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From pole to shoreline: constraining mantle structure and flow to understand past sea-level change
No full textAccurately predicting the magnitude, timing, and spatial distribution of sea-level change over the coming centuries is crucial for understanding its impact on coastal communities around the world. As the climate continues to warm, efforts to model and predict the response of Earth’s ice sheets to climate warming requires deep knowledge of how ice sheets and sea level interact with the solid Earth. Reconstructing sea level during past warm periods can provide unique constraints on ice sheet processes during warming but requires the correction of paleo shorelines for solid Earth deformation.
Chapters 2 and 3 of this thesis focus on reconstructing sea level during Pliocene warm periods from paleo shorelines by understanding their geomorphology and deformation history. The solid Earth also directly affects ice sheets since it provides important boundary conditions (e.g., heat flow) and feedback mechanisms (e.g., glacial isostatic adjustment). Chapter 4 of this thesis provides a new model of seismic attenuation below Antarctica, which is an important constraint for temperature and viscosity that govern the state of the Antarctic mantle.
In Chapter 2, I present an estimate of early Pliocene (~5 Ma) global mean sea level inferred from three paleo shorelines in Patagonian Argentina. Despite their similar age (~5 Ma), these shorelines are observed today at elevations that vary by >50 m. They archive not only sea level millions of years in the past but also dynamic changes in Earth’s topography arising from glacial isostatic adjustment and thermally driven mantle convection. We model and correct for both processes and infer that global mean sea level during the early Pliocene peaked at 17.5 6.4 m (1). This implies significant sectors of West Antarctica and parts of East Antarctica were likely ice free during this time, a constraint which ice sheet models can leverage to improve the parameterization of ice sheet instability mechanisms. Our simulations further elucidate patterns of mantle flow through the Patagonian slab window.
In Chapter 3, I apply a similar approach, expanding to a global dataset of ten wave cut escarpments that formed during mid-Pliocene times (~3 Ma). In addition to better constraining -mid-Pliocene sea level using direct inferences from paleo shorelines corrected for geodynamic deformation, this study provides an observational dataset for benchmarking convection models. We include Pliocene scarps from the US East Coast, Nome (Alaska), De Hoop (South Africa), Mahafaly (Madagascar), Kongo Central (DRC), Benghazi (Libya), Al Wusta (Oman), Socotra (Yemen), Darling (Australia), and Roe Plain (Australia), constrain their elevations with high-resolution remote sensing, and correct for talus deposition on the surface. This reveals short wavelength patterns of topographic change, which we compare against geodynamic predictions.
Our best estimate of mid-Pliocene global mean sea level, after correcting for paleo shoreline deformation, comes from De Hoop, South Africa from which we use to infer a peak GMSL of 11.6 ± 5.2 m (1). This estimate is lower than our early Pliocene inference, which is in line with cooling over the course of the Pliocene and provides further constraints on Antarctic ice sheet change. Lastly, our data-model comparison informs future model development and highlights the need for robust parameterization of compositional and thermal anomalies in the mantle.
The final chapter aims to constrain lateral variations in attenuation in the Antarctic upper mantle. Attenuation is a critical geophysical observable that informs inferences of mantle properties, such as temperature and viscosity, from seismic tomography models, enabling better parameterization of glacial isostatic adjustment, which can stabilize or slow ice sheet retreat. Rock mechanics experiments have characterized the anelastic processes that drive a nonlinear relationship between slow seismic waves speeds and high mantle temperatures. This relationship includes 7 free parameters that can be constrained using various geophysical constraints. Here we use full wavefield simulations and waveform amplitude measurements to constraint these parameters. This results in a new high-resolution 3-D upper mantle attenuation model computed using seismic wave speeds and the laboratory-based anelastic parameterization. The preferred model reduces the total amplitude misfit relative to a 1-D reference model by 13.1% and 0.4% on the 25 – 60 and 50 – 150 second period bands, respectively.
From pole to shoreline, this thesis connects topographic change driven by slab window mantle flow beneath Argentina to millions-years old escarpments around the world to ice sheet-ice shelf collapse processes in Antarctica and the mantle properties underneath. The results highlight the important role that the mantle below coastlines and ice sheets plays in improving our understanding of past, present, and future ice sheet variability and sea-level change
Hydrodynamic limits and fluctuations for interacting particle systems
No full textIn this thesis, we study the limiting behavior of several different models in the KPZ universality class.
