608 research outputs found
A Stark decelerator on a chip
A microstructured array of 1254 electrodes on a substrate has been configured
to generate an array of local minima of electric field strength with a
periodicity of 120 m about 25 m above the substrate. By applying
sinusoidally varying potentials to the electrodes, these minima can be made to
move smoothly along the array. Polar molecules in low-field seeking quantum
states can be trapped in these traveling potential wells. Recently, we
experimentally demonstrated this by transporting metastable CO molecules at
constant velocities above the substrate [Phys. Rev. Lett. 100 (2008) 153003].
Here, we outline and experimentally demonstrate how this microstructured array
can be used to decelerate polar molecules directly from a molecular beam. For
this, the sinusoidally varying potentials need to be switched on when the
molecules arrive above the chip, their frequency needs to be chirped down in
time, and they need to be switched off before the molecules leave the chip
again. Deceleration of metastable CO molecules from an initial velocity of 360
m/s to a final velocity as low as 240 m/s is demonstrated in the 15-35 mK deep
potential wells above the 5 cm long array of electrodes. This corresponds to a
deceleration of almost , and about 85 cm of kinetic energy is
removed from the metastable CO molecules in this process.Comment: 17 pages, 6 figure
Trapping molecules on a chip in traveling potential wells
A microstructured array of over 1200 electrodes on a substrate has been
configured to generate an array of local minima of electric field strength with
a periodicity of m about m above the substrate. By applying
sinusoidally varying potentials to the electrodes, these minima can be made to
move smoothly along the array. Polar molecules in low field seeking quantum
states can be trapped in these traveling potential wells. This is
experimentally demonstrated by transporting metastable CO molecules in 30 mK
deep wells that move at constant velocities above the substrate.Comment: 4 pages, 3 figure
An electrostatic elliptical mirror for neutral polar molecules
Focusing optics for neutral molecules finds application in shaping and
steering molecular beams. Here we present an electrostatic elliptical mirror
for polar molecules consisting of an array of microstructured gold electrodes
deposited on a glass substrate. Alternating positive and negative voltages
applied to the electrodes create a repulsive potential for molecules in
low-field-seeking states. The equipotential lines are parallel to the substrate
surface, which is bent in an elliptical shape. The mirror is characterized by
focusing a beam of metastable CO molecules and the results are compared to the
outcome of trajectory simulations.Comment: 5 pages, 4 figure
Stress and estrous cycle affect strategy but not performance of female C57BL/6J mice
Stress induces a switch in learning strategies of male C57BL/6J mice from predominantly spatial to more stimulus-response learning. To study generalization of these findings over sex, we investigated female C57BL/6J mice at three phases of the estrous cycle under non stress and acute (10 min) restraint stress conditions. On a circular hole board (CHB) task, about half of the naive female mice used spatial and stimulus-response strategies to solve the task. Under stress, female mice favored spatial over stimulus-response strategies, with 100% of female mice in the estrus phase. Performance expressed as latency to solve the task is only improved in stressed female mice in the estrus phase. We conclude that the use of learning strategies is influenced by sex and this difference between sexes is aggravated by acute stress
Not just âsmall potatoesâ: Knowledge of the idiomatic meanings of collocations
© 2016, © The Author(s) 2016. This study investigated learner knowledge of the figurative meanings of 30 collocations that can be both literal and figurative. One hundred and seven Chilean Spanish-speaking university students of English were asked to complete a meaning-recall collocation test in which the target items were embedded in non-defining sentences. Results showed limited collocation knowledge, with a mean score of 33% correct. The study also examined the effects of frequency, semantic transparency, year at university, and everyday engagement with the second language (L2) outside the classroom on this collocation knowledge. Mixed-effects modelling indicated that there was no relationship between frequency and semantic transparency and the knowledge of the figurative meanings. However, a positive relationship was found between this knowledge and year at university, time spent in an English-speaking country, and time spent reading
Fermi observations of high-energy gamma-ray emission from GRB 080825C
