11,713 research outputs found
Noise-assisted spike propagation in myelinated neurons
We consider noise-assisted spike propagation in myelinated axons within a
multi-compartment stochastic Hodgkin-Huxley model. The noise originates from a
finite number of ion channels in each node of Ranvier. For the subthreshold
internodal electric coupling, we show that (i) intrinsic noise removes the
sharply defined threshold for spike propagation from node to node, and (ii)
there exists an optimum number of ion channels which allows for the most
efficient signal propagation and it corresponds to the actual physiological
values.Comment: 8 pages, 12 figures, accepted for publication in Phys. Rev.
Componential coding in the condition monitoring of electrical machines Part 2: application to a conventional machine and a novel machine
This paper (Part 2) presents the practical application of componential coding, the principles of which were described in the accompanying Part 1 paper. Four major issues are addressed, including optimization of the neural network, assessment of the anomaly detection results, development of diagnostic approaches (based on the reconstruction error) and also benchmarking of componential coding with other techniques (including waveform measures, Fourier-based signal reconstruction and principal component analysis). This is achieved by applying componential coding to the data monitored from both a conventional induction motor and from a novel transverse flux motor. The results reveal that machine condition monitoring using componential coding is not only capable of detecting and then diagnosing anomalies but it also outperforms other conventional techniques in that it is able to separate very small and localized anomalies
Influence of the anion potential on the charge ordering in quasi-one dimensional charge transfer salts
We examine the various instabilities of quarter-filled strongly correlated
electronic chains in the presence of a coupling to the underlying lattice. To
mimic the physics of the (TMTTF)X Bechgaard-Fabre salts we also include
electrostatic effects of intercalated anions. We show that small displacements
of the anion can stabilize new mixed Charged Density Wave-Bond Order Wave
phases in which central symmetry centers are suppressed. This finding is
discussed in the context of recent experiments. We suggest that the recently
observed charge ordering is due to a cooperative effect between the Coulomb
interaction and the coupling of the electronic stacks to the anions. On the
other hand, the Spin-Peierls instability at lower temperature requires a
Peierls-like lattice coupling.Comment: Latex, 4 pages, 4 postscript figure
Threshold effects in excited charmed baryon decays
Motivated by recent results on charmed baryons from CLEO and FOCUS, we
reexamine the couplings of the orbitally excited charmed baryons. Due to its
proximity to the [Sigma_c pi] threshold, the strong decays of the
Lambda_c(2593) are sensitive to finite width effects. This distorts the shape
of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple
Breit-Wigner resonance, which has implications for the experimental extraction
of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO
data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV and h2^2 =
0.24^{+0.23}_{-0.11}, with h2 the Lambda_{c1}-> Sigma_c pi strong coupling in
the chiral Lagrangian. We also comment on the new orbitally excited states
recently observed by CLEO.Comment: 9 pages, 3 figure
The Forgotten Topic: Teaching Plant Closing to Executives and Graduate Students
Executive education programs and graduate-level business programs generally devote substantial time and resources to training professionals to open businesses, generate business growth, and manage on-going operations. Few programs, however, devote any time to a topic that many executives will one day be forced to confront: plant closings. Because relatively few managers have actually gone through the plant closing process, there are rarely âexpertsâ available to guide a company through the practical day-to-day aspects of shutting down a facility. This paper addresses the key topics needed for an advanced level program dealing with the operational aspects of closing a facility. Such topics include operations management issues, human resources considerations, and legal compliance. Following an executive level training program of this type should increase the chances of having a successful closure: one that minimizes the negative impact and uncertainty related to the closure
Physical Results from Unphysical Simulations
We calculate various properties of pseudoscalar mesons in partially quenched
QCD using chiral perturbation theory through next-to-leading order. Our results
can be used to extrapolate to QCD from partially quenched simulations, as long
as the latter use three light dynamical quarks. In other words, one can use
unphysical simulations to extract physical quantities - in this case the quark
masses, meson decay constants, and the Gasser-Leutwyler parameters L_4-L_8. Our
proposal for determining L_7 makes explicit use of an unphysical (yet
measurable) effect of partially quenched theories, namely the double-pole that
appears in certain two-point correlation functions. Most of our calculations
are done for sea quarks having up to three different masses, except for our
result for L_7, which is derived for degenerate sea quarks.Comment: 26 pages, 12 figures (discussion on discretization errors at end of
sec. IV clarified; minor improvements in presentation; results unchanged
Bound State and Order Parameter Mixing Effect by Nonmagnetic Impurity Scattering in Two-band Superconductors
We investigate nonmagnetic impurity effects in two-band superconductors,
focusing on the effects of interband scatterings. Within the Born
approximation, it is known that interband scatterings mix order parameters in
the two bands. In particular, only one averaged energy gap appears in the
excitation spectrum in the dirty limit. [G. Gusman: J. Phys. Chem. Solids {\bf
28} (1967) 2327.] In this paper, we take into account the interband scattering
within the -matrix approximation beyond the Born approximation in the
previous work. We show that, although the interband scattering is responsible
for the mixing effect, this effect becomes weak when the interband scattering
becomes very strong. In the strong interband scattering limit, a two-gap
structure corresponding to two order parameters recovers in the superconducting
density of states. We also show that a bound state appears around a nonmagnetic
impurity depending on the phase of interband scattering potential.Comment: 28pages, 10 figure
Persistence of instanton connections in chemical reactions with time dependent rates
The evolution of a system of chemical reactions can be studied, in the
eikonal approximation, by means of a Hamiltonian dynamical system. The fixed
points of this dynamical system represent the different states in which the
chemical system can be found, and the connections among them represent
instantons or optimal paths linking these states. We study the relation between
the phase portrait of the Hamiltonian system representing a set of chemical
reactions with constant rates and the corresponding system when these rates
vary in time. We show that the topology of the phase space is robust for small
time-dependent perturbations in concrete examples and state general results
when possible. This robustness allows us to apply some of the conclusions on
the qualitative behavior of the autonomous system to the time-dependent
situation
1/N_c Expansion of the Heavy Baryon Isgur-Wise Functions
The 1/N_c expansion of the heavy baryon Isgur-Wise functions is discussed.
Because of the contracted SU(2N_f) light quark spin-flavor symmetry, the
universality relations among the Isgur-Wise functions of \Lambda_b to \Lambda_c
and \Sigma_b^{(*)} to \Sigma_c^{(*)} are valid up to the order of 1/N_c^2.Comment: 7 pages, latex, no figures, to appear in Phys. Rev.
The ferroelectric Mott-Hubbard phase of organic (TMTTF)2X conductors
We present experimental evidences for a ferro-electric transition in the
family of quasi one- dimensional conductors (TMTTF)2X. We interpret this new
transition in the frame of the combined Mott-Hubbard state taking into account
the double action of the spontaneous charge disproportionation on the TMTTF
molecular stacks and of the X anionic potentials
- âŠ