6,524 research outputs found
Analysis and assessment of film materials and associated manufacturing processes for a solar sail
Candidate resin manufacturers and film producers were surveyed to determine the availability of key materials and to establish the capabilities of fabricators to prepare ultrathin films of these materials within the capacity/cost/time constraints of the Halley program. Infrared spectra of three candidate samples were obtained by pressing each sample against an internal reflection crystal with the polymer sandwiched between the crystal and the metal backing. The sample size was such that less than one-fourth of the surface of the crystal was covered with the sample. This resulted in weak spectra requiring a six-fold expansion. Internal reflection spectra of the three samples were obtained using both a KRS-5 and a Ge internal reflection crystal. Subtracted infrared spectra of the three samples are presented
Pedagogy First, Technology Second: teaching & learning information literacy online
This paper explores the pedagogical and technical issues, challenges and outcomes of creating an online information literacy course. Currently under development, this course will be offered as a parallel study option to Advanced Information Retrieval Skills (AIRS:IFN001 ) for QUT postgraduate students, a compulsory face-to-face course for all QUT research students. The aim of this project is to optimise students’ access to AIRS:IFN001 and meet the University’s objectives regarding flexible delivery and online teaching. Still in its developmental stages, AIRS::Online extends beyond the current notion of static online information literacy tutorials by providing a facilitated, student focussed learning environment comprising content and learning experiences enhanced by appropriate multimedia technology and resources which engage students in planned facilitated and/or self-paced learning events. Course assessment is formative and summative, and is comprised of a research log and reflective journal to provide a means for reviewing the content and key process of advanced information searching and retrieval
X-ray Flares from Markarian 501
Motivated by the recent finding of hierarchical X-ray flaring phenomenon in
Mrk 421, we conducted a systematic search for X-ray flares from Mrk 501,
another well-known TeV blazar, by making use of the rich {\em RXTE} archival
database. We detected flares over a wide range of timescales, from months down
to minutes, as in the case of Mrk 421. However, the flares do not seem to occur
nearly as frequently in Mrk 501 as in Mrk 421 on any of the timescales. The
flaring hierarchy also seems apparent in Mrk 501, suggesting that it might be
common among TeV blazars. The results seem to imply a scale-invariant physical
origin of the flares (large or small). The X-ray spectrum of the source shows a
general trend of hardening toward the peak of long-duration flares, with
indication of spectral hysteresis, which is often seen in TeV blazars. However,
the data are not of sufficient quality to allow us to draw definitive
conclusions about spectral variability associated with more rapid but weaker
flares. We critically examine a reported sub-hour X-ray flare from Mrk 501, in
light of intense background flaring activity at the time of the observation,
and concluded that the flare is likely an artifact. On the other hand, we did
identify a rapid X-ray flare that appears to be real. It lasted only for about
15 minutes, during which the flux of the source varied by about 30%.
Sub-structures are apparent in its profile, implying variabilities on even
shorter timescales. Such rapid variabilities of Mrk 501 place severe
constraints on the physical properties of the flaring region in the jet, which
have serious implications on the emission models proposed for TeV blazars.Comment: 23 pages, 11 figures, accepted for publication in Ap
Upper Limits on the Extragalactic Background Light from the Gamma-Ray Spectra of Blazars
The direct measurement of the extragalactic background light (EBL) is
difficult at optical to infrared wavelengths because of the strong foreground
radiation originating in the Solar System. Very high energy (VHE, E100 GeV)
gamma rays interact with EBL photons of these wavelengths through pair
production. In this work, the available VHE spectra from six blazars are used
to place upper limits on the EBL. These blazars have been detected over a range
of redshifts and a steepening of the spectral index is observed with increasing
source distance. This can be interpreted as absorption by the EBL. In general,
knowledge of the intrinsic source spectrum is necessary to determine the
density of the intervening EBL. Motivated by the observed spectral steepening
with redshift, upper limits on the EBL are derived by assuming that the
intrinsic spectra of the six blazars are . Upper limits are
then placed on the EBL flux at discrete energies without assuming a specific
spectral shape for the EBL. This is an advantage over other methods since the
EBL spectrum is uncertain.Comment: 33 pages, 14 figures, accepted by Ap
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Risk communication in environmental restoration programs
The author advocates adoption of a convergence model in place of the traditional source-receiver model of communication for communicating with members of the public who have a stake in remediation of a nearby site. The source-receiver model conceives of communication as the transmission of a message from a risk management agency (sender) to a target audience of the public (receivers). The underlying theme is that the sender intends to change the perception of the receiver of either the issue or the sender of information. The theme may be appropriate for health campaigns which seek to change public behavior; however, the author draws on her experience at a DOE site undergoing remediation to illustrate why the convergence model is more appropriate in the context of cleanup. This alternative model focuses on the Latin derivation of communication as sharing or making common to many, i.e., as involving a relationship between participants who engage in a process of communication. The focus appears to be consistent with recently issued DOE policy that calls for involving the public in identifying issues and problems and in formulating and evaluating decision alternatives in cleanup. By emphasizing context, process and participants, as opposed to senders and receivers, the model identifies key issues to address in facilitating consensus concerning the risks of cleanup. Similarities between the institutional context of DOE and DOD suggest that a convergence model may also prove to be an appropriate conceptual foundation for risk communication at contaminated DOD sites
A four year prospective study of age-related cognitive change in adults with Down's syndrome
Background. While neuropathological studies indicate a
high risk for Alzheimer's disease in adults
with Down's syndrome, neuropsychological studies suggest a lower prevalence
of dementia. In this
study, cognitive deterioration in adults with Down's syndrome was
examined prospectively over
4 years to establish rates and profiles of cognitive deterioration.Methods. Fifty-seven people with Down's syndrome aged
30 years or older were assessed using a
battery of neuropsychological tests on five occasions across 50 months.
Assessments of domains of
cognitive function known to change with the onset of Alzheimer related
dementia were employed.
These included tests of learning, memory, orientation, agnosia, apraxia
and aphasia. The individual
growth trajectory methodology was used to analyse change over time.Results. Severe cognitive deterioration, such as acquired,
apraxia and agnosia, was evident in 28·3%
of those aged over 30 and a higher prevalence of these impairments was
associated with older age.
The rate of cognitive deterioration also increased with age and degree
of pre-existing cognitive
impairment. Additionally, deterioration in memory, learning and orientation
preceded the
acquisition of aphasia, agnosia and apraxia.Conclusions. The prevalence of cognitive impairments consistent
with the presence of Alzheimer's
disease is lower than that suggested by neuropathological studies. The
pattern of the acquisition of
cognitive impairments in adults with Down's syndrome is similar to
that seen in individuals with
Alzheimer's disease who do not have Down's syndrome.</jats:p
Content moderators’ strategies for coping with the stress of moderating content online
Content moderators are exposed to a range of stressors at work, including analysing content that has been flagged as harmful. However, not much is known about their specific coping strategies. Depth interviews were conducted with 11 content moderators exposed to child sexual abuse material (CSAM) as part of their job, and thematically analysed to investigate both individual coping strategies and those deployed organisationally. Results highlighted the importance of social support especially from colleagues. Supportive relationships fulfilled several needs including helping content moderators process emotions, normalise their reactions and reducing feelings of isolation. Additionally, the ability to create boundaries between work and home life was important for distancing and distracting themselves from the work. Moderators expressed a preference for mandatory, individual therapy with professionals who had specific experience supporting those exposed to CSAM and reported disclosure was hindered if not, due to worries about traumatising the therapist. How content moderators cope and can be further supported are discussed
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