A note on a one-parameter family of Catalan-like numbers

We study a family of sequences of Catalan-like numbers based on the series reversion process. Properties of these sequences are derived, including continued fraction expansions, associated orthogonal polynomials and associated Aigner matrices, which turn out to be Riordan arrays

Ecological Modelling with the Calculus of Wrapped Compartments

The Calculus of Wrapped Compartments is a framework based on stochastic multiset rewriting in a compartmentalised setting originally developed for the modelling and analysis of biological interactions. In this paper, we propose to use this calculus for the description of ecological systems and we provide the modelling guidelines to encode within the calculus some of the main interactions leading ecosystems evolution. As a case study, we model the distribution of height of Croton wagneri, a shrub constituting the endemic predominant species of the dry ecosystem in southern Ecuador. In particular, we consider the plant at different altitude gradients (i.e. at different temperature conditions), to study how it adapts under the effects of global climate change.Comment: A preliminary version of this paper has been presented in CMC13 (LNCS 7762, pp 358-377, 2013

Sustainable entrepreneurship and the Sustainable Development Goals:Community-led initiatives, the social solidarity economy and commons ecologies

The social solidarity economy is an approach to the production and consumption of goods, services and knowledge that promises to address contemporary economic, social and environmental crises more effectively than business as usual. The paper employs the concept of commons ecologies to examine the practices, relationships and interactions among actors and organisations in the social solidarity economy, as well as between them and the mainstream economy, which shape the field and its degree of autonomy in relation to capitalism, through a process defined as boundary commoning. Such process shapes both local and regional commons ecologies, as well as the participation of local and regional actors in wider networks at national, international and global levels. The paper takes a case study-based approach to identify practices, relationships and interactions of commons ecologies in relation to selected community-led initiatives in the UK, Portugal, Brazil and Senegal. Each case study illuminates different qualities of local/regional commons ecologies and their forms of engagement with wider networks. Further, the paper shows that these cases demonstrate how the social solidarity economy may facilitate delivery of the Sustainable Development Goals in a distinctive way. In each case, SSE acts as a vehicle for expressing participants' values and principles consistent with those underlying the SDGs. Local implementation of SDGs is thus an in-built feature of these commons ecologies. The participation of community-led initiatives in international and global networks offers opportunities to learn from local level experiences and successes, potentially strengthening SDG implementation more generally.</p

Residual-based stabilization of the finite element approximation to the acoustic perturbation equations for low Mach number aeroacoustics

This is the peer reviewed version of the following article: [Guasch, O., Sánchez-Martín, P., Pont, A., Baiges, J., and Codina, R. (2016) Residual-based stabilization of the finite element approximation to the acoustic perturbation equations for low Mach number aeroacoustics. Int. J. Numer. Meth. Fluids, 82: 839–857. doi: 10.1002/fld.4243], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/fld.4243/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The acoustic perturbation equations (APE) are suitable to predict aerodynamic noise in the presence of a non-uniform mean flow. As for any hybrid computational aeroacoustics approach, a first computational fluid dynamics simulation is carried out from which the mean flow characteristics and acoustic sources are obtained. In a second step, the APE are solved to get the acoustic pressure and particle velocity fields. However, resorting to the finite element method (FEM) for that purpose is not straightforward. Whereas mixed finite elements satisfying an appropriate inf–sup compatibility condition can be built in the case of no mean flow, that is, for the standard wave equation in mixed form, these are difficult to implement and their good performance is yet to be checked for more complex wave operators. As a consequence, strong simplifying assumptions are usually considered when solving the APE with FEM. It is possible to avoid them by resorting to stabilized formulations. In this work, a residual-based stabilized FEM is presented for the APE at low Mach numbers, which allows one to deal with the APE convective and reaction terms in its full extent. The key of the approach resides in the design of the matrix of stabilization parameters. The performance of the formulation and the contributions of the different terms in the equations are tested for an acoustic pulse propagating in sheared-solenoidal mean flow, and for the aeolian tone generated by flow past a two-dimensional cylinder.Peer ReviewedPostprint (author's final draft

Population Models: Flexibility, Advances, and Applications to Wildlife Conservation. The Bonelli’s Eagle as a Study Case

