Coupling time-stepping numerical methods and standard aerodynamics codes for instability analysis of flows in complex geometries

The development of a global instability analysis code coupling a time-stepping approach, as applied to the solution of BiGlobal and TriGlobal instability analysis 1, 2 and finite-volume-based spatial discretization, as used in standard aerodynamics codes is presented. The key advantage of the time-stepping method over matrix-formulation approaches is that the former provides a solution to the computer-storage issues associated with the latter methodology. To-date both approaches are successfully in use to analyze instability in complex geometries, although their relative advantages have never been quantified. The ultimate goal of the present work is to address this issue in the context of spatial discretization schemes typically used in industry. The time-stepping approach of Chiba 3 has been implemented in conjunction with two direct numerical simulation algorithms, one based on the typically-used in this context high-order method and another based on low-order methods representative of those in common use in industry. The two codes have been validated with solutions of the BiGlobal EVP and it has been showed that small errors in the base flow do not have affect significantly the results. As a result, a three-dimensional compressible unsteady second-order code for global linear stability has been successfully developed based on finite-volume spatial discretization and time-stepping method with the ability to study complex geometries by means of unstructured and hybrid meshes

Contradictio in terminis: dialéctica de la ambigüedad en la arquitectura contemporánea

The twentieth century brought a new sensibility characterized by the discredit of cartesian rationality and the weakening of universal truths, related with aesthetic values as order, proportion and harmony. In the middle of the century, theorists such as Theodor Adorno, Rudolf Arnheim and Anton Ehrenzweig warned about the transformation developed by the artistic field. Contemporary aesthetics seemed to have a new goal: to deny the idea of art as an organized, finished and coherent structure. The order had lost its privileged position. Disorder, probability, arbitrariness, accidentality, randomness, chaos, fragmentation, indeterminacy... Gradually new terms were coined by aesthetic criticism to explain what had been happening since the beginning of the century. The first essays on the matter sought to provide new interpretative models based on, among other arguments, the phenomenology of perception, the recent discoveries of quantum mechanics, the deeper layers of the psyche or the information theories. Overall, were worthy attempts to give theoretical content to a situation as obvious as devoid of founding charter. Finally, in 1962, Umberto Eco brought together all this efforts by proposing a single theoretical frame in his book Opera Aperta. According to his point of view, all of the aesthetic production of twentieth century had a characteristic in common: its capacity to express multiplicity. For this reason, he considered that the nature of contemporary art was, above all, ambiguous. The aim of this research is to clarify the consequences of the incorporation of ambiguity in architectural theoretical discourse. We should start making an accurate analysis of this concept. However, this task is quite difficult because ambiguity does not allow itself to be clearly defined. This concept has the disadvantage that its signifier is as imprecise as its signified. In addition, the negative connotations that ambiguity still has outside the aesthetic field, stigmatizes this term and makes its use problematic. Another problem of ambiguity is that the contemporary subject is able to locate it in all situations. This means that in addition to distinguish ambiguity in contemporary productions, so does in works belonging to remote ages and styles. For that reason, it could be said that everything is ambiguous. And that’s correct, because somehow ambiguity is present in any creation of the imperfect human being. However, as Eco, Arnheim and Ehrenzweig pointed out, there are two major differences between current and past contexts. One affects the subject and the other the object. First, it’s the contemporary subject, and no other, who has acquired the ability to value and assimilate ambiguity. Secondly, ambiguity was an unexpected aesthetic result in former periods, while in contemporary object it has been codified and is deliberately present. In any case, as Eco did, we consider appropriate the use of the term ambiguity to refer to the contemporary aesthetic field. Any other term with more specific meaning would only show partial and limited aspects of a situation quite complex and difficult to diagnose. Opposed to what normally might be expected, in this case ambiguity is the term that fits better due to its particular lack of specificity. In fact, this lack of specificity is what allows to assign a dynamic condition to the idea of ambiguity that in other terms would hardly be operative. Thus, instead of trying to define the idea of ambiguity, we will analyze how it has evolved and its consequences in architectural discipline. Instead of trying to define what it is, we will examine what its presence has supposed in each moment. We will deal with ambiguity as a constant presence that has always been latent in architectural production but whose nature has been modified over time. Eco, in the mid-twentieth century, discerned between classical ambiguity and contemporary ambiguity. Currently, half a century later, the challenge is to discern whether the idea of ambiguity has remained unchanged or have suffered a new transformation. What this research will demonstrate is that it’s possible to detect a new transformation that has much to do with the cultural and aesthetic context of last decades: the transition from modernism to postmodernism. This assumption leads us to establish two different levels of contemporary ambiguity: each one related to one these periods. The first level of ambiguity is widely well-known since many years. Its main characteristics are a codified multiplicity, an interpretative freedom and an active subject who gives conclusion to an object that is incomplete or indefinite. This level of ambiguity is related to the idea of indeterminacy, concept successfully introduced into contemporary aesthetic language. The second level of ambiguity has been almost unnoticed for architectural criticism, although it has been identified and studied in other theoretical disciplines. Much of the work of Fredric Jameson and François Lyotard shows reasonable evidences that the aesthetic production of postmodernism has transcended modern ambiguity to reach a new level in which, despite of the existence of multiplicity, the interpretative freedom and the active subject have been questioned, and at last denied. In this period ambiguity seems to have reached a new level in which it’s no longer possible to obtain a conclusive and complete interpretation of the object because it has became an unreadable device. The postmodern production offers a kind of inaccessible multiplicity and its nature is deeply contradictory. This hypothetical transformation of the idea of ambiguity has an outstanding analogy with that shown in the poetic analysis made by William Empson, published in 1936 in his Seven Types of Ambiguity. Empson established different levels of ambiguity and classified them according to their poetic effect. This layout had an ascendant logic towards incoherence. In seventh level, where ambiguity is higher, he located the contradiction between irreconcilable opposites. It could be said that contradiction, once it undermines the coherence of the object, was the better way that contemporary aesthetics found to confirm the Hegelian judgment, according to which art would ultimately reject its capacity to express truth. Much of the transformation of architecture throughout last century is related to the active involvement of ambiguity in its theoretical discourse. In modern architecture ambiguity is present afterwards, in its critical review made by theoreticians like Colin Rowe, Manfredo Tafuri and Bruno Zevi. The publication of several studies about Mannerism in the forties and fifties rescued certain virtues of an historical style that had been undervalued due to its deviation from Renacentist canon. Rowe, Tafuri and Zevi, among others, pointed out the similarities between Mannerism and certain qualities of modern architecture, both devoted to break previous dogmas. The recovery of Mannerism allowed joining ambiguity and modernity for first time in the same sentence. In postmodernism, on the other hand, ambiguity is present ex-professo, developing a prominent role in the theoretical discourse of this period. The distance between its analytical identification and its operational use quickly disappeared because of structuralism, an analytical methodology with the aspiration of becoming a modus operandi. Under its influence, architecture began to be identified and studied as a language. Thus, postmodern theoretical project discerned between the components of architectural language and developed them separately. Consequently, there is not only one, but three projects related to postmodern contradiction: semantic project, syntactic project and pragmatic project. Leading these projects are those prominent architects whose work manifested an especial interest in exploring and developing the potential of the use of contradiction in architecture. Thus, Robert Venturi, Peter Eisenman and Rem Koolhaas were who established the main features through which architecture developed the dialectics of ambiguity, in its last and extreme level, as a theoretical project in each component of architectural language. Robert Venturi developed a new interpretation of architecture based on its semantic component, Peter Eisenman did the same with its syntactic component, and also did Rem Koolhaas with its pragmatic component. With this approach this research aims to establish a new reflection on the architectural transformation from modernity to postmodernity. Also, it can serve to light certain aspects still unaware that have shaped the architectural heritage of past decades, consequence of a fruitful relationship between architecture and ambiguity and its provocative consummation in a contradictio in terminis. Esta investigación centra su atención fundamentalmente sobre las repercusiones de la incorporación de la ambigüedad en forma de contradicción en el discurso arquitectónico postmoderno, a través de cada uno de sus tres proyectos teóricos. Está estructurada, por tanto, en torno a un capítulo principal titulado Dialéctica de la ambigüedad como proyecto teórico postmoderno, que se desglosa en tres, de títulos: Proyecto semántico. Robert Venturi; Proyecto sintáctico. Peter Eisenman; y Proyecto pragmático. Rem Koolhaas. El capítulo central se complementa con otros dos situados al inicio. El primero, titulado Dialéctica de la ambigüedad contemporánea. Una aproximación realiza un análisis cronológico de la evolución que ha experimentado la idea de la ambigüedad en la teoría estética del siglo XX, sin entrar aún en cuestiones arquitectónicas. El segundo, titulado Dialéctica de la ambigüedad como crítica del proyecto moderno se ocupa de examinar la paulatina incorporación de la ambigüedad en la revisión crítica de la modernidad, que sería de vital importancia para posibilitar su posterior introducción operativa en la postmodernidad. Un último capítulo, situado al final del texto, propone una serie de Proyecciones que, a tenor de lo analizado en los capítulos anteriores, tratan de establecer una relectura del contexto arquitectónico actual y su evolución posible, considerando, en todo momento, que la reflexión en torno a la ambigüedad todavía hoy permite vislumbrar nuevos horizontes discursivos. Cada doble página de la Tesis sintetiza la estructura tripartita del capítulo central y, a grandes rasgos, la principal herramienta metodológica utilizada en la investigación. De este modo, la triple vertiente semántica, sintáctica y pragmática con que se ha identificado al proyecto teórico postmoderno se reproduce aquí en una distribución específica de imágenes, notas a pie de página y cuerpo principal del texto. En la columna de la izquierda están colocadas las imágenes que acompañan al texto principal. Su distribución atiende a criterios estéticos y compositivos, cualificando, en la medida de lo posible, su condición semántica. A continuación, a su derecha, están colocadas las notas a pie de página. Su disposición es en columna y cada nota está colocada a la misma altura que su correspondiente llamada en el texto principal. Su distribución reglada, su valor como notación y su posible equiparación con una estructura profunda aluden a su condición sintáctica. Finalmente, el cuerpo principal del texto ocupa por completo la mitad derecha de cada doble página. Concebido como un relato continuo, sin apenas interrupciones, su papel como responsable de satisfacer las demandas discursivas que plantea una investigación doctoral está en correspondencia con su condición pragmática.

