Structure and Properties of TiB2 ― AlN Coatings Made by Spark and Laser Methods

Studies have been done on how various concentrated energy forms (spark discharge and laser beam) affect the formation, composition, and structure of coatings made from the new composite material TiB₂ ― AlN (1:1). The working surfaces have been examined by x-ray phase analysis, microprobe, and metallography. It is found that the composition and structure of a spark coating differ from those of the depositing electrode. The TiB₂ ― AlN material is recommended for hardening low-carbon steels.     

The mechanism of the oxidative polymerization of aniline and the formation of supramolecular polyaniline structures

Polyaniline is one of the most important conducting and responsive polymers. A molecular mechanism for the oxidation of aniline is proposed. This mechanism explains the specific features of aniline oligomerization and polymerization in various acidity ranges. The formation of polyaniline precipitates, colloids and thin films is reviewed and discussed on the basis of the chemistry of aniline oxidation. The generation of nanostructures, i.e. granules, nanotubes, nanowires and microspheres, is also considered. Oligomers containing phenazine constitutional units play an important role in self‐assembly to form templates. Polyaniline chains then grow from these templates and produce the various individual morphologies. Copyright © 2008 Society of Chemical Industry     

Magnetometric Studies of Catalyst Refuses in Nanocarbon Materials

It is shown that magnetometry can be employed as an effective tool to control the content of a ferromagnetic constituent in nanocarbon materials. We propose a thermochemical treatment protocol to achieve extensive cleaning of the source nanocarbon materials from ferromagnetic refuses.     

Synthesis and characterization of grafted copolymers of aromatic polyimides and ε‐caprolactam

Anionic polymerization of ε‐caprolactam was performed in the presence of only 5 wt % of aromatic polyimides having five‐ and six‐membered imide cycles and bearing hexafluoroisopropylidene, ether, fluorene, siloxane, phthalide, or SO₃H? groups, both in the polymer backbone and as side moieties. The synthesized new copolymers were fully characterized by IR spectroscopy, thermomechanical analysis, dilatometry, and X‐ray diffraction. Tough and frictional properties of the obtained copolymers were estimated as well. It was found that on the selection of polyimide activator it is possible to gain the desirable control over the polymer properties, namely the gel‐fraction content, phase composition, compression modulus, notched Izod impact strength, temperature of frictional contact, friction coefficient, etc. These investigations will facilitate the choice of the optimum macromolecular activator for the modification of both the synthetic method and the properties of the commercial polycaproamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phase behavior of gelatin in the presence of pectin in water-acid medium

Summary Phase separation of alkaline gelatin in water-acid solutions in the presence of low etherified pectin (ED 38%) were investigated. The effects of the pectin weight fraction in pectin/gelatin mixture (q_o) as well as two conditions of complex formation, namely, mixing of the binary biopolymer-solvent systems at pH 3.5 (‘mixing conditions’), or preparation of the ternary gelatin-pectin-water systems at pH 7.5 and their subsequent acidification up to pH 3.5 (‘titration conditions’), on phase equilibrium and macrostructure of the concentrated complex phase were established using phase analysis, and optical microscopy. At q_o<0.5 the aggregative phase separation was observed in both conditions of complex formation leading to the almost complete concentration of both biopolymers in the bottom phase at q_o=0.3 (‘mixing conditions’) and at q_o=0.5 (‘titration conditions’). At q_o>0.5 unusual three phase separation took place in the ‘mixing conditions’, leading to formation of supernatant (phase 1), complex coacervate (phase 2) and concentrated pectin solution (phase 3). Possible mechanism of such phenomenon was discussed in term of segregative and aggregative phase separations.     

