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Precise control of the temperature rise is a prerequisite for proper photothermal therapy. In retinal laser therapy, the heat deposition is primarily governed by the melanin concentration, which can significantly vary across the retina and from patient to patient. In this work, we present a method for determining the optical and thermal properties of layered materials, directly applicable to the retina, using low-energy laser heating and phase-resolved optical coherence tomography (pOCT). The method is demonstrated on a polymer-based tissue phantom heated with a laser pulse focused onto an absorbing layer buried below the phantom’s surface. Using a line-scan spectral-domain pOCT, optical path length changes induced by the thermal expansion were extracted from sequential B-scans. The material properties were then determined by matching the optical path length changes to a thermo-mechanical model developed for fast computation. This method determined the absorption coefficient with a precision of 2.5% and the temperature rise with a precision of about 0.2°C from a single laser exposure, while the peak did not exceed 8°C during 1 ms pulse, which is well within the tissue safety range and significantly more precise than other methods.

Architected materials with nanoscale features have enabled extreme combinations of properties by exploiting the ultralightweight structural design space together with size-induced mechanical enhancement at small scales. Apart from linear waves in metamaterials, this principle has been restricted to quasi-static properties or to low-speed phenomena, leaving nanoarchitected materials under extreme dynamic conditions largely unexplored. Here, using supersonic microparticle impact experiments, we demonstrate extreme impact energy dissipation in three-dimensional nanoarchitected carbon materials that exhibit mass-normalized energy dissipation superior to that of traditional impact-resistant materials such as steel, aluminium, polymethyl methacrylate and Kevlar. In-situ ultrahigh-speed imaging and post-mortem confocal microscopy reveal consistent mechanisms such as compaction cratering and microparticle capture that enable this superior response. By analogy to planetary impact, we introduce predictive tools for crater formation in these materials using dimensional analysis. These results substantially uncover the dynamic regime over which nanoarchitecture enables the design of ultralightweight, impact-resistant materials that could open the way to design principles for lightweight armour, protective coatings and blast-resistant shields for sensitive electronics.

Nanofibrous hydrogels are pervasive in animal and plant bodies and have been widely seen in engineering applications. Electrospinning is one of the most widely used methods for the fabrication of nanofibrous hydrogels. Whereas the biological nanofibrous hydrogels can maintain high strength and high toughness under multiple cycles of mechanical loads, such fatigue-resistant properties have not been achieved in electrospun nanofibrous hydrogels. Here, we report a bioinspired design of strong and fatigue-resistant nanofibrous hydrogels that can closely mimic the bouligand structure of the natural hydrogel in the lobster underbelly. The resultant nanofibrous hydrogel can reach high nominal strength up to 8.4 MPa and high fatigue threshold up to 770 J/m2. We further demonstrate the superior impact resistance of the bioinspired bouligand-type nanofibrous hydrogel with specific penetration energy of 40 kJ/kg. We show that it is critical to weld the interfaces between nanofibers and introduce intrinsically high-energy phases (nanocrystalline domains) into nanofibers.

Thermosets—polymeric materials that adopt a permanent shape upon curing—have a key role in the modern plastics and rubber industries, comprising about 20 per cent of polymeric materials manufactured today, with a worldwide annual production of about 65 million tons1,2. The high density of crosslinks that gives thermosets their useful properties (for example, chemical and thermal resistance and tensile strength) comes at the expense of degradability and recyclability. Here, using the industrial thermoset polydicyclopentadiene as a model system, we show that when a small number of cleavable bonds are selectively installed within the strands of thermosets using a comonomer additive in otherwise traditional curing workflows, the resulting materials can display the same mechanical properties as the native material, but they can undergo triggered, mild degradation to yield soluble, recyclable products of controlled size and functionality. By contrast, installation of cleavable crosslinks, even at much higher loadings, does not produce degradable materials. These findings reveal that optimization of the cleavable bond location can be used as a design principle to achieve controlled thermoset degradation. Moreover, we introduce a class of recyclable thermosets poised for rapid deployment.

