4-dimensional minimal CR submanifolds of the sphere S satisfying Chen's equality

In this paper, we classify 4-dimensional minimal CR submanifolds M of the nearly Kähler 6-sphere S⁶(1) which satisfy Chen's equality, i.e. , where δM(p)=τ(p)−infK(p) for every p∈M.     

Chemical oxidative polymerization of safranines

Phenosafranine and safranine have been oxidized with ammonium peroxydisulfate in acidic aqueous solution. The oxidative coupling of both safranines was proved by gel permeation chromatography demonstrating the presence of oligomeric chains of mass-average molar masses 6500 and 4500 g mol-1 for polyphenosafranine and polysafranine, respectively. A theoretical study of the mechanism of safranine and phenosafranine polymerization was based on the MNDO-PM3 semiempirical quantum chemical computations of the heat of formation of dimeric reaction intermediates, taking into account solvation effects. The study of the redox properties of the hydrated safranines and their reactive species shows that nitrenium cations are the main reactive species generated by the oxidation of the parent safranines with a two-electron oxidant, peroxydisulfate, in the initiation phase. The dominant dimers of safranines are formed by N-C coupling reactions between nitrenium cations and the parent safranines. The main coupling reactions of phenosafranine are N-C2 (C8) and N-C4 (C6); N-C4 (C6) is the dominant coupling mode for safranine. The molecular structure of oligosafranines has been studied by FTIR, Raman, and UV-vis spectroscopies. Besides prevalent unoxidized monomeric units, polymerization products of safranines contain also the iminoquinonoid and newly formed fused phenazine units.     

A short stereoselective synthesis of the protected uracil 3′-epi-polyoxin C

A short synthetic approach to the protected uracil 3′-epi-polyoxin C 20 has been developed. The stereoselective [3,3]-sigmatropic rearrangement of the corresponding 7-thiocyanato-α-d-xylo-hept-5-enfuranose 6 was employed as the key step to construct the C-5 stereocentre in 5-isothiocyanato-α-d-gluco-hept-6-enfuranose 8 and the formal synthesis of uracil 3′-epi-polyoxin C has been accomplished for the first time. This synthesis provides a facile method for multigram scale preparation and thus is useful for the research into the polyoxins’ structure-activity relationship and to search for more potent and effective anticandidal agents.     

Multi-wall carbon nanotubes with nitrogen-containing carbon coating

Polyaniline coating was deposited on the surface of multi-wall carbon nanotubes of Russian and Taiwanese origin in situ during the polymerization of aniline. The deposited polyaniline film was subsequently carbonized under an inert atmosphere at various temperatures to produce coaxial coating of the carbon nanotubes with nitrogen-containing carbon. The new materials were investigated by infrared and Raman spectroscopies, which demonstrated the conversion of the polyaniline coating to a carbonized structure. X-ray photoelectron spectroscopy proved that the carbonized overlayer contains nitrogen atoms in various covalent bonding states. Transmission electron microscopy confirmed the coaxial structure of the composites. The Brunauer-Emmett-Teller method was used to estimate the specific surface area, the highest being 272 m² g^?1. The conductivity of 0.9–16 S cm^?1 was measured by the four-point method, and it was only a little affected by the carbonization of the polyaniline coating.     

Electrolyte system for fast preparative focusing in wide pH range based on bidirectional isotachophoresis

In this paper, we suggest new electrolyte system for fast preparative electrofocusing in wide pH range. It is based on bidirectional ITP with multiple counterions and spacers created by commercially available defined simple buffers. The migration course of proposed focusing model can be simulated in advance by using separation conditions and electrolyte components that are consequently applied during the experiments. The suggested electrolyte system allows high current densities at the initial stages of focusing without danger of local overheating, which strongly reduces the time needed for analysis completion. The performance of the electrolyte system is demonstrated by the focusing of synthetic colored low molecular weight indicators and proteins in the arrangements with both linear narrow strip and nonwoven fabric sheet with continuous flow.     

Biodegradation of Benzo[a]Pyrene through the use of algae

In this work for disposal of the biologically hard decomposed pollutant Benzo[a]Pyrene (BaP) photooxidation Chlorella kessleri was used. The simulation model system under the different experimental conditions (varying biomass and light intensity) was evaluated. For quantitative analysis of the decrease in BaP, GC/MS technique was used. The highest degradation efficiency was achieved in the case of biomass from the culture of live algae (29%) and light intensity at level of 13.5 W m^?2. When the dry biomass was used, degradation under the same conditions was lower because of lack of enzymatic activity in the system.      

