The evolution of cooperation in an arid-zone bird: bet-hedging, plasticity and constraints

The evolution of cooperation represents a long-standing puzzle in evolutionary biology. From insects to mammals, this behaviour has evolved multiple times in separate lineages. Even though inclusive fitness theory provides a solid theoretical framework to understand the evolution of cooperation, there are still many research challenges in the evolutionary study of cooperation. First, most of the evidence for the effects of cooperation on the reproductive success of beneficiaries in vertebrate societies is based on correlational studies, which can be confounded by several environmental factors. Second, there are recent theoretical formulations to explain the evolution of cooperation that have not been empirically tested yet but could shed new light on the selective pressures that facilitate the evolution of cooperation. Third, we still have a poor understanding of the sources of among individual variation in cooperative behaviours. In particular, few studies have investigated whether the level of cooperation expressed by individuals is heritable and, therefore, could respond to natural selection. In this thesis, I combine nine years of life-history and behavioural information with field experiments and genomics to investigate (i) the routes for non-breeding individuals to acquire indirect fitness benefits and (ii) the sources of among-individual variation in cooperation in white-browed sparrow-weavers (Plocepasser mahali), an arid-zone cooperative breeder. After a general introduction to the subject of cooperative breeding, in Chapter 2 I test a novel hypothesis for the evolution of cooperation, the ‘altruistic bet-hedging’ hypothesis. There, I show that non-breeding helpers reduce variation in the reproductive success of breeders without affecting their arithmetic mean reproductive success. Furthermore, I show that this reproductive variance compression appears to arise because helpers specifically reduce unpredictable rainfall-induced variation in reproductive success, just as hypothesised by global comparative studies of the evolution of cooperative breeding in birds. Then, I investigate alternative routes through which helpers may gain indirect fitness benefits. Specifically, in Chapter 3 I investigate the effects of helpers on pre- and post-natal maternal investment in reproduction. The findings in Chapter 3 provide clear evidence for maternal plasticity in pre-natal investment in reproduction (egg volume) in response to the number of helpers. Moreover, the helper effect of increased pre-natal maternal investment is associated with a decrease in post-natal maternal investment. In Chapter 4, I test the philopatry hypothesis for the evolution of sex differences in cooperation within animal societies and find strong support for this hypothesis in white-browed sparrow-weavers. Furthermore, Chapter 4 highlights the need to consider both sex differences in direct fitness benefits and costs when trying to understand sex differences in cooperation. Finally, in Chapter 5 I investigate among-helper variation in cooperative generosity, finding consistent individual differences and providing evidence for heritable variation in this trait. To conclude, in Chapter 6 I discuss the implications of these results for our general understanding of the evolution of cooperation in animal societies and highlight methodological approaches for future empirical studies of cooperation in the wild.Centre for Environment, Fisheries and Aquaculture Scienc

Bacterial ageing in the absence of external stressors

This is the final version. Available from the Royal Society via the DOI in this record.Evidence of ageing in the bacterium Escherichia coli was a landmark finding in senescence research, as it suggested that even organisms with morphologically symmetrical fission may have evolved strategies to permit damage accumulation. However, recent work has suggested that ageing is only detectable in this organism in the presence of extrinsic stressors, such as the fluorescent proteins and strong light sources typically used to excite them. Here we combine microfluidics with brightfield microscopy to provide evidence of ageing in E. coli in the absence of these stressors. We report (i) that the doubling time of the lineage of cells that consistently inherits the 'maternal old pole' progressively increases with successive rounds of cell division until it reaches an apparent asymptote, and (ii) that the parental cell divides asymmetrically, with the old pole daughter showing a longer doubling time and slower glucose accumulation than the new pole daughter. Notably, these patterns arise without the progressive accumulation or asymmetric partitioning of observable misfolded-protein aggregates, phenomena previously hypothesized to cause the ageing phenotype. Our findings suggest that ageing is part of the naturally occurring ecologically-relevant phenotype of this bacterium and highlight the importance of alternative mechanisms of damage accumulation in this context.Medical Research CouncilEPSRCBBSRCRoyal SocietyWellcome Trus

