CORONAcredits: Program Innovations to Aid Student Completion of Disrupted Fieldword Abroad Due to the COVID-19 Pandemic

The Spring 2020 semester provided unique challenges for global experiences of all types to meet the intended learning objectives for students due to the COVID-19 pandemic disruption. This was especially true for experiential language and cultural immersion programs where engineering students were in the midst of their fieldwork experience abroad. The COVID-19 disruption presented unique challenges to recreate language and cultural understanding within international engineering fieldwork experiences in the US. This article outlines the response to the COVID-19 pandemic by the Interdisciplinary Global Programs (IGP) at Northern Arizona University (NAU). The IGP response was an innovative interdisciplinary and cross-institutional collaboration between NAU’s international office and faculty across three academic colleges to assist students in completing the interdisciplinary engineering, language, and cultural understanding objectives, absent direct immersion abroad. IGP developed “CORONAcredits” focused on exploration of the worldwide impact of COVID-19 to help students complete their fieldwork experience. The CORONAcredits engaged students in exploration of their personal experiences within the greater context of how different cultures handled the worldwide pandemic, enabling students to continue to build their global understanding from the US. Students analyzed the worldwide response of the unfolding pandemic across cultures and engaged in a mix of assignments that included discussion contributions where students shared their personal experiences abroad. CORONAcredits exposed students to a diversity of approaches to highlight cultural differences and deepen understanding of global, economic, environmental, and societal contexts present in the way that each student navigated the pandemic both domestically and abroad. Findings highlight the importance of flexibility and an interdisciplinary design, guiding students in their intercultural reflections, and incorporating new materials into module design. CORONAcredits can provide a “break in case of emergency” navigation plan that can be employed when unforeseen circumstances arise in engineering study abroad contexts

TGD1, -2, and -3 Proteins Involved in Lipid Trafficking Form ATP-binding Cassette (ABC) Transporter with Multiple Substrate-binding Proteins

Background: ATP-binding cassette transporters exist in all life forms and usually require only one substrate-binding domain. Results: The TRIGALACTOSYLDIACYLGLYCEROL (TGD) complex contains 8–12 substrate-binding proteins. Conclusion: Multiple substrate-binding proteins may be needed by the TGD complex to enhance its putative lipid transport activity. Significance: Knowing the subunit stoichiometry of the TGD complex furthers understanding of lipid transfer between chloroplast membranes

TGD1, -2, and -3 Proteins Involved in Lipid Trafficking Form ATP-binding Cassette (ABC) Transporter with Multiple Substrate-binding Proteins

Background: ATP-binding cassette transporters exist in all life forms and usually require only one substrate-binding domain. Results: The TRIGALACTOSYLDIACYLGLYCEROL (TGD) complex contains 8–12 substrate-binding proteins. Conclusion: Multiple substrate-binding proteins may be needed by the TGD complex to enhance its putative lipid transport activity. Significance: Knowing the subunit stoichiometry of the TGD complex furthers understanding of lipid transfer between chloroplast membranes

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

Densely packed surface fractal aggregates form in systems with high local volume fractions of particles with very short diffusion lengths, which effectively means that particles have little space to move. However, there are no prior mathematical models, which would describe scattering from such surface fractal aggregates and which would allow the subdivision between inter- and intraparticle interferences of such aggregates. Here, we show that by including a form factor function of the primary particles building the aggregate, a finite size of the surface fractal interfacial sub-surfaces can be derived from a structure factor term. This formalism allows us to define both a finite specific surface area for fractal aggregates and the fraction of particle interfacial sub-surfaces at the perimeter of an aggregate. The derived surface fractal model is validated by comparing it with an ab initio approach that involves the generation of a "brick-in-a-wall" von Koch type contour fractals. Moreover, we show that this approach explains observed scattering intensities from in situ experiments that followed gypsum (CaSO4 · 2H2O) precipitation from highly supersaturated solutions. Our model of densely packed "brick-in-a-wall" surface fractal aggregates may well be the key precursor step in the formation of several types of mosaic- and meso-crystals

A J-Like Protein Influences Fatty Acid Composition of Chloroplast Lipids in Arabidopsis

