Oberlin College
  • Oberlin, United States
Recent publications
Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled intermolecular para-cycloadditions are rare. Herein, a method to achieve photochemical cycloaddition of quinolines and alkenes is shown. Emphasis is placed on generating sterically congested products and reaction of highly substituted alkenes and allenes. In addition, the mechanistic details of the process are studied, which revealed a reversible radical addition and a selectivity-determining radical recombination. The regio- and stereochemical outcome of the reaction is also rationalized.
Symmetry analysis characterizes ∼1300 geometric designs on bowl interiors from five sites of the Mimbres culture tradition, AD 1000–1150, of southwestern New Mexico. The analysis reveals a distinct homogeneity in pattern structure and color on three layouts (pendant, centered and band) that, classified by plane pattern symmetries, shows a preference for four finite structures (C2, C4, D2, D4) and two one-dimensional structures (p112, pmm2) and a diversity of one-color, colored, and two-color arrangements of solid and hatched motifs. The analysis reveals common shared symmetries among neighboring cultural traditions to the south in northern Mexico, to the west among the Hohokam, and to the north among the Ancestral Pueblo of central New Mexico. Classification of the designs by symmetry enables detection of experimentation in the evolution of the design system wherein finite designs were placed within banded layouts.
As one of the leading six generation directors, Lou Ye often captures the changing social and political atmospheres in China by portraying melodramatic relationships with jolted camerawork, convoluted time frames, and emotionally charged narratives. The intimate, damaging, and symbiotic ties among individuals in the private, domestic space in Lou’s works are often symptomatic of the trenchant social inequality and the inherent violence in capitalist values. This paper studies Lou’s 2018 crime drama, Feng zhong you duo yu zuo de yun (The Shadow Play) and analyzes the way the film unpacks the upward narrative of capitalism as inherently gendered and discriminative. As the diegesis unfolds in a disjointed temporal order and heterotopic spaces in which high-rise skyscrapers and demolished residential buildings coexist, the film documents the way China’s thirty years of reform and opening up perpetuate heteronormative gender performance and subjugation of women. Illuminated by Lauren Berlant’s notion of “cruel optimism” that characterizes modern individuals’ futile yet tenacious struggles and negotiation in their everyday experience with capitalist mores under the false hope of prosperity and success, the paper investigates the way the female characters’ conformity to norms and improvised coping mechanisms lead to their downfall and insinuate a yearning for an alternative form of human bonding to that prescribed by masculinist hegemony.
In this study, we compare mechanistic and empirical approaches to reconstruct the air‐sea flux of biological oxygen (FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$) by parameterizing the physical oxygen saturation anomaly (ΔO2[phy]) in order to separate the biological contribution from total oxygen. The first approach matches ΔO2[phy] to the monthly climatology of the argon saturation anomaly from a global ocean circulation model's output. The second approach derives ΔO2[phy] from an iterative mass balance model forced by satellite‐based physical drivers of ΔO2[phy] prior to the sampling day by assuming that air‐sea interactions are the dominant factors driving the surface ΔO2[phy]. The final approach leverages the machine‐learning technique of Genetic Programming (GP) to search for the functional relationship between ΔO2[phy] and biophysicochemical parameters. We compile simultaneous measurements of O2/Ar and O2 concentration from 14 cruises to train the GP algorithm and test the validity and applicability of our modeled ΔO2[phy] and FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$. Among the approaches, the GP approach, which incorporates ship‐based measurements and historical records of physical parameters from the reanalysis products, provides the most robust predictions (R² = 0.74 for ΔO2[phy] and 0.72 for FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$; RMSE = 1.4% for ΔO2[phy] and 7.1 mmol O2 m⁻² d⁻¹ for FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$). We use the empirical formulation derived from GP approach to reconstruct regional, inter‐annual, and decadal variability of FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$ based on historical oxygen records. Overall, our study represents a first attempt at deriving FO2bio_as ${\mathrm{F}}_{{\left[{\mathrm{O}}_{2}\right]}_{{\text{bio}}^{\_\text{as}}}}$ from snapshot measurements of oxygen, thereby paving the way toward using historical O2 data and a rapidly growing number of O2 measurements on autonomous platforms for independent insight into the biological pump.
