3,882 research outputs found
Nonlinear alternating current responses of graded materials
When a composite of nonlinear particles suspended in a host medium is
subjected to a sinusoidal electric field, the electrical response in the
composite will generally consist of alternating current (AC) fields at
frequencies of higher-order harmonics. The situation becomes more interesting
when the suspended particles are graded, with a spatial variation in the
dielectric properties. The local electric field inside the graded particles can
be calculated by the differential effective dipole approximation, which agrees
very well with a first-principles approach. In this work, a nonlinear
differential effective dipole approximation and a perturbation expansion method
have been employed to investigate the effect of gradation on the nonlinear AC
responses of these composites. The results showed that the fundamental and
third-harmonic AC responses are sensitive to the dielectric-constant and/or
nonlinear-susceptibility gradation profiles within the particles. Thus, by
measuring the AC responses of the graded composites, it is possible to perform
a real-time monitoring of the fabrication process of the gradation profiles
within the graded particles.Comment: 18 pages, 4 figure
Electrorotation of colloidal suspensions
When a strong electric field is applied to a colloidal suspension, it may
cause an aggregation of the suspended particles in response to the field. In
the case of a rotating field, the electrorotation (ER) spectrum can be modified
further due to the local field effects arising from the many-particle system.
To capture the local field effect, we invoke the Maxwell-Garnett approximation
for the dielectric response. The hydrodynamic interactions between the
suspended particles can also modify the spin friction, which is a key to
determine the angular velocity of ER. By invoking the spectral representation
approach, we derive the analytic expressions for the characteristic frequency
at which the maximum angular velocity of ER occurs. From the numerical
caculation, we find that there exist two sub-dispersions in the ER spectrum.
However, the two characteristic frequencies are so close that the two peaks
actually overlap and become a single broad peak. We report a detailed
investigation of the dependence of the characteristic frequency and the
dispersion strength of ER on various material parameters.Comment: RevTeX, 4 eps figures; clarifying discussion added in accord with
referees' reports; accepted by Physics Letters
Invariance of the relativistic one-particle distribution function
The one-particle distribution function is of importance both in
non-relativistic and relativistic statistical physics. In the relativistic
framework, Lorentz invariance is possibly its most fundamental property. The
present article on the subject is a contrastive one: we review, discuss
critically, and, when necessary, complete, the treatments found in the standard
literature
Operadic formulation of topological vertex algebras and Gerstenhaber or Batalin-Vilkovisky algebras
We give the operadic formulation of (weak, strong) topological vertex
algebras, which are variants of topological vertex operator algebras studied
recently by Lian and Zuckerman. As an application, we obtain a conceptual and
geometric construction of the Batalin-Vilkovisky algebraic structure (or the
Gerstenhaber algebra structure) on the cohomology of a topological vertex
algebra (or of a weak topological vertex algebra) by combining this operadic
formulation with a theorem of Getzler (or of Cohen) which formulates
Batalin-Vilkovisky algebras (or Gerstenhaber algebras) in terms of the homology
of the framed little disk operad (or of the little disk operad).Comment: 42 page
Theory of ac electrokinetic behavior of spheroidal cell suspensions with an intrinsic dispersion
The dielectric dispersion, dielectrophoretic (DEP) and electrorotational (ER)
spectra of spheroidal biological cell suspensions with an intrinsic dispersion
in the constituent dielectric constants are investigated. By means of the
spectral representation method, we express analytically the characteristic
frequencies and dispersion strengths both for the effective dielectric constant
and the Clausius-Mossotti factor (CMF). We identify four and six characteristic
frequencies for the effective dielectric spectra and CMF respectively, all of
them being dependent on the depolarization factor (or the cell shape). The
analytical results allow us to examine the effects of the cell shape, the
dispersion strength and the intrinsic frequency on the dielectric dispersion,
DEP and ER spectra. Furthermore, we include the local-field effects due to the
mutual interactions between cells in a dense suspension, and study the
dependence of co-field or anti-field dispersion peaks on the volume fractions.Comment: accepted by Phys. Rev.
Thermodynamic Comparison and the Ideal Glass Transition of A Monatomic Systems Modeled as an Antiferromagnetic Ising Model on Husimi and Cubic Recursive Lattices of the Same Coordination Number
Two kinds of recursive lattices with the same coordination number but
different unit cells (2-D square and 3-D cube) are constructed and the
antiferromagnetic Ising model is solved exactly on them to study the stable and
metastable states. The Ising model with multi-particle interactions is designed
to represent a monatomic system or an alloy. Two solutions of the model exhibit
the crystallization of liquid, and the ideal glass transition of supercooled
liquid respectively. Based on the solutions, the thermodynamics on both
lattices was examined. In particular, the free energy, energy, and entropy of
the ideal glass, supercooled liquid, crystal, and liquid state of the model on
each lattice were calculated and compared with each other. Interactions between
particles farther away than the nearest neighbor distance are taken into
consideration. The two lattices show comparable properties on the transition
temperatures and the thermodynamic behaviors, which proves that both of them
are practical to describe the regular 3-D case, while the different effects of
the unit types are still obvious.Comment: 27 pages, 13 figure
SQC: secure quality control for meta-analysis of genome-wide association studies.
