247 research outputs found
Familiarity and Its Impact on Consumer Decision Biases and Heuristics
The impact of familiarity on consumer decision biases and heuristics is examined. Subjects at three different familiarity levels revealed interesting differences in perceptual category breadth, usage of functional and nonfunctional product dimensions, decision time, and confidence
Thermal fluctuation field for current-induced domain wall motion
Current-induced domain wall motion in magnetic nanowires is affected by
thermal fluctuation. In order to account for this effect, the
Landau-Lifshitz-Gilbert equation includes a thermal fluctuation field and
literature often utilizes the fluctuation-dissipation theorem to characterize
statistical properties of the thermal fluctuation field. However, the theorem
is not applicable to the system under finite current since it is not in
equilibrium. To examine the effect of finite current on the thermal
fluctuation, we adopt the influence functional formalism developed by Feynman
and Vernon, which is known to be a useful tool to analyze effects of
dissipation and thermal fluctuation. For this purpose, we construct a quantum
mechanical effective Hamiltonian describing current-induced domain wall motion
by generalizing the Caldeira-Leggett description of quantum dissipation. We
find that even for the current-induced domain wall motion, the statistical
properties of the thermal noise is still described by the
fluctuation-dissipation theorem if the current density is sufficiently lower
than the intrinsic critical current density and thus the domain wall tilting
angle is sufficiently lower than pi/4. The relation between our result and a
recent result, which also addresses the thermal fluctuation, is discussed. We
also find interesting physical meanings of the Gilbert damping alpha and the
nonadiabaticy parameter beta; while alpha characterizes the coupling strength
between the magnetization dynamics (the domain wall motion in this paper) and
the thermal reservoir (or environment), beta characterizes the coupling
strength between the spin current and the thermal reservoir.Comment: 16 page, no figur
Interplay between plastic deformations and optical properties of metal surfaces : a multiscale study
Heterologously-expressed and Liposome-reconstituted Human Transient Receptor Potential Melastatin 4 Channel (TRPM4) is a Functional Tetramer
Mutation, irregular expression and sustained activation of the Transient Receptor Potential Channel, type Melastatin 4 (TRPM4), have been linked to various cardiovascular diseases. However, much remains unknown about the structure of this important ion channel. Here, we have purified a heterologously expressed TRPM4-eGFP fusion protein and investigated the oligomeric state of TRPM4-eGFP in detergent micelles using crosslinking, native gel electrophoresis, multi-angle laser light scattering and electron microscopy. Our data indicate that TRPM4 is tetrameric, like other TRP channels studied to date. Furthermore, the functionality of liposome reconstituted TRPM4-eGFP was examined using electrophysiology. Single-channel recordings from TRPM4-eGFP proteoliposomes showed inhibition of the channel using Flufenamic acid, a well-established inhibitor of TRPM4, suggesting that the channels are functional upon reconstitution. Our characterisation of the oligomeric structure of TRPM4 and the ability to reconstitute functional channels in liposomes should facilitate future studies into the structure, function and pharmacology of this therapeutically relevant channel
Why is the bandwidth of sodium observed to be narrower in photoemission experiments?
The experimentally predicted narrowing in the bandwidth of sodium is
interpreted in terms of the non-local self-energy effect on quasi-particle
energies of the electron liquid. The calculated self-energy correction is a
monotonically increasing function of the wavenumber variable. The usual
analysis of photo-emission experiments assumes the final state energies on the
nearly-free-electron-like model and hence it incorrectly ascribes the non-local
self-energy correction to the final state energies to the occupied state
energies, thus leading to a seeming narrowing in the bandwidth.Comment: 9 page
Resonant-Cavity-Induced Phase Locking and Voltage Steps in a Josephson Array
We describe a simple dynamical model for an underdamped Josephson junction
array coupled to a resonant cavity. From numerical solutions of the model in
one dimension, we find that (i) current-voltage characteristics of the array
have self-induced resonant steps (SIRS), (ii) at fixed disorder and coupling
strength, the array locks into a coherent, periodic state above a critical
number of active Josephson junctions, and (iii) when active junctions are
synchronized on an SIRS, the energy emitted into the resonant cavity is
quadratic with . All three features are in agreement with a recent
experiment [Barbara {\it et al}, Phys. Rev. Lett. {\bf 82}, 1963 (1999)]}.Comment: 4 pages, 3 eps figures included. Submitted to PRB Rapid Com
Full capacitance-matrix effects in driven Josephson-junction arrays
We study the dynamic response to external currents of periodic arrays of
Josephson junctions, in a resistively capacitively shunted junction (RCSJ)
model, including full capacitance-matrix effects}. We define and study three
different models of the capacitance matrix : Model A
includes only mutual capacitances; Model B includes mutual and self
capacitances, leading to exponential screening of the electrostatic fields;
Model C includes a dense matrix that is constructed
approximately from superposition of an exact analytic solution for the
capacitance between two disks of finite radius and thickness. In the latter
case the electrostatic fields decay algebraically. For comparison, we have also
evaluated the full capacitance matrix using the MIT fastcap algorithm, good for
small lattices, as well as a corresponding continuum effective-medium analytic
evaluation of a finite voltage disk inside a zero-potential plane. In all cases
the effective decays algebraically with distance, with
different powers. We have then calculated current voltage characteristics for
DC+AC currents for all models. We find that there are novel giant capacitive
fractional steps in the I-V's for Models B and C, strongly dependent on the
amount of screening involved. We find that these fractional steps are quantized
in units inversely proportional to the lattice sizes and depend on the
properties of . We also show that the capacitive steps
are not related to vortex oscillations but to localized screened phase-locking
of a few rows in the lattice. The possible experimental relevance of these
results is also discussed.Comment: 12 pages 18 Postscript figures, REVTEX style. Paper to appear in July
1, Vol. 58, Phys. Rev. B 1998 All PS figures include
Dynamics of a Josephson Array in a Resonant Cavity
We derive dynamical equations for a Josephson array coupled to a resonant
cavity by applying the Heisenberg equations of motion to a model Hamiltonian
described by us earlier [Phys. Rev. B {\bf 63}, 144522 (2001); Phys. Rev. B
{\bf 64}, 179902 (E)]. By means of a canonical transformation, we also show
that, in the absence of an applied current and dissipation, our model reduces
to one described by Shnirman {\it et al} [Phys. Rev. Lett. {\bf 79}, 2371
(1997)] for coupled qubits, and that it corresponds to a capacitive coupling
between the array and the cavity mode. From extensive numerical solutions of
the model in one dimension, we find that the array locks into a coherent,
periodic state above a critical number of active junctions, that the
current-voltage characteristics of the array have self-induced resonant steps
(SIRS's), that when active junctions are synchronized on a SIRS, the
energy emitted into the resonant cavity is quadratic in , and that when a
fixed number of junctions is biased on a SIRS, the energy is linear in the
input power. All these results are in agreement with recent experiments. By
choosing the initial conditions carefully, we can drive the array into any of a
variety of different integer SIRS's. We tentatively identify terms in the
equations of motion which give rise to both the SIRS's and the coherence
threshold. We also find higher-order integer SIRS's and fractional SIRS's in
some simulations. We conclude that a resonant cavity can produce threshold
behavior and SIRS's even in a one-dimensional array with appropriate
experimental parameters, and that the experimental data, including the coherent
emission, can be understood from classical equations of motion.Comment: 15 pages, 10 eps figures, submitted to Phys. Rev.
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