243,362 research outputs found
Nanocrystalline iron at high pressure
X-ray diffraction measurements were performed on nanocrystalline iron up to 46 GPa. For nanocrystalline epsilon-Fe, analysis of lattice parameter data provides a bulk modulus, K, of 179±8 GPa and a pressure derivative of the bulk modulus, K[prime], of 3.6±0.7, similar to the large-grained control sample. The extrapolated zero-pressure unit cell volume of nanocrystalline epsilon-Fe is 22.9±0.2 Å^3, compared to 22.3±0.2 Å^3 for large-grained epsilon-Fe. No significant grain growth was observed to occur under pressure
Diagnostics of macroscopic quantum states of Bose-Einstein condensate in double-well potential by nonstationary Josephson effect
We propose a method of diagnostic of a degenerate ground state of Bose
condensate in a double well potential. The method is based on the study of the
one-particle coherent tunneling under switching the time-dependent weak
Josephson coupling between the wells. We obtain a simple expression that allows
to determine the phase of the condensate and the total number of the particles
in the condensate from the relative number of the particles in two wells
measured before the Josephson coupling is switched on and
after it is switched off. The specifics of the application of the method in the
cases of the external and the internal Josephson effect are discussed.Comment: 3 page
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Laser-assisted photothermal imprinting of nanocomposite
We report on a laser-assisted photothermal imprinting method for directly patterning carbon
nanofiber-reinforced polyethylene nanocomposite. A single laser pulse from a solid state
Nd:YAG laser (10 ns pulse, 532 nm and 355 nm wavelengths) is used to melt/soften a thin skin
layer of the polymer nanocomposite. Meanwhile, a fused quartz mold with micro-sized surface
relief structures is pressed against the surface of the composite. Successful pattern transfer is
realized upon releasing the quartz mold. Although polyethylene is transparent to the laser beam,
the carbon nanofibers in the high density polyethylene (HDPE) matrix absorb the laser energy
and convert it into heat. Numerical heat conduction simulation shows the HDPE matrix is
partially melted or softened, allowing for easier imprinting of the relief pattern of the quartz
mold.Mechanical Engineerin
The role of components in the N(1440) resonance
The role of 5-quark components in the pion and electromagnetic decays and
transition form factors of the N(1440) is explored. The
components, where the 4-quark subsystem has the flavor-spin symmetries
and , which are expected to have
the lowest energy of all configurations, are considered in detail
with a nonrelativistic quark model. The matrix elements between the 5-quark
components of the N(1440) and the nucleon, , play a
minor role in these decays, while the transition matrix elements and that involve quark antiquark annihilation are very
significant. Both for the electromagnetic and strong decay the change from the
valence quark model value is dominated by the confinement triggered
annihilation transitions. In the case of pion decay the calculated decay width
is enhanced substantially both by the direct and also by the
confinement triggered transitions. Agreement with the
empirical value for the pion decay width may be reached with a 30%
component in the N(1440).Comment: 23 pages revte
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