Interplay between optical, viscous and elastic forces on an optically trapped Brownian particle immersed in a viscoelastic fluid

We provide a detailed study of the interplay between the different interactions which appear in the Brownian motion of a micronsized sphere immersed in a viscoelastic fluid measured with optical trapping interferometry. To explore a wide range of viscous, elastic and optical forces, we analyze two different viscoelastic solutions at various concentrations, which provide a dynamic polymeric structure surrounding the Brownian sphere. Our experiments show that, depending of the fluid, optical forces, even if small, slightly modify the complex modulus at low frequencies. Based on our findings, we propose an alternative methodology to calibrate this kind of experimental set-up when non-Newtonian fluids are used. Understanding the influence of the optical potential is essential for a correct interpretation of the mechanical properties obtained by optically-trapped probe-based studies of biomaterials and living matter.Comment: Accepted for publication in Applied Physics Letter

Tipificación y caracterización de granjas cinegéticas de faisán (Phasianus colchicus) en España

This research typified and characterised the pheasant (Phasianus colchicus) game farms in Spain using structural and marketing variables. A structured survey was given to 25 private-owned farms in May 2010. A categorical principal components analysis performed to typify the farms yielded two dimensions. First dimension explained 50.5% of the variance and included the variables “number of females in the breeding flock”, and “the farm is of complete-cycle or not”. Second dimension explained 32.3% of the variance and included the variables “age of the farm” and “the farm advertises its activity in the game press”. A cluster analysis differentiated four farm typologies. Farm type 1 included 28% of the farms, being recent (established between 1990 and 2003), complete-cycle and medium-sized (breeding flock of 15 to 300 females), with low advertising activity in the game press and without a hunting preserve. Farm type 2 included 28% of the farms, being the most recent (established between 1994 and 2008), without breeding flock, with low advertising activity, and most have hunting preserve. Farm type 3 included 20% of the farms, being old (established between 1983 and 1992), without breeding flock and with high advertising activity; 40% of them have hunting preserve. Farm type 4 included 24% of the farms, being old (established between 1980 and 1995), complete-cycle and high-sized (breeding flock of 50 to 1,000 females), with high advertising activity; most have hunting preserve. In conclusion, this is an alternative poultry sub-sector consolidated in Spain, despite being only three decades old.Se tipificaron y caracterizaron granjas cinegéticas de faisán (Phasianus colchicus) en España usando variables de estructura y comercialización obtenidas mediante encuesta a 25 granjas privadas en 2010. Un análisis de componentes principales categóricos realizado para tipificar las granjas generó dos dimensiones. La primera dimensión explicó el 50,5% de la varianza e incluyó las variables “número de hembras reproductoras” y “la granja es de ciclo completo o no”. La segunda dimensión explicó el 32,3% de la varianza e incluyó las variables “edad de la granja” y “la granja se publicita en prensa cinegética”. Un análisis de conglomerados subsiguiente diferenció cuatro tipologías de granjas. La tipología 1 incluyó al 28% de las granjas, siendo recientes (fundadas entre 1990 y 2003), de ciclo completo y tamaño medio (15 a 300 hembras reproductoras), con baja actividad publicitaria en prensa cinegética y sin coto de caza. La tipología 2 incluyó un 28% de las granjas, siendo las más recientes (fundadas entre 1994 y 2008), sin reproductores, con baja actividad publicitaria y la mayoría con coto. La tipología 3 incluyó un 20% de las granjas, siendo antiguas (fundadas entre 1983 y 1992), sin plantel reproductor y con elevada actividad publicitaria; el 40% tienen coto. La tipología 4 incluyó un 24% de las granjas, siendo antiguas (fundadas entre 1980 y 1995), de ciclo completo y gran tamaño (50 a 1.000 hembras reproductoras), con elevada actividad publicitaria y la mayoría con coto. Con sólo tres décadas de existencia este subsector avícola alternativo está consolidado en Españ

A shift in the spatial pattern of Iberian droughts during the 17th century

In this paper, series of drought occurrence and drought extension in the Iberian Peninsula are constructed for the 1600–1750 period from seven rogation series. These rogation ceremony records come from Bilbao, Catalonia, Zamora, Zaragoza, Toledo, Murcia and Seville. They are distributed across the Peninsula and include the areas with the most characteristic Iberian climate types, influenced by the Atlantic and the Mediterranean conditions, described from modern data. A seasonal division of the series shows that spring is a critical season for rogation series in most of Iberia, being Bilbao the only site were the highest number of rogations is detected for a different season. The annual analysis of the series shows a dramatic difference between the first half of the 17th century when droughts are characterized by its local character; and the rest of the period, when they affect to broader regions or even to the whole Peninsula. The analysis of spring series confirms the existence of the two periods detected in the annual analysis. Finally, secondary documentary sources are used to further characterise the two most extended droughts in the period, 1664 and 1680, and to verify the extension of the areas affected by droughts recorded through rogation series

