10,227 research outputs found
Dissipationless Anomalous Hall Current in the Ferromagnetic Spinel CuCrSeBr
In a ferromagnet, an applied electric field invariably produces an
anomalous Hall current that flows perpendicular to the plane
defined by and (the magnetization). For decades, the question
whether is dissipationless (independent of the scattering rate),
has been keenly debated without experimental resolution. In the ferromagnetic
spinel CuCrSeBr, the resistivity (at low temperature)
may be increased 1000 fold by varying (Br), without degrading the .
We show that (normalized per carrier, at 5 K) remains unchanged
throughout. In addition to resolving the controversy experimentally, our
finding has strong bearing on the generation and study of spin-Hall currents in
bulk samples.Comment: 7 pages, 6 figure
Anomalous thermopower and Nernst effect in : entropy-current loss in precursor state
The heavy-electron superconductor CeCoIn exhibits a puzzling precursor
state above its superconducting critical temperature at = 2.3 K. The
thermopower and Nernst signal are anomalous. Below 15 K, the entropy current of
the electrons undergoes a steep decrease reaching 0 at .
Concurrently, the off-diagonal thermoelectric current is
enhanced. The delicate sensitivity of the zero-entropy state to field implies
phase coherence over large distances. The prominent anomalies in the
thermoelectric current contrast with the relatively weak effects in the
resistivity and magnetization.Comment: 5 figures, 4 page
A fluorescence in situ staining method for investigating spores and vegetative cells of Clostridia by confocal laser scanning microscopy and structured illuminated microscopy
Non-pathogenic spore-forming Clostridia are of increasing interest due to their application in biogas production
and their capability to spoil different food products. The life cycle for Clostridium includes a spore stage that can
assist in survival under environmentally stressful conditions, such as extremes of temperature or pH. Due to their
size, spores can be investigated by a range of microscopic techniques, many of which involve sample pretreatment.
We have developed a quick, simple and non-destructive fluorescent staining procedure that allows a
clear differentiation between spores and vegetative cells and effectively stains spores, allowing recovery and
tracking in subsequent experiments. Hoechst 34580, Propidium iodide and wheat germ agglutinin WGA 488
were used in combination to stain four strains of Clostridia at different life cycle stages. Staining was conducted
without drying the sample, preventing changes induced by dehydration and cells observed by confocal laser
scanner microscopy or using a super-resolution microscope equipped with a 3D-structured illumination module.
Dual staining with Hoechst/Propidium iodide differentiated spores from vegetative cells, provided information
on the viability of cells and was successfully applied to follow spore production induced by heating. Superresolution
microscopy of spores probed by Hoechst 34580 also allowed chromatin to be visualised. Direct
staining of a cheese specimen using Nile Red and Fast Green allowed in situ observation of spores within the
cheese and their position within the cheese matrix. The proposed staining method has broad applicability and
can potentially be applied to follow Clostridium spore behaviour in a range of different environments
Topological Dislocations and Mixed State of Charge Density Waves
We discuss the possibility of the ``mixed state'' in incommensurate charge
density waves with three-dimensional order. It is shown that the mixed state
can be created by applying an electric field perpendicular to the chains. This
state consists of topological dislocations induced by the external field and is
therefore similar to the mixed states of superfluids (type-II superconductor or
liquid Helium II). However, the peculiar coupling of charge density waves with
the electric field strongly modifies the nature of the mixed state compared to
the conventional superfluids. The field and temperature dependence of the
properties of the mixed state are studied, and some experimental aspects are
discussed.Comment: 10 pages, Revtex format, no figures, to appear in Phys. Rev. Let
Thermal Hall Conductivity as a Probe of Gap Structure in Multi-band Superconductors: The Case of
The sign and profile of the thermal Hall conductivity gives
important insights into the gap structure of multi-band superconductors. With
this perspective, we have investigated and the thermal
conductivity in which display large
peak anomalies in the superconducting state. The anomalies imply that a large
hole-like quasiparticle (qp) population exists below the critical temperature
. We show that the qp mean-free-path inferred from
reproduces the observed anomaly in , providing a consistent
estimate of a large qp population. Further, we demonstrate that the hole-like
signal is consistent with a theoretical scenario where despite potentially
large gap variations on the electron pockets, the minimal homogeneous gap of
the superconducting phase resides at a hole pocket. Implications for probing
the gap structure in the broader class of pnictide superconductors are
discussed.Comment: 5 pages, 4 figures. Orientation significantly updated from previous
(0811.4668v1) reflecting new theoretical understanding of experimental
results and physical implications. Introduction, discussion, and figures
updated including additional figure for model calculatio
The likely implications of the 1997 Coroners Ordinance on the autopsy service of a teaching hospital
The new Hong Kong Coroners Ordinance was published in April 1997. It introduced an expanded set of guidelines for reporting deaths to the coroner as well as the threat of criminal proceedings for non-compliance. The Ordinance is due to be implemented in early 1998. The aim of this study is to determine the likely effect of the new law on the relative proportion of coroner's and hospital (consent) autopsies. A total of 352 consecutive autopsy cases were reviewed; 170 (48.3%) were referred for coroner's autopsies and 182 (51.7%) for hospital autopsies. But applying the criteria of the current ordinance, there should have been 213 (60.5%) coroner's cases and 139 (39.5%) hospital autopsiesԸ?that is, 43 hospital autopsies should have been coroner's autopsies. Under the new Coroners Ordinance, there would be 300 (85.2%) coroner's autopsies and only 52 (14.8%) hospital autopsies. The new Coroners Ordinance is likely to result in a greater number of requests for coroner's autopsies with a corresponding decline in hospital autopsiesԸ?in our case, a shift from 48.3% of all autopsies performed to 85.2%! This increase would be due largely to the requirement for reporting stillbirths but would also be due to increased reporting for fear of Ը?criminal proceedings' for non-compliance. An absolute increase in the number of autopsies is also anticipated, although the magnitude cannot as yet be predicted.published_or_final_versio
Ferromagnetism below 10 K in Mn doped BiTe
Ferromagnetism is observed below 10 K in [Bi0.75Te0.125Mn0.125]Te. This
material has the BiTe structure, which is made from the stacking of two
Te-Bi-Te-Bi-Te blocks and one Bi-Bi block per unit cell. Crystal structure
analysis shows that Mn is localized in the Bi2 blocks, and is accompanied by an
equal amount of TeBi anti-site occupancy in the Bi2Te3 blocks. These TeBi
anti-site defects greatly enhance the Mn solubility. This is demonstrated by
comparison of the [Bi1-xMnx]Te and [Bi1-2xTexMnx]Te series; in the former, the
solubility is limited to x = 0.067, while the latter has xmax = 0.125. The
magnetism in [Bi1-xMnx]Te changes little with x, while that for
[Bi1-2xTexMnx]Te shows a clear variation, leading to ferromagnetism for x >
0.067. Magnetic hysteresis and the anomalous Hall Effect are observed for the
ferromagnetic samples.Comment: Accepted for publication in Phys. Rev.
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