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Chitosans are natural aminopolysaccharides, whose low cytotoxicity suggests their potential use for nonadhesive, antibacterial coatings on biomaterials implant surfaces. Here, the antiadhesive behavior and ability to kill bacteria upon adhesion ("contact killing") of chitosan coatings were evaluated for two strains of Enterococcus faecalis, isolated from clogged biliary stents. Chitosan coatings covalently grafted or applied as chitosan/kappa-carrageenan multilayers were characterized by ellipsometry, scanning force microscopy (SFM), X-ray photoelectron spectroscopy (XPS), and electrokinetic measurements. Decreases in initial bacterial deposition rates and the number of bacteria adhering in a more advanced state of the adhesion process were observed on both types of modified surfaces, with more pronounced effects on highly hydrated multilayers. Adhesion of negatively charged enterococci was slightly enhanced on chitosan-terminated multilayers, but antibacterial effect was absent on kappa-carrageenan-terminated multilayers. Thus, the efficacy of multilayers remains an interesting interplay between the promoting effect of cationically charged groups on adhesion of negatively charged bacteria and, on the other hand, their antibacterial effects.

The origin of magnetic frustration was stated and the ions whose shift is accompanied by emerging magnetic ordering and ferroelectricity in TbMn 2 O 5 and BiMn 2 O 5 were determined on the basis of calculation of magnetic coupling parameters by using the structural data. The displacements accompanying the magnetic ordering are not polar, they just induce changes of bond valence (charge disordering) of Mn1 and Mn2, thus creating instability of the crystal structure. To approximate again the bond valence to the initial value (charge ordering) under magnetic ordering conditions is possible only due to polar displacement of Mn2 (or O1) and O4 ions along the b axis that is the cause of ferroelectric transition.

Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13 C and 15 N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the glucosamine unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitates cross-linkages formation at −10 °C and, despite lower modification degrees compared to those of gels obtained at room temperature, supermacroporous chitosan cryogels with Young's moduli up to 90 kPa can be fabricated in one step. Investigations of chitosan cryogels biocompatibility in a mouse model have shown that a moderate inflammatory reaction around the implants is accompanied by formation of a normal granulation tissue. No toxic, immunosuppressive, and sensitizing effects on the recipient's tissues have been observed.

In this paper we examine the role of crystal chemistry factors in creating conditions for formation of magnetoelectric ordering in BiFeO 3 . It is generally accepted that the main reason of the ferroelectric distortion in BiFeO 3 is concerned with a stereochemical activity of the Bi lone pair. However, the lone pair is stereochemically active in the paraelectric orthorhombic ß-phase as well. We demonstrate that a crucial role in emerging of phase transitions of the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order types belongs to the change of the degree of the lone pair stereochemical activity -its consecutive increase with the temperature decrease. Using the structural data, we calculated the sign and strength of magnetic couplings in BiFeO 3 in the range from 945º down to 25º С and found the couplings, which undergo the antiferromagneticferromagnetic transition with the temperature decrease and give rise to the antiferromagnetic ordering and its delay in regard to temperature, as compared to the ferroelectric ordering. We discuss the reasons of emerging of the spatially modulated spin structure and its suppression by doping with La 3+ .

Toward accurate thermochemical models for transition metals: G3Large basis sets for atoms Sc-Zn Density functional study of mononitrosyls of first-row transition-metal atomsThe sign and strength of magnetic interactions not only between nearest neighbors, but also for longer-range neighbors in the Cr 1/3 NbS 2 intercalation compound have been calculated on the basis of structural data. It has been found that left-handed spin helices in Cr 1/3 NbS 2 are formed from strength-dominant at low temperatures antiferromagnetic (AFM) interactions between triangular planes of Cr 3þ ions through the plane of just one of two crystallographically equivalent diagonals of side faces of embedded into each other trigonal prisms building up the crystal lattice of magnetic Cr 3þ ions. These helices are oriented along the c axis and packed into two-dimensional triangular lattices in planes perpendicular to these helices directions and lay one upon each other with a displacement. The competition of the above AFM helices with weaker inter-helix AFM interactions could promote the emergence of a long-period helical spin structure. One can assume that in this case, the role of Dzyaloshinskii-Moriya interaction consists of final ordering and stabilization of chiral spin helices into a chiral magnetic soliton lattice. The possibility of emergence of solitons in M 1/3 NbX 2 and M 1/3 aX 2 (M ¼ Cr, V, Ti, Rh, Ni, Co, Fe, and Mn; X ¼ S and Se) intercalate compounds has been examined. Two important factors caused by the crystal structure (predominant chiral magnetic helices and their competition with weaker inter-helix interactions not destructing the system quasi-one-dimensional character) can be used for the crystal chemistry search of solitons. V C 2014 AIP Publishing LLC. [http://dx.

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