50,409 research outputs found
Giant magnetoimpedance in crystalline Mumetal
We studied giant magnetoimpedance (GMI) effect in commercial crystalline
Mumetal, with the emphasis to sample thickness dependence and annealing
effects. By using appropriate heat treatment one can achieve GMI ratios as high
as 310%, and field sensitivity of about 20%/Oe, which is comparable to the best
GMI characteristics obtained for amorphous and nanocrystalline soft magnetic
materials.Comment: 8 pages, 3 figure
Controlling Condensate Collapse and Expansion with an Optical Feshbach Resonance
We demonstrate control of the collapse and expansion of an 88Sr Bose-Einstein
condensate using an optical Feshbach resonance (OFR) near the 1S0-3P1
intercombination transition at 689 nm. Significant changes in dynamics are
caused by modifications of scattering length by up to +- ?10a_bg, where the
background scattering length of 88Sr is a_bg = -2a0 (1a0 = 0.053 nm). Changes
in scattering length are monitored through changes in the size of the
condensate after a time-of-flight measurement. Because the background
scattering length is close to zero, blue detuning of the OFR laser with respect
to a photoassociative resonance leads to increased interaction energy and a
faster condensate expansion, whereas red detuning triggers a collapse of the
condensate. The results are modeled with the time-dependent nonlinear
Gross-Pitaevskii equation.Comment: 5 pages, 3 figure
Linear Rheological Response of a Series of Densely Branched Brush Polymers
We have examined the linear rheological responses of a series of welldefined, dense, regularly branched brush polymers. These narrow molecular weight distribution brush polymers had polynorobornene backbones with degrees of
polymerization (DP) of 200, 400, and 800 and polylactide side chains with molecular weight of 1.4 kDa, 4.4 kDa, and 8.7 kDa. The master curves for these brush polymers
were obtained by time temperature superposition (TTS) of the dynamic moduli over the range from the glassy region to the terminal flow region. Similar to other long chain branched polymers, these densely branched brush polymers show a sequence of relaxation. Subsequent to the glassy relaxation, two different relaxation processes can be observed for samples with the high molecular weight (4.4 and 8.7 kDa) side chains, corresponding to the relaxation of the side chains and the brush polymer backbone. Influenced by the large volume fraction of high molecular weight side chains, these brush polymers are unentangled. The lowest plateau observed in the dynamic response is not the rubbery entanglement plateau but is instead associated with the steady state recoverable compliance. Side chain properties affect the rheological responses of these
densely branched brush polymers and determine their glassy behaviors
Impact of motion along the field direction on geometric-phase-induced false electric dipole moment signals
Geometric-phase-induced false electric dipole moment (EDM) signals, resulting
from interference between magnetic field gradients and particle motion in
electric fields, have been studied extensively in the literature, especially
for neutron EDM experiments utilizing stored ultracold neutrons and
co-magnetometer atoms. Previous studies have considered particle motion in the
transverse plane perpendicular to the direction of the applied electric and
magnetic fields. We show, via Monte Carlo studies, that motion along the field
direction can impact the magnitude of this false EDM signal if the wall
surfaces are rough such that the wall collisions can be modeled as diffuse,
with the results dependent on the size of the storage cell's dimension along
the field direction.Comment: 7 pages, 3 figures, NIM A, in pres
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