Search Results (9)

Many swimming protists travel by actuating whip-like flagella to generate thrust. While many organisms’ flagella have been observed to have hair-like protrusions called mastigonemes, the function of these mastigonemes is not known. In particular, however, although theory, numerics, and some experiments suggest that mastigonemes can initiate the reversal in direction of thrust generated relative to the direction of traveling waves propagated along flagella, other experiments have found that they do not have hydrodynamic effects. Thus, it remains unclear whether mastigonemes have a hydrodynamic effect and function; additionally, any hydrodynamic effects may be species-dependent, which calls for the investigation of additional species. In this work, we report experimental observations of the cryptophyte C. paramecium that obtain their cell body, flagellar, and mastigoneme geometries, as well as their swimming kinematics and behavior. We then use the observed geometries and kinematics to numerically simulate swimming trajectories for a particularly well-characterized reorientation event, with and without various configurations of the mastigonemes. The comparison of numerical and experimental results shows that a configuration of mastigonemes in the beating plane best reproduces the observed reorientation dynamics, suggesting that in C. paramecium, although mastigonemes do not lead to gross changes in motility, such as thrust reversal, they do exert important quantitative effects. Full article

The venom-containing barb attached to their ‘whip-like’ tail provides stingrays a defensive mechanism for evading predators such as sharks. From human encounters, dermal stingray envenomation is characterized by intense pain often followed by tissue necrosis occurring over several days to weeks. The bioactive components in stingray venoms (SRVs) and their molecular targets and mechanisms that mediate these complex responses are not well understood. Given the utility of venom-derived proteins from other venomous species for biomedical and pharmaceutical applications, we set out to characterize the bioactivity of SRV extracts from three local species that belong to the Dasyatoidea ‘whiptail’ superfamily. Multiple cell-based assays were used to quantify and compare the in vitro effects of these SRVs on different cell lines. All three SRVs demonstrated concentration-dependent growth-inhibitory effects on three different human cell lines tested. In contrast, a mouse fibrosarcoma cell line was markedly resistant to all three SRVs, indicating the molecular target(s) for mediating the SRV effects are not expressed on these cells. The multifunctional SRV responses were characterized by an acute disruption of cell adhesion leading to apoptosis. These findings aim to guide future investigations of individual SRV proteins and their molecular targets for potential use in biomedical applications. Full article

Badminton, a dynamic racquet sport demanding agility and power, features the overhead forehand smash as a pivotal offensive shot. Utilizing 3D motion analysis, this research delves into the intricate biomechanical facets underpinning this pivotal shot, with a dual focus on both novice and proficient players. Through a comparative analysis of these two player cohorts, the investigation aims to elucidate the fundamental factors influencing the quality of the forehand smash. Our findings reveal that skilled players exhibit significant improvements in smash quality, including a 60.2% increase in shuttlecock speed, reduced clearance height, and flight angle at release. These enhancements are associated with specific determinants, such as consistent positioning, racket angle at impact, and range of motion (ROM) in various joints. More crucially, full-body tension-arc formation and a four-segment whip-like smash contribute to these improvements. Unique to the whip-like smash is the rapid trunk and shoulder rotations in early whip-like control inducing passive elbow flexion and wrist over-extension, enhancing the stretch-shortening cycle (SSC) effect of muscles for a more powerful smash. Emphasizing this uniqueness and the determinants simplify smash learning, potentially boosting training effectiveness. This research contributes to a deeper understanding of badminton’s biomechanics and offers practical implications for coaches and players to enhance their forehand smashes, especially among beginners. Full article

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis. Full article

Coral forests are vulnerable marine ecosystems formed by arborescent corals (e.g., Anthozoa of the orders Alcyonacea and Antipatharia). The population structure of the habitat-forming corals can inform on the status of the habitat, representing an essential aspect to monitor. Most Mediterranean corals live in the mesophotic and aphotic zones, and their population structures can be assessed by analyzing images collected by underwater vehicles. This is still not possible in whip-like corals, whose colony lengths and flexibilities impede the taking of direct length measurements from images. This study reports on the occurrence of a monospecific forest, of the whip coral Viminella flagellum in the Aeolian Archipelago (Southern Tyrrhenian Sea; 149 m depth), and the assessment of its population structure through an ad-hoc, non-invasive method to estimate a colony height based on its width. The forest of V. flagellum showed a mean density of 19.4 ± 0.2 colonies m⁻² (up to 44.8 colonies m⁻²) and no signs of anthropogenic impacts. The population was dominated by young colonies, with the presence of large adults and active recruitment. The new model proved to be effective for non-invasive monitoring of this near threatened species, representing a needed step towards appropriate conservation actions. Full article

