La eficiencia del equilibrio competitivo a la luz de la hipótesis de las expectativas racionales

This paper analyzes the current state of the theory of market equilibrium under asymmetric information. The essential features of the models that investigate the implications of the walrasian mechanisms for the equilibrium structure of prices are reviewed, along with the current state of thinking about the efficient market hypothesis. The paper stresses the importante of endogenous (keynesian) price uncertainty, relative to the standard (Arrow-Debreu) exogenous uncertainty about states of nature, and emphasizes that endogenous price uncertainty is by itself a cause of non-efficient allocations and a source of failures in macroeconomic coordination, Finally, I argue that the walrasian model is not one in which the informational efficiency of the price system can be properly evaluated, because walrasian traders ignore the information content of the futures price and form their demands using only their own private information. We conclude that the walrasian model is unsuitable when there is diverse information about the future and when the worth of a current risky decision to each trader in the economy depends on other traders current information.Este artículo analiza el estado actual de la teoría del equilibrio del mercado en presencia de información asimétrica, Las características esenciales de los modelos que investigan las implicaciones de los mecanismos walrasianos para la estructura de los precios de equilibrio son analizadas, junto con el estado actual del pensamIento en torno a la hipótesis de los mercados eficientes, El artículo muestra la importancia de la incertidumbre endógena (keynesiana) en torno a los precios, en relación con la incertidumbre exógena (tradicionalmente asociada al modelo de Arrow-Debreu) acerca de los estados de naturaleza, y pone de relieve que la incertidumbre endógena es por si misma una causa de asignaciones no eficientes y una fuente de fracasos en la coordinación macroeconómica, Finalmente se argumenta que el modelo walrasiano no es apropiado para evaluar adecuadamente la eficiencia informacional del sistema de precios, dado que los agentes walrasianos ignoran la información contenida en el precio de futuros y forman sus demandas utilizando solamente la información privada de que disponen. Llegamos a la conclusión de que el modelo walrasiano es inapropiado cuando existe diversa información sobre el futuro, y cuando el valor de una decisión con riesgo tomada en el momento presente depende de la información poseída actualmente por otros agentes

AN ANALYTICAL NON-STATIONARY DISPERSION-DEPOSITION MODEL

In this work an atmospheric dispersion-deposition model to describe the radionuclides concentration after a hypothetical nuclear accident is presented. The developed model has two parts. The first one describes the concentration due to the material released after an arbitrary period from a given source. The second one describes the concentration change during the current period due to the dispersion of the material that is in the atmosphere. Here the solution for the first part is presented. A non-stationary analytical solution is obtained from the atmospheric diffusion equation. The model solves the transport (convection-diffusion) equation in which the contaminant settling is explicitly incorporated. Regarding the boundary conditions, it is assumed a null diffusion through the mixed layer top and an albedo at the ground level. From the general solution obtained for the contaminant concentration the Gaussian plume formula is derived as a particular case when it is assumed a stationary point source, vd =0 (total reflection) and vs,=0 (without settling). Assuming vd ≠ 0 and vs,= 0, is compared with the Source Depletion Model (SoDM) and with the Surface Depletion Model (SuDM). The agreement is excellent when comparing with the SuDM, which is the exact solution for the diffusion equation when the settling is modeled only in the boundary condition. Two additional cases are presented, the former is the steady state solution: vd ≠ 0 and vs, ≠ 0, and the last one is a non-stationary simulation with a transport time of 3600 s with vd ≠ 0 and vs, ≠ 0. For the last case, two Erf functions appear in the solution as result of time integration that model the plume front traveling in the atmosphere. This new contaminant transport model describes the concentration evolution in a more realistic way, representing the plume falling. This is an improvement respect to the known dispersion-deposition models (SoDM, SuDM)

ALGUNOS ASPECTOS DE LA PREHISTORIA DE LA MATEMÁTICA

Entre las primeras actividades del hombre prehistórico se pueden nombrar la conservación del fuego, la creación de trampas para cazar animales, la construcción de casas y tumbas. También el cálculo de distancias con su cuerpo y sus pasos, el grabado de escenas en sus cavernas, la observación del movimiento de los astros y las direcciones espaciales. En esas actividades están prefigurados los conceptos básicos de la matemática: número, medida, orden. Si bien la Historia comienza con la escritura, existen numerosas conjeturas acerca del quehacer humano en la Prehistoria. Se exponen algunas de ellas relacionadas con conceptos matemáticos, basadas en los registros disponibles más antiguos

