135 research outputs found
Cu–Polymetallic Deposit Exploration under Thick Cover in Gucheng–Yaxi Area Using Audio-Magnetotelluric and Spread-Spectrum-Induced Polarization
No full textSuccessful geophysical exploration projects in the Gucheng–Yaxi area located in Gaochun District, Jiangsu Province, China, have been limited partly due to the complex geological conditions of the area and high artificial noise in data acquired using electrical and electromagnetic methods. In this study, we deployed the new anti-interference spread-spectrum-induced polarization method (SSIP) and the audio-magnetotelluric (AMT) method to detect a copper–polymetallic deposit in the area. Two-dimensional inversion results in the Gucheng–Yaxi area revealed a high chargeability anomalous zone on the SSIP profile that coincided with a zone of moderate resistivity located between two resistor bodies on the AMT profile. A follow-up 1200 m drill hole was established at this high-chargeability, moderate-resistivity zone which encountered polymetallic (copper, lead, zinc, gold, and silver) mineralization at a depth of ≥400 m. Drill hole data analysis showed that mineralization occurred interspaced in the marble rock mass at varying depths. Furthermore, several low-resistivity, weak-chargeability sections were revealed and attributed to Cretaceous sediments and faults. These faults are thought to have played a critical role in the polymetallic mineralization genesis. In summary, this study demonstrated the successful of application of SSIP and AMT in detecting a metallic deposit in an area with high artificial noise. Hence, the geophysical prospection potential of the Gucheng–Yaxi area is great
Nanomaterials for Surface-Enhanced Raman Spectroscopy and Application in Trace Detection
No full textWith the advances in nanomaterials and nanofabrication, surface-enhanced Raman spectroscopy (SERS) has been extensively developed and applied in the trace detection of various analytes in either a simple or a complicated sample matrix. This includes, but is not limited to, the detection of antibiotic residues in animal-producing meat products, detection of pathogenic bacteria in human body fluid, and detection of heavy metal contamination of water. This book, consisting two review articles and five research articles, covers the most recent progress and advancement in the development and application of various nanomaterials in SERS trace detection. In this book, a broad range of topics is covered, from the synthesis of novel nanomaterials that can provide improved reproducibility of SERS signals to the development of new application protocols that can facilitate the reliable detection of trace amounts of analytes without interfered by the sample matrices significantly. This book is a useful source for both new and advanced researchers in the field of SERS and its application
Nanomaterials for Surface-Enhanced Raman Spectroscopy and Application in Trace Detection
No full textWith the advances in nanomaterials and nanofabrication, surface-enhanced Raman spectroscopy (SERS) has been extensively developed and applied in the trace detection of various analytes in either a simple or a complicated sample matrix. This includes, but is not limited to, the detection of antibiotic residues in animal-producing meat products, detection of pathogenic bacteria in human body fluid, and detection of heavy metal contamination of water. This book, consisting two review articles and five research articles, covers the most recent progress and advancement in the development and application of various nanomaterials in SERS trace detection. In this book, a broad range of topics is covered, from the synthesis of novel nanomaterials that can provide improved reproducibility of SERS signals to the development of new application protocols that can facilitate the reliable detection of trace amounts of analytes without interfered by the sample matrices significantly. This book is a useful source for both new and advanced researchers in the field of SERS and its application
Development of innovative techniques for food authentication - the last barrier to prevent food fraud
No full textFood fraud was estimated to cost the global food industry $10-15 billion per year. Various traceability and risk assessment systems have been developed to deter food fraud. With rapid globalization and complex supply chain, effective product tracing and tracking and accurate vulnerability assessment have been inevitably hindered. Serving as the last barrier to ensure food authenticity, reliable techniques to identify fraudulent foods are indispensable. Traditional techniques (e.g. liquid chromatography-based assays) are usually time-consuming, labor- intensive, lack the sensitivity and/or specificity, and/or complicated. Therefore, the overall objective of my Ph.D. thesis project was to validate the feasibility of spectroscopic techniques [i.e. Raman, mid-infrared, and nuclear magnetic resonance (NMR) spectroscopies] and an advanced DNA amplification method [i.e. loop-mediated isothermal amplification (LAMP)] to detect food fraud.
During my studies, an optimized protocol was developed to authenticate ground beef meat and identify and quantify the offal adulterants using mid-infrared spectroscopy coupled with chemometric models, providing a limit of detection (LOD) <10% w/w of offal in ground beef meat. With simple/no sample pretreatment, solution NMR spectroscopy and solid-state NMR spectroscopy were confirmed to detect 6.7 and 128.6 mg/kg Sudan I in paprika powder in <30 min, respectively. A confocal micro-Raman spectrometer and a portable Raman spectrometer were applied to identify 11 species of raw finfish purchased from seafood markets in Vancouver. The method developed using the portable Raman spectrometer exhibited promising results with a
100% accuracy in differentiating Salmonidae and non-Salmonidae, 88% accuracy in identifying four species of salmon, and 91% accuracy in separating the seven species of non-Salmonidae fish. A LAMP-based assay was developed to authenticate pure pomegranate juice from juice adulterated by apple and/or grape juice. With a novel paper-based DNA extraction device and a simple LAMP result visualization method, the overall sample-to-result analysis was completed in ~1 h with a LOD of 10~100 ng of DNA.
Methods and devices developed in my studies may be used to authenticate many other food commodities and have the potential to be adopted by governmental laboratories, food industries and even consumers to rapidly authenticate food products, and thus better ensure the integrity of foods.Land and Food Systems, Faculty ofGraduat
Development of innovative biosensors for the determination of melamine in milk
No full textAfter discovering the potential detriment of melamine to humans, the society calls for novel techniques to accomplish accurate, rapid, high-throughput, and on-line or in-field detection of melamine in foods, as required by the food industry and government laboratories. The aim of this study was to investigate different innovative biosensors combining antibodies or molecularly imprinted polymers (MIPs) with surface enhanced Raman spectroscopy (SERS) to determine melamine in a representative dairy product (i.e. milk).
