Overpressured thin-layer chromatography

The properties, apparatus and applications of overpressured thin-layer chromatography (OPTLC) have been reviewed. In the Introduction planar chromatography has been briefly characterized, with particular attention to TLC. The general properties of OPTLC and methods of development of chromatograms in this technique have been then given. The construction of chambers and equipment for OPTLC has been described, paying attention to two-dimensional columns. The properties of chambers for OPTLC have been characterized considering the flow of eluent, sorbent-eluent interactions and the efficiency of various systems. OPTLC, TLC and HPTLC have been compared and also a comparison between OPTLC with a constant (linear) eluent flow-rate and with a decreasing eluent flow-rate has been made. Analytical applications of OPTLC have been described and examples of separations of mixtures have been given.     

Phase structure of silanol-modified ethylene-vinyl acetate copolymers

For (ethylene-vinyl acetate copolymer)-tetraethoxysilane and (ethylene-vinyl acetate copolymer)-polydimethylsiloxane systems, the solubility of components has been studied in a wide range of temperatures and compositions. Phase diagrams have been constructed, pair interaction parameters have been calculated, and diffusion coefficients and activation energies of diffusion have been estimated. The temperature and concentration ranges of a change in solubility related to chemical interactions between the components have been revealed, and the structure of the modified copolymers has been studied. On the basis of the kinetic data on the movement of isoconcentration planes in diffusion zones of component mixing, time intervals corresponding to the onset of the chemical reaction between the components have been determined and the apparent activation energies of the process have been computed. Complex-shaped binodal and boundary curves have been interpreted within the framework of the classical Flory-Huggins theory.     

Isothermal Flows of Micropolar Liquids: Formulation of Problems and Analytical Solutions

Models for flows of a non-Newtonian liquid have been considered within the framework of the micropolar theory. Different forms of constitutive equations and boundary conditions have been compared. Available analytical solutions and possible applications of the micropolar theory have been reviewed. A mechanically substantiated formulation of the problem relevant to the flow of a micropolar liquid in a Brinkman porous medium has been considered. Formulations of the boundary problem have been proposed for a micropolar liquid flowing in a porous cell.     

Fine structure analysis of the even parity configuration system of Ti I

Even-parity configuration system of Ti I has been considered on the basis of the experimental data available in literature. The fine structure analysis has been performed with the aid of a linked-parameter method of level-fitting calculations in a large multiconfiguration basis. Fine structure parameters have been determined and precise wavefunctions of even energy levels have been evaluated. Appropriate pseudorelativistic Hartree-Fock ab initio calculations of fine structure parameters have been presented for comparison purposes. Configuration interaction effects on even-parity configurations have been discussed.     

On the thermodynamic theory of the strength of solids: 5. Energetic characteristics of a crack with a meniscus and ultimate solid strength

The thermodynamic relations describing the formation work of a crack with a meniscus inside it have been analyzed for capillary condensation and evaporation processes. The conformal and depth mechanisms of crack growth have been discussed. It has been shown that the capillary forces alone cannot cause the fracture of a solid upon the formation of a meniscus in a crack. Criteria have been established for the strength upon the brittle fracture, and corrections related to the presence of a meniscus in a crack have been calculated. As a rule, the formation of a meniscus reduces the ultimate strength.     

The Synthesis and Biological Evaluation of Regioisomeric Benzothiazolyl Coumarins

Various 4-aryloxymethylcoumarins have been obtained by the r.t. allylic substitution with formylphenols. These have been further reacted with o-aminothiophenol resulting in the formation of a benzothiazole skeleton. These compounds have been synthesised with a view to study their potential as microbial growth inhibitors. Comparative studies on the spectral and antimicrobial activities have also been carried out.     

Photoinduced electron transfer via nonbuttressed metal-metal bonds. The photochemical study of binuclear complexes with platinum-thallium bonds

The photochemistry of binuclear metal-metal bonded complexes [(NC) 5Pt-Tl(solv) x ] (solv is water or dimethylsulfoxide) has been studied in aqueous and dimethylsulfoxide solutions. Both stationary and nanosecond laser flash photolysis have been carried out on the species. The metal-metal bonded complexes have been photolyzed by irradiation into the corresponding intense MMCT absorption bands. Photoexcitation results in the cleavage of the platinum-thallium bond and the formation of a solvated thallous ion and a cyano complex of platinum(IV), [Pt(CN) 5(solv)] (-), in both cases. The species have been characterized by multinuclear NMR and optical spectroscopy. The products of the photoreaction indicate a complementary two-electron transfer occurring between platinum and thallium ions in the binuclear Pt-Tl species. Quantum yield values for the photodecomposition of the species have been determined. The intermediates of the photoinduced metal-to-metal electron transfer have been detected and characterized by optical spectroscopy. The kinetics of transient formation and decomposition have been studied, and mechanisms of the photoactivated redox reaction have been suggested.     