Study about the Problem of Dropping of Subjects by Students During an Academinc Year at the University.

In university studies, it is not unusual for students to drop some of the subjects they have enrolled in for the academic year. They start by not attending lectures, sometimes due to neglect or carelessness, or because they find the subject too difficult, this means that they lose the continuity in the topics that the professor follows. If they try to attend again they discover that they hardly understand anything and become discouraged and so decide to give up attending lectures and study on their own. However some fail to turn up to do their final exams and the failure rate of those who actually do the exams is high. The problem is that this is not only the case with one specific subject, but it is often the same with many subjects. The result is that students arent’s productive enough, wasting time and also prolonging their years of study which entails a great cost for families. Degree courses structured to be conducted and completed in three academic courses, it may in fact take up to an average of six or more academic courses. In this paper, we have studied this problem, which apart from the waste of money and time, produces frustration in the student, who finds that he has not been able to achieve what he had proposed at the beginning of the course. It is quite common, to find students who do not even pass nor 50% of the subjects they had enrolled in for the academic year. If this happens repeatedly to a student, it can be the point when he considers dropping out altogether. This is also a concern for the universities, especially in the early courses. In our experience as professors, we have found that students, who attend lectures regularly and follow the explanations, approach the final exams with confidence and rarely fail the subject. In this proposal we present some techniques and methods carried out to solve in possible, the problem of lack of attendance to lectures. This involves "rewarding students for their assistance and participation in lectures". Rewarding assistance with a "prize" that counts for the final mark on the subject and involving more participation in the development of lectures. We believe that we have to teach students to use the lectures as part of their learning in a non-passive way. We consider the professor's work as fundamental in terms of how to convey the usefulness of these topics explained and the applications that they will have for their professional life in the future. In this way the student see for himself the use and importance of what he is learning. When his participation is required, he will feel more involved and confident participating in the educational system. Finally we present statistical results of studies carried out on different degrees and on different subjects over two consecutive years. In the first year we assessed only the final exams without considering the students attendance, or participation. In the second year, we have applied the techniques and methods proposed here. In addition we have compared the two ways of assessing subjects.

Conceptualización e Infraestructura para la Investigación Experimental en Ingeniería del Software

