National Science Foundation
  • Alexandria, United States
Recent publications
Mixing among sub-populations, as well as heterogeneity in characteristics affecting their reproduction numbers, must be considered when evaluating public health interventions to prevent or control infectious disease outbreaks. In this overview, we apply a linear algebraic approach to re-derive some well-known results pertaining to preferential within- and proportionate among-group contacts in compartmental models of pathogen transmission. We give results for the meta-population effective reproduction number ([Formula: see text]) assuming different levels of vaccination in the sub-populations. Specifically, we unpack the dependency of [Formula: see text] on the fractions of contacts reserved for individuals within one's own subgroup and, by obtaining implicit expressions for the partial derivatives of [Formula: see text], we show that these increase as this preferential-mixing fraction increases in any sub-population.
Prior research has shown that searching for multiple targets in a visual search task enhances distractor memory in a subsequent recognition test. Three non-mutually exclusive accounts have been offered to explain this phenomenon. The mental comparison hypothesis states that searching for multiple targets requires participants to make more mental comparisons between the targets and the distractors, which enhances distractor memory. The attention allocation hypothesis states that participants allocate more attention to distractors because a multiple-target search cue leads them to expect a more difficult search. Finally, the partial match hypothesis states that searching for multiple targets increases the amount of featural overlap between targets and distractors, which necessitates greater attention in order to reject each distractor. In two experiments, we examined these hypotheses by manipulating visual working memory (VWM) load and target-distractor similarity of AI-generated faces in a visual search (i.e., RSVP) task. Distractor similarity was manipulated using a multidimensional scaling model constructed from facial landmarks and other metadata of each face. In both experiments, distractors from multiple-target searches were recognized better than distractors from single-target searches. Experiment 2 additionally revealed that increased target-distractor similarity during search improved distractor recognition memory, consistent with the partial match hypothesis.
Cryogenic cave carbonates have been described from several formerly or presently glaciated karst caves. In most of these occurrences, they precipitated as loose grains or aggregates with various morphologies and sizes. Here, we report on a new speleothem type ( cryogenic ridges ) identified in Sohodoalele Mici Cave (SW Romania) within a large chamber near the entrance shaft. This study was motivated by the presence of a network of calcite ridges over the stalactites’ surface and by the observation that during winter, these speleothems are covered by a thin ice layer. The higher δ18O (−3.5 to –1‰) and δ13C (0 to 7‰) values found in the calcite ridges relative to δ18O (–7.5 to –4‰) and δ13C (–9 to –2‰) values of calcite from the inner stalactite indicate that the ridges are of cryogenic origin and formed during relatively rapid carbonate precipitation associated with evaporative cooling and freezing of the water. Four U-series ages suggest that the stalactites with ridges formed during cold winters of the Holocene, when cave air temperatures dropped below freezing.
Enzymatic deconstruction of poly(ethylene terephthalate) (PET) is under intense investigation, given the ability of hydrolase enzymes to depolymerize PET to its constituent monomers near the polymer glass transition temperature. To date, reported PET hydrolases have been sourced from a relatively narrow sequence space. Here, we identify additional PET-active biocatalysts from natural diversity by using bioinformatics and machine learning to mine 74 putative thermotolerant PET hydrolases. We successfully express, purify, and assay 51 enzymes from seven distinct phylogenetic groups; observing PET hydrolysis activity on amorphous PET film from 37 enzymes in reactions spanning pH from 4.5–9.0 and temperatures from 30–70 °C. We conduct PET hydrolysis time-course reactions with the best-performing enzymes, where we observe differences in substrate selectivity as function of PET morphology. We employed X-ray crystallography and AlphaFold to examine the enzyme architectures of all 74 candidates, revealing protein folds and accessory domains not previously associated with PET deconstruction. Overall, this study expands the number and diversity of thermotolerant scaffolds for enzymatic PET deconstruction.
In 2020, the Federal government completed the first major restructuring of its interagency coordination for meteorological services in over 50 years. The Interagency Council for Advancing Meteorological Services (ICAMS) now provides White House-level coordination of Federal resources to advance the full suite of meteorological services now and into the future. Of particular relevance to the external community is ICAMS’ objective to strengthen and expand partnerships with non-government sectors. This article outlines ICAMS intellectual foundations, progress and near-term plans, including efforts to develop a longterm strategy, as means to foster community engagement. ICAMS will continue to provide coordination across Federal agencies and opportunities for input from, and engagement with, non-governmental entities. The development of a long-term strategy is a process that ICAMS is embarking on in earnest, and sustained external community engagement is key to sound development and effective implementation.
