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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.
291

Dynamic Chemical Imaging And Analysis Within Biologically Active Materials

Alex M Sherman (10711971) 06 May 2021 (has links)
A thorough understanding of pharmaceutical and therapeutic products and materials is important for an improved quality of life. By probing the complex behaviors and properties of these systems, new insights can allow for a better understanding of current treatments, improved design and synthesis of new drug products, and the development of new treatments for various health conditions. Often, the impact of these new insights are limited by current technology and instrumentation and by the methods in which existing data is processed. Additionally, current standards for characterization of pharmaceuticals and therapeutics are time-consuming and can delay the timeline in which these products become available to the consumer. By addressing the limitations in current instrumentation and data science methods, faster and improved characterization is possible.<div><br></div><div>Development and improvement in optical instrumentation provides potential solutions to the current limitations of characterization methods by conventional instrumentation. Limitations in speed can be addressed through the use of nonlinear optical (NLO) methods, such as second harmonic generation (SHG) and two-photon excited ultraviolet fluorescence (TPE-UVF) microscopy, or by linear methods such as fluorescence recovery after photobleaching (FRAP). For these methods, a high signal-to-noise ratio (SNR) and a nondestructive nature decrease the overall sample size requirements and collections times of these methods. Furthermore, by combination of these optical techniques with other techniques, such as thermal analysis (e.g. differential scanning calorimetry (DSC)), polarization modulation, or patterned illumination, the collection of more complex and higher quality data is possible while retaining the improved speed of these methods. Thus, this modified instrumentation can allow for improved characterization of properties such as stability, structure, and mobility of pharmaceutical and therapeutic products.<br></div><div><br></div><div>With an increase in data quantity and complexity, improvements to existing methods of analysis, as well as development of new data science methods, is essential. Machine learning (ML) architectures and empirically validated models for the analysis of existing data can provide improved quantification. Using the aforementioned optical instrumentation, auto-calibration of data acquired by SHG microscopy is one such method in which quantification of sample crystallinity is enabled by these ML and empirical models. Additionally, ML approaches utilizing generative adversarial networks (GANs) are able to improve on identification of data tampering in order to retain data security. By use of GANs to tamper with experimentally collected and/or simulated data used in existing spectral classifiers, knowledge of adversarial methods and weakness in spectral classification can be ascertained. Likewise, perturbations in physical illumination can be used to ascertain information on classification of real objects by use of GANs. Use of this knowledge can then be used to prevent further data tampering or by improving identification of data tampering.<br></div>
292

Detection of Anti-hGH Antibodies in Serum Samples of Children Treated with RhGH

Ritter, Nina 10 October 2012 (has links)
The present study deals with the comparison and establishment of methods for the detection of antibodies against recombinant human growth hormone (rhGH). Therefore, different methods for the detection of hGH-Abs were evaluated and compared in order to establish a test system that can be used for the detection of neutralizing antibodies against hGH, which could be developed under rhGH treatment. This manuscript describes in detail the validation of a newly developed biological assay, the neutralizing hGH-antibody assay (NAb assay). Therefore, a cell line transfected with the growth hormone receptor, that proliferates in the presence of hGH, was used. This proliferation was quantified by an increase of the optical density (OD/ absorbance) after addition of a colorimetric reagent, whereas the presence of hGH-antibodies leads to an inhibition of cell proliferation. To validate the test system for the detection of hGH-antibodies, we tested serum samples of 4 patients suffering from neurosecretory dysfunction (NSD) and samples taken from 6 patients with growth hormone deficiency (GHD) which were treated with rhGH and were highly suspected for a-hGH antibodies. These samples were tested in two different immunological assays, capable to screen sera for anti-hGH immunreactivity in the case of hGH-insensitivity during GH treatment. Using the NAb assay the neutralizing activity of specific hGH-antibodies was proved in serum samples of NSD and GHD type 1A patients. In case of neutralizing hGH-antibody activity, a clinically based decision can be made whether rhGH therapy should be stopped or the rhGH dosis should be increased. By the use of our test system, we offer the measurement of anti-hGH-antibody activity to other laboratories in cases when secondary hGH-insensitivity is assumed or observed.
293