Antecedentes: Esta investigación se enmarca principalmente en la replicación y secundariamente en la síntesis de experimentos en Ingeniería de Software (IS). Para poder replicar, es necesario disponer de todos los detalles del experimento original. Sin embargo, la descripción de los experimentos es habitualmente incompleta debido a la existencia de conocimiento tácito y a la existencia de otros problemas tales como: La carencia de un formato estándar de reporte, la inexistencia de herramientas que den soporte a la generación de reportes experimentales, etc. Esto provoca que no se pueda reproducir fielmente el experimento original. Esta problemática limita considerablemente la capacidad de los experimentadores para llevar a cabo replicaciones y por ende síntesis de experimentos. Objetivo: La investigación tiene como objetivo formalizar el proceso experimental en IS, de modo que facilite la comunicación de información entre experimentadores. Contexto: El presente trabajo de tesis doctoral ha sido desarrollado en el seno del Grupo de Investigación en Ingeniería del Software Empírica (GrISE) perteneciente a la Escuela Técnica Superior de Ingenieros Informáticos (ETSIINF) de la Universidad Politécnica de Madrid (UPM), como parte del proyecto TIN2011-23216 denominado “Tecnologías para la Replicación y Síntesis de Experimentos en Ingeniería de Software”, el cual es financiado por el Gobierno de España. El grupo GrISE cumple a la perfección con los requisitos necesarios (familia de experimentos establecida, con al menos tres líneas experimentales y una amplia experiencia en replicaciones (16 replicaciones hasta 2011 en la línea de técnicas de pruebas de software)) y ofrece las condiciones para que la investigación se lleve a cabo de la mejor manera, como por ejemplo, el acceso total a su información. Método de Investigación: Para cumplir este objetivo se opta por Action Research (AR) como el método de investigación más adecuado a las características de la investigación, para obtener resultados a través de aproximaciones sucesivas que abordan los problemas concretos de comunicación entre experimentadores. Resultados: Se formalizó el modelo conceptual del ciclo experimental desde la perspectiva de los 3 roles principales que representan los experimentadores en el proceso experimental, siendo estos: Gestor de la Investigación (GI), Gestor del Experimento (GE) y Experimentador Senior (ES). Por otra parte, se formalizó el modelo del ciclo experimental, a través de: Un workflow del ciclo y un diagrama de procesos. Paralelamente a la formalización del proceso experimental en IS, se desarrolló ISRE (de las siglas en inglés Infrastructure for Sharing and Replicating Experiments), una prueba de concepto de entorno de soporte a la experimentación en IS. Finalmente, se plantearon guías para el desarrollo de entornos de soporte a la experimentación en IS, en base al estudio de las características principales y comunes de los modelos de las herramientas de soporte a la experimentación en distintas disciplinas experimentales. Conclusiones: La principal contribución de la investigación esta representada por la formalización del proceso experimental en IS. Los modelos que representan la formalización del ciclo experimental, así como la herramienta ISRE, construida a modo de evaluación de los modelos, fueron encontrados satisfactorios por los experimentadores del GrISE. Para consolidar la validez de la formalización, consideramos que este estudio debería ser replicado en otros grupos de investigación representativos en la comunidad de la IS experimental. Futuras Líneas de Investigación: El cumplimiento de los objetivos, de la mano con los hallazgos alcanzados, han dado paso a nuevas líneas de investigación, las cuales son las siguientes: (1) Considerar la construcción de un mecanismo para facilitar el proceso de hacer explícito el conocimiento tácito de los experimentadores por si mismos de forma colaborativa y basados en el debate y el consenso , (2) Continuar la investigación empírica en el mismo grupo de investigación hasta cubrir completamente el ciclo experimental (por ejemplo: experimentos nuevos, síntesis de resultados, etc.), (3) Replicar el proceso de investigación en otros grupos de investigación en ISE, y (4) Renovar la tecnología de la prueba de concepto, tal que responda a las restricciones y necesidades de un entorno real de investigación. ABSTRACT Background: This research addresses first and foremost the replication and also the synthesis of software engineering (SE) experiments. Replication is impossible without access to all the details of the original experiment. But the description of experiments is usually incomplete because knowledge is tacit, there is no standard reporting format or there are hardly any tools to support the generation of experimental reports, etc. This means that the original experiment cannot be reproduced exactly. These issues place considerable constraints on experimenters’ options for carrying out replications and ultimately synthesizing experiments. Aim: The aim of the research is to formalize the SE experimental process in order to facilitate information communication among experimenters. Context: This PhD research was developed within the empirical software engineering research group (GrISE) at the Universidad Politécnica de Madrid (UPM)’s School of Computer Engineering (ETSIINF) as part of project TIN2011-23216 entitled “Technologies for Software Engineering Experiment Replication and Synthesis”, which was funded by the Spanish Government. The GrISE research group fulfils all the requirements (established family of experiments with at least three experimental lines and lengthy replication experience (16 replications prior to 2011 in the software testing techniques line)) and provides favourable conditions for the research to be conducted in the best possible way, like, for example, full access to information. Research Method: We opted for action research (AR) as the research method best suited to the characteristics of the investigation. Results were generated successive rounds of AR addressing specific communication problems among experimenters. Results: The conceptual model of the experimental cycle was formalized from the viewpoint of three key roles representing experimenters in the experimental process. They were: research manager, experiment manager and senior experimenter. The model of the experimental cycle was formalized by means of a workflow and a process diagram. In tandem with the formalization of the SE experimental process, infrastructure for sharing and replicating experiments (ISRE) was developed. ISRE is a proof of concept of a SE experimentation support environment. Finally, guidelines for developing SE experimentation support environments were designed based on the study of the key features that the models of experimentation support tools for different experimental disciplines had in common. Conclusions: The key contribution of this research is the formalization of the SE experimental process. GrISE experimenters were satisfied with both the models representing the formalization of the experimental cycle and the ISRE tool built in order to evaluate the models. In order to further validate the formalization, this study should be replicated at other research groups representative of the experimental SE community. Future Research Lines: The achievement of the aims and the resulting findings have led to new research lines, which are as follows: (1) assess the feasibility of building a mechanism to help experimenters collaboratively specify tacit knowledge based on debate and consensus, (2) continue empirical research at the same research group in order to cover the remainder of the experimental cycle (for example, new experiments, results synthesis, etc.), (3) replicate the research process at other ESE research groups, and (4) update the tools of the proof of concept in order to meet the constraints and needs of a real research environment.

