The last decade has witnessed a significant growth of research into materials with coupled magnetic and electric properties. Reviewed here are the main types and mechanisms of magnetoelectric interactions and conditions of their origin. Special attention is given to potentially practical materials that display magnetoelectric properties at room temperature. Example applications of magnetoelectric materials and multiferroics in information and energy saving technologies are discussed.

Dense quantum plasmas are ubiquitous in planetary interiors and in compact astrophysical objects (e.g., the interior of white dwarf stars, in magnetars, etc.), in semiconductors and micromechanical systems, as well as in the next-generation intense laser solid density plasma interaction experiments and in quantum X-ray free-electron lasers. In contrast to classical plasmas, quantum plasmas have extremely high plasma number densities and low temperatures. Quantum plasmas are composed of electrons, positrons and holes, which are degenerate. Positrons (holes) have the same (slightly different) mass as electrons, but opposite charge. The degenerate charged particles (electrons, positrons, and holes) obey the Fermi-Dirac statistics. In quantum plasmas, there are new forces associated with (i) quantum statistical electron and positron pressures, (ii) electron and positron tunneling through the Bohm potential, and (iii) electron and positron angular momentum spin. Inclusion of these quantum forces allows the existence of very high-frequency dispersive electrostatic and electromagnetic waves (e.g., in the hard X-ray and gamma-ray regimes) with extremely short wavelengths. In this review paper, we present theoretical backgrounds for some important nonlinear aspects of wave wave and wave electron interactions in dense quantum plasmas. Specifically, we focus on nonlinear electrostatic electron and ion plasma waves, novel aspects of three-dimensional quantum electron fluid turbulence, as well as nonlinearly coupled intense electromagnetic waves and localized plasma wave structures. Also discussed are the phase-space kinetic structures and mechanisms that can generate quasistationary magnetic fields in dense quantum plasmas. The influence of the external magnetic field and the electron angular momentum spin on the electromagnetic wave dynamics is discussed. Finally, future perspectives of the nonlinear quantum plasma physics are highlighted.

Recent results in magnonics-a topical and rapidly developing branch of spintronics and magnetoelectronics-are presented. The paper describes measurement techniques and theoretical approaches used to explore physical processes associated with the spin-wave propagation in complex nano- and micro-dimensional magnetic structures. The results of the application of magnetic structures in signal processing and transmission systems are discussed. In particular, results on spin wave propagation in distributed magnetic periodic structures, lumped systems, coupled waveguide structures, and controllable magnonic structures are considered. Specific examples of circuitry based on magnonic structures are discussed, and possibilities for further developing this circuitry are explored.

The field of optical nanoantennas, a rapidly developing area of optics, is reviewed. The basic concept of an optical antenna is formulated and major characteristics relevant to this structure are identified. A classification of nanoantennas into metallic and dielectric (the latter including semiconductor nanoantennas) is made. For either category, the literature is reviewed and strengths and weaknesses of different approaches are discussed. The basics of nonlinear optical antennas are outlined. Future avenues of research and application areas for the field are highlighted, and its prospects are examined.

It is well known that periodic discrete defect-containing systems support both traveling waves and vibrational defect localized modes. It turns out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Because the nodes of the system are all on equal footing, only a special choice of the initial conditions allows selecting a group of nodes on which such a mode, called a discrete breather (DB), can be excited. The DB frequency must be outside the frequency range of small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically preserve its vibrational energy forever if no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery of DBs in them was only a matter of time. Experimental studies of DBs encounter major technical difficulties, leaving atomistic computer simulations as the primary investigation tool. Despite definitive evidence for the existence of DBs in crystals, their role in solid-state physics remains unclear. This review addresses some of the problems that are specific to real crystal physics and which went undiscussed in the classical literature on DBs. In particular, the interaction of a moving DB with lattice defects is examined, the effect of elastic lattice deformations on the properties of DBs and the possibility of their existence are discussed, and recent studies of the effect of nonlinear lattice perturbations on the crystal electron subsystem are presented.

