Occidental College
  • Los Angeles, United States
Recent publications
We report the isolation and characterization of a series of three cobalt(II) bis(phosphine) complexes with varying numbers of coordinated solvent ligands in the axial position. X-ray quality crystals of [Co(dppv)2][BF4]2 (1), [Co(dppv)2(NCCH3)][BPh4]2 (2), and [Co(dppv)2(NCCH3)2][BF4]2 (3) (dppv = cis-1,2-bis(diphenylphosphino)ethylene) were grown under slightly different conditions, and their structures were compared. This analysis revealed multiple crystallization motifs for divalent cobalt(II) complexes with the same set of phosphine ligands. Notably, the 4-coordinate complex 1 is a rare example of a square-planar cobalt(II) complex, the first crystallographically characterized square-planar Co(II) complex containing only neutral, bidentate ligands. Characterization of the different axial geometries via EPR and UV-visible spectroscopies showed that there is a very shallow energy landscape for axial ligation. Ligand field angular overlap model calculations support this conclusion, and we provide a strategy for tuning other ligands to be axially labile on a phosphine scaffold. This methodology is proposed to be used for designing cobalt phosphine catalysts for a variety of oxidation and reduction reactions.
As fossil fuel activity declines, workers and communities dependent upon this activity will face negative economic and social consequences. Mitigating these impacts and including socio-economic considerations in the energy transition is often referred to as “just transition.” While there is robust discussion on what is meant by a just transition, there is not a uniform definition or vision of what a just transition entails. Moreover, the dynamics of community-based engagement and advocacy in advancing a just transition is often downplayed. This study contributes to the body of just transition research through an analysis of just transition advocacy in the U.S. states of California, Kentucky, Louisiana, and New York that sought to understand what is needed for a just transition and how just transition can be advanced at the state-level. While many cross-state comparisons focus on policy regimes, this research focused on the underlying balance of community power, and the ability to face established interests. A key finding of our research is that many of our interviewees noted that the current system of providing power was deeply impacted by the current configuration of economic and political power. For them, just transition was not just a policy package but a political project. The paper begins with a discussion of what is meant by just transition in existing literature. We then move into presenting the results of our study with a particular focus on how just transition stakeholders envision the idea and whether they saw just transition as a clean energy transition or something more transformative. We conclude with a discussion of how these findings can contribute to better understandings of just transitions, the role that community-based advocacy plays in confronting and overcoming entrenched interests, and the importance of state-based actions.
The diocotron mode of an off-axis electron column is studied in a coaxial version of the Malmberg–Penning trap. Measurements of the diocotron frequency as a function of the bias on the central conductor agree well with a derived theory including finite-length corrections and confinement potential contributions. When the experimental parameters are adjusted to give a very low diocotron frequency, the column motion abruptly changes from an axis-encircling orbit to a large banana-shaped orbit in the [Formula: see text] plane with extent [Formula: see text] and [Formula: see text], where R is the wall radius. This banana motion is apparently in response to a previously unknown background construction asymmetry. The size of the asymmetric potential is deduced from orbit data and found to be 45–100 mV. Theoretical modeling shows this to be consistent with a small radial offset δ in the center wire position of [Formula: see text]. Implications and applications of these findings are discussed and a note on obtaining the line density of an electron column in a coaxial trap is given.
