Frequency doubling of femtosecond pulses in walk-off compensated npp

Summary form only given. N-(4-nitrophenyl)-L-prolinol (NPP) is an organic molecular crystal developped by molecular engineering, that exhibits one of the highest phase-matchable second-order susceptibilities reported so far in the near-infrared spectral range (d/sub eff//spl ap/56 pm/V). However, the large spatial and temporal walk-off existing in NPP can limit severely the usefulness of the material away from the noncritical phase-matching (ncpm) wavelength and for shorter pulses. Here we show that subpicosecond pulses can be efficiently frequency-doubled and mixed in NPP with moderate pump intensities, by employing tilted pulse techniques. These techniques make use of the large Poynting vector walk-off exhibited by NPP crystals outside the ncpm. Such techniques are based on the diffraction of the input pump wave by a grating so that each spectral component is dispersed in a different direction, thus the resulting signal is a tilted pulse.Peer ReviewedPostprint (published version

Intercalation and dynamics of hydrated Fe2+ in the vermiculites from Santa Olalla and Ojén

Although the intercalation of Fe3+ into layered phyllosicilicates-especially into smectites-attracted much attention in the past two decades, the information about Fe2+ loaded phyllosilicates is sparse. Here we present an investigation of the Fe2+ exchanged vermiculites from Santa Olalla and Ojén (Andalusia, Spain) by means of Mössbauer spectroscopy. The room temperature Mössbauer spectra are very similar to those of the starting compounds (Na forms) except for a decrease of the contribution of structural Fe3+ and a concomitant increase of the contribution of Fe2+ sites, indicating an internal redox process. The extent of this redox reaction is different for the two vermiculites. Thus, the intercalated Fe2+ acts as an electron mediator from the external medium to the structural Fe3+ ions. A new component attributable to intercalated Fe2+ is practically invisible in the room temperature Mössbauer spectra, but increases strongly and continuously during cooling to 4.2 K, where it is the dominant feature of the Mössbauer patterns. At 4.2 K, its quadruple splitting amounts to 3.31 mm/s, which is in excellent agreement with the quadrupole slitting of Fe2+ coordinated to six water molecules in a highly symmetric octahedral arrangement. The strong decrease of the Mössbauer-Lamb factor of this component with increasing temperature indicates a weak bonding of the Fe 2+ in the interlayer space

Anquilosis de la articulación coxofemoral y alteraciones biomecánicas en un individuo medieval de la necrópolis de la catedral de Sigüenza (Guadalajara)

X Congreso Nacional de Paleopatología. Univesidad Autónoma de Madrid, septiembre de 200

Three dimensionality in the wake of the flow around a circular cylinder at Reynolds number 5000

The turbulent flow around a circular cylinder has been investigated at Re=5000Re=5000 using direct numerical simulations. Low frequency behavior, vortex undulation, vortex splitting, vortex dislocations and three dimensional flow within the wake were found to happen at this flow regime. In order to successfully capture the wake three dimensionality, different span-wise lengths were considered. It was found that a length LZ=2pDLZ=2pD was enough to capture this behavior, correctly predicting different aspects of the flow such as drag coefficient, Strouhal number and pressure and velocity distributions when compared to experimental values. Two instability mechanisms were found to coexist in the present case study: a global type instability originating in the shear layer, which shows a characteristic frequency, and a convective type instability that seems to be constantly present in the near wake. Characteristics of both types of instabilities are identified and discussed in detail. As suggested by Norberg, a resonance-type effect takes place in the vortex formation region, as the coexistence of both instability mechanisms result in distorted vortex tubes. However, vortex coherence is never lost within the wake.Peer ReviewedPostprint (author's final draft

Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field ${\bm H}_a$, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude $H_a$ of the applied magnetic field and its angle of rotation $\alpha_s$ upon the magnetization of the superconductor sample is analyzed. When $H_a$ is smaller than the penetration field $H_P$, the magnetization components, parallel and perpendicular to ${\bm H_a}$, oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, $H_a$, is larger than $H_P$, both magnetization components become constant functions of $\alpha_s$ at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.Comment: 12 pages, 29 figure

Remarks on propagating waves in non-linear vacuum electrodynamics

Using the quadratic expansion in the photon fields of Euler-Heisemberg (EH) non-linear electrodynamics (NLED) Lagrangian model we study relevant vacuum properties in a scenario involving the propagation of a photon probe in the presence of a background constant and static magnetic field, $B_e$. We compute the gauge invariant, symmetric and conserved energy-momentum tensor (EMT) and the angular momentum tensor (AMT) for arbitrary magnetic field strength using the Hilbert method under the soft-photon approximation. We discuss how the presence of magneto-electric terms in the EH Lagrangian is a source of anisotropy and induce the non-zero trace in the EMT, the latter being connected to the non-conformal anomaly of the non-linear Lagrangian and with the non-conservation of the light cone in Minkowski space-time inducing birefringence. From the EMT we analyze some quantities of interest such as the energy density, pressures, Poynting vector, and angular momentum vector and we compare them with those obtained from the Noether method. The magnetized vacuum properties are also studied showing that a photon-effective magnetic moment can be defined for different polarization modes. The calculations are done in terms of derivatives of the two scalar invariants of electrodynamics hence, extension to other NLED Lagrangian is straightforward. We discuss further physical implications and experimental strategies to test magnetization, photon pressure and efective magnetic moment.Comment: 24 pages, 3 figure

Cuban creole pig in Bayamo jurisdiction

The former jurisdiction of Bayamo, as political colonial division began its way in the century XVI, after its foundation in 1513 as the second Cuban village. Currently the Bayamo village is integrated by 15 local districts, an extension of 835.12 km2 and a population 68690 inhabitants. In spite of have elapsed more than 470 years from the arrival of the first pigs from Spain, this region has maintained 6176 breeders of this native pig breed as direct descendant of the Mediterranean pigs. In this work is presented the racial, ecological and human factors, that they have permitted the maintenance of this population with origin in the Iberian pig.La antigua jurisdicción de Bayamo, como división política de la colonia comenzó su andadura en el siglo XVI, tras su fundación en 1513 como la segunda villa de Cuba. Actualmente el municipio de Bayamo lo integran 15 consejos populares, una superficie de 835,12 km2 y una población de 68690 habitantes. A pesar de haber transcurrido más de 470 años desde la llegada de los primeros cerdos desde España, esta región ha mantenido 6176 reproductores de la raza cerdo Criollo como descendiente directo de los cerdos mediterráneos. En este trabajo se presenta los factores racial, ecológico y humano, que han permitido la perdurabilidad de esta raza descendiente del cerdo Ibérico