In Chapters 1 and 2, we study the hydrodynamic limits of the -PNG model and the inhomogeneous stochastic six-vertex model with periodic weights using soft techniques. We show that the height functions of both models converge almost surely to a deterministic limit shape. The key element of the proofs is the construction of colored versions of both models, which allows us to apply the superadditive ergodic theorem. Along the way, we also construct the stationary -PNG model and prove a version of Burke's theorem for it.
In Chapter 3, we consider the stochastic six-vertex model with step initial conditions and a single second-class particle at the origin. We show almost sure convergence of the speed of the second-class particle to a random limit. This allows us to define the stochastic six-vertex model speed process, whose law we show to be ergodic and stationary for the dynamics of the multi-class stochastic six-vertex process. The proof requires the development of precise bounds on the fluctuations of the height function of the stochastic six-vertex model around its limit shape using methods from integrable probability. As part of the proof, we also obtain a novel geometric stochastic domination result that states that a second-class particle to the right of any number of third-class particles will at any fixed time be overtaken by at most a geometric number of third-class particles.
In Chapters 4 and 5, we show that under a certain moderate deviation scaling, the multiplicative-noise stochastic heat equation describes the fluctuations of the quenched density of two different models of diffusion in a time-dependent random environment. The first model is the motion of a particle under a continuum random environment whose distribution is given by the Howitt-Warren flow. The second model is a 1D nearest-neighbor random walk in a space-time random environment. The proofs rely on certain Girsanov transforms and showing that the quenched density solves a prelimiting SPDE that resembles the stochastic heat equation. For the random walk model, we also show that independent noise is generated in the limit, in the sense that the prelimiting noise field does not converge to the driving noise of the limiting SPDE
Investigating the contributions of eIF3 subunits to translation initiation
No full textThe transfer of genetic information is a necessity for all life on earth. The final step in this information flow is the translation of messenger RNA (mRNA) into protein by the ribosome. The molecular machinery responsible for translation includes the ribosome itself and a suite of factors responsible for getting the ribosome onto the mRNA at the correct time in a process called translation initiation. In addition to correct timing, translation initiation must also both be highly accurate and begin at the correct location (called the start codon), otherwise the incorrect protein product will be made.
This process involves several factors across all domains of life. In eukaryotes, these factors are called eukaryotic initiation factors (eIFs). There are over a dozen eIFs that are all required for the process of translation initiation. The primary focus of this thesis is on the molecular mechanisms used by one of these factors, a protein complex called eIF3. However, because eIF3 makes extensive functional and/or physical interactions with other eIFs and functions throughout many of the mechanistic steps of translation initiation, the insights gained into eIF3 function inform the understanding of the process of translation initiation broadly.
Generally, when studying molecular mechanism, it is often necessary and always desired to have the most control of the system under study as possible. In the case of eIF3, a large fraction of our knowledge about its function over the previous decades has come from in vivo genetic or cell-extract-based studies, which inherently lack precise control over components. While these studies have provided immense information regarding the impact of eIF3 across translation initiation and are the foundation for all future work, they lack information regarding the molecular mechanisms eIF3 employs.
Therefore, to develop a system capable of interrogating such mechanisms, Chapter 2 of this thesis presents a recombinantly reconstituted eIF3 complex that is functional in vitro and is used as a basis for site-specific fluorophore labeling of an individual eIF3 subunit. This biochemically active, reconstituted eIF3 is used throughout the rest of the thesis as it allows for enhanced control over the composition and identity of the eIF3 species under investigation.
In Chapter 3, the mRNA-binding activity of eIF3 is explored. The mRNA-binding activity ascribed to eIF3 is shown to be largely driven by a single eIF3 subunit, with the other subunits modulating this activity. Specifically, the largest eIF3 subunit, eIF3a, is shown to be the primary driver of mRNA-binding by eIF3 and the interactions of other subunits are shown to alter the observed binding. Following up on the study of mRNA-binding by individual eIF3 subunits, Chapter 4 expands to the study of eIF3 subunits and their coordination in additional biochemical activities, including the ability to bind to the ribosome itself. Lastly, the involvement of eIF3 in the attachment of mRNA to the ribosome is investigated. Specifically, Chapter 5 investigates the role of eIF3 in the process of loading the mRNA into the ribosome, a process that necessitates the handoff of the mRNA from the eIFs responsible for initial recognition of the mRNA to the ribosome.