Diffusion-driven superplasticity in ceramics: Modeling and comparison with available data

The discovery of superplasticity in ceramics polycrystals led to debates about whether or not earlier models developed for metallic polycrystals can apply to these systems. In particular, all existing models require some mobility of lattice or grain-boundary dislocations whereas such activity is not observed in most ceramic systems. A model is presented that accounts for the occurrence of superplasticity in the absence of dislocation motion. It is based on a mechanism of grain-boundary sliding by pure-shear motion under stationary conditions, which is accommodated by lattice or grain-boundary diffusion. The prediction of this model regarding the temperature dependences of the stress exponent and of the effective activation energy are found in agreement with experimental results and literature data on five ceramic systems where dislocation activity could not be recorded: -SiAlON polycrystals, Al-doped SiC polycrystals, nanocrystalline MgO, yttria-tetragonal zirconia polycrystals, and alumina ceramics polycrystal

Model-driven Test Engineering: A Practical Analysis in the AQUA-WS Project

The effective application of test phases has been one of the most relevant, critical and cost phases in the life cycle of software projects in the last years. During the test phase, the test team has to assure the quality of the system and the concordance with the initial requirements of the system. The model driven paradigm is offering suitable results in some areas and the test phase could be one of them. This paper presents how the application of this paradigm can help to improve this aspect in the functional test generation and it analyses the experience in a real project developed under this approach.Ministerio de Ciencia e Innovación TIN2010-20057-C03-02Ministerio de Ciencia e Innovación TIN 2010-12312-EJunta de Andalucía TIC-578

Accounting for inertia effects to access the high-frequency microrheology of viscoelastic fluids

We study the Brownian motion of microbeads immersed in water and in a viscoelastic wormlike micelles solution by optical trapping interferometry and diffusing wave spectroscopy. Through the mean-square displacement obtained from both techniques, we deduce the mechanical properties of the fluids at high frequencies by explicitly accounting for inertia effects of the particle and the surrounding fluid at short time scales. For wormlike micelle solutions, we recover the 3/4 scaling exponent for the loss modulus over two decades in frequency as predicted by the theory for semiflexible polymers

Modelización de las inestabilidades en la deformación plástica de monocristales de circona estabilizada con itria (YCSZ)

En este trabajo se presenta un modelo para explicar las inestabilidades dinámicas observadas durante la deformación plástica a alta temperatura de monocristales de circona estabilizada con itria, (YCSZ, yttria cubic stabilized zirconia) con alto contenido en itria. El modelo se basa en el fenómeno Portevin-Le Chatelier (PLC), que consiste en episodios sucesivos de anclaje y desanclaje de dislocaciones cuando éstas se mueven con una velocidad del mismo orden que los defectos que obstaculizan su movimiento. La evaluación numérica de los parámetros implicados en el modelo muestra que las inestabilidades plásticas son totalmente compatibles con el efecto Portevin- Le Chatelie

Dynamic instabilities in zirconia-based single- crystalline ceramics

Las cerámicas monocristalinas han sido objeto de un considerable interés a lo largo de estos años, debido a la posibilidad de obtener información esencial sobre propiedades fundamentales que puedan ayudar a la comprensión de sistemas policristalinos complejos. La circona dopada con itria ha merecido un estudio particular, debido a los interesantes fenómenos que manifiesta (endurecimiento por presencia de soluto disuelto en la red, precipitación de segundas fases, etc.). Entre las propiedades menos estudiadas hasta ahora se encuentran las inestabilidades plásticas que se presentan en la deformación a alta temperatura de monocristales con alto dopado de itria. Este trabajo recoge algunas de las experiencias mecánicas que se han realizado de forma sistemática para la comprensión del fenómeno y de las condiciones requeridas para que éste se produzca. Se han realizado ensayos de deformación en compresión uniaxial a lo largo de la dirección cristalográfica , de monocristales de circona completamente estabilizada con itria (≥21 mol%), a temperaturas entre 1310 y 1410 °C. La modelización de estas inestabilidades ha requerido un análisis detallado mediante microscopía electrónica de transmisión de la estructura de dislocaciones activadas durante la deformación.Single-crystalline ceramics have been the object of a considerable interest over the past years because they offer the possibility of obtaining essential information on fundamental properties which may help us to understand complex polycrystalline systems. Yttria-doped zirconia has deserved a particular study, since it exhibits quite interesting properties (solute hardening, precipitation hardening, etc.). Amongst the less studied properties up to now, plastic instabilities are found. These instabilities occur at high temperature deformation in highly-doped yttria-zirconia single crystals. This work summarizes some of the mechanical tests carried out systematically to understand this phenomenon and the conditions required for its occurrence. Yttria fully-stabilized cubic zirconia single crystals (≥21 mol% yttria content) have been deformed plastically under uniaxial compression in an axis, in the temperature range 1310-1410°C. Modelling of these instabilities has also required a thorough analysis by transmission electron microscopy of the deformed samples