41 research outputs found
Subdiffusive axial transport of granular materials in a long drum mixer
Granular mixtures rapidly segregate radially by size when tumbled in a
partially filled horizontal drum. The smaller component moves toward the axis
of rotation and forms a buried core, which then splits into axial bands. Models
have generally assumed that the axial segregation is opposed by diffusion.
Using narrow pulses of the smaller component as initial conditions, we have
characterized axial transport in the core. We find that the axial advance of
the segregated core is well described by a self-similar concentration profile
whose width scales as , with . Thus, the
process is subdiffusive rather than diffusive as previously assumed. We find
that is nearly independent of the grain type and drum rotation rate
within the smoothly streaming regime. We compare our results to two
one-dimensional PDE models which contain self-similarity and subdiffusion; a
linear fractional diffusion model and the nonlinear porous medium equation.Comment: 4 pages, 4 figures, 1 table. Submitted to Phys Rev Lett. For more
info, see http://www.physics.utoronto.ca/nonlinear
The United States COVID-19 Forecast Hub dataset
Academic researchers, government agencies, industry groups, and individuals have produced forecasts at an unprecedented scale during the COVID-19 pandemic. To leverage these forecasts, the United States Centers for Disease Control and Prevention (CDC) partnered with an academic research lab at the University of Massachusetts Amherst to create the US COVID-19 Forecast Hub. Launched in April 2020, the Forecast Hub is a dataset with point and probabilistic forecasts of incident cases, incident hospitalizations, incident deaths, and cumulative deaths due to COVID-19 at county, state, and national, levels in the United States. Included forecasts represent a variety of modeling approaches, data sources, and assumptions regarding the spread of COVID-19. The goal of this dataset is to establish a standardized and comparable set of short-term forecasts from modeling teams. These data can be used to develop ensemble models, communicate forecasts to the public, create visualizations, compare models, and inform policies regarding COVID-19 mitigation. These open-source data are available via download from GitHub, through an online API, and through R packages
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Fluorescent Tracking of Yeast Division Clarifies the Essential Role of Spleen Tyrosine Kinase in the Intracellular Control of Candida glabrata in Macrophages
Macrophages play a critical role in the elimination of fungal pathogens. They are sensed via cell surface pattern-recognition receptors and are phagocytosed into newly formed organelles called phagosomes. Phagosomes mature through the recruitment of proteins and lysosomes, resulting in addition of proteolytic enzymes and acidification of the microenvironment. Our earlier studies demonstrated an essential role of Dectin-1-dependent activation of spleen tyrosine kinase (Syk) in the maturation of fungal containing phagosomes. The absence of Syk activity interrupted phago-lysosomal fusion resulting in arrest at an early phagosome stage. In this study, we sought to define the contribution of Syk to the control of phagocytosed live Candida glabrata in primary macrophages. To accurately measure intracellular yeast division, we designed a carboxyfluorescein succinimidyl ester (CFSE) yeast division assay in which bright fluorescent parent cells give rise to dim daughter cells. The CFSE-labeling of C. glabrata did not affect the growth rate of the yeast. Following incubation with macrophages, internalized CFSE-labeled C. glabrata were retrieved by cellular lysis, tagged using ConA-647, and the amount of residual CFSE fluorescence was assessed by flow cytometry. C. glabrata remained undivided (CFSE bright) for up to 18 h in co-culture with primary macrophages. Treatment of macrophages with R406, a specific Syk inhibitor, resulted in loss of intracellular control of C. glabrata with initiation of division within 4 h. Delayed Syk inhibition after 8 h was less effective indicating that Syk is critically required at early stages of macrophage–fungal interaction. In conclusion, we demonstrate a new method of tracking division of C. glabrata using CFSE labeling. Our results suggest that early Syk activation is essential for macrophage control of phagocytosed C. glabrata
Body postures of <i>C. elegans</i> swimming in water.
<p>(A) -shaped and (B) sine-shaped nematode postures. Left column: experimental images. Right column: the corresponding skeletonized data and single-mode harmonic-curvature fits.</p
Loop turn with two distinct piecewise curvature modes.
<p>(A) Experimental image. (B) The two-mode harmonic-curvature representation (solid line); the skeleton data (open circles); the location of the piecewise-mode change (filled circle).</p