Le systeme binaire fluorure de rubidium-fluorure d'hydrogene

Résumé Le diagramme des équilibres liquide-solide du système fluorure de rubidium-fluorure d'hydrogène a été tracé dans sa totalité. Six espèces stables se manifestent RbF · nHF (avecn=7, 4, 3, 2, 3/2, 1). Un septième composé dont la composition probable est 2RbF · 5HF se manifeste à l'état métastable.

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Liquid-solid equilibria are studied in the complete binary system RbF-HF. Several compounds are observed: RbF ·nHF withn=7, 4, 3, 2, 3/2 and 1. A seventh compound, 2RbF · 5HF, is detected as an unstable form.

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Zusammenfassung Flüssig-fest Gleichgewichte des Binärsystems RbF-HF wurden umfassend untersucht. Sechs stabile Verbindungen wurden beobachtet: RbF ·n HF (n=7, 4, 3, 2, 3/2 und 1). Eine siebente Verbindung, 2 RbF · 5 HF ist metastabil.

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- RbF-HF. RbF·nHF =7,4,3,2, 3/2 1. — 2RbF·5HF — .

     

Modelisation Des Nappes De Solubilite Du Diagramme De Phases Mg(NO3)2–Al(NO3)3–H2O

A program has been written to describe solubility surfaces of the polythermal ternary phase diagram Mg(NO₃)₂–Al(NO₃)₃–H₂O, using the model proposed by Cohen-Adad et al. [2]. In this work we present the calculation of the solubility surface of Mg(NO₃)₂×6H₂O and Al(NO₃)₃×9H₂O in the phase diagram. The calculated isothermal sections are in a good agreement with experimental determinations. Coefficients of the fitting equation that describes the solubility field allow drawing any isothermal section. The monovariant line was also calculated. The chosen model is well adapted to calculations of these solubility surfaces and gives very good results. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diagramme Polythermique Du Systeme Ternaire KCl–FeCl2–H2O Entre 0 Et 70°C

Polytherm diagram of the ternary system KCl–FeCl₂ –H₂ O between 0 and 70°C. Phase equilibria in the KCl–FeCl₂ –H₂ O system were studied over the temperature range 0–70°C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl₂ 6H₂ O (at 0°C), KCl and FeCl₂ 4H₂ O (at 15, 30 and 40°C) and KCl, FeCl₂ 4H₂ O and of a double salt KClFeCl₂ 2H₂ O are obtained at 70°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Growth of pure and RE-doped Y2O3 single crystals by LHPG technique

High-quality and crack-free Y₂O₃ single crystals containing low concentrations of Tm³⁺, Tb³⁺ and Yb³⁺ were obtained. The crystals were grown in the form of monocrystalline fibers by using a floating zone method with laser heating (laser-heated pedestal growth).     

Vaporisation dEcomposition thermique de dimethylhydrazine,d'hydrate d'hydrazine de leur melange UH25

Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH₃)₂NNH₂. An addition of a small amount of hydrazine hydrate N₂H₄×H₂O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH₃)₂NNH₂/N₂H₄×H₂O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning conditions requires a good knowledge of their vaporisation and of their thermal decomposition kinetics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diagramme Polythermique du Systeme Ternaire NaCl-FeCl2-H2O entre 0 et 70°C

The phase diagram of ternary system Na⁺ , Fe²⁺ /Cl⁻ -H₂ O was established over the temperature range 0–70°C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. For each temperature, we have determined the nature of the solid phase in equilibrium with the solution and the limit of its area of existence. This revised version was published online in July 2006 with corrections to the Cover Date.     

Equilibres solide ⇄ liquide ⇆ vapeur du systeme binaire CoCl2-H2O

Résumé Les équilibres solide liquide vapeur du système binaire CoCl₂-H₂O sont étudiés dans le domaine de température 120–720. La pression de la solution saturée est mesurée entre 1 et 60 atm. et le diagramme de phases est établi.Deux composés intermédiaires: CoCl₂ · 2H₂O et CoCl₂ · H₂O sont observés; ils subissent une décomposition péritectique à 206 et 335.Un tri et un tétrahydrate n'ont pas été obtenus malgré une étude systématique faisant intervenir des mesures d'analyse thermique, de thermogravimétrie et d'ébulliométrie.L'enthalpie et l'entropie de fusion du chlorure de cobalt sont évaluées à partir de la pente de la courbe de liquidus.Les valeurs calculées de l'enthalpie de déshydration de CoCl₂ · 2H₂O et CoCl₂ · H₂O entre 1 et 60 bars sont respectivement de 17 et 16 Kcal. mole^–1.

