Droplets displacement and oscillations induced by ultrasonic surface acoustic waves: a quantitative study

We present an experimental study of a droplet interacting with an ultrasonic surface acoustic wave (SAW). Depending on the amplitude of the wave, the drop can either experience an internal flow with its contact-line pinned, or (at higher amplitude) move along the direction of the wave also with internal flow. Both situations appear together with oscillations of the drop free-surface. The physical origins of the internal mixing flow as well as the drop displacement and surface waves are still not well understood. In order to give insights of the underlying physics involved in these phenomena, we carried out an experimental and numerical study. The results suggest that the surface deformation of the drop can be related as a combination between acoustic streaming effect and radiation pressure inside the drop.Comment: 9 pages, 14 figures. To appear in Physical Review

Dual phononic and photonic band gaps in a periodic array of pillars deposited on a thin plate

We study theoretically the simultaneous existence of phononic and photonic band gaps in a periodic array of silicon pillars deposited on a homogeneous thin silica plate. Several lattices, namely, square, triangular, and honeycomb are investigated for a wide range of geometrical parameters. We discuss the most suitable cases for dual phononic-photonic band gaps, especially in comparison to the more conventional structures constituted by a periodic array of holes in a membrane

La estructura del domo de la Rabassa y del sector oriental del sinclinal de Llavorsí (Pirineo Central)

The Rabassa dome and the Llavorsí syncline are two structural units of the Hercynian basement of the Central Pyrenees. Their internal structure results from the superposition of hercynian thrusts and folds. Detailed structural analysis reveals that the pre-main cleavage structures are very significant. They are a southward directed thrust, which overthrusts the Silurian rocks over the highest positioned Devonian materials, and close hectometric to kilometric-sized folds. These pre-cleavage folds give rise to the antiform and the synfom structures of the Rabassa dome and the Llavorsí syncline respectively. Their axial planes are inclined to the south and strike from NE-SW to NW-SE. This early folding and the present topographic surface make the Silurian black shales overlying the Devonian formations to appear in some synform structures, which correspond to the bands of Silurian rocks extended along the centre of the Llavorsí syncline. Shortening related to the main cleavage development produces decametric and smaller scale folds of bedding and make the previous folds to be tighter. The early structural configuration is only modified by a set of E-W trending northward dipping inverse faults which cut the southern limb of the Llavorsí syncline.La configuración del Domo de la Rabassa y del Sinclinal de Llavorsí resulta de diferentes estructuras de cabalgamiento y de plegamiento hercínicas. El análisis estructural llevado a cabo pone de manifiesto la importancia de las estructuras de deformación que preceden al desarrollo de la foliación dominante. Tienen un carácter precoz un cabalgamiento de vergencia sur, que superpone el Silúrico sobre la más reciente de las formaciones devónicas, y pliegues de la estratificación de dimensiones hectométricas y kilométricas. Estos primeros pliegues son responsables de las estructuras antiforme y sinforme del Domo de la Rabassa y del Sinclinal de Llavorsí respectivamente. Son pliegues cerrados, vergentes al sur, y dispuestos entre las direcciones NE-SO y NO-SE. Debido a este plegamiento precoz y al nivel actual de erosión, el contacto entre el Silúrico alóctono y el Devónico infrayacente aparece sólo en algunas estructuras sinformes. Estas corresponden a las franjas de rocas silúricas que se extienden a lo largo del núcleo del Sinclinal de Llavorsí. El posterior desarrollo de la foliación dominante convierte a los pliegues precoces en apretados e isoclinales. La estructura conformada aparece sólo modificada por un sistema de fallas inversas, de vergencia sur y dirección E-O, que compartimenta el flanco sur del Sinclinal de Llavorsí

Performance of polyester-based electrospun scaffolds under in vitro hydrolytic conditions: From short-term to long-term applications

The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °C. The scaffolds for short-time applications were PLGA and PDO, in which the molar mass diminished down to 20% in a 20-30 days lifespan. While PDO developed crystallinity that prevented the geometry of the fibres, those of PLGA coalesced and collapsed. The scaffolds for long-term applications were PCL and PHB, in which the molar mass followed a progressive decrease, reaching values of 10% for PCL and almost 50% for PHB after 650 days of immersion. This resistant pattern was mainly ascribed to the stability of the crystalline domains of the fibres, in which the diameters remained almost unaffected. From the perspective of an adequate balance between the durability and degradation, this study may serve technologists as a reference point to design polyester-based scaffolds for biomedical applications

Estimation of urban sensible heat flux using a dense wireless network of observations

