Using the Intact Human Hand to Benchmark Real-Time Myoelectric Control Performance for Robotic Interfaces.

The objective of our study was to demonstrate how the intact human hand can be used as a benchmark for electromyogram (EMG)-based myoelectric control of robotic interfaces (e.g., myoelectric prostheses). Using the intact human hand as a gold standard for control algorithms is attractive because able-bodied participants are widely available, have stereotypical movements, and possess highly refined motor control. We compared within-subjects performance of a real-time virtual posture-matching task between a musculoskeletal model-based EMG controller (model trials) and the human hand (goniometer trials). Goniometer trials had lower (i.e., better) normalized path length (2.0±1.6) and task duration (3.3±3.4 sec) than model trials (4.1±4.3 and 12.3±10.7 sec, respectively; p<0.0001). Though, qualitatively, actual (measured by goniometers) and virtual joint angles assumed similar relative postures during model trials, there was a constant offset between them. Additionally, joint angles were more variable during model trials than goniometer trials. The results quantified the extent to which task performance and movement characteristics were not as good with the EMG controller (in this case, the musculoskeletal model-based controller) as with the gold-standard intact human hand. How EMG controllers compare with intact human hand control can drive and inform controller advancements.Clinical Relevance- The gold-standard intact human hand provides an objective way to decide which EMG control algorithms to translate to clinical robotic interfaces.

A survey of the management and development of captive African elephant (Loxodonta africana) calves: birth to three months of age.

We used four surveys to collect information about the birth, physical growth, and behavioral development of 12 African elephant calves born in captivity. The management of the birth process and neonatal care involved a variety of standard procedures. All of the calves were born at night, between 7PM and 7AM. The calves showed a systematic progression in behavioral and physical development, attaining developmental milestones at least a quickly as calves in situ. This study emphasized birth-related events, changes in the ways that calves used their trunks, first instances of behaviors, and interactions of the calves with other, usually adult, elephants. Several behaviors, such as the dam covering her calf with hay and the calf sucking its own trunk, were common in the captive situation and have been observed in situ. Overall, the behaviors of the calves resembled those observed for African elephant calves in situ. These data should help in the management of African elephants under human care by providing systematic reference values for the birth and development of elephant calves.

Sinking velocity of sub-millimeter microplastic.

Sinking experiments were conducted using irregularly shaped polyamide (PA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET) particles sized 6 to 251 µm. Certified PS spheres were used to validate experiments and showed that the effect of particle size on terminal sinking velocity is well reproduced by the method. As expected sinking velocities of irregularly shaped particles were considerably lower than theoretical values for spheres of the same size range calculated via several approximations available in the literature. Despite the influence of particle shape, the dependence of terminal sinking velocity on particle size can reasonably well be described by a quadratic linear regression, with an average determination of 63%. To generalize results we present a model that predicts terminal sinking velocity as a function of particle size and particle excess density over the fluid. Improving the predictive power of this model requires further experiments with a range of particle characteristics.

Sinking rates of microplastics and potential implications of their alteration by physical, biological, and chemical factors.

To follow the pathways of microplastics in aquatic environments, profound knowledge about the behaviour of microplastics is necessary. Therefore, sinking experiments were conducted with diverse polymer particles using fluids with different salinity. Particles ranged from 0.3 and 3.6mm with sinking rates between 6 and 91×10(-3)ms(-1). The sinking velocity was not solely related to particle density, size and fluid density but also to the particles shape leading to considerable deviation from calculated theoretical values. Thus, experimental studies are indispensable to get basic knowledge about the sinking behaviour and to gain representative datasets for model approaches estimating the distribution of microplastics in aquatic systems. The sinking behaviour may be altered considerably by weathering and biofouling demanding further studies with aged and fouled plastic particles. Furthermore, assumptions are made about the influence of sinking fouled microplastics on the marine carbon pump by transferring organic carbon to deeper water depths.