Image Subtraction Reduction of Open Clusters M35 & NGC 2158 In The K2 Campaign-0 Super-Stamp

Observations were made of the open clusters M35 and NGC 2158 during the initial K2 campaign (C0). Reducing these data to high-precision photometric time-series is challenging due to the wide point spread function (PSF) and the blending of stellar light in such dense regions. We developed an image-subtraction-based K2 reduction pipeline that is applicable to both crowded and sparse stellar fields. We applied our pipeline to the data-rich C0 K2 super-stamp, containing the two open clusters, as well as to the neighboring postage stamps. In this paper, we present our image subtraction reduction pipeline and demonstrate that this technique achieves ultra-high photometric precision for sources in the C0 super-stamp. We extract the raw light curves of 3960 stars taken from the UCAC4 and EPIC catalogs and de-trend them for systematic effects. We compare our photometric results with the prior reductions published in the literature. For detrended, TFA-corrected sources in the 12--12.25 $\rm K_{p}$ magnitude range, we achieve a best 6.5 hour window running rms of 35 ppm falling to 100 ppm for fainter stars in the 14--14.25 $\rm K_{p}$ magnitude range. For stars with $\rm K_{p}> 14$, our detrended and 6.5 hour binned light curves achieve the highest photometric precision. Moreover, all our TFA-corrected sources have higher precision on all time scales investigated. This work represents the first published image subtraction analysis of a K2 super-stamp. This method will be particularly useful for analyzing the Galactic bulge observations carried out during K2 campaign 9. The raw light curves and the final results of our detrending processes are publicly available at \url{http://k2.hatsurveys.org/archive/}.Comment: Accepted for publication in PASP. 14 pages, 5 figures, 2 tables. Light curves available from http://k2.hatsurveys.org/archive

High Precision Photometry for K2 Campaign 1

The two reaction wheel K2 mission promises and has delivered new discoveries in the stellar and exoplanet fields. However, due to the loss of accurate pointing, it also brings new challenges for the data reduction processes. In this paper, we describe a new reduction pipeline for extracting high precision photometry from the K2 dataset, and present public light curves for the K2 Campaign 1 target pixel dataset. Key to our reduction is the derivation of global astrometric solutions from the target stamps, from which accurate centroids are passed on for high precision photometry extraction. We extract target light curves for sources from a combined UCAC4 and EPIC catalogue -- this includes not only primary targets of the K2 campaign 1, but also any other stars that happen to fall on the pixel stamps. We provide the raw light curves, and the products of various detrending processes aimed at removing different types of systematics. Our astrometric solutions achieve a median residual of ~ 0.13". For bright stars, our best 6.5 hour precision for raw light curves is ~20 parts per million (ppm). For our detrended light curves, the best 6.5 hour precisions achieved is ~15 ppm. We show that our detrended light curves have fewer systematic effects (or trends, or red-noise) than light curves produced by other groups from the same observations. Example light curves of transiting planets and a Cepheid variable candidate, are also presented. We make all light curves public, including the raw and de-trended photometry, at http://k2.hatsurveys.org.Comment: submitted to MNRA

Ogbu and the debate on educational achievement: an exploration of the links between education, migration, identity and belonging

This paper looks at some of the issues raised by Ogbu’s work in relation to the education of different minority ethnic groups. Ogbu poses questions such as the value attached to education, its links to the future and its measurable outcomes in terms of ‘success’ as experienced by black participants. The desire for better life chances leads families to consider migration to a new country or resettlement within the same country, thus making migration both a local and a global phenomenon. As an example, attention is drawn to the situation facing South Asian children and their families in the UK. In terms of ethnicity and belonging, the wider question that is significant for many countries in the West after ‘Nine-Eleven’ is the education of Muslim children. A consideration of this current situation throws Ogbu’s identification of ‘autonomous minority’ into question. It is argued that a greater understanding of diverse needs has to be accompanied by a concerted effort to confront racism and intolerance in schools and in society, thus enabling all communities to make a useful contribution and to avoid the ‘risk’ of failure and disenchantment

