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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Synthesis, physico-chemical properties and analytical applications of calixpyrrole and calixarenes

Alharthi, Salman S. January 2015 (has links)
This thesis consists of three parts. The first part provides an introduction to the calix[4]pyrroles and calix[4]arenes chemistry and their applications as ion selective electrodes for the determination of the mercury(II) ion in aqueous solution and as extracting agents for the removal of pollutants from water. The second part describes the experimental works carried out in the laboratory. The third part presents results, and discussion as follows: i. The compounds 5, 11, 17, 23-p-tetra-tert-butyl 25, 27 dihydroxy 26, 28-bis(2-ethoxymethoxy) calix[4]arene (L1), 5,11,17,23-tetra-tert-butyl 25,27-bis(diethylamino)ethoxy 26,28-(bis methoxyethoxy) calix[4]arene (L2) and mesotetramethyltetrakis-[(N,N-diethylacetamide)phenoxymethyl] calix[4]-pyrrole (CPA) dimer were successfully synthesised and characterised using different techniques. ii. The interaction of the receptors meso-tetramethyl-tetrakis-(4-hydroxyphenyl) calix[4]-pyrrole, (CPII), and mesotetramethyltetrakis-[(N,Ndiethylacetamide)phenoxymethyl] calix[4]-pyrrole (CPA), (previously synthesised) as well as L1 and L2 ligands with different metal cations in CD3CN at 298 K was investigated using the 1H NMR technique. It is concluded that CPA and L2 ligands interact with Li+, Na+, Ca2+, Sr2+, Ba2+, Cd2+, Zn2+, Pb2+ and Hg2+ cations whereas CP(II) and L1 ligands do not interact with cations tested. iii. Conductance and thermodynamic studies of complexing of CPA and L2 with metal cations in acetonitrile at 298.15 K were investigated with the Nano Isothermal Titration Calorimeter. iv. Complexation studies proved by 1H NMR, conductance and ITC techniques of CPA and metal cations in acetonitrile were compared to those previously reported in the Thermochemistry Laboratory. v. The ability of the CPA dimer for the removal of Hg2+, Pb2+, Zn2+, Cu2+ and Cd2+ ions from an aqueous solution was proved under different experimental conditions. vi. The preparation and characterization of Hg2+ ion selective membranes using different components based on CPA and L2 ionophores are described. Also, the influence of a number of experimental parameters and interferences on the response of the electrodes as well as analytical applications of these ISEs were studied.

New CVD methods for energy efficient glazing

Warwick, M. E. A. January 2014 (has links)
This work studies the use of the novel electric field assisted chemical vapour deposition (EACVD) process in the production of thermochromic thin films of vanadium dioxide on glass substrates. The investigation studies the effects an applied electric field has on both aerosol assisted chemical vapour deposition (AACVD) and atmospheric pressure chemical vapour deposition (APCVD) reactions of vanadyl acetylacetonate. The electric field was generated by applying a potential difference between two transparent conducting oxide coated glass substrates. The electric field was varied between 0 – 3000 Vm-1. The deposited films were analysed and characterized using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, atomic force microscopy and contact angle measurements. It was found that applying an electric field led to large changes in film microstructure, preferential orientation and changes in the film growth rate. This led to significant changes in materials properties such as increased surface roughness and enhanced wetting behaviour. Electric field assisted chemical vapour deposition shows great promise as a method for nano-structuring and tailoring the properties of metal oxide thin films. Further to the work carried out depositing thermochromic materials a computation building study is carried out to assess the energy saving potential of thermochromic thin films in as intelligent glazing. The building simulation is used to examine the effect of the thermochromic transition, hysteresis width and hysteresis gradient on the energy demand characteristics of a model system in a variety of climates. The results are also compared against current industry standard glazing products. The results suggest that ideal thermochromic systems can give potential savings between 20 – 50 % depending on the specific climate. The building model is also used to asses the energy saving potential of VO2 thin films prepared by electric field assisted atmospheric pressure chemical vapour deposition.

