129 research outputs found

    Generation and characterisation of cold atmospheric liquid-containing plasmas

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    This thesis presents an experimental study of non-thermal atmospheric pressure gas plasmas in presence of liquid as an efficient source of transient and reactive species to initiate chemical reactions necessary for many important applications. Two types of liquid-containing plasmas are considered: discharges formed between a needle electrode and a liquid electrode, and plasma jets formed in a water vapour flow mixed in helium or argon gas. Two plasma modes (the pulsed and the continuous mode) are observed in the needle-to-liquid plasma. A comparative study of the needle-to-liquid plasma in the continuous mode with DC and AC excitations reveals that the plasmas are glow discharges, and AC excited plasmas have the highest energy efficiency. A study of helium/water vapour plasma jet shows that “plasma bullets” are formed even with water vapour in the gas mixture, but become quenched when the moist helium flow rate is above 300sccm (~1800ppm water concentration). Moderate amount of water vapour (~250ppm water concentration) is beneficial for active species production mainly due to the high electron density. Hydrogen peroxide production in saline solution with three different plasma sources is investigated due to the importance of H2O2 in several important applications. Long lifetime of H2O2 in the liquid after plasma treatment indicates an exciting possibility of plasma pharmacy

    Chemically bonded phosphate ceramics reinforced with carbon nanotubes

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    We report herein, a scalable method for the preparation of alumina (Al2O3)-phosphate ceramics reinforced with carbon nanotubes (CNTs). All composites were manufactured by direct on-site growth of CNTs on ceramic particles via catalytic chemical vapour deposition. Introduction of catalyst metals to the substrate was achieved through two simple approaches, drip-coating and vacuum filtration, both of which have been reviewed. Transmission electron microscopy was utilised to investigate the interface between the Al2O3 surface and the in-situ CNTs. Resultant ceramics were produced by impregnating phosphoric acid into the Al2O3+CNT nanocomposite powder followed by die-pressing. In order to maintain the integrity of the CNTs, dehydration/curing was performed at 130-150â—‹C. Scanning electron microscopy was elected to comparatively characterise the microstructure of this type of ceramic nanocomposite against its monolithic equivalent. Possible mechanisms by which specific features have formed are discussed

    Manganese Promoted CO Hydrogenation Catalysts: A Study of Metal Promoter Interaction Effects

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    One of the biggest societal challenges nowadays is the quest for alternative fuels that can provide us sustainable energy, the catalytic conversion of syngas, a mixture of CO and H2, is capable of producing a various kinds of alternative fuels such as Ethanol and long chain hydrocarbons. The aim of my PhD work is to investigate the rational design of promoted metal catalysts for CO hydrogenation reactions. The use of promoters is ubiquitous in CO hydrogenation reactions to increase active metal’s activities as well as the selectivity towards desired products. The main body of my work focuses on the use of simple techniques and common elemental precursors to improve the interactions in between a promoter and active metal. One of the many ways of achieving this is through the use of Strong Electrostatic Adsorption (SEA). Special attention to the surface charging parameters of mixed oxide as a function of solution pH can create a driving force to selectively adsorb a precursor complex onto a single phase of a binary mixture. Although, the precise active site of promoters in reactions and how they interact with active metals to react the reactants require many more studies, it is agreed that a key design objective is to increase the metal-promoter interactions. This work demonstrates a procedure to achieve this with Mn promoted catalysts

    Research data for "Exploring stakeholder engagement in urban village renovation projects through a mixed-method approach to social network analysis"

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    Included in this database are raw data on stakeholder relationships and values of stakeholder centrality indicators.</p

    Quantitation of Thioprolines in Grape Wine by Isotope Dilution–Liquid Chromatography–Tandem Mass Spectrometry

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    Cysteine reacts with reactive carbonyls to form thioprolines, which have been demonstrated to possess various pharmaceutical properties. Therefore, thioproline formation is considered as a major detoxification pathway for carcinogenic reactive carbonyls. In this study, we report the initial identification of thiazolidine-4-carboxylic acid (<b>1</b>) and 2-methylthiazolidine-4-carboxylic acid (<b>2</b>), two very common thioprolines, formed by reacting formaldehyde and acetaldehyde with cysteine in grape wine samples. We have developed an isotope dilution–liquid chromatography–tandem mass spectrometry method featuring high sensitivity (limit of detection of ≤1.5 ng/mL) and selectivity to quantitate compounds <b>1</b> and <b>2</b>. The method after validated to be highly accurate (recovery of ≥92%) and precise [intraday relative standard deviation (RSD) of ≤4.1% and interday RSD of ≤9.7%] was applied to determine the varying compound <b>1</b> and <b>2</b> contents in grape wine samples. Results revealed the grape type and storage duration-dependent formation of thioprolines in grape wines. Overall, the results are expected to facilitate compound-dependent investigations of the health benefits of grape wine, and our findings could be adopted to predict the age of grape wine

    ZNF503 combined with GATA3 is a prognostic factor in triple-negative breast cancer

