Design and Implementation of Position-Encoded Microfluidic Microsphere-Trap Arrays

Microarray devices are useful for detecting and analyzing biological targets, such as DNAs, mRNAs, proteins, etc. Applications of microarrays range from fundamental research to clinical diagnostics and drug discovery. In this dissertation, we consider a microsphere array device with predetermined positions of the microspheres. The microspheres are conjugate on their surfaces with molecular probes to capture the targets, and the targets are identified by the microspheres\u27 positions. We implement the microsphere arrays by employing microfluidic technology and a hydrodynamic trapping mechanism. We call our device microfluidic microsphere-trap arrays. To fully realize the potential of the device in biomedical applications, we utilize statistical performance analysis, mathematical optimization, and finite element fluid dynamics simulations to optimize device design, fabrication, and implementation. Our device is promising as a cost-effective and point-of-care lab-on-a-chip system. We first analyze the statistical performance of position-encoded microsphere arrays in imaging biological targets at different signal-to-noise ratio (SNR) levels. We compute the Ziv-Zakai bound (ZZB) on the errors in estimating the unknown parameters, including the target concentrations. Through numerical examples, we find the SNR level below which the ZZB provides a more accurate prediction of the error than the posterior Cramer-Rao bound (PCRB) does. We further apply the ZZB to select the optimal design parameters, such as the distance between the microspheres, and to investigate the effects of the experimental variables such as the microscope point-spread function. We implement the arrays by using microfluidic technology and hydrodynamic trapping. We design a novel geometric structure for the device, and develop a comprehensive and robust framework to optimize its geometric parameters that maximize the microsphere arrays\u27 packing density. We also simultaneously optimize multiple criteria, such as high microsphere trapping efficiency and low fluidic and imaging errors. Microsphere-trapping experiments performed using the optimized device and an un-optimized device demonstrate easy control of the microspheres\u27 transportation and manipulation in the optimized device. They also show that the optimized device greatly outperforms the un-optimized one. We extend our optimization framework to build a device that enables simultaneous, efficient, and accurate screening of multiple targets in a single microfluidic channel, by immobilizing different-sized microspheres at different regions. Different biomolecules captured on the surfaces of the different-sized microspheres can thus be detected simultaneously by the microspheres\u27 positions. We employ finite element fluid dynamics simulations to investigate hydrodynamic trapping of microspheres, and to study the effects of the geometric parameters and critical fluid velocity. The accuracy of the time-dependent simulations is validated by experimental results. The simulations guide the device design and experimental operation. The guidelines on the simulation set-up and the openly available model will help researchers apply the simulation to similar microfluidic systems that may accommodate a variety of structured particles

Study of internet usage in the fresh produce supply chain in the UK and China

A thesis submitted for the degree of Master of Philosophy of the University of BedfordshireFresh produce supply chain management faces a high level of complexity and uncertainty and a number of challenges due to fresh produce's perishable, seasonal and fragile characteristics. It is argued that effective implementation of Information and Communication Technologies (leTs) has great potential for improving efficiency and reducing wastage within the fresh produce (fruit and vegetable) supply chain. While' the Internet is used by many small and medium-sized enterprises (SMEs) in the fresh produce industry, the extent to which it is applied and further developed after the initial adoption varies widely. Much research has been carried out to investigate Internet adoption and usage, but very limited effort has been focused on the identification of the current level of technology integration and deve!opment and the factors affecting the level of the development after the adoption, especially in the context of SMEs in the fresh produce supply chain. This research attempts to address this issue by developing a theoretical framework to illustrate the evolutionary process of Internet adoption and diffusion and to identify factors affecting the development of Internet-based supply chains by following the Technological/Organisational/Environmental (TOE) framevork. First, five development levels of post-adoption of Internet technologies in the supply chain were defined, and factors from the technological, organisational and environmentalcontexts were identified according to literatures and exploratory interviews. Second, questionnaire surveys were conducted in the UK and China to investigate the current situation of internet technologies used by SMEs in the fresh produce supply chains in the two countries. Finally, factors the proposed framework were validated and discussed. The empirical findings show that the Internet is no longer a new technology for most fresh produce SMEs in the UK and China. However, a large proportion of SMEs surveyed are still using basic functions of the Internet, and there is little difference between the UK and Chinese SMEs when comparing the use of complex applications in the supply chains. The results also show that most of the factors in the organisational and technological contexts are positively related to the current development levels of the Internet-based supply chain, whereas, in the environmental context, pressures from customers in the UK and mutual trust among partners in China have a significant impact on current development levels. Additionally, in both countries, companies in a better development level of Internet-based supply chain would achieve a higher degree of integration in their supply chain in five years. Overall, the research has made a number of important contributions to knowledge, current debate and practice in an under-researched sector. The five-level post-adoption framework can be adapted to identify ICT development levels and key factors in other sectors. The empirical data collected has added value to and sheds lights on the current applications of the Internet in the supply chain in general, and in the fresh produce SMEs in China and the UK in particular. The key factors identified as impeding the further development of the Internet, such as factors related to the business environments in the UK and China, will help government policy-makers, supply chain facilitators and IT service providers to be more focused in their efforts to improve the situation and to stimulate the further diffusion of emerging Internet technologies. The research has certain limitations due to the time constraints and sample selections. These limitations provide a platform for directing future research

