Combustion theory for liquids with a free surface. 3: Special problems

Two special problems concerning the combustion of liquids with a free surface, i.e., flame quenching during the mixing of a burning liquid inside a container and liquid burnout from a porous layer, are analyzed using a quasi-one-dimensional model. The critical parameters corresponding to the quenching of a burning fluid with a free surface are determined. Determinations are also made of the limiting pressure gradients corresponding to the transition from the combustion mode where the liquid evaporates from the surface of a porous layer to the mode where the phase transition surface lies inside the porous layer

Magnetophononics: ultrafast spin control through the lattice

Using a combination of first-principles and magnetization-dynamics calculations, we study the effect of the intense optical excitation of phonons on the magnetic behavior in insulating magnetic materials. Taking the prototypical magnetoelectric \CrO\ as our model system, we show that excitation of a polar mode at 17 THz causes a pronounced modification of the magnetic exchange interactions through a change in the average Cr-Cr distance. In particular, the quasi-static deformation induced by nonlinear phononic coupling yields a structure with a modified magnetic state, which persists for the duration of the phonon excitation. In addition, our time-dependent magnetization dynamics computations show that systematic modulation of the magnetic exchange interaction by the phonon excitation modifies the magnetization dynamics. This temporal modulation of the magnetic exchange interaction strengths using phonons provides a new route to creating non-equilibrium magnetic states and suggests new avenues for fast manipulation of spin arrangements and dynamics.Comment: 11 pages with 7 figure

Perturbations in generalized Galileon theories

We discuss the approaches by Deffayet et al. (DPSV) and Kobayashi et al. (KYY) to the analysis of linearized scalar perturbations about a spatially flat FLRW background in Horndeski theory. We identify additional, potentially important terms in the DPSV approach. However, these terms vanish upon a judicious gauge choice. We derive a gauge invariant quadratic action for metric and Galileon perturbations in $\mathcal{L}_3$ and $\mathcal{L}_3+\mathcal{L}_4$ theories and show that actions obtained in the DPSV and KYY approaches follow from this gauge invariant action in particular gauges.Comment: This is a journal version of the article. The proof of the statement made in Section 3 has been considerably revised. The paper consists of 13 page

Discrete structure of ultrathin dielectric films and their surface optical properties

The boundary problem of linear classical optics about the interaction of electromagnetic radiation with a thin dielectric film has been solved under explicit consideration of its discrete structure. The main attention has been paid to the investigation of the near-zone optical response of dielectrics. The laws of reflection and refraction for discrete structures in the case of a regular atomic distribution are studied and the structure of evanescent harmonics induced by an external plane wave near the surface is investigated in details. It is shown by means of analytical and numerical calculations that due to the existence of the evanescent harmonics the laws of reflection and refraction at the distances from the surface less than two interatomic distances are principally different from the Fresnel laws. From the practical point of view the results of this work might be useful for the near-field optical microscopy of ultrahigh resolution.Comment: 25 pages, 16 figures, LaTeX2.09, to be published in Phys.Rev.

U.S. Public Diplomacy in the Middle East in the 21st Century: Evolution of Strategies, Instruments, Challenges, and Prospects

The article was submitted on 30.04.2025.Статья посвящена анализу публичной дипломатии США на Ближнем Востоке в XXI в. Автор рассматривает эволюцию американских стратегий в регионе на фоне глобальных изменений и возрастающей конкуренции со стороны Китая, России и Турции. Особое внимание уделяется изучению ключевых инструментов публичной дипломатии США, включая образовательные программы, культурные инициативы, гуманитарную помощь, медийные проекты и цифровую дипломатию. В работе проанализированы политические и экономические выгоды, получаемые Соединенными Штатами, а также основные вызовы, стоящие перед американской дипломатией в регионе. Делается вывод о необходимости адаптации публичной дипломатии США к новым международным условиям и усилении ее эффективности в борьбе за влияние на Ближнем Востоке.The article focuses on the analysis of the United States’ public diplomacy strategies in the Middle East in the 21st century. The author examines the evolution of American approaches in the region against the backdrop of global shifts and growing competition from China, Russia, and Turkey. Particular attention is paid to key instruments of U.S. public diplomacy, including educational initiatives, cultural programs, humanitarian assistance, media projects, and digital diplomacy. The study analyzes the political and economic benefits gained by the United States, as well as the main challenges facing American diplomacy in the region. The article concludes that adapting U.S. public diplomacy to new international conditions is essential for strengthening its effectiveness in the ongoing struggle for influence in the Middle East

POLICRYPS Composite Materials: Features and Applications

Physical chemistr