Energetics, lifestyle, and reproduction in birds

Theoretical and empirical studies of life history aim to account for resource allocation to the different components of fitness: survival, growth, and reproduction. The pioneering evolutionary ecologist David Lack [(1968) Ecological Adaptations for Breeding in Birds (Methuen and Co.,London)] suggested that reproductive output in birds reflects adaptation to environmental factors such as availability of food and risk of predation, but subsequent studies have not always supported Lack’s interpretation. Here using a dataset for 980 bird species (Dataset S1), a phylogeny, and an explicit measure of reproductive productivity, we test predictions for how mass-specific productivity varies with body size, phylogeny,and lifestyle traits. We find that productivity varies negatively with body size and energetic demands of parental care and positively with extrinsic mortality. Specifically: (i) altricial species are 50% less productive than precocial species; (ii) species with female-only care of offspring are about 20% less productive than species with other methods of parental care; (iii) nonmigrants are 14% less productive than migrants; (iv) frugivores and nectarivores are about 20% less productive than those eating other foods; and (v) pelagic foragers are 40% less productive than those feeding in other habitats. A strong signal of phylogeny suggests that syndromes of similar life-history traits tend to be conservative within clades but also to have evolved independently in different clades. Our results generally support both Lack’s pioneering studies and subsequent research on avian life history.

Widespread supplementary feeding in domestic gardens explains the return of reintroduced Red Kites Milvus milvus to an urban area

Reintroductions are used worldwide to mitigate biodiversity loss. One prominent case is a charismatic raptor of conservation concern, the Red Kite Milvus milvus. This species has been reintroduced across the UK over the last 25 years following its near extinction after centuries of persecution. The species was not expected to recolonize urban areas; its historical association with human settlements is attributed to scavenging on human waste and refuse, a resource now greatly reduced on the streets of modern Western cities. However, the species has become a common day-time visitor to a large conurbation centred on the town of Reading, southern England, approximately 20 km from the first English reintroduction site. Given a near-absence of breeding and roost sites, we investigated foraging opportunities and habitat associations that might explain use by Red Kites of this urban area. Surveys of discarded human foods and road-kill suggested that these could support at most 13−29 kites/day. Face-to-face surveys of a cross-section of residents revealed that 4.5% (equivalent to 4349 households) provided supplementary food for kites. Using estimates of per-household resource provision from another study, we calculated that this level is potentially sufficient to provision 142−320 kites, a substantial proportion of the total estimated to visit the conurbation each day (between 140 and 440). Road transects found positive associations between Red Kites and residential areas. We therefore suggest that the decision made by thousands of individuals to provide supplementary food for Red Kites is the primary factor explaining their day-time abundance in this urban area.

Olfactory selection of Plantago lanceolata by snails declines with seedling age

Background and Aims Despite recent recognition that (1) plant–herbivore interactions during the establishment phase, (2) ontogenetic shifts in resource allocation and (3) herbivore response to plant volatile release are each pivotal to a comprehensive understanding of plant defence, no study has examined how herbivore olfactory response varies during seedling ontogeny. Methods Using a Y-tube olfactometer we examined snail (Helix aspersa) olfactory response to pellets derived from macerated Plantago lanceolata plants harvested at 1, 2, 3, 4, 5, 6 and 8 weeks of age to test the hypothesis that olfactory selection of plants by a generalist herbivore varies with plant age. Plant volatiles were collected for 10 min using solid-phase microextraction technique on 1- and 8-week-old P. lanceolata pellets and analysed by gas chromatography coupled with a mass spectrometer. Key Results Selection of P. lanceolata was strongly negatively correlated with increasing age; pellets derived from 1-week-old seedlings were three times more likely to be selected as those from 8-week-old plants. Comparison of plant selection experiments with plant volatile profiles from GC/MS suggests that patterns of olfactory selection may be linked to ontogenetic shifts in concentrations of green leaf volatiles and ethanol (and its hydrolysis derivatives). Conclusions Although confirmatory of predictions made by contemporary plant defence theory, this is the first study to elucidate a link between seedling age and olfactory selection by herbivores. As a consequence, this study provides a new perspective on the ontogenetic expression of seedling defence, and the role of seedling herbivores, particularly terrestrial molluscs, as selective agents in temperate plant communities.

Prediction of dynamical, nonlinear, and unstable process behavior

Process scheduling techniques consider the current load situation to allocate computing resources. Those techniques make approximations such as the average of communication, processing, and memory access to improve the process scheduling, although processes may present different behaviors during their whole execution. They may start with high communication requirements and later just processing. By discovering how processes behave over time, we believe it is possible to improve the resource allocation. This has motivated this paper which adopts chaos theory concepts and nonlinear prediction techniques in order to model and predict process behavior. Results confirm the radial basis function technique which presents good predictions and also low processing demands show what is essential in a real distributed environment.

