In a recent paper Paczuski, Maslov and Bak present a comprehensive theory of avalanche dynamics in models of growth, interface depinning and evolution. One of their main results is the so-called gamma equation, which is claimed to be exact. In this note it is shown that this equation requires a numerical correction factor in order to become exact. The exactness is needed when using the equation...

We study the evolution and failure of a granular slope as a function of prepared volume fraction, ϕ(0). We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45° angle while we monitor the motion of grains from the side and top with high-speed video cameras. The dynamics of grain motion during the tilt process depended sensitively on ϕ(0)∈[0.58-0.63] and...

Avalanche (grainflow) processes are fundamental drivers of dune morphodynamics and are typically initiated by grainfall accumulations. In sedimentary systems, however, the dynamism between grainfall and grainflow remains unspecified because simple measurements are hampered by the inherent instability of lee slopes. Here, for the first time, terrestrial laser scanning is used to quantify key asp...

Self-organized critical states are found in many natural systems, from earthquakes to forest fires, they have also been observed in neural systems, particularly, in neuronal cultures. However, the presence of critical states in the awake brain remains controversial. Here, we compared avalanche analyses performed on different in vivo preparations during wakefulness, slow-wave sleep, and REM slee...

In this paper two-dimensional Direct Numerical Simulations (DNS) of dense clouds moving down steep slopes are presented for the first time. The results obtained are in good agreement with the overall characteristics – that is, the spatial growth rate and velocity variations – of clouds studied in the laboratory. Direct numerical simulations give, in addition to the overall flow structure, local...

The article reports on recent developments in the theory of secondary instability in drift–ion temperature gradient turbulence. Specifically, the article explores secondary instability as a mechanism for zonal flow generation, transport barrier dynamics and avalanche formation. These in turn are related to the space–time statistics of the drift wave induced flux, the scaling of transport with c...

We introduce a self-organized critical model of punctuated equilibrium with many internal degrees of freedom (M) per site. We find exact solutions for M ! ` of cascade equations describing avalanche dynamics in the steady state. This proves the existence of simple power laws with critical exponents that verify general scaling relations for nonequilibrium phenomena. Punctuated equilibrium is des...

A series of automatic time-lapse cameras installed along the southwestern side Tasiapik Valley, near village Umiujaq, Nunavik (northern Québec) documented several departure modes and types snow involved in avalanches during winter 2017–2018. These included cornice–avalanche dynamics, slab loose avalanches, clean dirty avalanches. At top selected slope, a camera monitored development cornice beg...