A low-cost alternative scheme to detect a 100 Gbps PM-DQPSK signal

We propose and demonstrate a low-cost alternative scheme of direct-detection to detect a 100Gbps polarization-multiplexed differential quadrature phase-shift keying (PM-DQPSK) signal. The proposed scheme is based on a delay line and a polarization rotator; the phase-shift keying signal is first converted into a polarization shift keying signal. Then, this signal is converted into an intensity modulated signal by a polarization beam splitter. Finally, the intensity-modulated signal is detected by balanced photodetectors. In order to demonstrate that our proposed receiver is suitable for using as a PM-DQPSK demodulator, a set of simulations have been performed. In addition to testing the sensitivity, the performance under various impairments, including narrow optical filtering, polarization mode dispersion, chromatic dispersion and polarization sensitivity, is analyzed. The simulation results show that our performance receiver is as good as a conventional receiver based on four delay interferometers. Moreover, in comparison with the typical receiver, fewer components are used in our receiver. Hence, implementation is easier, and total cost is reduced. In addition, our receiver can be easily improved to a bit-rate tunable receiver

Quasiconvex Constrained Multicriteria Continuous Location Problems: Structure of Nondominated Solution Sets

In this paper, we consider constrained multicriteria continuous location problems in two-dimensional spaces. In the literature, the continuous multicriteria location problem in two-dimensional spaces has received special attention in the last years, although only particular instances of convex functions have been considered. Our approach only requires the functions to be strictly quasiconvex and inf-compact. We obtain a geometrical description that provides a unified approach to handle multicriteria location models in two-dimensional spaces which has been implemented in MATHEMATIC

Recruitment patterns of decapod crustacean megalopae in a shallow inlet (SW Spain) related to life history strategies

Decapod crustacean megalopae were sampled weekly (spring/neap tides) during late-spring/summer of 1998 by using two planktonic nets located close to the surface and the bottom, at a fixed station in the mouth of the Rı́o San Pedro inlet (SW Spain). Sampling was carried out during 25 h cycles to ascertain the flux of megalopae in relation to the main environmental (diel, tidal, tidal amplitude) cycles. The hypothesis that megalopae of some species may be using tidal-stream transport as a mechanism of re-invading the inlet was tested and the relationship between megalopal behaviour and life history strategy was analysed. In general, the flux of megalopae was higher during spring tides, but such differences were only statistically significant for Pisidia longicornis and Liocarcinus sp.2 due to the considerable interdate variation. With the exception of Macropodia sp., megalopae were more abundant close to the bottom. The diel/tidal flux of most abundant species suggested two different patterns of behaviour: megalopae of Liocarcinus spp., Panopeus africanus, Uca tangeri and Brachynotus sexdentatus seemed to be re-invading the inlet (specially at nocturnal floods), while megalopae of Ilia nucleus, Nepinnotheres pinnotheres and Macropodia sp. may have been just looking for a suitable place for settlement. The first group corresponded to the species whose zoeal development occurs in open sea, and the second one to species that complete their life cycle within the studied system, suggesting a relationship between the duration of the larval phase and the life cycle strategy of the species

Maxillary Incisors of the Horse before and at the Beginning of the Teeth Shedding: Radiographic and CT Study

To gain insight into the radiographic appearance of maxillary deciduous incisors and dental germs of maxillary permanent incisors in the period prior to teeth shedding, radiographs and computed tomography (CT) of 25 horse skulls, with an estimated age of between 12 and 42 months, were studied. Data regarding morphology and development were obtained. Dental germs of first maxillary permanent incisors were identified radiographically as rounded radiolucent areas at the level of the apical parts of the first deciduous incisors, in skulls with an estimated age of twelve months. The first sign of crown mineralization of these dental germs appeared in skulls supposedly a few months older. Before teeth shedding, the unerupted, mineralized crowns of the first permanent incisor could be identified radiographically relatively caudal to the corresponding first deciduous incisors. The results of the present study indicate that radiographic intraoral images are suitable to identify the grade of development of the dental germs of maxillary permanent incisors. A detailed description of the radiographic appearance of deciduous incisors and dental germs of permanent incisors will help clinicians to expand their knowledge for diagnostic or treatment purposes

