From magnets to metals: the response of tetragonal bisdiselenazolyl radicals to pressure

The bromo-substituted bisdiselenazolyl radical 4b (R(1) = Et, R(2) = Br) is isostructural with the corresponding chloro-derivative 4a (R(1) = Et, R(2) = Cl), both belonging to the tetragonal space group P(4)2(1)m and consisting of slipped π-stack arrays of undimerized radicals. Variable temperature, ambient pressure conductivity measurements indicate a similar room temperature conductivity near 10(-4) S cm(-1) for the two compounds, but 4b displays a slightly higher thermal activation energy E(act) (0.23 eV) than 4a (0.19 eV). Like 4a, radical 4b behaves as a bulk ferromagnet with an ordering temperature of T(C) = 17.5 K. The coercive field H(c) (at 2 K) of 1600 Oe for 4b is, however, significantly greater than that observed for 4a (1370 Oe). High pressure (0-15 GPa) structural studies on both compounds have shown that compression reduces the degree of slippage of the π-stacks, which gives rise to changes in the magnetic and conductive properties of the radicals. Relatively mild loadings (<2 GPa) cause an increase in T(C) for both compounds, that of 4b reaching a maximum value of 24 K; further compression to 5 GPa leads to a decrease in T(C) and loss of magnetization. Variable temperature and pressure conductivity measurements indicate a decrease in E(act) with increasing pressure, with eventual conversion of both compounds from a Mott insulating state to one displaying weakly metallic behavior in the region of 7 GPa (for 4a) and 9 GPa (for 4b).     

A transparent photo-responsive organogel based on a glycoluril supergelator

The synthesis of an azo-benzene glycoluril supergelator is reported. The control over the gel/sol state can be accomplished by irradiation and heat, but also (in a unidirectional sense) by incorporation of the glycoluril into a more stable supramolecular assembly.     

Development of a dispersive liquid–liquid microextraction method for the determination of fluoroquinolones in chicken liver by high performance liquid chromatography

A simple and cost effective sample pre-treatment method, dispersive liquid–liquid microextraction (DLLME), has been developed for the extraction of six fluoroquinolones (FQs) from chicken liver samples. Clean DLLME extracts were analyzed for fluoroquinolones using liquid chromatography with diode array detection (LC-DAD). Parameters such as type and volume of disperser solvent, type and volume of extraction solvent, concentration and composition of phosphoric acid in the disperser solvent and pH were optimized. Linearity in the concentration range of 30–500 μg kg⁻¹ was obtained with regression coefficients ranging from 0.9945 to 0.9974. Intra-day repeatability expressed as % RSD was between 4 and 7%. The recoveries determined in spiked blank chicken livers at three concentration levels (i.e. 50, 100 and 300 μg kg⁻¹) ranged from 83 to 102%. LODs were between 5 and 19 μg kg⁻¹ while LOQs ranged between 23 and 62 μg kg⁻¹. All of the eight chicken liver samples obtained from the local supermarkets were found to contain at least one type of fluoroquinolone with enrofloxacin being the most commonly detected. Only one sample had four fluoroquinolone antibiotics (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin). Norfloxacin which is unlicensed for use in South Africa was also detected in three of the eight chicken liver samples analyzed. The concentration levels of all FQs antibiotics in eight samples ranged from 8.8 to 35.3 μg kg⁻¹, values which are lower than the South African stipulated maximum residue limits (MRL).     

Elektrometrische Untersuchungen über die Komplexbildung von La(III) mit 3.5-Dinitrosalicylsäure

Zusammenfassung Die Komplexbildung zwischen La(III) und 3.5-Dinitrosalicylsäure in 0.1m-KNO₃ wurde potentiometrisch und konduktometrisch untersucht. Wir erforschten die Bildung von 11- und 12-Komplexen oberhalb pH 3.5. Der 11-Komplex bildet sich in Lösung, während der 12-Komplex ausfällt. Die Stabilitätskonstante des 11-Komplexes wurde durch Anwendung der vonCalvin undMelchior erweiterten Methode vonBjerrum bestimmt. Für logK fand man Werte von 4.92, 5.00 und 5.12 bei 25°, 30°, beziehungsweise 35° C. Die Werte für F, H und S wurden für 30° C berechnet und bestimmt zu–6.97 Kcal/Mol,–7.49 Kcal/Mol, beziehungsweise –1.70 cal/Mol/Grad.

