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Geometry and self-righting of turtles
TLDR
This study illustrates how evolution solved a far-from-trivial geometrical problem and equipped some turtles with monostatic shells: beautiful forms, which rarely appear in nature otherwise.
Geologic history of Martian regolith breccia Northwest Africa 7034: Evidence for hydrothermal activity and lithologic diversity in the Martian crust
The timing and mode of deposition for Martian regolith breccia Northwest Africa (NWA) 7034 were determined by combining petrography, shape analysis, and thermochronology. NWA 7034 is composed of
Universality of fragment shapes
TLDR
It is demonstrated that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions, and it is shown that a discrete stochastic model of fragmentation reproduces both the size andshape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws.
Constrained euler buckling
SummaryWe consider elastic buckling of an inextensible beam confined to the plane and subject to fixed end displacements, in the presence of rigid, frictionless side-walls which constrain overall
Shell geometry and habitat determination in extinct and extant turtles (Reptilia: Testudinata)
TLDR
The method, combined with inferences based on limb proportions, indicates a diverse range of ecotypes represented by Late Triassic stem turtles, which implies that the ecological diversification of stem-group turtles may have been rapid, or that a substantial period of currently cryptic diversification preceded the first fossil appearance of the turtle stem lineage during the Late Tri Jurassic.
Shape evolution of ooids: a geometric model
TLDR
It is hypothesized that mineral precipitation, and erosion due to wave-current transport, compete to give rise to novel and invariant geometric forms, and it is shown that a planar (2D) mathematical model predicts time-invariant shapes that result from a balance between precipitation and abrasion.
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