NiH3IO6 · 6H2O — Kristallstruktur und Schwingungsspektren

NiH₃IO₆ · 6 H₂O — Crystal Structures and Vibrational Spectra The crystal structure of NiH₃IO₆ · 6 H₂O has been determined by X-ray single-crystal diffraction (Pc, Z = 2, a = 516.74(9), b = 981.5(2), c = 1052.5(2) pm, β = 116.496(8)°) on the basis of 4169 unique reflections (R = 1.96%). The structure is built up of distorted Ni(H₂O)₆²⁺ and H₃IO₆^2? octahedra linked by hydrogen bonding. IR and Raman spectra of both the title compound and isostructural MgH₃IO₆ · 6 H₂O as well as of deuterated specimens are given. There are up to 14 different OH(OD) modes in the spectra of isotopically dilute samples due to the 15 different hydrogen positions of the structure. The internal modes of the meridional H₃IO₆^2? ions (pseudo C_2v symmetry) are discussed with respect to that double T-shaped entity, which gives rise to only two instead of 3I? O, I? O(H), and OH stretches in the IR and Raman spectra, i.e. the same as for facial (C_3v) structured ions.     

über den Unterschied im Thermischen Verhalten von Gewöhnlichen und Deuterierten Hydraten Anorganischer Verbindungen I

Zusammenfassung In der vorliegenden Arbeit wird der Isotopeneffekt als Einflu\faktor nicht nur beim thermischen Dehydratationsproze\, sondern auch beim thermischen Zersetzungsvorgang der aus gewöhnlichen und deuterierten Hydraten erhaltenen wasserfreien Verbindungen bewiesen. Diese Untersuchungen werden mit der Hilfe der DTA- und DSC-Methode durchgeführt. Die Unterschiede in der thermischen StabilitÄt der Hydrate werden durchT _Deh,T _Ph, H _Deh und kinetische Parameter (E ^* undA) charakterisiert. Es werden durch EM-Aufnahmen die verschiedene KristallinitÄt und Partikelgrö\e der Oxide als Endprodukte der thermischen Zersetzung von gewöhnlichen und deuterierten Nitrat-Hydraten festgestellt.

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In the present work the isotope effect has been studied by DTA and DSC technique not only in the thermal dehydration process but also in the thermal decomposition of water-free compounds formed from normal and deuterated hydrates. The differences in the thermal stability of the hydrates were characterized byT _Deh,T _Ph, H _Deh and kinetic parameters (E ^* andA). The degree of crystallinity and particle size of the oxides formed as products of thermal decomposition of normal and deuterated hydrates of nitrates have been determined by electron microscopy.

     

Effect of the Structure of 1- and 3-Methylpyrimidin-4-ones on the Rate of Nucleophilic Substitution of the 2-Methylsylfanyl Group

Rate constants for substitution of the 2-methylsulfanyl group in 1- and 3-methyl-2-methylsulfanyl-pyrimidin-4-ones and their 5-fluoro analogs were measured in the reaction with butylamine, alkaline hydrolysis, and methanolysis. The rate of substitution in 1-methyl isomers having a zwitterionic structure is greater by a factor of ~2 than the rate of substitution in 3-methyl isomers with conjugated double bonds in the ring. The presence of a fluorine atom in position 5 accelerates nucleophilic substitution in 1-methyl isomers, while 5-fluoro-3-methyl-2-methylsulfanylpyrimidin-4-ones react at a lower rate than their 5-unsubstituted analogs. According to the NMR data, the reactions involve formation of a tetrahedral intermediate. Anchimeric effect of the methyl group on N¹ hampersattack by basic reagent on the C⁶atom.     

Polarization holography for measuring photoinduced optical anisotropy

A new experimental method for measuring the optical anisotropy induced at photochemical reactions is proposed. The method is based on polarization holography and is a zero-background high sensitive technique. It is used to measure the molecular dichroism of fluorescein and the birefrigence induced at the additional photopolymerization of PMMA.     

Justification and numerical realization of the uniform method for finding point estimates of interval elicited scaling constants

The form of the utility function over multi-dimensional consequences depends on the point estimates of the scaling constants. Fuzzy rational decision makers elicit those in the form of uncertainty intervals. The paper proposes an analytical justification and a numerical realization of the uniform method that finds point estimates of interval scaling constants. The main assumption of the technique is that constants are uniformly distributed in their uncertainty intervals. The density of the constants’ sum is constructed using preliminarily chosen knots. A new numerical procedure to calculate the I type error p _value of a two-tail test for singularity of the constants’ sum is proposed. All numerical procedures are embodied into program functions. The application of the method is demonstrated in examples. The connection between precision and time for analysis is investigated. Comparison of the analytical uniform method and an earlier proposed simulation realization is also conducted.     

A survey on proper codes

The performance of a linear t-error correcting code over a q-ary symmetric memoryless channel with symbol error probability ε is characterized by the probability that a transmission error will remain undetected. This probability is a function of ε involving the code weight distribution and the weight distribution of the cosets of minimum weight at most t. When the undetectable error probability is an increasing function of ε, the code is called t-proper.

The paper presents sufficient conditions for t-properness and a list of codes known to be proper, many of which have been studied by these sufficient conditions. Special attention is paid to error detecting codes of interest in modern communication.     

Study on the Kinetics of Non-isothermal Dehydration of Alkaline Earth Metal Selenites

Summary. The dehydration kinetics of crystallohydrates of beryllium, magnesium and calcium selenites were studied under non-isothermal conditions. The values of the activation energy of dehydration, the pre-exponential factor in Arrhenius equation and the change of entropy for the formation of the activated complex were calculated using the calculation procedure of Coats and Redfern. Thermal stability and activation energy of dehydration of the crystallohydrates were found to increase by the same order. The relationships observed were interpreted using Klopman’s generalized perturbation theory of chemical reactivity. The same theory was applied to explain the differences in the IR spectra of the selenite crystallohydrates studied.     

Polarization characteristics of volume holograms in Bi12SiO20

The polarization sensitivity of holographic recording in Bi₁₂SiO₂₀ is experimentally studied. The shape of the obtained curves depends on the magnitude of the applied electric field, crystal thickness, spatial frequency of the recorded gratings, and the order of diffraction.     

The physical solution of the inverse vibrational problem: III. An application of intensity data for an unambiguous assignment

The ambiguity of the solution of the inverse vibrational problem is related to the results of the intensity calculations for two isotopic molecular species. A relationship between the derivatives ?μ_i/?Q_j for both molecules is derived. The theory is applied to the case of the isotopic pair HCN-DCN. Comparison of the solutions obtained separately from the vibrational data and the intensity data allowed us to distinguish the physical solution.