Self-similar solutions of the one-dimensional Landau-Lifshitz-Gilbert equation

We consider the one-dimensional Landau-Lifshitz-Gilbert (LLG) equation, a model describing the dynamics for the spin in ferromagnetic materials. Our main aim is the analytical study of the bi-parametric family of self-similar solutions of this model. In the presence of damping, our construction provides a family of global solutions of the LLG equation which are associated to a discontinuous initial data of infinite (total) energy, and which are smooth and have finite energy for all positive times. Special emphasis will be given to the behaviour of this family of solutions with respect to the Gilbert damping parameter. We would like to emphasize that our analysis also includes the study of self-similar solutions of the Schr\"odinger map and the heat flow for harmonic maps into the 2-sphere as special cases. In particular, the results presented here recover some of the previously known results in the setting of the 1d-Schr\"odinger map equation

Global existence for a kinetic model of chemotaxis via dispersion and Strichartz estimates

We investigate further the existence of solutions to kinetic models of chemotaxis. These are nonlinear transport-scattering equations with a quadratic nonlinearity which have been used to describe the motion of bacteria since the 80's when experimental observations have shown they move by a series of 'run and tumble'. The existence of solutions has been obtained in several papers [Chalub et al. Monatsh. Math. 142, 123--141 (2004), Hwang et al. SIAM J. Math. Anal. 36, 1177--1199 (2005)] using direct and strong dispersive effects. Here, we use the weak dispersion estimates of [Castella et al. C. R. Acad. Sci. Paris 322, 535--540 (1996)] to prove global existence in various situations depending on the turning kernel. In the most difficult cases, where both the velocities before and after tumbling appear, with the known methods, only Strichartz estimates can give a result, with a smallness assumption.Comment: 19 pages, 2 figure

Espacios públicos en la frontera: estudio comparativo Ciudad Juárez Chihuahua - El Paso Texas

El siguiente trabajo de investigación abarcara el complicado tema del espacio público, este espacio pretende será estudiado a partir de la perspectiva de una frontera como es el caso: Ciudad Juárez Chihuahua y El Paso Texas. El objetivo es el lograr identificar los factores que alteran la morfología urbana de las dos ciudades con respecto a la configuración de sus espacios públicos analizando sus usos y características pero siempre teniendo en perspectiva el factor de ser una frontera, como en este caso: México-Estados Unidos. La metodología que se lleva a cabo para la realización de este trabajo de investigación es de tipo mixto cualitativa y cuantitativa de carácter comparativo.de donde entre las teorías urbanísticas de espacio público, los conceptos sociológicos y los datos estadísticos de ambas ciudades se pretende llegar a resultados los cuales revelaran las diferencias de los modelos urbanos tanto mexicanos y americanos, pero sobre todo el modelo morfológico de las ciudades fronterizas denominadas “ciudades-espejo”, tal cual es el caso de estudio pero identificando como esto afecta la perspectiva del espacio público tradicional como lo son las plazas del centro histórico de ambas ciudades.The following research work covering the complicated subject of public space, this space is intended to be studied from the perspective of a border city as is the case: Ciudad Juarez Chihuahua and El Paso Texas. The intention is to be able to identify facts that modify the urban morphology and the configuration of the public spaces by analyzing their characteristics and uses but always keeping in perspective the fact to be a frontier, as in this case: Mexico-USA. The methodology used on this research is mixed-qualitative and quantitative comparative nature, supported of theories of urban public space, sociological concepts and statistical data from both cities to obtain results which reveal the differences of urban models in both urban models Mexicans and Americans, but especially the cities called " mirror cities ", as is the case of study but identifying how it affects the perspective of traditional public spaces such as the down town of both cities.Peer Reviewe

Self-similar shrinkers of the one-dimensional Landau-Lifshitz-Gilbert equation

International audienceThe main purpose of this paper is the analytical study of self-shrinker solutions of the one-dimensional Landau-Lifshitz-Gilbert equation (LLG), a model describing the dynamics for the spin in ferromagnetic materials. We show that there is a unique smooth family of backward self-similar solutions to the LLG equation, up to symmetries, and we establish their asymptotics. Moreover, we obtain that in the presence of damping, the trajectories of the self-similar profiles converge to great circles on the sphere, at an exponential rate.In particular, the results presented in this paper provide examples of blow-up in finite time, where the singularity develops due to rapid oscillations forming limit circles

Capacidad Cardiovascular en Adultos Sedentarios Obesos sometidos a prueba de esfuerzo en banda sin fin con Protocolo de Bruce modificado en el Centro de Medicina de la Actividad Física y el Deporte, año 2012

