Classical BV formalism for group actions

We study the derived critical locus of a function f: [X/G] \u2192 1 on the quotient stack of a smooth affine scheme X by the action of a smooth affine group scheme G. It is shown that dCrit(f) R [Z/G] is a derived quotient stack for a derived affine scheme Z, whose dg-algebra of functions is described explicitly. Our results generalize the classical BV formalism in finite dimensions from Lie algebra to group actions

ON THE TURBULENCE IN A VISCOUS HEAT-CONDUCTING GAS

The problem of the emergence of turbulence is one of the unsolved problems of physics and technology of the 20th century. It is noted that in order to understand the emergence of turbulence in a viscous heat-conducting gas, it is necessary to take into account the compressibility of the medium. A definition of turbulence in a viscous heat-conducting gas is given, which is a cyclically repeating process of the emergence and decay of coherent vortex structures described by a vector wave equation. The decay of vortex structures is accompanied by an explosive, asymptotic increase in pressure pulsations, which triggers a new cycle of turbulence generation. The emergence and decay of coherent vortex structures in the boundary layer on a plate and in a round jet is considered

The angular momentum of two collided rarefied preplanetesimals and the formation of binaries

This paper studies the mean angular momentum associated with the collision of two celestial objects in the earliest stages of planet formation. Of primary concern is the scenario of two rarefied preplanetesimals (RPPs) in circular heliocentric orbits. The theoretical results are used to develop models of binary or multiple system formation from RPPs, and explain the observation that a greater fraction of binaries originated farther from the Sun. At the stage of RPPs, small-body satellites can form in two ways: a merger between RPPs can have two centers of contraction, or the formation of satellites from a disc around the primary or the secondary. Formation of the disc can be caused by that the angular momentum of the RPP formed by the merger is greater than the critical angular momentum for a solid body. One or several satellites of the primary (moving mainly in low-eccentricity orbits) can be formed from this disc at any separation less than the Hill radius. The first scenario can explain a system such as 2001 QW322 where the two components have similar masses but are separated by a great distance. In general, any values for the eccentricity and inclination of the mutual orbit are possible. Among discovered binaries, the observed angular momenta are smaller than the typical angular momenta expected for identical RPPs having the same total mass as the discovered binary and encountering each other in circular heliocentric orbits. This suggests that the population of RPPs underwent some contraction before mergers became common.Comment: 12 pages, Monthly Notices of Royal Astron. Society, in pres

Giant planet formation: episodic impacts vs. gradual core growth

We describe the growth of gas giant planets in the core accretion scenario. The core growth is not modeled as a gradual accretion of planetesimals but as episodic impacts of large mass ratios, i.e. we study impacts of 0.02 - 1 Earth masses onto cores of 1-15 Earth masses. Such impacts could deliver the majority of solid matter in the giant impact regime. We focus on the thermal response of the envelope to the energy delivery. Previous studies have shown that sudden shut off of core accretion can dramatically speed up gas accretion. We therefore expect that giant impacts followed by periods of very low core accretion will result in a net increase in gas accretion rate. This study aims at modelling such a sequence of events and to understand the reaction of the envelope to giant impacts in more detail. To model this scenario, we spread the impact energy deposition over a time that is long compared to the sound crossing time, but very short compared to the Kelvin-Helmholtz time. The simulations are done in spherical symmetry and assume quasi-hydrostatic equilibrium. Results confirm what could be inferred from previous studies: gas can be accreted faster onto the core for the same net core growth speed while at the same time rapid gas accretion can occur for smaller cores -- significantly smaller than the usual critical core mass. Furthermore our simulations show, that significant mass fractions of the envelope can be ejected by such an impact

Binary planetesimals and their role in planet formation

One of the main evolutionary stages of planet formation is the dynamical evolution of planetesimal disks. These disks are thought to evolve through gravitational encounters and physical collisions between single planetesimals. In recent years, many binary planetesimals have been observed in the Solar system, indicating that the binarity of planetesimals is high. However, current studies of planetesimal disks formation and evolution do not account for the role of binaries. Here we point out that gravitational encounters of binary planetesimals can have an important role in the evolution of planetesimal disks. Binary planetesimals catalyze close encounters between planetesimals, and can strongly enhance their collision rate. Binaries may also serve as additional heating source of the planetesimal disk, through the exchange of the binaries gravitational potential energy into the kinetic energy of planetesimals in the disk.Comment: Accepted to ApJ

