Gravitational stability and dynamical overheating of stellar disks of galaxies

We use the marginal stability condition for galactic disks and the stellar velocity dispersion data published by different authors to place upper limits on the disk local surface density at two radial scalelengths $R=2h$. Extrapolating these estimates, we constrain the total mass of the disks and compare these estimates to those based on the photometry and color of stellar populations. The comparison reveals that the stellar disks of most of spiral galaxies in our sample cannot be substantially overheated and are therefore unlikely to have experienced a significant merging event in their history. The same conclusion applies to some, but not all of the S0 galaxies we consider. However, a substantial part of the early type galaxies do show the stellar velocity dispersion well in excess of the gravitational stability threshold suggesting a major merger event in the past. We find dynamically overheated disks among both seemingly isolated galaxies and those forming pairs. The ratio of the marginal stability disk mass estimate to the total galaxy mass within four radial scalelengths remains within a range of 0.4---0.8. We see no evidence for a noticeable running of this ratio with either the morphological type or color index.Comment: 25 pages, 5 figures, accepted to Astronomy Letter

Entropy production in the Au + Au reaction between 150 and 800 A MeV

The entropy per nucleon (S/A) has been extracted for the Au [(150—800)A MeV] + Au reaction by using the phase I setup of the 4 pi facility at GSI, Darmstadt. The entropy has been obtained from the comparison of various observables characterizing the dM/dZ fragment multiplicity distributions, extending up to Z~15, with those calculated with the quantum statistical model. It is the first time that S/A values are determined by considering the full ensemble of charged products detected in the reaction. Consistent values of S/A are found from different methods. These entropy values are shown to be fairly independent of the volume of the ``participant'' region considered. They are somewhat lower than those extracted in earlier works but are in good agreement with hydrodynamic calculations and suggest a low viscosity for the hot and dense nuclear matter

RESEARCH OF DYNAMIC MODEL AIR FIELD HARVESTER

The mathematical model of the air field harvester supplied with the device for clearing of a snow and the rotating drum with a brush is developed. The analysis of this model and optimization of parameters is made with the purpose of maintenance of qualitative clearing an air field covering

Synthesis and structure of 3,4,5-triazidopyridine-2,6-dicarbonitrile possessing the record positive heat of formation

3,4,5-Triazidopyridine-2,6-dicarbonitrile, the first aromatic triazide with three adjacent azido groups in the ring, possessing the record positive heat of formation, was synthesized by azidation of 3,4,5-trichloropyridine-2,6-dicarbonitrile and characterized with X-ray analysis, thermogravimetry, differential scanning calorimetry and spectroscopic methods. © 201

Synthesis and structure of 3,4,5-triazidopyridine-2,6-dicarbonitrile possessing the record positive heat of formation

3,4,5-Triazidopyridine-2,6-dicarbonitrile, the first aromatic triazide with three adjacent azido groups in the ring, possessing the record positive heat of formation, was synthesized by azidation of 3,4,5-trichloropyridine-2,6-dicarbonitrile and characterized with X-ray analysis, thermogravimetry, differential scanning calorimetry and spectroscopic methods. © 201

The EPR Spectrum of Triplet Mesitylphosphinidene: Reassignment and New Assignment

Low-temperature UV-photolysis of mesitylphosphiranes under highly anaerobic conditions leads to the formation of the triplet mesitylphosphinidene (MesP). The recorded X-band EPR spectrum of triplet MesP and the derived zero-field splitting parameter D=4.116 cm−1 differ significantly from those reported previously for this intermediate. New magnetic parameters of mesitylphosphinidene are discussed along with the results of DFT calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

The EPR Spectrum of Triplet Mesitylphosphinidene: Reassignment and New Assignment

Low-temperature UV-photolysis of mesitylphosphiranes under highly anaerobic conditions leads to the formation of the triplet mesitylphosphinidene (MesP). The recorded X-band EPR spectrum of triplet MesP and the derived zero-field splitting parameter D=4.116 cm−1 differ significantly from those reported previously for this intermediate. New magnetic parameters of mesitylphosphinidene are discussed along with the results of DFT calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Synthesis, Structure and Magnetic Properties of Mn<inf>2</inf>Tb<inf>2</inf> Tetranuclear Complex with p-tert-Butylthiacalix[4]arene

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A new tert-buthylthiacalix[4]arene-based tetranuclear 3d-4f metal complex with the Mn2Tb2 core has been synthesized and its molecular and crystal structures have been studied by X-ray diffraction. The complex geometry is similar to that of the earlier synthesized tert-buthylthiacalix[4]arene-based M2Ln2 complexes with M=Mn(II), Co(II), and Ln=Gd, Pr, Eu, but unlike those systems, it exhibits intricated cooperative low-temperature magnetic properties arising from the presence of intercluster interactions. At T<8.5 K the complex shows weak spin-canted ferromagnetism and field induced metamagnetic phase transition. The paramagnetic behavior observed at temperatures higher than 8.5 K is similar to that previously reported for the Mn2Gd2 complex, this being indicative of the existence of competitive ferro- and antiferromagnetic intracluster interactions