The nitrogen efficiency is the ratio between the output of nitrogen in the animal products and the input required for the livestock production. This ratio is a driver of the economic profitability and can be calculated at various levels of the production system: animal, field or farm. Calculated at the scale of the animal, it is generally low with less than half-ingested nitrogen remaining in the milk, the eggs or the meat in the form of proteins; the major part of the nitrogen being rejected in the environment. Significant gains were achieved in the past via the genetic improvement and the adjustment of feed supply. At the farm level, the efficiency increases to 45% to 50%, thanks to the recycling of animal excreta as fertilisers. From excretion to land application of manure, the losses of nitrogen are very variable depending on the animal species and the manure management system. Considering the risks of pollution swapping, all management and handling steps need to be considered. Collective initiatives or local rules on agricultural practices allow new opportunities to restore nitrogen balances on local territory.

Presents interviews with the French actors in the film, `Queen Margot.' Jean-Hugues Anglade; Julien Rassam; Pascal Greggory; Vincent Perez.

La polyculture-élevage est souvent citée comme étant un idéal agronomique source d’économies pour l’agriculteur et à moindre impact environnemental négatif. La complémentarité entre les ateliers élevage et culture devrait permettre l’utilisation partagée de facteurs de production, et donc une réduction de l’utilisation d’intrants. Au-delà du concept, cette étude a pour objectif d’observer si, dans un bassin de production, les fermes produisant de la viande bovine et de grandes cultures affichent des performances productives et économiques différentes des fermes herbagères spécialisées bovins viande. À partir des données d’un échantillon d’exploitations de bovins allaitants charolais du centre de la France, nous observons que les exploitations dites de polyculture-élevage sont systématiquement plus grandes que les exploitations herbagères spécialisées. La grande taille des exploitations entraîne une forte augmentation des besoins en équipement et des charges induites. Ces charges ne se partagent pas entre productions animales et végétales. Au final, nous n’observons pas de différence de coût de production du kilogramme de viande produit ou de revenu par travailleur, entre exploitations herbagères spécialisées et exploitations de polyculture-élevage. Le concept vertueux de la polyculture-élevage se heurte à des réalités structurelles et socio-économiques. Afin de pourvoir bénéficier d’avantages économiques potentiels liés à la diversification, il faudrait réfléchir à de nouvelles formes de structure d’exploitations d’élevage françaises.

Investigating high-speed microparticle impact responses into soft tissue is essential to several fields like medicine and transdermal delivery of pharmaceuticals. Various simulants such as ballistic gelatin, rubber, and polymers have been developed to replace the biological body in experimental investigation, considering the practical and ethical issues. The synthetic polymer SEBS gel (styrene-ethylene-butylene-styrene) interests some scientists in recent years because it involves several benefits like environmental stability, reproducibility, mechanical consistency, transparency, and biofidelic ability to reproduce human soft tissue behavior. A few experiments have been performed on the penetration of SEBS gel. But its physical behavior under high-velocity impact, especially in micro-scale, is yet to be investigated. As the earliest meshless method, Smoothed Particles Hydrodynamics (SPH) has been identified to have a great potential in simulating extremely large deformation. This study employs a numerical model by the SPH method to investigate the response of the SEBS gel under micro-penetration, combined with an elastic-hydrodynamic constitutive law. The range of Young’s modulus is firstly described for the SEBS gel under micro-impacts, which is validated against experimental data. Supplementally, the suitability of three types of analytical models depending on fitting coefficients is also discussed for micro penetrations into soft tissue.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Investigating high-speed microparticle impact responses into soft tissue is essential to several fields such as medicine and biology with technological applications like transdermal delivery of pharmaceuticals. The understanding of the physical process involved in such a phenomenon is complex and few experimental tools are available to study high-velocity microparticle penetration in soft tissues, generally substituted by simulants like gels in the literature. One way to overcome these issues is to use numerical simulation as an efficient way of investigation, but also include difficulties such as accurate models for materials properties, microscale computation, and mathematical formulations. As the earliest meshless method, Smoothed Particles Hydrodynamics (SPH) has been applied in solid dynamics because of its great potentials in simulating extremely large deformation and perforation of targets by various projectiles. This paper develops an original numerical model based on SPH to study the dynamical phenomena during microscale impact of spheres into ballistic gelatin (BG), a common human tissue surrogate. By simulating a series of particle penetrations into 10 wt%BG initial velocities, the projectile trajectories and penetration depths in gelatin are investigated. The effects of the gelatin’s elastic modulus in ballistic impact are also studied. The numerical results show that this numerical model appears to be an promising approach to simulate high-velocity microparticle penetrating ballistic gelatine materials.