67 research outputs found
Pleijel’s Theorem for Schrödinger Operators
No full textWe are concerned in this paper with the real eigenfunctions of Schrödinger operators.We prove an asymptotic upper bound for the number of their nodal domains, which implies in particular that the inequality stated in Courant’s theorem is strict, except for finitely many eigenvalues. Results of this type originated in 1956 with Pleijel’s theorem on the Dirichlet Laplacian and were obtained for some classes of Schrödinger operators by the first author, alone and in collaboration with B. Helffer and T. Hoffmann-Ostenhof. Using methods in part inspired by work of the second author on Neumann and Robin Laplacians, we greatly extend the scope of these previous results
Asymptotic behavior of generalized capacities with applications to eigenvalue perturbations: The higher dimensional case
No full textWe provide a full series expansion of a generalization of the so-called u-capacity related to the Dirichlet-Laplacian in dimension three and higher, extending the results of Abatangelo et al. (2021); Abatangelo, Lena and Musolino (2022) dealing with the planar case. We apply the result in order to study the asymptotic behavior of perturbed eigenvalues when Dirichlet conditions are imposed on a small regular subset of the domain of the eigenvalue problem. (c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Geometric bounds for the magnetic Neumann eigenvalues in the plane
No full textWe consider the eigenvalues of the magnetic Laplacian on a bounded domain Omega of R-2 with uniform magnetic field beta > 0 and magnetic Neumann boundary conditions. We find upper and lower bounds for the ground state energy lambda(1) and we provide semiclassical estimates in the spirit of Kroger for the first Riesz mean of the eigenvalues. We also discuss upper bounds for the first eigenvalue for non-constant magnetic fields beta = beta(x) on a simply connected domain in a Riemannian surface. In particular: we prove the upper bound lambda(1) infinity and consists of the semiclassical limit 2 pi k/ |Omega| plus an oscillating term.We also construct several examples, showing the importance of the topology: in particular we show that an arbitrarily small tubular neighborhood of a generic simple closed curve has lowest eigenvalue bounded away from zero, contrary to the case of a simply connected domain of small area, for which lambda(1) is always small.(c) 2023 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/)
Subordonnées conditionnelles en Quechua Cochabambino
No full textThis record deals with the if-clauses in Quechua Cochabambino. This elicitation aims at elaborating a typology of these clauses.Cet enregistrement traite des subordonnées conditionnelles en Quechua Cochabambino. Il s'agit d'une élicitation cherchant à élaborer une typologie des conditionnelles dans cette langue
Caractérisation de l’impact des perturbations hydrologiques sur la fonctionnalité de la tête de bassin-versant de l’Ellez dans les monts d’Arrée (Finistère, Bretagne)
No full textThe moors and peatlands of Yeun-Ellez located in the Monts d'Arrée (Finistère) are remarkable natural areas, home to unique but vulnerable biodiversity. Positioned at the head of the watershed, they play a predominant role in regulating hydrological flows. Two sources of hydrological disturbance have been identified on this site: the presence of a drainage ditch network and alterations to the river. The extent of the drainage ditch network has been mapped through photo interpretation and field surveys. Protocols at the scale of individual ditches and at the network level through modeling and hydromorphological assessment have been conducted to determine their impact on the functionality of the surrounding ecosystems. A hydromorphological assessment of the Ellez has also been carried out to evaluate its functionality and identify the causes of observed malfunctions. This study has revealed the level of incision of the river caused by channelization at its source and the connected drainage ditches, leading to a disconnection of the watercourse from the groundwater and an acceleration of flows. The negative impact of ditches on the hydrological functionality of the moors and peat bogs has been demonstrated. In the most affected areas downstream and in close proximity to the ditches, hydrological dysfunction is coupled with generalized dysfunction, particularly in terms of peat accumulation capacity. The most disruptive ditches for functionality appear to be those connected to the watercourse in the upstream area of the Ellez. This study identifies priority areas for restoration measures, to be undertaken by the Parc Naturel Régional d’Armorique as part of the Life Landes d'Armorique project. It also allows for the testing of monitoring protocols