Approximations of the nucleus size spectrum in nucleation kinetics under gradually varied external conditions

Several simple approximations have been presented for describing evolution of a condensing system at the stage of nucleation under dynamic conditions. All of them have been compared with the exact numerical solution, and their errors have been determined. All relative errors have been shown to be rather small.     

Short peptides as biosensor transducers

This review deals with short peptides (up to 50 amino acids) as biomimetic active recognition elements in sensing systems. Peptide-based sensors have been developed in recent years according to different strategies. Synthetic peptides have been designed on the basis of known interactions between single or a few amino acids and targets, with attention being paid to the presence of peptide motifs known to allow intermolecular self-organization of the sensing peptides over the sensor surface. Sensitive and sophisticated sensors have been obtained in this way, but the use of designed peptides is limited by severe difficulties in their in silico design. Short peptides from random phage display have been selected in a random way from large, unfocussed, and often preexisting and commercially available phage display libraries, with no design elements. Such peptides often perform better than antibodies, but they are difficult to select when the target is a small molecule because of the need to immobilize it with considerable modifications of its structure. Artificial, miniaturized receptors have been obtained from the reduction of the known sequence of a natural receptor down to a synthesizable and yet stable one. Alternatively, binding sites have been created over a designed, stable peptide scaffold. Short peptides have also been used as active elements for the detection of their own natural receptors: pathogenic bacteria have been detected with antimicrobial and cell-penetrating peptides, but key challenges such as detection of bacteria in real samples, improved sensitivity, and improved selectivity have to be faced. Peptide substrates have been conjugated to fluorescent quantum dots to obtain disposable sensors for protease activity with high sensitivity. Ferrocene–peptide conjugates have been used for electrochemical sensing of protease activity.     

Vibrational spectra,normal coordinates and infrared intensities of four isotopic phenyl acetates

The i.r. and Raman spectra of phenyl acetate and its deuteromethyl and deuterophenyl derivatives have been recorded. The fundamental frequencies of the four isotopic species have been assigned by referring to the Raman depolarization ratios and isotopic frequency shifts. The normal coordinates have been calculated on the basis of a valence force field. The general valence type force constants have been refined by the least-squares method. The i.r. spectra of the four isotopes have been simulated by using the obtained force field in combination with a suitable set of the atomic charges and their fluxes.     

3-芳氧基-6-取代哒嗪的合成及其除草活性

合成了系列3-芳氧基-6-取代哒嗪类化合物.化合物结构经¹HNMR、元素分析、IR和MS确证.生物活性测试结果表明,该类化合物具有很好的除草活性,讨论了其结构与除草活性的关系.     

Frequency-modulated simultaneous multielement atomic absorption spectrometry using electrothermal atomizer and deuterium background correction

Characteristic data of the frequency-modulated simultaneous multielement atomic absorption spectrometry (FREMSAAS) using electrothermal atomizer with deuterium background correction, have been determined. The data obtained have been processed by using several statistical tests recommended for quality control purposes. The instrumentation has been presented as well as procedures of separating elements into measure groups and fixing of variable conditions. Detection limits, characteristic masses and working ranges have been given for the eleven elements examined. The data have been in good agreement to results obtained with conventional one-channel AAS instruments. The eleven elements have been simultaneously determined in a standard reference material (SRM) and all results are compatible with a 95% certainty with the certified values. FREMSAAS has been applied to a real sample.Dedicated to Professor Dr. Dieter-Klockow on the occasion of his 60th birthday     

Sulfonamide carbazole receptors for anion recognition

Carbazole-based receptors functionalized with two sulfonamide groups have been synthesized and their properties as anion receptors have been evaluated. The receptor with bis(trifluoromethyl)aniline groups has shown a very high affinity for halide ions, especially remarkable as only two hydrogen bonds are formed in the complexes. (1)H NMR and fluorescence titrations have been carried out and binding constants up to 7.9 × 10(6) M(-1) have been reached. X-ray structures have been obtained and a modelling study has shown the possible reasons for the large affinity of these compounds for halide anions.     

