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CDC42 and Rac1 control different actin-dependent processes in the Drosophila wing disc epithelium.
Cdc42 and Rac1 are members of the rho family of small guanosinetriphosphatases and are required for a diverse set of cytoskeleton-membrane interactions in different cell types. Here we show that these two proteins contribute differently to the organization of epithelial cells in the Drosophila wing imaginal disc. Drac1 is required to assemble actin at adherens junctions. Failure of adherens junction actin assembly in Drac1 dominant-negative mutants is associated with increased cell death. Dcdc42, on the other hand, is required for processes that involve polarized cell shape changes during both pupal and larval development. In the third larval instar, Dcdc42 is required for apico-basal epithelial elongation. Whereas normal wing disc epithelial cells increase in height more than twofold during the third instar, cells that express a dominant-negative version of Dcdc42 remain short and are abnormally shaped. Dcdc42 localizes to both apical and basal regions of the cell during these events, and mediates elongation, at least in part, by effecting a reorganization of the basal actin cytoskeleton. These observations suggest that a common cdc42-based mechanism may govern polarized cell shape changes in a wide variety of cell types
Theoretical modeling of spatial and temperature dependent exciton energy in coupled quantum wells
Motivated by a recent experiment of spatial and temperature dependent average
exciton energy distribution in coupled quantum wells [S. Yang \textit{et al.},
Phys. Rev. B \textbf{75}, 033311 (2007)], we investigate the nature of the
interactions in indirect excitons. Based on the uncertainty principle, along
with a temperature and energy dependent distribution which includes both
population and recombination effects, we show that the interplay between an
attractive two-body interaction and a repulsive three-body interaction can lead
to a natural and good account for the nonmonotonic temperature dependence of
the average exciton energy. Moreover, exciton energy maxima are shown to locate
at the brightest regions, in agreement with the recent experiments. Our results
provide an alternative way for understanding the underlying physics of the
exciton dynamics in coupled quantum wells.Comment: 8 pages, 5 figure
Diversity and Adaptation in Large Population Games
We consider a version of large population games whose players compete for
resources using strategies with adaptable preferences. The system efficiency is
measured by the variance of the decisions. In the regime where the system can
be plagued by the maladaptive behavior of the players, we find that diversity
among the players improves the system efficiency, though it slows the
convergence to the steady state. Diversity causes a mild spread of resources at
the transient state, but reduces the uneven distribution of resources in the
steady state.Comment: 8 pages, 3 figure
Optimization of ultrasound-assisted extraction of total phenol from betel (Areca catechu L.) nut seed and evaluation of antioxidant activity in vitro
Optimization of the ultrasound-assisted extraction technology for total phenol from betel (Areca catechu L.) nut seed was carried out. On the basis of one factor tests, the method of response surface analysis with 3 factors including extracting temperature, time and solvent-material ratio on the content of total phenol was adopted. The optimal extracting conditions are as follows: extraction temperature 58°C, extraction time 42 min and solvent-material ratio 53 ml/g. The predicted value and measured value of total phenol was 164.74 mg catechin equivalents/g of betel nut seed (mg CE/g BNS) and 160.95 mg CE/g BNS under this condition, respectively. The results indicate that the obtained model developed by response surface methodology is feasible for practical prediction. The experiments of antioxidant activity showed that the betel nut seed extract presents the strong antioxidant activities to the DPPH and ABTS radical and the EC50 is 113.42 and 105.69 μg/ml, respectively.Key words: Betel nut seed, total phenol, ultrasound extraction, antioxidant activity
A volume inequality for quantum Fisher information and the uncertainty principle
Let be complex self-adjoint matrices and let be a
density matrix. The Robertson uncertainty principle gives a bound for the quantum
generalized covariance in terms of the commutators . The right side
matrix is antisymmetric and therefore the bound is trivial (equal to zero) in
the odd case .
Let be an arbitrary normalized symmetric operator monotone function and
let be the associated quantum Fisher information. In
this paper we conjecture the inequality that gives a
non-trivial bound for any natural number using the commutators . The inequality has been proved in the cases by the joint efforts
of many authors. In this paper we prove the case N=3 for real matrices
Metric adjusted skew information: Convexity and restricted forms of superadditivity
We give a truly elementary proof of the convexity of metric adjusted skew
information following an idea of Effros. We extend earlier results of weak
forms of superadditivity to general metric adjusted skew informations.
Recently, Luo and Zhang introduced the notion of semi-quantum states on a
bipartite system and proved superadditivity of the Wigner-Yanase-Dyson skew
informations for such states. We extend this result to general metric adjusted
skew informations. We finally show that a recently introduced extension to
parameter values of the WYD-information is a special case of
(unbounded) metric adjusted skew information.Comment: An error in the literature is pointed ou
Chaperone-assisted translocation of a polymer through a nanopore
Using Langevin dynamics simulations, we investigate the dynamics of
chaperone-assisted translocation of a flexible polymer through a nanopore. We
find that increasing the binding energy between the chaperone and
the chain and the chaperone concentration can greatly improve the
translocation probability. Particularly, with increasing the chaperone
concentration a maximum translocation probability is observed for weak binding.
For a fixed chaperone concentration, the histogram of translocation time
has a transition from long-tailed distribution to Gaussian distribution with
increasing . rapidly decreases and then almost saturates with
increasing binding energy for short chain, however, it has a minimum for longer
chains at lower chaperone concentration. We also show that has a minimum
as a function of the chaperone concentration. For different , a
nonuniversal dependence of on the chain length is also observed.
These results can be interpreted by characteristic entropic effects for
flexible polymers induced by either crowding effect from high chaperone
concentration or the intersegmental binding for the high binding energy.Comment: 10 pages, to appear in J. Am. Chem. So
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