[eng] In this thesis, we took advantage of recent advances in the degree of sophistication and flexibility of population models to study the population dynamics and conservation of long-lived species. As main objective, we aimed at understanding the effects of permanent emigration in the estimation of survival from mark-recapture analyses and its multiple implications for the interpretation of population dynamics and the reliability of population viability projections. In second term, we aimed at generating evidence-based knowledge based on quantitative population analysis to guide the management of long-lived raptors. To address these issues, we used two populations of the long-lived Bonelli’s eagle as study cases (Catalonia and Mallorca, western Mediterranean), for which extensive demographic and ecological data were available. The thesis was divided into the four following chapters. In Chapter 1, we implemented individual-based population viability analyses (PVA) to evaluate the effectiveness of different release strategies used in the reintroduction of the Bonelli’s eagle in Mallorca. Our results suggested that relocating wild-reared nonjuvenile raptors from natural populations to reintroduction areas may better favour reintroduction success in comparison to more expensive, widely implemented alternatives based on captive breeding. The better performance of relocations was related to their capacity to promote early reproduction in the reintroduction area, which may enhance population growth. In Chapter 2, we developed a spatially-explicit capture-mark-recapture model adapted to the multistate formulation to separate true survival and permanent emigration in longlived species. In addition, we compared the obtained stage-structured true survival estimates to apparent survival estimates. Our results showed that the magnitude of the differences between true and apparent survival may vary across population stages in longlived species (i.e., age, sex, breeding status) because of intrapopulation variation in the effect of permanent emigration. In addition, our findings suggested that the use of heavytailed distributions to model natal dispersal may provide more effective separations of true survival and permanent emigration in cases of mark-recapture data limited to restricted study areas. In Chapter 3, we integrated the model developed in chapter 2 into a spatially-explicit Integrated Population Model (SEIPM) aimed at insightfully describing the long-term dynamics of the Bonelli’s eagle population in Catalonia (1986-2020) and extracting relevant knowledge for long-lived species demography. The use of SEIPMs enabled an explicit estimation of emigration, immigration, and sink-source status along time, together with key demographic parameters and the dynamics of relevant population stages. Our results allowed a deep understanding of the retrospective dynamics of the study population and revealed new insights about the long-term variations of sink-source status and floater populations in long-lived species. In Chapter 4, we used the estimates of apparent and true survival from chapter 2 to compare the outcomes of PVAs using both types of estimates and their respective fits to census data. In addition, we explicitly modelled emigration and immigration to evaluate how these processes may improve or decrease the fits of PVAs based on each type of survival estimate. Our results suggested that each of both survival types may only provide accurate PVA projections in specific population scenarios where emigration and immigration match the particularities of each type of estimate. Thus, we emphasized the importance of either modelling migration processes or using calibration to real data for accurate PVA outcomes. In conclusion, this thesis provided useful extensions of demographic models for the estimation of true survival and the fine-scale study of population dynamics in long-lived species. In addition, important insights were revealed about the reliability of PVA outcomes relative to the characteristics of survival estimates. Finally, the thesis emphasized the relevance of generating evidence-based knowledge from the analysis of quantitative data for conservation decision-making.