1,911 research outputs found
Metal Complexes in Molecular Junctions.
International audienceThe use of metal complexes to achieve conductive molecular junction with a special focus on organometallics is overviewed and illustrated with representative examples. The perspectives offered by such compounds owing to their specific properties are discussed
Cannabidiol : exploring new synthetic pathways for late-stage functionalization
LâintĂ©rĂȘt grandissant suscitĂ© par les propriĂ©tĂ©s thĂ©rapeutiques exhibĂ©es par les cannabinoĂŻdes a motivĂ© la naissance du projet dĂ©crit dans ce mĂ©moire de maĂźtrise. La synthĂšse efficace de diffĂ©rents cannabinoĂŻdes est devenue essentielle afin de pouvoir mieux comprendre les mĂ©canismes rĂ©gulant les propriĂ©tĂ©s mĂ©dicales de ces composĂ©s ainsi que pour promouvoir le dĂ©veloppement de nouveaux traitements mĂ©dicamenteux. Le cannabidiol est dâintĂ©rĂȘt particulier en raison des propriĂ©tĂ©s anti-inflammatoires, et anticancĂ©reuses exhibĂ©es par cette molĂ©cule. Ce projet vise Ă explorer diffĂ©rentes routes permettant la fonctionnalisation du cannabidiol en phase avancĂ©e dans le but de faciliter lâaccĂšs aux dĂ©rivĂ©s de ce produit naturel.
La premiĂšre partie de ce mĂ©moire se concentre sur le dĂ©veloppement dâune voie de synthĂšse permettant la fonctionnalisation dâun prĂ©curseur du cannabidiol en utilisant le 1,3-dimĂ©thoxybenzĂšne, un produit de dĂ©part abordable et commercialement disponible. Lâapproche proposĂ©e comporte six Ă©tapes et sâappuie sur une rĂ©action de Diels-Alder pour gĂ©nĂ©rer lâadduit bicyclique du cannabidiol. Plusieurs routes ont Ă©tĂ© explorĂ©es pour obtenir la fonctionnalisation de ce prĂ©curseur, Ă savoir une borylation de Hartwig-Miyaura et une bromination du cycle aromatique.
La deuxiĂšme partie de ce projet se concentre sur la fonctionnalisation du cannabidiol en phase avancĂ©e en sâappuyant sur la fonctionnalitĂ© de lâamide de Weinreb. Ces travaux ont abouti au dĂ©veloppement dâune voie de synthĂšse efficace et durable pour la production de lâolivetol, un fragment clĂ© pour la production Ă grande Ă©chelle de cannabidiol dans lâindustrie pharmaceutique. Cette mĂ©thode se base sur une approche en quatre Ă©tapes sâappuyant sur un amide de Weinreb en utilisant un produit de dĂ©part abordable, lâacide 3,5-dimethoxy benzoĂŻque. La synthĂšse de lâamide de Weinreb puis de la cĂ©tone correspondante, suivie dâune rĂ©duction de Wolff-Kishner, et enfin la dĂ©methylation du substrat ont permis dâobtenir le produit dĂ©sirĂ©. La versatilitĂ© de cette approche tolĂšre une fonctionnalisation variĂ©e de la molĂ©cule, permettant la synthĂšse potentielle de divers dĂ©rivĂ©s de lâolivetol.The increasing interest around the therapeutic possibilities offered by cannabinoids was the motivation for the project described in this Masterâs thesis. The efficient synthesis of various CBs has become critical to deepen the understanding of the mechanisms behind the medical properties of cannabinoids as well as for the development of novel drug treatments. Cannabidiol is of particular interest as the molecule exhibits anti-inflammatory, and anticarcinogenic properties. This work aims to explore different routes to enable the late-stage functionalization of cannabidiol in order to easily access derivatives of the natural compound.
The first part of this work focuses on developing a route enabling the functionalization of the cannabidiol precursor utilizing the affordable and commercially available starting material 1,3-Dimethoxybenzene. The proposed six-step approach relies on a Diels-Alder reaction to generate the bicyclic adduct of cannabidiol. Several routes were then explored to obtain the functionalization of the precursor namely a Hartwig-Miyaura borylation and a bromination of the aromatic ring.
The second part of this project focuses on the functionalization of cannabidiol relying on the Weinreb amide functionality. This work led to the development of an efficient and sustainable route for the synthesis of olivetol, a key fragment for the large-scale production of cannabidiol within the pharmaceutical industry. The method relies on a four-step approach relying on a Weinreb amide synthesized using the affordable 3,5-Dimethoxybenzoic acid. The synthesis of the Weinreb amide followed by the formation of the corresponding ketone, subsequent Wolff-Kishner reduction, and finally demethylation of the substrate allowed to generate the desired product. The versatility of the approach allows for variations in functionalization, enabling potential formation of various olivetol derivatives
Photometric Variability Among the Brightest Asymptotic Giant Branch Stars Near the Center of M32
Deep K' images with 0.1 arcsec angular resolution, obtained with ALTAIR+NIRI
on Gemini North, are used to investigate photometric variablity among the
brightest asymptotic giant branch (AGB) stars in the central regions of M32.
