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  1. A hydrostatic skeleton allows a soft body to transmit muscular force via internal pressure. A human's tongue, an octopus' arm and a nematode's body illustrate the pervasive presence of hydrostatic skeletons among animals, which has inspired the design of soft engineered actuators. However, there is a need for a theoretical basis for understanding how hydrostatic skeletons apply mechanical work. We therefore modeled the shape change and mechanics of natural and engineered hydrostatic skeletons to determine their mechanical advantage (MA) and displacement advantage (DA). These models apply to a variety of biological structures, but we explicitly consider the tube feet of a sea star and the body segments of an earthworm, and contrast them with a hydraulic press and a McKibben actuator. A helical winding of stiff, elastic fibers around these soft actuators plays a critical role in their mechanics by maintaining a cylindrical shape, distributing forces throughout the structure and storing elastic energy. In contrast to a single-joint lever system, soft hydrostats exhibit variable gearing with changes in MA generated by deformation in the skeleton. We found that this gearing is affected by the transmission efficiency of mechanical work (MA×DA) or, equivalently, the ratio of output to input work. The transmission efficiency changes with the capacity to store elastic energy within helically wrapped fibers or associated musculature. This modeling offers a conceptual basis for understanding the relationship between the morphology of hydrostatic skeletons and their mechanical performance. 
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    Free, publicly-accessible full text available April 15, 2025
  2. A composite counterstory about a learner, Anabel, connecting her lived experiences to a mathematics problem. 
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    Free, publicly-accessible full text available February 14, 2025
  3. Our research collective explores Latine learner’s experiences with mathematics. Therefore, we must consider possible methods to de-settle the white gaze surveilling and erasing Latine learners in K-12 schools, as well as the white ideologies in educational research. In this book review, we discuss KiMi Wilson’s Black Boys’ Lived and Everyday Experiences in STEM (2021) and explore his use of ethnographic research to tell the story of his boys (Carter, Malik, Darius, and Thomas). Wilson highlights how he disrupts the norms of educational ethnography through his research and posits the need to amplify Black voices and experiences in STEM education. He challenges the reader to push against white ideologies and reconsider the deficit narratives surrounding Black boys. By reflecting on Wilson’s work and our own, we consider two points of reflection: Centering humanity and emotionality, and the importance of place. We explore how Wilson addresses these two points through his stories of his boys and how our research collective considers these ideas in our work with Latine learners in mathematics. As educators, educational researchers, and policy makers, we must reflect, acknowledge, and create transformative actions centered around humanity and emotionality, as well as the importance of place, to ensure equitable learning spaces for Black and Latine learners. 
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  4. Reef-building crustose coralline algae (CCA) are known to facilitate the settlement and metamorphosis of scleractinian coral larvae. In recent decades, CCA coverage has fallen globally and degrading environmental conditions continue to reduce coral survivorship, spurring new restoration interventions to rebuild coral reef health. In this study, naturally produced chemical compounds (metabolites) were collected from two pantropical CCA genera to isolate and classify those that induce coral settlement. In experiments using four ecologically important Caribbean coral species, we demonstrate the applicability of extracted, CCA-derived metabolites to improve larval settlement success in coral breeding and restoration efforts. Tissue-associated CCA metabolites induced settlement of one coral species,Orbicella faveolata, while metabolites exuded by CCA (exometabolites) induced settlement of three species:Acropora palmata,Colpophyllia natansandOrbicella faveolata. In a follow-up experiment, CCA exometabolites fractionated and preserved using two different extraction resins induced the same level of larval settlement as the unfractionated positive control exometabolites. The fractionated CCA exometabolite pools were characterized using liquid chromatography tandem mass spectrometry, yielding 145 distinct molecular subnetworks that were statistically defined as CCA-derived and could be classified into 10 broad chemical classes. Identifying these compounds can reveal their natural prevalence in coral reef habitats and facilitate the development of new applications to enhance larval settlement and the survival of coral juveniles.

     
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    Free, publicly-accessible full text available October 25, 2024
  5. This study explores the relationship Latino/a students developed with Computer Science (CS) and Mathematics while experiencing the Advancing Out-of-School Learning in Mathematics and Engineering (AOLME) curriculum in an after-school setting. Guided by sociocultural perspectives, the authors employed a mixed methods research design to explore how AOLME affects Latino/a students’ knowledge and enjoyment of CS and Mathematics (CSM). Findings show that AOLME is a successful example of integrated CSM curriculum design for K-12 learners by balancing the individual and social classroom setting. Quantitative data analysis indicates that students had significant increases in their self-reported enjoyment and knowledge in CS and Mathematics as they engaged in AOLME. Qualitative data provide evidence that AOLME prepared students with the foundational knowledge, skills, and practices for future endeavors in STEM fields. 
