Tag

Diffusion

All articles tagged with #diffusion

science2 days ago•5 min saved

Light as a Nanoscale Brake: Quantum Friction Slows Nanotubes in Water

Scientists report that shining light on fluorescent carbon-mesh nanotubes suspended in water slows their diffusion due to light-induced quantum friction: excited electrons (excitons) couple with nearby water and transfer momentum, effectively acting as a nanoscale brake. The slowdown grows with light intensity and vanishes when exciton mobility is hindered by defects, a finding confirmed by terahertz spectroscopy. This reveals a blurred boundary between solid and liquid behavior at the nanoscale and could enable light-controlled nanorobots and reaction tuning.

via ScienceAlert|

#diffusion #excitons #nanotubes

science3 months ago•22 min saved

Insect giants escape oxygen-diffusion limits in flight muscles

A cross-species analysis of 44 insect species across 10 orders (plus the 100 g Meganeuropsis permiana) shows the tracheolar space in flight muscles rises only about 1.8-fold over a 10,000‑fold range in body mass and is typically 1% or less. This argues that diffusion of oxygen through the tracheolar–muscle system does not constrain maximum insect size, including gigantism. The study highlights that even a threefold increase in tracheolar space would markedly affect oxygen delivery but have only modest effects on flight, challenging the long-held view that atmospheric oxygen limits insect gigantism and pointing to other factors shaping their evolution.

via Nature|

#diffusion #evolution #gigantism

science3 months ago•6 min saved

Bow and Arrow Arrive in North America About 1,400 Years Ago, Study Finds

Radiocarbon dating of carefully selected North American weapons places the bow and arrow’s emergence at roughly 1,400 years ago. Adoption was rapid in the south, where the bow quickly supplanted the atlatl, while in the north the bow coexisted with the atlatl for centuries, implying a single origin with regionally varying diffusion. The study highlights a context-dependent pattern of technological evolution influenced by environment and social networks, with faster replacement in some regions and prolonged toolkit diversity in others.

via Ars Technica|

#atlatl #bow-and-arrow #diffusion