upwelling induced by trade winds. All these factors affect biogeochemical processes insediments that have different sources and conditions of transport, sedimentation and preservation. Accordingly, it raises asfundamental objective of this paper to describe some environmental parameters of bottom water and some geochemicalcharacteristics such as texture, mineralogy and organic carbon content (Corg), sulfur (S), total phosphorus (TP) and totalnitrogen (TN) from surface sediments of the study region. The texture was performed according to the modified pipettemethod and mineralogy by X-ray diffraction. The Corg was determined by dry combustion technique after acid attack, S byEA-ICP, while the PT and NT by the method of VALDERRAMA (1981). Iso-concentration maps for the distribution of theseparameters on the continental shelf north of the Peninsula (PP) and Gulf of Paria (GP) were prepared. In general, thesediment has a texture or grain size of sandy-loam and sandy-silty type, mineralogical composition consists of quartz,muscovite, kaolinite, calcite for some PP stations and zircon for GP, making mineral distinctive environments sedimentationand sediment source. The average concentrations were Corg 1.53%, S 0.23%, PT 0.04% and NT 0.03%. Ocean currents andcoastal upwelling patterns may influence the spatial distribution of these variables. There is an effect on the production,distribution and sedimentation of OM in the study area, caused by the discharge of the Orinoco and Amazon River through theflow of Guyana, which directly impacts surface waters and sediments of the Paria Gulf. These results allow distinguishing twoenvironments of sedimentation with suspended matter inputs from different sources. The PP surface sediments with typicalcharacteristics of coastal marine sediment with input from autochthonous organic matter, resulting from primary productivitythat are influenced by the phenomenon of coastal upwelling. There is greater variability in the GP, indicating different sourcesof sediment that result in a mixture, confirming the contributions of the Orinoco and Amazon River. The GP provides marineenvironments, transitional and continental. In the other hand, the PP only provides marine environments that lead todifferentiation in composition, texture, mineralogy and distribution between the two regions. Sea currents and the source ofthe sediment may be the most important factors controlling the spatial distribution of sediments and the elements consideredin the region

Molecular epidemiology of Plasmodium vivax in Latin America: polymorphism and evolutionary relationships of the circumsporozoite gene

BACKGROUND: The origins and dispersal of Plasmodium vivax to its current worldwide distribution remains controversial. Although progress on P. vivax genetics and genomics has been achieved worldwide, information concerning New World parasites remains fragmented and largely incomplete. More information on the genetic diversity in Latin America (LA) is needed to better explain current patterns of parasite dispersion and evolution. METHODS: Plasmodium vivax circumsporozoite protein gene polymorphism was investigated using polymerase chain reaction amplification and restriction fragment length polymorphism (PCR-RFLP), and Sanger sequencing in isolates from the Pacific Ocean coast of Mexico, Nicaragua, and Peru. In conjunction with worldwide sequences retrieved from the Genbank, mismatch distribution analysis of central repeat region (CRR), frequency estimation of unique repeat types and phylogenetic analysis of the 3′ terminal region, were performed to obtain an integrative view of the genetic relationships between regional and worldwide isolates. RESULTS: Four RFLP subtypes, vk210a, b, c and d were identified in Southern Mexico and three subtypes vk210a, e and f in Nicaragua. The nucleotide sequences showed that Mexican vk210a and all Nicaraguan isolates were similar to other American parasites. In contrast, vk210b, c and d were less frequent, had a domain ANKKAEDA in their carboxyl end and clustered with Asian isolates. All vk247 isolates from Mexico and Peru had identical RFLP pattern. Their nucleotide sequences showed two copies of GGQAAGGNAANKKAGDAGA at the carboxyl end. Differences in mismatch distribution parameters of the CRR separate vk247 from most vk210 isolates. While vk247 isolates display a homogeneous pattern with no geographical clustering, vk210 isolates display a heterogeneous geographically clustered pattern which clearly separates LA from non-American isolates, except vk210b, c and d from Southern Mexico. CONCLUSIONS: The presence of vk210a in Mexico and vk210e, f and g in Nicaragua are consistent with other previously reported LA isolates and reflect their circulation throughout the continent. The vk210b, c and d are novel genotypes in LA. Their genetic relationships and low variability within these vk210 and/or within the vk247 parasites in Southern Mexico suggest its recent introduction and/or recent expansion to this region. The global analysis of P. vivax csp suggests this parasite introduction to the region and likely LA by different independent events