Variability of pathogenicity factors representative of the human microbiome under the influence of γ-Fe2O3 nanoparticles

Biomedical applications of nanoparticles require deep understanding of their interaction with normal human microflora. Previously, the toxic and mutagenic properties of iron oxide nanoparticles as well as their effect on the growth and morphology of the microflora were extensively investigated. However, the studies related to the variability of microbial pathogenicity factors induced by iron oxide nanoparticles are very limited. Meanwhile, this characteristic of microbes is genetically determined and is important for their survival and distribution in the human body. Therefore, pathogenicity factors are significant indicators of the experimental studies. In this work, the effect of the presence of Fe2O3 nanoparticles obtained by laser target evaporation (LTE) on selected enzymes that demonstrate invasion and aggression factors was evaluated for three reference strains of Candida albicans, Staphylococcus aureus, and Escherichia coli. It was found that the presence of LTE Fe2O3 nanoparticles supplied in the form of water-based suspensions does not induce changes of the above-mentioned parameters

Forming Jupiter, Saturn, Uranus and Neptune in Few Million Years by Core Accretion

Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the solar system's giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks' lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial solar system orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.Comment: 11 pages, 3 figures, in press (Icarus

Biological Impact of γ-Fe2O3 Magnetic Nanoparticles Obtained by Laser Target Evaporation: Focus on Magnetic Biosensor Applications

The biological activity of γ-Fe2O3 magnetic nanoparticles (MNPs), obtained by the laser target evaporation technique, was studied, with a focus on their possible use in biosensor applications. The biological effect of the MNPs was investigated in vitro on the primary cultures of human dermal fibroblasts. The effects of the MNPs contained in culture medium or MNPs already uptaken by cells were evaluated for the cases of the fibroblast’s proliferation and secretion of cytokines and collagen. For the tests related to the contribution of the constant magnetic field to the biological activity of MNPs, a magnetic system for the creation of the external magnetic field (having no commercial analogues) was designed, calibrated, and used. It was adapted to the size of standard 24-well cell culture plates. At low concentrations of MNPs, uptake by fibroblasts had stimulated their proliferation. Extracellular MNPs stimulated the release of pro-inflammatory cytokines (Interleukin-6 (IL-6) and Interleukin-8 (IL-8) or chemokine (C-X-C motif) ligand 8 (CXCL8)) in a concentration-dependent manner. However, the presence of MNPs did not increase the collagen secretion. The exposure to the uniform constant magnetic field (H ≈ 630 or 320 Oe), oriented in the plane of the well, did not cause considerable changes in fibroblasts proliferation and secretion, regardless of presence of MNPs. Statistically significant differences were detected only in the levels of IL-8/CXCL8 release.The study was supported by the program of the Ministry of Health of the Russian Federation (project 121032300335-1). This work was financially supported, in part, by the Ministry of Science and Higher Education of the RF (grant FEUZ-2020-0051) (G.Yu. Melnikov) and University of the Basque Country Research Groups Funding (grant IT1245-19) (G.V. Kurlyandskaya)

The role of the initial surface density profiles of the disc on giant planet formation: comparing with observations

In order to explain the main characteristics of the observed population of extrasolar planets and the giant planets in the Solar System, we need to get a clear understanding of which are the initial conditions that allowed their formation. To this end we develop a semi-analytical model for computing planetary systems formation based on the core instability model for the gas accretion of the embryos and the oligarchic growth regime for the accretion of the solid cores. With this model we explore not only different initial discs profiles motivated by similarity solutions for viscous accretion discs, but we also consider different initial conditions to generate a variety of planetary systems assuming a large range of discs masses and sizes according to the last results in protoplanetary discs observations. We form a large population of planetary systems in order to explore the effects in the formation of assuming different discs and also the effects of type I and II regimes of planetary migration, which were found to play fundamental role in reproducing the distribution of observed exoplanets. Our results show that the observed population of exoplanets and the giant planets in the Solar System are well represented when considering a surface density profile with a power law in the inner part characterized by an exponent of -1, which represents a softer profile when compared with the case most similar to the MMSN model case.Comment: 14 pages, 12 figures, MNRAS, 412, 211