A “two-step” antibody-SERS biosensor was developed to detect melamine in whole milk. The anti-melamine antibody, produced by immunizing New Zealand white rabbits with melamine hapten-ovalbumin immunogen, was used to extract melamine from whole milk exclusively. After releasing melamine from the antibody, the eluents were deposited onto silver dendrite SERS-active substrate for SERS spectral collection. The limit of detection (LOD) calculated by the principal component analysis (PCA) model was lower than 0.79×10-³ mmol/L. The overall analysis was completed in 20 min.
The MIP for the “two-step” MIPs-SERS biosensor was synthesized by bulk polymerization of melamine, methacrylic acid, ethylene glycol dimethacrylate and 2,2’-azobisisobutyronitrile. After confirming the specific affinity of the MIP towards melamine by adsorption capacity tests, MIP was used as sorbent for solid phase extraction (SPE) to extract melamine from whole milk. SERS spectra were collected by depositing the eluents from MISPE onto silver dendrite. The LOD and limit of quantification (LOQ) calculated by the linear regression model correlating relative intensity of melamine SERS band at 703 cm-¹ and melamine concentration in whole milk were 0.012 mmol L-¹ and 0.039 mmol L-¹, respectively, and the full analysis was accomplished in 18 min.
“One-step” MIPs-SERS biosensor incorporated silver nanoparticles (AgNPs) into MIPs synthesized by bulk polymerization. Adsorption capacity tests verified the specific affinity of MIPs-AgNPs to melamine, and PCA model resulted in the LOD between 0.01 and 0.017 mmol L-¹ melamine in skim milk. The time required to detect melamine in skim milk was 25 min.
The low LOD and LOQ, as well as rapid detection confirm the potential of applying these three types of biosensors for accurate and high-throughput detection of melamine in dairy products.Land and Food Systems, Faculty ofGraduat
Modelling and development of a resonator-based noise mitigation system
No full textAnthropogenic underwater noise generated by pile driving has been an issue of serious concernfor a long period of time. The underwater noise pollution from pile driving could pose a threatto marine mammals. To reduce the low-frequency noise, many offshore companies developvarious treatments and alternatives for pile driving. In this study, the focus is placed on aresonator-based noise mitigation technique.The first part of the thesis focuses on the investigation of the existing resonator-based noisemitigation systems. A mathematical expression for the resonance frequency of an individualopen-ended resonator is derived. To validate this expression, a finite element model is built inCOMSOL. To compare the acoustic performance with the HSD, a finite element model is alsobuilt for the HSD mitigation system. To describe the acoustic performance of the resonatorsfor generic use, the frequency response function of an open-ended resonator is analyticallyderived based on the assumption that the resonator behaves as a linear SDoF system. Thederivation of the parameters of the equivalent SDoF system representing each individualresonator is based on appropriate fitting of numerical results obtained in COMSOL.The second part of the thesis deals with the development of a new design of a resonator systemnamed Qiu. To install the resonator system in a more flexible way, the air is encapsulated inthe resonator. A finite element model is also developed in COMSOL for the Qiu resonator.In the last part of the thesis, a three-dimensional vibroacoustic model is developed in orderto find the optimal properties of the underwater resonator and to improve the existing noisemitigation techniques. The model requires the proper description of the noise source, theresonator and the acoustic waveguide. The normal mode method is used to compose theGreen’s function of the waveguide. The boundary element method is then employed in orderto obtain the total pressure field. The frequency response functions derived in the first partof the thesis are subsequently used to describe the acoustic behaviour of the resonators. Aparametric study is presented in order to define the principal factors for effective noise mitigation.In addition, the several cases are investigated in order to obtain the optimal propertiesof the resonator and the optimum configuration of the array of resonators surrounding thesound source to maximise noise reduction.Offshore and Dredging Engineerin
Numerical Convergence Study of Heterogeneous Multi-scale Method Piezoelectric Composites
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Rapid Pomegranate Juice Authentication Using a Simple Sample-to-Answer Hybrid Paper/Polymer-Based Lab-on-a-Chip Device
No full textThe impact of market imperfections on stock prices : an empirical analysis of AH price premium in China
No full textWith the development of financial market, many Chinese companies have taken the opportunity to go public by listing on various stock exchanges. Besides mainland China, many companies have chosen Hong Kong Stock Exchange to benefit from its international recognition and its tie with mainland China. Contrary to what has been observed in other countries with similar dual-class structures, H shares that are open for off-board investors in Hong Kong trade at a discount relative to A shares that are restricted to domestic investors in mainland China. Such price difference, known as ”Puzzles in the Chinese Stock Market”, exists persistently at both cross-sectional and time-series horizon. We argue that price difference between A shares and H shares could be a result of market imperfections in China. Structural market imperfections, such as asymmetric information, speculative motive, liquidity preference, market sentiment and differential demand, have explanatory power in the existence of AH price premium. We utilize Ordinary Least Squared (OLS) estimation and Generalized Method of Moment (GMM) estimation to study all existing hypotheses thoroughly. Moreover, we argue that capital control in China plays a unique and significant role in interpreting AH price premium. By using panel data, our empirical results reinforce most of existing hypotheses and provide strong quantitative support for proposed hypotheses of capital control. We find, for example, a company with higher oversea revenue ratio tends to have lower AH price premium.Bachelor of Arts in Economic
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