Fourteen boronated cyanometallates ([M(CN-BR3)6]3/4/5– (M = Cr, Mn, Fe, Ru, Os, R = BPh3, B(2,4,6,-F3C6H2)3, B(C6F5)3) have been characterized by X-ray crystallography and spectroscopy [UV-vis-NIR, NMR, IR, spectroelectrochemistry, and magnetic circular dichroism (MCD)]; CASSCF+NEVPT2 methods were employed in calculations of electronic structures. For (t2g)5 electronic configurations, the lowest energy ligand-to-metal charge transfer (LMCT) absorptions and MCD C terms in the spectra of boronated species have been assigned to transitions from cyanide σ+π + B-C borane σ orbitals. CASSCF+NEVPT2 calculations including t1u and t2u orbitals reproduced t1u/t2u → t2g excitation energies. All ([M(CN-BR3)6]3/4− complexes exhibited highly electrochemically reversible redox couples. Notably, the formal potentials of all five [M(CN-B(C6F5)3)6]3− anions scale with LMCT energies; and Mn(I) and Cr(II) compounds, (K(18-crown-6))5[Mn(CN-B(C6F5)3)6] and (TBA)4[Cr(CN-B(C6F5)3)6], are surprisingly stable. Continuous wave and pulsed electron paramagnetic resonance (hyperfine sublevel correlation) spectra were collected for all Cr(III) complexes; as expected, 14N hyperfine splittings are greater for (TBA)3[Cr(NC-BPh3)6] than for (TBA)3[Cr(CN-BPh3)6]. Using (TBA)4[Fe(CN-B(C6F5)3)6] and (TBA)3[Fe(CN)6], a model flow battery was constructed and found to have an 80% energy effi-ciency.
Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores ¹ ; these interhemispheric connections may have existed during previous glacial cycles.
As phylogenomics focuses on comprehensive taxon sampling at the species and population/subspecies levels, incorporating genomic data from historical specimens has become increasingly common. While historical samples can fill critical gaps in our understanding of the evolutionary history of diverse groups, they also introduce additional sources of phylogenomic uncertainty, making it difficult to discern novel evolutionary relationships from artifacts caused by sample quality issues. These problems highlight the need for improved strategies to disentangle artifactual patterns from true biological signal as historical specimens become more prevalent in phylogenomic datasets. Here, we tested the limits of historical specimen-driven phylogenomics to resolve subspecies-level relationships within a highly polytypic family, the New World quails (Odontophoridae), using thousands of ultraconserved elements (UCEs). We found that relationships at and above the species-level were well-resolved and highly supported across all analyses, with the exception of discordant relationships within the two most polytypic genera which included many historical specimens. We examined the causes of discordance and found that inferring phylogenies from subsets of taxa resolved the disagreements, suggesting that analyzing subclades can help remove artifactual causes of discordance in datasets that include historical samples. At the subspecies-level, we found well-resolved geographic structure within the two most polytypic genera, including the most polytypic species in this family, Northern Bobwhites (Colinus virginianus), demonstrating that variable sites within UCEs are capable of resolving phylogenetic structure below the species level. Our results highlight the importance of complete taxonomic sampling for resolving relationships among polytypic species, often through the inclusion of historical specimens, and we propose an integrative strategy for understanding and addressing the uncertainty that historical samples sometimes introduce to phylogenetic analyses.
Low-income communities and communities of color face multiple, cumulative environmental and social burdens. Methods development in environmental justice research has largely focused on spatial and quantitative approaches. Less attention has been paid to developing methodologies that help collect information on everyday stressors and quality of life experiences for residents in overburdened communities. Mixed methods approaches can be one way to structure study designs that help consider how residents experience environmental and socioeconomic impacts in a localized community context. In neighborhoods burdened by cumulative stressors, traditional cross-sectional epidemiological research designs can also be challenging, as well as limited or narrow in their application. However, repeat sampling of measures within a vulnerable population can approach a quasi-experimental design and help consider variations within residents in a single neighborhood as well as better parse relationships between exposures and outcomes. Through a community-academic partnership with university partners, local community partners, and a local promotores de salud (community health workers) network, we pilot tested a novel mobile daily diary approach in both English and Spanish in an urban, predominantly immigrant community in South Los Angeles as a potential method to collect information on daily stress, environmental quality, and health status/symptoms. We collected resident responses via a once per day 7-day SMS/text messaging survey. We sought to gather granular data on daily resident experiences of air pollution and environmental hazards. Residents reported acute health symptoms and stressors, with repeat measures demonstrating how residents might rank, categorize, or cope with stressors. We find that residents in environmental justice communities record variation in their daily diary responses and document changes in environmental quality, stressors, and odors. Refining this type of method could enable a more rigorous examination of co-occurrences of environmental quality and acute health symptoms. This approach supports the inclusion of residents in the research process and helps more systematically integrate open-ended environmental health relevant data in environmental justice efforts. Used with measured data such as air monitoring or health measures, mixed methods generated data can help support efforts that aim to alleviate sources of daily stress, alongside efforts to reduce overall pollution burdens. Mobile daily diaries can be one way to capture variable responses to environmental quality, acute health symptoms, and stressors.
