Teses / dissertações sobre o tema "Chirality density"
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Veja os 18 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Chirality density".
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Han, Jeong Woo. "Density functional theory studies for separation of enantiomers of a chiral species by enantiospecific adsorption on solid surfaces". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34848.
Texto completo da fonteDauvergne, Guillaume. "Hydrocarbures polycycliques aromatiques et chiralité : synthèse et modélisation". Electronic Thesis or Diss., Aix-Marseille, 2022. http://theses.univ-amu.fr.lama.univ-amu.fr/220114_DAUVERGNE_514pegpm797ly207jyhru699kmoiq_TH.pdf.
Texto completo da fonteIn this manuscript, we describe how we have developed the chemistry of aryne atropisomers with an ortho reactive triple bond to the stereogenic axis. These reaction intermediates are easily generated in situ and react in enantiospecific manners, and allow the synthesis of novel atropisomers. In particular, we describe the generation and applications of a synthetic equivalent of a BINOL-derived bis(aryne) atropisomer, as well as the semi-experimental measurement of the reaction barrier of such arynes in the presence of a standard arynophile. At the end of the manuscript, we describe our efforts to develop a synthetic approach to two regioisomers triple helices
Lam, Polo Chun Hung. "Experimental and Computational Studies in Bioorganic and Synthetic Organic Chemistry". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/40013.
Texto completo da fontePh. D.
Cui, Lingfei. "Antennes photoniques pour amplifier les interactions entre la lumière et la matière chirale". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS392.
Texto completo da fonteThe detection of molecules based on fluorescence or Raman scattering has been widely studied and is currently used in industry and laboratories. However, many organic molecules of interest are chiral, and their chemical and biological properties depend on their enantiomer as well as on the chirality of their secondary structure. The quantity and chirality of biomolecules are classically determined by measuring the differential absorption between the two opposite circular polarizations (chiroptic method). However, this method is limited by the low differential absorption of chiral molecules, which is of the order of 10-3 in the UV part of the spectrum. Plasmonic resonators have the ability to resonantly interact with light and are characterized by a moderate quality factor and a low effective volume. This resonant interaction allows (i) to increase the coupling between molecules and light and (ii) to control the polarization properties of light. So far, the latest advances concern the implementation of nanostructured chiral surfaces with gammadion-type resonators or stacked twisted resonators that interact preferentially with a given helicity of light. However, the mechanism behind the differential response of biomolecules coupled to chiral resonators to circularly polarized light is still unclear, preventing the optimization of such detection. Moreover, in the research published so far, two different chiral sensors are needed to interact with right- and left-handed circularly polarized light, which requires complex calibration procedures. During the course of my PhD, I have studied the use of anisotropic achiral nanostructures to interact with chiral molecules. Indeed, they have the significant advantage over chiral nanostructures of changing the sign of the circular dichroism by controlling the incident polarization or the direction of propagation. Indeed, the symmetries of the electromagnetic field in close proximity to the resonators can be manipulated at will by changing illumination conditions hence providing a unique tool for studying the origin of the electromagnetic coupling between chiral biomolecule and nanoresonators. Consequently, in my PhD project I propose to use plasmonic nanoresonators to increase the light - “chiral matter” interactions in order to detect and study chiral molecules. I will use the concept of achiral plasmonic nanostructures (nanoslits) to develop innovative nanoresonators that will be used, once functionalized, to detect chiral biomolecules with enantiomer sensitivity. Indeed, achiral resonators can generate both signs of chiral fields as opposed to chiral resonators which would make their use very flexible. This work implies characterizing, describing and understanding the origins of chiral fields and how to make them homogeneous. Through the study of nanoslits, I demonstrate numerically and theoretically how to design a nanosource of pure superchiral light, free of any background and for which the sign of the chirality is tunable on-demand in wavelength and polarization. In the perspective, I will present experimental methods that could monitor the CD via fluorescence emission (FDCD for Fluorescence Detected Circular Dichroism) in the case of light harvesting molecules for molecules that need to be excited in the UV, autofluorescence may be used in conjunction with aluminum resonators. Without loss of generality, these considerations lead to the decision of investigating plasmonic resonators with resonance at 680 nm which correspond to the chiral absorption band of LHCII. The idea of blocking the excitation beam to collect only the emission of the chiral molecules leaded to the idea of investigating the resonances of openings in an opaque layer of gold
Karimova, Natalia Vladimirovna. "Theoretical study of the optical properties of the noble metal nanoparticles: CD and MCD spectroscopy". Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38177.
