147 research outputs found
The Heisenberg product seen as a branching problem for connected reductive groups, stability properties
In this article we study, in the context of complex representations of
symmetric groups, some aspects of the Heisenberg product, introduced by Marcelo
Aguiar, Walter Ferrer Santos, and Walter Moreira in 2017. When applied to
irreducible representations, this product gives rise to the Aguiar
coefficients. We prove that these coefficients are in fact also branching
coefficients for representations of connected complex reductive groups. This
allows to use geometric methods already developped in a previous article,
notably based on notions from Geometric Invariant Theory, and to obtain some
stability results on Aguiar coefficients, generalising some of the results
concerning them given by Li Ying
A Geometric Approach to the stabilisation of certain sequences of Kronecker coefficients
We give another proof, using tools from Geometric Invariant Theory, of a
result due to S. Sam and A. Snowden in 2014, concerning the stability of
Kro-necker coefficients. This result states that some sequences of Kronecker
coefficients eventually stabilise, and our method gives a nice geometric bound
from which the stabilisation occurs. We perform the explicit computation of
such a bound on two examples, one being the classical case of Murnaghan's
stability. Moreover, we see that our techniques apply to other coefficients
arising in Representation Theory: namely to some plethysm coefficients and in
the case of the tensor product of representations of the hyperoctahedral group.Comment: Manuscripta mathematica, Springer Verlag, In press,
\&\#x3008;https://doi.org/10.1007/s00229-018-1021-4\&\#x300
Micelles sensibles Ă la chaleur, au PH et Ă la lumiĂšre
L'ouverture des micelles de copolymĂšre Ă blocs (CPB) contrĂŽlĂ©e par un stimulus (chaleur, pH, lumiĂšre, etc.) suscite beaucoup d'intĂ©rĂȘts dans le domaine de la libĂ©ration contrĂŽlĂ©e de mĂ©dicaments. L'amĂ©lioration du contrĂŽle de l'ouverture des micelles Ă un endroit spĂ©cifique et Ă un temps prĂ©cis est un enjeu majeur. La plupart des micelles sensibles Ă la chaleur utilisent la tempĂ©rature critique infĂ©rieure (LCST) d'un bloc pour dĂ©stabiliser les micelles. Dans un premier temps, l'Ă©tude porte sur l'Ă©laboration d'un nouveau type de micelles CPB qui sont sensibles Ă la chaleur via un groupement protecteur thermolabile. Le copolymĂšre Ă©tudiĂ© est le poly(oxyde d'Ă©thylĂšne)-bloc-poly(mĂ©thacrylate de 2-tĂ©trahydropyranyl) (PEO-b-PTHPMA). En effet, l'hydrolyse du groupement tĂ©trahydropyranyl (THP) est sensible Ă la chaleur ainsi qu'au pH acide. Le copolymĂšre a Ă©tĂ© synthĂ©tisĂ© par polymĂ©risation radicalaire par transfert d'atome (ATRP). L'analyse du CPB a Ă©tĂ© effectuĂ©e par chromatographie de permĂ©ation de gel (GPC), spectroscopie infrarouge, rĂ©sonance magnĂ©tique nuclĂ©aire du proton (RMN 1H), et par calorimĂ©trie diffĂ©rentielle Ă balayage (DSC). Pour ce qui est de l'effet de la chaleur et du pH sur les micelles du PEO-b-PTHPMA, la spectroscopie de fluorescence, la diffusion dynamique de la lumiĂšre (DLS), ainsi que la microscopie Ă©lectronique Ă balayage (MEB) ont Ă©tĂ© utilisĂ©es. L'Ă©tude dĂ©montre que la dĂ©stabilisation des micelles est influencĂ©e par la chaleur, le pH et la longueur des blocs du copolymĂšre. De plus, pour la premiĂšre fois trois Ă©vĂ©nements liĂ©s Ă l'ouverture des micelles ont Ă©tĂ© suivis. La seconde partie du mĂ©moire est consacrĂ©e Ă l'Ă©tude de micelles photosensibles. Un deuxiĂšme nouveau CPB a Ă©tĂ© synthĂ©tisĂ© par ATRP, soit le copolymĂšre poly(oxyde d'Ă©thylĂšne)-bloc-poly(mĂ©thacrylate de [7-(diĂ©thylamino)coumarine-4-yl]mĂ©thyl) (PEO-b-PDEACMMA). Le bloc contenant la molĂ©cule de coumarine est photosensible. Elle peut ĂȘtre clivĂ©e par l'absorption d'un photon UV ou de deux photons proche infrarouge, dĂ©plaçant ainsi la balance hydrophile/hydrophobe vers la dĂ©stabilisation des micelles. La caractĂ©risation du copolymĂšre ainsi que des micelles a Ă©tĂ© effectuĂ©e avec les mĂȘmes mĂ©thodes que pour le premier projet. L'Ă©tude dĂ©montre une amĂ©lioration de la sensibilitĂ© des micelles Ă l'absorption Ă deux photons, ce qui est un avantage pour la libĂ©ration de mĂ©dicaments Ă l'aide de la lumiĂšre
