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1. Bundle analytics, a computational framework for investigating the shapes and profiles of brain pathways across populations

   https://doi.org/10.1038/s41598-020-74054-4  

   Chandio, Bramsh Qamar; Risacher, Shannon Leigh; Pestilli, Franco; Bullock, Daniel; Yeh, Fang-Cheng; Koudoro, Serge; Rokem, Ariel; Harezlak, Jaroslaw; Garyfallidis, Eleftherios (December 2020, Scientific Reports)

   null (Ed.)

   Abstract Tractography has created new horizons for researchers to study brain connectivity in vivo. However, tractography is an advanced and challenging method that has not been used so far for medical data analysis at a large scale in comparison to other traditional brain imaging methods. This work allows tractography to be used for large scale and high-quality medical analytics. BUndle ANalytics (BUAN) is a fast, robust, and flexible computational framework for real-world tractometric studies. BUAN combines tractography and anatomical information to analyze the challenging datasets and identifies significant group differences in specific locations of the white matter bundles. Additionally, BUAN takes the shape of the bundles into consideration for the analysis. BUAN compares the shapes of the bundles using a metric called bundle adjacency which calculates shape similarity between two given bundles. BUAN builds networks of bundle shape similarities that can be paramount for automating quality control. BUAN is freely available in DIPY. Results are presented using publicly available Parkinson’s Progression Markers Initiative data. 

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2. Implications of Spatially Constrained Bipennate Topology on Fluidic Artificial Muscle Bundle Actuation

   https://doi.org/10.3390/act11030082  

   Duan, Emily; Bryant, Matthew (March 2022, Actuators)

   In this paper, we investigate the design of pennate topology fluidic artificial muscle bundles under spatial constraints. Soft fluidic actuators are of great interest to roboticists and engineers, due to their potential for inherent compliance and safe human–robot interaction. McKibben fluidic artificial muscles are an especially attractive type of soft fluidic actuator, due to their high force-to-weight ratio, inherent flexibility, inexpensive construction, and muscle-like force-contraction behavior. The examination of natural muscles has shown that those with pennate fiber topology can achieve higher output force per geometric cross-sectional area. Yet, this is not universally true for fluidic artificial muscle bundles, because the contraction and rotation behavior of individual actuator units (fibers) are both key factors contributing to situations where bipennate muscle topologies are advantageous, as compared to parallel muscle topologies. This paper analytically explores the implications of pennation angle on pennate fluidic artificial muscle bundle performance with spatial bounds. A method for muscle bundle parameterization as a function of desired bundle spatial envelope dimensions has been developed. An analysis of actuation performance metrics for bipennate and parallel topologies shows that bipennate artificial muscle bundles can be designed to amplify the muscle contraction, output force, stiffness, or work output capacity, as compared to a parallel bundle with the same envelope dimensions. In addition to quantifying the performance trade space associated with different pennate topologies, analyzing bundles with different fiber boundary conditions reveals how bipennate fluidic artificial muscle bundles can be designed for extensile motion and negative stiffness behaviors. This study, therefore, enables tailoring the muscle bundle parameters for custom compliant actuation applications. 

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3. Ptycho-endoscopy on a lensless ultrathin fiber bundle tip

   https://doi.org/10.1038/s41377-024-01510-5  

   Song, Pengming; Wang, Ruihai; Loetgering, Lars; Liu, Jia; Vouras, Peter; Lee, Yujin; Jiang, Shaowei; Feng, Bin; Maiden, Andrew; Yang, Changhuei; et al (July 2024, Light: Science & Applications)

