Placido-based indices of corneal irregularity

Purpose: To construct a set of metrics computed from the raw keratoscopic data collected by any Placido corneal topographer. These indices that measure the irregularity of the anterior corneal surface are computed directly from the image of the mires reflected on the cornea, which is the most primary data possible. Besides the high sensitivity and specificity, this approach allows bypassing the surface or curvature reconstruction step that is currently performed by the software of any commercial Placido topographer. Methods: Several basic indices are proposed in order to detect irregularities on the anterior surface of the cornea, via analyzing some geometric and mathematical properties of the mires. These individual primary indices are built in a natural and intuitive way directly from the displacement of the digitized images of the rings reflected on the cornea. Additionally, compound indices are proposed (such as the generalized linear model or the classification trees) by combining some of the so-called primary indices to improve their efficiency. The computed metrics were developed and tested for the CSO topography system (CSO, Firenze,Italy), but the methodology proposed here extends easily to any other commercial Placido disks topographer. Results: The primary indices allow to discriminate, with excellent accuracy, between normal eyes and eyes with keratoconic corneas. Sensitivity and specificity of the primary indices is analyzed by using the ROC (receiver operating characteristic) curve methodology. Some combined indices are presented, and raise the efficiency to optimal. Conclusions: All the primary indices proposed exhibit very good performance at discriminating between normal and irregular corneas. The combined indices accuracy is optimal, so avoiding their use in clinical practice as corneal markers of disease. All these indices are fast to compute and can be easily implemented in any corneal topography system. Keywords: Corneal irregularities keratoconus irregularity index diagnosis corneal topography Placido disk

Screening subclinical keratoconus with Placido-based corneal indices

Purpose: To assess in a sample of normal, keratoconic and keratoconus suspect eyes the performance of a set of new topographic indices computed directly from the digitized images of the Placido rings. Methods: This comparative study comprised a total of 124 eyes of 106 patients from the ophthalmic clinics Vissum Alicante and Vissum Almería (Spain), in three groups: control group (50 eyes), keratoconus group (50 eyes) and keratoconus suspect group (24 eyes). In all cases, a comprehensive examination was performed including the corneal topography with a Placido-based CSO topography system. Clinical outcomes were compared among groups, along with the discriminating performance of the proposed irregularity indices. Results: Significant differences at level 0.05 were found on the values of the indices among groups by means of Mann-Witney-Wilcoxon non-parametric test and Fisher’s exact test. Additional statistical methods, such as receiver operating characteristic analysis and K- fold cross-validation, confirmed the capability of the indices to discriminate between the three groups. Conclusions: Direct analysis of the digitized images of the Placido mires projected on the cornea is a valid and effective tool for detection of corneal irregularities. Although based only on the data from the anterior surface of the cornea, the new indices performed well even when applied to the keratoconus suspect eyes. They have the advantage of simplicity of calculation combined with high sensitivity in corneal irregularity detection, and thus can be used as supplementary criteria for diagnosing and grading keratoconus that can be added to the current keratometric classifications. Keywords: Corneal irregularities; subclinical keratoconus; irregularity index; diagnosis; corneal topography; Placido disk

Optimal sampling patterns for Zernike polynomials

A pattern of interpolation nodes on the disk is studied, for which the inter- polation problem is theoretically unisolvent, and which renders a minimal numerical condition for the collocation matrix when the standard basis of Zernike polynomials is used. It is shown that these nodes have an excellent performance also from several alternative points of view, providing a numer- ically stable surface reconstruction, starting from both the elevation and the slope data. Sampling at these nodes allows for a more precise recovery of the coefficients in the Zernike expansion of a wavefront or of an optical surface. Keywords: Interpolation Numerical condition Zernike polynomials Lebesgue constant

Theoretical and experimental study on the autoignition phenomena of homogeneous reactive mixtures

