On the stability of incompressible MHD modes in magnetic cylinder with twisted magnetic field and flow

In this work, we studied MHD modes in a magnetically twisted flux tube with a twisted flow that is embedded in the uniform magnetic field. We consider when the azimuthal magnetic field and velocity are linear functions of radius (case i) and also more generally when they are arbitrary functions of radius (case ii). Under these assumptions, we obtain the dispersion equation in the incompressible limit. This solution can also be used to describe the MHD perturbations in plasma pinches and vortices. The dispersion equation is simplified by implementing the thin flux tube approximation. It is shown that sausage modes (m = 0) become unstable for large enough azimuthal flow speeds. Also, we obtained the unstable modes for m > 0. It is shown that the stability criterion of the m = 1 mode (for case i) is independent of the background azimuthal components of the plasma velocity and magnetic field. These criteria fully coincide with the result that was previously obtained by Syrovatskiy for a plane interface. Moreover, this result even remains valid when the azimuthal magnetic field and velocity have an arbitrary dependence on radius (case ii). A criterion for the stability of the m ≥ 2 modes is also obtained. It was found that instability of these modes is determined by both longitudinal and azimuthal flows. It is shown that if there is sufficient azimuthal background flow, then all modes with m ≥ 2 will become unstable

Bastroviruses (<i>Astroviridae</i>): genetic diversity and potential impact on human and animal health

Introduction. Bastroviruses were discovered in the Netherlands in 2016 in human stool samples and show partial genetic similarities to astroviruses and hepatitis E viruses. Their association with disease onset has not yet been established. Materials and methods. Metagenomic sequencing of fecal samples of Nyctalus noctula bats collected in the Russian Federation in 2023 was performed. Two almost complete genomes of bastroviruses were assembled. The zoonotic potential of these viruses was assessed using machine learning methods, their recombination was studied, and phylogenetic trees were constructed. Results. A nearly complete bastrovirus genome was de novo assembled in one of the samples, and it was used to assemble another genome in another sample. The zoonotic potential of the virus from one of these samples was estimated as high. The existence of recombination between structural and non-structural polyproteins was demonstrated. Conclusion. Two bastrovirus genomes were assembled, phylogenetic and recombination analyses were performed, and the zoonotic potential was evaluated

Incompressible magnetohydrodynamic modes in the thin magnetically twisted flux tube

Context. Observations have shown that twisted magnetic fields naturally occur, and indeed are omnipresent in the Sun’s atmosphere. It is therefore of great theoretical interest in solar atmospheric waves research to investigate the types of magnetohydrodynamic (MHD) wave modes that can propagate along twisted magnetic flux tubes. Aims. Within the framework of ideal MHD, the main aim of this work is to investigate small amplitude incompressible wave modes of twisted magnetic flux tubes with m ≥ 1. The axial magnetic field strength inside and outside the tube will be allowed to vary, to ensure the results will not be restricted to only cold plasma equilibria conditions. Methods. The dispersion equation for these incompressible linear MHD wave modes was derived analytically by implementing the long wavelength approximation. Results. It is shown, in the long wavelength limit, that both the frequency and radial velocity profile of the m = 1 kink mode are completely unaffected by the choice of internal background magnetic twist. However, fluting modes with m ≥ 2 are sensitive to the particular radial profile of magnetic twist chosen. Furthermore, due to background twist, a low frequency cut-off is introduced for fluting modes that is not present for kink modes. From an observational point of view, although magnetic twist does not affect the propagation of long wavelength kink modes, for fluting modes it will either work for or against the propagation, depending on the direction of wave travel relative to the sign of the background twist

Geologic structure and composition of Munilkan massif Verkhoyansk-Kolyma orogenic area

This article presents the results of detailed study of geologic structure and composition of Munilkan massif of the Main batholith belt of Verkhoyansk-Kolyma mesozoides (Tas-Khayakhtakh Ridge). Granites include numerous xenoblocks of gabbro, dolerites and subvolcanic granites they are intruded by fissure bodies and dikes of leucogranites-alaskites and trachybasalts-trachydolerites and have neutral ratio with gabbro-diorites, diorites and monzonites, which were formed during interaction of basite and granite magma. Igneous activity occurred at some stages, from Oxfordian to the end of the Early Cretaceous (157-119 Ma). Composition parameters of magmatic rocks correspond to formation of early derivatives in island-arc conditions, late derivatives - in post-collisional and intraplate conditions, that is covers the entire cycle of geologic development of Verkhoyansk-Kolyma mesozoides

Wide-band spatially distributed TE10 substrate integrated waveguide transition for high-power generation at mm-wave frequencies

\u3cp\u3eAn array of microstrip lines is used for the direct excitation of the spatially distributed TE10 substrate integrated waveguide (SIW) mode. The proposed configuration can generate 4x more power with a 4x smaller form factor relative to a single microstrip-to-SIW transition, while offering a larger bandwidth. This is an important step toward the generation of high power in densely integrated mm-wave antenna systems.\u3c/p\u3

N-way spatial power combining in SIW for high power generation MMICs-scalability bounds

\u3cp\u3eAn N-way transition between an array of amplifiers and a single substrate integrated waveguide (SIW) is presented. Its operation principle is based on excitation of the spatially distributed TE10 mode with an array of parallel and strongly coupled microstrip lines (MLs). The paper discusses and evaluates the approximate scalability bounds of such a structure in terms of the number of input channels. The model shows that, by employing a thin substrate, more amplifiers are capable of interfacing a single SIW to increase the output power, which is an important conclusion in regards to a future on-chip implementation of the structure. The model has also been validated by numerical simulations.\u3c/p\u3