Cu1—xAgxInSe2 Solid Solutions

CuInSe₂, AgInSe₂, ternary compounds and Cu_1—xAg_xInSe₂ solid solutions were synthesized by one-temperature method. The composition and structure of indicated materials were established by chemical and X-ray analysis methods, lattice constants, values of σ positional parameter and bond lengths were also calculated. Temperatures of phase transformations were determined by differential thermal analysis (DTA) method and phase diagram of AgInSe₂-CuInSe₂ system was built which is characterized by small crystallization interval and presence of solid state transformations throughout the concentration interval.     

Study of the Electron Density in an Inductively Coupled Plasma of Fluorine-Hydrogen-Argon Gas Mixture

Plasma Chemistry and Plasma Processing - In this paper, we present the results of non-contact measurements of electron density in an inductively coupled chemically active plasma at a pressure of...     

Peculiarities of the Discharge Formation in a Plasma Accelerator and Structure of a Jet Flowing into Vacuum

Technical Physics - We report on results of investigation into the structure of a plasma jet generated by a coaxial plasma accelerator with conical insert in the discharge formation region. Using...     

An improved in vivo deuterium labeling method for measuring the biosynthetic rate of cytokinins

An improved method for determining the relative biosynthetic rate of isoprenoid cytokinins has been developed. A set of 11 relevant isoprenoid cytokinins, including zeatin isomers, was separated by ultra performance liquid chromatography in less than 6 min. The iP-type cytokinins were observed to give rise to a previously-unknown fragment at m/z 69; we suggest that the diagnostic (204-69) transition can be used to monitor the biosynthetic rate of isopentenyladenine. Furthermore, we found that by treating the cytokinin nucleotides with alkaline phosphatase prior to analysis, the sensitivity of the detection process could be increased. In addition, derivatization (propionylation) improved the ESI-MS response by increasing the analytes' hydrophobicity. Indeed, the ESI-MS response of propionylated isopentenyladenosine was about 34% higher than that of its underivatized counterpart. Moreover, the response of the derivatized zeatin ribosides was about 75% higher than that of underivatized zeatin ribosides. Finally, we created a web-based calculator (IZOTOP) that facilitates MS/MS data processing and offer it freely to the research community.     

Determination of fluoroquinolone antibiotics in wastewater using ultra high‐performance liquid chromatography with mass spectrometry and fluorescence detection

A new ultra HPLC (UHPLC) method using both MS and fluorescence detection (FD) was developed for the determination of five fluoroquinolones in wastewaters. Systematic method development approach was compared with a conventional one. During the systematic approach, a possibility of automatic switching among four independent analytical columns of different chemistries has been used. Acidic as well as basic pH using ACN and methanol as organic modifiers was tested. The best separation of fluoroquinolones was obtained on phenyl analytical column at pH 10.5, which is a completely novel approach for separation of fluoroquinolones. Further, a new SPE procedure was developed for the sample preparation using basic pH as well. The sensitivity and selectivity of FD and MS detection were compared. FD at basic pH 10.5 demonstrated lower sensitivity than at acidic pH, which is conventionally performed. At basic pH, UHPLC‐MS/MS was found about two orders of magnitude more sensitive than FD. Both methods were validated and subsequently UHPLC‐FD method was used for the evaluation of stability of fluoroquinolones. UHPLC‐MS/MS method was used for the analysis of wastewater samples. Norfloxacin and ciprofloxacin were detected in samples of influent and effluent from wastewater treatment plant. Ofloxacin was detected only in influent from wastewater treatment plant.     