[cat] Aquesta tesi utilitza els avenços recents en el grau de sofisticació i la flexibilitat dels models poblacions per a generar coneixement rellevant per a l’estudi de la dinàmica de poblacions i la conservació d’espècies de vida llarga. Com a objectiu principal, la tesi se centra en entendre els efectes de la migració permanent en l’estimació de supervivència en anàlisis de captura-recaptura, així com els efectes que això pot tenir per a la interpretació de la demografia, les estimes de viabilitat, l’estat de conservació i la gestió de les poblacions de vida llarga. En segon pla, la tesi se centra en generar coneixement basat en evidències quantitatives per guiar la gestió d’aus rapinyaires de vida llarga. Per afrontar aquests objectius, hem utilitzat com a casos d’estudi dues poblacions de l’àliga perdiguera (Catalunya i l’illa de Mallorca), de les quals es disposa d’una extensa quantitat de dades de seguiment demogràfic i ecològic. La tesi s’ha dividit en els següents capítols: Al Capítol 1, es van desenvolupar anàlisis de viabilitat poblacional basades en individus (PVA) per avaluar l’efectivitat de les diferents estratègies d’alliberament emprades en la reintroducció de l’àliga perdiguera a Mallorca. Els resultats suggerien que la translocació d’individus no-polls salvatges d’altres poblacions cap a l’àrea de reintroducció afavoria l’èxit de la reintroducció en comparació amb altres metodologies més cares basades en la cria en captivitat. Aquesta major efectivitat estava lligada a la capacitat de les translocacions de no-polls d’accelerar una ràpida reproducció a l’àrea d’estudi, fet que promovia un ràpid creixement poblacional. Al Capítol 2, vam desenvolupar models de captura-recaptura espacialment explícits adaptats a la formulació multi-estat per estimar separadament supervivència real i migració permanent en espècies de vida llarga. Les estimes de supervivència real obtingudes, estructurades per fracció poblacional, van ser comparades amb estimes de supervivència aparent. Les comparacions mostraven que aquestes diferències variaven en intensitat al llarg de les diferents fraccions (edat, sexe, estat reproductor) degut a variacions intrapoblacionals en l’efecte de la migració permanent. Per altra banda, els nostres resultats suggereixen que l’ús de distribucions estadístiques de cua ampla per modelar dispersió natal poden ajudar a separar supervivència real i migració permanent de manera més efectiva quan les dades disponibles sobre captura-recaptura estan restringides a l’àrea d’estudi. Al Capítol 3, vam incorporar el model desenvolupat al capítol 2 dins un model integrat poblacional espacialment explícit (SEIPM) amb l’objectiu de descriure detalladament la dinàmica de la població d’àliga perdiguera a Catalunya durant les darreres quatre dècades (1986-2020), i extreure coneixement general rellevant sobre la demografia de les espècies de vida llarga. L’ús de SEIPMs va permetre una estimació explícita dels processos d’immigració i emigració, així com de l’estat font-embornal de la població al llarg del temps, juntament amb paràmetres demogràfics clau i la dinàmica d’importants fraccions poblacionals. Els resultats van permetre entendre detalladament la dinàmica retrospectiva de la població, i van revelar nous aspectes sobre la demografia de les poblacions flotants i les dinàmiques font embornal a llarg termini. Al Capítol 4, vam emprar les estimes de supervivència aparent i real del capítol 2 per comparar els resultats de PVAs basats en ambdós tipus d’estimes i el respectiu ajust de cada model a dades reals de cens. A més, vam modelar de manera explícita emigració i immigració per avaluar com aquests dos processos poden millorar o empobrir l’ajust dels models basats en els dos tipus d’estima de supervivència. Els resultats mostraven que ambdues supervivències només tenien capacitat de generar estimes precises de viabilitat en escenaris poblacionals específics on els processos d’emigració i immigració tinguessin unes magnituds molt concretes. En conseqüència, vam subratllar la importància de modelitzar processos migratoris dins els PVAs - o bé de calibrar els resultats amb dades reals - per millorar la fiabilitat d’aquests models. En resum, en aquesta tesi s’han desenvolupat extensions de models poblacionals per a l’estimació de supervivència real i l’estudi detallat de les dinàmiques poblacionals en espècies de vida llarga. A més, la tesi ha aportat troballes importants sobre la fiabilitat i la precisió dels PVAs segons les particularitats de les estimes de supervivència emprades. Finalment, s’hi ha destacat la importància de generar coneixement basat en l’evidència científica per a la gestió de poblacions salvatges a través de models poblacionals

