Independent and combined effects of egg pro- and anti-oxidants on gull chick phenotype

Oviparous mothers transfer to their eggs components that have both independent and combined effects on offspring phenotype. The functional interaction between egg components, such as antioxidants and hormones, suggests that a change in the concentration of one component will have effects on offspring traits that depend on the concentration of other interacting components. However, the combined effects of variation in different egg components are virtually unknown. Bird eggs contain vitamin E, a major antioxidant, and also maternal corticosterone. The independent consequences of variation in the egg concentrations of these compounds for offspring phenotype are largely unknown and no study has investigated their combined effects. We manipulated the concentration of vitamin E and corticosterone in the eggs of the yellow-legged gull (Larus michahellis) by administering a physiological (2 s.d.) dose both independently and in combination. We tested for an effect on chick post-natal growth, plasma antioxidant capacity (TAC) and oxidative compounds (TOS). Separate administration of vitamin E or corticosterone caused a reduction in body mass relative to controls, whereas the combined administration of the two compounds reversed their negative effects. These results suggest that maternal egg components, such as antioxidants and steroid hormones, interact and mothers must balance their concentrations in order to achieve optimal offspring phenotype. The functional relationship between vitamin E and corticosterone is corroborated by the observation of positive covariation between these compounds

The Mitogenome Relationships and Phylogeography of Barn Swallows (Hirundo rustica)

The barn swallow (Hirundo rustica) poses a number of fascinating scientific questions, including the taxonomic status of postulated subspecies. Here, we obtained and assessed the sequence variation of 411 complete mitogenomes, mainly from the European H. r. rustica, but other subspecies as well. In almost every case, we observed subspecies-specific haplogroups, which we employed together with estimated radiation times to postulate a model for the geographical and temporal worldwide spread of the species. The female barn swallow carrying the Hirundo rustica ancestral mitogenome left Africa (or its vicinity) around 280 thousand years ago (kya), and her descendants expanded first into Eurasia and then, at least 51kya, into the Americas, from where a relatively recent (<20kya) back migration to Asia took place. The exception to the haplogroup subspecies specificity is represented by the sedentary Levantine H. r.Transitiva that extensively shares haplogroup A with the migratory European H. r. rustica and, to a lesser extent, haplogroup B with the Egyptian H. r. savignii. Our data indicate that rustica and transitiva most likely derive from a sedentary Levantine population source that split at the end of the Younger Dryas (YD) (11.7kya). Since then, however, transitiva received genetic inputs from and admixed with both the closely related rustica and the adjacent savignii. Demographic analyses confirm this species' strong link with climate fluctuations and human activities making it an excellent indicator for monitoring and assessing the impact of current global changes on wildlife

Gas Storage Valuation: A Comparative Simulation Study

The purpose of this paper is the comparative analysis of four natural gas storage valuation approaches. In competitive natural gas markets the optimal valuation and operation of natural gas storages is a key task for natural gas companies operating storages. Within this paper, four spot based valuation approaches are analyzed regarding computational time and accuracy. In particular, explicit and implicit finite differences, multinomial recombining trees, and Least Squares Monte Carlo Simulation are compared. These approaches are applied to the valuation of a gas storage facility considering three different underlying price processes. Major characteristics of historical natural gas prices are: seasonality, mean reversion and jumps. Therefore, we consider a mean reversion process as underlying price process. In a first step, we extend this mean reversion process to a mean reversion jump diffusion process, to account for jumps, occurring in historical gas spot price time series. Moreover, we consider a more general price process accounting for mean reversion as well as seasonal patterns as observed in the historical time series. Besides the analysis of the numerical results, the benefits and drawbacks of the methodologies are discussed

A stochastic dynamic programming approach for integrating supply chain network design and new product diffusion

We focus on the problem of designing a supply chain for a new product. We propose a stochastic dynamic program based on a Stochastic Bass Model of the product demand dynamics. We heuristically solve our model using Monte Carlo simulation and math programming techniques. We apply our approach to the case of a new distribution service for Made-in-Italy wine and food products, benchmarking the performance of our heuristic policy against the performance of an easier to compute heuristic policy and a lower bound