Laser-guided lightning.

Lightning discharges between charged clouds and the Earth's surface are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that laser-induced filaments-formed in the sky by short and intense laser pulses-can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was conducted on the Säntis mountain in north-eastern Switzerland during the summer of 2021 with a high-repetition-rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by very-high-frequency interferometric measurements, and the number of X-ray bursts detected during guided lightning events greatly increased. Although this research field has been very active for more than 20 years, this is the first field-result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures.

Test of a customized compliant ankle rehabilitation device in unpowered mode.

Presented is the design, implementation, and initial gait testing of a lightweight, compliant robotic device for ankle rehabilitation. Many patients with neuromuscular disorders suffer deficits in sensorimotor control of the ankle joint, leading to an abnormal walking pattern. Robotic devices have been used to assist ankle rehabilitation. However, these devices are usually heavy and rigid, which can deviate a natural gait pattern. To address these issues, our team has developed a light weight, compliant ankle robotic device actuated by artificial pneumatic muscles. A total of 3 healthy subjects were recruited to test whether the mechanical structure of the device deviates gait. We used a 3-dimensional (3D) motion analysis system to record and analyze subjects' ankle kinematics during gait while walking barefoot and while wearing the device unpowered. The preliminary results suggest that the device caused some, but minimal changes in ankle kinematics during gait. The changes were mainly caused by the device's rigid footplate, used to support the foot and connect to the pneumatic muscles. The preliminary results will be used for future improvement of the device.