76,933 research outputs found
Adaptive Ising Model and Bacterial Chemotactic Receptor Network
We present a so-called adaptive Ising model (AIM) to provide a unifying
explanation for sensitivity and perfect adaptation in bacterial chemotactic
signalling, based on coupling among receptor dimers. In an AIM, an external
field, representing ligand binding, is randomly applied to a fraction of spins,
representing the states of the receptor dimers, and there is a delayed negative
feedback from the spin value on the local field. This model is solved in an
adiabatic approach. If the feedback is slow and weak enough, as indeed in
chemotactic signalling, the system evolves through quasi-equilibrium states and
the ``magnetization'', representing the signal, always attenuates towards zero
and is always sensitive to a subsequent stimulus.Comment: revtex, final version to appear in Europhysics Letter
Charge Transfer Fluctuations as a QGP Signal
In this study, we analyze the recently proposed charge transfer fluctuations
within a finite pseudo-rapidity space. As the charge transfer fluctuation is a
measure of the local charge correlation length, it is capable of detecting
inhomogeneity in the hot and dense matter created by heavy ion collisions. We
predict that going from peripheral to central collisions, the charge transfer
fluctuations at midrapidity should decrease substantially while the charge
transfer fluctuations at the edges of the observation window should decrease by
a small amount. These are consequences of having a strongly inhomogeneous
matter where the QGP component is concentrated around midrapidity. We also show
how to constrain the values of the charge correlations lengths in both the
hadronic phase and the QGP phase using the charge transfer fluctuations.
Current manuscript is based on the preprints hep-ph/0503085 (to appear in
Physical Review C) and nucl-th/0506025.Comment: To appear in the proceedings of 18th International Conference on
Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005),
Budapest, Hungary, 4-9 Aug 200
Novel thick-foam ferroelectret with engineered voids for energy harvesting applications
This work reports a novel thick-foam ferroelectret which is designed and engineered for energy harvesting applications. We fabricated this ferroelectret foam by mixing a chemical blowing agent with a polymer solution, then used heat treatment to activate the agent and create voids in the polymer foam. The dimensions of the foam, the density and size of voids can be well controlled in the fabrication process. Therefore, this ferroelectret can be engineered into optimized structure for energy harvesting applications
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ICARUS: Intelligent coupon allocation for retailers using search
Many retailers run loyalty card schemes for their customers offering incentives in the form of money off coupons. The total value of the coupons depends on how much the customer has spent. This paper deals with the problem of finding the smallest set of coupons such that each possible total can be represented as the sum of a pre-defined number of coupons. A mathematical analysis of the problem leads to the development of a genetic algorithm solution. The algorithm is applied to real world data using several crossover operators and compared to well known straw-person methods. Results are promising showing that considerable time can be saved by using this method, reducing a few days worth of consultancy time to a few minutes of computation
Octet Baryon Charge Radii, Chiral Symmetry and Decuplet Intermediate States
We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon
chiral perturbation theory. We examine the effect of including the decuplet of
spin-3/2 baryons explicitly. We find that it does no t improve the level of
agreement between the HBchiPT and experimental values for the Sigma^- charge
radius.Comment: 9 pages, 2 figures. Uses axodraw.sty, include
The Droplet State and the Compressibility Anomaly in Dilute 2D Electron Systems
We investigate the space distribution of carrier density and the
compressibility of two-dimensional (2D) electron systems by using the local
density approximation. The strong correlation is simulated by the local
exchange and correlation energies. A slowly varied disorder potential is
applied to simulate the disorder effect. We show that the compressibility
anomaly observed in 2D systems which accompanies the metal-insulator transition
can be attributed to the formation of the droplet state due to disorder effect
at low carrier densities.Comment: 4 pages, 3 figure
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