Case Studies in Critical Reflection Praxis in University Studies: The Stance and Dance

This article articulates the experience of three professors from different disciplines, teaching at three levels of University Studies, Portland State University\u27s general education program, for whom the toggling between personal/professional critical practices and use of reflective practices in the classroom has led to transformative learning experiences for them and their students. It describes the specific reflective tools and methods they used for teaching and professional development, and considers the challenges to sustaining critical reflection and how those challenges might be addressed. The authors argue that critical reflection (CR) is an important practice for teachers and students of general education. In particular, CR engages the habits of mind and capacities, such as critical thinking, central to the goals of general education, as well as engaging the practical skills needed to procure jobs and succeed as professionals. As a professional practice for teachers, it contributes to improved and purposeful teaching methods and rationales, and can build rapport, trust, and credibility with students. Because CR takes time and practice, it is important for students to be exposed to many different methods and have opportunities to practice CR methods from a variety of disciplines/backgrounds throughout their general education

Variable‐Threshold Behavior in Rivers Arising From Hillslope‐Derived Blocks

Geomorphologists often rely on simple models of river channel incision for predicting rates of landscape evolution and channel response to perturbations, as well as extracting climatic and tectonic signals from river longitudinal profiles. Recent work has shown that large, hillslope‐derived blocks delivered to rivers may noticeably alter the form and evolution of river profiles from the behavior predicted by the most common models. Here we use a 1‐D model of river reach erosion and hillslope block delivery to explore the conditions under which block delivery strongly influences channel evolution. We use global sensitivity analysis to understand which model parameters most strongly affect the channel longitudinal profile. We explore the effects of blocks on the relationship between erosion rate and channel gradient, and on the erosion rate‐channel steepness exponent ϕ, and find that block effects result in highly variable slope and ϕ over the range of erosion rates and climatic conditions (discharge mean and variability) tested. The influence of blocks on erosion rate‐slope scaling may be approximated by a piecewise model: The erosion threshold imposed by blocks scales linearly with erosion rate when blocks are infrequently mobile and remains constant when blocks are frequently mobile. We explore the implications of this variable‐threshold model for the erosion rate‐channel steepness relationship and find that erosion rate‐dependent thresholds imposed by hillslope‐derived blocks cause significant departures from previous models but may be consistent with existing field data sets. Our work has implications for landscape evolution modeling and the inversion of channel profiles for forcing information

Terrainbento 1.0: a Python package for multi-model analysis in long-term drainage basin evolution

Models of landscape evolution provide insight into the geomorphic history of specific field areas, create testable predictions of landform development, demonstrate the consequences of current geomorphic process theory, and spark imagination through hypothetical scenarios. While the last 4 decades have brought the proliferation of many alternative formulations for the redistribution of mass by Earth surface processes, relatively few studies have systematically compared and tested these alternative equations. We present a new Python package, terrainbento 1.0, that enables multi-model comparison, sensitivity analysis, and calibration of Earth surface process models. Terrainbento provides a set of 28 model programs that implement alternative transport laws related to four process elements: hillslope processes, surface-water hydrology, erosion by flowing water, and material properties. The 28 model programs are a systematic subset of the 2048 possible numerical models associated with 11 binary choices. Each binary choice is related to one of these four elements – for example, the use of linear or nonlinear hillslope diffusion. Terrainbento is an extensible framework: base classes that treat the elements common to all numerical models (such as input/output and boundary conditions) make it possible to create a new numerical model without reinventing these common methods. Terrainbento is built on top of the Landlab framework such that new Landlab components directly support the creation of new terrainbento model programs. Terrainbento is fully documented, has 100&thinsp;% unit test coverage including numerical comparison with analytical solutions for process models, and continuous integration testing. We support future users and developers with introductory Jupyter notebooks and a template for creating new terrainbento model programs. In this paper, we describe the package structure, process theory, and software implementation of terrainbento. Finally, we illustrate the utility of terrainbento with a benchmark example highlighting the differences in steady-state topography between five different numerical models.</p

