On the pulsating instability of two-dimensional flames

We consider a well-known thermo-diffusive model for the propagation of a premixed, adiabatic flame front in the large-activation-energy limit. That model depends only on one nondimensional parameter β, the reduced Lewis number. Near the pulsating instability limit, as β↓β0= 32/3, we obtain an asymptotic model for the evolution of a quasi-planar flame front, via a multi-scale analysis. The asymptotic model consists of two complex Ginzburg–Landau equations and a real Burgers equation, coupled by non-local terms. The model is used to analyse the nonlinear stability of the flame front

Global stability properties of a hyperbolic system arising in pattern formation

Global stability properties of a hyperbolic system arising in pattern formatio

Animal Avatars: Reconstructing Animatable 3D Animals from Casual Videos

We present a method to build animatable dog avatars from monocular videos. This is challenging as animals display a range of (unpredictable) non-rigid movements and have a variety of appearance details (e.g., fur, spots, tails). We develop an approach that links the video frames via a 4D solution that jointly solves for animal's pose variation, and its appearance (in a canonical pose). To this end, we significantly improve the quality of template-based shape fitting by endowing the SMAL parametric model with Continuous Surface Embeddings, which brings image-to-mesh reprojection constaints that are denser, and thus stronger, than the previously used sparse semantic keypoint correspondences. To model appearance, we propose an implicit duplex-mesh texture that is defined in the canonical pose, but can be deformed using SMAL pose coefficients and later rendered to enforce a photometric compatibility with the input video frames. On the challenging CoP3D and APTv2 datasets, we demonstrate superior results (both in terms of pose estimates and predicted appearance) to existing template-free (RAC) and template-based approaches (BARC, BITE)

Finite size effects near the onset of the oscillatory instability

A system of two complex Ginzburg - Landau equations is considered that applies at the onset of the oscillatory instability in spatial domains whose size is large (but finite) in one direction; the dependent variables are the slowly modulated complex amplitudes of two counterpropagating wavetrains. In order to obtain a well posed problem, four boundary conditions must be imposed at the boundaries. Two of them were already known, and the other two are first derived in this paper. In the generic case when the group velocity is of order unity, the resulting problem has terms that are not of the same order of magnitude. This fact allows us to consider two distinguished limits and to derive two associated (simpler) sub-models, that are briefly discussed. Our results predict quite a rich variety of complex dynamics that is due to both the modulational instability and finite size effects

Estudio de resistencia a antibióticos del género Pseudomonas en muestras de agua del río Limay. Tramo de estudio: Senillosa – Plottier.

Uno de los problemas aparejados a la contaminación de los ríos es la presencia en el agua de bacterias patógenas o no, las cuales poseen resistencia a antibióticos. En el presente trabajo se investigó sobre la resistencia a antibióticos en cepas del género Pseudomonas que habitan en el curso de agua del río Limay, tramo comprendido entrelas localidades de Senillosa y Plottier. Dentro del género Pseudomonas, se encuentra el grupo fluorescente conformado por las especies Pseudomonas aeruginosa, Pseudomonas fluorescens y Pseudomonas putida. Hasta el momento, casi todos los estudios de resistencia a antimicrobianos de estas bacterias son de ambientes hospitalarios. Para lograr el objetivo del trabajo se muestreó en cinco lugares en dos campañas durante marzo y abril. Los análisis microbiológicos realizados consistieron en pruebas de presencia-ausencia, recuento, aislamiento y pruebas de identificación de bacterias del género Pseudomonas. Por último se evaluó la susceptibilidad frente a los antibióticos del grupo Carbapenemes mediante la técnica de difusión en agar. Se confirmó la presencia de bacterias del género Pseudomonas que presentan fluorescencia en los cinco sitios de muestreo estudiados. La evaluación de susceptibilidad de las cepas aisladas frente al antibiótico Imipenem dio un 50% de resistencia y frente a Meropenem dio un 20% de resistencia. Asimismo, los resultados de susceptibilidad a los dos antibióticos juntos revelaron resistencia en un 20% de las cepas aisladas, y sensibilidad disminuida en un 25% de las cepas. La exposición humana ya sea por contacto directo o indirecto con bacterias del grupo Pseudomonas fluorescente y con genes de resistencia antibiótica en el tramo de estudio del río Limay son un hecho comprobable.Fil: Sabathier, Laura Lorena. Universidad Nacional del Comahue. Facultad de Ciencias del Ambiente y la Salud; Argentina

