Young and middle age pulsar light-curve morphology: Comparison of Fermi observations with gamma-ray and radio emission geometries

Thanks to the huge amount of gamma-ray pulsar photons collected by the Fermi Large Area Telescope since June 2008, it is now possible to constrain gamma-ray geometrical models by comparing simulated and observed light-curve morphological characteristics. We assumed vacuum-retarded dipole pulsar magnetic field and tested simulated and observed morphological light-curve characteristics in the framework of two pole emission geometries, Polar Cap (PC), radio, and Slot Gap (SG), and Outer Gap (OG)/One Pole Caustic (OPC) emission geometries. We compared simulated and observed/estimated light-curve morphological parameters as a function of observable and non-observable pulsar parameters. The PC model gives the poorest description of the LAT pulsar light-curve morphology. The OPC best explains both the observed gamma-ray peak multiplicity and shape classes. The OPC and SG models describe the observed gamma-ray peak-separation distribution for low- and high-peak separations, respectively. This suggests that the OPC geometry best explains the single-peak structure but does not manage to describe the widely separated peaks predicted in the framework of the SG model as the emission from the two magnetic hemispheres. The OPC radio-lag distribution shows higher agreement with observations suggesting that assuming polar radio emission, the gamma-ray emission regions are likely to be located in the outer magnetosphere. The larger agreement between simulated and LAT estimations in the framework of the OPC suggests that the OPC model best predicts the observed variety of profile shapes. The larger agreement between observations and the OPC model jointly with the need to explain the abundant 0.5 separated peaks with two-pole emission geometries, calls for thin OPC gaps to explain the single-peak geometry but highlights the need of two-pole caustic emission geometry to explain widely separated peaks.Comment: 28 pages, 20 figures, 8 tables; accepted for publication in Astronomy and Astrophysic

Light-curve modelling constraints on the obliquities and aspect angles of the young Fermi pulsars

In more than four years of observation the Large Area Telescope on board the Fermi satellite has identified pulsed $\gamma$-ray emission from more than 80 young pulsars, providing light curves with high statistics. Fitting the observations with geometrical models can provide estimates of the magnetic obliquity $\alpha$ and aspect angle $\zeta$, yielding estimates of the radiation beaming factor and luminosity. Using $\gamma$-ray emission geometries (Polar Cap, Slot Gap, Outer Gap, One Pole Caustic) and radio emission geometry, we fit $\gamma$-ray light curves for 76 young pulsars and we jointly fit their $\gamma$-ray plus radio light curves when possible. We find that a joint radio plus $\gamma$-ray fit strategy is important to obtain ($\alpha$, $\zeta$) estimates that can explain simultaneous radio and $\gamma$-ray emission. The intermediate-to-high altitude magnetosphere models, Slot Gap, Outer Gap, and One pole Caustic, are favoured in explaining the observations. We find no evolution of $\alpha$ on a time scale of a million years. For all emission geometries our derived $\gamma$-ray beaming factors are generally less than one and do not significantly evolve with the spin-down power. A more pronounced beaming factor vs. spin-down power correlation is observed for Slot Gap model and radio-quiet pulsars and for the Outer Gap model and radio-loud pulsars. For all models, the correlation between $\gamma$-ray luminosity and spin-down power is consistent with a square root dependence. The $\gamma$-ray luminosities obtained by using our beaming factors not exceed the spin-down power. This suggests that assuming a beaming factor of one for all objects, as done in other studies, likely overestimates the real values. The data show a relation between the pulsar spectral characteristics and the width of the accelerator gap that is consistent with the theoretical prediction for the Slot Gap model.Comment: 90 pages, 80 figures (63 in Appendices), accepted for publication in Astronomy and Astrophysic

Using functional analysis diagrams to improve product reliability and cost

Failure Mode and Effects Analysis (FMEA) and Value Engineering (VE) are well-established methods in the manufacturing industry, commonly applied to optimize product reliability and cost respectively. Both processes, however, require cross-functional teams to identify and evaluate the product/process functions and are resource-intensive, hence their application is mostly limited to large organizations. In this paper, we present a methodology involving the concurrent execution of FMEA and VE, assisted by a set of hierarchical Functional Analysis Diagram (FAD) models, along with the outcomes of a pilot application in a UK-based manufacturing Small-Medium Enterprise (SME). Analysis of the results indicate that this new approach could significantly enhance the resource efficiency and effectiveness of both FMEA and VE processes

Risk factors for active trachoma in The Gambia.

Trachoma has been endemic in The Gambia for decades but national surveys indicate that the prevalence is falling. Risk factor data can help guide trachoma control efforts. This study investigated risk factors for active trachoma and ocular Chlamydia trachomatis infection in children aged below 10 years in two Gambian regions. The overall prevalence of C. trachomatis infection was only 0.3% (3/950) compared with 10.4% (311/2990) for active trachoma, therefore analyses were only performed for active trachoma. After adjustment, increased risk of trachoma was associated with being aged 1-2 years (odds ratio (OR) 2.20, 95% CI 1.07-4.52) and 3-5 years (OR 3.62, 95% CI 1.80-7.25) compared with <1 year, nasal discharge (OR 2.07, 95% CI 1.53-2.81), ocular discharge (OR 2.68, 95% CI 1.76-4.09) and there being at least one other child in the household with active trachoma (OR 11.28, 95% CI 8.31-15.31). Compared with other occupations, children of traders had reduced risk (OR 0.53, 95% CI 0.30-0.94). At the household level, only the presence of another child in the household with active trachoma was associated with increased risk of active trachoma, suggesting that current trachoma control interventions are effective at this level. In contrast, child-level factors were associated with increased risk after adjustment, indicating a need to increase control efforts at the child level