The main goal of dialogue disentanglement is to separate the mixed utterances from a chat slice into independent dialogues. Existing models often utilize either an utterance-to-utterance (U2U) prediction to determine whether two utterances that have the “reply-to” relationship belong to one dialogue, or an utterance-to-thread (U2T) prediction to determine which dialogue-thread a given utterance should belong to. Inspired by mutual leaning, we propose MuiDial, a novel dialogue disentanglement model, to exploit the intent of each utterance and feed the intent to a mutual learning U2U-U2T disentanglement model. Experimental results and in-depth analysis on several benchmark datasets demonstrate the effectiveness and generalizability of our approach.
This essay examines Blanckenburg's theory of the novel in relation to Leibniz's metaphysics. It argues that Blanckenburg theorizes the novel as uniquely suited to respond to the problem in Leibniz's metaphysics of how to bridge the gap between the apparent contingency of first‐person experience and the promise that the world is actually a well‐ordered whole. Whereas Leibniz must appeal to the Principle of Sufficient Reason to bridge this gap, Blanckenburg suggests that the novel can aid philosophical cognition by doing what philosophical thought cannot: create a world depicting the development of a human life in its totality. However, freed from its ontological basis, Blanckenburg's theory provides an important starting point for early Romantic aesthetic theory. Following Blanckenburg, the novel becomes a privileged medium not for copying life, but for offering a model for it, thereby providing an important impulse in Romanticism's reversal of rationalist hierarchies of philosophy and aesthetics.
Relatively few victims of gender-based violence (GBV) seek help from nonprofit organizations, healthcare providers, or law enforcement agencies, choosing instead to disclose to friends and family or to nobody at all. This article presents a systematic review of GBV research in sociology showing that, despite low rates of formal service utilization, 68% of published articles use data from organizations including social service providers, hospitals, and police stations and courts. While data from organizations are essential for understanding the experiences of people who report to them, they may not be generalizable to victims broadly. Victims who seek formal help may differ from those who do not in their relative social advantage—along lines of race, socioeconomic status, gender identity, and more—and in their understandings of and responses to violence. We discuss how more non-organizational research might broaden our understanding of violence experienced by society’s most marginalized, elucidate ways to make formal organizational responses more inclusive, and sensitize stakeholders in the anti-GBV movement to interventions outside of the therapeutic and carceral state.
Understanding tropical biology is important for solving complex problems such as climate change, biodiversity loss, and zoonotic pandemics, but biology curricula view research mostly via a temperate-zone lens. Integrating tropical research into biology education is urgently needed to tackle these issues. Tropical biology is currently largely absent from undergraduate curricula. The integration of authentic research in tropical biology could promote internationality among scientists and provide experiential learning that enables students to address complex global problems.
The study of moral judgements often centres on moral dilemmas in which options consistent with deontological perspectives (that is, emphasizing rules, individual rights and duties) are in conflict with options consistent with utilitarian judgements (that is, following the greater good based on consequences). Greene et al. (2009) showed that psychological and situational factors (for example, the intent of the agent or the presence of physical contact between the agent and the victim) can play an important role in moral dilemma judgements (for example, the trolley problem). Our knowledge is limited concerning both the universality of these effects outside the United States and the impact of culture on the situational and psychological factors affecting moral judgements. Thus, we empirically tested the universality of the effects of intent and personal force on moral dilemma judgements by replicating the experiments of Greene et al. in 45 countries from all inhabited continents. We found that personal force and its interaction with intention exert influence on moral judgements in the US and Western cultural clusters, replicating and expanding the original findings. Moreover, the personal force effect was present in all cultural clusters, suggesting it is culturally universal. The evidence for the cultural universality of the interaction effect was inconclusive in the Eastern and Southern cultural clusters (depending on exclusion criteria). We found no strong association between collectivism/individualism and moral dilemma judgements.
