2,763 research outputs found

    The political hourglass: opportunistic behavior in local government policy decisions

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    The aim of this article is to determine whether there is opportunistic behavior in local government decisions related to contracting out, public-private partnership (PPP) and/or public externalization. Analysis of the results obtained from applying a fixed effects panel data model to a sample of 2,274 Spanish municipalities supports the existence of asymmetric opportunistic behavior. Specifically, there is strong evidence that in preelection years, there is less likelihood of contracting out and PPP decisions being approved, and a greater probability of public externalization taking place. In post-election years, an increase in capital spending is associated with a lower probability of contracting out and of PPP. An increase in current spending in preelection years reduces the probability of decisions being taken on contracting out and PPP. These empirical results highlight the extent of opportunistic behavior in selecting management forms for the delivery of local government services

    Elevated CO<sub>2</sub> alleviates high PAR and UV stress in the unicellular Chlorophyte Dunaliella tertiolecta

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    The effects of increased CO2 and irradiance on the physiological performance of the chlorophyte Dunaliella tertiolecta were studied at different PAR and UVR (UVA+UVB) irradiances, simulating the solar radiation at different depths, under present (390 ppmv, LC) and predicted CO2 levels (1000 ppmv, HC). Cell stress after UVR-exposure was mostly attenuated under HC levels, as evidenced by a decrease in reactive oxygen species accumulation. DNA damage showed a 42-fold increase in cyclobutane-pyrimidine dimers formation under the highest irradiance in LC with respect to the lowest irradiance. Photolyase gene expression was upregulated under HC resulting in a drastic decrease in CPDs accumulation to only 25% with respect to LC. However, the expression of genes related to the replacement of photosynthetic apparatus proteins (PsbA and LHCII) were downregulated at HC compared to LC. Proliferating cell nuclear antigen (PCNA) accumulation was always higher in HC and the accumulation pattern indicated its involvement in DNA repair or growth depending on the irradiance doses. Our results suggest that marine unicellular chlorophytes might possibly become more resilient to UVR exposure under future CO2 regimes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Observational evidence for the accretion-disk origin for a radio jet in an active galaxy

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    Accretion of gas onto black holes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy(1-3). In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the Xray fluxes(1). This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk(4) as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot(5). No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62888/1/nature00772.pd

    Operational forecasting of daily summer maximum and minimum temperatures in the Valencia Region

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    Extreme-temperature events have a great impact on human society. Thus, knowledge of summer temperatures can be very useful both for the general public and for organizations whose workers operate in the open. An accurate forecasting of summer maximum and minimum temperatures could help to predict heatwave conditions and permit the implementation of strategies aimed at minimizing the negative effects that high temperatures have on human health. The objective of this work is to evaluate the skill of the regional atmospheric and modelling system (RAMS) model in determining daily summer maximum and minimum temperatures in the Valencia Region. For this, we have used the real-time configuration of this model currently running at the Centro de Estudios Ambientales de Mediterráneo Foundation. This operational system is run twice a day, and both runs have a 3-day forecast range. To carry out the verification of the model in this work, the information generated by the system has been broken into individual simulation days for a specific daily run of the model. Moreover, we have analysed the summer forecast period from 1 June to 31 August for 2007, 2008, 2009 and 2010. The results indicate good agreement between observed and simulated maximum temperatures, with RMSE in general near 2 °C both for coastal and inland stations. For this parameter, the model shows a negative bias around −1.5 °C in the coast, while the opposite trend is observed inland. In addition, RAMS also shows good results in forecasting minimum temperatures for coastal locations, with bias lower than 1 °C and RMSE below 2 °C. However, the model presents some difficulties for this parameter inland, where bias higher than 3 °C and RMSE of about 4 °C have been found. Besides, there is little difference in both temperatures forecasted within the two daily RAMS cycles and that RAMS is very stable in maintaining the forecast performance at least for three forecast days

    Asymptotics for models of non-stationary diffusion in domains with a surface distribution of obstacles

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    We consider a time-dependent model for the diffusion of a substance through an incompressible fluid in a perforated domain ??, urn:x-wiley:mma:media:mma5323:mma5323-math-0001 with n?=?3,4. The fluid flows in a domain containing a periodical set of ?obstacles? (?\??) placed along an inner (n???1)?dimensional manifold urn:x-wiley:mma:media:mma5323:mma5323-math-0002. The size of the obstacles is much smaller than the size of the characteristic period ?. An advection term appears in the partial differential equation linking the fluid velocity with the concentration, while we assume a nonlinear adsorption law on the boundary of the obstacles. This law involves a monotone nonlinear function ? of the concentration and a large adsorption parameter. The ?critical adsorption parameter? depends on the size of the obstacles , and, for different sizes, we derive the time?dependent homogenized models. These models contain a ?strange term? in the transmission conditions on ?, which is a nonlinear function and inherits the properties of ?. The case in which the fluid velocity and the concentration do not interact is also considered for n???3.The authors would like to thank the anonymous referees for their careful reading of the manupscript and useful comments. The work has been partially supported by MINECO, MTM2013-44883-P

