Proof Blocks: Autogradeable Scaffolding Activities for Learning to Write Proofs

Proof Blocks is a software tool which enables students to write proofs by dragging and dropping prewritten proof lines into the correct order. These proofs can be graded completely automatically, enabling students to receive rapid feedback on how they are doing with their proofs. When constructing a problem, the instructor specifies the dependency graph of the lines of the proof, so that any correct arrangement of the lines can receive full credit. This innovation can improve assessment tools by increasing the types of questions we can ask students about proofs, and can give greater access to proof knowledge by increasing the amount that students can learn on their own with the help of a computer

A survey of X-ray emission from 100 kpc radio jets

We have completed a Chandra snapshot survey of 54 radio jets that are extended on arcsec scales. These are associated with flat spectrum radio quasars spanning a redshift range z=0.3 to 2.1. X-ray emission is detected from the jet of approximately 60% of the sample objects. We assume minimum energy and apply conditions consistent with the original Felten-Morrison calculations in order to estimate the Lorentz factors and the apparent Doppler factors. This allows estimates of the enthalpy fluxes, which turn out to be comparable to the radiative luminosities.Comment: Conference Proceedings IAU Symposium No. 313, Extragalactic jets from every angle, pp. 219-224, 4 figure

Student Misconceptions about Cybersecurity Concepts: Analysis of Think-Aloud Interviews

We conducted an observational study to document student misconceptions about cybersecurity using thematic analysis of 25 think-aloud interviews. By understanding patterns in student misconceptions, we provide a basis for developing rigorous evidence-based recommendations for improving teaching and assessment methods in cybersecurity and inform future research. This study is the first to explore student cognition and reasoning about cybersecurity. We interviewed students from three diverse institutions. During these interviews, students grappled with security scenarios designed to probe their understanding of cybersecurity, especially adversarial thinking. We analyzed student statements using a structured qualitative method, novice-led paired thematic analysis, to document patterns in student misconceptions and problematic reasoning that transcend institutions, scenarios, or demographics. Themes generated from this analysis describe a taxonomy of misconceptions but not their causes or remedies. Four themes emerged: overgeneralizations, conflated concepts, biases, and incorrect assumptions. Together, these themes reveal that students generally failed to grasp the complexity and subtlety of possible vulnerabilities, threats, risks, and mitigations, suggesting a need for instructional methods that engage students in reasoning about complex scenarios with an adversarial mindset. These findings can guide teachers’ attention during instruction and inform the development of cybersecurity assessment tools that enable cross-institutional assessments that measure the effectiveness of pedagogies

The X-ray Afterglows of GRB 020813 and GRB 021004 with Chandra HETGS: Possible Evidence for a Supernova Prior to GRB 020813

We report on the detection of an emission line near 1.3 keV, which we associate with blue-shifted hydrogen-like sulfur (S XVI), in a 76.8 ksec Chandra HETGS spectrum of the afterglow of GRB 020813. The line is detected at 3.3 sigma significance. We also find marginal evidence for a line possibly due to hydrogen-like silicon (Si XIV) with the same blue-shift. A line from Fe is not detected, though a very low significance Ni feature may be present. A thermal model fits the data adequately, but a reflection model may provide a better fit. There is marginal evidence that the equivalent width of the S XVI line decrease as the burst fades. We infer from these results that a supernova likely occurred >~ 2 months prior to the GRB. We find no discrete or variable spectral features in the Chandra HETGS spectrum of the GRB 021004 afterglow.Comment: 26 pages, 11 figures, submitted to Ap

The PEER Collaborative: Supporting Engineering Education Research Faculty with Near-peer Mentoring Unconference Workshops

The PEER Collaborative National Network is a national peer mentoring network for early career tenure-track or mid-career tenured faculty who conduct and are primarily evaluated based on their research related to engineering education. This paper discusses the development, logistics, and outcomes of two PEER workshops built around a community of practice framework. Data from internal and external evaluations are presented to provide insights into aspects that worked well and aspects that need further development. Additionally, by reflecting on the workshops, participants crafted vignettes describing the impact the PEER workshops had on their personal and professional lives. The paper concludes with a discussion on the future of PEER (and potential spin-off groups from the PEER cohorts), and the changes that will be made in future workshops. Recommendations are provided for other organizers interested in developing successful “near peer” groups to address specific community needs

Results from an extensive simultaneous broadband campaign on the underluminous active nucleus M81*: further evidence for mass-scaling accretion in black holes

We present the results of a broadband simultaneous campaign on the nearby low-luminosity active galactic nucleus M81*. From February through August 2005, we observed M81* five times using the Chandra X-ray Observatory with the High-Energy Transmission Grating Spectrometer, complemented by ground-based observations with the Giant Meterwave Radio Telescope, the Very Large Array and Very Large Baseline Array, the Plateau de Bure Interferometer at IRAM, the Submillimeter Array and Lick Observatory. We discuss how the resulting spectra vary over short and longer timescales compared to previous results, especially in the X-rays where this is the first ever longer-term campaign at spatial resolution high enough to nearly isolate the nucleus (17pc). We compare the spectrum to our Galactic center weakly active nucleus Sgr A*, which has undergone similar campaigns, as well as to weakly accreting X-ray binaries in the context of outflow-dominated models. In agreement with recent results suggesting that the physics of weakly-accreting black holes scales predictably with mass, we find that the exact same model which successfully describes hard state X-ray binaries applies to M81*, with very similar physical parameters.Comment: 58 pages (preprint version), 22 figures, accepted for publication in the Astrophysical Journa

Genomics and transcriptomics yields a system-level view of the biology of the pathogen Naegleria fowleri

Background The opportunistic pathogen Naegleria fowleri establishes infection in the human brain, killing almost invariably within 2 weeks. The amoeba performs piece-meal ingestion, or trogocytosis, of brain material causing direct tissue damage and massive inflammation. The cellular basis distinguishing N. fowleri from other Naegleria species, which are all non-pathogenic, is not known. Yet, with the geographic range of N. fowleri advancing, potentially due to climate change, understanding how this pathogen invades and kills is both important and timely. Results Here, we report an -omics approach to understanding N. fowleri biology and infection at the system level. We sequenced two new strains of N. fowleri and performed a transcriptomic analysis of low- versus high-pathogenicity N. fowleri cultured in a mouse infection model. Comparative analysis provides an in-depth assessment of encoded protein complement between strains, finding high conservation. Molecular evolutionary analyses of multiple diverse cellular systems demonstrate that the N. fowleri genome encodes a similarly complete cellular repertoire to that found in free-living N. gruberi. From transcriptomics, neither stress responses nor traits conferred from lateral gene transfer are suggested as critical for pathogenicity. By contrast, cellular systems such as proteases, lysosomal machinery, and motility, together with metabolic reprogramming and novel N. fowleri proteins, are all implicated in facilitating pathogenicity within the host. Upregulation in mouse-passaged N. fowleri of genes associated with glutamate metabolism and ammonia transport suggests adaptation to available carbon sources in the central nervous system. Conclusions In-depth analysis of Naegleria genomes and transcriptomes provides a model of cellular systems involved in opportunistic pathogenicity, uncovering new angles to understanding the biology of a rare but highly fatal pathogen.publishedVersio