Bounds on the dipole moments of the tau-neutrino via the process e+e−→ννˉγe^{+}e^{-}\rightarrow \nu \bar \nu \gamma in a 331 model

We obtain limits on the anomalous magnetic and electric dipole moments of the $\nu_{\tau}$ through the reaction $e^{+}e^{-}\rightarrow \nu \bar \nu \gamma$ and in the framework of a 331 model. We consider initial-state radiation, and neglect $W$ and photon exchange diagrams. The results are based on the data reported by the L3 Collaboration at LEP, and compare favorably with the limits obtained in other models, complementing previous studies on the dipole moments.Comment: 13 pages, 4 figures, to be published in The European Physical J C. arXiv admin note: substantial text overlap with arXiv:hep-ph/060527

Obtaining foot bone structure applying global and adaptive thresholding

La descripción del comportamiento mecánico de tejidos duros mediante el empleo de modelos discretos pasa por diferentes etapas de análisis, que van desde el procesamiento digital de la imagen hasta la especificación de las propiedades físicas del tejido al modelo discreto. Para lograr un buen resultado es esencial la descomposición de esos modelos en sus partes constitutivas. En este trabajo se discute un método para la descripción geométrica de los huesos del pie a partir de una secuencia de imágenes (cortes) de tomografía computarizada (TC). La investigación propone la combinación de la umbralización global y de la adaptativa para la determinación del dominio geométrico de los huesos en cada corte, así como el análisis de las relaciones espaciales entre contornos en planos consecutivos a fin de obtener las isosuperficies de los huesos. Se propone un algoritmo semiautomático basado en 4 etapas: la lectura de los cortes de imágenes de TC; la determinación de los contornos que definen el tejido óseo presentes en cada corte; la formación de los volúmenes a través del agrupamiento de los contornos cuya relación espacial cumple un criterio determinado; y la eliminación de las isosuperficies no válidas. Como resultado se obtiene la definición de la mayoría de los huesos del pie cuyo rango de valores en la escala de Hounsfield es [–1.000; 1.383].The description of the mechanical behavior of hard tissues by means of discrete models goes through various stages of analysis, which range from digital image processing to the specification of tissues physical properties to the discrete model. To achieve good results it is essential to decompose these models into their constituent parts. In this paper we discuss a method for geometrical description of foot bones from a sequence of computed tomography (CT) images. This research proposes a combination between global and adaptive thresholdings to determine the geometric domain of bones in each slice and the analysis of the spatial relationships between contours in consecutive planes in order to obtain bones’ isosurfaces. The algorithm proposed is based on 4 stages: the reading of computed tomography (CT) images; the determination of the contours that define the bone tissue present on each slice; the grouping of contours whose relationship meet a given criteria; the elimination of non-valid volumes. As a result, it is possible to obtain the geometrical domain of a great number of foot bones whose range in the Hounsfield is [–1000; 1383].Peer Reviewe

