1,169 research outputs found
BL Lac X-ray Spectra: simpler than we thought
We report results from {\it XMM-Newton} observations of thirteen X-ray bright
BL Lacertae objects, selected from the {\it Einstein} Slew Survey sample. The
spectra are generally well fit by power-law models, with four objects having
hard () spectra that indicates
synchrotron peaks at keV. None of our spectra show line features,
indicating that soft X-ray absorption ``notches'' must be rare amongst BL Lacs,
rather than common or ubiquitous as had previously been asserted. We find
significant curvature in most of the spectra. This curvature is almost
certainly intrinsic, as it appears nearly constant from 0.5 to 6 keV, an
observation which is inconsistent with the small columns seen in these sources.Comment: 4 pages, 1 figure; to be published in proceedings of the Cozumel
meeting on "Multiwavelength Surveys for AGN", Cozumel 200
Burning Both Ends: Examining Overload, Trait Motivation, and Burnout Through the Person-Environment Interaction
Burnout has received substantial attention in academic literature and popular media due to its extensive breadth and detrimental impact on individual and organizational outcomes. To effectively address and combat the phenomenon, it is important to understand the boundary conditions in which burnout occurs and the individual and environmental interactions that predict burnout. In the current study, the relationships among burnout, overload, and trait motivation were investigated. Data were collected via Amazon Mechanical Turk from a sample of working professionals. Overload was negatively related to approach motivation and positively related to avoidance motivation and burnout. Approach motivation was negatively related to burnout, while avoidance motivation was positively related. A series of moderation models were tested to understand the interaction between trait motivation and overload in the relationship to burnout. The moderation results were not confirmed, but the main effects were significant. Understanding relevant boundary conditions and individual differences associated with motivation and burnout will equip organizational leaders and decision-makers to effectively combat the phenomenon and preserve employee well-being
Report on an all-sky LIGO search for periodic gravitational waves in the S4 data
We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50-1000 Hz and having a negative
frequency time derivative with magnitude between zero and Hz/s. Data
from the fourth LIGO science run have been used in this search. Three different
semi-coherent methods of summing strain power were applied. Observing no
evidence for periodic gravitational radiation, we report upper limits on strain
amplitude and interpret these limits to constrain radiation from rotating
neutron stars.Comment: 5 pages, 1 figure, presented at Amaldi7, Sydney (July 2007
Monitoring the Large Proper Motions of Radio Sources in the Orion BN/KL Region
We present absolute astrometry of four radio sources in the
Becklin-Neugebauer/Kleinman-Low (BN/KL) region, derived from archival data
(taken in 1991, 1995, and 2000) as well as from new observations (taken in
2006). All data consist of 3.6 cm continuum emission and were taken with the
Very Large Array in its highest angular resolution A configuration. We confirm
the large proper motions of the BN object, the radio source I (GMR I) and the
radio counterpart of the infrared source n (Orion-n), with values from 15 to 26
km/s. The three sources are receding from a point between them from where they
seem to have been ejected about 500 years ago, probably via the disintegration
of a multiple stellar system. We present simulations of very compact stellar
groups that provide a plausible dynamical scenario for the observations. The
radio source Orion-n appeared as a double in the first three epochs, but as
single in 2006. We discuss this morphological change. The fourth source in the
region, GMR D, shows no statistically significant proper motions. We also
present new, accurate relative astrometry between BN and radio source I that
restrict possible dynamical scenarios for the region. During the 2006
observations, the radio source GMR A, located about 1' to the NW of the BN/KL
region, exhibited an increase in its flux density of a factor of ~3.5 over a
timescale of one hour. This rapid variability at cm wavelengths is similar to
that previously found during a flare at millimeter wavelengths that took place
in 2003.Comment: Accepted for publication in Ap
ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1<z<4
We investigate the properties of galaxies as they shut off star formation
over the 4 billion years surrounding peak cosmic star formation. To do this we
categorize galaxies from into groups based on the shape
of their spectral energy distributions (SEDs) and build composite SEDs with
resolution. These composite SEDs show a variety of spectral shapes
and also show trends in parameters such as color, mass, star formation rate,
and emission line equivalent width. Using emission line equivalent widths and
strength of the 4000\AA\ break, , we categorize the composite SEDs
into five classes: extreme emission line, star-forming, transitioning,
post-starburst, and quiescent galaxies. The transitioning population of
galaxies show modest H emission (\AA) compared to
more typical star-forming composite SEDs at
(\AA). Together with their smaller sizes (3 kpc vs. 4 kpc)
and higher S\'ersic indices (2.7 vs. 1.5), this indicates that morphological