Texto completo da fonteDepartment of Chemistry
Christine M. Aikens
Gold and silver particles with dimensions less than a nanometer possess unique characteristics and properties that are different from the properties of the bulk. They demonstrate a non–zero HOMO–LUMO gap that can reach up to 3.0 eV. These differences arise from size quantization effects in the metal core due to the small number of atoms. These nanoparticles have attracted great interest for decades both in fundamental and applied research. Small gold clusters protected by various types of ligands are of interest because ligands allow obtaining gold nanoclusters with given sizes, shapes and properties. Three main families of organic ligands are usually used for stabilization of gold nanoclusters: phosphine ligands, thiolate ligands and DNA. Usually, optical properties of these NPs are studied using optical absorption spectroscopy. Unfortunately, sometimes this type of spectrum is poorly resolved and tends to appear very similar for different complexes. In these cases, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopy can be applied. However, the interpretation of experimental CD and MCD spectra is a complicated process. In this thesis, theoretically simulated CD and MCD spectra were combined with optical absorption spectra to study optical activity for octa– and nona– and undecanuclear gold clusters protected by mono– and bidentate phosphine ligands. Additionally, optical properties of bare and DNA protected silver NPs were studied. Theoretical CD spectra were examined to learn more about the origin of chirality in chiral organometallic complexes, and to contribute to the understanding of the difference in chiroptical activity of gold clusters stabilized by different phosphine ligands and DNA–stabilized silver clusters. Furthermore, optical properties of the small centered gold clusters Au₈(PPh₃)₈²⁺ and Au₉(PPh₃)₈³⁺ were examined by optical absorption and MCD spectra using TDDFT. Theoretical MCD spectra were also used to identify the plasmonic behavior of silver nanoparticles. These results showed that CD and MCD spectroscopy yield more detailed information about optical properties and electronic structure of the different chemical systems than optical absorption spectroscopy alone. Theoretical simulation of the CD and MCD spectra together with optical absorption spectra can be used to assist in the understanding of empirically measured CD and MCD and provide useful information about optical properties and electronic structure.
Hsu, Danny Chung. "Mechanistic Studies on Memory of Chirality Alkylations of 1,4-Benzodiazepin-2-ones & Structure-based Design of Insecticidal AChE Inhibitors for Malaria Mosquito, Anopheles gambiae". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29192.
Texto completo da fontePh. D.
MacQuarrie, Stephanie Lee. "Design and Synthesis of Novel Benzodiazepines". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/30209.
Texto completo da fontePh. D.
Hedman, Daniel. "A Theoretical Study: The Connection between Stability of Single-Walled Carbon Nanotubes and Observed Products". Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62321.
Texto completo da fonteShanmugam, Janaki. "Correlation of optical anisotropy with structural changes in Ge2Sb2Te5". Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:8cee7355-0ff6-4939-a606-a406c7a9823d.
Texto completo da fonteSchneider, Nathanaëlle. "N-heterocyclic carbenes with an oxazoline unit : Synthesis, coordination chemistry and application in asymmetric catalysis". Strasbourg 1, 2008. http://www.theses.fr/2008STR13057.
