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Compliant sutures surrounded by stiff matrices are present in biological armors and carapaces, providing enhanced mechanical performance. Understanding the mechanisms through which these sutured composites achieve outstanding properties is key to developing engineering materials with improved strength and toughness. This article studies the impact of suture geometry and load direction on the performance of suture joints using a two-stage reactive polymer resin that enables facile photopatterning of mechanical heterogeneity within a single polymer network. Compliant sinusoidal sutures with varying geometries are photopatterned into stiff matrices, generating a modulus contrast of two orders of magnitude. Empirical relationships are developed connecting suture wavelength and amplitude to composite performance under parallel and perpendicular loading conditions. Results indicate that a greater suture interdigitation broadly improves composite performance when loading is applied perpendicular to suture joints, but has deleterious effects when loading is applied parallel to the joint. Investigations into the failure mechanisms under perpendicular loading highlight the interplay between suture geometry and crack growth stability after damage initiation occurs. Our findings could enable a framework for engineering composites and bio-inspired structures in the future. 

We investigated how gender is represented in children’s books using a novel 200,000 word corpus comprising 247 popular, contemporary books for young children. Using human judgments and word co-occurrence data, we quantified gender biases of words in individual books and in the whole corpus. We find that children’s books contain many words that adults judge as gendered. Semantic analyses based on co-occurrence data yielded word clusters related to gender stereotypes (e.g., feminine: emotions; masculine: tools). Co-occurrence data also indicate that many books instantiate gender stereotypes identified in other research (e.g., girls are better at reading and boys at math). Finally, we used large-scale data to estimate the gender distribution of the audience for individual books, and find that children are more often exposed to gender stereotypes for their own gender. Together the data suggest that children’s books may be an early source of gender associations and stereotypes. 

The study of mental representations of concepts has histori- cally focused on the representations of the “average” person. Here, we shift away from this aggregate view and examine the principles of variability across people in conceptual rep- resentations. Using a database of millions of sketches by peo- ple worldwide, we ask what predicts whether people converge or diverge in their representations of a specific concept, and which kinds of concepts tend to be more or less variable. We find that larger and more dense populations tend to have less variable representations, and concepts high in valence and arousal tend to be less variable across people. Further, two countries tend to have people with more similar conceptual representations when they are linguistically, geographically, and culturally similar. Our work provides the first characteri- zation of the principles of variability in shared meaning across a large, diverse sample of participants. 

Reversibly programmable liquid crystal elastomer microparticles (LCEMPs), formed as a covalent adaptable network (CAN), with an average diameter of 7 μm ± 2 μm, were synthesized via a thiol-Michael dispersion polymerization. The particles were programmed to a prolate shape via a photoinitiated addition–fragmentation chain-transfer (AFT) exchange reaction by activating the AFT after undergoing compression. Due to the thermotropic nature of the AFT-LCEMPs, shape switching was driven by heating the particles above their nematic–isotropic phase transition temperature ( T NI ). The programmed particles subsequently displayed cyclable two-way shape switching from prolate to spherical when at low or high temperatures, respectively. Furthermore, the shape programming is reversible, and a second programming step was done to erase the prolate shape by initiating AFT at high temperature while the particles were in their spherical shape. Upon cooling, the particles remained spherical until additional programming steps were taken. Particles were also programmed to maintain a permanent oblate shape. Additionally, the particle surface was programmed with a diffraction grating, demonstrating programmable complex surface topography via AFT activation.