Detection and pattern recognition applied to leaves and chromosomes

The Project you are about to see it is based on the technologies used on object detection and recognition, especially on leaves and chromosomes. To do so, this document contains the typical parts of a scientific paper, as it is what it is. It is composed by an Abstract, an Introduction, points that have to do with the investigation area, future work, conclusions and references used for the elaboration of the document. The Abstract talks about what are we going to find in this paper, which is technologies employed on pattern detection and recognition for leaves and chromosomes and the jobs that are already made for cataloguing these objects. In the introduction detection and recognition meanings are explained. This is necessary as many papers get confused with these terms, specially the ones talking about chromosomes. Detecting an object is gathering the parts of the image that are useful and eliminating the useless parts. Summarizing, detection would be recognizing the objects borders. When talking about recognition, we are talking about the computers or the machines process, which says what kind of object we are handling. Afterwards we face a compilation of the most used technologies in object detection in general. There are two main groups on this category: Based on derivatives of images and based on ASIFT points. The ones that are based on derivatives of images have in common that convolving them with a previously created matrix does the treatment of them. This is done for detecting borders on the images, which are changes on the intensity of the pixels. Within these technologies we face two groups: Gradian based, which search for maximums and minimums on the pixels intensity as they only use the first derivative. The Laplacian based methods search for zeros on the pixels intensity as they use the second derivative. Depending on the level of details that we want to use on the final result, we will choose one option or the other, because, as its logic, if we used Gradian based methods, the computer will consume less resources and less time as there are less operations, but the quality will be worse. On the other hand, if we use the Laplacian based methods we will need more time and resources as they require more operations, but we will have a much better quality result. After explaining all the derivative based methods, we take a look on the different algorithms that are available for both groups. The other big group of technologies for object recognition is the one based on ASIFT points, which are based on 6 image parameters and compare them with another image taking under consideration these parameters. These methods disadvantage, for our future purposes, is that it is only valid for one single object. So if we are going to recognize two different leaves, even though if they refer to the same specie, we are not going to be able to recognize them with this method. It is important to mention these types of technologies as we are talking about recognition methods in general. At the end of the chapter we can see a comparison with pros and cons of all technologies that are employed. Firstly comparing them separately and then comparing them all together, based on our purposes. Recognition techniques, which are the next chapter, are not really vast as, even though there are general steps for doing object recognition, every single object that has to be recognized has its own method as the are different. This is why there is not a general method that we can specify on this chapter. We now move on into leaf detection techniques on computers. Now we will use the technique explained above based on the image derivatives. Next step will be to turn the leaf into several parameters. Depending on the document that you are referring to, there will be more or less parameters. Some papers recommend to divide the leaf into 3 main features (shape, dent and vein] and doing mathematical operations with them we can get up to 16 secondary features. Next proposition is dividing the leaf into 5 main features (Diameter, physiological length, physiological width, area and perimeter] and from those, extract 12 secondary features. This second alternative is the most used so it is the one that is going to be the reference. Following in to leaf recognition, we are based on a paper that provides a source code that, clicking on both leaf ends, it automatically tells to which specie belongs the leaf that we are trying to recognize. To do so, it only requires having a database. On the tests that have been made by the document, they assure us a 90.312% of accuracy over 320 total tests (32 plants on the database and 10 tests per specie]. Next chapter talks about chromosome detection, where we shall pass the metaphasis plate, where the chromosomes are disorganized, into the karyotype plate, which is the usual view of the 23 chromosomes ordered by number. There are two types of techniques to do this step: the skeletonization process and swiping angles. Skeletonization progress consists on suppressing the inside pixels of the chromosome to just stay with the silhouette. This method is really similar to the ones based on the derivatives of the image but the difference is that it doesnt detect the borders but the interior of the chromosome. Second technique consists of swiping angles from the beginning of the chromosome and, taking under consideration, that on a single chromosome we cannot have more than an X angle, it detects the various regions of the chromosomes. Once the karyotype plate is defined, we continue with chromosome recognition. To do so, there is a technique based on the banding that chromosomes have (grey scale bands] that make them unique. The program then detects the longitudinal axis of the chromosome and reconstructs the band profiles. Then the computer is able to recognize this chromosome. Concerning the future work, we generally have to independent techniques that dont reunite detection and recognition, so our main focus would be to prepare a program that gathers both techniques. On the leaf matter we have seen that, detection and recognition, have a link as both share the option of dividing the leaf into 5 main features. The work that would have to be done is to create an algorithm that linked both methods, as in the program, which recognizes leaves, it has to be clicked both leaf ends so it is not an automatic algorithm. On the chromosome side, we should create an algorithm that searches for the beginning of the chromosome and then start to swipe angles, to later give the parameters to the program that searches for the band profiles. Finally, on the summary, we explain why this type of investigation is needed, and that is because with global warming, lots of species (animals and plants] are beginning to extinguish. That is the reason why a big database, which gathers all the possible species, is needed. For recognizing animal species, we just only have to have the 23 chromosomes. While recognizing a plant, there are several ways of doing it, but the easiest way to input a computer is to scan the leaf of the plant. RESUMEN. El proyecto que se puede ver a continuación trata sobre las tecnologías empleadas en la detección y reconocimiento de objetos, especialmente de hojas y cromosomas. Para ello, este documento contiene las partes típicas de un paper de investigación, puesto que es de lo que se trata. Así, estará compuesto de Abstract, Introducción, diversos puntos que tengan que ver con el área a investigar, trabajo futuro, conclusiones y biografía utilizada para la realización del documento. Así, el Abstract nos cuenta qué vamos a poder encontrar en este paper, que no es ni más ni menos que las tecnologías empleadas en el reconocimiento y detección de patrones en hojas y cromosomas y qué trabajos hay existentes para catalogar a estos objetos. En la introducción se explican los conceptos de qué es la detección y qué es el reconocimiento. Esto es necesario ya que muchos papers científicos, especialmente los que hablan de cromosomas, confunden estos dos términos que no podían ser más sencillos. Por un lado tendríamos la detección del objeto, que sería simplemente coger las partes que nos interesasen de la imagen y eliminar aquellas partes que no nos fueran útiles para un futuro. Resumiendo, sería reconocer los bordes del objeto de estudio. Cuando hablamos de reconocimiento, estamos refiriéndonos al proceso que tiene el ordenador, o la máquina, para decir qué clase de objeto estamos tratando. Seguidamente nos encontramos con un recopilatorio de las tecnologías más utilizadas para la detección de objetos, en general. Aquí nos encontraríamos con dos grandes grupos de tecnologías: Las basadas en las derivadas de imágenes y las basadas en los puntos ASIFT. El grupo de tecnologías basadas en derivadas de imágenes tienen en común que hay que tratar a las imágenes mediante una convolución con una matriz creada previamente. Esto se hace para detectar bordes en las imágenes que son básicamente cambios en la intensidad de los píxeles. Dentro de estas tecnologías nos encontramos con dos grupos: Los basados en gradientes, los cuales buscan máximos y mínimos de intensidad en la imagen puesto que sólo utilizan la primera derivada; y los Laplacianos, los cuales buscan ceros en la intensidad de los píxeles puesto que estos utilizan la segunda derivada de la imagen. Dependiendo del nivel de detalles que queramos utilizar en el resultado final nos decantaremos por un método u otro puesto que, como es lógico, si utilizamos los basados en el gradiente habrá menos operaciones por lo que consumirá más tiempo y recursos pero por la contra tendremos menos calidad de imagen. Y al revés pasa con los Laplacianos, puesto que necesitan más operaciones y recursos pero tendrán un resultado final con mejor calidad. Después de explicar los tipos de operadores que hay, se hace un recorrido explicando los distintos tipos de algoritmos que hay en cada uno de los grupos. El otro gran grupo de tecnologías para el reconocimiento de objetos son los basados en puntos ASIFT, los cuales se basan en 6 parámetros de la imagen y la comparan con otra imagen teniendo en cuenta dichos parámetros. La desventaja de este método, para nuestros propósitos futuros, es que sólo es valido para un objeto en concreto. Por lo que si vamos a reconocer dos hojas diferentes, aunque sean de la misma especie, no vamos a poder reconocerlas mediante este método. Aún así es importante explicar este tipo de tecnologías puesto que estamos hablando de técnicas de reconocimiento en general. Al final del capítulo podremos ver una comparación con los pros y las contras de todas las tecnologías empleadas. Primeramente comparándolas de forma separada y, finalmente, compararemos todos los métodos existentes en base a nuestros propósitos. Las técnicas de reconocimiento, el siguiente apartado, no es muy extenso puesto que, aunque haya pasos generales para el reconocimiento de objetos, cada objeto a reconocer es distinto por lo que no hay un método específico que se pueda generalizar. Pasamos ahora a las técnicas de detección de hojas mediante ordenador. Aquí usaremos la técnica explicada previamente explicada basada en las derivadas de las imágenes. La continuación de este paso sería diseccionar la hoja en diversos parámetros. Dependiendo de la fuente a la que se consulte pueden haber más o menos parámetros. Unos documentos aconsejan dividir la morfología de la hoja en 3 parámetros principales (Forma, Dentina y ramificación] y derivando de dichos parámetros convertirlos a 16 parámetros secundarios. La otra propuesta es dividir la morfología de la hoja en 5 parámetros principales (Diámetro, longitud fisiológica, anchura fisiológica, área y perímetro] y de ahí extraer 12 parámetros secundarios. Esta segunda propuesta es la más utilizada de todas por lo que es la que se utilizará. Pasamos al reconocimiento de hojas, en la cual nos hemos basado en un documento que provee un código fuente que cucando en los dos extremos de la hoja automáticamente nos dice a qué especie pertenece la hoja que estamos intentando reconocer. Para ello sólo hay que formar una base de datos. En los test realizados por el citado documento, nos aseguran que tiene un índice de acierto del 90.312% en 320 test en total (32 plantas insertadas en la base de datos por 10 test que se han realizado por cada una de las especies]. El siguiente apartado trata de la detección de cromosomas, en el cual se debe de pasar de la célula metafásica, donde los cromosomas están desorganizados, al cariotipo, que es como solemos ver los 23 cromosomas de forma ordenada. Hay dos tipos de técnicas para realizar este paso: Por el proceso de esquelotonización y barriendo ángulos. El proceso de esqueletonización consiste en eliminar los píxeles del interior del cromosoma para quedarse con su silueta; Este proceso es similar a los métodos de derivación de los píxeles pero se diferencia en que no detecta bordes si no que detecta el interior de los cromosomas. La segunda técnica consiste en ir barriendo ángulos desde el principio del cromosoma y teniendo en cuenta que un cromosoma no puede doblarse más de X grados detecta las diversas regiones de los cromosomas. Una vez tengamos el cariotipo, se continua con el reconocimiento de cromosomas. Para ello existe una técnica basada en las bandas de blancos y negros que tienen los cromosomas y que son las que los hacen únicos. Para ello el programa detecta los ejes longitudinales del cromosoma y reconstruye los perfiles de las bandas que posee el cromosoma y que lo identifican como único. En cuanto al trabajo que se podría desempeñar en el futuro, tenemos por lo general dos técnicas independientes que no unen la detección con el reconocimiento por lo que se habría de preparar un programa que uniese estas dos técnicas. Respecto a las hojas hemos visto que ambos métodos, detección y reconocimiento, están vinculados debido a que ambos comparten la opinión de dividir las hojas en 5 parámetros principales. El trabajo que habría que realizar sería el de crear un algoritmo que conectase a ambos ya que en el programa de reconocimiento se debe clicar a los dos extremos de la hoja por lo que no es una tarea automática. En cuanto a los cromosomas, se debería de crear un algoritmo que busque el inicio del cromosoma y entonces empiece a barrer ángulos para después poder dárselo al programa que busca los perfiles de bandas de los cromosomas. Finalmente, en el resumen se explica el por qué hace falta este tipo de investigación, esto es que con el calentamiento global, muchas de las especies (tanto animales como plantas] se están empezando a extinguir. Es por ello que se necesitará una base de datos que contemple todas las posibles especies tanto del reino animal como del reino vegetal. Para reconocer a una especie animal, simplemente bastará con tener sus 23 cromosomas; mientras que para reconocer a una especie vegetal, existen diversas formas. Aunque la más sencilla de todas es contar con la hoja de la especie puesto que es el elemento más fácil de escanear e introducir en el ordenador.