Untersuchungen zum Vorkommen von Toxoplasma gondii in Wild in Brandenburg

Stollberg, Kaya Christina 16 June 2023 (has links)
Die Toxoplasmose, nach ihrem Verursacher, dem Parasiten Toxoplasma gondii (T. gondii) benannt, ist eine weltweit häufig auftretende Zoonose. Einen wichtigen Infektionsweg stellt der Verzehr von nicht ausreichend erhitztem oder rohem Fleisch, welches Gewebezysten enthält, dar. In Deutschland hat der Konsum von Wildbret in den letzten 10 Jahren zugenommen. Schwarzwild (Sus scrofa), Rehwild (Capreolus capreolus), Damwild (Dama dama) und Rotwild (Cervus elaphus) sind das am häufigsten gejagte Schalenwild in Deutschland. Dennoch gibt es nur wenige Informationen über das Vorkommen von T. gondii in Wildtieren in Deutschland, so dass die Bedeutung von Wild als Quelle für eine Infektion des Menschen mit T. gondii weitgehend unbekannt ist. Ziel dieser Studie war es, die Datenlage zum Vorkommen von T. gondii in Schwarzwild, Rehwild, Damwild und Rotwild in Deutschland zu verbessern und eine fundierte Bewertung des von dem Verzehr von Wildtieren ausgehenden potenziellen Risikos zu ermöglichen. Neben dem indirekten serologischen Nachweis soll der Nachweis mittels direkter Nachweisverfahren einen Einblick in die tatsächliche Anwesenheit von T. gondii im Muskelgewebe und einen potenziellen Zusammenhang von Seropositivität und der Anwesenheit von T. gondii im Gewebe geben. In den Jahren 2017-2020 wurden in Brandenburg 306 Stück Schwarzwild, 184 Stück Rehwild, 80 Stück Damwild und 65 Stück Rotwild beprobt. Den 635 Wildtieren wurden Blutproben und Proben von Herz- und Vorderlaufmuskulatur entnommen. Das aus den Blutproben gewonnene Serum wurde mittels eines kommerziell erhältlichen ELISA untersucht. Zum direkten Nachweis von T. gondii wurde zur Analyse der aus den Muskelproben gewonnenen DNA eine real-time PCR (qPCR) eingesetzt, die auf das 529-bp-repetitive Element abzielt. Die DNA wurde auf drei unterschiedliche Arten gewonnen: direkt aus 5 g Muskelgewebe extrahiert, aus einem Pellet nach saurem Pepsinverdau von 50 g Muskelgewebe extrahiert, und die Ziel-DNA durch Magnetic Capture aus weiteren 50 g Muskelgewebe angereichert. Die Übereinstimmung der Ergebnisse des molekularen Nachweises und ihre Übereinstimmung mit den ELISA-Ergebnissen wurde ermittelt. Der molekulare Nachweis wurde bei 23 Proben von einem Maus-Bioassay begleitet. Zusätzlich wurde eine PCR-RFLP zur Genotypisierung bei qPCR-positiven Proben durchgeführt. Fisher’s exact Test, Cohen’s kappa (κ) und Odds Ratio wurden für die statistische Analyse genutzt. T. gondii-spezifische Antikörper wurden in 20,3 % der Schwarzwildproben, 10,9 % der Rehwildproben und 6,2 % der Rotwildproben nachgewiesen. Bei allen untersuchten Wildarten wurde ein Anstieg der Seroprävalenz mit zunehmendem Alter festgestellt, welcher bei Schwarzwild und Rehwild statistisch signifikant war (p = 0,004 und < 0,001). Bei der Untersuchung von Herzmuskulatur wurde T. gondii-DNA mit mindestens einer direkten Nachweismethode in 11,8 % der Schwarzwildproben, 5,5 % der Rehwildproben, 2 % der Damwildproben und 1,9 % der Rotwildproben nachgewiesen. Der höchste Anteil an Tieren, die positiv auf T. gondii-DNA getestet wurden, wurde durch die qPCR-Analyse von DNA aus 50 g Herzmuskulatur nach Magnetic Capture nachgewiesen (10 %). Die Ergebnisse der Methoden zeigten insgesamt eine mäßige Übereinstimmung (κ = 0,47-0,59). Die höchste Übereinstimmung zeigten die Ergebnisse von DNA aus 50 g Herzmuskulatur nach Pepsin-Verdau und DNA aus 50 g Herzmuskulatur nach Magnetic Capture (κ = 0,59). Insgesamt ergab die Untersuchung von 50 g Herzmuskulatur einen signifikant höheren Anteil an positiven qPCR-Ergebnissen als die Analyse von 5 g Herzmuskulatur (p = 0,048). Die qPCR-Ergebnisse von Herz- und Vorderlaufmuskelgewebe zeigten beim Schwarzwild eine beachtliche und bei der gemeinsamen Betrachtung aller untersuchten Wildarten eine mäßige Übereinstimmung (κ = 0,62 bzw. 0,46). Ein statistisch signifikanter Zusammenhang zwischen Seropositivität und direktem Nachweis war bei Schwarzwild und Rehwild erkennbar (p < 0,001). In allen T. gondii-DNA-positiven Proben, bei denen zusätzlich ein Bioassay durchgeführt wurde, konnte Infektiosität bestätigt werden (4/4). Sowohl in den T. gondii-DNA-positiven Schwarzwildproben als auch in den positiven Rehwildproben waren die spezifischen Allele von T. gondii-Typ II am weitesten verbreitet. Die durch diese Arbeit generierten Daten zeigen, dass T. gondii in Schwarzwild, Rehwild, Damwild und Rotwild in Brandenburg vorkommt und Wild eine relevante Quelle für T. gondii-Infektionen beim Menschen darstellen könnte.
294

