Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Asymmetric info.
Thèses sur le sujet « Asymmetric info »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 49 meilleures thèses pour votre recherche sur le sujet « Asymmetric info ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les thèses sur diverses disciplines et organisez correctement votre bibliographie.
1
BONAZZI, LEDA MARIA. « Essays on Entry in Vertical Relationships ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/258913.
Texte intégralRésumé :
Dall'inizio degli anni '90, i problemi di contrattazione verticale e le loro implicazioni sono stati ampiamente studiati nella letteratura dell'Organizzazione Industriale. Infatti, l'analisi della relazione tra mercati upstream e downstream è importante non solo per valutare l'impatto che le diverse forme di contratti hanno sul benessere totale e sul surplus del consumatore, ma anche per comprendere la caratterizzazione della struttura del mercato. Questa tesi è divisa in due capitoli riguardanti la contrattazione verticale e la struttura del mercato. Tenuto conto del fatto che sono presenti numerosi elementi che giocano un ruolo interessante, come la contrattazione sotto l'informazione asimmetrica, le decisioni di entrata e la scelta del mercato da parte delle imprese verticali, tutto il lavoro è orientato ad un’analisi di come questi elementi interagiscono tra loro e come le diverse forme di accordi contrattuali tra produttori e dettaglianti (two-part tariffs, i contratti lineari, la clausola di mantenimento dei prezzi di rivendita o il quantity forcing) influiscano sulle decisioni di ingresso e sulla scelta del mercato. Inoltre, una novità di questo articolo è considerare la struttura del mercato come endogena e studiare le conseguenze di questa ipotesi, aggiungendo nuove intuizioni a questo fiorente filone di letteratura.Since the beginning of 90's, vertical contracting issues and their implications have been widely studied in the Industrial Organization literature. For instance, analyzing the relationship between upstream and downstream markets is important not only to evaluate the impact that the different forms of vertical contracts have on total welfare and on consumer surplus, but also to better understand market structure. This thesis is organized in two chapters dealing with vertical contracting and market structure. Since, in this set-up there are many elements playing an interesting role, like contracting under asymmetric information, entry decisions and market choice by vertical related firm, throughout the work there is an analysis of how these elements interact between each others, and how different forms of contractual agreements between manufacturers and retailers, as two-part tariffs, resale price maintenance and quantity forcing, affect entry decisions and market choice. A novelty of this thesis is to consider market structure as endogenous and to study the consequences of this assumption, by adding new insights to the burgeoning existing literature on entry in vertical relationships.
2
Bena, Luvuyo Clifford. « Investigations into the asymmetric reduction of ketones ». Thesis, University of Port Elizabeth, 2003. http://hdl.handle.net/10948/323.
Texte intégralRésumé :
A six-step synthesis of salbutamol from methyl salicylate with an overall yield of 17% has been completed, although the yield was not optimised. In the process, Zn(BH4)2 was found to selectively reduce a ketone carbonyl group in the presence of an ester unit. In contrast, borane was found to reduce both the ketone and ester carbonyl groups. Reduction of phenacyl bromide with borane in the presence of chiral catalysts based on (R)-alaninol and (R,S)-ephidrine resulted a measure of enantioselectivity in the product. However, the configuration of the alcohol obtained in the case of (R)-alaninol was contrary to expectations based both on experimental trends observed elsewhere as well as our own theoretical predictions. The asymmetric reduction of methyl 5-bromoacetyl-2-benzyloxybenzoate was accomplished with both borane and Zn(BH4)2 in the presence of a range of chiral catalysts. Optically active products were obtained in all cases, although the optical rotations were significantly smaller in the case of Zn(BH4)2. Unfortunately, we were not successful in determining the enantiomeric excesses of these reactions. The use of a NMR lanthanide shift reagent resulted in a complex spectrum that was impossible to interpret unambiguously. This presumably arises from the presence of several Lewis base sites in the product at which complexation with the shift reagent can take place. It was also not possible to determine the optical rotation of salbutamol itself owing to the relatively small amount of material obtained. A conformational analysis of salbutamol, where NMR data was correlated with molecular modelling results, was successfully carried out and revealed a strong preference for that conformer family characterised by O–C–C–N and Ar–C–C–N torsion angles of ca. 60º and 180º, respectively. Interestingly, these conformers are found to be stabilised by OH…N rather than NH…O hydrogen bonding. This study has also confirmed the effectiveness of the MMFF94 force field for conformational analysis studies in compounds of this kind. Lastly, a relatively simple method for modelling the BH3/oxazaborolidine reduction of ketones at the PM3 semiempirical MO level of approximation was devised. This approach has provided insights into the mechanism of the reaction and has furthermore enabled us to predict the enantioselectivities likely to result from various catalysts and ketones. In comparing our theoretical and experimental findings, an anomalous result was observed in the case of (R)-alaninol; this will have to be investigated further, particularly at the experimental level. However, we believe that our approach provides a sound basis for aiding the design and screening of new, potentially better catalysts.
3
Evans, Gareth J. S. « Theoretical investigation into asymmetric iminium ion organocatalysis ». Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/55527/.
Texte intégralRésumé :
The scope of this thesis covered three main areas of this emerging area of chemistry. A reaction pathway is proposed for the formation of iminium ion intermediates from the reaction of secondary amines with carbonyl compounds. This suggests the deprotonation of the amine as the rate-determining step. The effect of modification of amine structure on this pathway was studied, and rationalised using Atoms-in-Molecules analysis. Molecular properties were used to describe a range of secondary amines with an aim to find a relationship between composition and reactivity. A number of catalytic candidates were suggested for synthesis. Two reaction types that directly and indirectly utilise iminium ions as catalysts or intermediates were covered. This included studies of model amines, as well as those in current use as asymmetric catalysts. The Diels-Alder reaction was studied in depth for a number of iminium ions. The alpha-acyloxylation of enamines was also studied, and reaction profiles in gas-phase and solvent identified, and possible mechanisms of asymmetric induction explored.
4
Jankowski, Piotr. « New insights into asymmetric hydrogenation using monodentate phosphorus ligands ». Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551301.
Texte intégralRésumé :
The synthesis and coordination chemistry of monodentate phosphorus ligands that span a range of stereoelectronic effects is the topic of this thesis. It is shown that many Rh complexes of the type [Rh(L)2(olefin)]BF4 (L = ligand) exhibit restricted Rh-P bond rotation, which is slow enough to be observed on the NMR timescale. Variable temperature NMR studies of a range of Rh complexes of mono ph os ligands reveal similarities in the observed pattern, suggesting that the M-P restricted rotation is a more general phenomenon of the cis-ligated square planar complexes. OFT calculations and solid state analysis are employed to shed light on the structures of the Cl- and C2-symmetrical rotamers observed in the NMR spectra. The improvement of the separation of enantiomers of optically active 1,3,5,7- tetramethyl-4,6,8-trioxa-2-phospha-adamantane, CgPH is reported, allowing the recovery of the previously inaccessible a-CgPH. Optically active a-CgPH yields a highly selective catalyst in the asymmetric hydrogenation of various olefins, producing ee of up to 95%. Rh complexes of CgPH are extensively studied by NMR techniques and OFT calculations in order to understand the unexpectedly high enantioselectivity obtained with Rh-CgPH catalysts; it is proposed that the enantioselectivity arises from the presence of a Cl-symmetrical rotamer in solution. A series of 3,3' -dimethylphosphonite ligands of a type (binolate)PR (R = Me, iPr, Cy, tBu) are synthesised and their coordination chemistry is investigated. Most of the ligands upon reaction with [Rh(cod)2]BF 4 produce complexes of a type [Rh(L)2(cod)]BF4• The tBu-phosphonite does not follow this reactivity pattern, presumably due to the steric bulk of the ligand, making the incorporation of two ligands in the cis arrangement unfavourable. Of all the above mentioned ligands, the iPr- and Cy-phosphonite are the best catalysts for the hydrogenation of a- dehydroaminoacid derivative substrates, methyl-(Z)-a-acetamidocinnamate (up to 94%) and methyl-a-acetamidoacrylate (up to 97%), but they are less selective for dimethylitaconate (up to 75%). A series of ligands bearing extended aromatic systems are synthesised in order to probe the possibility of the backbone formation using pi-pi interactions in cis square planar complexes. Some circumstantial evidence for the interactions have been observed and the presence of the extended pi systems is shown not to be beneficial on the asymmetric hydrogenation outcome.
5
Bowman, Iain Niall Reginald. « A study of mass injection into an asymmetric supersonic wake ». Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386256.
Texte intégral
6
Mazloumi, Khatebeh. « An investigation into a series of asymmetric intramolecular Nicholas cyclisation reactions ». Thesis, Kingston University, 2013. http://eprints.kingston.ac.uk/27740/.
