Development of a Novel Microwave Sensing System for Lab on a Chip Applications

Microwave technology presents tremendous potential as a remote-sensing technology for a wide range of applications spanning from life science research to food industries, pharmaceutical research, and new material discoveries. Integration of microwave sensing with microfluidics for sample processing makes it an ideal choice for point of care applications highly demanded in resourcelimited areas. The vast majority of the existing microwave sensors are manufactured using sophisticated soft lithography technology which has largely limited its development and applications. There is a large demand for developing new fabrication approaches for the feasibility of mass production at a reasonable cost. In this thesis, a new, yet simple method is developed to fabricate split ring resonator (SRR) based microwave sensors. A simple RLC model is used to characterize the resonant frequency of the SRR, and the equations for calculating the RLC’s resonant frequency is modified to predict the SRR’s resonant frequency base on its geometry. The design is also validated by comparing the simulation results obtained using the commercial software HFSS, and measurements from a real SRR developed sensor. The double ring structure was fabricated onto a printed circuit board by using the industrial photolithograph method. Coating with PDMS and epoxy layer as the passivation layer was tested and compared. Two testing approaches using the SRR sensor developed in this thesis are implemented in this thesis. Their performance for real-time sensing is characterized by applying it to differentiate chemical diary samples and other chemical solutions. In the dipping mode, the sensor is dipped in the material under test (MUT), and in the microfluidic channel mode, the sensor is integrated with a microchannel. The MUT is characterized by analyzing the spectrum data of the reflection coefficient as the function of frequencies. Experimental results indicate that this sensor is capable of differentiating various liquid samples such as DI water, ethanol, isopropanol, oil and salt solutions. Linear relationships between the resonant frequency and the concentrations of chemical composites are also observed in ethanol solutions (0-90%), and salt solutions (NaCl). This sensor is also used to differentiate various milk samples and milk dilutions and it is capable of distinguishing milks with different fat percentages and protein contents. A fully customized vector network analyzer (VNA) is also developed. The circuit structure is designed by referring the existing customized VNAs that were implemented in previous work by iv other lab colleagues. Modifications are made including replacement of the microwave source, using Arduino platform to perform controlling and data acquisition, addition of a harmonic filtering device, and development of a calibration algorithm. The device is validated by comparing its measuring result with a commercial VNA. The customized VNA is able to output a similar spectrum pattern as the commercial VNA, but with slightly shift of the peak frequency

The Expression of Soluble and Active Recombinant Haemophilus influenzae

Immunoglobulin A1 (IgA1) proteases from Haemophilus influenzae are extracellular proteases that specifically cleave the hinge region of human IgA1, the predominant class of immunoglobulin present on mucosal membranes. The IgA1 proteases may have the potential to cleave IgA1 complexes in the kidney and be a therapeutic agent for IgA1 nephropathy (IgAN), a disease characterized by deposition of the IgA1 antibody in the glomerulus. We have screened for the expression of recombinant H. influenzae IgA1 protease by combining various expression plasmids, IgA1 protease constructs, and E. coli strains under multiple conditions. Using the method we have developed, approximately 20–40 mg/L of soluble and active H. influenzae IgA1 protease can be produced from E. coli strain C41(DE3), a significant increase in yield compared to the yield upon expression in H. influenzae or other related bacteria

Family control, institutional environment and cash dividend policy: Evidence from China

Using a sample of 1486 Chinese A-share listed companies for the period 2004–2008, this study empirically tests the impact of family control, institutional environment and their interaction on the cash dividend policy of listed companies. Our results indicate that (1) family firms have a lower cash dividend payout ratio and propensity to pay dividends than non-family firms; (2) a favorable regional institutional environment has a significant positive impact on the cash dividend payout ratio and propensity to pay dividends of listed companies; and (3) the impact of the regional institutional environment on cash dividends is stronger in family firms than in non-family firms. Somewhat surprisingly, we find that controlling family shareholders in China may intensify Agency Problem I (the owner–manager conflict) rather than Agency Problem II (the controlling shareholder–minority shareholder conflict), and thus have a significant negative impact on cash dividend policy. In contrast, a favorable regional institutional environment plays a positive corporate governance role in mitigating Agency Problem I and encouraging family firms to pay cash dividends

State Control, Legal Investor Protection, and Ownership Concentration: Evidence from China

National Natural Science Foundation of China [70588001, 70802002]; Ministry of Education of China [08JC630001]Empirical To control for the omitted-variables and aggregation biases problem existing in previous cross-country studies, our paper investigates the relationship of ownership concentration and legal investor protection across regions and over time in one emerging economy, China, during the period 1992 to 2003. Moreover, this paper examines whether state control affects this relationship. For state-controlled firms, we cannot find the typical inverse relationship between ownership concentration and legal investor protection documented by La Porta, Lopez-de-Silanes, Shleifer, and Vishny (1998), since state per se works as a substitute for formal legal investor protection in protecting property rights by exploiting political power. However, for non-state-controlled firms, the inverse relationship does hold. Our findings suggest that the nature of the controlling shareholder should be taken into account when examining the relationship between ownership concentration and legal investor protection. Moreover, our findings give new insights, especially to the study on other emerging economies that share similar characteristics with China in terms of legal development and government control. Finally, the cross-region study within one country provides a new perspective on the research in this area. First, to provide a level playing field for different types of investors, the state's dual role of controlling shareholder and political power holder should be separated. Second, it is important to build up a good legal system to protect investors in order for a country to develop its capital markets, especially for the development of the non-state sector

MRI T2 mapping and shear wave elastography for identifying main pain generator in delayed-onset muscle soreness: muscle or fascia?

Abstract Introduction The main generator of delayed onset muscle soreness (DOMS) is still unknown. This study aimed to clarify the main generator of DOMS. Methods Twelve participants performed eccentric exercise (EE) on lower legs. MRI and ultrasound were used to assess changes of calf muscle and deep fascia before and after EE. These results were then compared to the muscle pain level. Results Compared to baseline, muscle pain peaked at 24–48 h after EE (downstairs 22.25 ± 6.196, 57.917 ± 9.298, F = 291.168, p < 0.01; resting 5.833 ± 1.899, 5.083 ± 2.429, F = 51.678, p < 0.01). Shear wave speed (SWE) of the deep fascia and T2 values of the gastrocnemius muscle and deep fascia all increased and peaked at 48 h after EE (1.960 ± 0.130, F = 22.293; 50.237 ± 2.963, F = 73.172; 66.328 ± 2.968, F = 231.719, respectively, p < 0.01). These measurements were positively correlated with DOMS (downstairs: r = 0.46, 0.76, 0.87, respectively, p < 0.001; resting: r = 0.42, 0.70, 0.77, respectively, p < 0.001). There was a significant positive correlation between SWE and T2 values of deep fascia (r = 0.54, p < 0.01). Conclusion DOMS is a common result of muscle and fascia injuries. Deep fascia edema and stiffness play a crucial role in DOMS, which can be effectively evaluated MR-T2 and SWE. Critical relevance statement Delayed-onset muscle soreness is a common result of muscle and deep fascia injuries, in which the edema and stiffness of the deep fascia play a crucial role. Both MRI and shear wave elastography can be effectively used to evaluate soft tissue injuries. Key points • The deep fascia is the major pain generator of delayed-onset muscle soreness. • There is a significant correlation between fascia injury and delayed-onset muscle soreness. • MRI and shear wave elastography are preferred methods for assessing fascia injuries. Graphical Abstrac