Algorithm for defining skeletal structures in biomedical models

La descripción del comportamiento mecánico de tejidos duros mediante el empleo de modelos discretos pasa por diferentes etapas de análisis, desde el procesamiento digital de la imagen hasta la especificación de las propiedades físicas del tejido. Para ello, es necesario tener en cuenta un elemento clave: la descomposición del modelo en sus partes constitutivas. Se realizó un estudio bibliográfico de diversas propuestas para realizar la descomposición y se llegó a la conclusión de la inexistencia de una estrategia única. Existe un cúmulo de propuestas genéricas, pero estas no ofrecen una solución válida a los casos analizados, correspondientes a las articulaciones de la rodilla, la pelvis y el hombro. Por tanto, se propone un algoritmo para realizar la descomposición mediante el análisis de las relaciones espaciales entre los contornos presentes en planos consecutivos, que se basa en 4 etapas: la lectura de los cortes de imágenes de tomografía computarizada; la determinación de los contornos que definen el tejido óseo presente en cada corte; el agrupamiento de los contornos cuya relación espacial cumple un criterio determinado, y la eliminación de los volúmenes no válidos. Los resultados del algoritmo se compararon con otros obtenidos mediante el empleo de la librería Visualization ToolKit (VTK) y pyFormex, cuyos métodos se utilizan en la visualización y análisis de imágenes médicas y en la modelación de estructuras tridimensionales. Como resultado del algoritmo propuesto tenemos —bajo las mismas condiciones y en un corto tiempo de procesamiento— una descomposición de los modelos anatómicos superior a la realizada por VTK y pyFormex, con aproximadamente el 90% de confianza.Description of mechanical behavior of hard tissues by means of discrete models goes through various stages of analysis, which range from digital image processing to the specification of physical properties of tissue to the discrete model. This requires taking into account a key element: the decomposition of the model into its constituent parts. We conducted a bibliographic study of existing proposals for such decomposition, leading to the conclusion of the absence of a single strategy. There are several generic proposals, but these proved not to give a valid solution applicable to the cases examined corresponding to the articulations of the knee, hip and shoulder. In this paper we propose an algorithm to perform this decomposition by analyzing the spatial relationships between the contours present in consecutive planes. It is based on four stages: reading computer tomography (CT) slices; determining the contours that define bone tissue present on each slice; grouping of contours whose relationship meets a given criterion; and eliminating non-valid volumes. Results were compared with those obtained by means of Visualization ToolKit (VTK) and pyFormex, widely used in the visualization and analysis of medical imaging and modeling three-dimensional structures. As a main result, proposed algorithm under the same conditions and short processing time performs a better decomposition of anatomical models than the one made by VTK and pyFormex, with about a 90% of confidence.Peer Reviewe

Feeding Patterns of Greenland halibut (Reinhardtius hippoglossoides) in Flemish Pass (Northwest Atlantic)

A qualitative study of the food composition of Greenland halibut (Reinhardtius hippoglossoides) was made by on-board analysis of commercially caught fish in 1992. The fish were caught east of Newfoundland (NAFO Div. 3LM) in unusually deep waters, with an average of 1 040 m. Variations in feeding according to predator size, depth and month were studied. The annual average percentage of empty stomachs was 69%, increasing through the year for specimens over 60 cm. The frequency of occurrence (FO) of food items was used to evaluate the importance of prey groups. Fish (39%), cephalopods (32%) and decapod crustaceans (22%) were the main items, with cannibalism reaching 2%. An abrupt change in diet composition occurred in fish between 60 and 69 cm, from feeding on decapod crustaceans and cephalopods to fish and factory ship discarded offal. The influence of the fishery itself on the diet of Greenland halibut was observed when an important food component in the largest specimens (>60 cm) consisted of offal discarded after fish processing. This study indicates that the FO of the main prey groups bears more relation to the size of fish than with depth

Effect of dopants on the structure of titanium oxide used as a photocatalyst for the removal of emergent contaminants

Photocatalysts composed of titanium dioxide modified with B, F, N and P have been synthesized, characterized and applied to the degradation of caffeine, diclofenac, ibuprofen and salicylic acid. The modified TiO2 samples were prepared by the sol–gel technique starting from titanium(IV) isopropoxide and using H3BO3, NH4F, N(C2H5OH)3 and H3PO4 as precursors of the modifiers, with the content varying between 0 and 5 wt%. Structural characterization was based on nitrogen physisorption at −196 °C, powder X-ray diffraction (PXRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS). The structural properties of the modified TiO2 solids were significantly different depending on the nature and amount of modifiers and the calcination temperature. TiO2 in the anatase phase was obtained in all cases and was stable upon calcination at 400 °C. The photocatalytic degradation of caffeine, diclofenac, ibuprofen and salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 25 °C. The photocatalytic degradation behavior followed the order: caffeine > diclofenac = ibuprofen > salicylic acid. B-doped TiO2 was the most efficient catalyst in the degradation of these selected emerging contaminants