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A two-dimensional problem of stationary nonlinear waves on the surface of a layer of finite-thickness ideal fluid is considered. The solution to the problem using the proposed technique includes the following steps. Firstly, the stream function trace is used to change the kinematic condition on the free surface. Secondly, the Bernoulli–Cauchy integral is applied to present the dynamic condition in a new form. Thirdly, an integral operator of the convolution type is introduced, which allows one to simplify the nonlinear boundary-value problem of determining four functions of one variable, the main ones of which are a wave profile shape and a stream function trace at the surface level. This technique allows reducing the two-dimensional problem to a one-dimensional one. Two forms of the nonlinear dispersion relation are obtained: the dependence of the wave velocity on the amplitude of the fundamental harmonic of the wave and the dependence of the wave velocity on the wave amplitude. The cases of short and long waves are considered.

The classical problem of stationary waves on the surface of an ideal incompressible homogeneous fluid of finite depth is considered. The solution approach to the problem is related to Stokes’ second method, but has the following differences: due to the one-dimensional integro-differential equation with cubic nonlinearity obtained for the profile of a stationary wave on the surface of the finite-depth fluid, the original problem is reduced to a one-dimensional one. The solution is obtained up to the seventh approximation.

Dirac fermions with highly dispersive linear bands 1 – 3 are usually considered weakly correlated due to the relatively large bandwidths ( W ) compared to Coulomb interactions ( U ). With the discovery of nodal-line semimetals, the notion of the Dirac point has been extended to lines and loops in momentum space. The anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. However, experimental evidence for the anticipated enhanced correlations in nodal-line semimetals is sparse. Here, we report on prominent correlation effects in a nodal-line semimetal compound, ZrSiSe, through a combination of optical spectroscopy and density functional theory calculations. We observed two fundamental spectroscopic hallmarks of electronic correlations: strong reduction (1/3) of the free-carrier Drude weight and also the Fermi velocity compared to predictions of density functional band theory. The renormalization of Fermi velocity can be further controlled with an external magnetic field. ZrSiSe therefore offers the rare opportunity to investigate correlation-driven physics in a Dirac system. What happens to topological materials when their electrons are strongly interacting is an open question. Shao and others demonstrate that ZrSiSe is a material that can address this as it has a topological band structure and non-trivial correlations.

Upon exposure to ultra-intense, hard X-ray pulses, polyatomic molecules containing one heavy atom reach a much higher degree of ionization than do individual heavy atoms, contrary to previous assumptions. Ultrafast molecular response to intense X-rays X-ray free-electron lasers offer many new applications such as the ability to structurally probe fast biological processes. This requires the use of hard and intense X-ray pulses, but the behaviour of matter under such conditions has not been fully explored. Artem Rudenko et al . show that when exposing small polyatomic molecules that contain one heavy atom to hard X-ray pulses with ultra-high intensities, the response is qualitatively different from what is seen in experiments carried out under less extreme conditions. The observed ionization of the molecule is considerably enhanced compared to that of an individual heavy atom under the same conditions, owing to ultrafast charge transfer within the molecule that replenishes the electrons removed from the heavy atom, enabling further ionization. Being able to account for this effect will aid further use of X-ray free-electron lasers for studying biological systems. X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions 1 , 2 , 3 , 4 , 5 , 6 , 7 . Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre) 3 , 5 . However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 . Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption 8 , 12 , 13 , 18 , which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge 14 , 15 , 16 , 17 , 19 , 20 . In serial femtosecond crystallography of biological objects—an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure 2 , 3 —the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects 21 , 22 and has been suggested as a way of phasing the diffraction data 23 , 24 . On the basis of experiments using either soft or less-intense hard X-rays 14 , 15 , 16 , 17 , 18 , 19 , 25 , it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

A bstract A method for measuring the average longitudinal polarization of the electron beam at an electron-positron collider operating near the J / ψ resonance is proposed. The method utilizes the differential cross-section of J / ψ → Λ → p π − Λ → p ¯ π + decay. It can be used to measure the average longitudinal polarization of electrons with the statistical precision better than 10 −3 at a Super Charm-Tau factory operating at the luminosity of 10 35 cm −2 s −1 . The method is discussed in the context of the weak mixing angle measurement in the same experiment.

The free expansion of a planar plasma surface is a fundamental non-equilibrium process relevant for various fields but as-yet experimentally still difficult to capture. The significance of the associated spatiotemporal plasma motion ranges from astrophysics and controlled fusion to laser machining, surface high-harmonic generation, plasma mirrors, and laser-driven particle acceleration. Here, we show that x-ray coherent diffractive imaging can surpass existing approaches and enables the quantitative real-time analysis of the sudden free expansion of laser-heated nanoplasmas. For laser-ionized SiO 2 nanospheres, we resolve the formation of the emerging nearly self-similar plasma profile evolution and expose the so far inaccessible shell-wise expansion dynamics including the associated startup delay and rarefaction front velocity. Our results establish time-resolved diffractive imaging as an accurate quantitative diagnostic platform for tracing and characterizing plasma expansion and indicate the possibility to resolve various laser-driven processes including shock formation and wave-breaking phenomena with unprecedented resolution.

