Assessing Doha's Street Network from the Perspective of 'Complete Streets' Concept

Streets are considered dynamic spaces in cities, and their design should be safe, comfortable and efficient for all users. Well-functioning streets can create a healthy lifestyle for a city and its users. Many cities are suffering from transportation issues because of their poorly designed street networks that do not integrate the different modes of transportation, or establish safe environments in which pedestrian and cyclists are treated as kings. In this manner, Doha as a city is experiencing the same kind of problem, creating corridors that do not take into consideration different travel modes, which causes severe congestion, delay and shortage in street capacity and, most importantly, users’ dissatisfaction. Therefore, there is a need to investigate and explore some methods that aim to improve cities’ street networks. “Complete Streets” is a roadway design concept initiated with the intention of integrating numerous modes of transportation and their variety of users. Complete Streets are also envisioned to provide traffic, safety and public health benefits, and integrate a healthy lifestyle into built environments worldwide. The newly-emerging concept can be adapted in contexts that fail to combine the different street elements that a street should have. Considering the low quality of the current street network, this thesis aims to evaluate the current streets in Doha city based on the degree of users’ satisfaction, and provide approaches to enhance them from the perspective of the ‘Complete Streets’ concept. The study analyzes two international case studies that have successfully implemented the concept and improved their current street network and enhanced users’ built environment. The analysis will help in extracting criteria that are used to assess the current performance of the street network and recommending ways to improve them. The methodological approach of this research will focus on the selection of two neighborhoods in Doha based on their contextual location and types of land use: a downtown area or urban center exemplified in Fereej bin Mahmoud, and a suburban area or residential district of Al Waab. Three nominated streets of the existing network within the two areas will be selected based on an evaluation matrix, and assessed according to the users’ perspectives and future preferences and aspirations. This approach is supported by two major data collection tools: a visual questionnaire survey and semi-structured interviews with local authorities. A total of 100 questionnaires were collected for the two selected areas from different types of users. Results showed that users are completely unsatisfied with the current conditions of the selected streets in the two areas, which lack the major components of Complete Street variables: pedestrian, bicycle, green and transit improvements, which has resulted in the absence of safety. The produced results along with the evaluation criteria have helped in improving the current streets’ designs and have created a new enhanced cross-section that meets the concept of Complete Streets

Former à la classe inversée en contexte de visioconférence : retours sur deux itérations d'une recherche orientée par la conception

National audienceAs part of a collaborative design-based research project, flipped classroom training in a videoconferencing context was given twice to teachers. The pedagogical design of this training was structured in a framework based on the creation of a learning community, the learning presence and the real experience as a learner of a flipped classroom experience in a videoconferencing context. Following the first iteration, empirical findings, from the point of view of learning, as well as the activity of the instructors or the technopedagogical features implemented, led to the development of a first research project aimed at describing the presence created within this community, according to the learning presence model [11]. This work helped to highlight a certain lack of socio-cognitive presence and to raise questions about the pedagogical presence.Dans notre projet de recherche collaborative orientée par la conception, une formation sur la classe inversée en contexte de visioconférence a été donnée à deux reprises à des enseignants et conseillers pédagogiques. Le design pédagogique de cette formation se structurait dans un cadre misant sur la création d'une communauté d'apprentissage, la présence à distance et le vécu en tant qu'apprenant d'une expérience de classe inversée en contexte de visioconférence. Suite à la première itération, des constats empiriques, tant du point de vue de l'apprentissage, que de l'activité des formateurs ou des caractéristiques technopédagogiques mises en oeuvre, ont motivé l'élaboration d'un premier travail de recherche visant à décrire la présence suscitée au sein de cette communauté, selon le modèle de la présence à distance [11]. Ce travail a notamment permis de mettre en évidence une certaine carence en matière de présence sociocognitive et de soulever des questions sur la présence pédagogique

New Procedures for Catalytic Carbophilic Activation by Gold and Gallium π-Acids

International audienc

Concerted vs Nonconcerted Metalation–Deprotonation in Orthogonal Direct C–H Arylation of Heterocycles with Halides: A Computational Study

