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1. Effects of shortening velocity on the stiffness to force ratio during isometric force redevelopment suggest mechanisms of residual force depression

   https://doi.org/10.1038/s41598-023-28236-5  

   Jeong, Siwoo ; Nishikawa, Kiisa ( January 2023 , Scientific Reports)

   Although the phenomenon of residual force depression has been known for decades, the mechanisms remain elusive. In the present study, we investigated mechanisms of residual force depression by measuring the stiffness to force ratio during force redevelopment after shortening at different velocities. The results showed that the slope of the relationship between muscle stiffness and force decreased with decreasing shortening velocity, and the y-intercept increased with decreasing shortening velocity. The differing slopes and y-intercepts indicate that the stiffness to force ratio during isometric force redevelopment depends on the active shortening velocity at a given muscle length and activation level. The greater stiffness to force ratio after active shortening can potentially be explained by weakly-bound cross bridges in the new overlap zone. However, weakly-bound cross bridges are insufficient to explain the reduced slope at the slowest shortening velocity because the reduced velocity should increase the proportion of weakly- to strongly-bound cross bridges, thereby increasing the slope. In addition, if actin distortion caused by active shortening recovers during the force redevelopment period, then the resulting slope should be similar to the non-linear slope of force redevelopment over time. Alternatively, we suggest that a tunable elastic element, such as titin, could potentially explain the results.

    

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2. Force Spectroscopy of Single Protein Molecules Using an Atomic Force Microscope

   https://doi.org/10.3791/55989  

   Scholl, Zackary N. ; Li, Qing ; Josephs, Eric ; Apostolidou, Dimitra ; Marszalek, Piotr E. ( January 2019 , Journal of Visualized Experiments)
3. Rapid Probe Engagement and Withdrawal With Force Minimization in Atomic Force Microscopy: A Learning-Based Online-Searching Approach

   https://doi.org/10.1109/TMECH.2020.2971464  

   Wang, Jingren ; Zou, Qingze ( April 2020 , IEEE/ASME Transactions on Mechatronics)
4. Three-Dimensional Atomic Force Microscopy: Interaction Force Vector by Direct Observation of Tip Trajectory

   https://doi.org/10.1021/nl403423p  

   Sigdel, Krishna P. ; Grayer, Justin S. ; King, Gavin M. ( November 2013 , Nano Letters)
5. Large-range high-speed dynamic-mode atomic force microscope imaging: adaptive tapping towards minimal force

   https://doi.org/10.1088/1361-6528/acd700  

   Chen, Jiarong ; Zou, Qingze ( May 2023 , Nanotechnology)

   Abstract This paper presents a software-hardware integrated approach to high-speed large-range dynamic mode imaging of atomic force microscope (AFM). High speed AFM imaging is needed to interrogate dynamic processes at nanoscale such as cellular interactions and polymer crystallization process. High-speed dynamic-modes such as tapping-mode AFM imaging is challenging as the probe tapping motion is sensitive to the highly nonlinear probe-sample interaction during the imaging process. The existing hardware-based approach via bandwidth enlargement, however, results in a substantially reduction of imaging area that can be covered. Contrarily, control (algorithm)-based approach, for example, the recently developed adaptive multiloop mode (AMLM) technique, has demonstrated its efficacy in increasing the tapping-mode imaging speed without loss of imaging size. Further improvement, however, has been limited by the hardware bandwidth and online signal processing speed and computation complexity.Thus, in this paper, the AMLM technique is further enhanced to optimize the probe tapping regulation and integrated with a field programmable gate array (FPGA) platform to further increase the imaging speed without loss of imaging quality and range. Experimental implementation of the proposed approach demonstrates that the high-quality imaging can be achieved at a high-speed scanning rate of 100 Hz and higher, and over a large imaging area of over 20 µm.  

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