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1. Effect of vocal tract morphology on tongue shaping for American English /ɹ/

   https://doi.org/10.1121/10.0008076  

   Lu, Yijing; Hsu, Haley; Goldstein, Louis; Toutios, Asterios (October 2021, The Journal of the Acoustical Society of America)

   There is a lack of general agreement among previous studies (e.g., Bakst, 2016; Dediu & Moisik, 2019; Westbury et al., 1998) on whether measurements of vocal tract morphology are robust predictors of inter-speaker variation in tongue shaping for American English /ɹ/. One possible reason is the different quantifications of /ɹ/ tongue shapes that were employed. The current study compares the relationships between a single set of anatomical measurements and three different measures of lingual articulation for /ɹ/ in /ɑɹɑ/ in midsagittal real-time MRI data. A novel method was developed to quantify the palatal constriction location and length, which served as the first two measures of tongue shape. A linear Support Vector Machine divided the constriction location and length measures into regions that approximate the visually identified categories of “retroflex” and “bunched.” The third shape measurement is the signed distance of each token of /ɹ/ to the division boundary, representing the degree of “retroflexion” or “bunchedness” based on palatal constriction properties. These three measures showed marginally to moderately significant linear relationships with two specific measures of individual speakers’ vocal tract anatomy: the degree of mandibular inclination and the length of the oral cavity roof. Overall, the effect of anatomy on the lingual articulation of /ɹ/ is not strong. [Work supported by NSF, Grant 1908865.] 

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2. A mechanical model reveals that non-axisymmetric buckling lowers the energy barrier associated with membrane neck constriction

   https://doi.org/10.1039/c9sm01494b  

   Vasan, R.; Rudraraju, S.; Akamatsu, M.; Garikipati, K.; Rangamani, P. (January 2020, Soft Matter)

   Membrane neck formation is essential for scission, which, as recent experiments on tubules have demonstrated, can be location dependent. The diversity of biological machinery that can constrict a neck such as dynamin, actin, ESCRTs and BAR proteins, and the range of forces and deflection over which they operate, suggest that the constriction process is functionally mechanical and robust to changes in biological environment. In this study, we used a mechanical model of the lipid bilayer to systematically investigate the influence of location, symmetry constraints, and helical forces on membrane neck constriction. Simulations from our model demonstrated that the energy barriers associated with constriction of a membrane neck are location-dependent. Importantly, if symmetry restrictions are relaxed, then the energy barrier for constriction is dramatically lowered and the membrane buckles at lower values of forcing parameters. Our simulations also show that constriction due to helical proteins further reduces the energy barrier for neck formation when compared to cylindrical proteins. These studies establish that despite different molecular mechanisms of neck formation in cells, the mechanics of constriction naturally leads to a loss of symmetry that can lower the energy barrier to constriction. 

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3. Modulating Wrist-Hand Kinematics in Motorized-Assisted Grasping With C5-6 Spinal Cord Injury

   https://doi.org/10.1109/TMRB.2023.3328639  

   Chang, Erin Y; McPherson, Andrew IW; Adolf, Ryan C; Gloumakov, Yuri; Stuart, Hannah S (October 2023, IEEE Transactions on Medical Robotics and Bionics)

   Loss of hand function severely impacts the independence of people with spinal cord injuries (SCI) between C5 and C7. To achieve limited grasps or strengthen grip around small objects, these individuals commonly employ a compensatory technique to passively induce finger flexion by extending their wrist. Passive body-powered devices using wrist-driven actuation have been developed to assist this function, in addition to advancements in active robotic devices aimed at finger articulation for dexterous manipulation. Nevertheless, neither passive nor active devices see wide adoption and retention in the long-term. Here we present an unconventional system for combining aspects of both passive and active actuation and show that actively modulating the relationship between passive wrist and finger movement can impact both performance and kinematic metrics of upper body compensation. This study comprises six unique case studies of individuals with C5-6 SCI because morphology and response can vary widely across this population. While only some individuals’ performance improved with the shared system over passive-only operation, all six participants stated that they preferred the shared system, regarding added motorization with a sense of trust and embodiment. This outcome motivates the ongoing study of how motors can alter body kinematics to augment body-power without replacing it. 

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4. Pterion variation in the skulls of rhesus macaques from Cayo Santiago: Inheritance, development, and pathology

   https://doi.org/10.1002/ar.25417  

   Francis, George; Wang, Qian (February 2024, The Anatomical Record)

   Abstract The pterion is the sutural juncture of the frontal, parietal, sphenoidal, temporal, and zygomatic bones on the lateral aspect of the cranium. As a craniometric landmark, the pterion has a taxonomic valence, in addition to a common neurosurgical entry point in medicine. Variation in the articulation patterns at the pterion have been documented between primate species yet have a high degree of uniformity within species, suggesting a genetic control for this complex region of the skull. In this study, pterion pattern variation was investigated in 1627 Rhesus macaque crania of the Cayo Santiago colony. The colony's associated skeletal collections accompany known age, sex, and maternal lineages. Pterion pattern prevalence rates were tested against matrilines, as well as cranial shape, and cranial sutural fusion ages (including individuals with prematurely fused sutures). Five patterns were identified, the most prominent being the prevailing Old World Monkey frontotemporal (FT) articulation (83.4%). The relative frequency of those not exhibiting the FT pattern was found to vary considerably between matrilineal families (p = 0.037), ranging from 5.3% to 34.2%. Mothers with the non‐FT pterion pattern were three times as likely to bear non‐FT offspring. Cranial shape additionally varied with pterion type. Males exhibiting zygomaticotemporal (ZT) and sphenoparietal (SP) articulations possessed a relatively longer and narrower cranium than those with the default FT type (p = < 0.001). Cranial sutural fusion ages were not found to differ between pterion types, though all individuals with craniosynostosis (6; 0.38%) exhibited the FT type. The study provided strong evidence for a genetic source for pterion pattern as well as outlining a relatively novel relationship with cranial shape and sutural fusion ages. A unifying explanation may lie in those genes involved in both sutural and craniofacial development, or in the variation of brain growth processes channeling sutural articulation at the pterion. Both may be heritable and responsible for producing observed matrilineal differences in the pterion. 

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5. An Ultrasound Study of Connemara Irish Palatalization and Velarization

   Bennett, Ryan; Ní Chiosáin, Máire; Padgett, Jaye; McGuire, Grant (January 2018, Journal of the International Phonetic Association)

   We present the first ultrasound analysis of the secondary palatalization contrast in Irish, analyzing data from five speakers from the Connemara dialect group. Word-initial /pʲ(bʲ),pˠ(bˠ),tʲ,tˠ,kʲ,kˠ,fʲ,fˠ,sʲ,sˠ,xʲ,xˠ/ are analyzed in the context of /iː,uː/. We find, first, that tongue body position robustly distinguishes palatalized from velarized consonants, across place of articulation, manner, and vowel place contexts, with palatalized consonants having fronter and/or higher tongue body realizations than their velarized counterparts. This conclusion holds equally for labial consonants, contrary to some previous descriptive claims. Second, the nature and degree of palatalization and velarization depend in systematic ways on consonant place and manner. In coronal consonants, for example, velarization is weaker or absent. Third, the Irish consonants examined resist coarticulation in backness with a following vowel. In all of these respects Irish palatalization is remarkably similar to that of Russian. Our results also support an independent role for pharyngeal cavity expansion/retraction in the production of the palatalization contrast. Finally, we discuss preliminary findings on the dynamics of the secondary articulation gestures. Our use of principal component analysis (PCA) in reaching these findings is also of interest, since PCA has not been employed a great deal in analyses of tongue body movement. 

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