Effect of the turbulent biological tissues on the propagation properties of coherent Laguerre-Gaussian beams

In this paper, the effects of turbulent biological tissues (TBT) on the propagation properties of the coherent Laguerre-Gaussian (CLG) beams are studied. Based on the turbulence theory and using the power spectrum refractive-index model, the expression formulae of the average irradiance intensity and spreading properties of a CLG beam propagating in TBT are derived. The influence of propagation distance, beam orders, wavelengths and tissue turbulence parameters are then investigated numerically. It found that, the central dark zone of the circular/elliptical LG beams rises more rapidly as the propagation distance and the structural constant of the refractive index of the biological tissue increase and the beams become eventually more like Gaussian beams in the far-field under the influence of the turbulence biological tissues. Also, the numerical results proved that the effective beam spot radius increases as turbulence, wavelength, and propagation distance are increasing. Ultimately, the beams become circular under the influence of the turbulence of the biological tissue. As found that the effective beam spot radius along the x-axis becomes equal to that of the y-axis in high TBT which explain why an elliptical LG beam is converted into a circular one in higher structural constant of the turbulent tissue. Moreover, our results show that, the influence of the beam order m slightly greater than that of l on the beam spreading.

Determination of structural constant and size of crystallites in thin magnetic films by ferromagnetic resonance

We demonstrate the possibility of determination of the structural constant S and the average size of crystallites in an anisotropic nanocrystalline magnetic film by the analysis of the shape of the sharp microwave absorption peak observed when the external magnetic field is swept along the hard magnetization axis. In the theory of magnetization ripple, the constant S is linked to the surface density of local magnetic anisotropy energy and S can be used to estimate the quality of nanocrystalline films. The performance of the new method for determination of S was demonstrated on a 300-nm-thick nanocrystalline Co-P film. The absorption spectrum was measured on a local film area of ~ 1 mm2 by the scanning ferromagnetic resonance spectrometer. The calculated from the analysis of the spectrum value for S allowed us to determine an average size of crystallites in the film that agrees well with the transmission electron microscopy results.

Language expression of the argumentative framework “From popular opinion vs. from expert opinion” in the text of popular science article

The paper discusses argumentation in popular science articles written by scholars. The authors focus on argumentative framework, which is presented by opposition of an expert’s judgment (argument from expert opinion) and a common, “naive” view (one from popular opinion). The framework consists of a thesis being opposed (by a subject of common sense); its authorization marker; an opposing structural constant/propositional connective; an expert’s thesis; its authorization marker; general conclusion. In summary, this paper argues that the elements of the argumentative framework can be explicit, implicit, or be presented grammatically. Text analysis of popular science articles leads to the following conclusions. (1) The opposed thesis and opposing link are typically explicit. (2) The subject of common sense can be represented by lexical and syntactic expressions of indefinite-personality, impersonality together with unreal mood and epistemic modality of uncertain knowledge (One would think…; smth may seem…; many noticed that…) etc. (3) An expert’s thesis, as a rule, is presented as a negation of the opposed statement. (4) An authorization marker of the expert’s opinion is consistently implicit. The reason is that an expert writes the entire text (except for parts with authorization markers), and in this case the additional expression of this fact is optional. (5) Normally, the general conclusion is the same as the expert’s thesis, therefore it is rarely if ever explicit.

NON-MINIMAL COUPLING, VARIABLE SPEED OF LIGHT AND COSMOLOGY

Presently, there exists some renewed interest in time varying speed of light theories as possible solutions of the major cosmological problems1. It is often believed that the local Lorentzian invariance is broken if the speed of light in a vacuum is not a constant. We point out that this belief is not necessarily founded and that a variable speed of light is perfectly consistent with general relativity under the assumption of non-minimal coupling between electromagnetism and curvature. Two kinds of arguments may be invoked in favour of such an assumption. First, a theorem due to Horndeski2 shows that in a four-dimensional space-time the Einstein-Maxwell field equations are not the only second-order vector potential field equations which stem from a Lagrangian scalar density, are consistent with the charge conservation and reduce to Maxwell's equations in a flat space-time (see also3). Second, according to QED4,5, vacuum polarization induces tidal gravitational effects which imply that photons propagating in a curved space-time have velocities exceeding the value of the "Lorentzian structural constant" c. The modified electromagnetic field equations given by Horndeski2 are studied here in the geometrical optics limit. Considering the case of Friedmann-Robertson-Walker cosmological models, we find the value of the speed of light as a function of the energetic content of the universe. We deduce from this result a new equation of state for a photon gas and we discuss the consequences of this equation on the evolution of the scale factor during the radiation-dominated era.