Aims. We aim to clarify the origin of the multiple jet features emanating from the binary protostar SVS 13A (=VLA4A/VLA4B). Methods. We used the Plateau de Bure Interferometer to map at 0.3–0.8′′ ...(~70–190 au) dust emission at 1.4 mm, CO(2–1), SiO(5–4), SO(65–54). Revised proper motions for VLA4A/4B and jet wiggling models are computed to clarify their respective contribution. Results. VLA4A shows compact dust emission suggestive of a disk <50 au, and is the hot corino source, while CO/SiO/SO counterparts to the small-scale H2 jet originate from VLA4B and reveal the jet variable velocity structure. This jet exhibits ≃ 3″ wiggling consistent with orbital motion around a yet undetected ≃20–30 au companion to VLA4B, or jet precession. Jet wiggling combined with velocity variability can explain the large apparent angular momentum in CO bullets. We also uncover a synchronicity between CO jet bullets and knots in the HH7–11 chain demonstrating that they trace two distinct jets. Their ≃300 yr twin outburst period may be triggered by close perihelion approach of VLA4A in an eccentric orbit around VLA4B. A third jet is tentatively seen at PA ≃ 0°. Conclusions. SVS13 A harbors at least 2 and possibly 3 distinct jet sources. The CO and HH7-11 jets are launched from quasi-coplanar disks, separated by 20–70 au. Their synchronous major events every 300 yr favor external triggering by close binary interactions, a scenario also invoked for FU Or outbursts.
Objective
The aim of this study was to explore the efficacy of two different passive back-support exoskeleton (BSE) designs during repetitive lifting in different postures.
Background
Although BSEs ...have been proposed as a potential intervention for reducing physical demands, limited information is available about the impacts of different exoskeleton designs in diverse work scenarios.
Method
Eighteen participants (gender-balanced) performed lab-based simulations of repetitive lifting tasks. These tasks were performed in 12 different conditions, involving two BSEs and a control condition, two levels of lifting symmetry (symmetric and asymmetric), and two postures (standing and kneeling). Outcome measures described muscle activity and energy expenditure, along with perceived discomfort, balance, and usability.
Results
Using both BSEs significantly reduced peak activity of the trunk extensor muscles (by ~10%–28%) and energy expenditure (by ~4%–13%) in all conditions tested. Such reductions, though, were task dependent and differed between the two BSEs. In most of the tested conditions, using BSEs positively affected subjective responses regarding perceived exertion and usability.
Conclusion
Our results suggest that the beneficial effects of a BSE are task specific and depend on the specific BSE design approach. More work is needed, though, to better characterize this task specificity and to determine the generalizability of BSE effects on objective and subjective outcomes for a wider range of conditions and users.
Application
Our results provide new evidence to guide the selection and application of passive BSE designs in diverse lifting tasks.
Abstract The prevalence of low back pain (LBP) increases with age, yet the underlying mechanism(s) responsible for this remains unclear. To explore the role of biomechanical factors, we investigated ...age-related differences in lower-back biomechanics during sagittally-symmetric simulated manual material handling tasks. For each task, trunk kinematics and mechanical demand on the lower back were examined, from among 60 participants within five equal-sized and gender-balanced age groups spanning from 20 to 70 years old. The tasks involved lowering a 4.5 kg load from an upright standing posture to both knee height and a fixed height and then lifting the load back to the initial upright posture. During these tasks, segmental body kinematics and ground reaction forces were collected using wireless inertial measurement units and a force platform. Overall, older participants completed the tasks with larger pelvic rotation and smaller lumbar flexion. Such adopted trunk kinematics resulted in larger peak shearing demand at the lower back in older vs. younger participants. These results suggest that older individuals may be at a higher risk for developing lower back pain when completing similar manual material handling tasks, consistent with epidemiological evidence for higher risks of occupational low back pain among this cohort.
