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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.
391

Využití plynové chromatografie ke studiu permeace toxických látek bariérovými materiály / The Study of Permeation of Toxic Compounds through Barrier Materials Using Gas Chromatography

Brtníková, Jana January 2009 (has links)
Transport phenomenon of gas and vapors through polymer barrier materials as well as the factors affecting permeability of gaseous and liquid toxic compounds were investigated and results are presented in this thesis. Permeation characteristics investigation methods were elaborated and verified with focusing on utilization of gas chromatographic method and its instrumental modifications.
392

The Chemistry of Metal Oxyhydroxides and their 3D Porous Hybrid Materials for the Capture, Transport and Degradation of Toxic Chemicals

Devulapalli, Venkata Swaroopa Datta, 0000-0003-1860-9888 January 2023 (has links)
Growing concerns regarding chemical weapons and toxic chemicals require the development and testing of robust materials and methods to capture and destroy these harmful chemicals. This dissertation discusses the fundamental properties (e.g., structure, stability and activity) of metal oxyhydroxide based 3-dimensional porous materials, such as metal organic frameworks (MOFs), and covalent organic frameworks (COFs), and their applications for gas capture and degradation, especially for toxic gases and chemical warfare agent simulants. We report and verify that the active sites in UiO-67 MOFs are the metal nodes (oxyhydroxides) and developed a paradigm which correlates the activities of the MOFs, the metal oxyhydroxides and their precursors. This new understanding can help researchers choose the optimum metal for the intended applications by avoiding the tedious and time-consuming procedures of MOF synthesis and purification. In addition, to characterize and understand the structures of active sites in UiO-67 MOFs, temperature programmed desorption mass spectrometry (TPD-MS) and in situ Fourier-transform infrared (FTIR) spectroscopy were performed under ultra-high vacuum (UHV) and revealed unconventional binding sites and assisted in the successful characterization of missing linker defects. Here, our research helped in identification of a new class of binding sites, via NH-π interactions, in UiO-67 MOFs will assist researchers working in the areas of gas storage/release in developing better materials. This study should facilitate the structural understanding of MOFs, their important attributes such as defects and their chemistry in the presence of toxic gases. After successful identification of active species in MOFs, with the ultimate goal of isolating andii depositing the active sites on porous carbonaceous materials, e.g., COFs, we have engineered a facile technique to synthesize robust nanoparticle-COF and evaluated the reasons for its improved catalytic properties over other materials. The discoveries and their implications discussed in this thesis address fundamental knowledge gaps and should aid the rational design of superior materials for in operando applications. / Chemistry
393

Novel plasma-based ambient desorption/ionization source / 新規大気圧プラズマ解離/電離源 / シンキ タイキアツ プラズマ カイリ デンリゲン / 新規大気圧プラズマ解離電離源

Joey Kim Tumbali Soriano 22 March 2020 (has links)
周囲プラズマベースの周囲脱離/イオン化ソースにより、従来の大気圧イオン化では不可能な周囲条件下でのサンプルの直接分析が可能になります。これにより、面倒な準備と、多くの有害で複雑なサンプルの分析用質量分析計への導入が解消されます。既存のプラズマベースのアンビエント脱離/イオン化ソースは、通常、2つの電極間にキロヘルツから数メガヘルツの範囲の周波数で直流(DC)または交流(AC)電圧を印加することによって形成されます。この研究では、新しいプラズマベースの周囲脱離/イオン化は、13.56 MHz RFソースから供給される非常に低い電力密度で動作する誘導結合によって生成されたワイヤ安定化大気圧プラズマで構成されています。ワイヤ安定化大気圧プラズマの点火特性、安定性およびプラズマ特性を研究した。 / Ambient plasma-based ambient desorption/ionization source enables direct analysis of samples under ambient conditions that traditional atmospheric pressure ionization is incapable. It overcomes the tedious preprocessing and often detrimental and complicated sample introduction to the mass spectrometer for analysis. Existing plasma-based ambient desorption/ionization sources feature an electrical discharge typically formed between two electrodes by applying either a direct-current (DC) voltage or an alternating-current (AC) voltage with frequencies ranging from kilohertz to several megahertz. In this study, a novel plasma-based ambient desorption/ionization consists of a wire stabilized atmospheric pressure plasma produced by inductive coupling operated at very low power density supplied by a 13.56 MHz RF source. The ignition characteristics, stability and plasma properties of the wire stabilized atmospheric pressure plasma were studied. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University
394