Advancements in the design and validation of an air pollution integrated assessment model for Spain

This paper describes the design and application of the Atmospheric Evaluation and Research Integrated model for Spain (AERIS). Currently, AERIS can provide concentration profiles of NO2, O3, SO2, NH3, PM, as a response to emission variations of relevant sectors in Spain. Results are calculated using transfer matrices based on an air quality modelling system (AQMS) composed by the WRF (meteorology), SMOKE (emissions) and CMAQ (atmospheric-chemical processes) models. The AERIS outputs were statistically tested against the conventional AQMS and observations, revealing a good agreement in both cases. At the moment, integrated assessment in AERIS focuses only on the link between emissions and concentrations. The quantification of deposition, impacts (health, ecosystems) and costs will be introduced in the future. In conclusion, the main asset of AERIS is its accuracy in predicting air quality outcomes for different scenarios through a simple yet robust modelling framework, avoiding complex programming and long computing times.

Modelado y análisis del comportamiento hidro-elástico de rotores para DAECS

La transformación de la energía cinética del mar en una fuente renovable de energía eléctrica podría ser un hecho relevante desde el punto de visto tecnológico en un futuro cercano. En el campo de las energías renovables marinas, las turbinas de corrientes de eje horizontal son posiblemente el dispositivo más adecuado para la obtención de electricidad. Las técnicas de cálculo existentes en la actualidad para obtener las distribuciones de cargas a las que está sometida una pala de una turbina de corrientes son las siguientes: Modelos de disco actuador, Método de líneas sustentadoras y método de elementos finitos. Estas técnicas presentan ciertas dificultades para su implementación y obtención de resultados preliminares, ya que entrañan gran complejidad conceptual y su entendimiento no resulta sencillo ni tampoco elaborar procedimientos de cálculo que se puedan utilizar durante la fase de diseño conceptual o básico de una turbina. En este trabajo, se analizarán los conceptos físicos y matemáticos que intervienen en el funcionamiento de una turbina de corrientes, para confeccionar un método o procedimiento de cálculo que sea relativamente intuitivo y sencillo de manejar. Esta herramienta de cálculo permitirá obtener resultados para el diseño básico, y también puede ser un punto de partida para manejar otras herramientas de cálculo más avanzadas ya que los principios fundamentales son los mismos. En la parte final del trabajo se aplicarán las ecuaciones obtenidas a varios casos reales de turbinas de corrientes. ABSTRACT Transforming the kinetic energy of the sea into renewable useful source electricity could be a relevant technologic development in the near future. In this field, marine horizontal axis turbines (HAT) are possibly, the most important devices. The current calculation techniques used to obtain the acting forces or loads in the marine current horizontal axis rotor blades: Actuator disc models, lifting lines and finite element method, have certain disadvantages which lead difficulties to obtain relatively quick results, in addition, these methods are not easy to understand and mastering, and furthermore, complex computing tools are required to obtain results. In the present work, the common physical and mathematic fundamentals will be studied and analyzed with the aim to create a new easier managing calculating tool. The proposed procedure of this document can be considered as a help towards to calculate preliminary solutions easier, and also a starting point to manage physical ideas which could be used with other calculation tools. And finally, the mathematic fundamentals will be explained and the implementation of the equations in a real case. Nevertheless, due to the real complexity of the problem, the assumed simplifications of this model must be taken into account, in order to know the possible calculating limitations of this procedure and consequently use it correctly.