    Characteristic Evolution and Matching

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    I review the development of numerical evolution codes for general relativity based upon the characteristic initial value problem. Progress in characteristic evolution is traced from the early stage of 1D feasibility studies to 2D axisymmetric codes that accurately simulate the oscillations and gravitational collapse of relativistic stars and to current 3D codes that provide pieces of a binary black hole spacetime. Cauchy codes have now been successful at simulating all aspects of the binary black hole problem inside an artificially constructed outer boundary. A prime application of characteristic evolution is to extend such simulations to null infinity where the waveform from the binary inspiral and merger can be unambiguously computed. This has now been accomplished by Cauchy-characteristic extraction, where data for the characteristic evolution is supplied by Cauchy data on an extraction worldtube inside the artificial outer boundary. The ultimate application of characteristic evolution is to eliminate the role of this outer boundary by constructing a global solution via Cauchy-characteristic matching. Progress in this direction is discussed.Comment: New version to appear in Living Reviews 2012. arXiv admin note: updated version of arXiv:gr-qc/050809

    Meta-analysis shows no consistent evidence for senescence in ejaculate traits across animals

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    Male reproductive traits such as ejaculate size and quality, are expected to decline with advancing age due to senescence. It is however unclear whether this expectation is upheld across taxa. We perform a meta-analysis on 379 studies, to quantify the effects of advancing male age on ejaculate traits across 157 species of non-human animals. Contrary to predictions, we find no consistent pattern of age-dependent changes in ejaculate traits. This result partly reflects methodological limitations, such as studies sampling a low proportion of adult lifespan, or the inability of meta-analytical approaches to document non-linear ageing trajectories of ejaculate traits; which could potentially lead to an underestimation of senescence. Yet, we find taxon-specific differences in patterns of ejaculate senescence. For instance, older males produce less motile and slower sperm in ray-finned fishes, but larger ejaculates in insects, compared to younger males. Notably, lab rodents show senescence in most ejaculate traits measured. Our study challenges the notion of universal reproductive senescence, highlighting the need for controlled methodologies and a more nuanced understanding of reproductive senescence, cognisant of taxon-specific biology, experimental design, selection pressures, and life-history

    Contribution of Collaborative Work to Teacher Reflection and the Transformation of Pedagogical Practices of School and University Science Teachers // Contribución del trabajo colaborativo en la reflexión docente y en la transformación de las prácticas pedagógicas de profesores de ciencia escolares y universitarios

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    Poor results of science learning, both at school and university, have led us to acknowledge the need to transform our teaching. Currently, reflection and collaborative work with colleagues are conceived as being key factors in the process of the transformation of practices. Based on the experiences of a group of school and university science teachers working on action-research, we describe the contribution that collaborative work has on reflection for the transformation of practices. The main aspects are the recognition of strengths and weaknesses, listening to and learning from the experience of others, and the discussion of specific classroom practices. On the other hand, these reflections contribute to the transformation at different levels: the teacher, classroom teaching practices, and the school community. The fact that it is a diverse group that includes both school and university teachers generate enriching reflections that help to transform practices in both areas. These reflections not only benefit the school system, but also science teachers education, and provide insights on a new University-School relationship // Los deficientes resultados de aprendizaje en el área de las ciencias, tanto en el ámbito escolar como universitario, nos han llevado a la necesidad de transformar nuestra enseñanza. En la actualidad, la reflexión y el trabajo colaborativo con colegas se conciben como claves en el proceso de transformación de las prácticas. A partir de la experiencia de un grupo de docentes escolares y universitarios de ciencia que realiza una investigación-acción, describimos la contribución que tiene el trabajo colaborativo sobre la reflexión para la transformación de las prácticas. Destacan aspectos como el reconocimiento de debilidades y fortalezas, el escuchar y aprender de la experiencia de otros y la discusión de prácticas concretas de aula. Por otra parte, estas reflexiones contribuyen a la transformación en diferentes niveles: del profesor, de las prácticas del docente en el aula y de la comunidad escolar. El hecho de que sea un grupo diverso, que incluye a profesores tanto del sistema escolar como universitario, genera reflexiones enriquecedoras, que ayudan a transformar las prácticas en estos dos ámbitos, beneficiando no solo al sistema escolar, sino también a la formación de profesores de ciencia, y dando luces acerca de una nueva relación universidad-escuela

    Principios de Desarrollo Profesional Docente construidos por y para Profesores de Ciencia: una propuesta sustentable que emerge desde la indagación de las propias prácticas / Principles of Teacher Professional Development built by and for Science Teachers: a sustainable proposal that emerges from the inquiry of self-practices

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    La transformación de las prácticas de los docentes en el área de ciencias, tanto a nivel escolar como universitario (incluida la formación inicial), constituye una necesidad urgente si pretendemos alfabetizar científicamente a la población. Este estudio muestra una propuesta de cinco principios para el desarrollo profesional docente en ciencias, que emergen desde la indagación colaborativa de las propias prácticas de un conjunto de docentes de educación primaria, secundaria y universitaria, quienes trabajan hace cuatro años en un proceso de desarrollo profesional conjunto. Estos principios incluyen la construcción de una visión común acerca del para qué enseñar ciencias, la indagación de las prácticas a partir de las particularidades de la educación científica, la reflexión individual y colectiva sobre las prácticas, la valoración de la autoridad de la experiencia para el aprendizaje docente y la promoción de un ambiente de desarrollo profesional que involucre diversidad de contextos y niveles de enseñanza. // The transformation of teaching practices in the area of sciences, both at school and university levels (including initial training), is an urgent need if we intend to achieve scientific literacy in the population. This study shows a proposal of five principles for teacher professional development in sciences, emerged from the collaborative inquiry of self-practices in a group of primary, secondary and university teachers, who have been working together for four years in a professional development process. These principles include the construction of a common vision on the purpose for teaching sciences; the inquiry of practices starting from the distinctive features of scientific education; individual and collective reflection on practices; the valuation of the authority of experience for teacher learning; and the promotion of an environment of professional development involving diverse contexts and teaching levels. Implications for professional development are discussed
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