980 research outputs found
Anomalous NMR Spin-Lattice Relaxation in SrB_{6} and Ca_{1-x}La_{x}B_{6}
We report the results of {11}B nuclear magnetic resonance (NMR) measurements
of SrB_{6} and Ca_{0.995}La_{0.05}B_{6} below room temperature. Although the
electrical resistivities of these two materials differ substantially, their
{11}B-NMR responses exhibit some strikingly common features. Both materials
exhibit ferromagnetic order, but their {11}B-NMR spectra reveal very small
hyperfine fields at the Boron sites. The spin lattice relaxation T_{1}^{-1}
varies considerably with external field but changes with temperature only below
a few K. We discuss these unusual results by considering various different
scenarios for the electronic structure of these materials.Comment: Accepted for publication in Phys. Rev. B Rapid communication, 4
pages, 3 figures. This manuscript replaces an earlier version and includes
some minor changes in the text and in Fig.
Liver copper concentrations in cull cattle in the UK: are cattle being copper loaded?
With the release of the Department for the Environment, Food and Rural Affairs/Advisory Committee on Animal Feed Guidance Note for Supplementing Copper to Bovines it was noted that the current copper status of the national herd was not known. Liver samples were recovered from 510 cull cattle at a single abattoir across a period of three days. The samples were wet-ashed and liver copper concentrations determined by inductively coupled plasma mass spectrometry analysis. Breed, age and previous location information were obtained from the British Cattle Movement Service. Dairy breeds had higher liver copper concentrations than beef breeds. Holstein-Friesian and âotherâ dairy breeds had 38.3 per cent and 40 per cent of cattle above the Animal Health and Veterinary Laboratories Agency (AHVLA) reference range (8000â
”mol/kg dry matter), respectively, whereas only 16.9 per cent of animals in the combined beef breeds exceeded this value. It was found that underlying topsoil copper concentration was not related to liver copper content and that age of the animal also had little effect on liver concentration. In conclusion, over 50 per cent of the liver samples tested had greater-than-normal concentrations of copper with almost 40 per cent of the female dairy cattle having liver copper concentrations above the AHVLA reference range, indicating that a significant proportion of the UK herd is at risk of chronic copper toxicity
Fermi Surface Measurements on the Low Carrier Density Ferromagnet Ca1-xLaxB6 and SrB6
Recently it has been discovered that weak ferromagnetism of a dilute 3D
electron gas develops on the energy scale of the Fermi temperature in some of
the hexaborides; that is, the Curie temperature approximately equals the Fermi
temperature. We report the results of de Haas-van Alphen experiments on two
concentrations of La-doped CaB6 as well as Ca-deficient Ca1-dB6 and
Sr-deficient Sr1-dB6. The results show that a Fermi surface exists in each case
and that there are significant electron-electron interactions in the low
density electron gas.Comment: 4 pages, 5 figures, submitted to PR
The Debye-Waller Factor in solid 3He and 4He
The Debye-Waller factor and the mean-squared displacement from lattice sites
for solid 3He and 4He were calculated with Path Integral Monte Carlo at
temperatures between 5 K and 35 K, and densities between 38 nm^(-3) and 67
nm^(-3). It was found that the mean-squared displacement exhibits finite-size
scaling consistent with a crossover between the quantum and classical limits of
N^(-2/3) and N^(-1/3), respectively. The temperature dependence appears to be
T^3, different than expected from harmonic theory. An anisotropic k^4 term was
also observed in the Debye-Waller factor, indicating the presence of
non-Gaussian corrections to the density distribution around lattice sites. Our
results, extrapolated to the thermodynamic limit, agree well with recent values
from scattering experiments.Comment: 5 figure
Charge dynamics and "ferromagnetism" of A1-xLaxB6 (A=Ca and Sr)
Ferromagnetism has been reported recently in La-doped alkaline-earth
hexaborides, A1-xLaxB6 (A=Ca, Sr, and Ba). We have performed the reflectivity,
Hall resistivity, and magnetization measurements of A1-xLaxB6. The results
indicate that A1-xLaxB6 can be regarded as a simple doped semimetal, with no
signature of an excitonic state as suggested by several theories. It is also
found that the surface of as-grown samples (10 micrometer in thickness) has a
different electronic structure from a bulk one, and a fairly large number of
paramagnetic moments are confined in this region. After eliminating these
paramagnetic moments at the surface, we could not find any evidence of an
intrinsic ferromagnetic moment in our samples, implying the possibility that
the ferromagnetism of A1-xLaxB6 reported so far is neither intrinsic.Comment: 7 pages, 8 figure
Solidification of Al-Sn-Cu based immiscible alloys under intense shearing
