Table of contents

We review the current status of the theory of discontinuous magnetohydrodynamic (MHD) flows and its application to the physics of magnetic reconnection in astrophysical plasmas and in laboratory and numerical simulation studies. The emphasis is on the study of continuous transitions occurring between different types of discontinuities under gradual and continuous variation of the plasma flow parameters. The properties of the Syrovatskii reconnecting current sheet are described, and the possibility of the splitting of the current sheet into a system of MHD discontinuities is demonstrated. A simplified analytic model of magnetic reconnection is used to study the system of shock waves associated with the current sheet. With this system as an example, some implications of the conditions of continuous transitions and the possibility of additional plasma heating by a shock wave are considered.

The unique properties of diamond have stimulated the study of and search for its applications in many fields, including optics, optoelectronics, electronics, biology, and electrochemistry. Whereas chemical vapor deposition allows the growth of polycrystalline diamond plates more than $200\ {\text{mm}}$ in diameter, most current diamond application technologies require large-size ($25\ {\text{mm}}$ and more) single-crystal diamond substrates or films suitable for the photolithography process. This is quite a challenge, because the largest diamond crystals currently available are $10\ {\text{mm}}$ or less in size. This review examines three promising approaches to fabricating large-size diamond single crystals: growing large-size single crystals, the deposition of heteroepitaxial diamond films on single-crystal substrates, and the preparation of composite diamond substrates.

We review research aimed at understanding the phenomena occurring in a complex plasma under microgravity conditions. Some aspects of the work already performed are considered that have not previously been given sufficient attention but which are potentially crucial for future work. These aspects, in particular, include the observation of compact dust structures that are estimated to be capable of confining all components of a dust plasma in a bounded spatial volume; experimental evidence of the nonlinear screening of dust particles; and experimental evidence of the excitation of collective electric fields. In theoretical terms, novel collective attraction processes between likely charged dust particles are discussed and all schemes of the shadowy attraction between dust particles used earlier, including in attempts to interpret observations, are reviewed and evaluated. Dust structures are considered from the standpoint of the current self-organization theory. It is emphasized that phase transitions between states of self-organized systems differ significantly from those in homogeneous states and that the phase diagrams should be constructed in terms of the parameters of a self-organized structure and cannot be constructed in terms of the temperature and density or similar parameters of homogeneous structures. Using the existing theoretical approaches to modeling self-organized structures in dust plasmas, the parameter distribution of a structure is recalculated for a simpler model that includes the quasineutrality condition and neglects diffusion. These calculations indicate that under microgravity conditions, any self-organized structure can contain a limited number of dust particles and is finite in size. The maximum possible number of particles in a structure determines the characteristic inter-grain distance in dust crystals that can be created under microgravity conditions. Crystallization criteria for the structures are examined and the quasispherical chambers proposed for future experiments are discussed.

Advances in the studies of metamaterials have pushed the development of invisibility cloaks, which suppress scattering by objects within certain frequency ranges. During recent years, there has been a transition from a purely theoretical consideration of the cloaking effect to its practical implementation. This paper is an overview of the current state of the art in the area of invisibility cloaks. Special emphasis is put on experimental realizations of such devices.

Three new approaches to the laser mass spectrometry of organic samples are presented, which are based on the soft ionization of organic and bioorganic molecules and on the use of pulsed laser radiation.

The power formula for turbulent velocity profiles in a circular tube offered by G I Barenblatt, A J Chorin, and V M Prostokishin in their paper "Turbulent flows at very large Reynolds numbers: new lessons learned" (Phys. Usp.57 250 (2014); Usp. Fiz. Nauk184 265 (2014)) is discussed.

The problem of turbulent flow in pipes, although at first sight of purely engineering interest, has since the 1930s been the subject of much attention by mathematicians and physicists, including such outstanding figures as Th von Kármán, L Prandtl, and L D Landau. It has turned out that despite — or perhaps due to — the seemingly simple formulation of this problem, research on it has revealed new aspects of the still very mysterious phenomenon of turbulence. Reference [1] briefly summarizes our work over the last twenty years on the problem. Some of our results strongly disagree with commonly accepted views which, unsurprisingly, makes them difficult to accept. This is well exemplified by letter [2], so its analysis here may hopefully be of interest to UFN's (Physics –Uspekhi) readers.