Williams College
  • United States
Recent publications
La novela en curso de Rosario, cuyo título provisional es How the Medicines Go Down, ofrece visiones reparadoras de un futuro no muy lejano poblado por residentes del Sur Global que han recuperado la dirección de su propio bienestar y del medioambiente. La narrativa es hilada por un médico dominicano que sueña con ejercer la medicina en MedIsla, un lujoso destino de turismo médico para viajeros adinerados.
In this communication, we report an open system consisting of three self-replicating peptides in which peptide 1 inhibits the duplex template of peptide 2, peptide 2 inhibits duplex 3, and peptide 3 inhibits duplex 1 to complete the negative feedback loop. This interacting chemical network yields oscillations in the concentrations of all species over time and establishes a possible mechanism for pre-biotic chemical systems organization. The first focus of our analysis is the effect of altering rates of duplex formation and inhibition on oscillations. We then examine the autocatalytic rate constant in the symmetric and asymmetric cases.
The Dipsea Race is a longstanding annual trail race that takes place in Marin County, California. A unique feature of the Dipsea is that runners are given head starts based on their age and sex, computed in an attempt to give runners of every age and sex a similar chance of winning the race. However, runners in the “scratch group” (19- to 30-year-old men, who receive no head start) have not won in the past 50 years, and nobody between the ages of 9 and 45 has won for the past two decades. In this article, we investigate whether the head starts are too large, giving younger and older runners an advantage, or whether the gap in the age distribution of winners is due to participation differences. We find that if anything, the head starts are smaller than they would need to be for the median or mean time to be similar across age and sex groups; rather, exceptional young and old runners participate at a higher rate than exceptional runners in the scratch group.
YouTube has long been a top-choice destination for independent video content creators to share their work. A large part of YouTube's appeal is owed to its practice of sharing advertising revenue with qualifying content creators through the YouTube Partner Program (YPP). In recent years, changes to the monetization policies and the introduction of algorithmic systems for making monetization decisions have been a source of controversy and tension between content creators and the platform. There have been numerous accusations suggesting that the underlying monetization algorithms engage in preferential treatment of larger channels and effectively censor minority voices by demonetizing their content. In this paper, we conduct a measurement of the YouTube monetization algorithms. We begin by measuring the incidence rates of different monetization decisions and the time taken to reach them. Next, we analyze the relationships between video content, channel popularity and these decisions. Finally, we explore the relationship between demonetization and a channel's view growth rate. Taken all together, our work suggests that demonetization after a video is publicly listed is not a common occurrence, the characteristics of the process are associated with channel size and (in unexplainable ways) video topic, and demonetization appears to have a harsh influence on the growth rate of smaller channels. We also highlight the challenges associated with conducting large-scale algorithm audits such as ours and make an argument for more transparency in algorithmic decision-making.
This article discusses the emergence of a discourse on ‘political Islam’ in the policy circles of European elites. It interprets this discourse on one hand as a manifestation of the further criminalization of Muslimness emanating from programs of countering ‘extremism’ and deradicalizing Muslim youth in the wake of the global war on terror. More specifically, the discourse on ‘political Islam’ is seen as an extension of countering violent extremism projects to counter an alleged non-violent ‘extremism.’ The article discusses three cases: Austria, Germany, and France to analyze what the fight against ‘political Islam’ (in Austria), ‘legalistic Islamism’ (in Germany), and ‘Islamist separatism’ (in France) respectively mean. These terminologies are analyzed as ‘empty signifiers’ and (Foucauldian) dispositifs that are used deliberately to legitimize state interventions to shape their respective societies. It is argued that the main shared idea is not that Muslims break the law or commit violence. Rather, the argument is that Muslims use the law to subvert their European nation-states. This aims at excluding Muslims from political life and not allowing them to shape the future of these countries. A simultaneous effort is the nurturing of an unpolitical, submissive Muslim that does not question hegemonial power structures, a project which is pursued by creating a domesticated or ‘national Islam.’ The article discusses these three terminologies' similarities and differences in the respective countries. In sum, the apparatus of ‘political Islam’ is interpreted as a means to 1) push back or exclude Muslims from the public sphere; 2) crackdown on organized Muslims; and 3) silence critical voices to these policies.
