Second generation diffusion model of interacting gravity waves on the surface of deep fluid

We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum

Second generation diffusion model of interacting gravity waves on the surface of deep fluid

International audienceWe propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum

Self-similarity of wind-driven seas

International audienceThe results of theoretical and numerical study of the Hasselmann kinetic equation for deep water waves in presence of wind input and dissipation are presented. The guideline of the study: nonlinear transfer is the dominating mechanism of wind-wave evolution. In other words, the most important features of wind-driven sea could be understood in a framework of conservative Hasselmann equation while forcing and dissipation determine parameters of a solution of the conservative equation. The conservative Hasselmann equation has a rich family of self-similar solutions for duration-limited and fetch-limited wind-wave growth. These solutions are closely related to classic stationary and homogeneous weak-turbulent Kolmogorov spectra and can be considered as non-stationary and non-homogeneous generalizations of these spectra. It is shown that experimental parameterizations of wind-wave spectra (e.g. JONSWAP spectrum) that imply self-similarity give a solid basis for comparison with theoretical predictions. In particular, the self-similarity analysis predicts correctly the dependence of mean wave energy and mean frequency on wave age Cp / U10. This comparison is detailed in the extensive numerical study of duration-limited growth of wind waves. The study is based on algorithm suggested by Webb (1978) that was first realized as an operating code by Resio and Perrie (1989, 1991). This code is now updated: the new version is up to one order faster than the previous one. The new stable and reliable code makes possible to perform massive numerical simulation of the Hasselmann equation with different models of wind input and dissipation. As a result, a strong tendency of numerical solutions to self-similar behavior is shown for rather wide range of wave generation and dissipation conditions. We found very good quantitative coincidence of these solutions with available results on duration-limited growth, as well as with experimental parametrization of fetch-limited spectra JONSWAP in terms of wind-wave age Cp / U10

Coexistence of Weak and Strong Wave Turbulence in a Swell Propagation

By performing two parallel numerical experiments -- solving the dynamical Hamiltonian equations and solving the Hasselmann kinetic equation -- we examined the applicability of the theory of weak turbulence to the description of the time evolution of an ensemble of free surface waves (a swell) on deep water. We observed qualitative coincidence of the results. To achieve quantitative coincidence, we augmented the kinetic equation by an empirical dissipation term modelling the strongly nonlinear process of white-capping. Fitting the two experiments, we determined the dissipation function due to wave breaking and found that it depends very sharply on the parameter of nonlinearity (the surface steepness). The onset of white-capping can be compared to a second-order phase transition. This result corroborates with experimental observations by Banner, Babanin, Young.Comment: 5 pages, 5 figures, Submitted in Phys. Rev. Letter

Токсичність МАРК у карциномах щитоподібної залози. Механізми пригнічення сигнального каскаду (огляд літератури та власних даних)

The aim of the work: to study the activity and expression of the main effector protein kinase cascade in tumors of thyroid gland. There is a strong evidence that the Ras/Raf/MEK/ERK (МАРК) signaling cascade promotes cell proliferation and malignancy by stimulating cell growth and division, as well as inhibiting apoptosis. The mitogenic MAPK cascade associates growth factor signals at cell surface receptors with the transcription factors AP-1, NF-κB, Ets, leading to the induction of c-Fos, cyclin D1 and c-Myc. These factors regulate the expression of genes that control survival, angiogenesis, growth, proliferation, and cell motility. However, the hyperactivity of this cascade in tumor tissues can lead to sensescence, growth retardation, apoptosis or increased autophagy. This phenomenon was called "oncogenic toxicity".Цель работы: исследование в опухолях щитовидной железы активности и экспрессии главной эффекторной протеинкиназы каскада – ERK1/2. Получены убедительные доказательства того, что сигнальный каскад Ras/Raf/MEK/ERK (МАРК) способствует пролиферации и злокачественной трансформации клеток путем стимуляции клеточного роста и деления, а также подавления апоптоза. Митогенный МАРК-каскад связывает сигналы факторов роста на рецепторах клеточной поверхности с транскрипционными факторами АР-1, NF-κB, Ets, что приводит к индукции с-Fos, циклина D1 и с-Мус. Эти факторы регулируют экспрессию генов, контролирующих выживание, ангиогенез, рост, пролиферацию и подвижность клеток. Однако гиперактивность этого каскада в опухолевых тканях может привести к сенесценции, задержке роста, апоптозу или усилению аутофагии. Этот феномен назвали “токсичностью онкогенов”.Мета роботи: дослідження в пухлинах щитоподібної залози (ЩЗ) активності та експресії головної ефекторної протеїнкінази каскаду – ERK1/2. Отримано переконливі докази того, що сигнальний каскад Ras/Raf/MEK/ERK (МАРК) сприяє проліферації і злоякісній трансформації клітин шляхом стимуляції клітинного росту і ділення, а також пригнічення апоптозу. Мітогенний МАРК-каскад пов’язує сигнали факторів росту на рецепторах клітинної поверхні з транскрипційними факторами АР-1, NF-κB, Ets, що приводить до індукції с-Fos, цикліну D1 і с-Мус. Ці фактори регулюють експресію генів, що контролюють виживання, ангіогенез, ріст, проліферацію і мобільність клітин. Однак гіперактивність цього каскаду в пухлинних тканинах може привести до сенесценції, затримки росту, апоптозу або посилення автофагії. Цей феномен назвали “токсичністю онкогенів”

