Ion Transport in Temperature Sensitive Polyelectrolytes

Temperature sensors are widely employed and play a key role in many industries, such as automotive vehicles, medical devices, environmental monitoring, and process control. The state-of-the-art thermal sensing elements are made of rigid and costly inorganic materials, such as vanadium oxide and platinum. These materials have limitations for emerging applications such as wearable devices and prosthetic devices. Ideal temperature sensing materials for such applications need to be flexible, reliable under mechanical deformation, and suitable for large-area production. Electrical conductive polymers were found to be a promising solution because of their flexibility and solution processability. However, they often lag in temperature resolution compared to their inorganic counterparts. A recent discovery revealed that the ionic conductivity of crosslinked pectin, a biopolymer extracted from plant cell walls, has a record-high temperature response. It is biocompatible, flexible when hydrated, and solution-processable, making it a strong candidate for wearable temperature sensing and conformal temperature mapping. However, open questions remain about the origin of its temperature sensitivity and the principles governing its ion transport. Furthermore, the heterogeneity of the complex molecular structure of pectin presents challenges to its integration in sensing devices. In this thesis, we study the origin of the high thermal sensitivity in pectin and develop a synthetic polyelectrolyte that mimics its key structure and properties. In Chapter 3, we focus on the ion transport mechanism in crosslinked pectin. We show that the binding between multivalent ions and certain chemical functional groups of pectin plays a critical role in its temperature sensitivity. In Chapter 4, the impact of water content on the ion transport and dielectric processes in crosslinked pectin is also investigated. In the following chapter, we present a novel synthetic polyelectrolyte designed to mimic pectin with a simpler structure. It has superior flexibility, high temperature sensitivity, and is stable under mechanical deformation. To further study this new material, we examine its ion transport dynamics under varying humidity and temperature conditions in Chapter 7. We discover that temperature and humidity have a similar effect on ion transport. Overall, we showed a biomimetic approach to design temperature sensitive polymers where the strong ion-polymer binding is the key to the ultrahigh temperature response.</p

Optimal bike allocations in a competitive bike sharing market

This paper studies the bike allocation problem in a competitive bike sharing market. To overcome computational challenges, a continuum approximation (CA) approach is applied, where the allocation points and user demand are assumed to be continuously distributed in a two-dimensional region. Companies offering bike sharing service bear both allocation cost and bike depreciation cost while earning revenue from fare collection. The user's selection of bike service is affected by both walking distance and preference towards bike quality. The elasticity of the demand is considered in relation to the density of allocation points in the market. A leader-follower Stackelberg competition model is developed to derive the optimal allocation strategy for market leader. Two sets of numerical studies - one hypothetical case and one from a real case - are conducted to specify the impact of the parameters on model performance and illustrate how the proposed model can be applied to support the decision making.<br/

Enhanced 6D Measurement by Integrating an Inertial Measurement Unit (IMU) with a 6D Sensor Unit of a Laser Tracker

Six-degree-of-freedom (6D) sensors enhance the measurement capability of traditional three-degree-of-freedom (3D) laser trackers. However, the classical 6D measurement techniques still have shortcomings in actual use, such as the problem of line of sight and relatively low data acquisition rate. The proposed approach by integrating an Inertial Measurement Unit (IMU) with a 6D sensor unit of a laser tracker is effective to overcome these limitations. The error is corrected by the combination of a Kalman filter and a backward smoothing algorithm. The Kalman filter only works when the 6D sensor's data is being sent through, while the backward smoothing algorithm works during the whole process. The experiments are performed to compare the error in three positions and three rotational orientations between the proposed method and the Kalman filter and evaluate the effects of different rates and IMU frequencies on the algorithm. The simulations are also performed to estimate the maximum outage time. The results verify that the proposed method can solve the problem of line of sight and low data acquisition rate effectively.</p

Design and development of a ceiling-mounted workshop measurement positioning system for large-scale metrology

This paper presents a new ceiling-mounted workshop Measurement Positioning System (C-wMPS) compensating for many deficiencies shown by conventional metrology systems, especially on the possibility of task-oriented designing for coverage ability, measurement accuracy and efficiency. A hybrid calibration system consisting of a high-precision coordinate control field and standard lengths is developed and implemented for the C-wMPS, which can be designed concretely to provide both traceability and the ability of local accuracy enhancement. Layout optimization using a genetic algorithm based on grids is applied to design an appropriate layout of the system, therefore promotes the system’s performance and reduce cost. An experiment carried out at the Guidance, Navigation and Control laboratory (GNC lab, 40×30×12m) validates the prominent characteristic of C-wMPS and the fitness of the new calibration system and layout optimization method.<br/

Construction of sterile system of Buchloe dactyloides (Nutt.) Engelm.

The stems of male and female strains of Bison grass (Buchloe dactyloides (Nutt.) Engelm.) were taken as explants, and 1 / 2MS and MS medium were used, and different concentrations of NAA, KT and 6-BA were added to study the rapid propagation technology of ferison grass. Results indicated that 75% alcohol was treated for 30s with another 0.1 g ꞏL-1The disinfection effect of mercury solution for 12 min; The MS + 1.5 mg ꞏL-1 NAA + 0.4 mg ꞏL-1 KT female strain showed the best induction effect, The MS + 1.5 mg ꞏL-1 NAA + 0.6 mg ꞏL-1 KT male strain had the best induction effect; 1 / 2 MS + 2 mg + L-1 NAA + 1.5 mg ꞏL-1 6-BA the female and male strains had the best proliferation effect; The highest number of roots and root root rate of 1 / 2 MS + 1.5 mg ꞏL-1 female and male NAA strains were combined

The Inhibitory Effect of Regulatory T Cells on the Intimal Hyperplasia of Tissue-Engineered Blood Vessels in Diabetic Pigs

Severe inflammatory response and functional impairment of endothelial progenitor cells (EPCs) often lead to the implantation failure of EPC-captured tissue-engineered blood vessels (TEBVs) in diabetes. Regulatory T cells (Treg cells) are the most important inhibitory immune cells, but their effects in angiogenesis remain undefined, and the differences in the microenvironment may be an important reason. Here, we constructed a TEBV coated with an anti-CD34 antibody-functionalized heparin-collagen multilayer (anti-CD34 antibody-modified TEBV) using layer-by-layer self-assembly. Then, TEBVs were implanted into diabetic pigs. All TEBVs remained unobstructed 60 days after implantation, although varying degrees of intimal hyperplasia were detectable. Severe intimal hyperplasia was observed in the control group and peripheral injection of Treg cells group. Intravenous injection of Treg cells significantly inhibited intimal hyperplasia, inflammation, and cell apoptosis. Moreover, intravenous injection increased the proportion of circulating EPCs, while peripheral injection did not have these effects and reduced microvessel density around the TEBV. Interestingly, many Nestin+ cells could be detected in TEBVs, most of which were fusiform, showing the characteristics of smooth-muscle cells. Treg cell intravenous transplantation markedly reduced the number of Nestin+ cells in the TEBV. In conclusion, Treg cells inhibited the intimal hyperplasia of TEBVs in diabetic pigs by promoting EPC mobilization, anti-inflammatory action, and cellular protection