changes initiate before the cessation of star formation. The transitional group
shows a strong increase of over one dex in number density from to
, similar to the growth in the quiescent population, while
post-starburst galaxies become rarer at . We calculate average
quenching timescales of 1.6 Gyr at and 0.9 Gyr at and
conclude that a fast quenching mechanism producing post-starbursts dominated
the quenching of galaxies at early times, while a slower process has become
more common since .Comment: Accepted for publication in The Astrophysical Journa
Patterns of strain and the determination of the safe arc of motion after subscapularis repair—A biomechanical study
This study characterizes the strain patterns and safe arcs for passive range of motion (ROM) in the superior and inferior subscapularis tendon in seven cadaveric shoulders, mounted for controlled ROM, after deltopectoral approach to the glenohumeral joint, including tenotomy of the subscapularis tendon 1 cm medial to its insertion on the lesser tuberosity. The tenotomy was repaired with end‐to‐end suture in neutral rotation. Strain patterns were measured during passive ROM in external rotation (ER), ER with 30° abduction (ER+30), abduction, and forward flexion in the scapular plane (SP) before and after surgery. Percentages were calculated from 35 trials corresponding to five trials of each motion across seven specimens. With ER of 0−30°, 89% of trials of superior subscapularis tendon and 100% of trials of inferior subscapularis tendon achieved strains >3%, with very similar patterns noted in ER+30. In abduction of 0−90°, 5.8% of trials of superior and 85.3% of trials of inferior tendon achieved >3% strain. With passive ROM in SP, 26.5% of trials reached 3% strain in superior tendon compared to 100% in inferior tendon. Strain patterns in abduction and SP differed significantly (p < 0.001). Selective tenotomy and repair of the superior subscapularis tendon with open reparative or reconstructive shoulder procedures, when feasible, may be favorable for protected early passive ROM and rehabilitation postoperatively. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:518–524, 2016.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137457/1/jor23045-sup-0002-SuppData-S2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137457/2/jor23045.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137457/3/jor23045_am.pd
Searching for stochastic gravitational-wave background with the co-located LIGO interferometers
This paper presents techniques developed by the LIGO Scientific Collaboration
to search for the stochastic gravitational-wave background using the co-located
pair of LIGO interferometers at Hanford, WA. We use correlations between
interferometers and environment monitoring instruments, as well as time-shifts
between two interferometers (described here for the first time) to identify
correlated noise from non-gravitational sources. We veto particularly noisy
frequency bands and assess the level of residual non-gravitational coupling
that exists in the surviving data.Comment: Proceedings paper from the 7th Edoardo Amaldi Conference on
Gravitational Waves, held in Sydney, Australia from 8-14 July 2007. Accepted
to J. Phys.: Conf. Se
The distribution of satellites around massive galaxies at 1<z<3 in ZFOURGE/CANDELS: dependence on star formation activity
We study the statistical distribution of satellites around star-forming and
quiescent central galaxies at 1<z<3 using imaging from the FourStar Galaxy
Evolution Survey (ZFOURGE) and the Cosmic Assembly Near-IR Deep Extragalactic
Legacy Survey (CANDELS). The deep near-IR data select satellites down to
at z<3. The radial satellite distribution around centrals
is consistent with a projected NFW profile. Massive quiescent centrals,
, have 2 times the number of satellites compared
to star-forming centrals with a significance of 2.7 even after
accounting for differences in the centrals' stellar-mass distributions. We find
no statistical difference in the satellite distributions of intermediate-mass
quiescent and star-forming centrals, . Comparing
to the Guo2011 semi-analytic model, the excess number of satellites indicates
that quiescent centrals have halo masses 0.3 dex larger than star-forming
centrals, even when the stellar-mass distributions are fixed. We use a simple
toy model that relates halo mass and quenching, which roughly reproduces the
observed quenched fractions and the differences in halo mass between
star-forming and quenched galaxies only if galaxies have a quenching
probability that increases with halo mass from 0 for
11 to 1 for 13.5. A single
halo-mass quenching threshold is unable to reproduce the quiescent fraction and
satellite distribution of centrals. Therefore, while halo quenching may be an
important mechanism, it is unlikely to be the only factor driving quenching. It
remains unclear why a high fraction of centrals remain star-forming even in
relatively massive halos.Comment: 19 pages, 17 figures, accepted by ApJ. Information on ZFOURGE can be
found at http://zfourge.tamu.ed
Low-Intrusion Techniques and Sensitive Information Management for Warhead Counting and Verification: FY2012 Annual Report
Progress in the second year of this project is described by the series of technical reports and manuscripts that make up the content of this report. These documents summarize successes in our goals to develop our robust image-hash templating and material-discrimination techniques and apply them to test image data
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