The research presented in this dissertation involves the synthesis, characterization, and application of novel anionic and cationic chiral molecular micelles in capillary electrophoresis (CE) for the separation of diverse chiral compounds. Chapter 1 presents brief overview of the surfactants, micelle polymer, CE and micellar electrokinetic chromatography (MEKC). Chapter 2 describes the simultaneous enantioseparation of eight single chiral center â-blockers using two novel leucine and isoleucine based polymeric surfactants. The simultaneous enantioseparation of multichiral center bearing â-blockers, nadolol and labetalol is described in chapter 3. A synergistic approach, using a combination of polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) and sulfated â-CD showed dramatic enantioseparation of four stereoisomers of nadolol. On the other hand for labetalol, enantiomeric separation remains unaffected using the dual chiral selector system. Chapter 4 deals with the enantiomeric separation of the binaphthyl derivatives that was found to be influenced by pH, type and concentration of the background electrolyte as well as concentration of the polymeric surfactant. In chapter 5, characterization of five alkenoxy leucine-based surfactants with variations in chain length (C8-C11), polymerization concentration and degree of polymerization showed significant effects on the chiral resolution and efficiency of hydrophobic â-blockers. The synthesis and characterization of two positively charged amino acid derived chiral ionic liquids (ILs) and their corresponding polymers is presented in chapter 6. Chiral separation of two acidic analyte (difficult to resolve with anionic micelles) can be achieved with both monomers and polymers of ILs. In chapter 7, the synthesis and detailed characterization of three pH independent amino acids derived (L-leucinol, L-isoleucinol and L-valinol) sulfated chiral polymeric surfactants is presented. These chiral sulfated surfactants are thoroughly characterized and the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy. The work clearly demonstrates for the first time the superiority of chiral separation in MEKC coupled to mass spectrometry at low pH. Finally, in chapter 8, six amino acid derived chiral surfactants with carboxylate and sulfate head groups were compared for enantioseparation of broad range of structurally diverse racemic compounds at neutral and basic pH conditions.

Interactions of simvastatin with zwitterionic dipalmitoyl phosphotidylcholine (DPPC) multilamellar liposomes were investigated as a function of temperature and simvastatin concentration. And acyl chain length effect on the simvastatin-model membrane interactions was monitored with DPPC and dimyristoyl phosphotidylcholine (DMPC) lipids. All studies were carried out by two non-invasive techniques, namely Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The results showed that as simvastatin concentration increased, the main phase transition temperature decreased, the main phase transition curve broadened, and the characteristic pretransition was disappeared for both DMPC and DPPC model membranes. All concentrations of simvastatin disordered and decreased the fluidity of phospholipid membranes. Analysis of C=O stretching band showed that simvastatin either strengthen the existing hydrogen bonds of the glycerol skeleton closer to the head groups or caused the formation of new hydrogen bonds. A dehydration effect caused by simvastatin around the PO2- functional groups in the polar part of the lipids was monitored. This dehydration effect in the gel phase was more profound than in the liquid crystalline phase for 1, 6, and 12 mol% of simvastatin concentrations. DSC peaks broadened and shifted to lower temperature values by increasing the simvastatin concentration. For both lipids, simvastatin-induced lateral phase separation was observed in the DSC thermograms. Any change caused by the acyl chain length difference of DMPC and DPPC lipids was not observed on the simvastatin-membrane interactions. Also, for both of the lipids similar trends were observed in the FTIR and DSC results. More profound effects of simvastatin on the less stable DMPC membranes were observed.

Freshwater ecosystems are some of the most threatened on the planet. Efforts to conserve, restore, or otherwise manage large rivers and the services they provide are hindered by limited understanding of the functional dynamics of these systems. This shortcoming is especially evident with regard to trophic structure and energy flow. In this study I use natural abundances of carbon and nitrogen isotopes to examine patterns of energy flow and food-chain length of large-river food webs characterized by different landscape-scale hydrologic features. Ten locations along an approximately 500 km stretch of the Upper Paraná River Basin, Brazil, provided the setting for this work. Carbon derived from C3 plants and phytoplankton were the dominant energy sources across all webs, but relative contributions differed among landscape types (low-gradient river, high-gradient river, river stretches downstream of reservoirs, and reservoirs). Increases in food chain length corresponded with higher relative importance of phytoplankton derived carbon, likely due to size-structured effects of the phytoplankton-zooplankton-secondary consumer trophic link. River impoundment corresponded with decreased ecological and economic efficiency of fisheries production, an important ecosystem service provided by many tropical rivers.