Texte intégralRésumé :
The Nicholas reaction is the reaction of a cobalt-stabilised propargyl cation with a nucleophile and the aim of this project was to attempt this reaction with a chiral substrate in an effort to effect an asymmetric Nicholas reaction. A range of contemporary techniques were applied to reach this goal. Initially an attempt was made to reproduce an earlier successful racemic synthesis of a fused carbocyclic compound using a chiral precursor. It was envisaged that this would be approached using a 1,4-conjugate addition to an enone using a chiral ligand to install the C-3 alkenyl group selectively. Although the conjugate addition reactions were successful, using well tried and tested ligands, the enantiomeric excesses were very low and unfortunately a suitable chelating catalyst that prevent fulfil the requirements was not identified at this stage of the investigation. The next approach made use of an asymmetric alkynylation reaction to an aldehyde. This was successfully carried out using a Carreira asymmetric alkynylation reaction to afford optically active propargyl alcohols with good to excellent enantiomeric excess (50%-82% ees). The desired optical active propargyl alcohols were then complexed, with dicobalt octacarbonyl, to afford the corresponding dicobalt hexacarbonyl complexes. These then successfully underwent the corresponding Nicholas cyclisation reaction to afford, after oxidative decomplexation of the cobalt species, a range of optically active chromane and isochromanes with ees of (45%-81%). In a second study a series of optically active benzopyran derivatives were also successfully synthesised, using the same methodology, again with high levels of enantiomeric excess (87% - 94%). In the final phase of this investigations it was explored the use of chiral derivatives of the chiral pool molecule citronellal as well as an achiral analogue in an effort to afford novel chiral aldehydes for propargylation and cyclisation. The new chiral centres were successfully installed using chiral auxiliary technology however unexpectedly difficulties were encountered in the removal of the chiral auxiliary. A lack of time, in order to further explore the removal step, unfortunately meant that this was put on hold for further studies.
7
Valette, Damien. « Studies into asymmetric Diels-Alder reactions of anthracene derivatives using cationic oxazaborolidines ». Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544175.
Texte intégral
8
Brawn, Peter. « An investigation into the asymmetric synthesis of novel benzopyrans for biological evaluation ». Thesis, Kingston University, 2012. http://eprints.kingston.ac.uk/24046/.
Texte intégralRésumé :
The aim of this project was to prepare a novel range of dicobalt hexacarbonyl-alkyne complexes for testing as anticancer agents and benzopyrans as antihypertensives. In addition an investigating into the stereoselectivity of the Nicholas reaction will be undetaken. Hypertension and cancer are two very different dieases that are becoming more prevalent in modern life. Interest in antiproliferatory compounds containing metallic substituents has intensified since the serendipitous discovery of cisplatin in 1969. More recently Co-ASS, a dicobalt hexacarbonyl alkyne complex derived from aspirin, was found to out perform Cisplatin in the inhibition of MCF-7 breast cancer cells. This has led to a number of cobalt-alkyne complexes being found to possess anticancer activity. The preparation of a range novel cobalt-alkyne complexes is herein described along with the testing of their efficacy against CaCo-2 cancer cells. This Study showed that the presence of aromatic ring substituents had a large detrimental effect on their activity with the unsubstituted counterpart eliciting an IC50 value of 16.02 µM relative to >100 µM for the substituted counterparts. The observed IC50 of 16.02 is similar to those found in the literature for the cobalt-alkyne complexes of propargyl amides Co-ASSAM and Co-Phthal giving values of 8.8 and 22.2 repectively on MCF-7 cells. Benzopyrans are known to relax smooth muscle by activating transmembrane potassium channels. Cromakalim, the bench mark potassium channel activator however is not used clinically due to undesirable side effects. This has led to a large amount of work into the preparation of novel benzopyrans that maintain this activity whilst eliminating these side effects. Although the novel benzopyrans prepared were shown to be less active, as vasorelaxants, compared to cromakalim, they do, show greater activity compared to compounds that had been previously prepared within the Tyrrell group. Finally we show the exclusive cis diastereoselective nature of our studied Nicholas reaction in the simultaneous formation of two chiral centres. The effect of chiral induction on the formation of these two centres is also investigated showing the ee of the Nicholas reaction to be >99% and a de of 68% in the most selective instance.
9
Lamping, Logan Joseph. « An investigation into an asymmetric fuel nozzle in a GE CFM56-5B burner ». Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/12061.
Texte intégral
10
Cornish, Alix. « Investigations into chiral adsorption systems relevant to asymmetric heterogeneous catalysis on metal surfaces ». Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553037.
Texte intégralRésumé :
Two chiral adsorption systems are investigated, adsorption of a known chiral modifier, alanine, onto Ni surfaces and the interaction of chiral homoserine on intrinsically chiral Cu {531}. Alanine is known to act as a chiral modifier in the enantioselective hydrogenation of ~-ketoesters, but the reaction mechanism has yet to be determined. Two approaches are employed to investigate how alanine acts as a chiral modifier. Adsorption onto single crystal Ni{111} and {11O} surfaces is studied by XPS and angle resolved NEXAFS. It was shown that in the chemisorbed layer, alanine adsorbs in an anionic state with a deprotonated carboxylate group on both surfaces. This arrangement was also observed for achiral glycine on Ni {Ill}. A triangular adsorption footprint is created with surface bonds between both carboxylate oxygen atoms and the amino nitrogen. The growth of zwitterionc multi layer alanine is also observed for both systems but on Ni{11O} the multi layer is shown to segregate into alanine crystallites with a Stranskiy-Krastanov-like morphology at 240 K. On Ni {111}, the tilt angle of the carboxylate group from the surface is 45' compared to 55' on the Ni {Il O}, determined by angle resolved NEXAFS. Decomposition of these amino acids is shown to proceed via initial cleavage of the Ca-COO bond to release CO2 followed by cleavage of the Ca-CH3 bond to ultimately produce (Hx)C=N and atomic carbon. On the Ni {11O} surface, these final decomposition products coexist until -700 K whereas on Ni {Ill} only atomic species exist on the surface after 450 K, for both alanine and glycine. Ultimately, the atomic N recombines to form N2 which is detected by TPD at mass 28 and 14 amu. The second approach involved alanine adsorption on polycrystalline Ni. Previous experiments to probe this system had either been performed in UHV on single crystal surfaces, or in solution based studies with high surface area catalyst particles. This complexity gap is a poignant problem in the attempt to understand the mechanistic details of this reaction. Polycrystals were seen as a bridge between these two systems since they offer several different surface terminations and boundaries, which are analogous to reactive, defect sites on catalyst particles. PEEM and LEEM were successfully used to identify the surface facets of polycrystalline Ni and allowed the application of several surface science techniques. The oxidation of poly crystalline Ni is successfully probed using PEEM and LEEM. For oxygen exposure at temperatures of 473 K and higher, spatially resolved NEXAFS spectra clearly identify NiO crystallites in the I urn range with areas of clean Ni surface between them. Certain boundary regions are devoid of crystalIites. For lower temperatures a uniform chemisorbed oxygen layer with a different spectroscopic signature is formed. The same technique was applied to study alanine adsorption. It is shown that alanine is capable of restructuring grain boundaries of polycrystalline Ni, possibly creating chiral facets, where the enantioselective reaction could occur. The adsorption of homoserine on chiral Cu{531} was performed to improve our understanding of the interactions between chiral molecules and chiral substrates, specifically, the influence of longer side chains. XPS and angle resolved NEXAFS experiments were performed to probe enantiomeric differences. Homoserine was found to exist on the surface in an anionic state involving a deprotonated carboxylate group and a neutral amino group. It was found that three surface bonds are always made, one from the amino nitrogen and one from each of the carboxylate oxygen atoms, creating a triangular footprint, typical for a-amino acids. Under certain conditions; 50% saturation coverage of D-homoserine and also 85 and 100% saturation coverage of L- homoserine, the alcohol side chain makes an additional bond to the surface via the oxygen atom, creating a rectangular footprint. Both enantiomers are shown to occupy both adsorption sites equally but a 12' rotational difference in adsorption between the two enantiomers is found to exist for low coverages.
11
Brimage, Rebecca Ann. « Investigations into the asymmetric synthesis of a-amino acid functionalised calix[4]arenes ». Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435021.
Texte intégral
12
Russell, Keith Casey. « Design and asymmetric synthesis of unusual amino acids for incorporation into peptide hormones ». Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185750.
Texte intégralRésumé :
One of the central goals of peptide and protein chemistry is the development of peptides with specific biological, chemical, and physical properties. An important method directed towards attaining this goal is the use of conformationally restricted amino acids. The conformationally restricted amino L-isomers of 2'-methyltyrosine, 2',6'-dimethyltyrosine, erythro- and threo-2',β-dimethyltyrosine, and erythro- and threo-2',6',β-trimethyltyrosine were asymmetrically synthesized in good yields and high optical purities. The synthesis of these compounds was based on the chiral boron imidate methodology. Acid precursors were prepared from either 5-methyl-2-nitrophenol, 3-methylanisole, or 3,5-dimethylansole and coupled to optically active 4-phenyl-2-oxazolidinone. Unsaturated coupled products were subjected to 1,4 conjugate additions to set the stereochemistry at the β-carbon with superior stereoselectivity (88-99% de). The Michael adducts and other acyloxazolidinones were asymmetrically brominated to set the chirality at the α-carbon also with excellent stereoselectivity (80-98% de). The bromides were displaced with azide ion to afford the α-azidocyloxazolinones without any detectable racemization. The chiral auxiliary was hydrolyzed and recovered. The azido acids were reduced and methyl ether hydrolyzed to yield the tyrosine derivatives with high optical purity. The absolute stereochemistry of three of the bromide intermediates was determined by X-ray crystallography providing evidence for the selective reactions. The superiority of 4-phenyl-2-oxazolidinone over 4-phenylmethyl-2-oxazolidinone for asymmetric induction was also demonstrated. To examine the sensitivity of the 2' position of tyrosine in oxytocin, (D,L-2'-methylTyr²) oxytocin was synthesized using the standard techniques of solid phase synthesis. Racemic 2'-methyltyrosine was prepared via the classical malonate synthesis. Computer models suggest that the [L-2'-methylTyr²] oxytocin should be a weak agonist.
