9,789 research outputs found
Decision-tree early warning score (DTEWS) validates the design of the National Early Warning Score (NEWS)
An Extraordinary Scattered Broad Emission Line in a Type 2 QSO
An infrared-selected, narrow-line QSO has been found to exhibit an
extraordinarily broad Halpha emission line in polarized light. Both the extreme
width (35,000 km/sec full-width at zero intensity) and 3,000 km/sec redshift of
the line centroid with respect to the systemic velocity suggest emission in a
deep gravitational potential. An extremely red polarized continuum and partial
scattering of the narrow lines at a position angle common to the broad-line
emission imply extensive obscuration, with few unimpeded lines of sight to the
nucleus.Comment: 4 pages, 1 figure, to appear in the Astrophysical Journal Letter
Measuring the Cosmic Ray Muon-Induced Fast Neutron Spectrum by (n,p) Isotope Production Reactions in Underground Detectors
While cosmic ray muons themselves are relatively easy to veto in underground
detectors, their interactions with nuclei create more insidious backgrounds
via: (i) the decays of long-lived isotopes produced by muon-induced spallation
reactions inside the detector, (ii) spallation reactions initiated by fast
muon-induced neutrons entering from outside the detector, and (iii) nuclear
recoils initiated by fast muon-induced neutrons entering from outside the
detector. These backgrounds, which are difficult to veto or shield against, are
very important for solar, reactor, dark matter, and other underground
experiments, especially as increased sensitivity is pursued. We used fluka to
calculate the production rates and spectra of all prominent secondaries
produced by cosmic ray muons, in particular focusing on secondary neutrons, due
to their importance. Since the neutron spectrum is steeply falling, the total
neutron production rate is sensitive just to the relatively soft neutrons, and
not to the fast-neutron component. We show that the neutron spectrum in the
range between 10 and 100 MeV can instead be probed by the (n, p)-induced
isotope production rates 12C(n, p)12B and 16O(n, p)16N in oil- and water-based
detectors. The result for 12B is in good agreement with the recent KamLAND
measurement. Besides testing the calculation of muon secondaries, these results
are also of practical importance, since 12B (T1/2 = 20.2 ms, Q = 13.4 MeV) and
16N (T1/2 = 7.13 s, Q = 10.4 MeV) are among the dominant spallation backgrounds
in these detectors
The van Hove distribution function for Brownian hard spheres: dynamical test particle theory and computer simulations for bulk dynamics
We describe a test particle approach based on dynamical density functional
theory (DDFT) for studying the correlated time evolution of the particles that
constitute a fluid. Our theory provides a means of calculating the van Hove
distribution function by treating its self and distinct parts as the two
components of a binary fluid mixture, with the `self' component having only one
particle, the `distinct' component consisting of all the other particles, and
using DDFT to calculate the time evolution of the density profiles for the two
components. We apply this approach to a bulk fluid of Brownian hard spheres and
compare to results for the van Hove function and the intermediate scattering
function from Brownian dynamics computer simulations. We find good agreement at
low and intermediate densities using the very simple Ramakrishnan-Yussouff
[Phys. Rev. B 19, 2775 (1979)] approximation for the excess free energy
functional. Since the DDFT is based on the equilibrium Helmholtz free energy
functional, we can probe a free energy landscape that underlies the dynamics.
