<p>This Thesis describes applications of standing-waveultrasonic traps for sensitive biomedical analysis. Two majorapproaches have been investigated where functionalizedmicroparticles are employed in bioaffinity assays. In the firstapproach, a longitudinal flow-through capillary ultrasonic trapis used for size selective separation and retention ofdifferently sized microparticles. This device may be used fordetection of particle pairs, which are formed during theinitial stage of microparticle immunoagglutination. Theperformance of the capillary ultrasonic trap for enrichment andcounting of particle pairs is characterized by a model systemof differently sized homogeneous fluorescent microparticles.The selectivity of this detection method relies on thecharacteristics of the force field inside the narrow borecapillary, which is formed by the competition between acousticradiation forces and viscous drag forces from the fluidflow.</p><p>The second approach is an investigation of the potential forsensitive protein quantification by combining ultrasonicenrichment and confocal laser-scanning fluore-scence detection.Here, the design of the ultrasonic trap is tailor-made for theimaging properties of a confocal microscope, resulting inrearrangement and concentration of suspended microparticlesinto single, dense layers that is scanned by a focused laserbeam. The bioaffinity assay employed is based on detecting thetarget molecules via fluorescent tracer antibodies immobilizedon the surface of each single particle.</p><p>The final part of the work presented in this Thesis is athorough investigation of both the biochemical and the physicalproperties that determine the performance and potentialsensitivity of the particle doublet assay. In thisinvestigation, a novel approach is presented for doubletdetection, namely fluorescence-microscopy-based classificationof doublets and singlets by a pattern recognition algorithm.The experimental results are also compared with the resultsfrom flow cytometry analysis. Furthermore, the initial stage ofimmuno-agglutination is theoretically investigated by a modelbased on diffusion-limited agglutination combined with a stericfactor determined by the geometry of the bio-molecules and theamount of specific and non-specific binding that is present inthe particular assay.</p><p>To conclude, the Thesis presents several approaches wherestanding-wave ultrasonic fields may be used for sensitiveparticle-based biomedical analysis. The best prospect for highsensitivity was found for the confocal laser-scanningfluorescence detection system, with a detection limit of theorder of 10^-14M. On the other hand, the agglutination-basedassay may give sensitivity of the order of 10^-11-10^-10M with very simple and inexpensiveequipment.</p>

<p>Sampling and sample introduction are two key steps in quantitative gas chromatography. In this thesis, a development of a previously described sampling technique as well as a novel concept for sample introduction in gas chromatography are presented. The thesis is based on two papers.</p><p>Paper I describes a method for preparing physically mixed polymers for use as sorbent phases in open tubular trapping of gaseous analytes. The concept is based on mechanical disintegration and mixing of solid or liquid poly(ethylene glycol), PEG, into poly(dimethylsiloxane), PDMS, in a straightforward manner. The resulting mixture exhibits a higher affinity towards polar analytes, as compared to pure PDMS.</p><p>Paper II describes a novel approach to liquid sample introduction with the split/splitless inlet, used in gas chromatography. Classical injection techniques struggle with discrimination of high boiling analytes and poor repeatability of the injected amount of analytes. The presented injection technique utilizes high voltage to obtain a spraying effect of the injected liquid. The spraying effect can be achieved with a cold needle, which is unprecedented for gas chromatographic injections. The cold needle spraying results in highly repeatable injections, free from discrimination of high boiling analytes.</p>

Thesis (Ph.D.)--Lehigh University, 2009. / Adviser: Tianbo Liu.

<p> The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. </p><p> X-ray absorption spectroscopy (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the &Delta;&mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The &Delta;&mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the &Delta;&mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.</p>

