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1. Adhesion and Running Speed of a Tropical Arboreal Ant (Cephalotes atratus) on Rough, Narrow, and Inclined Substrates

   https://doi.org/10.1093/icb/icaa078  

   Stark, Alyssa Y; Yanoviak, Stephen P (June 2020, Integrative and Comparative Biology)

   null (Ed.)

   Synopsis Arboreal ants must navigate variably sized and inclined linear structures across a range of substrate roughness when foraging tens of meters above the ground. To achieve this, arboreal ants use specialized adhesive pads and claws to maintain effective attachment to canopy substrates. Here, we explored the effect of substrate structure, including small and large-scale substrate roughness, substrate diameter, and substrate orientation (inclination), on adhesion and running speed of workers of one common, intermediately-sized, arboreal ant species. Normal (orthogonal) and shear (parallel) adhesive performance varied on sandpaper and natural leaf substrates, particularly at small size scales, but running speed on these substrates remained relatively constant. Running speed also varied minimally when running up and down inclined substrates, except when the substrate was positioned completely vertical. On vertical surfaces, ants ran significantly faster down than up. Ant running speed was slower on relatively narrow substrates. The results of this study show that variation in the physical properties of tree surfaces differentially affects arboreal ant adhesive and locomotor performance. Specifically, locomotor performance was much more robust to surface roughness than was adhesive performance. The results provide a basis for understanding how performance correlates of functional morphology contribute to determining local ant distributions and foraging decisions in the tropical rainforest canopy. 

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2. Navigating Nature's Terrain: Jumping Performance Robust to Substrate Moisture and Roughness by Blackspotted Rockskippers ( Entomacrodus striatus )

   https://doi.org/10.1002/jez.2903  

   Bartlett, Daniel T; Raffle, Kaylin O; Pettit, Hayley N; Brainard, Miranda K; Houglan, Paityn M; Gamel, Kaelyn; Nopper, Zachary O; Harden, Rebekah K; Garner, Austin M; Londraville, Richard L; et al (January 2025, Journal of Experimental Zoology Part A: Ecological and Integrative Physiology)

   ABSTRACT Escape responses are vital for the survival of prey. The high speeds and accelerations needed to evade predators successfully require exerting forces on the environment. Unlike water, terrestrial habitats can vary in ways that constrain the forces applied, requiring animals to adjust their behavior in response to variable conditions. We evaluated the terrestrial jumping of an amphibious fish, the blackspotted rockskipper (Entomacrodus striatus), to determine if substrate roughness and wetness influence jumping performance. We predicted that rockskippers would produce a greater force output as substrate roughness increased and wetness decreased. Using a novel waterproof force plate capable of detecting millinewton loads, we collected ground reaction forces from rockskippers jumping on wet and dry sandpapers of varying grits. We also used micro‐CT scans to quantify muscle mass as a relative fraction of body mass to determine if these jumps could be performed without power amplification. Mixed‐model analysis of jumps revealed significantly higher maximum horizontal forces, jump duration, and maximum power on dry versus wet substrates, but no effect of substrate roughness. However, the final jump outcomes (takeoff speed and angle) were unaffected. Peak jump power was within the range of typical fish muscle. Thus, these fish display a jumping behavior which is robust to substrate property variation. 

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3. Selection of Silica Type and Amount for Flowability Enhancements via Dry Coating: Contact Mechanics Based Predictive Approach

   https://doi.org/10.1007/s11095-023-03561-6  

   Kunnath, Kuriakose T.; Tripathi, Siddharth; Kim, Sangah S.; Chen, Liang; Zheng, Kai; Davé, Rajesh N. (December 2023, Pharmaceutical Research)

   Purpose: To investigate the effect of dry coating the amount and type of silica on powder flowability enhancement using a comprehensive set of 19 pharmaceutical powders having different sizes, surface roughness, morphology, and aspect ratios, as well as assess flow predictability via Bond number estimated using a mechanistic multi-asperity particle contact model. Method: Particle size, shape, density, surface energy and area, SEM-based morphology, and FFC were assessed for all powders. Hydrophobic (R972P) or hydrophilic (A200) nano-silica were dry coated for each powder at 25%, 50%, and 100% surface area coverage (SAC). Flow predictability was assessed via particle size and Bond number. Results: Nearly maximal flow enhancement, one or more flow category, was observed for all powders at 50% SAC of either type of silica, equivalent to 1 wt% or less for both the hydrophobic R972P or hydrophilic A200, while R972P generally performed slightly better. Silica amount as SAC better helped understand the relative performance. The power-law relation between FFC and Bond number was observed. Conclusion: Significant flow enhancements were achieved at 50% SAC, validating previous models. Most uncoated very cohesive powders improved by two flow categories, attaining easy flow. Flowability could not be predicted for both the uncoated and dry coated powders via particle size alone. Prediction was significantly better using Bond number computed via the mechanistic multi-asperity particle contact model accounting for the particle size, surface energy, roughness, and the amount and type of silica. The widely accepted 200 nm surface roughness was not valid for most pharmaceutical powders. 

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4. On the surface roughness and smoothing in the 3D printed THz reflectors

   Adibelli, P. Juyal (July 2019, Digest - IEEE Antennas and Propagation Society. International Symposium)

   This paper presents the effect of surface roughness on the performance of the 3D printed near field focused THz Cassegrain antenna configuration. It is found that the roughness affects the focal plane parameters. The nearfield directivity is reduced by ~ 3.5 dB for 60 µm rough surface, there is only a small effect on the focus spot width. A smoothing process, which reduces the conductive coating surface roughness to 4 µm, is also described. The roughness loss is less than 0.1 dB at 300GHz. 

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5. Biotic interactions and stream network position affect body size of aquatic vertebrates across watersheds

   https://doi.org/10.1002/ecs2.70299  

   Penaluna, Brooke E; Johnson, Sherri L; Pollock, Amanda_M M; Arismendi, Ivan; Warren, Dana R (June 2025, Ecosphere)

   Abstract The body size of aquatic vertebrates is declining across populations and ecosystems worldwide owing to warmer water temperature and changing streamflow. In freshwaters, the effects of stream network position and density‐dependent factors on body size are less understood. We used an extensive dataset spanning 41 stream sites over 7 years to evaluate how density‐dependent and density‐independent factors influence the size of two top predators in small watersheds, Coastal Cutthroat TroutOncorhynchus clarkii clarkiiand Coastal Giant SalamandersDicamptodon tenebrosus. We tested three hypotheses of body‐size variation for trout and salamanders, including intraspecific density dependence, interspecific density dependence, and resource availability, using empirical observations in hierarchical linear mixed models in a model‐selection framework. In our best‐supported models, the strongest predictors of size were conspecific negative density dependence, as expected, suggesting greater intraspecific interactions probably owing to conspecific individuals having similar requirements. We reveal a biogeographic pattern in which body size peaks in middle stream‐network positions and plateaus or declines at lower and upper locations, proposing that stream network position also plays a role in determining body size in small watersheds. Salamander density also has a quadratic effect on adult trout size, with salamanders having a greater overall effect on the body size of both species than trout, suggesting that salamanders might be more dominant than trout in some interactions. Collectively, we found that biotic interactions, mainly conspecific but also interspecific, and stream‐network position affect trout and salamander body sizes in small watersheds. 

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