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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.
541

NMR STUDY OF EXCHANGE AND HYDRATION SITE IDENTIFICATION IN MCM-41

Hassan, Jamal 12 1900 (has links)
Deuteron 1D and 2D NMR spectroscopy was used to study the dynamics of water molecules within the mesoporous material MCM-41. The deuteron spectra show three magnetization components for a sample hydrated to a 0.2 monolayer level. One component was assigned to the pore surface silanol group deuterons that exhibit a broad Gaussian line of 32.6 kHz FWHM and the other components were assigned to the water deuterons. At room temperature one water deuteron component has a powder pattern line shape (splitting of about 4.2 kHz and population of about 61%) and the other has a Lorentzian line shape (about 388 Hz FWHM and population of 39%). Magnetization exchange occurs between these components. An exchange model, based on multi-site exchange, was constructed and used to analyse the results for exchange. For the 0.2 monolayer sample the rate of magnetization exchange out of the hydration site where the water deuterons exhibit a Lorentzian line in the deuteron spectra is 1.3 ms. 2D measurements at 233 K and room temperature confirmed the magnetization exchange scenario for the two water deuteron sites. Combining the deuteron results with proton-silicon cross polarization magic angle spinning experiments together with heat treatment of the sample, definitive hydration site identification for MCM-41 was achieved. This study has shown that the water molecules bound to the hydrogen-bonded silanol groups produce the powder pattern while water molecules bound to the single silanol groups produce the Lorentzian line. This represents a necessary first step toward a meaningful modeling of NMR observables in terms of site-specific water molecule coordination and dynamics in MCM-41.
542

Characterization and Genetic Manipulation of D-cysteine Desulfhydrase from Solanum lycopersicum

Todorovic, Biljana January 2008 (has links)
Progress in DNA sequencing of plant genomes has revealed that, in addition to microorganisms, a number of plants contain genes which share similarity to microbial 1-aminocyclopropane-1-carboxylate (ACC) deaminases. ACC deaminases break down ACC, the immediate precursor of ethylene in plants, into ammonia and α-ketobutyrate. We therefore sought to isolate putative ACC deaminase cDNAs from tomato plants with the objective of establishing whether the product of this gene is a functional ACC deaminase. It was demonstrated that the enzyme encoded by the putative ACC deaminase cDNA does not have the ability to break the cyclopropane ring of ACC, but rather that it utilizes D-cysteine as a substrate, and in fact encodes a D-cysteine desulfhydrase. Kinetic characterization of the enzyme has shown that it is similar to other previously characterized D-cysteine desulfhydrases. Using site-directed mutagenesis, it was shown that altering two amino acid residues within the predicted active site changed the enzyme from D-cysteine desulfhydrase to ACC deaminase. Concomitantly, it was shown that by altering two amino acids residues at the same position within the active site of ACC deaminase from Pseudomonas putida UW4 changed this enzyme into D-cysteine desulfhydrase.
543

One Church in One Location: Questioning the Biblical, Theological, and Historical Claims of the Multi-Site Church Movement

Gaines, Grant 14 December 2012 (has links)
This dissertation argues that a multi-site church that is not characterized by campus-wide gatherings does not have a sound biblical or theological basis for considering itself one church and is inconsistent with historic congregationalism. This argument is made in six steps. First, a framework for determining whether or not a church practice is biblical is put forward. Second, it is shown that the people of God as one assembly is a central theme in the Old Testament. Third, it is demonstrated that this theme of the people of God as one assembly is also a central theme of the New Testament. Fourth, it is argued that there is not precedent for multi-site church structure in the house churches of the New Testament. Fifth, it is shown that multi-site is not consistent with historic congregationalism as seen in Baptist ecclesiology. And sixth, it is argued that multi-site church structure is consistent with historic connectionalism as seen, for example, in Methodist ecclesiogy--a fact that only serves to heighten the problem with multi-site from a congregationalist point of view.
544

Structure-function relationship study of a loop structure in allosteric behaviour and substrate inhibition of <i>Lactococcus lactis</i> prolidase