Kinetic studies of the atmospherically implicated halogen oxide radical and peroxy radical cross-reactions

Ward, M. K. M. January 2014 (has links)
The occurrence of halogen oxide radicals, XO (X = Cl, Br, I), which are formed by the reaction of photolytically released halogen atoms with ozone, has a profound impact on atmospheric chemistry. XO radicals not only react with themselves but they are also believed to react in the atmosphere with other key radical species. In particular, XO can react with peroxy radicals, RO2, which are key members of the so called “odd hydrogen” radical family, HOx. Detailed laboratory studies of the kinetics of reactions of the type XO + RO2 → Products are therefore important in assessing their atmospheric importance and understanding the atmospheric implications of such chemistry. The kinetics of several XO + RO2 (X = Cl or Br and R = H or CH3) reactions have been studied as a function of temperature (T = 210 – 314 K) at p = 760 ± 20 Torr, using the laser flash photolysis technique coupled with UV absorption spectroscopy employing a charge coupled device (CCD) detection system for radical monitoring. Application of CCD detection facilitated the real time monitoring of the XO radical species concentration in each reaction studied. This was afforded by the rapid acquisition of broadband sequential spectra by the CCD where transmitted light intensities were converted into absorbances by Beer’s law. Exploiting the vibronic structure characteristic to XO radicals via ‘differential’ spectroscopy, unequivocal monitoring of XO was afforded by converting the resultant differential absorbances into concentrations using the Beer-Lambert law. The obtained temporal XO concentration profiles were then analysed using detailed numerical models. Strict control of successive experimental conditions and constraints in each fitting model used allowed the initial concentrations of RO2 to be inferred and their temporal behaviour simulated alongside the measured temporal XO profiles to obtain kinetic information on each reaction investigated.

The asymmetric synthesis of oxo-piperidines and oxo-pyrrolidines

Yau, K. C. January 2014 (has links)
Chapter 1 describes the attempts to synthesize piperidin-2-ones via an aza-Michael-Michael annulation, which were unsuccessful. A general route for the synthesis of piperidin-2,4-diones from β-keto esters via a Dieckmann cyclisation was proposed and five piperidin-2,4-diones with different substituents at positions-5 and -6 were prepared. An asymmetric route to 1-unsubstituted piperidin-2,4-diones was also developed which involved the use of Davies' chiral auxiliary to induce an asymmetric Michael addition. Chapter 2 describes a new approach to the synthesis of codeine. The piperidin-4-one ring was prepared by a Dieckmann cyclisation; a Robinson annulation was performed to construct the cyclohexenone ring and the key bicyclic intermediate was made. However, attempts to prepare the corresponding benzomorphan via a Grewe cyclisation of the α,β-unsaturated ketone were not successful. Synthesis of various 2,3-disubstituted piperidin-4-ones using the same strategy as the codeine synthesis was attempted; six different piperidin-4-ones with alkyl and aryl substituents at the 2-position were prepared. Chapter 3 describes the attempts to synthesize 1,2-dihydropyrrol-3-ones employing the same strategy used to make piperidin-4-ones in Chapter 2. Seven different diester intermediates were successfully prepared but attempts for Dieckman cyclisation failed. The focus was changed to prepare 5-substituted pyrrolidin-3-ones by the protocol used to make piperidin-2,4-diones in chapter 1 and four pyrrolidin-3-ones were made. Enantioselective syntheses using the Davies' chiral auxiliary were attempted and enantiopure 5-methylpyrrolidin-3-one was prepared.

Continuous hydrothermal flow synthesis of lithium ion battery materials

Wu, O. Y. January 2014 (has links)
There are a number of ways to improve the capacity of rechargeable batteries as suggested in the literature; carbon coating and reducing the particle size of the active material appear to be the most effective. In this work, the synthesis of pure phase LiFePO₄ nanoparticles was carried out directly in one step using the continuous hydrothermal flow synthesis (CHFS) system. Conventional synthesis methods require many steps and longer duration to obtain this cathode material. Microscopic data confirmed that the particles were successfully covered with an even carbon coating in situ where fructose was used. Through the use of the CHFS pilot plant, larger batches of the samples were made to allow thorough characterisation and electrochemical analysis. Coin cells were assembled from electrode sheets with the samples synthesised as the active material. The data collected from carbon coated LiFePO₄ cells showed good performance in terms of high C rate cycling and the specific capacity the cells provided. The results were comparable to those seen in the literature and amongst the highest of LiFePO₄ produced from a CHFS method. The doping of LiFePO₄ with manganese was successful as confirmed by various analysis techniques but it did not appear to have improved the electrochemical operation of LiFePO₄. However, upon certain doping levels the energy density of the material was approaching the theoretical value. The CHFS system was also used in an attempt to synthesise cathode materials optimised for electrochemical performance. For example, reaction conditions were tailored to produce samples with reduced particle sizes and samples intimately mixed with conductive carbon in situ. Further work will be to optimise the material ratio for electrodes and increase the amount of active material to be used. Also, to investigate fully how the morphology and thickness of an electrode can affect the performance of the cell.

