A three-dimensional lattice gas approximation for multilayer adsorption

A three-dimensional lattice gas approximation for multilayer adsorbates is substantiated on the basis of statistical physics. In addition, some problems of equilibrium thermodynamics and kinetics are formulated, and a number of approximations are derived. A detailed kinetic theory of thin film growth, which is complementary to the applied approaches based on phenomenological models, thermodynamics of nonequilibrium processes, and solid medium and lattice gas models, is developed.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 105, No. 1, pp. 130–148, October, 1995.     

Synthesis of o-(dimethylamino)aryl ketones and acridones by the reaction of 1,1-dialkylhydrazones and arynes

A novel, efficient route to biologically and pharmaceutically important o-(dimethylamino)aryl ketones and acridones has been developed starting from readily available 1,1-dimethylhydrazones of aldehydes and o-(trimethylsilyl)aryl triflates. The reaction proceeds under mild conditions, tolerates a wide range of functional groups, and provides the final products in good to excellent yields.     

Temperature behavior of the antiferromagnetic susceptibility of nanoferrihydrite from the measurements of the magnetization curves in fields of up to 250 kOe

The cross-breeding problem of the temperature dependence of the antiferromagnetic susceptibility of ferrihydrite nanoparticles is considered. Iron ions Fe3+ in ferrihydrite are ordered antiferromagnetically; however, the existence of defects on the surface and in the bulk of nanoparticles induces a noncompensated magnetic moment that leads to a typical superparamagnetic behavior of ensemble of the nanoparticles with a characteristic blocking temperature. In an unblocked state, magnetization curves of such objects are described as a superposition of the Langevin function and the linear-in-field contribution of the antiferromagnetic “core” of the nanoparticles. According to many studies of the magnetization curves performed on ferrihydrite (and related ferritin) nanoparticles in fields to 60 kOe, dependence χ_AF(T) decreases as temperature increases, which was related before to the superantiferromagnetism effect. As the magnetic field range increases to 250 kOe, the values of χ_AF obtained from an analysis of the magnetization curves become lower in magnitude; however, the character of the temperature evolution of χ_AF is changed: now, dependence χ_AF(T) is an increasing function. The latter is typical for a system of AF particles with random orientation of the crystallographic axes. To correctly determine the antiferromagnetic susceptibility of AF nanoparticles (at least, ferrihydrite) and to search for effects related to the superantiferromagnetism effect, it is necessary to use in experiments the range of magnetic field significantly higher than that the standard value 60 kOe used in most experiments. The study of the temperature evolution of the magnetization curves shows that the observed crossover is due to the existence of small magnetic moments in the samples.     

Synthesis of 3,7-diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans: functional building blocks for the design of new conjugated polymers

3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported.     

Analytical methods of solution of the relaxational equations

The master equations system for rotational, vibrational and chemical kinetics in nonuniform gas flows with the sources is studied. Two approximate analytical methods of its solution for the arbitrary rate constants are developed for the case of the smooth distributions. The first method is based on the introduction of slow variables to the discrete equations. The second one uses WKB solution for diffusion approximation in Fokker-Planck form. The particular cases of harmonic and weakly anharmonic oscillators relaxation are examined.     

Specific features of magnetic properties of ferrihydrite nanoparticles of bacterial origin: A shift of the hysteresis loop

The results of the experimental investigation into the magnetic hysteresis of systems of superparamagnetic ferrihydrite nanoparticles of bacterial origin have been presented. The hysteresis properties of these objects are determined by the presence of an uncompensated magnetic moment in antiferromagnetic nanoparticles. It has been revealed that, under the conditions of cooling in an external magnetic field, there is a shift of the hysteresis loop with respect to the origin of the coordinates. These features are associated with the exchange coupling of the uncompensated magnetic moment and the antiferromagnetic “core” of the particles, as well as with processes similar to those responsible for the behavior of minor hysteresis loops due to strong local anisotropy fields of the ferrihydrite nanoparticles.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Iodocyclization, followed by palladium-catalyzed coupling: a versatile strategy for heterocyclic library construction

The iodocyclization of functionally-substituted alkynes provides an excellent way to prepare a wide range of iodoheterocycles, which can then be readily elaborated through palladium-catalyzed Suzuki-Miyaura, Sonogashira, Heck, Hartwig-Buchwald, and carbonylation processes into libraries of medicinally relevant heterocycles. The synthesis of libraries of indoles, benzofurans, benzothiophenes, isocoumarins and pyrones, cyclic imidates, isoxazoles, furans using this approach is reviewed. This technology is very versatile, proceeds under mild reaction conditions in high yields, and tolerates considerable functionality.     

One-pot synthesis of 1-alkyl-1H-indazoles from 1,1-dialkylhydrazones via aryne annulation

The reaction of readily accessible 1,1-dialkylhydrazones with commercially available o-(trimethylsilyl)aryl triflates provides a direct one-step route to pharmaceutically important 1-alkylindazoles. The products are obtained in high yields by one-pot NCS-chlorination/aryne annulation or Ac(2)O-acylation/deprotection/aromatization protocols.     

Synthesis of benzisoxazolines by the coupling of arynes with nitrones

A variety of substituted benzisoxazolines have been synthesized by the [3 + 2] cycloaddition of nitrones and arynes. The reaction scope is broad, the reaction conditions are mild, and the process tolerates a variety of functional groups.