The Fermi Gamma-ray Space Telescope (FGST) has opened a new high-energy
window in the study of Gamma-Ray Bursts (GRBs). Here we present a thorough
analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor
(GBM), and was the first firm detection of a GRB by the Fermi Large Area
Telescope (LAT). We discuss the LAT event selections, background estimation,
significance calculations, and localization for Fermi GRBs in general and GRB
080825C in particular. We show the results of temporal and time-resolved
spectral analysis of the GBM and LAT data. We also present some theoretical
interpretation of GRB 080825C observations as well as some common features
observed in other LAT GRBs.Comment: 18 pages, 7 figures. Accepted for publication in ApJ. Corresponding
authors: A. Bouvier, J. Granot, A.J. van der Hors
Fermi observations of high-energy gamma-ray emission from GRB 090217A
The Fermi observatory is advancing our knowledge of Gamma-Ray Bursts (GRBs)
through pioneering observations at high energies, covering more than 7 decades
in energy with the two on-board detectors, the Large Area Telescope (LAT) and
the Gamma-ray Burst Monitor (GBM). Here we report on the observation of the
long GRB 090217A which triggered the GBM and has been detected by the LAT with
a significance greater than 9 sigma. We present the GBM and LAT observations
and on-ground analyses, including the time-resolved spectra and the study of
the temporal profile from 8 keV up to 1 GeV. All spectra are well reproduced by
a Band model. We compare these observations to the first two LAT-detected, long
bursts GRB 080825C and GRB 080916C. These bursts were found to have
time-dependent spectra and exhibited a delayed onset of the high-energy
emission, which are not observed in the case of GRB 090217A. We discuss some
theoretical implications for the high-energy emission of GRBs.Comment: 17 pages, 4 figures. Contact Authors: Fred, Piron; Sara, Cutini;
Andreas, von Kienli
Swift and Fermi observations of the early afterglow of the short Gamma-Ray Burst 090510
We present the observations of GRB090510 performed by the Fermi Gamma-Ray
Space Telescope and the Swift observatory. This is a bright, short burst that
shows an extended emission detected in the GeV range. Furthermore, its optical
emission initially rises, a feature so far observed only in long bursts, while
the X-ray flux shows an initial shallow decrease, followed by a steeper decay.
This exceptional behavior enables us to investigate the physical properties of
the GRB outflow, poorly known in short bursts. We discuss internal shock and
external shock models for the broadband energy emission of this object.Comment: Comments: Submitted to ApJ Letters. Contact Authors: Massimiliano De
Pasquale ([email protected]), Mathew Page ([email protected]), Kenji Toma
([email protected]), Veronique Pelassa ([email protected]). Minor change
in the authorlis
Fermi detection of delayed GeV emission from the short GRB 081024B
We report on the detailed analysis of the high-energy extended emission from
the short Gamma-Ray Burst (GRB) 081024B, detected by the Fermi Gamma-ray Space
Telescope. Historically, this represents the first clear detection of temporal
extended emission from a short GRB. The light curve observed by the Fermi
Gamma-ray Burst Monitor lasts approximately 0.8 seconds whereas the emission in
the Fermi Large Area Telescope lasts for about 3 seconds. Evidence of longer
lasting high-energy emission associated with long bursts has been already
reported by previous experiments. Our observations, together with the earlier
reported study of the bright short GRB 090510, indicate similarities in the
high-energy emission of short and long GRBs and open the path to new
interpretations.Comment: 19 pages, 4 figures, 2 tables. Accepted for publication in Ap
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Pacific Northwest GridWiseâą Testbed Demonstration Projects; Part II. Grid Friendlyâą Appliance Project
Fifty residential electric water heaters and 150 new residential clothes dryers were modified to respond to signals received from underfrequency, load-shedding appliance controllers. Each controller monitored the power-grid voltage signal and requested that electrical load be shed by its appliance whenever electric power-grid frequency fell below 59.95 Hz. The controllers and their appliances were installed and monitored for more than a year at residential sites at three locations in Washington and Oregon. The controllers and their appliances responded reliably to each shallow underfrequency eventâan average of one event per dayâand shed their loads for the durations of these events. Appliance owners reported that the appliance responses were unnoticed and caused little or no inconvenience for the homesâ occupants
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