The Development, Implementation and Application of Ambient Ionization Mass Spectrometry to Complex Polymeric Systems

Whitson, Sara E. 17 December 2008 (has links)
No description available.
395

Indoor Air Monitoring of Ethanol and Benzene in a Pilot Winery Using Active Sampling

Kaneda, Andrew I 01 March 2019 (has links) (PDF)
Acute indoor concentrations of benzene and ethanol were evaluated in the California Polytechnic State University San Luis Obispo’s pilot winery workroom. Air samples were collected during four different wine-making activities: fermentation, fermentation with Brix content testing, post-alcoholic fermentation pressing, and storage/finishing. Average workroom benzene concentrations ranged from 0.05 to 0.12 mg/m3. Ethanol concentrations in the winery workroom varied with the activity, ranging from 0.9 to 12 mg/m3. Pressing and fermentation with Brix content testing both led to higher indoor ethanol concentrations than fermentation without Brix content testing and storage/finishing. Tracer gas decay air exchange tests were conducted to determine the air exchange rate of the winery workroom. A single-space mass-balance model was used to estimate the air exchange rate for the entire workroom. The calculated air exchange rates were correlated with wind speeds and wind direction to create a linear model estimating air exchange rates based on wind speed. These air exchange rates and the indoor concentrations of ethanol were used with the single-space mass-balance model to calculate an ethanol emission rate for each activity. Total estimated ethanol emissions for the four activities were 3.1 lbs. ethanol per 1000 gallons of wine produced.
396

Chemical analysis of hazardous substances in permanent tattoo inks available on the market / Kemisk analys av skadliga substanser i permanenta tatueringsfärger tillgängliga på marknaden

Bevin, Anna, Lay, An Na, Ullmark, Daniel, Hagman, Jessika January 2020 (has links)
As permanent tattoos are becoming more popular and common, an increased number of allergic reactions to tattoos is reported. The purpose of this project was to analyze tattoo inks for hazardous substances, and whether they comply to current Swedish and European legislative requirements. The tattoo inks were qualitatively analyzed for pigments, and quantitatively analyzed for metals. A total of 73 tattoo inks were collected from various sources such as a tattoo ink supplier, online retailers, and provided directly from tattoo artists. The labels of each tattoo ink bottle were inspected to investigate their compliance with the Council of Europe and the Swedish Medical Products Agency. Matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-ToF-MS) was used to qualitatively analyze 20 selected tattoo inks for different pigments. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantitatively analyze trace metals in 70 of the samples. A large majority (90%) of the tested samples violated the requirements and criteria in the European resolution ResAP 2008(1), such as information on name and address of the manufacturer, minimum date of durability, sterility, batch number, and storage. Patch and allergy testing were incorrectly recommended for many samples in a way that is not accepted by dermatologists. In a worst-case scenario, this testing could be a sensitizing step. Also, it can not prevent future allergic reactions from occurring or provide any juridical insurance. Only one brand, World Famous, fulfilled the requirements for labeling for six of the seven samples (one sample failed due to a faulty declared pigment). The brands Tang Dragon and Dynamic did not fulfill any of the requirements listed in ResAP 2008(1). The list of ingredients was incorrect for all samples from Tang Dragon (bought prior to 2019 online). Also, six of the other 50 samples from different brands (World Famous, Intenze, Fusion Tattoo Ink, Eternal Ink, Solid Ink) declared at least one pigment incorrectly in their ingredients list. 25% of the declared and theoretically detectable pigments were detected by means of MALDI-ToF-MS, whereas the other pigments were either absent or below the limit of detection. Future analyses should include an MS/MS analysis. Polyethylene glycol (PEG) was identified qualatively in 15 of the 20 samples analyzed with MALDI-ToF-MS but was not listed in any of the ingredients lists. ICP-QQQ-MS is a very sensitive technique and could both detect and verify the presence of all metal-containing pigments, as well as the level of impurities. Copper was clearly more present in green and blue colors, regardless of the brand. The metal content was evidently dependent on the brand for arsenic, aluminum, bismuth, chromium, nickel, zinc, and strontium. Elevated levels of barium and strontium (partially very high levels: up to 727 mg/kg barium and up to 8.06 g/kg strontium) were found in several samples. High amounts of aluminum (4 to 11,0 g/kg) and titanium (as judged from white precipitates and ingredients lists) were present in most samples. Nickel (0.1 to 41 mg/kg) and chromium (0.1 to 139 mg/kg) were also present in the samples. Some other impurities were also present (arsenic – 3.8 mg/kg, mercury – 1.6 mg/kg, and lead – 5.4 mg/kg for one sample, respectively). Known sensitizing pigments were declared and partially confirmed by MALDI-ToF-MS in 17 of 53 samples of the brands Radiant Colour, Eternal Ink, Fusion Tattoo Ink, and Kuro Sumi. Four samples (from Intenze, Eternal Ink, and Kuro Sumi) also declared pigments listed as non-suitable substance according to the European Commission regulation on cosmetic products from 2009.
397

