Black hole shadow of a rotating polytropic black hole by the Newman--Janis algorithm without complexification

In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman--Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.Comment: 9 pages, 2 figures, some references adde

Optical Absorptivity versus Molecular Composition of Model Organic Aerosol Matter

Aerosol particles affect the Earth’s energy balance by absorbing and scattering radiation according to their chemical composition, size, and shape. It is generally believed that their optical properties could be deduced from the molecular composition of the complex organic matter contained in these particles, a goal pursued by many groups via high-resolution mass spectrometry, although: (1) absorptivity is associated with structural chromophores rather than with molecular formulas, (2) compositional space is a small projection of structural space, and (3) mixtures of polar polyfunctional species usually exhibit supramolecular interactions. Here we report a suite of experiments showing that the photolysis of aqueous pyruvic acid (a proxy for aerosol α-dicarbonyls absorbing at λ > 300 nm) generates mixtures of identifiable aliphatic polyfunctional oligomers that develop absorptions in the visible upon standing in the dark. These absorptions and their induced fluorescence emissions can be repeatedly bleached and retrieved without carbon loss or ostensible changes in the electrospray mass spectra of the corresponding mixtures and display unambiguous signatures of supramolecular effects. The nonlinear additivity of the properties of the components of these mixtures supports the notion that full structural speciation is insufficient and possibly unnecessary for understanding the optical properties of aerosol particles and their responses to changing ambient conditions

Thermochromism of Model Organic Aerosol Matter

Laboratory experiments show that the optical absorptivity of model organic matter is not an intrinsic property, but a strong function of relative humidity, temperature, and insolation. Suites of representative polyfunctional C_(x)H_(y)O_(z) oligomers in water develop intense visible absorptions upon addition of inert electrolytes. The resulting mixtures reach mass absorption cross sections σ(532 nm) ~ 0.1 m^(2)/gC in a few hours, absorb up to 9 times more solar radiation than the starting material, can be half-bleached by noon sunlight in ~ 1 h, and can be repeatedly recycled without carbon loss. Visible absorptions red-shift and evolve increasingly faster in subsequent thermal aging cycles. Thermochromism and its strong direct dependences on ionic strength and temperature are ascribed to the dehydration of >CH−C(OH)C═C< unsaturations by a polar E1 mechanism, and bleaching to photoinduced retrohydration. These transformations are deemed to underlie the daily cycles of aerosol absorption observed in the field, and may introduce a key feedback in the earth’s radiative balance

Expression of X chromosome fragility in Holstein-Friesian cattle: a preliminary study

International audienc

Efficient Markov perfect Nash equilibria: theory and application to dynamic fishery games

In this paper, we present a method for the characterization of Markov perfect Nash equilibria being Pareto efficient in non-linear differential games. For that purpose, we use a new method for computing Nash equilibria with Markov strategies by means of a system of quasilinear partial differential equations. We apply the necessary and sufficient conditions derived to characterize efficient Markov perfect Nash equilibria to dynamic fishery games.We are grateful to the editor Kenneth L. Judd and an anonymous referee for helpful comments. The research of the first author was supported by MCYT under project BEC2002-02361 and JCYL under project VA51/03, cofinanced by FEDER funds. The research of the second author was supported by MCYT under project BFM2002–00425 and JCYL under project VA099/04 cofinanced by FEDER funds.Publicad

El juego y el aprendizaje cooperativo en la enseñanza de las ecuaciones de primer grado

Este estudio se enfoca en identificar algunas ventajas del juego como actividad de aprendizaje. En particular, las actividades lúdicas que se llevaron al aula, la Balanza y el Memorama, se implementaron aplicando la estrategia de aprendizaje cooperativo. Esto con la finalidad de abordar el estudio de la solución de ecuaciones lineales desde una perspectiva dinámica, interactiva y divertida. El estudio se llevó a cabo en una telesecundaria ubicada en una comunidad semirural y con un nivel socioeconómico bajo. Las condiciones sociales, culturales, y económicas de la comunidad hacen que el impacto positivo de los juegos lúdicos en el salón de clase de la telesecundaria se manifieste de manera clara y contundente. Con la implementación de los juegos se logró el objetivo didáctico: la resolución de ecuaciones de primer grado. Además, se ganó que los alumnos favorecieran la interacción entre iguales, la aceptación de normas y discusión de ideas, el reconocimiento de los éxitos de los demás y la comprensión de los propios errores

El ABP en la enseñanza de las matemáticas como estrategia didáctica para el desarrollo del pensamiento crítico en el nivel medio básico y modalidad telesecundaria

En 1968 surge en México el modelo de telesecundarias enfocado a la acumulación de conocimientos, actualmente se establece la necesidad de preparar a los estudiantes hacia un aprendizaje autónomo. Ante esta problemática y con el objetivo de conocer en qué medida el ABP permite a los estudiantes formular procedimientos de manera autónoma en torno a las cuestiones matemáticas, la investigación se basó en este modelo y en la técnica didáctica del aprendizaje basado en problemas, en la cual se observó que es el proceso el que facilita el aprendizaje de conceptos y contenidos propios de la asignatura de matemáticas

Direct method comparing efficient and non-efficient payoffs in differential games

The original publication is available at www.springerlink.comIn this note, we present a method that allows us to decide when a Markov-perfect Nash equilibrium is not Pareto optimum, without the explicit knowledge of the respective solutions. For that purpose, we establish a sufficient condition in terms of an algebraic inequality where the gradient of the value functions of the cooperative and noncooperative games as well as the state and control variables are involved.The first author acknowledges financial support from Junta de Castilla y León Project VA 108 01 and Dirección General de Investigación Project BFM2002–00425. The second author acknowledges financial support from JCYL Project VA051 03 and MCYT Project BEC2002-0236, cofinanced by FEDER funds.Publicad