Curves in the Lorentz-Minkowski plane with curvature depending on their position

Motivated by the classical Euler elastic curves, David A. Singer posed in 1999 the problem of determining a plane curve whose curvature is given in terms of its position. We propound the same question in the Lorentz-Minkowski plane, focusing on spacelike and timelike curves. In this article, we study those curves in 2 whose curvature depends on the Lorentzian pseudodistance from the origin, and those ones whose curvature depends on the Lorentzian pseudodistance through the horizontal or vertical geodesic to a fixed lightlike geodesic. Making use of the notions of geometric angular momentum (with respect to the origin) and geometric linear momentum (with respect to the fixed lightlike geodesic), respectively, we get two abstract integrability results to determine such curves through quadratures. In this way, we find out several new families of Lorentzian spiral, special elastic and grim-reaper curves whose intrinsic equations are expressed in terms of elementary functions. In addition, we provide uniqueness results for the generatrix curve of the Enneper surface of second kind and for Lorentzian versions of some well-known curves in the Euclidean setting, like the Bernoulli lemniscate, the cardioid, the sinusoidal spirals and some nondegenerate conics. We are able to get arc-length parametrizations of them and they are depicted graphically.European Union (EU) Spanish Government MTM2017-89677-PMECD FPU16/0309

More time is better : an evaluation of the fulltime school program in Uruguay

This paper estimates the impact of the full-time school program in Uruguay on standardized test scores of 6th grade students. The program lengthened the school day from a half day to a full day, and provided additional inputs to schools to make this possible, such as additional teachers and construction of classrooms. The program was not randomly placed, but targeted poor urban schools. Using propensity score matching, the authors construct a comparable group of schools, and show that students in very disadvantaged schools improved in their test scores by 0.07 of a standard deviation per year of participation in the full-time program in mathematics, and 0.04 in language. While the program is expensive, it may, if well targeted, help address inequalities in education in Uruguay, at an increase in cost per student not larger than the current deficit in spending between Uruguay and the rest of the region.Tertiary Education,Education For All,Teaching and Learning,Primary Education,Secondary Education

Despues de 1605. La ventura bibliográfica de una leyenda editorial: La primera salida de El ingenioso hidalgo don Quijote de la Mancha (Madrid, Juan de la Cuesta, 1605) (II: 1871-1946)

Todo trabajo que continúa uno anterior, necesita una justificación previa. Eso sí, breve. Llevo –llevamos el Grupo de Investigación prinQeps 1605– un par de años intentado desentrañar las peripecias editoriales de la primera parte de El ingenioso hidalgo don Quijote de la Mancha de Miguel de Cervantes Saavedra, impresa en Madrid, por Juan de la Cuesta en 1605

Historia mínima (y desde luego incompleta) de los impresos de una sola hoja. I. Los primeros tiempos de la imprenta.

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Modeling circulation patterns induced by spatial cross-shore wind variability in a small-size coastal embayment

This contribution shows the importance of the cross-shore spatial wind variability in the water circulation in a small-sized micro-tidal bay. The hydrodynamic wind response at Alfacs Bay (Ebro River delta, NW Mediterranean Sea) is investigated with a numerical model (ROMS) supported by in situ observations. The wind variability observed in meteorological measurements is characterized with meteorological model (WRF) outputs. From the hydrodynamic simulations of the bay, the water circulation response is affected by the cross-shore wind variability, leading to water current structures not observed in the homogeneous-wind case. If the wind heterogeneity response is considered, the water exchange in the longitudinal direction increases significantly, reducing the water exchange time by around 20%. Wind resolutions half the size of the bay (in our case around 9 km) inhibit cross-shore wind variability, which significantly affects the resultant circulation pattern. The characteristic response is also investigated using idealized test cases. These results show how the wind curl contributes to the hydrodynamic response in shallow areas and promotes the exchange between the bay and the open sea. Negative wind curl is related to the formation of an anti-cyclonic gyre at the bay's mouth. Our results highlight the importance of considering appropriate wind resolution even in small-scale domains (such as bays or harbors) to characterize the hydrodynamics, with relevant implications in the water exchange time and the consequent water quality and ecological parameters.Peer ReviewedPostprint (author's final draft

La educación impresa

Se trata en este artículo de un acercamiento a los testimonios impresos de las obras destinadas al aprendizaje lector y a la de los distintos grados de la formación elemental. Se analizan los elementos constitutivos de los diferentes modelos editoriales de los siglos XVI y XVII: Cartillas, Doctrinas, Gramáticas, Tratados, etc. y se elabora una tipología de sus extensiones y sus contenidos, en relación con los estamentos y niveles de aplicación de los textos