Applications taking advantage of fluorine-fluorine interactions for separations are a recent analytical trend, with benefits in terms of cost, ease of use and specificity cited as advantages of these so-called “fluorous” techniques. While most current fluorous separations employ columns packed with microspheres, columns based on entrapped microspheres, porous polymer monoliths (PPMs) and open tubes all represent viable alternatives to conventional packed capillaries. In this thesis, the design, optimization and implementation of fluorous stationary phases based on all three of these new technologies are explored. Development of methods and techniques using these systems are presented, with factors affecting their performance being examined. Doing this, the specificity of the fluorous interaction can also be explored, and potential applications for these new materials can be discussed. For the work with entrapped microspheres, the columns that were formed did not prove to have an advantage over those that were unentrapped. Although affixing spheres within a matrix is known to have benefits in terms of bed stability over repeated use, the inclusion of a polymer coating proved to represent a greater concern for the availability of the bead-based stationary phases. Layers of polymer forming over the surface were shown to limit the access of analytes to the entrapped microspheres, restricting the usefulness of these materials. The work with fluorous monoliths proved the most successful, providing clear evidence of improved selectivity when compared to analogs made without fluorination. Fluorous retention specificity was also effectively examined, with secondary effects probed and compared to those that had been discussed for commercially-available fluorous microspheres. Results showed that the monoliths were very much in-line with what had already been seen for sphere-based systems, with residual substrate character providing only a slight contribution to the observed separations. Finally, development of open-tubular columns based on microstructured optical fibers was the most speculative of the projects discussed here. The introduction of a fluorous stationary phase through silanization was demonstrated to be an effective method for imparting chromatographic selectivity into these columns, and controllable factors such as treatment protocol and silane character were shown to affect the performance of the resulting materials. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-05-06 17:03:14.803

<p> This dissertation describes metabolic engineering of cyanobacterium <i> Synechococcus elongatus</i> PCC7942 as a photosynthetic host for the conversion of CO₂ into 2,3-butanediol. Current advances in pathway design, genetic tool development, and yield improvement are described (Chapter 1). A pathway for the synthesis of 2,3-butanediol is designed based on collective concepts of pathway strength, robustness, and irreversibility, and extensively tested through the generation of mutants (Chapter 2). This pathway is then optimized through modulation of translation by combinatorial mixing of ribosome binding sites (Chapter 3). Finally, photosynthetic productivity is investigated through expression of an exogenous pathway targeting every step between fixation and product (Chapter 4). All materials and methods are given separately for easy reference (Chapter 5).</p>

<p> Heavy metal pollution is a growing concern as growing worldwide population and industrial processes increase pollution levels in most environments. High metal concentrations throughout ecosystems pose a serious threat to wild-life and human health. Methods to monitor rising threat levels of metals are a primary concern for monitoring overall ecosystem health. Mechanisms which spread pollution must be intimately understood because of the persistence of heavy metals. Heavy metal contamination in the Tar Creek superfund site provides a great case study to selectively observe differences in heavy metals concentrations both upstream and downstream of mining activity. Thus, research is able to identify natural and man-made point sources of pollution. </p><p> The abilities of bivalves to filter-feed and sediment-feed provide a unique monitoring tool for analyzing heavy metals. Mussels are constantly filtering the environment around them. A mussel's seasonal and annual growth layers provide an excellent sample media for obtaining historical records of environmental data. Many species of mussels are found in most freshwater ecosystems throughout the United States. Mussels have low migration rates, live for a suitable amount of time, and leave relic shells. These features make mussels very practical for monitoring heavy metal pollution. </p><p> Various studies were conducted to obtain insight into developing methods for using LA-ICP-MS as a tool for monitoring heavy metals in mussel shells. Surface laser ablations, compared at additional depths, resulted in a more than 20% increase in signal intensity. Theoretical and experimental designs show signal changes as a function of depth. Mussel tissue and shell digestions were found to be best when using approximately 1.0 mL of hydrogen peroxide and 1.0 mL of nitric acid for each 0.1 grams of sample. Mussel tissue was found to have greater heavy metal concentrations than shells. Shells were found to average a 96% weight of calcium carbonate; however, the organic layers contained the greatest concentrations of heavy metals per weight. </p>

<p> The objective in this thesis is to study the structure of peptides using molecular spectroscopy. Molecular spectroscopy, both vibrational and electronic, can be used as a sensitive tool to study molecular structure. Since it is an inherently low resolution method, theoretical calculations are essential for a complete understanding of vibrational and electronic spectra. The first part of this thesis contains quantum chemical calculations of the molecular spectra of several small peptide systems with different secondary structures. Optical trapping is a method that allows for the manipulation of sub-micron scale objects using tightly focused laser light. Raman spectroscopy, which is sensitive to molecular vibrations also requires intense laser light. Combined with optical tweezing, Raman spectroscopy can prove to be a very powerful tool to study small sample volumes and probe single living cells. In the second part of this thesis, I detail the construction an such an instrument, an optical trapping Raman spectrometer (OTRS). Our OTRS can measure Raman spectra from sub micron systems while at the same time quantifying the mechanical forces that are acting upon them. Thus the OTRS can give insight into the relationship between mechanical forces acting upon cells and their molecular structure. </p>