Collectively, this thesis establishes a toolkit for studying the mechanistic roles of individual eIF3 subunits throughout translation initiation and uses this toolkit to describe how a single factor can accomplish such a wide range of biochemical activities
Rhyme and Reason: How Intellectual Property Can Inform the Use of Rap Lyrics as Evidence in Criminal Trials
No full textOver the past two decades, the use of rap lyrics as evidence in criminal prosecutions in the United States has become increasingly common. The introduction of these rap lyrics into evidence proves uniquely problematic and dangerous, specifically for Black and Latino boys and men who already face systemic oppression, bias, and incarceration. Common objections to the use of these rap lyrics as evidence include a First Amendment Constitutional argument, as well as those grounded in existing evidence rules. Proposed solutions are also divergent and include: the categorical exclusion of rap lyrics as evidence, the mandated use of expert witnesses to dissect the rap lyrics in the context of the genre more generally, and the lyrics’ admission only when they explicitly discuss the crime at issue at trial. However, because this is such a new and evolving area of the law, what these solutions often lack is solid doctrinal foundations, which make it harder for consistent legislation and adjudications to follow.This Note proposes two solutions for the admission of rap lyrics as evidence grounded in two existing Intellectual Property (“IP”) frameworks. The first solution addresses, as a threshold matter, how to determine whether rap lyrics in any given case should be admissible at all. Borrowing from trademark law’s spectrum of distinctiveness, this Note creates a similar spectrum of distinctiveness based on the proximity of the rap lyrics to the specific crime at issue in the trial. This spectrum of distinctiveness in many ways encompasses the evidence rule against unfair prejudice and should be used by judges, who themselves are subject to implicit biases and are not qualified to dissect rap lyrics. Second, for situations where rap lyrics are deemed admissible, this Note propose a solution that requires judges to, at the defendant’s request, either (1) provide a court-appointed expert to testify and contextualize the lyrics or (2) allow the defense to bring forth their own expert witness. This solution is based on a cautionary tale from copyright law: the infringement by reproduction doctrine, famously and confusingly codified in the 2nd Circuit case of Arnstein v. Porter. The Arnstein court’s categorical exclusion of expert testimony during the improper appropriation stage of analysis, relying instead on the response of the ordinary lay hearer (i.e., the jury) is “universally repudiated” by legal copyright scholars. Thus, especially when transferred to the criminal context where the stakes are much higher, the aftermath of Arnstein emphasizes the importance of always permitting, and perhaps even mandating, the use of expert testimony
Regulating AI: Differences Between the U.S. and the EU
No full textThe topic for this lecture is very much about the future. Basically, we are talking about things we are only starting to see. So, it may still be premature to talk about regulating Artificial Intelligence (“AI”). Not too long ago, several experts and tycoons in the AI community issued an open letter last year saying, in effect, “let’s pause it a bit. Let’s see how to regulate it.”
Since then, we have seen the rise of ever more forms of AI, notably ChatGPT, Stable Diffusion, and all these AI systems and processes of diffusing images, adding noise to them and then de-noising them, so as to subsequently generate a different image or a different audiovisual recording at the request of a prompt. Creators and professionals are concerned about that. And so are we, professors. In fact, AI seems to be a game changer in the world of copyright. We are not Luddites but we are starting to sympathize with them (if I may put it that way). This is how much AI is shaking our lives
Motivators and Hindrances of Consuming Reusable Water Bottles: An Exploratory Case Study at Columbia University
No full textThis pilot study explores the factors that motivate and hinder tap water consumption and reusable water bottle usage among students at Columbia University. Despite Manhattan's tap water being among the highest quality globally, the prevalence of single-use plastic water bottles on campus remains significant. Choosing reusable water bottles over single-use plastics is a pro-environmental behavior that can reduce plastic production and waste. This research investigates the underlying reasons behind students' choices regarding tap water consumption and reusable bottle usage. The data were collected from 58 students selected through convenience sampling utilizing questionnaires and participant observation. The questionnaire responses were thematically coded, and descriptive statistics, including percentages and frequencies, were used to analyze the data. Findings indicate that, while a relatively high percentage of students consume tap water compared to other universities, hygiene concerns related to water quality are the main hindrances. In terms of bottle usage, the primary motivation for carrying a reusable water bottle was to increase water intake. The major barrier was the inconvenience and lack of portability of reusable bottles. Notably, students overestimated the positive environmental impact of using reusable water bottles, which could potentially lead to greater environmental harm due to misconceptions. This pilot study underscores the need for further in-depth research to identify and address the misconceptions and barriers affecting students' pro-environmental behaviors
Reflections on Section 367(b) Regulations and Inbound Transactions
No full textCross-border combinations of U.S. and foreign public companies are unusual but happen from time to time. Our broad and often arbitrary anti-inversion rules discourage such transactions utilizing a foreign parent company for the combined group. But using a U.S. parent company can also be painful to the foreign company shareholders. Our section 367(b) regulations require gain recognition for the foreign company’s material shareholders subject to U.S. tax. That seems to be a high price to pay for the pleasure of bringing the foreign corporate group into the U.S. tax net.
