Adding Stiffness to the Foot Modulates Soleus Force-Velocity Behaviour during Human Walking

Previous studies of human locomotion indicate that foot and ankle structures can interact in complex ways. The structure of the foot defines the input and output lever arms that influences the force-generating capacity of the ankle plantar flexors during push-off. At the same time, deformation of the foot may dissipate some of the mechanical energy generated by the plantar flexors during push-off. We investigated this foot-ankle interplay during walking by adding stiffness to the foot through shoes and insoles, and characterized the resulting changes in in vivo soleus muscle-tendon mechanics using ultrasonography. Added stiffness decreased energy dissipation at the foot (p < 0.001) and increased the gear ratio (i.e., ratio of ground reaction force and plantar flexor muscle lever arms) (p < 0.001). Added foot stiffness also altered soleus muscle behaviour, leading to greater peak force (p < 0.001) and reduced fascicle shortening speed (p < 0.001). Despite this shift in force-velocity behaviour, the whole-body metabolic cost during walking increased with added foot stiffness (p < 0.001). This increased metabolic cost is likely due to the added force demand on the plantar flexors, as walking on a more rigid foot/shoe surface compromises the plantar flexors’ mechanical advantage

Adding Stiffness to the Foot Modulates Soleus Force-Velocity Behaviour during Human Walking

Previous studies of human locomotion indicate that foot and ankle structures can interact in complex ways. The structure of the foot defines the input and output lever arms that influences the force-generating capacity of the ankle plantar flexors during push-off. At the same time, deformation of the foot may dissipate some of the mechanical energy generated by the plantar flexors during push-off. We investigated this foot-ankle interplay during walking by adding stiffness to the foot through shoes and insoles, and characterized the resulting changes in in vivo soleus muscle-tendon mechanics using ultrasonography. Added stiffness decreased energy dissipation at the foot (p \u3c 0.001) and increased the gear ratio (i.e., ratio of ground reaction force and plantar flexor muscle lever arms) (p \u3c 0.001). Added foot stiffness also altered soleus muscle behaviour, leading to greater peak force (p \u3c 0.001) and reduced fascicle shortening speed (p \u3c 0.001). Despite this shift in force-velocity behaviour, the whole-body metabolic cost during walking increased with added foot stiffness (p \u3c 0.001). This increased metabolic cost is likely due to the added force demand on the plantar flexors, as walking on a more rigid foot/shoe surface compromises the plantar flexors’ mechanical advantage

Forecast dataset associated with “From Random Forests to Flood Forecasts: A Research to Operations Success Story”

Gridded forecasts from the Colorado State University-Machine Learning Probabilities (CSU-MLP) system for excessive rainfall prediction over the continental United States. The dataset includes probabilistic forecasts for days 1, 2, and 3 from the 2017, 2019, and 2020 versions of the CSU-MLP forecast system. For the day 2 and 3 forecasts, daily forecasts are included from 19 June 2018 through 15 October 2020; for day-1 forecasts a period from 15 March 2019 through 15 October 2020 is used.Because excessive rainfall is poorly defined and difficult to forecast, there is a need for tools for Weather Prediction Center (WPC) forecasters to use when generating Excessive Rainfall Outlooks (EROs), which are issued for the contiguous United States at lead times of 1--3 days. To address this need, a probabilistic forecast system for excessive rainfall, known as the Colorado State University-Machine Learning Probabilities (CSU-MLP) system, was developed based on ensemble reforecasts, precipitation observations, and machine learning algorithms, specifically random forests. The CSU-MLP forecasts were designed to emulate the EROs, with the goal being a tool that forecasters can use as a ``first guess'' in the ERO forecast process. Resulting from close collaboration between CSU and WPC and evaluation at the Flash Flood and Intense Rainfall experiment, iterative improvements were made to the forecast system and it was transitioned into operational use at WPC. Quantitative evaluation shows that the CSU-MLP forecasts are skillful and reliable, and they are now being used as a part of the WPC forecast process. This project represents an example of a successful research-to-operations transition, and highlights the potential for machine learning and other post-processing techniques to improve operational predictions.This research and operational transition was supported by NOAA Joint Technology Transfer Initiative grants NA16OAR4590238 and NA18OAR4590378