Chen, Jian An 25 February 2011 (has links)
<p><i>Lactococcus lactis,</i> prolidase (<i>Lla</i>prol) hydrolyzes Xaa-Pro dipeptides. Since Xaa-Pro is known as bitter peptides, <i>Lla</i>prol is potentially applicable to reduce bitterness of fermented foods. <i>Lla</i>prol shows allosteric behaviour and substrate inhibition, which are not reported in other prolidases. Computer models of <i>Lla</i>prol based on an X-ray structure of non-allosteric <i>Pyrococcus furiosus</i> prolidase showed that a loop structure (Loop<sup>32-43</sup>) is located at the interface of the protomers of this homodimeric metallodipeptidase. This study investigated roles of four charged residues (Asp<sup>36</sup>, His<sup>38</sup>, Glu<sup>39</sup>, and Arg<sup>40</sup>) of Loop<sup>32-43</sup> in <i>Lla</i>prol using a combination of kinetic examinations of ten mutant enzymes and their molecular models. Deletion of the loop structure by Î36-40 mutant resulted in a loss of activity, indicating Loop<sup>32-43</sup> is crucial for the activity of <i>Lla</i>prol. D36S and H38S exhibited 96.2 % and 10.3 % activity of WT, whereas little activities (less than 1.0 % of WT activity) were observed for mutants E39S, D36S/E39S, R40S, R40E, R40K and H38S/R40S. These results implied that Glu<sup>39</sup> and/or Arg<sup>40</sup> play critical role(s) in maintaining the catalytic activity of <i>Lla</i>prol. These observations suggested that the loop structure is flexible and this attribute, relying on charge-charge interactions contributed by Arg<sup>40</sup>, Glu<sup>39</sup> and Lys<sup>108</sup>, is important in maintaining the activity of <i>Lla</i>prol. When the loop takes a conformation close to the active site (closed state), Asp<sup>36</sup> and His<sup>38</sup> at the tip of the loop can be involved in the catalytic reaction of <i>Lla</i>prol. The two active mutant prolidases (D36S and H38S) resulted in modifications of the unique characteristics; the allosteric behaviour was not observed for D36S, and H38S <i>Lla</i>prol showed no substrate inhibition. D36E/R293K, maintaining the negative charge of position 36 and positive charge of position 293, still possessed the allosteric behaviour, whereas the loss of the charges at these positions (D36S of this study and R293S of a previous study (Zhang et al., 2009 BBA-Proteins Proteom 1794, 968-975) eliminated the allosteric behaviour. These results indicated the charge-charge attraction between Asp<sup>36</sup> and Arg<sup>293</sup> is important for the allostery of <i>Lla</i>prol. In the presence of either zinc or manganese divalent cations as the metal catalytic centre, D36S and H38S enzymes also showed different substrate preferences from WT <i>Lla</i>prol, implying the influence of Asp<sup>36</sup> and His<sup>38</sup> on the substrate binding. D36S and H38S also showed higher activities at pH 5.0 to 6.0, in which range WT <i>Lla</i>prol steeply decreased its activity, indicating Asp<sup>36</sup> and His<sup>38</sup> are involved in the active centre and influence the microenvironment of catalytic His<sup>296</sup>. The above observations are attributed to modifications of their local structure in the active centre since the temperature dependency and thermal denaturing temperature indicated little effects on the overall structure of the <i>Lla</i>prol mutants.</p> <p>From these results, we concluded that the unique behaviours of <i>Lla</i>prol are correlated to Loop<sup>32-43</sup> and Asp<sup>36</sup> and His<sup>38</sup> on it. When Loop<sup>32-43</sup> takes a closed conformation, Asp<sup>36</sup> interacts with Arg<sup>293</sup> via charge-charge attraction to form an allosteric subsite. The saturation of the allosteric site with substrates further allowed the communications of His<sup>38</sup> with S<sub>1</sub> site residues to complete the active site. When the substrate concentration becomes higher than it is required to saturated productive S<sub>1</sub>' site, His<sup>38</sup>, Phe<sup>190</sup> and Arg<sup>293</sup> would resemble the residue arrangement of S<sub>1</sub>' site residues (His<sup>292</sup>, Tyr<sup>329</sup>, and Arg<sup>337</sup>) and bind to the proline residue of substrates. This non-productive binding would prevent the conformational change of Loop<sup>32-43</sup>, which further results in the substrate inhibition. For further confirmation of this mechanism, crystallographic studies will be conducted. In this thesis, we have indentified the conditions to produce crystals of <i>Lla</i>prol proteins.</p>
545