Empowering manufacturing personnel through functional understanding

A growing interest in organizational knowledge management, along with increasingly widespread adoption of Quality Standards such as ISO 9001, has increasingly led organizations to implement training programs for all employees. Training for the manufacturing workforce, however, remains limited to informal “On-the-Job” training, administered by peer colleagues or supervisors - particularly in Small and Medium Enterprises (SMEs) where economic, educational, cognitive and cultural constraints to training are often deeply embedded. This paper proposes a methodology for training the manufacturing workforce on the functions of products and their constituent parts, and presents a case study conducted in a UK-based manufacturing SME - aiming to verify our two research hypotheses: Functional Analysis Diagrams (FAD) of the company’s products and parts would assist in knowledge assimilation; and, the knowledge assimilation has a positive effect on work quality and productivity levels. This intervention provided training on the purpose of the processes the participants are involved, aiming to empower them in supporting the optimization of these same processes. By using surveys and applying statistical inference on long-term quantitative data, the study confirmed subjective observations of substantial improvements in work quality (scrap reduction of 63%) and increased productivity (setup time reduced by 67%). To our knowledge, we were the first to examine the effect of functional modelling methods for workforce training in a manufacturing setup. Although this paper presents a single case study, the results suggest that the proposed methodology can be a promising solution for the industry

Use of strategies to improve retention in primary care randomised trials: a qualitative study with in-depth interviews

Objective To explore the strategies used to improve retention in primary care randomised trials.&lt;p&gt;&lt;/p&gt; Design Qualitative in-depth interviews and thematic analysis.&lt;p&gt;&lt;/p&gt; Participants 29 UK primary care chief and principal investigators, trial managers and research nurses.&lt;p&gt;&lt;/p&gt; Methods In-depth face-to-face interviews.&lt;p&gt;&lt;/p&gt; Results Primary care researchers use incentive and communication strategies to improve retention in trials, but were unsure of their effect. Small monetary incentives were used to increase response to postal questionnaires. Non-monetary incentives were used although there was scepticism about the impact of these on retention. Nurses routinely used telephone communication to encourage participants to return for trial follow-up. Trial managers used first class post, shorter questionnaires and improved questionnaire designs with the aim of improving questionnaire response. Interviewees thought an open trial design could lead to biased results and were negative about using behavioural strategies to improve retention. There was consensus among the interviewees that effective communication and rapport with participants, participant altruism, respect for participant's time, flexibility of trial personnel and appointment schedules and trial information improve retention. Interviewees noted particular challenges with retention in mental health trials and those involving teenagers.&lt;p&gt;&lt;/p&gt; Conclusions The findings of this qualitative study have allowed us to reflect on research practice around retention and highlight a gap between such practice and current evidence. Interviewees describe acting from experience without evidence from the literature, which supports the use of small monetary incentives to improve the questionnaire response. No such evidence exists for non-monetary incentives or first class post, use of which may need reconsideration. An exploration of barriers and facilitators to retention in other research contexts may be justified.&lt;p&gt;&lt;/p&gt

Force-free magnetosphere of an aligned rotator with differential rotation of open magnetic field lines

Here we briefly report on results of self-consistent numerical modeling of a differentially rotating force-free magnetosphere of an aligned rotator. We show that differential rotation of the open field line zone is significant for adjusting of the global structure of the magnetosphere to the current density flowing through the polar cap cascades. We argue that for most pulsars stationary cascades in the polar cap can not support stationary force-free configurations of the magnetosphere.Comment: 5 pages, 4 figures. Presented at the conference "Isolated Neutron Stars: from the Interior to the Surface", London, April 24-28, 2006; to appear in Astrophysics and Space Science. Significantly revised version, a mistake found by ourselfs in the numerical code was corrected, all presented results are obtained with the correct version of the cod

An intraoperative surprise : occult case of non-functional parathyroid carcinoma

Parathyroid carcinoma (PC) exists in <1% of patients with hyperparathyroidism (Figure 1) and typically presents with a robust constellation of findings that rarely go unnoticed. Mean serum parathyroid hormone (PTH) concentrations are commonly 3-to 10-fold higher than the upper limit of normal with a mean serum calcium concentration that frequently exceeds 14 mg/dL. PCs also tend to metastasize to cervical lymph nodes (30%) which is a distinctly ominous sign when associated with this rare pathology as compared to its benign counterpart, parathyroid adenomas. Non-functioning parathyroid carcinomas (NPC), less than 10% of PCs, are exceptionally rare, and can more closely resemble parathyroid adenoma/hyperplasia on preoperative workup further obscuring diagnosis. This disease represents a unique subset of PCs that are rarely addressed in the literature

Saxon and Medieval Settlement on the Northern Edge of Wimborne Minster, Dorset

An excavation on the northern edge of Wimborne Minster revealed elements of a middle to late Saxon and medieval rural settlement fronting onto the west side of the road that leads north out of the town. The Saxon phase comprised a number of rectangular enclosures flanking the road, within and to the west of which were numerous pits and postholes as well as a number of features probably related to industrial activity, including iron smelting. Although no clear structures were identified, the material recovered from the features include Saxon pottery, animal bone, and charred crop remains indicative of settlement within a mixed agricultural economy. Radiocarbon dating of cereal grain from four features gave date ranges in the early/middle and middle/late Saxon periods. The enclosures were subsequently extended during the late Saxon/medieval period, with pottery indicating occupation possibly continuing into the 13th–14th centuries. The site also produced very limited evidence of prehistoric and Romano-British activity