690 research outputs found
Measuring galaxy [OII] emission line doublet with future ground-based wide-field spectroscopic surveys
The next generation of wide-field spectroscopic redshift surveys will map the
large-scale galaxy distribution in the redshift range 0.7< z<2 to measure
baryonic acoustic oscillations (BAO). The primary optical signature used in
this redshift range comes from the [OII] emission line doublet, which provides
a unique redshift identification that can minimize confusion with other single
emission lines. To derive the required spectrograph resolution for these
redshift surveys, we simulate observations of the [OII] (3727,3729) doublet for
various instrument resolutions, and line velocities. We foresee two strategies
about the choice of the resolution for future spectrographs for BAO surveys.
For bright [OII] emitter surveys ([OII] flux ~30.10^{-17} erg /cm2/s like
SDSS-IV/eBOSS), a resolution of R~3300 allows the separation of 90 percent of
the doublets. The impact of the sky lines on the completeness in redshift is
less than 6 percent. For faint [OII] emitter surveys ([OII] flux ~10.10^{-17}
erg /cm2/s like DESi), the detection improves continuously with resolution, so
we recommend the highest possible resolution, the limit being given by the
number of pixels (4k by 4k) on the detector and the number of spectroscopic
channels (2 or 3).Comment: 5 pages, 1 figur
M32+/-1
WFPC-2 images are used to study the central structure of M31, M32, and M33.
The dimmer peak, P2, of the M31 double nucleus is centered on the bulge to
0.1", implying that it is the dynamical center of M31. P2 contains a compact
source discovered by King et al. (1995) at 1700 A. This source is resolved,
with r_{1/2} approx0.2 pc. It dominates the nucleus at 3000 A, and is
consistent with late B-early A stars. This probable cluster may consist of
young stars and be an older version of the cluster of hot stars at the center
of the Milky Way, or it may consist of heavier stars built up from collisions
in a possible cold disk of stars orbiting P2. In M32, the central cusp rises
into the HST limit with gamma approx0.5, and the central density
rho_0>10^7M_sol pc^-3. The V-I and U-V color profiles are flat, and there is no
sign of an inner disk, dust, or any other structure. This total lack of
features seems at variance with a nominal stellar collision time of 2 X 10^10
yr, which implies that a significant fraction of the light in the central pixel
should come from blue stragglers. InM33, the nucleus has an extremely steep
gamma=1.49 power-law profile for 0.05"<r<0.2" that becomes shallower as the HST
resolution limit is approached. The profile for r<0.04" has either a gamma
approx 0.8 cusp or a small core with r_c ~<0.13 pc. The central density is
rho_0 > 2 10^6M_sol pc^-3, and the implied relaxation time is only ~3 X 10^6
yr, indicating that the nucleus is highly relaxed. The accompanying short
collision time of 7 X 10^9 yr predicts a central blue straggler component
quantitatively consistent with the strong V-I and B-R color gradients seen with
HST and from the ground.Comment: 44 pages, 22 figures (7 as separate JPEG images), submitted to The
Astronomical Journal. Full postscript image available at
http://www.noao.edu/noao/staff/lauer/lauer_paper
Energy dependence of {\rm K} and hyperon production at CERN SPS
Recent results on K and hyperon production in Pb-Pb collisions at
40 and 158 GeV/ beam momentum from the NA57 experiment at CERN SPS are
presented. Yields and ratios are compared with those measured by the NA49
experiment, where available. The centrality dependence of the yields and a
comparison with the higher collision energy data from RHIC are discussed.Comment: 4 pages, 3 figures, proceedings of QM2004 conferenc
Intrinsic Decoherence Dynamics in Smooth Hamiltonian Systems: Quantum-classical Correspondence
A direct classical analog of the quantum dynamics of intrinsic decoherence in
Hamiltonian systems, characterized by the time dependence of the linear entropy
of the reduced density operator, is introduced. The similarities and
differences between the classical and quantum decoherence dynamics of an
initial quantum state are exposed using both analytical and computational
results. In particular, the classicality of early-time intrinsic decoherence
dynamics is explored analytically using a second-order perturbative treatment,
and an interesting connection between decoherence rates and the stability
nature of classical trajectories is revealed in a simple approximate classical
theory of intrinsic decoherence dynamics. The results offer new insights into
decoherence, dynamics of quantum entanglement, and quantum chaos.Comment: 12 pages, 7 figures, to appear in Physical Review
Space based astronomy: Teacher's guide with activities
This curriculum guide uses hands-on activities to help students and teachers understand the significance of space-based astronomy - astronomical observations made from outer space. The guide contains few of the traditional activities found in many astronomy guides such as constellation studies, lunar phases, and planetary orbits. Instead, it tells the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. The guide begins with a survey of astronomy related NASA spacecraft. This is followed by a collection of activities in four units: (1) the atmospheric filter; (2) the electromagnetic spectrum; (3) collecting electromagnetic radiation; and (4) down to Earth. A curriculum index identifies the curriculum areas each activity addresses. The guide concludes with a glossary, reference list, a NASA Resources list, and an evaluation card. It is designed for students in grades 5 through 8
The Middle Way: East Asian masters students’ perceptions of critical argumentation in U.K. universities.
