On the Indicatrixes of Waves Scattering from the Random Fractal Anisotropic Surface

Millimeter and centimeter wave scattering from the random fractal anisotropic surface has been theoretically investigated. Designing of such surfaces is based on the modifications of non-differentiable two-dimensional Weierstrass function. Wave scattering on a random surface is interesting for many sections of physics, mathematics, biology, and so on. Questions of a radar location and radio physics take the predominating position here. There are many real surfaces and volumes in the nature that can be carried to fractal objects. At the same time, the description of processes of waves scattering of fractal objects differs from classical approaches markedly. There are many monographs in the world on the topic of classical methods of wave scattering but the number of books devoted to waves scattering on fractal stochastic surfaces is not enough. These results of estimation of three-dimensional scattering functions are a priority in the world and are important in radar of low-contrast targets near the surface of the earth and the sea

Revisiting perfect fluid dark matter: Observational constraints from our galaxy

We revisit certain features of an assumed spherically symmetric perfect fluid dark matter halo in the light of the observed data of our galax

Can massless wormholes mimic a Schwarzschild black hole in the strong field lensing?

Recent trend of research indicates that not only massive but also massless (asymptotic Newtonian mass zero) wormholes can reproduce post-merger initial ring-down gravitational waves characteristic of black hole horizon. In the massless case, it is the non-zero charge of other fields, equivalent to what we call here the "Wheelerian mass", that is responsible for mimicking ring-down quasi-normal modes. In this paper, we enquire whether the same Wheelerian mass can reproduce black hole observables also in an altogether different experiment, viz., the strong field lensing. We examine two classes of massless wormholes, one in the Einstein-Maxwell-Dilaton (EMD) theory and the other in the Einstein-Minimally-coupled-Scalar field (EMS) theory. The observables such as the radius of the shadow, image separation and magnification of the corresponding Wheelerian masses are compared with those of a black hole (idealized SgrA* chosen for illustration) assuming that the three types of lenses share the same minimum impact parameter and distance from the observer. It turns out that, while the massless EMS\ wormholes can closely mimic the black hole in terms of strong field lensing observables, the EMD wormholes show considerable differences due to the presence of dilatonic charge. The conclusion is that masslessless alone is enough to closely mimic Schwarzschild black hole strong lensing observables in the EMS theory but not in the other, where extra parameters also influence those observables. The motion of timelike particles is briefly discussed for completeness.Comment: 13 pages, 2 figure

Cold Trauma in the Structure of External Causes of Mortality and Disability in the Republic of Sakha (Yakutia)

The purpose of this study was to analyze the data of official medical statistics on mortality and disability in the Republic of Sakha (Yakutia) (RS(Y)) as a result of exposure to excessively low natural temperatures. For the retrospective epidemiological analysis, we used the data of the official statistics of RS(Y) for 2011-2015, data on the disability of the Federal State Institution "Main Bureau of Medical and Social Expertise of RS(Y)" for 2014-2016, and data of the burn department of the Center for Emergency Medical Care of Yakutsk for 2014-2016. In Yakutia, during 2011-2015, 662 people died in road accidents, and 812 died as a result of exposure to excessive natural cold; the mortality rates were 13.8 and 17.0 per 100,000 population, respectively. In the structure of external causes of mortality, the share of cold trauma in 2015 was 10.4% (15.1 per 100,000 population), which put cold trauma in the third rank after suicide and murders, having displaced road accidents in fourth place (5.6%, 7.8 per 100,000 population). The disability rate due to frostbites was 1.19 per 100,000 population in 2014 and 1.73 per 100,000 population in 2015 and 2016