Pre-dispersal seed predation by weevils (Curculio spp.): The role of host-specificity, resource availability and environmental factors

[eng] Pre-dispersal seed predation (PDSP, hereafter) significantly reduces plant reproductive output. The negative effects on plant fitness have triggered the development of different strategies to protect the seeds and/or reduce the impact of PDSP. These strategies, in turn, have promoted insect trophic specialization by means of morphological, physiological and behavioral adaptations. The close relationship between specialist insects and their host plants conditions insect community assemblage and population dynamics. Specialization would favour multi-species co-occurrence according to the Competitive Exclusion Principle, as different species cannot use the same limited resources. At the same time, specificity makes these species strongly dependent on a particular trophic resource, so that host plant population dynamics may lead to bottom-up forces influencing insect numbers. In this Thesis, I have studied the consequences of trophic specialization on species assemblage and demography in the most prevalent pre-dispersal predators of oak Quercus spp., chestnuts Castanea sativa and hazelnut Corylus avellana seeds, namely the weevils of the genus Curculio (Coleoptera: Curculionidae). Using DNA barcoding I could identify larvae infesting the seeds to the species level and hence assess resource partitioning among Curculio spp. in oak-hazelnut mixed forests. These forests were distributed along a latitudinal gradient in which the degree of overlap in the timing of seeding between the two species differed. The results showed that there was a strict host-based segregation, as the species found in hazelnuts was never recorded on oak acorns and vice versa. Contrary to other studies, segregation of seed parasites was not driven by seed size, as the seeds of both plants were large enough to host the larvae of any species. Rather, co-existence was more likely modulated by the combination of time partitioning, and probably by dissimilarities in dispersal-dormancy strategies among weevils. The timing of oogenesis differs among Curculio spp. and does the timing of seeding between oaks and hazelnuts. Early maturing hazelnuts are thus exploited only by Curculio nucum, as its eggs mature earlier too. Such specialization on a patchily distributed host plant conditioned its population genetics, as gene-flow between populations showed restrictions undetected in the other Curculio spp. that fed on the widespread oaks. Regarding the bottom-up effects of food availability on insect numbers we assessed that, as expected, irregular seed crops (masting) conditions weevil population dynamics and certainly help reducing acorn predation in Mediterranean oaks. However, we found that the effects of rainfall stochasticity on the success of weevil emergence from the soil (i.e. rain is needed to soften the soil) contributed to decrease seed predation in a similar magnitude to masting. The present Thesis stresses the need of introducing the time/phenology component (i. e. egg maturation, timing of seeding) to assess the mechanisms underlying host plant-specialist insect associations. Also, it shows that, despite their specificity, other environmental variables apart from food availability condition weevil numbers. This result must be considered in further studies on the significance of oak masting as a strategy to reduce pre-dispersal seed predation. Lastly, the results provide an insight into the potential consequences of Global Change on the communities of these specialist insects linked to oaks. The populations of a narrow specialist like the hazelnut feeding C. nucum will be very vulnerable to forest fragmentation, which will reduce more severely inter-population gene-flow and lead to population bottlenecks. In turn, climate change (e.g. temperature rising, rainfall decrease) could disrupt the matching phenologies of insects and their host plants and reduce insect population size.[spa] La depredación de semillas predispersión (PDSP, de aquí en adelante) reduce significativamente el desempeño reproductivo de las plantas. Los efectos negativos han desencadenado el desarrollo de diferentes estrategias para proteger las semillas y/o reducir el impacto de PDSP. Estas estrategias, han promovido la especialización trófica de insectos a través de adaptaciones morfológicas, fisiológicas y de comportamiento. La estrecha relación entre los insectos especialistas y sus plantas hospedantes condiciona el ensamblaje de las comunidades de insectos y la dinámica poblacional. La especialización favorecería la coexistencia de múltiples especies de acuerdo con el Principio de Exclusión Competitiva, ya que estas no pueden usar los mismos recursos limitados. Al mismo tiempo, la especificidad hace que estas especies dependan fuertemente de un recurso trófico particular, de modo que la dinámica poblacional de plantas hospedadoras puede conllevar a que las fuerzas “bottom-up” influyan en el número de insectos. En esta Tesis, he estudiado las consecuencias de la especialización trófica en el ensamblaje de especies y la demografía en los depredadores pre-dispersión más prevalentes de Quercus spp., castañas Castanea sativa y avellanas Corylus avellana, principalmente los gorgojos del género Curculio (Coleoptera: Curculionidae). Usando técnicas de secuenciación de ADN pude identificar las larvas que parasitan las semillas a nivel de especie y, por lo tanto, evaluar la segregación de recursos entre especies de Curculio spp. en bosques mixtos de roble y avellana. Estos bosques se distribuyeron a lo largo de un gradiente latitudinal en el cual el grado de superposición de su distribución espacial difería entre las dos especies hospederas. Los resultados mostraron que hubo una estricta segregación basada en el hospedador, ya que la especie encontrada en avellanas nunca se registró en bellotas de roble y viceversa. Contrariamente a otros estudios, la segregación de los parásitos de las semillas no se debió al tamaño de la semilla, ya que las semillas de ambas plantas eran lo suficientemente grandes como para albergar las larvas de cualquier especie. Por el contrario, la coexistencia fue modulado con mayor probabilidad por la combinación de la partición de tiempo, y las diferencias en las estrategias de latencia y dispersión entre los gorgojos. El periodo de oogénesis de Curculio spp difiere con el periodo producción de semillas en robles y avellanas. Las avellanas de maduración temprana son explotadas solo por Curculio nucum, ya que sus huevos también maduran antes. Dicha especialización en una planta hospedera distribuida en forma dispersa condicionó su genética poblacional, ya que el flujo genético entre poblaciones mostró restricciones no detectadas en las otras especies de Curculio spp. que se alimentaban de los robles con distribución continua. Con respecto a los efectos “bottom-up” de la disponibilidad de alimentos sobre el número de insectos, evaluamos que, como era de esperar, la producción irregular de semillas (masting) condicionan la dinámica poblacional de los gorgojos y ciertamente contribuyen a reducir la depredación de las bellotas en los robles del Mediterráneo. Sin embargo, encontramos que los efectos de la estocasticidad de las lluvias sobre el éxito de la emergencia del gorgojo desde el suelo (la lluvia es necesaria para ablandar el suelo) contribuyeron a disminuir la depredación de semillas en una magnitud similar a la del masting. La presente Tesis enfatiza la necesidad de introducir el componente tiempo/fenología (es decir, la maduración del óvulo, el momento producción de semillas) para evaluar los mecanismos que subyacen a las asociaciones de insectos especialistas en plantas hospederas. Además, muestra que, a pesar de su especificidad, otras variables ambientales aparte de la disponibilidad de alimentos condicionan el número de gorgojos. Este resultado debe considerarse en estudios posteriores sobre la importancia de la producción irregular de semillas de roble como una estrategia para reducir la depredación de semillas pre-dispersión. Por último, los resultados proporcionan una idea de las posibles consecuencias del cambio global en las comunidades de estos insectos especializados vinculados a los robles. Las poblaciones de un especialista, como C. nucum que se alimenta de la avellana, será muy vulnerables a la fragmentación de los bosques, lo que reducirá el flujo genético entre las poblaciones y provocará cuellos de botella en la población. A su vez, el cambio climático (por ejemplo, aumento de la temperatura, disminución de las precipitaciones) podría alterar las coincidentes fenologías de los insectos y sus plantas hospederas y reducir el tamaño de la población de insectos

