Ion assisted deposition of thin films by substrate tuned radio frequency magnetron sputtering

The substrate tuning technique was applied to a radio frequency magnetron sputtering system to obtain a variable substrate bias without an additional source. The dependence of the substrate bias on the value of the external impedance was studied for different values of chamber pressure, gas composition and rf input power. A qualitative explanation of the results is given, based on a simple model, and the role of the stray capacitance is clearly disclosed. Langmuir probe measurements show that this system allows independent control of the ion flux and the ion energy bombarding the growing film. For an argon flow rate of 2.8 sccm and a radio frequency power of 300 W (intermediate values of the range studied) the ion flux incident on the substrate was 1.3 X 1020-m-2-s-1. The maximum ion energy available in these conditions can be varied in the range 30-150 eV. As a practical application of the technique, BN thin films were deposited under different ion bombardment conditions. An ion energy threshold of about 80 eV was found, below which only the hexagonal phase was present in the films, while for higher energies both hexagonal and cubic phase were present. A cubic content of about 60% was found for an ion energy of 120 V.

Efectos del clobazam sobre la memoria, atención y tiempo de reacción

A través de un diseño intrasujeto contrabalanceado, y sobre una base de doble ciego, se han estudiado, en relación al placebo, 1os efectos de una dosis única de 20 mg. de clobazam sobre la memoria, atencion y tiempo de reaccion medidos a traves de pruebas de laboratorio. Se ha utilizado una muestra de 9 sujetos, universitarios voluntarios, sin patologia orgánica conocida y con puntuaciones medias en 10s factores neuroticismo y extroversión del E.P.I. No se han encontrado diferencias significativas entre el clobazam y el placebo, salvo en la prueba de Tolouse-Pieron, la cua1 pone de manifiesto un efecto detrimental del clobazam. Por otra parte, aunque no estadisticamente significativas, se han apreciado dos tendencias. En primer lugar, el clobazam tiende a disminuir el rendimiento mnemico y de atencion y a incrementar la rapidez de respuesta en comparación con el placebo; en segundo lugar, el clobazam inhibe el efecto de practica en las aplicaciones sucesivas de las pruebas de atención y memoria y 10 potencia en el caso del tiempo de reaccion. Por todo ello se requiere una investigacion adicional con mas sujetos y un diseño experimental más complejo.

Particle dispersion in synthetic turbulent flows

We study particle dispersion advected by a synthetic turbulent flow from a Lagrangian perspective and focus on the two-particle and cluster dispersion by the flow. It has been recently reported that Richardson¿s law for the two-particle dispersion can stem from different dispersion mechanisms, and can be dominated by either diffusive or ballistic events. The nature of the Richardson dispersion depends on the parameters of our flow and is discussed in terms of the values of a persistence parameter expressing the relative importance of the two above-mentioned mechanisms. We support this analysis by studying the distribution of interparticle distances, the relative velocity correlation functions, as well as the relative trajectories.

Reaction-diffusion fronts under stochastic advection

We study front propagation in stirred media using a simplified modelization of the turbulent flow. Computer simulations reveal the existence of the two limiting propagation modes observed in recent experiments with liquid phase isothermal reactions. These two modes respectively correspond to a wrinkled although sharp propagating interface and to a broadened one. Specific laws relative to the enhancement of the front velocity in each regime are confirmed by our simulations.

Langevin approach to generate synthetic turbulent flows

We present an analytical scheme, easily implemented numerically, to generate synthetic Gaussian turbulent flows by using a linear Langevin equation, where the noise term acts as a stochastic stirring force. The characteristic parameters of the velocity field are well introduced, in particular the kinematic viscosity and the spectrum of energy. As an application, the diffusion of a passive scalar is studied for two different energy spectra. Numerical results are compared favorably with analytical calculations.

Front dynamics in turbulent media

A study of a stable front propagating in a turbulent medium is presented. The front is generated through a reaction-diffusion equation, and the turbulent medium is statistically modeled using a Langevin equation. Numerical simulations indicate the presence of two different dynamical regimes. These regimes appear when the turbulent flow either wrinkles a still rather sharp propagating interfase or broadens it. Specific dependences of the propagating velocities on stirring intensities appropriate to each case are found and fitted when possible according to theoretically predicted laws. Different turbulent spectra are considered.