AMBIENT ELECTROSTATICS OF IONS AND CHARGED MICRODROPLETS PRODUCED VIA NANOELECTROSPRAY IONIZATION

Saquib Rahman (12030023) 25 July 2023 (has links)
<p>Mass spectrometry, the science and technology of ions, owes much of its current popularity to the development of electrospray ionization. The development of electrospray ionization, along with its low flow-rate analog nanoelectrospray ionization, has increased the chemical space that can be investigated using mass spectrometers by orders of magnitude. While the interfacial chemistry of charged microdroplets that are generated by nanoelectrospray has been studied in detail, the physics of their motion, particularly in the presence of an applied field at ambient pressures, remains relatively unexplored. In this dissertation, an increase in ion currents detected by a commercial triple quadrupole mass spectrometer is used to demonstrate that: (i) the orthogonal injection of counterions into an electrode assembly can compensate for space charge effects and enhance the sampling of charged microdroplets from a nanoelectrospray focused electrostatically under ambient conditions into the mass spectrometer; and (ii) the ease of ion evaporation from charged microdroplets may be elucidated for small molecules based on their relative transmission through an electrode assembly for the simultaneous ambient electrostatic focusing of two nanoelectrosprays. In each case, the development is characterized by using ion trajectory calculations in conjunction with experiments, using homebuilt devices designed and fabricated in-house as rapid prototypes via 3D printing. In the open air, charged microdroplets have low kinetic energies with a narrow energy spread. Despite these limitations, this dissertation demonstrates, through the electrostatic manipulation of charged microdroplets produced via nanoelectrospray ionization, that a better understanding of the physics of moving charges in the open air can be used to increase the sensitivity of atmospheric pressure ionization.</p>
295

GAS-PHASE ION CHEMISTRY AND ION TRAP METHODOLOGIES FOR TRANSMETALATION REACTIONS AND IN-DEPTH LIPID ANALYSIS

Kimberly C Fabijanczuk (17364238) 14 November 2023 (has links)
<p dir="ltr">Originating from J. J. Thomsons original work and the development of electrospray ionization (ESI) by John B. Fenn, mass spectrometry offers a versatile analytical tool to measure beyond an ion’s m/z, especially for biomolecules. Gas-phase ion/ion reactions within a mass spectrometer offers an attractive approach to study biomolecules as they take place on the millisecond and sub millisecond time scale, have high efficiency, allow oppositely charged ions to interact with each other in a controlled manner, and a allows for selection of each reactant prior to the reaction via ion isolation. This can be used to probe gas-phase chemistry that can reflect reactions in solution, however gas-phase reactions have no solvent effects and happen faster, making it a simpler experiment. Here, a variety of gas-phase ion/ion reactions and ion trap methodologies are described to study mostly lipids with a minor amount of transmetalation at the beginning.</p><p dir="ltr">First, a series of multivalent metals complexed to neutral ligands are demonstrated to form ion-pairs with tetraphenylborate anions via ion/ion reactions. The resulting products were subjected to collision induced activation (CID) to observe their involvement in transmetalation, complementary density functional theory (DFT) calculations are provided as well. Next, sequential ion/ion reactions were performed to convert isomeric phosphoinositol phosphates dianions to monocations to reveal structural characterization and isomeric differentiation utilizing tandem MS and dissociation kinetics. The following two chapters after, reports on complementary efforts to separate lipids in the gas-phase of different mass and charge but similar mass-to-charge (m/z) resulting in overlapping m/z signals. The first report demonstrates a physical approach where singly and double charged lipids are separated in space from each other, trapped simultaneously such that no information is lost. The second utilizes a lanthanide, Yb3+ trication complex that underwent ion/ion reactions with singly and doubly charged lipid anions of similar m/z that result in different m/z products for each singly and doubly charged lipids. Lastly, a sequential ion/ion approach utilizing hexa(ethylene glycol) dithiol as a novel reagent to charge invert structurally uninformative lipid cations to structurally informative anions with subsequent carbon-carbon double bond localization.</p>
296