The use of interactive or "smart" textiles that have sensing material(s) incorporated into them supports an emerging technology for physical activity assessment called smart textile systems (STSs). ...STSs are an increasingly useful technology for researchers, athletes, patients, and others. In this paper, we developed and assessed a novel smart undershirt (SUS) that was designed to monitor low-back (thorax versus pelvis) and shoulder motions. The SUS consists of stretchable undershirt, electronic components, and an array of 11 body-worn sensors (BWSs) printed on the clothing. The BWSs are developed by coating electroactive polymers (i.e., polymerization) on the fabric and are wired using conductive threads. This shirt is the first smart garment for tracking both lower back and shoulder motions using printed textile sensors. The 16 participants performed 10 upper body movements while wearing the SUS for the purpose of assessing the accuracy of task classification and angle estimation. Input from the SUS led to classification accuracy at the individual levels up to 94% and planar angle estimations with errors on the order of 1.3° and 9.4° for the low back and shoulder, respectively. The performance was poorer, though, at the group level. The SUS appears to be a promising alternative for the purpose of monitoring upper body motions and activities.
Indoor fall monitoring is challenging for community-dwelling older adults due to the need for high accuracy and privacy concerns. Doppler radar is promising, given its low-cost and contactless ...sensing mechanism. However, the line-of-sight restriction limits the application of radar sensing in practice, as the Doppler signature will vary when the sensing angle changes, and signal strength will substantially degrade with large aspect angles. Additionally, the similarity of the Doppler signatures among different fall types makes classification challenging. To address these problems, we first present an experimental study to obtain Doppler signals under large and arbitrary aspect angles for diverse types of simulated activities. We then develop a novel, explainable, multi-stream, feature-resonated neural network (eMSFRNet) that achieves fall detection and a pioneering study of classifying seven fall types. eMSFRNet is robust to radar sensing angles and subjects, and is the first method that can resonate and enhance feature information from noisy/weak Doppler signatures. The multiple feature extractors - from ResNet, DenseNet, and VGGNet - extract diverse feature information with various spatial abstractions from a pair of Doppler signals. The resonated-fusion translates the multi-stream features to a single salient feature that is critical to fall detection and classification. eMSFRNet achieved 99.3% accuracy detecting falls and 76.8% accuracy classifying seven fall types. Our work is the firstmultistatic robust sensing system that overcomes the challenges associated with Doppler signatures under large and arbitrary aspect angles. Our work also demonstrates the potential to accommodate radar monitoring tasks that demand precise and robust sensing.
Industrial exoskeletons are a promising ergonomic intervention to reduce the risk of work-related musculoskeletal disorders by providing external physical support to workers. Passive exoskeletons, ...having no power supplies, are of particular interest given their predominance in the commercial market. Understanding the mechanical behavior of the torque generation mechanisms embedded in passive exoskeletons is, however, essential to determine the efficacy of these devices in reducing physical loads (e.g., in manual material handling tasks). We introduce a novel approach using a computerized dynamometer to quantify the assistive torque profiles of two passive back-support exoskeletons (BSEs) at different support settings and in both static and dynamic conditions. The feasibility of this approach was examined using both human subjects and a mannequin. Clear differences in assistive torque magnitudes were evident between the two BSEs, and both devices generated more assistive torques during trunk/hip flexion than extension. Assistive torques obtained from human subjects were often within similar ranges as those from the mannequin, though values were more comparable over a narrow range of flexion/extension angles due to practical limitations with the dynamometer and human subjects. Characterizing exoskeleton assistive torque profiles can help in better understanding how to select a torque profile for given task requirements and user anthropometry, and aid in predicting the potential impacts of exoskeleton use by incorporating measured torque profiles in a musculoskeletal modeling system. Future work is recommended to assess this approach for other occupational exoskeletons.
We study the process qq¯,gg→A→Z⁎h in a 2-Higgs Doublet Model Type-II where the mass of the CP-odd Higgs state A is lower than the rest mass of the Z and h particles (the latter being the Standard ...Model-like Higgs state discovered at the Large Hadron Collider in 2012), i.e., mA<mZ+mh≈215 GeV. This is a mass range which is not being currently tested by ATLAS and CMS, yet we show that there can be sensitivity to it already during Runs 2 & 3, assuming leptonic decays of the gauge boson and bottom-antibottom quark ones for the Higgs boson.
