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  1. Abstract

    Eukaryotic flagella (synonymous with cilia) rely on a microtubule-based axoneme, together with accessory filaments to carryout motility and signaling functions. While axoneme structures are well characterized, 3D ultrastructure of accessory filaments and their axoneme interface are mostly unknown, presenting a critical gap in understanding structural foundations of eukaryotic flagella. In the flagellum of the protozoan parasiteTrypanosoma brucei(T. brucei), the axoneme is accompanied by a paraflagellar rod (PFR) that supports non-planar motility and signaling necessary for disease transmission and pathogenesis. Here, we employed cryogenic electron tomography (cryoET) with sub-tomographic averaging, to obtain structures of the PFR, PFR-axoneme connectors (PACs), andmore »the axonemal central pair complex (CPC). The structures resolve how the 8 nm repeat of the axonemal tubulin dimer interfaces with the 54 nm repeat of the PFR, which consist of proximal, intermediate, and distal zones. In the distal zone, stacked “density scissors” connect with one another to form a “scissors stack network (SSN)” plane oriented 45° to the axoneme axis; and ~370 parallel SSN planes are connected by helix-rich wires into a paracrystalline array with ~90% empty space. Connections from these wires to the intermediate zone, then to overlapping layers of the proximal zone and to the PACs, and ultimately to the CPC, point to a contiguous pathway for signal transmission. Together, our findings provide insights into flagellum-driven, non-planar helical motility ofT. bruceiand have broad implications ranging from cell motility and tensegrity in biology, to engineering principles in bionics.

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  2. Free, publicly-accessible full text available May 20, 2022
  3. Solar module recycling is unprofitable today. In this paper potential revenues from waste Si modules are analyzed. The biggest revenue potential comes from the Si cells, extracted intact or broken. The second revenue source is the bulky materials in the modules including Al frame, Cu wiring and glass. The total revenue is estimated between US$11–30/module depending on the percentage of cells extracted intact. This revenue is 4–10 times better than today’s recycling process that recovers only the bulky materials. Experimentally a special furnace has been demonstrated to successfully separate thin commercial Si cells of 160 microns from glass unbroken. Frommore »damaged cells a new chemistry has been developed to recover solar-grade Si and Ag. It requires fewer steps than today’s recycling process, with Ag recovery of 97% and Si recovery of 90%. A prototype recycling line is needed to assess the cost of the new process.« less
  4. Solar module recycling is unprofitable today. In this paper potential revenues from waste Si modules are analyzed. The biggest revenue potential comes from the Si cells, extracted intact or broken. The second revenue source is the bulky materials in the modules including Al frame, Cu wiring and glass. The total revenue is estimated between US$11–30/module depending on the percentage of cells extracted intact. This revenue is 4–10 times better than today’s recycling process that recovers only the bulky materials. Experimentally a special furnace has been demonstrated to successfully separate thin commercial Si cells of 160 microns from glass unbroken. Frommore »damaged cells a new chemistry has been developed to recover solar-grade Si and Ag. It requires fewer steps than today’s recycling process, with Ag recovery of 97% and Si recovery of 90%. A prototype recycling line is needed to assess the cost of the new process.« less
  5. We report the asymmetric reconstruction of the single-stranded RNA (ssRNA) content in one of the three otherwise identical virions of a multipartite RNA virus, brome mosaic virus (BMV). We exploit a sample consisting exclusively of particles with the same RNA content—specifically, RNAs 3 and 4—assembled in planta by agrobacterium-mediated transient expression. We find that the interior of the particle is nearly empty, with most of the RNA genome situated at the capsid shell. However, this density is disordered in the sense that the RNA is not associated with any particular structure but rather, with an ensemble of secondary/tertiary structures thatmore »interact with the capsid protein. Our results illustrate a fundamental difference between the ssRNA organization in the multipartite BMV viral capsid and the monopartite bacteriophages MS2 and Qβ for which a dominant RNA conformation is found inside the assembled viral capsids, with RNA density conserved even at the center of the particle. This can be understood in the context of the differing demands on their respective lifecycles: BMV must package separately each of several different RNA molecules and has been shown to replicate and package them in isolated, membrane-bound, cytoplasmic complexes, whereas the bacteriophages exploit sequence-specific “packaging signals” throughout the viral RNA to package their monopartite genomes.

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