Assessing variations in water availability to vegetation and its consequences on the riparian forest of the arid southwestern USA in service of ecosystem conservation

As Earth’s climate changes, a solid understanding of ecosystems’ sensitivity and reactivity to climatic and environmental controls is critical. Vegetation is considered a key structural element of habitats and ecosystems. By studying changes in vegetation communities’ (specific species assemblages) distribution, health, and timing of main life events, compared with potential controls, such as water availability, it is possible to infer important information on the interactions between vegetation communities (an indicator of habitat integrity) and a changing climate. This comprehension of vegetation dynamics is also crucial for the conservation of species vulnerable to changes and their habitat, even more so in the case of species that are already considered endangered. To fulfil their conservation mission, natural resources managers of lands, regardless of ownership, need a regional-scale understanding of climatic and environmental controls on habitat distribution, condition and vulnerability to climate change. They also need to be able to monitor habitat condition and distribution efficiently and accurately with limited resources. This thesis examines the case of riparian habitats in drylands. Intermittent streams and their streamside vegetation act as moist and cool refuges, support a high species richness and buffer sensitive populations from drought. But they are also rare, isolated, and highly sensitive to changes in water availability. My goal is to reconstruct the complex links between water distribution, water availability to vegetation, and vegetation distribution across a diverse landscape covering a range of elevation, topography and geology, supporting diverse ecosystems. To achieve this landscape-scale overview, I use remote sensing to map the main vegetation communities distribution, their long-term evolution, health, and sensitivity to drought, and conductivity sensors to detect flow and open water presence in-non perennial streams. These methods provide high spatiotemporal resolution datasets that can cover wide areas. The resulting information on vegetation and flow is then compared to climatic and environmental factors, including local geology and rainfall, to better understand their potential vulnerability to drought. This work is focused on applied research and is set in a wider context of providing knowledge and tools for natural resources managers to keep track of rare and sensitive habitats’ condition and extent. The methods and tools used were chosen to test their suitability as accessible and efficient monitoring tools. This thesis focuses on an area in the Southwest USA, covering the upper basin of the San Pedro River (an intermittent river of the Colorado basin), the Huachuca Mountains (an isolated mountain range) and the semi-arid valley in between. My research was conducted on military lands and, as such, the natural resources management side of this work is seen through the lens of military installations and their specific approach to ecosystem conservation. However, the findings of my thesis, both on the ecosystem functioning and the management implications sides, can be more widely applied to monitoring of isolated ecosystems in drylands. This work provides an overall understanding of water availability to vegetation across a diverse landscape, and how this availability controls vegetation distribution and health, from rainfall-supported grassland to groundwater-fed dense riparian forests. I study the differences in long-term, interannual vegetation density variations between ephemeral and perennial reaches along a dryland river, showing how local geology and groundwater levels can buffer riparian ecosystems against drought. I also describe the spatiotemporal distribution of flow in mountain ephemeral streams, from perennial springs to rainfall-fed washes. I link flow permanence to underlying geology, consider how different reaches might be impacted by prolonged drought, and the consequences on local flora and fauna. Finally, I look at short-term, intra-annual changes in vegetation phenology along mountain streams and show how droughts, with higher temperatures and lower precipitation, might shorten the growing season and negatively impact vegetation leaf density. Throughout the thesis, I relate my findings to natural resources management questions and needs, with the goal of providing tools and conclusions useful for endangered and critical habitat monitoring

Helium precipitation study in UO2 by Transmission Electron Microscopy

International audienc

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR