Twelve-Nitrogen-Atom Cyclic Structure Stabilized by 3d-Element Atoms: Quantum Chemical Modeling

Using various versions of density functional theory (DFT), DFT M06/TZVP, DFT B3PW91/TZVP, DFT OPBE/TZVP, and, partially, the MP2 method, the possibility of the existence of 3d-element (M) compounds with nitrogen having unusual M: nitrogen ratio 1:12, unknown for these elements at the present, was shown. Structural parameter data were presented. It was shown that all MN4 groupings have tetragonal-pyramidal structure. It was noted that the bond lengths formed by nitrogen atoms and an M atom were equal to each other only in the case of M = Ti, V, Cr and Co, whereas for other Ms, they were slightly different; moreover, the bond angles formed by nitrogen atoms and an M atom were equal to 90.0°, or practically did not differ from this value. Thermodynamic parameters, NBO analysis data and HOMO/LUMO images for this compound were also presented. Good agreement between the calculated data obtained using the above three quantum chemical methods was also noted.     

Sperm of Fruit Fly Drosophila melanogaster under Space Flight

Studies of reproductive function under long-term space flight conditions are of interest in planning the exploration of deep space. Motility, including the use of various inhibitors, cellular respiration, and the content of cytoskeletal proteins were studied, assessing the level of expression of the corresponding genes in spermatozoa of Drosophila melanogaster, which were in space flight conditions for 12 days. The experiment was carried out twice on board the Russian Segment of the International Space Station. Sperm motility speed after space flight, and subsequently 16 h after landing, is reduced relative to the control by 20% (p < 0.05). In comparison with the simulation experiment, we showed that this occurs as a result of the action of overloads and readaptation to the Earth’s gravity. At the same time, cellular respiration, the content of proteins of the respiratory chain, and the expression of their genes do not change. We used kinase inhibitor 6-(dimethylamino)purine (6-DMAP) and phosphatase inhibitors; 6-DMAP restored the reduced the speed of spermatozoa in the flight group to that of the control. These results can be useful in developing a strategy for protecting reproductive health during the development of other bodies in the solar system.     

不同热变形工艺大塑性变形加工超细晶1570C铝合金的组织、强度和超塑性

将Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si(质量分数,％)合金铸锭进行多向等温锻造(应变12)或等径角挤压(应变10,325℃),再进行热轧(325℃)和冷轧(20℃),对比研究合金变形后的组织和力学行为.结果表明,对(亚)晶粒尺寸dUFG=2μm的超细晶组织合金进行多向等温锻造...     

Development of a rational roll pass design for a rolling mill using performance criteria

A new technique is developed to analyze the roll pass design of a section rolling mill. Metal forming nonuniformity and efficiency coefficients, which determine the degree of working of a metal microstructure in rolling of section bars, are used as performance criteria. The system of roll passes intended for the production of a round bar 28 mm in diameter is used as an example to analyze possible deformation schemes and the advantages and disadvantages of each scheme.     

Current flow through metal shunts in ohmic contacts to n +-Si

It is experimentally found that an ohmic contact based on Au-Pt-Ti-Pd-n ⁺-Si metallization is formed due to nanoscale metal shunts containing Si, Au, and Pt in the region of the interface with n ⁺-Si, which appears during heat treatment at T = 450°C for 10 min in a vacuum chamber with a residual pressure of 10^?6 Torr. The high density of shunts adjoining dislocations and other imperfections is confirmed by the temperature dependence of the specific contact resistance ρ _c (T). The density of conductive dislocations, calculated from the temperature dependence of ρ _c is ～5 × 10⁹ cm^?2 which correlates with the density of structural defects, determined by the etch pits after removal of the metallization layers.