An investigation of pulsar searching techniques with the Fast Folding Algorithm

Here we present an in-depth study of the behaviour of the Fast Folding Algorithm, an alternative pulsar searching technique to the Fast Fourier Transform. Weaknesses in the Fast Fourier Transform, including a susceptibility to red noise, leave it insensitive to pulsars with long rotational periods (P > 1 s). This sensitivity gap has the potential to bias our understanding of the period distribution of the pulsar population. The Fast Folding Algorithm, a time-domain based pulsar searching technique, has the potential to overcome some of these biases. Modern distributed-computing frameworks now allow for the application of this algorithm to all-sky blind pulsar surveys for the first time. However, many aspects of the behaviour of this search technique remain poorly understood, including its responsiveness to variations in pulse shape and the presence of red noise. Using a custom CPU-based implementation of the Fast Folding Algorithm, ffancy, we have conducted an in-depth study into the behaviour of the Fast Folding Algorithm in both an ideal, white noise regime as well as a trial on observational data from the HTRU-S Low Latitude pulsar survey, including a comparison to the behaviour of the Fast Fourier Transform. We are able to both confirm and expand upon earlier studies that demonstrate the ability of the Fast Folding Algorithm to outperform the Fast Fourier Transform under ideal white noise conditions, and demonstrate a significant improvement in sensitivity to long-period pulsars in real observational data through the use of the Fast Folding Algorithm.Comment: 19 pages, 15 figures, 3 table

Sampling and handling of desert soils

Sampling and handling of desert soils - area site, transportation, processing, and storag

Thanks, but no thanks: women's avoidance of help-seeking in the context of a dependency-related stereotype

The stereotype that women are dependent on men is a commonly verbalized, potentially damaging aspect of benevolent sexism. We investigated how women may use behavioral disconfirmation of the personal applicability of the stereotype to negotiate such sexism. In an experiment (N = 86), we manipulated female college students’ awareness that women may be stereotyped by men as dependent. We then placed participants in a situation where they needed help. Women made aware of the dependency stereotype (compared to controls who were not) were less willing to seek help. They also displayed a stronger negative correlation between help-seeking and post help-seeking affect - such that the more help they sought, the worse they felt. We discuss the relevance of these findings for research concerning women’s help-seeking and their management of sexist stereotyping in everyday interaction. We also consider the implications of our results for those working in domains such as healthcare, teaching and counseling, where interaction with individuals in need and requiring help is common

Limits to solar cycle predictability: Cross-equatorial flux plumes

Within the Babcock-Leighton framework for the solar dynamo, the strength of a cycle is expected to depend on the strength of the dipole moment or net hemispheric flux during the preceding minimum, which depends on how much flux was present in each hemisphere at the start of the previous cycle and how much net magnetic flux was transported across the equator during the cycle. Some of this transport is associated with the random walk of magnetic flux tubes subject to granular and supergranular buffeting, some of it is due to the advection caused by systematic cross-equatorial flows such as those associated with the inflows into active regions, and some crosses the equator during the emergence process. We aim to determine how much of the cross-equatorial transport is due to small-scale disorganized motions (treated as diffusion) compared with other processes such as emergence flux across the equator. We measure the cross-equatorial flux transport using Kitt Peak synoptic magnetograms, estimating both the total and diffusive fluxes. Occasionally a large sunspot group, with a large tilt angle emerges crossing the equator, with flux from the two polarities in opposite hemispheres. The largest of these events carry a substantial amount of flux across the equator (compared to the magnetic flux near the poles). We call such events cross-equatorial flux plumes. There are very few such large events during a cycle, which introduces an uncertainty into the determination of the amount of magnetic flux transported across the equator in any particular cycle. As the amount of flux which crosses the equator determines the amount of net flux in each hemisphere, it follows that the cross-equatorial plumes introduce an uncertainty in the prediction of the net flux in each hemisphere. This leads to an uncertainty in predictions of the strength of the following cycle.Comment: A&A, accepte

Full pf shell study of A = 47 and A = 49 nuclei

Complete diagonalizations in the pf major shell, lead to very good agreement with the experimental data (level schemes, transitions rates, and static moments) for the A=47 and A=49 isotopes of Ca, Sc, Ti, V, Cr, and Mn. Gamow-Teller and M1 strength functions are calculated. The necessary monopole modifications to the realistic interactions are shown to be critically tested by the spectroscopic factors for one particle transfer from 48Ca, reproduced in detail by the calculations. The collective behaviour of 47Ti, and of the mirror pairs 47V-47Cr and 49Cr-49Mn is found to follow at low spins the particle plus rotor model. It is then analysed in terms of the approximate quasi-SU(3) symmetry, for which some new results are given.Comment: 30 Pages, RevTeX and epsf.sty, 23 figures included. Postscript version available at http://www.ft.uam.es/~gabriel/a47-49.ps.g