Minghe Li thesis final.pdf

Minghe Li (14184599) 29 November 2022 (has links)
<p>The thesis consists of two main parts of nonlinear optical instrumentation development. </p> <p>Fluorescence-detected mid-infrared photothermal (F-PTIR) microscopy is demonstrated for sub-diffraction limited mid-infrared microspectroscopy of model systems and applied to probe phase transformations in amorphous solid dispersions. To overcome the diffraction limit in infrared imaging, a highly localized temperature-dependent photothermal effect is an attractive alternative indicator to infrared absorption. Photothermal atomic force microscopy infrared spectroscopy (AFM-IR) achieves nanometer resolution by monitoring heat caused expansion but only restricted on the surface. For 3D imaging, optically detected photothermal infrared (O-PTIR) combines an infrared laser with a visible probe source with to transduce photothermal refractive index changes (e.g., from changes in beam divergence or scattering). The sensitivity of O-PTIR is ultimately limited by the relatively weak dependence of refractive index with temperature, exhibiting changes of ~0.01% per oC. Fluorescence-detected photothermal mid-infrared (F-PTIR) spectroscopy (Fig. 1) is demonstrated herein to support 3D imaging with improved photothermal sensitivity. In F-FTIR, the sensitivity of fluorescence quantum efficiency to temperature change (~1-2% per oC) is used to transduce transient heat flux from localized IR absorption. The infrared spatial resolution of F-FTIR is defined by fluorescence microscopy and the thermal diffusivity of the sample instead of infrared wavelength. Initial F-PTIR proof of concept studies are described for microparticle assemblies of silica gel and polyethylene glycol, followed by applications of F-PTIR for analysis of localized composition within phase-separated domains induced by water vapor exposure of an amorphous solid dispersion (ritonavir in copovidone).</p> <p>Fluorescence recovery while photobleaching (FRWP) is demonstrated as a method for quantitative measurements of rapid diffusion mapping over the microsecond to millisecond time scale. Diffusion measurements are critical for molecular mobility assessment in cell biology, materials science and pharmacology. Fluorescence recovery after photobleaching (FRAP) is a well-known noninvasive optical microscopy method for measuring diffusion coefficients of macromolecules, such as proteins in cells and viscous solutions. However, conventional point-bleach FRAP is challenging to implement with multi-photon excitation and typically only supports diffusion analysis over millisecond time scales due to camera frame rate limitations. FRWP with patterned illumination addresses these limitations of FRAP by probing the fluorescence intensity changes while bleaching a comb pattern within a field of view (FoV). Fast-scanning of an ultrafast excitation beam distributes heat rapidly over multiple adjacent pixels, minimizing local heating effects that could complicate analogous diffusion measurements by point-bleach FRAP with multiphoton excitation. In FRWP, time-scales of the probed diffusion events are defined by a single line-pass time of a resonant scanning-mirror with a period of 125  s. In FRWP, the bleach pattern spans locations across the whole FoV, enabling diffusion mapping through image segmentation. More than a hundred bleaching and recovery events can be recorded during a single 10s measurement. Normal and anomalous diffusion of rhodamine-labeled bovine serum albumin (BSA) molecules was studied as a model system, with applications targeting rapid assessment of therapeutic macromolecule mobility within heterogeneous biological environments.</p>
297