Electron-Induced Decomposition of Different Silver(I) Complexes: Implications for the Design of Precursors for Focused Electron Beam Induced Deposition

Martinović, Petra, Rohdenburg, Markus, Butrymowicz, Aleksandra, Sarigül, Selma, Huth, Paula, Denecke, Reinhard, Szymańska, Iwona B., Swiderek, Petra 31 August 2023 (has links)
Focused electron beam induced deposition (FEBID) is a versatile tool to produce nanostructures through electron-induced decomposition of metal-containing precursor molecules. However, the metal content of the resulting materials is often low. Using different Ag(I) complexes, this study shows that the precursor performance depends critically on the molecular structure. This includes Ag(I) 2,2-dimethylbutanoate, which yields high Ag contents in FEBID, as well as similar aliphatic Ag(I) carboxylates, aromatic Ag(I) benzoate, and the acetylide Ag(I) 3,3-dimethylbutynyl. The compounds were sublimated on inert surfaces and their electron-induced decomposition was monitored by electron-stimulated desorption (ESD) experiments in ultrahigh vacuum and by reflection−absorption infrared spectroscopy (RAIRS). The results reveal that Ag(I) carboxylates with aliphatic side chains are particularly favourable for FEBID. Following electron impact ionization, they fragment by loss of volatile CO2. The remaining alkyl radical converts to a stable and equally volatile alkene. The lower decomposition efficiency of Ag(I) benzoate and Ag(I) 3,3-dimethylbutynyl is explained by calculated average local ionization energies (ALIE) which reveal that ionization from the unsaturated carbon units competes with ionization from the coordinate bond to Ag. This can stabilise the ionized complex with respect to fragmentation. This insight provides guidance with respect to the design of novel FEBID precursors.
398

