Numerical Simulation of Fluid Flow and Mixing Dynamics inside Planetary Roller Extruders

In this contribution, the fluid flow and mixing dynamics inside planetary roller extruders are simulated using the finite element method (FEM) and the mesh superposition technique (MST). Three-dimensional configurations with planetary spindles of varying number and geometry of planetary spindles were created to analyse the influence of the spindle configuration and the rotational speed on the process behavior. Therefore, pressure gradients, flow velocities and directions, shear rates, the mixing index and residence time distributions were evaluated. The distributive and dispersive mixing efficiencies varied depending on the planetary spindle configuration, and these configurations thus suit different processing tasks. In comparison to the standard planetary spindles, the TT3 spindles, with their incomplete toothing, and the knob spindles, with their double transversal helical toothing, showed intense axial and radial mixing. In general, the mixing performance of the planetary roller extruder is explained by a high rate of extensional flow and frequent changes in flow type. The reported numerical approach allows, for the first time, a comprehensive observation of the process behavior of planetary roller extruders.

Four-dimensional chromosome reconstruction elucidates the spatiotemporal reorganization of the mammalian X chromosome

Chromosomes are segmented into domains and compartments, but how these structures are spatially related in three dimensions (3D) is unclear. Here, we developed tools that directly extract 3D information from Hi-C experiments and integrate the data across time. With our “4DHiC” method, we use X chromosome inactivation (XCI) as a model to examine the time evolution of 3D chromosome architecture during large-scale changes in gene expression. Our modeling resulted in several insights. Both A/B and S1/S2 compartments divide the X chromosome into hemisphere-like structures suggestive of a spatial phase-separation. During the XCI, the X chromosome transits through A/B, S1/S2, and megadomain structures by undergoing only partial mixing to assume new structures. Interestingly, when an active X chromosome (Xa) is reorganized into an inactive X chromosome (Xi), original underlying compartment structures are not fully eliminated within the Xi superstructure. Our study affirms slow mixing dynamics in the inner chromosome core and faster dynamics near the surface where escapees reside. Once established, the Xa and Xi resemble glassy polymers where mixing no longer occurs. Finally, Xist RNA molecules initially reside within the A compartment but transition to the interface between the A and B hemispheres and then spread between hemispheres via both surface and core to establish the Xi.

Evaluating distributional regression strategies for modelling self-reported sexual age-mixing

The age dynamics of sexual partnership formation determine patterns of sexually transmitted disease transmission and have long been a focus of researchers studying human immunodeficiency virus. Data on self-reported sexual partner age distributions are available from a variety of sources. We sought to explore statistical models that accurately predict the distribution of sexual partner ages over age and sex. We identified which probability distributions and outcome specifications best captured variation in partner age and quantified the benefits of modelling these data using distributional regression. We found that distributional regression with a sinh-arcsinh distribution replicated observed partner age distributions most accurately across three geographically diverse data sets. This framework can be extended with well-known hierarchical modelling tools and can help improve estimates of sexual age-mixing dynamics.

Bighorn sheep show similar in-host responses to the same pathogen strain in two contrasting environments

Ecological context – the particular environment, and how it shapes mixing dynamics and individual susceptibility surrounding infectious disease events – can have major bearing on epidemic outcomes, yet directly comparable disease events with contrasting ecological contexts are relatively rare in wildlife systems due to concurrent differences in host genetics or pathogen strain. Here, we present a case study of one such event: a spillover of a “goat-clade” Mycoplasma ovipneumoniae strain into one bighorn sheep population that played out against two very different ecological backdrops. One event occurred on the herd’s home range near the Rio Grande Gorge in New Mexico, while the other progressed in a captive facility at Hardware Ranch in Utah. We collected data on antibody and pathogen load patterns through time at the individual level, and examined demographic responses to pathogen invasion to compare the intensity of, and in-host responses to, infection in both settings. While data collection regimens varied between the two sites, general patterns of antibody expansion and gross timing of symptoms were consistent. Symptoms emerged in the captive setting 12.9 days post-exposure, and we estimated an average time to seroconversion among the captive animals of 24.9 days. Clinical signs peaked among the captive animals at approximately 36 days post-infection, consistent with subsequent declines in symptom intensity in the free-ranging herd. At the captive site, older animals exhibited more severe declines in body condition as determined through declines in loin thickness, higher symptom burdens, and a decelerated antibody response to the pathogen. Younger animals were more likely than older animals to clear infection at or before the time of sampling at both sites. This study presents one of the richest datasets on immune responses in bighorn sheep over the course of a newly introduced M. ovipneumoniae strain available to-date.