The trilobite Liostracina has been recognized as important in taxonomic and stratigraphic studies for more than a century. Until now, the genus Liostracina and family Liostracinidae have been known from only incomplete holaspid material, a degree 2 meraspis, and protaspides. A new locality in the Longha Formation (Cambrian: Guzhangian) of southeastern Yunnan, China, yields a rich collection of articulated holaspid exoskeletons and disarticulated sclerites of a new species, Liostracina fuluensis n. sp. These specimens reveal thoracic and ventral morphology that was previously unknown for Liostracina; they demonstrate that it has a rostral plate plus rostral and connective sutures, rather than a ventral median suture on the cephalic doublure. This confirms a natant hypostomal condition for the genus. Holaspid exoskeletal features, combined with evidence of a non-asaphoid-type protaspis, indicate that Liostracina is neither a primitive trinucleoid nor a primitive asaphoid. The family Liostracinidae is excluded from the superfamily Trinucleoidea and the order Trinucleida and reassigned to the order Ptychopariida.

UUID: http://zoobank.org/48dcbe31-e25d-4657-8441-732d5ea2b49d

Power scaling based on traditional ytterbium-doped fibers (YDFs) is limited by optical nonlinear effects and transverse mode instability (TMI) in high-power fiber lasers. Here, we propose a novel long tapered fiber with a constant cladding and tapered core (CCTC) along its axis direction. The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering (SRS) threshold and suppress higher-order mode resonance in the laser cavity. The CCTC YDF was fabricated successfully with a modified chemical vapor deposition (MCVD) method combined with solution doping technology, which has a cladding diameter of 400 μm and a varying core with a diameter of ~24 μm at both ends and ~31 μm in the middle. To test the performance of the CCTC fiber during high-power operation, an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally. As a result, a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%, although the TMI effect was observed at an output power of ~3.12 kW. The measured beam quality (M2 factor) was ~1.7, and no sign of the Raman component was observed in the spectrum. We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects, and further power scaling is promising by optimizing the structure of the YDF.

Post-irradiation plastic strain spreading in ferritic grains is investigated by means of three-dimensional dislocation dynamics simulations, whereby dislocation-mediated plasticity mechanisms are analyzed in the presence of various disperse defect populations, for different grain size and orientation cases. Each simulated irradiation condition is then characterized by a specific “defect-induced apparent straining temperature shift” (ΔDIAT) magnitude, reflecting the statistical evolutions of dislocation mobility. It is found that the calculated ΔDIAT level closely matches the ductile-to-brittle transition temperature shift (ΔDBTT) associated with a given defect dispersion, characterized by the (average) defect size D and defect number density N. The noted ΔDIAT/ΔDBTT correlation can be explained based on plastic strain spreading arguments and applicable to many different ferritic alloy compositions, at least within the range of simulation conditions examined herein. This systematic study represents one essential step toward the development of a fully predictive, dose-dependent fracture model, adapted to polycrystalline ferritic materials.

The TiCxN1−x(001)/TiC(001) interface was studied by the first-principles method to provide the theoretical basis for developing TiCxN1−x/TiC coatings. The partial density of state (PDOS), charge density, charge density difference, and Mulliken population analysis were utilized to investigate the bonding nature and the electronic characteristic of the TiC0.25N0.75/TiC interface. The corresponding results indicate that the bonding nature at the interface is ionic and covalent characteristics, which also exist in bulk materials. The extreme similarity of PDOS among interfacial C, N, and Ti atoms and their bulk counterparts reveals that the electronic structure transition at the interface is smooth. The results of Mulliken population analysis and plots of charge density and charge density difference demonstrate that the charge increased for C in the TiC side is less than that for N in the TiC0.25N0.75 side, which reveals that the ionic bond in TiC0.25N0.75 is stronger than that in TiC. Therefore, TiC0.25N0.75 coating can be an alternative choice to combine with TiC coating in the actual production process of multilayer coatings.

We introduce the mean topological dimension for random bundle transformations, and show that continuous bundle random dynamical systems with finite topological entropy or satisfying the small boundary property have zero mean topological dimensions.

Parablackwelderia is the oldest known stalk-eyed trilobite and thrived during the middle-late Cambrian (Guzhangian Age) in eastern Gondwanaland. the elongated palpebral lobe extends outward and forward from the anterior corner of the cranidium and shows positive allometry, becoming markedly longer and relatively thinner in large specimens. the animal occurred in muddy environments and may have been a predator that burrowed for concealment. Stalked-eyes were independently derived in several trilobite clades, but whenever they appeared were restricted to small numbers of taxa and thus do not appear to have served as a key innovation that promoted extensive diversification of species bearing the structure. the stalk-eyed condition in trilobites has a striking modern analog in the hypercephaly of diopsinid flies, where it is commonly associated with mate recognition and mate selection. We document the first occurrence of Parablackwelderia in Shandong, North China and describe a new species, Parablackwelderia luensis sp. nov.