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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.
161

The chemistry of Algoa Bay ascidians

Bromley, Candice Leigh January 2016 (has links)
This thesis investigates the chemistry of 25 ascidian species collected from Algoa Bay, South Africa with a concerted focus on metal accumulation by these ascidians and the possible interaction of these metals with ascidian metabolites. Chapter 2 details the screening techniques employed to establish the presence of nitrogenous metabolites (1H- 15N HMBC), hyper-accumulated metal ions (ICP-MS) and potential metal ion/ ascidian metabolite complexes (LC-ICP-MS/ESI-MS). Unfortunately, exhaustive attempts to detect intact metal ion/ascidian metabolite complexes through the use of liquid chromatography with parallel inductively coupled plasma mass spectrometry/electrospray mass spectrometry (LC-ICPMS/ ESI-MS) were unsuccessful. However, the LC-ICP-MS/ESI-MS data obtained for the crude organic extracts of six of the Algoa Bay ascidian species, Distaplia skoogi, Aplidium monile, Aplidium sp., Didemnum sp., Leptoclindines sp. and Polycitor sp. enabled identification of a number of ten halogenated metabolites, namely the indoles 2.28-2.30, and the tyramine and tyrosine derivatives (2.31-2.33, 2.41, 2.43, 2.44 and 2.46), within the ascidian extracts. This study confirmed that LC-ICP-MS/ESI-MS is a powerful tool for the dereplication of halogenated metabolites in complex mixtures especially where these compounds are present in very small amounts. This study is also the first report of these compounds (eight of which are known) in African ascidians. Compounds 2.32 and 2.46 have not been reported before from a marine source. Compounds 2.28-2.30 and 2.33 were present in sufficient amounts in the respective ascidian extracts to allow their isolation and structure elucidation using standard spectroscopic techniques Chapter 3 explores the ability of ascidians to accumulate a wide range of metal ions at concentrations which are often orders of magnitude higher than those of the surrounding sea water. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total ion concentrations of 24 metals in 25 Algoa Bay ascidian species. To the best of our knowledge this is the largest and most extensive investigation of metal concentrations in a group of different ascidians occurring in the same area. Hypotheisizing that the metal ion concentrations for each ascidian specimen screened may represent a unique fingerprint for each specimen principal component analysis (PCA) was used in an attempt to establish whether there were spatial, temporal or phylogenetic relationships associated with the metal concentration fingerprints of the ascidians that formed part of this study. The PCA results showed that there were no statistically significant relationships between ascidian metal ion concentrations and either the collection year or the collection site of the ascidians. However, species from the family Didemnidae provided the clearest statistical evidence supporting a phylogenetic relationship between these ascidians and their hyperaccumulated metal ion profiles. Furthermore, these results suggested that ascidian species are indeed actively concentrating metal ions from the surrounding sea water and are not simply sinks for passively accumulated metal ions. Interestingly, the concentration of vanadium in the set of ascidians studied did not appear to correlate with any of the other metals accumulated by these ascidians suggesting that there is possibly a unique method employed for the accumulation of vanadium by ascidians. Chapter 4 investigated this possibility further after the nucleosides 4.10, 4.11, 4.13, 4.15, 4.17 and 4.40 were isolated from the vanadium accumulating ascidian Aplidium monile. Studies into the interactions between nucleosides and vanadyl are unfortunately rare and usually qualitative in nature with limited information provided about the stability or structures of the complexes formed. The vanadyl accumulating aplousobranch ascidians e.g. Aplidium monile dominated our study of Algoa Bay ascidians therefore providing us with the rationale to investigate the relatively little studied binding ability and stability of vandyl-nucleoside complexes. Potentiometric studies were conducted to determine the stability constants of complexes formed between the oxovanadium ion vanadyl (VO2+) and the commercially available nucleosides 4.10-4.14. The data afforded by this analysis clearly confirmed the complexity of the vanadyl/nucleoside complexation and suggested that guanosine (4.12) formed the most stable complex with oxovanadium ions. We were also able to establish a third protonation constant for the hydroxyl moiety in 4.12 with a logK 8.87 which has not been previously reported. Finally, Chapter 5 revisited the cytoxicity two Algoa Bay ascidians, Clavelina sp. and Atriolum marinense the extracts from which produced promising bioactivity results in previous studies against oesophageal cancer cells. The HP-20 fractionated extracts of Clavelina sp. and Atriolum marinense proved to be similalrly cytotoxic to breast cancer cells. With the exception for the 100% acetone(aq)fractions the NMR data for both species suggested that most active non polar fractions were dominated by what appeared to be structurally unremarkable fatty acid glycerides and as such were not pursued further. Purification of the 100% acetone(aq)fraction of A. marinense resulted in the isolation of a styrene trimer, 5.1, common to both ascidian extracts. The NMR simulation software WIN-DAISY was employed to confirm the structure of 5.1. Attempts to establish if 5.1 was an isolation artefact or a product of marine pollution were inconclusive
162