We study the microscopic origin of magnetism in suspended and dielectrically embedded CrI3 monolayer by down-folding minimal generalized Hubbard models from ab initio calculations using the constrained random phase approximation. These models are capable of describing the formation of localized magnetic moments in CrI3 and of reproducing electronic properties of direct ab initio calculations. Utilizing the magnet force theorem, we find a multi-orbital super-exchange mechanism as the origin of magnetism in CrI3 resulting from an interplay between ferro- and anti-ferromagnetic Cr-Cr d coupling channels, which is decisively affected by the ligand p orbitals. We show how environmental screening, such as resulting from encapsulation with hexagonal boron nitride, affects the Coulomb interaction in the film and how this controls its magnetic properties. Driven by a non-monotonic interplay between nearest and next-nearest neighbor exchange interactions we find the magnon dispersion and the Curie temperature to be non-trivially affected by the environmental screening.

—Molten mixtures of sodium and potassium cryolites KF–(10 wt %)NaF–AlF 3 with a cryolite ratio CR = 1.5 are promising electrolytes for the production of aluminum alloys with scandium, yttrium, zirconium, and boron using aluminothermic and electrochemical reduction of alloying component oxides at temperatures of 800–850°C. The viscosity is not only an important technological parameter, but also an information source for the structure and mechanism of viscous flow of a liquid. The dynamic viscosity of the KF–(10 wt %)NaF–AlF 3 (CR = 1.5) melt containing Sc 2 O 3 (to 9.9 wt %) and Y 2 O 3 (to 6.5 wt %) oxide additives has been measured at a constant shear rate of 12 s –1 in the temperature range from the liquidus point to 930°C. The viscosity of the KF–(10 wt %)NaF–AlF 3 (CR = 1.5) melt is found to change from 1.8 to 1.3 mPa s in the temperature range 800–930°C, which is substantially lower than the viscosity of the KF–AlF 3 melt (CR = 1.5), which is 1.7–2.4 MPa s, in a lower temperature range of 800–730°C. Sc 2 O 3 and Y 2 O 3 oxide additives substantially increase the viscosity, which is related to the formation of complex REM ions and oxifluoroaluminates in the melt during dissolution of the oxides.

New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF 2 molecules following X-ray absorption at the Xe site. Two-color X-ray pulses with controlled time delay allow exciting one site of a molecule and then probing a different site of the same molecule with femtosecond resolution. Here, the authors use this hetero-site pump-probe technique to study charge redistribution and dissociation of the xenon difluoride molecule.

Background: Dilated cardiomyopathy is common in dogs. This form of cardiomyopathy is the main cause of death due to heart disease in dogs. Death can occur suddenly in clinically normal animals as a result of the progression of congestive heart failure (CHF). The pathogenesis of heart failure syndrome in dogs with dilated cardiomyopathy involves activation of the neurohumoral system and immune-mediated inflammation, which leads to further progression of the condition. Heart failure syndrome in dogs with dilated cardiomyopathy is caused by the progressive loss of cardiomyocytes, apoptosis, remodeling of the left ventricle, systolic and diastolic dysfunction, arrhythmias, reduced cerebral blood flow, the involvement of other key internal organs, and intestinal dysbiosis. Aim: This study aimed to determine the immunological and inflammatory mechanisms surrounding the development of heart failure syndrome in dogs with dilated cardiomyopathy. Materials and Methods: The subjects of this study were dogs with a dilated form of cardiomyopathy (n=159), complicated by various functional classes of heart failure syndrome. Evaluation of myocardial remodeling, systolic function, and systemic hemodynamics was performed using EMP-860 Vet and PU-2200V ultrasound scanners according to the standard technique. Electrocardiography was performed with all dogs in right lateral recumbency using the EK1T-04 Midas electrocardiograph (50 mm/s speed and 1 mV gain = 1 cm). Results: In some affected animals, especially in cases of compensated dilated cardiomyopathy, leukocytosis was noted. In patients with dilated cardiomyopathy complicated by heart failure syndrome of various functional classes, the number of neutrophils was significantly increased, and the number of lymphocytes was decreased by 1.9-2.1 times when compared with those in clinically normal animals. In dogs with dilated cardiomyopathy, neutrophilic leukocytosis develops with a simple regenerative shift to the left. The results of immunological studies indicate that dogs with dilated cardiomyopathy develop T lymphocytopenia as compared with clinically normal animals. Conclusion: The central component of heart failure syndrome in dogs with dilated cardiomyopathy is the activation of the neurohumoral system and immune-mediated inflammation. The development of CHF in dogs with dilated cardiomyopathy is caused by the progressive loss of cardiomyocytes, apoptosis, remodeling of the left ventricle, systolic and diastolic dysfunction, arrhythmias, reduced cerebral blood flow, involvement of other key internal organs, and intestinal dysbiosis.