Analytic nonlinear theory of shear banding in amorphous solids.

September 29, 2026| Source: Proceedings of the National Academy of Sciences of the United States of America

The aim of this paper is to offer an analytic theory of the shear banding instability in amorphous solids that are subjected to athermal quasi-static shear. To this aim we derive nonlinear equations for the displacement field, including the consequences of plastic deformation on the mechanical response of amorphous solids. The plastic events collectively induce distributed dipoles that are responsible for screening effects and the creation of typical length-scales that are absent in classical elasticity theory. The nonlinear theory exposes an instability that results in the creation of shear bands. By solving the weakly nonlinear amplitude equation we present analytic expressions for the displacement fields that are associated with shear bands, explaining the role of the elastic moduli that determine the width of a shear band from ductile to brittle characteristics. We derive an energy functional whose Hessian possesses an eigenvalue that goes to zero at the shear-banding instability, providing a prediction for the critical value of the accumulated stress that results in an instability.

Read the original source →

Nutrient legacies from elephant megacarcasses create coldspots of biodiversity and hotspots of ecosystem processes.

Terrestrial megafauna (animals >1,000 kg) have substantial impacts on ecosystems while alive; yet, we know little about the impacts of these ecosystem engineers after they die. Like whale carcasses in the ocean, terrestrial megacarcasses may leave ecological legacies via the nutrient pulses they create on the landscape. Here, we investigated the impact of elephant megacarcasses on savanna ecosystems in Kruger National Park, South Africa. To determine how elephant carcasses affect below- and a

EnvironmentOctober 20, 2026

Maternal ranging strategies facilitate offspring social play at energetic cost in the most solitary ape.

In most vertebrates, social play among peers is considered essential for behavioral development. Yet in solitary species bearing single offspring, opportunities for social play are inherently scarce. Whether mothers of such species actively facilitate play opportunities for their offspring, and at what cost, remains unknown. We used 15 y of behavioral and movement data (∼32,600 observation hours) from 31 wild Bornean orangutan ( Pongo pygmaeus wurmbii ) mother-offspring pairs to test whet

EnvironmentOctober 20, 2026

Evolution shapes ecosystem resilience through spatial self-organization.

Drylands are globally widespread and ecologically important but vulnerable to climate change. Many exhibit spatially self-organized vegetation patterns that enhance resilience by enabling vegetation to reorganize their patterns under drying, thereby optimizing water use and maintaining productivity. Plants can also undergo evolution in response to environmental change. Although both spatial self-organization and rapid evolution are fundamental mechanisms of resilience, their interaction remains

EnvironmentOctober 13, 2026

Continuous UV irradiation played an inconclusive role in selecting the canonical genetic alphabet.

An abundance of heterocyclic molecules analogous to canonical nucleobases (i.e., adenine, thymine, guanine, cytosine, and uracil) used as the genetic alphabet in DNA and RNA could have been present in various prebiotic environments on early Earth. However, extant biology generally uses the canonical nucleobases and nucleosides as the genetic alphabet, and not any number of possible noncanonical counterparts. Ultraviolet (UV) irradiation was likely abundant on the surface of the early Earth and h

EnvironmentOctober 13, 2026

Fault-controlled natural hydrogen reservoirs as underground hydrogen storage sites.

Underground hydrogen storage requires geological formations with demonstrated hydrogen containment, yet no conventional storage candidate (salt caverns, aquifers, or depleted hydrocarbon reservoirs) offers direct, prior evidence of H 2 -specific sealing. We propose that subcommercial natural hydrogen reservoirs, where H 2 has accumulated over geological timescales, can serve as precertified storage sites. This proposition is evaluated using the Bulqizë fault-controlled natural H 2 reservoir