The role of πσ* states in the ultrafast non-radiative dynamics of pyrrole, aniline and phenol

Kirkby, O. M. January 2015 (has links)
This thesis comprises three time-resolved photoelectron imaging (TRPEI) studies, examining the ultraviolet (UV) photorelaxation dynamics of molecules with low-lying πσ* states. Chapter 1 introduces important principles in molecular photochemistry, wavepacket dynamics and the relaxation mechanisms enabled by these πσ* states. Chapter 2 describes the experimental apparatus and data analysis techniques used to extract information from raw TRPEI spectra. Chapters 3-5 contain the experimental data. Chapter 3 examines the UV relaxation dynamics of pyrrole, where the lowest excited singlet state is of πσ* character. We observe a single sub-50 fs, dissociative decay for all wavelengths studied, in keeping with the literature. The pyrrole dimer is used as a model for microsolvation, where a new decay pathway opens, relating to relaxation into stabilised charge transfer states. Chapter 4 details the experimental study of aniline. Direct excitation to the S2 with various excess vibrational energies, shows that the S2/S1 conical intersection is located close to the S2(πσ*) origin and enables the dominant S2 → S1 internal conversion mechanism. Population on the S1(ππ*) surface (following relaxation or direct excitation) undergoes considerably slower internal conversion to the ground state, the invariance of this decay in deuterated aniline suggests that any S1 → S2 tunnelling is not favoured. Chapter 5 studies the UV photodynamics of phenol, finding that internal conversion to the ground state is the dominant relaxation mechanism in the S1(ππ*) state, in agreement with the literature. Increasing the excitation energy to access to the S2(πσ*) state opens a minority pathway to O-H dissociation, but IVR on the S1 surface followed by internal conversion continues to dominate. Finally, Chapter 6 summarises the surprising variety in the mechanisms that πσ* states facilitate, even in these closely related molecules, and provides an outlook for future work.

Future-proofing buildings : a novel approach to measure the performance of building structures

Xuereb, K. January 2015 (has links)
This research is a fundamental step towards intelligent building structures with load sensing characteristics. It is argued, with evidence from industry leaders, that these will become ubiquitous. It draws inspiration from developments in structural health monitoring of infrastructure projects. It addresses the current gap between the intellectual effort spent by design teams to conceive building structures that satisfy client brief and informational lacunae on the performance of the building structures. This gap restricts opportunities to adapt buildings in future investment cycles. The research poses a challenge: ‘can a novel system be implemented in a building structure to allow real-time monitoring of the performance of key structural elements?’ effectively moving towards intelligent, adaptable buildings. Infrastructure projects which had structural health monitoring systems implemented to monitor and mitigate damage are reviewed. These served as analogues on how to harness data acquired by sensors, transfer them to the building management system and inform decision making. The hypothesis that there is a need to incorporate smart sensors in building structures was put to the test in interviews with thirty business leaders in the construction industry. These interviews identified key attributes that needed to be satisfied by the sensors. Novel stress sensors based on nanocomposite polymer films were explored and tested in laboratory-based experiments both under short-term and long-term loading. The sensitivity of the sensors to a change in load was assessed. Scanning electron microscopy and Raman spectroscopy were carried out to assess the characteristics of the sensors. A novel stress sensor, based on a carbon nanotube/polycarboxylate polymer film sandwiched between cement grout layers, was found to be the most sensitive to change in electrical resistance measured when the imposed load was changed. A gauge factor two orders of magnitude greater than the highest factor reported to date on research on stress sensors was determined. This research prepares the ground and maps out the strategic and tactical challenges that are needed to arrive at operational, long timescale, load sensing for buildings.