Based on a comparison with brightnesses obtained from the K-band data discussed
by Davidge et al. (2000, ApJ, 545, L89), it is concluded that (1) at least 60%
of bright AGB stars near the center of M32 are photometrically variable, and
(2) the amplitudes of the light variations are similar to those of long period
variables in the Galactic bulge. We do not find evidence for a population of
large amplitude variables, like those detected by IRAS in the Galactic bulge.
The technique discussed here may prove useful for conducting an initial
reconnaisance of photometric variability among AGB stars in spheroids in the
Virgo cluster and beyond, where the required long exposure times may restrict
observations to only a few epochs.Comment: 8 pages of text, 3 postscript figures. ApJ (letters) in pres
Time Blocks Decomposition of Multistage Stochastic Optimization Problems
Multistage stochastic optimization problems are, by essence, complex because
their solutions are indexed both by stages (time) and by uncertainties
(scenarios). Their large scale nature makes decomposition methods appealing.The
most common approaches are time decomposition --- and state-based resolution
methods, like stochastic dynamic programming, in stochastic optimal control ---
and scenario decomposition --- like progressive hedging in stochastic
programming. We present a method to decompose multistage stochastic
optimization problems by time blocks, which covers both stochastic programming
and stochastic dynamic programming. Once established a dynamic programming
equation with value functions defined on the history space (a history is a
sequence of uncertainties and controls), we provide conditions to reduce the
history using a compressed "state" variable. This reduction is done by time
blocks, that is, at stages that are not necessarily all the original unit
stages, and we prove areduced dynamic programming equation. Then, we apply the
reduction method by time blocks to \emph{two time-scales} stochastic
optimization problems and to a novel class of so-called
\emph{decision-hazard-decision} problems, arising in many practical situations,
like in stock management. The \emph{time blocks decomposition} scheme is as
follows: we use dynamic programming at slow time scale where the slow time
scale noises are supposed to be stagewise independent, and we produce slow time
scale Bellman functions; then, we use stochastic programming at short time
scale, within two consecutive slow time steps, with the final short time scale
cost given by the slow time scale Bellman functions, and without assuming
stagewise independence for the short time scale noises
A Semantic Account of Quasi-Lexemes in Modern English - Processing Semiotic Units of Greek or Latin Origin into Lexical Units
Testing quasi-lexemes with theories of compounding enables me to analyze their specificity and limitations. Quasi-lexemes have a semantic content like complete lexemes do, but are constrained by their morphological incompleteness. Despite the fact that their lexical categories are not readily discernible, there is evidence for derivational lineages in Greek and Latin, and these derivations account for the division between primary and synthetic patterns in compounding. For that reason, quasi-lexemes can legitimately be said to obey the constraints of complete lexemes in terms of the syntactic and semantic relations. The only problem is their belonging to three lexical categories only (verb, noun, adjective), which compels me to defend that, although quasi-lexemes form compounds and are liable to undergo paradigmatic extension opening up the way for productivity, at the same time, they tend to participate in compounding in a more restrained and conventional way than complete lexemes
Polynuclear carbon-rich organometallic complexes: clarification of the role of the bridging ligand in the redox properties.
International audienceIn this Perspective, we highlight the non-innocent behaviour of the bridging ligand in organometallic polynuclear metallic complexes displaying metal-carbon Ï bonds between the metallic units and a strongly coupled conjugated carbon-rich bridging ligand. With the help of representative experimental and theoretical studies on polymetallic systems, but also on monometallic complexes, we point out that the level of implication of the carbon rich ligand in the redox processes is very sensitive to the nature of (i) the metal(s), (ii) the ancillary ligands and (iii) the carbon-rich ligand itself, and that this participation is frequently found to be major. Consequently, the general denomination M((n + 1)) that is usually used for oxidized species gives the picture that only the metal density is affected, which is misleading. Moreover, for polymetallic species, these elements make the mixed valence denomination and the use of standard methodologies to rationalize intramolecular electron transfer, such as the Hush model inaccurate. Indeed, these theoretical treatments of mixed-valent complexes have at their core the assumption of metal-based redox state changes. Quantum mechanical calculations, coupled with spectroscopic methods, such as EPR spectroscopy, turn out to be a valuable suite of tools to both identify and better describe those systems with appreciable ligand redox non-innocent character. Finally, some examples and perspectives of applications for this carbon-rich type of complexes that take advantage of their peculiar electronic structure are presented
GeMS: first on-sky results
GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results
The Stellar Content Near the Galactic Center
High angular resolution J, H, K, and L' images are used to investigate the
stellar content within 6 arcsec of SgrA*. The data, which are complete to K ~
16, are the deepest multicolor observations of the region published to date.Comment: 34 pages, including 12 figure
An upper limit to the sodium layer longitudinal and transversal altitude structure function from MCAO data
The Gemini Multi-Conjugate Adaptive Optics System is the first sodium-based Multi-Laser Guide Star (LGS) Adaptive Optics system used for astronomy. It uses five LGSs distributed on a 1 arcmin2 constellation to measure and compensate for atmospheric disto
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