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  1. Self-assembly of complex and functional materials remains a grand challenge in soft material science. Efficient assembly depends on a delicate balance between thermodynamic and kinetic effects, requiring fine-tuning affinities and concentrations of subunits. By contrast, we introduce an assembly paradigm that allows large error-tolerance in the subunit affinity and helps avoid kinetic traps. Our combined experimental and computational approach uses a model system of triangular subunits programmed to assemble intoT= 3 icosahedral capsids comprising 60 units. The experimental platform uses DNA origami to create monodisperse colloids whose three-dimensional geometry is controlled to nanometer precision, with two distinct bonds whose affinities are controlled tokBTprecision, quantified in situ by static light scattering. The computational model uses a coarse-grained representation of subunits, short-ranged potentials, and Langevin dynamics. Experimental observations and modeling reveal that when the bond affinities are unequal, two distincthierarchicalassembly pathways occur, in which the subunits first form dimers in one case and pentamers in another. These hierarchical pathways produce complete capsids faster and are more robust against affinity variation than egalitarian pathways, in which all binding sites have equal strengths. This finding suggests that hierarchical assembly may be a general engineering principle for optimizing self-assembly of complex target structures.

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    Free, publicly-accessible full text available February 13, 2025
  2. Gordon Holmes syndrome (GHS) is a neurological disorder associated with neuroendocrine, cognitive, and motor impairments with corresponding neurodegeneration. Mutations in the E3 ubiquitin ligaseRNF216are strongly linked to GHS. Previous studies show that deletion ofRnf216in mice led to sex-specific neuroendocrine dysfunction due to disruptions in the hypothalamic–pituitary–gonadal axis. To address RNF216 action in cognitive and motor functions, we testedRnf216knock-out (KO) mice in a battery of motor and learning tasks for a duration of 1 year. Although male and female KO mice did not demonstrate prominent motor phenotypes, KO females displayed abnormal limb clasping. KO mice also showed age-dependent strategy and associative learning impairments with sex-dependent alterations of microglia in the hippocampus and cortex. Additionally, KO males but not females had more negative resting membrane potentials in the CA1 hippocampus without any changes in miniature excitatory postsynaptic current (mEPSC) frequencies or amplitudes. Our findings show that constitutive deletion ofRnf216alters microglia and neuronal excitability, which may provide insights into the etiology of sex-specific impairments in GHS.

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  3. Free, publicly-accessible full text available August 21, 2024
  4. This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and large energy gaps. Blue Ir(tpz)3 and green Ir(ppy)3 phosphorescent devices were fabricated using these materials as hosts. Surprisingly, SB-Si demonstrated superior charge-transporting ability compared to SB-C, despite having similar energies for their valence orbitals. In particular, SB-Si proved to be a highly effective host for both blue and green devices, resulting in maximum efficiencies of 12.6% for the Ir(tpz)3 device and 9.6% for the Ir(ppy)3 device. These results highlight the benefits of appending the triphenylsilyl moiety onto host materials and underscore the importance of considering the morphology of hosts in the design of efficient PHOLEDs.

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    Free, publicly-accessible full text available July 1, 2024
  5. We report an experimental realization of a modified counterfactual communication protocol that eliminates the dominant environmental trace left by photons passing through the transmission channel. Compared to Wheeler’s criterion for inferring past particle paths, as used in prior protocols, our trace criterion provides stronger support for the claim of the counterfactuality of the communication. We verify the lack of trace left by transmitted photons via tagging the propagation arms of an interferometric device by distinct frequency-shifts and finding that the collected photons have no frequency shift which corresponds to the transmission channel. As a proof of principle, we counterfactually transfer a quick response code image with sufficient fidelity to be scanned with a cell phone. 
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    Free, publicly-accessible full text available September 12, 2024
  6. Taking a justice-oriented approach to equity in Computer Science (CS) education, this paper questions the dominant discourse in CS education and asks what truly makes CS learning consequential from the perspective of youth. We define CS learning as consequential by focusing on its transformative impact on youth identity, agency, and perceptions of the world within and beyond CS classrooms, regardless of whether or not they pursue CS in the future. Our research-practice partnership used qualitative data, specifically longitudinal interview data with 30 students up to three years after they first experienced a high school CS class in a large public school district on the west coast serving majority Latinx, urban, low-income students. Our findings suggest that in order for CS learning to be meaningful and consequential for youth, learning must involve: 1) freedom for youth to express their interests, passions, and concerns; 2) opportunities for youth to expand their views of CS and self; and 3) teacher care for students, learning community, and subject matter. The findings have significant implications for the broader “CS for All” movement and future efforts to reform policy agendas aiming for a more justice-centered CS education. 
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  7. Free, publicly-accessible full text available April 25, 2024