29,305 research outputs found
Improved electrode gives high-quality biological recordings
To obtain high quality waveforms from a subject engaged in physical activity, an improved electrode assembly has been devised. This consists of a cup containing an electrically conductive paste and a silver electrode. The paste maintains contact between the skin and the plate
Electrode for biological recording
Electrochemically reversible silver-silver chloride electrode for detecting bioelectric potential differences generated by human muscles and organ
Towards the Distributed Burning Regime in Turbulent Premixed Flames
Three-dimensional numerical simulations of canonical statistically-steady
statistically-planar turbulent flames have been used in an attempt to produce
distributed burning in lean methane and hydrogen flames. Dilatation across the
flame means that extremely large Karlovitz numbers are required; even at the
extreme levels of turbulence studied (up to a Karlovitz number of 8767)
distributed burning was only achieved in the hydrogen case. In this case,
turbulence was found to broaden the reaction zone visually by around an order
of magnitude, and thermodiffusive effects (typically present for lean hydrogen
flames) were not observed. In the preheat zone, the species compositions differ
considerably from those of one-dimensional flames based a number of different
transport models (mixture-averaged, unity Lewis number, and a turbulent eddy
viscosity model). The behaviour is a characteristic of turbulence dominating
non-unity Lewis number species transport, and the distinct limit is again
attributed to dilatation and its effect on the turbulence. Peak local reaction
rates are found to be lower in the distributed case than in the lower Karlovitz
cases but higher than in the laminar flame, which is attributed to effects that
arise from the modified fuel-temperature distribution that results from
turbulent mixing dominating low Lewis number thermodiffusive effects. Finally,
approaches to achieve distributed burning at realisable conditions are
discussed; factors that increase the likelihood of realising distributed
burning are higher pressure, lower equivalence ratio, higher Lewis number, and
lower reactant temperature
Smoking and Mortality Among US Astronauts
Astronauts have lower age-specific mortality risk than the U.S. general population from all natural causes of death, particularly cardiovascular disease and cancer. Yet, understanding if they are as healthy as their backgrounds predict they should be, requires that epidemiologists understand (and measure) all potentially confounding exposures in this cohort. Tobacco smoking prevalence has been measured in the U.S. astronaut cohort, but its impact on mortality has not been previously assessed. If smoking history has a negative impact on mortality, this could confound attempts to measure the relative health of astronauts
Correlations in Nuclear Matter
We analyze the nuclear matter correlation properties in terms of the pair
correlation function. To this aim we systematically compare the results for the
variational method in the Lowest Order Constrained Variational (LOCV)
approximation and for the Bruekner-Hartree-Fock (BHF) scheme. A formal link
between the Jastrow correlation factor of LOCV and the Defect Function (DF) of
BHF is established and it is shown under which conditions and approximations
the two approaches are equivalent. From the numerical comparison it turns out
that the two correlation functions are quite close, which indicates in
particular that the DF is approximately local and momentum independent. The
Equations of State (EOS) of Nuclear Matter in the two approaches are also
compared. It is found that once the three-body forces (TBF) are introduced the
two EOS are fairly close, while the agreement between the correlation functions
holds with or without TBF.Comment: 11 figure
Resonant tunneling in fractional quantum Hall effect: superperiods and braiding statistics
We study theoretically resonant tunneling of composite fermions through their
quasi-bound states around a fractional quantum Hall island, and find a rich set
of possible transitions of the island state as a function of the magnetic field
or the backgate voltage. These considerations have possible relevance to a
recent experimental study, and bring out many subtleties involved in deducing
fractional braiding statistics.Comment: Phys. Rev. Lett. in pres
San Marco D/L solar array system design and performance
The design and performance of the solar array system for the San Marco D/L spacecraft is described in detail. The solar array system design is shown to be suitable for spacecraft which have elastically sensitized outer surfaces to measure aerodynamic forces. However, the performance of this solar array system is shown to be at least 30 percent less efficient than conventional spacecraft solar array designs. An on-board experiment to compare the in-flight performances of Si and GaAs solar cell panels is also described. Preflight performance data show that at beginning-of-life, air mass zero solar illumination, 28 C and peak power output the Si panels are at last 20 percent less efficient than the GaAs panels
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