International audienc

Cycloisomerizations Catalyzed by Gallium Salts and NHC-Gallium(III) Complexes

Afin de développer des méthodes alternatives à l'activation de systèmes Pi en catalyse homogène par des métaux nobles coûteux et toxiques, nous nous sommes focalisés sur des complexes métalliques et plus particulièrement ceux de la colonne du group XIII. Cette thèse approche une contribution à ce champ d'études, et nous nous sommes particulièrement concentrés sur la chimie de gallium.Trois principaux aspects ont été étudiés dans ce manuscrit: la réactivité des halogénures de gallium(III), des complexes bien définis de gallium (III) portant carbènes N- hétérocycliques (NHCs), et leur activation de systèmes en catalyse.La thèse est divisée en trois chapitres. Le premier chapitre donne un aperçu des travaux effectués dans le domaine de la synthèse organique faisant intervenir des composés de gallium (III) , en se concentrant sur leur utilisation en tant qu acides de Lewis et .Dans le deuxième chapitre, nous avons tenté d'exploiter le potentiel catalytique de GaCl3 dans une nouvelle réaction de cycloisomérisation/Friedel-Crafts en tandem. Une section dédiée à l'étude sur l hydratation d alcyne catalysée par GaCl3 est également fournie.Le troisième chapitre commence par une description de la synthèse d'une série de complexes de gallium (III) portant diverses NHCs comme ligands pour surmonter les limites des halogénures de gallium(III) en catalyse. Ensuite, des études de méthodologie sur le processus de tandem impliquant arenynes-1,6 avec les gallium(III) complexes neutres et cationiques ont été décrits. Une évaluation cinétique pour des catalyseurs, des divers substrats et l'influence de contreanions sont discutés. En outre, les efforts dans la version asymétrique de cette tandem transformation et des autres cyclisations sont également présentés.Le dernier chapitre reprend les résultats les plus importants obtenus dans la thèse. Et les orientations futures de la recherche sur l'utilisation des complexes NHC- gallium (III) sont discutées.Recently, in order to develop alternative activation methods for Pi-systems in homogeneous catalysis instead of employing expensive and toxic noble metal catalysts, first row transition metals and main group metal complexes have attracted great attention. This thesis is a contribution to it, and we focus on gallium chemistry. There are three main aspects dominating this thesis: gallium(III) halides, well-defined gallium(III) complexes bearing N-heterocyclic carbenes (NHCs), and -systems activation in catalysis.The thesis is divided into three chapters. Chapter I provides an overview of the field of organic synthesis involving gallium(III) compounds, focusing on their use as - or -Lewis acids.In Chapter II, we expose our attempts to exploit the catalytic potential of gallium(III) chloride in a novel tandem cycloisomerization/Friedel-Crafts reaction. A section dedicated to the study on GaCl3-catalyzed alkyne hydration is also provided.Chapter III begins with a description of the synthesis of a series of gallium(III) complexes bearing various NHCs as ligands in order to overcome the limitations of gallium(III) halides in catalysis. Next, methodology studies on the tandem process involving 1,6-arenynes with the neutral and cationic gallium(III) complexes are described. The evaluation of scission kinetics for catalysts, substrates variation and influence of counteranions are discussed. In addition, efforts towards the asymmetric version of this tandem transformation and some other cyclizations are also presented.The concluding chapter reiterates the most important results obtained in the body chapters of the thesis. To conclude, the future directions for the research on the use of the NHC-gallium(III) complexes are discussed.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Évaluation des propriétés électroniques des composés à base de carbone(0) par la catalyse a l or et analyse des structures aux rayons-X.

