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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
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