12,106 research outputs found
Effect of regression to the mean on decision making in health care
Knowledge of regression to the mean can help with everything from interpreting test results to improving your career prospects. All healthcare professionals should be aware of its implication
Economic Mobility: Is the American Dream Alive and Well?
Draws on research analysis to outline what economic mobility is, why it matters in today's economy, and why it is important for policy makers to focus on mobility as part of the ongoing national economic debate
Dynamics of internetwork chromospheric fibrils: Basic properties and MHD kink waves
Using the spectroscopic imaging capabilities of the Swedish Solar Telescope,
we aim to provide the first investigation on the nature and dynamics of
elongated absorption features (fibrils) observed in H in the
internetwork. We observe and identify a number of internetwork fibrils, which
form away from the kilogauss, network magnetic flux, and we provide a synoptic
view on their behaviour. The internetwork fibrils are found to support
wave-like behaviour, which we interpret as Magnetohydrodynamic (MHD) kink
waves. The properties of these waves, that is, amplitude, period, and
propagation speed, are measured from time-distance diagrams and we attempt to
exploit them via magneto-seismology in order to probe the variation of plasma
properties along the wave-guides. We found that the Internetwork (IN) fibrils
appear, disappear, and re-appear on timescales of tens of minutes, suggesting
that they are subject to repeated heating. No clear photospheric footpoints for
the fibrils are found in photospheric magnetograms or H wing images.
However, we suggest that they are magnetised features as the majority of them
show evidence of supporting propagating MHD kink waves, with a modal period of
~s. Additionally, one IN fibril is seen to support a flow directed along
its elongated axis, suggesting a guiding field. The wave motions are found to
propagate at speeds significantly greater than estimates for typical
chromospheric sound speeds. Through their interpretation as kink waves, the
measured speeds provide an estimate for local average Alfv\'en speeds.
Furthermore, the amplitudes of the waves are also found to vary as a function
of distance along the fibrils, which can be interpreted as evidence of
stratification of the plasma in the neighbourhood of the IN fibril.Comment: Accepted Astronomy & Astrophysic
Helium energy levels including corrections
The correction to energy is expressed in terms of an effective
Hamiltonian for an arbitrary state of helium. Numerical calculations
are performed for levels, and the previous result for the centroid
is corrected. While the resulting theoretical predictions for the ionization
energy are in moderate agreement with experimental values for , ,
and states, they are in significant disagreement for the singlet state
.Comment: 11 pages, with erratum submitted to Phys. Rev. A (2007
Spin-dependent recombination in Czochralski silicon containing oxide precipitates
Electrically detected magnetic resonance is used to identify recombination
centers in a set of Czochralski grown silicon samples processed to contain
strained oxide precipitates with a wide range of densities (~ 1e9 cm-3 to ~
7e10 cm-3). Measurements reveal that photo-excited charge carriers recombine
through Pb0 and Pb1 dangling bonds and comparison to precipitate-free material
indicates that these are present at both the sample surface and the oxide
precipitates. The electronic recombination rates vary approximately linearly
with precipitate density. Additional resonance lines arising from iron-boron
and interstitial iron are observed and discussed. Our observations are
inconsistent with bolometric heating and interpreted in terms of spin-dependent
recombination. Electrically detected magnetic resonance is thus a very powerful
and sensitive spectroscopic technique to selectively probe recombination
centers in modern photovoltaic device materials.Comment: 8 pages, 8 figure
Electrified hydraulic power steering system in hybrid electric heavy trucks
Over the last 20 years, conventional automotive engine ancillaries have migrated from being mechanically powered to electrically powered in order to meet market demand. To adopt this trend in heavy trucks requires a higher power electrical system in order to cope with the higher loads placed upon it. Until the advent of the hybrid electric heavy truck (HET) this power infrastructure has not been available. HET's require a higher voltage system in order to reduce losses and provide adequate power and voltage levels for the traction motor. This study investigates for the first time the benefit of electrifying a hydraulic power assisted steering system in an HET. The developed electrical hydraulic power steering (EHPS), using a high-voltage traction battery, is found to drastically reduce the consumed energy over a drive cycle by optimal operation of the pump over the driving cycle. Empirical data from a prototype HET with EHPS confirms the simulation results from Dymola
Space-Time Variation of Physical Constants and Relativistic Corrections in Atoms
Detection of high-redshift absorption in the optical spectra of quasars have
provided a powerful tool to measure spatial and temporal variations of physical
``constants'' in the Universe. It is demonstrated that high sensitivity to the
variation of the fine structure constant alpha can be obtained from a
comparison of the spectra of heavy and light atoms (or molecules). We have
performed calculations for the pair FeII and MgII for which accurate quasar and
laboratory spectra are available. A possibility of times enhanced
effects of the fundamental constants variation suitable for laboratory
measurements is also discussed.Comment: 8 pages; LaTeX; Submitted to Phys. Rev. Let
Dynamic analysis of a lithium-boiling potassium refractory metal Rankine cycle power system for the Jet Propulsion Laboratory
Lithium-boiling potassium refractory metal Rankine cycle power system heat transfer model
The basic chemistry of exercise-induced DNA oxidation:oxidative damage, redox signalling and their interplay
Acute exercise increases reactive oxygen and nitrogen species generation. This phenomenon is associated with two major outcomes: (1) redox signalling and (2) macromolecule damage. Mechanistic knowledge of how exercise-induced redox signalling and macromolecule damage are interlinked is limited. This review focuses on the interplay between exercise-induced redox signalling and DNA damage, using hydroxyl radical (·OH) and hydrogen peroxide (H2O2) as exemplars. It is postulated that the biological fate of H2O2 links the two processes and thus represents a bifurcation point between redox signalling and damage. Indeed, H2O2 can participate in two electron signalling reactions but its diffusion and chemical properties permit DNA oxidation following reaction with transition metals and ·OH generation. It is also considered that the sensing of DNA oxidation by repair proteins constitutes a non-canonical redox signalling mechanism. Further layers of interaction are provided by the redox regulation of DNA repair proteins and their capacity to modulate intracellular H2O2 levels. Overall, exercise-induced redox signalling and DNA damage may be interlinked to a greater extent than was previously thought but this requires further investigation
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