Branching of equilibria of a system of micro/nanostrings at direct currents

Branching of equilibria of a system of three parallel conducting nano/microlayers, which is used to detect changes in the external and internal mechanical and electric characteristics (for example, conductivity, tension force, and gap between layers), has been investigated. A change in the physical parameters may cause asymmetric bending of the outer layers and deformation of the formerly neutral middle layer. By changing the current in one of the outer layers slowly, their initial symmetry (neutrality of the inner layer) can be restored and the change that occurred in the parameters can be determined.     

Highly Efficient One‐Pot Preparation of 1,2,4‐Oxadiazoles in the Presence of Diazabicycloundecene

New highly efficient method for the cyclization of acylamidoximes in the presence of diazabicycloundecene was developed and incorporated into a general and practical one‐pot synthesis of 1,2,4‐oxadiazoles (11 examples, 85–97% yields).     

A Noncatalytic Approach to Hetaryl‐Annulated 1,2,4‐Thiadiazine‐1,1‐dioxides

A set of synthetic procedures was developed to yield functionalized pyrido‐, pyrimido‐, and thiazo‐annulated thiadiazine‐1,1‐dioxides on a preparative scale. In all cases the thiadiazine‐1,1‐dioxide ring closure was carried out through a reaction of hetaryl‐sulfonyl chlorides with amidines under mild noncatalytic conditions. In the case of 2‐chloropyridine‐3‐sulfonyl chloride derivatives and 2,4‐dichlorothiazole‐5‐sulfonyl chloride open‐chain sulfonylated amidine intermediates were isolated and then subjected to the cyclization step. The reaction with 2,4‐dichloropyrimidine‐5‐sulfonyl chloride gave rise to the corresponding thiadiazine‐1,1‐dioxides in one‐pot. Similarly, a reaction of 2‐chloropyridine‐3‐sulfonamide with lactime ethers proceeded in one‐pot readily giving the corresponding thiadiazine‐1,1‐dioxides. Remaining chlorine atoms on the prepared hetaryl‐annulated benzothiadiazine‐1,1‐dioxides readily undergo aromatic nucleophilic displacement reactions serving thus as additional variation points for the design of biologically potent compounds.     

Synthesis of 5,10,15,20-tetra[6' -nitro-1,3,3-trimethylspiro- (indolino-2,2' -2H-chromen-5-yl)]porphyrin and its metal complexes

A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn²⁺ and Cu²⁺ ions were prepared and characterized by physicochemical methods of analysis.     

Controlled deactivation of a skeletal nickel catalyst with sodium silfide in liquid-phase hydrogenation reactions

The kinetics of the liquid-phase hydrogenation of sodium maleate on skeletal nickel catalysts subjected to controlled deactivation with sodium sulfide solutions was studied. The possibility of reactivating partially deactivated skeletal nickel was systematically studied for the first time, and it was found that its activity in liquid-phase hydrogenation reactions can be regulated by the introduction of a catalyst poison in small amounts into the system.     

Initiation of combustion in multilayer energetic compositions with a high-current electron beam

Experimental results on the ignition of energetic two- and three-layer potassium picrate- and lead(II, IV) oxide-based compositions with a high-current electron beam of nanosecond duration are reported. It is shown that the sustainability of explosive transformations in layered compositions depends on the boundary conditions and the additional impact of the cathode flame (high-temperature metal plasma).     

Direct Visualization of a Mechanochemically Induced Molecular Rearrangement

Recent progress in the field of mechanochemistry has expanded the discovery of mechanically induced chemical transformations to several areas of science. However, a general fundamental understanding of how mechanochemical reactions by ball milling occur has remained unreached. For this, we have now implemented in situ monitoring of a mechanochemically induced molecular rearrangement by synchrotron X‐ray powder diffraction, Raman spectroscopy, and real‐time temperature sensing. The results of this study demonstrate that molecular rearrangements can be accomplished in the solid state by ball milling and how in situ monitoring techniques enable the visualization of changes occurring at the exact instant of a molecular migration. The mechanochemical benzil–benzilic acid rearrangement is the focal point of the study.     

Investigation of dielectric spectra from moist soils during freezing-thawing processes

A frequency spectrum of the complex dielectric permittivity of soils is measured in the range of frequencies from 0.5 to 15.0 GHz in the course of frost penetration and thawing. The phase transitions taking place during frost penetration and thawing are analyzed within the concept of the generalized refractive mixing dielectric model (GRMDM). Two types of water concurrently present in the soil are identified: bound and free water. Temperature dependences of the Debye model parameters for each type of water are given, and parameters of a dielectric spectroscopic model of frozen and thawed soils are found. The hysteresis phenomenon during the phase transition of the soil moisture is investigated. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 24–28, September, 2008.