We review the status of cooling techniques aimed at achieving the deepest quantum degeneracy for atomic Fermi gases. We first discuss some physics motivations, providing a quantitative assessment of the need for deep quantum degeneracy in relevant physics cases, such as the search for unconventional superfluid states. Attention is then focused on the most widespread technique to reach deep quantum degeneracy for Fermi systems, sympathetic cooling of Bose Fermi mixtures, organizing the discussion according to the specific species involved. Various proposals to circumvent some of the limitations on achieving the deepest Fermi degeneracy, and their experimental realizations, are then reviewed. Finally, we discuss the extension of these techniques to optical lattices and the implementation of precision thermometry crucial to the understanding of the phase diagram of classical and quantum phase transitions in Fermi gases.

The current understanding of the superconductor-insulator transition is discussed level by level in a cyclic spiral-like manner. At the first level, physical phenomena and processes are discussed which, while of no formal relevance to the topic of transitions, are important for their implementation and observation; these include superconductivity in low electron density materials, transport and magnetoresistance in superconducting island films and in highly resistive granular materials with superconducting grains, and the Berezinskii-Kosterlitz-Thouless transition. The second level discusses and summarizes results from various microscopic approaches to the problem, whether based on the Bardeen-Cooper-Schrieffer theory (the disorder-induced reduction in the superconducting transition temperature; the key role of Coulomb blockade in high-resistance granular superconductors; superconducting fluctuations in a strong magnetic field) or on the theory of the Bose-Einstein condensation. A special discussion is given to phenomenological scaling theories. Experimental investigations, primarily transport measurements, make the contents of the third level and are for convenience classified by the type of material used (ultrathin films, variable composition materials, high-temperature superconductors, superconductor-poor metal transitions). As a separate topic, data on nonlinear phenomena near the superconductor-insulator transition are presented. At the final, summarizing, level the basic aspects of the problem are enumerated again to identify where further research is needed and how this research can be carried out. Some relatively new results, potentially of key importance in resolving the remaining problems, are also discussed.

We review some theoretical and phenomenological aspects of massive gravities in 4 dimensions. We start from the Fierz-Pauli theory with Lorentz-invariant mass terms and then proceed to Lorentz-violating masses. Unlike the former theory, some models with Lorentz violation have no pathologies in the spectrum in flat and nearly flat backgrounds and lead to an interesting phenomenology.

A brief review is given of scalar field theories with second-derivative Lagrangians yielding second-order field equations. Some of these theories permit solutions that violate the null energy condition but otherwise show no obvious inconsistencies. The use of these theories in constructing cosmological scenarios and in the context of a laboratory-created universe is illustrated with examples.

This paper reviews experimental research on nano composite protective coatings of various chemical compositions and structure. For adaptive multielement and multilayer systems with specific phase composition, structure, substructure, stress state, and high functional properties, formation conditions are considered; the behavior of such systems under extreme operating conditions and in tribological applications is examined; the structural, phase, and chemical composition are discussed as well as the hardness, friction and wear at elevated temperatures; and the adhesive strength of hierarchical protective coatings is analyzed. Finally, the adaptive behavior under different tribological test conditions of multifunctional, multi layer coatings as a function of their properties and structure is examined.

We review quantum mechanical and optical pseudo-Hermitian systems with an emphasis on PT-symmetric systems important for optics and electrodynamics. One of the most interesting and much discussed consequences of PT symmetry is a phase transition under which the system eigenvalues lose their PT symmetry. We show that although this phase transition is difficult to realize experimentally, a similar transition can be observed in quasi-PT-symmetric systems. Other effects predicted for PT-symmetric systems are not specific for these systems and can be observed in ordinary fully passive systems.

Various approaches to creating multicomponent nanocomposite coatings of high and superhigh hardness (from similar or equal to 30 to 100-120 GPa) are reviewed with particular emphasis placed on mechanisms underlying the increase in hardness in thin (<= 10 pm) coatings. The deposition technologies considered include magnetron sputtering, ion beam-assisted and vacuum arc depositions. A classification of hard and superhard coatings with high thermal stability is given. Possible applications of such nanostructured coatings are discussed and prospects for the field are outlined.

