3,733 research outputs found
The Infrared Imaging Spectrograph (IRIS) for TMT: Volume phase holographic grating performance testing and discussion
Maximizing the grating efficiency is a key goal for the first light
instrument IRIS (Infrared Imaging Spectrograph) currently being designed to
sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase
Holographic (VPH) gratings have been shown to offer extremely high efficiencies
that approach 100% for high line frequencies (i.e., 600 to 6000l/mm), which has
been applicable for astronomical optical spectrographs. However, VPH gratings
have been less exploited in the near-infrared, particularly for gratings that
have lower line frequencies. Given their potential to offer high throughputs
and low scattered light, VPH gratings are being explored for IRIS as a
potential dispersing element in the spectrograph. Our team has procured
near-infrared gratings from two separate vendors. We have two gratings with the
specifications needed for IRIS current design: 1.51-1.82{\mu}m (H-band) to
produce a spectral resolution of 4000 and 1.19- 1.37 {\mu}m (J-band) to produce
a spectral resolution of 8000. The center wavelengths for each grating are
1.629{\mu}m and 1.27{\mu}m, and the groove densities are 177l/mm and 440l/mm
for H-band R=4000 and J-band R=8000, respectively. We directly measure the
efficiencies in the lab and find that the peak efficiencies of these two types
of gratings are quite good with a peak efficiency of ~88% at the Bragg angle in
both TM and TE modes at H-band, and 90.23% in TM mode, 79.91% in TE mode at
J-band for the best vendor. We determine the drop in efficiency off the Bragg
angle, with a 20-23% decrease in efficiency at H-band when 2.5 degree deviation
from the Bragg angle, and 25%-28% decrease at J-band when 5{\deg} deviation
from the Bragg angle.Comment: Proceedings of the SPIE, 9147-33
The InfraRed Imaging Spectrograph (IRIS) for TMT: Reflective ruled diffraction grating performance testing and discussion
We present the efficiency of near-infrared reflective ruled diffraction
gratings designed for the InfraRed Imaging Spectrograph (IRIS). IRIS is a first
light, integral field spectrograph and imager for the Thirty Meter Telescope
(TMT) and narrow field infrared adaptive optics system (NFIRAOS). We present
our experimental setup and analysis of the efficiency of selected reflective
diffraction gratings. These measurements are used as a comparison sample
against selected candidate Volume Phase Holographic (VPH) gratings (see Chen et
al., this conference). We investigate the efficiencies of five ruled gratings
designed for IRIS from two separate vendors. Three of the gratings accept a
bandpass of 1.19-1.37 {\mu}m (J band) with ideal spectral resolutions of R=4000
and R=8000, groove densities of 249 and 516 lines/mm, and blaze angles of 9.86
and 20.54 degrees, respectively. The other two gratings accept a bandpass of
1.51-1.82 {\mu}m (H Band) with an ideal spectral resolution of R=4000, groove
density of 141 lines/mm, and blaze angle of 9.86{\deg}. We measure the
efficiencies off blaze angle for all gratings and the efficiencies between the
polarization transverse magnetic (TM) and transverse electric (TE) states. The
peak reflective efficiencies are 98.90 +/- 3.36% (TM) and 84.99 +/- 2.74% (TM)
for the H-band R=4000 and J-band R=4000 respectively. The peak reflective
efficiency for the J-band R=8000 grating is 78.78 +/- 2.54% (TE). We find that
these ruled gratings do not exhibit a wide dependency on incident angle within
+/-3{\deg}. Our best-manufactured gratings were found to exhibit a dependency
on the polarization state of the incident beam with a ~10-20% deviation,
consistent with the theoretical efficiency predictions.Comment: Proceedings of the SPIE, 9147-34
Who uses custom sports betting products?
Background: The expansion of online gambling in the UK has been accompanied by an increase in the number of novel betting products, particularly for soccer. The present research investigates which types of sports bettors are the most likely to use novel gambling products called ‘custom sports bets’ (CSBs), which allow gamblers to create their own unique bets.
Method: A large-scale, cross-sectional survey of online sports/horse racing bettors (N = 789, 32.7% female). The survey collected two measures of CSB usage and four validated gambling measures: the Problem Gambling Severity Index, the Gambling Related Cognition Illusion of Control Scale, the Short Gambling Harm Screen, and the Consumption Screen for Problem Gambling.
Results: Overall, 62.0% of participants reported having used a CSB, and those who had used a CSB did so on an average of 29.4 days over the last year. Overall, 16.0% of participants who had used a CSB were current problem gamblers, compared to 6.7% among those who had not. CSB users reported an average of 2.3 out of 10 possible gambling harms, compared to 1.5 harms for those who had not used a CSB. The illusion of control scale was significantly positively correlated with whether participants had ever used a CSB before, but not with past year frequency of CSB usage. The usage of CSB products was most strongly associated with the frequency of gambling consumption.
