Conditional solubility versus pO2− of cerium(III) oxide in molten equimolar NaCl+KCl at 727°C

Reactions between cerium trichloride and oxide ions were studied in NaCl+KCl (1/1) at 1000°K, by potentiometry with a calcia-stabilized zirconia membrane electrode. Titration curves clearly demonstrated the existence of soluble cerium oxychloride (CeO⁺) and precipitated cerium oxide (Ce₂O₃), with respective dissociation constants 10^?11 and 10^?30 (molality scale). The corresponding conditional solubility diagram {log S (Ce^III)=f(pO^2?)} is presented and discussed.     

SU(5) Higgs problem with adjoint + vector representations

Recently Kim has given a general method, using group-invariant orbit parameters, for determining the energy and residual symmetry of the Higgs potential minimum. In this paper we illustrate the method by working out the case of a quartic SU(5) Higgs potential with $\text{5}$ and $\text{24}$ higgsons. In this method the Gell-Mann-Slansky conjecture concerning possible little groups of the potential minimum takes a geometric form, which is verified for our case. The results are used to discuss the hierarchical symmetry breaking of SU(5) grand unification theory. We generalize our results to the SU(N) adjoint + vector models, which are all closely related.     

Lambda polarization in the K− fragmentation region

Results on Λ polarization in the inclusive reaction K^?p→Λ + X at 12 and 16 GeV/c for 0.6<x<1.0, are presented. These results, obtained with the CERN Omega Spectrometer, show that the polarization is important at large x and increases with p_t over the covered range 0<p_t<1.2 GeV/c. The average polarization for 31 857 lambdas with x>0.6 is P_Λ = 0.35 ± 0.02, along the direction $\text{K}{}^{\mathrm{?}}\text{×}\text{Λ}$. The polarization can be expressed as P(x, p_t) = (0.66±0.03)p_t independent of x in the range covered by the experiment.     

Addition photochimique (2+2) de composes organometalliques α-insatures aux derives carbonyles α,β-insatures: addition d'alcynylsilanes a la cyclopentenone

Alkynylsilanes add photochemically to cyclopentenone to give bicyclo[3.2.0]heptenones. The photochemical rearrangement of adducts was studied. A method to eliminate the trimethylsilyl substituent is proposed. The structure of adducts is proved by spectroscopy, mainly ¹³C NMR.     

Dilatometric study of β-alumina single crystals

Single crystals of β-alumina exhibit an important dilatometric anisotropy. The anisotropic factor is about three for βNa-alumina. Variations of this factor are followed according to the nature of the conducting ion and the stoichiometry. The dilatometric behaviour of these compounds is explained (up to 800°C) from previous structural results.     

How does geographical distance translate into genetic distance?

Geographic structure can affect patterns of genetic differentiation and speciation rates. In this article, we investigate the dynamics of genetic distances in a geographically structured metapopulation. We model the metapopulation as a weighted directed graph, with $d$ vertices corresponding to $d$ subpopulations that evolve according to an individual based model. The dynamics of the genetic distances is then controlled by two types of transitions — mutation and migration events. We show that, under a rare mutation–rare migration regime, intra subpopulation diversity can be neglected and our model can be approximated by a population based model. We show that under a large population-large number of loci limit, the genetic distance between two subpopulations converges to a deterministic quantity that can asymptotically be expressed in terms of the hitting time between two random walks in the metapopulation graph. Our result shows that the genetic distance between two subpopulations does not only depend on the direct migration rates between them but on the whole metapopulation structure.     

Proton-antiproton states in high energy photoproduction

Exclusive and inclusive $\text{p}\text{p}$ photoproduction (with ? 2 accompanying charged particles) have been measured in the photon energy range 44–70 GeV. The exclusive process shows no prominent features; the inclusive process shows evidence for S(1936) production as a resonant-like structure with mass 1930 ± 2 MeV and width 12 ± 7 MeV.     

Electrochemistry in molten NaAlCl4 (at 210°C): Identification of dissolved oxide-containing species,solubility of alumina in terms of pCl− and properties related to H2O in this melt

It has been shown that a nickel electrode is an indicator of the presence of oxide ions dissolved in chloroaluminate melts. From quantitative interpretation of electrochemical results (voltammograms and potentiometric measurements), O^2? has appeared to behave, in terms of the chloro-acidobasicity concept, as a strong dibase, through a solvolytic reaction giving AlOCl₂^? as solvated form. AlOCl₂^? itself is a weak base, according to the system:AlOCl₂^?AlOCl+Cl^?, pK_B/mol kg^1-=4.35 (at210°C) Thus O^2? behaves cumulatively as a tribase. AlOCl is the solvated form of O^?II in very acidic melts.A saturation effect by Al₂O₃ appeared when the concentration of O^?II was increased. The solubility of Al₂O₃ in chloroaluminate melts (one third of total O^?II solubility) was determined from the electrochemical results obtained. A minimum of 0.13% in weight (solubility of O^?II=4×10^?2 mol kg^?1), is observed for pCl^?=4.5 that is in a mixture containing 51.4 moles per cent of AlCl₃. The solubility is increased by adding either more AlCl₃ (formation of AlOCl) or NaCl (formation of AlOCl₂^?). Its variation versus pCl^? has been expressed quantitatively.Through a study of the system HCl/H₂O, it was pointed out that hydrolysis of chloroaluminate melt does not occur to a great extent in basic media. On the contrary, elimination of oxide ions through H₂O formation by reaction with HCl was shown to be possible. A quantitative relation, which binds the total concentration of O^?II, pCl^? and the respective partial pressures of gaseous HCl and H₂O in equilibrium with the melt, is given.A treatment in order to carry out this purification in these melts appears necessary in order to prevent many dissolved metallic ions from precipitating under the form of oxides.     

Decarboxylation,during their aromatization by Pd/C,of some 3,4-octahydronaphtho-7,8-benzocoumarins : Synthesis of 1,2'-binaphthyls and 2,2'-binaphthyls

Some 3',4'-cyclohexa-1',2'-dihydro- and 1',2'-cyclohexa-3',4'-dihydro-3,4,7,8-dibenzocoumarins 2 and 3 were prepared by catalytic condensation between a naphthol and a α-carbethoxy-cis- decalone (?1 or ?2). These compounds, when treated with Pd/C at 260°, undergo, beside aromatization, a complete decarboxylation of the lactone ring. A mechanism, involving H transfer through a π-allylic palladium complex is described.