for potential restoration work to be implemented.Les landes et tourbières du Yeun et des sources de l’Ellez des Monts d’Arrée (Finistère) sont des espaces naturels remarquables, supports d’une biodiversité originale mais vulnérable. Situées en tête de bassin-versant, elles jouent un rôle prédominant dans la régulation des flux hydriques. Deux sources de perturbation hydrologique ont été identifiées sur ce site : l’existence d’un réseau de fossés de drainage et la modification de l’Ellez. L’étendue du réseau de fossés de drainage a été cartographié par photo-interprétation et par des prospections de terrain. Des protocoles à l’échelle de fossés unitaires, et à l’échelle du réseau par modélisation et par diagnostic hydromorphologique ont été menés pour déterminer leur niveau d’impact sur la fonctionnalité des écosystèmes environnants. Un suivi hydromorphologique de l’Ellez a également été réalisé, pour évaluer son niveau de fonctionnalité et identifier les causes des dysfonctionnements observés. Cette étude a mis en évidence le niveau d’incision de l’Ellez causé par la chenalisation de sa source et par les fossés de drainage connectés, à l’origine d’une déconnexion du cours d’eau avec la nappe et d’une accélération des écoulements. L’impact négatif du drainage de la nappe par les fossés sur la fonctionnalité hydrologique des landes et tourbières a été démontré. Sur les zones les plus affectées à l’aval et proximité immédiate des fossés, la dysfonctionnalité hydrologique se couple à une dysfonctionnalité généralisée, notamment de la capacité d’accumulation de la tourbe. Les fossés les plus perturbateurs de la fonctionnalité semblent être les fossés connectés au cours d’eau, sur la zone amont de l’Ellez. Cette étude permet d’identifier les secteurs prioritaires d’action pour engager des mesures de restauration, portées par le Parc Naturel Régional d’Armorique dans le cadre du projet Life Landes d’Armorique. Il permet également de tester des protocoles de suivi pour les éventuels travaux de restauration qui seront mis en œuvre
Fables d'Ésope 2: Les Hommes
No full textThis is a tight little book, 6 x 7¾. It contains eighty-six of Aesop's fables drawn from either Chambry's 1927 translation or a version done by Hachette in 1913 without attribution to an author. To go with those texts there are eleven full-page illustrations noted on 85 and a number of other designs along the way. Six of the full-page illustrations are colored. For an inexpensive edition, this book does a good job with the art! There is a T of C at the back. I am not sure that I have ever seen Aesop's work divided into animals and people before this! See the companion volume on animals.This is a hardbound book (hard cover)This book has a dust jacket (book cover)Language note: FrenchOriginal language: greTraduction, introduction et notes par Daniel Loayz
The role of livestock farming in the conservation of wet grasslands and the ecosystem services they provide
No full textLe résumé de la journéeThis issu follows on from the Carrefour de l'innovation agronomique, forum dedicated to Grazing livestock : the contribution of biodiversity, from soils to landscapes event that took place on 12 December 2024 at the Institut Agro in Rennes, France. It provide an update on knowledge and feedback showing the trajectories of agroecological livestock farms that make the most of wild and domestic biodiversity and the interactions between them. The development of agroecological practices is necessary to adapt agri-food systems to climate change and its impacts, and to mitigate their environmental impact. Biodiversity has been identified as a key factor in the sustainability of farming systems in their environmental ecosystems, combining the genetic diversity of domestic species with that of wild species. This Agronomic Innovation Forum will present results on domestic biodiversity in herbivore farming and the environmental biodiversity impacted and mobilised, from the scale of soils to that of landscapes.International audienceWet grasslands are managed for livestock farming. They have been heavily drained in the past and their abandonment is now the main threat. Extensive management allows the conservation of these open ecosystems and the ecosystem services they provide, such as hosting a diverse fauna and flora, the production of quality fodder, the regulation of water flows and quality, pollination and carbon storage. The services are not all synergistic and there is no ideal habitat for all the services provided. However, the diversity of habitats, sometimes within the same marsh, makes it possible to offer interesting levels of services at the landscape scale. Wet grassland conservation depends above all on maintaining livestock farming with extensive management in marshy areas
Point defect engineering in Ge