13
Jiang, Lingfan. « Studies into iridium-catalysed asymmetric allylic alkylation towards the total synthesis of a dolabellane ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:29d0e1eb-62f4-4f5a-9187-506de113665a.
Texte intégralRésumé :
In recent years, iridium-catalysed asymmetric allylic substitution has received considerable attention because it is a valuable tool to selectively synthesise chiral compounds with high ee from simple starting materials. This thesis presents an efficient catalytic system for the decarboxylative iridium-catalysed asymmetric allylic alkylation (AAA) in which a wide range of allylic β-ketoester substrates was converted into chiral ketones in good yields with high regio- and enantioselectivities. A possible mechanism for decarboxylative iridium-catalysed AAA is also proposed in this thesis.
14
Ilyashenko, Gennadiy. « Investigations into new catalytic systems for the asymmetric epoxidation of alkenes using environmentally benign oxidants ». Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428690.
Texte intégral
15
Dwyer, Andrew Neil. « An investigation into the use of pyridine-cored molecular pincers for asymmetric resolution and catalysis ». Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431199.
Texte intégral
16
De, Faveri Giorgio. « Investigations into new methods for the efficient and environmentally benign catalytic asymmetric epoxidation of alkenes ». Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1304.
Texte intégralRésumé :
This thesis presents our investigations into the catalytic asymmetric epoxidation of alkenes. An introductory chapter highlights the importance of chirality in nature and industry. It focuses on a few relevant examples of syntheses in which the use of optically pure epoxides as building blocks is fundamental to the overall stereochemistry of the product. The introduction then continues describing the advances in the field of asymmetric epoxidation of olefins; it contains a review of a wide range of the ligands and metals employed in the recent literature together with a range of different oxidants. A section on organocatalytic epoxidations concludes this chapter. A second chapter presents attempts to impart enantioselectivity in the epoxidation of olefins by employing chiral additives (BINOL derivatives) in conjunction with a known oxidising system, TMTACN/manganese with hydrogen peroxide as the oxidant. A brief electrochemical study of the redox potential of the catalytic systems described in this chapter and a study of the effect of the electronic properties of the substrates on the reaction is also reported. The third and fourth chapters describe the synthesis of a series of tri- tetra- and pentadentate ligands based on the backbone of L-proline and trans-diaminocyclohexane. The chapters contain the results of the screening of the above mentioned ligands in the epoxidation of alkenes with a number of metal salts using either hydrogen peroxide or peracetic acid as the oxidant. Single crystal X-ray structures of some of the new ligands are also presented herein. A final experimental chapter presents the supporting characterisation data associated with the compounds synthesised.
17
Fernández, Pérez Héctor. « Towards highly efficent ligands for asymmetric hydrogenations : a covalent modular approach and investigations into bio-inspired supramolecular strategies ». Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/9041.
Texte intégralRésumé :
La preparación de nuevos ligandos quirales P-OP (fosfina-fosfinitos y fosfina-fosfitos), fácilmente preparados con una estrategia sintética en dos etapas desde una aproximación covalente, es descrita en la presente Tesis Doctoral. El mejor catalizador de la serie ha demostrado tener propiedades catalíticas excelentes en la hidrogenación asimétrica catalizada por rodio de una amplia variedad de olefinas funcionalizadas. El resultado excelente y el diseño modular de los ligandos sintetizados hacen éstos muy atractivos para futuras aplicaciones.La presente Tesis Doctoral describe también la preparación de nuevos ligandos quirales que pueden comportarse como catalizadores supramoleculares inspirados en el mecanismo de regulación alostérica de los enzimas.
A library of enantiomerically pure P-OP ligands (phosphine-phoshinites and phosphine-phosphites) straightforwardly available in two synthetic steps from enantiopure Sharpless epoxy ethers is reported in the present PhD. Thesis. The "lead" catalyst of the series has proven to have outstanding catalytic properties in the rhodium-catalysed asymmetric hydrogenation of a wide variety of functionalised alkenes. Their excellent performance and modular design makes them attractive for future applications.
This PhD. Thesis also reports the development of a practical route to chiral diphosphine ligands with supramolecular motifs, with potential for allosteric modulation, which we prepared for future catalytic studies.
18
Iwamura, Hiroshi. « Mechanistic insights from kinetic analysis by reaction calorimetry into proline-catalyzed asymmetric reactions and autocatalytic reaction ». 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136952.
Texte intégral
19
Marsh, Barrie. « Studies into the Asymmetric Reduction of Imides Using Oxazaborolidines Derived from cis-1-amino-indan-2-ol ». Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489726.
Texte intégral
20
Harvey, James Martin. « Investigations into the manipulation of 1,2,3-triazoles and towards an asymmetric 'click' reaction of meso bis-alkynes ». Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/57411/.
Texte intégralRésumé :
This thesis describes the synthetic approaches undertaken to generate various substituted 1,2,3-triazoles and a small group of bis alkyne-containing compounds, followed by their attempted application in an asymmetric ‘click’ reaction. The first chapter gives an outline to the importance of desymmetrization within organic synthesis, providing examples of the types of stereoselective reactions found within the literature. Attention is then focused on the field of ‘click’ chemistry, specifically the copper-catalysed azide-alkyne cycloaddition (CuAAC), its mechanistic studies and recent applications. Chapter two contains the results and discussion of the project and begins with the application of the CuAAC reaction to produce a simple 1,4-disubstituted 1,2,3-triazole from its two coupling partners, an azide and an alkyne, in near quantitative yields. The 1,4-disubstituted triazole is then transformed to its corresponding triazolium salt, with the longer alkyl chains only giving 40-45% product. They are then reacted with potassium tert-butoxide to generate the 1,5-disubstituted 1,2,3-triazole in yields of 83% or above. The reaction steps were optimised to give a standard procedure for the conversion of 1,4- to 1,5-triazoles, with a small series of test reactions giving overall yields of up to 90%. The second section of the results and discussion chapter centres on the development of meso bis-alkynes which were to be used in the evaluation of an asymmetric ‘click’ reaction. A number of synthetic approaches to these compounds are described, with most falling short of their final target compound, and either needing further work or a redesign of the target compound itself. One target compound, meso-1,2-bis-(prop2-yn-1-ol)benzene 29, was synthesised and a series of further meso bis-alkynes produced by various additions to the propargylic alcohol. Evaluation of the asymmetric ‘click’ reaction using this group of compounds under a wide selection of reaction conditions gave no successful results, all returning only starting material. Chapter two concludes with a brief summary of future work. Finally, chapter 3 contains full experimental details for the synthetic studies carried out in the preceding chapters.
21
Del, Vecchio Franklin A. « An investigation into the asymmetric synthesis of imidazolinones via reaction of chiral a-amino acid esters with nitriles / ». Online version of thesis, 1991. http://hdl.handle.net/1850/11069.
Texte intégral
22
Al-Ghamdi, Saleh A. « An Empirical Investigation into the Value of Credit Lines ». Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609149/.
Texte intégralRésumé :
Access to adequate liquidity to finance future investments is an essential element of financial management. The two main questions that this dissertation attempts to answer are (i) what is the net valuation effect of LoC? and (ii) if LoC create value, what are the sources of this value? To answer these questions, I constructed a sample of 85,232 firm-years spanning from 1993 to 2016, with credit line data obtained from Capital IQ and Bloomberg. I investigated the valuation effects of LoC with a methodology extensively used in the analysis of the valuation implications of cash. I used this methodology because cash and LoC are two alternatives to manage liquidity and estimated the changes in shareholders' value associated with changes in existing LoC undrawn balances and on new LoC agreements. The results from this analysis demonstrates a positive association between increases in LoC capacity and shareholder's value. These findings are also obtained in univariate and event study analyses. The results also suggest that LoC create more value for firms that are rich in cash, indicating the LoC and cash are complementary liquidity management tools.
I then focused on the sources of the value created by credit lines. I examined whether information asymmetry plays a role in LoC valuation by analyzing the association between firm value and LoC for firms with high- and low-information asymmetric. I also studied whether LoCs reduce agency problems by comparing firm value and LoC capacity in both poorly and well-governed firms. Furthermore, I examined whether firms benefit from an increase in financial flexibility provided by access to credit lines. I found results consistent with LoC being more valuable for firms with higher levels of informational asymmetries. The analysis also suggests that LoCs with longer maturity create more value than those with shorter maturity. Surprisingly, I find limited support for the hypothesis that shareholders place a higher value on LoCs in increasing financial flexibility. Moreover, I found no support for the role of credit lines in reducing agency problems.
23
Shah, Beena. « A study into the use of ephedrine, immobilised on a silica support and its use in asymmetric alkynylation reactions ». Thesis, Kingston University, 2015. http://eprints.kingston.ac.uk/32206/.