The main objective of this Thesis is the study of the autoignition phenomenon of reactive mixtures from a theoretical and experimental point of view. A wide parametric study has been carried out in a Rapid Compression-Expansion Machine (RCEM) for different initial temperatures, compression ratios, equivalence ratios and molar fractions of oxygen (by using synthetic EGR) for different fuels. The ignition delay referred to cool flames (if it can be identified), as well as the ignition delay referred to the high-temperature stage of the ignition, have been experimentally obtained and their trends have been explained regarding the chemical kinetics of each fuel. The different effects of the species that compose the synthetic EGR on the ignition delay have been studied, decoupling the thermodynamic effects from the chemical ones. Different compositions have been taken into account to generate the synthetic EGR, and validation limits have been obtained for each mixture. The thermodynamic and the chemical effects have shown to be opposed, while the dominant one is different depending on the working temperature. Several chemical kinetic mechanisms have been validated by comparison to the experimental results. A detailed mechanism for iso-octane and n-heptane blends and a reduced mechanisms for n-dodecane have been analyzed. Moreover, a sub-model for the generation and decay of excited OH* has been validated by comparison to chemiluminescence and spectroscopy results. The different radiation sources have been studied for iso-octane and n-heptane by means of spectroscopy techniques. Besides, chemiluminescence measurements filtered at 310nm (OH* emission wavelength) have been performed in order to analyze the generalization and propagation velocity of the autoignition front. The ignition propagation has shown to depend on the thermodynamic conditions reached in the combustion chamber when the first ignition spot occurs and not on the global reactivity of the mixture. Furthermore, two different radiation sources have been found at 310nm in the spectroscopic analysis depending on the ignition intensity: the decay of the OH* radical from excited to ground state and the oxidation of CO to CO2 (CO continuum). However, these optical techniques have been applied only in the experiments carried out with iso-octane and n-heptane due to technical limitations. Finally, a new predictive model has been theoretically developed starting from the Glassman's model for autoignition. This method is based on modeling the accumulation rate of chain carriers up to reach their critical concentration (obtaining the ignition delay referred to cool flames) and, afterwards, modeling the disappearance rate of such chain carriers up to their consumption (when the maximum heat release rate is reached, obtaining the ignition delay referred to the high-temperature stage of the process). The predictive capability of the model has been compared to the ability of other methods that can be found in the literature, such as the Livengood & Wu integral method. The validity of each method has been tested, defining a working methodology to obtain reasonable predictions for the ignition delay.El objetivo de esta Tesis Doctoral es el estudio del fenómeno de autoencendido de mezclas reactivas desde un punto de vista teórico y experimental. Se ha realizado un amplio estudio paramétrico en una Máquina de Compresión-Expansión Rápida (RCEM por sus siglas en inglés) barriendo diversas temperaturas iniciales, relaciones de compresión, dosados relativos y fracciones molares de oxígeno (mediante el uso de EGR sintético) para distintos combustibles. El tiempo de retraso del fenómeno de llamas frías (en el caso de existir), así como el tiempo de retraso de la etapa de alta temperatura, han sido obtenidos experimentalmente y sus tendencias explicadas mediante cinética química. Se han estudiado los diferentes efectos de las distintas especies involucradas en el EGR sintético sobre el tiempo de retraso, desligando aquellos de carácter termodinámico de los efectos puramente químicos. Se han tenido en cuenta distintas composiciones para definir dicho EGR, estableciendo límites de validez para cada una de las mezclas propuestas. Los efectos termodinámicos y químicos resultaron ser opuestos, siendo dominante uno u otro a distintos rangos de temperatura de trabajo. Varios mecanismos de cinética química han sido validados gracias a los resultados experimentales obtenidos. Además de un mecanismo detallado para mezclas PRF de iso-octano y n-heptano, se ha llevado a cabo la validación de otro mecanismo simplificado para el n-dodecano. Por otro lado, un submodelo de formación y decaimiento de OH* excitado ha sido validado contra resultados de quimioluminiscencia y espectroscopía. Se han estudiado las diferentes fuentes de radiación del proceso de autoencendido para el iso-octano y el n-heptano mediante técnicas de espectroscopía. Además, se han realizado medidas de quimioluminiscencia filtrada a 310nm (longitud de onda de emisión del radical OH*) para el análisis de la generalización y velocidad de propagación del frente de autoencendido. La propagación