Due to the limited power of small-scale genome-wide association studies (GWAS), researchers tend to collaborate and establish a larger consortium in order to perform large-scale GWAS. Genome-wide association meta-analysis (GWAMA) is a statistical tool that aims to synthesize results from multiple independent studies to increase the statistical power and reduce false-positive findings of GWAS. However, it has been demonstrated that the aggregate data of individual studies are subject to inference attacks, hence privacy concerns arise when researchers share study data in GWAMA.
In this article, we propose a secure quality control (SQC) protocol, which enables checking the quality of data in a privacy-preserving way without revealing sensitive information to a potential adversary. SQC employs state-of-the-art cryptographic and statistical techniques for privacy protection. We implement the solution in a meta-analysis pipeline with real data to demonstrate the efficiency and scalability on commodity machines. The distributed execution of SQC on a cluster of 128 cores for one million genetic variants takes less than one hour, which is a modest cost considering the 10-month time span usually observed for the completion of the QC procedure that includes timing of logistics.
SQC is implemented in Java and is publicly available at https://github.com/acs6610987/secureqc.
[email protected].
Supplementary data are available at Bioinformatics online
Are polymer melts "ideal"?
It is commonly accepted that in concentrated solutions or melts
high-molecular weight polymers display random-walk conformational properties
without long-range correlations between subsequent bonds. This absence of
memory means, for instance, that the bond-bond correlation function, , of
two bonds separated by monomers along the chain should exponentially decay
with . Presenting numerical results and theoretical arguments for both
monodisperse chains and self-assembled (essentially Flory size-distributed)
equilibrium polymers we demonstrate that some long-range correlations remain
due to self-interactions of the chains caused by the chain connectivity and the
incompressibility of the melt. Suggesting a profound analogy with the
well-known long-range velocity correlations in liquids we find, for instance,
to decay algebraically as . Our study suggests a precise
method for obtaining the statistical segment length \bstar in a computer
experiment.Comment: 4 pages, 3 figure
Corrections For Two Photon Decays of chi_{c0} and chi_{c2} and Color Octet Contributions
Using the fact that the c-quark inside a charmonium moves with a small
velocity v in the charmonium rest-frame, one can employ an expansion in v to
study decays of charmonia and results at the leading order for chi_{c0,2} -->
gamma gamma exist in the literature. We study corrections at the
next-to-leading order in the framework of nonrelativistic QCD(NRQCD)
factorization. The study presented here is different than previous approaches
where chi_{c0,2} is taken as a bound-state of a c cbar pair and a
nonrelativistic wave-function is used for the pair. We find that the
corrections are consist not only of relativistic corrections, but also of
corrections from Fock state components of chi_{c0,2} in which the c cbar pair
is in a color-octet state. For chi_{c2} there is also a contribution from a
Fock state component in which the pair is in a F-wave state. We determine the
factorization formula for decay widths in the form of NRQCD matrix elements
representing nonperturbative effects related to chi_{c0,2}, and calculate the
perturbative coefficients at tree-level. Because the NRQCD matrix elements are
unknown, a detailed prediction for the decay chi_{c0,2} --> gamma gamma can not
be made, but the effect of these corrections can be determined at certain
level. Estimations show that the effect is significant and can not be
neglected.Comment: 8 pages, 2 figures; typo in Eq.(24) and Eq.(26) are corrected. add
one referenc
Gravin orchestrates protein kinase A and 2-adrenergic receptor signaling critical for synaptic plasticity and memory
A kinase-anchoring proteins (AKAPs) organize compartmentalized pools of protein kinase A (PKA) to enable localized signaling events within neurons. However, it is unclear which of the many expressed AKAPs in neurons target PKA to signaling complexes important for long-lasting forms of synaptic plasticity and memory storage. In the forebrain, the anchoring protein gravin recruits a signaling complex containing PKA, PKC, calmodulin, and PDE4D (phosphodiesterase 4D) to the β2-adrenergic receptor. Here, we show that mice lacking the α-isoform of gravin have deficits in PKA-dependent long-lasting forms of hippocampal synaptic plasticity including β2-adrenergic receptor-mediated plasticity, and selective impairments of long-term memory storage. Furthermore, both hippocampal β2-adrenergic receptor phosphorylation by PKA, and learning-induced activation of ERK in the CA1 region of the hippocampus are attenuated in mice lacking gravin-α. We conclude that gravin compartmentalizes a significant pool of PKA that regulates learning-induced β2-adrenergic receptor signaling and ERK activation in the hippocampus in vivo, thereby organizing molecular interactions between glutamatergic and noradrenergic signaling pathways for long-lasting synaptic plasticity, and memory storage
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