Nanosized cation exchanger for the electrophoretic separation and preconcentration of catecholamines and amino acids

The first example of application of nanosized polystyrene-based cation exchanger (NSCE) with sulfo groups as a dynamic coating of capillary walls was demonstrated. The conditions of dynamic coating formation were optimized and ensured the long-term stability of the coating. Capillary-to-capillary and day-to-day repeatabilities were 4% and 3%, correspondingly. The NSCE coating stability at various pH and influence of pH on the EOF mobility were investigated. The developed NSCE-modified coated capillaries provided improved resolution (R_s = 0.9–3.2 for catecholamines and R_s = 1.7–2.8 for amino acids) and efficiencies (330–520 ×10³ t.p./m) of basic analytes, which are 1.5 times higher compared to untreated capillary. The optimized conditions were as follows: 50 mM phosphate buffer solution at pH 2.2 with 5 μM NSCE. The effect of the NSCE concentration in BGE on the electrophoretic mobilities of the analytes was investigated. The various online concentration techniques were tested in order to decrease the LODs. The simultaneous application of NSCE capillaries and field-amplified sample stacking provided the lowest LODs of catecholamines and amino acids and allowed to determine these analytes in human urine.     

Synthesis and evaluation of properties of the optically transparent (co)polyimides based on cyclic and alicyclic diamines and dianhydrides of aromatic tetracarboxylic acids

Russian Chemical Bulletin - Optically transparent polyimides (PIs) containing adamantane moieties in the structure of diamine unit were synthesized, and their properties were evaluated. The...     

Conversion of the frequency of emission of a neodymium laser by the method of resonance pumping of active media

Journal of Applied Spectroscopy -     

Reflection of Plane Acoustic Waves for an Oblique Incidence on a Tellurium Dioxide Crystal Face

Acoustical Physics - This paper describes the phenomenology of the reflection of acoustic body waves in an acoustooptical paratellurite crystal in the case of arbitrary elastic wave incidence on a...     

The shear modulus of the human vocal fold in a transverse direction

The aim of this study was to measure the shear modulus of the vocal fold in a human hemilarynx, such that the data can be related to direction of applied stress and anatomical context. Dynamic spring rate data were collected using a modified linear skin rheometer using human hemilarynges, and converted to estimated shear modulus via application of a simple shear model. The measurement probe was attached to the epithelial layer of the vocal fold cover using suction. A sinusoidal force of 3g was applied to the epithelium, and the resultant displacement logged at a rate of 1kHz. Force measurement accuracy was 20microg and position measurement accuracy was 4microm. The force was applied in a transverse direction at the midmembranous point between the vocal process and the anterior commissure. The shear modulus of the three female vocal folds ranged from 814 to 1232Pa. The shear modulus of the three male vocal folds ranged from 1021 to 1796Pa. These data demonstrate that it is possible to obtain estimates for the shear modulus of the vocal fold while preserving anatomical context. The modulus values reported here are higher than those reported using parallel plate rheometry. This is to be expected as the tissue is attached to surrounding structures, and is under natural tension.     

Catalytic Activity of Polyfunctional Ionic Liquids in Oxidation of Model Sulfur Organic Compounds

Russian Journal of Applied Chemistry - Ionic liquids based on 1-methylimidazole were synthesized. The liquids contain Bronsted acid centers in the cation and a transition metal atom in the anion....     

Nearly backward reflection of bulk acoustic waves at grazing incidence in a TeO2 crystal

Reflection of bulk acoustic waves in a TeO₂ acoustooptic single crystal is studied for the case of a grazing incidence on the free crystal-vacuum boundary. The propagation and reflection of elastic waves is considered in the XOY plane of the material cut out in the form of a rectangular prism. An extraordinary case of reflection at the grazing incidence, when the energy flow of one of the two reflected waves in the crystal is directed opposite to that of the incident wave, is studied. It is shown that the transformation of the incident elastic energy into the energy of the backward-reflected wave can occur with an efficiency close to 100% and can be observed in a wide range of crystal cut angles. An abrupt change of the reflection coefficients in the vicinity of the critical angle is predicted.     

Enhanced anisotropy in Paratellurite for inhomogeneous waves and its possible importance in the future development of acousto-optic devices

The anisotropic feature of most crystals, involves a direction dependent wave velocity for each of the possible modes. Paratellurite (Tellurium dioxide) is extraordinary because, for one of the propagation modes, i.e. the quasi shear horizontal (QSH) mode, the anisotropy is exceptional. This results, on the one hand in a very strong directional dependent sound velocity and on the other hand, in a low wave velocity in certain directions, resulting in a high figure of merit for the acousto-optical interaction. In the case of inhomogeneous waves, the slowness surfaces change their shape and magnitude, for all crystals. However, for paratellurite, this effect is again extraordinary. As soon as a relatively small inhomogeneity is considered, the sound velocity for the QSH mode becomes really exceptionally anisotropic, resulting in a slowness surface that is almost spherical, covered by pins. The velocity corresponding to those 'pins', is much lower than in the case of homogeneous plane waves, which is very promising for the future development of acousto-optic cells involving an even higher figure of merit.     

Carbon nanotubes, new material for purification of water-ethanol mixtures from isomers of propanol

The possibility of purification of water-ethanol mixtures from the unwanted admixtures of higher alcohol, in particular, of the isomeric propanols, with the help of carbon nanomaterial is discussed. Results of quantum-chemical calculations of n-propanol and isopropanol on the surface of the single-walled carbon nanotube of the “armchair” type are presented. Investigations are carried out within the frame of model of molecular cluster using semi-empirical quantum chemical MNDO method. The possibility of adsorption of molecules of propanol isomers on the outer surface of nanotubes of small diameter as well the absence of adsorption of ethanol molecules on them is shown. It indicates the possibility of selective sorption with carbon nanotubes. Main geometric, electronic, and energy characteristics of obtained adsorption complexes are evaluated. A conclusion is made on the possibility to use carbon nanotubes for superfine purification of water-ethanol mixtures from the unwanted admixtures of n- and isopropanol.     

Synthesis of 19-hydroxypregn-4-en-20-one and 19-hydroxy-5β-pregn-3-en-20-one that selectively bind to membrane progesterone receptors,and assessment of their immunomodulatory effects

Russian Chemical Bulletin - A new approach to the synthesis of isomeric 19-hydroxypregn-4-en-20-one (1) and 19-hydroxy-5β-pregn-3-en-20-one (2), the selective ligands of membrane progesterone...