Three-dimensional flow instability in a lid-driven isosceles triangular cavity

Linear three-dimensional modal instability of steady laminar two-dimensional states developing in a lid-driven cavity of isosceles triangular cross-section is investigated theoretically and experimentally for the case in which the equal sides form a rectangular corner. An asymmetric steady two-dimensional motion is driven by the steady motion of one of the equal sides. If the side moves away from the rectangular corner, a stationary three-dimensional instability is found. If the motion is directed towards the corner, the instability is oscillatory. The respective critical Reynolds numbers are identified both theoretically and experimentally. The neutral curves pertinent to the two configurations and the properties of the respective leading eigenmodes are documented and analogies to instabilities in rectangular lid-driven cavities are discussed.

A flexible (C)LP-based approach to the analysis of object-oriented programs

Static analyses of object-oriented programs usually rely on intermediate representations that respect the original semantics while having a more uniform and basic syntax. Most of the work involving object-oriented languages and abstract interpretation usually omits the description of that language or just refers to the Control Flow Graph(CFG) it represents. However, this lack of formalization on one hand results in an absence of assurances regarding the correctness of the transformation and on the other it typically strongly couples the analysis to the source language. In this work we present a framework for analysis of object-oriented languages in which in a first phase we transform the input program into a representation based on Horn clauses. This allows on one hand proving the transformation correct attending to a simple condition and on the other being able to apply an existing analyzer for (constraint) logic programming to automatically derive a safe approximation of the semantics of the original program. The approach is flexible in the sense that the first phase decouples the analyzer from most languagedependent features, and correct because the set of Horn clauses returned by the transformation phase safely approximates the standard semantics of the input program. The resulting analysis is also reasonably scalable due to the use of mature, modular (C)LP-based analyzers. The overall approach allows us to report results for medium-sized programs.

Effect of the temperature, strain rate and microstructure on flow and fracture characteristics of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD alloy

A series of quasi-static and dynamic tensile tests at varying temperatures were carried out to determine the mechanical behaviour of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD as-HIPed alloy. The temperature for the tests ranged from room temperature to 850  ∘C. The effect of the temperature on the ultimate tensile strength, as expected, was almost negligible within the selected temperature range. Nevertheless, the plastic flow suffered some softening because of the temperature. This alloy presents a relatively low ductility; thus, a low tensile strain to failure. The dynamic tests were performed in a Split Hopkinson Tension Bar, showing an increase of the ultimate tensile strength due to the strain rate hardening effect. Johnson-Cook constitutive relation was used to model the plastic flow. A post-testing microstructural of the specimens revealed an inhomogeneous structure, consisting of lamellar α2 + γ structure and γ phase equiaxed grains in the centre, and a fully lamellar structure on the rest. The assessment of the duplex-fully lamellar area ratio showed a clear relationship between the microstructure and the fracture behaviour.

RANS simulations of wind flow at the Bolund experiment

As part of their development, the predictions of numerical wind flow models must be compared with measurements in order to estimate the uncertainty related to their use. Of course, the most rigorous such comparison is under blind conditions. The following paper includes a detailed description of three different wind flow models, all based on a Reynolds-averaged Navier-Stokes approach and two-equation k-ε closure, that were tested as part of the Bolund blind comparison (itself based on the Bolund experiment which measured the wind around a small coastal island). The models are evaluated in terms of predicted normalized wind speed and turbulent kinetic energy at 2 m and 5 m above ground level for a westerly wind direction. Results show that all models predict the mean velocity reasonably well; however accurate prediction of the turbulent kinetic energy remains achallenge.

Modelling the post-failure stage of rainfall-induced landslides of the flow type

The geomechanical modeling of failure and post failure stages of rainfall induced shallow landslides represents a fundamental issue to properly assess the failure conditions and recognize the potential for long travel distances of the failed soil masses.

DNS of a hot-wire anemometer in a turbulent channel flow

A body with a shape similar to a hot wire with its sheath, but no prongs, has been placed close to the wall of a turbulent channel at Re_tau = 600. The results of the channel flow, without the wire, agree with previous published ones, despite the modest resolution and domain size. A simplified, two-dimensional version of the wire at the same Reynolds number has been studied to compare the dynamic response of cold and hot wires, where a slightly bigger perturbation is seen in the hot case, but an almost identical dynamic response. The cold wire seems to be able to measure instantaneous velocity with total drag after proper calibration. Being a DNS, the complete description of the flow field around the wire is obtained.

