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Channel Structure (channel + structure)
Selected AbstractsChemInform Abstract: Optical and Structural Properties of a Eu(II)-Doped Silicoaluminate with Channel Structure and Partial Site Occupation.CHEMINFORM, Issue 8 2008Andreas Rief Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008Wei-Guo Jia Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,×,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Think tanks with deliverables: How communities of practice helped LPL financial manage rapid growth and organizational complexityGLOBAL BUSINESS AND ORGANIZATIONAL EXCELLENCE, Issue 3 2010Jack Regan In the wake of acquisitions, new hiring, and a shift from a functional to a customer channel structure, the company pulled its best and brightest talent into practice centers (PCs) to share knowledge, transfer best practices, standardize policies and practices across the channels, drive key initiatives, and cement collaborative relationships. The authors present the business case for communities of practice; describe LPL's vision and process for implementing its PCs, including strategies for enhancing success and avoiding potential pitfalls; and highlight the PCs' accomplishments. They also share how the PCs facilitated the company's response to the 2008,2009 financial crisis. © 2010 Wiley Periodicals, Inc. [source] Predicting river width, depth and velocity at ungauged sites in England and Wales using multilevel modelsHYDROLOGICAL PROCESSES, Issue 20 2008D. J. Booker Abstract Using a dataset of gauged river discharges taken from sites in England and Wales, linear multilevel models (also known as mixed effects models) were applied to quantify the variability in discharge and the discharge-hydraulic geometry relationships across three nested spatial scales. A jackknifing procedure was used to test the ability of the multilevel models to predict hydraulic geometry, and therefore width, mean depth and mean velocity, at ungauged stations. These models provide a framework for making predictions of hydraulic geometry parameters, with associated levels of uncertainty, using different levels of data availability. Results indicate that as one travels downstream along a river there is greater variability in hydraulic geometry than is the case between rivers of similar sizes. This indicates that hydraulic geometry (and therefore hydrology) is driven by catchment area, to a greater extent than by natural geomorphological variations in the streamwise direction at the mesoscale, but these geomorphological variations can still have a major impact on channel structure. Copyright © 2008 John Wiley & Sons, Ltd. [source] A slotted multicode CDMA protocol for efficient integration of voice and data in cellular networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2002H. Zhang Abstract This paper presents a novel radio channel structure based on slotted CDMA technology intended for carrying traffic with diverse bandwidth/QoS requirements in mobile environments, e.g. personal communication systems (PCS). The essence of our approach is a combination of flexible slotting with allocation of multiple codes to high-bandwidth mobiles. As demonstrated by our performance studies, the proposed scheme efficiently integrates multiple traffic classes into a unified CDMA system. It is highly flexible and incurs low overheads for a wide range of realistic traffic conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] BaLn2Se4 (Ln = Er, Tm and Yb)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2009Daniel E. Bugaris The compounds BaLn2Se4 (Ln = rare-earth metal = lanthanide = Er, Tm and Yb), namely barium di(erbium/thulium/ytterbium) tetraselenide, crystallize in the orthorhombic space group Pnma in the CaFe2O4 structure type. In this structure type, all atoms possess m symmetry. The Ln atoms are octahedrally coordinated by six Se atoms. A three-dimensional channel structure is formed by the corner- and edge-sharing of these LnSe6 octahedra. The Ba atoms are coordinated to eight Se atoms in a bicapped trigonal,prismatic arrangement, and they occupy the channels of the three-dimensional framework. [source] Three solvates of a bis-mesoionic fluorescent yellow pigmentACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Jürgen Brüning p -Phenylenebis(2-oxo-3-phenyl-1,2-dihydropyrido[1,2- a]pyrimidin-5-ium-4-olate), C34H22N4O4, is a bis-mesoionic yellow pigment that shows fluorescence in the solid state. During a polymorph screening, single crystals of three solvates were grown and their crystal structures determined. Solvent-free crystals were not obtained. A solvate with N -methylpyrrolidone (NMP) and propan-2-ol, C34H22N4O4·2C5H9NO·C3H8O, (Ia), and an NMP trisolvate, C34H22N4O4·3C5H9NO, (Ib), crystallize with pigment molecules on inversion centres. The NMP/propan-2-ol mixed solvate (Ia) forms O,H...O hydrogen bonds between the different solvent molecules. In both structures, at least one of the solvent molecules is disordered. A third solvate structure, C34H22N4O4·0.5C5H9NO·C4H10O, (Ic), was obtained by crystallization from NMP and butan-1-ol. In this case, there are two symmetry-independent pigment molecules, both situated on inversion centres. The solvent molecules are heavily disordered and their contribution to the scattering was suppressed. This solvate displays a channel structure, whereas the other two solvates form layer structures. [source] Ba3Li2V2O7Cl4, a new vanadate with a channel structureACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008Thomas Reeswinkel The tribarium dilithium divanadate tetrachloride Ba3Li2V2O7Cl4 is a new vanadate with a channel structure and the first known vanadate containing both Ba and Li atoms. The structure contains four non-equivalent Ba2+ sites (two with m and two with 2/m site symmetry), two Li+ sites, two nonmagnetic V5+ sites, five O2, sites (three with m site symmetry) and four Cl, sites (m site symmetry). One type of Li atom lies in LiO4 tetrahedra (m site symmetry) and shares corners with VO4 tetrahedra to form