335 research outputs found

    Using Formative Student Feedback: A Continuous Quality Improvement Approach for Online Course Development

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    The objective of this study was to examine the use of frequent, anonymous student course surveys as a tool in supporting continuous quality improvement (CQI) principles in online instruction. The study used a qualitative, multiple-case design involving four separate online courses. Analysis methods included pattern matching/explanation building, time series analysis, and thematic analysis. Findings suggested that instructors used student feedback to make course changes that alleviated technical difficulties, added and clarified content, and contributed to future course changes. Students and instructors responded positively to the opportunity to give and receive anonymous feedback and felt that it helped improve the course. It is uncertain, however, whether using CQI principles had an impact on end-of-semester teacher course quality ratings. An important finding from the research is that students like to be asked to help improve their learning experience, as long as the instructor listens and responds to their feedback. Evaluation is a valuable component of instructional design theories, which are based on the philosophy that the best designs result from an iterative process. Using a synergistic CQI approach, this study indicates that it is possible for changes to be made more quickly to a course when students are involved in the process. The combination of frequent student feedback with a willing and experienced instructor who can make expert course revision decisions allows the process of course improvement to be enhanced

    SkyMapper Filter Set: Design and Fabrication of Large Scale Optical Filters

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    The SkyMapper Southern Sky Survey will be conducted from Siding Spring Observatory with u, v, g, r, i and z filters that comprise glued glass combination filters of dimension 309x309x15 mm. In this paper we discuss the rationale for our bandpasses and physical characteristics of the filter set. The u, v, g and z filters are entirely glass filters which provide highly uniform band passes across the complete filter aperture. The i filter uses glass with a short-wave pass coating, and the r filter is a complete dielectric filter. We describe the process by which the filters were constructed, including the processes used to obtain uniform dielectric coatings and optimized narrow band anti-reflection coatings, as well as the technique of gluing the large glass pieces together after coating using UV transparent epoxy cement. The measured passbands including extinction and CCD QE are presented.Comment: 9 pages, 2 tables, 7 figure

    The Planetary Nebulae Spectrograph: the green light for Galaxy Kinematics

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    Planetary nebulae are now well established as probes of galaxy dynamics and as standard candles in distance determinations. Motivated by the need to improve the efficiency of planetary nebulae searches and the speed with which their radial velocities are determined, a dedicated instrument - the Planetary Nebulae Spectrograph or PN.S - has been designed and commissioned at the 4.2m William Herschel Telescope. The high optical efficiency of the spectrograph results in the detection of typically ~ 150 PN in galaxies at the distance of the Virgo cluster in one night of observations. In the same observation the radial velocities are obtained with an accuracy of ~ 20 km/sComment: Accepted by PASP, to appear November 2002; the figures have been degraded for archival purpose

    Structure of 13^{13}Be probed via secondary beam reactions

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    The low-lying level structure of the unbound neutron-rich nucleus 13^{13}Be has been investigated via breakup on a carbon target of secondary beams of 14,15^{14,15}B at 35 MeV/nucleon. The coincident detection of the beam velocity 12^{12}Be fragments and neutrons permitted the invariant mass of the 12^{12}Be+nn and 12^{12}Be+nn+nn systems to be reconstructed. In the case of the breakup of 15^{15}B, a very narrow structure at threshold was observed in the 12^{12}Be+nn channel. Contrary to earlier stable beam fragmentation studies which identified this as a strongly interacting ss-wave virtual state in 13^{13}Be, analysis here of the 12^{12}Be+nn+nn events demonstrated that this was an artifact resulting from the sequential-decay of the 14^{14}Be(2+^+) state. Single-proton removal from 14^{14}B was found to populate a broad low-lying structure some 0.70 MeV above the neutron-decay threshold in addition to a less prominent feature at around 2.4 MeV. Based on the selectivity of the reaction and a comparison with (0-3)ω\hbar\omega shell-model calculations, the low-lying structure is concluded to most probably arise from closely spaced Jπ^\pi=1/2+^+ and 5/2+^+ resonances (Er_r=0.40±\pm0.03 and 0.850.11+0.15^{+0.15}_{-0.11} MeV), whilst the broad higher-lying feature is a second 5/2+^+ level (Er_r=2.35±\pm0.14 MeV). Taken in conjunction with earlier studies, it would appear that the lowest 1/2+^+ and 1/2^- levels lie relatively close together below 1 MeV.Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical Review

    Neutron-hole strength in the N = 81 isotones

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    The distribution of neutron-hole strength has been studied in the N 81 isotones 137Ba, 139Ce, 141Nd and 143Sm through the single-neutron removing reactions (p,d) and ( 3He,α), at energies of 23 and 34 MeV, respectively. Systematic cross section measurements were made at angles sensitive to the transferred angular momentum, and spectroscopic factors extracted through a distorted-wave Born approximation analysis. Application of the MacFarlane-French sum rules indicate an anomalously low summed g7/2 spectroscopic factor, most likely due to extensive fragmentation of the single-particle strength. Single-particle energies, based upon the centroids of observed strength, are presented. © Published under licence by IOP Publishing Ltd

    A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector

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    We describe a compact, ultra-clean device used to deploy radioactive sources along the vertical axis of the KamLAND liquid-scintillator neutrino detector for purposes of calibration. The device worked by paying out and reeling in precise lengths of a hanging, small-gauge wire rope (cable); an assortment of interchangeable radioactive sources could be attached to a weight at the end of the cable. All components exposed to the radiopure liquid scintillator were made of chemically compatible UHV-cleaned materials, primarily stainless steel, in order to avoid contaminating or degrading the scintillator. To prevent radon intrusion, the apparatus was enclosed in a hermetically sealed housing inside a glove box, and both volumes were regularly flushed with purified nitrogen gas. An infrared camera attached to the side of the housing permitted real-time visual monitoring of the cable's motion, and the system was controlled via a graphical user interface.Comment: Revised author affiliations, corrected typos, made minor improvements to text, and revised reference

    Search for extraterrestrial antineutrino sources with the KamLAND detector

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    We present the results of a search for extraterrestrial electron antineutrinos (νˉe\bar{\nu}_{e}'s) in the energy range 8.3MeV<Eνˉe<31.8MeV8.3 MeV < E_{\bar{\nu}_{e}} < 31.8 MeV using the KamLAND detector. In an exposure of 4.53 kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of 8^{8}B solar νe\nu_{e}'s converting into νˉe\bar{\nu}_{e}'s at 5.3×1055.3 \times 10^{-5} (90% C.L.), if we assume an undistorted νˉe\bar{\nu}_{e} shape. This limit corresponds to a solar νˉe\bar{\nu}_{e} flux of 93cm2s193 cm^{-2} s^{-1} or an event rate of 1.6events(ktonyear)11.6 events (kton-year)^{-1} above the energy threshold (Eνˉe>8.3MeV)(E_{\bar{\nu}_{e}} > 8.3 MeV). The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles.Comment: 22 pages, 6 figure

    Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector

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    We report a measurement of the neutrino-electron elastic scattering rate from 8B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5 MeV analysis threshold is 1.49+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1. The analysis threshold is driven by 208Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic 11Be. The measured rate is consistent with existing measurements and with Standard Solar Model predictions which include matter enhanced neutrino oscillation.Comment: 6 pages, 3 figure
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