In this paper, we present SCAMP – Social Configuration Affordances for Museum Play – an analytical framework we develop and use to highlight the relationship between designed affordances at interactive museum exhibits and different social playful behaviors they trigger and support. We do this through a selective case study analysis of Rainbow Agents, an interactive museum exhibit designed to support play across multiple social configurations. This variety of configurations is valuable for museum settings, as it helps museum visitors engage with each other according to their preferences and also enables the emergence of modes of collaboration and competition novel for learners in such contexts. Our SCAMP analysis of Rainbow Agents sheds light on design features which successfully support different forms of productive social play – including short and long episodes of competitive, collaborative and parallel play, spanning play, teaching, and receiving interpersonal interactions. In particular, we pay attention to behaviors representing a variety of mentoring and learning opportunities – in line with and extending the vision and goals of educational games’ and science museum exhibits’ designers and researchers.
Although corridors are frequently regarded as a way to mitigate the negative effects of habitat fragmentation, concerns persist that corridors may facilitate the spread of invasive species to the detriment of native species. The invasive fire ant, Solenopsis invicta, has two social forms. The polygyne form has limited dispersal abilities relative to the monogyne form. Our previous work in a large‐scale corridor experiment showed that in landscapes dominated by the polygyne form, fire ant density was higher and native ant species richness was lower in habitat patches connected by corridors than in unconnected patches. We expected that these observed corridor effects would be transient, that is, that fire ant density and native ant species richness differences between connected and unconnected patches would diminish over time as fire ants eventually fully established within patches. We tested this prediction by resampling the three landscapes dominated by polygyne fire ants 6 to 11 years after our original study. Differences in fire ant density between connected and unconnected habitat patches in these landscapes decreased, as expected. Differences in native ant species richness were variable but lowest in the last 2 years of sampling. These findings support our prediction of transient corridor effects on this invasive ant and stress the importance of temporal dynamics in assessing population and community impacts of habitat connectivity. Resasco et al. examine the effects of habitat corridors on polygyne fire ants (Solenopsis invicta) and native ants in a large‐scale experiment over a decade. Their findings show transient corridor effects on this invasive ant and stress the importance of temporal dynamics in assessing population and community impacts of connectivity.
Direct observations of the oceans acquired on oceanographic research ships operated across the international community support fundamental research into the many disciplines of ocean science and provide essential information for monitoring the health of the oceans. A comprehensive knowledge base is needed to support the responsible stewardship of the oceans with easy access to all data acquired globally. In the United States, the multidisciplinary shipboard sensor data routinely acquired each year on the fleet of coastal, regional and global ranging vessels supporting academic marine research are managed by the Rolling Deck to Repository (R2R, program. With over a decade of operations, the R2R program has developed a robust routinized system to transform diverse data contributions from different marine data providers into a standardized and comprehensive collection of global-ranging observations of marine atmosphere, ocean, seafloor and subseafloor properties that is openly available to the international research community. In this article we describe the elements and framework of the R2R program and the services provided. To manage all expeditions conducted annually, a fleet-wide approach has been developed using data distributions submitted from marine operators with a data management workflow designed to maximize automation of data curation. Other design goals are to improve the completeness and consistency of the data and metadata archived, to support data citability, provenance tracking and interoperable data access aligned with FAIR (findable, accessible, interoperable, reusable) recommendations, and to facilitate delivery of data from the fleet for global data syntheses. Findings from a collection-level review of changes in data acquisition practices and quality over the past decade are presented. Lessons learned from R2R operations are also discussed including the benefits of designing data curation around the routine practices of data providers, approaches for ensuring preservation of a more complete data collection with a high level of FAIRness, and the opportunities for homogenization of datasets from the fleet so that they can support the broadest re-use of data across a diverse user community.
Little is known about whether and how workers with disabilities participate in the many on-demand labor platforms that make up the growing gig economy. Understanding disabled gig workers' experiences is a vital step toward developing inclusive and equitable labor platforms. Through interviews with 24 disabled gig workers and observational fieldwork, we present a rich, in-depth picture of the opportunities and challenges presented by four main types of gig work (ridesharing, delivery, crowdwork, and freelancing) for workers with a wide range of disabilities. We identify a key tension: gig work can be a vital source of needed income for workers who have been excluded from traditional workplaces, but at the same time, the structure of gig platforms present workers with a host of new disability-related challenges, including around algorithmic control and performance evaluation. We discuss how this tension plays out in terms of how workers engage in gig work and protect themselves from risk. We also call attention to how many workers can face complicated, intersectional challenges based on multiple marginalized identities in addition to disability, such as race, gender, sexual orientation, and socioeconomic status. Our work contributes to research on the gig economy by centering the perspectives of workers who are marginalized based on disability and other identities. We show how workers face several penalties based on disability, including shouldering extensive invisible labor to mitigate the challenges they face. Based on our interviews, we suggest several ways that on-demand labor platforms can be designed to be more inclusive of disability, including how to improve the accessibility of various tasks while mitigating the discrimination and negative interactions faced by disabled workers.
