Search

The magnetoelectric (ME) effect is an electric output in response to an applied magnetic field. In a heterostructure configuration where the two-phases are engineered with close interface contact, a giant electric response to a magnetic field has been found, which is designated as the ME voltage (or charge) coefficient α^ME. This effect is mediated by a mechanical-coupling between magnetostrictive and piezoelectric phases. In this thesis, I concentrate on application study for ME sensors with respect to noise control and rejection, thermal stability, triple-axis sensor design, array imaging, DC and AC magnetic sources detection and active mode ME sensor development, which is important for future ME sensor device applications.

Nature is able to convert chemical energy into mechanical work under modest conditions, i.e., physiological pH and ambient temperature and pressure. One of the most interesting systems is muscle modeled as the "sliding filament" system. The sliding filament system is a combination of a thin actin filament and a thick myosin filament that slide over one another by breaking the "energy-rich" pyrophosphate bond of ATP. The energy from ATP hydrolysis is used for mechanical motion and the energy lost during this process is used to heat our body. In biology, the sliding filament system is taken as a fairly effective model. For engineering systems, the energy lost to heat needs to be reduced to build an efficient energy converter. In our research, we use a phosphate charged protein, casein, and react it with divinyl sulfone (DVS) through a Michael addition reaction to produce a cross-linked gel. The protein gel could be ephosphorylated at standard conditions using bovine phosphatase (bp) and re-phosporylated using casein kinase. When attached to the protein, the negatively charged phosphate groups cause the gel to expand from repulsion. When removed, the protein contracts. Therefore, work is realized without sliding friction, which is the origin of the large energy loss in muscle. FT-IR spectroscopy allows us to follow the two biochemical reactions. We also show a thermodynamic analysis of the work and offer an estimation of the most basic term.

The individual growth model is a relatively new statistical technique. It is now widely used to examine the trajectories of individuals and groups in repeated measures data. This study examines the association of the receptive vocabulary over time and characteristics of children who were treated for brain tumors. The children undertook different types of treatment from one to any combinations of surgery, radiation and chemotherapy. The individual growth model is used to analyze the longitudinal data and to address the issues behind the data. Results of this study present several factors' influences to the rate of change of PPVT scores. The conclusions of this thesis indicate that the decline in the PPVT scores is associated with gender, age at diagnosis, socioeconomic status, type of treatment and Neurological Predictor Scale.

The evolutionarily conserved JAK/STAT pathway plays a critical role in Drosophila hematopoiesis. A gain-of-function mutation of the Janus kinase (JAK), hopscotchTumorous-lethal (hopTum-l), leads to hemocyte overproliferation and abnormal lamellocyte differentiation. In this study, I demonstrated that effects of hopTum-l were manifested in different types of hemocytes and its activity was regulated in various ways. Firstly, hopTum-l affects proliferation and differentiation of hemocytes in a temperature-dependent manner. Male larvae raised at a lower temperature exhibited the most pronounced effect in hemocyte proliferation and were used for further study. Activation of the JAK/STAT pathway in specific compartments of the lymph gland resulted in different proportions of terminally differentiated hemocytes. Furthermore, to understand the regulatory roles of the Drosophila SUMO conjugase Lesswright (Lwr) and the putative Drosophila SUMO ligase protein inhibitor of activated STAT (dPIAS) in the JAK/STAT pathway, lwr and dpias were expressed in the hopTum-l background. Expression of lwr and dpias both suppressed hopTum-l-induced hemocyte overproduction and the effects were additive, which raises the possibility that lwr and dpias egatively regulate the JAK/STAT pathway through SUMOylation. Finally, the JAK/STAT pathway interacts with the Toll (Tl) pathway, another important pathway involved in larval hematopoiesis. Removal of the Tl pathway transcription factors, Dl and Dif, did not diminish hopTum-l-induced hemocyte overproduction. Moreover, activation of the Tl pathway led to nuclear accumulation of activated Stat mainly in lamellocytes, which suggests that the Tl pathway may be functionally upstream of the JAK/STAT pathway in lamellocyte differentiation. On the other hand, activation of the Tl pathway suppressed hopTum-l-induced hemocyte overproduction, possibly through downstream component Dl. This suppression was observed primarily in plasmatocytes, the professional phagocytes of Drosophila. This study revealed specific requirements of the JAK/STAT pathway and its interactions with the Tl pathway in a hemocyte type-specific manner. It has also demonstrated a functional relationship between the JAK/STAT and the Tl pathways in Drosophilalarval hematopoiesis.