Anatomical differentiation of isolated scales of amiiform fishes (Amiiformes, Actinopterygii) from the Early Cretaceous of Las Hoyas (Cuenca, Spain)

Les écailles des poissons amiiformes sont plus différentes les unes des autres que ce qu’on avait précédemment affirmé. L’anatomie des écailles des trois taxons d’amiiformes du Crétacé inférieur (Barrémien) de Las Hoyas (Cuenca, Espagne) est décrite en détail. Les différences observées permettent la répartition des écailles isolées de cette localité entre ces trois taxons, ce qui permet de disposer d’un échantillonnage assez large, autorisant des études paléobiologiques et paléoécologiques.The scales of amiiform fishes are more different from each other than previously stated. The anatomy of the scales of the three amiiform taxa from the Early Cretaceous (Barremian) of Las Hoyas (Cuenca, Spain) is described in detail. The differences between them has allowed the segregation of isolated scales form the fossil record of this site into the three taxa, providing relatively large population samples that can be studied from a palaeobiological and palaeoecological point of view

Actividades en análisis de datos

En este documento se busca poder explorar algunas de las potencialidades de la calculadora TI 92 referentes al análisis de datos, mediante la realización de actividades que pretenden servir de apoyo al desarrollo del pensamiento estadístico

Argumentación matemática y demostración en Cabri: el problema de la colinealidad

El trabajo con Cabri ha mostrado ser muy efectivo al permitir, mediante exploraciones sistemáticas, el estudio de las regularidades de las construcciones geométricas generando una forma de presentar la geometría escolar basada en la búsqueda de invariantes de las figuras geométricas diferente a la presentación tradicional a partir de demostraciones, en ocasiones, sin sentido. Sin embargo, un pensamiento matemático genuino necesita, además de la experimentación para obtener conclusiones y dar significado a las mismas, desarrollar esquemas de argumentación que admitan llegar a estas conclusiones a partir de hechos conocidos. Cabri permite el juego en ambos sentidos, es decir, además de ser muy útil en la búsqueda de regularidades, también ofrece la posibilidad de generar esquemas válidos de argumentación matemática

Disability, capacity for work and the business cycle: An international perspective

An important policy issue in recent years concerns the number of people claiming disability benefits for reasons of incapacity for work. We distinguish between ‘work disability’, which may have its roots in economic and social circumstances, and ‘health disability’ which arises from clear diagnosed medical conditions. Although there is a link between work and health disability, economic conditions, and in particular the ‘business cycle’ and variations in the risk of unemployment over time and across localities, may play an important part in explaining both the stock of disability benefit claimants and inflows to and outflow from that stock. We employ a variety of cross?country and country?specific household panel data sets, as well as administrative data, to test whether disability benefit claims rise when unemployment is higher, and also to investigate the impact of unemployment rates on flows on and off the benefit rolls. We find strong evidence that local variations in unemployment have an important explanatory role for disability benefit receipt, with higher total enrolments, lower outflows from rolls and, often, higher inflows into disability rolls in regions and periods of above?average unemployment. Although general subjective measures of selfreported disability and longstanding illness are also positively associated with unemployment rates, inclusion of self?reported health measures does not eliminate the statistical relationship between unemployment rates and disability benefit receipt; indeed including general measures of health often strengthens that underlying relationship. Intriguingly, we also find some evidence from the United Kingdom and the United States that the prevalence of self?reported ‘objective’ specific indicators of disability are often pro?cyclical – that is, the incidence of specific forms of disability are pro?cyclical whereas claims for disability benefits given specific health conditions are counter?cyclical. Overall, the analysis suggests that, for a range of countries and data sets, levels of claims for disability benefits are not simply related to changes in the incidence of health disability in the population and are strongly influenced by prevailing economic conditions. We discuss the policy implications of these various findings.Disability, capacity for work, business cycle, international comparisons

The effects of employment uncertainty and wealth shocks on the labor supply and claiming behavior of older American workers