del encendido ha mostrado ser dependiente de las condiciones termodinámicas alcanzadas en la cámara de combustión en el instante de ignición más que de la reactividad de la mezcla. Se han encontrado dos fuentes de radiación distintas a 310nm mediante espectroscopía, dependiendo de la intensidad del encendido: el decaimiento del radical OH* de estado excitado a estado natural y la oxidación del CO a CO2 (continuo del CO). No obstante, estas técnicas han sido utilizadas solamente para los dos combustibles de referencia de la escala de octanaje debido a limitaciones técnicas. Finalmente, se ha desarrollado un nuevo modelo predictivo de manera teórica partiendo del modelo de Glassman para el autoencendido. Este método se basa en modelar primero la tasa de acumulación de portadores de cadena hasta su concentración crítica (obteniendo así el tiempo de retraso referido a la etapa de llamas frías) y, tras dicho instante, modelar la tasa de consumo de dichos portadores de cadena hasta su completa desaparición (instante en el cual se produce la máxima exotermia del proceso, prediciendo el tiempo de retraso referido a la etapa de alta temperatura del encendido). La capacidad predictiva del modelo ha sido comprobada para cada uno de los seis combustibles ensayados. Además, dicha capacidad predictiva ha sido comparada con la de otros métodos existentes en la literatura, como la integral de Livengood & Wu. La validez de cada uno de los métodos ha sido analizada, definiendo una metodología de uso para obtener predicciones razonables del tiempo de retraso.L'objectiu d'aquesta Tesi Doctoral és l'estudi del fenomen d'autoencesa de mescles reactives des d'un punt de vista teòric i experimental. S'ha realitzat un ampli estudi paramètric en una Màquina de Compressió-Expansió Ràpida (RCEM per les seues sigles en anglès) cobrint diverses temperatures inicials, relacions de compressió, dosatges relatius i fraccions molars d'oxigen (mitjançant l'ús de EGR sintètic) per a diferents combustibles. El temps de retard del fenomen de flames fredes (en el cas d'existir), així com el temps de retard de l'etapa d'alta temperatura, han sigut obtinguts experimentalment i les seues tendències explicades mitjançant cinètica química. S'han estudiat els diferents efectes de les diferents espècies involucrades en l'EGR sintètic sobre el temps de retard, deslligant aquells de caràcter termodinàmic dels efectes purament químics. S'han tingut en compte diferents composicions per a definir aquest EGR, establint límits de validesa per a cadascuna de les mescles proposades. Els efectes termodinàmics i químics van resultar ser oposats, sent dominant un o un altre a diferents rangs de temperatura de treball. Diversos mecanismes de cinètica química han sigut validats gràcies als resultats experimentals obtinguts. A més d'un mecanisme detallat per a mescles PRF d'iso-octà i n-heptà, s'ha dut a terme la validació d'un altre mecanisme simplificat per al n-dodecà. D'altra banda, un submodel de formació i decaïment d'OH* excitat ha sigut validat contra resultats de quimioluminescència i espectroscopía. S'han estudiat les diferents fonts de radiació del procés d'autoencesa per a l'iso-octà i l'n-heptà mitjançant tècniques d'espectroscopía. A més, s'han realitzat mesures de quimioluminescència filtrada a 310nm (longitud d'ona d'emissió del radical OH*) per a l'anàlisi de la generalització i velocitat de propagació del front d'autoencesa. La propagació de l'encesa ha mostrat ser depenent de les condicions termodinàmiques aconseguides en la cambra de combustió en l'instant d'ignició més que de la reactivitat de la mescla. S'han trobat dues fonts de radiació diferents a 310nm mitjançant espectroscopía, depenent de la intensitat de l'encesa: el decaïment del radical OH* d'estat excitat a estat natural i l'oxidació del CO a CO2 (continu del CO). No obstant açò, aquestes tècniques han sigut utilitzades solament per als dos combustibles de referència de l'escala de octanaje a causa de limitacions tècniques. Finalment, s'ha desenvolupat un nou model predictiu de manera teòrica partint del model de Glassman per a l'autoencesa. Aquest mètode es basa a modelar primer la taxa d'acumulació de portadors de cadena fins a la seua concentració crítica (obtenint així el temps de retard referit a l'etapa de flames fredes) i, després d'aquest instant, modelar la taxa de consum d'aquests portadors de cadena fins a la seua completa desaparició (instant en el qual es produeix la màxima exotermia del procés, predient el temps de retard referit a l'etapa d'alta temperatura de l'encesa). La capacitat predictiva del model ha sigut comprovada per a cadascun dels sis combustibles assajats. A més, aquesta capacitat predictiva ha sigut comparada amb la d'altres mètodes existents en la literatura, com la integral de Livengood & Wu. La validesa de cadascun dels mètodes ha sigut analitzada, definint una metodologia d'ús per a obtenir prediccions raonables del temps de retard.López Pintor, D. (2017). Theoretical and experimental study on the autoignition phenomena of homogeneous reactive mixtures [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90642TESI

