3,043 research outputs found
Bioaccessibility and human health risk : chromium in Glasgow
The assessment of risk to human health from contaminated land is based on a
comparison of predicted human exposure to a contaminant with a Health Criteria Value
(HCV) that represents an exposure below which there is thought to be little or no risk to
human health. Most assessment tools, such as the Contaminated Land Exposure
Assessment Model (CLEA), use estimates of exposure based on intake (consumption rate)
rather than on measures of uptake (the amount of contaminant which enters the
bloodstream), thus allowing comparison with HCVs, which are also based on intake
apposed to uptake. Soil Guideline Values (SGVs) derived using the CLEA model assume
that a soil contaminant will be taken up into the body to the same extent as from the
medium of exposure used to derive the oral HCV (e.g. soluble salts of Cr(VI)). This is a
conservative assumption as contaminants can be tightly bound to other soil components,
thus reducing bioavailability (the fraction of a contaminant that can be absorbed by the
body)
Spectrum of a magnetized strong-leg quantum spin ladder
Inelastic neutron scattering is used to measure the spin excitation spectrum
of the Heisenberg ladder material (CHN)CuBr in its
entirety, both in the gapped spin-liquid and the magnetic field induced
Tomonaga-Luttinger spin liquid regimes. A fundamental change of the spin
dynamics is observed between these two regimes. DMRG calculations
quantitatively reproduce and help understand the observed commensurate and
incommensurate excitations. The results validate long-standing quantum field
theoretical predictions, but also test the limits of that approach
On a self-sustained process at large scale in the turbulent channel flow
Large-scale motions, important in turbulent shear flows, are frequently
attributed to the interaction of structures at smaller scale. Here we show
that, in a turbulent channel at Re_{\tau} \approx 550, large-scale motions can
self-sustain even when smaller-scale structures populating the near-wall and
logarithmic regions are artificially quenched. This large-scale self-sustained
mechanism is not active in periodic boxes of width smaller than Lz ~ 1.5h or
length shorter than Lx ~ 3h which correspond well to the most energetic large
scales observed in the turbulent channel
Crystalline Electric Field Randomness in the Triangular Lattice Spin-Liquid YbMgGaO
We apply moderate-high-energy inelastic neutron scattering (INS) measurements
to investigate Yb crystalline electric field (CEF) levels in the
triangular spin-liquid candidate YbMgGaO. Three CEF excitations from the
ground-state Kramers doublet are centered at the energies = 39,
61, and 97\,meV in agreement with the effective \mbox{spin-1/2} -factors and
experimental heat capacity, but reveal sizable broadening. We argue that this
broadening originates from the site mixing between Mg and Ga
giving rise to a distribution of Yb--O distances and orientations and, thus, of
CEF parameters that account for the peculiar energy profile of the CEF
excitations. The CEF randomness gives rise to a distribution of the effective
spin-1/2 -factors and explains the unprecedented broadening of low-energy
magnetic excitations in the fully polarized ferromagnetic phase of YbMgGaO,
although a distribution of magnetic couplings due to the Mg/Ga disorder may be
important as well.Comment: Accepted in Phys. Rev. Let
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