We explicitly construct the first universal cycles for strings with fixed-content—also known as strings with the same Parikh vector, or multiset permutations—using their shorthand encoding, which omits the final symbol as it is redundant. For example, 112312131132 is a universal cycle for content S={1,1,2,3}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$S = \{1,1,2,3\}$$\end{document}. Its first three windows—112, 123, and 231—are the shorthand representatives of 1123, 1231, and 2311, respectively. Our first construction V(S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {V}(S)$$\end{document} applies the classic cycle-joining approach on the first-inversion tree of necklace cycles with content S. For example, when S={1,1,2,3}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$S = \{1,1,2,3\}$$\end{document} the root is the necklace cycle 1123 and its children are 121̲3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1\underline{21}3$$\end{document} and 1132̲\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$11\underline{32}$$\end{document} by swapping their first (i.e., leftmost) inversions. From this construction, we derive a successor rule to generate successive symbols of V(S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {V}(S)$$\end{document} in O(n)-time, where n=|S|\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n=|S|$$\end{document} is the cardinality of S. Our second construction U(S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {U}(S)$$\end{document} concatenates fixed-content necklaces together in a cool-lex order using the necklace-prefix algorithm. For example, U(S)=1123·1213·1132\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {U}(S) = 1123 \cdot 1213 \cdot 1132$$\end{document} for S={1,1,2,3}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$S = \{1,1,2,3\}$$\end{document}. Central to this construction is the first shift Gray code for fixed-content necklaces, and a new efficient algorithm for generating these strings. From this construction, we can generate successive symbols of U(S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {U}(S)$$\end{document} in O(1)-amortized time while using O(n)-space. We complete our investigation with a pleasant surprise: V(S)=U(S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {V}(S) = \mathcal {U}(S)$$\end{document}. Our new results simultaneously generalize universal cycle constructions of shorthand permutations by Ruskey et al. (Algorithmica 64, 2012) and shorthand fixed-weight binary strings by Ruskey et al. (SIAM J Disc Math 26(2):605–617, 2012). They also provide a prefix-shift Gray code for multiset permutations in which the first symbol moves into the last or second-last position, which tightens the previous prefix-shift Gray code by Williams (Proceedings of the Twentieth Annual ACM-SIAM Symposium on Discrete Algorithms, 2009). Finally, we draw parallels between our constructions and the well-known granddaddy de Bruijn sequence for binary strings.
As air temperature increases, it has been suggested that smaller individual body size may be a general response to climate warming. However, for ectotherms inhabiting cold, highly‐seasonal environments, warming temperatures may increase the scope for growth and result in larger body size. In a long‐term study of individual brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) inhabiting a small stream network, individual lengths increased over the course of 15 years. As size‐selective gains and losses to the population acted to reduce body sizes and mean body size at first tagging in the autumn (< 60 mm) were not observed to change substantially over time, the increase in body size was best explained by higher individual growth rates. For brook trout, increasing water temperatures during the spring (when both trout species accomplish most of their total annual growth) was the primary driver of growth rate for juvenile fish and the environmental factor which best explained increases in individual body size over time. For brown trout, by contrast, reduction in and subsequent elimination of juvenile Atlantic salmon (Salmo salar) midway through the study period explained most of the increases in juvenile growth and body size. In addition to these major trends, a considerable amount of interannual variation in trout growth and body size was explained by other abiotic (stream flow) and biotic (population density) factors with the direction and magnitude of these effects differing by season, age‐class and species. For example, stream flow was the dominant growth rate driver for adult fish with strong positive effects in the summer and autumn, but flow variation could not explain increases in body size as we observed no trend in flow. Overall, our work supports the general contention that for high‐latitude ectotherms, increasing spring temperatures associated with a warming climate can result in increased growth and individual body size (up to a point), but context‐dependent change in other factors can substantially contribute to both interannual variation and longer‐term effects.