Motivación, flow e intención de práctica físico-deportiva en estudiantes de educación física de España y Latinoamérica

A pesar de los innegables beneficios físicos y psicosociales que la práctica de actividad física tiene para la población en las últimas décadas se observa un importante descenso en el nivel de práctica de actividad física durante la adolescencia. La Educación Física (EF) es una asignatura presente en las primeras etapas educativas de los currículums de todos los países y supone para la población infantil y adolescente, durante el periodo de escolarización obligatoria, un entorno de contacto cotidiano con la actividad física y deportiva lo que explica el creciente interés que existe por investigar en este contexto y extraer conclusiones que puedan ayudar a revertir el proceso de progresivo abandono de la práctica en estas edades. El presente trabajo se centra en un periodo, la adolescencia, especialmente sensible al abandono de la práctica de actividad física. Apoyándonos en tres de los marcos teóricos más importantes de los últimos años - Teoría de Metas de Logro, Teoría de la Autodeterminación y Teoría del Flow - hemos realizado un diseño con tres estudios complementarios que nos permitan avanzar en el conocimiento de las variables que afectan a esta realidad. En el primero de los estudios, en el que participaron 3990 estudiantes de EF de España, Argentina, Colombia y Ecuador con edades comprendidas entre 12 y 18 años, se fijaron como objetivos el establecimiento de perfiles motivacionales en estudiantes de EF considerando las orientaciones motivacionales, la motivación intrínseca y el flow disposicional; la comprobación de la posible estabilidad de los perfiles establecidos en cuatro países diferentes; y el análisis de la relación entre los perfiles motivacionales establecidos con la práctica de actividad física realizada en la actualidad y la intención de ser activo en el futuro. Los resultados revelaron la existencia de tres perfiles motivacionales en los estudiantes: perfil de motivación baja-moderada, perfil de motivación de alta motivación con bajo ego y perfil de alta motivación. Se encontraron similitudes en los perfiles motivacionales obtenidos en los cuatro países analizados, sugiriéndose la posibilidad de que la lengua materna compartida pueda ser una variable de influencia en la existencia de patrones conductuales similares. La orientación al ego resultó ser un elemento diferenciador en la relación de los dos perfiles que mostraron niveles más altos de motivación intrínseca, flow disposicional y orientación a la tarea con las variables de práctica. Mayores niveles de orientación al ego determinaron mayores valores de práctica e intención de práctica. En el segundo estudio, en el que participaron 365 estudiantes de EF de España, Argentina y Colombia con edades comprendidas entre 12 y 16 años, se testó un modelo explicativo de la intención de ser físicamente activo en el futuro en estudiantes de EF poco motivados introduciendo el flow disposicional como variable explicativa junto a las orientaciones motivacionales y la motivación intrínseca. El modelo de ecuaciones estructurales testado muestra que tanto la orientación al ego como la orientación a la tarea y la motivación intrínseca predijeron el flow disposicional. No se encontró un efecto significativo de la orientación a la tarea sobre la motivación intrínseca, ni de esta sobre la intención de práctica de AFD en el futuro. El flow disposicional resultó ser un mediador entre ambas orientaciones motivacionales y dicha intención, adquiriendo un papel relevante en la predicción de la intención de realizar actividad física en el futuro en los sujetos con poca motivación hacia la clase de EF. En el último estudio, con una muestra de 53 estudiantes de EF pertenecientes a dos clases de segundo curso de ESO con edades comprendidas entre 13 y 15 años, se analizó el efecto de una intervención de apoyo a las NPB sobre la satisfacción de las mismas, la motivación intrínseca, la disposición a experimentar flow y la intención de ser físicamente activo en el futuro; estudiándose también el efecto de la misma sobre ciertas variables presentes en el proceso de enseñanza-aprendizaje tales como la diversión, el aprendizaje y el gusto hacia el contenido y la metodología empleada. La intervención resultó efectiva en la mejora de todas las variables motivacionales analizadas a excepción de la satisfacción de la necesidad de relaciones sociales, variable que podría ser más difícilmente modificable en tanto que los grupos de clase suelen permanecer estables a lo largo de esta etapa educativa. Los alumnos de la condición experimental presentaron niveles más elevados de diversión, aprendizaje y gusto hacia el contenido y la metodología empleada. ABSTRACT Despite the undeniable physical and psychological benefits that physical activity has on health, a significant drop in the level of physical activity during adolescence has been observed over the last few decades. Physical education (PE) is present in the early stages of educational curricula of all countries, creating an environment in which children and adolescents can maintain daily contact with sport and physical activity during the period of compulsory education. There is thus a growing interest in research within this context, helping to draw conclusions aimed at reversing the progressive decline of physical activity in this age bracket. The work presented here focuses on adolescence – a period particularly sensitive when faced with declining rates of physical activity. Relying on three of the most important recent theoretical frameworks – Achievement Goal Theory, Self-Determination Theory and Flow Theory – we have carried out a design using three complementary studies that allow us to advance the understanding of variables affecting this reality. The first two studies employ a correlational methodology while the third follows a quasi-experimental design. The objectives of the first study, with the participation of 3990 PE students aged 12 to 18 from Spain, Argentina, Colombia and Ecuador, were: a) to establish motivational profiles in physical education students taking into consideration motivational orientations, intrinsic motivation and dispositional flow; b) to check the possible stability of the established profiles in the four countries; and c) to analyze the relationship between motivational profiles and both current levels of physical activity and intention to be physically active in the future. Results revealed the existence of three motivational profiles: low-moderate motivation profile, high motivation and low ego profile and high motivation profile. Similarities were found across the four countries, which presents the possibility that sharing the same mother tongue might influence the existence of similar behavioral patterns. Amongst the profiles that showed the highest levels of intrinsic motivation, dispositional flow and task orientation with practice variables, ego orientation became apparent as a differentiating element. Higher levels of ego orientation correlated with higher levels both in current level of physical activity and intention to be physically active in the future. In the second study, with the participation of 365 PE students aged 12 to 16 from Spain, Argentina and Colombia, an explanatory model of the intention to be physically active within the low-moderate motivation profile was tested, including dispositional flow as an influence variable together with motivational orientations and intrinsic motivation. The structural model equation in the low-moderate motivation profile shows some differences with respect to findings of similar studies using heterogeneous samples in motivational profiles. It was found that ego orientation, task orientation and intrinsic motivation predicted dispositional flow. No significant effects of task orientation on intrinsic motivation, or of intrinsic motivation on intention to be physically active in the future were found. Dispositional flow emerged as a mediator between both motivational orientations and intention, acquiring an important role in the prediction of future intentions to be physically active in adolescents who show low levels of motivation towards physical education. In the last of the three studies, with the participation of 53 PE students drawn from two classes in the second year of secondary education aged 13 to 15, the effect of an intervention to support basic psychological needs was tested against the satisfaction of these needs, intrinsic motivation, disposition to experience flow and intention to be physically active in the future. Alongside this, the aforementioned intervention was tested on certain variables present in the teaching-learning process such as fun, learning and taste for the activity and methodology. Supportive intervention was effective in improving all the motivational variables, except for the satisfaction of the relatedness variable, which may be more difficult to modify as class groups tend to remain stable throughout this educational state. Students in the experimental condition showed higher levels of fun, learning and taste for the content and methodology.