Texte intégralRésumé :
This work describes the preparation of an immobilised ephedrine silica supported catalyst and its application in asymmetric synthesis. (1R,2S)-(-)-Ephedrine is a controlled substance, whose use in synthesis is closely monitored by a licence regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). One way of reducing the demand for controlled substances as catalysts is to tether them onto a support medium so that afier use they may be recovered by filtration, washed and reactivated, if necessary, dried and then reused. In this project, (IR,ZS)-(-)-cphedrine was tethered onto a functionalised silica support and tested for its use in asymmetric alkynylation reactions involving a range of aromatic aldehydes and a terminal alkyne, phenylacetylene. The loading of the ephedrine on the supported catalyst was characterised by both elemental analysis and thermogravimetric analysis (TGA) due to the nature of the support material. The immobilised ephedrine catalyst was evaluated in asymmetric alkynylation reactions and was shown to provide good enantioselectivity (up to 92% for (R)-(+)- l ,3-diphenylprop-2-yn-l-ol) and high yields for the secondary propargylic alcohols (up to 97%). The use of the immobilised ephedrine catalyst in asymmetric alkynylation reactions was assumed to be novel. The results of the newly formed secondary propargylic alcohols proved to be comparable to those achieved by homogeneous systems. The secondary propargylic alcohols were analysed using a wide range of spectroscopic techniques such as nuclear magnetic resonance (NMR) spectroscopy, gas chromatography- mass spectrometry (GC-MS), optical rotation and high performance liquid chromatography (HPLC). Due to the restrictions placed on ephedrine, it was important to test the recyclability of the tethered catalyst to reduce the amount of the regulated drug in circulation. The catalyst demonstrated the ability to be recovered quantitatively from the reaction mixture using a simple filtration and then recycled in further asymmetric alkynylation reactions for three cycles before the yield was affected. In addition to the study, a novel tethering of ephedrine derivatives onto a silica support was investigation and its use in asymmetric alkynylation reactions explored. This was undertaken in an effort to optimise and improve upon the results obtained from N-methylcphedrine alone. Our initial results showed that it is possible to tether ephedrine derivatives onto a silica support and then employ them in asymmetric synthesis, thus opening up the possibility to use controlled ephedrine more efficiently.
24
Managa, Muthumuni Elizabeth. « Photophysical properties and photodynamic therapy activities of symmetrical and asymmetrical porphyrins embedded into Pluronic polymer micelles and nonlinear optical properties of an asymmetrical phthalocyanine ». Thesis, Rhodes University, 2019. http://hdl.handle.net/10962/67625.
Texte intégralRésumé :
This work reports on the synthesis of symmetrical and asymmetrical novel porphyrins that have been incorporated into Pluronic polymers, as well as the synthesis of asymmetrical phthalocyanine. The new compounds were characterized by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), mass spectrometry and UV–Visible spectroscopy. The porphyrins that are synthesised were not water soluble but upon incorporating into Pluronic polymer micelles, they became water soluble. The polymer was also modified and linked to folic acid, to enhance selectivity for photodynamic therapy application, where MCF7 breast cancer cells were used. The singlet oxygen quantum yields were lower for the metal free porphyrins as compared to metalled ones due to the heavy atom effect of ClGa, Zn and Cl2Si in the latter which encourages intersystem crossing to the triplet state. Singlet oxygen quantum yields for water soluble derivatives increased upon being encapsulated into the micelles for all. The Stern-Volmer constant (Ksv), binding constant (Kb) and number of binding sites (n) were investigated in order to understand the interaction between the polymer micelles and the porphyrins, and it was showed that the central metals play a role in the manner which the porphyrin interacts with the micelles. The dark toxicity and photodynamic activity of the novel porphyrins upon encapsulating to Pluronic polymer micelles is also reported. There was minimal dark toxicity for all complexes with > 90% cell survival. The photodynamic activity of water insoluble porphyrins improved when encapsulated into the micelles. Novel asymmetrical phthalocyanines were also synthesised for nonlinear optics (NLO) studies in solution and thin films.
25
Booth, Christopher. « Formal venture capital investment into early-stage biotechnology companies : information asymmetries in the screening process / ». [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19785.pdf.
Texte intégral
26
Winters, Stephen James. « Empirical investigations into the perceptual and articulatory origins of cross-linguistic asymmetries in place assimilation ». Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054756426.
Texte intégralRésumé :
Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xx, 351 p.; also includes graphics Includes bibliographical references (leaves 344-351). Available online via OhioLINK's ETD Center
27
Tchakounte, Wakem Seguy. « A Comparison of Methods Taking into Account Asymmetry when Evaluating Differential Expression in Gene Expression Experiments ». Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/28874.
Texte intégralRésumé :
Gene expression technologies allow expression levels to be compared across treatments for thousands of genes simultaneously. Asymmetry in the empirical distribution of the test statistics from the analysis of a gene expression experiment is often observed. Statistical methods exist for identifying differentially expressed (DE) genes while controlling multiple testing error while taking into account the asymmetry of the distribution of the effect sizes. This paper compares three statistical methods (Modified Q-value, Modified SAM, and Asymmetric Local False Discovery Rate) used to identify differentially expressed (DE) genes that take into account such patterns while controlling false discovery rate (FDR). The results of the simulation studies performed suggest that the Modified Q-values outperforms the other methods most of the time and also better controls the FDR.
28
Grounds, Helen. « Investigations into the use of C-H activation for aryl-aryl bond formation : the synthesis of novel chiral ferrocene ligands for asymmetric catalysis ». Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478994.
Texte intégral
29
Aldukhail, A. M. « An investigation into the relationships between strength, flexibility and anthropometric discrepancies, on lower limbs asymmetry in athletes ». Thesis, University of Salford, 2015. http://usir.salford.ac.uk/40900/.
Texte intégralRésumé :
Assessment of bilateral asymmetry (BA) in lower-limbs is crucial in the field of sport rehabilitation as it stands on the physical capabilities of athletes. Clinicians, in their daily practice, aim to objectively standardise their measurements when assessing athletes’ performance or produce norms. Such norms, enable assessors to track athletes’ performance in order to optimise it or on the other hand, to correct their BA as precautionary measure from risk of injury due to improper loading on the musculoskeletal system. Therefore, four main studies were conducted in this thesis to investigate the relationship between key criteria in lower limbs. The first study has sat thresholds for BA and once exceeded the athlete is doomed to be asymmetric. Thresholds were calculated based on the average of absolute asymmetry value percentage (AAV%) in sub-elite athletes [n=139]. An auxiliary study [n=63] was conducted within study one to examine the effect of different loads on the criteria of countermovement jump (CMJ) across jump sets. In study two, threshold norms of elite-athletes were established for four sport-specific groups and, a novel descriptive statistical approach (threshold boundary) was executed to examine the differences between them. In study three [n=144], the relationships between the criteria of CMJ and key criteria in lower limbs were examined based on a novel descriptive statistical approach called agreement in diagnosis of asymmetry. Furthermore, an investigation was conducted also, to examine the effect of manipulating leg length on the force platform profile across different sets of CMJ trials. Lastly, in study four, an investigation was conducted to examine the association between two functional tasks (CMJ and running) by using the asymmetry agreement statistical methodology [n=144]. BA were found throughout all tests and was clinically diagnosed using threshold percentage (Threshold% = mean of AAV% + SD). Moderate to high levels of association were found between criteria. The results from this thesis (0.8-38.1%) indicate that arbitrary percentages of 15% for BA in lower limbs found in literature do not reflect typical thresholds in athletes . Lastly, future studies should be conducted to define how detrimental these asymmetries in term of performance and injury risk. Keywords: biomechanics, asymmetry, imbalance, athletes, lower limbs and threshold.
30
Bedell, Willie B. « CAPITALIZATION OF GREEN SPACE AND WATER QUALITY INTO RESIDENTIAL HOUSING VALUES ». UKnowledge, 2018. https://uknowledge.uky.edu/agecon_etds/63.
Texte intégralRésumé :
This thesis investigates how proximity to parks, historic district designations, and water quality are valued at residential housing prices. The first essay argues that the negative influences of parks and historic districts, if not noticed, could promote negative externalities and unincentivized investments. I find a negative impact on housing values for a close proximity to a park, suggesting disamenities in park features. When the boundary discontinuity and park amenities are considered, I find a positive valuation for a park. Overall, these results imply a mixed influence of parks on homeowners. From the historic district standpoint, I find a positive valuation of the local historic districts over the surrounding neighborhoods. The latter findings indicate that the benefits of locally designated areas outweigh the negative impacts. The second essay researches a probable lead risk in the water supply on the residential market. I argue strongly for the possibility of hidden-type information relative to lead in water supplies. I find that the influence of lead risk in their water supply is not statistically significant. The test for asymmetric information validates the expectation that homes in the relatively high lead-risk neighborhoods might not be informed of the level of lead-risk in their water supply.
31
Spriggs, Amy. « An investigation into the use of fluctating asymmetry as a measure of low level air pollution stress in plants ». Thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/25951.
Texte intégral
32
Garrido, Varas Claudia E. « An investigation into bilateral asymmetry of the appendicular skeleton of the adult human and its use in physical and forensic anthropology ». Thesis, Teesside University, 2013. http://hdl.handle.net/10149/301633.