Entanglement entropy in de Sitter: no pure states for conformal matter

In this paper, we consider the entanglement entropy of conformal matter for finite and semi-infinite entangling regions, as well as the formation of entanglement islands in four-dimensional de Sitter spacetime partially reduced to two dimensions. We analyze complementarity and pure state condition of the entanglement entropy of pure states and show that they never hold in the given setup. We consider two different types of Cauchy surfaces in the extended static patch and flat coordinates, correspondingly. For former, we found that entanglement entropy of a pure state is always bounded from below by a constant and never becomes zero, as required by quantum mechanics. In turn, the difference between the entropies for some region and its complement, which should be zero for a pure state, in direct calculations essentially depends on how the boundaries of these regions evolve with time. Regarding the flat coordinates, it is impossible to regularize spacelike infinity in a way that would be compatible with complementarity and pure state condition, as opposed, for instance, to two-sided Schwarzschild black hole. Finally, we discuss the information paradox in de Sitter and show that the island formula does not resolve it. Namely, we give examples of a region with a time-limited growth of entanglement entropy, for which there is no island solution, and the region, for which entanglement entropy does not grow, but the island solution exists.Comment: v1: 25 pages, 10 figures; v2: 25 pages, 10 figures, references added, notation clarifie

Spontaneous and induced ferroelectricity in the BiFe1−xScxO3 perovskite ceramics

High-pressure synthesis method allows obtaining single-phase perovskite BiFe1-xScxO3 ceramics in the entire concentration range. As-prepared compositions with x from 0.30 to 0.55 have the antipolar orthorhombic Pnma structure but can be irreversible converted into the polar rhombohedral R3c or the polar orthorhombic Ima2 phase via annealing at ambient pressure. Microstructure defects and large conductivity of the high-pressure-synthesized ceramics make it difficult to study and even verify their ferroelectric properties. These obstacles can be overcome using piezoresponse force microscopy (PFM) addressing ferroelectric behavior inside single grains. Herein, the PFM study of the BiFe1-xScxO3 ceramics (0.30 ≤ x ≤ 0.50) is reported. The annealed samples show a strong PFM contrast. Switching of domain polarity by an electric field confirms the ferroelectric nature of these samples. The as-prepared BiFe0.5Sc0.5O3 ceramics demonstrate no piezoresponse in accordance with the antipolar character of the Pnma phase. However, application of a strong enough electric field induces irreversible transition to the ferroelectric state. The as-prepared BiFe0.7Sc0.3O3 ceramics show coexistence of ferroelectric and antiferroelectric grains without poling. It is assumed that mechanical stress caused by the sample polishing can be also a driving force of phase transformation in these materials alongside temperature and external electric field.publishe

Entanglement Islands and Infrared Anomalies in Schwarzschild Black Hole

In this paper, island formation for entangling regions of finite size in the asymptotically flat eternal Schwarzschild black hole is considered. We check the complementarity property of entanglement entropy which was implicitly assumed in previous studies for semi-infinite regions. This check reveals the emergence of infrared anomalies after regularization of a Cauchy surface. A naive infrared regularization based on ``mirror symmetry'' is considered and its failure is shown. We introduce an improved regularization that gives a correct limit agreed with the semi-infinite results from previous studies. As the time evolution goes, the endpoints of a finite region compatible with the improved regularization become separated by a timelike interval. We call this phenomenon the ``Cauchy surface breaking''. Shortly before the Cauchy surface breaking, finite size configurations generate asymmetric entanglement islands in contrast to the semi-infinite case. Depending on the size of the finite regions, qualitatively new behaviour arises, such as discontinuous evolution of the entanglement entropy and the absence of island formation. Finally, we show that the island prescription does not help us to solve the information paradox for certain finite size regions.Comment: v1: 55 pages, 19 figures; v2: 57 pages, 19 figures, references added, Sec. 5 presentation improve