Depozice bioaktivních keramických vrstev pomocí technologie RF-ICP / RF-ICP deposition of bioactive hydroxylapatite coatings

Dukovský, Daniel January 2021 (has links)
Tato diplomová práce se zabývá problematikou plazmového nanášení bioaktivních keramických povlaků hydroxylapatitu s využitím technologie radio-frekvenčně buzeného indukčně vázaného plazmatu. Cílem bylo optimalizovat proces a nanést kompaktní hydroxylapatitové povlaky na substráty z titanové slitiny Ti6Al4V. Nanesené vzorky byly následně podrobeny analýzám povrchové drsnosti, mikrostruktury a fázového složení. Ze získaných výsledků byly vyvozeny závěry, které byly srovnány s dalšími odbornými pracemi zabývajícími se příbuznou problematikou.
163

Stanovení toxických a esenciálních prvků v rostlinných materiálech / Determination of toxic and essential elements in plants

Filipčíková, Marcela January 2009 (has links)
The aim of diploma thesis is occurrence of toxic and essential elements in vegetables and fruit, especially in fruity baby food. The diploma thesis also dedicates processing of vegetables and fruit for production of baby food. Attention is direct to monitoring of baby food quality in the analytical aspects and also to legislative that is in this area. Samples for analysis are prepared using microwave mineralization and ICP-MS for detection. This is described in the experimental part of the diploma thesis.
164

Stanovení kovů ve vinné révě pěstované různými způsoby / Determination of selected metals in grapes cultivated by different techniques

Kubicová, Lenka January 2011 (has links)
The aim of this study is to determine the content of selected metals (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Se, Sn, Sr, Pb, V, Zn) in samples of leaves and grapes produced by ecologic agriculture and compare to results with leaves and grapes produced by integrated agriculture. The measured results used to assess the impact of agricultural technology on the quality of vines and grapes. The amount of elements was analysed using inductively coupled plasma mass spectrometry after previous digestion of sapmles using microwaves. Concentrations of elements in leaves and grapes from organic and integrated farming did not differ significantly only in the case of copper concentrations were measured higher concentrations in samples from organic farming. This difference is probably caused by different doses of authorized protective equipment based on copper in the organic and integrated farming.
165

Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Raman Spectroscopy Imaging of Biological Tissues

Gorishek, Emma Lee 05 1900 (has links)
Laser Ablation Inductively coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectroscopy are both powerful imaging techniques. Their applications are numerous and extremely potential in the field of biology. In order to improve upon LA-ICP-MS an in-house built cold cell was developed and its effectiveness studied by imaging Brassica napus seeds. To further apply LA-ICP-MS and Raman imaging to the field of entomology a prong gilled mayfly (Ephemeroptera: Leptophlebiidae) from the Róbalo River, located on Navarino Island in Chile, was studied. Analysis of both samples showcased LA-ICP-MS and Raman spectroscopy as effective instruments for imaging trace elements and larger molecules in biological samples respectively.
166

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
167

Comparing Theory and Experiment for Analyte Transport in the First Vacuum Stage of the Inductively Coupled Plasma Mass Spectrometer