Unemployment rates in developed countries have recently reached levels not seen in a generation, and workers of all ages are facing increasing probabilities of losing their jobs and considerable losses in accumulated assets. These events likely increase the reliance that most older workers will have on public social insurance programs, exactly at a time that public finances are suffering from a large drop in contributions. Our paper explicitly accounts for employment uncertainty and unexpected wealth shocks, something that has been relatively overlooked in the literature, but that has grown in importance in recent years. Using administrative and household level data we empirically characterize a life-cycle model of retirement and claiming decisions in terms of the employment, wage, health, and mortality uncertainty faced by individuals. Our benchmark model explains with great accuracy the strikingly high proportion of individuals who claim benefits exactly at the Early Retirement Age, while still explaining the increased claiming hazard at the Normal Retirement Age. We also discuss some policy experiments and their interplay with employment uncertainty. Additionally, we analyze the effects of negative wealth shocks on the labor supply and claiming decisions of older Americans. Our results can explain why early claiming has remained very high in the last years even as the early retirement penalties have increased substantially compared with previous periods, and why labor force participation has remained quite high for older workers even in the midst of the worse employment crisis in decades.employment uncertainty, wealth shocks, retirement, labor supply, life-cycle models

"How Well Do Individuals Predict the Selling Prices of Their Homes?"

Self-reported home values are widely used as a measure of housing wealth by researchers; the accuracy of this measure, however, is an open empirical question, and requires some type of market assessment of the values reported. In this study, the authors examine the predictive power of self-reported housing wealth when estimating housing prices, utilizing the portion of the University of Michigan's Health and Retirement Study covering 1992-2006. They find that homeowners, on average, overestimate the value of their properties by 5–10 percent. More importantly, the authors establish a strong correlation between accuracy and the economic conditions at the time of the property's purchase. While most individuals overestimate the value of their property, those who buy during more difficult economic times tend to be more accurate; in some cases, they even underestimate the property's value. The authors find a surprisingly strong, likely permanent, and in many cases long-lived effect of the initial conditions surrounding the purchase of properties, and on how individuals value them. This cyclicality of the overestimation of house prices provides some explanation for the difficulties currently faced by many homeowners, who were expecting large appreciations in home value to rescue them in case of interest rate increases--which could jeopardize their ability to live up to their financial commitments.

Estrategias aritmética, geométrica y algebraica en la resolución de un problema con la TI 92

El taller va dirigido a profesores de matemáticas de Educación Básica Secundaria. A partir de un ejercicio de optimización, se aprovecharán los recursos matemáticos de las versiones de los programas Derive, Hoja de Cálculo y Cabri, instalados en la calculadora TI 92, para establecer conexiones entre los pensamientos aritmético, algebraico, variacional y estadístico

A one dimensional discrete approach for the determination of the cross sectional properties of composite rotor blades

This work presents the theoretical aspects of a one dimensional computational approach for the determination of the cross sectional stiffness of composite rotor blades. The method is based on a vector variant of the classical lamination theory embedded into a geometrically exact large deformation-small strain thin-walled beam formulation, which is naturally oriented to multibody problems. The procedures rely on a one-dimensional discretization of the aerodynamic profile of the blade; this generates groups of finite segments of composite laminates which are assembled to find the stiffness properties of the blade cross section. The formulation accounts for warping of the cross section and transverse shear; the warping problem is solved numerically by means of a one dimensional finite element formulation. The numerical tests show that the formulation gives very accurate results.Fil: Saravia, César Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; ArgentinaFil: Saravia, César Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; ArgentinaFil: Cortínez, Víctor Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; Argentin

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Ingeniería estructural de grandes obras de arquitectura

Es un hecho que las obras de edificación singulares han sido un campo propicio para la colaboración entre ingenieros y arquitectos. Durante la edad antigua, medieval o moderna, no existía una diferencia explícita entre arquitecto, ingeniero, constructor o artesano. El siglo XIX, es sin duda el punto de inflexión en el que junto con la aparición del hierro y el acero como materiales de construcción, se comienza a regular el aprendizaje de la técnica de la construcción, apareciendo la disociación en la educación del ingeniero y el arquitecto que llega a nuestros días. Sin embargo, es notable la colaboración entre ambas disciplinas en el siglo XIX y el siglo XX, siendo el punto de encuentro tradicional, las obras de edificación singular, caracterizadas por las grandes luces, o las grandes dimensiones