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Electromeric studies on the complex formation between La(III) and 3.5-dinitrosalicylic acid

The complex formation between La(III) and 3.5-dinitrosalicylic acid in 0.1m-KNO₃ medium has been studied potentiometrically and conductometrically. The formation of 11 and 12 complexes beyond 3.5 pH was investigated. 11 complex is formed in solution while 12 complex is precipitated. The stability constant of the 11 complex was determined by applying the Calvin and Melchior's extension ofBjerrum's method. The logK values have been found to be 4.92, 5.00, and 5.12 at 25, 30 and 35°C, respectively. The values of F, H, and S have also been evaluated at 30°C and found to be–6.97 Kcal/mole,–7.49 Kcal/mole, and–1.70 Kcal/mole/degree, respectively.

     

Radiation stability study on cerium loaded iron phosphate glasses by ion irradiation method

Journal of Radioanalytical and Nuclear Chemistry - To study radiation stability of iron phosphate glasses, cerium is used as surrogate of actinides. Cerium doped iron phosphate glasses have been...     

Mapping Ideals to Sublocales

Applied Categorical Structures - A map that is well known in C(X), dating back to the work of L. Gillman, M. Henriksen and M. Jerison in 1954, is here used to construct a morphism of quantales,...     

Isocompactness in the Category of Locales

We study isocompactness in Loc defined, exactly as in Top, by requiring that every countably compact closed sublocale be compact. This is a genuine extension of the same-named topological concept since every Boolean (or, even more emphatically, every paracompact) locale is isocompact. A slightly stronger variant is defined by decreeing that the closure of every complemented countably compact sublocale be compact. Dropping the adjective “complemented” yields a formally even stronger property, which we show to be preserved by finite products. Metrizable locales (or, more generally, perfectly normal locales) do not distinguish between the three variants of isocompactness. Each of the stronger variants of isocompactness travels across a proper map of locales, and in the opposite direction if the map is a surjection in Loc.     

Spin-deposited nanocrystalline lithium ferrite thin films: Fabrication and characterization

Thin films of lithium ferrite (with general composition Li_0.5Fe_2.5O₄) were fabricated at low temperatures (up to 650 °C) by citrate-route using spin-deposition technique. Deposited films consisted of nanometer-sized grains as evidenced by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. XRD patterns for annealed films showed broad peaks exhibiting a spinel phase. Size of nanocrystallites is estimated to be 3-7 nm using Scherrer's equation. Average grain size ∼8.5 nm is observed from TEM images of films annealed at 650 °C. Scanning electron micrographs show the formation of spherical aggregates of around 130 nm in diameter. The AFM analysis clearly evidenced the development of nanograins even at low (∼500 °C) annealing temperatures. Significant decrease in complex dielectric permittivity (∈′ − j∈″) with frequency is observed in the low frequency (100 Hz-1 MHz) as well as in X-band microwave frequency (8-12 GHz) region. ∈′ is found to be in the range of 15.7-33.9 in low frequency region, whereas in X-band microwave frequency region, it is found to lie between 3.9 and 4.9. Similarly, ∈″ is found to be 0.16-5.9 in the low frequency region, and 0.002-0.024 in the X-band microwave frequency region. Room temperature dc resistivity of these films is estimated to lie in the range of 10⁶-10⁸ Ω cm. These results strongly suggest that citrate-route processed nanocrystalline lithium ferrite thin films are promising candidates for monolithic microwave integrated circuits (MMICs).     

Amenable and Locally Amenable Algebraic Frames

Order - We say a prime element of an algebraic frame is amenable if it comparable to every compact element. If every prime element of an algebraic frame L is amenable, we say L is an amenable...