Identification of new phase II metabolites of xanthohumol in rat in vivo biotransformation of hop extracts using high-performance liquid chromatography electrospray ionization tandem mass spectrometry

Polyphenolic compounds occurring in hop extracts and their phases I and II metabolites formed during in vivo rat biotransformation have been analyzed using HPLC/MS/MS with electrospray ionization (ESI). Two main groups of polyphenolics are present in the hops, i.e., xanthohumol related compounds and so called α- and β-bitter acids (humulones and lupulones). In our study, hybrid quadrupole-time-of-flight (QqTOF) analyzer is used for the identification of both natural phenolics and their metabolites due to the possibility of accurate mass measurements in full scan and tandem mass spectra supported by MSⁿ data obtained with the ion trap analyzer. Both ESI polarity modes are used for the determination of molecular weights based on [M+H]⁺ and [M−H]⁻ ions in the full scan spectra and the structural information in subsequent tandem mass spectra. The emphasis is given on the elemental composition determination of individual metabolites based on accurate masses typically better than 5 ppm even with the external calibration. Advanced software tools are used for the metabolite identification using the comparison of the blank chromatogram with the real incubation sample together with the software prediction and detection of possible metabolites. Chromatograms of rat incubations are also compared with chromatograms of pure rat feed, rat feed enriched with hop extracts and the placebo experiment. More than ten compounds originating from the hops are identified in rat feces, two of them belong to phase I metabolites and five compounds are phase II metabolites.     

A new [(1R,2R)‐1,2‐diaminocyclohexane]platinum(II) complex: formation by nitrate–acetonitrile ligand exchange

The title compound, cis‐diacetonitrile[(1R,2R)‐1,2‐diaminocyclohexane‐κ²N,N′]platinum(II) dinitrate monohydrate, [Pt(C₂H₃N)₂(C₆H₁₄N₂)](NO₃)₂·H₂O, is a molecular salt of the diaminocyclohexane–Pt complex cation. There are two formula units in the asymmetric unit. Apart from the two charge‐balancing nitrate anions, one neutral molecule of water is present. The components interact via N—H...O and O—H...O hydrogen bonds, resulting in supramolecular chains. The title compound crystallizes only from acetonitrile with residual water, with the acetonitrile coordinating to the molecule of cis‐[Pt(NO₃)₂(DACH)] (DACH is 1,2‐diaminocyclohexane) and the water forming a monohydrate.     

Application of perturbation theory to a mixture of hydrogen atoms and molecules with the Morse intermolecular interaction potential

The thermodynamic parameters of the two-component mixture of hydrogen atoms and molecules are calculated on the basis of perturbation theory with the use of the basic system of hard spheres. To eliminate the nonadditivity of hard sphere diameters and to obtain the best agreement of the calculated thermodynamic parameters with the Monte Carlo data, different schemes of subdivision of the interaction potential of hydrogen atoms and molecules into the basic and perturbing components are investigated.     

Nonideal regimes of deflagration and detonation of black powder

The explosive and deflagration properties of black powder differ significantly from those of modern propellants and compositions based on ammonium nitrate or ammonium perchlorate. Possessing a high combustibility, black powder is capable of maintaining stable combustion at high velocities in various shells, be it steel shells or thin-walled plastic tubes, without experiencing deflagration-to-detonation transition. It is extremely difficult to detonate black powder, even using a powerful booster detonator. The results of numerical simulations of a number of key experiments on the convective combustion and shock initiation of black powder described in the literature are presented. The calculations were performed within the framework of a model developed previously for describing the convective combustion of granulated pyroxylin powders, with small modifications being introduced to allow for the specific properties of black powder. The thermophysical properties of the products of combustion and detonation and the parameters of the equation of state of black powder were determined from thermodynamic calculations. The calculation results were found to be in close agreement with the experimental data. The simulation results were used to analyze the regularities of the wave processes in the system and their relation to the properties of black powder and the experimental conditions. It was demonstrated that the effects observed could be explained by a weak dependence of the burning rate of black powder on the pressure.     

Control variational method approach to bending and contact problems for Gao beam

This paper deals with a nonlinear beam model which was published by D.Y.Gao in 1996. It is considered either pure bending or a unilateral contact with elastic foundation, where the normal compliance condition is employed. Under additional assumptions on data, higher regularity of solution is proved. It enables us to transform the problem into a control variational problem. For basic types of boundary conditions, suitable transformations of the problem are derived. The control variational problem contains a simple linear state problem and it is solved by the conditioned gradient method. Illustrative numerical examples are introduced in order to compare the Gao beam with the classical Euler-Bernoulli beam.