The distribution of magnetization in single-crystal samples of silicon iron made in the form of thin disks after heat treatments under the influence of a magnetic field or mechanical stress was determined by Mössbauer spectroscopy. At contents of 5 and 8 at

Magnetoimpedance (MI) effect in stress -annealed Co -based amorphous ribbon was studied in the states without and in presence of the magnetic epoxy composite of cylindrical shape. Iron oxide FeOx magnetic microparticles of different concentrations (0 - 70 wt.%) were used as a magnetic filler. The condition of stress annealing (350 degrees C, 1 h and 250 MPa specific load) were selected in order to insure the high MI sensitivity with respect to external magnetic field in the field of a few Oersted. The MI responses were modified in the presence of the magnetic epoxy composites due to the contribution of the stray fields of embedded microparticles. It was experimentally found that degree of the MI curves modification depended on the microparticles concentration. The MI characteristics were also dependent on the length -to -width ratio of the MI element. The most sensitive MI element under study showed a linear dependence with a 1 %/weight percent microparticle concentration slope. Mathematical modeling using finite elements (FEM) protocol for the properties of short MI elements confirmed the results and highlighted the non -monotonic contribution of high -concentration composites to the MI responses.

Одной из основных проблем трансплантологии и тканевой инженерии, в том числе в области хирургической стоматологии, является выбор подходящего нетоксичного и неиммуногененого матрикса-носителя для закрепления на нем живых клеток. В частности, для этих целей представляют большой интерес материалы на основе коллагена, обладающие высокой прочностью и биосовместимостью (с определенным уровнем устойчивости к биодеградации).

Short-range order in soft magnetic FeGa alloys containing from 3 to 25 at

The magnetization distribution in a single-crystalline silicon iron after quenching in the paramagnetic state and after annealing in the ferromagnetic state has been determined by Mössbauer spectroscopy. The specimens containing 5, 6, and 8 at

Abstract—The atomic structure of single-crystal samples of soft-magnetic Fe–9 at

The purpose of this work is to establish the influence of the nature of solid alginate gels (alginic acid, AAG; calcium alginate, CAG) and the conditions of methylene blue (MB) introduction to alginate matrices upon its release into aqueous media. MB is an active photosensitizer, which is used in the photodynamic therapy of tumors and purulent wounds. Solid alginate gels based on AAG and CAG were obtained by adding hydrochloric acid and calcium chloride to sodium alginate. The dye was introduced into the matrix either at the stage of gelation or by immersing the gel in an aqueous solution of the dye. It has been shown that the strength of the dye’s attachment to AAG is higher than that of CAG, which leads to a higher rate of MB release from CAG into aqueous media. It has also been shown that, when introduced at the stage of gel formation, MB is released into both the water and buffer solutions. When MB is introduced by gel immersion into an MB solution, the dye may be released only into salt solutions. An alginate gel with immobilized MB can be used as a solid photosensitizing system with the controlled release of the photoactive agent into the wound cavity for photodynamic treatment.

Биоматериалы на основе коллагена и перикарда (наружная соединительнотканная оболочка сердца) находят большое применение во многих областях медицины, реконструктивной и пластической хирургии, в том числе при замене сердечных клапанов [1, 2].

The influence of amphiphilic polymers (APs): poly-N-vinylpyrrolidone, polyethylene glycol and pluronics F127, F108, as well as sodium alginate (SA) on the activity of methylene blue (MB) in the photogeneration of singlet oxygen 1 О 2 , specifically, in a model photooxidation reaction of tryptophan in water was studied. It was shown that in the presence of all the above-mentioned AP, an increase in the effective rate constant ( k eff ) of tryptophan photooxidation is observed. It was suggested that the observed effect is associated with the interaction of MB with APs, which leads to disaggregation of dye associates. Such disaggregation leads to an increase in the optical density and intensity of MB luminescence. It was also shown that the photocatalytic activity of MB decreases by a factor of 1.5–3.5 in the presence of SA, which is due to the ionic interaction of the cationic MB with polyanionic SA. The interaction of MB with polysaccharide is confirmed by changes in the absorption and fluorescence spectra of the dye. The introduction of APs into a solution containing MB and SA prevents the interaction between MB and polysaccharide, which leads to an increase in the k eff values of tryptophan photooxidation in the presence of MB-AP-SA system, as well as to an increase in the optical density and fluorescence intensity of MB when AP and SA are added. The existence of weak interactions between the hydrophobic groups of MB molecules and the AP (polyvinylpyrrolidone) is also evidenced by the data obtained through 1 H-NMR spectroscopy and the degree of MB fluorescence anisotropy. The AFM method shows the change in the surface structure of a thin film obtained by evaporating an aqueous solution of MB-F108-SA compared to the corresponding structure of a film obtained by evaporating an aqueous solution of MB-SA. MB-AP and MB-AP-SA systems may be promising for practical application in the aPDT treatment of chronic microbial superficial infections.

A nitrogen-containing additive MD-3 employed previously in steel phosphating was used to improve the technological properties of magnetite coatings (MCs) formed on low-carbon steel from a dilute solution of ammonium nitrate proposed as an alternative to environmentally polluted and energy-expensive alkaline bluing method. We showed that an increase in duration of the oxidation from 1 to 6 h linearly thickens the MСs in the presence of MD-3 without an increase in the size of the poorly adhered area of the coating. The flicker-noise spectroscopy study of the MC structure showed that MD-3 makes the surface smooth and more uniform. An increase in oxidation time also increases the homogeneity of MCs, although not as much as in the previous case. The corrosion tests according to the Akimov method and in a salt spray chamber correlate well with each other. The best results were obtained for MCs prepared in a solution of 20 g/L NH 4 NO 3 + 0.08 g/L MD-3 (85°C, 4 h) after passivation treatment in a solution of IFKhAN-39U.

