805 research outputs found
The effects of recruitment to direct predator cues on predator responses in meerkats
Behavioral responses of animals to direct predator cues (DPCs; e.g., urine) are common and may improve their survival. We investigated wild meerkat (Suricata suricatta) responses to DPCs by taking an experimental approach. When meerkats encounter a DPC they often recruit group members by emitting a call type, which causes the group members to interrupt foraging and approach the caller. The aim of this study was to identify the qualities of olfactory predator cues, which affect the strength of response by meerkats, and determine the benefits of responses to such cues. Experimental exposure to dog (Canis lupus) urine as a DPC revealed that the recruited individuals increased vigilance to fresh urine in comparison to older urine, whereas a higher quantity of urine did not induce such an effect. Both freshness and higher quantities increased the proportion of group members recruited. These results indicate that recruitment might play a crucial role in correctly assessing the current level of danger and that recruiting might facilitate group decision making. To test the prediction that the reaction to a DPC enhances early predator response, we presented a DPC of a predator and a control cue of a herbivore, and each time simultaneously moved a full-mounted caracal (Caracal caracal) in the vicinity of the group. Meerkats responded earlier to the caracal when the DPC was presented, indicating that the response to a DPC facilitates predator response and that they use information from the cue that reliably reflects the risk in the current momen
Accelerating CO2-Emission Reductions via Corporate Programmes; Analysis of an Existing Corporate Programme
This working paper analyzes and assesses the COYou2 Program of the company Swiss Re. This corporate program allows employees to claim subsidies for the realization of various activities reducing their energy consumption and CO2-emissions at home. Examples of such activities are the purchase of a hybrid car, energy efficient building renovation, or the installation of photovoltaic panels. We find that the uptake of such subsidies is very popular among employees. The three main reasons for this are that 1) activities are well communicated and participation and uptake of subsidies is simple and non-bureaucratic, 2) offered emission reduction activities very much fit the profile and needs of employees, and 3) financial incentives are substantial and thus motivating to realize those activities. Yet, we also show that a large share of emission reduction activities would have been realized also without the extra incentive, which calls into question the additionality of many emission reductions. We therefore suggest that in order to ensure additionally of emission reductions in employeesâ households, corporate programs may focus on subsidizing activities and green technologies which are not yet widespread. For example, activities such as highly efficient gasoline and diesel cars as well as carpooling have a high potential to reduce CO2-emissions and may be included in such corporate programs
Stellar archaeology with Gaia: the Galactic white dwarf population
Gaia will identify several 1e5 white dwarfs, most of which will be in the
solar neighborhood at distances of a few hundred parsecs. Ground-based optical
follow-up spectroscopy of this sample of stellar remnants is essential to
unlock the enormous scientific potential it holds for our understanding of
stellar evolution, and the Galactic formation history of both stars and
planets.Comment: Summary of a talk at the 'Multi-Object Spectroscopy in the Next
Decade' conference in La Palma, March 2015, to be published in ASP Conference
Series (editors Ian Skillen & Scott Trager
Dissecting Driver Behaviors Under Cognitive, Emotional, Sensorimotor, and Mixed Stressors
In a simulation experiment we studied the effects of cognitive, emotional, sensorimotor, and mixed stressors on driver arousal and performance with respect to (wrt) baseline. In a sample of nâ=â59 drivers, balanced in terms of age and gender, we found that all stressors incurred significant increases in mean sympathetic arousal accompanied by significant increases in mean absolute steering. The latter, translated to significantly larger range of lane departures only in the case of sensorimotor and mixed stressors, indicating more dangerous driving wrt baseline. In the case of cognitive or emotional stressors, often a smaller range of lane departures was observed, indicating safer driving wrt baseline. This paradox suggests an effective coping mechanism at work, which compensates erroneous reactions precipitated by cognitive or emotional conflict. This mechanismsâ grip slips, however, when the feedback loop is intermittently severed by sensorimotor distractions. Interestingly, mixed stressors did not affect crash rates in startling events, suggesting that the coping mechanismâs compensation time scale is above the range of neurophysiological latency
