Preliminary study on heartbeats and swimming behavior of free-ranging fish, red sea bream Pagrus major, measured with newly developed micro data-logger

To estimate the physiological condition or metabolic rate simultaneously with swimming behavior, we recorded a continuous electrocardiogram (ECG) in freely swimming fish, red sea bream Pagrus major, in a net pen during a 24h period. Swimming speed, swimming depth, and the bioelectric potential of the heart in the test fish were recorded with a micro data-logger. It is difficult to eliminate electric noise while recording ECGs of actively swimming fish. In the present experiment, we attached electrodes to two points on the ventral surface and successfully obtained data. Two types of micro data-loggers (one for recording ECG and another for swimming speed and depth) were attached to the dorsal side of the fish. The red sea bream swam slowly ( <1 total length/s) and stayed deeper in the net pen during most of the day, except for frequent burst of speed and vertical movements around dawn. An analysis of heartbeat variability, showed that high-frequency components, representing vagal (parasympathetic) nerve activity, rose only around midnight

HumanMimic: Learning Natural Locomotion and Transitions for Humanoid Robot via Wasserstein Adversarial Imitation

Transferring human motion skills to humanoid robots remains a significant challenge. In this study, we introduce a Wasserstein adversarial imitation learning system, allowing humanoid robots to replicate natural whole-body locomotion patterns and execute seamless transitions by mimicking human motions. First, we present a unified primitive-skeleton motion retargeting to mitigate morphological differences between arbitrary human demonstrators and humanoid robots. An adversarial critic component is integrated with Reinforcement Learning (RL) to guide the control policy to produce behaviors aligned with the data distribution of mixed reference motions. Additionally, we employ a specific Integral Probabilistic Metric (IPM), namely the Wasserstein-1 distance with a novel soft boundary constraint to stabilize the training process and prevent model collapse. Our system is evaluated on a full-sized humanoid JAXON in the simulator. The resulting control policy demonstrates a wide range of locomotion patterns, including standing, push-recovery, squat walking, human-like straight-leg walking, and dynamic running. Notably, even in the absence of transition motions in the demonstration dataset, robots showcase an emerging ability to transit naturally between distinct locomotion patterns as desired speed changes

Mutations in the stator protein PomA affect switching of rotational direction in bacterial flagellar motor

The flagellar motor rotates bi-directionally in counter-clockwise (CCW) and clockwise (CW) directions. The motor consists of a stator and a rotor. Recent structural studies have revealed that the stator is composed of a pentameric ring of A subunits and a dimer axis of B subunits. Highly conserved charged and neighboring residues of the A subunit interacts with the rotor, generating torque through a gear-like mechanism. The rotational direction is controlled by chemotaxis signaling transmitted to the rotor, with less evidence for the stator being involved. In this study, we report novel mutations that affect the switching of the rotational direction at the putative interaction site of the stator to generate rotational force. Our results highlight an aspect of flagellar motor function that appropriate switching of the interaction states between the stator and rotor is critical for controlling the rotational direction