   Abstract Synthetic aperture radar (SAR) utilizes an aircraft-carried antenna to emit electromagnetic pulses and detect the returning echoes. As the aircraft travels across a designated area, it synthesizes a large virtual aperture to improve image resolution. Inspired by SAR, we introduce synthetic aperture ptycho-endoscopy (SAPE) for micro-endoscopic imaging beyond the diffraction limit. SAPE operates by hand-holding a lensless fiber bundle tip to record coherent diffraction patterns from specimens. The fiber cores at the distal tip modulate the diffracted wavefield within a confined area, emulating the role of the ‘airborne antenna’ in SAR. The handheld operation introduces positional shifts to the tip, analogous to the aircraft’s movement. These shifts facilitate the acquisition of a ptychogram and synthesize a large virtual aperture extending beyond the bundle’s physical limit. We mitigate the influences of hand motion and fiber bending through a low-rank spatiotemporal decomposition of the bundle’s modulation profile. Our tests demonstrate the ability to resolve a 548-nm linewidth on a resolution target. The achieved space-bandwidth product is ~1.1 million effective pixels, representing a 36-fold increase compared to that of the original fiber bundle. Furthermore, SAPE’s refocusing capability enables imaging over an extended depth of field exceeding 2 cm. The aperture synthesizing process in SAPE surpasses the diffraction limit set by the probe’s maximum collection angle, opening new opportunities for both fiber-based and distal-chip endoscopy in applications such as medical diagnostics and industrial inspection. 

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4. NeuWS: Neural wavefront shaping for guidestar-free imaging through static and dynamic scattering media

   https://doi.org/10.1126/sciadv.adg4671  

   Feng, Brandon Y.; Guo, Haiyun; Xie, Mingyang; Boominathan, Vivek; Sharma, Manoj K.; Veeraraghavan, Ashok; Metzler, Christopher A. (June 2023, Science Advances)

   Diffraction-limited optical imaging through scattering media has the potential to transform many applications such as airborne and space-based imaging (through the atmosphere), bioimaging (through skin and human tissue), and fiber-based imaging (through fiber bundles). Existing wavefront shaping methods can image through scattering media and other obscurants by optically correcting wavefront aberrations using high-resolution spatial light modulators—but these methods generally require (i) guidestars, (ii) controlled illumination, (iii) point scanning, and/or (iv) statics scenes and aberrations. We propose neural wavefront shaping (NeuWS), a scanning-free wavefront shaping technique that integrates maximum likelihood estimation, measurement modulation, and neural signal representations to reconstruct diffraction-limited images through strong static and dynamic scattering media without guidestars, sparse targets, controlled illumination, nor specialized image sensors. We experimentally demonstrate guidestar-free, wide field-of-view, high-resolution, diffraction-limited imaging of extended, nonsparse, and static/dynamic scenes captured through static/dynamic aberrations. 

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5. Bundle Selection and Variety Seeking: The Importance of Combinatorics

   https://doi.org/10.1093/jcr/ucac017  

   O’Donnell, Michael; Critcher, Clayton R; Nelson, Leif D (May 2022, Journal of Consumer Research)

   Kirmani, Amna; Häubl, Gerald (Ed.)

   Abstract When consumers select bundles of goods, they may construct those sequentially (e.g., building a bouquet one flower at a time) or make a single choice of a prepackaged bundle (e.g., selecting an already-complete bouquet). Previous research suggested that the sequential construction of bundles encourages variety seeking. The present research revisits this claim and offers a theoretical explanation rooted in combinatorics and norm communication. When constructing a bundle, a consumer chooses among different choice permutations, but when selecting amongst prepackaged bundles, the consumer typically considers unique choice combinations. Because variety is typically overrepresented among permutations compared to combinations, certain consumers (in particular, those with similar attitudes toward items that could compose a bundle) are induced by these different numbers of pathways to variety to display more or less variety-seeking behavior. This is in part explained by the variety norms communicated by different choice architectures, cues most likely to be inferred and used by those who are indifferent between the potential bundle components and thus looking for guidance. Across 5 studies in the main text and 11 in the web appendix, this article tests this account and offers preliminary exploration of newly identified residual effects that the pathways-to-variety account cannot explain. 

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