Co-based rapidly quenched amorphous ribbons are soft ferromagnets with well-adjustable functional properties. Their effective magnetic anisotropy and magnetization processes depend on the preparation conditions and geometrical parameters. It was found that giant magnetoimpedance effect (MI) for the FeCoCrSiB ribbons without heat treatments after relaxation annealing and after stress annealing at 350 ∘ C shows critical dependence on the value of the demagnetizing factor. The range of FeCoCrSiB ribbons lengths with a significant change in properties is considered in a comparative analysis of the experimental results and model calculations. Quantitative analysis of the contribution of the demagnetizing fields and surface magnetic charges are discussed as the main mechanism for reducing the GMI properties of amorphous ribbons. These data are important for the development of the ribbon-based devices for practical applications of microelectronics.

Water-insoluble photosensitizing (PS) systems active in the generation of singlet 1 O 2 oxygen are obtained by immobilizing fluorinated tetraphenylporphyrin (FTPP) from a solution in acetone on films of polyelectrolyte complexes based on sodium alginate (SA) and chitosan (CT), and on solid water-insoluble gels of alginate and chitosan. The obtained polymer PS systems are used to establish the intensity of the photoluminescence of singlet oxygen in D 2 O and the activity of the photocatalytic oxidation of tryptophan in water. It is shown that the photocatalytic activity in the tryptophan oxidation of fluorinated tetraphenylporphyrin immobilized on a SA–CT polyelectrolyte complex and alginate solid gel is higher than that of FTPP immobilized on chitosan solid gel. Spectral-luminescent properties of polysaccharide–FTPP systems and the surface structure of carriers are studied via atomic force microscopy to determine the mechanism of the increase in porphyrin activity when it is fixed on alginate-containing carriers. It is suggested that aspects of the supramolecular structure of solid gels are responsible for the increase in the photocatalytic activity of FTPP upon immobilization on alginate-containing polysaccharide systems.

The influence of chitosan (CS) and amphiphilic polymers (AP: pluronic F108 and polyvinylpyrrolidone (PVP)) on the photocatalytic activity of rose bengal (RB) in a model reaction of tryptophan photo-oxidation in phosphate-buffered saline (PBS) was studied. It was shown that in the presence of CS, the effective rate constant keff of tryptophan photo-oxidation catalyzed by RB in PBS solution decreases by a factor of two. This is due to the ionic interaction of the RB with the chitosan. Rose bengal in a slightly acidic environment (pH 4.5) passes into a neutral lactone form, which sharply reduces the photosensitizing properties of the dye. It was demonstrated that the introduction of AP into a solution containing RB and CS prevents direct interaction between RB and CS. This is evidenced by the presence of photocatalytic activity of the dye in the RB-AP-CS systems, as well as bathochromic shifts of the main absorption bands of the dye, and an increase in the optical density and luminescence intensity of the RB when AP is introduced into a buffer solution containing RB and chitosan. The presence of RB-CS and RB-AP interaction in aqueous and PBS media is confirmed by the increase in the degree of fluorescence anisotropy (r) of these binary systems. In an aqueous solution, the value of r for the RB-F108-CS system decreases by a factor of 3.5 (compared to the value of r for the RB-CS system), which is associated with the localization of the dye in pluronic micelles. In PBS, the fluorescence anisotropy is practically the same for all systems, which is related to the stability of the dye structure in this medium. The presence of interaction between RB and AP in aqueous solutions was confirmed by the proton NMR method. In addition, the formation of RB-F108 macromolecular complexes, which form associates during solution concentration (in particular, during evaporation), was shown by AFM. Such RB-AP-CS systems may be promising for practical application in the treatment of local foci of infections by aPDT.

The structure, magnetic, and magnetoimpedance properties of Fe3Co67Cr3Si15B12 amorphous ribbons are studied using samples differing in the geometry, which are prepared by rapid quenching of the melt on a rotating wheel. The comparative analysis is performed for the as-quenched ribbons without additional treatments (A) and after relaxation annealing at 350°C (B) or thermomechanical treatment at 350°C under a specific load of 230 MPa (C). The selected treatments A and B correspond to the longitudinal magnetic anisotropy; in the case of annealed samples, the level of residual stresses is lower. Treatment C leads to the formation of transverse uniaxial magnetic anisotropy and record high sensitivity of giant magnetoimpedance effect (~200%/Oe) to the external magnetic field in the range of low fields ~2–3 Oe.

In this paper, we propose a facile approach to the management of graphene oxide (GO) chemistry via its synthesis using KMnO4/K2Cr2O7 oxidizing agents at different ratios. Using Fourier Transformed Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, and X-ray Absorption Spectroscopy, we show that the number of basal-plane and edge-located oxygenic groups can be controllably tuned by altering the KMnO4/K2Cr2O7 ratio. The linear two-fold reduction in the number of the hydroxyls and epoxides with the simultaneous three-fold rise in the content of carbonyls and carboxyls is indicated upon the transition from KMnO4 to K2Cr2O7 as a predominant oxidizing agent. The effect of the oxidation mixture’s composition on the structure of the synthesized GOs is also comprehensively studied by means of X-ray diffraction, Raman spectroscopy, transmission electron microscopy, atomic-force microscopy, optical microscopy, and the laser diffraction method. The nanoscale corrugation of the GO platelets with the increase of the K2Cr2O7 content is signified, whereas the 10–100 μm lateral size, lamellar, and defect-free structure is demonstrated for all of the synthesized GOs regardless of the KMnO4/K2Cr2O7 ratio. The proposed method for the synthesis of GO with the desired chemistry opens up new horizons for the development of graphene-based materials with tunable functional properties.