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Orvosi Hetilap
Authors: László Andrássy, Gyula Maros, István János Kovács, Ágnes Horváth, Katalin Gulyás, Éva Bertalan, Anikó Besnyi, Judit Füri, Tamás Fancsik, Zoltán Szekanecz and Harjit Pal Bhattoa

A csontszövet és a geológiai képződmények szerkezeti felépítése közötti hasonlóság lehetővé teszi, hogy a csontszövet szervetlen részét matematikai modellekkel közelítsük. Az elemi összetétel ellenőrizhető a lézerindukált plazmaspektroszkópiai és induktív csatolású plazmaoptikai emissziós spektrometriás mérésekből meghatározott elemoxidkoncentráció-értékekkel. A számításokból és a laboratóriumi mérésekből egyértelműen következik, hogy a csontszövet tulajdonságait elsősorban a hidroxiapatit határozza meg. A szervetlen csontszerkezet igen jól tanulmányozható a lézerindukált plazmaspektroszkópiai technikával megbízhatóan mérhető kalcium-oxid-koncentrációértékek eloszlásainak segítségével. Jelen tanulmányban a szerzők hím szarvasmarha lábszárcsontjaiból készült vékonycsiszolatokon szelvény menti, lézerindukált plazmaspektroszkópiai mérésekből számított kalcium-oxid-koncentráció eloszlásai mutatják be. A kalcium-oxid-koncentrációértékek felületi eloszlásait, „gyakorisági eloszlási” görbék támasztják alá. A több csoportba sorolt kalcium-oxid-koncentrációértékek alapján a corticalis és trabecularis csontszerkezet élesen megkülönböztethető. A szerzők a csontokon elvégzett kvantitatív komputertomográfiái mérésekből számított attenuációs együttható (összsűrűség) és geológiában használt „ρ”-sűrűség között szignifikáns pozitív korrelációt találtak. Továbbá a kiszámított „ρ”-sűrűség és a meghatározott átlag-kalcium-oxid-koncentrációértékek inverz korrelációt mutattak. Orv. Hetil., 2014, 155(45), 1783–1793.

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Abstract  

Kinetics of CaO desulphurization reaction and the effects of alkali carbonates on it have been investigated by thermogravimetric analysis. A grain model was applied successfully to describe the kinetic behavior of the reactions. The activation energy of surface reaction and that of the product layer diffusion were determined by using the model. It was found that the overall desulphurization rate was controlled initially by surface chemical reaction and, in a later stage, by product layer diffusion. Addition of alkali carbonates can decrease the activation energy of the surface chemical reaction, with increasing effectiveness in the order of potassium, sodium and lithium. Such a property of alkali carbonates has also been demonstrated on a raw coal. The process is discussed in terms of a working mechanism of solid-state ionic diffusion.

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The interaction of V2O5 with calcium oxide and calcium carbonate was studied by thermal analysis. The results indicated that the macrosuccession of the phase transformations in the systems CaO-V2O5 and CaCO3-V2O5 corresponds to an increasing calcium content in each successively formed calcium vanadate. Thermodynamical calculations carried out by methods available in the literature for determining the primary products and the succession of the subsequently formed products demonstrate that chemical reactions proceeding in the above systems are controlled by kinetic and not by thermodynamic factors.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: I. Kádár, D. Berényi, G. Mórik, D. Varga, E. Vatai, I. Somosi and J. Vitéz

Abstract  

An equipment and procedure were developed to determine the CaO content of bauxite by X-ray fluorescence method using scintillation techniques and a tritium/Ti exciting source. The time needed for the whole sample preparation procedure and measurement is less than 10 min. The range of concentration where analysis is feasible by the equipment, is from 0.3% upwards.

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Abstract  

Effect of 5% tartaric, succinic and citric acids on the decomposition of CaCO3 have been studied by TG-DSC and X-ray diffraction techniques. The decomposition temperature of CaCO3 is not decreased and at the same time particle size distribution and morphology of CaO are changed as determined by laser granulometer and SEM studies.