Modes et approches du cinéma documentaire : réflexion autour du projet American Utopias
Ce mĂ©moire de recherche-crĂ©ation prend comme point de dĂ©part le film documentaire American Utopias que jâai rĂ©alisĂ© en 2014-2015. Le film nous plonge au cĆur du quotidien de cinq communautĂ©s alternatives et expĂ©rimentales des Ătats-Unis et rĂ©flĂ©chit aux multiples dĂ©fis et enjeux que vivent leurs membres. OrganisĂ© autour du thĂšme de lâutopie, ce rĂ©cit de voyage documentaire nous fait connaĂźtre tour Ă tour une communautĂ© de mini-maisons Ă Washington D.C., une communautĂ© « Earthship » Ă Ithaca, une communautĂ© vivant sans Ă©lectricitĂ© et sans pĂ©trole au Missouri, un laboratoire urbain dans le dĂ©sert de lâArizona et le festival Burning Man au Nevada.
La portion thĂ©orique de ce mĂ©moire sâorganise quant Ă elle autour de la question des approches du cinĂ©ma documentaire. Prenant comme appui la typologie de Bill Nichols, il sâagit ici de voir comment chaque approche privilĂ©giĂ©e par le crĂ©ateur de documentaire renvoie au rĂ©el dâune maniĂšre qui lui est propre. GrĂące Ă une approche autopoĂŻĂ©tique et un travail dâanalyse de films, ce mĂ©moire cherche Ă©galement Ă circonscrire les forces et les limites intrinsĂšques Ă chaque mode. Ce faisant, le lecteur est amenĂ© Ă mieux comprendre les motivations qui soutiennent certains choix de crĂ©ation dans American Utopias.This research-creation project explores the theories of Bill Nichols, in particular his typology of documentary modes, from a creatorâs perspective. Our intention is to revisit the creative process of American Utopias, a documentary on alternative communities in United States of America, by linking some of the key creative choices of the filmmaker to Nicholsâ work. Furthermore, our objective is to help defining the strengths and weaknesses of each mode described by the theoretician with concrete examples derived from movies analysis and direct experience. Created in 2014-15, American Utopias aims to show how different people have conceived and created original, ecofriendly and sustainable homes. It focuses on a three months journey made by the director through the USA to visit ecovillages, earthships, tiny house communities, the Burning Man Festival and other creative and unique places. On a philosophical and human point of view, it also reflects on the notion of utopia
Hares and rabbits at Regourdou (Montignac-sur-VĂ©zĂšre, Dordogne, France): paleontological and taphonomic studies of two naturally-occurring bone accumulations
Depuis la fin du XIXe siĂšcle, lâEurope occidentale a fait lâobjet de trĂšs nombreux travaux pour Ă©tudier les modes de subsistance des sociĂ©tĂ©s prĂ©historiques. Ă partir du PalĂ©olithique moyen, les Hommes vont alors sâintĂ©resser au petit gibier, tels que les lĂ©poridĂ©s, taxons relativement abondants sur ce territoire. Or, distinguer lâorigine de leur accumulation dans un site archĂ©ologique ne constitue pas une tĂąche aisĂ©e tant les agents pouvant en ĂȘtre responsables sont nombreux (i.e. mortalitĂ© naturelle, humains, carnivores terrestres, rapaces nocturnes ou diurnes). Dans cette contribution, nous avons menĂ© des Ă©tudes taphonomique et palĂ©ontologique sur les lĂ©poridĂ©s de Regourdou, gisement moustĂ©rien ayant livrĂ© le squelette dâun NĂ©andertalien. Les indices recensĂ©s suggĂšrent quâaucun prĂ©dateur nâest intervenu dans les processus dâaccumulation des restes de liĂšvres et de lapins, mais leurs assemblages seraient dus, respectivement, Ă une mortalitĂ© naturelle de type accidentelle et de type attritionnelle. La mise en Ă©vidence du premier processus montre que la cavitĂ© aurait fonctionnĂ© comme un aven-piĂšge Ă un moment donnĂ© de son histoire, tandis que le second rĂ©vĂšle lâexistence dâune Garenne in situ, interprĂ©tĂ©e comme la derniĂšre occupation du site durant le MIS 4 ou 3, avant la fin du comblement sĂ©dimentaire. Les variations morphologiques