49,150 research outputs found
The Onset of Chaotic Motion of a Spinning Particle around the Schwarzchild Black Hole
In the Schwarzchild black hole spacetime, we show that chaotic motion can be
triggered by the spin of a particle. Taking the spin of the particle as a
perturbation and using the Melnikov method, we find that the perturbed stable
and unstable orbits are entangled with each other and that illustrates the
onset of chaotic behavior in the motion of the particle.Comment: 14 pages in Revtex4 style, 9 figures(eps files
Norm Estimates for the Difference Between Bochner's Integral and the Convex Combination of Function's Values
Norm estimates are developed between the Bochner integral of a vector-valued
function in Banach spaces having the Radon-Nikodym property and the convex
combination of function values taken on a division of the interval [a,b]
On the String Pair Creation in Dp-Dp' Brane System
We address the bosonic string pair creation in a system of parallel Dp-Dp'
(p<p') branes by applying the path integral formalism. We drive the string pair
creation rate by calculating the one loop vacuum amplitude of the setup in
presence of the background electric field defined over the Dp'-brane. It is
pointed out that just the components of the electric field defined over the
spatial directions (the common directions along which the both D-branes are
extended) give rise to the pair creationComment: Accepted for publication in Mod. Phys. Lett.
On Signatures of Atmospheric Features in Thermal Phase Curves of Hot Jupiters
Turbulence is ubiquitous in Solar System planetary atmospheres. In hot
Jupiter atmospheres, the combination of moderately slow rotation and thick
pressure scale height may result in dynamical weather structures with unusually
large, planetary-size scales. Using equivalent-barotropic, turbulent
circulation models, we illustrate how such structures can generate a variety of
features in the thermal phase curves of hot Jupiters, including phase shifts
and deviations from periodicity. Such features may have been spotted in the
recent infrared phase curve of HD 189733b. Despite inherent difficulties with
the interpretation of disk-integrated quantities, phase curves promise to offer
unique constraints on the nature of the circulation regime present on hot
Jupiters.Comment: 22 pages, 6 figures, 1 table, accepted for publication in Ap
Least-squares methods for identifying biochemical regulatory networks from noisy measurements
<b>Background</b>:
We consider the problem of identifying the dynamic interactions in biochemical networks from noisy experimental data. Typically, approaches for solving this problem make use of an estimation algorithm such as the well-known linear Least-Squares (LS) estimation technique. We demonstrate that when time-series measurements are corrupted by white noise and/or drift noise, more accurate and reliable identification of network interactions can be achieved by employing an estimation algorithm known as Constrained Total Least Squares (CTLS). The Total Least Squares (TLS) technique is a generalised least squares method to solve an overdetermined set of equations whose coefficients are noisy. The CTLS is a natural extension of TLS to the case where the noise components of the coefficients are correlated, as is usually the case with time-series measurements of concentrations and expression profiles in gene networks.
<b>Results</b>:
The superior performance of the CTLS method in identifying network interactions is demonstrated on three examples: a genetic network containing four genes, a network describing p53 activity and <i>mdm2</i> messenger RNA interactions, and a recently proposed kinetic model for interleukin (IL)-6 and (IL)-12b messenger RNA expression as a function of ATF3 and NF-κB promoter binding. For the first example, the CTLS significantly reduces the errors in the estimation of the Jacobian for the gene network. For the second, the CTLS reduces the errors from the measurements that are corrupted by white noise and the effect of neglected kinetics. For the third, it allows the correct identification, from noisy data, of the negative regulation of (IL)-6 and (IL)-12b by ATF3.
<b>Conclusion</b>:
The significant improvements in performance demonstrated by the CTLS method under the wide range of conditions tested here, including different levels and types of measurement noise and different numbers of data points, suggests that its application will enable more accurate and reliable identification and modelling of biochemical networks
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