No-core shell model for 48-Ca, 48-Sc and 48-Ti

We report the first no-core shell model results for $^{48}Ca$, $^{48}Sc$ and $^{48}Ti$ with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited $\hbar\Omega$ range around $45/A^{1/3}-25/A^{2/3} = 10.5 MeV$ and a limited model space up to $1\hbar\Omega$. No single-particle energies are used. We find that the charge dependence of the bulk binding energy of eight A=48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, the resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. We then introduce additive isospin-dependent central terms plus a tensor force to our Hamiltonian and achieve accurate binding energies and reasonable spectra for all three nuclei. The resulting no-core shell model opens a path for applications to the double-beta ($\beta\beta$) decay process.Comment: Revised content and added reference

Steady-State Visual Evoked Potentials Can Be Explained by Temporal Superposition of Transient Event-Related Responses

<p><b>Background:</b> One common criterion for classifying electrophysiological brain responses is based on the distinction between transient (i.e. event-related potentials, ERPs) and steady-state responses (SSRs). The generation of SSRs is usually attributed to the entrainment of a neural rhythm driven by the stimulus train. However, a more parsimonious account suggests that SSRs might result from the linear addition of the transient responses elicited by each stimulus. This study aimed to investigate this possibility.</p> <p><b>Methodology/Principal Findings::</b> We recorded brain potentials elicited by a checkerboard stimulus reversing at different rates. We modeled SSRs by sequentially shifting and linearly adding rate-specific ERPs. Our results show a strong resemblance between recorded and synthetic SSRs, supporting the superposition hypothesis. Furthermore, we did not find evidence of entrainment of a neural oscillation at the stimulation frequency.</p> <p><b>Conclusions/Significance:</b> This study provides evidence that visual SSRs can be explained as a superposition of transient ERPs. These findings have critical implications in our current understanding of brain oscillations. Contrary to the idea that neural networks can be tuned to a wide range of frequencies, our findings rather suggest that the oscillatory response of a given neural network is constrained within its natural frequency range.</p&gt

Magnetoencephalographic assessment of changes in brain activity in normal aging when performing a task under interference conditions

Determinar si la realización de una tarea de reconocimiento con interferencia activa, producía cambios en los patrones de activación cerebral con respecto a la presentación de otra con interferencia pasiva. Población y metodología: en veinte ancianos sanos se midió con magnetoencefalografía. Se realizó a cada uno de ellos la escala de Memoria de Wechsler-III (WMS-III), la escala de Inteligencia de Wechsler, el Boston Naming Test, el test de fluidez verbal, el test de clasificación de tarjetas de Wisconsin, el trail Making Test y el test de colores y palabras (STROOP). Los registros se llevaron a cabo mediante un magnetoencefalógrafo de 148 canales capaz de medir la actividad magnética generada en toda la convexidad craneal. Resultados: encontramos una mayor activación en la condición de interferencia activa en las regiones mediales temporales, corteza visual, y región ventral anterior durante los primeros 400 milisegundos en el hemisferio izquierdo y únicamente en el derecho para la corteza visual, mientras que en la condición de interferencia pasiva, se obtuvo una mayor activación en la región ventral anterior durante los 700-800 milisegundos en el hemisferio izquierdo. Conclusión: la presentación de estos dos tipos de interferencia, activa y pasiva, modula los patrones de activación fronto-temporales en el envejecimiento normalTo determine whether performing a recognition task under interference conditions produces changes in brain activity pattern compared with the activity seen under conditions of passive interference. Population and methods: Twenty healthy elderly subjects were subjected to magnetoencephalography. In each patient we applied the Wechsler Memory Scale-III (WMS-III), the Wechsler Intelligence Scale, the Boston Naming Test, the verbal fluency test, the Wisconsin card classification test, the Trail Making Test and the colors and words test (STROOP). The recordings were made using a 148-channel magnetoencephalograph capable of measuring the magnetic activity generated within the entire cranial convexity. Results: Greater activation was recorded under active interference conditions in the medial temporal regions, visual cortex and anterior ventral area in the first 400 ms in the left hemisphere and only in the right hemisphere for the visual cortex, while under passive interference conditions, increased activation was obtained in the anterior ventral region during the 700-800 ms in the left hemisphere. Conclusion: The presentation of both types of interference, active and passive, modulates the fronto-temporal activation patterns in normal agin

Changes in brain activity in normal aging in an interference task tested by magnetoencephalography