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  6. Understanding how students compose CSM ideas is essential for engagement, the development of content knowledge, and a robust STEM identity. This case study focuses on the linguistic and pedagogical transformations during computer science and mathematics learning. We document these transformations accompanying idea formation and authorship to identify three essential findings: 1) Translanguaging provides a pedagogical tool for epistemic generativity, 2) Idea-crafting and pedagogical modeling, and 3) The concept of self-pedagogy. Students use translanguaging, exercising epistemic agency to order their learning experience and providing opportunities to reposition themselves and others. In one learning sequence, Joaquin, a student co-facilitator, uses space-time marking to help manage/organize current activity with past experience. These links establish an episodic account of learning that is managed, organized, and referenced as part of a larger narrative. In doing so, he authors a model that provides a substantive connection to content for his peers. 
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  7. This work introduces a computational method for designing ceramic scaffolds fabricated via direct ink writing (DIW) for maximum bone growth, whereby the deposited rods are curvilinear. A mechanobiological model of bone adaptation is used to compute bone growth into the scaffold, taking into account the shape of the defect, the applied loading, and the density distribution of bone in which the scaffold is implanted. The method ensures smooth, continuously varying rod contours are produced which are ideal for the DIW process. The method uses level sets of radial basis functions to fully define the scaffold geometry with a small number of design variables, minimizing the optimization’s computational cost. Effective elastic and diffusive properties of the scaffold as a function of the scaffold design and the bone density are obtained from previously constructed surrogates. These property surrogates are in turn used to perform bone adaptation simulations of the scaffold-bone system. Design sensitivities of the bone ingrowth within the scaffold are efficiently obtained using a finite difference scheme implemented in parallel. A demonstration of the methodology on a scaffold implanted in a pig mandible is presented. The scaffold is optimized to maximize bone ingrowth with geometric constraints to conform to the manufacturing process. 
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  8. Fujimura, Atsushi (Ed.)
    Larval settlement in wave-dominated, nearshore environments is the most critical life stage for a vast array of marine invertebrates, yet it is poorly understood and virtually impossible to observe in situ . Using a custom-built flume tank that mimics the oscillatory fluid flow over a shallow coral reef, we isolated the effect of millimeter-scale benthic topography and showed that it increases the settlement of slow-swimming coral larvae by an order of magnitude relative to flat substrates. Particle tracking velocimetry of flow fields revealed that millimeter-scale ridges introduced regions of flow recirculation that redirected larvae toward the substrate surface and decreased the local fluid speed, effectively increasing the window of time for larvae to settle. Regions of recirculation were quantified using the Q -criterion method of vortex identification and correlated with the settlement locations of larvae for the first time. In agreement with experiments, computational fluid dynamics modeling and agent-based larval simulations also showed significantly higher settlement onto ridged substrates. Additionally, in contrast to previous reports on the effect of micro-scale substrate topography, we found that these topographies did not produce key hydrodynamic features linked to increased settlement. These findings highlight how physics-based substrate design can create new opportunities to increase larval recruitment for ecosystem restoration. 
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  9. null (Ed.)
    Abstract This work introduces a computational method for designing bone scaffolds for maximum bone growth. A mechanobiological model of bone adaptation is used to compute the bone growth, taking into account the shape of the defect, the applied loading, and the existing density distribution of the bone in which the scaffold has been implanted. Numerical homogenization and a geometry projection technique are used to efficiently obtain surrogates of the effective elastic and diffusive properties of the scaffold as a function of the scaffold design and the bone density. These property surrogates are in turn used to perform bone adaptation simulations of the scaffold–bone system for a sampling of scaffold designs. Surrogates of the bone growth in the scaffold at the end of the simulated time and of the strain energy of the scaffold at implantation time are subsequently constructed from these simulations. Using these surrogates, we optimize the design of a scaffold implanted in a rabbit femur to maximize volume bone growth into the scaffold while ensuring a minimum stiffness at implantation. The results of the optimization demonstrate the effectiveness of the proposed method by showing that maximizing bone growth with a constraint on structural compliance renders scaffold designs with better bone growth than what would be obtained by only minimizing compliance. 
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