1,874 research outputs found
Tuning the Steric and Electronic Properties of Hemilabile NHC ligands for Gold(I/III) Catalyzed Oxyarylation of Ethylene: A Computational Study
Full text linkMechanistic studies on 1,2-oxyarylation of ethylene promoted by gold catalysts bearing hemilabile N-Heterocyclic Carbene (NHC^X) ligands were conducted by DFT calculations, exploring the whole catalytic cycle. After highest energy transition state (TS) barriers were located for NHC^N gold catalyst, and experimental results with different iodoarenes and alcohols rationalized, the study was extended to modified NHC^X catalysts, to observe how electronic and steric effects could affect the rate determining step TS. Electronic effects were investigated on NHC^X (X=H, N, O, P, and S), whereas steric effects emerged when comparing catalysts with different N-R groups (R=Dipp, Mes, tBu and Me). Finally, we suggest a different catalyst design based on N-aryl N-o-donor-aryl NHC, with different donors and NHC backbones to search for better performing systems
Steric and Electronic Properties of NHC ligands for Gold(I/III) catalyzed Oxyarylation of Ethylene: A Computational Study
No full textOxyarylations of alkenes represent a powerful tool to build new organic scaffolds from simple
and cheap substrates. Although 1,2-oxyarylation of alkenes traditionally required exogenous
oxidants,1,2 the very recent synthesis of gold catalysts, bearing a chelating (C^N) NHeterocyclic
Carbene (NHC) ligand, allowed to react the alkene directly with an alcohol and
an aryl iodine (Scheme 1).3 Herein, we report a DFT study on the whole catalytic cycle of 1,2-oxyarylation of ethylene in
the presence of NHC-Au catalyst 13 (Scheme 2) with the intent to identify the rate determining
steps. The computational study shows how the presence of a donor on the NHC is able to
stabilize Au(III) species and how electronic and steric modifications of the ligand (2 and 3 in
Scheme 2) can affect the rate determining step barriers.
(1) Zhang, G.; Cui, L.; Wang, Y.; Zhang, L. J. Am. Chem. Soc. 2010, 132, 1474–1475.
(2) Harper, M.J.; Emmett, E.J.; Bower, J.F.; Russell, C. A. J. Am. Chem. Soc. 2017, 139, 12386−12389.
(3) Scott. S.C; Cadge, J.A.; Boden, G.K.; Bower, J.F.; Russell, C.A. Angew. Chem. Int. Ed. 2023, 62, e202301526
Controllo del territorio e vie di comunicazione nella politica di espansione della S.ma Trinità di Cava: l’esempio del Castellum Abbatis (secoli XII-XIII)
No full text
Seven Bodies. Parametric design dialogues around the body
No full textThe essay explores the possible horizons of fashion oriented research from a perspective of technological manipulation of the body. Through an intense and critical dialogue series, the body's construction is projected on the border between tangible and virtual to rediscover new expressive possibilities. Specifically, the essay describes the first phase of the Postdigital Manufacturing Processes. Body hacking for productive systems project funded under the VALERE Program at University of Campania “L.Vanvitelli”. From an analytical case study mapping phase, the project aimed to experiment with an interactive engagement of a series of focus groups with advanced digital technologies. Through this methodological practice based research, the essay describes the phase that involved seven international personalities in the fashion and design industry. The cycle of seminars, which lasted six months, was elaborated to have a direct dialogue with some of the most emblematic protagonists of the panorama relate d to fashion tech. (Toeters, 2020). The meetings contributed to the deepening of the project's themes by introducing new knowledge and technological processes. The second part of the essay illustrates a parametric study aimed at the definition of seven animations dedicated to each lecture. The seven animations, executed through the software Grasshopper, accompany the different dialogues intended as different perspectives around the digital body
Hybrid G-PRNU: Optimal parameter selection for scale-invariant asymmetric source smartphone identification
No full textDesign and Development of multi-biometric systems
No full textLa reconnaissance biométrique a été utilisée longtemps dans des espaces confinés, généralement à l'intérieur, où les opérations de sécurité exigeaient des systèmes de haute précision, par exemple dans les postes de police, les banques, les entreprises, les aéroports. Les activités de terrain, au contraire, exigent plus de flexibilité et portabilité conduisant au développement de dispositifs pour l'acquisition des traits biométriques et des algorithmes pour la reconnaissance biométrique dans des conditions moins contraintes. L'application de la reconnaissance biométrique "portable" est limitée dans des domaines spécifiques, par exemple pour le contrôle de l'immigration, et exige des dispositifs dédiés. Pour étendre l'utilisation de la biométrie sur les appareils personnels, des tentatives ont été faites par l’intégration des scanners d'empreintes digitales dans les ordinateurs portables ou les smartphones. Mais la reconnaissance biométrique sur les appareils personnels a été utilisée seulement pour un nombre limité de tâches, comme le déverrouillage d'écrans à l'aide des empreintes digitales au lieu de mots de passe. Les activités décrites dans cette thèse se sont portées sur le développement de solutions pour la reconnaissance de l'iris sur les appareils mobiles: - Acquisition: collection de la base de données MICHE, contenant des images d'iris capturée par des appareils mobiles; - Segmentation: développement d'un algorithme de segmentation innovante; - Extraction de caractéristiques: la reconnaissance de l'iris a été combinée avec le visage et la reconnaissance du smartphone.Enfin, la reconnaissance du regard a été étudiée afin de vérifier sa possible fusion avec l'irisBiometric recognition for a long time has been used in confined spaces, usually indoor, where security-critical operations required high accuracy recognition systems, e.g. in police stations, banks, companies, airports. Field activities, on the contrary, required more portability and flexibility leading to the development of devices for less constrained biometric traits acquisition and consequently of robust algorithms for biometric recognition in less constrained conditions. However, the application of "portable" biometric recognition, was still limited in specific fields e.g. for immigration control, and still required dedicated devices. A further step would be to spread the use of biometric recognition on personal devices, as personal computers, tablets and smartphones. Some attempts in this direction were made embedding fingerprint scanners in laptops or smartphones. So far biometric recognition on personal devices has been employed just for a limited set of tasks, as to unlock the screen using fingerprints instead of passwords. The research activities described in this thesis were focused on studying and developing solutions for iris recognition on mobile devices. This topic has been analyzed in all its main phases: - Acquisition: collection of the MICHE database, containing pictures of irises acquired by mobile devices; - Segmentation: development of an innovative iris segmentation algorithm; - Feature extraction and matching: iris recognition has been combined with the face and with sensor (smartphone) recognition. Finally, the use of gaze analysis for human recognition has been investigated in order to verify its possible fusion with iris
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