Basic experimental data are presented for a new class of high-temperature superconductors - iron-based layered compounds of the types REOFeAs (RE = La, Ce, Nd, Pr, Sm,...), AFe(2)As(2) (A = Ba, Sr,...), AFeAs (A = Li,...), and FeSe(Te). The structure of electronic spectra in these compounds is discussed, including the correlation effects, as is the spectrum and role of collective excitations (phonons and spin waves). Basic models for describing various types of magnetic! ordering and Cooper pairing are reviewed.

Results obtained using continuous and discrete wavelet transforms as applied to problems in neurodynamics are reviewed, with the emphasis on the potential of wavelet analysis for decoding signal information from neural systems and networks. The following areas of application are considered: (1) the microscopic dynamics of single cells and intracellular processes, (2) sensory data processing, (3) the group dynamics of neuronal ensembles, and (4) the macrodynamics of rhythmical brain activity (using multichannel EEG recordings). The detection and classification of various oscillatory patterns of brain electrical activity and the development of continuous wavelet-based brain activity monitoring systems are also discussed as possibilities.

We review quantum mechanical and optical pseudo-Hermitian systems with an emphasis on PT-symmetric systems important for optics and electrodynamics. One of the most interesting and much discussed consequences of PT symmetry is a phase transition under which the system eigenvalues lose their PT symmetry. We show that although this phase transition is difficult to realize experimentally, a similar transition can be observed in quasi-PT-symmetric systems. Other effects predicted for PT-symmetric systems are not specific for these systems and can be observed in ordinary fully passive systems.

The paper examines the prospects of using laser plasma as a source of high-energy ions for the purpose of hadron beam therapy an approach which is based on both theory and experimental results (ions are routinely observed to be accelerated in the interaction of high-power laser radiation with matter). Compared to therapy accelerators like synchrotrons and cyclotrons, laser technology is advantageous in that it is more compact and is simpler in delivering ions from the accelerator to the treatment room. Special target designs allow radiation therapy requirements for ion beam quality to be satisfied.

The properties of dusty plasmas - low-temperature plasmas containing charged macroparticles - are considered. The most important elementary processes in dusty plasmas and the forces acting on dust particles are investigated. The results of experimental and theoretical investigations of different states of strongly nonideal dusty plasmas - crystal-like, liquid-like, gas-like - are summarized. Waves and oscillations in dusty plasmas, as well as their damping and instability mechanisms, are studied. Some results on dusty plasma investigated under microgravity conditions are presented. New directions of experimental research and potential applications of dusty plasmas are discussed.

Topological Lifshitz transitions involve many types of topological structures in momentum and frequency momentum spaces, such as Fermi surfaces, Dirac lines, Dirac and Weyl points, etc., each of which has its own stability-supporting topological invariant (N-1, N-2, N-3, N-3, etc.). The topology of the shape of Fermi surfaces and Dirac lines and the interconnection of objects of different dimensionalities produce a variety of Lifshitz transition classes. Lifshitz transitions have important implications for many areas of physics. To give examples, transition-related singularities can increase the superconducting transition temperature; Lifshitz transitions are the possible origin of the small masses of elementary particles in our Universe, and a black hole horizon serves as the surface of the Lifshitz transition between vacua with type-I and type-II Weyl points.

The early 21st century is witnessing a breakthrough in the study of the thermal radiation of neutron stars. Observations with modern space telescopes have provided a wealth of valuable information, which, when properly interpreted, can elucidate the physics of superdense matter in the interior of these starts. This interpretation is underlain by the theory of formation of the neutron star thermal spectra, which is in turn based on plasma physics and on the understanding of radiative processes in stellar photospheres. In this paper, the current status of the theory is reviewed, with particular emphasis on neutron starts with strong magnetic fields. In addition to the conventional deep (semi-infinite) atmospheres, radiative condensed surfaces of neutron stars and 'thin' (finite) atmospheres are considered.