Mercados internos de capital: uma questão de sobrevivência

Procuramos apresentar neste trabalho a importância e os efeitos dos mercados internos de capitais, e as conseqüências quando da sua aplicação. Para isso, aplicamos inicialmente um modelo básico de mercados internos de capitais, avaliando os pontos atingidos e algumas idéias não abrangidas por ele. Exemplificamos com uma situação de aplicação de recursos entre divisões de uma pequena empresa diversificada e seu fracasso devido à má alocação desses recursos. Na seqüência, identificamos modelos que, quando aplicados às situações em que os mercados internos de capitais não funcionaram, foram capazes de apontar o porquê, indicando possíveis interferências e impedimentos. Por fim, aplicamos um modelo que permite comprovar a ineficiência na transferência de recursos quando esses vão na direção das divisões com as piores oportunidades de investimento.

On choice of technique in the Robinson-Solow-Srinivasan model

We report results on the optimal \choice of technique" in a model originally formulated by Robinson, Solow and Srinivasan (henceforth, the RSS model) and further discussed by Okishio and Stiglitz. By viewing this vintage-capital model without discounting as a speci c instance of the general theory of intertemporal resource allocation associated with Brock, Gale and McKenzie, we resolve longstanding conjectures in the form of theorems on the existence and price support of optimal paths, and of conditions suÆcient for the optimality of a policy rst identi ed by Stiglitz. We dispose of the necessity of these conditions in surprisingly simple examples of economies in which (i) an optimal path is periodic, (ii) a path following Stiglitz' policy is bad, and (iii) there is optimal investment in di erent vintages at di erent times. (129 words)

Teorias em estratégia

A estratégia empresarial é uma disciplina jovem. Comparado com os campos de estudo de economia e sociologia o campo de estratégia empresarial pode ser visto como um fenômeno de formação mais recente, embora extremamente dinâmico em sua capacidade de criar abordagens teóricas diferenciadas. Este trabalho discute a recente proliferação de teorias em estratégia empresarial, propondo um modelo de classificação destas teorias baseado na análise empírica do modelo de escolas de pensamento em estratégia empresarial desenvolvido por Mintzberg, Ahlstrand e Lampel em seu livro Safári de Estratégia (1998). As possíveis conseqüências relativas à interação entre teoria e prática são também discutidas apresentando o que definimos como a síndrome do ornitorrinco.

Orçamento e alocação de recursos em universidades: uma aproximação da escolha pública

As demandas exigindo a melhoria da produtividade em faculdades e universidades estão surgindo dramática e rapidamente no Brasil. Muitos estudos têm sugerido sistemas de avaliação e critérios externos para controlar a produção universitária em termos quantitativos e qualitativos. Considerando-se que as universidades e faculdades não são organizações com fins lucrativos (excetuando-se, é claro, as caça-níqueis), as variáveis microeconômicas e administrativas tradicionais usadas para medir a eficiência não possuem nenhuma função direta. Nesse sentido, dever-se-ia criar um sistema de controle à la mercado (imitando o mercado) para se avaliar a produção em universidades e faculdades. O orçamento e o mecanismo de alocação de recursos contido no mesmo pode ser usado como um mecanismo de incentivo para melhorar a qualidade e a produtividade. Esse será o principal tema deste artigo.

Estrutura de propriedade e teoria da agência: um estudo de empresas brasileiras e seus diferentes tipos de controladores

A estrutura de propriedade anglo-saxônica, e o seu clássico problema de agência, com conflitos entre gestores e acionistas, caracterizados por propriedades pulverizadas, apesar de ser predominante na literatura, não constituí a regra, mas sim a exceção. O Brasil, diferentemente dos Estados Unidos e da Inglaterra, possuí uma estrutura de propriedade concentrada, onde é forte a presença de acionistas majoritários. Nesse caso, o conflito verificado não é entre gestores e acionistas (conflito agente X principal), mas sim entre acionistas majoritários e acionistas minoritários (conflito principal X principal). No mercado de capitais brasileiro, há duas classes de ações, as ordinárias (com direito a voto), e as preferências (sem direito a voto), o que viola a regra existente em muitos países, como nos Estados Unidos, de uma ação, um voto. Sendo assim, em muitos casos, ocorre uma combinação de muito poder com pouca alocação de recursos próprios na empresa. Diante disso, o presente estudo teve como objetivo estimar a magnitude dos direitos de votos, de fluxo de caixa, e do excesso de votos dos acionistas majoritários (das ações ordinárias) das empresas listadas no índice Bovespa – Ibovespa para os anos de 2009 e 2010 (carteira teórica do terceiro quadrimestre dos respectivos anos), separando-as por setor de atuação e por tipo de acionista majoritário. Para este estudo foi analisada uma amostra de 121 empresas, utilizando a metodologia quanto aos fins (descritiva e explicativa), e quanto aos meios (bibliográfica e documental). A coleta de dados foi feita no sistema Economática e nos IAN’s da CVM. Como resultados a pesquisa corroborou as hipóteses da literatura existente de que a estrutura de capital das empresas brasileiras de capital aberto é concentrada, principalmente no capital acionário (média de 51,95% e mediana de 51,20% em 2009, e 47,16% e 51,70% em 2010), e ocorrendo em vários casos uma distância considerável entre o poder de voto e o poder do fluxo de caixa dos acionistas majoritários (média de 1,10 em 2009 e mediana de 1,24, e 1,07 e 0,98 em 2010). Com isso, também se verifica que o conflito principal X principal é o predominante no Brasil.

