Browsing by Subject "invasion"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item From Theory to Application: Extreme Fire, Resilience, Restoration, and Education in Social-Ecological Disciplines(2012-07-16) Twidwell, DiracConceptual and theoretical advancements have been developed in recent years to break down the assumptions and traditional boundaries that establish seemingly independent disciplines, and the research outlined in this dissertation aspires to build on these advancements to provide innovative solutions to a broad array of modern problems in social-ecological. I used a variety of techniques to address challenges ranging from disconnections between theory and application, perceived versus realized roles of prescribed fire in resprouting shrublands, and the need for broader participation in research as part of undergraduate education. The chapters in this dissertation serve as a case-study approach across multiple scientific disciplines that overcome the traditions and assumptions that conflict with our ability to develop innovative solutions to modern social-ecological problems. First, I bridge theoretical and applied concepts by showing how recent theoretical advancements in resilience can be integrated into a predictive framework for environmental managers. Second, experimental data from multiple experiments were collected in two ecological regions of Texas to assess the potential for using extreme fire, in isolation and in combination with herbicide, as a novel intervention approach in resprouting shrublands of the southern Great Plains. The findings from these experiments demonstrate the importance of moving past traditional assumptions of when prescribed fire should be applied to demonstrate new patterns of woody plant responses to the applications of ?more extreme? prescribed fires while not causing undesirable invasions by exotic grasses and exotic insects. Finally, I initiated a PhD instructed course on undergraduate research that sought to increase undergraduate participation while lowering the costs of conducting research. This chapter shows how traditional approaches of supporting undergraduate research are incapable of meeting the broader goals established by society and reveal a novel approach that can provide an additional pathway for supporting undergraduate student participation at large, research-based universities. Ultimately, this research suggests that our capacity to enhance services in social-ecological systems ultimately hinges upon the integration of theoretical and applied concepts that drive policy and governance and overcoming the assumptions and traditions that limit their integration.Item The Impact of Extracellular Matrix Stiffness on Angiogensis(2012-12-06) Lee, Po-Feng 1976-Sprouting endothelial cells (ECs) use soluble and insoluble cues to guide migration and expand the existing vascular network to meet changing trophic needs of the tissue during angiogenesis. A noninvasive and non-destructive nonlinear optical microscopy (NLOM) technique was used to optically image endothelial sprouting morphogenesis in three dimensional (3D) collagen matrices with simultaneously captured signals from collagen fibers and endothelial cells using second harmonic generation (SHG) and two-photon excited fluorescence (TPF), respectively. Sprout advancement and lumen expansion companying with ECM alteration were the synergistic results of membrane-associated matrix metalloproteinase and cell traction evidenced by proteinase inhibition and Rho-associated kinase (p160ROCK) inhibition experiments. These physical EC-ECM interactions suggest that ECM mechanical properties may influence angiogenic responses. In a 3D angiogenesis model, we measure angiogenic responses as a function of collagen matrix stiffness by inducing collagen cross-linking with microbial transglutaminase (mTG). Collagen matrices stiffen with both mTG treatment and incubation time as evidenced with biaxial mechanical test results and collagen TPF intensity increases with mTG treatment and that the ratio of TPF/SHG correlates with biaxial tested mechanical stiffness. SHG and optical coherence microscopy (OCM) are further used to show that other physical properties of the matrix do not change with mTG treatment, thus providing the same density but different stiffness with which to measure angiogenic responses. Stiffer matrices promote angiogenesis with more invading sprouts that invade deeper. No differences in lumen size were observed between control and mTG stiffened 3D cultures, but there was evidence of greater matrix remodeling in stiffer gels using NLOM. Results of this study show angiogenic responses are enhanced with increasing stiffness and suggest that these properties may be used in tissue engineering and regenerative medicine applications to engineer angiogenesis.