The determination of the sensible heat flux over urban terrain is challenging due to irregular surface geometry and surface types. To address this, in 2006-07, a major field campaign (LUCE) took place at the École Polytechnique Fédérale de Lausanne campus, a moderately occupied urban site. A distributed network of 92 wireless weather stations was combined with routine atmospheric profiling, offering high temporal and spatial resolution meteorological measurements. The objective of this study is to estimate the sensible heat flux over the built environment under convective conditions. Calculations were based on Monin-Obukhov similarity for temperature in the surface layer. The results illustrate a good agreement between the sensible heat flux inferred from the thermal roughness length approach and independent calibrated measurements from a scintillometer located inside the urban canopy. It also shows that using only one well-selected station can provide a good estimate of the sensible heat flux over the campus for convective conditions. Overall, this study illustrates how an extensive network of meteorological measurements can be a useful tool to estimate the sensible heat flux in complex urban environment

Priming of plant resistance by natural compounds. Hexanoic acid as a model

Some alternative control strategies of currently emerging plant diseases are based on the use of resistance inducers. This review highlights the recent advances made in the characterization of natural compounds that induce resistance by a priming mechanism. These include vitamins, chitosans, oligogalacturonides, volatile organic compounds, azelaic and pipecolic acid, among others. Overall, other than providing novel disease control strategies that meet environmental regulations, natural priming agents are valuable tools to help unravel the complex mechanisms underlying the induced resistance (IR) phenomenon. The data presented in this review reflect the novel contributions made from studying these natural plant inducers, with special emphasis placed on hexanoic acid (Hx), proposed herein as a model tool for this research field. Hx is a potent natural priming agent of proven efficiency in a wide range of host plants and pathogens. It can early activate broad-spectrum defenses by inducing callose deposition and the salicylic acid (SA) and jasmonic acid (JA) pathways. Later it can prime pathogen-specific responses according to the pathogen’s lifestyle. Interestingly, Hx primes redox-related genes to produce an anti-oxidant protective effect, which might be critical for limiting the infection of necrotrophs. Our Hx-IR findings also strongly suggest that it is an attractive tool for the molecular characterization of the plant alarmed state, with the added advantage of it being a natural compound.This work was supported by grants from the Spanish Ministry of Science and Innovation (AGL2010-22300-C03-01-02-03) co-funded by European Regional Development Fund (ERDF) and Generalitat Valenciana Grupos de Excelencia (PROMETEO/2012/066). Maria de la O Leyva and Ivan Finiti were recipients of a research contract from AGL2010-22300-C03-01. We thank the SCIE Greenhouse section at the University of Valencia and the SCIC at the Universitat Jaume I for technical support

The effects of varying glenohumeral joint angle on acute volume load, muscle activation, swelling, and echo-Intensity on the biceps brachii in resistance-trained individuals

There is a paucity of data on how manipulating joint angles during isolation exercises may impact overall session muscle activation and volume load in resistance-trained individuals. We investigated the acute effects of varying glenohumeral joint angle on the biceps brachii with a crossover repeated measure design with three different biceps curls. One session served as the positive control (CON), which subjects performed 9 sets of bicep curls with their shoulder in a neutral position. The experimental condition (VAR), varied the glenohumeral joint angle by performing 3 sets in shoulder extension (30 degrees), 3 sets neutral (0 degrees), and 3 sets in flexion (90 degrees). Volume load and muscle activation (EMG) were recorded during the training sessions. Muscle swelling and strain were assessed via muscle thickness and echo-intensity responses at pre, post, 24 h, 48 h, and 72 h. There were no significant differences between conditions for most dependent variables. However, the overall session EMG amplitude was significantly higher (p = 0.0001) in VAR compared to CON condition (95%-CI: 8.4% to 23.3%). Our findings suggest that varying joint angles during resistance training (RT) may enhance total muscle activation without negatively affecting volume load within a training session in resistance-trained individuals7

Relato de una experiencia de investigación-acción con respecto al abandono en la FRA – UTN.

El presente trabajo se ubica en el marco de las investigaciones del Programa Fénix de retención institucional que se pregunta cuáles son las estrategias y los modos de intervención que contribuyen para resolver los problemas de retención y rendimiento de alumnos en la universidad pública. Tiene por objetivos identificar y conceptualizar vías alternativas y también, acumular y evaluar experiencias donde las estrategias, como los sistemas tutoriales implementados, resultan eficaces. En el año 2006 decidimos profundizar sobre el comportamiento de un grupo de alumnos ingresantes que tomaron la decisión de abandonar el Seminario de Ingreso, habiendo aprobado el examen diagnóstico del área de Matemática. El trabajo está pensado en cuatro partes: en la primera se presenta una breve explicitación del Programa Fénix como marco de la experiencia; en la segunda, el Seminario Universitario de acceso a la universidad como contexto en donde se realizó la experiencia; en la tercera se relata la historia de la experiencia y la generación de una nueva alternativa de retención y por último se extraen algunas conclusiones preliminares

Minsky machines and algorithmic problems

This is a survey of using Minsky machines to study algorithmic problems in semigroups, groups and other algebraic systems.Comment: 19 page