The effect of flow speed and food size on the capture efficiency and feeding behaviour of the cold-water coral Lophelia pertusa

Acknowledgements The authors acknowledge L. Wicks and B. de Francisco for helping in coral sampling and coral care in the aquaria facilities at SAMS. Thanks to C. Campbell and the CCAP for kind support and help. Scientific party and crew on board the RVs Calanus and Seol Mara, as well as on board the RRS James Cook during the Changing Oceans cruise (JC_073) are greatly acknowledged. Thanks to colleagues at SAMS for their support during our stay at SAMS. We are in debt with A. Olariaga for his help modifying the cylindrical experimental chambers used in the experiments, and C.C. Suckling for assistance with the flume experiment. Many thanks go to G. Kazadinis for preparing the POM used in the feeding experiments. We also thank two anonymous reviewers and the editor for their constructive comments, which contribute to improve the manuscript. This work has been supported by the European Commission through two ASSEMBLE projects (grant agreement no. 227799) conducted in 2010 and 2011 at SAMS, as well as by the UK Ocean Acidification Research Programme's Benthic Consortium project (awards NE/H01747X/1 and NE/H017305/1) funded by NERC. [SS]

Lateral magma flow in mafic sill complexes

We benefitted from discussions with many Earth scientists in different disciplines over the years; we particularly thank Ken Thomson, Donny Hutton, Brian O’Driscoll, Mike Petronis, Ken McDermott, Derek Keir, Ben van Wyk de Vries, and Davie Brown for their insights. We thank Schlumberger for software and data provision, and Department of Communications, Energy, and Natural Resources (Petroleum Affairs Division) in Ireland, Geoscience Australia, and PGS (Petroleum Geo-Services) for provision of seismic data. This work was completed as part of Magee’s Junior Research Fellowship funded by Imperial College London. Muirhead acknowledges support from Fulbright New Zealand and the Ministry of Science and Innovation. We thank Shan de Silva for his editorial handling of the manuscript and Tyrone Rooney, Agust Gudmundsson, and Mattia Pistone for the time and effort they put in to their constructive reviews

In situ investigation of rapid subsurface flow : Temporal dynamics and catchment-scale implication

Non peer reviewed

In situ investigation of rapid subsurface flow : Identification of relevant spatial structures beyond heterogeneity

Non peer reviewed

Long-term expression of protein kinase C in adult mouse hearts improves postischemic recovery

