Run-and-Tumble-Like Motion of Active Colloids in Viscoelastic Media

Run-and-tumble (RNT) motion is a prominent locomotion strategy employed by many living microorganisms. It is characterized by straight swimming intervals (runs), which are interrupted by sudden reorientation events (tumbles). In contrast, directional changes of synthetic microswimmers (active particles, APs) are caused by rotational diffusion, which is superimposed with their translational motion and thus leads to rather continuous and slow particle reorientations. Here we demonstrate that active particles can also perform a swimming motion where translational and orientational changes are disentangled, similar to RNT. In our system, such motion is realized by a viscoelastic solvent and a periodic modulation of the self-propulsion velocity. Experimentally, this is achieved using light-activated Janus colloids, which are illuminated by a time-dependent laser field. We observe a strong enhancement of the effective translational and rotational motion when the modulation time is comparable to the relaxation time of the viscoelastic fluid. Our findings are explained by the relaxation of the elastic stress, which builds up during the self-propulsion, and is suddenly released when the activity is turned off. In addition to a better understanding of active motion in viscoelastic surroundings, our results may suggest novel steering strategies for synthetic microswimmers in complex environments.Comment: 6 figures, New Journal of Physics accepte

RCS of engine inlets by a spectral iterative technique

A novel algorithm designed to compute efficiently and accurately the HF electromagnetic scattering from open-ended waveguide cavities is presented. The cavity is converted into a stepped-waveguide model so that the field spectrums are propagated, forward and backward, along each waveguide section. As boundary conditions for perfect electric conductors are applied via image theory, they are of local nature and take into account only the first order interactions between each pair of waveguide sections. Accordingly, additional forward-backward iterations must be performed if multiple interactions are to be taken into account. Finally, the RCS due to the interior irradiation is calculated by a Kirchhoff-based aperture integral. Good agreement with Method of Moments and Hybrid Modal solutions is found, as well as with experimental data, for 2-D and 3-D cavities.Peer ReviewedPostprint (published version

La sección de Torrellano (Mioceno Superior – Plioceno, Cuenca del Bajo Segura, Cordillera Bética Oriental): estratigrafía general y bioestratigrafía mediante foraminíferos planctónicos

En este trabajo se estudia la sección estratigráfica de Torrellano, ubicada en el sector norte de la cuenca neógena del Bajo Segura. El objetivo del mismo es ilustrar los rasgos estratigráficos de los sintemas Tortoniense-Messiniense I (T-MI), Messiniense II (MII) y Plioceno (P) de la sección estudiada. Además se ha realizado un análisis bioestratigráfico mediante foraminíferos planctónicos del sintema T-MI, que resulta clave para precisar, por un lado las condiciones ambientales que reinaron en la cuenca previamente al climax de la Crisis de Salinidad del Mediterráneo, y por otro lado, el momento en el que se inicia la misma. Se han descrito los rasgos litológicos de la sección, y tomando como referencia básica la escala de Lourens et al. (2004; ATNTS2004), se han identificado un total de seis bioeventos correspondientes a las subzonas MMi12b (Tortoniense superior) y MMi13a+b (Messiniense)

Plata y sangre: la guerra en la frontera norte de la Nueva España (1540-1600)

La expansión del imperio colonial español hacia el norte de México en busca de metales preciosos experimentó lentos avances y varios retrocesos por la dilatada y enconada resistencia indígena. El trabajo trata de los pueblos llamados chichimecas, sus relaciones con los vecinos indígenas antes y después de la llegada de los españoles, los debates jurídicos sobre su naturaleza, el origen y desarrollo de la guerra a la par de la labor evangelizadora y la explotación minera en su ámbito territorial. El conflicto fue largo y supuso nuevas líneas de actuación en relación con el deseo de pacificar una región de gran importancia minera por las explotaciones de plata.The expansion of the Spanish colonial empire towards the north of Mexico in search of precious metals experienced slow advances and several setbacks due to the long and fierce indigenous resistance. The work deals with the Chichimeca peoples, their relations with their indigenous neighbours before and after the arrival of the Spaniards, the legal debates about their nature, the origin and the development of the war, at the same time as the evangelizing work and the mining exploitation in their territorial area. The conflict was long, and involved new lines of action in relation to the desire to pacify a region of great importance for silver mining.Grado en Histori

Psychometric Properties of the Alcohol Expectancy Scale in Argentinean Adolescents Applying the Rating Scale Analysis

The goal of this study was to analyze the psychometric properties of the Alcohol Expectancy Scale (AES-AA) applying item response theory. Data were obtained from 592 adolescents enrolled in private and public schools of the city of Córdoba (Argentina). This psychometric study was carried out with the Rating Scale Model (RSM), a polytomous Rasch model. Out of the 45 items that make up the scale, 42 items had adequate fit indexes, explaining 91.3% of the adolescents’ response patterns. The estimation error of the parameters was low, indicating adequate precision of the items. In general, the participants’ scores fell within the range of the continuum where the test is most precise. Adolescents’ least frequent expectancies about alcohol consumption were related to sexual behavior (positive expectancies), whereas their most frequent expectancies corresponded both with the Sociability Scale (positive expectancies) and to the Cognitive and Behavioral Impairment Scale (negative expectancies). Implications for preventive programs are discussed.Fil: Pilatti, Angelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones y Estudio sobre Cultura y Sociedad. Centro de Investigaciones de la Facultad de Psicología - Grupo Vinculado CIPSI; ArgentinaFil: Godoy, Juan Carlos. Universidad Nacional de Córdoba. Facultad de Psicología. Laboratorio de Psicologia; ArgentinaFil: Lozano, Oscar. Universidad de Huelva; EspañaFil: Brussino, Silvina Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones y Estudio sobre Cultura y Sociedad. Centro de Investigaciones de la Facultad de Psicología - Grupo Vinculado CIPSI; Argentin

Development of an Analytic Nodal Diffusion Solver in Multigroups for 3D Reactor Cores with Rectangular or Hexagonal Assemblies.

