177,792 research outputs found
The Tobermorite-Like Layer in Non-Tobermorite Minerals
No full textThe tobermorite-like layer (TLL) is a characteristic feature in all the structures of the natural and synthetic compounds of the tobermorite group /1/. In those structures eptahedra of calcium cations, characterized by ‘a pyramidal part on one side and a dome part on the other side joining the equatorial oxygen atoms’, form columns through edge sharing; the columns are connected each other, once again through edge sharing, and adjacent columns present the pyramidal apical ligands on opposite sides of the resulting infinite layers. These layers, decorated with wollastonite chains on both sides, build up the ‘complex layers’ which are the basic structural module in all the phases of the tobermorite group (Fig. 1). TLL is a recurrent feature in several natural phases belonging to distinct mineral groups. In the structures of the compounds of the rinkite group the TLL is decorated on both sides by disilicate groups and is accompanied by an infinite ‘octahedral’ layer in building up the structural arrangement. Dovyrenite /2/ and roumaite /3/ are closely related to the minerals of the rinkite group and differ only in the way of decoration of the TLL by the disilicate groups. Fukalite /4/ too presents the TLL, decorated on both sides by four-repeat silicate chains and carbonate groups; tilleyite-type polyhedral layers are also present as distinct modules in building up the structural arrangement. The ubiquitous occurrence of TLL is related to its chemical and structural flexibility: the chemical and geometrical variations of the TLL in the different structures are described and discussed. Key-words: layered silicates, crystal structures, mineralogical crystallography. References /1/ Merlino S., Bonaccorsi E., Armbruster T. (1999): American Mineralogist, 84, 1613–1621. /2/ Kadiyski M., Armbruster T., Galuskin E.V., Pertsev N.N., Zadov A.E., Galuskina I.O., Wrzalik R., Dzierżanowski P., Kislov E.V. (2008): American Mineralogist, 93, 456-462. /3/ Biagioni C., Bonaccorsi E., Merlino S., Parodi G.C., Perchiazzi N., Chevrier V. (2008): Plinius, 34, 211. /4/ Merlino S., Bonaccorsi E., Grabezhev A.I., Zadov A.E., Pertsev N.N., Chukanov N.V. (2009): American Mineralogist, 94, 323–333
J. Bonaccorsi, M. S. C. : Noël. Notes d'exégèse et d'histoire; Il Natale. Appunti d'esegesi e di storia.
No full textBousquet R. J. Bonaccorsi, M. S. C. : Noël. Notes d'exégèse et d'histoire; Il Natale. Appunti d'esegesi e di storia.. In: Échos d'Orient, tome 8, n°51, 1905. p. 121
Value Creation in Emerging Technologies through Sentiment Analysis of Scientific Papers: The Case of Blockchain
No full textInvesting in R&D in Italy. Trends and firms strategies 2001-2010.
No full textThe article makes use for the first time of a time series of firms investing in R&D in Italy associated with their persistence, i.e. whether they invested the years before. The paper shows a remarkable low degree of persistence and investigates the causes and consequences
Factors affecting the distribution, and pigmentation pattern of Risso's dolphin (Grampus griseus) in the Liguro-Provencal Basin during 1990-1998
No full textSpring/Summer distribution and pigmentation pattern of Risso’s Dolphin (Grampus griseus) in the Liguro-Provencal basin from 1990 to 1998
No full textThe Crystal Structure of Tobermorite 14 Å (Plombierite), a C-S-H phase
No full textThe crystal structure of tobermorite 14 Å (plombierite) was solved by means of the application of the order-disorder (OD) theory and was refined through synchrotron radiation diffraction data. Two polytypes were detected within one very small crystal from Crestmore, together with possibly disordered sequences of layers, giving diffuse streaks along c*. Only one of the two polytypes, could be refined: it has B11b space group symmetry and cell parameters a = 6.735(2) Å, b = 7.425(2) Å, c = 27.987(5) A, γ = 123.25(1)° . The refinement converged to R = 0.152 for 1291 reflections with F 0>4σ(F 0). The characteristic reflections of the other polytype, F2dd space group, a ≈11.2 Å, b ≈ 7.3 Å, c ≈ 56 Å, were recognized but they were too weak and diffuse to be used in a structure refinement. The structure of tobermorite 14 Å is built up of complex layers, formed by sheets of sevenfold coordinated calcium cations, flanked on both sides by wollastonite-like chains. The space between two complex layers contains additional calcium cations and H 2O molecules; their distribution, as well as the system of hydrogen bonds, are presented and discussed. The crystal chemical formula indicated by the structural results is Ca 5Si 6O 16(OH) 2 ·7H 2O
The crystal structure of giuseppettite, the 16-layer member of the cancrinite-sodalite group
No full textGiuseppettite, chemical formula Na42K16Ca6Si48Al48O192(SO4)10Cl2 Æ 5H2O, space group P31c, a 1⁄4 12:856, c 1⁄4 42:256 A, is the
16-layer member of the cancrinite–sodalite group. It is characterised by an ABABABACBABABABC. . . stacking sequence of
layers. The crystal structure of giuseppettite was solved and refined against data collected at the Elettra synchrotron facility, using a
0.3 · 0.2 · 0.2 mm3 single crystal, twinned on (0 0 1), k 1⁄4 0:9989 A, R 1⁄4 0:074 for 3769 reflections, R 1⁄4 0:073 for 3706 reflections with
Fo > 4rðFoÞ. The structure contains two big cages (‘‘giuseppettite’’ cages) along 1⁄20; 0; z, and sequences CCSCCCS of ‘‘cancrinite’’
(C) and ‘‘sodalite’’ cages (S) both along 1⁄21=3; 2=3; z and 1⁄22=3; 1=3; z. Four sulphate groups surrounded by sodium cations, and
alternated with potassium cations, are located within the giuseppettite cages, whereas a partially ordered distribution of sulphate
groups and chlorine anions occurs within the sodalite cages. The cancrinite cages host sodium cations and water molecules
Expert biases in technology foresight. Why they are a problem and how to mitigate them
No full textThe paper addresses an issue largely discussed in the field of Forecasting and in many future-oriented scientific and professional disciplines, but less frequently considered in the Foresight literature, particularly in the technology foresight field- i.e. the extent to which biases of human experts influence the foresight process. The paper reviews the literature on cognitive biases and identifies the main areas of technology foresight in which biases are most likely to materialize. It offers a number of examples in which these biases may indeed create distortions. It also reviews the potential impact of several recently introduced methods, in the field of technology foresight and in related areas, to mitigate the distortions and calls for future research in this new field of investigation
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