Continental ultramafic rock systems, through the process of serpentinization, provide chemical and biochemical pathways that lead to the production of methane. The extent to which rock-water-gas reactions and organisms supply methane in these systems is a matter of considerable discussion and debate. Deciphering the interplay of abiotic and microbial methane observed at the surface requires several lines of reasoning as well as a variety of analyses. Despite using multiple models and interpretative tools, conclusions for the origin of methane at a particular site may vary or diverge from regional or global observations. Here, we critically address how possible conclusions of microbial versus abiotic methane in continental serpentinization systems may be interpreted and reinterpreted. We review fundamental concepts, advantages and limits, for three major methane origin models: (a) abiotic CO2 hydrogenation supplying gas reservoirs, (b) derivation from fluid inclusions in olivine-rich rocks, and (c) microbialgenesis in aquifers. We use the case of methane in the Samail ophiolite of Oman as an emblematic example of multiple interpretations; we identify ambiguous information offered by methane clumped isotopes and molecular gas compositions (e.g., the meaning of gaseous hydrocarbons heavier than methane), and suggest key tools, such as radiocarbon (¹⁴C) in methane, which may solve interpretative issues. The major constraint in any model of methane origin is the capability to sustain continuous gas flows, in terms of methane emission intensity, longevity and spatial extension, such as in natural gas sedimentary systems. Overall, this review suggests that any site interpretation can benefit from a holistic approach, integrating geochemical, geological and biological data with gas flow dynamics, as well as including regional and global contextualization.
When President Biden took office in January 2021, it was widely expected that he would reverse Trump-era policies and take steps to address climate change, racial justice, and rising inequality. Then-candidate Biden made strong commitments to addressing the climate crisis, including stating that “the Green New Deal is a crucial framework for meeting the climate challenges we face.” But with the parties evenly split in the Senate, this meant legislating ambitious climate policy would be difficult. This article analyzes the Biden Administration’s climate and environmental justice initiatives in its first year. The Biden administration successfully advanced some environmental policy through legislation but relied primarily on ambitious executive orders and with a particular focus on integrating equity and justice considerations into climate and environmental policy, while encountering challenges from Republican state officials.
Agricultural researchers in developing countries were not able to give much attention on the adoption studies of agricultural technologies until the period of Green Revolution. These technologies are disseminated in rural farming community by agricultural extension professionals to boost farm efficiencies and productivity. This paper presents the systematic review of methods employed by previous researchers in studying agricultural technology adoption with special reference to rice. The review focuses on the study of rice technologies adoption in the Philippines and other related studies conducted by a Filipino author in other countries in the Asian Region. From 391 adoption studies identified, 22 papers were selected and included in the review. These papers were retrieved from Scopus database. This review revealed that papers focused on studying the adoption of rice cultivation practices employed quantitative techniques. Institutional factors were found to critically influence the decision-making of the farmers to adopt production technologies.
A new family of stabilized benzylic nucleophiles for the palladium-catalyzed decarboxylative allylic alkylation reaction has been developed. Allyl esters derived from 3-carboxyphthalides were found to undergo palladium-catalyzed deallylation and decarboxylation under mild reaction conditions, a process facilitated by the formation of a stabilized aromatic anion. The regioselective allylic coupling of this intermediate afforded a variety of functionalized phthalides in 73-96% yields.
The 2006 eldercare facility ordinance of Los Angeles was designed to streamline permitting of senior housing development in the jurisdiction. Using California State Department of Social Services residential care and census place data, this study compares the pre and post effect of the ordinance on the number of large residential care facilities developed in Los Angeles with a comparison group using synthetic control analysis. In posttreatment, Los Angeles shows up to 33 percent more facilities per ten thousand older adults per year more than the synthetic control, underscoring the importance of such ordinances in increasing senior housing development in Los Angeles.
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1,346 members
Tamas Lengyel
  • Department of Mathematics
Gretchen B. North
  • Department of Biology
Gary G Martin
  • Department of Biology
Elizabeth Braker
  • Department of Biology
Ann Blythe
  • Department of Geology
Los Angeles, United States