NMR STUDY OF EXCHANGE AND HYDRATION SITE IDENTIFICATION IN MCM-41

Hassan, Jamal 12 1900 (has links)
Deuteron 1D and 2D NMR spectroscopy was used to study the dynamics of water molecules within the mesoporous material MCM-41. The deuteron spectra show three magnetization components for a sample hydrated to a 0.2 monolayer level. One component was assigned to the pore surface silanol group deuterons that exhibit a broad Gaussian line of 32.6 kHz FWHM and the other components were assigned to the water deuterons. At room temperature one water deuteron component has a powder pattern line shape (splitting of about 4.2 kHz and population of about 61%) and the other has a Lorentzian line shape (about 388 Hz FWHM and population of 39%). Magnetization exchange occurs between these components. An exchange model, based on multi-site exchange, was constructed and used to analyse the results for exchange. For the 0.2 monolayer sample the rate of magnetization exchange out of the hydration site where the water deuterons exhibit a Lorentzian line in the deuteron spectra is 1.3 ms. 2D measurements at 233 K and room temperature confirmed the magnetization exchange scenario for the two water deuteron sites. Combining the deuteron results with proton-silicon cross polarization magic angle spinning experiments together with heat treatment of the sample, definitive hydration site identification for MCM-41 was achieved. This study has shown that the water molecules bound to the hydrogen-bonded silanol groups produce the powder pattern while water molecules bound to the single silanol groups produce the Lorentzian line. This represents a necessary first step toward a meaningful modeling of NMR observables in terms of site-specific water molecule coordination and dynamics in MCM-41.
546

Characterization and Genetic Manipulation of D-cysteine Desulfhydrase from Solanum lycopersicum

Todorovic, Biljana January 2008 (has links)
Progress in DNA sequencing of plant genomes has revealed that, in addition to microorganisms, a number of plants contain genes which share similarity to microbial 1-aminocyclopropane-1-carboxylate (ACC) deaminases. ACC deaminases break down ACC, the immediate precursor of ethylene in plants, into ammonia and α-ketobutyrate. We therefore sought to isolate putative ACC deaminase cDNAs from tomato plants with the objective of establishing whether the product of this gene is a functional ACC deaminase. It was demonstrated that the enzyme encoded by the putative ACC deaminase cDNA does not have the ability to break the cyclopropane ring of ACC, but rather that it utilizes D-cysteine as a substrate, and in fact encodes a D-cysteine desulfhydrase. Kinetic characterization of the enzyme has shown that it is similar to other previously characterized D-cysteine desulfhydrases. Using site-directed mutagenesis, it was shown that altering two amino acid residues within the predicted active site changed the enzyme from D-cysteine desulfhydrase to ACC deaminase. Concomitantly, it was shown that by altering two amino acids residues at the same position within the active site of ACC deaminase from Pseudomonas putida UW4 changed this enzyme into D-cysteine desulfhydrase.
547

Further Development of Atmospheric Pressure, Self-Igniting Microplasma Devices (MPDs) for Elemental Analysis of Liquid Microsamples Using Atomic Emission Spectrometry (AES)

Weagant, Scott Richard January 2011 (has links)
The present elemental analysis workhorse worldwide is Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry (AES) and Mass Spectrometry (MS). Due to the high power requirements, large gas consumption and the more obvious attribute, size, the ICP is tethered to the lab. Usually, samples must be collected, bottled, sometimes stabilized by acids and then shipped back to the lab for analysis (hours to days to weeks turnover rate). Due to the demand for a portable analyzer this thesis will focus on further development of microplasma devices (MPDs) for portable on-site analysis, in (near) real-time. Mini-In-Torch Vapourization (mini-ITV) is the sample introduction method for MPDs which removes the need for sample preparation (further necessitates portability). Mini-ITV introduces the sample into the MPD via electrothermal vapourization of a dry (water-free) nano- to micro- volume sample. Pneumatic nebulization, the commercially available ICP sample introduction method would extinguish the microplasma. Microplasma stability is the first issue addressed by confining the microplasma to a quartz tube (“wall-stabilized”) in hopes of a more stable MPD background emission. Once stabilized MPD conditions were found key microplasma parameters were studied including MPD power, HVac frequency, operating mode, inter-electrode distance (IED) and observation location, in hopes of improved MPD analytical performance. Microplasma excitation mechanism and maximum energy available in the microplasma for analyte are discussed. Some fundamental characteristics such as excitation temperature (Texc) and changes in atom/ion population with variation in some of the key MPD parameters were also determined.
548

