The Canadian celiac health survey – the Ottawa chapter pilot

BACKGROUND: Celiac disease may manifest with a variety of symptoms which can result in delays in diagnosis. Celiac disease is associated with a number of other medical conditions. The last national survey of members of the Canadian Celiac Association (CCA) was in 1989. Our objective was to determine the feasibility of surveying over 5,000 members of the CCA, in addition to obtaining more health related information about celiac disease. METHODS: The Professional Advisory Board of the CCA in collaboration with the University of Ottawa developed a comprehensive questionnaire on celiac disease. The questionnaire was pre-tested and then a pilot survey was conducted on members of the Ottawa Chapter of the CCA using a Modified Dillmans' Total Design method for mail surveys. RESULTS: We had a 76% response to the first mailout of the questionnaire. The mean age of participants was 55.5 years and the mean age at diagnosis was 45 years. The majority of respondents presented with abdominal pain, diarrhea, fatigue or weight loss. Prior to diagnosis, 30% of respondents consulted four or more family doctors. Thirty seven percent of individuals were told they had either osteoporosis or osteopenia. Regarding the impact of the gluten-free diet (GFD), 45% of individuals reported that they found following a GFD was very or moderately difficult. The quality of life of individuals with celiac disease was comparable to the mean quality of life of Canadians. CONCLUSION: On the basis of our results, we concluded that a nationwide survey is feasible and this is in progress. Important concerns included delays in the diagnosis of celiac disease and the awareness of associated medical conditions. Other issues include awareness of celiac disease by health professionals and the impact of the GFD on quality of life. These issues will be addressed further in the national survey

Activation électronique de la dynamique de molécules organiques individuelles sur des semi-conducteurs

Au cours de cette thèse effectuée au Laboratoire de PhotoPhysique Moléculaire à Orsay au sein de l équipe Nanosciences moléculaires , j ai étudié l activation électronique, à l aide du STM, de la dynamique de molécules organiques individuelles adsorbées sur Si(100)-(2x1). Des dynamiques de plus en plus complexes ont été étudiées : le passage de la conformation faiblement chimisorbée à la conformation fortement chimisorbée dans le cas de la molécule de biphényle, la diffusion sur la surface de Si(100) dans le cas de la molécule de stilbène physisorbée et les changements de conformation dans le cas de la molécule d hexaphényle.Ces résultats illustrent les différentes possibilités pour contrôler la dynamique moléculaire, selon la localisation de l excitation électronique à l intérieur de la molécule et selon la conformation d adsorption de la molécule sur la surface. Cette thèse met aussi en évidence l irruption de nouvelles problématiques liées à la taille croissante de la molécule. En effet, ces résultats montrent combien l analyse de la dynamique d une molécule de la taille de l hexaphényle devient compliquée, du fait des nombreux endroits d excitation possibles et des nombreux changements de conformations possibles. De plus, ces résultats posent aussi de nouvelles questions sur la délocalisation de l énergie d excitation à l intérieur de la molécule aux différents stades du processus dynamique.The work presented in this thesis was carried out in the Molecular Nanoscience group in the Laboratory for Molecular Photophysics. During this thesis, I studied the electronic activation with the STM of the dynamics of individual organic molecules adsorbed on the Si(100)-2x1 surface. The molecular dynamics became progressively more complex as the size of the molecule increased: First, the change in adsorption of the biphenyl molecule from its weakly chemisorbed state to the strongly chemisorbed state. Second, the diffusion of the physisorbed stilben molecule. Third, the conformational changes induced in the hexaphenyl molecule.These results illustrate the different ways in which the molecular dynamics can be controlled depending on the localization of the electronic excitation inside the molecule and also the conformation of the molecule on the surface. This thesis also clearly demonstrates the new problems that arise due to the increasing size of the molecule. Indeed, these results show just how complicated a detailed analysis of the molecular dynamics becomes in the case of the hexaphenyl. This is due to the greater number of possible positions for the excitation combined with the different possible configurations. The results also raise new questions concerning the delocalization and propagation of the excitation within the molecule during the dynamic process.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Functionalization of 2D materials by intercalation

International audienceSince the discovery of graphene many studies focused on its functionalization by different methods. These strategies aim to find new pathways to overcome the main drawback of graphene, a missing band-gap, which strongly reduces its potential applications, particularly in the domain of nanoelectronics, despite its huge and unequaled charge carrier mobility. The necessity to contact this material with a metal has motivated a lot of studies of metal/graphene interactions and has led to the discovery of the intercalation process very early in the history of graphene. Intercalation, where the deposited atoms do not stay at the graphene surface but intercalate between the top layer and the substrate, may happen at room temperature or be induced by annealing, depending of the chemical nature of the metal. This kind of mechanism was already well-known in the earlier Graphite Intercalation Compounds (GICs), particularly famous for one current application, the Lithium-ion Battery, which is simply an application based on the intercalation of Lithium atoms between two sheets of graphene in a graphite anode. Among numerous discoveries the GICs community also found a way to obtain graphite with superconducting properties by using intercalated alkali metals. Graphene is now a playground to “revisit” and understand all these mechanisms and to discover possible new properties of graphene induced by intercalation. For example, the intercalation process may be used to decouple the graphene layer from its substrate, to change its doping level or even, in a more general way, to modify its electronic band structure and the nature of its Dirac fermions. In this paper we will focus on the functionalization of graphene by using intercalation of metal atoms but also of molecules. We will give an overview of the induced modifications of the electronic band structure possibly leading to spin-orbit coupling, superconductivity, …We will see how this concept of functionalization is also now used in the framework of other 2D materials beyond graphene and of van der Waals heterostructures based on these materials

