RESUMEN
We propose a new approach of using carbon nanoparticles for correlation optical diagnostics of а complex scalar optical field created by scattering and diffraction of radiation off a rough surface. This surface is simulated and we generate a diffraction pattern of the amplitude and phase distribution in the far field. Carbon nanoparticles of a certain size and concentration are obtained by the bottom-up methods of hydrothermal synthesis of citric acid and urea followed by centrifugation. The optical properties of carbon nanoparticles, such as luminescence and absorption in the visible spectrum that essentially differs for different wavelengths, as well as particle size of about dozen nanometers, are the determining criteria for using these particles as probes for the optical speckle field. Luminescence made it possible to register the coordinate position of carbon nanoparticles in real time. The algorithm for reconstruction of the scalar optical field intensity distribution through the analysis of the nanoparticle positions is here displayed. The skeleton of the optical speckle field is analyzed by Hilbert transform to restore the phase. Special attention is paid to the restoration of the speckle field's phase singularities.
RESUMEN
Two-time correlation functions of a system of Bose particles are studied. We find a relation of zeros of the correlation functions with the Lee-Yang zeros of the partition function of the system. The obtained relation gives the possibility to observe the Lee-Yang zeros experimentally. A particular case of Bose particles on two levels is examined, and zeros of two-time correlation functions and Lee-Yang zeros of the partition function of the system are analyzed.
RESUMEN
The regioselective base-catalyzed addition of nitromethane to 2-oxo-4-trifluoromethyl-1,2-dihydropyrimidine-5-carboxylates is reported. It was found that the Michael-like pathway is highly reversible and substantially dominating under conditions of kinetic control (0-5 °C, 10 h) whereas the aza-Henry reaction leads to thermodynamically stable adducts after 8-24 h exposure at room temperature. The adjacent nitro and alkoxycarbonyl groups were exploited to demonstrate the synthetic potential of the obtained products by converting to the isomeric trifluoromethylated pyrrolo[3,4-d]pyrimidine-2,5-diones. With this aim an efficient protocol for selective reduction of nitro-derivatives to the corresponding 4- or 6-aminomethyl-2-oxo-4-trifluoromethyl-1,2,3,4-tetrahydropyrimidine-5-carboxylates and their subsequent thermal cyclocondensations was applied.
RESUMEN
The keratin fibers contain small amount of the internal lipids which are in free state or bound with fiber proteins via tioester of 18-methyleicosanoic acid. Today the origin of these lipids, their composition and functional properties are still not found. Therefore, our objective was to examine the content and composition of internal lipids in sheep's wool with different defects. We observed that regardless of the type of fibers defect there are significant changes especially in the quality composition of the internal lipids, although the total content of free and covalently bound lipids in all cases is practically identical. Notably, both free and covalently bound lipids composition of felted and simultaneously felted and yellowed wool is characterized by changes in contents mainly of free fatty acids and ceramides whereas abnormal thinning of fibers is accompanied only by a decrease of sulfolipids.
Asunto(s)
Ceramidas/análisis , Colesterol/análisis , Lípidos/análisis , Lana/química , Animales , Cromatografía en Capa Delgada , Ácidos Eicosanoicos/química , Queratinas Específicas del Pelo/química , Microscopía Electrónica de Rastreo , Ovinos , Lana/ultraestructuraRESUMEN
The purpose of this study was to determine the fatty acid composition of structural lipids, isolated from normal and abnormal wool fibers. The results of these studies show that regardless of the type of wool fibers defect there are quantitative changes in their fatty acid composition. It was shown that the main fatty acid of the covalently bound lipids, isolated from the wool fibers, is 18-methyleicosanoic acid (18-MEA), comprising 40% of the total fatty acid, while its amount in free lipids in norm is less than 4%. The decrease of 18-MEA content in the covalently bound lipid both in pathological thin and entangled wool fibers was established, which is associated with damage of the cuticle layer surface. Increasing of 18-MEA content in the free lipids in the entangled wool fibers may indicate a rupture of tioester links between lipids and proteins of cuticle layer lamellar structures.