Terrainbento 1.0: a Python package for multi-model analysis in long-term drainage basin evolution

Models of landscape evolution provide insight into the geomorphic history of specific field areas, create testable predictions of landform development, demonstrate the consequences of current geomorphic process theory, and spark imagination through hypothetical scenarios. While the last 4 decades have brought the proliferation of many alternative formulations for the redistribution of mass by Earth surface processes, relatively few studies have systematically compared and tested these alternative equations. We present a new Python package, terrainbento 1.0, that enables multi-model comparison, sensitivity analysis, and calibration of Earth surface process models. Terrainbento provides a set of 28 model programs that implement alternative transport laws related to four process elements: hillslope processes, surface-water hydrology, erosion by flowing water, and material properties. The 28 model programs are a systematic subset of the 2048 possible numerical models associated with 11 binary choices. Each binary choice is related to one of these four elements &ndash; for example, the use of linear or nonlinear hillslope diffusion. Terrainbento is an extensible framework: base classes that treat the elements common to all numerical models (such as input/output and boundary conditions) make it possible to create a new numerical model without reinventing these common methods. Terrainbento is built on top of the Landlab framework such that new Landlab components directly support the creation of new terrainbento model programs. Terrainbento is fully documented, has 100 % unit test coverage including numerical comparison with analytical solutions for process models, and continuous integration testing. We support future users and developers with introductory Jupyter notebooks and a template for creating new terrainbento model programs. In this paper, we describe the package structure, process theory, and software implementation of terrainbento. Finally, we illustrate the utility of terrainbento with a benchmark example highlighting the differences in steady-state topography between five different numerical models.</p

The role of infrequently mobile boulders in modulating landscape evolution and geomorphic hazards

A landscape’s sediment grain size distribution is the product of, and an important influence on, earth surface processes and landscape evolution. Grains can be large enough that the motion of a single grain, infrequently mobile in size-selective transport systems, constitutes or triggers significant geomorphic change. We define these grains as boulders. Boulders affect landscape evolution; their dynamics and effects on landscape form have been the focus of substantial recent community effort. We review progress on five key questions related to how boulders influence the evolution of unglaciated, eroding landscapes: 1) What factors control boulder production on eroding hillslopes and the subsequent downslope evolution of the boulder size distribution? 2) How do boulders influence hillslope processes and long-term hillslope evolution? 3) How do boulders influence fluvial processes and river channel shape? 4) How do boulder-mantled channels and hillslopes interact to set the long-term form and evolution of boulder-influenced landscapes? 5) How do boulders contribute to geomorphic hazards, and how might improved understanding of boulder dynamics be used for geohazard mitigation? Boulders are produced on eroding hillslopes by landsliding, rockfall, and/or exhumation through the critical zone. On hillslopes dominated by local sediment transport, boulders affect hillslope soil production and transport processes such that the downslope boulder size distribution sets the form of steady-state hillslopes. Hillslopes dominated by nonlocal sediment transport are less likely to exhibit boulder controls on hillslope morphology as boulders are rapidly transported to the hillslope toe. Downslope transport delivers boulders to eroding rivers where the boulders act as large roughness elements that change flow hydraulics and the efficiency of erosion and sediment transport. Over longer timescales, river channels adjust their geometry to accommodate the boulders supplied from adjacent hillslopes such that rivers can erode at the baselevel fall rate given their boulder size distribution. The delivery of boulders from hillslopes to channels, paired with the channel response to boulder delivery, drives channel-hillslope feedbacks that affect the transient evolution and steady-state form of boulder-influenced landscapes. At the event scale, boulder dynamics in eroding landscapes represent a component of geomorphic hazards that can be mitigated with an improved understanding of the rates and processes associated with boulder production and mobility. Opportunities for future work primarily entail field-focused data collection across gradients in landscape boundary conditions (tectonics, climate, and lithology) with the goal of understanding boulder dynamics as one component of landscape self-organization

Pilot test of ANSI draft standard N13.29 environmental dosimetry -- Performance criteria for testing