Texte intégralRésumé :
The aim of this study was to establish whether the asymmetry of bilateral elements of the skeleton is useful for the reassociation of paired elements in the analysis of commingled skeletal remains; particularly addressing the forensic scenario of Chilean Human Rights cases. The asymmetry of the appendicular skeleton of the modern adult Chilean population was investigated in its morphological aspect, using both traditional anthropometry and geometric morphometrics. The sample was selected from the Colección Subactual de Santiago, housed in the University of Chile, Santiago, Chile, with N= 131 (69 males and 62 females). The traditional metric analysis of size and the geometric morphometric analysis of shape showed that there was a significant difference between sides in both sexes with a strong component of directional asymmetry. Mean metrics and ranges of asymmetry were established, contributing to the characterization of this population. A method to pair match elements from commingled settings, which is a combination of metric ranges of asymmetry and principal component analysis of shape variables, was created resulting in 95% accuracy when pair matching the humerus, radius, femur and tibia. This constitutes an important contribution to the analysis of shape in forensic contexts due to its strong mathematical component, objectivity and repeatability.
33
Court, Erin. « How transnational actors change inter-state power asymmetries : the role of the Indian diaspora in Indo-Canadian relations on migration ». Thesis, University of Oxford, 2011. https://ora.ox.ac.uk/objects/uuid:8501d594-e5c1-47e0-9a08-24b7645f29f2.
Texte intégralRésumé :
The overall aim of this thesis is to explore what emigration state power means in relation to the rules that govern international migration. This thesis challenges the conventional view that within a bilateral migration relationship the migrant-sending state is a 'rule-taker' compelled to accept the consequences of the migrant-receiving state's immigration and integration policies. Using India-Canada migration relations as its empirical case, this thesis examines how diaspora populations can serve as a transnational resource for the sending state to mitigate power asymmetries with the receiving state in bilateral migration relations. Part I of this thesis examines the Indo- Canadian diaspora's use of Canadian tribunal, electoral and lobby channels to advance immigration and integration policy outcomes that further both the interests of the diaspora and the Indian state. Part II considers the diffuse and ideational mechanisms through which the Indian state influences the diaspora's political mobilisation abroad. The diaspora's political activities in the host state, combined with the sending state's transnational influence over facets of diaspora identity, interests and organisational capacity, register important effects on Canadian migration policy that bear on the distribution of power between sending and receiving states. These effects cannot be explained on a purely inter-state model of migration relations, but are accounted for by the framework developed and applied in this thesis. The Conclusion addresses the scope conditions under which this thesis' theoretical framework and conclusions derived within it from the single-case study may allow for a wider comparative approach across other cases in future research.
34
Tsakalidou, Maria D. « Block pattern adaptation for Greek female adolescents with scoliosis of the spine : an investigation into the feasibility of incorporating body shape asymmetry into sizing systems to improve garment fit ». Thesis, University of the Arts London, 2016. http://ualresearchonline.arts.ac.uk/9195/.
Texte intégralRésumé :
Scoliosis of the spine is defined as a side-to-side deviation from the normal frontal axis of the body resulting in body asymmetry, and as a complex, three-dimensional and multifaceted deformity, not only affects a female adolescent’s appearance - fit, usability and appearance of clothing - but can also compromise her health and ability to function. Scoliosis affects at least 2.9% of the population in Greece, appearing particularly among children aged 8-14 years, and more frequently in girls (9 girls for 1 boy). This study traces previous initiatives and current provision for clothing people with divergent body figures, exploring issues at the intersection of human anatomy and fashion, while it takes place in Greece, starting with measuring procedures specifically adapted for body asymmetry that comply with the appropriate code of ethics. External body measurements provide non-invasive evaluation of changes in external asymmetry due to scoliosis, while analysis of the measurements related to the trunk can document the asymmetry arising from the different types and degrees of spinal curvature, providing a 3D classification of scoliotic deformities. Both right and left body halves of 75 females aged 16-22 years of age, diagnosed with Adolescent Idiopathic Scoliosis (AIS), are measured in order to register their different body shapes and to classify them in different scoliotic groups, according to the magnitude and type of their scoliosis. The asymmetric basic pattern blocks derived from the median body measurements for each scoliotic group will be more tolerant of bodies with scoliosis, providing a better garment fit than conventional symmetrical patterns. These new ‘blocks’ will have the potential to be used in mass production, after the development of sizing systems based on body asymmetry, whereby an ‘aesthetic’ and an ‘ethical’ dimension in design could be then incorporated. Applying auto-ethnography, as well as using participant observation and interviewing methods, this research will help gain a deeper understanding of the culture and the needs of the specific target group. Future challenges relate to design perspectives of fashionable clothing for females with non-standard body dimensions, with particular emphasis on scoliosis, having potential for wider application in mass customised apparel for scoliosis.
35
Knight, C. W. « An investigation into the influence of asymmetrical rolling on operations and strip shape during the roughing stages of a hot strip mill ». Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637811.
Texte intégralRésumé :
Asymmetrical conditions occurring during the rolling of hot strip can cause strip curvature and can lead to poor product shape, profile, quality and cause reduced productivity. In the most severe of cases, strip with a head-end turning towards the upper work roll, may fail to enter the roll gap on its next pass and result in ‘a cobble’. Finite element techniques have been used to decouple some of the major causes of strip curvature during the roughing stages of Port Talbot hot strip mill. A plane strain elastic-plastic finite element model is developed and applied to predict the direction and severity of strip curvature caused by asymmetrical factors at each pass of the rougher. Asymmetrical factors considered include work roll speed mismatch, temperature differentials across the thickness of the workpiece, pass height and differential frictional differences between upper and lower work-rolls. In addition, further studies utilising the rolling model have identified the influence of rolling parameters on the severity and direction of strip curvature. The rolling parameters include initial strip height, rolling reduction, mean coefficient of friction, mean roll speed and workpiece temperature. Two experimental factorials were designed and performed, using finite element predictions, to identify which asymmetrical factors were most influential to strip curvature and to determine, if any, interactions between asymmetrical factors and rolling parameters. Furthermore, trials were carried out on the reversing rougher of Corus Port Talbot hot strip mill to investigate the effectiveness of roll speed mismatch as a means of controlling strip curvature.
36
Collier, Christopher Thomas. « Experimental and computational investigation into light scattering by atmospheric ice crystals ». Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/16359.
Texte intégralRésumé :
An investigation was carried out into light scattering by Gaussian rough ice crystals. Gaussian rough crystal geometries were generated using roughness parameters derived from mineral dust grains, which have been reported to be suitable proxies for rough ice crystals. Light scattering data for these geometries was computed using the discrete dipole approximation (DDA) method. Phase functions, 2D scattering patterns, degree of linear polarisation patterns and asymmetry parameters were computed for smooth, moderately rough and highly rough crystals with a variety of orientations and size parameters. A sodium fluorosilicate ice analogue crystal with three partially roughened prism facets was created using focused ion beam (FIB) milling and 2D scattering patterns were collected from it using the small ice detector (SID) 3 cloud probe. It was found that roughness reduces features in the phase function compared to scattering by smooth hexagonal prisms, particularly when the roughness features were horizontally much larger than the wavelength. However, the most effective roughness model also takes account of horizontal features whose size is closer to that of the wavelength. Horizontal features smaller than the wavelength have very little effect.
37
Tagu, Jérôme. « Le rôle de la dominance oculaire dans la boucle perception-action : une propriété à l'origine d'asymétries perceptives et motrices How eye dominance strength modulates the influence of a distractor on saccade accuracy Isoler les effets de la dominance oculaire et du biais attentionnel sur la précision des saccades Influence de la dominance oculaire sur les sélections oculomotrice et attentionnelle Recentering bias for temporal saccades only : evidence from binocular recordings of eye movements Quantifying eye dominance strength – New insights into the neurophysiological bases of saccadic asymmetries ». Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=1818&f=14763.
