Contrasts in bedrock erodibility have been shown to drive landscape transience, but it is unclear whether horizontal tectonic displacements would enhance such effects. Furthermore, one might expect these factors to coexist, as tectonic convergence helps to create rock strength contrasts in settings like the Himalayas. How do landscapes respond when contacts separating units are raised vertically and shifted horizontally by tectonics? To evaluate such questions, we use landscape evolution models to simulate the exposure of a weak unit in a landscape equilibrated to a strong unit. We explore different simulations varying factors like weak unit erodibility, diffusivity, contact dip, and topographic advection rate. In these simulations, we assess the migration of the main drainage divide as well as changes in channel steepness and topographic relief within the strong unit. Our model results show that the horizontal movement of a contact does enhance drainage divide migration and increases in channel steepness, especially when the contact migrates along rivers with low drainage areas. Across all simulations, however, increases in topographic relief are minimal and temporary. Unexpected behaviors emerge in our simulations in which the mass balance of topography is influenced by horizontal tectonic displacements. For example, the exposure of the weak unit causes a gradual decline in the steepness of the strong unit. We interpret such behaviors to be artifacts related to the fixed boundaries of our domain and likely unrepresentative of natural landscapes. Instead, we focus on simulations where advection does not influence the mass balance of topography. These models show that the horizontal movement of contacts can enhance landscape transience, but this transience is marked by features one can use as diagnostic characteristics. Detecting such characteristics in natural landscapes featuring tectonic convergence would be difficult, however, due to the natural coincidence of factors such as faulting, folding, and landslides.
Designing Domain Specific Computing Systems
Domain specific computing is an idea that has been pro-posed as a path forward given the slowing of Moore’s Law and the breakdown of Dennard scaling. Two fundamental questions include: (1) how does one define a domain; and (2) how does one go about architecting hardware that performs well for that domain? We present our preliminary work towards answering these questions.
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- Award ID(s):
- 1763503
- NSF-PAR ID:
- 10183996
- Date Published:
- Journal Name:
- IEEE 28th Annual International Symposium on Field-Programmable Custom Computing Machines (FCCM)
- Page Range / eLocation ID:
- 221 to 221
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)In recent work, the Vanderbilt Holistic Processing Tests for novel objects (VHPT-NOs), were used to show that holistic processing for artificial objects increased as a function of parametric variation of experience. Here, novices are tested on the VHPT-Nos to address two questions. First, does the test detect any level of holistic processing for novel objects in novices? Second, how is part matching performance on this test related to object recognition ability, as measured by the Novel Object Memory Test (NOMT)? In a high-powered study, we provide substantial evidence of no holistic processing on the VHPT-NO in novices, including for arguably facelike symmetrical Greebles. Evidence of no correlations between measures of holistic processing suggests that these indices can be considered free of influences from domain-general selective attention. In contrast, overall performance in part matching in the VHPT-NO shows shared variance across categories, which we postulate is related to object recognition. A second study provides direct evidence that part matching measures to a large extent the same ability as whole object learning on the NOMT. Our results suggest that any holistic processing measured in the VHPT-NOs will not be contaminated by domain-general effects and can be considered entirely due to experience with a category. The VHPT-NO will therefore be useful in further examination of how different aspects of experience contribute to the development of holistic processing.more » « less
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Many proteins exhibit a property called ‘allostery’. In allostery, an input signal at a specific site of a protein – such as a molecule binding, or the protein absorbing a photon of light – leads to a change in output at another site far away. For example, the protein might catalyze a chemical reaction faster or bind to another molecule more tightly in the presence of the input signal. This protein ‘remote control’ allows cells to sense and respond to changes in their environment. An ability to rapidly engineer new allosteric mechanisms into proteins is much sought after because this would provide an approach for building biosensors and other useful tools. One common approach to engineering new allosteric regulation is to combine a ‘sensor’ or input region from one protein with an ‘output’ region or domain from another. When researchers engineer allostery using this approach of combining input and output domains from different proteins, the difference in the output when the input is ‘on’ versus ‘off’ is often small, a situation called ‘modest allostery’. McCormick et al. wanted to know how to optimize this domain combination approach to increase the difference in output between the ‘on’ and ‘off’ states. More specifically, McCormick et al. wanted to find out whether swapping out or mutating specific amino acids (each of the individual building blocks that make up a protein) enhances or disrupts allostery. They also wanted to know if there are many possible mutations that change the effectiveness of allostery, or if this property is controlled by just a few amino acids. Finally, McCormick et al. questioned where in a protein most of these allostery-tuning mutations were located. To answer these questions, McCormick et al. engineered a new allosteric protein by inserting a light-sensing domain (input) into a protein involved in metabolism (a metabolic enzyme that produces a biomolecule called a tetrahydrofolate) to yield a light-controlled enzyme. Next, they introduced mutations into both the ‘input’ and ‘output’ domains to see where they had a greater effect on allostery. After filtering out mutations that destroyed the function of the output domain, McCormick et al. found that only about 5% of mutations to the ‘output’ domain altered the allosteric