Photoelectric properties of MISM phthalocyanine structure

Langmuir-Blodgett films have been prepared from copper tetra-4-t-butylphthalocyanine. A voltage dependence of capacitance can be attributed to the presence of a Schottky depletion layer. The barrier potential was determined as l·4eV, and the carrier concentration about 10²⁴m^?3     

A New and Fast HPLC Method for Determination of Rutin, Troxerutin, Diosmin and Hesperidin in Food Supplements Using Fused-Core Column Technology

A new and fast high-performance liquid chromatography (HPLC) method using fused-core column for separation of rutin, troxerutin, diosmin, and hesperidin has been developed and used for determination of these flavonoids in food supplements. Efficient separation of flavonoids and internal standard methylparaben was achieved on the fused-core column Ascentis Express RP-Amide (100?×?3.0 mm), particle size 2.7 μm, with mobile phase acetonitrile/water solution of acetic acid pH?3 (30:70, v/v) at a flow rate of 1.0 mL?min^?1 and at temperature 50 °C. The detection wavelengths were set at 283 nm for hesperidin and at 255 nm for rutin, troxerutin, diosmin, and internal standard methylparaben. Under the optimal chromatographic conditions, good linearity with correlation coefficients in the range (r?=?0.9991–0.9998; n?=?7) for all flavonoids was achieved. Commercial samples of food supplements were extracted with 100 % dimethyl sulfoxide using ultrasound bath for 10 min and then diluted to methanol. A 5-μL sample volume of the filtered solution was directly injected into the HPLC system. Accuracy of the method defined as a mean recovery of flavonoids from food supplement matrix was in the range 96.2–104.4 % for all flavonoids. The intraday method precision was satisfactory, and relative standard deviations of sample analysis including preparation and determination of different food supplements were in the range 0.5–3.5 % for all flavonoids. The developed method has shown high sample throughput during sample preparation process, modern separation approach, and short time (5 min) of analysis.     

Dense fine-grained biphasic calcium phosphate (BCP) bioceramics designed by two-step sintering

In this study, dense, fine-grained biphasic calcium phosphate bioceramics were designed via the two-step sintering method. The starting powder was nanosized calcium-deficient hydroxyapatite, whose phase composition, average particle size and morphology were characterized by XRD, FTIR, Raman spectroscopy, laser diffraction and FE-SEM. The phase transformations of the initial powder during heating up to 1200 °C were examined using TG/DSC. At first, conventional sintering was performed and the recorded shrinkage/densification data were used to find out the appropriate experimental conditions for two-step sintering. The obtained results show that two-step sintering yields BCP ceramics, consisting of hydroxyapatite and β-TCP, with full dense, homogeneous structure with average grain size of 375 nm. Furthermore, BCP ceramics obtained by the two-step sintering method exhibit improved mechanical properties, compared to conventionally sintered BCP.     

Cell adhesion on modified polyethylene

Polyethylene (PE) was irradiated with 10 and 63 keV Ar⁺ ions to fluences of 1 × 10¹⁷ to 3 × 10¹⁹ m^–2 and then it was grafted with aminoacid (alanine). The changes of surface polarity, electrical conductivity, and oxygen concentration were examined on pristine, as-irradiated, and irradiated-grafted PE. The in vitro adhesion of mice fibroblasts on the modified PE was evaluated 24 hours after inoculation. It was proved that for the PE irradiated at 10 keV ion energy, the presence of chemically bound alanine increases cell adhesion and its homogenity. For PE irradiated with 63 keV ions, however, the alanine grafting leads to a reduction of the number of adhering cells. It was found that a rising surface polarity increases cell adhesion, but when its value is too high the cell adhesion starts to decrease. No correlation between electrical conductivity and cell adhesion was observed. In general, higher cell adhesion is observed on modified PE in comparison with pristine one.     

