Effect of Dual Ion Beam Irradiation (Helium and Deuterium) on Tungsten–Tantalum Alloys Under Fusion Relevant Conditions

The selection of tungsten (W) as a divertor material in ITER is based on its high melting point, low erosion, and strong mechanical properties. However, continued investigation has shown W to undergo severe morphology changes in fusion-like conditions. Recent literature suggests alloying W with other ductile refractory metals, viz. tantalum (Ta) may resolve some of these issues. These results provide further motivation for investigating W–Ta alloys as a plasma-facing component (PFC) for ITER and future DEMO reactors. Specifically, how these alloy materials respond to simultaneous He+ and D+ ion irradiation, and what is the effect on the surface morphology when exposed to fusion relevant conditions. In the present study, the surface morphology changes are investigated in several W–Ta targets (pure W, W-1%Ta, W-3%Ta, and W-5% Ta) due to simultaneous He+ and D+ ion irradiations. This comprehensive work allows for deeper understanding of the synergistic effects induced by dual ion irradiation on W and W–Ta alloy surface morphology. Pure W and W–Ta alloys were irradiated simultaneously by 100 eV He+ and/or D+ ions at various mixture ratios (100% He+, 60% D+ + 40% He+, 90% D+ + 10% He+ ions and 100% D+ ions), having a total constant He fluence of 6 × 1024 ion m−2, and at a target temperature of 1223 K. This work shows that slight changes in materials composition and He/D content have significant impact on surface morphology evolution and performance. While both the pure W and W–Ta alloys exhibit very damaged surfaces under the He+ only irradiations, there is a clear suppression of the surface morphology evolution as the ratio of D+/He+ ions is increased

Jaw Laterality and Related Handedness in the Hunting Behavior of a Scale-Eating Characin, Exodon paradoxus

BACKGROUND: Asymmetry in animal bodies and behavior has evolved several times, but our knowledge of their linkage is limited. Tanganyikan scale-eating cichlids have well-known antisymmetry in their bodies and behavior; individuals open their mouths leftward (righty) or rightward (lefty), and righties always attack the right flank of the prey, whereas lefties attack the left. This study analyzed the morphological asymmetry in a scale-eating characiform, Exodon paradoxus, and its behavioral handedness. METHODOLOGY/PRINCIPAL FINDINGS: Each eight E. paradoxus was observed for 1-h with a prey goldfish in an aquarium to detect the behavioral handedness. Following the experiment, the lateral differences in the mandibles and head-inclination of these eight and ten additional specimens were analyzed. Both measurements on the morphology showed a bimodal distribution, and the laterality identified by these two methods was always consistent within a given individual, indicating that the characin has morphological antisymmetry. Furthermore, this laterality significantly corresponded to behavioral handedness; that is, lefties more often rasped scales from the right flank of the prey and vice versa. However, the correlation between laterality and handedness is the opposite of that in the cichlids. This is due to differences in the feeding apparatus and technique. The characin has cuspids pointing forward on the external side of the premaxilla, and it thrusts its dominant body side outward from its body axis on the flank of the prey to tear off scales. By contrast, the cichlids draw their dominant body side inward toward the axis or rotate it to scrape or wrench off scales with the teeth lined in the opened mouth. CONCLUSIONS/SIGNIFICANCE: This study demonstrated that the antisymmetry in external morphology and the corresponding behavioral handedness have evolved in two lineages of scale-eating fishes independently, and these fishes adopt different utilization of their body asymmetry to tear off scales

Inside the guts of wood-eating catfishes: can they digest wood?

To better understand the structure and function of the gastrointestinal (GI) tracts of wood-eating catfishes, the gross morphology, length, and microvilli surface area (MVSA) of the intestines of wild-caught Panaque nocturnus, P. cf. nigrolineatus “Marañon”, and Hypostomus pyrineusi were measured, and contrasted against these same metrics of a closely related detritivore, Pterygoplichthys disjunctivus. All four species had anatomically unspecialized intestines with no kinks, valves, or ceca of any kind. The wood-eating catfishes had body size-corrected intestinal lengths that were 35% shorter than the detritivore. The MVSA of all four species decreased distally in the intestine, indicating that nutrient absorption preferentially takes place in the proximal and mid-intestine, consistent with digestive enzyme activity and luminal carbohydrate profiles for these same species. Wild-caught Pt. disjunctivus, and P. nigrolineatus obtained via the aquarium trade, poorly digested wood cellulose (<33% digestibility) in laboratory feeding trials, lost weight when consuming wood, and passed stained wood through their digestive tracts in less than 4 h. Furthermore, no selective retention of small particles was observed in either species in any region of the gut. Collectively, these results corroborate digestive enzyme activity profiles and gastrointestinal fermentation levels in the fishes’ GI tracts, suggesting that the wood-eating catfishes are not true xylivores such as beavers and termites, but rather, are detritivores like so many other fishes from the family Loricariidae