Variable Response to Chemotherapeutics by a Subpopulation of MCF-7 Breast Cancer Cells

Several different morphologies can be observed in a population of MCF-7 breast cancer cells, but the typical epithelial morphology vastly predominates. After treatment with the chemotherapeutic doxorubicin, the proportion of abnormal morphologies greatly increases. Over the course of recovery from this drug treatment, the population returns back to high proportions of the normal morphologies. However, previous studies in the Brock lab have shown that in rare instances after recovery from doxorubicin treatment, a phenotype termed the "spiky cells" became stable at higher proportions. This population of spiky cells appeared to have characteristics associated with drug-resistant and metastatic cell populations. In this thesis, I tested the aggressive tumor characteristics of this stable spiky subpopulation and whether it responds differently to doxorubicin. I hypothesized that the growth rate, invasiveness, and drug sensitivity of this population would more closely resemble aggressive tumor cells compared with the naïve MCF-7 population. First, I repeated the induction of the spiky subpopulation with a larger sample size, to determine how frequently this spiky subpopulation occurred. Second, I characterized this subpopulation by comparing four groups: untreated controls of both the normal MCF-7 population and the stable spiky population as well as groups from both populations treated with the same concentration of doxorubicin. I performed these comparisons over the 8-week course of recovery from the treatment. These tests included proliferation rate calculations, invasion assays, staining for a critical protein component of cell-cell junctions, and drug sensitivity tests. We found that the spiky subpopulation appeared more aggressive and resistant, with higher invasion and proliferation, fewer surface markers related to cell connections, and decreased drug sensitivity.Biomedical Engineerin

Dynamic testing of docking system hardware

Extensive dynamic testing was conducted to verify the flight readiness of the Apollo docking hardware. Testing was performed on a unique six degree-of-freedom motion simulator controlled by a computer that calculated the associated spacecraft motions. The test system and the results obtained by subjecting flight-type docking hardware to actual impact loads and resultant spacecraft dynamics are described

Inter-Pixel Crosstalk in Teledyne Imaging Sensors (TIS) H4RG-10 Detectors

CMOS-hybrid arrays have recently surfaced as competitive optical detectors for use in ground- and space-based astronomy. One source of error in these detectors that does not appear in more traditional CCD arrays is the inter-pixel capacitance component of crosstalk. In this paper we use a single pixel reset method to model inter-pixel capacitance (IPC). We combine this IPC model with a model for charge diffusion to estimate the total crosstalk on H4RG arrays. Finally, we compare our model results to Fe55 data obtained using an astrometric camera built to test the H4RG-B0 generation detectors.Comment: Accepted to Applied Optics 03-26-1

Generalized universal instability: Transient linear amplification and subcritical turbulence

In this work we numerically demonstrate both significant transient (i.e. non-modal) linear amplification and sustained nonlinear turbulence in a kinetic plasma system with no unstable eigenmodes. The particular system considered is an electrostatic plasma slab with magnetic shear, kinetic electrons and ions, weak collisions, and a density gradient, but with no temperature gradient. In contrast to hydrodynamic examples of non-modal growth and subcritical turbulence, here there is no sheared flow in the equilibrium. Significant transient linear amplification is found when the magnetic shear and collisionality are weak. It is also demonstrated that nonlinear turbulence can be sustained if initialized at sufficient amplitude. We prove these two phenomena are related: when sustained turbulence occurs without unstable eigenmodes, states that are typical of the turbulence must yield transient linear amplification of the gyrokinetic free energy