9,643 research outputs found
Statistical Thermodynamics of General Minimal Diffusion Processes: Constuction, Invariant Density, Reversibility and Entropy Production
The solution to nonlinear Fokker-Planck equation is constructed in terms of
the minimal Markov semigroup generated by the equation. The semigroup is
obtained by a purely functional analytical method via Hille-Yosida theorem. The
existence of the positive invariant measure with density is established and a
weak form of Foguel alternative proven. We show the equivalence among
self-adjoint of the elliptic operator, time-reversibility, and zero entropy
production rate of the stationary diffusion process. A thermodynamic theory for
diffusion processes emerges.Comment: 23 page
Stochastic Dynamics of Electrical Membrane with Voltage-Dependent Ion Channel Fluctuations
Brownian ratchet like stochastic theory for the electrochemical membrane
system of Hodgkin-Huxley (HH) is developed. The system is characterized by a
continuous variable , representing mobile membrane charge density, and
a discrete variable representing ion channel conformational dynamics. A
Nernst-Planck-Nyquist-Johnson type equilibrium is obtained when multiple
conducting ions have a common reversal potential. Detailed balance yields a
previously unknown relation between the channel switching rates and membrane
capacitance, bypassing Eyring-type explicit treatment of gating charge
kinetics. From a molecular structural standpoint, membrane charge is a
more natural dynamic variable than potential ; our formalism treats
-dependent conformational transition rates as intrinsic
parameters. Therefore in principle, vs. is experimental
protocol dependent,e.g., different from voltage or charge clamping
measurements. For constant membrane capacitance per unit area and
neglecting membrane potential induced by gating charges, , and
HH's formalism is recovered. The presence of two types of ions, with different
channels and reversal potentials, gives rise to a nonequilibrium steady state
with positive entropy production . For rapidly fluctuating channels, an
expression for is obtained.Comment: 8 pages, two figure
Sensitivity Amplification in the Phosphorylation-Dephosphorylation Cycle: Nonequilibrium steady states, chemical master equation and temporal cooperativity
A new type of cooperativity termed temporal cooperativity [Biophys. Chem. 105
585-593 (2003), Annu. Rev. Phys. Chem. 58 113-142 (2007)], emerges in the
signal transduction module of phosphorylation-dephosphorylation cycle (PdPC).
It utilizes multiple kinetic cycles in time, in contrast to allosteric
cooperativity that utilizes multiple subunits in a protein. In the present
paper, we thoroughly investigate both the deterministic (microscopic) and
stochastic (mesoscopic) models, and focus on the identification of the source
of temporal cooperativity via comparing with allosteric cooperativity.
A thermodynamic analysis confirms again the claim that the chemical
equilibrium state exists if and only if the phosphorylation potential
, in which case the amplification of sensitivity is completely
abolished. Then we provide comprehensive theoretical and numerical analysis
with the first-order and zero-order assumptions in
phosphorylation-dephosphorylation cycle respectively. Furthermore, it is
interestingly found that the underlying mathematics of temporal cooperativity
and allosteric cooperativity are equivalent, and both of them can be expressed
by "dissociation constants", which also characterizes the essential differences
between the simple and ultrasensitive PdPC switches. Nevertheless, the degree
of allosteric cooperativity is restricted by the total number of sites in a
single enzyme molecule which can not be freely regulated, while temporal
cooperativity is only restricted by the total number of molecules of the target
protein which can be regulated in a wide range and gives rise to the
ultrasensitivity phenomenon.Comment: 42 pages, 13 figure
Holomorphic harmonic analysis on complex reductive groups
We define the holomorphic Fourier transform of holomorphic functions on
complex reductive groups, prove some properties like the Fourier inversion
formula, and give some applications. The definition of the holomorphic Fourier
transform makes use of the notion of -admissible measures. We prove that
-admissible measures are abundant, and the definition of holomorphic Fourier
transform is independent of the choice of -admissible measures.Comment: 15 pages, revision of a preprint by the first author in 200
AAANE: Attention-based Adversarial Autoencoder for Multi-scale Network Embedding
Network embedding represents nodes in a continuous vector space and preserves
structure information from the Network. Existing methods usually adopt a
"one-size-fits-all" approach when concerning multi-scale structure information,
such as first- and second-order proximity of nodes, ignoring the fact that
different scales play different roles in the embedding learning. In this paper,
we propose an Attention-based Adversarial Autoencoder Network Embedding(AAANE)
framework, which promotes the collaboration of different scales and lets them
vote for robust representations. The proposed AAANE consists of two components:
1) Attention-based autoencoder effectively capture the highly non-linear
network structure, which can de-emphasize irrelevant scales during training. 2)
An adversarial regularization guides the autoencoder learn robust
representations by matching the posterior distribution of the latent embeddings
to given prior distribution. This is the first attempt to introduce attention
mechanisms to multi-scale network embedding. Experimental results on real-world
networks show that our learned attention parameters are different for every
network and the proposed approach outperforms existing state-of-the-art
approaches for network embedding.Comment: 8 pages, 5 figure
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