Material and Energy Interactions between Milling Bodies,Milled Particles,and Milling Environment

Changes in particle size, surface state, and composition brought about by planetary and vibration milling of silicon and quartz in various permittivity liquids were investigated. Using a variety of spectroscopic techniques (IRS, XPS, and Mössbauer spectroscopy) the changes in quality of the superficial layers of milled particles have been determined. During energy-intensive milling, the material being milled intensively interacts with the media and milling environment. The nature of the interaction and quality of the surface shell covering the milled particles depend on the reactivity and hardness of the interacting solids and of the milling environment. During planetary milling of silicon with tungsten carbide media, the superficial layers are formed by silicon suboxides and silicon oxide. The thickness of the superficial layer and the share of SiO₂ increase with increasing permittivity of liquids. Milling with steel media results in a more complicated composition of the superficial layer. According to Mössbauer spectra, the iron is present in two main forms: as a magnetically ordered form identical with basic material of balls and in a paramagnetic form as a product of a mechanically stimulated surface reaction between Si and Fe. The presence of the superficial layers on the milled particles of silicon and quartz markedly influences the values of the specific surface area. This influence should be taken into consideration when calculating the specific contamination of the milled powder.     

Mechanically Induced Cation Redistribution and Spin Canting in Nickel Ferrite

The structural and magnetic evolution in nickel ferrite (NiFe₂O₄) caused by high-energy milling are investigated by Mössbauer spectroscopy. It is found that the nanostructural state of the milled NiFe₂O₄ is characterized by a reduced concentration of iron ions on tetrahedral sites. The degree of inversion in NiFe₂O₄ is calculated from the subspectral area ratio of both high- and zero-field Mössbauer spectra. Several interesting features are involved in the work, e.g., superparamagnetic relaxation, mechanically induced cation redistribution, and spin-canting effect.     

On decentralized stabilization and structure of linear large scale systems

Connective stabilizability of large-scale systems, which are composed of interconnected subsystems, is considered using decentralized feedback. Both analytical and graph-theoretic conditions are derived directly in terms of the interconnection structure, which ensure that stability of the overall closed-loop system is invariant under the structural perturbations caused by disconnections and reconnections of links among the subsystems. The conditions characterize a large class of decentrally stabilizable systems, which includes all classes of connectively stabilizable interconnected systems considered so far.     

Coupling of diffusion flux and chemical reaction in an asymmetric catalytically active membrane

The behaviour of a catalytically active membrane vectorized by a permanent transversal gradient of catalytic activity has been analysed mathematically. Under the simplifying assumption that the gradient of the catalytic activity profile across the membrane is linear, it is possible to express the steady state concentrations of the reaction components inside the membrane, governed by the diffusion-controlled chemical reaction, by means of tabulated Airy functions. For enzyme-catalysed reactions which follow Michaelis-Menten kinetics, two analytical solutions have been found for high and low substrate concentrations, respectively. If such an asymmetric membrane separates two compartments with the same (and constant) substrate concentrations, it behaves as an active barrier capable of pumping the product against its own concentration gradient. The effects of membrane thickness, slope of the activity profile and diffusion coefficient on the overall rate of product formation and on the pumping efficiency of the membrane are discussed.     

Study of the preparation of ruthenia based catalytic materials by heating their precursors

Thermal behaviour of hydrous ruthenia (RuO₂·nH₂O) and ruthenia containing 10% titania ((RuO₂)_0.9–(TiO₂)_0.1nH₂O) was characterised on heating in air by emanation thermal analysis (ETA), thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA). The anhydrous ruthenia and ruthenia containing 10% titania samples were prepared by heating their hydrous precursors at 500°C in air. The temperature intervals of the samples dehydration and crystallisation were determined. XRD, TEM and surface area measurements were also used for the characterisation of the samples. The ETA results, evaluated by a mathematical model, brought about new information about surface area and microstructure development of the intermediate products of the oxides under in situ conditions of the heating in air. A good agreement between ETA and the results of other methods was obtained. The NO_x reduction by CO was used to test the catalytic properties of these samples.     

A study on the crystallization of amorphous arsenic

The results of DTA analysis of amorphous arsenic in combination with electron microscopical study of the samples through the whole temperature range reveal that no changes of the initial state of the sample occur on heating up to crystallization temperature. Close above this temperature the spontaneous crystallization starts. It differs markedly from the case of glassy materials, like As₂Te₃, in which case at temperatures as low as the transition region T_g the crystallization nuclei of geometrically defined shapes appear and grow into crystalline grains on further heating.