MALDI MASS SPECTROMETRY BASED ASSAYS FOR SCREENING AMINOGLYCOSIDE KINASES

Smith, Anne Marie E. 04 1900 (has links)
<p>Aminoglycoside antibiotics are commonly used to treat bacterial infections but are highly susceptible to chemical modification, leading to resistance. Chemical modification can be hindered through the use of small molecule inhibitors that target bacterial enzymes involved in resistance, most notably kinases. Current methods for the discovery of small molecule inhibitors of kinases and related “kinase-like” enzymes are limited in throughput and utilize slow, tedious, and expensive assays. This thesis is focused on the development of highly versatile and scaleable kinase and “kinase-like” screening platforms for the discovery of small molecule inhibitors of these drug targets. The work begins with the validation of a matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS) platform utilizing phosphorylation of kanamycin, an aminoglycoside antibiotic, by aminoglycoside phosphotransferase 3ʹIIIa (APH 3ʹIIIa) as a model system. Using a product-to-substrate signal ratio as an internal standard, the assay was used to functionally screen over 200 compounds, combined into mixtures to enhance assay throughput. Moreover, the assay was used to determine inhibitory dissocation constants for newly discovered modulators. Throughput was further increased to a novel dual-kinase assay targeting a bacterial enzyme, APH 3ʹIIIa and a human kinase, protein kinase A (PKA), which was validated using the previous small molecule library. Alternative assay development platforms were also studied using imaging mass spectrometry of reaction microarrays and the fabrication of sol-gel derived bioaffinity chromatography columns. The MS-based kinase assays developed herein are highly amenable to high throughput screening, and have the potential to be extended to other important therapeutic targets.</p> / Doctor of Philosophy (PhD)
399

Structure and Ozone Decomposition Reactivity of Supported Manganese Oxide Catalysts

Radhakrishnan, Rakesh 26 January 2001 (has links)
Manganese oxide catalysts supported on Al₂O₃, ZrO₂, TiO₂ and SiO₂ supports were used to study the effect of support on ozone decomposition kinetics. X-ray diffraction (XRD), in-situ laser Raman spectroscopy, temperature programmed oxygen desorption, surface area measurements, extended and near edge x-ray absorption fine structure (EXAFS and NEXAFS) showed that the manganese oxide was highly dispersed on the surface of the supports. EXAFS spectra suggest that the manganese active centers on all of the surfaces were surrounded by five oxygen atoms. These metal centers were of a mononuclear type for the Al₂O₃ supported catalyst and multinuclear for the other supports. NEXAFS spectra for the catalysts showed a chemical shift to lower energy and an intensity change in the L-edge features which followed the trend Al₂O₃ > ZrO₂ > TiO₂ > SiO₂. The trends provided insights into the positive role of available empty electronic states required in the reduction step of a redox reaction. The catalysts were tested for their ozone decomposition reactivity and reaction rates had a fractional order dependency (n < 1) with ozone partial pressure. The apparent activation energies for the reaction was low (3-15 kJ/mol). The support influenced the desorption step (a reduction step) and this effect manifested itself in the pre-exponential factor of the rate constant for desorption. Trends for this pre-exponential factor correlated with trends in NEXAFS features and reflected the ease of electron donation from the adsorbed species to the active center. / Ph. D.
400

Interaction of Na, O₂, CO₂ and water on MnO(100): Modeling a complex mixed oxide system for thermochemical water splitting

Feng, Xu 14 October 2015 (has links)
A catalytic route to hydrogen production via thermochemical water splitting is highly desirable because it directly converts thermal energy into stored chemical energy in the form of hydrogen and oxygen. Recently, the Davis group at Caltech reported an innovative low-temperature (max 850°C) catalytic cycle for thermochemical water splitting based on sodium and manganese oxides (Xu, Bhawe and Davis, PNAS, 2012). The key steps are thought to be hydrogen evolution from a Na₂CO₃/MnO mixture, and oxygen evolution by thermal reduction of solids formed by Na⁺ extraction from NaMnO₂. Our work is aimed at understanding the fundamental chemical processes involved in the catalytic cycle, especially the hydrogen evolution from water. In this project, efforts are made to understand the interactions between the key components (Na, O₂, CO₂, and water) in the hydrogen evolution steps on a well-defined MnO(100) single crystal surface, utilizing x-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD). While some of the behavior of the catalytic system is observed with the model system developed in this work, hydrogen is only produced from water in the presence of metallic sodium, in contrast to the proposal of Xu et al. that water splitting occurs from the reaction of water with a mixture of Na₂CO₃ and MnO. These differences are discussed in light of the different operating conditions for the catalytic system and the surface science model developed in this work. / Ph. D.

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