Texto completo da fonteThe efficiency of an asymmetric organometallic catalyst is determined by the appropriate design of the chiral ligand. The combination of the kinetic robustness of N-heterocyclic carbenes with oxazolines as stereodirecting elements appears to be very promising. A novel family of imidazolium salts, where both heterocycles are connected by a (dimethyl)methylene bridge was generated. Reacting various bromide derivatives with imidazoles bearing an oxazoline unit has afforded a family of seven different ligand precursors (60-90% yield). The free carbenes 1-(1-methyl-1-((4S)-iso-propyl- and tert-butyl-4,5-dihydrooxazol-2-yl)ethyl)-3-(di(-naphtyl)methyl)imidazole-2-ylidene (11a, 11b) could be isolated by simple deprotonation of the imidazolium salt. Reaction of the imidazolium salt 9d with the Karstedt catalyst in the presence of potassium tertbutoxide led to the formation of the monodendate trigonal planar Pt(0) complex 13, which could be oxidised to the bidendate Pt(II) complex 15 by reaction with CsBr3. Subsequent deprotonation of the imidazolium salt 9g and reaction with [Rh(nbd)Cl]2 gave the neutral square-planar Rh(I) complex 18 that is converted into the cationic bidendate complex 19 by bromide abstraction. The methyl substituents on the methylene bridge proved to provide more stability to complexes towards air and to enhance the chelating capacity of the ligand in solution. At the same time, the limit of the chelating capacity of the ligands previously developed in the group, where both heterocycles are directly connected, was emphasised by the generation of the Cu(I) complexes 12a and 12b, which crystallised as dimer and coordination oligomers. The cationic analogues of the rhodium complexes 16b, 18 and 20 were tested in the catalytic asymmetric hydrosilylation of ketones and afforded different activities and selectivities. The commonly accepted Ojima mechanism not accounting for some of the experimental observations, a comprehensive theoretical investigation of the catalysis mechanism via DFT calculations was carried out. Three viable mechanistic pathways could be established. They all involve a first oxidative addition step and differ in the mode of insertion of the ketone, either into the Rh-Si bond (Ojima mechanism), into the Si-H bond (Chan mechanism) or via the formation of a silylene intermediate (new mechanistic pathway). The latter is energetically favoured with regard to the postulated ones, by respectively 55 kJ. Mol-1 (Ojima mechanism) and 120 kJ. Mol-1 (Chan mechanism). Being only accessible when a dihydrosilane is used, this explains the observed rate enhancement when secondary silanes are used instead of tertiary silanes. Moreover, it accounts for the inverse kinetic isotope effect
Aviles-Moreno, Juan-Ramón. "Flexibilité conformationnelle dans les amines, les sucres et leurs complexes hydratés étudiée par spectroscopie à impulsions microondes et calculs de chimie quantique". Lille 1, 2006. https://ori-nuxeo.univ-lille1.fr/nuxeo/site/esupversions/65353286-2f4b-4a09-9c9a-243841438735.
Texto completo da fonteBiguet, Alexandre. "Modèles Nambu--Jona-Lasinio pour l’étude des phases de la chromodynamique quantique : qualités des prédictions et phases hautes densités". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1179/document.
Texto completo da fonteNambu--Jona-Lasinio models can be used to study finite density and finite temperature quantum chromodynamics phases. Finite temperature and low density predictions of these models can be compared to lattice results. Such a comparison is not possible at larger density because of the so called sign problem. In this thesis the proposed systematic method allows to compute the stability of a prediction with respect to the inputs of the model. In this way a quantitative criterium is constructed which can be used to evaluate the predictive power of the studied model. Finally the high density phases which can exist in the interior of compact stellar objects are discussed along with color superconductivity in NJL type models
Martin-Gassin, Gaelle. "Etude statique et dynamique par réflectance linéaire et Génération de Second Harmonique de films de molécules et de nanoparticules métalliques à l'interface air / eau". Phd thesis, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00150850.
Texto completo da fonteCarter, Rachel Mary. "Form factors in a hybrid chiral soliton model with continuous baryon density". Thesis, 2015. http://hdl.handle.net/10539/16489.
Texto completo da fonteHe, Jiangtao. "Investigation of the stereo structures of chiral molecules using vibrational circular dichroism, optical rotation, and density functional theory". Diss., 2005. http://etd.library.vanderbilt.edu/ETD-db/available/etd-11222005-105458/.
Texto completo da fonteBřezina, Václav. "Spektroskopické a teoretické studium supramolekulárních komplexů symetrických porfyrinů s chirálními guesty". Master's thesis, 2014. http://www.nusl.cz/ntk/nusl-336614.
Texto completo da fonteŠikorský, Tomáš. "Studium chirálních vlastností supramolekulárních komplexů". Master's thesis, 2011. http://www.nusl.cz/ntk/nusl-296381.
Texto completo da fontePartyka, Tomasz. "Nonuniform condensates in the phase diagram of the strongly interacting matter". Praca doktorska, 2011. https://ruj.uj.edu.pl/xmlui/handle/item/53008.
Texto completo da fonte