Atomic-scale structural evolution of Ta-Ni-Si amorphous metal thin films

We investigated the thermal stability of a new ternary amorphous metal thin film, Ta₂.₄Ni₂.₂Si, and assessed its suitability as a Cu diffusion barrier for semiconductor device applications. Transmission electron microscopy was coupled with atom probe tomography to provide a detailed understanding of the atomic-scale evolution of both structure and composition as a function of annealing temperature. We show that the amorphous structure is stable up to >800 °C under ultrahigh vacuum, while annealing to 900 °C induces nano-crystallization of a single ternary phase in an amorphous matrix. The implications of crystallization and solute partitioning are examined in the context of high-temperature stability to aid in the design and understanding of this new class of thin film materials.Keywords: Amorphous metal thin film, Transmission electron microscopy, Atom probe tomographyKeywords: Amorphous metal thin film, Transmission electron microscopy, Atom probe tomograph

Charge Asymmetry in the Brane World and Formation of Charged Black Holes

In theories with an infinite extra dimension, free particles localized on the brane can leak out to the extra space. We argue that if there were color confinement in the bulk, electrons would be more able to escape than quarks and than protons (which are composed states). Thus, this process generates an electric charge asymmetry on brane matter densities. A primordial charge asymmetry during Big Bang Nucleosynthesis era is predicted. We use current bounds on this and on electron disappearance to constrain the parameter space of these models. Although the generated asymmetry is generically small, it could be particularly enhanced on large densities as in astrophysical objects, like massive stars. We suggest the possibility that such accumulation of charge may be linked, upon supernova collapse, to the formation of a charged Black Hole and the generation of Gamma-Ray Bursts.Comment: Four pages, one figure. Minor changes, conclusions remai

Continuous flow mesofluidic synthesis of Cu₂ZnSnS₄ nanoparticle inks

Copper zinc tin sulfide (CZTS) nanoparticles were synthesized using ethylene glycol as a solvent via a continuous flow mesofluidic reactor. In this study reaction temperature, residence time, and precursor concentrations were used to control CZTS composition. It was found that CZTS initially forms by the nucleation of Cu₂₋ₓS with subsequent incorporation of the remaining metal species as dictated by the cation reactivity, where Cu⁺>Sn⁺⁴>Zn⁺². CZTS nanoparticle films annealed in a selenium-containing atmosphere resulted in the formation of copper zinc tin selenide nanoparticles with much larger particle sizes.This is the authors' final peer-reviewed manuscript. The version of record is copyrighted by Elsevier and can be found here: http://www.journals.elsevier.com/materials-letters

Amorphous In-Ga-Zn-O thin-film transistors fabricated by microcontact printing

The authors present a facile, low-cost methodology to fabricate high-performance In-Ga-Zn-O (IGZO) bottom contact, bottom gate thin-film transistors (TFTs) by soft lithography. The IGZO channel and indium tin oxide (ITO) source and drain were patterned using microcontact printing of an octadecylphosphonic acid self-assembled monolayer (SAM). A polymer stamp was used for the pattern transfer of the SAMs, which were then used as a chemical protection layer during wet etching. Excellent pattern transfer was obtained with good resolution and sharp step profiles. X-ray photoelectron spectroscopy indicated that the microcontact printed SAMs can be effectively removed from the ITO source/drain surfaces, allowing a high-quality interface to the IGZO channel for good device performance. Scanning electron microscopy cross-sections of the devices indicate a smooth and defect-free transition regions between the source/drain and semiconductor regions. The fabricated TFTs have negligible gate-leakage currents, high average electron mobilities of 10.2 cm²/Vs, and excellent on-off ratios of 2.1 x 10⁸. These results may provide new methodologies for low-cost and large-area integration of IGZO-TFTs for a range of applications including flexible and transparent displays.Copyright 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Vacuum Science and Technology B and may be found at: http://scitation.aip.org/content/avs/journal/jvst