Single-spin scanning magnetic microscopy with radial basis function reconstruction algorithm

Exotic magnetic structures, such as magnetic skyrmions and domain walls, are becoming more important in nitrogen-vacancy center scanning magnetometry. However, a systematic imaging approach to mapping stray fields with fluctuation of several milliteslas generated by such structures is not yet available. Here we present a scheme to image a millitesla magnetic field by tracking the magnetic resonance frequency, which can record multiple contour lines for a magnetic field. The radial basis function algorithm is employed to reconstruct the magnetic field from the contour lines. Simulations with shot noise quantitatively confirm the high quality of the reconstruction algorithm. The method was validated by imaging the stray field of a frustrated magnet. Our scheme had a maximum detectable magnetic field gradient of 0.86 mT per pixel, which enables the efficient imaging of millitesla magnetic fields.Comment: 5 pages, 3 figure

Focusing particles by induced charge electrokinetic flow in a microchannel

This is the peer reviewed version of the following article: Song, Y., Wang, C., Li, M., Pan, X. and Li, D. (2016), Focusing particles by induced charge electrokinetic flow in a microchannel. ELECTROPHORESIS, 37: 666–675. doi:10.1002/elps.201500361, which has been published in final form at http://dx.doi.org/10.1002/elps.201500361. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A novel method of sheathless particle focusing by induced charge electrokinetic flow in a microchannel is presented in this paper. By placing a pair of metal plates on the opposite walls of the channel and applying an electrical field, particle focusing is achieved due to the two pairs of vortex that constrain the flow of the particle solution. As an example, the trajectories of particles under different electrical fields with only one metal plate on one side channel wall were numerically simulated and experimentally validated. Other flow focusing effects, such as the focused width ratio (focused width/channel width) and length ratio (focused length/half-length of metal plate) of the sample solution, were also numerically studied. The results show that the particle firstly passes through the gaps between the upstream vortices and the channel walls. Afterwards, the particle is focused to pass through the gap between the two downstream vortices that determine the focused particle position. Numerical simulations show that the focused particle stream becomes thin with the increases in the applied electrical field and the length of the metal plates. As regards to the focused length ratio of the focused stream, however, it slightly increases with the increase in the applied electrical field and almost keeps constant with the increase in the length of the metal plate. The size of the focused sample solution, therefore, can be easily adjusted by controlling the applied electrical field and the sizes of the metal plates

Master of Arts

thesisThis thesis investigates the predicate cleft (PC) constructions in Mandarin Chinese. Cheng & Vicente conclude that the topicalized verb and the lower verb in bare PC form a long head movement relation, discarding a remnant movement analysis based on vP-external scrambling. However, to be complete, the argument also needs to consider vP-internal scrambling observed by Soh and a selective deletion analysis. I show that vP-internal scrambling cannot serve to derive a plausible remnant movement analysis; nor can a selective deletion analysis be accomplished. Long head movement is necessary to account for Mandarin bare PC. However, although this conclusion converges with cross-linguistic treatment of predicate clefts, I point out the unreliability of idiom interpretation as a diagnostic for long head movement used in several studies. Moreover, I present the puzzling restriction on the types of categories that can undergo pied-piping with the fronted verb. Last, I show that the verb doubling effect, an unresolved issue in Cheng & Vicente, can be accounted for, if the proposal on parallel chains is adopted. The necessity of a long head movement analysis supports bare phrase structure whereby head-to-spec movement is expected. In addition, it constitutes as an empirical argument against eliminating syntactic head movement. The compositionality of idiom interpretation and the restriction on full PC are worth further study

A compact high-power-density servo drive design

Brushless DC motors are indispensable components in contemporary industrial, medical, military and household appliances. Due to its high efficiency, long life, large starting torque and flexible control speed control, it has received extensive attention. With the rapid development of modern motor technology and communication technology, the size of heavy-duty industrial equipment, precision control instruments and advanced detection devices is reduced, and a compact brushless DC motor driver with high integration and reliability and advanced communication networks interface is compatible to meet the requirement of the market and industrial. This thesis is investigating how to design and evaluate a compact drive module to drive three-phase BLDC motor with both hardware and software for the brushless DC motor control system in a significant compact size, which could be used on medical equipment, robot arm and vehicles in a small scale. This research investigates the fundamental mathematical BLDC motor model and develops controllers and motor driver according to certain design requirements. The motor driver is designed based on the STM32F107 microcontroller from STMicroelectronics and the DRV8332 Integrated Digital Motor Control module with a three-stage power supply strategy. To achieve the correct computation of the BLDC motor, three complementary PWM drive signals, motor control communication command and several warning structures have been built. Finally, a compact PCB board with the corresponding driving program are presented with proved performance

