Hind limbs can undergo dramatic changes in loading conditions during the transition from quadrupedal to bipedal locomotion. For example, the most early diverging bipedal jerboas (Rodentia: Dipodidae) are some of the smallest mammals in the world, with body masses that range 2-4 grams. The larger jerboa species exhibit developmental and evolutionary fusion of the central three metatarsals into a single cannon bone. We hypothesize that body size reduction and metatarsal fusion are mechanisms to maintain the safety factor of the hind limb bones despite the higher ground reaction forces associated with bipedal locomotion. Using finite element analysis to model collisions between the substrate and the metatarsals, we found that body size reduction was insufficient to reduce bone stress on unfused metatarsals, based on the scaled dynamics of larger jerboas, and that fused bones developed lower stresses than unfused bones when all metatarsals are scaled to the same size and loading conditions. Based on these results, we conclude that fusion reinforces larger jerboa metatarsals against high ground reaction forces. Because smaller jerboas with unfused metatarsals develop higher peak stresses in response to loading conditions scaled from larger jerboas, we hypothesize that smaller jerboas use alternative dynamics of bipedal locomotion that reduces the impact of collisions between the foot and substrate.
Villacis Nunez, Ray, Cooper, Moore (submitted). Body size reduction and metatarsal fusion were distinct mechanisms to resist bending as jerboas (Dipodidae) transitioned from quadrupedal to bipedal.
Reconstructed CT slices for a right cuboid of Cantius mckennai (University of Michigan Museum of Paleontology catalog number UMMP VP 81823), as a series of TIFF images. Raw projections are not included in this dataset.
Reconstructed CT slices for the partial cranium of the holotype specimen of Saadanius hijazensis in DICOM format. Data supporting the publication: New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys, https://doi.org/10.1038/nature09094
Raw projections are not included in this dataset.
Zalmout, I., Sanders, W., MacLatchy, L. et al. New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys. Nature 466, 360–364 (2010). https://doi.org/10.1038/nature09094, A cast of this specimen is held by the University of Michigan Museum of Paleontology (UMMP) under catalog number 14200., and 3D surface model viewable on UMORF site : https://umorf.ummp.lsa.umich.edu/wp/specimen-data/?Model_ID=1408
Reconstructed CT slices for a right navicular of Cantius mckennai (University of Michigan Museum of Paleontology catalog number UMMP VP 81831), as a series of TIFF images. Raw projections are not included in this dataset.
Journals sometimes focus the attention of the research community by having a special collection, sometimes an entire special issue, devoted to a single topic. A reasonable question to ask is whether the extra effort of organizing, promoting, and maintaining the special collection is worthwhile. The paper that this data set accompanies examines paper impact in the Journal of Geophysical Research Space Physics, separating the special collection papers from the non-special-collection submissions. The conclusion is that special collections are worth the extra work.
Liemohn, M. W., & Wooden, P. (2019). Editorial: Impact of special collections in JGR Space Physics. Journal of Geophysical Research Space Physics. https://doi.org/10.1002/essoar.10501036.2
Reconstructed CT slices for a right medial cuneiform (entocuneiform) of Cantius mckennai (University of Michigan Museum of Paleontology catalog number UMMP VP 81820), as a series of TIFF images. Raw projections are not included in this dataset.
Reconstructed CT slices for vertebrae of Phenacolemur (University of Michigan Museum of Paleontology catalog number UMMP VP 94723) as a series of TIFF images. Raw projections are not included in this dataset. The reconstructed slice data from the scan are offered here as a series of unsigned 16-bit integer TIFF images. The upper left corner of the first image (*_0000.tif) is the XYZ origin.
Non-thermal plasma systems offer unique opportunities in the fields of bio-imaging, drug delivery, photovoltaics, microelectronics manufacturing. Such interests are largely inspired by the fact that hot plasma electrons coexist with neutral species and ions close to room-temperature under non-thermal plasma conditions. Modeling of these systems requires a deep understanding of the atomistic processes underlying the rich chemistry of the various radicals and ions with the nascent nanoparticle surface. A key parameter for determining the contribution of a certain radical/ion species to the nanoparticle surface growth, called sticking coefficient, is computed as a weighted sum from the simulated sticking outcomes with different collision velocities drawn from a Maxwell-Boltzmann distribution at certain temperatures. In this work, the collisions of SiHx (x=1-4) fragments and silicon cluster (Si4, Si2H6, and Si29H36) surfaces, responsible for the sticking coefficients, are simulated by molecular dynamics (MD) with a reactive force field. The dependence of sticking coefficients on temperature, H coverage of both silane fragments and cluster surfaces, and the size of the cluster, are systematically examined. And the mechanism underlying the sticking events, specifically the conversion of physical aggregation to chemisorption is investigated to better understand the complex interplay between factors influencing the surface growth. The detailed and multi-parameter model of sticking coefficients, accompanied by the mechanism study of physisorption to chemisorption conversion, provides a more accurate and robust approximation of surface growth rate using sticking coefficients, and a deeper understanding of surface growth processes, for the wider non-thermal plasma simulation community.
Shi, X., Elvati, P., Violi, A. (2021). On the growth of Si nanoparticles in non-thermal plasma: physisorption to chemisorption conversion. J. Phys. D. Submitted.
This database contains spacecraft and ground-based magnetic field observations made to study the propagation of the preliminary impulse triggered by interplanetary shocks with different inclinations in the XZ plane.
(to be submitted) Vidal-Luengo, S. E., Moldwin, M. B. (2021). Shock Inclination Effects in Preliminary Impulse Propagation Observed by Ground-Based Magnetometers and the Heliophysics System Observatory
Reconstructed CT slices for vertebrae of Hyopsodus (University of Michigan Museum of Paleontology catalog number UMMP_VP_102495) as a series of TIFF images. Raw projections are not included in this dataset. The reconstructed slice data from the scan are offered here as a series of unsigned 16-bit integer TIFF images. The upper left corner of the first image (*_0000.tif) is the XYZ origin.