El estilo de vida sedentario es uno de los principales factores de riesgo para enfermedades de alta prevalencia, como la diabetes tipo 2, las enfermedades cardiovasculares, la osteoporosis y algunos cánceres. (1). La asociación del sedentarismo con la actual pandemia de obesidad y con el síndrome metabólico (SM) es clara. En consecuencia, el sedentarismo es un factor asociado con una peor calidad de vida y un incremento de la mortalidad general

Graptolitos del Tremadociense (Ordovícico Inferior) de la formación Volcancito, Sistema de Famatina (La Rioja, Argentina)

El Miembro Peña Negra de la Formación Volcancito(Tremadociense) del Sistema de Famatina (noroeste argentino) consta de pizarras negras graptolíticas, que se investigaron paleontológicamente, capa a capa, a lo largo de 400 m de sucesión en las secciones complementarias de Peña Negra y río Volcancito, la segunda de las cuales incluye los niveles más modernos. Los resultados bioestratigráficos permiten una correlación precisa con las asociaciones evolutivas y cronozonas globales de graptolitos del Tremadociense, y la reevaluación de todas las dataciones e identificaciones previas de la unidad. Los graptolitos más antiguos se localizan en el Miembro Filo Azul de la formación (Cámbrico Superior-Tremadociense) y se adscriben muy probablemente a la cronozona de Rhabdinopora fl abelliformis parabola de la base del Ordovícico, lo que concuerda con los datos suministrados por los trilobites y conodontos. Las asociaciones graptolíticas de la parte baja del Miembro Peña Negra pertenecen a las cronozonas de Anisograptus matanensis and R. f. anglica, indicativas del Tremadociense superior tardío. Los dos tercios restantes del Miembro Peña Negra se correlacionan probablemente con el Tremadociense superior temprano (cronozona de Adelograptus?), en ausencia de asociaciones batipelágicas típicas con adelográptidos delicados, o formas epipelágicas de aguas cálidas como Psigraptus. Esta posible atribución se apoya también en el registro de conodontos y graptolitos del Tremadociense superior en la Formación Bordo Atravesado suprayacente. Las pizarras negras graptolíticas de la Formación Volcancito se depositaron en fondos anóxicos profundos (de plataforma externa a planicie cuencal) en el margen de Gondwana occidental, previamente al nacimiento y emersión del Arco Volcánico Famatinense. El desarrollo de condiciones anóxicas tuvo que ver con la aparición de un área de afloramiento oceánica con elevada productividad orgánica, que constituyó el hábitat favorable para los rhabdinoporínidos holo- y mesopelágicos, donde se desarrollaron algunas formas endémicas. Desde el punto de vista paleontológico, se identifican y describen Rhabdinopora fl abelliformis fl abelliformis, R. f. anglica, R. f. socialis, R. f. bryograptoides?, R. cf. enigma, Anisograptus matanensis y Bryograptus? sp. La forma Rhabdinopora fl abelliformis famatinensis se propone restringirla al holotipo para obviar su mala caracterización taxonómica. Las nuevas formas Rhabdinopora turneri sp. nov. y R. fl abelliformis acenolazai subsp. nov., guardan ciertas similitudes con los graptolitos planctónicos primitivos R. praeparabola y R. fl abelliformis parabola, respectivamente. Sin embargo, los nuevos taxones del Famatina coexisten en horizontes más modernos de las cronozonas de A. matanensis y R. f. anglica, que claramente postdatan la aparición del desarrollo proximal trirradiado. Además de las formas planctónicas, se describen algunos restos transportados de graptolitos bentónicos como Dendrograptus sp., Dictyonema sp. nov. 1, Aspidograptus cuerdai sp. nov., Pseudocallograptus? sp. y Airograptus? guillermoi sp. nov.. Otro graptolito bentónico notable, Dictyonema? sp. cf. D. cordillerensis, se cita por vez primera en la Formación Bordo Atravesado del Tremadociense superior. [ABSTRACT] Tremadocian graptolites from the Famatina System (NW Argentina) occurred mainly in the black shales that characterized the Peña Negra Member of the Volcancito Formation. Bed-by-bed collecting of graptolites through the 400 m thick sequence of the Peña Negra and Volcancito river sections, resulted in a complete taxonomic and biostratigraphic reappraisal of the abundant graptolite record, which is merited by recent review and correlation of the Tremadocian chronozones and global graptolite assemblages. The two sections are not exactly time equivalent as there were considered largely until the present study, reaching younger beds in Volcancito river. The oldest Ordovician graptolites occur in the upper part of the Filo Azul Member of the Volcancito Formation, with an assemblage probably representative of the Early Tremadocian Rhabdinopora fl abelliformis parabola chronozone, placed slightly above the Cambrian-Ordovician boundary as indicated by trilobite and conodont distributions. Graptolite assemblages from the lower part of the Peña Negra Member of the Volcancito Formation are correlated with the Anisograptus matanensis and R. f. anglica graptolite chronozones of the upper Lower Tremadocian. Above the respective biozones, the remaining upper two thirds of the formation probably correlate with the lowest Upper Tremadocian ?Adelograptus Zone, in absence of batipelagic assemblages of delicate adelograptids or the epipelagic warm-water genus Psigraptus. This data agrees with the occurrence of Upper Tremadocian conodonts and graptolites, namely the Paltodus deltifer conodont biozone and the graptolitic “Assemblage 4”, in the overlying Bordo Atravesado Formation. The black graptolite shales of the Volcancito Formation were deposited under anoxic conditions in an outer shelf to basin plain along the margings of western Gondwana, before the origination and emersion of the Famatinian Volcanic Arch. The anoxic conditions probably developed under a restricted upwelling area with high productivity that was a favourable habitat for some endemic holopelagic and mesopelagic rhabdinoporinids. From a paleontological point of view, the identifi ed and described forms are Rhabdinopora fl abelliformis fl abelliformis, R. f. anglica, R. f. socialis, R. f. ?bryograptoides, R. cf. enigma, Anisograptus matanensis and ?Bryograptus sp. The bad characterized form Rhabdinopora fl abelliformis famatinensis is here restricted to the holotype. Two new taxa, Rhabdinopora turneri sp. nov. and R. fl abelliformis acenolazai subsp. nov., are respectively reminiscent of R. praeparabola and R. f. parabola, both global elements of the earliest Tremadocian graptolite “Assemblage 1”. However the record of the new Famatinian forms, besides different average morphology and measurements, is rather younger and clearly postdate the appearance of rhabdosomes with triradiate development, being distributed in the A. matanensis and R. f. anglica zones. Together with the planktic graptolites, some transported remains of rooted (benthic) dendroids are recorded from some levels and described as Dendrograptus sp., Dictyonema sp. nov. 1, Aspidograptus cuerdai sp. nov., ?Pseudocallograptus sp. and ?Airograptus guillermoi sp. nov.. The fi rst occurrence of a remarkable benthic graptolite (?Dictyonema sp. cf. D. cordillerensis) in the Tremadocian Bordo Atravesado Formation is also reported

