Statistical estimation of the results of differential thermal analysis of cement materials

The paper describes the results of statistical analysis of DTA diagrams. A connection is found between the second and third endothermal effects. An analysis of geometrical characteristics of theT, S andh values of DTA diagrams confirms the absence of reliable connections. The rank correlation coefficients are determined according to Spearman. Non-linear programming is formulated to obtain the kinetic dependencies of the process of hydration of cement studied by DTA.

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Zusammenfassung Es wurden die Ergebnisse von statistischen Analysen der DTA Kurven besprochen, und ein Zusammenhang zwischen dem zweiten und dritten endothermischen Effekt gefunden. Durch Untersuchung der geometrischen Kennzeichen derT, S undh Werte der DTA Diagramme konnten keine verlÄ\lichen ZusammenhÄnge festgestellt werden. Die Koeffizienten der Rangkorrelation wurden nach Spearman bestimmt. Zur KlÄrung der kinetischen ZusammenhÄnge der Zementhydratation durch DTA wurde eine nichtlineare Programmaufgabe formuliert.

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Résumé On décrit les résultats de l'analyse statistique des courbes d'ATD. On a trouvé une connexion entre le second et troisième effet endothermiques. L'analyse des caractéristiques géométriques des effets des valeursT, S eth qui apparaissent sur les courbes d'ATD confirme l'absence de connexions sûres. On a déterminé les coefficients de la corrélation de rang suivant Spearman. On propose un programme non linéaire pour obtenir les dépendances cinétiques du processus d'hydratation du ciment étudié par ATD.

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. . T, S h . . , .

     

Photochemische Reaktionen. 68. Mitteilung. Die Photoisomerisierung von α,β-ungesättigten γ,δ-Epoxyketonen: 9α, 10α- und 9β, 10β-Oxido-3-oxo-17β-acetoxy-Δ4-östren

Irradiation in the n→π* absorption band of the α,β-unsaturated γ,δ-epoxyketone 5 in ethanol at ?65° exclusively afforded the rearranged ene-dione 13 , whereas at + 24° under otherwise unchanged reaction conditions or upon triplet sensitization with Michler's ketone and with acetophenone at + 24° essentially identical mixtures of 13 (major product), 14 , and 15 were obtained. Selective π→π* excitation of 5 at ?78° and + 24° led to similar product patterns. The 9β,10β-epimeric epoxyketone 7 selectively isomerized to 14 and 15 at + 24° and n → π* or π → π* excitation. Neither the epoxyketones 5 and 7 nor the photoproducts 13–15 were photochemically interconverted. In separate photolyses each of the latter gave the double bond isomers 16 , 18 , and 19 , respectively. Cleavage of 13 to the dienone aldehyde 17 competed with the double bond shift ( → 16 ) when photolyzed in alcoholic solvents instead of benzene. The selective transformations 5 → 13 (at ?65° and n → π* excitation) and 7 → 14 + 15 are attributed to stereoelectronic factors facilitating the skeletal rearrangements of the diradicals 53 and 55 , the likely primary photoproducts resulting from epoxide cleavage in the triplet-excited compounds 5 and 7 , via the transition states 54 , 56 , and 57 . The loss of selectivity in product formation from 5 at higher temperature and n → π* excitation or triplet sensitization is explicable in terms of radical dissociation into 58 and 59 increasingly participating at the secondary thermal transformations of 53 . The similar effect of π → π* excitation even at ?78° indicates that some of the π,π* singlet energy may become available as thermal activation energy. It is further suggested that the considerably lesser ring strain in 14 and 15 , as compared with 13 , is responsible that selectivity in product formation from 7 is maintained also at +24° and at π → π* excitation.     

Acid-base interactions and adhesion capacity in the system constituted by an epoxy coating and a metal

Free surface energy and acidity parameter of solid surfaces of polyepoxides used as anticorrosive coatings were measured. Formulations of epoxy resins with various curing agents were studied. The adhesion capacity of epoxy films to various metallic surfaces was evaluated.     

The Mechanism of Low-Temperature Ammonia Oxidation on Metal Oxides According to the Data of Spectrokinetic Measurements

Low temperature ammonia oxidation on MoO₃, Fe₂O₃, Cr₂O₃, and ZnO is studied by the spectrokinetic method. It is shown that the following adsorbed species are intermediates in this reaction: NH₃ and N₂O on Fe₂O₃ and ZnO; NH₃, N₂O, and NO on Cr₂O₃. All of the detected intermediates are used to construct the mechanism of the process. In the framework of the proposed mechanism, stationary and nonstationary spectral and kinetic data are quantitatively processed. The dependence of the rate constants of the same steps on different oxides on their physicochemical properties is discussed.     