Der sehnsüchtige Androgyne

Die Kulturgeschichte der männlichen Homosexualität und deren filmischen Darstellungen im Queer-Film in China; die Arbeit beinhaltet eine DVD mit Filmszenen

User Multi-Interest Modeling for Behavioral Cognition

Representation modeling based on user behavior sequences is an important direction in user cognition. In this study, we propose a novel framework called Multi-Interest User Representation Model. Specifically, the model consists of two sub-models. The first sub-module is used to encode user behaviors in any period into a super-high dimensional sparse vector. Then, we design a self-supervised network to map vectors in the first module to low-dimensional dense user representations by contrastive learning. With the help of a novel attention module which can learn multi-interests of user, the second sub-module achieves almost lossless dimensionality reduction. Experiments on several benchmark datasets show that our approach works well and outperforms state-of-the-art unsupervised representation methods in different downstream tasks.Comment: during peer revie

Leverage Business Analytics and OWA to Recommend Appropriate Projects in Crowdfunding Platform

Nowadays, crowdfunding is becoming more and more popular. Many studies have been published on the crowdfunding platform from different perspectives. However, among all these studies, few are concerned about the recommendation methods, which, in effect, are highly beneficial to crowdfunding websites and the participants. Having considered the situation talked above, this paper works out the several features from the relative projects of user’s current browsing project. Then we give different weights to each feature based on selective attention phenomenon, and adopt the method of OWA operator to calculate the final score of each relative project and accomplish our model by picking out the four projects with different outstanding characteristics. Finally, according to the statistics on China’s famous crowdfunding website, we conducted a group of contrast experiments and eventually testified that our proposed model could, to some extent, help classify and give recommendation effectively. Furthermore, the results of this research can give guidance to the management of crowdfunding websites and they are also very significant advices for the future crowdfunding website development

Effect of Cured Time on Creep of Lightweight Aggregate Concrete

Creep and shrinkage are such properties that will occur in concrete when they are under load and exposed to surrounding. Since this property will cause deformation which may decrease the design strength of the concrete, it is necessary to do have more knowledge on this phenomenon. So, we will study the effect of creep on 7 and 14 days of cured time of specimens which sealed or unsealed will be considered, respectively. The specimens have shown how the concrete strains when they are under sustained load with time. Besides, the sealed specimens have shown how the basic creep is different from the total creep of concrete. Further, the specimens of loading at different ages have shown how the age at application of load influences creep. The result of the experiment has shown the relationship of strain under sustained load and time. Moreover, it is shown that creep is mainly related to the strength developed in the concrete

Study of Water Permeability of Lightweight Concrete

The relationship between water permeability and different levels of the tested layers from the top surface to the bottom surface of the lightweight concrete specimens is determined in this study. It is beneficial to develop the design criteria for a durable lightweight concrete. The water permeability coefficient K of the samples was determined by water permeability test using GWT. It is found that the water permeability coefficient K of the three layers in each set of samples tends to decrease as the level of the tested from the top surface increase. Larger Rebound Number and higher density in the bottom layer and more coarse lightweight aggregates in top layer correlate with the result of the descending water permeability trend and also indicate the existence of floatation of lightweight aggregates. Therefore, concrete uniform is very important for lightweight concrete

Preparation and Supercooling Modification of Salt Hydrate Phase Change Materials Based on CaCl2 2H2O/CaCl2

Salt hydrates have issues of supercooling when they are utilized as phase change materials (PCMs). In this research, a new method was adopted to prepare a salt hydrate PCM (based on a mixture of calcium chloride dihydrate and calcium chloride anhydrous) as a novel PCM system to reduce the supercooling phenomenon existing in CaCl2 6H2O. Six samples with different compositions of CaCl2 were prepared. The relationship between the performance and the proportion of calcium chloride dihydrate (CaCl2 2H2O) and calcium chloride anhydrous (CaCl2) was also investigated. The supercooling degree of the final PCM reduced with the increase in volume of CaCl2 2H2O during its preparation. The PCM obtained with 66.21 wt % CaCl2 2H2O reduced the supercooling degree by about 96.8%. All six samples, whose ratio of CaCl2 2H2O to (CaCl2 plus CaCl2 2H2O) was 0%, 34.03%, 53.82%, 76.56%, 90.74%, and 100% respectively, showed relatively higher enthalpy (greater than 155.29 J/g), and have the possibility to be applied in buildings for thermal energy storage purposes. Hence, CaCl2 2H2O plays an important role in reducing supercooling and it can be helpful in adjusting the solidification enthalpy. Thereafter, the influence of adding different percentages of Nano-SiO2 (0.1 wt %, 0.3 wt %, 0.5 wt %) in reducing the supercooling degree of some PCM samples was investigated. The test results showed that the supercooling of the salt hydrate PCM in Samples 6 and 5 reduced to 0.2 C and 0.4 C respectively. Finally, the effect of the different cooling conditions, including frozen storage (20 C) and cold storage (5 C), that were used to prepare the salt hydrate PCM was considered. It was found that both cooling conditions are effective in reducing the supercooling degree of the salt hydrate PCM. With the synergistic action of the two materials, the performance and properties of the newly developed PCM systems were better especially in terms of reducing the supercooling degree of the PCM. The novel composite PCMs are promising candidates for thermal energy storage applications