American National Standards Institute Draft N13.29 describes performance tests for environmental radiation dosimetry providers. If approved it would be the first step toward applying the types of performance testing now required in personnel dosimetry to environmental radiation monitoring. The objective of this study was to pilot test the draft standard, before it undergoes final balloting, on a small group of dosimetry providers that were selected to provide a mix of facility types, thermoluminescent dosimeter designs and monitoring program applications. The first phase of the pilot test involved exposing dosimeters to laboratory photon, beta, and x-ray sources at routine and accident dose levels. In the second phase, dosimeters were subjected to ninety days of simulated environmental conditions in an environmental chamber that cycled through extremes of temperature and humidity. Two out of seven participants passed all categories of the laboratory testing phase, and all seven passed the environmental test phase. While some relatively minor deficiencies were uncovered in the course of the pilot test, the results show that draft N13.29 describes useful tests that could be appropriate for environmental dosimetry providers. An appendix to this report contains recommendations that should be addressed by the N13.29 working group before draft N13.29 is submitted for balloting

Off-fault deformation rate along the southern San Andreas Fault at Mecca Hills inferred from landscape modeling of curved drainages

Quantifying off-fault deformation (OFD) rates on geomorphic timescales (10^2-10^5 yr) along strike-slip faults is critical for resolving discrepancies between geologic and geodetic slip-rate estimates, improving knowledge of seismic hazard, and understanding the influence of tectonic motion on landscapes. Quantifying OFD over these timescales is challenging without displacement markers such as offset terraces or geologic contacts. We present a landscape evolution model coupled with distributed lateral tectonic shear to show how drainage basins sheared by lateral tectonic motion can reveal OFD rates. The model shows that OFD rate can control the orientation of drainage basin topography: the faster the OFD rate, the greater the deflection of drainage basins towards a fault-parallel orientation. We apply the model to the southern San Andreas Fault near the Mecca Hills, where drainages basins change in orientation with proximity to the fault. Comparison of observed and modeled topography suggests that the OFD rate in the Mecca Hills follows an exponential-like spatial pattern with a maximum rate nearest the fault of 3.5 ± 1.5 mm/yr, which decays to approximately zero at ~600 m distance from the fault. This rate is applicable since the initiation of differential rock uplift in the Mecca Hills at approximately 760 ka. Our results suggest that OFD in this 800 m study area may be as high as 10% of total plate motion. This example demonstrates that curved drainage basins may be used to estimate OFD rates along strike slip faults

Subliminal versus supraliminal stimuli activate neural responses in anterior cingulate cortex, fusiform gyrus and insula:a meta-analysis of fMRI studies

Background: Non-conscious neural activation may underlie various psychological functions in health and disorder. However, the neural substrates of non-conscious processing have not been entirely elucidated. Examining the differential effects of arousing stimuli that are consciously, versus unconsciously perceived will improve our knowledge of neural circuitry involved in non-conscious perception. Here we conduct preliminary analyses of neural activation in studies that have used both subliminal and supraliminal presentation of the same stimulus. Methods: We use Activation Likelihood Estimation (ALE) to examine functional Magnetic Resonance Imaging (fMRI) studies that uniquely present the same stimuli subliminally and supraliminally to healthy participants during functional magnetic resonance imaging (fMRI). We included a total of 193 foci from 9 studies representing subliminal stimulation and 315 foci from 10 studies representing supraliminal stimulation. Results: The anterior cingulate cortex is significantly activated during both subliminal and supraliminal stimulus presentation. Subliminal stimuli are linked to significantly increased activation in the right fusiform gyrus and right insula. Supraliminal stimuli show significantly increased activation in the left rostral anterior cingulate. Conclusions: Non-conscious processing of arousing stimuli may involve primary visual areas and may also recruit the insula, a brain area involved in eventual interoceptive awareness. The anterior cingulate is perhaps a key brain region for the integration of conscious and non-conscious processing. These preliminary data provide candidate brain regions for further study in to the neural correlates of conscious experience