The Effect of Different Magnetospheric Structures on Predictions of Gamma-ray Pulsar Light Curves

The second pulsar catalogue of the Fermi Large Area Telescope (LAT) will contain in excess of 100 gamma-ray pulsars. The light curves (LCs) of these pulsars exhibit a variety of shapes, and also different relative phase lags with respect to their radio pulses, hinting at distinct underlying emission properties (e.g., inclination and observer angles) for the individual pulsars. Detailed geometric modelling of the radio and gamma-ray LCs may provide constraints on the B-field structure and emission geometry. We used different B-field solutions, including the static vacuum dipole and the retarded vacuum dipole, in conjunction with an existing geometric modelling code, and constructed radiation sky maps and LCs for several different pulsar parameters. Standard emission geometries were assumed, namely the two-pole caustic (TPC) and outer gap (OG) models. The sky maps and LCs of the various B-field and radiation model combinations were compared to study their effect on the resulting LCs. As an application, we compared our model LCs with Fermi LAT data for the Vela pulsar, and inferred the most probable configuration in this case, thereby constraining Vela's high-altitude magnetic structure and system geometry.Comment: 6 pages, 4 figures, conference article, appears in Proceedings of SAIP2012, the 57th Annual Conference of the South African Institute of Physics, edited by Johan Janse van Rensburg, ISBN: 978-1-77592-070-

Constraining viewing geometries of pulsars with single-peaked gamma-ray profiles using a multiwavelength approach

Since the launch of the Large Area Telescope (LAT) on board the Fermi spacecraft in June 2008, the number of observed gamma-ray pulsars has increased dramatically. A large number of these are also observed at radio frequencies. Constraints on the viewing geometries of 5 of 6 gamma-ray pulsars exhibiting single-peaked gamma-ray profiles were derived using high-quality radio polarization data (Weltevrede et al., 2010). We obtain independent constraints on the viewing geometries of 6 by using a geometric emission code to model the Fermi LAT and radio light curves (LCs). We find fits for the magnetic inclination and observer angles by searching the solution space by eye. Our results are generally consistent with those previously obtained (Weltevrede et al., 2010), although we do find small differences in some cases. We will indicate how the gamma-ray and radio pulse shapes as well as their relative phase lags lead to constraints in the solution space. Values for the flux correction factor corresponding to the fits are also derived (with errors).Comment: 6 pages, 2 figures, 1 table, Proceedings of SAIP2011, the 56th Annual Conference of the South African Institute of Physics (ISBN: 978-1-86888-688-3), ed. I. Basson and A. E. Botha, http://www.saip.org.za, pp. 531-53

Modeling the Pulse Profiles of Millisecond Pulsars in the Second LAT Catalog of gamma-ray Pulsars

Significant gamma-ray pulsations have been detected from ~40 millisecond pulsars (MSPs) using 3 years of sky-survey data from the Fermi LAT and radio timing solutions from across the globe. We have fit the radio and gamma-ray pulse profiles of these MSPs using geometric versions of slot gap and outer gap gamma-ray emission models and radio cone and core models. For MSPs with radio and gamma-ray peaks aligned in phase we also explore low-altitude slot gap gamma-ray models and caustic radio models. The best-fit parameters provide constraints on the viewing geometries and emission sites. While the exact pulsar magnetospheric geometry is unknown, we can use the increased number of known gamma-ray MSPs to look for significant trends in the population which average over these uncertainties.Comment: 4 pages, 2 figures, to appear in the proceedings of the 5th International Symposium on High-Energy Astronom

Towards the discrimination of milk (origin) applied in cheddar cheese manufacturing through the application of an artificial neural network approach on Lactococcus lactis profiles

Published ArticleAn artificial neural network (ANN) that is able to distinguish between Cheddar cheese produced with milk from mixed and single breed sources was designed. Samples of each batch (4 pure Ayrshire/4 mixed with no Ayrshire milk) were ripened for 92 days and analysed every 14 days. A novel ANN was designed and applied which, based only on Lactococcus lactis counts, provided an acceptable classification of the cheeses. The ANN consisted of a multi-layered network with supervised training arranged in an ordered hierarchy of layers, in which connections were allowed only between nodes in immediately adjacent layers