On the integration of trust with negotiation, argumentation and semantics

Agreement Technologies are needed for autonomous agents to come to mutually acceptable agreements, typically on behalf of humans. These technologies include trust computing, negotiation, argumentation and semantic alignment. In this paper, we identify a number of open questions regarding the integration of computational models and tools for trust computing with negotiation, argumentation and semantic alignment. We consider these questions in general and in the context of applications in open, distributed settings such as the grid and cloud computing. © 2013 Cambridge University Press.This work was partially supported by the Agreement Technology COST action (IC0801). The authors would like to thank for helpful discussions and comments all participants in the panel on >Trust, Argumentation and Semantics> on 16 December 2009, Agia Napa, CyprusPeer Reviewe

Habitat loss causes long extinction transients in small trophic chains

Transients in ecology are extremely important since they determine how equilibria are approached. The debate on the dynamic stability of ecosystems has been largely focused on equilibrium states. However, since ecosystems are constantly changing due to climate conditions or to perturbations driven by the climate crisis or anthropogenic actions (habitat destruction, deforestation, or defaunation), it is important to study how dynamics can proceed till equilibria. This article investigates the dynamics and transient phenomena in small food chains using mathematical models. We are interested in the impact of habitat loss in ecosystems with vegetation undergoing facilitation. We provide a dynamical study of a small food chain system given by three trophic levels: primary producers, i.e., vegetation, herbivores, and predators. Our models reveal how habitat loss pushes vegetation towards tipping points, how the presence of herbivores in small habitats could promote ecosystem's extinction (ecological meltdown), or how the loss of predators produce a cascade effect (trophic downgrading). Mathematically, these systems exhibit many of the possible local bifurcations: saddle-node, transcritical, Andronov-Hopf, together with a global bifurcation given by a heteroclinic bifurcation. The associated transients are discussed, from the ghost dynamics to the critical slowing down tied to the local and global bifurcations. Our work highlights how the increase of ecological complexity (trophic levels) can imply more complex transitions. This article shows how the pernicious effects of perturbations (i.e., habitat loss or hunting pressure) on ecosystems could not be immediate, producing extinction delays. These theoretical results suggest the possibility that some ecosystems could be currently trapped into the (extinction) ghost of their stable past