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 121-127).In 1947, the first transistor was made of germanium, but soon silicon became the core material of computer chips because of its processability. However, as the typical dimensions of transistors are getting closer to the atomic size, the traditional approach of scaling down transistors to improve performance is reaching its limits, and other elements need to be used in conjunction with silicon. Germanium is one of the key materials to empower silicon based devices because it possesses electronic and optoelectronic properties complementary to those of silicon, among them higher carrier mobilities and a direct band gap (G-valley) at 1.55 [mu]m (the telecom C-band, therefore adding new capabilities to silicon integrated microphotonics). Furthermore, good quality Ge layers can be grown epitaxially on a Si substrate, allowing a monolithic integration of devices. However, compared to silicon, little is known about the point defects in germanium. The goal of the present doctoral work is to remedy this gap. To this end, we have used radiation (gamma rays, alpha particles, and neutrons) to controllably introduce point defects in crystalline germanium, which were then characterized by Deep-Level Transient Spectroscopy (DLTS), a technique that allows the determination of the activation energy, capture cross-section, and concentration of the said defects. By studying their electronic properties, annealing kinetics, and introduction rates, we were able to separate vacancy-containing from interstitial-containing defects and gain insight on their physical nature and formation process. We especially identified a di-interstitial defect and a tri-interstitial defect. In addition, we proved that in the case of alpha particles and neutron irradiation, the fact that defects are generated in a collision cascade influences their carrier capture rates and annealing behaviors. We have also characterized the impact of radiation on commercial germanium-on-silicon photodetectors, and showed that point defects associate with dislocations in epitaxial Ge-on-Si layers. Finally, we have investigated the passivation of midgap states by implanting germanium with fluorine, and showed how the interaction between the halogen element, the amorphous/crystalline interface during the solid phase epitaxy, and the implantation damage is key in obtaining a high performance materialby Corentin Monmeyran.Ph. D
Dufour et al. Source Data.xlsx
No full textDataset used to create every graph of the paper "Phenotypic characterization of single CD4+ T cells harboring genetically intact and inducible HIV genomes" in Nature Communications
Author list: Caroline Dufour1, Corentin Richard1, Marion Pardons1, Marta Massanella1, Antoine Ackaoui1, Ben Murrell2, Bertrand Routy1, Réjean Thomas3, Jean-Pierre Routy4, Rémi Fromentin1, Nicolas Chomont1
1Centre de Recherche du CHUM and Department of Microbiology, Infectiology and Immunology, Université de Montréal, Montreal, H2X 0A9, Quebec, Canada
2Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, 171 77, Sweden
3Clinique médicale l’Actuel, Montreal, H2L 4P9, Quebec, Canada
4Division of Hematology & Chronic Viral Illness Service, McGill University Heath Centre, Montreal, H4A 3J1, Quebec, Canada</p
Estimation of the modulation of friction from the mechanical impedance variations
No full textUltrasonic surface-haptic touchscreens produce compelling tactile sensations directly on the users' fingertips. The tactile sensations stem from the modulation of friction produced by acoustic radiation pressure, which reduces the contact between the skin and the glass plate. During this process, some of the vibrations are partly absorbed by the tissues, resulting in a conspicuous change in the vibration amplitude of the plate upon contact with the finger, which manifests as a net change in the system mechanical impedance. In this study, we leverage the observable change of impedance to estimate the acoustic levitation and the frictional force. The self-sensing method utilizes a model of the first principles governing the physical interaction between the plate and the skin, which relies on multi-scale contact theory. The model accurately describes the experimental influence of the amplitude on the observed impedance (i.e., the amount of energy absorbed and reflected) and can be used to estimate the friction coefficient (R2=0.93). These results provide additional evidence of the partial levitation mechanism at play in ultrasonic friction-modulation. This finding can be useful for designing energy-efficient devices and provide design suggestions for using ultrasonic impedance for self-sensing friction forces.Accepted Author ManuscriptHuman-Robot Interactio
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