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Drosophila melanogaster hemocytes are highly motile cells that are crucial for successful embryogenesis and have important roles in the organism's immunological response. Here we measure the motion of hemocytes using selective plane illumination microscopy. Every hemocyte cell in one half of an embryo is tracked during embryogenesis and analysed using a deep learning neural network. We show that the anomalous transport of the cells is well described by fractional Brownian motion that is heterogeneous in both time and space. LanB1 and SCAR mutants disrupt the collective cellular motion and reduce its persistence due to the modification of laminin and actin-based motility respectively. The anomalous motility of the hemocytes oscillated in time with alternating periods of varying persistent motion. Touching hemocytes appear to experience synchronised contact inhibition of locomotion. A quantitative statistical framework is presented for hemocyte motility which provides biological insights. Understanding how cells move is of great important for many biological processes but collective cell motion is hard to image in vivo. The authors experimentally and numerically study in vivo cell population migration during embryogenesis, quantify anomalous transport, that is affected by mutations, and showing time dependencies and interactions between cells. [ABSTRACT FROM AUTHOR]

Two catastrophic landslides occurred in quick succession on 13 and 16 May 2019, from the north face of Joffre Peak, Cerise Creek, southern Coast Mountains, British Columbia. With headscarps at 2560 m and 2690 m elevation, both began as rock avalanches, rapidly transforming into debris flows along middle Cerise Creek, and finally into debris floods affecting the fan. Beyond the fan margin, a flood surge on Cayoosh Creek reached bankfull and attenuated rapidly downstream; only fine sediment reached Duffey Lake. The toe of the main debris flow deposit reached 4 km from the headscarp, with a travel angle of 0.28, while the debris flood phase reached the fan margin 5.9 km downstream, with a travel angle of 0.22. Photogrammetry indicates the source volume of each event is 2–3 Mm3, with combined volume of 5 Mm3. Lidar differencing, used to assess deposit volume, yielded a similar total result, although error in the depth estimate introduced large volume error masking the expected increase due to dilation and entrainment. The average velocity of the rock avalanche-debris flow phases, from seismic analysis, was ~ 25–30 m/s, and the velocity of the 16 May debris flood on the upper fan, from super-elevation and boulder sizes, was 5–10 m/s. The volume of debris deposited on the fan was ~ 104 m3, 2 orders of magnitude less than the avalanche/debris flow phases. Progressive glacier retreat and permafrost degradation were likely the conditioning factors; precursor rockfall activity was noted at least ~6 months previous; thus, the mountain was primed to fail. The 13 May landslide was apparently triggered by rapid snowmelt, with debuttressing triggering the 16 May event. [ABSTRACT FROM AUTHOR]

The article "Observations on the May 2019 Joffre Peak landslides, British Columbia", written by Pierre Friele, Tom H. Millard, Andrew Mitchell, Kate E. Allstadt, Brian Menounos, Marten Geertsema and John J. Clague, was originally published electronically on the publisher's internet portal (currently SpringerLink) on January 2020 without open access. [ABSTRACT FROM AUTHOR]