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    Triple-negative breast cancer (TNBC) is a subtype of breast cancer with poor prognosis. Therefore, there is an urgent need to identify prognostic markers to improve current treatment and therapeutic strategies. The transcriptional factor ZNF503 has been reported to promote aggressive breast cancer development through the down-regulation of GATA3 expression and has been identified as a candidate predictive marker. In this study, we explored whether ZNF503 and GATA3 could serve as prognostic markers independently or in combination. We performed a survival analysis of 989 breast cancer patients from The Cancer Genome Atlas (TCGA), and validated the findings in 202 breast cancer patients from tissue microarray (TMA). In TCGA database, the mRNA expression of GATA3 and ZNF503 could not predict TNBC prognosis alone, though the ratio index, ZNF503/GATA3 could be a novel prognostic biomarker in TNBC patients. In TMA database, we detected the protein expression of ZNF503 and GATA3 and found that the combination of the two genes, ZNF503-GATA3, significantly improved the predictive ability of clinical outcomes. The results indicated that the binding index of ZNF503 and GATA3 could be used as a prognostic biomarker in TNBC.</p

    Identification of Protein Thiazolidination as a Novel Molecular Signature for Oxidative Stress and Formaldehyde Exposure

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    Chemical modifications of proteins have been well-documented to play important roles in normal cell physiology such as cell signaling and protein functions. They have also been demonstrated to be one of the milestones in the pathophysiology of many human diseases such as cancer, age-related pathology, and neurodegenerative disorders. Here, we report the initial identification of a novel protein modification, cysteine thiazolidination, through reaction with endogenous and exogenous formaldehyde with cysteine residues in proteins. Using an isotope-dilution liquid chromatography–tandem mass spectrometric (LC–MS<sup>3</sup>) method, we initiated the study by quantitating thioproline in formaldehyde-treated <i>Escherichia coli</i> (<i>E. coli</i>) protein. The study was then extended to quantitate thioproline in protein obtained from formaldehyde- and oxidant-exposed <i>E. coli</i>. Furthermore, <i>N</i><sup>6</sup>-formyllysine, a well-defined formylation product between formaldehyde and lysine, was exploited in a comparative study to evaluate the relative reactivity and amount of cysteine thiazolidination in the reaction of formaldehyde with proteins. It is anticipated that cysteine thiazolidination may serve as a novel biomarker for oxidative stress and formaldehyde exposure

    Study on the Polarization and Relaxation Processes of Ferroelectric Polymer Films Using the Sawyer–Tower Circuit with Square Voltage Waveform

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    Displacement-vs-electric field hysteresis (<i>D–E</i>) loops constructed on the Saywer–Tower circuit have been widely utilized to characterize the ferroelectric performance of ferroelectric materials. To overcome the disadvantages of the current Sawyer–Tower (ST) circuit in overestimated polarization from conduction loss and the disability in reflecting the polarization and relaxation processes, a ST circuit with square voltage waveform is developed for measuring the displacement of ferroelectric materials as a function of time under fixed electric field. By eliminating the conduction loss from the polarization and fitting the experimental results with the theoretical one, the characteristic parameters of a model ferroelectric material, poly­(vinylidene fluoride-trifluoroethylene), have been obtained. The polarization and relaxation processes of the dipoles along the electric field have been finely illustrated for the first time, which cannot be given by the traditional ST possibly. Besides, more accurate parameters are obtained from the ST circuit with square voltage waveform than the traditional one to give an in-depth understanding of the energy storage and energy loss. This work might offer a robust method for the measurement of the polarization and relaxation processes in ferroelectric materials with desired accuracy

    Optically Active Metasurface with Non-Chiral Plasmonic Nanoantennas

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    We design, fabricate, and experimentally demonstrate an optically active metasurface of λ/50 thickness that rotates linearly polarized light by 45° over a broadband wavelength range in the near IR region. The rotation is achieved through the use of a planar array of plasmonic nanoantennas, which generates a fixed phase-shift between the left circular polarized and right circular polarized components of the incident light. Our approach is built on a new supercell metasurface design methodology: by judiciously designing the location and orientation of individual antennas in the structural supercells, we achieve <i>an effective chiral metasurface</i> through <i>a collective operation of nonchiral antennas</i>. This approach simplifies the overall structure when compared to designs with chiral antennas and also enables a chiral effect which <i>quantitatively</i> depends solely on the supercell geometry. This allows for greater tolerance against fabrication and temperature effects

    Regiospecific Ficini [2 + 2] Cycloaddition of Ynamides with Cyclic Isoimidium Salts under Catalyst-Free Conditions

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    The regiospecific [2 + 2] cycloaddition of cyclic isoimidium salts with ynamides is described. This effort led to the development of the first successful example of a catalyst-free, thermally driven Ficini [2 + 2] cycloaddition process of ynamides with α,β-unsaturated carbonyl compounds, giving the stable cyclobutenamides in excellent yields (up to 99%)
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