Memories are stored in the brain via specific patterns of connectivity between individual neurons. Learning occurs through changes in this pattern of connectivity in response to activity, such that a synapse becomes more or less effective at influencing a postsynaptic neuron. This process, called synaptic plasticity, has been demonstrated at excitatory glutamatergic synapses of the hippocampus, where precise patterns of activity can either increase (long-term potentiation, LTP) or decrease (long-term depression, LTD) synaptic strength. Both LTP and LTD are carried out through changes in the number of postsynaptic AMPA-type glutamate receptors (AMPARs). Therefore, to understand synaptic plasticity, we must also understand the trafficking of AMPARs. In the case of LTP expression, the AMPAR subunit GluA1 is specifically required, and modifications of its cytoplasmic tail (C-tail) are thought to be particularly important for the activity-dependent recruitment of AMPARs. To identify the minimum region of the GluA1 C-tail required for LTP, I used a single-cell molecular replacement strategy where all endogenous AMPARs are replaced with transfected subunits. Surprisingly, I found no requirement for the GluA1 C-tail or for GluA1 generally for expression of LTP. Instead, molecular replacement with either GluA2 or the kainate receptor subunit GluK1 resulted in normal LTP. The only conditions under which LTP was impaired were those with a dramatically decreased pool of receptors on the neuronal surface. Similar to LTP, I also found no specific AMPAR subunit requirement for LTD, which was expressed normally in neurons only expressing GluK1. These results suggest that synaptic plasticity is not necessarily a direct modification of the glutamate receptors subunits themselves, but a broader change in the ability of the synapse to anchor postsynaptic receptors.

The development of efficient tools for plant genome engineering is key to dramatically expedite basic research approaches and, at the same time, facilitate translational and biotechnological strategies in agriculture to improve crops and meet future food demand. For decades, technologies enabling precise Gene Targeting (GT) and efficient DNA knock-in or sequence replacement via Homology-Directed Repair (HDR) in plants has remained challenging, and although some recent reports suggest that progress is being made, no efficient and reproducible protocols have yet been established. Agrobacterium tumefaciens-mediated insertion entails the mobilization of the T-DNA into the host plant genome. However, this process occurs randomly and the system is very inefficient for targeted knock-ins. For this project, we capitalize on the extensive knowledge of Agrobacterium tumefaciens biology and combine it with CRISPR-Cas9 genome editing technologies to develop a novel strategy for high efficiency targeted knock-in. To do so, we decided to engineer Agrobacterium tumefaciens to help us reduce the distance between the T-DNA (harboring the cassette for knock-in) and the Cas9 cut site that marks the location where specifically the targeted insertion will occur. The set of tools we are presenting here will serve not to only accelerate basic research but also assist in engineering crop genomes in order to meet our future food demand in an efficient and sustainable manner.

Today, a billion people lack access to safe drinking water. Climate change, a host of

unsustainable practices, and emerging contaminants threaten to exacerbate the problem.

For the developing-world communities disproportionately affected, limited infrastructure and

resources often preclude the developed-world solutions. New technologies will be necessary.

Unfortunately, even mature technologies often fail in these settings. This work presents two

efforts: one to advance understanding of robust technical interventions and one to improve

water treatment technology for such settings.

In the Poshiir River watershed study, we built comparative case studies of single-village

piped-water drinking water schemes in rural Maharashtra. In-depth datasets were built from

direct technical observations, evaluation of records at national, district, and local levels, and

structured interviews with scheme users and administrators. Redundant information sources

were used to triangulate and assess confidence in our factual findings, which were formalized

in novel node-network models of each scheme-village pair. Hypotheses were developed and

mapped onto these networks via process tracing. We theorize that resilience of a scheme

is dependent on healthy, positive feedback loops within these social-technical networks. We

also took early steps toward typological theories on scheme failures.

In the course of the Poshiir study, we developed a method for rigorously and objectively

reconciling data from disparate sources. For a number of queries on a given topic, the

method takes the array of agreements and disagreements between all sources as inputs; it

generates most-probable values for the validity of each source's response, as well as mean

validities for the sources themselves. Early tests of the method with a verifiable dataset

provide meaningful results, and application to the Poshiir study have returned consistent

scores when assessing comparable cases. While further investigation is certainly required,

the method appears promising.

We also sought to improve the effective flow rate for capacitive deionization (CDI), a

treatment technology for removing ionic species from brackish water. We first proposed two

novel powering arrangements that would accomplish this by increasing effective ion mobility:

optimal powering profiles and pulse-charged CDI. We developed a theoretical model and

governing equations that would allow us to measure internal ion drift rates from externally

observable variables. We then designed, built, and tested a prototype CDI cell capable of operating

in either mode. We performed experimental work, as well as numerical simulations for

pulse-charged CDI over a range of realistic conditions, capturing a set of crucial timescales.

We find that practical restrictions required to avoid redox reactions in pulse-charged CDI

ensure that optimal powering profiles will always offer the greater benefit.

Providing safe drinking water access in the developing world will require a new generation

of technologies. These must be paired, however, with an improved understanding of how to

implement such projects, such that infrastructure proves resilient and impacts prove permanent.

I am optimistic that the work presented here may contribute, incrementally, to each

of these efforts.

California has been an oil and gas state throughout its history. In the latter half of 19th Century and first half of the 20th Century, hydrocarbon extraction helped define both Californian prosperity and the early promise of the West. Many decades later, the Energy Act of 2005 helped to revitalize domestic oil and gas production by exempting a suite of new “enhanced recovery techniques” for well stimulation, commonly referred to as “fracking”, under major federal environmental regulations. This dissertation research engages the subsoil political ecology of California’s petroleum sector in order to explain how well stimulation regulation evolved in California following the rapid deployment of fracking technology across the country that triggered a decade of “Shale Revolution” beginning in 2006. Well stimulation in California represents a case study of the intensely politicized and contested evolution of extractive regimes and their environmental governance at subnational scales in the wake of disruptive technological change. The embedded single-case design employed in this research targets two units of analysis: regulation and frames. Regulation is analyzed using Governance and Political Economy Analysis to assess the structural, institutional, and stakeholder dynamics of California’s oil and gas sector, while frames are analyzed using Frame Analysis of news media and semi-structured open-ended interviews to examine how discourse coalitions construct narratives with which to advance their agendas. This dissertation research contributes to the academic literatures relating to energy systems and their sociotechnical transitions by situating the case of well stimulation regulation in California within the substantive, theoretical, and philosophical debates surrounding the environmental governance of extraction.