This publication is a digital comic short story based on autoethnographic research. The story takes as its foundation a photo of an African storefront window in the 18th arrondissement of Paris, France in summer 2019. The narrative queries from multiple perspectives and types of information my relationship as an African American woman with several things: the West African jewellery and cloth on display, the window that framed the products for sale, the store, and the neighbourhood that featured a predominately African diasporic population. In this publication, I also address some of the following questions: 1) Can I see myself in this Black, French and African diasporic site of commerce? 2) How does this marketing display relate to American and French marketing and media history’s invisibility of Black women as desired consumers? 3) Has my shared ascribed status of race and increased awareness of West African culture after travels to Ghana and Senegal changed my fit in this Francophone African space?
The wildfire season in the Western United States (U.S.) was anomalously large in 2020, with a majority of burned area due to lightning ignitions resulting in overall fire emissions of carbon monoxide (CO) in the Western region almost 3 times the 2001–2019 average. We used the Community Atmosphere Model version 6 with Chemistry (CAM-chem) to investigate how the 2020 fires in the Western U.S. affected air quality locally as well as in surrounding regions that received transported pollution. Simulations with and without fire emissions over the Western U.S. (32.5–49°N, 115–125°W) in July–December 2020 were used to determine average changes in atmospheric composition across the country. Comparisons against satellite and ground-based column CO observations show that the model generally underestimated CO from fires but adequately reproduced spatial and temporal variability. Simulations showed the 2020 fire season contributed 14.5% to atmospheric CO over the Contiguous United States in September, and ∼3% to CO averaged across the Northern Hemisphere; these enhancements lasted several months. Fire emissions in 2020 continued later into the year than usual, resulting in sustained air pollution over the Western U.S. region, with noticeable meridional transport of ozone (O3) and fine particulate matter (PM2.5). Finally, we use the model to identify two transported fire events at Boulder, Colorado.
In 1983–1984, an unknown waterborne pathogen caused the mass mortality of long-spined sea urchin (Diadema antillarum) across the Caribbean and western tropical Atlantic. After approximately 15 years, urchin populations began to recover at some locations, yet few have reached pre-mortality densities. To date, no study has documented a recovery in the western tropical Atlantic outside of the Caribbean. Over a 25-year period (1991–2015), we documented an 8–17% population growth rate of D. antillarum in the central Bahamas. However, our mean observed densities, 0.06–0.38 urchins m⁻², remained below pre-pandemic levels. Combined with observations from other locations in the Caribbean, it appears that D. antillarum populations are increasing, yet have not fully recovered from their 1980s mass mortality throughout much of their geographic range.
Archives are loci of power where state (and archive creators’) hegemony is reproduced and sustained through the stories they allow to be told and the ones they suppress. However, this applies only to contexts in which archives actually exist and are organized. I argue that Morocco’s postcolonial history challenges Western notions of archives and begs for a conceptualization of “other-archives” in which silenced stories find their way to the public arena and resist authoritarian amnesia. Not only do other-archives liberate history (re)writing from archival hegemony, but they also open up space for an interdisciplinary study of history. Other-archives, as I theorize them, allow the inscription of the voices of the subaltern into the other-archival documents while also helping to decenter history and historiographical discourses by creating the need for historians to collaborate with specialists in other non-history-focused disciplines, such as cinema, literature, sociology, and political science. This article reveals how the existence and wide dissemination of other-archives within the context of the Equity and Reconciliation Commission’s work in Morocco (2004–2005) spurred transformative debates among Moroccan historians and incited them to push the boundaries of their discipline through the use of tārīkh al-zaman al-rāhin (history of the present).