ProtoDESI: First On-Sky Technology Demonstration for the Dark Energy Spectroscopic Instrument
The Dark Energy Spectroscopic Instrument (DESI) is under construction to
measure the expansion history of the universe using the baryon acoustic
oscillations technique. The spectra of 35 million galaxies and quasars over
14,000 square degrees will be measured during a 5-year survey. A new prime
focus corrector for the Mayall telescope at Kitt Peak National Observatory will
deliver light to 5,000 individually targeted fiber-fed robotic positioners. The
fibers in turn feed ten broadband multi-object spectrographs. We describe the
ProtoDESI experiment, that was installed and commissioned on the 4-m Mayall
telescope from August 14 to September 30, 2016. ProtoDESI was an on-sky
technology demonstration with the goal to reduce technical risks associated
with aligning optical fibers with targets using robotic fiber positioners and
maintaining the stability required to operate DESI. The ProtoDESI prime focus
instrument, consisting of three fiber positioners, illuminated fiducials, and a
guide camera, was installed behind the existing Mosaic corrector on the Mayall
telescope. A Fiber View Camera was mounted in the Cassegrain cage of the
telescope and provided feedback metrology for positioning the fibers. ProtoDESI
also provided a platform for early integration of hardware with the DESI
Instrument Control System that controls the subsystems, provides communication
with the Telescope Control System, and collects instrument telemetry data.
Lacking a spectrograph, ProtoDESI monitored the output of the fibers using a
Fiber Photometry Camera mounted on the prime focus instrument. ProtoDESI was
successful in acquiring targets with the robotically positioned fibers and
demonstrated that the DESI guiding requirements can be met.Comment: Accepted versio
Roll Maneuver Control of UCAV Wing Using Anisotropic Piezoelectric Actuators
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76333/1/AIAA-2002-1720-656.pd
Transiting Disintegrating Planetary Debris around WD 1145+017
More than a decade after astronomers realized that disrupted planetary
material likely pollutes the surfaces of many white dwarf stars, the discovery
of transiting debris orbiting the white dwarf WD 1145+017 has opened the door
to new explorations of this process. We describe the observational evidence for
transiting planetary material and the current theoretical understanding (and in
some cases lack thereof) of the phenomenon.Comment: Invited review chapter. Accepted March 23, 2017 and published October
7, 2017 in the Handbook of Exoplanets. 15 pages, 10 figure
Fast spectrophotometry of WD 1145+017
WD 1145+017 is currently the only white dwarf known to exhibit periodic
transits of planetary debris as well as absorption lines from circumstellar
gas. We present the first simultaneous fast optical spectrophotometry and
broad-band photometry of the system, obtained with the Gran Telescopio Canarias
(GTC) and the Liverpool Telescope (LT), respectively. The observations spanned
h, somewhat longer than the -h orbital period of the debris.
Dividing the GTC spectrophotometry into five wavelength bands reveals no
significant colour differences, confirming grey transits in the optical. We
argue that absorption by an optically thick structure is a plausible
alternative explanation for the achromatic nature of the transits that can
allow the presence of small-sized (m) particles. The longest (
min) and deepest ( per cent attenuation) transit recorded in our data
exhibits a complex structure around minimum light that can be well modelled by
multiple overlapping dust clouds. The strongest circumstellar absorption line,
Fe II 5169, significantly weakens during this transit, with its
equivalent width reducing from a mean out-of-transit value of \AA\ to
\AA\ in-transit, supporting spatial correlation between the circumstellar gas
and dust. Finally, we made use of the Gaia Data Release 2 and archival
photometry to determine the white dwarf parameters. Adopting a helium-dominated
atmosphere containing traces of hydrogen and metals, and a reddening
we find K, ,
corresponding to M_\mathrm{WD}=0.63\pm0.05\ \mbox{\mathrm{M}_{\odot}} and a
cooling age of Myr.Comment: 13 pages, 9 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Society (2018 Aug 22
IGAPS: the merged IPHAS and UVEX optical surveys of the northern Galactic plane
The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i, r, narrow-band Ha, g, and URGO. The IGAPS footprint fills the Galactic coordinate range, |b| 5s confidence).Peer ReviewedPostprint (published version
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