et de taille corporelle des individus permettent Ă©galement de prĂ©ciser les changements dâordre palĂ©o-environnementaux depuis le dĂ©but du fonctionnement du site, confirmant lâattribution des niveaux infĂ©rieurs Ă la pĂ©riode tempĂ©rĂ©e du MIS 5, et les niveaux supĂ©rieurs Ă une phase plus rĂ©cente du MIS 4 ou 3.Since the end of the nineteenth century, a great deal of work studying subsistence patterns of prehistoric societies in Western Europe has been done. During the Middle Paleolithic, humans were interested in small game, particularly the Leporidae, taxa that were abundant in their territories. However, distinguishing the exact nature of their origin in an archaeological site is not an easy task, given that numerous agents could be responsible for their accumulation (i.e., natural mortality, acquisition by humans and/or other terrestrial carnivores, or even nocturnal or diurnal raptors). In this contribution, we put forth a new taphonomic and paleontological study of the leporids of Regourdou, a Mousterian site that has yielded a Neandertal skeleton. This study suggests that no predators were involved in the accumulation of the hare or rabbit remains, but rather that they are due to natural (accidental) mortality for the former, and natural (attritional) mortality for the latter. Specifically, the evidence suggests that at one point in its history (for the hares), the cavity functioned as a natural pitfall trap, while for the rabbits it appears to show the existence of a warren, which we interpret as having existed during the last occupation of the site during MIS 4 or 3, before the end of the accumulation of sediments in the site. Morphological variation and body size of individuals also allows us to specify the order of paleoenvironmental changes since the siteâs functional beginning, confirming the attribution of the inferior levels to the MIS 5 temperate period, and the upper levels to a more recent phase in MIS 4 or 3
Spatial dependency and independency of nitrogen in lowbush blueberry commercial fields
Rhizomes of wild lowbush blueberry (Vaccinium angustifolium Aiton) extend horizontally, creating spatial dependency when
fertilization trials are performed. Knowing this spatial dependency would help researchers to better design field studies. Here, we used labelled nitrogen (N) fertilizer (15N-(NH4)2SO4) to measure N translocation among blueberry stems for one old (56 year) and one younger (15 year) commercial field. Leaf 15N concentrations at the tip-dieback stage were used to monitor N acquisition. No difference between sites suggests no field age effect on N translocation. Spatial dependency and independency were reached for distances of â€0.75 and â„1.75 m from the fertilizer application point, respectively
Metabolic counterparts of sodium accumulation in multiple sclerosis: A whole brain 23Na-MRI and fast 1H-MRSI study
Increase of brain total sodium concentrations (TSC) is present in multiple sclerosis (MS), but its pathological involvement has not been assessed yet.
To determine in vivo the metabolic counterpart of brain sodium accumulation.
Whole brain
Na-MR imaging and 3D-
H-EPSI data were collected in 21 relapsing-remitting multiple sclerosis (RRMS) patients and 20 volunteers. Metabolites and sodium levels were extracted from several regions of grey matter (GM), normal-appearing white matter (NAWM) and white matter (WM) T
lesions. Metabolic and ionic levels expressed as Z-scores have been averaged over the different compartments and used to explain sodium accumulations through stepwise regression models.
MS patients showed significant
Na accumulations with lower choline and glutamate-glutamine (Glx) levels in GM;
Na accumulations with lower N-acetyl aspartate (NAA), Glx levels and higher Myo-Inositol (m-Ins) in NAWM; and higher
Na, m-Ins levels with lower NAA in WM T
lesions. Regression models showed associations of TSC increase with reduced NAA in GM, NAWM and T
lesions, as well as higher total-creatine, and smaller decrease of m-Ins in T
lesions. GM Glx levels were associated with clinical scores.
