71 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/)
Regional Assessment of COCTS HY1-C/D Chlorophyll-a and Suspended Particulate Matter Standard Products over French Coastal Waters
No full textChlorophyll-a (Chla) and suspended particulate matter (SPM) are key indicators of water quality, playing critical roles in understanding marine biogeochemical processes and ecosystem health. Although satellite data from the Chinese Ocean Color and Temperature Scanner (COCTS) onboard the Haiyang-1C/D satellites is freely available, there has been limited validation of its standard Chla and SPM products. This study is a first step to address this gap by evaluating COCTS-derived Chla and SPM products against in situ measurements in French coastal waters. The matchup analysis showed robust performance for the Chla product, with a median symmetric accuracy (MSA) of 50.46% over a dynamic range of 0.13–4.31 mg·m−3 (n = 24, Bias = 41.11%, Slope = 0.93). In contrast, the SPM product showed significant limitations, particularly in turbid waters, despite a reasonable performance in the matchup exercise, with an MSA of 45.86% within a range of 0.18–10.52 g·m−3 (n = 23, Bias = −14.59%, Slope = 2.29). A comparison with another SPM model and Moderate Resolution Imaging Spectroradiometer (MODIS) products showed that the COCTS standard algorithm tends to overestimate SPM and suggests that the issue does not originate from the input radiometric data. This study provides the first regional assessment of COCTS Chla and SPM products in European coastal waters. The findings highlight the need for algorithm refinement to improve the reliability of COCTS SPM products, while the Chla product demonstrates suitability for water quality monitoring in low to moderate Chla concentrations. Future studies should focus on the validation of COCTS ocean color products in more diverse waters
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
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
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
The author and the literary publisher (1945-2023) : a study of a relationship of domination
No full textLes mutations du milieu culturel à partir de la fin de la seconde guerre mondiale bouleversent le monde du livre en France. Ces multiples transformations impactent notablement les liens entre les créateurs d'œuvres, les producteurs contribuant à insérer ces dernières au sein d'un marché, et les autres acteurs composant dans leur ensemble la « chaîne du livre ». Ce travail de thèse propose ainsi d'explorer la particularité d'un phénomène relativement peu étudié : celui de la relation entre l'auteur et l'éditeur littéraire. En explorant les dimensions économiques, juridiques et symboliques de cette relation, son but sera d'observer en quoi le rapport qui se tisse entre ces deux instances paraît manifestement déséquilibré, et ce en dépit de la très grande hétérogénéité des profils, des postures, et des structures existantes. La nécessaire médiatisation des œuvres – fruit du lien entre ces deux entités – fait intervenir une pluralité d'agents externes à cette relation première mais dont les rôles devront aussi être interrogés, en raison de leur contribution à la légitimation, à la consécration, ou à la simple visibilité de ce qu'ils exposent, ou inversement délaissent. Les changements visibles à partir du XXIème siècle seront enfin considérés : les nouvelles possibilités apparaissant suite à l'émergence du numérique sont exploitées par tous ces maillons composant la « chaîne » évoquée. Mais ces dernières mutations en date doivent-elles être perçues comme des opportunités de changer la nature des rapports existants, en favorisant notamment l'émancipation des auteurs, ou ne se révèlent-elles que comme la transposition du déséquilibre institué ?The mutations in the cultural environment since the end of the Second World War have profoundly changed the world of books in France. These multiple transformations have had a significant impact on the links between creators, producers who help place their works on the market, and other players who make up the "book industry" as a whole. This thesis explores the particularities of a relatively little-studied phenomenon: the relationship between the author and the literary publisher. By exploring the economic, legal and symbolic aspects of this relationship, its aim will be to observe how what weaves itself between these two entities seems manifestly unbalanced, despite the great heterogeneity of profiles, postures and existing structures. The necessary mediatization of works - the fruit of the link between these two actors mentioned - brings into play a plurality of players who are external to this initial relationship, but whose roles will also have to be questioned, because of their contribution to the legitimization, consecration or simple visibility - of what they exhibit, or conversely neglect. Finally, we'll look at the changes that have taken place since the 21st century: the new possibilities created by the emergence of digital technology are being exploited by all the links in this "industry". But should these latest mutations be seen as opportunities to change the nature of existing relationships, in particular by promoting the emancipation of authors, or are they merely the transposition of the established imbalance
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