A PRELIMINARY GUIDE TO BUILDING NEW FUTURES IN THE NARRAGANSETT BAY

Water, the Ocean and its coasts, estuaries, tidal zones, and waterways are fundamentally necessary to the existence of all life on earth. About half of the world’s population (3 Billion people) live approximately 120 miles from a coastline. The oceans themselves shelter half of all life and sequester about 30% of global carbon emissions – some two gigatons a year. Although they occupy only 0.2% of the seafloor, seagrass ecosystems absorb as much as a tenth of all the organic carbon absorbed by the ocean every year. However, only a fraction of Narragansett Bay’s eelgrass beds remain, having been compromised by impacts of coastal development, nutrient loading from runoff and wastewater discharge, and climate change since the Industrial Revolution in the late 1800s. By reimagining the Narragansett Bay as a coastal and estuarine commons, where humans possess a common stake in the ocean’s future alongside all life on earth, how might competing interests be united under the goal of rebuilding the Narragansett Bay’s eelgrass meadows? This thesis seeks to investigate, map, and iterate on new methods to create accessibility and community involvement in future coastal remediation

Anisotropic chiral d+id superconductivity in NaxCoO2 yH2O

Since its discovery, the superconducting phase in water-intercalated sodium cobaltates NaxCoO2 yH2O (x~0.3, y~1.3) has posed fundamental challenges in terms of experimental investigation and theoretical understanding. By a combined dynamical mean-field and renormalization group approach, we find an anisotropic chiral d+id wave state as a consequence of multi-orbital effects, Fermi surface topology, and magnetic fluctuations. It naturally explains the singlet property and close-to-nodal gap features of the superconducting phase as indicated by experiments.Comment: 4 pages plus references, 5 figure

Fairer, faster, more foreseeable: incentives, throughput and stability of proof of work blockchains

Blockchains employ internal and external incentive structures to influence participant behaviour, maintain network security, and ensure stable throughput. Internal incentives, like block rewards and transaction fees, are embedded within the blockchain design, while external incentives arise from market forces and competition. Both incentive structures are crucial for shaping blockchain behaviour and network efficiency. The primary motivation of this thesis is to examine how misaligned incentive structures can negatively affect stability in Proof-of-Work blockchains, focusing on stable block and transaction throughput. The thesis aims to provide novel insights into the negative impact of unstable throughput on individual agents and the network as a whole. Additionally, it evaluates potential attack vectors resulting from misconstructed incentive structures, past exploits, and proposes fairer and more robust mechanisms to align incentives, ensuring higher throughput stability and network security. The contributions of this thesis include the development of an open-source simulation framework called PoolSim. It enables the analysis of miner behaviour under different mining pool reward distribution schemes, including the profitability evaluation of queue-based manipulation strategies and pool-hopping between such pools. The thesis introduces the uncle traps attack, specific to Ethereum queue-based mining pools, which adversely affects block throughput and presents a fix to the uncle block reward distribution mechanism. Furthermore, this thesis examines the impact of difficulty adjustment algorithms on block throughput. It identifies instability in block solve times due to cyclicality observed in Bitcoin Cash and analyses how miners' behaviour contributes to this phenomenon. A novel difficulty algorithm based on a negative exponential filter is derived, eliminating oscillations and ensuring more stable block solve times. Lastly, the thesis addresses transaction throughput improvement by presenting a gas price prediction model for Ethereum. It combines deep-learning-based price forecasting with an urgency-based algorithm, optimising the trade-off between timely inclusion and transaction cost. Empirical analysis and real-world evaluation demonstrate significant cost savings with minimal delays compared to existing mechanisms.Open Acces

Multiplexed biochemical imaging reveals the extent and complexity of non-genetic heterogeneity in DNA damage-induced caspase dynamics.

Genetically identical cells show a heterogeneous response to a multitude of signals such as growth factors and DNA damage. While this heterogeneity has been shown to be a major determinant of treatment success in several diseases including cancer, little is known about how differences in biochemical signalling networks underlie such heterogeneity. State-of-the-art methodologies to study biochemical networks are often invasive and enable to quantify biochemical events only on cell populations or at a single point in time for a single cell, and therefore, cannot adequately quantify the fast, asynchronous and heterogeneous responses. In order to address these limitations, we have developed a unique sensing platform based on fluorescence lifetime imaging microscopy (FLIM) capable to multiplex at least three biosensors by utilizing Förster Resonance Energy Transfer (FRET) efficiently. After an overall introduction in Chapter 1, I describe the rational design and characterization of novel FRET pairs aiming to utilize the visible spectrum efficiently in combination with FLIM in Chapter 2. We combined blue, green and red donor fluorescent proteins that are excited at the same wavelength (840 nm for two-photon excitation) with genetically encoded quenchers, i.e. non-fluorescent chromoproteins as acceptors. This sensing platform enables the simultaneous detection of three biochemical reactions within single living cells providing new opportunities to characterize and understand non-genetic heterogeneity. In Chapter 3, I will demonstrate the first application of this novel platform by studying the activity of three key enzymes in DNA damage-induced cell death, caspase-2, -3, and -9. We confirm the heterogeneous nature of Cisplatin-induced cell death in genetically identical cells but reveal the existence of at least three subpopulations of cells characterized by distinct caspase dynamics. By combining biochemical and morphological information we infer the existence of different biochemical network topologies that are associated with alternative death phenotypes each cell adopts, such as apoptosis and programmed necrosis. Finally, deconvolution of cellular populations and direct measurement of a three-node caspase network - formerly impossible - permitted us to design perturbations of cell fate choices utilizing clinically relevant inhibitors. These perturbations resulted in changes in cell fate in response to Cisplatin, a clinically desirable outcome that suggests new avenues for combinatorial drugging and a new strategy to reveal cancer vulnerabilities that may be otherwise confounded by typical genetic and non-genetic heterogeneity.Gates Cambridge Trus

Electric quantum walks with individual atoms

We report on the experimental realization of electric quantum walks, which mimic the effect of an electric field on a charged particle in a lattice. Starting from a textbook implementation of discrete-time quantum walks, we introduce an extra operation in each step to implement the effect of the field. The recorded dynamics of such a quantum particle exhibits features closely related to Bloch oscillations and interband tunneling. In particular, we explore the regime of strong fields, demonstrating contrasting quantum behaviors: quantum resonances vs. dynamical localization depending on whether the accumulated Bloch phase is a rational or irrational fraction of 2\pi.Comment: 5 pages, 4 figure