<p>This thesis addresses the mechanisms involved in cellulosedegradation in general and Totally Chlorine Free (TCF) bleachingof pulp in particular. The thesis shows that the cellulosedegradation during high consistency ozone bleaching is explainedby free radical chain reactions.</p><p>By simulation, it has been shown that the number, weight andviscosity average of liner polymer chain length can be used tocalculate the number of random scissions in a linear polymer ofany molecular weight distribution, provided that there is acalibrated Mark-Houwink equation. A model describing partialdegradation of molecular weight distributions of linear polymersmeasured with viscometry was developed and verifiedexperimentally. The model predicts viscometric measurement ofchemical cellulose degradation by a rapidly reacting reagent tobe strongly dependent on cellulose accessibility.</p><p>The role of free radical reactions in cellulose degradationwas studied by varying the amount of ferrous ions and ozone addedto the cotton linters. The result was compared to the resultsobtained from cellulose of lower crystallinity (cellulose beads)by measuring average chain length. When a ferryl ion reacted withcotton linters in the presence of ozone, the very formation ofone glycosidic radical was more significant to degradation thanthe final step of forming one oxidised glycoside. The inefficientdegradation observed of the oxidation step is explainable by theamount of accessible glycosides being too small to influenceviscometry. The efficient degradation observed in associationwith the glycosidic radical formation is explained by initiationof free radical chain reactions that are propagated as long asthere is ozone in the system. As none of these phenomena werefound in the less crystalline cellulose, cellulose structureappears to be important for how free radical mediated cellulosedegradation develops.</p><p>The theory of free radical chain reactions coupled withdiffusion suggests a concentric expansion of the chain reactionsoutwards from the initial site of radical formation duringozonation of carbohydrates. This was confirmed by demonstratingfree radical chain reactions spreading from a spot of initiationoutwards during ozonation of a filter paper, using a pH-indicatorto monitor acid formation. Furthermore, the interior and exteriorof cellulose fibres doped with initiator were shown to bepermeated by small holes after ozonation.</p><p>Ethylene glycol was shown to improve the selectivity duringozone bleaching of oxygen bleached kraft pulp at pH 3. Optimalconditions were obtained at pH 3 for 25 wt% ethylene glycol. Theinfluence of ethylene glycol on selectivity is explained by aproportion of the free radical chain reactions being carried bythe ethylene glycol instead of the cellulose during ozonebleaching. The observations were summarised in the form of amodel where the observed degradations for pulp, bleached pulp andcotton fibres during both ozone bleaching and ethylene glycolassisted ozone bleaching were shown to agree with each other.</p><p>From g-irradiation of ozonised aqueous solutions of alcohol,the rate constant of superoxide formation from the peroxylradical of methanol was estimated to be 10 s^-1. Rate constants of the reactions between ozone andalkylperoxyl radicals were determined to be around 10⁴M^-1s^-1. The possibility of the reaction betweenalkylperoxyl radicals and ozone contributing significantly tofree radical chain reactions during ozonation of carbohydratesand alcohols could therefore be ruled out.</p><p>Cellulose, degradation, free radical, ozone, selectivity,ethylene glycol, alcohol, bleaching, kraft pulp, cotton linters,delignification, fibre, fibril, crystallinity, ferryl ion, freeradical chain reactions, TCF, viscometry, molecular weightdistributions, random scissions.</p>

