Sodium penta­potassium penta­nickel tetra­(diphosphate), NaK5Ni5(P2O7)4

The structure of the title compound, NaK5Ni5(P2O7)4, is characterized by the presence of two crystallographically independent P2O7 groups with different conformations. The conformation of the first P2O7 group is eclipsed, whereas that of the second is staggered. All atoms are in general positions except for two nickel and one potassium ions which lie on symmetry centers. Moreover, the structure exhibits disorder of the cationic sites with one general position fully occupied equally by Na+ and Ni2+ cations. This mixed site is surrounded by five O atoms forming a square-based pyramid. The crystal structure consists of edge-sharing [NiO6] octa­hedra forming infinite zigzag chains [Ni3O14] running parallel to [100]. Adjacent chains are connected through apices to P2O7 groups and to another [NiO6] or to a [KO6] octa­hedron. The resulting three-dimensional framework presents inter­secting tunnels running along the [010] and [001] directions in which the seven- and nine-coordinated potassium cations are located. The crystal structure of this new phosphate represents a new structural type

Literary studies and the academy

In 1885 the University of Oxford invited applications for the newly created Merton Professorship of English Language and Literature. The holder of the chair was, according to the statutes, to ‘lecture and give instruction on the broad history and criticism of English Language and Literature, and on the works of approved English authors’. This was not in itself a particularly innovatory move, as the study of English vernacular literature had played some part in higher education in Britain for over a century. Oxford University had put English as a subject into its pass degree in 1873, had been participating since 1878 in extension teaching, of which literary study formed a significant part, and had since 1881 been setting special examinations in the subject for its non-graduating women students. What was new was the fact that this ancient university appeared to be on the verge of granting the solid academic legitimacy of an established chair to an institutionally marginal and often contentious intellectual pursuit, acknowledging the study of literary texts in English to be a fit subject not just for women and the educationally disadvantaged but also for university men

Structural and magnetic properties of layered perovskite manganite LaCaBiMn

The layered perovskite oxide, LaCaBiMn2O7, has been prepared by the conventional aqueous solution precipitation method. The powder X-ray diffraction studies suggest that the phase crystallizes with tetragonal unit cell in the space group I4/mmm. The magnetic properties suggest that the ferromagnetic interactions are dominant and manganese ion in the phase is present in mixed valence states Mn3+and Mn4+. The thermomagnetization curve is found to obey the Bloch law. Spin wave stiffness constant D and the approximate value for JMnMnexchange interaction were estimated from the experimental results

Structural, magnetic and magnetocaloric properties of layered perovskite La1.1Bi0.3Sr1.6Mn2O7

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Dilithium manganese(II) catena-tetrakis(polyphosphate), Li2Mn(PO3)4

The poly-phosphate Li2Mn(PO3)4 was synthesized and its structure characterized from powder diffraction data by Averbuch-Pouchot & Durif [J. Appl. Cryst. (1972), 5, 307–308]. These authors showed that the structure of this phosphate is isotypic to that of Li2Cd(PO3)4, as confirmed by the present work. The structure is built from infinite zigzag polyphosphate chains, [(PO3)−]n, extending along [010]. These polyphosphate chains are connected by sharing vertices with MnO6 octahedra (site symmetry .m.) and Li2O7 polyhedra, which form also chains parallel to [010]. Adjacent chains are linked by common vertices of polyhedra in such a way as to form porous layers parallel to (100). The three-dimensional framework delimits empty channels extending along [010]

Potassium trinickel(II) orthophosphate diphosphate, KNi3(PO4)P2O7

The structure of the title compound is characterized by the presence of two different anions, (PO4)3− and (P2O7)4− with an eclipsed conformation. The crystal structure consists of edge-sharing [NiO6] octahedra forming an [Ni3O14] chain running parallel to [001]. Adjacent chains are connected through edges and apices to PO4 and P2O7 groups in such a way as to build a three-dimensional host lattice. The resulting framework presents intersecting tunnels running along [010] and [101] in which the 11-coordinated potassium cation is located. The crystal structure of this new phosphate probably represents a new structural type

Synthesis, Structure and Magnetic Properties of Layered Perovskite Sm1.5SrBa0.5Mn2O7

