Jamming and unjamming of concentrated colloidal dispersions in channel flow

We investigated the pressure driven flow of concentrated colloidal dispersions in a converging channel geometry. Optical microscopy and image analysis were used to track tracer particles mixed into dispersions of sterically stabilized poly(methyl methacrylate) (PMMA) spheres. The dispersions were drawn into a round \unit[0.5]{mm} capillary at one of two pump speeds ($\equiv$ applied pressure): v_1=\unit[0.245]{ml\,\, min^{-1}} and v_2=\unit[0.612]{ml\,\, min^{-1}}. We observed that the dispersions at particle volume fractions $\phi\leqslant0.50$ followed Hagen-Poiseuille flow for a simple fluid; i.e. the mean flow rate $\langle V\rangle$ is approximately proportional to pressure drop (pump speed) and inversely proportional viscosity $\eta$. Above this concentration ($\phi\geqslant0.505$), the dispersions exhibit granular-like jamming behavior with $\langle V\rangle$ becoming independent of the pressure drop. However, at the highest applied pressure ($v_2$), the dispersions are able to unjam and switch from granular-like behaviour back to a simple hard-sphere liquid like system, due to the formation of rotating vortices in the spatial flow pattern. This mechanism is consistent with computer simulations of granular systems and supports for example proposed explanations of anomalously low friction in earthquake faults

Effect of rolling on dissipation in fault gouges

Sliding and rolling are two outstanding deformation modes in granular media. The first one induces frictional dissipation whereas the latter one involves deformation with negligible resistance. Using numerical simulations on two-dimensional shear cells, we investigate the effect of the grain rotation on the energy dissipation and the strength of granular materials under quasistatic shear deformation. Rolling and sliding are quantified in terms of the so-called Cosserat rotations. The observed spontaneous formation of vorticity cells and clusters of rotating bearings may provide an explanation for the long standing heat flow paradox of earthquake dynamics

Plan de negocio de una start-up universitaria dedicada al diseño de objetos de uso cotidiano que se pueden producir mediante la artesanía, la auto fabricación y la producción en serie industrial

Este proyecto pretende desarrollar un plan de negocio que facilite la comercialización de productos de mobiliario minimalista-ergonómico y objetos de tipo wearable diseñados en la universidad con el inconveniente de tener bajo valor diferencial por su sencilla concepción, y por lo tanto, generalmente, con dificultad para convertirse en una realidad y salir al mercado. Con el objetivo de solventar este problema, se propondrá la creación de una start-up (UNIGAD) que, mediante el e-commerce, haga de puente directo entre los proyectos concebidos en la universidad y el mercado. La start-up se sustentará sobre dos pilares: el primero será aprovechar la capacidad creativa de la comunidad universitaria como fuente de ideas e innovación, vinculándose a través de las fórmulas de colaboración previstas (spin-off) a la investigación, el desarrollo y la innovación (I+D+i) de la empresa; y el segundo será compensar la falta de valor diferencial de esos productos con un valor añadido que será aportado con calidad en el diseño y utilidad del producto, y con eficiencia en los procesos de fabricación, encargando la producción a diferentes colectivos profesionales como artesanos, pequeños industriales, talleres de auto fabricación o círculos de trabajo colaborativo. El business plan tiene como objetivo demostrar la viabilidad de la idea de negocio planteada. Se empezará con un exhaustivo estudio de mercado para analizar posibles competidores y tendencias del sector. A continuación, se explicará en profundidad la estrategia de marketing que se perseguirá, seguida de un plan de operaciones en el que se analizarán en detalle las acciones necesarias para el lanzamiento del producto ofrecido. Finalmente, después de definir el plan de recursos humanos y de analizar el marco legal en el que UNIGAD se verá inmersa, se concluirá con un plan financiero con el que se argumentará mediante un estudio económico la viabilidad económica de la empresa

Mineral and biological ice-nucleating particles above the South East of the British Isles

A small fraction of aerosol particles known as Ice-Nucleating Particles (INPs) have the potential to trigger ice formation in cloud droplets at higher temperatures than homogeneous freezing. INPs can strongly reduce the water content and albedo of shallow mixed-phase clouds and also influences the development of convective clouds. Therefore, it is important to understand which aerosol types serve as INP and how effectively they nucleate ice. Using a combination of INP measurements and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), we both quantify the INP concentrations over a range of activation temperatures and the size-resolved composition. We show that the INP population of aerosol samples collected from an aircraft over the UK during July of 2017 is consistent with ice-nucleation on mineral dust below about –20 oC, but some other INP type must account for ice-nucleation at higher temperatures. Biological aerosol particles above ~2 µm were detected based on visual detection of their morphological features in all the analysed samples in concentrations of at least 10 to 100 L-1 in the boundary layer. We suggest that given the presence of biological material, it could substantially contribute to the enhanced ice-nucleation ability of the samples at above –20 oC. Organic material attached to mineral dust could be responsible for at least part of this enhancement. These results are consistent with a growing body of data which suggests mineral dust alone cannot explain the INP population in the mid-latitude terrestrial atmosphere and that biological ice nucleating particles are most likely important for cloud glaciation