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Solid liquid vapor equilibria of the binary system CoCl₂-H₂O are investigated in the temperature range 120–720. The pressure of saturated solutions is measured between 1 and 60 atm, and the phase-diagram is established.Two intermediate compounds, CoCl₂ · 2H₂O and CoCl₂ · H₂O, are observed; they undergo peritectic decomposition at 206 and 335.Tri- and tetrahydrate have not been detected in spite of systematic research involving thermal analysis, thermogravimetry and ebulliometry.The enthalpy and entropy of fusion of cobalt chloride are calculated from the slope of the liquidus curve.The calculated enthalpy of dehydration values of CoCl₂ · 2H₂O and CoCl₂ · H₂O between 1 and 60 atm are 17 and 16 Kcal · mole^–1, respectively.

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Zusammenfassung Die Gleichgewichte Festkörper Flüssigkeit Dampf des binären Systems CoCl₂-H₂O wurden im Temperaturbereich von 120 bis 720C untersucht. Der Druck der gesättigten Lösung wurde zwischen 1 und 60 Atm. gemessen und das Phasendiagramm aufgenommen.Zwei Intermediärverbindungen: CoCl₂ · 2H₂O und CoCl₂ · H₂O wurden beobachtet; diese zersetzen sich bei 206 und 335 peritektisch.Ein Tri- und ein Tetrahydrat wurden trotz systematischer Untersuchungen mittels thermoanalytischer, thermogravimetrischer und ebulliometrischer Messung nicht gefunden.Die Enthalpie und Entropie der Kobaltchloridschmelze wurden aus der Steigung der Liquiduskurve ermittelt.Die errechneten Werte der Dehydratierungsenthalpie betrugen für CoCl₂ · 2H ₂ O und CoCl₂ · H₂O zwischen 1 und 60 bar 17 bzw. 16 Kcal₂ mol^–1.

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l₂-₂ 120–720. 1 60 . . CoCl₂. 2₂ l₂ · ₂, 206 335. , , , . . l₂. 2₂ l₂. ₂ 1 60 ., , 17 16 . ^–1.

     

Characterization of cardiac-related noise in fMRI of the cervical spinal cord

Magnetic resonance imaging (MRI) has recently been applied to study spinal cord function in humans. However, spinal functional MRI (fMRI) encounters major technical challenges with cardiac noise being considered a major source of noise. The present study relied on echo-planar imaging of the cervical cord at short TR (TR=250 ms; TE=40 ms; flip=45 degrees), combined with plethysmographic recordings to characterize the spatiotemporal properties of cardiac-induced signal changes in spinal fMRI. Frequency-based analyses examining signal change at the cardiac frequency confirmed mean fluctuations of about 10% (relative to the mean signal) in the spinal cord and surrounding cerebrospinal fluid (CSF), with maximal responses reaching up to 66% in some voxels. A spatial independent component analysis (sICA) confirmed that cardiac noise is an important source of variance in spinal fMRI with several components showing a response coherent with the cardiac frequency spectrum. The time course of the main cardiac components approximated a sinusoidal function tightly coupled to the cardiac systole with at least one component showing a comparable temporal profile across runs and subjects. Spatially, both the frequency-domain analysis and the sICA demonstrated cardiac noise distributed irregularly along the full rostrocaudal extent of the segments scanned with peaks concentrated in the ventral part of the lateral slices in all scans and subjects, consistent with the major channels of CSF flow. These results confirm that cardiac-induced changes are a significant source of noise likely to affect the detection of spinal Blood Oxygen Level Dependent (BOLD) responses. Most importantly, the complex spatiotemporal structure of cardiac noise is unlikely to be accounted for adequately by ad hoc linear methods, especially in data acquired using long TR (i.e. aliasing the cardiac frequency). However, the reliable spatiotemporal distribution of cardiac noise across scanning runs and within subjects may provide a valid means to identify and extract cardiac noise based on sICA methods.