Browsing by Author "Zhang, Ping"
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Item Design, Fabrication And Assembly Of 3-D Microstructures(Electrical Engineering, 2007-08-23T01:56:30Z)The primary goal of a micro-electro-mechanical system (MEMS) is to integrate electronics, sensors and actuators into a tiny system, which can be easily fabricated and packaged. Currently there is no standard process for manufacturing all the sub-components since a lot of them are made from different materials and fabrication technologies. Therefore, there is a great interest to develop a reliable manufacturing approach that allows for the integration of multiple micro devices on a single chip. This work describes two approaches to achieve this heterogeneous integration: (1) hybrid material integration by introducing new materials into a well-known self-assembly platform (PolyMUMPs) to develop new devices which cannot be achieved by a conventional process. Organic polymer was applied on self-assembled polysilicon microstructures to create new optomechanical devices which can work together with existing micro devices on the same platform. (2) Direct integration of different microcomponents on a common platform by using direct micoassembly. A new active joining mechanism was proposed for this purpose. It can be used for the assembly of microcomponents that are made of different materials, dimensions and shapes. Both of the two techniques have been successfully demonstrated in this thesis. The microparts have been designed, fabricated, and then assembled into self-aligned 3-D out-of-plane structures. In the first approach, polymer was successfully integrated as the optical interface of a transmission-type thin-film filter with self-assembled microstructures. It overcame the inherent high absorption of optical signals in polysilicon, which has restricted its application only to reflection-type devices. In the second approach, an innovative active lock mechanism is developed. It provides both the mechanical and electrical interconnections between the microparts and the target substrate or subassembly. This technique allows each of the microcomponents to be fabricated optimally using respective processes then assembled together. Several proof-of-concept devices, such as free space filters and multiple micro-manipulators for parallel assembly, have been constructed. The results of this work have provided a new way for heterogeneous integration of 3-D microstructures and have resulted in a number of contributions to the MEMS field.Item Projecting U.S. cotton prices in an international market(Texas Tech University, 1991-05) Zhang, Ping.Item The selective effect of dietary n-3 polyunsaturated fatty acids on murine Th1 and Th2 cell development(Texas A&M University, 2006-10-30) Zhang, PingTo examine how dietary n-3 polyunsaturated fatty acids affect Th2 cell development, female C57BL/6 mice were fed a washout corn oil (CO) diet for 1 wk followed by 2 wk of either the same CO diet or a fish oil (FO) diet. CD4+ T cells were isolated from spleens and cultured under both neutral (anti-CD3 and phorbol myristate acetate (PMA)) and Th2 polarizing conditions (anti-CD3 and PMA, in presence of rIL-4, rIL-2, and anti-IFN-????) in the presence of homologous mouse serum (HMS) or fetal bovine serum (FBS) for 2 d. Dietary n-3 PUFA significantly enhanced Th2 cell development and suppressed Th1 development under neutral conditions as assessed by intracellular cytokine staining for IL-4 and IFN-???? as the two prototypic Th2 and Th1 cytokines, respectively. However, under Th2 polarizing conditions, while the suppression of Th1 cells was maintained in FO-fed mice, no dietary effect was observed in Th2 cells. Dietary FO increased the Th2/Th1 ratio under both neutral and Th2 polarizing conditions with HMS in the cultures. To examine the effect of dietary n-3 PUFA on Th1 development, DO11.10 Rag2-/- mice expressing transgenic T cell receptor specific for ovalbumin (OVA) peptide were used. CD4+ T cells were isolated from spleens and lymph nodes and stimulated with ovalbumin (OVA) peptide and irradiated BALB/c splenocytes in the presence of rIL-12, anti-IL-4, and rIL-2 in HMS for 2d. Cells were expanded for another 3 d in the presence of rIL-2 and rIL-12. Dietary n-3 PUFA did not affect Th1 differentiation as assessed by the proportion of IFN-????+, IL-4- T cells in the cultures, but suppressed rIL-2 induced expansion. The suppressed expansion was due to suppressed proliferation (p<0.05). In vivo expansion of antigen-specific T cells was visualized by flow cytometric analysis of CFSE-positive transgenic T cells. Dietary n-3 PUFA did not appear to affect antigen-induced CD4+ T cell cycle progression in vivo. Overall, these results suggest dietary n-3 PUFA have no direct effect on Th2 cell development but do directly suppress Th1 cell development following both mitogenic and antigenic stimulation in vitro.