Within the mean-field approximation we find that as the particle density
increases, this landscape develops a minimum, while an exact treatment of a
model confined situation shows that for an ergodic fluid this landscape should
be monotonic. We discuss possible implications for slow, glassy and arrested
dynamics at high densities.Comment: Submitted to Journal of Chemical Physic
Here or There Instruction: Lessons Learned in Implementing Innovative Approaches to Blended Synchronous Learning
Here or There (HOT) instruction is a blended synchronous approach that enables students from on-campus (âhereâ) or a remote location (âthereâ) to participate together in class activities in real time. The purpose of this article is to share three different cases at two universities that illustrate different implementations of HOT instruction, explain the affordances of these varied approaches, provide best practices that are common to each, and share lessons learned along the way. Readers will gain a better understanding of how to implement a range of innovative HOT approaches, and in what context(s) they might choose one approach over another. The authorsâ experience indicates that sound pedagogical principles along with pragmatic considerations, such as class size, available technology, and instructorâs skills, should guide decisions regarding use of these blended synchronous approaches. Future research should look towards what impact
blended synchronous environments have on student outcomes
Precise Experimental Investigation of Eigenmodes in a Planar Ion Crystal
The accurate characterization of eigenmodes and eigenfrequencies of
two-dimensional ion crystals provides the foundation for the use of such
structures for quantum simulation purposes. We present a combined experimental
and theoretical study of two-dimensional ion crystals. We demonstrate that
standard pseudopotential theory accurately predicts the positions of the ions
and the location of structural transitions between different crystal
configurations. However, pseudopotential theory is insufficient to determine
eigenfrequencies of the two-dimensional ion crystals accurately but shows
significant deviations from the experimental data obtained from resolved
sideband spectroscopy. Agreement at the level of 2.5 x 10^(-3) is found with
the full time-dependent Coulomb theory using the Floquet-Lyapunov approach and
the effect is understood from the dynamics of two-dimensional ion crystals in
the Paul trap. The results represent initial steps towards an exploitation of
these structures for quantum simulation schemes.Comment: 5 pages, 4 figures, supplemental material (mathematica and matlab
files) available upon reques
Insensitivity of alkenone carbon isotopes to atmospheric CO<sub>2</sub> at low to moderate CO<sub>2</sub> levels
Atmospheric pCO2 is a critical component of the global carbon system and is considered to be the major control of Earthâs past, present and future climate. Accurate and precise reconstructions of its concentration through geological time are, therefore, crucial to our understanding of the Earth system. Ice core records document pCO2 for the past 800 kyrs, but at no point during this interval were CO2 levels higher than today. Interpretation of older pCO2 has been hampered by discrepancies during some time intervals between two of the main ocean-based proxy methods used to reconstruct pCO2: the carbon isotope fractionation that occurs during photosynthesis as recorded by haptophyte biomarkers (alkenones) and the boron isotope composition (ÎŽ11B) of foraminifer shells. Here we present alkenone and ÎŽ11B-based pCO2 reconstructions generated from the same samples from the Plio-Pleistocene at ODP Site 999 across a glacial-interglacial cycle. We find a muted response to pCO2 in the alkenone record compared to contemporaneous ice core and ÎŽ11B records, suggesting caution in the interpretation of alkenone-based records at low pCO2 levels. This is possibly caused by the physiology of CO2 uptake in the haptophytes. Our new understanding resolves some of the inconsistencies between the proxies and highlights that caution may be required when interpreting alkenone-based reconstructions of pCO2
Cardiac stroke volume in females and its correlation to blood volume and cardiac dimensions
We aimed to continuously determine the stroke volume (SV) and blood volume (BV) during incremental exercise to evaluate the individual SV course and to correlate both variables across different exercise intensities. Twenty-six females with heterogeneous endurance capacities performed an incremental cycle ergometer test to continuously determine the oxygen uptake (VÌO(2)), cardiac output (QÌ) and changes in BV. QÌ was determined by impedance cardiography and resting cardiac dimensions by 2D echocardiography. Hemoglobin mass and BV were determined using a carbon monoxide-rebreathing method. VÌO(2max) ranged from 32 to 62 mL·kg(â1)·min(â1). QÌ(max) and SV(max) ranged from 16.4 to 31.6 L·min(â1) and 90â170 mL, respectively. The SV significantly increased from rest to 40% and from 40% to 80% VÌO(2max). Changes in SV from rest to 40% VÌO(2max) were negatively (r = â0.40, p = 0.05), between 40% and 80% positively correlated with BV (r = 0.45, p < 0.05). At each exercise intensity, the SV was significantly correlated with the BV and the cardiac dimensions, i.e., left ventricular muscle mass (LVMM) and end-diastolic diameter (LVEDD). The BV decreased by 280 ± 115 mL (5.7%, p = 0.001) until maximum exercise. We found no correlation between the changes in BV and the changes in SV between each exercise intensity. The hemoglobin concentration [Hb] increased by 0.8 ± 0.3 g·dL(â1), the capillary oxygen saturation (ScO(2)) decreased by 4.0% (p < 0.001). As a result, the calculated arterial oxygen content significantly increased (18.5 ± 1.0 vs. 18.9 ± 1.0 mL·dL(â1), p = 0.001). A 1 L higher BV at VÌO(2max) was associated with a higher SV(max) of 16.2 mL (r = 0.63, p < 0.001) and QÌ(max) of 2.5 L·min(â1) (r = 0.56, p < 0.01). In conclusion, the SV strongly correlates with the cardiac dimensions, which might be the result of adaptations to an increased volume load. The positive effect of a high BV on SV is particularly noticeable at high and severe intensity exercise. The theoretically expected reduction in VÌO(2max) due to lower SV as a consequence of reduced BV is apparently compensated by the increased arterial oxygen content due to a higher [Hb]
Aggregate National Early Warning Score (NEWS) values are more important than high scores for a single vital signs parameter for discriminating the risk of adverse outcomes
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