La plupart des composés organiques ont un atome de carbone tétravalent, où tous les électrons de valence sont utilisés pour former des liaisons covalentes. En parallèle, la chimie des composés divalents ayant un carbone(II) s est développée après l isolement de carbènes stables par Bertrand en 1985. Auparavant, en 1961, Ramirez a rapporté l isolement de l hexaphénylcarbodiphosphorane, que l on peut considérer comme un composé présentant un carbone(0) avec ses deux doublets libres, lui permettant de coordiner jusqu à deux acides de Lewis. A partir de 2006, les propriétés électroniques de ces ligands ont été étudiées au travers d études théoriques par Frenking ; ce qui a permis à Bertrand et Fürstner d isoler et d ajouter des nouveaux membres à cette famille. Cette classe de ligand est aujourd hui connue sous le nom de carbônes , avec comme formule générale CL2 (L = PR3 ou carbène).Cette famille n a jamais été utilisée dans le domaine de la catalyse. C est pourquoi nous avons, décidé d etudier les propriétés électroniques de ce ces composés au travers de la catalyse à l or, afin de les comparer aux NHC, phosphines, et phosphites. Récemment, nous avons utilisé ces composés pour générer des complexes donneur accepteur avec du GaCl3, et de corréler leurs différentes caractéristiques géometriques à leurs propriétés électroniques en utilisant les règles de Gutmann sur des adduits acide/base de Lewis. De plus, nous avons isolé des dimères ioniques dont la formation peut être expliquée par les propriétés intrinsèques des ligands. Nous avons ainsi démontré par ces deux approches que les carbônes sont de meilleurs donneurs que les NHC.Most organic compounds which are stable in the condensed phase contain tetravalent carbon atoms, where all four valence electrons are being engaged in chemical bonds. On the other hand, the chemistry of divalent carbon(II) was only recognized after the isolation of a stable persistent carbene by Bertrand and co-workers in 1985. Such products display one s-type lone pair orbital and are thus good ligands. Earlier on, concern was also paid to a new family of compounds, first reported in 1961 by Ramirez and co-workers. They can be considered as divalent carbon(0) derivatives with two lone pairs at the central carbon, with a possibility of double coordination of two Lewis acids to this carbon. This feature was proposed by Kaska in 1973, and verified later by the isolation of di-metalated adducts. From 2006, these compounds were the centre of extensive theoretical investigations by Frenking, which led to the isolation of new members of this family by Fürstner and Bertrand. This family is now referred to as carbones , of general formula CL2 (L =PR3 or carbene). Carbones are still virtually unused in catalysis. Thus, we have decided to study these derivatives, especially in the field of gold catalysis, and to compare them with well-known ligands such as NHCs, phosphines and phosphites. Recently, we were able to synthesize their corresponding GaCl3 complexes and to rationalize their electronic properties through Gutmann s rules for Lewis acid/Lewis base adducts. In addition, we obtained some ionic dimers and we explained their formation on the basis of ligand s electronic properties. We have shown through these two approaches that carbones are far better donors than NHCs.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Enantioselective Total Synthesis of Cymoside through a Bioinspired Oxidative Cyclization of a Strictosidine Derivative

International audienceThe first total synthesis of the caged monoterpene indole alkaloid cymoside is reported. This natural product displays a unique hexacyclic-fused skeleton whose biosynthesis implies an early oxidative cyclisation of strictosidine. Our approach to the furo[3,2-b]indoline framework relied on an unprecedented biomimetic sequence which started by the diastereoselective oxidation of the indole ring into a hydroxyindolenine which triggered the addition of an enol ether and was followed by the trapping of an oxocarbenium intermediate

Calcium(II)-Catalyzed Intermolecular Hydroarylation of Deactivated Styrenes in Hexafluoroisopropanol

International audienc

Synthesis and photovoltaic performances in solution-processed BHJs of oligothiophene-substituted organocobalt complexes [([small eta]4-C4(nT)4)Co([small eta]5-C5H5)]

International audienceWe describe an efficient synthetic route toward novel organocobalt complexes [([small eta]4-C4(nT)4)Co([small eta]5-C5H5)] with n = 1, 2, 3 thiophene rings. Solution-processed bulk heterojunctions solar cells based on CpCoCb(3T)4:PCBM blends achieve power conversion efficiencies of up to 2.1%