425 research outputs found
Copper cable theft: revisiting the price–theft hypothesis
Objectives: To test the commonly espoused but little examined hypothesis that fluctuations in the price of metal are associated with changes in the volume of metal theft. Specifically, we analyze the relationship between the price of copper and the number of police recorded 'live’ copper cable thefts from the British railway network (2006 to 2012)
Temperature dependence of the resonance and low energy spin excitations in superconducting FeTeSe
We use inelastic neutron scattering to study the temperature dependence of
the low-energy spin excitations in single crystals of superconducting
FeTeSe ( K). In the low-temperature superconducting
state, the imaginary part of the dynamic susceptibility at the electron and
hole Fermi surfaces nesting wave vector ,
, has a small spin gap, a two-dimensional
neutron spin resonance above the spin gap, and increases linearly with
increasing for energies above the resonance. While the intensity
of the resonance decreases like an order parameter with increasing temperature
and disappears at temperature slightly above , the energy of the mode is
weakly temperature dependent and vanishes concurrently above . This
suggests that in spite of its similarities with the resonance in electron-doped
superconducting BaFe(Co,Ni)As, the mode in
FeTeSe is not directly associated with the superconducting
electronic gap.Comment: 7 pages, 6 figure
A rare schizophrenia risk variant of CACNA1I disrupts CaV3.3 channel activity
CACNA1I is a candidate schizophrenia risk gene. It encodes the pore-forming human CaV3.3 α1 subunit, a subtype of voltage-gated calcium channel that contributes to T-type currents. Recently, two de novo missense variations, T797M and R1346H, of hCaV3.3 were identified in individuals with schizophrenia. Here we show that R1346H, but not T797M, is associated with lower hCaV3.3 protein levels, reduced glycosylation, and lower membrane surface levels of hCaV3.3 when expressed in human cell lines compared to wild-type. Consistent with our biochemical analyses, whole-cell hCaV3.3 currents in cells expressing the R1346H variant were ~50% of those in cells expressing WT hCaV3.3, and neither R1346H nor T797M altered channel biophysical properties. Employing the NEURON simulation environment, we found that reducing hCaV3.3 current densities by 22% or more eliminates rebound bursting in model thalamic reticular nucleus (TRN) neurons. Our analyses suggest that a single copy of Chr22: 39665939G > A CACNA1I has the capacity to disrupt CaV3.3 channel-dependent functions, including rebound bursting in TRN neurons, with potential implications for schizophrenia pathophysiology
Self-gravitating clouds of generalized Chaplygin and modified anti-Chaplygin Gases
The Chaplygin gas has been proposed as a possible dark energy, dark matter
candidate. As a working fluid in a Friedmann-Robertson-Walker universe, it
exhibits early behavior reminiscent of dark matter, but at later times is more
akin to a cosmological constant. In any such universe, however, one can expect
local perturbations to form. Here we obtain the general equations for a
self-gravitating relativistic Chaplygin gas. We solve these equations and
obtain the mass-radius relationship for such structures, showing that only in
the phantom regime is the mass-radius relationship large enough to be a serious
candidate for highly compact massive objects at the galaxy core. In addition,
we study the cosmology of a modified anti-Chaplygin gas. A self-gravitating
cloud of this matter is an exact solution to Einstein's equations.Comment: 16 page
Spin fluctuations associated with the collapse of the pseudogap in a cuprate superconductor
Theories of the origin of superconductivity in cuprates are dependent on an
understanding of their normal state which exhibits various competing orders.
Transport and thermodynamic measurements on LaSrCuO show
signatures of a quantum critical point, including a peak in the electronic
specific heat versus doping p, near the doping p*, where the pseudogap
collapses. The fundamental nature of the fluctuations associated with this peak
is unclear. Here we use inelastic neutron scattering to show that close to
and near p*, there are low-energy collective spin excitations with
characteristic energies 5 meV. The correlation length of the spin
fluctuations does not diverge in spite of the low energy scale and we conclude
that the underlying quantum criticality is not due to antiferromagnetism but
most likely to a collapse of the pseudogap. We show that the large specific
heat near p* can be understood in terms of collective spin fluctuations. The
spin fluctuations we measure exist across the superconducting phase diagram and
may be related to the strange metal behaviour observed in overdoped cuprates
Spin density wave induced disordering of the vortex lattice in superconducting LaSrCuO
We use small angle neutron scattering to study the superconducting vortex
lattice in LaSrCuO as a function of doping and magnetic field.