A fundamental goal of scientific research is to learn about causal relationships. However, despite its critical role in the life and social sciences, causality has not had the same importance in Natural Language Processing (NLP), which has traditionally placed more emphasis on predictive tasks. This distinction is beginning to fade, with an emerging area of interdisciplinary research at the convergence of causal inference and language processing. Still, research on causality in NLP remains scattered across domains without unified definitions, benchmark datasets and clear articulations of the challenges and opportunities in the application of causal inference to the textual domain, with its unique properties. In this survey, we consolidate research across academic areas and situate it in the broader NLP landscape. We introduce the statistical challenge of estimating causal effects with text, encompassing settings where text is used as an outcome, treatment, or to address confounding. In addition, we explore potential uses of causal inference to improve the robustness, fairness, and interpretability of NLP models. We thus provide a unified overview of causal inference for the NLP community.1
Rhodoliths occur extensively around the shores of Fuerteventura Island in the Canary Archipelago, with Lithothamnion cf. corallioides being the most prominent species. A large number of rhodoliths end up washed onshore, the debris from which contributes to the formation of sediments constituting modern beaches. In a previous study by one of the co-authors (MEJ), the northern coast of Fuerteventura was shown to comprise various types of rhodolith deposits such as beach, platform overwash, tidal pools, coastal dunes, and others. An extraordinary example of stranded rhodoliths is located near Caleta del Bajo de Mejillones, approximately 3 km west of Corralejo, on the north coast of the island. The deposit forms a supratidal beach 120 m long and 10 m wide that sits above the landward termination of an extensive wavecut platform eroded in basalt and exposed at low tide to a width of 130 m perpendicular to shore. Here, rhodoliths are very small (<3 cm) resembling popcorn, and the locality is known as the “Popcorn Beach”. Other examples are berms up to 150 m long and 9 m wide at Caleta del Bajo de Mejillones, or an exposed beach at Playa del Hierro with an area of more than 1500 m2 covered entirely of very coarse rhodolith sand. Extensive living rhodolith beds were found at a water depth of 22 m.
Most of the hydrogen in the intergalactic medium (IGM) was rapidly ionized at high-redshifts. While observations have established that reionization occurred, observational constraints on the high-redshift ionizing emissivity remain elusive. Here, we present a new analysis of the Low-redshift Lyman Continuum Survey (LzLCS) and literature observations, a combined sample of 89 star-forming galaxies at redshifts near 0.3 with Hubble Space Telescope observations of their ionizing continua (or Lyman Continuum, LyC). We find a strong (6σ significant) inverse correlation between the continuum slope at 1550 Å (defined as F$_\lambda \propto \lambda ^{\beta ^{1550}_{\rm obs}}$) and both the LyC escape fraction (fesc, LyC) and fesc, LyC times the ionizing photon production efficiency (ξion). On average, galaxies with redder continuum slopes have smaller fesc, LyC than galaxies with bluer slopes mainly due to higher dust attenuation. More than 5% (20%) of the LyC emission escapes galaxies with $\beta _{\rm obs}^{1550}$ <−2.1 (-2.6). We find strong correlations between $\beta _{\rm obs}^{1550}$ and the [O iii]/[O ii] flux ratio (at 7.5σ significance), galaxy stellar mass (at 5.9σ), the gas-phase metallicity (at 4.6σ), and the observed FUV absolute magnitude (at 3.4σ). Using previous observations of $\beta _{\rm obs}^{1550}$ at high-redshift, we estimate the evolution of fesc, LyC with both redshift and galaxy magnitude. The LzLCS observations suggest that fainter and lower mass galaxies dominate the ionizing photon budget at higher redshift, possibly due to their rapidly evolving metal and dust content. Finally, we use our correlation between $\beta _{\rm obs}^{1550}$ and fesc, LyC × ξion to predict the ionizing emissivity of galaxies during the epoch of reionization. Our estimated emissivities match IGM observations, and suggest that star-forming galaxies emit sufficient LyC photons into the IGM to exceed recombinations near redshifts of 7–8.
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1,146 members
Cesar E. Silva
  • Department of Mathematics and Statistics
Enrique Peacock-Lopez
  • Department of Chemistry
George E. Marcus
  • Department of Political Science
Frank Morgan
  • Department of Mathematics and Statistics
Ronadh Cox
  • Department of Geosciences
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