Progenitor-Dependent Explosion Dynamics in Self-Consistent, Axisymmetric Simulations of Neutrino-Driven Core-Collapse Supernovae

We present self-consistent, axisymmetric core-collapse supernova simulations performed with the Prometheus-Vertex code for 18 pre-supernova models in the range of 11–28 M ⊙, including progenitors recently investigated by other groups. All models develop explosions, but depending on the progenitor structure, they can be divided into two classes. With a steep density decline at the Si/Si–O interface, the arrival of this interface at the shock front leads to a sudden drop of the mass-accretion rate, triggering a rapid approach to explosion. With a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. Early explosions are facilitated by high mass-accretion rates after bounce and correspondingly high neutrino luminosities combined with a pronounced drop of the accretion rate and ram pressure at the Si/Si–O interface. Because of rapidly shrinking neutron star radii and receding shock fronts after the passage through their maxima, our models exhibit short advection timescales, which favor the efficient growth of the standing accretion-shock instability. The latter plays a supportive role at least for the initiation of the re-expansion of the stalled shock before runaway. Taking into account the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. We validate the robustness of our findings by testing the influence of stochasticity, numerical resolution, and approximations in some aspects of the microphysics.

Reassembled, Slightly Askew:Composition & Sound Design

Reassembled, Slightly Askew is an autobiographical, immersive audio-based artwork based on Shannon Sickels’ experience of falling critically ill with a rare brain infection and her journey of rehabilitation with an acquired brain injury. Audience members experience Reassembled individually, listening to the audio via headphones while lying on a bed. The piece makes use of binaural microphone technology and spatial sound design techniques, causing listeners to feel they are inside Shannon’s head, viscerally experiencing her descent into coma, brain surgeries, early days in the hospital, and re-integration into the world with a hidden disability. It is a new kind of storytelling, never done before about this topic, that places the listener safely in the first-person perspective with the aim of increasing empathy and understanding. Reassembled… was made through a 5-year collaboration with an interdisciplinary team of artists led by Shannon Sickels (writer & performer), Paul Stapleton (composer & sound designer), Anna Newell (director), Hanna Slattne (dramaturgy), Stevie Prickett (choreography), and Shannon’s consultant neurosurgeon and head injury nurse. It’s development and production has been made possible with the support of a Wellcome Trust Arts Award, the Arts Council NI, Sonic Arts Research Centre, Belfast's Metropolitan Arts Centre, and grants from the Arts & Disability Award Ireland scheme. In its 2015 premiere year, Reassembled had 99 shows across Northern Ireland, including at the Cathedral Quarter Arts Festival (the MAC, Belfast) and BOUNCE Arts & Disability Forum Festival (Lyric Theatre, Belfast). It was awarded 5 stars in the Stage, a Hospital Club h100 Theatre & Performance Award, and been shared at medical conferences and trainings across the UK. It continues to be presented in diverse artistic and educational contexts, including as part of A Nation’s Theatre Festival in 2016 at Battersea Arts Centre in London where it was given 4 star reviews in the Guardian, Time Out London and the Evening Standard. "A real-life ordeal, captured by a daring, disorientating artistic collaboration, which works brilliantly on so many levels…It should be available on prescription.” — The Stage ★★★★★ www.reassembled.co.uk Audio clips and documentary footage available here: http://www.paulstapleton.net/portfolio/reassembled-slightly-askew

Resilience of small-scale societies’ livelihoods: a framework for studying the transition from food gathering to food production

The origins of agriculture and the shift from hunting and gathering to committed agriculture is regarded as one of the major transitions in human history. Archeologists and anthropologists have invested significant efforts in explaining the origins of agriculture. A period of gathering intensification and experimentation and pursuing a mixed economic strategy seems the most plausible explanation for the transition to agriculture and provides an approach to study a process in which several nonlinear processes may have played a role. However, the mechanisms underlying the transition to full agriculture are not completely clear. This is partly due to the nature of the archeological record, which registers a practice only once it has become clearly established. Thus, points of transitions have limited visibility and the mechanisms involved in the process are difficult to untangle. The complexity of such transitions also implies that shifts can be distinctively different in particular environments and under varying historical and social conditions. In this paper we discuss some of the elements involved in the transition to food production within the framework of resilience theory. We propose a theoretical conceptual model in which the resilience of livelihood strategies lies at the intersection of three spheres: the environmental, economical, and social domains. Transitions occur when the rate of change, in one or more of these domains, is so elevated or its magnitude so large that the livelihood system is unable to bounce back to its original state. In this situation, the system moves to an alternative stable state, from one livelihood strategy to another.

