3,059 research outputs found
Relationship Between Morbidity and Performance in Feedlot Cattle
Five datasets from Canada, Oklahoma, Illinois, and Nebraska were used to determine the impact of bovine respiratory disease (BRD) on performance, with emphasis on dry matter intake (DMI) and feed to gain ratio (F:G). Data included pens and individually fed cattle. In general, cattle treated for BRD had lower DMI and average daily gain (ADG) with little to no effect on F:G. When BRD occured early in the feeding period (days), little change in performance was observed
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
An Ultra-Compact X-Ray Free-Electron Laser
In the field of beam physics, two frontier topics have taken center stage due
to their potential to enable new approaches to discovery in a wide swath of
science. These areas are: advanced, high gradient acceleration techniques, and
x-ray free electron lasers (XFELs). Further, there is intense interest in the
marriage of these two fields, with the goal of producing a very compact XFEL.
In this context, recent advances in high gradient radio-frequency cryogenic
copper structure research have opened the door to the use of surface electric
fields between 250 and 500 MV/m. Such an approach is foreseen to enable a new
generation of photoinjectors with six-dimensional beam brightness beyond the
current state-of-the-art by well over an order of magnitude. This advance is an
essential ingredient enabling an ultra-compact XFEL (UC-XFEL). In addition, one
may accelerate these bright beams to GeV scale in less than 10 meters. Such an
injector, when combined with inverse free electron laser-based bunching
techniques can produce multi-kA beams with unprecedented beam quality,
quantified by ~50 nm-rad normalized emittances. These beams, when injected into
innovative, short-period (1-10 mm) undulators uniquely enable UC-XFELs having
footprints consistent with university-scale laboratories. We describe the
architecture and predicted performance of this novel light source, which
promises photon production per pulse of a few percent of existing XFEL sources.
We review implementation issues including collective beam effects, compact
x-ray optics systems, and other relevant technical challenges. To illustrate
the potential of such a light source to fundamentally change the current
paradigm of XFELs with their limited access, we examine possible applications
in biology, chemistry, materials, atomic physics, industry, and medicine which
may profit from this new model of performing XFEL science.Comment: 80 pages, 24 figure
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
Five-dimensional gauge theory and compactification on a torus
We study five-dimensional minimally supersymmetric gauge theory compactified
on a torus down to three dimensions, and its embedding into string/M-theory
using geometric engineering. The moduli space on the Coulomb branch is
hyperkaehler equipped with a metric with modular transformation properties. We
determine the one-loop corrections to the metric and show that they can be
interpreted as worldsheet and D1-brane instantons in type IIB string theory.
Furthermore, we analyze instanton corrections coming from the solitonic BPS
magnetic string wrapped over the torus. In particular, we show how to compute
the path-integral for the zero-modes from the partition function of the M5
brane, or, using a 2d/4d correspondence, from the partition function of N=4 SYM
theory on a Hirzebruch surface.Comment: 30 pages, 2 figures; v2: typos corrected, added references, JHEP
versio
Characterization of the n-TOF EAR-2 neutron beam
The experimental area 2 (EAR-2) at CERNs neutron time-of-flight facility (n-TOF), which is operational since 2014, is designed and built as a short-distance complement to the experimental area 1 (EAR-1). The Parallel Plate Avalanche Counter (PPAC) monitor experiment was performed to characterize the beam prole and the shape of the neutron 'ux at EAR-2. The prompt γ-flash which is used for calibrating the time-of-flight at EAR-1 is not seen by PPAC at EAR-2, shedding light on the physical origin of this γ-flash
280 one-opposition near-Earth asteroids recovered by the EURONEAR with the <i>Isaac Newton</i> Telescope
Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions.
Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets).
Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS.
Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O−C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015.
Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys
Measurement of 73 Ge(n,γ) cross sections and implications for stellar nucleosynthesis
© 2019 The Author(s). Published by Elsevier B.V.73 Ge(n,γ) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT=30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.Peer reviewe
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