Coupled Nonlinear Ginzburg-Landau and Mechanics Model for Martensitic Transformations in Polycrystals

Las transformaciones martensíticas (MT) se definen como un cambio en la estructura del cristal para formar una fase coherente o estructuras de dominio multivariante, a partir de la fase inicial con la misma composición, debido a pequeños intercambios o movimientos atómicos cooperativos. En el siglo pasado se han descubierto MT en diferentes materiales partiendo desde los aceros hasta las aleaciones con memoria de forma, materiales cerámicos y materiales inteligentes. Todos muestran propiedades destacables como alta resistencia mecánica, memoria de forma, efectos de superelasticidad o funcionalidades ferroicas como la piezoelectricidad, electro y magneto-estricción etc. Varios modelos/teorías se han desarrollado en sinergia con el desarrollo de la física del estado sólido para entender por qué las MT generan microstructuras muy variadas y ricas que muestran propiedades muy interesantes. Entre las teorías mejor aceptadas se encuentra la Teoría Fenomenológica de la Cristalografía Martensítica (PTMC, por sus siglas en inglés) que predice el plano de hábito y las relaciones de orientación entre la austenita y la martensita. La reinterpretación de la teoría PTMC en un entorno de mecánica del continuo (CM-PTMC) explica la formación de los dominios de estructuras multivariantes, mientras que la teoría de Landau con dinámica de inercia desentraña los mecanismos físicos de los precursores y otros comportamientos dinámicos. La dinámica de red cristalina desvela la reducción de la dureza acústica de las ondas de tensión de red que da lugar a transformaciones débiles de primer orden en el desplazamiento. A pesar de las diferencias entre las teorías estáticas y dinámicas dado su origen en diversas ramas de la física (por ejemplo mecánica continua o dinámica de la red cristalina), estas teorías deben estar inherentemente conectadas entre sí y mostrar ciertos elementos en común en una perspectiva unificada de la física. No obstante las conexiones físicas y diferencias entre las teorías/modelos no se han tratado hasta la fecha, aun siendo de importancia crítica para la mejora de modelos de MT y para el desarrollo integrado de modelos de transformaciones acopladas de desplazamiento-difusión. Por lo tanto, esta tesis comenzó con dos objetivos claros. El primero fue encontrar las conexiones físicas y las diferencias entre los modelos de MT mediante un análisis teórico detallado y simulaciones numéricas. El segundo objetivo fue expandir el modelo de Landau para ser capaz de estudiar MT en policristales, en el caso de transformaciones acopladas de desplazamiento-difusión, y en presencia de dislocaciones. Comenzando con un resumen de los antecedente, en este trabajo se presentan las bases físicas de los modelos actuales de MT. Su capacidad para predecir MT se clarifica mediante el ansis teórico y las simulaciones de la evolución microstructural de MT de cúbicoatetragonal y cúbicoatrigonal en 3D. Este análisis revela que el modelo de Landau con representación irreducible de la deformación transformada es equivalente a la teoría CM-PTMC y al modelo de microelasticidad para predecir los rasgos estáticos durante la MT, pero proporciona una mejor interpretación de los comportamientos dinámicos. Sin embargo, las aplicaciones del modelo de Landau en materiales estructurales están limitadas por su complejidad. Por tanto, el primer resultado de esta tesis es el desarrollo del modelo de Landau nolineal con representación irreducible de deformaciones y de la dinámica de inercia para policristales. La simulación demuestra que el modelo propuesto es consistente fcamente con el CM-PTMC en la descripción estática, y también permite una predicción del diagrama de fases con la clásica forma ’en C’ de los modos de nucleación martensítica activados por la combinación de temperaturas de enfriamiento y las condiciones de tensión aplicada correlacionadas con la transformación de energía de Landau. Posteriomente, el modelo de Landau de MT es integrado con un modelo de transformación de difusión cuantitativa para elucidar la relajación atómica y la difusión de corto alcance de los elementos durante la MT en acero. El modelo de transformaciones de desplazamiento y difusión incluye los efectos de la relajación en borde de grano para la nucleación heterogenea y la evolución espacio-temporal de potenciales de difusión y movilidades químicas mediante el acoplamiento de herramientas de cálculo y bases de datos termo-cinéticos de tipo CALPHAD. El modelo se aplica para estudiar la evolución microstructural de aceros al carbono policristalinos procesados por enfriamiento y partición (Q&P) en 2D. La microstructura y la composición obtenida mediante la simulación se comparan con los datos experimentales disponibles. Los resultados muestran el importante papel jugado por las diferencias en movilidad de difusión entre la fase austenita y martensita en la distibución de carbono en las aceros. Finalmente, un modelo multi-campo es propuesto mediante la incorporación del modelo de dislocación en grano-grueso al modelo desarrollado de Landau para incluir las diferencias morfológicas entre aceros y aleaciones con memoria de forma con la misma ruptura de simetría. La nucleación de dislocaciones, la formación de la martensita ’butterfly’, y la redistribución del carbono después del revenido son bien representadas en las simulaciones 2D del estudio de la evolución de la microstructura en aceros representativos. Con dicha simulación demostramos que incluyendo las dislocaciones obtenemos para dichos aceros, una buena comparación frente a los datos experimentales de la morfología de los bordes de macla, la existencia de austenita retenida dentro de la martensita, etc. Por tanto, basado en un modelo integral y en el desarrollo de códigos durante esta tesis, se ha creado una herramienta de modelización multiescala y multi-campo. Dicha herramienta acopla la termodinámica y la mecánica del continuo en la macroescala con la cinética de difusión y los modelos de campo de fase/Landau en la mesoescala, y también incluye los principios de la cristalografía y de la dinámica de red cristalina en la microescala. ABSTRACT Martensitic transformation (MT), in a narrow sense, is defined as the change of the crystal structure to form a coherent phase, or multi-variant domain structures out from a parent phase with the same composition, by small shuffles or co-operative movements of atoms. Over the past century, MTs have been discovered in different materials from steels to shape memory alloys, ceramics, and smart materials. They lead to remarkable properties such as high strength, shape memory/superelasticity effects or ferroic functionalities including piezoelectricity, electro- and magneto-striction, etc. Various theories/models have been developed, in synergy with development of solid state physics, to understand why MT can generate these rich microstructures and give rise to intriguing properties. Among the well-established theories, the Phenomenological Theory of Martensitic Crystallography (PTMC) is able to predict the habit plane and the orientation relationship between austenite and martensite. The re-interpretation of the PTMC theory within a continuum mechanics framework (CM-PTMC) explains the formation of the multivariant domain structures, while the Landau theory with inertial dynamics unravels the physical origins of precursors and other dynamic behaviors. The crystal lattice dynamics unveils the acoustic softening of the lattice strain waves leading to the weak first-order displacive transformation, etc. Though differing in statics or dynamics due to their origins in different branches of physics (e.g. continuum mechanics or crystal lattice dynamics), these theories should be inherently connected with each other and show certain elements in common within a unified perspective of physics. However, the physical connections and distinctions among the theories/models have not been addressed yet, although they are critical to further improving the models of MTs and to develop integrated models for more complex displacivediffusive coupled transformations. Therefore, this thesis started with two objectives. The first one was to reveal the physical connections and distinctions among the models of MT by means of detailed theoretical analyses and numerical simulations. The second objective was to expand the Landau model to be able to study MTs in polycrystals, in the case of displacive-diffusive coupled transformations, and in the presence of the dislocations. Starting with a comprehensive review, the physical kernels of the current models of MTs are presented. Their ability to predict MTs is clarified by means of theoretical analyses and simulations of the microstructure evolution of cubic-to-tetragonal and cubic-to-trigonal MTs in 3D. This analysis reveals that the Landau model with irreducible representation of the transformed strain is equivalent to the CM-PTMC theory and microelasticity model to predict the static features during MTs but provides better interpretation of the dynamic behaviors. However, the applications of the Landau model in structural materials are limited due its the complexity. Thus, the first result of this thesis is the development of a nonlinear Landau model with irreducible representation of strains and the inertial dynamics for polycrystals. The simulation demonstrates that the updated model is physically consistent with the CM-PTMC in statics, and also permits a prediction of a classical ’C shaped’ phase diagram of martensitic nucleation modes activated by the combination of quenching temperature and applied stress conditions interplaying with Landau transformation energy. Next, the Landau model of MT is further integrated with a quantitative diffusional transformation model to elucidate atomic relaxation and short range diffusion of elements during the MT in steel. The model for displacive-diffusive transformations includes the effects of grain boundary relaxation for heterogeneous nucleation and the spatio-temporal evolution of diffusion potentials and chemical mobility by means of coupling with a CALPHAD-type thermo-kinetic calculation engine and database. The model is applied to study for the microstructure evolution of polycrystalline carbon steels processed by the Quenching and Partitioning (Q&P) process in 2D. The simulated mixed microstructure and composition distribution are compared with available experimental data. The results show that the important role played by the differences in diffusion mobility between austenite and martensite to the partitioning in carbon steels. Finally, a multi-field model is proposed by incorporating the coarse-grained dislocation model to the developed Landau model to account for the morphological difference between steels and shape memory alloys with same symmetry breaking. The dislocation nucleation, the formation of the ’butterfly’ martensite, and the redistribution of carbon after tempering are well represented in the 2D simulations for the microstructure evolution of the representative steels. With the simulation, we demonstrate that the dislocations account for the experimental observation of rough twin boundaries, retained austenite within martensite, etc. in steels. Thus, based on the integrated model and the in-house codes developed in thesis, a preliminary multi-field, multiscale modeling tool is built up. The new tool couples thermodynamics and continuum mechanics at the macroscale with diffusion kinetics and phase field/Landau model at the mesoscale, and also includes the essentials of crystallography and crystal lattice dynamics at microscale.

