As the demand for wearable devices and mobile technology is increasing rapidly, a smaller but more powerful integrated circuit (IC) is needed. However, as the chip technology has reached its limit to extend Moore’s law, the 3D packaging technology is currently the most promising way to improve transistor density while fulfilling the downsizing requirement of a silicon chip. Compared to currently applied 2D IC system, one of the most distinctive structures to realize the vertical stacking in 3D IC is the use of microbumps to join the through-Si vias (TSV) vertically. The diameter of microbumps (<10 μm) is much smaller than the traditional control-collapse-chip-connection (C-4) flip chip solder joints (~100 μm) and ball-grid-array joints (BGA, ~760 μm). The dramatic change in solder joint size brings new challenges in two aspects: (i) The intermetallic compound (IMC) formed in solder joint will eventually turn into only one grain structure from a polycrystalline structure. Structural anisotropy begins to strongly affect microstructure evolution kinetics and properties. (ii) The surface-to-volume ratio is greatly increased. In this thesis, a systematic study of Cu-Sn surface interdiffusion is conducted on both 30 �m wide Cu-Sn free surface which is fabricated by FIB and Sn/Cu pillars with diameter of 2 �m. A 2-step surface IMC formation mechanism is proposed to explain the protrusion of surface IMC formation on Cu-Sn surface. In the first step, the surface IMC forms much faster on the surface of Cu3Sn layer than on any other layers. In the second step, the surface IMC will form on Cu surface. The IMC forms in the first step will have a potential threat to 3D IC reliability when the diameter of the microbump is below 2 �m. A simple kinetic model of surface diffusion-controlled surface IMC growth at Cu3Sn layer is proposed which explains the tendency of the lateral IMC growth, and it can be used to estimate the failure time for 3D IC which is caused by contact shorting due to the surface IMC growth.

Sustainable Urban Water Management (SUWM), a new approach to manage stormwater as a water resource instead of nuisance, has the potential to supplement the diminishing traditional water supplies as well as reducing surface water pollution from storm runoff. Uncertainties of public health risks represent one of the main barriers for the smooth transition to SUWM approach as urban stormwater is known to be highly variable in water quality and is less studied than the conventional water supplies. My research is aimed at improving our state-of-knowledge for the public health risks associated with the SUWM practices. Using the Quantitative Microbial Risk Assessment (QMRA) framework as my main research tool, I investigated the risk implications of three SUWM scenarios: 1) rainwater harvesting, 2) stormwater harvesting, and 3) discharging stormwater into recreational water. As household-level rainwater harvesting is the most readily implementable SUWM approach, I first investigated the public health risks associated with using the rooftop harvested rainwater for household produce irrigation—a reasonable scenario considering the relatively clean water quality of rainwater. My result showed that the risk associated with consuming produce irrigated by harvested rainwater exceeded the EPA’s benchmark for safe drinking water, but is still at least ten-fold lower than when reclaimed water is used for the same purpose. To investigate the risks associated with capturing, treating, and reusing urban stormwater collected from urban developments, I examined three non-potable household applications: 1) toilet-flushing, 2) showering, and 3) foodcrop irrigation. My results showed that harvested stormwater is only safe for toilet-flushing under the circumstances considered. However, interpretations of the risks also differ depending on the risk benchmark used for comparison. In my final case study, I adopted a new contamination source apportionment QMRA method to investigate the recreational health risks associated with discharging stormwater into a popular recreational beach. My results showed that sewage contamination of urban stormwater is the governing factor for elevated risks in the water. However, the risk levels are within the acceptable risk set by the U.S. EPA in most of the cases in spite of the violation of water quality standard due to contribution of fecal bacteria from non-human sources. The overall finding of my research demonstrated that the QMRA is a powerful tool to provide a scientific basis for SUWM decisions. The risk outcomes can be used to set the appropriate public health risk management guidelines and water legislation that are necessary for the progress of SUWM practices.

During times of unpredictable stress, organisms must adapt their gene expression to maximize survival. Along with changes in transcription, one conserved means of gene regulation during conditions that quickly represses translation is the formation of cytoplasmic phase-separated mRNP (messenger ribonucleoprotein) granules. Two well-known stress-induced mRNP granules are processing bodies (P-bodies) and stress granules. Previously, we identified that distinct steps in gene expression can be coupled during glucose starvation stress as promoter sequences in the nucleus are able to direct the subcellular localization to or excluded from the phase-separated granules and translatability of mRNAs in the cytosol. During my Ph.D., I have been investigating the underlying mechanisms of how promoter dictates the cytoplasmic fate of mRNAs during glucose starvation. Chapter 1 is a background introduction of the questions I asked. In chapter 2, I led a discovery of a promoter-directed mechanism mediated by AAA+ proteins Rvb1/Rvb2 that couple the transcription, mRNA cytoplasmic localization, and translation of select genes during glucose starvation. In chapter 3, colleagues and I reviewed recent findings regarding stress-related phase-separated granules and shared our insights. Chapter 4 describes 3 projects that aimed to answer the promoter-dictation question from other perspectives, such as expression timing and promoter motifs. Finally, Chapter 5 discusses insights and future directions for my thesis work. I anticipate that these studies will provide us with more insights into complex gene regulation during stressful and pathological conditions.