17,669 research outputs found
Non-linear vortex dynamics and transient effects in ferromagnetic disks
We report a time resolved imaging and micromagnetic simulation study of the
relaxation dynamics of a magnetic vortex in the non-linear regime. We use
time-resolved photoemission electron microscopy and micromagnetic calculations
to examine the emergence of non-linear vortex dynamics in patterned Ni80Fe20
disks in the limit of long field pulses. We show for core shifts beyond ~20-25%
of the disk radius, the initial motion is characterized by distortions of the
vortex, a transient cross-tie wall state, and instabilities in the core
polarization that influence the core trajectories.Comment: 11 pages, 3 figures, submitted to Phys. Rev. Let
Search for antiproton decay at the Fermilab Antiproton Accumulator
A search for antiproton decay has been made at the Fermilab Antiproton
Accumulator. Limits are placed on thirteen antiproton decay modes. The results
include the first explicit experimental limits on the muonic decay modes of the
antiproton, and the first limits on the decay modes e- gamma gamma, and e-
omega. The most stringent limit is for the decay mode pbar-> e- gamma. At 90%
C.L. we find that tau/B(pbar-> e- gamma) > 7 x 10^5 yr. The most stringent
limit for decay modes with a muon in the final state is for the decay pbar->
mu- gamma. At 90% C.L. we find that tau/B(pbar-> mu- gamma) > 5 x 10^4 yr.Comment: 20 pages, 8 figures. Submitted to Phys. Rev. D. Final results on 13
channels (was 15) are presente
Search for muonic decays of the antiproton at the Fermilab Antiproton Accumulator
A search for antiproton decay has been made at the Fermilab Antiproton
Accumulator. Limits are placed on six antiproton decay modes which contain a
final-state muon. At the 90% C.L. we find that
tau/B(mu gamma) > 5.0 x 10^4 yr,
tau/B(mu pi0) > 4.8 x 10^4 yr,
tau/B(mu eta) > 7.9 x 10^3 yr,
tau/B(mu gamma gamma) > 2.3 x 10^4 yr,
tau/B(mu K0S > 4.3 x 10^3 yr, and
tau/B(mu K0L) > 6.5 x 10^3 yr.Comment: 8 pages + 3 Postscript figure
Kinetic pathways of multi-phase surfactant systems
The relaxation following a temperature quench of two-phase (lamellar and
sponge phase) and three-phase (lamellar, sponge and micellar phase) samples,
has been studied in an SDS/octanol/brine system. In the three-phase case we
have observed samples that are initially mainly sponge phase with lamellar and
micellar phase on the top and bottom respectively. Upon decreasing temperature
most of the volume of the sponge phase is replaced by lamellar phase. During
the equilibriation we have observed three regimes of behaviour within the
sponge phase: (i) disruption in the sponge texture, then (ii) after the sponge
phase homogenises there is a lamellar nucleation regime and finally (iii) a
bizarre plume connects the lamellar phase with the micellar phase. The
relaxation of the two-phase sample proceeds instead in two stages. First
lamellar drops nucleate in the sponge phase forming a onion `gel' structure.
Over time the lamellar structure compacts while equilibriating into a two phase
lamellar/sponge phase sample. We offer possible explanatioins for some of these
observations in the context of a general theory for phase kinetics in systems
with one fast and one slow variable.Comment: 1 textfile, 20 figures (jpg), to appear in PR
Depression, School Performance, and the Veridicality of Perceived Grades and Causal Attributions
An external criterion was assessed to test whether depressives have distorted perceptions of covariation information and whether their attributions are consistent with this information. Students’ actual and self-perceived grades, depression status, and attributions for failures were assessed. Furthermore, partici pants estimated average grades. Generally, self-perceived own past grades were inflated. Depressed students and those with low grades distorted their own grades (but not the average grade) more to their favor than individuals low in depression and those with high grades. Depression went along with lower actual grades and with internal, stable, and global failure attributions. Mood differences in attributions were not due to differences in previous grades. Depressed individuals drew (unrealistically) more depressogenic causal inferences when they perceived average grades to be low than when average grades were perceived to be high. However, they (realistically) attributed failure more in a depressogenic fashion than did nondepressives when their own grade history was low
Morphological Observations of Mineralizing Pericardium Cardiac Grafts
Pericardial patch grafters were implanted in the hearts of young sheep for periods ranging from two to 120 days. Explants seven to 21 days old revealed the formation of a pseudoneointima (PNI) on the blood contacting surface of the pericardium. The PNI was more heavily mineralized than the pericardium. Mineralization was most intense on the blood contacting surface of the PNI and on the chamber surface of the pericardium. After three weeks of implantation, the PNI was much thinner and was organized into a thin fibrous capsule without any signs of mineralization. In the pericardium, mineral deposits were seen in fibroblasts. Moreover, cell-related mineralization was evident prior to calcification of the surrounding collagen matri
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