Muscle protein synthesis by positron-emission tomography with l-[methyl-11C]methionine in adult humans

Existing methods for assessing protein synthetic rates (PSRs) in human skeletal muscle are invasive and do not readily provide information about individual muscle groups. Recent studies in canine skeletal muscle yielded PSRs similar to results of simultaneous stable isotope measurements using l-[1-13C, methyl-2H3]methionine, suggesting that positron-emission tomography (PET) with l-[methyl-11C]methionine could be used along with blood sampling and a kinetic model to provide a less invasive, regional assessment of PSR. We have extended and refined this method in an investigation with healthy volunteers studied in the postabsorptive state. They received ≈25 mCi of l-[methyl-11C]methionine with serial PET imaging of the thighs and arterial blood sampling for a period of 90 min. Tissue and metabolite-corrected arterial blood time activity curves were fitted to a three-compartment model. PSR (nmol methionine⋅min−1⋅g muscle tissue−1) was calculated from the fitted parameter values and the plasma methionine concentrations, assuming equal rates of protein synthesis and degradation. Pooled mean PSR for the anterior and posterior sites was 0.50 ± 0.040. When converted to a fractional synthesis rate for mixed proteins in muscle, assuming a protein-bound methionine content of muscle tissue, the value of 0.125 ± 0.01%⋅h−1 compares well with estimates from direct tracer incorporation studies, which generally range from ≈0.05 to 0.09%⋅h−1. We conclude that PET can be used to estimate skeletal muscle PSR in healthy human subjects and that it holds promise for future in vivo, noninvasive studies of the influences of physiological factors, pharmacological manipulations, and disease states on this important component of muscle protein turnover and balance.

Head direction cells and episodic spatial information in rats without a hippocampus

To successfully navigate through the environment animals rely on information concerning their directional heading and location. Many cells within the postsubiculum and anterior thalamus discharge as a function of the animal’s head direction (HD), while many cells in the hippocampus discharge in relation to the animal’s location. We placed lesions in the hippocampus and recorded from HD cells in the postsubiculum and anterior thalamus. Lesions of the hippocampus did not disrupt the HD cell signal in either brain area, indicating that the HD cell signal must be generated by structures external to the hippocampus. In addition, each cell’s preferred firing direction remained stable across days when the lesioned animal was placed into a novel environment. This stability appeared to weaken after several weeks of nonexposure to the new enclosure for two out of five animals, and subsequently recorded cells from these two animals established a new angular relationship between the familiar and novel environments. Our results suggest that extra-hippocampal structures are capable of creating and maintaining a novel representation of the animal’s environmental context. This representation shares features in common with mnemonic processes involving episodic memory that until now were assumed to require an intact hippocampus.

