63,454 research outputs found
Reversal Modes of Simulated Iron Nanopillars in an Obliquely Oriented Field
Stochastic micromagnetic simulations are employed to study switching in
three-dimensional magnetic nanopillars exposed to highly misaligned fields. The
switching appears to proceed through two different decay modes, characterized
by very different average lifetimes and different average values of the
transverse magnetization components.Comment: 3 pages, 4 figure
Reaction cross-section predictions for nucleon induced reactions
A microscopic calculation of the optical potential for nucleon-nucleus
scattering has been performed by explicitly coupling the elastic channel to all
the particle-hole (p-h) excitation states in the target and to all relevant
pickup channels. These p-h states may be regarded as doorway states through
which the flux flows to more complicated configurations, and to long-lived
compound nucleus resonances. We calculated the reaction cross sections for the
nucleon induced reactions on the targets Ca, Ni, Zr and
Sm using the QRPA description of target excitations, coupling to all
inelastic open channels, and coupling to all transfer channels corresponding to
the formation of a deuteron. The results of such calculations were compared to
predictions of a well-established optical potential and with experimental data,
reaching very good agreement. The inclusion of couplings to pickup channels
were an important contribution to the absorption. For the first time,
calculations of excitations account for all of the observed reaction
cross-sections, at least for incident energies above 10 MeV.Comment: 6 pages, 6 figures. Submitted to INPC 2010 Conference Proceeding
Analysis techniques for multivariate root loci
Analysis and techniques are developed for the multivariable root locus and the multivariable optimal root locus. The generalized eigenvalue problem is used to compute angles and sensitivities for both types of loci, and an algorithm is presented that determines the asymptotic properties of the optimal root locus
A ratio model of perceived speed in the human visual system
The perceived speed of moving images changes over time. Prolonged viewing of a pattern (adaptation) leads to an exponential decrease in its perceived speed. Similarly, responses of neurones tuned to motion reduce exponentially over time. It is tempting to link these phenomena. However, under certain conditions, perceived speed increases after adaptation and the time course of these perceptual effects varies widely. We propose a model that comprises two temporally tuned mechanisms whose sensitivities reduce exponentially over time. Perceived speed is taken as the ratio of these filters' outputs. The model captures increases and decreases in perceived speed following adaptation and describes our data well with just four free parameters. Whilst the model captures perceptual time courses that vary widely, parameter estimates for the time constants of the underlying filters are in good agreement with estimates of the time course of adaptation of direction selective neurones in the mammalian visual system
Observation of Free-Space Single-Atom Matterwave Interference
We observe matterwave interference of a single cesium atom in free fall. The
interferometer is an absolute sensor of acceleration and we show that this
technique is sensitive to forces at the level of N with a
spatial resolution at the micron scale. We observe the build up of the
interference pattern one atom at a time in an interferometer where the mean
path separation extends far beyond the coherence length of the atom. Using the
coherence length of the atom wavepacket as a metric, we directly probe the
velocity distribution and measure the temperature of a single atom in free
fall.Comment: 5 pages, 4 figure
Hemostatic factors and risk of coronary heart disease in general populations: new prospective study and updated meta-analyses
<p>Background: Activation of blood coagulation and fibrinolysis may be associated with increased risk of coronary heart disease. We aimed to assess associations of circulating tissue plasminogen activator (t-PA) antigen, D-dimer and von Willebrand factor (VWF) with coronary heart disease risk.</p>
<p>Design: Prospective case-control study, systematic review and meta-analyses.</p>
<p>Methods: Measurements were made in 1925 people who had a first-ever nonfatal myocardial infarction or died of coronary heart disease during follow-up (median 19.4 years) and in 3616 controls nested within the prospective population-based Reykjavik Study.</p>
<p>Results: Age and sex-adjusted odds ratios for coronary heart disease per 1 standard deviation higher baseline level were 1.25 (1.18, 1.33) for t-PA antigen, 1.01 (0.95, 1.07) for D-dimer and 1.11 (1.05, 1.18) for VWF. After additional adjustment for conventional cardiovascular risk factors, corresponding odds ratios were 1.07 (0.99, 1.14) for t-PA antigen, 1.06 (1.00, 1.13) for D-dimer and 1.08 (1.02, 1.15) for VWF. When combined with the results from previous prospective studies in a random-effects meta-analysis, overall adjusted odds ratios were 1.13 (1.06, 1.21) for t-PA antigen (13 studies, 5494 cases), 1.23 (1.16, 1.32) with D-dimer (18 studies, 6799 cases) and 1.16 (1.10, 1.22) with VWF (15 studies, 6556 cases).</p>
<p>Conclusions: Concentrations of t-PA antigen, D-dimer and VWF may be more modestly associated with first-ever CHD events than previously reported. More detailed analysis is required to clarify whether these markers are causal risk factors or simply correlates of coronary heart disease.</p>
Volunteer studies replacing animal experiments in brain research - Report and recommendations of a Volunteers in Research and Testing workshop
Fano resonance resulting from a tunable interaction between molecular vibrational modes and a double-continuum of a plasmonic metamolecule
Coupling between tuneable broadband modes of an array of plasmonic
metamolecules and a vibrational mode of carbonyl bond of poly(methyl
methacrylate) is shown experimentally to produce a Fano resonance, which can be
tuned in situ by varying the polarization of incident light. The interaction
between the plasmon modes and the molecular resonance is investigated using
both rigorous electromagnetic calculations and a quantum mechanical model
describing the quantum interference between a discrete state and two continua.
The predictions of the quantum mechanical model are in good agreement with the
experimental data and provide an intuitive interpretation, at the quantum
level, of the plasmon-molecule coupling
- …