Structure of the molecular bushing of the bacterial flagellar motor

The basal body of the bacterial flagellum is a rotary motor that consists of several rings (C, MS and LP) and a rod. The LP ring acts as a bushing supporting the distal rod for its rapid and stable rotation without much friction. Here, we use electron cryomicroscopy to describe the LP ring structure around the rod, at 3.5 Å resolution, from Salmonella Typhimurium. The structure shows 26-fold rotational symmetry and intricate intersubunit interactions of each subunit with up to six partners, which explains the structural stability. The inner surface is charged both positively and negatively. Positive charges on the P ring (the part of the LP ring that is embedded within the peptidoglycan layer) presumably play important roles in its initial assembly around the rod with a negatively charged surface.

Study on the SUAM Double Magnet System for Polishing

Superconductive assisted machining (SUAM) is a novel machining method that eliminates tool interference via magnetic levitation tools. In our study, we developed a double magnet system (DMS) to increase the maximum power of the holding force and stabilize the magnetic rotation during polishing via the higher magnetic flux compared to a single magnet system (SMS). The maximum magnetic flux density of the DMS was approximately 100 mT higher than that of the SMS. In these cases, the entire holding force increases as the distance between the superconducting bulk and lower magnet decreases. The attractive forces are maximum around a displacement of 6 mm, although the repulsive and restoring forces increase spontaneously. The polishing performances of the DMS on the SUS304 and A1100P plates were evaluated using water-based diamond slurries, for equal levitation amounts. The amount removed by the DMS increased for the A1100P and SUS304 substrates compared to that by the SMS. In this case, we observe that the deviation of the polishing area on the DMS decreases compared to that of the SMS, reflecting a more stable rotation and movement due to the higher holding force.

One-way rotation of a chemically anchored single molecule-rotor

Superimposed STM images of the six stable rotation stations of a DMBI-P molecule during a step by step clockwise rotation induced by voltage pulses (V = 0.5 V, I = 0.5 nA, t = 10 s).

Design and Optimization of a Magnetically Levitated Inductive Reaction Sphere for Spacecraft Attitude Control

The inductive reaction sphere (RS) brings the benefit of simple, economical, and miniaturized design, and it is capable of multi-DOF torque generation. Thus, it is a suitable choice for the angular momentum exchange actuator in attitude control of micro-spacecrafts. To synthesize symmetric distribution of eddy currents and improve the speed and stability of rotation, a novel 4-pole winding design is proposed. However, the developed simplified analytical model shows that reduced pole number degrades the torque generation. To enhance the output torque of 4-pole RS, its curved cores and electromagnets are redesigned to enable the side teeth to be functional. As the analytical torque model for the RS with the slotted cores is not available, a constrained optimization problem is formulated, and the optimized parameters are calculated based on the prediction model from supported vector machine and finite element analysis. The lab prototypes are developed to validate the proposed design and test the speed performance. The experimental results show that the 4-pole RS prototype obtains a stable rotation over 700 rpm about X, Y and Z axis respectively with the angular momentum of 0.08 kg·m 2 /s, being superior to the 6-pole counterpart.