response of their engineered enzyme. In fact, most mutations that disrupted allostery were found near the site where the ‘input’ domain was inserted, while mutations that enhanced allostery were sprinkled throughout the enzyme, often on its protein surface. This was surprising in light of the commonly-held assumption that mutations on protein surfaces have little impact on the activity of the ‘output’ domain. Overall, the effect of individual mutations on allostery was small, but McCormick et al. found that these mutations can sometimes be combined to yield larger effects. McCormick et al.’s results suggest a new approach for optimizing engineered allosteric proteins: by introducing mutations on the protein surface. It also opens up new questions: mechanically, how do surface sites affect allostery? In the future, it will be important to characterize how combinations of mutations can optimize allosteric regulation, and to determine what evolutionary trajectories to high performance allosteric ‘switches’ look like.more » « less
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This paper reviews key properties and major unsolved problems about Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence. We first introduce the basic characteristics of STEVE and historical observations of STEVE-like emissions, particularly the case on 11 September 1891. Then, we discuss major open questions about STEVE: 1) Why does STEVE preferentially occur in equinoxes? 2) How do the solar wind and storm/substorm conditions control STEVE? 3) Why is STEVE rare, despite that STEVE does not seem to require extreme driving conditions? 4) What are the multi-scale structures of STEVE? 5) What mechanisms determine the properties of the picket fence? 6) What are the chemistry and emission mechanisms of STEVE? 7) What are the impacts of STEVE on the ionosphere−thermosphere system? Also, 8) what is the relation between STEVE, stable auroral red (SAR) arcs, and the subauroral proton aurora? These issues largely concern how STEVE is created as a unique mode of response of the subauroral magnetosphere−ionosphere−thermosphere coupling system. STEVE, SAR arcs, and proton auroras, the three major types of subauroral emissions, require energetic particle injections to the pre-midnight inner magnetosphere and interaction with cold plasma. However, it is not understood why they occur at different times and why they can co-exist and transition from one to another. Strong electron injections into the pre-midnight sector are suggested to be important for driving intense subauroral ion drifts (SAID). A system-level understanding of how the magnetosphere creates distinct injection features, drives subauroral flows, and disturbs the thermosphere to create optical emissions is required to address the key questions about STEVE. The ionosphere−thermosphere modeling that considers the extreme velocity and heating should be conducted to answer what chemical and dynamical processes occur and how much the STEVE luminosity can be explained. Citizen scientist photographs and scientific instruments reveal the evolution of fine-scale structures of STEVE and their connection to the picket fence. Photographs also show the undulation of STEVE and the localized picket fence. High-resolution observations are required to resolve fine-scale structures of STEVE and the picket fence, and such observations are important to understand underlying processes in the ionosphere and thermosphere.more » « less
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Flexible classroom spaces, which have movable tables and chairs that can be easily rearranged into different layouts, make it easier for instructors to effectively implement active learning than a traditional lecture hall. Instructors can move throughout the room to interact with students during active learning, and they can rearrange the tables into small groups to facilitate conversation between students. Classroom technology, such as wall-mounted monitors and movable whiteboards, also facilitates active learning by allowing students to collaborate. In addition to enabling active learning, the flexible classroom can still be arranged in front-facing rows that support traditional lecture-based pedagogies. As a result, instructors do not have to make time- and effort-intensive changes to the way their courses are taught in order to use the flexible classroom. Instead, they can make small changes to add active learning. We are in the second year of a study of flexible classroom spaces funded by the National Science Foundation’s Division of Undergraduate Education. This project asks four research questions that investigate the relationships between the instructor, the students, and the classroom: 1) What pedagogy do instructors use in a flexible classroom space? 2) How do instructors take advantage of the instructional affordances (including the movable furniture, movable whiteboards, wall-mounted whiteboards, and wall-mounted monitors) of a flexible classroom? 3) What is the impact of faculty professional development on instructors’ use of flexible classroom spaces? and 4) How does the classroom influence the ways students interpret and engage in group learning activities? In the first year of our study we have developed five research instruments to answer these questions: a three-part classroom observation protocol, an instructor interview protocol, two instructor surveys, and a student survey. We have collected data from nine courses taught in one of ten flexible classrooms at the University of Michigan during the Fall 2018 semester. Two of these courses were first-year introduction to engineering courses co-taught by two instructors, and the other seven courses were sophomore- and junior-level core technical courses taught by one instructor. Five instructors participated in a faculty learning community that met three times during the semester to discuss active learning, to learn how to make the best use of the flexible classroom affordances, and to plan activities to implement in their courses. In each course we gathered data from the perspective of the instructor (through pre- and post-semester interviews), the researcher (through observations of three class meetings with our observation protocol), and the students (through conducting a student survey at the end of the semester). This poster presents qualitative and qualitative analyses of these data to answer our research questions, along with evidence based best practices for effectively using a flexible classroom.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/FCCM48280.2020.00052