Approximations by finite elements, shape sensitivity analysis and functional analysis

Este proyecto continúa el proyecto 06/G512 con título Resolución numérica de ecuaciones diferenciales, problemas de optimización y temas de análisis relacionados desarrollado en el período 2016-2018. Motivado por problemas en los que estructuras elásticas se encuentran sumergidas en un fluido provenientes de la ingeniería nuclear (como por ejemplo, elementos combustibles sumergidos el fluido refrigerante) se estudia el análisis espectral de su formulación como operadores compactos no-autoadjuntos que surgen en problemas de vibraciones de sistemas fluido-estructura. Se estudiarán problemas de optimización relacionados con la forma y topología de materiales elásticos anisotrópicos, se implementará en un código la derivada topológica y se analizarán distintas funciones objetivos a minimizar o maximizar según corresponda. Se realizarán aplicaciones en problemas médicos provenientes de lesiones óseas. Por otro lado, se han estudiado dentro del proyecto BNCT (que estudia la Terapia de Captura Neutrónica en Boro), en forma experimental, sobre la temperatura de la piel de la bolsa del cachete de hamsters, inoculados con tumores, en el tratamiento de cáncer bucal en hámster. La temperatura superficial esta controlada por la perfusión de la sangre, la actividad metabólica y la conducción de calor entre la piel y el medio ambiente. Estas propiedades fisiológicas pueden cambiar dentro del tejido tumoral, lo cual modifica la temperatura superficial. Utilizando esta temperatura superficial, se pueden plantear problemas inversos para determinar ciertos parámetros relevantes del problema, como por ejemplo la conductividad térmica.This project is a continuation of project 06 / G512 with the title Numerical resolution of differential equations, optimization problems and related analysis topics developed in the period 2016-2018. Motivated by problems in which elastic structures are immersed in a fluid (for example, fuel elements immersed in the cooling fluid), the modes of vibration and resonance frequencies are studied, establishing their formulation as compact non-self-adjoint operators. Optimization problems related to the shape and topology of anisotropic elastic materials will be studied, the topological derivative will be implemented in a code and different objective functions will be analyzed to minimize or maximize according to the cases considered. Applications will be made in medical problems from bone injuries. On the other hand, they have been studied in the BNCT project (which studies Boron Neutron Capture Therapy), experimentally, on the skin temperature of the bag of hamsters' cheeks, inoculated with tumors, in the treatment of cancer oral in hamster. The surface temperature is controlled by blood perfusion, metabolic activity and heat conduction between the skin and the environment. These physiological properties can change within the tumor tissue, which modifies the surface temperature. Using this surface temperature, inverse problems can arise to determine certain relevant parameters of the problem, such as thermal conductivity

A posteriori error estimates for non-conforming approximation of eigenvalue problems

We consider the approximation of eigenvalue problem for the Laplacian by the Crouzeix– Raviart non-conforming finite elements in two and three dimensions. Extending known techniques for source problems, we introduce a posteriori error estimators for eigenvectors and eigenvalues. We prove that the error estimator is equivalent to the energy norm of the eigenvector error up to higher order terms. Moreover, we prove that our estimator provides an upper bound for the error in the approximation of the first eigenvalue, also up to higher order terms. We present numerical examples of an adaptive procedure based on our error estimator in two and three dimensions. These examples show that the error in the adaptive procedure is optimal in terms of the number of degrees of freedom.Fil: Dari, Enzo Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duran, Ricardo Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Padra, Claudio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Helicobacter suis infection alters glycosylation and decreases the pathogen growth inhibiting effect and binding avidity of gastric mucins