Conclusions: Overall, these findings suggest that CSB products raise distinctive concerns around consumer protection for frequent sports bettors which deserve further investigation
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Direction of visual apparent motion driven solely by timing of a static sound
In temporal ventriloquism, auditory events can illusorily attract perceived timing of a visual onset [1,2,3]. We investigated whether timing of a static sound can also influence spatio-temporal processing of visual apparent motion, induced here by visual bars alternating between opposite hemifields. Perceived direction typically depends on the relative interval in timing between visual left-right and right-left flashes (e.g., rightwards motion dominating when left-to-right interflash intervals are shortest [4]). In our new multisensory condition, interflash intervals were equal, but auditory beeps could slightly lag the right flash, yet slightly lead the left flash, or vice versa. This auditory timing strongly influenced perceived visual motion direction, despite providing no spatial auditory motion signal whatsoever. Moreover, prolonged adaptation to such auditorily driven apparent motion produced a robust visual motion aftereffect in the opposite direction, when measured in subsequent silence. Control experiments argued against accounts in terms of possible auditory grouping, or possible attention capture. We suggest that the motion arises because the sounds change perceived visual timing, as we separately confirmed. Our results provide a new demonstration of multisensory influences on sensory-specific perception [5], with timing of a static sound influencing spatio-temporal processing of visual motion direction
Request-a-bet sports betting products indicate patterns of bettor preference and bookmaker profits
Background and aims
Request-a-bet services are a modern gambling product delivered via the social network Twitter, which allow sports bettors to design custom bets. The public nature of Twitter data provided a unique opportunity to investigate patterns of bettor preference and the bookmaker profit margin in soccer, the UK’s favorite sport.
Methods
Two multi-method studies. Twitter users’ engagement with request-a-bet services was monitored unobtrusively (n = 1,406), meaning that potential patterns across users’ requests could be observed, and the bookmaker profit margin could be estimated. Twitter users were also surveyed directly (n = 55), providing self-report measures of request-a-bet usage.
Results
Twitter users requested bets with an average potential payoff of £56.5 per £1 risked (median = £9). Overall, 9.7% of requested bets paid-off, but these were mostly bets at short odds. This meant that requests yielded a high bookmaker profit margin of 43.7% (roughly eight times higher than current margins in conventional soccer bets), which increased to 74.6% for bets at longer odds. Requested bets also tended to involve star players from the best teams. Finally, 92.7% of surveyed Twitter users reported placing at least one bet via request-a-bet services (mean = 44.4 bets).
Discussion and conclusions
Researchers can use request-a-bet products to increase their understanding of sports betting behavior. Sports bettors should be given information about how much higher the bookmaker profit margin can be in modern sports bets compared to the conventional sports bets that they may be more familiar with
Nucleosynthesis in the Early Galaxy
Recent observations of r-process-enriched metal-poor star abundances reveal a
non-uniform abundance pattern for elements . Based on non-correlation
trends between elemental abundances as a function of Eu-richness in a large
sample of metal-poor stars, it is shown that the mixing of a consistent and
robust light element primary process (LEPP) and the r-process pattern found in
r-II metal-poor stars explains such apparent non-uniformity. Furthermore, we
derive the abundance pattern of the LEPP from observation and show that it is
consistent with a missing component in the solar abundances when using a recent
s-process model. As the astrophysical site of the LEPP is not known, we explore
the possibility of a neutron capture process within a site-independent
approach. It is suggested that scenarios with neutron densities
or in the range best
explain the observations.Comment: 28 pages, 7 Postscript figures. To be published in The Astrophysical
Journa
The Wide Integral Field Infrared Spectrograph: Commissioning Results and On-sky Performance
We have recently commissioned a novel infrared ( m) integral
field spectrograph (IFS) called the Wide Integral Field Infrared Spectrograph
(WIFIS). WIFIS is a unique instrument that offers a very large field-of-view
(50 x 20) on the 2.3-meter Bok telescope at
Kitt Peak, USA for seeing-limited observations at moderate spectral resolving
power. The measured spatial sampling scale is and
its spectral resolving power is and in the
( m) and ( m) modes, respectively.
WIFIS's corresponding etendue is larger than existing near-infrared (NIR)
IFSes, which are mostly designed to work with adaptive optics systems and
therefore have very narrow fields. For this reason, this instrument is
specifically suited for studying very extended objects in the near-infrared
such as supernovae remnants, galactic star forming regions, and nearby
galaxies, which are not easily accessible by other NIR IFSes. This enables
scientific programs that were not originally possible, such as detailed surveys
of a large number of nearby galaxies or a full accounting of nucleosynthetic
yields of Milky Way supernova remnants. WIFIS is also designed to be easily
adaptable to be used with larger telescopes. In this paper, we report on the
overall performance characteristics of the instrument, which were measured
during our commissioning runs in the second half of 2017. We present
measurements of spectral resolving power, image quality, instrumental
background, and overall efficiency and sensitivity of WIFIS and compare them
with our design expectations. Finally, we present a few example observations
that demonstrate WIFIS's full capability to carry out infrared imaging
spectroscopy of extended objects, which is enabled by our custom data reduction
pipeline.Comment: Published in the Proceedings of SPIE Astronomical Telescopes and
Instrumentation 2018. 17 pages, 13 figure
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