1,472 research outputs found
On the use of electron-multiplying CCDs for astronomical spectroscopy
Conventional CCD detectors have two major disadvantages: they are slow to
read out and they suffer from read noise. These problems combine to make
high-speed spectroscopy of faint targets the most demanding of astronomical
observations. It is possible to overcome these weaknesses by using
electron-multiplying CCDs (EMCCDs). EMCCDs are conventional frame-transfer
CCDs, but with an extended serial register containing high-voltage electrodes.
An avalanche of secondary electrons is produced as the photon-generated
electrons are clocked through this register, resulting in signal amplification
that renders the read noise negligible. Using a combination of laboratory
measurements with the QUCAM2 EMCCD camera and Monte Carlo modelling, we show
that it is possible to significantly increase the signal-to-noise ratio of an
observation by using an EMCCD, but only if it is optimised and utilised
correctly. We also show that even greater gains are possible through the use of
photon counting. We present a recipe for astronomers to follow when setting up
a typical EMCCD observation which ensures that maximum signal-to-noise ratio is
obtained. We also discuss the benefits that EMCCDs would bring if used with the
next generation of extremely large telescopes. Although we mainly consider the
spectroscopic use of EMCCDs, our conclusions are equally applicable to imaging.Comment: 18 figures, 3 tables, 18 page
Case studies to enhance online student evaluation: Bond University – Surveying students online to improve learning and teaching
One of the most sensible ways of improving learning and teaching is to ask the students for feedback. At the end of each teaching period (i.e. semester or term) all universities and many schools survey their students. Usually these surveys are managed online. Questions ask for student perceptions about teaching, assessment and workload. The survey administrators report four common problems
Cognitive improvement following repair of a basal encephalocele.
We report the case of a 55-year-old woman presenting with progressive memory impairment secondary to a transsphenoidal encephalocele involving her dominant medial temporal lobe. Her clinical deterioration was accompanied by radiological progression in the encephalocele's size and associated encephalomalacia. Through a temporal craniotomy, her encephalocele was resected and the defect closed. Baseline neuropsychological assessment indicated global cognitive impairment, but post-operatively, she reported improved memory and concentration. Standardized assessment reflected an improvement in perceptual skills and an associated improved recall of a complex figure. This is the first case report to date of a patient's memory improving following treatment of a basal encephalocele
Tight constraints on the existence of additional planets around HD 189733
We report a transit timing study of the transiting exoplanetary system HD
189733. In total we observed ten transits in 2006 and 2008 with the 2.6-m
Nordic Optical Telescope, and two transits in 2007 with the 4.2-m William
Herschel Telescope. We used Markov-Chain Monte Carlo simulations to derive the
system parameters and their uncertainties, and our results are in a good
agreement with previously published values. We performed two independent
analyses of transit timing residuals to place upper mass limits on putative
perturbing planets. The results show no evidence for the presence of planets
down to 1 Earth mass near the 1:2 and 2:1 resonance orbits, and planets down to
2.2 Earth masses near the 3:5 and 5:3 resonance orbits with HD 189733b. These
are the strongest limits to date on the presence of other planets in this
system.Comment: 10 pages, 4 figures, accepted by MNRA
Challenges That Hinder Parturients to Deliver in Health Facilities: a Qualitative Analysis in Two Districts of Indonesia
Background: There are many challenges women face to be able to give birth in health facilities in many parts of Indonesia. This study explores the roles and observations of close-to-community maternal health providers and other community members on potential barriers faced by women to deliver in health facilities in two districts within The Archipelago. Methods: Employing an explorative qualitative approach, 110 semi-structured interviews and 7 focus group discussions were conducted in 8 villages in Southwest Sumba, in the East Nusa Tenggara province, and in 8 villages in Cianjur, in the West Java province. The participants included village midwives, Posyandu volunteer (village health volunteers), traditional birth attendants (TBAs), mothers, men, village heads and district health officials. Results: The main findings were mostly similar in the two study areas. However, there were some key differences. Preference for TBA care, traditional beliefs, a lack of responsiveness of health providers to local traditions, distance, cost of travel and indirect costs of accompanying family members were all barriers to patients attending health facilities for the birth of their child. TBAs were the preferred health providers in most cases due to their close proximity at the time of childbirth and their adherence to traditional practices during pregnancy and delivery. Conclusions: Improving collaborations between midwives and TBAs, collaboration, and responsiveness to traditional practices within health facilities and effective health promotion campaigns about the benefits of giving birth in health facilities may increase the use of health facilities in both study areas. 
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