Evaluating Comparative Effectiveness of Simultaneous Liver and Kidney Transplant versus Liver Transplant Alone using Instrumental Variables

Improving the quality of medical care often requires assessment of comparative effectiveness between treatments. Although randomized controlled trials (RCTs) are considered as the gold standard for generating evidence, they may not be feasible or ethical to conduct for some comparisons. Therefore, observational studies are required to address many research questions. However, observational data may lead to a high potential for selection bias because subjects or physicians choose their treatments, which may complicate the estimation of causal effects. As one approach to overcome these issues, instrumental variables (IVs) can be used to potentially estimate unbiased causal effect in the setting of observational comparative effectiveness research. The goal of this thesis is reducing unmeasured confounding in an observational study to compare the effectiveness of simultaneous liver and kidney transplants (SLKT) versus liver-only transplants (LTA) in patients who were on the liver transplant wait list with dialysis. We hypothesize that SLKT could lower mortality by replacing both organs in the same operation. A two-stage least squares (2SLS) was used to estimate causal effects. The first stage was regressing treatment on IV and covariates to determine whether IV met the assumption of strongly predicting treatment. Then, the second stage least squares analysis was performed by regressing outcome on estimated treatment and covariates. This analysis used several strategies for formulating the IV based on geographic region, with similar results. Although our IV met the necessary assumptions, results did not show a significant causal relationship between treatment and mortality. Findings of this thesis are significant to public health because more than ten thousand patients in the US are on the liver transplant waiting list. While performing both a kidney and liver transplant in these patients may save lives, we are not aware of any other studies that evaluated this problem using IVs or other approaches that potentially account for unmeasured confounding. By evaluating the causal effects of the different transplant approaches, physician and patients can make more informed decision. The information may also be important for organ allocation strategies nationally

A114: Promoting Exercise Behavior for College Students by Compensating Intervention of Beliefs

Purpose: Compensatory Health Beliefs (CHBs) are essential to resolving the motivational conflicts between the desired and healthy goal in college students. Theory of Planned Behavior (TPB) framework is used to design a multidimensional training model, which compensates belief as a mediator, to research the influence of belief intervention compensation on promoting right exercise cognitive and behavior in college students. The purpose of this study was to discover whether this training model is able to inspire college students to attend exercise more effectively. Methods: A cohort of 218 college students from Guangzhou were involved in the research (20.04±1.5). The objects were divided into two groups. A total of 110 objects in the control group were mentored by professional physical exercise instructor, while for the rest 108 objects in the interventional group who received 45-minute lessons about compensatory beliefs 5 days per week for 12 weeks on top of professional physical exercise instructor. All objects were asked to write a tracker daily for self-monitor daily exercise behavior and mental condition. All objects were asked by the researcher to fill out the Exercise Motivational Conflict Questionnaire and the International Physical Activity Questionnaire one week before and after the intervention. The correlations of compensated beliefs and other two variables were analyzed with descriptive data analysis, independent sample T-test, and multiple regression. Results: The subjects in the intervention group had higher levels of the exercise behavior than those in the control group. Multiple regression analysis indicated that the exercise motivational conflict has significantly positive correlations to exercise behavior (β = 0.47, SE = 0. 41, P \u3c 0. 01). By adding compensated belief in the intervention group, exercise motivational conflict still has significantly positive correlations to exercise behavior（β = 0.47, SE = 0.41, P \u3c 0.01）. The compensated belief has a significant effect among exercise motivational conflict and exercise behavior (β=0.26，SE=0.16，95% CI= (0.03 ~ 0.11) indirectly. Therefore, the mediating effect of compensated belief plays a significant role in promoting the effect between exercise motivational conflict and exercise behavior. Conclusion: The study indicated that the training model can positively predict college students’ exercise motivational conflict and exercise behavior and encourage college students to do exercise effectively. Meanwhile, compensated belief is an effective mediator which can reduce the problem of lack of exercise among college students