Pilot Testing and Psychometric Validation of the Nijmegen Professionalism Scale for Spanish Nursing

Background and purpose: Professional commitment is frequently used as a humanistic care indicator. Thus, it is important to design and validate a tool which is able to measure professional commitment of nurses in Spain. In this study we aimed to analyze the psychometric properties of the Nijmegen Professionalism Scale for Spanish (NPS-S) nursing in order to verify its validity and reliability. Methods: We undertook the pilot testing and psychometric validation of the NPS-S. A total sample of 249 nursing professionals from a variety of areas of expertise took part in this study. The STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) Statement was used for reporting this research. Results: The NPS-S achieved a high degree of content validity, construct validity, internal consistency, temporal stability, and usability; this version is, thus, equivalent to the Nijmegen Professionalism Scale in its original version. Implications for practice: Based on the results obtained from the validation of this tool, it is possible to affirm that the NPS-S is an effective instrument for measuring professional commitment in this population. The NPS-S will evaluate and thus contribute to the promotion of professional commitment in Spanish nursing. Additionally, it will serve to establish correlations between professional commitment and other variables including quality of care and patient satisfaction. Future studies should analyze the evaluation capacity of this tool

The anisotropy of granular materials

The effect of the anisotropy on the elastoplastic response of two dimensional packed samples of polygons is investigated here, using molecular dynamics simulation. We show a correlation between fabric coefficients, characterizing the anisotropy of the granular skeleton, and the anisotropy of the elastic response. We also study the anisotropy induced by shearing on the subnetwork of the sliding contacts. This anisotropy provides an explanation to some features of the plastic deformation of granular media.Comment: Submitted to PR

Bottlenecks in granular flow: When does an obstacle increase the flowrate in an hourglass?

Bottlenecks occur in a wide range of applications from pedestrian and traffic flow to mineral and food processing. We examine granular flow across a bottleneck using particle-based simulations. Contrary to expectations we find that the flowrate across a bottleneck actually increases if an opti- mized obstacle is placed before it. The dependency of flowrate on obstacle diameter is derived using a phenomenological velocity-density relationship that peaks at a critical density. This relationship is in stark contrast to models of traffic flow, as the mean velocity does not depend only on density but attains hysteresis due to interaction of particles with the obstacle.Comment: Submitted to Phys. Rev. Let

Granular Solid Hydrodynamics

Granular elasticity, an elasticity theory useful for calculating static stress distribution in granular media, is generalized to the dynamic case by including the plastic contribution of the strain. A complete hydrodynamic theory is derived based on the hypothesis that granular medium turns transiently elastic when deformed. This theory includes both the true and the granular temperatures, and employs a free energy expression that encapsulates a full jamming phase diagram, in the space spanned by pressure, shear stress, density and granular temperature. For the special case of stationary granular temperatures, the derived hydrodynamic theory reduces to {\em hypoplasticity}, a state-of-the-art engineering model.Comment: 42 pages 3 fi

Rotational excitation of the Hoyle state in 12C

12C is synthesised in stars by fusion of three α particles. This process occurs through a resonance in the 12C nucleus, famously known as the Hoyle state. In this state, the 12C nucleus exists as a cluster of α particles. The state is the band-head for a rotational band with the 2+ rotational excitation predicted in the energy region 9 - 11 MeV. This rotational excitation can affect the triple-α process reaction rate by more than an order of magnitude at high temperatures (109 K). Depending on the energy of the resonance, the knowledge of the state can also help determine the structure of the Hoyle state. In the work presented here, the state of interest is populated by beta decay of radioactive 12N ion beam delivered by the IGISOL facility at JYFL, Jyväskylä

The experiments to determine the electron capture and β-decay of 8B into the highly excited states of 8Be

The main goal of this work is to study the structure of the highest energy states in 8Be populated following the β+-decay and the electron capture (EC) of 8B. With this aim, two experiments were performed at ISOLDE-CERN in 2017 and 2018. The first experiment had the aim to resolve the 2+ doublet at 16.6 and 16.9 MeV, in order to study their isospin mixing. The second experiment aimed to determine a value or give an experimental upper limit to the branching ratio of the exotic EC-p decay. In this paper, we present the experimental setups and we discuss the analysis and present the preliminary results obtained so far