Search results for "Crista"
showing 10 items of 180 documents
The Mediterranean vermetid reefs: distribution and conservation status
2016
The vermetid reef is an intertidal bioconstruction distributed in the warmest waters of the Mediterranean Sea, and is built by the gregarious vermetid gastropodDendropomaspp. cemented by the coralline red algae of the genusNeogoniolithon.Thisbiogenichabitatisonly generically protected under the European Habitat Directive, but to date it is not explicitly taken into account in many conservation plans. Despite the documented local extinction of Dendropomain the some Eastern Mediterranean locations, its role as habitat engineer and the high numbers of ecosystem services provided, vermetid reef is among the least known marine bioconstruction of the Mediterranean. We counted 112 reefs along the …
Effects of preorganization in the chelation of UO22+ by hydroxamate ligands: cyclic PIPO– vs linear NMA–
2018
International audience; Many siderophores incorporate as bidentate chelating subunits linear and more seldomly cyclic hydroxamate groups. In this work, a comparative study of the uranyl binding properties in aqueous solution of two monohydroxamic acids, the prototypical linear N-methylacetohydroxamic acid (NMAH) and the cyclic analog 1-hydroxypiperidine-2-one (PIPOH), has been carried out. The complex [UO2(PIPO)(2)(H2O)] crystallized from slightly acidic water solutions (pH < 5), and its molecular structure was determined by X-ray diffraction. The uranyl speciation in the presence of both ligands has been thoroughly investigated in a 0.1 M KNO3 medium at 298.2 K by the combined use of four …
Designing dicyanamide bridged 1D molecular architecture from a mononuclear copper(II) Schiff base precursor: Syntheses, structural variations and mag…
2009
International audience; A new tridentate N2O donor Schiff base ligand [(C6H5C(OH)CHC(CH3)NCH2C5H4N)LH] was obtained by 1:1 condensation of benzoylacetone with 2-picolylamine and has been used to synthesise a mononuclear [CuLCl] (1) and an end-to-end dicyanamide bridged polynuclear {[Cu2(μ-L)2(μ2-1,5-(CN)2N)]ClO4}n (2) copper(II) complexes. The ligand, 1 and 2 were clearly characterised by elemental analysis, FT-IR, 1H NMR, UV–Vis spectral studies, electrochemical studies and in addition single crystal X-ray diffraction studies were performed for 1 and 2. The Schiff base ligand [LH] shows a significant variation in its coordination behaviour with copper(II) ion in absence and in presence of …
REATTORE E PROCEDIMENTO PER EFFETTUARE REAZIONI SELETTIVE
2015
La presente invenzione riguarda un reattore e un procedimento per eseguire processi di cristallizzazione reattiva con elevata selettività, consentendo di evitare la miscelazione diretta tra le due soluzioni contenenti i reagenti della reazione e di minimizzare l’effetto di reazioni secondarie indesiderate. Per brevità, nel testo seguente tale reattore e procedimento verrà indicato con l’acronimo CrIEM (Crystalliser with Ion Exchange Membrane).
Dialkyl(butadiene)cyclopentadienylmolybdenum(III) Complexes. Synthesis, Characterization, and Reactivity
2000
International audience; Treatment of CpMo(η4-diene)Cl2 (diene = 1,3-butadiene, C4H6, 1‘; isoprene, C5H8, 1‘ ‘; 2,3-dimethyl-1,3-butadiene, C6H10, 1‘ ‘) in diethyl ether at low temperature with 2 equiv of alkylmagnesium RMgX reagents affords the corresponding dialkyl complexes CpMo(η4-1,3-diene)R2 (2, 2‘, 2‘ ‘, R = CH3, a; CH2Ph, b; CH2SiMe3, c). These species are isolable in moderate yields and have been fully characterized by EPR, elemental analyses, and cyclic voltammetry. They all show a reversible reduction process at relatively low potentials and an irreversible oxidation. The structure of 2‘ ‘a was confirmed by single-crystal X-ray diffraction. The mixed complex CpMo(η4-C4H6)Cl(CH3), …
Snapshots of a solid-state transformation: Coexistence of three phases trapped in one crystal
2016
Crystal-to-crystal transformations have been crucial in the understanding of solid-state processes, since these may be studied in detail by means of single crystal X-ray diffraction (SCXRD) techniques. The description of the mechanisms and potential intermediates of those processes remains very challenging. In fact, solid-state transient states have rarely been observed, at least to a sufficient level of detail. We have investigated the process of guest extrusion from the non-porous molecular material [Fe(bpp)(HL)](ClO)·1.5CHO (bpp = 2,6-bis(pyrazol-3-yl)pyridine; HL = 2,6-bis(5-(2-methoxyphenyl)-pyrazol-3-yl)pyridine; CHO = acetone), which occurs through ordered diffusion of acetone in a c…
On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures
2007
International audience; With an increasing number of biomacromolecular crystal structures being measured to ultra-high resolution, it has become possible to extend to large systems experimental charge-density methods that are usually applied to small molecules. A library has been built of average multipole populations describing the electron density of chemical groups in all 20 amino acids found in proteins. The library uses the Hansen & Coppens multipolar pseudo-atom model to derive molecular electron density and electrostatic potential distributions. The library values are obtained from several small peptide or amino acid crystal structures refined against ultra-high-resolution X-ray diff…
Discovery of new boron-rich chalcogenides: Orthorhombic B6X (X=S, Se)
2020
The authors thank T. Chauveau (LSPM) for help with Rietveld analysis, A. Jamali (LRCS) for assistance with SEM measurements, and Drs. Y. Tange (SPring-8) and N. Guignot (SOLEIL) for help in synchrotron experiments that were carried out during beamtimes allocated to proposals 2017A1047 & 2018A1121 at SPring-8 and proposal 20170092 at SOLEIL. Ab initio calculations have been performed using Rurik and Arkuda supercomputers. This work was financially supported by the European Union’s Horizon 2020 Research and Innovation Programme under Flintstone2020 project (grant agreement No. 689279). Z.W. thanks the National Science Foundation of China (grant No. 11604159). A.R.O. thanks the Russian Ministr…
Noise-Assisted Crystallization of Opal Films
2012
International audience; An improvement of the crystal quality of opal fi lms self-assembled from polymer spheres in a moving meniscus using the agitation by white noise acoustic vibrations is demonstrated. A tenfold higher ordering of a hexagonal sphere packing in the (111) plane is achieved. This crystallization method, the mechanism of which is described in terms of the stochastic resonance, is a contrast to the widely used approach based on maintaining equilibrium conditions during the crystallization process. The precise quantifi cation of the incremental lattice order improvement as a function of acoustic noise intensity is achieved by calculating the probability of finding an opposite…
Über die Richtung der phyletischen Wanderung der Sakralregion bei Triton cristatus und Triton taeniatus [Par Triton cristatus un Triton taeniatus sak…
1929
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