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

Administering labelled water to exclusively breast-fed infants in studies involving stable isotope techniques

Stable isotope techniques using deuterium or 18O are reference methods for assessing total body water (TBW) for body composition. In combination, they provide total energy expenditure and human milk intake in exclusively breast-fed (EBF) infants. These techniques require an oral administration of an accurately quantified dose of labelled water to infants, who often have no prior experience of consuming water. In the present study, 18O labelled water was administered to 47 EBF infants at two time points. Route of administration, duration of dosing and spills were quantified and recorded. Eighty-seven out of 94 (92.6%) dose administrations were successful. In two-thirds of dose administrations,>90% of the prepared dose was consumed. Spills ranged from 0.2% to 57%. Approaches to correct for spills can introduce bias in the calculation of TBW. Minimising and recording all dose spills is an important issue for the accuracy and precision of stable isotope techniques, when applied to EBF infants

10-year Cognition in Preterms After Random Assignment to Fatty Acid Supplementation in Infancy

OBJECTIVE: To test the hypothesis that long-chain polyunsaturated fatty acid (LCPUFA) supplementation in infancy would improve cognition into later childhood (after 9 years) at both general and specific levels. METHODS: A comprehensive cognitive battery was completed by 107 formerly preterm infants (mean age: 128 months). As infants, they had been assigned randomly to receive LCPUFA-supplemented (N = 50) or control (N = 57) formula, between birth and 9 months; the docosahexaenoic acid level (DHA) in the supplemented formulas was 0.5%. In addition to randomized comparisons, we planned supplementary analyses to examine the effects of both gender and feeding group (those receiving some maternal breast milk versus those receiving none). RESULTS: There were no significant differences between randomized diet groups on any cognitive measure. There was significant interaction between gender and supplementation; girls only showed beneficial effects of LCPUFAs on literacy. Significant interaction also occurred between feeding group and supplementation; increases of 0.7 SD in verbal IQ, full-scale IQ, and memory scores were found for the LCPUFA group, but only for infants who received only formula and no maternal breast milk. CONCLUSIONS: The results of this post-9-year cognitive follow-up study in a randomized trial of LCPUFA-supplemented formula for preterm infants suggest no overall group effects but indicate that gender-specific and diet-specific effects may exist. The data provide some evidence that LCPUFAs are a key factor in the cognitive benefits of breast milk. Caution is advised in data interpretation because of the small groups used. Pediatrics 2011;128:e890-e89

Body composition in children in remission from acute lymphoblastic leukemia

Background: Changes in body composition are commonly reported in pediatric survivors of acute lymphoblastic leukemia (ALL). However, the effect of ALL and of its treatment on body composition in children in remission from ALL has not been fully examined with the use of a reference method. Objectives: We aimed to determine the body composition and composition of fat-free mass (FFM) in children in remission from ALL. We also aimed to compare the effects that prednisolone and dexamethasone had on the body composition of an ALL survivor population. Design: This cross-sectional study measured height, weight, body volume, total body water, and bone mineral content in 24 children in remission from ALL and 24 age-matched, healthy control subjects. Body composition and FFM composition were evaluated by using the 4-component model. Results: The mean body mass index and fat mass index were significantly (P = 0.05 for both) higher in the ALL survivors than in age-matched control subjects. The composition of the FFM in the 2 treatment groups was not observed to differ significantly. Examination of the composition of FFM made it evident that children in remission from ALL had both significantly greater hydration (P = 0.001) and lower density (P = 0.0001) of FFM than did the control children. Conclusions: Children in remission from ALL may develop excess body fat. To measure body composition accurately in an ALL population, the high hydration and low density of FFM in this population should be taken into consideration