Synthesis and spectral-luminescent properties of 5-substituted polyaryl derivatives of barbituric acid

New substituted barbituric acid derivatives containing a 4,5,6,7-tetrahydroindole moiety have been synthesized by three-component condensation. Luminescence of crystals and solutions of the compounds synthesized have been studied; a maximum luminescence intensity and a minimum Stokes shift have been found in the 1-naphthyl derivative.     

Solvent extraction of Cu(II) by Schiff bases—II

Aromatic 2-hydroxyaldehydes have been condensed with a number of aliphatic and aromatic amines to form a series of bi-, tri- and tetradentate Schiff bases. These have been used to extract Cu(II) into chloroform, methyl isobutyl ketone and toluene; most have been found to be effective extractants. The characteristics of these extraction systems have been explained in terms of extraction rates and the stability of the reagents to hydrolysis.     

Electrokinetic studies on a thorium oxide membrane : I. Electroosmosis and electrophoresis

Electroosmotic transport of dimethyl formamide through a thorium oxide plug membrahe has been studied and the data have been analysed from the standpoint of thermodynamics of irreversible processes. Electroosmotic flow and eleetroosmotic pressure have been found to be nonlinearly dependent on the applied potential difference. Various phenomenological coefficients have been evaluated from the nonlinear transport equation. Onsager's reciprocity relation has been verified by measurements of streaming potentials. The electrophoretic velocity of thorium oxide particles dispersed in dimethyl formamide has also been found to be nonlinear. Zeta potentials have been evaluated from electroosmotic and electrophoretic data. The results have been explained on the basis of the change in the structure of the electrical double layer. The degree of coupling and the efficiency of electrokinetic energy conversion have been calculated for both electroosmosis and streaming potential.     

Thermodynamic behavior of water-acetonitrile mixtures excess volumes and viscosities

Densities of water+acetonitrile mixture have been measured from 308.15 to 278.15 K over the entire composition range. Partial molal volumes of both components of the mixed system have been calculated and deviations from ideal volumes of mixing have been evaluated. Literature data on viscosity have also been treated by a least square method and activation thermodynamic functions of viscous flow computed. Structural correlations have been made with previous results on acid-base properties; they allow to distinguish several interaction regions between components of binary systems.     

Copper ferrocyanide — polyurethane foam as a composite ion exchanger for removal of radioactive cesium

A method has been developed for the removal of cesium from the aqueous radioactive waste using a composite ion-exchanger consisting of Copper-Ferrocyanide Powder (CFC) and Polyurethane (PU) Foam. Polyvinyl acetate has been used as a binder in the preparation of CFC-PU foam. The physical properties of CFC such as density, surface area, IR stretching frequency and lattice parameters have been evaluated and also its potassium and copper(II) content have been estimated. Optimization of loading of CFC on PU foam has been studied. The CFC-PU was viewed under microscope to find out the homogeneity of distribution. Exchange capacities of the CFC-PU foam in different media have been determined and column studies have been carried out. Studies have been undertaken on extraction of cesium from CFC foam and also on digestion of spent CFC-PU foam and immobilization of digested solution in cement matrix. The cement matrices have been characterized with respect to density, bio-resistance and leaching resistance.     

高硅Y沸石的研制及吸附热力学性质

Ｙ沸石用ＬｉＣｌ溶液交换得ＬｉＮａＹ沸石,再经ＳｉＣｌ４气相同晶取代进行脱铝补硅,获得高结晶度的高硅Ｙ沸石,硅铝比可大于１００［１］．在脱铝过程中,随着硅铝比的升高其孔结构和表面性质均发生变化,直接关联到Ｙ沸石在炼油中的催化裂化性能．通过对不同大小、结?..     

A FLASH PHOTOLYSIS STUDY OF INTERMEDIATES IN PHOTOCHEMICAL REACTIONS OF CHLOROPHYLL

Abstract— The photochemical reactions of chlorophyll intermediates in vitro have been studied by the flash photolysis method. The flash excitation of pigment solutions has been shown to involve the population of a chlorophyll triplet state where the oxidation-reduction processes occur. The mechanism and kinetics of pigment triplet decay have been investigated from 20°to — 50°C and the ability of chlorophyll molecules to carry out triplet-triplet energy transfer has been established. The latter phenomenon has been used to show up the role of chlorophyll triplets in the reversible photooxidation reaction with P -quinone. There have been studied initial products of pigment photoreduction with ascorbic acid and phenylhydrazine. Experimental data of the mechanism of the initial oxidation and reduction in chlorophyll photosensitized reactions have been analysed. There have been also obtained the differential spectra of chlorophyll triplets and radicals. A calculation has been made of rate constants for a few elementary reactions.