Zachreson, Matthew R 01 July 2015 (has links) (PDF)
The inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation Monte Carlo algorithm capable of modeling this transitional flow through the mass spectrometer interface, the transitional flow from disorganized plasma to focused ion beam. Their previous work describes how FENIX simulates the neutral ion flow. While understanding the argon flow is essential to understanding the ICP-MS, the true goal is to improve its analyte detection capabilities. In this work, we develop a model for adding analyte to FENIX and compare it to previously collected experimental data. We also calculate how much ambipolar fields, plasma sheaths, and electron-ion recombination affect the ion beam formation. We find that behind the sampling interface there is no evidence of turbulent mixing. The behavior of the analyte seems to be described simply by convection and diffusion. Also, ambipolar field effects are small and do not significantly affect ion beam formation between the sampler and skimmer cones. We also find that the plasma sheath that forms around the sampling cone does not significantly affect the analyte flow downstream from the skimmer. However, it does thermally insulate the electrons from the sampling cone, which reduces ion-electron recombination. We also develop a model for electron-ion recombination. By comparing it to experimental data, we find that significant amounts of electron-ion recombination occurs just downstream from the sampling interface.
168

Testing Direct Simulation Monte Carlo Methods Against the Fluid Equations in the Inductively Coupled Plasma Mass Spectrometer

Somers, William R. 21 August 2008 (has links) (PDF)
A Direct Simulation Monte Carlo fluid dynamics code named FENIX has been employed to study gas flow-through properties of the inductively coupled plasma mass spectrometer (ICP-MS). Simulation data have been tested against the Navier-Stokes and heat equations in order to see if FENIX functions properly. The Navier-Stokes and heat equations have been constructed from simulation data and are compared term by term. This comparison shows that FENIX is able to correctly reproduce fluid dynamics throughout the ICP-MS simulation, with an exception immediately behind the ICP-MS sampler cone, where the continuum criterion for the Navier-Stokes equation is not met. Testing the data produced by Fenix also shows that this DSMC method correctly produces momentum and thermal boundary layer phenomenon as well. FENIX output data produce statistical fluctuations of about 2%. Limitations occur from fitting data near surfaces, incurring a relative error of about 5%, and fitting data to take second derivatives where fluid velocity gradients are steep, introducing a relative error of about 10%.
169

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.
170

A compositional analysis of Roman and early post-Roman glass and glassworking waste from selected British sites. Towards an understanding of the technology of glass-making through analysis by inductively-coupled plasma spectrometry of glass and glass production debris from the Roman/Saxon sites at York, Leicester, Mancetter and Worcester.

Jackson, Caroline Mary January 1992 (has links)
This study is concerned with the compositional analysis of Roman and early post-Roman glass from both domestic assemblages and the remains derived from glass working and producing sites in Britain, using Inductively Coupled Plasma Spectrometry (ICPS). Samples analysed were from glassworking waste from Mancetter (midsecond century), Leicester (third century) and Worcester (first to third centuries), glass production debris, probably manufactured from the raw materials, in conjuncton with a domestic assemblage, from Coppergate (first to fourth centuries, or possibly later), and a domestic assemblage from Fishergate (spanning both the Roman and immediate post- Roman periods). All the glass analysed was shown to be of a typical and uniform soda-limesilica composition, except for a small number of vessel fragments from York which were higher in calcium. Any compositional differences between blue-green glasses typologically dated either to the Roman or Saxon periods, were found not to be consistent. Analysis of the colourless glass showed that the majority appeared to be actively decolorized using antimony, in conjunction with apparent differences In the compositions of the raw materials, when compared to glass of the same date in other 0 colours. Compositional differences between melted waste from Mancetter, Leicester and Worcester, were apparent, but not to an extent which allowed characterization to be successful. Analysis of glassmelting pots from Coppergate showed some high temperature glassworking (and possibly glassmaking) could have occurred. Other debris, thought to be indicative of glassmaking was also analysed and compared to the composition of the Roman domestic assemblage.

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