Search results for "composition"
showing 10 items of 2675 documents
Das kompositorische Verfahren in Jean Moutons Quadrupelkanon Nesciens mater virgo virum
2012
Anhand der kompositorischen Probleme, die sich bei der Konzeption mehr als zweistimmiger Kanons ergeben, wird der Frage nachgegangen, wie der konkrete Kompositionsprozess um 1500 ausgesehen haben konnte. Eine Analyse von Jean Moutons Motette Nesciens mater zeigt, dass die Wechselwirkungen zwischen Kanonkonzeption, Klangfolge und melodischer Gestaltung eine simultane Kompositionsweise voraussetzen, in der die Klangfolge wechselnde Verhaltnisbestimmungen als Resultat und Voraussetzung der kontrapunktischen Konfiguration erfahrt: Der Wechsel von der Sukzessiv- zur Simultankonzeption erscheint in Bezug auf komplexe Kanonbildungen als ein verfahrenstechnisches Erfordernis.
An X-ray powder diffraction study of lanthanum–strontium ferromanganites
2001
Abstract Various lanthanum–strontium ferromanganites (La 1− x Sr x )(Mn 1− y Fe y )O 3± δ (LSMF) with x =0.2, 0.5 and 0.7 and y =0.2, 0.5 and 0.8 were prepared by a glycine–nitrate combustion route and conditioned into two different oxygenation states which are likely to be encountered in cathode materials for solid oxide fuel cells (SOFC). Crystal symmetries for both the low and the fully oxygenated states were determined by X-ray diffractometry. Most perovskite compositions crystallized in either cubic or rhombohedral symmetry with the exception of La 0.5 Sr 0.5 Mn 0.2 Fe 0.8 O 3± δ , where a transition from rhombohedral to cubic occurred in going from the full to the low oxygenation stat…
A comparative study of the surface and bulk properties of lanthanum-strontium-manganese oxides La1âxSrxMnO3±δ as a function of Sr-content, oxygen…
1999
Abstract The properties of the perovskite-type La 1− x Sr x MnO 3± δ oxides (0≤ x ≤1) are related to the reversible redox reaction of manganese ions Mn 3+ ↔Mn 4+ . This reaction plays an essential role both in the interfacial transfers and transport properties and depends on relative cation concentrations and experimental conditions. In this paper we present experimental investigations aiming to determine, to compare and to control some of the surface and bulk properties of these oxides. The bulk and surface Mn 4+ contents were investigated by thermogravimetry analysis (TGA) in hydrogen and X-ray photo-electron spectroscopy (XPS) respectively. With a finely divided La 0.8 Sr 0.2 MnO 3 powde…
Spectrochemical Rubidium-Strontium Method for Geological Age Determination
1960
The age values of lepidolites from South Africa and from Varutrask as well as that of a microcline from Varutrask have been determined and are discussed in connection with determination according to the potassium-argon method, applied to the same materials A method is suggested which allows the spectrochemical determination of Rb and Sr with sufficient accuracy. The isotopic composition is determined by means of a Fabry-Perot etalon and hollow-cathode excitation, investigating the hyper-fine structure of the Sr line at 4078 A.
Groups are not always the same
1993
The idea of supporting group meetings at the same time and at the same place by computer raises the problem of how salient features of group behaviors are understood in meetings. In this paper we take a critical look at several beliefs about group behaviors in research dealing with electronic meeting systems (EMS). The paper argues based on an empirical study that the concept of a small, cohesive business team, so widely held, in all EMS research is not necessarily a valid starting point in thinking of meeting support. In particular, the paper critically evaluates a number of beliefs of user aspects, group features such as composition, structure and protocols, and task characteristics such …
Influence of the composition and the structure of different media on the release of aroma compounds
2004
International audience; The release of 2-nonanone and hexenol (hex-4-en-3-ol) was studied in model media with different structures and compositions: water, a gel of $\beta$-lactoglobulin, gelified or non-gelified emulsions (5.0% Miglyol, 6.9% $\beta$-lactoglobulin; the gelation was realized by heating) and milk. The aroma compounds were analyzed by gas chromatography. A strong influence of the nature of the volatile compound on its behavior towards the food matrix was observed: in the case of 2-nonanone, a hydrophobic compound (log P = 2.9) with a relatively high vapor-water partition coefficient (Kmol = 33.6), the release was greatly influenced by the composition and the structure of the m…
Melting behaviour of d-sucrose, d-glucose and d-fructose
2004
The melting behaviour of d-sucrose, d-glucose and d-fructose was studied. The melting peaks were determined with DSC and the start of decomposition was studied with TG at different rates of heating. In addition, melting points were determined with a melting point apparatus. The samples were identified as d-sucrose, alpha-d-glucopyranose and beta-d-fructopyranose by powder diffraction measurements. There were differences in melting between the different samples of the same sugar and the rate of heating had a remarkable effect on the melting behaviour. For example, T(o), DeltaH(f) and T(i) (initial temperature of decomposition) at a 1 degrees Cmin(-1) rate of heating were 184.5 degrees C, 126…
Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition p…
2010
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition…
Magnetic Nanocomposites Formed by FeNi3 Nanoparticles Embedded in Graphene. Application as Supercapacitors
2013
A general family of magnetic nanocomposites formed by FeNi3 ferromagnetic nanoparticles (NPs) embedded in a graphitized carbon matrix is reported. The soft chemical approach used relies on the catalytic effect of the NPs resulting from the thermal decomposition of the layered double hydroxide precursor, which acts as a multilayered nanoreactor enabling the formation of a range of carbon nanoforms (CNFs). This is followed by acid treatment of the as-prepared nanocomposites to isolate the different CNFs formed. These range from carbon nano-onions to graphene depending on the temperature of the thermal decomposition. This synthetic process paves the way for the rational design of metal–carbon …
Ab initiothermodynamics ofBacSr(1−c)TiO3solid solutions
2005
Based on ab initio calculations for a number of the ${\mathrm{Ba}}_{\mathrm{c}}{\mathrm{Sr}}_{(1\ensuremath{-}\mathrm{c})}\mathrm{Ti}{\mathrm{O}}_{3}$ (BST) superlattices, we developed a thermodynamic approach to these solid solutions. In particular, we calculate the BST phase diagram and show that at relatively low temperatures (below $400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.5$ and $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.1$) the spinodal decomposition of the solid solution occurs. As a result, we predict for small Ba concentrations formation of $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ nanoregions in a predominantly $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ matrix and …