152 research outputs found
Macroscopic model of formation of the domain of multiple filamentation in glass and water
The results of natural experiments of the propagation of powerful femtosecond laser radiation in glass and water
Evidence for an energy scale for quasiparticle dispersion in Bi_2Sr_2CaCu_2O_8
Quasiparticle dispersion in is investigated with
improved angular resolution as a function of temperature and doping. Unlike the
linear dispersion predicted by the band calculation, the data show a sharp
break in dispersion at binding energy where the velocity
changes by a factor of two or more. This change provides an energy scale in the
quasiparticle self-energy. This break in dispersion is evident at and away from
the d-wave node line, but the magnitude of the dispersion change decreases with
temperature and with increasing doping.Comment: 4 figure
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The partial oxidation of methane over Pd/Al2O3 catalyst nanoparticles studied in-situ by near ambient-pressure x-ray photoelectron spectroscopy
Near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to study the chemical state of methane oxidation catalysts in-situ. Al2O3{supported Pd catalysts are prepared with different particle sizes ranging from 4 nm to 10 nm. These catalysts were exposed to conditions similar to those used in the partial oxidation of methane (POM) to syn-gas and simultaneously monitored by NAP-XPS and mass spectrometry. NAP-XPS data show changes in the oxidation state of the palladium as the temperature in-
creases, from metallic Pd0 to PdO, and back to Pd0.
Mass spectrometry shows an increase in CO production whilst the Pd is in the oxide phase, and the metal is reduced back under presence of newly formed H2. A particle size effect is observed, such that CH4 conversion starts at lower temperatures with larger sized
particles from 6 nm to 10 nm. We find that all nanoparticles begin CH4 conversion at lower temperatures than polycrystalline Pd foil
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