A comprehensive understanding of the lipid and fatty acid metabolic machinery is needed for optimizing production of oils and fatty acids for fuel, industrial feedstocks and nutritional improvement in plants. T-DNA mutants in the poorly annotated Arabidopsis thaliana gene At1g08640 were identified as containing moderately high levels (50–100%) of 16∶1Δ7 and 18∶1Δ9 leaf fatty acids and subtle decreases (5–30%) of 16∶3 and 18∶3 (http://www.plastid.msu.edu/). TLC separation of fatty acids in the leaf polar lipids revealed that the chloroplastic galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were the main lipid types affected by this mutation. Analysis of the inferred amino acid sequence of At1g08640 predicted the presence of a transit peptide, three transmembrane domains and an N-terminal J-like domain, and the gene was named CJD1 for Chloroplast J-like Domain 1. GFP reporter experiments and in vitro chloroplast import assays demonstrated CJD1 is a chloroplast membrane protein. Screening of an Arabidopsis cDNA library by yeast-2-hybrid (Y2H) using the J-like domain of CJD1 as bait identified a plastidial inner envelope protein (Accumulation and Replication of Chloroplasts 6, ARC6) as the primary interacting partner in the Y2H assay. ARC6 plays a central role in chloroplast division and binds CJD1 via its own J-like domain along with an adjacent conserved region whose function is not fully known. These results provide a starting point for future investigations of how mutations in CJD1 affect lipid composition

Vivianite-parasymplesite solid solution: A sink for arsenic in ferruginous environments?

Vivianite, a hydrated ferrous phosphate [FeII3(PO4)2 · 8 H2O] that forms in oxygen-poor, but Fe2+-rich conditions is important in nutrient cycling in anoxic environments. In natural vivianites, isomorphic substitution of divalent cations for structural Fe(II) are typical. However, anion substitution is rare; in particular, arsenate (AsVO43−) substitution has never been documented in natural vivianites. Only partial substitution has been reported in synthetic analogues, and parasymplesite [FeII3(AsO4)2 · 8 H2O], the arsenic end member of the vivianite mineral group, is found in hydrothermal deposits. In this study, we detail structural changes in synthesised As-vivianites (FeII3[(PO4)1−x(AsO4)x]2 · 8 H2O) with systematically increased degrees of As(V) substitution (0.22 ≤ x ≤ 0.95). As(V) was successfully incorporated into the vivianite crystal structure, creating a homogenous, solid solution between AsVO43− and PO43−. Like both end members, the intermediate As-vivianites crystallised in the monoclinic system (C2/m space group), and retained the platelet crystal habit of As-free vivianite, even at the highest As(V) substitution. This uniform incorporation of As(V), and its replacement of PO43−, provides a potentially stable sink for arsenic in anoxic soils and sediments, and may have implications in ferruginous early Earth oceans

Two-Stage Rotational Disordering of a Molecular Crystal Surface: C60

We propose a two-stage mechanism for the rotational surface disordering phase transition of a molecular crystal, as realized in C$_{60}$ fullerite. Our study, based on Monte Carlo simulations, uncovers the existence of a new intermediate regime, between a low temperature ordered $(2 \times 2)$ state, and a high temperature $(1 \times 1)$ disordered phase. In the intermediate regime there is partial disorder, strongest for a subset of particularly frustrated surface molecules. These concepts and calculations provide a coherent understanding of experimental observations, with possible extension to other molecular crystal surfaces.Comment: 4 pages, 2 figure

A combined first and second order variational approach for image reconstruction

In this paper we study a variational problem in the space of functions of bounded Hessian. Our model constitutes a straightforward higher-order extension of the well known ROF functional (total variation minimisation) to which we add a non-smooth second order regulariser. It combines convex functions of the total variation and the total variation of the first derivatives. In what follows, we prove existence and uniqueness of minimisers of the combined model and present the numerical solution of the corresponding discretised problem by employing the split Bregman method. The paper is furnished with applications of our model to image denoising, deblurring as well as image inpainting. The obtained numerical results are compared with results obtained from total generalised variation (TGV), infimal convolution and Euler's elastica, three other state of the art higher-order models. The numerical discussion confirms that the proposed higher-order model competes with models of its kind in avoiding the creation of undesirable artifacts and blocky-like structures in the reconstructed images -- a known disadvantage of the ROF model -- while being simple and efficiently numerically solvable.Comment: 34 pages, 89 figure