4,543 research outputs found
EXAFS Analysis of Size-Constrained Semiconducting Materials
Semiconducting materials such as CdSe, CdS, PbS and GaP are included in crystalline zeolite Y and mordenite and structurally flexible ethylene-methacrylic acid copolymer solid matrices. EXAFS analysis reveals formation of species with dimensions of molecular size up to ca. 13 A in the crystalline hosts, while the polymer matrices allow agglomeration of larger semiconducting particles. Zeolite anchored structures are distinctively different to small particles with bulk crystal structure as usually found in colloidal systems
EXAFS study of nickel exchanged into zeolite Y
EXAFS and near edge spectroscopy were used to monitor changes i n Ni coordination
as a function of treatment conditions after aqueous exchange into zeolite Y. Our
results suggest that after calcination and dehydration under the conditions of
this study, major site occupancy for Ni appears to be in the tri-coordinate
exchange sites , and not i n the hexagonal prisms as suggested by previous x-ray
diffraction results
EXAFS study of nickel tetracarbonyl and nickel clusters in zeolite Y
Adsorption and thermal decomposition of Ni(CO)4 in the cage system of zeolite Y
have been studied with EXAFS, electron microscopy and IR spectroscopy , Ni(CO)4
is adsorbed as an intact molecule in both cation - free zeolite Y and NaY. Symmetry
changes of the molecule in NaY are assigned to the formation of Na—OC-IMi bridges.
Thermal treatment of the Ni(CO)4/NaY adduct leads to loss of CO concomitant with
the formation of a binodal Ni phase. A major part of the forms clusters with
diameter between 0.5 and about 1.5 nm, in addition to larger crystallites
(5-30 nm), sticking at the outer surface of the zeolite matrix.,
The Ni-Ni scattering amplitude indicates increasing average particle size with
increasing temperature
Designing zeolite catalysts for shape-selective reactions: Chemical modification of surfaces for improved selectivity to dimethylamine in synthesis from methanol and ammonia
The relative contributions of external and intracrystalline acidic sites of small pore H-RHO zeolite for the selective synthesis of methylamines from methanol and ammonia have been studied. Nonselective surface reactions which produce predominantly trimethylamine can be eliminated by “capping” the external acidic sites with trimethylphosphite (TMP) and other reagents, thus improving the selectivity toward the formation of dimethylamine. For small pore zeolites, neither the zeolite pore size nor the internal acidic sites is significantly affected by this treatment. In situ infrared and MAS-NMR studies show that TMP reacts irreversibly with the zeolite acidic sites via a modified Arbusov rearrangement to form surface-bound dimethylmethylphosphonate
Towards a public analysis database for LHC new physics searches using MadAnalysis 5
We present the implementation, in the MadAnalysis 5 framework, of several
ATLAS and CMS searches for supersymmetry in data recorded during the first run
of the LHC. We provide extensive details on the validation of our
implementations and propose to create a public analysis database within this
framework.Comment: 20 pages, 15 figures, 5 recast codes; version accepted by EPJC (Dec
22, 2014) including a new section with guidelines for the experimental
collaborations as well as for potential contributors to the PAD;
complementary information can be found at
http://madanalysis.irmp.ucl.ac.be/wiki/PhysicsAnalysisDatabas
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