A Comparison of Machine-Learning Methods to Select Socioeconomic Indicators in Cultural Landscapes

Cultural landscapes are regarded to be complex socioecological systems that originated as a result of the interaction between humanity and nature across time. Cultural landscapes present complex-system properties, including nonlinear dynamics among their components. There is a close relationship between socioeconomy and landscape in cultural landscapes, so that changes in the socioeconomic dynamic have an effect on the structure and functionality of the landscape. Several numerical analyses have been carried out to study this relationship, with linear regression models being widely used. However, cultural landscapes comprise a considerable amount of elements and processes, whose interactions might not be properly captured by a linear model. In recent years, machine-learning techniques have increasingly been applied to the field of ecology to solve regression tasks. These techniques provide sound methods and algorithms for dealing with complex systems under uncertainty. The term ‘machine learning’ includes a wide variety of methods to learn models from data. In this paper, we study the relationship between socioeconomy and cultural landscape (in Andalusia, Spain) at two different spatial scales aiming at comparing different regression models from a predictive-accuracy point of view, including model trees and neural or Bayesian networks

Apropiación y alienación: consideraciones hermenéutico-existenciales a propósito de la Pastoral Americana de Philip Roth

Starting from a basic formulation of relevant elements of Heidegger’s phenomenological hermeneutics, this article proposes a reading of the work of the american writer Philip Roth, which earned him a Pulitzer Prize in 1989, entitled American Pastoral -- The main purpose of this reading is to show how elementary existential phenomena like being-away (Wegsein), staying-awake (Wachsein), being-there (Dasein) allow an appropriate articulation of meaning of the work of Roth, in which it declares his particular existential commitmentPartiendo de una formulación básica de algunos elementos relevantes de la hermenéutica fenomenológica de Heidegger, el presente artículo propone una lectura de la obra del escritor norteamericano Philip Roth titulada Pastoral americana, que lo hizo acreedor al premio Pulitzer en 1989 -- El propósito central de esa lectura consiste en mostrar de qué manera fenómenos existenciales elementales como estar-lejos (Wegsein), estar-despierto (Wachsein), estar-ahí (Dasein) permiten una articulación propia del sentido de la obra de Roth en la que ésta manifiesta su particular compromiso existencia

The Role of Cultural Landscapes in the Delivery of Provisioning Ecosystem Services in Protected Areas

The aim of this paper is to assess and highlight the significance of cultural landscapes in protected areas, considering both biodiversity and the delivery of provisioning ecosystem services. In order to do that, we analyzed 26 protected areas in Andalusia (Spain), all of them Natural or National Parks, regarding some of their ecosystem services (agriculture, livestock grazing, microclimate regulation, environmental education and tourism) and diversity of the four terrestrial vertebrate classes: amphibians, reptiles, mammals, and birds. A cluster analysis was also run in order to group the 26 protected areas according to their dominant landscape. The results show that protected areas dominated by dehesa (a heterogeneous system containing different states of ecological maturity), or having strong presence of olive groves, present a larger area of delivery of provisioning ecosystem services, on average. These cultural landscapes play an essential role not only for biodiversity conservation but also as providers of provisioning ecosystem services

El derecho internacional en el tiempo

La epopeya de la Independencia de la América Latina se inicia con la misma ocupación extranjera. Recordemos que el hijo de la MALINCHE, compañera de Hernán Cortés se le sublevó. Interior a las Guerras, que finalizaran la gesta emancipadora, fueron muchas las insurrecciones que se dieron al interior del Continente Americano. Luchando contra las tremendas injusticias del sistema colonial, peones, indios, esclavos, africanos y criollos, se levantaron contra el régimen del sistema colonial

The Judicial power and the formation of tthe State of Corrientes in the 19th Century

La formación y consolidación del Estado correntino se ha dado paulatinamente al son de las pulsaciones de los tiempos políticos, no ajenos a las revoluciones y movimientos violentos. Precisamente en referencia al Poder Judicial, éste no fue ajeno a aquellas turbulencias que se manifestaron constantemente. Durante el período del siglo XIX, que corresponde al surgimiento del Estado provincial correntino, existe una función dentro de las esferas jurisdiccionales y políticas que adquiere una importancia relevante: el Juez de paz. Vinculado con un fuerte nexo al poder político, era a su vez caja de resonancia inmediata de cada uno de los Departamentos de la Provincia. Las múltiples facetas y facultades que desempeñaba el Juez de paz, lo convertían en el epicentro de casi toda actividad judicial, política, económica, cultural y social de los Departamentos. Si bien el Juez de paz, por su naturaleza constitucional, formaba parte del Poder Judicial, sus facultades desbordaban a aquélla, ramificándose a todos los estratos y funciones del quehacer estadual de la Provincia. Se avocaba a gran parte de las cuestiones de control y participación del Estado.The formation and consolidation of the Corrientes State has gradually taken place to the rhythm of the pulsations of political times, not alien to violent revolutions and movements. Precisely in reference to the Judicial Power, this was not alien to those turbulences that were constantly manifested. During the period of the nineteenth century, which corresponds to the emergence of the provincial state, there is a function within the jurisdictional and political spheres that acquires a relevant importance: the Judge of peace. Linked with a strong link to political power, it was in turn an immediate resonance box for each of the Departments of the Province. The multiple facets and faculties that the Judge of Peace played, made it the epicenter of almost all judicial, political, economic, cultural and social activities of the Departments. Although the Judge of peace, by its constitutional nature, was part of the Judiciary, its powers overflowed to it, branching out to all strata and functions of the state's task of the Province. It addressed a large part of the questions of State control and participatio