Helicobacter suis is the most prevalent non-Helicobacter pylori Helicobacter species in the human stomach and is associated with chronic gastritis, peptic ulcer disease, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. H. suis colonizes the gastric mucosa of 60-95% of pigs at slaughter age, and is associated with chronic gastritis, decreased weight gain, and ulcers. Here, we show that experimental H. suis infection changes the mucin composition and glycosylation, decreasing the amount of H. suis-binding glycan structures in the pig gastric mucus niche. Similarly, the H. suis-binding ability of mucins from H. pylori-infected humans is lower than that of noninfected individuals. Furthermore, the H. suis growth-inhibiting effect of mucins from both noninfected humans and pigs is replaced by a growth-enhancing effect by mucins from infected individuals/pigs. Thus, Helicobacter spp. infections impair the mucus barrier by decreasing the H. suis-binding ability of the mucins and by decreasing the antiprolific activity that mucins can have on H. suis. Inhibition of these mucus-based defenses creates a more stable and inhabitable niche for H. suis. This is likely of importance for long-term colonization and outcome of infection, and reversing these impairments may have therapeutic benefits

Helicobacter suis binding to carbohydrates on human and porcine gastric mucins and glycolipids occurs via two modes

Helicobacter suis colonizes the stomach of most pigs and is the most prevalent non-Helicobacter pylori Helicobacter species found in the human stomach. In the human host, H. suis contributes to the development of chronic gastritis, peptic ulcer disease and MALT lymphoma, whereas in pigs it is associated with gastritis, decreased growth and ulcers. Here, we demonstrate that the level of H. pylori and H. suis binding to human and pig gastric mucins varies between individuals with species dependent specificity. The binding optimum of H. pylori is at neutral pH whereas that of H. suis has an acidic pH optimum, and the mucins that H. pylori bind to are different than those that H. suis bind to. Mass spectrometric analysis of mucin O-glycans from the porcine mucin showed that individual variation in binding is reflected by a difference in glycosylation; of 109 oligosaccharide structures identified, only 14 were present in all examined samples. H. suis binding to mucins correlated with glycans containing sulfate, sialic acid and terminal galactose. Among the glycolipids present in pig stomach, binding to lactotetraosylceramide (Gal beta 3GlcNAc beta 3Gal beta 4Glc beta 1Cer) was identified, and adhesion to Gal beta 3GlcNAc beta 3Gal beta 4Glc at both acidic and neutral pH was confirmed using other glycoconjugates. Together with that H. suis bound to DNA (used as a proxy for acidic charge), we conclude that H. suis has two binding modes: one to glycans terminating with Gal beta 3GlcNAc, and one to negatively charged structures. Identification of the glycan structures H. suis interacts with can contribute to development of therapeutic strategies alternative to antibiotics

BabA-mediated adherence of pediatric ulcerogenic H. pylori strains to gastric mucins at neutral and acidic pH

Funding This work was supported by the Familjen Erling-Perssons Stiftelse;Fundação para a Ciência e a Tecnologia [FCTPTDC/BIM-MEC/1051/2012];Swedish research council [521-2011-2370];Swedish research council [621-2014-4361]; Swedish cancer society;Åke Wibergs ;Ragnar Söderbergs stiftelse;Stiftelserna Wilhelm och Martina Lundgrens;Svenska Forskningsrådet Formas [221-2013-590];Svenska Forskningsrådet Formas [221-2011-1036].Helicobacter pylori infection can result in non-ulcer dyspepsia (NUD), peptic ulcer disease (PUD), adenocarcinoma, and gastric lymphoma. H. pylori reside within the gastric mucus layer, mainly composed of mucins carrying an array of glycan structures that can serve as bacterial adhesion epitopes. The aim of the present study was to characterize the binding ability, adhesion modes, and growth of H. pylori strains from pediatric patients with NUD and PUD to gastric mucins. Our results showed an increased adhesion capacity of pediatric PUD H. pylori strains to human and rhesus monkey gastric mucins compared to the NUD strains both at neutral and acidic pH, regardless if the mucins were positive for Lewis b (Leb), Sialyl-Lewis x (SLex) or LacdiNAc. In addition to babA positive strains being more common among PUD associated strains, H. pylori babA positive strains bound more avidly to gastric mucins than NUD babA positive strains at acidic pH. Binding to Leb was higher among babA positive PUD H. pylori strains compared to NUD strains at neutral, but not acidic, pH. PUD derived babA-knockout mutants had attenuated binding to mucins and Leb at acidic and neutral pH, and to SLex and DNA at acidic pH. The results highlight the role of BabA-mediated adherence of pediatric ulcerogenic H. pylori strains, and points to a role for BabA in adhesion to charged structures at acidic pH, separate from its specific blood group binding activity.publishersversionpublishe