eight-tetrahedron Li3V5O24 rings and six-tetrahedron Li2V4O18 rings; these rings are linked within porous layers parallel to the ab plane and contain Ba2+ and Cl, ions. The other Li atoms are located on inversion centres and form isolated chains of face-sharing LiCl6 octahedra. [source] Synthesis and Electrochemical Properties of Semicrystalline Gyroidal Mesoporous MnO2CHINESE JOURNAL OF CHEMISTRY, Issue 7 2006Qin Zhou Abstract Mesoporous silica KIT-6 has novel three-dimensional gyroidal channel structure, space group of Ia-3d, and ordered tunable pores up to 10 nm. In this paper, such mesostructured silica was employed as hard template to prepare semicrystalline gyroidal mesoporous MnO2. The structure was investigated by XRD, TEM and HRTEM, and found to be of high quality Ia- 3d symmetry, in good accordance with the template structure. The material has a BET surface of 118 m2·g -1 and pore volume of 0.35 cm3·g,1 after eliminating template. Mesoporous MnO2 has shown good electrochemical property as supercapacitor material in 1 mol·L,1 Na2SO4 and 1 mol·L,1 LiClO4 solutions, but interesting pseudocapacitance behavior was observed in the case of 6 mol·L,1 KOH. It was found that mesoporous MnO2 performed stable reversible electrochemical behavior with capacitance of 220 F·g,1 in a potential range of ,0.1,0.55 V vs. Hg/HgO in alkaline solution, demonstrating that it is a promising novel electrode material for the fabrication of electrochemical capacitors. [source] A Novel Self-assembled Supramolecular Complex {[Cu(n) (en)2·H2O] [Cu(I)2(CN)4]}n with Honeycomb-like Structure and Its Adsorption PropertiesCHINESE JOURNAL OF CHEMISTRY, Issue 12 2002Xiao-Ping Shen Abstract A novel supramolecular complex {[Cu(n)(en)2·H2O]·[Cu(I)2(CN)4]}n (en = ethylenediamine), in which the cyanide-bridged Cu(I) forms the honeycomb-like skeleton host and the Cu(n) complex ion [Cu(en)2·H2O]2+ is encapsulated in the center of the channel cavity of the skeleton, was synthesized by two different methods. The complex was also characterized by elemental analysis, ICP analysis, IR spectra and thermal analysis. The adsorption and desorption studies of the complex indicate that H2O and NH3 can be desorbed and re-adsorbed without collapse of the channel structure of the supramolecule. [source] ILLUMINATING THE STRUCTURE AND FUNCTION OF CYS-LOOP RECEPTORSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2008Stephan A Pless SUMMARY 1Cys-loop receptors are an important class of ligand-gated ion channels. They mediate fast synaptic neurotransmission, are implicated in various ,channelopathies' and are important pharmacological targets. Recent progress in X-ray crystallography and electron microscopy has provided a considerable insight into the structure of Cys-loop receptors. However, data from these experiments only provide ,snapshots' of the proteins under investigation. They cannot provide information about the various conformations the protein adopts during transition from the closed to the open and desensitized states. 2Voltage-clamp fluorometry helps overcome this problem by simultaneously monitoring movements at the channel gate (through changes in current) and conformational rearrangements in a domain of interest (through changes in fluorescence) in real time. Thus, the technique can provide information on both transitional and steady state conformations and serves as a real time correlate of the channel structure and its function. 3Voltage-clamp fluorometry experiments on Cys-loop receptors have yielded a large body of data concerning the mechanisms by which agonists, antagonists and modulators act on these receptors. They have shed new light on the conformational mobility of both the ligand-binding and the transmembrane domain of Cys-loop receptors. [source] Multifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity, Separation Capability and Three-Dimensional Magnetic Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2008Kunhao Li Abstract Microporous materials [M3(HCOO)6],·,DMF (M,=,Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X-ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ,5,6,Å. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi-fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p-xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic-based process. Three-dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets. [source] Loading Dependence of Self-Diffusivities of Gases in ZeolitesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2007R. Krishna Abstract Experimental data on the self-diffusivities, Di,self, of a variety of gases (CH4, N2, Kr, C2H6, and C3H8) in three different zeolites, LTA, FAU, and MFI, show different dependences on the molar loading, qi. In LTA, Di,self appears to increase with qi for all molecules except N2. In FAU and in MFI the Di,self shows a sharp decrease with increasing qi. In order to gain insights into the causes behind the loading dependences, molecular dynamics (MD) simulations were carried out to determine the self-diffusivities of seven gases (CH4, N2, Kr, C2H6, C3H8, Ar, and Ne) in six different all-silica zeolite structures (MFI, AFI, FAU, CHA, DDR, and LTA). The simulation results show that the variation of Di,self with qi is determined by a variety of factors that include molecular size and shape, and degree of confinement within the zeolite. For one-dimensional channels (AFI) and intersecting channel structures (MFI), the Di,self invariably decreases with increasing qi. For zeolite structures that consist of cages separated by windows (FAU, CHA, DDR, LTA), the size of the windows is an important determinant. When the windows are wide (FAU), the Di,self decreases with qi for all molecules. If the windows are narrow (CHA, DDR and LTA), the Di,self often exhibits a sharp increase with qi, reaches a maximum and reduces to near-zero values at saturation. The sharpness with which Di,self increases with qi, is dictated by the degree of confinement at the window. Weakly confined molecules, such as Ne, do not exhibit an increase of Di,self with qi. [source] | |||||||||||||