Ultrathin oxides: bulk-oxide-like model surfaces or unique films?

To better understand the electronic and chemical properties of wide-gap oxide surfaces at the atomic scale, experimental work has focused on epitaxial films on metal substrates. Recent findings show that these films are considerably thinner than previously thought. This raises doubts about the transferability of the results to surface properties of thicker films and bulk crystals. By means of density-functional theory and approximate GW corrections for the electronic spectra we demonstrate for three characteristic wide-gap oxides (silica, alumina, and hafnia) the influence of the substrate and highlight critical differences between the ultrathin films and surfaces of bulk materials. Our results imply that monolayer-thin oxide films have rather unique properties.Comment: 5 pages, 3 figures, accepted by PR

Numerical Applicability of Different Sound Source Formulations to Compute Combustion Noise Using Acoustic Perturbation Equations for Reacting Flows

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76947/1/AIAA-2008-2948-818.pd

La personalidad del judio en la obra de Martino de Leon

Ponencias del I Congreso Internacional sobre Santo Martino en el VIII Centenario de su obra literaria 1185-1985 (Isidoriana. Colectanea de la Catedra de San Isidro, 1)Se analizan las líneas fundamentales que, según Martino de León, definen la personalidad judía. Hay dos momentos en la elaboración de mi trabajo: la encuesta y el análisis de los datos. La encuesta es simplemente bibliográfica, dada la imposibilidad total de poner en práctica la observación directa y participada. A través del análisis traté de poner en relación unos con otros, los datos entresacados de la lectura de las obras del autor, para descubrir una serie de convergencias que permiten apreciar las grandes constelaciones de imágenes, más o menos constantes, que caracterizan la personalidad judía. El desarrollo del trabajo es discursivo y tiene un comienzo lógico; esto no quiere decir que lo primero metodológicamente, lo sea también ontológicamente.Peer reviewe

Spectral Emission Properties of a Nitrogen-doped Diamond(001) Photocathode: Hot Electron Transport and Transverse Momentum Filtering

The electron emission properties of a single-crystal nitrogen-doped diamond(001) photocathode inserted in a 10kV DC photoelectron gun are determined using a tunable (235-410nm) ultraviolet laser radiation source for photoemission from both the back nitrogen-doped substrate face and the front homo-epitaxially grown and undoped diamond crystal face. The measured spectral trends of the mean transverse energy (MTE) and quantum efficiency (QE) of the emitted electrons are both anomalous and non-monotonic, but are shown to be consistent with (i) the known physics of electron photoexcitation from the nitrogen substitution states into the conduction bands of diamond, (ii) the energy position and dispersion characteristics of the conduction bands of diamond in the (001) emission direction, (iii) the effective electron affinity of the crystal faces, (iv) the strong electron-(optical)phonon coupling in diamond, and (v) the associated hot electron transport dynamics under energy equipartition with the optical phonons. Notably, the observed hot electron emission is shown to be restricted parallel to the photocathode surface by the low transverse effective masses of the emitting band states - a transverse momentum filtering effect.Comment: 14 pages, 4 figure