727 research outputs found
On the spin modulated circular polarization from the intermediate polars NY Lup and IGRJ1509-6649
We report on high time resolution, high signal/noise, photo-polarimetry of
the intermediate polars NY Lup and IGRJ1509-6649. Our observations confirm the
detection and colour dependence of circular polarization from NY Lup and
additionally show a clear white dwarf, spin modulated signal. From our new high
signal/noise photometry we have unambiguously detected wavelength dependent
spin and beat periods and harmonics thereof. IGRJ1509-6649 is discovered to
also have a particularly strong spin modulated circularly polarized signal. It
appears double peaked through the I filter and single peaked through the B
filter, consistent with cyclotron emission from a white dwarf with a relatively
strong magnetic field.
We discuss the implied accretion geometries in these two systems and any
bearing this may have on the possible relationship with the connection between
polars and soft X-ray-emitting IPs. The relatively strong magnetic fields is
also suggestive of them being polar progenitors.Comment: 8 pages, 6 figures and 1 table. Accepted for publication in MNRA
Exploring the potential of knowledge brokering to enhance natural resource management : findings from the Catchment Knowledge Exchange project in Victoria
Despite significant efforts in natural resource management (NRM), the environmental condition of Victoria’s catchments is mostly ‘poor to moderate’, and continuing to decline in many places. NRM is a complex undertaking involving social, economic, and environmental objectives, across policy, research, and practice dimensions. It is therefore not easy to ensure that the knowledge required to underpin effective NRM is readily available to practitioners. Knowledge brokering is an emerging approach with the potential to improve knowledge sharing and exchange. While it has attracted attention in other areas of public interest (such as health and information technology), its potential in NRM has received relatively limited attention. This article reports on a Victorian knowledge brokering case study which was a major element in the Catchment Knowledge Exchange project. A key finding is that knowledge brokering is a role that is being undertaken informally, without proper acknowledgement or definition. This raises challenges for knowledge management in the context of NRM. We conclude that the ‘people’ component of knowledge brokering is the driving element, although organisational processes and information technologies are critical in enhancing the effectiveness of knowledge brokers. Demonstrating the benefits of knowledge brokering in terms of the ultimate measure of its contribution towards improving the condition of catchments remains a challenge
The first WASP public data release
The WASP (wide angle search for planets) project is an exoplanet transit survey that has been automatically taking wide field images since 2004. Two instruments, one in La Palma and the other in South Africa, continually monitor the night sky, building up light curves of millions of unique objects. These light curves are used to search for the characteristics of exoplanetary transits. This first public data release (DR1) of the WASP archive makes available all the light curve data and images from 2004 up to 2008 in both the Northern and Southern hemispheres. A web interface () to the data allows easy access over the Internet. The data set contains 3 631 972 raw images and 17 970 937 light curves. In total the light curves have 119 930 299 362 data points available between them
Bostonia: The Boston University Alumni Magazine. Volume 11
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Polarized QPOs from the INTEGRAL polar IGRJ14536-5522 (=Swift J1453.4-5524)
We report optical spectroscopy and high speed photometry and polarimetry of
the INTEGRAL source IGRJ14536-5522 (=Swift J1453.4-5524). The photometry,
polarimetry and spectroscopy are modulated on an orbital period of 3.1564(1)
hours. Orbital circularly polarized modulations are seen from 0 to -18 per
cent, unambiguously identifying IGRJ14536-5522 as a polar.
Some of the high speed photometric data show modulations that are consistent
with quasi-periodic oscillations (QPOs) on the order of 5-6 minutes.
Furthermore, for the first time, we detect the (5-6) minute QPOs in the
circular polarimetry. We discuss the possible origins of these QPOs. We also
include details of HIPPO, a new high-speed photo-polarimeter used for some of
our observations.Comment: Accepted for publication by MNRAS. The paper contains 7 figures and 1
tabl
The bright unidentified gamma-ray source 1FGL J1227.9-4852: Can it be associated with an LMXB?
We present an analysis of high energy (HE; 0.1-300 GeV) gamma-ray
observations of 1FGL J1227.9-4852 with the Fermi Gamma-ray Space Telescope,
follow-up radio observations with the Australia Telescope Compact Array, Giant
Metrewave Radio Telescope and Parkes radio telescopes of the same field and
follow-up optical observations with the ESO VLT. We also examine archival
XMM-Newton and INTEGRAL X-ray observations of the region around this source.
The gamma-ray spectrum of 1FGL J1227.9-4852 is best fit with an exponentially
cutoff power-law, reminiscent of the population of pulsars observed by Fermi. A
previously unknown, compact radio source within the 99.7% error circle of 1FGL
J1227.9-4852 is discovered and has a morphology consistent either with an AGN
core/jet structure or with two roughly symmetric lobes of a distant radio
galaxy. A single bright X-ray source XSS J12270-4859, a low-mass X-ray binary,
also lies within the 1FGL J1227.9-4852 error circle and we report the first
detection of radio emission from this source. The potential association of 1FGL
J1227.9-4852 with each of these counterparts is discussed. Based upon the
available data we find the association of the gamma-ray source to the compact
double radio source unlikely and suggest that XSS J12270-4859 is a more likely
counterpart to the new HE source. We propose that XSS J12270-4859 may be a
millisecond binary pulsar and draw comparisons with PSR J1023+0038.Comment: Accepted for publication in MNRAS; 9 pages, 8 figures, 2 table
Increasing Dominance - the Role of Advertising, Pricing and Product Design
Despite the empirical relevance of advertising strategies in concentrated markets, the economics literature is largely silent on the effect of persuasive advertising
strategies on pricing, market structure and increasing (or decreasing) dominance. In a simple model of persuasive advertising and pricing with differentiated goods,
we analyze the interdependencies between ex-ante asymmetries in consumer appeal, advertising and prices. Products with larger initial appeal to consumers will
be advertised more heavily but priced at a higher level - that is, advertising and price discounts are strategic substitutes for products with asymmetric initial appeal.
We find that the escalating effect of advertising dominates the moderating effect of pricing so that post-competition market shares are more asymmetric than pre-competition differences in consumer appeal. We further find that collusive advertising (but competitive pricing) generates the same market outcomes, and that network effects lead to even more extreme market outcomes, both directly and via
the effect on advertising
The association between subjective memory complaint and objective cognitive function in older people with previous major depression
The goal of this study is to investigate associations between subjective memory complaint and objective cognitive performance in older people with previous major depression-a high-risk sample for cognitive impairment and later dementia. A cross-sectional study was carried out in people aged 60 or over with previous major depression but not fulfilling current major depression criteria according to DSM-IV-TR. People with dementia or Mini-Mental State Examination score less than 17 were excluded. Subjective memory complaint was defined on the basis of a score ≧4 on the subscale of Geriatric Mental State schedule, a maximum score of 8. Older people aged equal or over 60 without any psychiatric diagnosis were enrolled as healthy controls. Cognitive function was evaluated using a series of cognitive tests assessing verbal memory, attention/speed, visuospatial function, verbal fluency, and cognitive flexibility in all participants. One hundred and thirteen older people with previous major depression and forty-six healthy controls were enrolled. Subjective memory complaint was present in more than half of the participants with depression history (55.8%). Among those with major depression history, subjective memory complaint was associated with lower total immediate recall and delayed verbal recall scores after adjustment. The associations between subjective memory complaint and worse memory performance were stronger in participants with lower depressive symptoms (Hamilton Depression Rating Scale score<7). The results suggest subjective memory complaint may be a valid appraisal of memory performance in older people with previous major depression and consideration should be given to more proactive assessment and follow-up in these clinical samples
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