Fussy eating and feeding difficulties in infants and toddlers consuming a cows’ milk exclusion diet

Cows’ milk allergy (CMA) is the most common infant food allergy in the United Kingdom, requiring a strict exclusion diet. Feeding difficulties and fussy eating are also very common problems in young children and can negatively influence feeding and dietary intake in an infant with CMA. The aim of this study was to compare the levels of fussy eating and feeding difficulties in two groups of young children: a group consuming an exclusion diet for CMA and a control group of children consuming an unrestricted diet.MethodParticipants were recruited from allergy and health visitor clinics on the Isle of Wight. Parents completed a number of questionnaires about their child's feeding behaviour.ResultsOne hundred and twenty-six participants (mean age 13 months) were recruited. Participants consuming an exclusion diet for CMA had significantly higher scores for both fussy eating and feeding difficulties (p < 0.05), although overall both groups were within the normal range. A number of symptoms were found to be positively moderately correlated with higher feeding difficulty score (p < 0.05). A higher consumption of milk/milk substitute consumed per day was positively correlated to both feeding difficulties and fussy eating (p < 0.05).ConclusionParticipants consuming an exclusion diet for CMA have higher scores for feeding difficulties and fussy eating than those consuming an unrestricted diet; however, the majority of participants’ scores were within the normal range and did not affect the growth

An exploratory investigation of food choice behavior of teenagers with and without food allergies

Background - Understanding food choice behavior in adolescence is important because many core eating habits may be tracked into adulthood. The food choices of at least 2.3% of teenagers living in the United Kingdom are determined by food allergies. However, the effect of food allergies on eating habits in teenagers has not yet been studied.Objective - To provide an understanding of how teenagers with food allergies make food choice decisions and how these differ from those of non–food-allergic teenagers.Methods - One focus group discussion with non–food-allergic teenagers (n = 11) and 14 semistructured interviewers (7 with food-allergic and 7 with non–food-allergic teenagers) were performed (age range, 12-18 years). The focus group discussion and interviews were audiorecorded, transcribed verbatim, and analyzed using thematic content analysis.Results - Teenagers from both groups (food-allergic and non–food-allergic) named sensory characteristics of foods as the main reason for choosing them. Some food-allergic teenagers downplayed their allergy and frequently engaged in risk-taking behavior in terms of their food choices. However, they reported difficulties in trying new foods, especially when away from home. Parental control was experienced as protective by those with food allergies, whereas non–food-allergic teenagers felt the opposite. Most teenagers, including food-allergic ones, expressed the wish to eat similar foods to their friends. Other themes did not vary between the 2 groups.Conclusion - Food-allergic teenagers strive to be able to make similar food choices to their friends, although differences to non–food-allergic teenagers exist. It is important to address these differences to improve their dietary management

Does concurrent breastfeeding alongside the introduction of solid food prevent the development of food allergy?

The timing of introduction of solid food on the subsequent development of food allergy is under debate and the role of concurrent breastfeeding is unclear. The aim of the present study was to investigate the role of solid food introduction whilst concurrently breastfeeding on food allergy outcome, with a specific focus on cows’ milk allergy. Prospectively collected infant feeding data from a birth cohort were analysed. Participants with histories suggestive of food allergy underwent diagnostic food challenges. Children with food allergy were matched to control participants for age and sex. Mann–Whitney U tests, χ2, Fisher exact tests and logistic regression calculations were undertaken. A total of thirty-nine food-allergic children and seventy-eight matched controls were identified, including twenty-two cows’ milk-allergic children and forty-four matched controls. The control group introduced solid food earlier than the food-allergic group (P < 0·05). There was no effect of concurrent breastfeeding alongside cows’ milk introduction or other food allergens on the development of food allergy. Due to small numbers, it was not possible to explore differences for food allergy phenotype. We have therefore found no evidence that introducing solids, or food allergens, whilst breastfeeding has an allergy-preventative effect; however, the results should be interpreted with caution due to sample size. Recommendations regarding infant feeding and food allergy should be carefully considered. Although breastfeeding should be promoted for many health reasons, larger studies looking at the introduction of food allergens on the development of food allergy are needed to make a final conclusion