Porosity-driven large amplitude dynamics for nitroaromatic sensing with fluorescent films of alternating D-π-A molecules

International audienceWe report herein the structural properties and nitroaromatic sensing performances of fluorescent thin films formed by alternating donor-acceptor pi-conjugated chromophores. The incorporation of a flexible one-dimensional alkyl chain in the chromophore backbone drastically accelerates by more than one order of magnitude the sensing dynamics for the detection of 2,4-dinitrotoluene (DNT) vapors

Highly n-doped graphene generated through intercalated terbium atoms

We obtained highly n-type doped graphene by intercalating terbium atoms between graphene and SiC(0001) through appropriate annealing in ultrahigh vacuum. After terbium intercalation angle-resolved-photoelectron spectroscopy (ARPES) showed a drastic change in the band structure around the K points of the Brillouin zone: the well-known conical dispersion band of a graphene monolayer was superposed by a second conical dispersion band of a graphene monolayer with an electron density reaching 10(15) cm(-2). In addition, we demonstrate that atom intercalation proceeds either below the buffer layer or between the buffer layer and the monolayer graphene. The intercalation of terbium below a pure buffer layer led to the formation of a highly n-doped graphene monolayer decoupled from the SiC substrate, as evidenced by ARPES and x-ray photoelectron spectroscopy measurements. The band structure of this highly n-doped monolayer graphene showed a kink (a deviation from the linear dispersion of the Dirac cone), which has been associated with an electron-phonon coupling constant one order of magnitude larger than those usually obtained for graphene with intercalated alkali metals

Generating long supra-molecular pathways with a continuous density of states by physically linking conjugated molecules via their end-groups

International audienceSelf-assembly of conjugated 2,5-dialkoxy-phenylene-thienylene-based oligomers on epitaxial monolayer graphene was studied in ultrahigh vacuum by low-temperature scanning tunneling microscopy (STM). The formation of long one-dimensional (1D) supramolecular chain-like structures has been observed, associated to a physical linking of their ends which involved the rotation of the end thiophene rings in order to allow π–π stacking of these end-groups. dI/dV maps taken at an energy corresponding to the excited states showed a continuous electronic density of states, which tentatively suggests that within such molecular chains conjugation of electrons is preserved even across physically linked molecules. Thus, in a self-organization process conjugation may be extended by appropriately adapting conformations of neighboring molecules. Our STM results on such self-organized end-linked molecules potentially represent a direct visualization of J-aggregates

STM Studies of Self-Assembled Tetrathiafulvalene (TTF) Derivatives on Graphene: Influence of the Mode of Deposition

The conformations and the self-assembly process of tetrathiafulvalene (TTF) derivatives functionalized by lateral alkylthio chains deposited on graphene/SiC(0001) in ultrahigh vacuum (UHV) and at the solid–liquid interface are studied by scanning tunneling microscopy (STM). The study in UHV evidences a “molecular fastener” effect induced by the increase of van der Waals interactions between the alkylthio side chains which forces the major part of the molecules to self-organize in π–π stacked edge-on conformation. The study at the solid–liquid interface reveals a drastically different behavior with molecules lying flat on the surface as the solvent is involved in the stabilization of the molecular layer. This work raises a burning issue concerning the choice of the deposition method for graphene functionalization with such molecules

One- and two-photon absorption and emission properties of an oligo(phenylenethienylene)s series

International audienceThe photophysical and nonlinear absorption properties of an oligo(phenylenethienylene)s series (nTBT) are investigated in this article. The length of the chromophore is gradually increased from one to four phenylenethienylene repeating units in order to evaluate the effects of the electronic delocalization on the two-photon absorption cross sections (δ). According to the excitation anisotropy measurements and quantum chemical calculations, two electronic transitions with distinctive symmetries, 1Ag → 1Bu and 1Ag → 2Ag, are present in the low energy region of the linear absorption spectrum. The lowest-energy transition 1Ag → 1Bu is one-photon allowed but two-photon forbidden and implies an electronic charge delocalization all along the oligomer segment whereas the weakly-allowed 1Ag → 2Ag transition exhibits a transition moment perpendicular to the average plane of the chromophore. The latter transition mainly contributes to the two-photon absorption ability of the oligomers. All derivatives are poorly solvatochromic and the breakdown of the mirror symmetry rule observed between absorption and fluorescence spectra at room temperature has been attributed to a photoinduced geometrical relaxation leading to a very efficient planarization process of the oligomer irrespective of its size. Increasing the oligomer length results in a slight shift of the two-photon absorption band ([similar]1300 cm−1) and in a drastic increase of δ from 2 ± 1 GM up to 802 ± 160 GM for 1TBT and 4TBT respectively. Based on a three-level model, it was found that main contributions to the strong increase of δ stem from the transition moments Mge and Mee′ which are multiplied by a factor of 2.8 and 5 when going from 1TBT to 4TBT