36,962 research outputs found
Robust H∞ feedback control for uncertain stochastic delayed genetic regulatory networks with additive and multiplicative noise
The official published version can found at the link below.Noises are ubiquitous in genetic regulatory networks (GRNs). Gene regulation is inherently a stochastic process because of intrinsic and extrinsic noises that cause kinetic parameter variations and basal rate disturbance. Time delays are usually inevitable due to different biochemical reactions in such GRNs. In this paper, a delayed stochastic model with additive and multiplicative noises is utilized to describe stochastic GRNs. A feedback gene controller design scheme is proposed to guarantee that the GRN is mean-square asymptotically stable with noise attenuation, where the structure of the controllers can be specified according to engineering requirements. By applying control theory and mathematical tools, the analytical solution to the control design problem is given, which helps to provide some insight into synthetic biology and systems biology. The control scheme is employed in a three-gene network to illustrate the applicability and usefulness of the design.This work was funded by Royal Society of the U.K.; Foundation for the Author of National Excellent Doctoral Dissertation of China. Grant Number: 2007E4; Heilongjiang Outstanding Youth Science Fund of China. Grant Number: JC200809; Fok Ying Tung Education Foundation. Grant Number: 111064; International Science and Technology Cooperation Project of China. Grant Number: 2009DFA32050; University of Science and Technology of China Graduate Innovative Foundation
Temperature dependence of the impurity-induced resonant state in Zn-doped Bi_2Sr_2CaCu_2O by Scanning Tunneling Spectroscopy
We report on the temperature dependence of the impurity-induced resonant
state in Zn-doped Bi_2Sr_2CaCu_2O by scanning tunneling
spectroscopy at 30 mK < T < 52 K. It is known that a Zn impurity induces a
sharp resonant peak in tunnel spectrum at an energy close to the Fermi level.
We observed that the resonant peak survives up to 52 K. The peak broadens with
increasing temperature, which is explained by the thermal effect. This result
provides information to understand the origin of the resonant peak.Comment: 4 pages, 3 figures, to appear in Phys. Rev.
Josephson scanning tunneling microscopy
We propose a set of scanning tunneling microscopy experiments in which the
surface of superconductor is scanned by a superconducting tip. Potential
capabilities of such experimental setup are discussed. Most important
anticipated results of such an experiment include the position-resolved
measurement of the superconducting order parameter and the possibility to
determine the nature of the secondary component of the order parameter at the
surface. The theoretical description based on the tunneling Hamiltonian
formalism is presented.Comment: 6 pages, 7 figures, submitted to Phys. Rev.
Microphase transitions of block copolymer/homopolymer under shear flow
Cell dynamics simulation is used to investigate the phase behavior of block
copolymer/homopolymer mixture subjected to a steady shear flow. Phase
transitions occur from transverse to parallel and then to perpendicular
lamellar structure with an increase of shear rate and this is the result of
interaction between the shear flow and the concentration fluctuation.
Rheological properties, such as normal stress differences and shear viscosity,
are all closely related with the direction of the lamellae. Furthermore, we
specifically explore the phase behavior and the order parameter under weak and
strong shear of two different initial states, and realize the importance of the
thermal history. It is necessary to apply the shear field at the appropriate
time if we want to get what we want. These results provide an easy method to
create ordered, defect-free materials in experiment and engineering technology
through imposing shear flow.Comment: 14 pages, 9 figure
Superconductivity and magnetic order in the non-centrosymmetric Half Heusler compound ErPdBi
We report superconductivity at K and magnetic order at K in the semi-metallic noncentrosymmetric Half Heusler compound ErPdBi.
The upper critical field, , has an unusual quasi-linear temperature
variation and reaches a value of 1.6 T for . Magnetic order is
found below and is suppressed at T for . Since , the interaction of superconductivity and magnetism
is expected to give rise to a complex ground state. Moreover, electronic
structure calculations show ErPdBi has a topologically nontrivial band
inversion and thus may serve as a new platform to study the interplay of
topological states, superconductivity and magnetic order.Comment: 6 pages, 5 figures; accepted for publication in Europhysics Letter
Structural, optical, magnetic and electrical properties of Zn1-x Co (x) O thin films
Despite a considerable effort aiming at elucidating the nature of
ferromagnetism in ZnO-based magnetic semiconductor, its origin still remains
debatable. Although the observation of above room temperature ferromagnetism
has been reported frequently in the literature by magnetometry measurement, so
far there has been no report on correlated ferromagnetism in magnetic, optical
and electrical measurements. In this paper, we investigate systematically the
structural, optical, magnetic and electrical properties of Zn1-x Co (x) O:Al
thin films prepared by sputtering with x ranging from 0 to 0.33. We show that
correlated ferromagnetism is present only in samples with x > 0.25. In
contrast, samples with x < 0.2 exhibit weak ferromagnetism only in magnetometry
measurement which is absent in optical and electrical measurements. We
demonstrate, by systematic electrical transport studies that carrier
localization indeed occurs below 20-50 K for samples with x < 0.2; however,
this does not lead to the formation of ferromagnetic phase in these samples
with an electron concentration in the range of 6 x 10(19) cm(-3) 1 x 10(20)
cm(-3). Detailed structural and optical transmission spectroscopy analyses
revealed that the anomalous Hall effect observed in samples with x > 0.25 is
due to the formation of secondary phases and Co clusters.Comment: 28 pages, 8 figure
Convex optimization problem prototyping for image reconstruction in computed tomography with the Chambolle-Pock algorithm
The primal-dual optimization algorithm developed in Chambolle and Pock (CP),
2011 is applied to various convex optimization problems of interest in computed
tomography (CT) image reconstruction. This algorithm allows for rapid
prototyping of optimization problems for the purpose of designing iterative
image reconstruction algorithms for CT. The primal-dual algorithm is briefly
summarized in the article, and its potential for prototyping is demonstrated by
explicitly deriving CP algorithm instances for many optimization problems
relevant to CT. An example application modeling breast CT with low-intensity
X-ray illumination is presented.Comment: Resubmitted to Physics in Medicine and Biology. Text has been
modified according to referee comments, and typos in the equations have been
correcte
The Euler-Lagrange Cohomology and General Volume-Preserving Systems
We briefly introduce the conception on Euler-Lagrange cohomology groups on a
symplectic manifold and systematically present the
general form of volume-preserving equations on the manifold from the
cohomological point of view. It is shown that for every volume-preserving flow
generated by these equations there is an important 2-form that plays the analog
role with the Hamiltonian in the Hamilton mechanics. In addition, the ordinary
canonical equations with Hamiltonian are included as a special case with
the 2-form . It is studied the other volume preserving
systems on . It is also explored the relations between
our approach and Feng-Shang's volume-preserving systems as well as the Nambu
mechanics.Comment: Plain LaTeX, use packages amssymb and amscd, 15 pages, no figure
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