Optimal growth in a two-sector model without discounting: a geometric investigation

We characterize optimal policy in a two-sector growth model with xed coeÆcients and with no discounting. The model is a specialization to a single type of machine of a general vintage capital model originally formulated by Robinson, Solow and Srinivasan, and its simplicity is not mirrored in its rich dynamics, and which seem to have been missed in earlier work. Our results are obtained by viewing the model as a specific instance of the general theory of resource allocation as initiated originally by Ramsey and von Neumann and brought to completion by McKenzie. In addition to the more recent literature on chaotic dynamics, we relate our results to the older literature on optimal growth with one state variable: speci cally, to the one-sector setting of Ramsey, Cass and Koopmans, as well as to the two-sector setting of Srinivasan and Uzawa. The analysis is purely geometric, and from a methodological point of view, our work can be seen as an argument, at least in part, for the rehabilitation of geometric methods as an engine of analysis.

Graphical constraints: a graphical user interface for constraint problems

A constraint satisfaction problem is a classical artificial intelligence paradigm characterized by a set of variables (each variable with an associated domain of possible values), and a set of constraints that specify relations among subsets of these variables. Solutions are assignments of values to all variables that satisfy all the constraints. Many real world problems may be modelled by means of constraints. The range of problems that can use this representation is very diverse and embraces areas like resource allocation, scheduling, timetabling or vehicle routing. Constraint programming is a form of declarative programming in the sense that instead of specifying a sequence of steps to execute, it relies on properties of the solutions to be found, which are explicitly defined by constraints. The idea of constraint programming is to solve problems by stating constraints which must be satisfied by the solutions. Constraint programming is based on specialized constraint solvers that take advantage of constraints to search for solutions. The success and popularity of complex problem solving tools can be greatly enhanced by the availability of friendly user interfaces. User interfaces cover two fundamental areas: receiving information from the user and communicating it to the system; and getting information from the system and deliver it to the user. Despite its potential impact, adequate user interfaces are uncommon in constraint programming in general. The main goal of this project is to develop a graphical user interface that allows to, intuitively, represent constraint satisfaction problems. The idea is to visually represent the variables of the problem, their domains and the problem constraints and enable the user to interact with an adequate constraint solver to process the constraints and compute the solutions. Moreover, the graphical interface should be capable of configure the solver’s parameters and present solutions in an appealing interactive way. As a proof of concept, the developed application – GraphicalConstraints – focus on continuous constraint programming, which deals with real valued variables and numerical constraints (equations and inequalities). RealPaver, a state-of-the-art solver in continuous domains, was used in the application. The graphical interface supports all stages of constraint processing, from the design of the constraint network to the presentation of the end feasible space solutions as 2D or 3D boxes.

Delays in stabilization or in reforms? The debt crisis

Empirical analyses attributing the 1980s' debt crisis to inconsistent stabilization policies rest on an inappropriate long-run approach. Revising this long-run approach yields opposite results: terms of trade shocks and foreign indebtedness explain this crisis, regardless of domestic stabilization policies. This prompts us to consider a new hypothesis, of delays in trade-policy reforms, with a model in which terms-of-trade variation (under shocks) is endogenous to export structure and efficiency of resource allocation. Evidence from the structural equations model shows that allocation distortions negatively affect changes in terms of trade, which then explain this crisis. A political economy extension demonstrates that income inequality and regional trade policy determine the distortions, which in turn leads to this crisis.

Evolving Future Internet clean-slate Entity Title Architecture with quality-oriented control-plane extensions

A Internet atual vem sofrendo vários problemas em termos de escalabilidade, desempenho, mobilidade, etc., devido ao vertiginoso incremento no número de usuários e o surgimento de novos serviços com novas demandas, propiciando assim o nascimento da Internet do Futuro. Novas propostas sobre redes orientadas a conteúdo, como a arquitetura Entidade Titulo (ETArch), proveem novos serviços para este tipo de cenários, implementados sobre o paradigma de redes definidas por software. Contudo, o modelo de transporte do ETArch é equivalente ao modelo best-effort da Internet atual, e vem limitando a confiabilidade das suas comunicações. Neste trabalho, ETArch é redesenhado seguindo o paradigma do sobreaprovisionamento de recursos para conseguir uma alocação de recursos avançada integrada com OpenFlow. Como resultado, o framework SMART (Suporte de Sessões Móveis com Alta Demanda de Recursos de Transporte), permite que a rede defina semanticamente os requisitos qualitativos das sessões para assim gerenciar o controle de Qualidade de Serviço visando manter a melhor Qualidade de Experiência possível. A avaliação do planos de dados e de controle teve lugar na plataforma de testes na ilha do projeto OFELIA, mostrando o suporte de aplicações móveis multimídia com alta demanda de recursos de transporte com QoS e QoE garantidos através de um esquema de sinalização restrito em comparação com o ETArch legado

Bottom-up and top-down effects in a pre-dispersal seed predation system: are non-predated seeds damaged?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)