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Do Small Classes in Higher Education Reduce Performance Gaps in STEM?
Get PDFPerformance gaps in science are well documented, and an examination of underlying mechanisms that lead to underperformance and attrition of women and underrepresented minorities (URM) may offer highly targeted means to promote such students. Determining factors that influence academic performance may provide a basis for improved pedagogy and policy development at the university level. We examined the impact of class size on students in 17 biology courses at four universities. Although the female students underperformed on high-stakes exams compared with the men as class size increased, the women received higher scores than the men on nonexam assessments. The URM students underperformed across grade measures compared with the majority students regardless of class size, suggesting that other characteristics of the education environment affect learning. Student enrollment is expected to increase precipitously in the next decade, underscoring the need to prioritize individual student potential rather than yield to budget constraints when considering equitable pedagogy and caps on classroom sizes.PublishedYe
Two-Dimensional Particle-in-Cell Simulation of Magnetosonic Wave Excitation in a Dipole Magnetic Field
Get PDFThe excitation of magnetosonic waves in the meridian plane of a rescaled dipole magnetic field is investigated, for the first time, using a general curvilinear particle-in-cell simulation. Our simulation demonstrates that the magnetosonic waves are excited near the equatorial plane by tenuous ring distribution protons. The waves propagate nearly perpendicularly to the background magnetic field along both radially inward and outward directions. Different speeds of inward and outward propagation result in the asymmetrical distribution about the source region. The waves are accompanied by energization of both cool protons and electrons near the wave source region. The cool protons are heated perpendicularly, while the cool electrons can be heated in the parallel direction and also experience enhanced perpendicular drift at the presence of intense wave power. The implications of simulation results to the observations of magnetosonic waves and related particle heating in the inner magnetosphere are also discussed. Plain Language Summary The Earth's radiation belt is a natural space environment consisting of relativistic electrons trapped in geospace. It exhibits great variability due to solar activities and poses a great threat to spacecraft orbiting in the regions and to astronauts. The primary physical process involved for radiation belt variability is through interaction with electromagnetic waves. Magnetosonic waves are one of the important waves that are capable of electron scattering, the efficiency of which depends on the wave detailed properties. Previous simulation has investigated the wave excitation in a homogeneous plasma. Here we present for the first time a 2-D particle-in-cell simulation to understand magnetosonic wave excitation and propagation in an inhomogeneous dipole magnetic field. The simulation results not only illustrate the wave temporal evolution and spatial distribution, both in radial and latitudinal distribution, but also reveal their effects on thermal electron and proton heating. These results are ready for verification against wave and particle measurement from the ongoing magnetospheric missions such as Van Allen Probes.PublishedYe
SEED - Speech Exemplars and Evaluation Database
No full textThis is a database of recordings of children's speech patterns, with and without pathologies.N
Embryological development and global change: how do reptile embryos respond to thermal stress in urban environments?
No full textTwo components of global change, climate change and urbanization, both contribute to increased ambient temperatures that may induce heat stress or mortality in animals. Each phenomenon independently results in both increased mean temperatures and increased maximum day-time temperatures; however, there is also the potential for these components to act synergistically: extreme temperatures due to the urban heat island effect are likely to be exacerbated as the earth’s surface warms due to climate change. Many animals can respond to harmful temperatures behaviorally, by altering their periods of activity or shifting their habitat use. Such behavioral compensation, however, is unavailable to embryos of ectotherms which typically develop inside eggs in the ground and receive little or no parental care. Thus, this early life stage is expected to be more vulnerable to harmful temperatures caused by aspects of global change, and yet, the effects of ecologically relevant thermal stress on these embryos has received little attention. We sought to understand the consequences of such extreme temperatures on embryological development by utilizing two species of lizard (Anolis sagrei and Anolis cristatellus) that commonly inhabit urban areas. We measured ground temperatures in an urban landscape where lizards nest and modeled daily thermal fluctuations that included brief periods of extremely high temperatures. We then subjected eggs of both species to various magnitudes and frequencies of these thermal fluctuations at multiple stages of embryological development. We report the effects on survival, physiology, morphology, and performance of these ecologically relevant thermal regimes and highlight the potential for extreme incubation temperatures to differentially impact species.N
Scholarliness in George Eliot Criticism
No full textArticle from the George Eliot Review, digitized and hosted by the George Eliot Review Online.Publishe
Biomechanical factors influencing successful self-righting in the pleurodire turtle Emydura subglobosa
Get PDFSelf-righting performance is a key ability for most terrestrial animals, and has been used as a metric of fitness, exhaustion and thermal limits in a variety of taxa. However, there is little understanding of the underlying mechanisms that drive variation in self-righting performance. To evaluate the mechanical factors that contribute to success versus failure when animals attempt to self-right, we compared force production and kinematic behavior in the rigid-bodied, pleurodire turtle Emydura subglobosa between successful and unsuccessful self-righting efforts. We found that the moment exerted during efforts to roll the body and the velocity of that roll are the primary drivers behind self-righting success. Specifically, turtles that self-righted successfully produced both larger moments and faster rolls than turtles that failed. In contrast, the angle at which the head was directed to lever the body and the extent of yaw that was incorporated in addition to roll had little impact on the likelihood of success. These results show that specific performance metrics can predict the ability of animals to self-right, providing a framework for biomimetic applications as well as future comparisons to test for differences in self-righting performance across animals from different environments, sexes, populations and species.PublishedYe
The Role of Breccia Lenses in Regolith Generation From the Formation of Small, Simple Craters: Application to the Apollo 15 Landing Site
Get PDFImpact cratering is likely a primary agent of regolith generation on airless bodies. Regolith production via impact cratering has long been a key topic of study since the Apollo era. The evolution of regolith due to impact cratering, however, is not well understood. A better formulation is needed to help quantify the formation mechanism and timescale of regolith evolution. Here we propose an analytically derived stochastic model that describes the evolution of regolith generated by small, simple craters. We account for ejecta blanketing as well as regolith infilling of the transient crater cavity. Our results show that the regolith infilling plays a key role in producing regolith. Our model demonstrates that because of the stochastic nature of impact cratering, the regolith thickness varies laterally, which is consistent with earlier work. We apply this analytical model to the regolith evolution at the Apollo 15 site. The regolith thickness is computed considering the observed crater size-frequency distribution of small, simple lunar craters (< 381m in radius for ejecta blanketing and <100m in radius for the regolith infilling). Allowing for some amount of regolith coming from the outside of the area, our result is consistent with an empirical result from the Apollo 15 seismic experiment. Finally, we find that the timescale of regolith growth is longer than that of crater equilibrium, implying that even if crater equilibrium is observed on a cratered surface, it is likely that the regolith thickness is still evolving due to additional impact craters.
Plain Language Summary Impact cratering likely generates much of the regolith (the surface layer made up of a mixture of rocks, rock fragments, sand, and dust) observed on airless planetary surfaces. However, the way that the regolith layer evolves and thickens over time due to impact cratering events is not well understood. When a small, simple crater forms into hard rock, regolith is produced by fracturing the target rock and is deposited in the crater's ejecta blanket and within its transient crater cavity. Here we discuss an analytically derived stochastic model that describes the evolution of regolith developed by simple craters. Our results indicate that the regolith deposited on crater interiors is particularly important to consider when describing the distribution of regolith. Our model also indicates that the regolith thickness varies from one location to another. We apply this model to the regolith at the Apollo 15 landing site by considering the size distribution of observed small, simple lunar craters. Allowing for some regolith coming from outside of the area of the landing site, our result is consistent with an empirical result from the Apollo 15 seismic experiment.Publishe