Keefer (2022) argues that theoretical commitments to conceptual metaphor theory (CMT) impede research on metaphor in psychology. To jumpstart the field, he suggests adopting Lacan’s perspective. I disagree with this argument for a few reasons. First, CMT has a much more nuanced place in current research on metaphor than it would seem from the target article. Second, the field does engage with the hypotheses enumerated by Keefer: that metaphors emerge from a complex web of associations, have unconscious influence, and reflect deep-seated motivations. I review how contemporary research has approached these questions and show how the constraints cited in Keefer’s article stem from the field’s commitments to the scientific method and the computational theory of mind, rather than CMT. Finally, contrary to how they are framed in Keefer’s article, I argue that these constraints have enabled scientific progress to date and limit the impact of Lacan’s perspective moving forward.
The analysis of pattern design on ceramics, textiles, tile and other plane surfaces remains dominated by typological, design element and stylistic approaches. In this paper, I compare these approaches with a classification system that describes patterns by the geometric symmetries that combine and repeat the pattern parts. I argue that these standard plane pattern symmetry classes enable systematic, objective descriptions of decorated material. I use an analysis of the symmetric structures and colors of designs on whole and partial Chihuahuan polychrome vessels from the Pueblo IV period site of Paquimé (Casas Grandes), Chihuahua, Mexico, to illustrate how a standardized classification system that focuses on the structure of pattern parts rather than on the pattern parts themselves reveals a number of new insights on a body of well-studied material.
We report on an artificial language learning experiment testing the learnability of a typologically rare pattern of reduplication. Our model comes from syllable-copy reduplication in Hiaki (aka Yaqui, Uto-Aztecan), a base-dependent pattern wherein the shape of reduplication depends crucially on syllabification in the base: coda consonants can copy in reduplication if and only if there is a corresponding coda in the base. Using a controlled artificial language experiment with a forced-choice paradigm, we show that native English speakers who have no prior exposure to any language with a grammar employing syllable-copy reduplication are in many cases able to learn a variable CV or CVC syllable-copying rule as measured by eventual above-chance selection of the correct form. However, compared to participants learning either a consistent CV or CVC copying rule, the performance of participants tasked with learning such a variable syllable-copying rule improves more slowly, and these participants make more errors overall. We suggest that this difference in learnability may be one of a number of factors helping to explain the typological rarity of certain morphological patterns.
Over the past century, lake degradation has increased around the world. Jiuzhaigou World Natural Heritage Site in southwestern China has been experiencing water nutrient enrichment, accelerated swamping, and algal biomass increases. These problems are likely associated with enhanced local anthropogenic activities over the past decades. In this study, radioactivities of 137Cs and 210Pb, diatoms, and nutrient accumulation rates in a lake sediment core from Tiger Lake in Jiuzhaigou World Natural Heritage Site were used as proxies to reconstruct a > 100-year record of environmental change to understand the extent and temporal variability of anthropogenic effects on lake water nutrients. Diatom communities reveal four distinct phases, relating to documented local human activities including (a) Primitive agriculture from 1871 to the mid-1930s, (b) Opium cultivation—logging from the mid-1930s to the mid-1970s, (c) Large-scale logging—the beginning of tourism from the mid-1970s to the early 1990s, and (d) Tourism development from the early 1990s to 2013. Nutrients in the lake (including total organic carbon, total nitrogen, and total phosphorus) steadily increased from 1871 until the late 1990s, declined from the late 1990s to the mid-2000s, and increased rapidly after the mid-2000s. Our data suggest that (a) Opium cultivation, deforestation, and tourism development led to the increase of lake nutrients and primary productivity, (b) Ecological protection measures taken from 1999 to 2004 effectively controlled water pollution, and (c) Post-2005 intensification of tourism further accelerated water quality deterioration. Additional monitoring and mitigation strategies are needed to further reduce nutrient input. Global studies suggest that while water quality of lakes in protected area is better than that of other lakes, care is still required to ensure that tourism activities do not inadvertently increase lake water nutrients.
