An Empirical Pixel-Based Correction for Imperfect CTE. I. HST's Advanced Camera for Surveys

We use an empirical approach to characterize the effect of charge-transfer efficiency (CTE) losses in images taken with the Wide-Field Channel of the Advanced Camera for Surveys. The study is based on profiles of warm pixels in 168 dark exposures taken between September and October 2009. The dark exposures allow us to explore charge traps that affect electrons when the background is extremely low. We develop a model for the readout process that reproduces the observed trails out to 70 pixels. We then invert the model to convert the observed pixel values in an image into an estimate of the original pixel values. We find that when we apply the image-restoration process to science images with a variety of stars on a variety of background levels, it restores flux, position, and shape. This means that the observed trails contain essentially all of the flux lost to inefficient CTE. The Space Telescope Science Institute is currently evaluating this algorithm with the aim of optimizing it and eventually providing enhanced data products. The empirical procedure presented here should also work for other epochs (eg., pre-SM4), though the parameters may have to be recomputed for the time when ACS was operated at a higher temperature than the current -81 C. Finally, this empirical approach may also hold promise for other instruments, such as WFPC2, STIS, the ACS's HRC, and even WFC3/UVIS.Comment: 86 pages, 25 figures (6 in low resolution). PASP accepted on July 21, 201

Annular Solar Eclipse of 10 May 1994

An annular eclipse of the Sun will be widely visible from the Western Hemisphere on 10 May 1994. The path of the Moon's shadow passes through Mexico, the United States of America, maritime Canada, the North Atlantic, the Azores and Morocco. Detailed predictions for this event are presented and include tables of geographic coordinates of the annular path, local circumstances for hundreds of cities, maps of the path of annular and partial eclipse, weather prospects, and the lunar limb profile

Impact of Inundation and Changes in Garrison Diversion Project Plans on the North Dakota Economy

This report attempts to identify the economic consequences of the Garrison Diversion Unit and North Dakota's Missouri River impoundments from the state's perspective. The authors hope it will assist individuals and groups making decisions affecting the future development of North Dakota's water resources.Resource /Energy Economics and Policy,

Genetic improvement of passionfruit to achieve improved disease resistance

The purpose of this report is to present the final results of all activities conducted under HAL Project PF04001 'Genetic improvement of passionfruit to achieve improved disease resistance'. The report provides a summary of project findings, a description of technology transfer activities, and recommendations arising from the outcomes of the project. The overall objective of this project was to develop improved disease management strategies for the Australian passionfruit industry through breeding and improvements in our understanding of fungal and viral diseases of passionfruit. This project targeted three areas; 1) breeding of rootstocks and scions with improved virus and cold tolerance, 2) the investigation of defence enzymes in passionfruit and the use of defence activators and 3) understanding the role of infection by single and multiple viruses and examining the use of PWV mild-strain cross-protection

Toward High-Precision Astrometry with WFPC2. I. Deriving an Accurate PSF

The first step toward doing high-precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to avoiding systematic positional error in undersampled images is to determine an extremely accurate point-spread function (PSF). We apply the concept of the {\it effective} PSF, and show that in images that consist of pixels it is the ePSF, rather than the often-used instrumental PSF, that embodies the information from which accurate star positions and magnitudes can be derived. We show how, in a rich star field, one can use the information from dithered exposures to derive an extremely accurate effective PSF by iterating between the PSF itself and the star positions that we measure with it. We also give a simple but effective procedure for representing spatial variations of the HST PSF. With such attention to the PSF, we find that we are able to measure the position of a single reasonably bright star in a single image with a precision of 0.02 pixel (2 mas in WF frames, 1 mas in PC), but with a systematic accuracy better than 0.002 pixel (0.2 mas in WF, 0.1 mas in PC), so that multiple observations can reliably be combined to improve the accuracy by $\surd N$.Comment: 33 pp. text + 15 figs.; accepted by PAS

The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters

We present new measurements of the centers for 65 Milky Way globular clusters. Centers were determined by fitting ellipses to the density distribution within the inner 2\arcmin of the cluster center, and averaging the centers of these ellipses. The symmetry of clusters was also analyzed by comparing cumulative radial distributions on opposite sides of the cluster across a grid of trial centers. All of the determinations were done with stellar positions derived from a combination of two single-orbit ACS images of the core of the cluster in $F606W$ and $F814W$. We find that the ellipse-fitting method provides remarkable accuracy over a wide range of core sizes and density distributions, while the symmetry method is difficult to use on clusters with very large cores, or low density. The symmetry method requires a larger field, or a very sharply peaked density distribution.Comment: 17 pages, 8 figures, Accepted for publication in AJ, supplementary material will be available upon publicatio

Students\u27 Reflection on Community Service Learning

Internships are a rapidly expanding educational technique to enhance students\u27 ability to learn. Internships permit and encourage students to experience the real world while receiving academic credit. Seekonk High School in Seekonk, Massachusetts, has an internship program for high school seniors called Independent Study. It allows students to leave school one day a week for the school year and volunteer within the community. Students receive academic credit for their participation in community service learning

Development and Evaluation of a Mentoring Framework for Technology & Engineering Teachers in Alpine School District

It’s the beginning of a new school year. Administrators are preparing teacher trainings and best procedures and policies for their students. Thoughtful counselors methodically plan the right schedule so students can have the most success. The group with the most excitement might just be the students. Who will be in your class? Who will be your new teacher? What will your classroom be decorated like? Do you have all of the needed supplies? Then we come to the last group: the teachers. For the teachers, there is also a lot of excitement within this group accompanied by some worry and apprehension. For the veteran teachers, there is excitement, to start over with new kids and the new opportunities to learn and teach. New teachers finally get to do what they have been studying and preparing for the past few years. Their name is on the door. The new teachers are responsible for these kids. Are they ready for this? Do these new teachers have the right lesson plans? Do they have enough teaching skills to pull this off? This scenario illustrates the need for and benefit of new teacher mentoring programs. Mentoring programs are designed to help reassure and enable new teachers that they can be successful. Mentors visit new teachers, giving help and aid wherever possible. Often this aid comes in the form of collaboration and the sharing of experience. Mentors share ideas on classroom organization, classroom management, lesson delivery method, interaction with parents, and what lessons to teach. Beyond collaboration, mentors observe how new teachers’ lessons are taught to provide positive feedback and constructive criticism

Leave School and Learn : Seekonk High School\u27s Independent Study Program

Change comes slowly to education. Schools are bound by tradition and a high school curriculum often remains constant. There are many reasons for a curriculun1 not changing, including meeting the course pre-requisites for college admission. Often, however, there is a resistance to change. As a result, many students take the same courses as their parents took when in school