The present thesis investigates some long standing problems in radical polymerization (RP). The major aim is to consider the feasibility of using simple techniques to provide more insight into the kinetics of RP. This can contribute to fundamental knowledge of radical polymerizations, particularly with respect to the mode of termination (λ), average termination rate coefficient (<kt>), chain-length dependence of termination (CLDT) and chain transfer through in-depth investigations of the rate of polymerization (Rp) and molar mass distribution (MMD), the latter especially via mass spectrometric (MS) analysis. The termination process was first investigated. Observation of changes of <kt> (or equivalently Rp) and MMD by a variety of factors such as solvent, monomer and initiator concentrations, temperature, pressure and growing radical size were explored. Non-classical kinetics and chain-length dependency of termination were confirmed. Accessibility of CLDT information was clearly evident. Although observed results meet fully with composite-model expectations, issues such as chain transfer were found to have an effect on the CLDT parameters determined from rate measurements. Specifically, dilute-solution polymerization of methyl methacrylate (MMA) in methyl isobutyrate (MIB) showed evidence of such an effect. Scaling of quantities that are experimentally accessible such as <kt> with DPn yield CLDT parameters in good agreement with what has been reported from recent PLP experiments. This was confirmed for several monomers. The temperature dependence of termination was also investigated and found to show evidence for CLDT. In contrast, the variation of <kt> with pressure did not demonstrate similarly strong CLDT effects. Evidence for and determination of chain transfer to MIB was also obtained. This was followed up by investigations into the important parameter λ using the MS technique. Surprisingly little is known about λ despite its long history and its apparent importance to polymer properties. Firstly, the robustness of using MS was explored, with the method passing numerous consistency checks. Although no large dependence of MS instrument was found, electrospray-ionization mass spectrometry (ESI-MS) provided best resolution. Second, the type of initiator, the initiator concentration and the solvent were found to have no measurable effect on λ, even when chain transfer occurred. In further work, increasing temperature seemed to have an influence on λ, leading to an increase in the proportion of disproportionation. However, pressure was found to have only a small influence on λ. The effect of monomer on λ was also studied. In the final part of this work, a preliminarily investigation into the viability of using Raman spectroscopic techniques to study auto-acceleration, also called the gel effect, for bulk MMA radical polymerization was presented. The results showed the possibility of using such a technique to follow the reaction to high conversion. The effect of temperature and initiator concentration on auto-acceleration were also presented. The outstanding results of this thesis are: (1) The application of CLDT theory to better understand rate results from low-conversion polymerizations. (2) In particular, the use of CLDT principles to explain termination activation energies across a range of monomers. (3) The validation of the MS method for quantitative determination of mode of termination by carrying out an array of consistency checks. (4) Showing that MS results are consistent with CLDT theory. (5) Utilization of the MS method for the first ever reliable measurement of the variation of mode of termination with temperature, pressure and monomer.

No description available.

Food web structure is of underlying importance to ecological functions and processes. Whilst it is understood that a range of biotic and abiotic factors affect structure, relatively little is known of the role of biodiversity per se in structuring food webs. In this thesis I utilise novel multi-dimensional estimates of food web structure based on stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) to quantify structural responses to changing community diversity. I additionally investigate methodological aspects of sample preparation and stable isotope quantifications of food chains. Using an arthropod prey-predator system, in chapter 2 I demonstrate that tissue selection and lipid extraction are important methodological procedures for deriving accurate δ15N and δ13C signatures. In chapter 3 I test the utility of δ15N to quantify food chain length, and δ13C to trace primary energy sources through to end consumers. Bayesian resampling of variance in sample means for plant and arthropod food chains produces robust isotopic estimates that match known food chain length well despite some error variance, and estimates of δ13C-range that trace trophic transfers. Chapter 4 represents a change in system from lab to field as I determine δ15N and δ13C signatures for plant and invertebrate species within three grassland communities representing a gradient of biodiversity. Quantifications of community bivariate isotopic space using isotopic metrics revealed that greater taxonomic richness increased both diversity of resource space exploited and overlap in resource space. These results therefore suggest that loss of diversity affected structure through altering relative patterns of niche partitioning in resource exploitation amongst community members. In chapter 5, I additionally find evidence that grassland management mediated changes in food web compartmental structure that were associated with differences in generalist invertebrate predator feeding habits. Taken together, these findings develop and demonstrate the utility of isotopic approaches to quantifying food web structure, and provide evidence of important mechanisms by which biodiversity affects food web structure. I conclude that the preservation of natural food web structure and trophic dynamics are further reasons for halting loss of biodiversity.

