Environmental conditions during early life accelerate the rate of senescence in a short-lived passerine bird

Environmental conditions experienced in early life may shape subsequent phenotypic traits including life history. We investigated how predation risk caused by domestic cats (Felis silvestris catus) and local breeding density affected patterns of reproductive and survival senescence in Barn Swallows (Hirundo rustica) breeding semicolonially in Denmark. We recorded the abundance of cats and the number of breeding pairs at 39 breeding sites during 24 years and related these to age-specific survival rate and reproductive senescence to test predictions of the life history theory of senescence. We found evidence for actuarial senescence for the first time in this species. Survival rate increased until reaching a plateau in midlife and then decreased later. We also found that survival rate was higher for males than females. Local breeding density or predation risk did not affect survival as predicted by theory. Barn Swallows with short lives did not invest more in reproduction in early life, inconsistent with expectations for trade-offs between reproduction and survival as theory suggests. However, we found that the rate of reproductive decline during senescence was steeper for individuals exposed to intense competition, and predation pressure accelerated the rate of reproductive senescence, but only in sites with many breeding pairs. These latter results are in accordance with one of the predictions suggested by the life history theory of aging. These results emphasize the importance of considering intraspecific competition and interspecific interactions such as predation when analyzing reproductive and actuarial senescence

Catedral Ciudad-Rodrigo

Tít tomado de la cub.Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Arithmetic behaviour of the sums of three squares

AbstractLet n ≠ 4a(8b + 7) be an integer. We deal with the problem of the solvability of the equation n = x12 + x22 + x32 in integers x1, x2, x3 prime to n. By a theorem of Vila (Arch. Math. 44 (1985), 424–437), the existence of such a solution implies that every central extension of the alternating group An, for n ≡ 3 (mod 8), can be realized as a Galois group over Q

Multilayer Networks

In most natural and engineered systems, a set of entities interact with each other in complicated patterns that can encompass multiple types of relationships, change in time, and include other types of complications. Such systems include multiple subsystems and layers of connectivity, and it is important to take such "multilayer" features into account to try to improve our understanding of complex systems. Consequently, it is necessary to generalize "traditional" network theory by developing (and validating) a framework and associated tools to study multilayer systems in a comprehensive fashion. The origins of such efforts date back several decades and arose in multiple disciplines, and now the study of multilayer networks has become one of the most important directions in network science. In this paper, we discuss the history of multilayer networks (and related concepts) and review the exploding body of work on such networks. To unify the disparate terminology in the large body of recent work, we discuss a general framework for multilayer networks, construct a dictionary of terminology to relate the numerous existing concepts to each other, and provide a thorough discussion that compares, contrasts, and translates between related notions such as multilayer networks, multiplex networks, interdependent networks, networks of networks, and many others. We also survey and discuss existing data sets that can be represented as multilayer networks. We review attempts to generalize single-layer-network diagnostics to multilayer networks. We also discuss the rapidly expanding research on multilayer-network models and notions like community structure, connected components, tensor decompositions, and various types of dynamical processes on multilayer networks. We conclude with a summary and an outlook.Comment: Working paper; 59 pages, 8 figure

Ceruloplasmina y su implicación en la enfermedad cardiovascular

INTRODUCTION: Inflammation and oxidative stress play a key role in the initiation and maintenance of atherosclerosis and are related to the occurrence of events leading to vessel occlusion, both in the venous system (thromboembolic disease) and in the arterial system (cardiovascular disease). Although there are no clear theories on how these occlusive diseases in both arterial and venous territories are linked, they share the increase of certain inflammatory and oxidative-stress markers. Ceruloplasmin (CP) is a protein involved in copper metabolism that has also been linked to inflammatory responses, whereas the association to occlusive vascular diseases has not been fully characterized. HYPOTHESIS: Our hypothesis is that high levels of CP would be associated with the incidence of cardiovascular events. OBJECTIVES: 1) To evaluate whether high levels of plasma CP are associated with increased incidence of atrial fibrillation. 2) To evaluate whether high levels of plasma CP are associated with increased incidence of venous thromboembolism. 3) To perform a systematic review of the current evidence on whether high levels of plasma CP are associated to a higher risk of coronary heart disease. METHODS: a) We conducted a first analysis evaluating the association of CP with AF incidence in a large cohort, the Atherosclerosis Risk in Communities (ARIC) Study. b) We conducted other investigation to test the association between CP and VTE incidence in the same ARIC study population. c) Finally, to evaluate the influence of CP on CHD, we conducted a systematic review exploring the impact of CP on the risk of CHD over the last three decades. RESULTS: Higher plasma CP levels were associated with incident AF in the ARIC cohort. Regarding VTE, higher concentrations of plasma CP were also associated with greater incident VTE rates. Finally, most of 18 eligible studies reviewed supported a direct relationship between CP elevated levels and incidence of CHD. CONCLUSIONS: We have evaluated the association between CP and three highly prevalent diseases derived from alterations in the cardiovascular system, both venous and arterial location, establishing that high CP levels are related to the occurrence of these conditions.INTRODUCCIÓN: La inflamación y el estrés oxidativo desempeñan un papel fundamental en el inicio y desarrollo del proceso aterosclerótico y están relacionados con la aparición de eventos que conducen a la oclusión de los vasos, tanto en el sistema venoso (enfermedad tromboembólica) como en el arterial (enfermedad cardiovascular). Aunque no hay teorías claras sobre cómo se relacionan estas enfermedades oclusivas en los territorios arteriales y venosos, comparten la elevación de ciertos marcadores inflamatorios y de estrés oxidativo. La ceruloplasmina (CP) es una proteína que actúa en el metabolismo del cobre que se ha relacionado con la respuesta inflamatoria, la cual no se relacionado hasta el momento con las enfermedades vasculares oclusivas. HIPÓTESIS: Nuestra hipótesis es que altos niveles de CP estarían implicados en la aparición de nuevos eventos cardiovasculares. OBJETIVOS: 1) Evaluar si niveles elevados de CP en plasma se asocian a una mayor incidencia de fibrilación auricular. 2) Evaluar si niveles elevados de CP en plasma se asocian a una mayor incidencia de tromboembolismo venoso. 3) Realizar una revisión sistemática de la evidencia actual sobre si niveles elevados de CP en plasma se asocian a un mayor riesgo de enfermedad coronaria. MÉTODOS: a) En un primer análisis, evaluamos la asociación de la CP con la incidencia de FA en el estudio ARIC (Atherosclerosis Risk in Communities), una cohorte comunitaria. b) Realizamos otro trabajo de investigación para comprobar la asociación de CP e incidencia de ETV en la misma población. c) Por último, para evaluar la influencia de la CP en la cardiopatía isquémica, realizamos una revisión sistemática en la que exploramos el impacto de la CP en el riesgo de cardiopatía isquémica en las tres últimas décadas. RESULTADOS: Niveles más altos de CP circulante se asociaron con mayor incidencia de FA en la cohorte ARIC. En relación con la ETV, las mayores concentraciones de CP circulante también se asociaron con mayores tasas de ETV. Por último, la mayoría de los 18 estudios revisados apoyaron una relación directa entre niveles elevados de CP y la incidencia de cardiopatía isquémica. CONCLUSIONES: Tras evaluar la asociación entre la CP y tres enfermedades altamente prevalentes derivadas de alteraciones del sistema cardiovascular, tanto de localización venosa como arterial, podemos concluir que niveles elevados de CP están relacionados con la aparición de estas enfermedades