Increase of TSC in RRMS is mainly related to neuronal mitochondrial dysfunction while dysfunction of neuro-glial interactions within GM is linked to clinical scores
Importance of field data for understanding a potential Mousterian funerary deposit : the case of the Regourdou 1 skeleton (Montignac-sur-VézÚre, Dordogne, France)
Aside from the work of Bonifay (see Bonifay et al. 2007 for one of the more recent papers) and various articles following these earlier works (e.g., Binant 1991, Defleur 1993, Maureille et Vandermeersch 2007, Pettitt 2011, see also May 1986 for a more critical analysis), the in situ position of the remains of Regourdou 1 from layer 4 has never actually been discussed on the basis of available data from the salvage operation carried out in October 1957 by E. Bonifay and G. Laplace-Jauretche, under the administrative authority of François Bordes, or from the subsequent, more systematic, excavations directed by E. Bonifay between 1961 and 1964. Via the compilation of available information from a number of unpublished documents (François Bordesâ field notes, drawings made during the salvage operation, photographs taken in 1957, 1961 and 1962, as well as databases from the 1961 to 1964 excavations), and also a new inventory of human remains (both previously known and recently discovered), it is now possible to more accurately reconstruct the position of the human remains in a Cartesian system. In this, we assume that the concentration of remains uncovered during the salvage operation was in square G2, according to the preliminary systematic excavations carried out in 1961. They also bring to light that while practically no anatomical connections can be demonstrated with any certainty â and despite significant disruptions (all of the hominin remains are spread over 9 squares : G1 to G3, F1 to F3, E1 and E2, D2) â they are mainly positioned in squares G2 and G3 to some degree with respect to the anatomical logic of the human body. We therefore assume that Regourdou 1 was lying flat, with its head to the west â perhaps upon its trunk â close to the wall of the cavity. This result is different from the fetal position hypothesis proposed in Bonifay et al. (2007). Moreover many post-depositional (albeit Pleistocene) disturbances are also evident. We believe that they were likely the result of the utilization and modification of the cavity by brown bears and lagomorphs.Only new excavations at the site, and a better taphonomic understanding of Bonifayâs (1964) layer 4 (in which Regourdou 1 was found), and the exact role of humans in its formation, i.e., their anthropic impact on the layer, will allow us to discuss in more detail the nature of the deposition of the body, and, hopefully, the absence of the skull
Wafer-scale detachable monocrystalline Germanium nanomembranes for the growth of III-V materials and substrate reuse
Germanium (Ge) is increasingly used as a substrate for high-performance
optoelectronic, photovoltaic, and electronic devices. These devices are usually
grown on thick and rigid Ge substrates manufactured by classical wafering
techniques. Nanomembranes (NMs) provide an alternative to this approach while
offering wafer-scale lateral dimensions, weight reduction, limitation of waste,
and cost effectiveness. Herein, we introduce the Porous germanium Efficient
Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of
wafer-scale detachable monocrystalline Ge NMs on porous Ge (PGe) and substrate
reuse. We demonstrate monocrystalline Ge NMs with surface roughness below 1 nm
on top of nanoengineered void layer enabling layer detachment. Furthermore,
these Ge NMs exhibit compatibility with the growth of III-V materials.
High-resolution transmission electron microscopy (HRTEM) characterization shows
Ge NMs crystallinity and high-resolution X-ray diffraction (HRXRD) reciprocal
space mapping endorses high-quality GaAs layers. Finally, we demonstrate the
chemical reconditioning process of the Ge substrate, allowing its reuse, to
produce multiple free-standing NMs from a single parent wafer. The PEELER
process significantly reduces the consumption of Ge during the fabrication
process which paves the way for a new generation of low-cost flexible
optoelectronics devices.Comment: 17 pages and 6 figures along with 3 figures in supporting informatio
Epigenetic loss of RNAâmethyltransferase NSUN5 in glioma targets ribosomes to drive stress adaptive translational program
Tumors have aberrant proteomes that often do not match their corresponding transcriptome profiles. One possible cause of this discrepancy is the existence of aberrant RNA modification landscapes in the so-called epitranscriptome. Here, we report that human glioma cells undergo DNA methylation-associated epigenetic silencing of NSUN5, a candidate RNA methyltransferase for 5-methylcytosine. In this setting, NSUN5 exhibits tumor-suppressor characteristics in vivo glioma models. We also found that NSUN5 loss generates an unmethylated status at the C3782 position of 28S rRNA that drives an overall depletion of protein synthesis, and leads to the emergence of an adaptive translational program for survival under conditions of cellular stress. Interestingly, NSUN5 epigenetic inactivation also renders these gliomas sensitive to bioactivatable substrates of the stress-related enzyme NQO1. Most importantly, NSUN5 epigenetic inactivation is a hallmark of glioma patients with long-term survival for this otherwise devastating disease
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