High-strength cellulose fibres enabled by molecular packing
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Experimental observation of gapped shear waves and liquid-like to gas-like dynamical crossover in active granular matter
Unlike crystalline solids, liquids lack long-range order, resulting in diffusive shear fluctuations rather than propagating waves. Simulations predict that liquids exhibit a k-gap in wave-vector space, where solid-like transverse waves reappear above this gap. Experimental evidence in classical liquids has been limited, observed only in 2D dusty plasmas. Here, we investigate this phenomenon using active Brownian vibrators and uncover distinct gas-like and liquid-like phases depending on the packing fraction. We measure key properties, including pair correlation functions, mean square displacements, velocity auto-correlation functions, and vibrational density of states. In the liquid-like phase, we confirm the k-gap in transverse excitations, whose size grows as the packing fraction decreases and eventually disappears in the gas phase. Our findings extend the concept of the k-gap to active granular systems and reveal striking parallels with supercritical fluids.
Crossover scaling of structural and mechanical properties in 3D assemblies of non-spherical, frictional particles
The stability of particle assemblies is strongly affected by particle shape, yet definitive laws describing key properties, such as the mean contact number and apparent friction coefficient, remain elusive. Using X-ray computed tomography and discrete element simulations, we study 70 assemblies of 3D frictional particles. Once properly rescaled, our data collapse onto master curves, revealing linear relationships linking particle shape to these properties for short-axis particles below certain crossover points. These data suggest that the scaling behavior for the mean contact number can be maintained at lower sphericity than the apparent friction coefficient, indicating different sensitivity of the system’s structural versus mechanical properties to particle shape. Through analyzing elongated particles beyond the crossover points, we find that while particle elongation increases the contact number, it has limited effects on improving mechanical stability. This insight, along with the law, paves the route towards optimizing granular packing via manipulating particle shape.
Development of accessible and scalable maize pollen storage technology
The inherent short lifespan of Zea mays (maize, corn) pollen hinders crop improvement and challenges the hybrid seed production required to produce food, fuel, and feed. Decades of scientific effort on maize pollen storage technology have been unable to deliver a widely accessible protocol that works for liters of pollen at a hybrid seed production scale. Here we show how suppressing the pollen cellular respiration rate through refrigeration and optimizing gas exchange within the storage environment are the critical combination of factors for maintaining pollen viability in storage. The common practice of preserving maize pollen by mixing the pollen with talcum powder is critically examined using pollen tube germination testing, electron microscopy of pollen-silk (stigma) interaction, and test pollinations in production environments. These techniques lead to mixing maize pollen collected for storage with anti-clumping carrier compounds, including microcrystalline cellulose. These carriers improve stored pollen flowability during pollination and enable increased seed sets to be obtained from stored pollen. Field testing in maize seed production demonstrates that a wide range of pollen volumes can be stored for up to seven days using low-cost, globally available materials and that stored pollen can achieve seed-set equivalency to fresh pollen.
Microbiome-based interventions to modulate gut ecology and the immune system
The gut microbiome lies at the intersection between the environment and the host, with the ability to modify host responses to disease-relevant exposures and stimuli. This is evident in how enteric microbes interact with the immune system, e.g., supporting immune maturation in early life, affecting drug efficacy via modulation of immune responses, or influencing development of immune cell populations and their mediators. Many factors modulate gut ecosystem dynamics during daily life and we are just beginning to realise the therapeutic and prophylactic potential of microbiome-based interventions. These approaches vary in application, goal, and mechanisms of action. Some modify the entire community, such as nutritional approaches or faecal microbiota transplantation, while others, such as phage therapy, probiotics, and prebiotics, target specific taxa or strains. In this review, we assessed the experimental evidence for microbiome-based interventions, with a particular focus on their clinical relevance, ecological effects, and modulation of the immune system.
Accurately adjusted phenothiazine conformations: reversible conformation transformation at room temperature and self-recoverable stimuli-responsive phosphorescence
Conformational flexibility is essential to the stimuli-responsive property of organic materials, but achieving the reversible molecular transformation is still challenging in functional materials for the high energy barriers and restriction by intermolecular interactions. Herein, through the incorporation of various steric hindrances into phenothiazine derivatives with different positions and quantities to tune the molecular conformations by adjustable repulsive forces, the folded angles gradually changed from 180° to 90° in 17 compounds. When the angle located at 112° with moderated steric effect, dynamic and reversible transformation of conformations under mechanical force has been achieved for the low energy barriers and mutually regulated molecular motions, resulting in both self-recoverable and stimuli-responsive phosphorescence properties for the first time. It opened up a new way to realize the self-recovery property of organic materials, which can facilitate the multi-functional property of smart materials with the opened avenue for other fields with inspiration.
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