Needle Trap Device and Solid Phase Microextraction Combined with Portable GC-MS for On-Site Applications

Warren, Jamie January 2011 (has links)
Needle trap device (NTD) is a technique that is useful for a wide variety of applications involving the sample preparation of compounds with a wide range of chemico-physico properties, and varying volatilities. A newly designed NTD that improves the performance relative to previous NTD designs is simple to produce is developed. The NTD utilizes a side-hole needle with a modified tip to improve the sealing between the NTD and narrow neck liner of the GC injector, thereby increasing the desorption efficiency. The slurry packing method was applied, evaluated, and NTDs prepared by this method were compared to NTDs prepared using the vacuum aspiration method. NTD geometries including blunt tip with a side-hole needle, tapered tip with side-hole needle, dome tapered tip with side-hole, sliding tip with side-hole and blunt tip with no side-hole needle (expanded desorptive flow) were prepared and evaluated. Sampling performance and desorption efficiency were investigated using automated headspace extraction of benzene, toluene, ethylbenzene, p¬-xylene (BTEX), anthracene and pyrene. The tapered tip and sliding tip NTDs were found to have increased desorption efficiency. SPME and NTDs are valuable sample preparation tools for on-site analysis. Combining both extraction techniques allows for the differentiation of free and particle-bound compounds in a sample matrix. Portable GC/MS instrumentation can achieve fast separation, identification, and quantitation of samples prepared by the above techniques on-site without the need for transport to the laboratory. This minimizes the effects of volatiles lost and sample degradation during storage time. Here, SPME and tapered tip NTDs combined with portable GC/MS are used to investigate free and total emissions of BTEX and select PAHs from gasoline and diesel exhaust. Using the above optimized technologies, cigarette smoke in a smoking area where people were actively smoking and inside a smoker’s car were also investigated. Target contaminants were found in the investigated matrices at ng/mL levels.
549

Site productivity of poplars in Canada : relationships with soil properties and competition intensity

Pinno, Brad 15 August 2008 (has links)
Site quality, or the ability of land to grow trees, is an important component for identifying the most appropriate locations for establishing plantations of fast growing tree species to meet societys demands for timber and other environmental benefits. The goal of this thesis project was to predict site quality for poplars using soil and site information in Saskatchewan, Alberta and Quebec and to examine the effect of site quality on competition control in hybrid poplar plantations in Saskatchewan.<p>The first study examined factors affecting trembling aspen productivity in the boreal shield ecozone of Quebec on till and fluvial parent materials using general map data and measured soil and site information. Relationships with productivity were stronger using measured soil and site variables for individual parent materials (R2>0.6) than using general map data only (R2<0.25). Including biological variables, such as overstory species composition, had a major impact on site quality with conifer dominance negatively impacting the growth of trembling aspen.<p>The second study examined the factors affecting trembling aspen productivity in the boreal transition ecoregion of Saskatchewan on three different soil parent materials: fluvial, lacustrine and till. Relationships with productivity were stronger using soil and site variables for individual parent materials (R2 0.48-0.58) than using agricultural capability classes or other soil properties for all plots combined (R2<0.2). For fluvial and lacustrine sites, increasing clay content and nutrient availability (e.g. pH and total N) were positively related to productivity while tree productivity was negatively related to poor drainage for till sites. <p>The third study examined the factors affecting site quality for a single hybrid poplar clone in industrial plantations in Alberta at both the local scale (between plantations) and the microsite scale (within plantations). At the local scale, foliar P and Cu concentrations, soil water availability and drainage, and Ca and Mn in the C horizon were related to hybrid poplar productivity. There were also curved relationships with productivity and soil texture in the B horizon and pH of the A horizon, indicating an optimal range for poplar growth. At the microsite scale, soil texture was the best predictor of productivity with different relationships at each site depending on where the sites were in relation to the optimal soil texture.<p>The final study examined the response of hybrid poplar plantations in Saskatchewan to interspecific competition control on a range of site productivities. Competition control greatly increased tree growth with the greatest benefit being on the best quality sites. Both water and nutrients were highly competed for between trees and weeds. In the weed-free plots, tree growth was positively related to the amount of silt and clay in the soil and foliar P concentrations. This series of studies has demonstrated that it should be possible to predict poplar productivity reasonably well using only soil and site information within limited areas across Canada. However, the important drivers of productivity varied between the regions studied and between site groupings, such as by parent material, within local areas. This information can now be used to help land managers make better decisions regarding the establishment and management of plantations of fast growing tree species, notably hybrid poplar plantations.
550