We show that near optimally doping the vortex lattice coordination and the
superconducting coherence length are controlled by a van-Hove singularity
crossing the Fermi level near the Brillouin zone boundary. The vortex lattice
properties change dramatically as a spin-density-wave instability is approached
upon underdoping. The Bragg glass paradigm provides a good description of this
regime and suggests that SDW order acts as a novel source of disorder on the
vortex lattice.Comment: Accepted in Phys. Rev.
BRCA1 and BRCA2 mutations in a population-based study of male breast cancer
Background: The contribution of BRCA1 and BRCA2 to the incidence of male breast cancer (MBC)
in the United Kingdom is not known, and the importance of these genes in the increased risk of female
breast cancer associated with a family history of breast cancer in a male first-degree relative is unclear.
Methods: We have carried out a population-based study of 94 MBC cases collected in the UK. We
screened genomic DNA for mutations in BRCA1 and BRCA2 and used family history data from these
cases to calculate the risk of breast cancer to female relatives of MBC cases. We also estimated the
contribution of BRCA1 and BRCA2 to this risk.
Results: Nineteen cases (20%) reported a first-degree relative with breast cancer, of whom seven also
had an affected second-degree relative. The breast cancer risk in female first-degree relatives was 2.4
times (95% confidence interval [CI] = 1.4–4.0) the risk in the general population. No BRCA1 mutation
carriers were identified and five cases were found to carry a mutation in BRCA2. Allowing for a
mutation detection sensitivity frequency of 70%, the carrier frequency for BRCA2 mutations was 8%
(95% CI = 3–19). All the mutation carriers had a family history of breast, ovarian, prostate or
pancreatic cancer. However, BRCA2 accounted for only 15% of the excess familial risk of breast
cancer in female first-degree relatives.
Conclusion: These data suggest that other genes that confer an increased risk for both female and
male breast cancer have yet to be found
Field-Induced Magnetostructural Transitions in Antiferromagnetic Fe1+yTe1-xSx
The transport and structural properties of Fe1+yTe1-xSx (x=0, 0.05, and 0.10)
crystals were studied in pulsed magnetic fields up to 65 T. The application of
high magnetic fields results in positive magnetoresistance effect with
prominent hystereses in the antiferromagnetic state. Polarizing microscope
images obtained at high magnetic fields showed simultaneous occurrence of
structural transitions. These results indicate that magnetoelastic coupling is
the origin of the bicollinear magnetic order in iron chalcogenides.Comment: 5 pages, 5 figures, accepted for publication in Journal of the
Physical Society of Japa
Hour-glass magnetic spectrum in an insulating, hole-doped antiferromagnet
Superconductivity in layered copper-oxide compounds emerges when charge
carriers are added to antiferromagnetically-ordered CuO2 layers. The carriers
destroy the antiferromagnetic order, but strong spin fluctuations persist
throughout the superconducting phase and are intimately linked to
super-conductivity. Neutron scattering measurements of spin fluctuations in
hole-doped copper oxides have revealed an unusual `hour-glass' feature in the
momentum-resolved magnetic spectrum, present in a wide range of superconducting
and non-superconducting materials. There is no widely-accepted explanation for
this feature. One possibility is that it derives from a pattern of alternating
spin and charge stripes, an idea supported by measurements on stripe-ordered
La1.875Ba0.125CuO4. However, many copper oxides without stripe order also
exhibit an hour-glass spectrum$. Here we report the observation of an
hour-glass magnetic spectrum in a hole-doped antiferromagnet from outside the
family of superconducting copper oxides. Our system has stripe correlations and
is an insulator, which means its magnetic dynamics can conclusively be ascribed
to stripes. The results provide compelling evidence that the hour-glass
spectrum in the copper-oxide superconductors arises from fluctuating stripes.Comment: 13 pages, 4 figures, to appear in Natur
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