4,021 research outputs found
Photon splitting in atomic fields
Photon splitting due to vacuum polarization in the electric field of an atom
is considered. We survey different theoretical approaches to the description of
this nonlinear QED process and several attempts of its experimental
observation. We present the results of the lowest-order perturbation theory as
well as those obtained within the quasiclassical approximation being exact in
the external field strength. The experiment where photon splitting was really
observed for the first time is discussed in details. The results of this
experiment are compared with recent theoretical estimations.Comment: 45 pages, 24 figure
Quasi-Optimal Filtering in Inverse Problems
A way of constructing a nonlinear filter close to the optimal Kolmogorov -
Wiener filter is proposed within the framework of the statistical approach to
inverse problems. Quasi-optimal filtering, which has no Bayesian assumptions,
produces stable and efficient solutions by relying solely on the internal
resources of the inverse theory. The exact representation is given of the
Feasible Region for inverse solutions that follows from the statistical
consideration.Comment: 9 pages, 240 K
Hydration of a B-DNA Fragment in the Method of Atom-atom Correlation Functions with the Reference Interaction Site Model Approximation
We propose an efficient numerical algorithm for solving integral equations of
the theory of liquids in the Reference Interaction Site Model (RISM)
approximation for infinitely dilute solution of macromolecules with a large
number of atoms. The algorithm is based on applying the nonstationary iterative
methods for solving systems of linear algebraic equations. We calculate the
solvent-solute atom-atom correlation functions for a fragment of the B-DNA
duplex d(GGGGG).d(CCCCC) in infinitely dilute aqueous solution. The obtained
results are compared with available experimental data and results from computer
simulations.Comment: 9 pages, RevTeX, 9 pages of ps figures, accepted for publications in
JC
Condensation of Silica Nanoparticles on a Phospholipid Membrane
The structure of the transient layer at the interface between air and the
aqueous solution of silica nanoparticles with the size distribution of
particles that has been determined from small-angle scattering has been studied
by the X-ray reflectometry method. The reconstructed depth profile of the
polarizability of the substance indicates the presence of a structure
consisting of several layers of nanoparticles with the thickness that is more
than twice as large as the thickness of the previously described structure. The
adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the
hydrosol/air interface is accompanied by the condensation of anion silica
nanoparticles at the interface. This phenomenon can be qualitatively explained
by the formation of the positive surface potential due to the penetration and
accumulation of Na+ cations in the phospholipid membrane.Comment: 7 pages, 5 figure
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