Kenyon College
  • Gambier, United States
Recent publications
Purpose: The purpose of this review was to estimate the prevalence of screen-based disordered eating (SBDE) and several potential risk factors in university undergraduate students around the world. Methods: An electronic search of nine data bases was conducted from the inception of the databases until 1st October 2021. Disordered eating was defined as the percentage of students scoring at or above established cut-offs on validated screening measures. Global data were also analyzed by country, research measure, and culture. Other confounders in this review were age, BMI, and sex. Results: Using random-effects meta-analysis, the mean estimate of the distribution of effects for the prevalence of SBDE among university students (K = 105, N = 145,629) was [95% CI] = 19.7% [17.9%; 21.6%], I2 = 98.2%, Cochran's Q p-Value = 0.001. Bayesian meta-analysis produced an odd estimate of 0.24 [0.20, 0.30], τ = 92%. Whether the country in which the students were studying was Western or non-Western did not moderate these effects, but as either the mean BMI of the sample or the percentage of the sample that was female increased, the prevalence of SBDE increased. Conclusions: These findings support previous studies indicating that many undergraduate students are struggling with disordered eating or a diagnosable eating disorder, but are neither receiver effective prevention nor accessing accurate diagnosis and available treatment. It is particularly important to develop ever more valid ways of identifying students with high levels of disordered eating and offering them original or culturally appropriate and effective prevention or early treatment.
Conservation of mobile organisms is difficult in the absence of detailed information about movement and habitat use. While the miniaturization of tracking devices has eased the collection of such information, it remains logistically and financially difficult to track a wide range of species across a large geographic scale. Predictive distribution models can be used to fill this gap by integrating both telemetry and census data to construct distribution maps and inform conservation goals and planning. We used tracking data from 520 individuals of 14 seabird species in Atlantic Canada to first compare foraging range and distance to shorelines among species across colonies, and then developed tree-based machine-learning models to predict foraging distributions for more than 5000 breeding sites distributed along more than 5000 km of shoreline. Despite large variability in foraging ranges among species, tracking data revealed clusters of species using similar foraging habitats (e.g., nearshore vs. offshore foragers), and within species, foraging range was highly colony-specific. Even with this variability, distance from the nesting colony was an important predictor of distribution for nearly all species, while distance from coastlines and bathymetry (slope and ruggedness) were additional important predictors for some
Reproduction in procellariiform birds is characterized by a single egg clutch, slow development, a long breeding season and obligate biparental care. Female Leach’s Storm Petrels Hydrobates leucorhous, nearly monomorphic members of this order, produce eggs that are between 20 and 25% of adult body weight. We tested whether female foraging behaviour differs from male foraging behaviour during the ~ 44‐day incubation period across seven breeding colonies in the Northwest Atlantic. Over six breeding seasons, we used a combination of Global Positioning System and Global Location Sensor devices to measure characteristics of individual foraging trips during the incubation period. Females travelled significantly greater distances and went farther from the breeding colony than did males on individual foraging trips. For both sexes, the longer the foraging trip, the greater the distance. Independent of trip duration, females travelled farther, and spent a greater proportion of their foraging trips prospecting widely as defined by behavioural categories derived from a Hidden Markov Model. For both sexes, trip duration decreased with date. Sex differences in these foraging metrics were apparently not a consequence of morphological differences or spatial segregation. Our data are consistent with the idea that female foraging strategies differed from male foraging strategies during incubation in ways that would be expected if females were still compensating for egg formation.
The vertebrate peripheral nervous system (PNS) is an intricate network that conveys sensory and motor information throughout the body. During development, extracellular cues direct the migration of axons and glia through peripheral tissues. Currently, the suite of molecules that govern PNS axon-glial patterning is incompletely understood. To elucidate factors that are critical for peripheral nerve development, we characterized the novel zebrafish mutant, stl159, that exhibits abnormalities in PNS patterning. In these mutants, motor and sensory nerves that develop adjacent to axial muscle fail to extend normally, and neuromasts in the posterior lateral line system, as well as neural crest-derived melanocytes, are incorrectly positioned. The stl159 genetic lesion lies in the basic helix-loop-helix (bHLH) transcription factor tcf15, which has been previously implicated in proper development of axial muscles. We find that targeted loss of tcf15 via CRISPR-Cas9 genome editing results in the PNS patterning abnormalities observed in stl159 mutants. Because tcf15 is expressed in developing muscle prior to nerve extension, rather than in neurons or glia, we predict that tcf15 non-cell-autonomously promotes peripheral nerve patterning in zebrafish through regulation of extracellular patterning cues. Our work underscores the importance of muscle-derived factors in PNS development.