Committees touch nearly every facet in the science, technology, engineering, and mathematics research enterprise. However, the role of gatekeeping through committee work has received little attention in Earth and space sciences. We propose a novel concept called, “regenerative gatekeeping” to challenge institutional inertia, cultivate belonging, accessibility, justice, diversity, equity, and inclusion in committee work. Three examples, a hiring committee process, a seminar series innovation, and an awards committee, highlight the need to self‐assess policies and practices, ask critical questions and engage in generative conflict. Rethinking committee work can activate distributed mechanisms needed to promote change.
Oceanic crust formed at mid-ocean ridges may be later modified by off-ridge magmatism forming seamounts, guyots, and islands. We investigate processes associated with seamount formation in the Gulf of Alaska Seamount Province using two coincident seismic reflection/wide-angle profiles. A north-south profile crosses the Kodiak-Bowie Seamount Chain and Aja fracture zone (FZ), and an orthogonal east-west profile is located about 90 km south of the seamount chain over Pacific plate oceanic crust. Structure along the profile away from the seamount chain is consistent with typical oceanic crust. Crust in our study region is thinnest (about 5.6 km) at the Aja FZ. Unlike observations from active transform faults, no low-velocity anomaly is observed at the Aja FZ suggesting that the crustal velocities have recovered to normal values through crack closure and crack healing. Higher lower crustal velocities (~7.3 and > 7.5 km/s) and thicker crust (~8.5 and ~ 7.0 km) are observed near the Pratt and Durgin Seamounts and at the intersection of the Kodiak-Bowie Seamount Chain linear trend, respectively. These observations are attributed to magmatic underplating associated with seamount province magmatism. Lithospheric thickness variations across the Aja FZ may form a barrier or impediment to magmatic flow. The thickest crust (8.5 km) along our two profiles is located on the younger side of the FZ, and we suggest that the majority of magmatism jumped south of the Aja FZ when thinner lithosphere was encountered by the Bowie hot spot. The crustal structure near the Kodiak-Bowie Seamount Chain is most similar to that of other seamounts and guyots that formed on similarly young lithosphere (8–12 Ma). Our results suggest that lithospheric thickness at the time of hot spot interaction has a large control on magmatic underplating at seamounts and seamount provinces.
This paper presents a new Lp-primal–dual weak Galerkin (PDWG) finite element method for the div–curl system with the normal boundary condition for p>1. Two crucial features for the proposed Lp-PDWG finite element scheme are as follows: (1) it offers an accurate and reliable numerical solution to the div–curl system under the low Wα,p-regularity (α>0) assumption for the exact solution; (2) it offers an effective approximation of the normal harmonic vector fields on domains with complex topology. An optimal order error estimate is established in the Lq-norm for the primal variable where 1p+1q=1. A series of numerical experiments are presented to demonstrate the performance of the proposed Lp-PDWG algorithm.
Let $D>1$ be a fixed integer. Given a smooth bounded, convex domain $\Omega \subset \mathbb{R}^D$ and $H:\mathbb{R}^D\rightarrow [0,\infty )$ a convex, even, and $1$-homogeneous function of class $C^{3,\alpha }(\mathbb{R}^D\setminus \lbrace 0\rbrace )$ for which the Hessian matrix $D^2(H^p)$ is positive definite in $\mathbb{R}^D\setminus \lbrace 0\rbrace $ for any $p\in (1,\infty )$, we study the monotonicity of the principal frequency of the anisotropic $p$-Laplacian (constructed using the function $H$) on $\Omega $ with respect to $p\in (1,\infty )$. As an application, we find a new variational characterization for the principal frequency on domains $\Omega $ having a sufficiently small inradius. In the particular case where $H$ is the Euclidean norm in $\mathbb{R}^D$, we recover some recent results obtained by the first two authors in [3, 4].
Reliable access to Arctic research infrastructure is critical to the future of polar science. In cultivating proposals, it is essential that researchers have a deep understanding of existing platforms when selecting the appropriate research site and experimental design for projects. However, Arctic infrastructure platforms are often funded as national assets, and choices for what would be the best platform for the project are sometimes at odds with a researcher’s ability to gain access. Researchers from Arctic and non-Arctic nations are poised to benefit from reducing barriers and increasing cooperation around transnational access to Arctic infrastructure, allowing scientists to successfully execute the research that is most needed rather than what is just logistically feasible. This commentary provides a summary of findings from a workshop held at the 2021 Arctic Science Summit Week to discuss navigating “transnational” or “cross-border” access to national research infrastructure. This workshop brought together users and operators of Arctic infrastructure platforms with the three goals of identifying challenges, best practices, and possible next steps for improved collaboration.
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269 members
Eduard Babulak
  • Research Panelist
David Boboltz
  • Division of Astronomical Sciences (AST)
Babak Behnam
  • Regulatory Affairs
Michael Sieracki
  • Division of Ocean Sciences (OCE)
Alex Simonian
  • Chemical, Bioengineering, Environmental and Transport Systems (CBET) Division
Alexandria, United States