More accurate modelling of physical phenomena involved in present and future nuclear reactors requires a multi-scale and multi-physics approach. This challenge can be accomplished by the coupling of best-estimate core-physics, thermal-hydraulics and multi-physics solvers. In order to make viable that coupling, the current trends in reactor simulations are along the development of a new generation of tools based on user-friendly, modular, easily linkable, faster and more accurate codes to be integrated in common platforms. These premises are in the origin of the NURESIM Integrated Project within the 6th European Framework Program, which is envisaged to provide the initial step towards a Common European Standard Software Platform for nuclear reactors simulations. In the frame of this project and to reach the above-mentioned goals, a 3-D multigroup nodal solver for neutron diffusion calculations called ANDES (Analytic Nodal Diffusion Equation Solver) has been developed and tested in-depth in this Thesis. ANDES solves the steady-state and time-dependent neutron diffusion equation in threedimensions and any number of energy groups, utilizing the Analytic Coarse-Mesh Finite-Difference (ACMFD) scheme to yield the nodal coupling equations. It can be applied to both Cartesian and triangular-Z geometries, so that simulations of LWR as well as VVER, HTR and fast reactors can be performed. The solver has been implemented in a fully encapsulated way, enabling it as a module to be readily integrated in other codes and platforms. In fact, it can be used either as a stand-alone nodal code or as a solver to accelerate the convergence of whole core pin-by-pin code systems. Verification of performance has shown that ANDES is a code with high order definition for whole core realistic nodal simulations. In this paper, the methodology developed and involved in ANDES is presented

Vehículos eléctricos : hacia la sostenibilidad en la movilidad

Los automoviles de propulsión convencional están destinados a desaparecer hacia 2050 y a ser sustituidos por alternativas mucho más eficientes. La electricidad, de momento y a pesar de que aún queda mucho por pulir, ha tomado ventaja y es la apuesta más firme que baraja Europa de cara al futuro

Hacia la integración de los sistemas de formación para el empleo. Una perspectiva desde Andalucía

És indubtable el gran desenvolupament dels processos de formació professional en els darrers anys. De tota manera, per bé que aquest ha estat extens i divers, no ha estat així pel que fa a unitat i coherència. Les exigències i demandes, i les oportunitats polítiques i formatives, han configurat una multiplicitat de sistemes de formació (reglada, ocupacional i contínua) entre els quals cal trobar i buscar un punt de confluència i de coordinació. La nostra intenció és aproximar-nos als esmentats reptes, per bé que hem d’analitzar prèviament la caracterització dels subsistemes, per tal que, en un segon moment, ens apropem, especialment en el nostre cas i des de la perspectiva de la Comunitat Autònoma d’Andalusia, a la configuració d’un sistema de formació professional amb major coordinació a través del sistema de qualificacions professionals i a la posada en marxa dels centres integrats de formació professional.That doubts fits for the great development of the processes of vocational training in the last decades. But if this it has been extensive and diverse, it has not been so much in unit and coherence. The requirements and demands, and the political opportunities and formatives have been forming a system multiplicity of vocational training (ruled, occupational and constant), between that we must find and look for a point of confluence and coordination. It is our intention to come closer the above mentioned challenges, but we must analyze before the characterization of the subsystems, for in the second moment, to approach, specially in our case from a perspective of the Autonomous Community of Andalusia, the configuration of a system and vocational training with bigger coordination across the System of Professional Qualifications and the putting in march of the Integrated Centers of Vocational Training.Que duda cabe del gran desarrollo de los procesos de Formación Profesional en las últimas décadas. Pero si este ha sido extenso y diverso, no lo ha sido tanto en unidad y coherencia. Las exigencias y demandas, y las oportunidades políticas y formativas han ido configurando una multiplicidad de sistemas de Formación Profesional (reglada, ocupacional y continua), entre los que debemos encontrar y buscar un punto de confluencia y de coordinación. Es nuestra intención aproximarnos a dichos retos, pero debemos analizar previamente la caracterización de los subsistemas, para en un segundo momento, acercarnos, especialmente en nuestro caso desde una perspectiva de la Comunidad Autónoma de Andalucía, a la configuración de un sistema de Formación Profesional con mayor coordinación a través del sistema de cualificaciones profesionales y la puesta en marcha de los centros integrados de Formación Profesional

Espacio europeo de educación y formación profesional : estrategias e instrumentos

La educación, desde la dimensión del aprendizaje permanente, cobra protagonismo y se convierte en una pieza clave para el desarrollo de las sociedades actuales, las sociedades de la información y del conocimiento