The paper explores the learning experiences of East Asian masters students in dealing with Western academic norms of critical thinking in classroom debate and assignment writing. The research takes a cultural approach, and employs grounded theory and case study methodology, the aims being for students to explain their perceptions of their personal learning journeys. The data suggest that the majority of students interviewed rejected full academic acculturation into Western norms of argumentation. They instead opted for a ‘Middle Way’ that synergizes the traditional cultural academic values held by many East Asian students with those elements of Western academic norms that are perceived to be aligned with these. This is a relatively new area of research which represents a challenge for British lecturers and students
Reversal of renal allograft rejection with intravenous methylprednisolone "pulse" therapy,
Intravenous administration of large doses of methylprednisolone sodium succinate was demonstrated to modify rejection in both canine and human renal allografts. One dose of intravenous methylprednisolone 30 mg./kg. administered during acute rejection in dogs resulted in an increase in urine volume and osmolality, and a decrease in serum and urine LDH. In two dogs treated with a single dose and in one dog treated with four consecutive daily doses histologic evidence of reversal of rejection with reduction of cellular infiltrate was achieved. Ninety-two percent of rejections encountered in 100 consecutive human recipients of renal allografts were halted or reversed with intravenous methylprednisolone 30 mg./ kg. given every 48-72 hours to a maximum of three or four doses. No significant side effects were observed either in dogs or humans with this therapy. The mean circulating half-life of intravenous methylprednisolone was determined to be 3.48 +/- 0.7 hours in dogs. Intermittent intravenous administration of methylprednisolone has the potential advantage of being associated with fewer side effects than frequent oral administration and has been shown to be an effective method for modifying rejection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34145/1/0000430.pd
Metaphylactic antimicrobial effects on occurrences of antimicrobial resistance in \u3ci\u3eSalmonella enterica, Escherichia coli\u3c/i\u3e and \u3ci\u3eEnterococcus\u3c/i\u3e spp. measured longitudinally from feedlot arrival to harvest in high-risk beef cattle
Aims: Our objective was to determine how injectable antimicrobials affected populations of Salmonella enterica, Escherichia coli and Enterococcus spp. in feedlot cattle.
Methods and Results: Two arrival date blocks of high-risk crossbred beef cattle (n = 249; mean BW = 244 kg) were randomly assigned one of four antimicrobial treatments administered on day 0: sterile saline control (CON), tulathromycin (TUL), ceftiofur (CEF) or florfenicol (FLR). Faecal samples were collected on days 0, 28, 56, 112, 182 and study end (day 252 for block 1 and day 242 for block 2). Hide swabs and subiliac lymph nodes were collected the day before and the day of harvest. Samples were cultured for antimicrobial-resistant Salmonella, Escherichia coli and Enterococcus spp. The effect of treatment varied by day across all targeted bacterial populations (p ≤ 0.01) except total E. coli. Total E. coli counts were greatest on days 112, 182 and study end (p ≤ 0.01). Tulathromycin resulted in greater counts and prevalence of Salmonella from faeces than CON at study end (p ≤ 0.01). Tulathromycin and CEF yielded greater Salmonella hide prevalence and greater counts of 128ERYR E. coli at study end than CON (p ≤ 0.01). No faecal Salmonella resistant to tetracyclines or third-generation cephalosporins were detected. Ceftiofur was associated with greater counts of 8ERYR Enterococcus spp. at study end (p ≤ 0.03). By the day before harvest, antimicrobial use did not increase prevalence or counts for all other bacterial populations compared with CON (p ≥ 0.13).
Conclusions: Antimicrobial resistance (AMR) in feedlot cattle is not caused solely by using a metaphylactic antimicrobial on arrival, but more likely a multitude of environmental and management factors
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