2,2‐Bis(methoxy‐NNO‐azoxy)ethyl Derivatives of 4,8‐Dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine: The Synthesis and X‐ray Investigation

The first synthesis of 4,8‐dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine bearing 2,2‐bis(methoxy‐NNO‐azoxy)ethyl groups has been developed. These compounds are obtained by aza‐Michael reaction of 1,1‐bis(methoxy‐NNO‐azoxy)ethene or its equivalents, such as 2,2‐bis(methoxy‐NNO‐azoxy)ethanol derivatives, with 4,8‐dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine.     

Metric betweenness,Ptolemaic spaces,and isometric embeddings of pretangent spaces in ℝ

We study some properties of pretangent spaces describing the infinitesimal geometry of general metric spaces. The necessary and sufficient conditions characterizing Ptolemaic pretangent spaces and pretangent spaces, where every three points are situated “on a single straight line,” are found. As a corollary, we obtain a criterion of embeddability of pretangent spaces into the set ℝ of real numbers endowed by the natural metric.     

Optical properties and electronic structure of methylammonium iodocuprate as an X-ray scintillator

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Polyhydrazide-Based Organic Nanotubes as Efficient and Selective Artificial Iodide Channels

Reported herein is a series of pore-containing polymeric nanotubes based on a hydrogen-bonded hydrazide backbone. Nanotubes of suitable lengths, possessing a hollow cavity of about a 6.5 Å diameter, mediate highly efficient transport of diverse types of anions, rather than cations, across lipid membranes. The reported polymer channel, having an average molecular weight of 18.2 kDa and 3.6 nm in helical height, exhibits the highest anion-transport activities for iodide (EC₅₀=0.042 μm or 0.028 mol % relative to lipid), whcih is transported 10 times more efficiently than chlorides (EC₅₀=0.47 μm ). Notably, even in cholesterol-rich environment, iodide transport activity remains high with an EC₅₀ of 0.37 μm . Molecular dynamics simulation studies confirm that the channel is highly selective for anions and that such anion selectivity arises from a positive electrostatic potential of the central lumen rendered by the interior-pointing methyl groups.     

Adaptive stabilized interferometer with laser diode

We describe a diode laser interferometer with an electronic adaptive system of fringe pattern stabilization and vibrations suppression. The interferometer allows to obtain up to four high-quality images with relative phase shifts. Also an algorithm for fringe pattern processing has been proposed.     

Quantum-chemical study of potassium and ammonium hexafluorozirconates

A number of fluorozirconate clusters serving as structural models for K₂ZrF₆ and (NH₄)₂ZrF₆ crystals were investigated by the Hartree-Fock ab initio method. Based on the results of quantum-chemical calculations it is shown that the differences in the structure of these compounds and in the behavior of the temperature dependence of the second moment of the ¹⁹F NMR spectra are due to differences in the binding between the cation and anion sublattices. A mechanism responsible for ionic mobility is suggested.Original Russian Text Copyright © 2004 by E. I. Voit, A. V. Voit, V. Ya. Kavun, and V. I. SergienkoTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 644–650, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Internal Mobility, Phase Transition, and Ionic Conductivity in Thallium(I) Heptafluorodiantimonate(III)

The internal mobility of fluorine ions and the electrophysical properties of TlSb₂F₇ were studied by the ¹⁹F NMR method and impedance spectroscopy. Modes of ionic motions in the fluoride subsystem were determined in the temperature range 213–430 K. A structural phase transition is found to occur at 400 K, resulting in the TlSb₂F₇ modification characterized by high ionic (superionic) conductivity in the temperature range of 400–430 K 2.5·10^-3 S/cm at 430 K).     

A regularized point cloud registration approach for orthogonal transformations

An important part of the well-known iterative closest point algorithm (ICP) is the variational problem. Several variants of the variational problem are known, such as point-to-point, point-to-plane, generalized ICP, and normal ICP (NICP). This paper proposes a closed-form exact solution for orthogonal registration of point clouds based on the generalized point-to-point ICP algorithm. We use points and normal vectors to align 3D point clouds, while the common point-to-point approach uses only the coordinates of points. The paper also presents a closed-form approximate solution to the variational problem of the NICP. In addition, the paper introduces a regularization approach and proposes reliable algorithms for solving variational problems using closed-form solutions. The performance of the algorithms is compared with that of common algorithms for solving variational problems of the ICP algorithm. The proposed paper is significantly extended version of Makovetskii et al. (CCIS 1090, 217–231, 2019).

     

Dynamics of hexafluoroanions in complexes of tin and titanium with mixed alkaline metal cations

Dynamics of anions in LiMSnF₆ and NaMTiF₆ (M=K, Rb, Cs) are studied in the temperature range 170–400 (470) K. Types of internal mobility of anions are established, anion activation energies are estimated, and effects on the activation barrier are discussed. Institute of Chemistry, Far East Branch, Russian Academy of Sciences. Translated fromzhurnal Strukturnoi Khimii, Vol. 39, No. 1, pp. 61–65, January–February, 1998.     

Estimation of uncertainty in electrochemical amperometric measurement of dissolved oxygen concentration

A procedure for the estimation of measurement uncertainty of dissolved oxygen (DO) concentration measurement based on the ISO approach is presented. It is based on a mathematical model that involves 14 input parameters. The uncertainty of DO concentration strongly depends on changes in experimental details (temperature difference between calibration and measurement, the time interval between calibration and measurement, etc.). The relative measurement uncertainty is, however, practically independent of the DO concentration itself. The uncertainty is the lowest if the calibration and the measurement are done at the same temperature and on the same day. A calculation tool is provided (in the form of a GUM Workbench file) for practitioners that can be used for uncertainty calculation of DO concentrations at very different experimental conditions.Electronic Supplementary Material The uncertainty calculation example is available as a GUM Workbench calculation file C_O2_meas.smu (GUM Workbench ver. 1.3.3, Metrodata GmbH) together with its data file Input_values.xls (MS Excel 97). For those users who do not have GUM Workbench, the full report of the GUM Workbench calculation is available as a PDF file C_O2_meas.pdf. This material is available via the Internet at .