The official published version of the Article can be accessed from the link below - Copyright @ 2009 The Minerals, Metals & Materials Society and ASM InternationalThe growing importance of Al-Sn based alloys as materials for engineering applications
necessitates the development of uniform microstructures with improved performance. Guided by the recently thermodynamically assessed Al-Sn-Cu system, two model immiscible alloys, Al-45Sn-10Cu and Al-20Sn-10Cu, were selected to investigate the effects of intensive melt shearing provided by the novel melt conditioning by advanced shear technology (MCAST) unit on the uniform dispersion of the soft Sn phase in a hard Al matrix. Our experimental results have confirmed that intensive melt shearing is an effective way to achieve fine and uniform
dispersion of the soft phase without macro-demixing, and that such dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm and 60 seconds will be adequate to produce fine and uniform dispersion of the Sn phase, and that higher shearing speed and prolonged shearing time can only achieve minor further refinement.This work is funded by the EPSRC and
DT
High Temperature Electron Localization in dense He Gas
We report new accurate mesasurements of the mobility of excess electrons in
high density Helium gas in extended ranges of temperature and density to ascertain
the effect of temperature on the formation and dynamics of localized electron
states. The main result of the experiment is that the formation of localized
states essentially depends on the relative balance of fluid dilation energy,
repulsive electron-atom interaction energy, and thermal energy. As a
consequence, the onset of localization depends on the medium disorder through
gas temperature and density. It appears that the transition from delocalized to
localized states shifts to larger densities as the temperature is increased.
This behavior can be understood in terms of a simple model of electron
self-trapping in a spherically symmetric square well.Comment: 23 pages, 13 figure
Azimuthal Correlations in the Target Fragmentation Region of High Energy Nuclear Collisions
Results on the target mass dependence of proton and pion pseudorapidity
distributions and of their azimuthal correlations in the target rapidity range
are presented. The data have been taken with the
Plastic-Ball detector set-up for 4.9 GeV p + Au collisions at the Berkeley
BEVALAC and for 200 GeV/ p-, O-, and S-induced reactions on
different nuclei at the CERN-SPS. The yield of protons at backward rapidities
is found to be proportional to the target mass. Although protons show a typical
``back-to-back'' correlations, a ``side-by-side'' correlation is observed for
positive pions, which increases both with target mass and with impact parameter
of a collision. The data can consistently be described by assuming strong
rescattering phenomena including pion absorption effects in the entire excited
target nucleus.Comment: 7 pages, figures included, complete postscript available at
ftp://qgp.uni-muenster.de/pub/paper/azi-correlations.ps submitted to Phys.
Lett.
T-Cell Depleted Allografts From Unrelated Donors Confer A Low Risk Of Relapse On Patients With Hematologic Malignancies
Hydromorphological, hydraulic and ecological effects of restored wood: findings and reflections from an academic partnership approach
This is the peer reviewed version of the following article: Pinto, C. , Ing, R. , Browning, B. , Delboni, V. , Wilson, H. , Martyn, D. and Harvey, G. L. (2019), Hydromorphological, hydraulic and ecological effects of restored wood: findings and reflections from an academic partnership approach. Water and Environment Journal. doi:10.1111/wej.12457, which has been published in final form at https://doi.org/10.1111/wej.12457. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions© 2019 CIWEM Large wood (re)introduction can deliver multiple benefits in river restoration, but there is a dearth of the detailed and longer-term post-project monitoring and evaluation required for improving best practice. We present findings from an academic partnership approach to post-project evaluation, based on successive MSc research projects on restored large wood in the Loddon catchment, UK. Field and modelling data reveal: (i) key differences in large wood features between restored and natural reaches; (ii) increased hydraulic retention and changes to mesohabitats associated with large wood; (iii) differences in macroinvertebrate community composition around large wood but a lack of site-level effects; (iv) interactions between macrophytes and large wood that may be specific to restored reaches; (v) a need for further field and modelling studies to inform the accurate representation of large wood in hydraulic models. Some key challenges in partnership working are identified to aid planning and effectiveness of future collaborations
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