Comparación de metodologías de valor en riesgo para portafolios con derivados de cobertura de monedas

El propósito de este trabajo de grado de la Maestría en Administración Financiera de la Universidad EAFIT es calcular el valor en riesgo de portafolios compuestos por diferentes clases de activos con variaciones en los porcentajes de cobertura con el fin de dar recomendaciones aproximadas a los diferentes agentes de mercado, en especial a las Administradoras de Fondos de Pensiones, de la metodología que mejor se ajuste a las condiciones del mercado actual teniendo en cuenta las ventajas y desventajas evidenciadas en cada una de ella

Imagen social del bibliotecario : Indagación de la imagen social del bibliotecario que construye el usuario de bibliotecas

This work is based on the investigation of the image that is currently having the / the library / as by library users. Inquire about this in a society where the book is not the mainstay of the information, and new technologies (internet, virtual databases, digital archives, etc.) come increasingly different views is necessary for informational revalue the importance of human contact. In the theoretical literature outlines a path in various authors on the capabilities and roles of the traditional figure of the drive current and librarian. We find that the emphasis is on what should be, and the negative image that is mentioned librarian. In the methodological part is chosen to survey library users "Jean Jeaurés" Luján and Leandro N. Alem of General Rodriguez. We decided to compare two pieces of information to view in contrasting claims users see differences and similarities in the perception of / librarians. Also, we analyze the total vision users scored both libraries

Chain‑End Functional di‑Sorbitan Oleate Monomer Obtained from Renewable Resources as Precursors for Bio‑Based Polyurethanes

Artículo derivado de una tesis de MCMA three-step synthetic route was proposed and tested to obtain a chain-end functional di-sorbitan oleate monomer: First, 1,18-octadec-9-enedioic acid compound was produced by self-metathesis reaction of an oleic acid; then, the 1,18-octadec 9-enoyl dichloride compound was yielded by chlorination of the di-acid with thionyl chloride, and fnally, the 1,18-di-sorbitan oleate monomer was yielded by esterifcation of the dichloride with 1,4-sorbitan. The di-sorbitan oleate monomer was purifed and then characterized by FTIR, 1 H-NMR, DSC and TGA to establish its structure and properties. A bio-based polyurethane (PU) was synthesized by reacting the obtained 1,18-di-sorbitan oleate monomer and MDI. Rheological analysis showed that a curing reaction occurs as a signifcant increase of the storage modulus (G’) and the complex viscosity (η*) at 100 °C. The obtained bio-based PU was characterized by FTIR, TGA and DMA, confrming that 1,18-di-sorbitan oleate is a feasible monomer for synthesizing polyurethanes.Conacyt CB-2015–01-257591