4,992 research outputs found
Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles
We have studied the magnetic behavior of dextran-coated magnetite
(FeO) nanoparticles with median particle size \left=8 .
Magnetization curves and in-field M\"ossbauer spectroscopy measurements showed
that the magnetic moment of the particles was much smaller than the bulk
material. However, we found no evidence of magnetic irreversibility or
non-saturating behavior at high fields, usually associated to spin canting. The
values of magnetic anisotropy from different techniques indicate that
surface or shape contributions are negligible. It is proposed that these
particles have bulk-like ferrimagnetic structure with ordered A and B
sublattices, but nearly compensated magnetic moments. The dependence of the
blocking temperature with frequency and applied fields, ,
suggests that the observed non-monotonic behavior is governed by the strength
of interparticle interactions.Comment: 11 pages, 7 figures, 3 Table
Remote sensing and hydrologic models for performance assessment in Sirsa Irrigation Circle, India
Irrigation management / Irrigation systems / Irrigation canals / Performance evaluation / Remote sensing / GIS / Models / Irrigated farming / Hydrology / Satellite surveys / Irrigation scheduling / Evapotranspiration / India
Steady-state spin densities and currents
This article reviews steady-state spin densities and spin currents in
materials with strong spin-orbit interactions. These phenomena are intimately
related to spin precession due to spin-orbit coupling which has no equivalent
in the steady state of charge distributions. The focus will be initially on
effects originating from the band structure. In this case spin densities arise
in an electric field because a component of each spin is conserved during
precession. Spin currents arise because a component of each spin is continually
precessing. These two phenomena are due to independent contributions to the
steady-state density matrix, and scattering between the conserved and
precessing spin distributions has important consequences for spin dynamics and
spin-related effects in general. In the latter part of the article extrinsic
effects such as skew scattering and side jump will be discussed, and it will be
shown that these effects are also modified considerably by spin precession.
Theoretical and experimental progress in all areas will be reviewed
Looking for defects in the 2PI correlator
Truncations of the 2PI effective action are seen as a promising way of
studying non-equilibrium dynamics in quantum field theories. We probe their
applicability in the non-perturbative setting of topological defect formation
in a symmetry-breaking phase transition, by comparing full classical lattice
field simulations and the 2PI formulation for classical fields in an O()
symmetric scalar field theory. At next-to-leading order in 1/N, the 2PI
formalism fails to reproduce any signals of defects in the two-point function.
This suggests that one should be careful when applying the 2PI formalism for
symmetry breaking phase transitions.Comment: 22 pages, 6 figure
Observation of electronic and atomic shell effects in gold nanowires
The formation of gold nanowires in vacuum at room temperature reveals a
periodic spectrum of exceptionally stable diameters. This is identified as
shell structure similar to that which was recently discovered for alkali metals
at low temperatures. The gold nanowires present two competing `magic' series of
stable diameters, one governed by electronic structure and the other by the
atomic packing.Comment: 4 pages, 4 figure
The Chiral Condensate of Strongly Coupled QCD in the 't Hooft Limit
Using the recently proposed generalization to an arbitrary number of colors
of the strong coupling approach to lattice gauge
theories\cite{Grignani:2003uv}, we compute the chiral condensate of massless
QCD in the 't Hooft limit.Comment: 12 pages, revtex
Investigation of the Domain Wall Fermion Approach to Chiral Gauge Theories on the Lattice
We investigate a recent proposal to construct chiral gauge theories on the
lattice using domain wall fermions. We restrict ourselves to the finite volume
case, in which two domain walls are present, with modes of opposite chirality
on each of them. We couple the chiral fermions on only one of the domain walls
to a gauge field. In order to preserve gauge invariance, we have to add a
scalar field, which gives rise to additional light mirror fermion and scalar
modes. We argue that in an anomaly free model these extra modes would decouple
if our model possesses a so-called strong coupling symmetric phase. However,
our numerical results indicate that such a phase most probably does not exist.
---- Note: 9 Postscript figures are appended as uuencoded compressed tar file.Comment: 27p. Latex; UCSD/PTH 93-28, Wash. U. HEP/93-6
The Hartree ensemble approximation revisited: The "symmetric phase"
The Hartree ensemble approximation is studied in the ``symmetric phase'' of
1+1 dimensional lambda phi^4 theory. In comparison with the ``broken phase''
studied previously, it is shown that the dynamical evolution of observables
such as the particle distribution, energy exchange and auto-correlation
functions, is substantially slower. Approximate thermalization is found only
for relatively large energy densities and couplings.Comment: 17 pages RevTeX, 16 figures, 3 tables, uses amsmath and feynmp.
Extended some sections, reordered Sec.IV, added 3 refs, numerical typo
corrected, published versio
Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV
Intermediate mass fragments (IMF) from the interaction of Al,
Co and Au with 200 MeV protons were measured in an angular range
from 20 degree to 120 degree in the laboratory system. The fragments, ranging
from isotopes of helium up to isotopes of carbon, were isotopically resolved.
Double differential cross sections, energy differential cross sections and
total cross sections were extracted.Comment: accepted by Phys. Rev.
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