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If a body is in a plasma and/or is exposed to streams of charged particles with different signs, or is under UV electromagnetic radiation, etc., then the distribution of the different sign charges on the surface is random. As a result, the surface of the dielectric will be covered by microscopic “spots” with different signs and values of charges, continuously changing in shapes and sizes. A Coulomb force acting on a dust particle lying near the center of such a spot is proportional to the square of the local surface charge density. A stochastic differential equation describing the dynamics of an ensemble of these spots was derived and solved in the article. A solution was obtained also for the dependence of the average spot size, its lifetime, and the standard deviation of the charge density as a function of the plasma species fluxes incident on the surface. It is shown that for normal values of plasma parameters, the Coulomb force repelling a submicron dust particle from a charge spot of somewhat larger size can reach a few tenths of pN, which is comparable to the value of the adhesive van der Waals force that holds dust particles on the surface. The possibility of improving the cleaning efficiency with changes in surface treatment conditions is analyzed as well.

The cross-bridge working stroke is regarded as a continuous (without jumps) change of myosin head internal state under the action of a force exerted within the nucleotide-binding site. Involvement of a concept of continuous cross-bridge conformation enables discussion of the nature of the force propelling muscle, and the Coulomb repulsion of like-charged adenosine triphosphate (ATP) fragments ADP(2-) and P (i) (2-) can quite naturally be considered as the source of this force. Two entirely different types of working stroke termination are considered. Along with the fluctuation mechanism, which controls the working stroke duration t (w) at isometric contraction, another interrupt mechanism is initially taken into account. It is triggered when the lever arm shift amounts to the maximal value S ≈ 11 nm, the back door opens, and P(i) crashes out. As a result, t (w) becomes inversely proportional to the velocity v of sliding filaments t (w) ≈ S/v for a wide range of values of v. Principal features of the experimentally observed dependences of force, efficiency, and rate of heat production on velocity and ATP concentration can then be reproduced by fitting a single parameter: the velocity-independent time span t (r) between the termination of the last and beginning of the next working stroke. v becomes the principal variable of the model, and the muscle force changes under external load are determined by variations in v rather than in the tension of filaments. The Boltzmann equation for an ensemble of cross-bridges is obtained, and some collective effects are discussed.