1,709 research outputs found
Implications of adiabatic phases for a vortex in a superconductor film
Based on ideas of off-diagonal long range order and two-fluid model, we
demonstrate that adiabatic phases for a slow motion of a vortex in a
superconductor film give rise naturally to the Magnus force at finite
temperatures.Comment: 6 pages, Late
Structure of Stochastic Dynamics near Fixed Points
We analyze the structure of stochastic dynamics near either a stable or
unstable fixed point, where force can be approximated by linearization. We find
that a cost function that determines a Boltzmann-like stationary distribution
can always be defined near it. Such a stationary distribution does not need to
satisfy the usual detailed balance condition, but might have instead a
divergence-free probability current. In the linear case the force can be split
into two parts, one of which gives detailed balance with the diffusive motion,
while the other induces cyclic motion on surfaces of constant cost function.
Using the Jordan transformation for the force matrix, we find an explicit
construction of the cost function. We discuss singularities of the
transformation and their consequences for the stationary distribution. This
Boltzmann-like distribution may be not unique, and nonlinear effects and
boundary conditions may change the distribution and induce additional currents
even in the neighborhood of a fixed point.Comment: 7 page
Stochastic Thermodynamics Across Scales: Emergent Inter-attractoral Discrete Markov Jump Process and Its Underlying Continuous Diffusion
The consistency across scales of a recently developed mathematical
thermodynamic structure, between a continuous stochastic nonlinear dynamical
system (diffusion process with Langevin or Fokker-Planck equations) and its
emergent discrete, inter-attractoral Markov jump process, is investigated. We
analyze how the system's thermodynamic state functions, e.g. free energy ,
entropy , entropy production , and free energy dissipation ,
etc., are related when the continuous system is describe with a coarse-grained
discrete variable. We show that the thermodynamics derived from the underlying
detailed continuous dynamics is exact in the Helmholtz free-energy
representation. That is, the system thermodynamic structure is the same as if
one only takes a middle-road and starts with the "natural" discrete
description, with the corresponding transition rates empirically determined. By
"natural", we mean in the thermodynamic limit of large systems in which there
is an inherent separation of time scales between inter- and intra-attractoral
dynamics. This result generalizes a fundamental idea from chemistry and the
theory of Kramers by including thermodynamics: while a mechanical description
of a molecule is in terms of continuous bond lengths and angles, chemical
reactions are phenomenologically described by the Law of Mass Action with rate
constants, and a stochastic thermodynamics.Comment: 21 pages, 1 figur
Analysis the Role Conflict of Trade Union Chairman and Its Types
With the development of the market economy, the trade union work has become increasingly complex. As a special group, trade union chairman plays multiple roles. On the one hand, the trade union chairman should safeguard the rights and interests of enterprise employees, on the other hand, as the workers of the enterprise, they have to create benefits for the enterprise, this kind of dual role trigger a trade union chairman role conflict. In this paper, through reviewing the relevant literature, from the personal angle of the trade union chairman, trade union chairman of role conflict from three dimensions divided responsibility, time, interests. Through the division of the three dimension classifying trade union chairman of role conflict, and explain the causes of different types of role conflict and the corresponding countermeasures and suggestions, so as to eliminate the role of the trade union chairman conflict, give full play to the role of the trade union chairman
The Zeroth Law of Thermodynamics and Volume-Preserving Conservative Dynamics with Equilibrium Stochastic Damping
We propose a mathematical formulation of the zeroth law of thermodynamics and
develop a stochastic dynamical theory, with a consistent irreversible
thermodynamics, for systems possessing sustained conservative stationary
current in phase space while in equilibrium with a heat bath. The theory
generalizes underdamped mechanical equilibrium: , with and respectively
representing phase-volume preserving dynamics and stochastic damping. The
zeroth law implies stationary distribution . We find an
orthogonality as a hallmark of the system. Stochastic
thermodynamics based on time reversal
is formulated: entropy
production ; generalized "heat" ,
being "internal energy", and "free
energy" never increases.
Entropy follows . Our formulation is shown to
be consistent with an earlier theory of P. Ao. Its contradistinctions to other
theories, potential-flux decomposition, stochastic Hamiltonian system with even
and odd variables, Klein-Kramers equation, Freidlin-Wentzell's theory, and
GENERIC, are discussed.Comment: 25 page
Stochastic Physics, Complex Systems and Biology
In complex systems, the interplay between nonlinear and stochastic dynamics,
e.g., J. Monod's necessity and chance, gives rise to an evolutionary process in
Darwinian sense, in terms of discrete jumps among attractors, with punctuated
equilibrium, spontaneous random "mutations" and "adaptations". On an
evlutionary time scale it produces sustainable diversity among individuals in a
homogeneous population rather than convergence as usually predicted by a
deterministic dynamics. The emergent discrete states in such a system, i.e.,
attractors, have natural robustness against both internal and external
perturbations. Phenotypic states of a biological cell, a mesoscopic nonlinear
stochastic open biochemical system, could be understood through such a
perspective.Comment: 10 page
p38α MAPK regulates proliferation and differentiation of osteoclast progenitors and bone remodeling in an aging-dependent manner.
Bone mass is determined by the balance between bone formation, carried out by mesenchymal stem cell-derived osteoblasts, and bone resorption, carried out by monocyte-derived osteoclasts. Here we investigated the potential roles of p38 MAPKs, which are activated by growth factors and cytokines including RANKL and BMPs, in osteoclastogenesis and bone resorption by ablating p38α MAPK in LysM+monocytes. p38α deficiency promoted monocyte proliferation but regulated monocyte osteoclastic differentiation in a cell-density dependent manner, with proliferating p38α-/- cultures showing increased differentiation. While young mutant mice showed minor increase in bone mass, 6-month-old mutant mice developed osteoporosis, associated with an increase in osteoclastogenesis and bone resorption and an increase in the pool of monocytes. Moreover, monocyte-specific p38α ablation resulted in a decrease in bone formation and the number of bone marrow mesenchymal stem/stromal cells, likely due to decreased expression of PDGF-AA and BMP2. The expression of PDGF-AA and BMP2 was positively regulated by the p38 MAPK-Creb axis in osteoclasts, with the promoters of PDGF-AA and BMP2 having Creb binding sites. These findings uncovered the molecular mechanisms by which p38α MAPK regulates osteoclastogenesis and coordinates osteoclastogenesis and osteoblastogenesis
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