Single-input divergent flow IEF for preparative analysis of proteins

The instrument for continuous divergent flow IEF based on our principles set and outlined previously was further extended and tested. The separation and focusing area of a trapezoidal shape had a porous bed made from a nonwoven textile material with thickness decreasing from narrow input to wide output. A narrow end was used as a single input to continuously bring a single solution into separation space with a flow rate of 0.18 mL/min. Two pairs of electrodes were positioned close to both narrow and wide ends of the separation area with equilibrium state voltage of 75 V at the narrow input and 384 V at the wide output. Under dynamic equilibrium state, the zones of both pH gradient components and analytes were separated close to the input point and focused with increasing resolution while transporting through the separation space. The long-term stability experiments had shown the suitability of the device for preparative analysis; the zones of pI markers, hemoglobin and cytochrome C remained focused and separated over 15 h with deviations from the mean focusing positions ranging from 1.26 to 3.96% of the bed output width.     

Chemical oxidative polymerization of aminodiphenylamines

The course of oxidation of 4-aminodiphenylamine with ammonium peroxydisulfate in an acidic aqueous ethanol solution as well as the properties of the oxidation products were compared with those of 2-aminodiphenylamine. Semiconducting oligomers of 4-aminodiphenylamine and nonconducting oligomers of 2-aminodiphenylamine of weight-average molecular weights 3700 and 1900, respectively, were prepared by using an oxidant to monomer molar ratio of 1.25. When this ratio was changed from 0.5 to 2.5, the highest conductivity of oxidation products of 4-aminodiphenylamine, 2.5 x 10 (-4) S cm (-1), was reached at the molar ratio [oxidant]/[monomer] = 1.5. The mechanism of the oxidative polymerization of aminodiphenylamines has been theoretically studied by the AM1 and MNDO-PM3 semiempirical quantum chemical methods combined with the MM2 molecular mechanics force-field method and conductor-like screening model of solvation. Molecular orbital calculations revealed the prevalence of N prim-C10 coupling reaction of 4-aminodiphenylamine, while N prim-C5 is the main coupling mode between 2-aminodiphenylamine units. FTIR and Raman spectroscopic studies confirm the prevalent formation of linear N prim-C10 coupled oligomers of 4-aminodiphenylamine and suggest branching and formation of phenazine structural units in the oligomers of 2-aminodiphenylamine. The results are discussed with respect to the oxidation of aniline with ammonium peroxydisulfate, leading to polyaniline, in which 4-aminodiphenylamine is the major dimer and 2-aminodiphenylamine is the most important dimeric intermediate byproduct.     

Modeling of Polymer Network Formation from Preformed Precursors

Statistical and kinetic methods of modeling of polymer networks formation from pre‐prepared precursors are described and illustrated. Such precursors are characteristic of distributions of molecular weight and numbers of reactive groups of distinguishable type and reactivity, and contain branch points which get elastically active in the crosslinking stage. The examples include telechelic polymers with functionality distribution, functional copolymers composed of functional and non‐functional units and groups of different reactivity. The basics of statistical and kinetic network formation methods are outlined and their adaptation to cover the non‐uniform collection of precursor molecules as one of the components. The distributions of properties of the precursors are expressed by probability generating functions which serve as input for the crosslinking stage.

     

Evolution of polyaniline nanotubes: the oxidation of aniline in water

The course of aniline oxidation with ammonium peroxydisulfate in aqueous solutions has been investigated. The reaction was terminated at various times and the intermediates collected. Besides the precipitates, the films deposited in situ on silicon windows have also been studied. The kinetic course of polymerization is controlled by the acidity level, which changes during the polymerization from pH 8 to a final value close to pH 1. It has two distinct exothermic phases. Gel-permeation chromatography indicates that aniline oligomers are produced at first at high pH, while polyaniline follows after the pH becomes sufficiently low. The growth of polyaniline nanotubes was observed by optical microscopy and confirmed by electron microscopy. The molecular structure of the reaction intermediates was studied in detail by FTIR spectroscopy. Oxidation products are markedly sulfonated, and they contain phenazine units. Aniline oligomers are more soluble in chloroform than the polymer fraction, which contains nanotubes.