Maculation on avian eggshells has the potential to serve as an identity signal, and this information might help females recognise their eggs/nest or reject foreign eggs laid by hetero‐ or conspecific brood parasites. Recognising eggs could be adaptive in cases where birds nest in dense colonies, as reports of conspecific brood parasitism are overrepresented in colony‐nesting species. We leveraged the variation in breeding biology (solitary vs. colonial breeding) and eggshell phenotype in the swallows and martins (Hirundinidae) to test for correlated evolution between these traits, while also accounting for nest type, as maculation may camouflage eggs in open‐cup nests. We found that maculated eggs were more likely to be laid by species that breed socially and build open‐cup nests where maculation would be more visible than in dark cavity nests.
ConspectusThis Account discusses the evolution of our strategy to conduct environmentally responsible research in the field of polymer chemistry. To contextualize our work, we begin with a broad historical overview of the modern environmental movement, the rise of sustainability as a concept, and how chemistry has responded to these forces, which were often sharply critical of our field. We then trace our own responses, from graduate school onward, chronicling a series of experiences and research projects that molded, challenged, and reshaped how we think about sustainability in polymer science.Since beginning our independent careers in 2004, we have recognized and worked to resolve the tension between designing synthetic polymers for specific desired thermomechanical properties and minimizing environmental impact. In our early years, we were most strongly guided by the 12 Principles of Green Chemistry (12PGC), which had only recently been proposed. The authors' early research agendas had a rather narrow focus on two areas, specifically catalysis and biobased monomers, which we saw as strongly linked to sustainability. Over time, we found these areas to be too narrow in their focus, ignoring important considerations such as the capacity of monomer supply to support scale-up and the impact polymers have at the end of their usage lifetimes. With respect to monomers and catalysts, we consider descriptive metrics that quantify waste production and the toxicity of compounds used during synthesis. In terms of polymer end-of-life, we discuss hydrophobicity as a tool to help understand susceptibility to degradation in the environment as well as some of the concerns with design for degradation, a critical component of 12PGC.Now, after nearly two decades of investigation, we believe that achieving sustainability in polymer science will require us to move beyond the qualitative use of the 12PGC to a portfolio of metrics. We note a heartening increase in the availability and use of such metrics and tools across the field. These include items that provide limited insight but are relatively trivial to integrate into existing workflows such as E factor or the Toxicity Estimation Software Tool. We also appreciate the increased use of Life Cycle Assessment (LCA), which is both dramatically more thorough and difficult to deploy. Finally, we propose the creation of a national LCA center, similar to instrumental core facilities. Such a resource would enable the use of this tool across multiple phases of research and we hope would more effectively guide us to a sustainable future.
Workers in female-dominated occupations earn less, on average, than workers in comparable male-dominated occupations. To explain the gendered occupational wage disparity, com pensating differentials theory focuses on women’s preferences and asserts that women cluster in occupations that pay less in exchange for family-friendly job amenities. On the other hand, the devaluation perspective argues these wage discrepancies are the result of the cultural devaluation of women’s work that leads to both lower wages and a lower likelihood of having job amenities. Using data from the 2017–2018 American Time Use Survey Leave Module, I examine whether workers in female-dominated occupations are indeed more likely to have access to family-friendly job amenities. I focus on workers’ access to three contemporary family-friendly job amenities: paid leave, remote work, and flexible scheduling. I find that workers in female-dominated jobs are no more likely to have access to family-friendly job amenities than workers in male-dominated jobs. Additionally, family-friendly job amenities are associated with higher wages, not the lower wages as compensating differentials posits. These findings suggest that compensating differentials theory cannot explain the clustering of women in lower-paying occupations.
This study explored the experiences of Head Start parents becoming involved in their pre-school age children’s individualized education program (IEP) process. Seven participants from the rural Midwest engaged in focus group ( N = 2) or interview ( N = 1) format discussions regarding barriers to involvement in the IEP process and recommendations to alleviate these barriers. Qualitative analysis with thematic coding was used to interpret the data. Results indicated that parents believed they lacked necessary information that could increase their advocacy for their children and reported the wording of the IEP was too difficult to understand. In addition, parents felt that their negative emotions barred them from being active members at IEP meetings. Parents described Head Start’s encouragement and positive parent–teacher communication helped alleviate some barriers but believed that a yearly class on IEPs and more frequent one-on-one meetings would help them become better advocates for their young children.