Context. Only indirect evidence of the role of magnetic braking in regulating gravitational collapse and the formation of circumstellar disks, such as compact disk sizes and the launching of ...high-velocity collimated protostellar jets, has been found from observational work. Aims. More direct tests of the magnetic braking shaping the angular momentum of the gas in Class 0 protostars are crucially needed to confirm and make progress on the magnetically regulated disk formation scenario. Methods. In the present work we used nonideal magnetohydrodynamic models of protostellar collapse and synthetic observations of molecular gas spectral emission, from the radiative transfer post-processing of these models. We analyzed the synthetic observations to test whether possible kinematic signatures of the magnetic braking in the gas velocity field can be captured from maps of the molecular gas emission in protostellar envelopes. Results. By comparing the 3D specific angular momentum of models with varying turbulent energy and magnetization, we show that, in the numerical models of protostellar evolution explored, the increase in magnetization and its consequences on the spatial redistribution of angular momentum modifies the shapes of the radial profiles of specific angular momentum probed along the equatorial plane. However, various analysis of gas kinematics from the synthetic observations of molecular line emission mostly fail to capture the magnitude and differences in radial profiles of specific angular momentum due to different magnetization. Finally, we compare our synthetic observations to observational datasets from the literature to discuss possible magnetic braking signatures in protostellar envelopes. Conclusions. We show that widely used observational methods fail to quantitatively capture the magnitude of angular momentum of the gas in protostellar envelopes, and that no method makes it possible to measure the differences in radial evolution of angular momentum due to different magnetization at all envelope radii. This is especially true in the more magnetized cases where the rotational velocities are of the order of the thermal broadening of the molecular lines. However, our analysis suggests that the detection of symmetric patterns and organized velocity fields in the moment 1 maps of the molecular line emission, and monotonous radial profiles of the specific angular momentum showing a power law decline, should be suggestive of a less magnetized scenario. Protostellar cores where efficient magnetic braking is at work are more likely to present a highly asymmetric velocity field, and more prone to show complex radial profiles of their specific angular momentum measured in the equatorial plane.
Abstract Localized muscle fatigue (LMF) during a repetitive task can be influenced by several aspects such as the level and duration of exertions. Among these aspects, though, the influence of cycle ...time remains unclear. Here, the effect of cycle time on LMF and performance was examined for a simple biomechanical system during repetitive static efforts. Participants performed 1-h trials of intermittent isometric index finger abduction with a duty cycle of 50% in all combinations of two cycle times (30 and 60 s) and two exertion levels (15% and 25% of maximum voluntary capacity). Measures of discomfort, performance (force fluctuations), and muscle capacity (voluntary strength and low-frequency twitch responses) were obtained, all of which demonstrated a beneficial effect of the 30 s cycle time. Specifically, the shorter cycle time led to lower rates of increase in perceived discomfort, lower rates of increase in force fluctuations, lower rates of decrease in voluntary capacity, and smaller changes in twitch responses. These benefits, reflecting less LMF development in the shorter cycle time, were quite consistent between genders and the two levels of effort. Results of this study can be used to modify current models predicting work–rest allowance and/or LMF, helping to enhance performance and reduce the risk of adverse musculoskeletal outcomes.
Arm-support exoskeletons (ASEs) are an emerging technology with the potential to reduce physical demands during diverse tasks, especially overhead work. However, limited information is available ...about the effects of different ASE designs during overhead work with diverse task demands. Eighteen participants (gender-balanced) performed lab-based simulations of a pseudo-static overhead task. This task was performed in six different conditions (3 work heights × 2 hand force directions), with each of three ASEs and in a control condition (i.e., no ASE). Using ASEs generally reduced the median activity of several shoulder muscles (by ∼12–60%), changed working postures, and decreased perceived exertion in several body regions. Such effects, though, were often task-dependent and differed between the ASEs. Our results support earlier evidence of the beneficial effects of ASEs for overhead work but emphasize that: 1) these effects depend on the task demands and ASE design and 2) none of the ASE designs tested was clearly superior across the tasks simulated.
•Three passive arm-support exoskeletons (ASEs) examined during simulated nutrunning.•Using ASEs reduced median muscle activity in the neck, shoulder complex, and back.•Using ASEs decreased perceived exertion.•Using ASEs led to changes in working postures.•Beneficial effects were task-specific and differed between ASE designs.
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