Texte intégralRésumé :
L'homme présente plusieurs préférences latérales, utilisant plutôt une main, un pied et un œil donnés. Si l'impact de la latéralité manuelle sur les performances perceptives et motrices a été très étudié, le rôle des autres latéralités est mal connu. Le premier axe de cette thèse avait pour objectif de mieux comprendre la place de la dominance oculaire dans les processus perceptivo-moteurs. L’œil dominant est celui choisi lors de la réalisation d'une tâche monoculaire. La neuroimagerie a montré qu'il était lié au cortex visuel primaire ipsilatéral, et du fait du croisement des voies optiques, à l'hémichamp visuel controlatéral. Dans cette thèse nous avons comparé les performances perceptives et oculomotrices dans les hémichamps controlatéral et ipsilatéral à l’œil dominant. Les participants devaient soit réaliser des saccades oculaires vers la gauche ou vers la droite, soit réaliser une tâche de discrimination visuelle sur une cible présentée à gauche ou à droite, soit réaliser une double-tâche de saccades et discrimination visuelle. Ces études ont montré que la relation entre l’œil dominant et le cortex visuel primaire ipsilatéral permettait un rehaussement perceptif des cibles visuelles de l'hémichamp controlatéral comparées à celles de l'hémichamp ipsilatéral. Ce rehaussement perceptif améliore à la fois les performances de discrimination visuelle et la précision des saccades oculaires dans l'hémichamp controlatéral à l’œil dominant comparé à l'hémichamp ipsilatéral. Nous avons ainsi montré que la dominance oculaire occupait une place importante dans les relations perception-action, engendrant des différences de traitement entre hémichamps visuels. Dans un deuxième axe, nous nous sommes intéressés à la quantification de la dominance oculaire. Contrairement aux questionnaires de latéralité manuelle permettant une mesure en pourcentages, les tests actuels de dominance oculaire ne fournissent qu'une mesure binaire (gauche ou droite). En vue d'attribuer à chaque individu un pourcentage de dominance oculaire, nous avons étudié les asymétries du système saccadique. Les saccades oculaires présentent en effet des pics de vitesse plus élevés vers la tempe (saccades vers la gauche de l’œil gauche et saccades vers la droite de l’œil droit) que vers le nez (saccades vers la droite de l’œil gauche et saccades vers la gauche de l’œil droit). Cette asymétrie semble liée à l'intensité de la dominance oculaire en ne s'exprimant que chez les participants ayant une dominance oculaire faible. En cas d'une forte dominance oculaire, les pics de vitesse sont plus élevés vers l'hémichamp ipsilatéral à l’œil dominant, que la saccade soit nasale ou temporale. Dans la présente thèse, nous avons également testé d'autres asymétries saccadiques avec l'idée que l'étude simultanée de plusieurs asymétries permettrait une quantification graduelle de dominance oculaire. Notamment, les pics de vitesse sont aussi plus élevés pour les saccades centripètes (vers le droit-devant) que centrifuges (vers l'extérieur). Nous avons utilisé une tâche de saccades depuis cinq positions de départ (afin d'analyser des saccades centripètes et centrifuges) et un enregistrement binoculaire (afin d'analyser des saccades temporales et nasales). Les résultats montrent (1) que les deux asymétries saccadiques sont liées, suggérant qu'elles partagent des bases neurophysiologiques communes, (2) que la dominance oculaire influence toutes les asymétries testées et (3) que l'analyse simultanée des deux asymétries permet d'assigner à chaque individu un pourcentage de dominance oculaire. L'absence de dominance oculaire correspondait à la manifestation de toutes les asymétries saccadiques, tandis qu'une dominance oculaire maximale correspondait à l'absence d'asymétries. Ainsi, cette thèse aura précisé les rôles de la dominance oculaire dans la boucle perception-action et permis d'élaborer une mesure graduelle de dominance oculaire, basée sur les performances visuo-motricesHumans present several lateral preferences, using more a given hand, foot and eye than the other one. If handedness has already been shown to influence perceptual and motor performance, the role of other lateral preferences is currently unknown. The first part of this thesis is dedicated to the study of the influence of eye dominance on visuo-motor tasks. The dominant eye, the one used to perform monocular tasks, is linked to the ipsilateral primary visual cortex. As such, it I s also linked to the contralateral hemifield. In this thesis, we thus compared performance in the contralateral and ipsilatereral hemifields relative to the dominant eye. Participants had either to make leftward and rightward saccades, a visual discrimination task, or both simultaneously. These studies have shown that the relationship between the dominant eye and the ipsilateral primary visual cortex induced a greater perceptual enhancement of visual targets presented in the contralateral than ipsilateral hemifield relative to the dominant eye. This perceptual enhancement leaded to both higher discrimination performance and higher saccade accuracy in this hemifield compared to the ipsilateral one. Thereby, we showed that eye dominance was an important property to consider in the perception-action links, leading to asymmetries between hemifields. In a second part of this thesis, we focused on the quantification of eye dominance. Indeed, contrary to handedness questionnaires which provide a percentage-based measure, tests of eye dominance only dissociate between left and right eye dominance. To assign to each participant a percentage of eye dominance, we studied the asymmetries of the saccadic system. Saccadic peak velocity is indeed higher toward the temple (i.e., rightward saccades of the right eye and leftward saccades of the left eye) than toward the nose (i.e., leftward saccades of the right eye and rightward saccades of the right eye). This asymmetry seems linked to the strength of eye dominance, as it is only observed in case of weak eye dominance. People with strong eye dominance show higher saccadic peak velocity toward the hemifield ipsilateral to their dominant eye, irrespective of the temporal or nasal nature of the saccade. In this thesis, we simultaneously tested several saccadic asymmetries, with the idea that it could provide a graduated measure of eye dominance strength. Peak velocities are also higher for centripetal (toward the straight-ahead direction) than centrifugal (away from the straight-ahead direction) saccades. Participants had to make saccades from five different starting position (to elicit centripetal and centrifugal saccades) while the movements of their both eyes were recorded (to analyze temporal and nasal saccades). The results showed (1) that both saccadic asymmetries are linked together, suggesting that they share a common structure in their neurophysiological bases, (2) that eye dominance modulates all the saccadic asymmetries tested, and (3) that the study of several saccadic asymmetries allows quantifying eye dominance strength on a percentage-based continuous model. Observation of huge saccadic asymmetries corresponded to very weak eye dominance, whereas strong eye dominance was associated to no asymmetry. All in all, in this thesis we clarified the roles of eye dominance in the perception-action loop, and we computed a graduated measure of eye dominance strength based on oculomotor performance
38
Than, Trong Emmanuel. « Le rôle de la signalisation Notch3 dans le maintien des cellules souches neurales du télencéphale adulte Neural stem cell quiescence and stemness are molecularly distinct outputs of the Notch3 signaling cascade in the vertebrate adult brain her4-expressing neural stem cells are maintained through population asymmetry and embedded into a hierarchy of progenitors responsible for their life-long expansion Radial Glia and Neural Progenitors in the Adult Zebrafish Central Nervous System ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS541.
Texte intégralRésumé :
Un certain nombre de régions du cerveau des vertébrés, y compris chez l’homme, continuent d’être le siège de l’ajout de nouveaux neurones à l’âge adulte. Ces nouveaux neurones sont produits à partir de cellules spécialisées, appelées cellules souches neurales (CSN). Celles-ci sont capables de s’auto-renouveler et sont principalement trouvées dans un état d’arrêt transitoire du cycle cellulaire que l’on appelle quiescence. A l’heure actuelle, les mécanismes cellulaires et moléculaires permettant aux CSN de trouver un équilibre entre maintien et différentiation, ainsi que les règles générales gouvernant l’évolution de leur population, ne sont que partiellement compris. A l’échelle moléculaire, plusieurs facteurs et voies de signalisation apparaissent déterminants pour l’homéostasie des CSN. Notamment, la voie de signalisation du récepteur Notch s’avère essentielle pour maintenir à la fois l’état de quiescence et le caractère souche des CSN. Il demeure néanmoins inconnu si la signalisation Notch affecte ces deux propriétés de manière indépendante ou non. A l’échelle cellulaire, la plupart des modèles actuels suggèrent que les CSN se divisent rarement et principalement de manière asymétrique. Cette dernière propriété permettrait aux CSN de se perpétuer tout en donnant naissance à des cellules filles déterminées à se différencier en neurones. Le pallium du poisson-zèbre abrite une population particulièrement importante de CSN, que l’on appelle glies radiaires (GR), et qui possèdent les mêmes caractéristiques fondamentales que leurs homologues chez les mammifères. Notre laboratoire avait précédemment démontré que le récepteur Notch3 était nécessaire au maintien de la quiescence des GR. Le travail présenté dans ce manuscrit se décompose en deux études complémentaires dont les objectifs respectifs étaient: (1) d’améliorer notre compréhension du rôle de la voie de signalisation Notch3 dans l’homéostasie des GR et (2) d’étudier les schémas de divisions adoptés par les GR afin de maintenir leur nombre sur une longue durée. Dans la première étude, nous démontrons que le rôle de la signalisation Notch3 s’étend au-delà du simple contrôle de la quiescence des GR en contribuant également au maintien de leur caractère souche par l’intermédiaire de son gène cible hey1. Un point important de cette découverte est que l’action du facteur Hey1 sur le caractère souche des GR apparaît indépendante du rôle de Notch3 dans le maintien de leur quiescence. Dans la seconde étude, nous avons réalisé une analyse clonale du devenir des GR exprimant le gène her4.1. Ceci nous a permis de mettre en évidence que leurs choix entre différentiation, amplification et auto-renouvellement apparaissent stochastiques, mais équilibrés, ce qui leur permet de maintenir leur population dans le temps. De façon très intéressante, nous avons aussi observé que le nombre total de GR du pallium augmente au cours de la vie, ce qui, au regard du comportement homéostatique de la population de GR exprimant her4.1, nous amène à proposer que la zone neurogénique du pallium est organisée selon une hiérarchie dans laquelle une population inconnue de progéniteurs produit continuellement de nouvelles GR, qui ensuite se maintiennent grâce à un équilibre probabiliste entre leurs différents lignagesNew neurons continue to be added into discrete brain regions of most adult vertebrate species, including humans. Adult born neurons arise from precursor cells, called neural stem cells (NSCs), endowed with self-renewal potential and mostly found in a state of reversible cell cycle arrest, named quiescence. Currently, the molecular, cellular and population rules allowing NSC to balance maintenance and differentiation remain incompletely understood. At the single cell level, several factors and signalling pathways were demonstrated to be essential for NSC homeostasis. Among them, the Notch signalling pathway is critically involved in the control of NSC quiescence and stemness. However, whether these two properties represent molecularly distinct or overlapping outputs of the Notch signalling pathway remains unknown. At the cellular level, current models state that NSCs divide rarely and mostly asymmetrically, allowing both self-renewal and the generation of a more committed progeny that ultimately exits the cell cycle and fulfils neuronal differentiation. The adult zebrafish pallium harbours NSCs, called radial glia (RG), which share with their mammalian counterparts the same basic properties. Previously, our laboratory demonstrated that Notch3 was necessary to maintain RG quiescence. Here, in two different and complementary works, we took advantage of the widespread neurogenic ventricular zone (VZ) of the adult zebrafish pallium to (1) explore further the role of Notch3 signalling in RG homeostasis and (2) investigate the division pattern and dynamics allowing the RG population to be maintained on the long run. In the first study, we demonstrate that the role of Notch3 signalling extends beyond the simple maintenance of RG quiescence and that Notch3 also contributes to RG stemness. By overlapping the transcriptomic profiles of both notch3 mutant RG and adult pallial VZ progenitors, we identified different sets of Notch3 target genes potentially responsible for its pleitropic effect in RG. Notably, we show that the Notch3 signalling contribution to RG stemness critically relies on the transcriptional activation of its canonical target gene hey1 and this, independently of Notch3 action on RG quiescence. In the second study, we performed a quantitative analysis of the fates of individual her4.1(Hes5)-expressing RG. We demonstrate that these cells adopt balanced stochastic fates, which allows their population to reach homeostasis. We also report that the overall RG population of the zebrafish pallium continues to grow during adulthood and that this expansion is very likely driven by a yet undefined upstream population of progenitors. As a consequence, we propose that the adult zebrafish is organised into a hierarchy of progenitors dominated by an unknown population that fuels the ongoing production of an intrinsically homeostatic population of RG which, itself, follows neutral drift dynamics
39
Kariyawasam, Bowithanthri Kalani. « Nouvelles métalloenzymes artificielles obtenues par couplage covalent de complexes métalliques dans une protéine naturelle (Xylanase A) et dans des protéines artificielles (αReps) Functionalized Artificial Bidomain Proteins Based on an α‑Solenoid Protein Repeat Scaffold : A New Class of Artificial Diels−Alderases Recent advances in the field of artificial hemoproteins : New efficient eco-compatible biocatalysts for nitrene-, oxene- and carbene-transfer reactions Artificial iron hydrogenase made by covalent grafting of Knölker’s complex into xylanase : Application in asymmetric hydrogenation of an aryl ketone in water A new artificial hemoprotein with inducible peroxidase- and monooxygenase-like activities ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS518.
