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The Cambrian radiation of euarthropods can be attributed to an adaptable body plan. Sophisticated brains and specialized feeding appendages, which are elaborations of serially repeated organ systems and jointed appendages, underpin the dominance of Euarthropoda in a broad suite of ecological settings. The origin of the euarthropod body plan from a grade of vermiform taxa with hydrostatic lobopodous appendages ('lobopodian worms') 1,2 is founded on data from Burgess Shale-type fossils. However, the compaction associated with such preservation obscures internal anatomy 3-6 . Phosphatized microfossils provide a complementary three-dimensional perspective on early crown group euarthropods 7 , but few lobopodians 8,9 . Here we describe the internal and external anatomy of a three-dimensionally preserved euarthropod larva with lobopods, midgut glands and a sophisticated head. The architecture of the nervous system informs the early configuration of the euarthropod brain and its associated appendages and sensory organs, clarifying homologies across Panarthropoda. The deep evolutionary position of Youti yuanshi gen. et sp. nov. informs the sequence of character acquisition during arthropod evolution, demonstrating a deep origin of sophisticated haemolymph circulatory systems, and illuminating the internal anatomical changes that propelled the rise and diversification of this enduringly successful group., (© 2024. The Author(s).)

Magmas vesiculate during ascent, producing complex interconnected pore networks, which can act as outgassing pathways and then deflate or compact to volcanic plugs. Similarly, in-conduit fragmentation events during dome-forming eruptions create open systems transiently, before welding causes pore sealing. The percolation threshold is the first-order transition between closed- and open-system degassing dynamics. Here, we use time-resolved, synchrotron-source X-ray tomography to image synthetic magmas that go through cycles of opening and closing, to constrain the percolation threshold Φ C at a range of melt crystallinity, viscosity and overpressure pertinent to shallow magma ascent. During vesiculation, we observed different percolative regimes for the same initial bulk crystallinity depending on melt viscosity and gas overpressure. At high viscosity (> 10 6  Pa s) and high overpressure (~ 1-4 MPa), we found that a brittle-viscous regime dominates in which brittle rupture allows system-spanning coalescence at a low percolation threshold ( Φ C ~0.17) via the formation of fracture-like bubble chains. Percolation was followed by outgassing and bubble collapse causing densification and isolation of the bubble network, resulting in a hysteresis in the evolution of connectivity with porosity. At low melt viscosity and overpressure, we observed a viscous regime with much higher percolation threshold ( Φ C  > 0.37) due to spherical bubble growth and lower degree of crystal connection. Finally, our results also show that sintering of crystal-free and crystal-bearing magma analogues is characterised by low percolation thresholds ( Φ C  = 0.04 - 0.10). We conclude that the presence of crystals lowers the percolation threshold during vesiculation and may promote outgassing in shallow, crystal-rich magma at initial stages of Vulcanian and Strombolian eruptions., (© The Author(s) 2020.)

The ascent of hydrous magma prior to volcanic eruptions is largely driven by the formation of H 2 O vesicles and their subsequent growth upon further decompression. Porosity controls buoyancy as well as vesicle coalescence and percolation, and is important when identifying the differences between equilibrium or disequilibrium degassing from textural analysis of eruptive products. Decompression experiments are routinely used to simulate magma ascent. Samples exposed to high temperature ( T ) and pressure ( P ) are decompressed and rapidly cooled to ambient T for analysis. During cooling, fluid vesicles may shrink due to decrease of the molar volume of H 2 O and by resorption of H 2 O back into the melt driven by solubility increase with decreasing T at P  < 300 MPa. Here, we quantify the extent to which vesicles shrink during cooling, using a series of decompression experiments with hydrous phonolitic melt (5.3-3.3 wt% H 2 O, T between 1323 and 1373 K, decompressed from 200 to 110-20 MPa). Most samples degassed at near-equilibrium conditions during decompression. However, the porosities of quenched samples are significantly lower than expected equilibrium porosities prior to cooling. At a cooling rate of 44 K·s -1 , the fictive temperature T f , where vesicle shrinkage stops, is up to 200 K above the glass transition temperature ( T g ), Furthermore, decreasing cooling rate enhances vesicles shrinkage. We assess the implications of these findings on previous experimental degassing studies using phonolitic melt, and highlight the importance of correctly interpreting experimental porosity data, before any comparison to natural volcanic ejecta can be attempted., (© The Author(s) 2020.)

We present new evidence that shows magma mingling can be a key process during highly explosive eruptions. Using fractal analysis of the size distribution of trachybasaltic fragments found on the inner walls of bubbles in trachytic pumices, we show that the more mafic component underwent fracturing during quenching against the trachyte. We propose a new mechanism for how this magmatic interaction at depth triggered rapid heterogeneous bubble nucleation and growth and could have enhanced eruption explosivity. We argue that the data support a further, and hitherto unreported contribution of magma mingling to highly explosive eruptions. This has implications for hazard assessment for those volcanoes in which evidence of magma mingling exists.