Earliest known use of marine resources by neanderthals

Numerous studies along the northern Mediterranean borderland have documented the use of shellfish by Neanderthals but none of these finds are prior to Marine Isotopic Stage 3 (MIS 3). In this paper we present evidence that gathering and consumption of mollusks can now be traced back to the lowest level of the archaeological sequence at Bajondillo Cave (Málaga, Spain), dated during the MIS 6. The paper describes the taxonomical and taphonomical features of the mollusk assemblages from this level Bj19 and briefly touches upon those retrieved in levels Bj18 (MIS 5) and Bj17 (MIS 4), evidencing a continuity of the shellfishing activity that reaches to MIS 3. This evidence is substantiated on 29 datings through radiocarbon, thermoluminescence and U series methods. Obtained dates and paleoenvironmental records from the cave include isotopic, pollen, lithostratigraphic and sedimentological analyses and they are fully coherent with paleoclimate conditions expected for the different stages. We conclude that described use of shellfish resources by Neanderthals (H. neanderthalensis) in Southern Spain started ~150 ka and were almost contemporaneous to Pinnacle Point (South Africa), when shellfishing is first documented in archaic modern humans.

Application of metabolic engineering to the production of scopolamine

Scopolamine is an alkaloid widely used in medicine for its anticholinergic activity. The aim of this review is to show that metabolic engineering techniques constitute a suitable tool to improve the production of tropane alkaloids, focusing in particular on scopolamine. We present an overview of results obtained by various research groups, including our own, who have studied the overexpression of genes involved in the biosynthesis of scopolamine in different plant species that produce tropane alkaloids. Experiments carried out to improve production in hairy root cultures will also be described, as well as those attempting to biotransform hyoscyamine into scopolamine in roots and transgenic tobacco cells.

Stochastic differential equations with random coefficients

In this paper we establish the existence and uniqueness of a solution for different types of stochastic differential equation with random initial conditions and random coefficients. The stochastic integral is interpreted as a generalized Stratonovich integral, and the techniques used to derive these results are mainly based on the path properties of the Brownian motion, and the definition of the Stratonovich integral.

Lagrangian-Hamiltonian unified formalism for field theory

The RuskSkinner formalism was developed in order to give a geometrical unified formalism for describing mechanical systems. It incorporates all the characteristics of Lagrangian and Hamiltonian descriptions of these systems (including dynamical equations and solutions, constraints, Legendre map, evolution operators, equivalence, etc.). In this work we extend this unified framework to first-order classical field theories, and show how this description comprises the main features of the Lagrangian and Hamiltonian formalisms, both for the regular and singular cases. This formulation is a first step toward further applications in optimal control theory for partial differential equations. 2004 American Institute of Physics.

Efectos del clobazam sobre la memoria, atención y tiempo de reacción

A través de un diseño intrasujeto contrabalanceado, y sobre una base de doble ciego, se han estudiado, en relación al placebo, 1os efectos de una dosis única de 20 mg. de clobazam sobre la memoria, atencion y tiempo de reaccion medidos a traves de pruebas de laboratorio. Se ha utilizado una muestra de 9 sujetos, universitarios voluntarios, sin patologia orgánica conocida y con puntuaciones medias en 10s factores neuroticismo y extroversión del E.P.I. No se han encontrado diferencias significativas entre el clobazam y el placebo, salvo en la prueba de Tolouse-Pieron, la cua1 pone de manifiesto un efecto detrimental del clobazam. Por otra parte, aunque no estadisticamente significativas, se han apreciado dos tendencias. En primer lugar, el clobazam tiende a disminuir el rendimiento mnemico y de atencion y a incrementar la rapidez de respuesta en comparación con el placebo; en segundo lugar, el clobazam inhibe el efecto de practica en las aplicaciones sucesivas de las pruebas de atención y memoria y 10 potencia en el caso del tiempo de reaccion. Por todo ello se requiere una investigacion adicional con mas sujetos y un diseño experimental más complejo.

Diseño e implementación de un framework de presentación para aplicaciones J2EE

El objetivo principal es analizar y desarrollar un framework que haga que el desarrollo de la capa de presentación sea más sencillo y fácil de implementar en el caso de aplicaciones J2EE con un cliente ligero.