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Abstract BackgroundCharacterizing deformation and failure mechanisms through small-scale testing has helped in the fundamental understanding of material response, and direct loading in a transmission electron microscope (TEM) has played a large role in this effort. However, crystalline materials exhibit incoherent scattering within the TEM and the resulting intensity variations inhibit direct optical metrology. ObjectiveIn this work, we seek to both validate anin situoptical full-field metrology method in the TEM for use with crystalline materials, and measure fracture properties of a MgAl₂O₄spinel single crystal at the microscale. MethodsMicroscale single edge notch bend beams were machined from a spinel single crystal and loaded in the TEM.In situimaging of a nanoscale speckle pattern allowed use of particle tracking (PT) to extract full-field measurements of the displacement field. A numerical analysis methodology was then used to obtain mixed mode stress intensity factor values. ResultsA discrepancy between PT and far-field actuator measurements of applied displacement was found (about a maximum of 35% difference), indicating the advantage of using near-field optical measurements in the TEM. For such small-scale testing it is also generally unavoidable to introduce asymmetry in loading. However, the PT results allowed measurement of bothK_IandK_II, which were found to be at the time of crack initiationK_IC= 1.51± 0.03 MPa∙m^0.5, K_IIC= 0.04± 0.002 MPa∙m^0.5, respectively. ConclusionsThe application of PT enables full-field deformation measurements on crystalline materials deformed in the TEM. The effectiveness of the inverse property extraction was demonstrated by good agreement between the full-field PT measurements and FEM results. The MgAl₂O₄spinel toughness values extracted also agreed well with previous literature results. 

This full research paper reports findings from a multitiered intervention focused on developing growth mindset among talented, low-income undergraduate students attending a College of Computing in the northeastern United States. Rooted in theories of intelligence, a growth mindset views intelligence and skills as being developed through persistent practice and learning from mistakes, while a fixed mindset sees skills as set at birth, never evolving, with mistakes becoming insurmountable barriers to success. The program in this study was designed to develop a community of learners with a shared framework for responding to academic challenges, to combat imposter syndrome, and to support persistence in their major and enter the workforce. During their first two years as college students, three undergraduate cohorts (totaling 32 participants) experienced four semesters of growth-mindset faculty mentoring concurrent with a community-building, growth mindset-focused seminar, and in their first year experienced two growth-mindset infused introductory programming courses. To address the research question, “How do talented, financially disadvantaged computing students understand growth and fixed mindsets?”, we report on qualitative data collected each semester, for each cohort. Focus group transcripts and individual written responses were thematically analyzed, drawing from a priori frameworks (social constructivism and self-efficacy in the context of mindset theory) and emergent codes to develop categories. Discussion is presented using frames of self-determination theory and positioning theory. We discuss the impact of these findings on students, implications for growth mindset interventions and provide guidance for using educational and developmental theories in the context of studies of growth mindset. 

Abstract In previous water quality modeling studies in Chesapeake Bay, the severity of summer hypoxia tended to be underestimated in the mid-lower Bay area. The underlying reason has not been well understood. In this study, we test a new hypothesis with respect to the estuary–ocean exchange. This hypothesis was motivated by observed high levels of dissolved organic carbon (DOC) near the Bay mouth that, if transported into the Bay, could potentially draw down the dissolved oxygen (DO) in the mid-lower Bay through the microbial respiration of DOC. Using a high-resolution 3D water quality model that includes both the Bay and a portion of the coastal ocean, we provide evidence that supports this hypothesis and demonstrates the important connection between the Bay and the coastal ocean that entrains DOC into the mid-lower Bay during the summer hypoxic season, which leads to a more realistic representation of DO dynamics there. We also outline remaining research questions about the DOC reactivity and sources in the Chesapeake Bay that warrant further study.