La presentación de estímulos que interfieren en el mantenimiento de una información previa dificulta el reconocimiento posterior de ésta. La resistencia a la interferencia disminuye en el envejecimiento normal, aspecto que se traduce en una peor ejecución de tareas que comprometen a la memoria operativa y que podría estar relacionado con una disfunción ejecutiva. Nuestro objetivo consistió en comprobar si la realización de una tarea de reconocimiento con interferencia activa, producía cambios en los patrones de activación cerebral con respecto a la presentación de otra con interferencia pasiva, en una muestra de veinte ancianos sanos y medido con magnetoencefalografía. Los resultados mostraron la presencia de una mayor activación en la condición de interferencia activa en las regiones mediales temporales, corteza visual, y región ventral anterior durante los primeros 400 milisegundos en el hemisferio izquierdo y únicamente en el derecho para la corteza visual, mientras que en la condición de interferencia pasiva, se obtuvo una mayor activación en la región ventral anterior durante los 700-800 milisegundos en el hemisferio izquierdo. Todo ello sugiere que la presentación de estos dos tipos de interferencia, activa y pasiva, modula los patrones de activación fronto-temporales en el envejecimiento normalThe presentation of stimuli interfering with the maintenance of previous information makes difficult the subsequent recognition of it. The interference resistance decreases in normal aging, which is evidenced as a worse performance in tasks affecting working memory and that could be related to an executive dysfunction. Our aim was to establish if performing a recognition task under active interference conditions caused changes in brain activation patterns from the performance of another task under passive interference conditions in a sample of 20 healthy elderly patients, measured with magnetoencephalography. The results evidenced the presence of a greater activation under active interference conditions in the medial temporal regions, visual cortex and anterior ventral area in the first 400 milliseconds in the left hemisphere and only in the right hemisphere for the visual cortex, while under passive interference conditions, a greater activation was obtained in the anterior ventral region during the 700-800 milliseconds in the left hemisphere. All of this suggests that the presentation of both types of interference, active and passive, modulates the fronto-temporal activation patterns in normal agin

Pvlearning: herramienta web para la enseñanza de la energía solar fotovoltaica

En este trabajo, se describe la web www.pvlearning.com, desarrollada en la Universidad de Alcalá para la enseñanza de la energía solar fotovoltaica. PVLEARNING asiste al alumno en la realización de tareas como la evaluación de la radiación solar disponible, la selección de los componentes del sistema, la configuración de éstos y la estimación del rendimiento global y la energía total producida. Frente a otros programas de simulación, la plataforma presenta la novedad de estar enfocada al aprendizaje de la ingeniería de proyectos, sin por ello perder todo el rigor y la funcionalidad necesarios en este tipo de simuladores.This work describes the web www.pvlearning.com, which has been developed at the Universidad de Alcalá for photovoltaic solar energy teaching. PVLEARNING assists the student in tasks such as the evaluation of the solar radiation, the selection of the system components, the configuration of the solar generator and the estimation of the performance ratio, the final yield and the total energy production. In contrast to other simulation programs, the platform has the novelty of being focused on the learning of project engineering, without losing the accuracy and functionality which is required in this kind of simulator

On opportunistic software reuse

The availability of open source assets for almost all imaginable domains has led the software industry toopportunistic design-an approach in which people develop new software systems in an ad hoc fashion by reusing and combining components that were not designed to be used together. In this paper we investigate this emerging approach. We demonstrate the approach with an industrial example in whichNode.jsmodules and various subsystems are used in an opportunistic way. Furthermore, to study opportunistic reuse as a phenomenon, we present the results of three contextual interviews and a survey with reuse practitioners to understand to what extent opportunistic reuse offers improvements over traditional systematic reuse approaches.Peer reviewe

Searches for neutrinoless double beta decay

Neutrinoless double beta decay is a lepton number violating process whose observation would also establish that neutrinos are their own anti-particles. There are many experimental efforts with a variety of techniques. Some (EXO, Kamland-Zen, GERDA phase I and CANDLES) started take data in 2011 and EXO has reported the first measurement of the half life for the double beta decay with two neutrinos of $^{136}$Xe. The sensitivities of the different proposals are reviewed.Comment: 8 pages, prepared for TAUP 201

Searches for neutrinoless double beta decay

Neutrinoless double beta decay is a lepton number violating process whose observation would also establish that neutrinos are their own anti-particles. There are many experimental efforts with a variety of techniques. Some (EXO, Kamland-Zen, GERDA phase I and CANDLES) started take data in 2011 and EXO has reported the first measurement of the half life for the double beta decay with two neutrinos of $^{136}$Xe. The sensitivities of the different proposals are reviewed.Comment: 8 pages, prepared for TAUP 201