Controlling an Invasive Forest Pest, the Asiatic Oak Weevil (cyrtepistomus castaneus), Using Prescribed Fire

Invasive species are non-native species whose presence is already or is likely to cause harm to the local ecosystem or economy, or human, animal, and plant health (Beck et al, 2006, p.415). The invasive Asiatic oak weevil is the primary leaf-feeding insect on oak trees in the Missouri Ozarks with larvae feeding on the roots of trees and the adults on the leaves (Marquis and Bhatti-Catano, 2017). The goal of this study was to determine if prescribed burns lower the abundance of adult and larval weevils. Eight pairs of 200 m x 200 m plots in the oak-hickory forest at the Tyson Research Station near Eureka, MO were used for the experimental environment. One of each plot pairs were surface-burned in early Spring 2018. In June 2018, mesh emergence traps with jars secured on top were placed under four white and four black oak trees on each plot. From late June-August 2018 the weevils were counted as they emerged and analyzed to determine effects of the sampling date, tree species, aspect, slope, weight, and ultimately weevil density in burned versus unburned plots. Notable differences in the density of weevils on burned vs. unburned plots were observed in favor of the hypothesis. These findings support the need for prescribed fire in the management of Missouri’s forests. References Beck, G. K. Zimmerman, J.D. Schardt, J. Stone, R.R. Lukens, S. Reichard, J. Randall, A.A. Cangelosi, D. Cooper, and J.P. Thompson. 2006. Invasive Species Defined in a Policy Context: Recommendations from the Federal Invasive Species Advisory Committee. Invasive Plant Science and Management 1(4):414-421. Marquis, R. J., & Bhatti-Catano, L. (2017). Impacts of the Asiatic oak weevil (Cyrtepistomus castaneus) on the growth and survivorship of black oak (Quercus velutina) seedlings. Retrieved February 10, 2019, from https://tyson.wustl.edu/allprojects/2017/10/4/impacts of-the-asiatic-oak-weevil-icyrtepistomus-castaneusi-on-the-growth-and-survivorship-of black-oak-iquercus-velutinai-seedling

Deceptive appearance of a normal variant of scaphoid bone in a teenage patient: a diagnostic challenge

Scaphoid fractures are a common injury in late teens and mid twenties with a peak period in skeletally immature children at about 15 years of age, although considered to be rare in first decade of life, its exact incidence in early teen age remains to be a subject of debate. We report an unusual case of anatomical variation of scaphoid bone at the level of waist which could potentially cause diagnostic confusion. A 14-years-old boy presented in the fracture clinic 2 weeks after injury to his Right wrist which was managed in a scaphoid cast. X-ray examinations, both at the time of injury and later on in the fracture clinic revealed features suspicious of a fracture at the level of waist of the scaphoid bone, however the clinical examination did not correlate with imaging, in view of that radiological imaging of the unaffected side was performed for comparison, which revealed it to be an anatomical variant of scaphoid at this age. To our knowledge there are very few cases of such variation reported in literature in this age group of patients. This case highlights the importance of anatomical variants in scaphoid bone in this age group, which might pose a diagnostic challenge and the need for appropriate management plan and reassurance to avoid unnecessary anxiety

Low-density series expansions for directed percolation III. Some two-dimensional lattices

We use very efficient algorithms to calculate low-density series for bond and site percolation on the directed triangular, honeycomb, kagom\'e, and $(4.8^2)$ lattices. Analysis of the series yields accurate estimates of the critical point $p_c$ and various critical exponents. The exponent estimates differ only in the $5^{th}$ digit, thus providing strong numerical evidence for the expected universality of the critical exponents for directed percolation problems. In addition we also study the non-physical singularities of the series.Comment: 20 pages, 8 figure