Activation of protein kinase C (PKC) protects the heart from ischemic injury; however, its mechanism of action is unknown, in part because no model for chronic activation of PKC has been available. To test whether chronic, mild elevation of PKC activity in adult mouse hearts results in myocardial protection during ischemia or reperfusion, hearts isolated from transgenic mice expressing a low level of activated PKCβ throughout adulthood (β-Tx) were compared with control hearts before ischemia, during 12 or 28 min of no-flow ischemia, and during reperfusion. Left-ventricular-developed pressure in isolated isovolumic hearts, normalized to heart weight, was similar in the two groups at baseline. However, recovery of contractile function was markedly improved in β-Tx hearts after either 12 (97 ± 3% vs. 69 ± 4%) or 28 min of ischemia (76 ± 8% vs. 48 ± 3%). Chelerythrine, a PKC inhibitor, abolished the difference between the two groups, indicating that the beneficial effect was PKC-mediated. 31P NMR spectroscopy was used to test whether modification of intracellular pH and/or preservation of high-energy phosphate levels during ischemia contributed to the cardioprotection in β-Tx hearts. No difference in intracellular pH or high-energy phosphate levels was found between the β-Tx and control hearts at baseline or during ischemia. Thus, long-term modest increase in PKC activity in adult mouse hearts did not alter baseline function but did lead to improved postischemic recovery. Furthermore, our results suggest that mechanisms other than reduced acidification and preservation of high-energy phosphate levels during ischemia contribute to the improved recovery.

Cytochrome c′ folding triggered by electron transfer: Fast and slow formation of four-helix bundles

Reduced (FeII) Rhodopseudomonas palustris cytochrome c′ (Cyt c′) is more stable toward unfolding ([GuHCl]1/2 = 2.9(1) M) than the oxidized (FeIII) protein ([GuHCl]1/2 = 1.9(1) M). The difference in folding free energies (ΔΔGf° = 70 meV) is less than half of the difference in reduction potentials of the folded protein (100 mV vs. NHE) and a free heme in aqueous solution (≈−150 mV). The spectroscopic features of unfolded FeII–Cyt c′ indicate a low-spin heme that is axially coordinated to methionine sulfur (Met-15 or Met-25). Time-resolved absorption measurements after CO photodissociation from unfolded FeII(CO)–Cyt c′ confirm that methionine can bind to the ferroheme on the microsecond time scale [kobs = 5(2) × 104 s−1]. Protein folding was initiated by photoreduction (two-photon laser excitation of NADH) of unfolded FeIII–Cyt c′ ([GuHCl] = 2.02–2.54 M). Folding kinetics monitored by heme absorption span a wide time range and are highly heterogeneous; there are fast-folding (≈103 s−1), intermediate-folding (102–101 s−1), and slow-folding (10−1 s−1) populations, with the last two likely containing methionine-ligated (Met-15 or Met-25) ferrohemes. Kinetics after photoreduction of unfolded FeIII–Cyt c′ in the presence of CO are attributable to CO binding [1.4(6) × 103 s−1] and FeII(CO)–Cyt c′ folding [2.8(9) s−1] processes; stopped-flow triggered folding of FeIII–Cyt c′ (which does not contain a protein-derived sixth ligand) is adequately described by a single kinetics phase with an estimated folding time constant of ≈4 ms [ΔGf° = −33(3) kJ mol−1] at zero denaturant.

Guanylyl cyclase C agonists regulate progression through the cell cycle of human colon carcinoma cells

The effects of Escherichia coli heat-stable enterotoxin (ST) and uroguanylin were examined on the proliferation of T84 and Caco2 human colon carcinoma cells that express guanylyl cyclase C (GC-C) and SW480 human colon carcinoma cells that do not express this receptor. ST or uroguanylin inhibited proliferation of T84 and Caco2 cells, but not SW480 cells, in a concentration-dependent fashion, assessed by quantifying cell number, cell protein, and [3H]thymidine incorporation into DNA. These agonists did not inhibit proliferation by induction of apoptosis, assessed by TUNEL (terminal deoxynucleotidyl transferase-mediated dNTP-biotin nick end labeling of DNA fragments) assay and DNA laddering, or necrosis, assessed by trypan blue exclusion and lactate dehydrogenase release. Rather, ST prolonged the cell cycle, assessed by flow cytometry and [3H]thymidine incorporation into DNA. The cytostatic effects of GC-C agonists were associated with accumulation of intracellular cGMP, mimicked by the cell-permeant analog 8-Br-cGMP, and reproduced and potentiated by the cGMP-specific phosphodiesterase inhibitor zaprinast but not the inactive ST analog TJU 1-103. Thus, GC-C agonists regulate the proliferation of intestinal cells through cGMP-dependent mechanisms by delaying progression of the cell cycle. These data suggest that endogenous agonists of GC-C, such as uroguanylin, may play a role in regulating the balance between epithelial proliferation and differentiation in normal intestinal physiology. Therefore, GC-C ligands may be novel therapeutic agents for the treatment of patients with colorectal cancer.