Manumycin antibiotics represent an important class of secondary metabolites produced by Streptomyces bacteria. They belong to a big class of polyketide metabolites and posses significant antimicrobial, anti-inflammatory, antitumor, and many other biological activities. They are characterized by two short polyketide chains, which are attached to a central subunit. Polyketide chains are synthesized by enzymes of the iterative type II polyketide-synthase. Mechanism of regulation of the polyketide chains length has not been known yet. Understanding mechanism can lead to biosynthesis of novel manumycin antibiotics with predetermined chain lengths what may improve their biological activities in favour of a practical use of these compounds. We prepared a mutant strain of asukamycin producer Streptomyces nodosus ssp. asukaensis with deletion of genes coding for type I/II β-ketoacylsynthase and protein AsuC14, which is a potential factor affecting lower polyketide chain length, for the identification of the chain length factor in manumycin antibiotics producers. Next, the genes for type I/II β-ketoacylsynthase and potential chain length-affecting factor C14 from strains producing manumycins with variable length of the lower polyketide chains were expressed in this mutant strain. Our results demonstrate...

Polymer electrolytes are widely used as ion transport media in vital applications such as energy storage devices and electrochemical displays. To further develop these materials, it is important to understand their ionic conductivity mechanisms. It has long been thought that ionic conduction in a polymer electrolyte occurs in the amorphous phase, while the crystalline phase is insulating. However, this picture has recently been challenged by the discovery of the crystalline system LiXF6∙PEO6 (X=P, As or Sb) which exhibits higher conductivity than its amorphous counterpart. Their structures comprise interlocking hemi-helical PEO-chain pairs containing Li+ ions and separating them from the XF6- anions. The first Molecular Dynamics (MD) simulation study of the LiPF6∙PEO6 system is presented in this thesis. Although its conductivity is too low for most applications at ambient temperature, it can be enhanced by iso- and aliovalent anion doping. It is shown that the diffraction-determined structure is well reproduced on simulating the system using an infinite PEO-chain model. The Li-Oet coordination number here becomes 6 instead of 5; minor changes also occur in the polymer backbone configuration. The crystallographic asymmetric unit and diffraction profiles are also reproduced. On simulating a shorter-chain system (n=22), more resembling the real material, the structure retains its double hemi-helices, but the polymer adopts a more relaxed conformation, facilitating the formation of Li+-PF6- pairs. Infinite-chain simulation shows the ionic conduction to be dominated by anion motion, in contrast to earlier NMR results. The effects of doping are also reproduced. Shortening the polymer chain-length has the effect of raising the transport number for lithium, thereby bring it into better agreement with experiment. It can be concluded that it is critical to take polymer chain-length and chain-termination into account when modelling ionic conductivity mechanisms in crystalline polymer electrolytes.

Polymer electrolytes are the most obvious candidates for safe "all-solid" Li-ion batteries and other electrochemical devices. However, they still have relatively poor ionic conductivities, which limits their wider adoption in commercial applications. It has earlier been the conventional wisdom that only amorphous phases of polymer electrolytes show usefully high ionic conduction, while crystalline forms are insulators. However, this has been challenged in the last decade by the discovery of highly organized, low-dimensional ion-conducting materials. Specifically, the crystalline phases of LiXF6.PEO6 exhibit higher ionic conductivities than their amorphous counterparts, with the Li-ion conduction taking place along the PEO channels. Polymer chain-length and chain-end registry has emerged as potentially significant in determining ionic conduction in these materials. Molecular Dynamics simulations have therefore been made of short-chain, monodisperse (Mw~1000), methoxy end-capped LiPF6.PEO6 to examine relationships between ion conduction and mode of chain-ordering. Studies of smectic and nematic arrangements of PEO chains have revealed that ion-transport mechanisms within the smectic planes formed by cooperative chain-end registry appear to be more suppressed by ion-pairing than in-channel conduction. Disorder phenomena in the chain-end regions emerge as a critical factor in promoting Li-ion migration across chain-gaps, as does the structural continuity of the PEO channels. Simulations incorporating ~1% aliovalent SiF62- dopants further suggest an increase in Li-ion conduction when the extra Li-ions reside within the PEO channels, with the anion influencing charge-carrier concentration through enhanced ion-pair formation. XRD techniques alone are shown to be inadequate in ascertaining the significance of the various short-chain models proposed; atomistic modelling is clearly a helpful complement in distinguishing more or less favourable situations for ion conduction. Though providing valuable insights, it must be concluded that this work has hardly brought us significantly closer to breakthroughs in polymer electrolyte design; the critical factors which will make this possible remain as yet obscure.