The On-orbit Calibrations for the Fermi Large Area Telescope

The Large Area Telescope (LAT) on--board the Fermi Gamma ray Space Telescope began its on--orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.Comment: 60 pages, 34 figures, submitted to Astroparticle Physic

Reintroduction of large predators in nature areas

The extirpation of predators in an ecosystem can result in overabundant herbivore popula-tions with cascading consequences on plant communities. Reintroducing predators could be a way to restore the natural ecosystem. The introduction of predators leads to a trophic cascade interfering in all levels. Lethal (density-mediated) and non-lethal (behaviourally-mediated) effects cause a decline in herbivore numbers, which in its turn has different influ-ences on the vegetation depending on several conditions. The aim of this thesis is to explore under which conditions the introduction of predators into nature areas can have a positive effect on the heterogeneity in vegetation structures and a case study will be carried out to investigate what might happen if a predator was introduced in nature reserve the Oost-vaardersplassen (the Netherlands). To increase heterogeneity in vegetation, high grazing pressure should be reduced by the removal of herbivores, which can be caused either by the lethal or non-lethal effects by the introduction of predators. Area size, heterogeneity prior to the introduction, predator and herbivore characteristics and abiotic conditions all influence the outcome of the cascading effects and the transformation into a heterogeneous vegeta-tion.

Simultaneous GPS-tracking of parents reveals a similar parental investment within pairs, but no immediate co-adjustment on a trip-to-trip basis

Abstract Background Parental care benefits the offspring, but comes at a cost for each parent, which in biparental species gives rise to a conflict between partners regarding the within-pair distribution of care. Pair members could avoid exploitation by efficiently keeping track of each other’s efforts and coordinating their efforts. Parents may, therefore, space their presence at the nest, which could also allow for permanent protection of the offspring. Additionally, they may respond to their partner’s previous investment by co-adjusting their efforts on a trip-to-trip basis, resulting in overall similar parental activities within pairs. Methods We investigated the coordination of parental care measured as nest attendance and foraging effort in the Lesser black-backed gull (Larus fuscus), a species with long nest bouts that performs extended foraging trips out of sight of their partner. This was achieved by GPS-tracking both pair members simultaneously during the entire chick rearing period. Results We found that the timing of foraging trips (and hence nest attendance) was coordinated within gull pairs, as individuals left the colony only after their partner had returned. Parents did not match their partner’s investment by actively co-adjusting their foraging efforts on a trip-by-trip basis. Yet, pair members were similar in their temporal and energetic investments during chick rearing. Conclusion Balanced investment levels over a longer time frame suggest that a coordination of effort may not require permanent co-adjustment of the levels of care on a trip-to-trip basis, but may instead rather take place at an earlier stage in the reproductive attempt, or over integrated longer time intervals. Identifying the drivers and underlying processes of coordination will be one of the next necessary steps to fully understand parental cooperation in long-lived species

Early life intervention with glucocorticoids has negative effects on motor development and neuropsychological function in 14-17 year-old adolescents.

Item does not contain fulltextOBJECTIVE: To reduce the risk of bronchopulmonary dysplasia, preterm infants receive neonatal treatment with glucocorticoids, mostly dexamethasone (DEX). Compared to current protocols, treatment regimens of the late 1980s - early 1990s prescribed high doses of DEX for an extensive period up to 6 weeks. Worldwide at least one million children have been treated with this dose regimen. Previous studies have shown adverse effects of neonatal treatment with the glucocorticoid dexamethasone (DEX) on outcome in children aged 7-10 years. On the other hand, treatment with another glucocorticoid, hydrocortisone (HC), was not related to adverse effects in childhood. In the current study we determined the consequences of early life intervention with DEX or HC in adolescents (age 14-17 years). Besides motor function and intellectual capacities, we also examined fundamental neuropsychological functions which have so far received little attention. METHODS: In an observational cohort study we compared 14-17 year-old adolescents who received DEX (.5 mg/kg/day tapering off to .1 mg/kg/day over 21 days, n=63), or HC (5 mg/kg/day tapering off to 1 mg/kg/day over 22 days, n=67), or did not receive neonatal glucocorticoids (untreated, n=71) after premature birth (gestational age<32 weeks). Because gestational age was shorter and duration of ventilation was longer in the DEX-treated group, all analyses were corrected for these potential confounders. Motor function, IQ, and neuropsychological functions were assessed. RESULTS: DEX-treated group participants scored lower on gross motor skill tasks than their HC-treated and untreated counterparts. A higher proportion of DEX-treated girls needed special education compared to the other groups. DEX-treated adolescents performed poorer on neuropsychological tasks measuring alertness, visuomotor coordination, and emotion recognition. The HC-treated group did not differ from the untreated group. CONCLUSIONS: Even after 14-17 years, neonatal treatment with .5 mg/kg/day DEX was associated with adverse effects on motor function, school level, and neuropsychological functions, whereas treatment with the clinically equally effective dose of 5 mg/kg/day HC was not. Potential physiological mechanisms underlying the differences in dexamethasone and hydrocortisone effects are discussed. Based on the current findings, we recommend early identification of neuropsychological deficits after DEX treatment in order to specify extra educational needs.1 juli 201