Investigating catalytic activity at oxide surfaces using a QM/MM methodology

Downing, C. A. January 2015 (has links)
A set of complementary studies has been undertaken to investigate the interaction of CO2 with metal oxide surfaces. Beginning with the simple and well-studied magnesium oxide surface, work progressed to include a manganese dopant near the MgO active site before shifting to manganese oxide. All work made use of the Quantum Mechanical/Molecular Mechanical (QM/MM) methodology implemented within the ChemShell code, which combines information from an electronic structure calculation on atoms in the vicinity of the adsorption site with relaxation effects from a large component of the surrounding catalyst system. Initial findings showed that CO2 interacts favourably with the MgO (100) terrace, and that the presence of trapped electrons at surface oxygen vacancies opens up the possibility for catalytic chemical processes to occur. Particular attention was paid to the CO2 radical anion species formed when the adsorbate binds to a vacancy containing a single electron, and the addition of hydrogen to the surface-adsorbate complex allowed for a number of catalytic cycles to be identi- fied. Manganese doping was used to investigate the effect of a transition metal on the interaction between the adsorbate and the vacancy, before moving on to the transition metal oxide where more complex effects such as lattice distortion and antiferromagnetic ordering were included in the model. Finally, work was performed on the related system Li-doped MgO in order to investigate an open question regarding the activation barrier for methyl radical formation as part of the oxidative coupling of methane reaction.

Synthesis of truncated analogues of ProTx-II as a novel form of pain relief

Wright, Z. V. F. January 2015 (has links)
Chronic pain affects almost 10 million people in the UK but despite this, few effective treatments exist. Research has shown that targeting the Nav1.7 ion channel provides a novel approach to treatment. ProTx-II, a 30 amino acid peptide isolated from Tarantula venom, is highly selective for the channel (IC50 value - 0.3nm in vitro) but in vivo results were less promising. ProTx-II contains three interlocking disulfide bonds connected in a distinctive pattern. To investigate the structure-activity relationship between the peptide and the ion channel, truncated analogues based on the individual cysteine rings were synthesised. This thesis investigates the effect of replacing the disulfide bond with a thioether linkage through the incorporation of a novel diastereoisomer of the non-natural amino acid lanthionine to produce hydrolytically stable compounds. Lanthionine can be thought of as two alanine residues connected by a thioether linkage at the β-carbon. Improvements in the synthesis allowed for the first large scale production of lanthionine enabling multiple attempts at peptide synthesis to be carried out. Work was also begun on the synthesis of cystathionine, a second thioether linker containing an extra CH2 group between the amino acid centres. Novel methodologies were investigated for the incorporation of a new diastereomer of lanthionine containing two L-amino acid centres using a new microwave-based methodology. This methodology has so far produced the largest known synthetic rings containing a lanthionine bridge, along with the first interlocking disulfide and thioether bridged compounds. The analogues produced were modelled using in silico mutagenesis techniques and the effect of these analogues on the hNav1.7 receptor was investigated using an automated patch clamp assay. Finally, analysis of the connectivity of ProTx-II was carried out using a combination of digestion and MS/MS experiments.

Appeals from utilities regulators in the US and the UK : what are the limits of judicial review of economic evidence?

Mantzari, D. January 2014 (has links)
The thesis examines the transformation of judicial review in the context of appeals from utilities regulators in the US and the UK, following the regulators’ greater recourse to expert economic evidence and analysis. It describes what is happening and also prescribes what should be happening in judicial review of economic evidence. It shows that the recourse to economic evidence has by and large transformed the scope, process and intensity of review of regulatory decisions in both jurisdictions. The by-product of this transformation is the gradual rise of a complementary relationship between the judge and the regulatory agency in the realm of utilities regulation. Rather than a state of institutional conflict between the two actors in the realms of law and policy (US) or a state of blanket deference (UK), one can observe a measure of judicial restraint predicated upon considerations of relative institutional competence. The normative claim of the thesis is that questions related to the appropriate scope of review of regulatory decisions or to the optimal institutional response to the pervasiveness of economic evidence should not be inattentive to the limits of judicial review of economic evidence. Following the examination of judicial scrutiny of economic evidence in generalist courts (US federal courts, the UK High Court) and specialist courts (UK Competition Appeal Tribunal), the study shows that those limits do not simply derive from the incapacity of the judge to deal with the appraisal of economic evidence but are owing to a host of micro-level (i.e. standard of review, and status of the reviewing court/tribunal) and macro-level institutional factors (i.e. the institutional design of the regulatory regime). The thesis concludes that any expectations that judicial review can ensure the soundness of the regulatory agencies’ decisions need to become aligned with those institutional factors as well as with the institutional capacity of judicial review to satisfy those expectations.

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