1,763 research outputs found
Calculation of surface temperature and surface fluxes in the GLAS GOM
Because the GLAS model's surface fluxes of sensible and latent heat exhibit strong 2 delta t oscillations at the individual grid points as well as in the zonal hemispheric averages and because a basic weakness of the GLAS model lower evaporation over oceans and higher evaporation over land in a typical monthly simulation, the GLAS model PBL parameterization was changed to calculate the mixed layer temperature gradient by solution of a quadratic equation for a stable PBL and by a curve fit relation for an unstable PBL. The new fluxes without any 2 delta t oscillation. Also, the geographical distributions of the surface fluxes are improved. The parameterization presented is incorporated into the new GLAS climate model. Some results which compare the evaporation over land and ocean between old and new calculations are appended
Compound transfer matrices: Constructive and destructive interference
Scattering from a compound barrier, one composed of a number of distinct
non-overlapping sub-barriers, has a number of interesting and subtle
mathematical features. If one is scattering classical particles, where the wave
aspects of the particle can be ignored, the transmission probability of the
compound barrier is simply given by the product of the transmission
probabilities of the individual sub-barriers. In contrast if one is scattering
waves (whether we are dealing with either purely classical waves or quantum
Schrodinger wavefunctions) each sub-barrier contributes phase information (as
well as a transmission probability), and these phases can lead to either
constructive or destructive interference, with the transmission probability
oscillating between nontrivial upper and lower bounds. In this article we shall
study these upper and lower bounds in some detail, and also derive bounds on
the closely related process of quantum excitation (particle production) via
parametric resonance.Comment: V1: 28 pages. V2: 21 pages. Presentation significantly streamlined
and shortened. This version accepted for publication in the Journal of
Mathematical Physic
Dynamical mean-filed approximation to small-world networks of spiking neurons: From local to global, and/or from regular to random couplings
By extending a dynamical mean-field approximation (DMA) previously proposed
by the author [H. Hasegawa, Phys. Rev. E {\bf 67}, 41903 (2003)], we have
developed a semianalytical theory which takes into account a wide range of
couplings in a small-world network. Our network consists of noisy -unit
FitzHugh-Nagumo (FN) neurons with couplings whose average coordination number
may change from local () to global couplings () and/or
whose concentration of random couplings is allowed to vary from regular
() to completely random (p=1). We have taken into account three kinds of
spatial correlations: the on-site correlation, the correlation for a coupled
pair and that for a pair without direct couplings. The original -dimensional {\it stochastic} differential equations are transformed to
13-dimensional {\it deterministic} differential equations expressed in terms of
means, variances and covariances of state variables. The synchronization ratio
and the firing-time precision for an applied single spike have been discussed
as functions of and . Our calculations have shown that with increasing
, the synchronization is {\it worse} because of increased heterogeneous
couplings, although the average network distance becomes shorter. Results
calculated by out theory are in good agreement with those by direct
simulations.Comment: 19 pages, 2 figures: accepted in Phys. Rev. E with minor change
STUDIES OF THE MECHANISM OF ACTION OF COBAMIDE COENZYMES
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73404/1/j.1749-6632.1964.tb45046.x.pd
Superconductivity-Related Insulating Behavior
We present the results of an experimental study of superconducting,
disordered, thin-films of amorphous Indium Oxide. These films can be driven
from the superconducting phase to a reentrant insulating state by the
application of a perpendicular magnetic field (). We find that the high-
insulator exhibits activated transport with a characteristic temperature,
. has a maximum value () that is close to the
superconducting transition temperature () at = 0, suggesting a
possible relation between the conduction mechanisms in the superconducting and
insulating phases. and display opposite dependences on the
disorder strength.Comment: Tex file and 5 figures; Revised version; To appear in Phys. Rev.
Lett. (2004
Clustering and Synchronization of Oscillator Networks
Using a recently described technique for manipulating the clustering
coefficient of a network without changing its degree distribution, we examine
the effect of clustering on the synchronization of phase oscillators on
networks with Poisson and scale-free degree distributions. For both types of
network, increased clustering hinders global synchronization as the network
splits into dynamical clusters that oscillate at different frequencies.
Surprisingly, in scale-free networks, clustering promotes the synchronization
of the most connected nodes (hubs) even though it inhibits global
synchronization. As a result, scale-free networks show an additional, advanced
transition instead of a single synchronization threshold. This cluster-enhanced
synchronization of hubs may be relevant to the brain with its scale-free and
highly clustered structure.Comment: Submitted to Phys. Rev.
Nonlocal mechanism for cluster synchronization in neural circuits
The interplay between the topology of cortical circuits and synchronized
activity modes in distinct cortical areas is a key enigma in neuroscience. We
present a new nonlocal mechanism governing the periodic activity mode: the
greatest common divisor (GCD) of network loops. For a stimulus to one node, the
network splits into GCD-clusters in which cluster neurons are in zero-lag
synchronization. For complex external stimuli, the number of clusters can be
any common divisor. The synchronized mode and the transients to synchronization
pinpoint the type of external stimuli. The findings, supported by an
information mixing argument and simulations of Hodgkin Huxley population
dynamic networks with unidirectional connectivity and synaptic noise, call for
reexamining sources of correlated activity in cortex and shorter information
processing time scales.Comment: 8 pges, 6 figure
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