Development of site investigation and remediation strategies at petroleum- hydrocarbon contaminated site

Yang, Jui-Hsin 13 February 2012 (has links)
Soil and groundwater is the final receptor environment of contamination on land, especially easy to contaminate groundwater aquifers, because of the underground environment often obscure, it is difficult to clarify the scope of pollution, in addition, the transport and chemical transformation process are also difficult to evaluate. Resulting that although consumes on huge cost and materials, and times on oil contaminated site investigation and remediation, obtaining the solution of the problem is still hard. In this study, it combines with the environmental site assessment and the triad rapid investigation, the establishment of site contamination conceptual model, the key designated contaminated area, collect samples of the implementation for laboratory analysis, Moreover, use cyclic evaluation process, continuously updated site conceptual model, to clarify the distribution of contaminated sites, impact of pollution, hydro-geological characteristics and pollution sources. It also discussed the effective reduction of pollution critical area, to obtain high-density results, in order to improve sampling and analysis to make the efficiency of the case of site investigation, and using environmental forensic techniques to determine and provide the evidence of pollution sources. ESA phase I implements the key results of the preliminary delineation of contaminated areas, soil and groundwater pollution concerns and possible sources of material. ESA phase II evaluates preliminary assessment of sites contaminated soil contamination is a high carbon number of oil and contaminants move to the surface to deeper soil 9 m at the lower, deeper pollution range is unknown. Groundwater test results garnered less than control standards, but the detection of trace gas station in MTBE, it is included in the possible sources of pollution. Taking ESA phase II assessment in a further analysis, the soil contaminants are TPHC10-C40 based, contamination depth of 8m, gas station area within the tank and pipeline testing values are low, there is no sign of oil leakage. Pollution more than 5m in depth the most serious, TPH concentrations in general are 10,000 mg/kg or more, the depth of 5m and the following have been significantly reduced, TPH concentrations than in the 5,000 mg/kg or less. Interviews showed that the specific relationship between the people, suspected underground oil refining line set 40 years ago, suspected of shipping oil from the waste obtained after the hull, after the system by then resold for profit. Identification of pollution sources than the results, TPHC10-C40 carbon number distribution or pattern of the peak are more similar to diesel. TIC illustration showed that the distillate oil mixture for two, than the peak apex, suggesting that the low-carbon should be diesel fuel, and the high-carbon would be fuel. Pr/Ph ratio than, presumably with the CPC diesel from different sources. Alkyl bicyclic sesquiterpene class fingerprint comparison results, the shape of the fingerprint sample slightly different, but the main features of the same types of compounds. Analysis of aromatic compounds, indicators showed that the samples compound ratio of methyl phenanthrene and methyl dibenzothiophene isomers, dibenzothiophene, and phenanthrene isomers are closer. Integrated fingerprint analysis (fingerprinting) results, similar to the site characteristics of pollutants, for the same pollution source. The site is semi-volatile pollutants, substances insoluble in water, more stored in the main pollution silt/clay layer, subject to geological conditions, ground remediation techniques are more difficult to grasp in the transmission path, remediation systems that require high density, break through the bottleneck transmission path, but a majority of sites on private land, during the remediation process it is difficult to obtain the burgage, therefore, it would be fit the inappropriate comprehensive ground handling. Subsequent remediation plan can be removed towards the high pollution of soil pollution, and long-term monitoring of permeable reactive barrier type with natural degradation. Recommendations for the future studies can be dust inhalation and skin contact with soil, groundwater ingestion, inhalation and skin contact exposure pathways for risk assessment, site management provided a basis for administrative control.

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