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Crystallographic and optical properties of Eu 3+ doped K 2 Na 3 P 3 O 10 triphosphate

International audienceThe crystal structure of the new triphosphate K2Na3P3O10: 5% Eu3+ (monoclinic, space group C2/c, unit cell parameters: a = 9.8695(3) Å; b = 5.6171(2) Å; c = 18.6404(6) Å; β = 96.0947(2) °) has been solved from single crystal data. The structure is closely related to that of the undoped material K2Na3P3O10 and indicates the presence of rare earth ions in all alkaline crystallographic sites. Eu3+ doped K2Na3P3O10 triphosphates were synthesized as polycrystalline samples by solid state reaction and characterized by powder X-ray diffraction and infrared spectroscopy. The optical properties were recorded in the VUV-visible range. Broad and intense bands are observed in the 150–250 nm range, corresponding to the absorption by the host matrix and Eu-O charge transfer state (CTS). The numbering of the Eu3+5D0 → 7FJ (J = 0–4) emission transitions observed in the visible domain is in good agreement with the crystal structure data and is discussed according to the symmetry of the different sites occupied by the lanthanide ions in the triphosphate lattice

Rapport VI-3 Soutien des étiages et régularisation des débits dans le bassin du Lot. Effets et adaptation des aménagements hydro-électriques existants

Flow disturbances in the Lot basin due to the many hydroelectric schemes called for steps to be taken (a) to increase minimum stream flows, and (b) to reduce daily variations. Increasing the minimum flows required that water stored for this purpose in the upper basin be made available downstream. The possibilities were (a) to release water from existing hydroelectric structures, (b) to create impounding reservoirs, or (c) to combine the two. Optimum solutions were selected by comparing the economic and energy-production effects of releasing water, and by estimating the cost of a new reservoir designed both for energy production and for low water control. Daily fluctuations in flow due to lockage water and to lake-sited plant in the upper basin were reduced by making optimum use of balancing reservoirs, by staggering the peak flows of the Lot and its tributaries, and by building new balancing reservoirs where necessary. To smooth the flow disturbances in the lower reaches caused by low-head hydroelectric plant operated by Electricité de France, factories and other private owners, a co-ordinated water management policy is needed. The policy is being defined with the aid of a mathematical hydrodynamics model which enables power plant operation to be simulated.Dans le bassin du Lot, très équipé au plan hydroélectrique, de nouveaux besoins se sont exprimés concernant le renforcement des étiages et la régularisation des débits fortement modulés par l’exploitation hydro-électrique. L’augmentation des débits d’étiage implique la disponibilité de volumes affectés à cet effet dans le haut bassin. Ils peuvent être obtenus par le déstockage de réservoirs hydroélectriques existants, par la création de nouveaux barrages-réservoirs, ou par une combinaison des deux options. La comparaison et le choix entre ces solutions sont rendus possibles après avoir analysé l’impact énergétique et économique des déstockages et après avoir quantifié l’intérêt d’associer les deux objectifs soutien d’étiage et hydroélectricité dans un nouveau réservoir. Pour réduire les variations journalières de débits dues aux centrales de lacs et d’éclusées du haut bassin, les moyens mis en œuvre consistent en l’utilisation optimum des bassins de compensation, en l’organisation du décalage des débits maximums entre rivière et affluents et si nécessaire, en la création de nouveaux bassins de compensation. Pour atténuer les perturbations de débits sur le cours aval, dues aux usines de basse-chute gérées par divers types d’exploitants (producteurs autonomes, industriels, E.D.F.), il faut définir une gestion coordonnée. La recherche de cette gestion s’appuie sur la conception et l’utilisation d’un modèle mathématique hydrodynamique permettant la simulation de fonctionnement des usines.Lamire J., Sormail Lucien, Cornillon P., Pineau J., Normand D., Megard J. Rapport VI-3 Soutien des étiages et régularisation des débits dans le bassin du Lot. Effets et adaptation des aménagements hydro-électriques existants . In: L'hydrotechnique au service d'une politique de l'eau. Evolution des problèmes de l'eau au cours de la dernière décennie. Compte rendu des XVes journées de l'hydraulique. Toulouse, 5, 6 et 7 septembre 1976. Tome 2, 1979