Texte intégralRésumé :
Dans un contexte de développement durable, les enzymes sont des outils biologiques puissants pour catalyser des réactions avec de très grandes efficacités et spécificités. Inspirée des enzymes et de la catalyse organométallique, l’élaboration de métalloenzymes artificielles émerge depuis plusieurs années comme une stratégie de choix pour fournir aux chimistes de nouveaux biocatalyseurs, en accord avec les principes de la chimie verte. Elles sont construites par l’insertion par interactions supramoléculaires ou couplage covalent, d’un ion ou d’un complexe métallique au sein d’une protéine, qui leur apporte un environnement hydrophobe protecteur et chiral. Lors de cette thèse, plusieurs métalloenzymes artificielles ont été construites par couplage covalent de complexes métalliques dans deux protéines hôtes, qui sont la Xylanase A (Xln) et les protéines artificielles de la famille des Reps. Dans un premier temps, une hydrogénase artificielle a été construite dans le mutant XlnS212C par ancrage covalent d’un complexe de fer appelé complexe de Knölker. L’hydrogénase artificielle obtenue, XlnS212CK, s’est avérée capable de catalyser l’hydrogénation par transfert d’hydrure de la trifluoroacétophénone, TFAC, sans excès énantiomérique. Dans un second temps, quatre Diels-Alderases artificielles ont été construites à partir de la protéine bidomaine (A3_A3’) de la famille des αReps. Les deux meilleures Diels-Alderases, qui ont conduit respectivement au meilleur rendement et la meilleure énantiosélectivité dans la réaction de l’azachalcone sur le cyclopentadiène, ont été élaborées respectivement par fixation covalente de complexe de cuivre de ligands phénanthroline et terpyridine dans un mutant F119C de A3_A3’ : (A3_A3’)F119Phen-Cu(II) et (A3_A3’)F119Terpy-Cu(II). Finalement, une nouvelle hémoprotéine artificielle a été construite par couplage covalent de la méso-tétraphénylporphyrine de manganèse Mn(III)TPP-NHMal dans le mutant (A3_A3’)Y26C. L’hémoprotéine artificielle formée BH MnTPP seule ne montre aucune activité catalytique pour l’oxydation de co-substrats par H2O2. Cependant, de manière inattendue, l’addition d’imidazole et d’une autre protéine αRep, bA3-2, qui se fixe de manière spécifique sur A3_A3 et provoque son ouverture, permet non seulement de déclencher l’activité peroxydase de BH MnTPP, mais également une activité monooxygénase qui catalyse la sulfoxydation du thioanisole par H2O2. Il s’agit du premier exemple décrit à ce jour de métalloenzyme artificielle dont l’activité peut être induite par la fixation d’une protéine partenaireIn a context of sustainable development, enzymes are powerful biological tools to catalyze reactions with very high efficiencies and specificities. Inspired by enzymes and organometallic catalysis, the development of artificial metalloenzymes has emerged for several years as a strategy of choice to provide the chemists with new biocatalysts, in accordance with the principles of green chemistry. They are constructed by the insertion by supramolecular interactions or covalent coupling of an ion or a metal complex within a protein, which provides them with a protective and chiral hydrophobic environment. In this thesis, several artificial metalloenzymes were constructed by covalent coupling of metal complexes into two host proteins, Xylanase A (Xln) and artificial proteins of the Reps family. Initially, an artificial hydrogenase was constructed in the XlnS212C mutant by covalent anchoring of an iron complex known as the Knölker complex. The artificial hydrogenase obtained, XlnS212CK, was found to be capable of catalyzing hydride hydrogenation of trifluoroacetophenone, TFAC, without enantiomeric excess. In a second time, four artificial Diel-Alderases were constructed from the bidomain protein (A3_A3') of the αReps family. The two best Diels-Alderases which led respectively to the best yield and the best enantioselectivity in the reaction of azachalcone on cyclopentadiene were developed respectively by covalent attachment of copper complex of phenanthroline and terpyridine ligands in a mutant F119C of A3_A3' (A3_A3')F119Phen-Cu (II) and (A3_A3')F119 Terpy-Cu (II). Finally, a new artificial hemoprotein was constructed by covalent coupling of the manganese meso-tetraphenylporphyrin Mn(III)TPP-NHMal in the (A3_A3')Y26C mutant. The artificial hemoprotein formed BH-MnTPP alone shows no catalytic activity for the oxidation of co-substrates by H2O2. However, unexpectedly, the addition of imidazole and another αRep protein, bA3-2, which binds specifically to A3_A3’ and causes it to be opened, not only triggers the BH-MnTPP peroxidase activity but also a monooxygenase activity which catalyzes the sulfoxidation of thioanisole by H2O2. This is the first example described to date of artificial metalloenzyme whose activity can be induced by the attachment of a partner protein
40
Huang, MingGang, et 黃銘鋼. « A study on anions intercalation into carbons for asymmetric supercapacitors ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/14150214930583139006.
Texte intégralRésumé :
碩士國立清華大學
化學工程學系
103
Abstract The thesis aims at studying the electrochemical behavior of anion intercalation into carbon materials and designing the asymmetric supercapacitors based on this energy storage mechanism. The first part introduces using carbon paper (GDL25BC), which is a gas diffusion layer in fuel cell, as an electrode for studying the electrochemical behavior of the anion intercalation. A three-electrode test system with electrolytes system was established and comparaed the electrochemical reaction on the carbon paper positive electrode with results of material analysis in this section. In conclusion: 1. Anion intercalation type carbon paper (GDL25BC) is a high specific capacity and good rate-performance electrode; 2.Carbon paper (GDL25BC) by the rolling process, can be made to flexible electrode. 3. It has a high rate performance and good cycling stability. The second part demonstrates comparing the electrochemical behavior of anion intercalation into commercial graphitic carbons. In summary: 1. Anion intercalation need occur at graphitic carbon materials with a high crystallinity degree, so that the soft carbon is not allowed; 2 Particle size affects on the electrode through charge transfer impedance (Rct) and Warburg diffusion impedance, a large particle size material greatly restricts its rate performance. 3. Mesosphere carbon microbeads (MCMB) has a high crystallinity degree, but also amorphous carbon peak. These amorphous carbon promote electrolyte diffusion transfer in the electrode, so that the electrode performance ratio has been greatly improved. In the third part, worms-like type expanded graphite was selected as new cathode based on the above conclusions. Modify expanded graphite by heat treatment, ultrasonic vibration, pitch carbon coated and phenolic resin coated. Get the best performance sample EG-600Up (expanded graphite treated treatment at 600 ℃, ultrasonic oscillation 4h, 75% pitch coated), it has a high rate capability (3A / g) and discharge stability (500cycle, retention 95.7%). Assembled asymmetric supercapcitors (AC /EG-600Up) which activated carbons as a negative electrode, EG-600Up as a positive electrode, measured in TEABF4 solving in propylene carbonate (PC). It has a good performance on energy density and power density: 51.47Wh / kg, 10.12kW / kg.
41
Enquist, John Andrew. « Total Synthesis of Cyanthiwigin Natural Products via Double Asymmetric Catalytic Alkylation and Investigations into the Nature of Double Asymmetric Processes ». Thesis, 2011. https://thesis.library.caltech.edu/6133/5/%284%29_Appendix_1.pdf.