Teaching and assessing consultation skills: an evaluation of a South African workshop on using the Leicester Assessment Package

BackgroundThe consultation is at the very centre of clinical practice. It is in the meeting between doctor and patient that the story is told (and in good practice properly heeded) and decisions are made about the cause and treatment of the patient's problem. Following one year of supervised internship, South African doctors are required to do a year of community service and these doctors mostly work in understaffed peripheral hospitals. A substantial component of this work is unsupervised consultations with patients suffering from new or complex continuing diseases. On graduation, these doctors therefore require a high level of consultation competence. They must be able to make accurate diagnoses and manage patients' problems reliably and efficiently.The Leicester Assessment Package (LAP) was originally developed to assess the consultation competence of general practitioners in the UK. It was subsequently adapted for use in undergraduate teaching. In 2002, the LAP was presented at a medical education conference in South Africa. As a result, the Department of Family Medicine at Pretoria University began using the LAP in the teaching and formative assessment of the consultation skills of senior students in outpatient clinics. In 2003, the University of the Witwatersrand introduced a four-year graduate entry medical curriculum. The Centre for Health Care Education was interested in assessing whether the LAP would be suitable for the summative assessment of the consultation performance of students during their third and four years of the new curriculum.A workshop course was organised to train senior clinicians from the Universities of Pretoria and the Witwatersrand in the use of the LAP as a means of teaching and assessing the consultation performance of South African medical students.MethodTwenty-two experienced South African medical educators participated in a three-day workshop. Their attitudes to the LAP and the forms of teaching that its use promotes were analysed by responses to pre- and post-workshop questionnaires with Likert-scale and free-text questions.ResultsThe participants were positive about the LAP at the end of the workshop. They all believed that it was a useful instrument, and a majority would apply this method in their own departments. There were continuing reservations about the feasibility of the method and some respondents felt it would require some adaptation, particularly to the criteria for awarding grades.ConclusionsThe workshop participants learnt to use an instrument developed in the United Kingdom that encourages an analytical approach to the assessment and teaching of consultation skills. They believed it would be useful in the contexts in which they worked.For full text, click here:SA Fam Pract 2006;48(3):14-14

The Overlooked Potential of Generalized Linear Models in Astronomy-III: Bayesian Negative Binomial Regression and Globular Cluster Populations

In this paper, the third in a series illustrating the power of generalized linear models (GLMs) for the astronomical community, we elucidate the potential of the class of GLMs which handles count data. The size of a galaxy's globular cluster population $N_{\rm GC}$ is a prolonged puzzle in the astronomical literature. It falls in the category of count data analysis, yet it is usually modelled as if it were a continuous response variable. We have developed a Bayesian negative binomial regression model to study the connection between $N_{\rm GC}$ and the following galaxy properties: central black hole mass, dynamical bulge mass, bulge velocity dispersion, and absolute visual magnitude. The methodology introduced herein naturally accounts for heteroscedasticity, intrinsic scatter, errors in measurements in both axes (either discrete or continuous), and allows modelling the population of globular clusters on their natural scale as a non-negative integer variable. Prediction intervals of 99% around the trend for expected $N_{\rm GC}$comfortably envelope the data, notably including the Milky Way, which has hitherto been considered a problematic outlier. Finally, we demonstrate how random intercept models can incorporate information of each particular galaxy morphological type. Bayesian variable selection methodology allows for automatically identifying galaxy types with different productions of GCs, suggesting that on average S0 galaxies have a GC population 35% smaller than other types with similar brightness.Comment: 14 pages, 12 figures. Accepted for publication in MNRA

High magnetic field studies of the Vortex Lattice structure in YBa2Cu3O7

We report on small angle neutron scattering measurements of the vortex lattice in twin-free YBa2Cu3O7, extending the previously investigated maximum field of 11~T up to 16.7~T with the field applied parallel to the c axis. This is the first microscopic study of vortex matter in this region of the superconducting phase. We find the high field VL displays a rhombic structure, with a field-dependent coordination that passes through a square configuration, and which does not lock-in to a field-independent structure. The VL pinning reduces with increasing temperature, but is seen to affect the VL correlation length even above the irreversibility temperature of the lattice structure. At high field and temperature we observe a melting transition, which appears to be first order, with no detectable signal from a vortex liquid above the transition