Analyse des signaux radars polarimétriques en bandes C et L pour le suivi de l'humidité du sol de sites forestiers

Résumé : Dans les couverts forestiers, le suivi de l’humidité du sol permet de prévenir plusieurs désastres tels que la paludification, les incendies et les inondations. Comme ce paramètre est très dynamique dans l’espace et dans le temps, son estimation à grande échelle présente un grand défi, d’où le recours à la télédétection radar. Le capteur radar à synthèse d’ouverture (RSO) est couramment utilisé grâce à sa vaste couverture et sa résolution spatiale élevée. Contrairement aux sols nus et aux zones agricoles, le suivi de l’humidité du sol en zone forestière est très peu étudié à cause de la complexité des processus de diffusion dans ce type de milieu. En effet, la forte atténuation de la contribution du sol par la végétation et la forte contribution de volume issue de la végétation réduisent énormément la sensibilité du signal radar à l’humidité du sol. Des études portées sur des couverts forestiers ont montré que le signal radar en bande C provient principalement de la couche supérieure et sature vite avec la densité de la végétation. Cependant, très peu d’études ont exploré le potentiel des paramètres polarimétriques, dérivés d’un capteur polarimétrique comme RADARSAT-2, pour suivre l’humidité du sol sur les couverts forestiers. L’effet du couvert végétal est moins important avec la bande L en raison de son importante profondeur de pénétration qui permet de mieux informer sur l’humidité du sol. L’objectif principal de ce projet est de suivre l’humidité du sol à partir de données radar entièrement polarimétriques en bandes C et L sur des sites forestiers. Les données utilisées sont celles de la campagne terrain Soil Moisture Active Passive Validation EXperiment 2012 (SMAPVEX12) tenue du 6 juin au 17 juillet 2012 au Manitoba (Canada). Quatre sites forestiers de feuillus ont été échantillonnés. L’espèce majoritaire présente est le peuplier faux-tremble. Les données utilisées incluent des mesures de l’humidité du sol, de la rugosité de surface du sol, des caractéristiques des sites forestiers (arbres, sous-bois, litières…) et des données radar entièrement polarimétriques aéroportées et satellitaires acquises respectivement, en bande L (UAVSAR) à 30˚ et 40˚ et en bande C (RADARSAT-2) entre 20˚ et 30˚. Plusieurs paramètres polarimétriques ont été dérivés des données UAVSAR et RADARSAT-2 : les coefficients de corrélation (ρHHVV, φHHVV, etc); la hauteur du socle; l’entropie (H), l’anisotropie (A) et l’angle alpha extraits de la décomposition de Cloude-Pottier; les puissances de diffusion de surface (Ps), de double bond (Pd) extraites de la décomposition de Freeman-Durden, etc. Des relations entre les données radar (coefficients de rétrodiffusion multifréquences et multipolarisations (linéaires et circulaires) et les paramètres polarimétriques) et l’humidité du sol ont été développées et analysées. Les résultats ont montré que 1) En bande L, plusieurs paramètres optimaux permettent le suivi de l’humidité du sol en zone forestière avec un coefficient de corrélation significatif (p-value < 0,05): σ[indice supérieur 0] linéaire et σ[indice supérieur 0] circulaire (le coefficient de corrélation, r, varie entre 0,60 et 0,96), Ps (r entre 0,59 et 0,84), Pd (r entre 0,6 et 0,82), ρHHHV_30˚, ρVVHV_30˚, φHHHV_30˚ and φHHVV_30˚ (r entre 0,56 et 0,81) alors qu’en bande C, ils sont réduits à φHHHV, φVVHV et φHHVV (r est autour de 0,90). 2) En bande L, les paramètres polarimétriques n’ont pas montré de valeur ajoutée par rapport aux signaux conventionnels multipolarisés d’amplitude, pour le suivi de l’humidité du sol sur les sites forestiers. En revanche, en bande C, certains paramètres polarimétriques ont montré de meilleures relations significatives avec l’humidité du sol que les signaux conventionnels multipolarisés d’amplitude.

High Quality Acoustic Time History Measurements of Rotor Harmonic Noise in Confined Spaces

A methodology has been developed and presented to enable the use of small to medium scale acoustic hover facilities for the quantitative measurement of rotor impulsive noise. The methodology was applied to the University of Maryland Acoustic Chamber resulting in accurate measurements of High Speed Impulsive (HSI) noise for rotors running at tip Mach numbers between 0.65 and 0.85 – with accuracy increasing as the tip Mach number was increased. Several factors contributed to the success of this methodology including: • High Speed Impulsive (HSI) noise is characterized by very distinct pulses radiated from the rotor. The pulses radiate high frequency energy – but the energy is contained in short duration time pulses. • The first reflections from these pulses can be tracked (using ray theory) and, through adjustment of the microphone position and suitably applied acoustic treatment at the reflected surface, reduced to small levels. A computer code was developed that automates this process. The code also tracks first bounce reflection timing, making it possible to position the first bounce reflections outside of a measurement window. • Using a rotor with a small number of blades (preferably one) reduces the number of interfering first bounce reflections and generally improves the measured signal fidelity. The methodology will help the gathering of quantitative hovering rotor noise data in less than optimal acoustic facilities and thus enable basic rotorcraft research and rotor blade acoustic design.

Luxación esternoclavicular posterior

Paciente masculino de 24 años, ingresa a urgencias por trauma contundente en clavícula derecha durante accidente de tránsito. Presenta dolor en articulación esternoclavicular que se exacerba con la movilización del hombro y disfagia. Al examen físico, leve depresión del extremo medial de la clavícula y limitación de los arcos de movimiento del hombro. Las imágenes confirmaron el diagnostico de LEC posterior. El paciente fue llevado a cirugía para reducción y cerclaje, sin complicaciones.