Texte intégralRésumé :
Since the initial isolation of the cyathane molecules in 1970, considerable synthetic interest has been invested into the preparation of these diterpenoid natural products. Owing to the biological activity and intriguing molecular architecture of these compounds, the members of the cyathane family of natural products have emerged as appealing targets for total synthesis. After a brief summary of the isolation and bioactivity properties of these diterpene compounds, previous synthetic efforts toward these molecules are reviewed.
A concise and versatile approach toward the preparation of the cyanthiwigin family of cyathane natural products is described. By leveraging a unique double asymmetric catalytic alkylation procedure it is possible to quickly establish two of the most critical stereocenters of the cyanthiwigin framework with high levels of selectivity and expediency. The synthesis additionally employs a tandem ring-opening and cross-metathesis reaction, and an aldehyde-olefin radical cyclization process, to rapidly arrive at the tricyclic cyathane core of the cyanthiwigin molecules. From this unifying intermediate, the preparation of cyanthiwigins B, F, and G are attained swiftly and without the need for protecting groups.
The nature of double asymmetric transformations is investigated from a historical, mathematical, and experimental perspective. The initial findings of Langenbeck and Horeau concerning the enantioenriching effects of scalemic duplication are described, with a specific focus on the impact of this phenomenon on total synthesis. A thorough mathematical examination, based on the work of Kagan, is then presented for situations involving double asymmetric transformations of prochiral starting materials. Expressions relating the final quantities of the stereoisomeric products to the intermediary selectivity of each stereoselective process are presented based on these formulae.
Finally, experiments designed to probe the selectivity of each stage of stereoselective bond construction in a double asymmetric process are presented. The compiled results are scrutinized in keeping with the previously derived equations, and these findings are analyzed to understand the nature of the double asymmetric processes in question.
42
Ralph, Mark S. « Investigations into the asymmetric synthesis and biological activities of some bisbenzyltetrahydroisoquinoline alkaloids / ». 2001.
Trouver le texte intégral
43
Andrews, Kurt Arthur. « Orifice coefficients for an asymmetrical flow into a slot ». Thesis, 1989. https://thesis.library.caltech.edu/6061/1/Andrews_ka_1989.pdf.
Texte intégralRésumé :
The purpose of this investigation is to determine what percentage, if any, of a freestream velocity head is recovered by the flow through a slot. In this experiment, fluid is drawn through a slot placed perpendicular to a passing flow. This project addresses orifice coefficients, a classic subject, which has been thoroughly investigated. However, unlike most of the previous experiments measuring orifice or resistance coefficients, the flow approaching the orifice, or slot in this case, is not symmetrical. Mainstream flow rate and orifice flows are explored systematically over a fairly wide range. The primary motivation is to gain a better understanding of the fluid dynamics associated with small orifices in the presence of a passing flow.
44
Prajapati, Sanjay. « A Novel Approach to Ambulatory Monitoring : An Investigation into Everyday Walking Activity in Patients With Sub-acute Stroke ». Thesis, 2010. http://hdl.handle.net/1807/24622.
Texte intégralRésumé :
Walking is an essential task important to recovery after stroke. However, there is a limited understanding regarding the characteristics of walking in in-patients with stroke. The objectives of this thesis were to: 1) develop an instrument capable of acquiring temporal characteristics of everyday walking; 2) investigate the quantity and control of everyday walking; and 3) profile the task-specific link between walking and cardiorespiratory response. In study 1 we developed and
validated a wireless monitoring system (ABLE system). Study 2 revealed low quantities of
everyday walking (4816 steps; SD 3247) characterized by short bout durations (59.8s; SD 23.4) and asymmetric walking. In study 3 we observed a modest task-related response in HR(19.4% HRR); however, the intensity and duration of everyday walking did not approach the guidelines for aerobic benefit. Monitoring in-patient walking can help guide clinical decision making in developing methods to maximize recovery after stroke.
45
Petersen, Charlotte Frances. « An Investigation Into the Significance of Dissipation in Statistical Mechanics ». Phd thesis, 2016. http://hdl.handle.net/1885/110514.
Texte intégralRésumé :
The dissipation function is a key quantity in nonequilibrium
statistical mechanics. It was originally derived for use in the
Evans-Searles Fluctuation Theorem, which quantitatively describes
thermal fluctuations in nonequilibrium systems. It is now the
subject of a number of other exact results, including the
Dissipation Theorem, describing the evolution of a system in
time, and the Relaxation Theorem, proving the ubiquitous
phenomena of relaxation to equilibrium. The aim of this work is
to study the significance of the dissipation function, and
examine a number of exact results for which it is the argument.
First, we investigate a simple system relaxing towards
equilibrium, and use this as a medium to investigate the role of
the dissipation function in relaxation. The initial system has a
non-uniform density distribution. We demonstrate some of the
existing significant exact results in nonequilibrium statistical
mechanics. By modifying the initial conditions of our system we
are able to observe both monotonic and non-monotonic relaxation
towards equilibrium.
A direct result of the Evans-Searles Fluctuation Theorem is the
Nonequilibrium Partition Identity (NPI), an ensemble average
involving the dissipation function. While the derivation is
straightforward, calculation of this quantity is anything but.
The statistics of the average are difficult to work with because
its value is extremely dependent on rare events. It is often
observed to converge with high accuracy to a value less than
expected. We investigate the mechanism for this asymmetric bias
and provide alternatives to calculating the full ensemble average
that display better statistics. While the NPI is derived exactly
for transient systems it is expected that it will hold in steady
state systems as well. We show that this is not true, regardless
of the statistics of the calculation.
A new exact result involving the dissipation function, the
Instantaneous Fluctuation Theorem, is derived and demonstrated
computationally. This new theorem has the same form as previous
fluctuation theorems, but provides information about the
instantaneous value of phase functions, rather than path
integrals. We extend this work by deriving an approximate form of
the theorem for steady state systems, and examine the validity of
the assumptions used.
46
Shih, You-Cheng, et 石祐承. « The novel triptycene-incorporated N-heterocyclic carbenes catalyzed Suzuki-Miyaura coupling reaction and application of chiral triptycene-incorporated gold complexes into the use of asymmetric 1,6-enyne cycloisomerization ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/6rr8y5.
Texte intégralRésumé :
碩士國立東華大學
化學系
100
Palladium homogeneous catalysis is known as a versatile tool for carbon–carbon bond formation in organic synthesis. The Suzuki–Miyaura coupling reaction of aryl halides with arylboronic acids is one of the most important palladium-catalyzed cross-coupling reactions. We use the 2,6-bis(bromomethyl)pyridine and the imidazole corporated with triptycene to make a CNC pincer, then being a ligand to catalyze the Suzuki coupling reaction with the palladium. We found the ligand 1-di is an active catalytic ligand which can giving the good results to react with aryl halides and heterocyclic halides then catalyzed the Suzuki reaction with phenylboranic acid. Under different conditions, the ideal yield could up to 99%. We also functionalized the imidazole salt that incorporate with triptycene, a chiral functional group. Then we catalyzed cycloisomerization of nitrogen-bridged 1,6-enynes proceeded in the presence of a cationic gold complex coordinated with a chiral triptycene incorporated NHCs ligand (S,S)-1-Au-im to give 52% yield of chiral 3-azabicyclo[4.1.0]heptenes with racemic mixture.
47
Salvati, Emmanuele. « Rare Decays in BaBar : Search for Decays of the Neutral B Meson into Two Leptons and Measurement of CP Asymmetry in Inclusive Radiative Decays of the B Meson into a Strange-quark System ». 2010. https://scholarworks.umass.edu/open_access_dissertations/201.
Texte intégral
48
Schenk, Paul Robert. « A measurement of the partial width of the Z⁰ boson into b quarks and the forward-backward asymmetry in the reaction e⁺e⁻ -> ; Z⁰ -> ; bb, using inclusive electrons ». Thesis, 1992. https://dspace.library.uvic.ca//handle/1828/9595.
Texte intégralRésumé :
The process e+e- → Z0 → bb is studied using prompt electrons. The partial width of the Z0 boson into bb pairs is found to be 400 ± 35 ± 57 ± 3 MeV, and the forward-backward asymmetry in the reaction e+e- → Z0 → bb is found to be 0.101 ± 0.029 ± 0.011 ± 0.006.Graduate
49
Choenyana, Kgapyane Samuel. « An investigation into the influence of credit ratings on credit risk of the South African banking industry ». Diss., 2020. http://hdl.handle.net/10500/26735.
Texte intégralRésumé :
The financial stability of banks is crucial if they are to fulfil their role in facilitating transactions between borrowers and lenders. The purpose of this study was to investigate the effect of credit risk on the South African banking industry following a movement in credit ratings by rating agencies. Data from a sample of 11 banks were collected from 2006 to 2015. Econometric regression analysis was used to analyse the data. The results show that inflation, credit ratings, exchange rate, gross domestic product, unemployment rate, capital adequacy ratio and size of the bank are significant factors that determine "non-performing loans". Therefore, it is imperative that banks continuously monitor these factors and adapt their credit policies on "non-performing loans". This action would prepare banks for any adverse effects and ensure that the banking industry remains a sound and efficient contributor to the growth of the South African economy.Business Management
M. Com. (Business Management)