The thesis describes infrared spectra recorded during the adsorption of water, acetone, acetic acid and hexifluaroacetone onto oxidized and reduced rutile, and the development of a technique for recording the infrared spectrum of a solid immersed in a liquid. Bands observed on the hydroxylated rutile surface have been assigned to hydroxyl groups on the (110) plane and water IrDlecules adsorbed onto strong and weak Lewis sites on all exposed planes. The hydroxyl groups exist as isolated or hydrogen bonded groups on surface titanium ions or as hydrogen ions on bridging oxygen ions. Reduction of the rutile surface considerably decreased the amount of rmlecular water adsorbed on the hydroxylated surface. The adsorption of acetone onto the hydroxylated surface took place in three consecutive stages, the first involved acetone molecules Lewis bonding to weak sites, the second resulted in the formation of mesityl oxide on strong surface sites and occurred with stage one in the absence of surface water molecules. In the third stage acetate molecules were formed as a result of the decomposition of mesityl oxide. Adsorption of acetic acid onto rutile resulted in the formation of water and arpeaxeme of bands due to acetate groups and Lewis-bonded co lexes on the weak sites. Hexafluoroacetone reacted with surface hydroxyls to produce a salt of the gem-diol hexifluoropropane-2,2-dio1, which decomposed on the removal of water to form trifluoroacetate species. An infrared cell has been developed enabling solid discs to be treated and inmiersed in a solution under inert conditions. The cell, of path length 0.7cm, has been used to study the adsorption of ether, from a solution in carbon tetrachloride, onto silica. Designs of variable path length cells for use Hexafluoroacetone reacted with surface hydroxyls to produce a salt of the gem-diol hexifluoropropane-2,2-dio1, which decomposed on the removal of water to form trifluoroacetate species. An infrared cell has been developed enabling solid discs to be treated and inmiersed in a solution under inert conditions. The cell, of path length 0.7cm, has been used to study the adsorption of ether, from a solution in carbon tetrachloride, onto silica. Designs of variable path length cells for use unier vacuum are included.

<p> We studied the interactions of glyoxylic acid, pyruvic acid and oxalic acid with ammonium and corresponding sodium salts in aqueous solutions simulating a dark and radical free atmospheric aqueous aerosol condition. Cleavage of a carbon-carbon bond in pyruvic acid and glyoxylic acid leading to the decarboxylation was observed in the presence of ammo&not;nium salts but was not observed from oxalic acid. At the beginning of the reaction, the decarboxylation appeared to proceeding slower compare to the later stage of reaction. The empirical rate constants for decarboxylation in the reaction solutions were estimated using a 'quasi-steady state' model: (i) glyoxylic acid and ammonium sulfate was 3.3 (&plusmn; 0.7)&times;10^-8 M^-1 s^-1; (ii) glyoxylic acid and ammonium nitrate was 1.4 (&plusmn; 0.3)&times;10^-8 M^-1 s^-1; (ii) glyoxylic acid and ammonium chloride was 1.9 (&plusmn; 0.2)&times;10^-8 M^-1 s^-1; and (iii) pyruvic acid and ammonium sulfate was 15.8 (&plusmn; 0.4)&times;10^-8 M^-1 s^-1. Negligible CO₂ was observed in the experiments with the corresponding sodium salts indicating the ammonium ion or ammonia is facilitating the carbon-carbon bond cleavage leading to carboxyl fragmentation of the &agr;-oxo carboxylic acids. It was observed that pyruvic acid undergoes decarboxylation at least four times faster than that of glyoxylic acid under similar reaction conditions. This indicates that the structure of the acid plays an important role in the decarboxylation. In the case of pyruvic acid, the reaction is likely faster because of the inhibited hydration of the carbonyl moiety due to the inductive effect of the adjacent methyl group. A tentative set of reaction mechanisms is proposed involving nucleophilic attack by ammonia on the carbonyl carbon leading to fragmentation of the carbon-carbon bond between the carbonyl and carboxyl carbons. Similar carbon-carbon bond cleavage is anticipated for &agr;-dicarbonyl compounds, which are structurally similar to the &agr;-oxo carboxylic acids. In the absence of photolysis and under limited availability of OH radicals, the decay of pyruvic acid can be dominated by the reaction with ammonium sulfate and can be an order of magnitude higher than the loss via reaction with the OH radical. Under similar conditions the reactions with ammonium salts are likely be a major sink for &agr;-oxo carboxylic acids in the atmospheric aqueous phase.</p>