Ol-Prx 3, a member of an additional class of homeobox genes, is unimodally expressed in several domains of the developing and adult central nervous system of the medaka (Oryzias latipes)

Large-scale genetic screens for mutations affecting early neurogenesis of vertebrates have recently been performed with an aquarium fish, the zebrafish. Later stages of neural morphogenesis have attracted less attention in small fish species, partly because of the lack of molecular markers of developing structures that may facilitate the detection of discrete structural alterations. In this context, we report the characterization of Ol-Prx 3 (Oryzias latipes-Prx 3). This gene was isolated in the course of a large-scale screen for brain cDNAs containing a highly conserved DNA binding region, the homeobox helix-three. Sequence analysis revealed that this gene belongs to another class of homeobox genes, together with a previously isolated mouse ortholog, called OG-12 [Rovescalli, A. C., Asoh, S. & Nirenberg, M. (1996) Proc. Natl. Acad. Sci. USA 93, 10691–10696] and with the human SHOX gene [Rao, E., Weiss, B., Fukami, M., Rump, A., Niesler, B., et al. (1997) Nat. Genet. 16, 54–62], thought to be involved in the short-stature phenotype of Turner syndrome patients. These three genes exhibit a moderate level of identity in the homeobox with the other genes of the paired-related (PRX) gene family. Ol-Prx 3, as well as the PRX genes, are expressed in various cartilaginous structures of head and limbs. These genes might thus be involved in common regulatory pathways during the morphogenesis of these structures. Moreover, this paper reports a complex and monophasic pattern of Ol-Prx 3 expression in the central nervous system, which differs markedly from the patterns reported for the PRX genes, Prx 3 excluded: this gene begins to be expressed in a variety of central nervous system territories at late neurula stage. Strikingly, it remains turned on in some of the derivatives of each territory during the entire life of the fish. We hope this work will thus help identify common features for the PRX 3 family of homeobox genes.

LvsA, a Protein Related to the Mouse Beige Protein, Is Required for Cytokinesis in DictyosteliumV⃞

We isolated a Dictyostelium cytokinesis mutant with a defect in a novel locus called large volume sphere A (lvsA). lvsA mutants exhibit an unusual phenotype when attempting to undergo cytokinesis in suspension culture. Early in cytokinesis, they initiate furrow formation with concomitant myosin II localization at the cleavage furrow. However, the furrow is later disrupted by a bulge that forms in the middle of the cell. This bulge is bounded by furrows on both sides, which are often enriched in myosin II. The bulge can increase and decrease in size multiple times as the cell attempts to divide. Interestingly, this phenotype is similar to the cytokinesis failure of Dictyostelium clathrin heavy-chain mutants. Furthermore, both cell lines cap ConA receptors but form only a C-shaped loose cap. Unlike clathrin mutants, lvsA mutants are not defective in endocytosis or development. The LvsA protein shares several domains in common with the molecules beige and Chediak–Higashi syndrome proteins that are important for lysosomal membrane traffic. Thus, on the basis of the sequence analysis of the LvsA protein and the phenotype of the lvsA mutants, we postulate that LvsA plays an important role in a membrane-processing pathway that is essential for cytokinesis.

Increased IGF-II protein affects p57kip2 expression in vivo and in vitro: Implications for Beckwith–Wiedemann syndrome

In both human and mouse, the Igf2 gene, localized on chromosomes 11 and 7, respectively, is expressed from the paternally inherited chromosome in the majority of tissues. Insulin-like growth factor-II (IGF-II) plays an important role in embryonic growth, and aberrant IGF2 expression has been documented in several human pathologies, such as Beckwith–Wiedemann syndrome (BWS), and a wide variety of tumors. Human and mouse genetic data strongly implicate another gene, CDKN1C (p57kip2), located in the same imprinted gene cluster on human chromosome II, in BWS. p57KIP2 is a cyclin-dependent kinase inhibitor and is required for normal mouse embryonic development. Mutations in CDKN1C (p57kip2) have been identified in a small proportion of patients with BWS, and removal of the gene from mice by targeted mutagenesis produces a phenotype with elements in common with this overgrowth syndrome. Patients with BWS with biallelic expression of IGF2 or with a CDKN1C (p57kip2) mutation, as well as overlapping phenotypes observed in two types of mutant mice, the p57kip2 knockout and IGF-II-overexpressing mice, strongly suggest that the genes may act in a common pathway of growth control in situations where Igf2 expression is abnormal. Herein, we show that p57kip2 expression is reduced on IGF-II treatment of primary embryo fibroblasts in a dose-dependent manner. In addition, p57kip2 expression is down-regulated in mice with high serum levels of IGF-II. These data suggest that the effects of increased IGF-II in BWS may, in part, be mediated through a decrease in p57kip2 gene expression.

Genetic analysis of calcium spiking responses in nodulation mutants of Medicago truncatula

The symbiotic interaction between Medicago truncatula and Sinorhizobium meliloti results in the formation of nitrogen-fixing nodules on the roots of the host plant. The early stages of nodule formation are induced by bacteria via lipochitooligosaccharide signals known as Nod factors (NFs). These NFs are structurally specific for bacterium–host pairs and are sufficient to cause a range of early responses involved in the host developmental program. Early events in the signal transduction of NFs are not well defined. We have previously reported that Medicago sativa root hairs exposed to NF display sharp oscillations of cytoplasmic calcium ion concentration (calcium spiking). To assess the possible role of calcium spiking in the nodulation response, we analyzed M. truncatula mutants in five complementation groups. Each of the plant mutants is completely Nod− and is blocked at early stages of the symbiosis. We defined two genes, DMI1 and DMI2, required in common for early steps of infection and nodulation and for calcium spiking. Another mutant, altered in the DMI3 gene, has a similar mutant phenotype to dmi1 and dmi2 mutants but displays normal calcium spiking. The calcium behavior thus implies that the DMI3 gene acts either downstream of calcium spiking or downstream of a common branch point for the calcium response and the later nodulation responses. Two additional mutants, altered in the NSP and HCL genes, which show root hair branching in response to NF, are normal for calcium spiking. This system provides an opportunity to use genetics to study ligand-stimulated calcium spiking as a signal transduction event.

Analysis of the Xenopus laevis CCAAT-enhancer binding protein α gene promoter demonstrates species-specific differences in the mechanisms for both auto-activation and regulation by Sp1

Transcription factors belonging to the CCAAT-enhancer binding protein (C/EBP) family have been implicated in the regulation of gene expression during differentiation, development and disease. Autoregulation is relatively common in the modulation of C/EBP gene expression and the murine and human C/EBPα genes have been shown to be auto-activated by different mechanisms. In the light of this finding, it is essential that autoregulation of C/EBPα genes from a wider range of different species be investigated in order to gauge the degree of commonality, or otherwise, that may exist. We report here studies that investigate the regulation of the Xenopus laevis C/EBPα gene (xC/EBPα). The –1131/+41 promoter region was capable of directing high levels of expression in both the human hepatoma Hep3B and the Xenopus kidney epithelial A6 cell lines, and was auto-activated by expression vectors specifying for xC/EBPα or xC/EBPβ. Deletion analysis showed that the –321/+41 sequence was sufficient for both the constitutive promoter activity and auto-activation and electrophoretic mobility shift assays identified the interaction of C/EBPs and Sp1 to this region. Although deletion of either the C/EBP or the Sp1 site drastically reduced the xC/EBPα promoter activity, multimers of only the C/EBP site could confer autoregulation to a heterologous SV40 promoter. These results indicate that, in contrast to the human promoter and in common with the murine gene, the xC/EBPα promoter was subject to direct autoregulation. In addition, we demonstrate a novel species-specific action of Sp1 in the regulation of C/EBPα expression, with the factor able to repress the murine promoter but activate the Xenopus gene.