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method and expressed by the function ( ). The function ( ) for calcium oxide, calcium hydroxide and calcium carbonate was 15.0 < < 18.4, 9.3 < < 5.0, 7.2 < < 9.3 [ 17 ]. In the literature, it was considered that CaO was deactivated probably due to

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Summary The results of investigation of MgO participation in the binding of SO2 with lime-containing materials as sorbents are presented. Experiments of SO2 binding into solid phase using model samples of reactive grade MgO and CaO varying the mole ratio of MgO/CaO from 9:1 to 1:9 were carried out. Besides, dolomite and limestone samples with different MgO/CaO mole ratio (from 1.24 to 0.13) and samples of ashes formed at combustion of Estonian oil shale (containing 35-40% of carbonates) and its semicoke were studied Initial samples, intermediate and final products were subjected to chemical, IR-spectroscopy, X-ray and BET specific surface area analyses. The results of the present study confirmed the active participation of MgO in the binding of SO2 into the solid phase. In addition to CaSO4 the formation of Ca,Mg-double sulphate CaMg3(SO4)4 and ß-MgSO4 was observed. The presence of CaMg3(SO4)4 was fixed in a large temperature range 400-900°C and that of ß-MgSO4 in between 500-700°C. The optimum temperature range for formation and durability of CaMg3(SO4)4 was 700-800°C.

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Abstract  

The role that can be played in the elucidation of the limestone sulphation mechanism by thermal analysis methods with some specific procedures is discussed. Contrasting examples of applications of thermoanalytical techniques using the variable conditions are provided. These examples deal with the programmed thermal analysis using different gas sequences, the influence the calcination and sulphation conditions on the capture of SO2, the effect of catalysts on limestone sulphation and the thermal stability of CaSO3. Two proposed mechanisms were supported by the phase identification of the solid products.

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energy determination of calcium carbonate dissociation reaction introduced by L'vov [ 6 , 7 ] is based upon the assumption of an initial step involving evaporation of the reactant followed by condensation of low volatile calcium oxide product. Since

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Abstract  

Scheelite (calcium tungstate)is the product of one of the processing methods of wolframite by its roasting with calcium oxide or limestone or its fusion with calcium chloride, followed by acid processing of calcium tungstate with the formation of tungstic acid. Scheelite occurs in contact metamorphic deposits, hydrothermal veins and pegmatites. The present work illustrates a thermal analysis study of synthesis of scheelite by sintering of wolframite with calcite and sintering of tungsten oxide with calcite or calcium oxide using a derivatograph. The reaction products were identified microscopically and by using a Siemens Crystalloflex diffractometer. The DTA curve of sintering of wolframite with calcite shows the beginning of the reaction at 560C with the formation of scheelite. The intensive formation of scheelite is represented by the medium and wide endothermic peak at 740C. This is followed directly by a large and sharp endothermic peak at 860C, representing the dissociation of unreacted calcite. The DTA curve of tungsten trioxide shows three thermal effects. The sharp exothermic peak at 320C represents the oxidation of tungsten oxide content of lower valency. The endothermic peaks at 750 and 1090C are related to polymorphic changes of tungsten trioxide. The beginning of its sublimation is observed at temperature higher than 800C. The DTA curves of sintering of tungsten trioxide with calcite or calcium oxide indicate that the intensive formation of scheelite takes place by endothermic reactions at 660 and 545C respectively. The medium and small endothermic peaks at 520 and 730Con the DTA curve of tungsten trioxide with calcium oxide represent the dehydration of calcium oxide and the loss of carbon dioxide due to some carbonatization of calcium oxide with carbon dioxide from air, respectively. The produced scheelite is colorless in thin sections, has distinct cleavage (101), crystallizes in the tetragonal system in the form of tabular crystals and is optically positive.

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