6,664 research outputs found
Slow Dynamics in Glasses
Minimalist theories of complex systems are broadly of two kinds: mean-field
and axiomatic. So far all theories of complex properties absent from simple
systems and intrinsic to glasses are axiomatic. Stretched Exponential
Relaxation (SER) is the prototypical complex temporal property of glasses,
discovered by Kohlrausch 150 years ago, and now observed almost universally in
microscopically homogeneous, complex non-equilibrium materials, including
luminescent electronic (Coulomb) glasses. Critical comparison of alternative
axiomatic theories with both numerical simulations and experiments strongly
favors dynamical trap models over static percolative or energy landscape
models.
PACS: 61.20.Lc; 67.40.F
Easy on that trigger dad: a study of long term family photo retrieval
We examine the effects of new technologies for digital photography on people's longer term storage and access to collections of personal photos. We report an empirical study of parents' ability to retrieve photos related to salient family events from more than a year ago. Performance was relatively poor with people failing to find almost 40% of pictures. We analyze participants' organizational and access strategies to identify reasons for this poor performance. Possible reasons for retrieval failure include: storing too many pictures, rudimentary organization, use of multiple storage systems, failure to maintain collections and participants' false beliefs about their ability to access photos. We conclude by exploring the technical and theoretical implications of these findings
Spectral representation of the effective dielectric constant of graded composites
We generalize the Bergman-Milton spectral representation, originally derived
for a two-component composite, to extract the spectral density function for the
effective dielectric constant of a graded composite. This work has been
motivated by a recent study of the optical absorption spectrum of a graded
metallic film [Applied Physics Letters, 85, 94 (2004)] in which a broad
surface-plasmon absorption band has been shown to be responsible for enhanced
nonlinear optical response as well as an attractive figure of merit. It turns
out that, unlike in the case of homogeneous constituent components, the
characteristic function of a graded composite is a continuous function because
of the continuous variation of the dielectric function within the constituent
components. Analytic generalization to three dimensional graded composites is
discussed, and numerical calculations of multilayered composites are given as a
simple application.Comment: Physical Review E, submitted for publication
Dissipationless Anomalous Hall Current in Films
The observation of dissipationless anomalous Hall current is one of the
experimental evidences to confirm the intrinsic origin of anomalous Hall
effect. To study the origin of anomalous Hall effect in iron,
Fe(SiO) granular films with volume fraction of SiO
0\le x \le 40.51 were fabricated using co-sputtering. Hall and longitudinal
resistivities were measured in the temperature range 5 to 350 K with magnetic
fields up to 5 Tesla. As x increased from 0 to 40.51, the anomalous Hall
resistivity and longitudinal resistivity increased about 4 and 3 orders in
magnitude, respectively. Analysis of the results revealed that the normalized
anomalous Hall conductivity is a constant for all the samples, the evidence of
dissipationless anomalous Hall current in Fe.Comment: 17 pages, 5 figures;
http://link.aps.org/doi/10.1103/PhysRevB.83.20531
Theory of Optical Transmission through Elliptical Nanohole Arrays
We present a theory which explains (in the quasistatic limit) the
experimentally observed [R. Gordon, {\it et al}, Phys. Rev. Lett. {\bf 92},
037401 (2004)] squared dependence of the depolarization ratio on the aspect
ratio of the holes, as well as other features of extraordinary light
transition. We calculated the effective dielectric tensor of a metal film
penetrated by elliptical cylindrical holes and found the extraordinarily light
transmission at special frequencies related to the surface plasmon resonances
of the composite film. We also propose to use the magnetic field for getting a
strong polarization effect, which depends on the ratio of the cyclotron to
plasmon frequencies.Comment: 4 pages, 4 figure
Dielectric Behavior of Nonspherical Cell Suspensions
Recent experiments revealed that the dielectric dispersion spectrum of
fission yeast cells in a suspension was mainly composed of two sub-dispersions.
The low-frequency sub-dispersion depended on the cell length, whereas the
high-frequency one was independent of it. The cell shape effect was
qualitatively simulated by an ellipsoidal cell model. However, the comparison
between theory and experiment was far from being satisfactory. In an attempt to
close up the gap between theory and experiment, we considered the more
realistic cells of spherocylinders, i.e., circular cylinders with two
hemispherical caps at both ends. We have formulated a Green function formalism
for calculating the spectral representation of cells of finite length. The
Green function can be reduced because of the azimuthal symmetry of the cell.
This simplification enables us to calculate the dispersion spectrum and hence
access the effect of cell structure on the dielectric behavior of cell
suspensions.Comment: Preliminary results have been reported in the 2001 March Meeting of
the American Physical Society. Accepted for publications in J. Phys.:
Condens. Matte
Optical nonlinearity enhancement of graded metal-dielectric composite films
We have derived the local electric field inside graded metal-dielectric
composite films with weak nonlinearity analytically, which further yields the
effective linear dielectric constant and third-order nonlinear susceptibility
of the graded structures. As a result, the composition-dependent gradation can
produce a broad resonant plasmon band in the optical region, resulting in a
large enhancement of the optical nonlinearity and hence a large figure of
merit.Comment: 11 pages, 2 figures. To be published in Europhysics Letter
Electrorotation of a pair of spherical particles
We present a theoretical study of electrorotation (ER) of two spherical
particles under the action of a rotating electric field. When the two particles
approach and finally touch, the mutual polarization interaction between the
particles leads to a change in the dipole moment of the individual particle and
hence the ER spectrum, as compared to that of the well-separated particles. The
mutual polarization effects are captured by the method of multiple images. From
the theoretical analysis, we find that the mutual polarization effects can
change the characteristic frequency at which the maximum angular velocity of
electrorotation occurs. The numerical results can be understood in the spectral
representation theory.Comment: Minor revisions; accepted by Phys. Rev.
Statistical-mechanical theory of the overall magnetic properties of mesocrystals
The mesocrystal showing both electrorheological and magnetorheological
effects is called electro-magnetorheological (EMR) solids. Prediction of the
overall magnetic properties of the EMR solids is a challenging task due to the
coexistence of the uniaxially anisotropic behavior and structural transition as
well as long-range interaction between the suspended particles. To consider the
uniaxial anisotropy effect, we present an anisotropic Kirkwood-Fr\"{o}hlich
equation for calculating the effective permeabilities by adopting an explicit
characteristic spheroid rather than a characteristic sphere used in the
derivation of the usual Kirkwood-Fr\"{o}hlich equation. Further, by applying an
Ewald-Kornfeld formulation we are able to investigate the effective
permeability by including the structural transition and long-range interaction
explicitly. Our theory can reduce to the usual Kirkwood-Fr\"{o}hlich equation
and Onsager equation naturally. To this end, the numerical simulation shows the
validity of monitoring the structure of EMR solids by detecting their effective
permeabilities.Comment: 14 pages, 1 figur
Fiber Optic Tactical Local Network (FOTLAN)
A 100 Mbit/s FDDI (fiber distributed data interface) network interface unit is described that supports real-time data, voice and video. Its high-speed interrupt-driven hardware architecture efficiently manages stream and packet data transfer to the FDDI network. Other enhancements include modular single-mode laser-diode fiber optic links to maximize node spacing, optic bypass switches for increased fault tolerance, and a hardware performance monitor to gather real-time network diagnostics
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