Regulation and Testing for Marine Biotoxins

Semones, Molly C. 14 September 2010 (has links)
No description available.
298

GAS-PHASE STUDIES OF METAL IONS IN BIOMOLECULE IONS

Nicole Michelle Brundridge (18290698) 03 April 2024 (has links)
<p dir="ltr">Metal ions are typically considered a nuisance for mass spectrometry, as they can introduce chemical noise and distribute an analyte’s signal into multiple peaks. In some cases however, metal ions in biological solutions are either necessary for biomolecular structures, or so ubiquitous in a sample’s native solution conditions that they are difficult to fully remove. In this work, the role of metal ions in biological analytes is explored. For analytes that require metal ions to maintain higher order structures, a mass spectrometry method was developed to determine whether a stable structure is formed from metal ion adducts, or if the metal ion adducts are nonspecifically bound. Electron transfer of these structures reveals complementary fragmentation information, with the added discovery of new radical fragmentation pathways. With mass spectrometry, specific ligand and metal ion affinities can even be determined for analytes at low enough concentrations. In addition to analytes that require metals, an exploration on unwanted metal ion adduction during the electrospray ionization process is shown via gas-phase ion/ion reactions. Observing how specific anionic ligands exchange metals with protons from proteins on a small and controlled scale gives a greater understanding of what solutions can lead to the cleanest results. In addition, this work shows the possibility of finding anionic ligands that will instead exchange protons with metal ions found on proteins. In the gas-phase, these experiments have a high degree of control, leading to a much greater understanding of how metal ions influence mass spectrometry samples.</p>
299

Contributions to Profile Monitoring and Multivariate Statistical Process Control

Williams, James Dickson 14 December 2004 (has links)
The content of this dissertation is divided into two main topics: 1) nonlinear profile monitoring and 2) an improved approximate distribution for the T² statistic based on the successive differences covariance matrix estimator. Part 1: Nonlinear Profile Monitoring In an increasing number of cases the quality of a product or process cannot adequately be represented by the distribution of a univariate quality variable or the multivariate distribution of a vector of quality variables. Rather, a series of measurements are taken across some continuum, such as time or space, to create a profile. The profile determines the product quality at that sampling period. We propose Phase I methods to analyze profiles in a baseline dataset where the profiles can be modeled through either a parametric nonlinear regression function or a nonparametric regression function. We illustrate our methods using data from Walker and Wright (2002) and from dose-response data from DuPont Crop Protection. Part 2: Approximate Distribution of T² Although the T² statistic based on the successive differences estimator has been shown to be effective in detecting a shift in the mean vector (Sullivan and Woodall (1996) and Vargas (2003)), the exact distribution of this statistic is unknown. An accurate upper control limit (UCL) for the T² chart based on this statistic depends on knowing its distribution. Two approximate distributions have been proposed in the literature. We demonstrate the inadequacy of these two approximations and derive useful properties of this statistic. We give an improved approximate distribution and recommendations for its use. / Ph. D.
300

Environmental and behavioral factors associated with the infestation of vineyards by larvae of grape root borer

Rijal, Jhalendra P. 03 April 2014 (has links)
Grape root borer, Vitacea polistiformis (Harris), is an oligophagous pest of grapevines in the eastern USA. Neonates must burrow into the soil to find grape roots. In Virginia, larvae feed on roots for ~2 years, then pupate just beneath the soil surface. Emerging adults leave an empty pupal exuviae at the soil surface around the vine base. There was no relationship between weekly captures in pheromone traps and pupal exuviae counts, indicating that exuviae sampling is most appropriate to assess infestations. Exuviae sampling in Virginia vineyards revealed infestations that ranged from light to very heavy. Eighteen biotic and abiotic variables were measured and used in analyses that assessed their relative contributions to differences in exuviae density. Water holding capacity and clay/sand ratio were most strongly associated with pupal exuviae density; these variables were used to develop a model for predicting the extent of infestation of individual vineyards. The spatial distribution of pupal exuviae was characterized using non-spatial and geospatial techniques. Although the non-spatial method (Taylor's Power Law) indicated that exuviae showed an aggregated distribution in all blocks, spatial methods (variograms, SADIE) revealed aggregated distributions only in blocks with ≥ 0.5 pupal exuviae per vine. Independent pupal exuviae samples for population assessment in vineyards can be achieved using sampling points separated by >8.8 m. Combined results from geospatial analyses and the temporal distribution of pupal exuviae within years enabled the development of a practical and quantitative sampling protocol. Bioassays used to measure the behavioral response of larvae to host stimuli revealed that neonates were attracted to grape root volatiles. In soil column bioassays, larvae moved vertically and horizontally over distances of up to 120 cm and apparently perceived the presence of grape roots from a distance of 5 cm in soil. Results are discussed in relation to their potential implications for monitoring and managing grape root borer. / Ph. D.

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