Identification of arches in 2D granular packings

We identify arches in a bed of granular disks generated by a molecular dynamic-type simulation. We use the history of the deposition of the particles to identify the supporting contacts of each particle. Then, arches are defined as sets of mutually stable disks. Different packings generated through tapping are analyzed. The possibility of identifying arches from the static structure of a deposited bed, without any information on the history of the deposition, is discussed.Comment: 12 pages, 7 figure

Variational analysis of self-focusing of intense ultrashort pulses in gases

By using perturbation theory we derive an expression for the electrical field of a Gaussian laser pulse propagating in a gas medium. This expression is used as a trial solution in a variational method to get quasianalytical solutions for the width, intensity and self-focusing distance of ultrashort pulse. The approximation gives an improved agreement with results of numerical simulations for a broad range of values of the input power of the pulse than previous analytical results available in the literature.Comment: 19 pages, 8 figure

Does the Badal optometer stimulate accommodation accurately?

Postprint (author's final draft

Analytical operator solution of master equations describing phase-sensitive processes

We present a method of solving master equations which may describe, in their most general form, phase sensitive processes such as decay and amplification. We make use of the superoperator technique.Comment: 10 pages, LaTex, 3 figures, accepted for publication in International Journal of Modern Physics

Estudio clínico morfológico de la deformación del borde dorsal del cuello en caballos cruzados de carruaje en Sevilla y Córdoba (Andalucía, España)

The aim of this study was to a clinical, morphological of deformation dorsal neck edge on in horse of carriage in Seville and Cordoba, Andalusia, Spain. We studied a total of 110 horses. Clinical examination was performed and morphological considering weight and body condition was measured cervical perimeter. Deformation of the dorsal edge of the neck in all cases studied was evident. Morphological study to consider the deformation of the dorsal edge of the neck taking into account the ridge of the neck (score of 1 to 5) evidenced: for score 0: 33.6%; score 1: 51.8%; Rankings 2: 10%; Rated: 4.5 % for score 4 and 5 no horse was observed in these categories. The average diameter of the neck was 92.54cm, the average neck length was 92.46 cm and the weight was 3.92kg. The statistical result of the degree of deformation of the neck with the weight was 0.465 and the correlation between the degrees of deformation with weight was 0.652. The degree of correlation between neck circumference and body condition was 0.634. In conclusion deformation dorsal edge of the collar in horses used for carriage crossed in Cordoba and Seville, Spain, was observed a prevalence of 66%.Se plantea como objetivo un estudio clínico morfológico de la deformación del borde dorsal del cuello en caballos de carruaje en Sevilla y Córdoba, Andalucía-España. Fueron estudiados un total de 110 caballos. Se practicó un examen clínico y morfológico considerando condición corporal peso y se midió el perímetro cervical. El estudio morfológico para considerar la deformación del borde dorsal del cuello tomando en cuenta la cresta de la nuca (puntuación del 1 al 5) evidencio: para la puntuación 0: 33.6%; puntuación 1: 51.8%; puntuación 2: 10%; puntuación: 4.5%, para la puntuación 4 y 5 ningún caballo se observó en estas categorías. El promedio del diámetro del cuello fue de 92.54cm, el promedio de la longitud del cuello fue de 92.46 cm y el peso fue de 3.92Kg. Los resultados estadísticos del grado de deformación del cuello con el peso fue de 0.465 y la correlación entre el grado de deformación con el peso fue de 0.652. El grado de correlación entre el perímetro cervical y la condición corporal fue de 0.634. En conclusión se observó la deformación del borde dorsal del cuello en caballos cruzados empleados para carruajes en Córdoba y Sevilla, España, con una prevalencia puntual de 66%

A contribution to the mechanism of “reduced” CO₂ adsorbates electro-oxidation from combined spectroelectrochemical and voltammetric data

The nature of reduced CO2 adsorbates, as well as the mechanisms for their electro-oxidation on platinum, have been reviewed through the light of new experimental data obtained by cyclic voltammetry and by Fourier transform infrared reflectance spectroscopy. Three different “reduced” CO2 adsorbates are described as “‘ensembles”. It is suggested that they involve different extents of adsorbed entities, among which weakly bound and strongly bound hydrogen atoms play the most important role.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Potential-dependent competitive processes on platinum in acid solution in the presence of propargyl alcohol

The electroadsorption interactions between dilute propargyl alcohol and smooth platinum in 0.5 M H2SO4 at 25° C have been investigated at different potentials. When the platinum electrode is covered by H atoms the hydrogenation of propargyl alcohol takes place. Otherwise, when the platinum electrode is held at a potential located in the double-layer region, the electroadsorption of propargyl alcohol involves a disruptive electro-oxidation yielding strongly bound adsorbed residues. The latter can be electrodesorbed presumably as carbon dioxide and protons. This process occurs within the O-electroadsorption potential range. The complete residue electrodesorption requires several voltammetric cycles. Competition between the hydrogenation reaction and the disruptive electroadsorption process can be observed at potentials where the platinum surface is partially covered by H atoms.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

PG 1211+143: probing high frequency lags in a high mass AGN

We present the timing analysis of the four archived XMM-Newton observations of PG 1211+143. The source is well-known for its spectral complexity, comprising a strong soft-excess and different absorption systems. Soft energy band (0.3-0.7 keV) lags are detected over all the four observations, in the frequency range \nu \lsim 6 \times 10^{-4} Hz, where hard lags, similar to those observed in black hole X-ray binaries, are usually detected in smaller mass AGN. The lag magnitude is energy-dependent, showing two distinct trends apparently connectable to the two flux levels at which the source is observed. The results are discussed in the context of disk- and/or corona-reprocessing scenarios, and of disk wind models. Similarities with the high-frequency negative lag of 1H 0707-495 are highlighted, and, if confirmed, they would support the hypothesis that the lag in PG 1211+143 represents the signature of the same underlying mechanism, whose temporal characteristics scale with the mass of the central object.Comment: 6 pages, 6 figures, accepted for publication in MNRAS Letter