STUDIES ON PYRAZINE DERIVATIVES. XL. SYNTHESIS,REACTIVITY, AND TUBERCULOSTATIC ACTIVITY OF 4-HYDROXYALKYL-5-PYRAZINYL4H-[1,2,4]-TRIAZOLE-3-THIONES

2,2′-Sulfinyl-bis(4-methyl phenol) 3 and it's thio derivative have been synthesized in this work. The reduction process of sulfoxide 3 to its thio derivative 5 was accomplished in the presence of Zn/AcOH/SiO₂, under microwave irradiation. The structures have been confirmed by spectroscopic (IR, ¹HNMR, ¹³CNMR) and single crystal x-ray diffraction methods. 2,2′-Sulfinyl-bis(4-methyl phenol) 3 crystallizes in the space group Cc of the monoclinic system with four molecules in the unit cell of dimensions a = 11.425(2) Å, b = 13.530(2) Å, c = 9.5215(17) Å, β = 117.289(4) Å, and 2,2′-thio-bis(4-methyl phenol) 5 crystallizes in the space group P 2₁2₁2₁ of the orthorhombic system with four molecules in the unit cell of dimensions a = 9.021(1) Å, b = 10.523(2) Å, c = 13.607(2) Å, α = 90. The structures have been refined to final values for the crystallographic R factor of 0.0189(3) and 0.0248(5) based on 2999 and 3720 observed independent reflections respectively.     

On extremal sizes of locally k-tree graphs

A graph G is a locally k-tree graph if for any vertex v the subgraph induced by the neighbours of v is a k-tree, k ⩾ 0, where 0-tree is an edgeless graph, 1-tree is a tree. We characterize the minimum-size locally k-trees with n vertices. The minimum-size connected locally k-trees are simply (k + 1)-trees. For k ⩾ 1, we construct locally k-trees which are maximal with respect to the spanning subgraph relation. Consequently, the number of edges in an n-vertex locally k-tree graph is between Ω(n) and O(n ²), where both bounds are asymptotically tight. In contrast, the number of edges in an n-vertex k-tree is always linear in n.     

The Bishop–Phelps–Bollobás and approximate hyperplane series properties

We study the Bishop–Phelps–Bollobás property for operators between Banach spaces. Sufficient conditions are given for generalized direct sums of Banach spaces with respect to a uniformly monotone Banach sequence lattice to have the approximate hyperplane series property. This result implies that Bishop–Phelps–Bollobás theorem holds for operators from ${?}_1$ into such direct sums of Banach spaces. We also show that the direct sum of two spaces with the approximate hyperplane series property has such property whenever the norm of the direct sum is absolute.     

Topological Ergodicity of Real Cocycles over Minimal Rotations

 We prove that for each minimal rotation on a compact metric group and each topological cocycle , either φ is a topological coboundary, or is topologically ergodic, or the partition into orbits is the decomposition of into minimal components. As an application, we generalize a result by Glasner and show that if is a minimal topologically weakly mixing flow, then whenever φ is universally ergodic the minimal map

Application of Voltammetric Method of Total Chromium Determination in the Presence of Cupferron for Selective Determination of Cr(VI) in Water Samples

A voltammetric method of Cr(VI) determination in a flow system based on the combination of selective accumulation of the product of Cr(VI) reduction on hanging mercury drop electrode and a very sensitive method of chromium determination in the presence of cupferron previously described is proposed. The calibration graphs were linear from 3 × 10⁻⁹ to 3 × 10⁻⁸ and from 5 × 10⁻¹⁰ to 5 × 10⁻⁹ mol L⁻¹ for accumulation times of 120 and 600 s, respectively. The detection limit for the accumulation time of 600 s was 9 × 10⁻¹¹ mol L⁻¹. The relative standard deviation was 5.1% (n = 5) for Cr(VI) concentration 1 × 10⁻⁸ mol L⁻¹ and the accumulation time of 120 s. The influence of foreign ions commonly present in water samples is presented. The validation of the method was made by studying the recovery of Cr(VI) from spiked natural water samples.     

Selective method for the determination of gold by anodic stripping voltammetry

A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au³⁺ reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5×10^–8 to 1×10^–6 mol/l. The relative standard deviation for 2×10^-7 mol/l HAuCl₄ was 4.2% (n=5). The detection limit was 4×10^-9 mol/l. The accuracy of the method was verified by the determination of gold in reference materials.     

Thin-Layer Chromatographic and Polarimetric Investigation of the Oscillatory In-Vitro Chiral Inversion of S-(+)-Ketoprofen

JPC – Journal of Planar Chromatography – Modern TLC - Our earlier thin-layer chromatographic and polarimetric investigations enabled discovery of the spontaneous in-vitro oscillatory...     

Isotherm equations for adsorption on heterogeneous microporous solids

The overall isotherm equations have been derived for adsorption from gaseous and liquid phases on heterogeneous microporous solids by solvingStoeckli's integral equation. In this integral theDublin-Radushkevich equation is used to describe the local adsorption on micropores having identical shape and dimensions. The above integral has been solved for different types of distribution functions characterizing heterogeneity of microporous structure of the solids.

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Adsorptionsisothermen für heterogene mikroporöse Feststoffe

Zusammenfassung Es wurden Isothermengleichungen für die Adsorption aus Gas- oder Flüssigphasen an heterogenen mikroporösen Feststoffen mittels der Lösung vonStoeckli's Integralgleichung abgeleitet. In diesem Integral wurde dieDubinin-Radushkevich-Gleichung für die Beschreibung der lokalen Adsorption an Mikroporen mit identem Umriß und identer Größe benutzt. Das oben erwähnte Integral wurde für verschiedene Typen von Verteilungsfunktionen, die die Heterogenität der mikroporösen Strukturen von Festkörpern charakterisieren, gelöst.