Spectral‐Luminescent Properties of Certain Substituted Arylpolyenes and Their Features

We investigated fluorescence and fluorescence excitation spectra of five substituted diphenylpolyenes with the number of double bonds in the chain n = 2 or n = 3 and substituents NO₂, N(CH₃)₂, and NH₂ in different media (toluene and noctane) at low (77 and 4.2 K) temperatures. The duration of fluorescence () and the quantum yield of fluorescence () of the four compounds investigated were measured at room temperature. The influence of the electron donoracceptor interaction in one of the compounds on its spectralluminescent properties has been analyzed.     

Purification and Characterization of Agarase from Marine Bacteria <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. PS12B and Its Use for Preparing Bioactive Hydrolysate from Agarophyte Red Seaweed <Emphasis Type="Italic">Gracilaria verrucosa</Emphasis>

Acinetobacter strain PS12B was isolated from marine sediment and was found to be a good candidate to degrade agar and produce agarase enzyme. The extracellular agarase enzyme from strain PS12B was purified by ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography. The specific activity of the crude enzyme which was 1.52 U increased to 45.76 U, after two-stage purification, with an enzyme yield of 9.76%. Purified enzyme had a molecular mass of 24 kDa. The optimum pH and temperature for activity of purified agarase were found to be 8.0 and 40 °C, respectively. The K_m and V_max values for agarase were 4.69 mg/ml and 0.5 μmol/min, respectively. Treatment with EDTA reduced the agarase activity by 58% at 5 mM concentration. The enzyme activity was stimulated by the presence of Fe²⁺, Mn²⁺, and Ca2⁺ ions while reducing reagents (β-mercaptoethanol and dithiothreitol, DTT) enhanced its activity by 30–40%. The purified agarase exhibited tolerance to both detergents and organic solvents. Major hydrolysis products of agar were DP4 and also a mixture of longer oligosaccharides DP6 and DP7. The enzyme hydrolysed seaweed (Gracilaria verrucosa) exhibited strong antioxidant activity in vitro. Successful hydrolysis of seaweed indicates the potential use of the enzyme to produce seaweed hydrolysate having health benefits as well as the industrial application like the production of biofuels.     

Synthesis of calix[4]resorcinarenes with phosphorylaryl substituents at the lower rim of the molecule

Reaction of resorcinarenes with 4-phosphorylbenzaldehydes afforded calix[4]resorcinarenes, bearing phosphorylaryl substituents at the lower rim of the molecule. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2269–2271, November, 2007.     

NiFeCo/Cu superlattices with high magnetoresistive sensitivity and weak hysteresis

The microstructure and the magetoresistive characteristics of [NiFeCo/Cu]₈ superlattices prepared by magnetron sputtering with various thickness of the buffer NiFeCr layer and exhibiting a giant magnetoresistive effect have been studied. It has been found that these nanostructures are formed with a strong or weak hysteresis depending on the structure (bcc or fcc) formed in the NiFeCr buffer layer. The method of the substantial decrease in the hysteresis loop width of the magnetoresistance by using the composite Ta/NiFeCr buffer layer has been suggested.     

Relationship between the Udwadia–Kalaba equations and the generalized Lagrange and Maggi equations

In their paper “A New Perspective on Constrained Motion,” F. E. Udwadia and R. E. Kalaba propose a new form of matrix equations of motion for nonholonomic systems subject to linear nonholonomic second-order constraints. These equations contain all of the generalized coordinates of the mechanical system in question and, at the same time, they do not involve the forces of constraint. The equations under study have been shown to follow naturally from the generalized Lagrange and Maggi equations; they can be also obtained using the contravariant form of the motion equations of a mechanical system subjected to nonholonomic linear constraints of second order. It has been noted that a similar method of eliminating the forces of constraint from differential equations is usually useful for practical purposes in the study of motion of mechanical systems subjected to holonomic or classical nonholonomic constraints of first order. As a result, one obtains motion equations that involve only generalized coordinates of a mechanical system, which corresponds to the equations in the Udwadia–Kalaba form.     

Photorefractive response of bulk periodically poled LiNbO3:Y:Fe at high and low spatial frequencies

Polydomain periodically poled samples of iron-doped lithium niobate allow for phase grating recording with the diffraction efficiency close to that ensured by a single-domain sample with identical thickness. At the same time the optical damage induced by a finite transverse size light beam is considerably reduced in the periodically poled sample as compared with single-domain material.     

Luminescence and absorption spectra of polyatomic molecules subjected to conformational transitions

A general approach and results of specific calculations of conjugated vibronic absorption and fluorescence spectra of “soft” molecules subjected to conformational transitions are presented. The vibronic spectra of these molecules exhibit significant anomalies such as a large energy gap between the fluorescence and absorption spectra, a strong deviation from the mirror symmetry, etc., which cannot be explained within the framework of the theory of vibronic spectra based on single-well adiabatic potentials.     

Sol–gel synthesis of mesostructured SiO<Subscript>2</Subscript> containers using vesicles of hydrolyzable bioactive gemini surfactant as a template

Peculiarities of the sol–gel synthesis of SiO₂ container particles using vesicles of a hydrolyzable bactericidal gemini surfactant, decamethoxin, as a template have been studied.     

Adsorption-desorption of water vapor on initial and modified peat samples

Specific features of adsorption-desorption of water vapor on the initial samples of valley-bog and raised-bog peat and on the samples modified with iron and aluminum salts were studied and interpreted in terms of the model of a process with two types of sorption sites.     

Study of magnetite nanoparticle suspensions by photometry and NMR relaxometry

A method has been described for preparation of suspensions of magnetite nanoparticles stabilized by porous silicon dioxide. The process of sedimentation of nanoparticles in suspensions of different compositions and concentrations has been analyzed by transmission coefficient measurements. Spectra of the transmission coefficient have been obtained for suspensions containing composite nanoparticles, the initial silicon dioxide, and macroscopic magnetite particles. The average effective radius of nanoparticles has been calculated from the time dependences of the transmission coefficient. It has been demonstrated that the synthesized nanoparticles possess magnetic-resonance contrast properties.