The purpose of this study was to propose a methodology which quantifies the ball-speed generating mechanism of baseball pitching with the use of inertial measurement units (IMUs). IMUs were attached to the upper trunk, upper arm, forearm, and hand segments. The initial orientation parameters of each segment were identified using the differential iteration method from the acceleration and angular velocity of the sensor coordinate system output by IMUs attached to each segment. The motion of each segment was calculated and the dynamic contributions were then calculated. The motion of a baseball pitcher, who was instructed to throw at the target, was measured with a motion capture (mocap) system and IMUs. The results show that quantitative analysis of the ball-speed generation mechanism by the proposed method is almost similar to that conducted by the mocap system. In the future, this method will be employed to evaluate the ball-speed generation mechanism outside controlled laboratory conditions in an effort to help understand and improve the player’s motion. Full article

The world record of the hammer throw has not been broken since 1986. This stagnation is multifactorial. One dominant factor could be the lack of evidence-based scientific/biofeedback training. This study aims to identify key parameters influencing throw quality and structure a new digital method for biofeedback training. Wire-tension measurement and 3D motion capture technology (VICON 12-camera system) were applied in quantifying and comparing throws of a national-level and a college-level athlete. Our results reveal that multi-joint coordination influences heavily on wire-tension generation. Four phases, i.e., initiation, transition, turns, and throw, play various roles in evaluating the quality of a throw. Among them, the transition, the third turn, and the throw display explosive/rapid increases of tension. For improving the effectiveness of the skill, the whip-like control and proper SSC (stretch-shortening cycle) of muscle groups involved should be established through years of training. Furthermore, our study unveils that quick and complex full-body control could be quantified and characterized by four key parameters: wire-tension, hand- and hip-height, and trunk tilt. Hence, a wearable digital device with tension and three Inertial Measurement Unit (IMU) sensors would have great potential in realizing real-time biomechanical feedback training in practice for evaluating and improving the efficiency of various training programs. Full article

To fully exploit the potential of hydrogel micro-fibers in the design of regenerative medicinal materials, we designed a simple, easy to replicate system for cell embedding in degradable fibrous scaffolds, and validated its effectiveness using alginate-based materials. For scaffold fabrication, cells are suspended in a hydrogel-precursor and injected in a closed-loop circuit, where a pump circulates the ionic cross-linking solution. The flow of the cross-linking solution stretches and solidifies a continuous micro-scaled, cell-loaded hydrogel fiber that whips, bends, and spontaneously assembles in a self-standing, spaghetti-like patch. After investigation and tuning of process- and solution-related parameters, homogeneous microfibers with controlled diameters and consistent scaffolds were obtained from different alginate concentrations and blends with biologically favorable macromolecules (i.e., gelatin or hyaluronic acid). Despite its simplicity, this coaxial-flow encapsulation system allows for the rapid and effortless fabrication of thick, well-defined scaffolds, with viable cells being homogeneously distributed within the fibers. The reduced fiber diameter and the inherent macro-porous structure that is created from the random winding of fibers can sustain mass transport, and support encapsulated cell survival. As different materials and formulations can be processed to easily create homogeneously cell-populated structures, this system appears as a valuable platform, not only for regenerative medicine, but also, more in general, for 3D cell culturing in vitro. Full article

Pseudopterosin, produced by the sea whip of the genus Antillogorgia, possesses a variety of promising biological activities, including potent anti-inflammatory effects. However, few studies examined pseudopterosin in the treatment of cancer cells and, to our knowledge, the ability to inhibit triple-negative breast cancer (TNBC) proliferation or invasion has not been explored. Thus, we evaluated the as-yet unknown mechanism of action of pseudopterosin: Pseudopterosin was able to inhibit proliferation of TNBC. Interestingly, analyzing breast cancer cell proliferation after knocking down glucocorticoid receptor α (GRα) revealed that the antiproliferative effects of pseudopterosin were significantly inhibited when GRα expression was reduced. Furthermore, pseudopterosin inhibited the invasion of MDA-MB-231 3D tumor spheroids embedded in an extracellular-like matrix. Remarkably, the knockdown of GRα in 3D tumor spheroids revealed increased ability of cells to invade the surrounding matrix. In a coculture, encompassing peripheral blood mononuclear cells (PBMC) and MDA-MB-231 cells, and the production of interleukin 6 (IL-6) and interleukin 8 (IL-8) significantly increased compared to a monoculture. Notably, pseudopterosin indicated to block cytokine elevation, representing key players in tumor progression in the coculture. Thus, our results reveal pseudopterosin treatment as a potential novel approach in TNBC therapy. Full article