Much has been discussed and written about the section 367(b) regulations that compel this result since the regulation’s finalization in 2000 and especially since the enactment of the 2017 Tax Cuts and Jobs Act. This article reflects our exploration into what led the original regulation writers down the path they took and suggests that maybe they were wrong in their thinking. Our hope is that it will stimulate a broader discussion of the goals of the section 367(b) regulations as applied to inbound transactions and how they should be implemented in the current regime of section 245A deductions and GILTI and Subpart F inclusions
Invisible Labor, Invisible Rights
No full textImmigrant women of color have long formed the backbone of the American domestic workforce, and in the past few decades, they have been increasingly stepping in to fill the country’s deepening childcare crisis. While scholars have examined the racialized, gendered, and classed dimensions of domestic labor and the transnational “global nanny chain,” far less attention has been paid to immigrant women of color who enter the United States through legal, temporary guest worker programs. This Note focuses on the United States’ au pair program—a J-1 Cultural Exchange initiative—to examine the intersectional vulnerabilities faced by au pairs from the Global South and other developing countries. It argues that these au pairs are uniquely exposed to exploitation not only because of the inherent precarity of live-in domestic labor but also due to their “liminal legality”: a form of legal marginalization that simultaneously grants and withholds rights, creating a precarious state of in-betweenness. Drawing on recent litigation, demographic shifts in the program, and an intersectional framework, this Note highlights how these au pairs are often excluded from effective labor protections and struggle to assert their rights within both legal and social structures. It concludes by calling for robust anti-retaliation protections and expanded access to labor organizing as essential mechanisms for empowering minority au pairs and addressing the structural harms they face
The breast cancer genetic testing experience: probing the potential utility of an online decision aid in risk perception and decision making
Get PDFBackground
Despite the association of pathogenic variants (PVs) in cancer predisposition genes with significantly increased risk of breast cancer (BC), uptake of genetic testing (GT) remains low, especially among ethnic minorities. Our prior study identified that a patient decision aid, RealRisks, improved patient-reported outcomes (including worry and perceived risk) relative to standard educational materials. This study examined patients’ GT experience and its influence on subsequent actions. We also sought to identify areas for improvement in RealRisks that would expand its focus from improved GT decision-making to understanding results.
Methods
Women enrolled in the parent randomized controlled trial were recruited and interviewed. Demographic data was collected from surveys in the parent study. Interviews were conducted, transcribed, and coded to identify recurring themes. Descriptive statistics were generated to compare the interviewed subgroup to the original study cohort of 187 women.
Results
Of the 22 women interviewed, 11 (50%) had positive GT results, 2 (9.1%) with a BRCA1/2 PV, and 9 (40.9%) with variants of uncertain significance (VUS). Median age was 40.5 years and 15 (71.4%) identified as non-Hispanic. Twenty (90.9%) reported a family history of BC, and 2 (9.1%) reported a family history of BRCA1/2 PV. The emerging themes included a preference for structured communication of GT results and the need for more actionable knowledge to mitigate BC risk, especially among patients with VUS or negative results. Few patients reported lifestyle changes following the return of their results, although they did understand that their behaviors can impact their BC risk.
Conclusions
Patients preferred a structured explanation of their GT results to facilitate a more personal testing experience. While most did not change lifestyle behaviors in response to their GT results, there was a consistent call for further guidance following the initial discussion of GT results. Empowering patients, especially those with negative or VUS results, with the context to internalize the implications of their results and form accurate risk perception represents a powerful opportunity to optimize subsequent risk management strategies. Informed by this study, future work will expand RealRisks to include the return of results and decision support to navigate concrete next steps