A mathematical model and numerical method for thermoelectric DNA sequencing

DNA sequencing is the process of determining the precise order of nucleotide bases, adenine, guanine, cytosine, and thymine within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases in a strand of DNA. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Thermoelectric DNA sequencing is a novel method to sequence DNA by measuring the heat that is released when DNA polymerase inserts a deoxyribonucleoside triphosphate into a growing DNA strand. The thermoelectric device for this project is composed of four parts: a microfluidic channel with a reaction zone that contains DNA template/primer complex, the device\u27s lower channel wall, the device\u27s upper channel wall and a thin-film thermopile attached to the external surface of the lower channel wall which measures the dynamic change in temperature that results when Klenow polymerase inserts a deoxyribonucleoside triphosphate into the DNA template. Mathematical models of DNA sequencing methods can be very helpful in specifying the important DNA sequencer design parameters for optimal sequencer performance. This dissertation is to propose mathematical models that can predict the temperature change in thermoelectric DNA sequencing devices. To this end, a two-dimensional model is first developed to simulate the chemical reaction in the reaction zone and the temperature distribution in a cross-section of the device. A more sophisticated three-dimensional model is then developed, which considers the convection-diffusion process in the microchannel, the chemical reaction in the reaction zone, and the temperature change in the whole device. Because of the nonlinearity of equations, the models must be solved numerically. In particular, in this research, a Crank-Nicolson scheme is employed to discretize the convection-diffusion equations and energy equations, and the ODE solver odel5s (which uses the Gear\u27s method) in MATLAB is used to solve the chemical reaction equations. As such, concentrations of the reactants and the temperature distributions in the device are obtained. Results indicate that when the nucleoside is complementary to the next base in the DNA template, polymerization occurs, lengthening the complementary polymer and releasing thermal energy with a measurable temperature change of about 0.4-0.5 mK. This implies that the thermoelectric conceptual device for sequencing DNA may be feasible for identifying specific genes in individuals. Furthermore, mathematical and numerical methods are used to test the influential elements of temperature change by varying operational parameters and microfluidic device design variables. Results can be useful to provide the information on optimizing the DNA sequencer design parameters

Phase Open Fault Tolerant Control of High Reliability Doubly-Salient Wound-Field Machine

Doubly Salient Wound-Field Machine (DSWFM) can be employed on aeronautics starter-generator because it has good performance on both power generation and starting. To improve the system reliability, a three-phase four bridge legs converter which has fault tolerant capability is proposed to solve one phase open-circuit fault problem of the DSWFM. And the advantage of the proposed converter to the full-bridge converter fault-tolerant mode is analyzed. With the study of DSWFM theory and torque equation, a constant torque fault-tolerant strategy is proposed to keep the performance and reduce the torque ripple. The drive system after fault identification can be reconstructed by the proposed method, and the machine performance can recover quickly. Simulations confirm the feasibility of the proposed fault tolerant system

Influence of Acculturation on Risk for Gestational Diabetes Among Asian Women.

INTRODUCTION:Asian women have a higher prevalence of gestational diabetes mellitus than women of other races/ethnicities. We aimed to compare the prevalence of gestational diabetes among Asian American women to other racial/ethnic groups and explore whether the higher occurrence of the disorder among Asian women can be explained by acculturation. METHODS:We conducted a population-based, cross-sectional study among 5,562 women who participated in the 2007 Los Angeles Mommy and Baby Study (LAMB) in Los Angeles County, California. All women included in this study had a live delivery in 2007 and did not have pre-pregnancy type I or II diabetes. We applied multivariate, weighted logistic regressions to compare gestational diabetes prevalence among racial/ethnic groups, adjusting for its known risk factors. We conducted mediation analysis to test whether the difference in prevalence across racial/ethnic groups could be explained by acculturation. RESULTS:Among the 5,562 women studied, the weighted prevalence of gestational diabetes was 15.5% among Asian American women, followed by 9.0% among non-Hispanic black women, 10.7% among Hispanic women, and 7.9% among non-Hispanic white women. Compared with non-Hispanic white women, Asian women had 2.44 (95% confidence interval [CI], 1.81-3.29; P < .001) times the odds of having gestational diabetes, independent of maternal age, education, marital status, income, prenatal care adequacy, prepregnancy BMI, and physical activity. Acculturation was negatively associated with having gestational diabetes (odds ratio [OR] = 0.93; 95% CI, 0.86-0.99) and explained 15.9% (95% CI, 11.38%-25.08%; P < .001) of the association between Asian race and the condition. CONCLUSION:We found that Asian race was an independent risk factor for gestational diabetes, and higher acculturation may play a protective role against it in Asian American women

Effect of Growth Temperature and Time on Morphology and Gas Sensitivity of Cu 2

A facile hydrothermal synthesis with CuSO4 as the copper source was used to prepare micro/nano-Cu2O. The obtained samples have been characterized by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). With increasing the reaction temperature and time, the final products were successively Cu2O octahedron microcrystals, Cu2O/Cu composite particles, and a wide range of Cu spherical particles. The gas sensitivity of products towards ethanol and acetone gases was studied. The results showed that sensors prepared with Cu2O/Cu composites synthesized at 65°C for 15 min exhibited optimal gas sensitivity. The gas sensing mechanism and the effect of Cu in the enhanced gas response were also elaborated. The excellent gas sensitivity indicates that Cu2O/Cu composites have potential application as gas sensors