Sintering-or coalescence-of viscous droplets is an essential process in many natural and industrial scenarios. Current physical models of the dynamics of sintering are limited by the lack of an explicit account of the evolution of microstructural geometry. Here, we use high-speed time-resolved x-ray tomography to image the evolving geometry of a sintering system of viscous droplets, and use lattice Boltzmann simulations of creeping fluid flow through the reconstructed pore space to determine its permeability. We identify and characterize a topological inversion, from spherical droplets in a continuous interstitial gas, to isolated bubbles in a continuous liquid. We find that the topological inversion is associated with a transition in permeability-porosity behavior, from Stokes permeability at high porosity, to percolation theory at low porosity. We use these findings to construct a unified physical description that reconciles previously incompatible models for the evolution of porosity and permeability during sintering.

We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres.

The study of fluid flow through solid matter by computed tomography (CT) imaging has many applications, ranging from petroleum and aquifer engineering to biomedical, manufacturing, and environmental research. To avoid motion artifacts, current experiments are often limited to slow fluid flow dynamics. This severely limits the applicability of the technique. In this paper, a new iterative CT reconstruction algorithm for improved a temporal/spatial resolution in the imaging of fluid flow through solid matter is introduced. The proposed algorithm exploits prior knowledge in two ways. First, the time-varying object is assumed to consist of stationary (the solid matter) and dynamic regions (the fluid flow). Second, the attenuation curve of a particular voxel in the dynamic region is modeled by a piecewise constant function over time, which is in accordance with the actual advancing fluid/air boundary. Quantitative and qualitative results on different simulation experiments and a real neutron tomography data set show that, in comparison with the state-of-the-art algorithms, the proposed algorithm allows reconstruction from substantially fewer projections per rotation without image quality loss. Therefore, the temporal resolution can be substantially increased, and thus fluid flow experiments with faster dynamics can be performed.

There are many cases where one needs to limit the X-ray dose, or the number of projections, or both, for high frame rate (fast) imaging. Normally, it improves temporal resolution but reduces the spatial resolution of the reconstructed data. Fortunately, the redundancy of information in the temporal domain can be employed to improve spatial resolution. In this paper, we propose a novel regularizer for iterative reconstruction of time-lapse computed tomography. The non-local penalty term is driven by the available prior information and employs all available temporal data to improve the spatial resolution of each individual time frame. A high-resolution prior image from the same or a different imaging modality is used to enhance edges which remain stationary throughout the acquisition time while dynamic features tend to be regularized spatially. Effective computational performance together with robust improvement in spatial and temporal resolution makes the proposed method a competitive tool to state-of-the-art techniques.

A study on the development and effect of experimental Sarcoptes scabiei var suis infestations in growing pigs is described. Pigs were infested at either weekly or fortnightly intervals throughout each experimental and individual growth rates and feed conversion ratios were determined. The animals were fed diets which contained either optimal or sub-optimal levels of protein. They were housed either intensively or extensively. In all experiments the majority of infested animals developed a generalised hypersensitivity to sarcoptes mites and performed significantly less efficiently than non-infested littermates. Mean growth rates were depressed from 9.2 to 12.5 per cent and feed conversion efficiencies by a similar margin. Well fed, intensively housed pigs developed a more severe hypersensitivity reaction than poorly fed, extensively housed pigs.

Animals were experimentally infested with Sarcoptes scabiei var suis at weekly intervals between birth and five weeks of age. Excoriations were observed on the luminal surface of the ear seven days after the initial infestation. Encrusted lesions developed in the ears of all pigs between the third and eighth weeks but spontaneously regressed and disappeared by the 14th week. A generalised pruritus, accompanied by focal erythematous skin lesions developed in a majority of pigs between seven and 11 weeks of age. The presence of pruritus was associated with an eosinophilia and histological changes in the skin which were consistent with an allergic reaction. The results are discussed in relation to their diagnostic significance and their importance in the control and eradication of the disease.

Two groups of 8 pigs were vaccinated and given a booster vaccination 6 weeks later each with a commercial dual L. pomona and L. tarassovi killed vaccine. Serum from bloods collected before and up to 30 weeks after vaccination had agglutinating antibodies only after the 0ooster vaccination and then only with 1 vaccine. Titres persisted less than 8 weeks when tested against L. pomona but up to 16 weeks when tested against L. tarassovi at the 1:300 dilution and up to 20 weeks at the 1:100 dilution.

The protection conferred on pregnant gilts by 2 commercially available leptospira interrogans serovars pomona and tarassovi bacterins was evaluated. Gilts vaccinated either 3, 6 or 12 months prior to natural challenge with L. interrogans serovar pomona had significantly lower abortion rates (2% vs 69%) and foetal mortality rates (14% vs 57%) than unvaccinated controls. One vaccine was significantly superior to the other and contained approximately twice the number of L. interrogans serovar pomona organisms per vaccine dose. Neither vaccine protected against renal colonisation but vaccination reduced urinary excretion of leptospires. Both vaccines reduced agglutinating antibody response to infection, as measured by the microscopic agglutination (MA) test. This may prevent the detection of a carrier animal by serology. Foetal pigs did not develop specific MA titres. Cultural methods were not reliable in making a diagnosis of foetal infection. Histopathology of foetal liver and kidneys helped in making a diagnosis of foetal infection.