Out-of-equilibrium, strong correlation in a many-body system can trigger emergent properties that act to constrain the natural dissipation of energy and matter. Signs of such self-organization appear in the avalanche, bifurcation, and quench of a state-selected Rydberg gas of nitric oxide to form an ultracold, strongly correlated ultracold plasma. Work reported here focuses on initial stages of avalanche and quench, and uses the mm-wave spectroscopy of an embedded quantum probe to characterize the intermolecular interaction dynamics associated with the evolution to plasma. Double-resonance excitation prepares a Rydberg gas of nitric oxide composed of a single selected state of principal quantum number, n 0 . Penning ionization, followed by an avalanche of electron-Rydberg collisions, forms a plasma of NO ⁺ ions and weakly bound electrons, in which a residual population of n 0 Rydberg molecules evolves to a state of high orbital angular momentum, l. Predissociation depletes the plasma of low- l molecules. Relaxation ceases and n 0 l(2) molecules with l {greater than or equal to} 4 persist for very long times. At short times, varying excitation spectra of mm-wave Rydberg-Rydberg transitions mark the rate of electron-collisional l-mixing. Deep depletion resonances that persist for long times signal energy redistribution in the basis of central-field Rydberg states. The widths and asymmetries of Fano lineshapes witness the degree to which coupling in the arrested bath i) broadens the allowed transition and ii) mixes the local network of levels in the ensemble.
Polycyclic codes are a generalization of cyclic and constacyclic codes. Even though they have been known since 1972 and received some attention more recently, there have not been many studies on polycyclic codes. This paper presents an in-depth investigation of polycyclic codes associated with trinomials. Our results include a number of facts about trinomials, some properties of polycyclic codes, and many new quantum codes derived from polycyclic codes. We also state several conjectures about polynomials and polycyclic codes. Hence, we show useful features of polycyclic codes and present some open problems related to them.
Multilayer heterostructures of the topological insulator Bi2Se3 and conventional semiconductor In2Se3, as well as solid solution layers of (Bi1-xInx)2Se3 layers were grown by molecular beam epitaxy and analyzed in-operando using spectroscopic ellipsometry (SE). SE spectra were obtained after the deposition of each layer to determine the respective dielectric functions and thicknesses of each layer. In contrast to ex-situ SE, where uncertainty in the dielectric function and thicknesses of individual layer impose limitations to extract a correct model for the dielectric function of such multilayer heterostructures from a single set of SE data, the step-by-step in-situ SE data recover more precise dielectric functions for Bi2Se3, In2Se3, (Bi0.7In 0.3)2Se3 and the cap-layer. The optical models developed for multilayer structures can decipher minute perturbations in layers as the growth progresses. Our models show that a ∼7 nm Bi2Se3 layer grown next to a sapphire substrate seems to disappear as the structure is annealed at 600 °C. Finally, when the dielectric functions were represented as a collection of Kramers-Kronig-consistent oscillators, in-situ SE predicted the quality of films; the weighted-average broadening parameter for oscillators used for Bi2Se3 films grown on (Bi0.7In 0.3)2Se3 layer is ∼20% smaller compared to Bi2Se3 films directly grown on sapphire, confirming that the former film is of better quality, and providing a direct metric to quantify film quality and defect concentration. These conclusions were corroborated by transport data.
In this chapter, we will begin exploring the Radiography/Tomography example discussed in Section 1.2.1.
Welcome to your first course in linear algebra—arguably the most useful mathematical subject you will encounter. Not only are the skills important for solving linear problems, they are a foundation for many advanced topics in mathematics, engineering, computer science, economics, business, and more.
The tomography problem—finding a brain image reconstruction based on radiographic data—has been challenging for a number of reasons. We have found that the radiographic transformation is, in general, not invertible and experimental data need not be in its range. This means that if we assume the given linear relationship, then we may either have no solution or infinitely many solutions. We should not be satisfied with such an answer. Instead, we use this result to motivate a deeper study.
In studying the behavior of heat states, we used a (linear) heat diffusion transformation E. Given a heat state u(t) at time t, the heat state at a later time t+Δt is given by u(t+Δt)=Eu(t). But, this works well only if the time step Δt is sufficiently small. So, in order to describe the evolution of heat states over a longer period of time, the heat diffusion transformation must be applied many times. For example, in Figure 6.1, u(3000Δt) requires 3000 applications of E.
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806 members
Andrew J Kerkhoff
  • Departments of Biology and Mathematics & Statistics
Wade H Powell
  • Department of Biology
Sarah K Murnen
  • Department of Psychology
Siobhan Fennessy
  • Department of Biology
Nuh Aydin
  • Department of Mathematics
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Gambier, United States