Public underestimation of support for climate change policy is striking. Social science research tells us this is bad news, but also tells us what to do about it. Climate change communication must hammer home the overwhelming support for action. A new study finds that Americans underestimate how many are concerned about climate change as well as support for major climate policies by nearly half, with climate policy supporters significantly outnumbering non-supporters.
Galaxy mergers are known to trigger both extended and central star formation. However, what remains to be understood is whether this triggered star formation is facilitated by enhanced star formation efficiencies, or an abundance of molecular gas fuel. This work presents spatially resolved measurements of CO emission collected with the Atacama Large Millimetre Array (ALMA) for 20 merging galaxies (either pairs or post-mergers) selected from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Eleven additional merging galaxies are selected from the ALMA MaNGA QUEnching and STar formation (ALMaQUEST) survey, resulting in a set of 31 mergers at various stages of interaction and covering a broad range of star formation rates (SFR). We investigate galaxy-to-galaxy variations in the resolved Kennicutt-Schmidt relation (rKS: $\Sigma_{H_2}$ vs. $\Sigma_{SFR}$), the resolved molecular gas main sequence (rMGMS: $\Sigma_{\star}$ vs. $\Sigma_{H_2}$), and the resolved star-forming main sequence (rSFMS: $\Sigma_{\star}$ vs. $\Sigma_{SFR}$). We quantify offsets from these resolved relations to determine if star formation rate, molecular gas fraction, and/or star formation efficiency (SFE) is enhanced in different regions of an individual galaxy. By comparing offsets in all three parameters we can discern whether gas fraction or SFE powers an enhanced $\Sigma_{SFR}$. We find that merger-induced star formation can be driven by a variety of mechanisms, both within a galaxy and between different mergers, regardless of interaction stage.
The universal ancestor at the root of the species tree of life depicts a population of organisms with a surprising degree of complexity, posessing genomes and translation systems much like that of microbial life today. As the first life forms were most likely to have been simple replicators, considerable evolutionary change must have taken place prior to the last universal common ancestor. It is often assumed that the lack of earlier branches on the tree of life is due to a prevalence of random horizontal gene transfer that obscured the delineations between lineages and hindered their divergence. Therefore, principles of microbial evolution and ecology may give us some insight into these early stages in the history of life. Here, we synthesize the current understanding of organismal and genome evolution from the perspective of microbial ecology and apply these evolutionary principles to the earliest stages of life on Earth. We focus especially on broad evolutionary modes pertaining to horizontal gene transfer, pangenome structure, and microbial mat communities.
Reactions that lead to destruction of aromatic ring systems often require harsh conditions and, thus, take place with poor selectivities. Selective partial dearomatization of fused arenes is even more challenging but can be a strategic approach to creating versatile, complex polycyclic frameworks. Herein we describe a general organophotoredox approach for the chemo- and regioselective dearomatization of structurally diverse polycyclic aromatics, including quinolines, isoquinolines, quinoxalines, naphthalenes, anthracenes and phenanthrenes. The success of the method for chemoselective oxidative rupture of aromatic moieties relies on precise manipulation of the electronic nature of the fused polycyclic arenes. Mechanistic studies show that the addition of a hydrogen atom transfer (HAT) agent helps favor the dearomatization pathway over the more thermodynamically downhill aromatization pathway. We show that this strategy can be applied to rapid synthesis of biologically valued targets and late-stage skeletal remodeling en route to complex structures. The synthesis of polycyclic structures bearing partially saturated (hetero)arenes is important as many of these structures have biological relevance. Here the authors develop a one-step method for selective dearomative functionalization of feedstock (hetero)arenes via organophotocatalysis.
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1,266 members
Chris Howell
  • Department of Politics
Patrick Simen
  • Department of Neuroscience
Amanda Henck Schmidt
  • Department of Geology
Albert Matlin
  • Department of Chemistry / Biochemistry
John E. Petersen
  • Environmental Studies Program
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