An artifact in fits to conic-based surfaces

It is common in Physiological Optics to fit the corneal and the lens surfaces to conic-based surfaces (usually ellipse-based surfaces), obtaining their characteristic radius of curvature and asphericity. Here we show that the variation in radius and asphericity due to experimental noise is strongly correlated. This correlation is seen both in experimental data of the corneal topographer Pentacam and in simulations. We also show that the effect is a characteristic of the geometry of ellipses, and not restricted to any experimental device or fitting procedure.Comment: 5 pages, 5 figure

Aberrometry: basic science and clinical applications

This paper addresses the concept, measurement and applications of wave aberrations. The ocular optics is not perfect. Apart from conventional low order aberrations (such as defocus and astigmatism) retinal images are degraded by other high order aberrations. Aberrometers typically measure ray deviations at the retinal plane, as a function of pupil position, i.e. local derivatives of the wave aberration. The paper discusses state of the art technology to measure the aberrations of the eye (cornea and crystalline lens), both monochromatic and polychromatic. The aberrometers described include the Hartmann-Shack wavefront sensor, laser ray tracing, spatially resolved refractometer or the corneal aberrations. This technology has been used to advance our understanding on several visual mechanisms, ocular conditions, and corrective methods. Applications include accommodation, myopia, aging, myopia, keratoconus, corneal refractive surgery, cataract surgery or contact lenses.Funding from Spanish Ministry of Science and Technology (FIS2005-04382) and a European Young Investigator Award.Peer Reviewe

Reconstrucció de la persona després del brot psicòtic: el risc de la identitat simptomàtica

L’objectiu d’aquest article és el de reflexionar sobre els efectesque produeix en la identitat de l’individu la irrupció del brotpsicòtic. Es planteja la influència que els factors socials,institucionals i personals - tant dels professionals com delspropis pacients - exerceixen en la construcció de la identitatdel pacient, podent ajudar a construir una identitatsuficientment saludable i integrada o bé una identitatsimptomàtica, de malalt mental greu o psicòtic

Discursos sobre cultura, etnicitat i salut. Maternitat en bengalís a Londres

La tesi doctoral de Laura Griffith s'emmarca dins dels abundants estudis fets a Europa, concretament a Anglaterra, sobre minories ètniques i salut, en el seu cas sobre maternitat en bengalís a Londres. ..

Experiments on PMMA model to predict the impact of corneal refractive surgery on corneal shape: Reply

2 pages.-- OCIS codes: 120.6650, 140.3390, 170.1020, 170.3890, 330.4460, 330.5370.A reply to the comment by Jiménez et al. on the paper "Experiments on PMMA model to predict the impact of corneal refractive surgery on corneal shape" by Dorronsoro et al., Opt. Express, 14, 6142-6156 (2006).Peer reviewe

Genes of different catabolic pathways are coordinately regulated by Dal81 in Saccharomyces cerevisiae

Yeast can use a wide variety of nitrogen compounds. However, the ability to synthesize enzymes and permeases for catabolism of poor nitrogen sources is limited in the presence of a rich one. This general mechanism of transcriptional control is called nitrogen catabolite repression. Poor nitrogen sources, such as leucine, γ-aminobutyric acid (GABA), and allantoin, enable growth after the synthesis of pathway-specific catabolic enzymes and permeases. This synthesis occurs only under conditions of nitrogen limitation and in the presence of a pathway-specific signal. In this work we studied the temporal order in the induction of AGP1, BAP2, UGA4, and DAL7, genes that are involved in the catabolism and use of leucine, GABA, and allantoin, three poor nitrogen sources. We found that when these amino acids are available, cells will express AGP1 and BAP2 in the first place, then DAL7, and at last UGA4. Dal81, a general positive regulator of genes involved in nitrogen utilization related to the metabolisms of GABA, leucine, and allantoin, plays a central role in this coordinated regulation.Fil: Palavecino Ruiz, Marcos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Correa Garcia, Susana Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Bermudez Moretti, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 ceramics

Different processing conditions and the effect of secondary phases on ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) are studied. Ceramic powders are prepared by solid state reaction and different sintering temperatures (temperatures between 1075 and 1150ºC) are analyzed. Finally, samples are characterized by X-ray diffraction, Raman microspectroscopy, Scanning Electron Microscopy, impedance spectroscopy, and density measurements. Through XRD patterns, the perovskite structure is stabilized; together with small peaks corresponding to a secondary phase associated with K2-xNaxTi6O13 phase. Moreover, the content of the secondary phase, d33 piezoelectric constant and dielectric properties increase with sintering temperature.Fil: Camargo, Javier Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ramajo, Leandro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Rubio Marcos, Fernando. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Vision Is Adapted to the Natural Level of Blur Present in the Retinal Image

Background The image formed by the eye's optics is inherently blurred by aberrations specific to an individual's eyes. We examined how visual coding is adapted to the optical quality of the eye.Methods and Findings We assessed the relationship between perceived blur and the retinal image blur resulting from high order aberrations in an individual's optics. Observers judged perceptual blur in a psychophysical two-alternative forced choice paradigm, on stimuli viewed through perfectly corrected optics (using a deformable mirror to compensate for the individual's aberrations). Realistic blur of different amounts and forms was computer simulated using real aberrations from a population. The blur levels perceived as best focused were close to the levels predicted by an individual's high order aberrations over a wide range of blur magnitudes, and were systematically biased when observers were instead adapted to the blur reproduced from a different observer's eye.Conclusions Our results provide strong evidence that spatial vision is calibrated for the specific blur levels present in each individual's retinal image and that this adaptation at least partly reflects how spatial sensitivity is normalized in the neural coding of blur.This work was supported by the following: Ministerio de Ciencia e Innovación (MICINN), Formación de Personal Investigador (FPI) Predoctoral Fellowship to LS; Consejo Superior de Investigaciones Científicas (CSIC) I3P Predoctoral Fellowship to PdG; EY-10834 to MW; MICINN FIS2008-02065 and EURYI-05-102-ES (European Heads of Research Councils-European Science Foundation EUROHORCs-ESF) to SM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Empiricism, the Scientia Umbrarum and the Reconciliation of the Two Cultures in Peter Ackroyd’s Hawksmoor

Peter Ackroyd (London, 1949–) is considered to be one of the most productive and inventive writers of the 1980s and a leading figure in contemporary English fiction. He occupies a central position in the generation of English writers of historiographic metafiction, the trend Linda Hutcheon considers to be the best literary expression of postmodernism. In keeping with the contradictory nature of postmodernist art, historiographic metafiction expresses incredulity toward grand narratives by levelling history and literature to the same status of human discourse. Echoing this, in Hawksmoor, Ackroyd defends not only the historical coexistence of the two basic forms of human knowledge: reason and intuition, represented in the novel by empiricism and the Scientia Umbrarum, but also their complementarity, through the juxtaposition of two plot lines. Thus, he alternates the story of the mysterious murders committed near the churches built by the early eighteenth-century architect, Nicholas Dyer, with the attempts of detective Nicholas Hawksmoor to puzzle out a similar round of murders committed in the same places in the twentieth century. The aim of the Dissertation is to analyse the dual plot and structure and the symbolism of the novel with a view to demonstrating that Ackroyd defends not only the historical coexistence of reason and magic, logic and intuition, as basic forms of knowledge, but also their complementarity, thus undermining the dominant assumptions since the Age of Reason that there is a radical antagonism and incompatibility between them. Together with this, the Dissertation argues that the confrontation of reason and magic initiated in the Enlightenment may be extended to the twentieth century, when the visibility of this separation may be said to have culminated in C. P. Snow’s lecture on the two cultures