Revisiting tetranitrophenolsulfonephthalein

Among the vast series of phenolsulfonephthalein dyes, the nitro derivatives and especially 3,3′,5,5′‐tetranitrophenolsulfonephthalein (nitrophenol crimson) remain practically unexplored, whereas the halogen and alkyl derivatives have been studied comprehensively. This striking difference is probably due to the enormous influence of the four NO₂ groups on the properties of the dye. As a result, the protolytic behaviour is unlike even that of tetrabromo phenolsulfonephthalein, and the recognised scheme of acid–base and tautomeric equilibrium of the sulfonephthaleins is unable to explain it. The molecular form H₂R was isolated as a sultonic tautomer, and an X‐ray crystal structure analysis was carried out. Our studies of the UV‐vis absorption spectra in water, methanol, dimethyl sulfoxide, acetonitrile, acetone, and dichloromethane, as well as in aqueous micellar solutions of surfactants, allowed us to evaluate the true molar absorptivity of the dianion R^2?, and to elucidate the enormous tendency to form yellow trianionic carbinol ROH^3?, even in the presence of traces of H₂O. Nuclear magnetic resonance and electrospray data confirm the proposed scheme of ionisation and tautomerism of nitrophenol crimson.     

The ecological peculiarities of the testate amoebae population in the Middle Ob flood plain

The biodiversity and distribution of testate amoebae in the Middle Ob flood plain soils have been studied. The biodiversity of Testacea in the soils consists of 83 species and varieties from 12 families. The population of Testacea in flood plain habitats is rich in water forms, especially in the flood plain part of the catena, because of annual floods. The study showed that the density of Testacea in the forest plots is approximately 10 times higher than in the meadow ones. The species diversity of Testacea in the meadows of the flood plain includes 40 species and varieties. It was found that there is an enrichment of the fauna of Testacea in the flood plain meadows with water forms and a decrease in the population of Testacea in the soil according to the depth. The decrease in the diversity and number down the soil profile is related to the decrease in the amount of the oxygen available and general induration of soil. On the whole, the population composition of Testacea in the soils of the pine forest consists of typical representatives of humus substrates with low values of pH, small stock of humus and mineral nutrition. The soils of mature pine forests are rich in Testacea; they have a similar complex of morphological types, mainly because of the moss cover and forest litter thickness.     

One‐Step Synthesis of Chiral Azamacrocycles via Palladium‐Catalyzed Enantioselective Amination of 1,5‐Dichloroanthraquinone and 1,5‐Dichloroanthracene

Asymmetric amination of 1,5‐dichloroanthraquinone and 1,5‐dichloroanthracene with di‐ and trioxadiamines catalyzed by palladium complexes with various chiral phosphine ligands gave chiral macrocycles with ee values of up to 60%. The dependence of the chemical yields and enantiomeric excess on the nature of the starting compounds and the phosphine ligands employed was demonstrated. An unexpected spontaneous resolution upon crystallization of the macrocycle comprising anthraquinone and dioxadiamine moieties was observed while in the case of the macrocycle with a trioxadiamine linker racemic monocrystals were obtained. Crystallization of the enantiomerically enriched mixtures afforded chiral macrocycles with 88–99% ee.     

Paenibacillus polymyxa purified bacteriocin to control Campylobacter jejuni in chickens

Campylobacter spp. cause numerous foodborne diseases. Poultry is thought to be a significant source of this zoonosis. Although many interventions designed to control this agent have been researched, none have succeeded. We evaluated a bacteriocin-based treatment to reduce Campylobacter jejuni colonization in poultry. A previously described purified bacteriocin (class IIa; molecular mass, 3,864 Da), secreted by Paenibacillus polymyxa NRRL-B-30509, was microencapsulated in polyvinylpyrrolidone, and 0.25 g of the purified bacteriocin was incorporated into 1 kg of chicken feed. One-day-old chickens were orally challenged and colonized with one of four isolates of C. jejuni, then reared in isolation facilities. Birds were provided ad libitum access to standard broiler starter feed and water for 7 days until 3 days before sampling, when only the treated groups of birds were provided the bacteriocin-emended feed described. In each of the eight (four by two replicates) trials, significant reductions in colonization by C. jejuni were observed (P < or = 0.05). As an example of this highly consistent data, in the first trial, 10 untreated 10-day-old chickens were colonized at a mean log 7.2 + 0.3 CFU/g of feces, whereas none of the 10 bacteriocin-treated 10-day-old chickens were colonized with detectable numbers of C. jejuni. Bacteriocin treatment dramatically reduced both intestinal levels and frequency of chicken colonization by C. jejuni. Feeding bacteriocins before poultry slaughter appears to provide control of C. jejuni to effectively reduce human exposure. This advance is directed toward on-farm control of pathogens, as opposed to the currently used chemical disinfection of contaminated carcasses.