Photo- and Thermochromic Spirans. New Metal Chelates Based on Azomethines and Hydrazones Containing a Spiropyran Fragment

Imine- and hydrazone-based metal chelates containing a spiropyran fragment derived from 3-methyl-4-oxo[2H]-1,3-benzoxazinone were prepared. Attempts are made to monitor the photochromic activity of spiropyran using nontraditional -acceptor substituents (products of condensation of the formyl group in 6"-dimethyl-8"-formylspiro-(4-oxo-3,4-dihydro-2H-1,3-benzoxazine-2,2"-[2H]chromene) with o- aminophenol and aromatic acid hydrazides) and using transition metal ions.     

Crystal Structures and Magnetic Properties of the Two Misfit Layer Compounds: [SrGd0.5S1.5]1.16 NbS2 and [Sr(Fe,Nb)0.5S1.5]1.13 NbS2

Crystal structures of two new misfit compounds, [SrGd_0.5S_1.5]_1.16NbS₂ and [Sr(Fe,Nb)_0.5S_1.5]_1.13NbS₂, were determined through the composite approach, i.e., by refining each subpart (Q, H-parts, and the common part) of these composite materials, separately. The Q-part is a three-atom-thick layer, with the NaCl-type structure, where external SrS planes enclose the inner GdS or (Fe,Nb)S plane; the structural difference between these two compounds lies in the central layer within the Q-part: Gd and S atoms are in special positions (octahedral coordination), while Fe and S atoms are statistically distributed on split (×4) positions (tetrahedral coordination) around a central unique site (=special position occupied by Nb). The H-part is a sandwich of sulfur planes enclosing the inner Nb plane as observed for the structure of the binary compound NbS₂ itself. The Sr-Gd derivative shows a paramagnetic behavior in the whole studied temperature range (2-300 K). On the other hand, antiferromagnetic interactions occur in the Sr-Fe derivative; the complex magnetic behavior of this compound is related to the statistical distribution of Fe atoms which leads to frustration of the magnetic interactions. At room temperature, experimental values obtained from Mössbauer spectrum correspond to Fe³⁺ in tetrahedral sulfur environment: isomer shift δ=0.32 mm s⁻¹, and quadrupole splitting ΔE=0.48 mm s⁻¹.     

2-Benzopyrylium salts. 27. Some transformations of 6-oxodibenzo[a,g]-quinolizinium salts

The synthesis of 6-oxodibenzo[a,g]quinolizinium perchlorate — an analog of the alkaloid berberine — and a number of its derivatives, including mesoionic compounds, was accomplished on the basis of a 1-unsubstituted 3-(2-methylenecarboxyaryl)-2-benzopyrylium salt. The interconversions of the compounds obtained in this research were studied.See [1] for communication 26.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1381–1387, October, 1982.     

Criteria of negative thixotropy for polymer solutions determined from the time dependence of the shear and normal stress

Summary The time dependences of shear and normal stress measured with a Weissenberg rheogoniometer were used in an investigation of the negative thixotropy of poly(methyl methacrylate) solutions in a low-viscosity solvent (mixture of cyclohexanone and isopropanol). A set of criteria was suggested for a complex quantitative evaluation of this phenomenon. The reproducibility of these criteria and their sensitivity towards a change in the velocity gradient were determined.

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Zusammenfassung Es wurde die negative Thixotropie der Lösungen von Polymethylmethacrylat in niedrigviskosem Lösungsmittel (Gemischen von Cyclohexanon und Isopropanol) studiert. Zeitänderungen der Schub- und Normalspannung wurden mit dem Weissenbergschen Rheogoniometer verfolgt und Kriterien zur komplexen quantitativen Beschreibung dieses Effektes wurden entworfen. Die Reproduzierbarkeit und Empfindlichkeit auf die Änderungen des Geschwindigkeitsgefälles wurden ermittelt.

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Dedicated to Prof. Dr.G. Rehage on the occasion of his 60th birthday.

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With 6 figures and 1 table     

Successive partitioning technique and Feenberg perturbation theory

Successive partitioning technique, when based on a modified bordering method for solving a system of linear equations and a relation for the inverse of a partitioned matrix leads to Feenberg's perturbation theory. This sheds light on the properties of the expansion, its bracketing properties and the nature of the “counting operators” used sometimes in this connection.