Frequency-angular characteristics of quasicharacteristic radiation in the case of plane channeling of relativistic electrons in crystals

In this paper, a theoretical study of the frequency-angular characteristics of short-wavelength quasicharacteristic radiation is presented. This radiation is produced as a result of transitions between the energy levels of transverse motion in the case of plane channeling of relativistic electrons in various crystals. Detailed numerical analysis shows that short-wavelength radiation, the parameters of which remain unchanged in a broad range of particle energies, exists at small angles in the domain of existence of the normal complex Doppler effect.     

The Effect of Evaporation Temperature on the Structure and Conductivity of Thin Films Obtained by the Moving Meniscus Method from Nanodispersions of Silver Particles

The effect of temperature (23–58°C) on the structure and conductivity of thin films obtained by the moving meniscus method from nanodispersions of silver particles with sizes of 6.5–70 nm has been studied. It has been shown that an increase in temperature leads to an exponential decrease in the specific conductivity of the films, with their thickness varying nonmonotonically. In the case of “large” particles, an increase in temperature decreases the efficiency of their deposition onto a substrate. The reasons for the observed regularities have been discussed.     

Ferromagnetic films with magnon bandgap periodic structures: Magnon crystals

A new type of photonic crystals is proposed. The new crystals have a forbidden gap in the microwave spectrum of magnetostatic spin waves, and, by analogy with photonic crystals, they are called magnon crystals. Specimens of such crystals were fabricated on the basis of yttrium iron garnet films. The surfaces of ferromagnetic films containing two-dimensional etched hole structures were studied by atomic force and magnetic force mag-netometry. The propagation of spin waves through the magnon crystals was investigated.     

A quantum chemical study of the formation of 2-hydroperoxy-coelenterazine in the Ca<Superscript>2+</Superscript>-regulated photoprotein obelin

The Ca²⁺-regulated photoprotein obelin determines the luminescence of the marine hydroid Obelia longissima. Bioluminescence is initiated by calcium and appears as a result of the oxidative decarboxylation related to the coelenterazine substrate. The luciferase of the luminescent marine coral Renilla muelleri (RM) also uses coelenterazine as a substrate. However, three proteins are involved in the in vivo bioluminescence of these animals: luciferase, green fluorescent protein, and Ca²⁺-regulated coelenterazine-binding protein (CBP). In fact, CBP that contains one strongly bound coelenterazine molecule is the RM luciferase substrate in the in vivo bioluminescent reaction. Coelenterazine becomes available for oxygen and the reaction with luciferase only after binding CBP with calcium ions. Unlike Ca²⁺-regulated photoproteins, the coelenterazine molecule is not activated by oxygen in the CBP molecule. In this work, by means of quantum chemical methods the behavior of substrates in these proteins is analyzed. It is shown that coelenterazine can form different tautomers: CLZ(2H) and CLZ(7H). The formation of 2-hydroperoxy-coelenterazine is studied. According to the obtained data, these proteins use different forms of the substrates for the reaction. In obelin, the substrate is in the CLZ(2H) form that affords hydrogen peroxide. In RM, coelenterazine is in the CLZ(7H) form, and therefore, CBP is not activated by oxygen.     

Production of Gold nanoparticles in aqueous solutions of cellulose derivatives

It is shown that gold nanoparticles can be produced using cellulose ethers, methylhydroxyethyl cellulose, and carboxymethyl cellulose as reducing agents that also play the role of nanoparticle stabilizers. Depending on the synthesis conditions, nanoparticle sizes vary in the range of 20–100 nm. The application of carboxymethyl cellulose as a stabilizer may give rise to the formation of a bimodal ensemble of nanoparticles with sizes of 4–5 and 30–40 nm. The differences in the mechanisms for the reduction and stabilization of gold nanoparticles in the presence of these cellulose derivatives are established by IR spectroscopy. The obtained colloidal dispersions of gold nanoparticles remain stable for a long time.     

Tricyclo[7.3.1.02,7]tridecanes with an Amino Group at the Bridging Carbon. Synthesis and Stereochemistry

Hydroamination of tricyclo[7.3.1.02,7]tridec-2(7)-en-13-one according to Leukart reaction furnished (tricyclo[7.3.1.02,7]tridec-2(7)-en-13-yl)methanamides stereoisomeric at C¹³ atom. The corresponding epoxides were prepared therefrom. The unsaturated and epoxidized methanamides were hydrolyzed into amines that were converted into Schiff bases.The configurations of substances were established.     

Magnetostatic volume waves in exchange-coupled ferrite films

The influence of exchange coupling of layers on the propagation of magnetostatic dipole volume waves in normally and tangentially magnetized two-layer epitaxial ferrite structures is investigated. It is shown that the indicated influence is manifested in the form of dynamic spin pinning effects on the interlayer boundary and formation of a common dipole-exchange wave spectrum for the entire structure. In this case, at the synchronism frequencies of the dipole and exchange waves the losses of the dipole waves grow and anomalous segments appear in the dispersion. In films magnetized in the “hard” direction relative to the axis of normal uniaxial surface anisotropy the magnetostatic dipole volume waves can interact resonantly with the surface spin waves supported by the boundaries with pinned spins. Zh. Tekh. Fiz. 68, 97–110 (July 1998)     

Magnetostatic spin waves in two-dimensional periodic structures (magnetophoton crystals)

Series of experiments are carried out to study the propagation of magnetostatic spin waves in ferromagnetic films containing 2D periodic structures formed by etched apertures. For spin waves, such films are analogous to photon crystals (namely, magnetophoton or magnon crystals). The spectra of waves transmitted through the structure display features associated with a change in the spin homogeneity due to etching or radiation loss, as well as with Bragg reflection effect or the emergence of forbidden gaps in the spectrum of propagating waves.