840 research outputs found
Local Magnetic Susceptibility of the Positive Muon in the Quasi 1D S=1/2 Antiferromagnet KCuF
We report muon spin rotation measurements of the local magnetic
susceptibility around a positive muon in the paramagnetic state of the quasi
one-dimensional spin 1/2 antiferromagnet KCuF. Signals from two distinct
sites are resolved which have a temperature dependent frequency shift which is
different than the magnetic susceptibility. This difference is attributed to a
muon induced perturbation of the spin 1/2 chain.Comment: 13 pages, 4 figures, The 2002 International Conference on Muon Spin
Rotation, Relaxation and Resonance, Virginia. US
Feminism, Abortion and Disability: irreconcilable differences?
There has been considerable discussion of the political allegiance between the feminist and disability movements, but the question of abortion remains a thorny one. Disability rights advocates have been keen to demonstrate that it is possible to believe in a woman's right to sovereignty over the body and, yet, be opposed to the selective abortion of an impaired foetus – describing the latter as a form of 'weak' eugenics.
The aim of this paper is to show that whilst there may be some points of agreement between the feminist and disability movements on the question of abortion, there exist fundamental and irreconcilable differences
Flow equation for Halpern-Huang directions of scalar O(N) models
A class of asymptotically free scalar theories with O(N) symmetry, defined
via the eigenpotentials of the Gaussian fixed point (Halpern-Huang directions),
are investigated using renormalization group flow equations. Explicit solutions
for the form of the potential in the nonperturbative infrared domain are found
in the large-N limit. In this limit, potentials without symmetry breaking
essentially preserve their shape and undergo a mass renormalization which is
governed only by the renormalization group distance parameter; as a
consequence, these scalar theories do not have a problem of naturalness.
Symmetry-breaking potentials are found to be ``fine-tuned'' in the large-N
limit in the sense that the nontrivial minimum vanishes exactly in the limit of
vanishing infrared cutoff: therefore, the O(N) symmetry is restored in the
quantum theory and the potential becomes flat near the origin.Comment: 18 pages, 4 figures, LaTeX, references added, presentation improved,
final version to appear in Phys. Rev.
Experimental support of the scaling rule for demographic stochasticity
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73613/1/j.1461-0248.2006.00903.x.pd
Correlations Between Charge Ordering and Local Magnetic Fields in Overdoped YBaCuO
Zero-field muon spin relaxation (ZF-SR) measurements were undertaken on
under- and overdoped samples of superconducting YBaCuO to
determine the origin of the weak static magnetism recently reported in this
system. The temperature dependence of the muon spin relaxation rate in
overdoped crystals displays an unusual behavior in the superconducting state. A
comparison to the results of NQR and lattice structure experiments on highly
doped samples provides compelling evidence for strong coupling of charge, spin
and structural inhomogeneities.Comment: 4 pages, 4 figures, new data, new figures and modified tex
Spin Glass Ordering in Diluted Magnetic Semiconductors: a Monte Carlo Study
We study the temperature-dilution phase diagram of a site-diluted Heisenberg
antiferromagnet on a fcc lattice, with and without the Dzyaloshinskii-Moriya
anisotropic term, fixed to realistic microscopic parameters for (IIB=Cd, Hg, Zn). We show that the dipolar Dzyaloshinskii-Moriya anisotropy
induces a finite-temperature phase transition to a spin glass phase, at
dilutions larger than 80%. The resulting probability distribution of the order
parameter P(q) is similar to the one found in the cubic lattice
Edwards-Anderson Ising model. The critical exponents undergo large finite size
corrections, but tend to values similar to the ones of the
Edwards-Anderson-Ising model.Comment: 4 pages plus 3 postscript figure
Duration of triple antithrombotic therapy and clinical outcomes after percutaneous coronary intervention in atrial fibrillation
Background: Triple antithrombotic therapy (TAT) with aspirin, a P2Y12 inhibitor, and oral anticoagulation in patients with atrial fibrillation (AF) undergoing percutaneous coronary intervention (PCI) raises concerns about increased bleeding. Regimens incorporating more potent P2Y12 inhibitors over clopidogrel have not been investigated adequately. Research design and methods: A retrospective observational study was performed on 387 patients with AF receiving TAT for 1 month (n = 236) or ≤1 week (n = 151) after PCI. Major and clinically relevant non-major bleeding and major adverse cardiac and cerebrovascular events (MACCE) were assessed up to 30 days post-procedure. Results: Bleeding was less frequent with ≤1 week versus 1 month of TAT (3.3 vs 9.3%; p = 0.025) while MACCE were similar (4.6 vs 4.7%; p = 0.998). No differences in bleeding or MACCE were observed between ticagrelor/prasugrel and clopidogrel regimens. For patients receiving ≤1 week of TAT, no excess of MACCE was seen in the subgroup given no further aspirin post-PCI compared with those given aspirin for up to 1 week (3.6 vs 5.2%). Conclusions: TAT post-PCI for ≤1 week was associated with less bleeding despite greater use of ticagrelor/prasugrel but similar MACCE versus 1-month TAT. These findings support further studies on safety and efficacy of dual therapy with ticagrelor/prasugrel immediately after PCI
A framework for predicting X-nuclei transmitter gain using 1H signal
Commercial human MR scanners are optimised for proton imaging, containing sophisticated prescan algorithms with setting parameters such as RF transmit gain and power. These are not optimal for X-nuclear application and are challenging to apply to hyperpolarised experiments, where the non-renewable magnetisation signal changes during the experiment. We hypothesised that, despite the complex and inherently nonlinear electrodynamic physics underlying coil loading and spatial variation, simple linear regression would be sufficient to accurately predict X-nuclear transmit gain based on concomitantly acquired data from the proton body coil. We collected data across 156 scan visits at two sites as part of ongoing studies investigating sodium, hyperpolarised carbon, and hyperpolarised xenon. We demonstrate that simple linear regression is able to accurately predict sodium, carbon, or xenon transmit gain as a function of position and proton gain, with variation that is less than the intrasubject variability. In conclusion, sites running multinuclear studies may be able to remove the time-consuming need to separately acquire X-nuclear reference power calibration, inferring it from the proton instead
A CsI(Tl) Scintillating Crystal Detector for the Studies of Low Energy Neutrino Interactions
Scintillating crystal detector may offer some potential advantages in the
low-energy, low-background experiments. A 500 kg CsI(Tl) detector to be placed
near the core of Nuclear Power Station II in Taiwan is being constructed for
the studies of electron-neutrino scatterings and other keV-MeV range neutrino
interactions. The motivations of this detector approach, the physics to be
addressed, the basic experimental design, and the characteristic performance of
prototype modules are described. The expected background channels and their
experimental handles are discussed.Comment: 34 pages, 11 figures, submitted to Nucl. Instrum. Method
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