Monodisperse polystyrene particles crosslinked with different concentrations of divinylbenzene were synthesized in the 3.2–9.1 μm size range by dispersion polymerization in an isopropyl alcohol/toluene mixed‐dispersion medium with poly(N‐vinylpyrrolidone) as a steric stabilizer and 2,2′‐azobisisobutyronitrile as a radical initiator. The effects of the reaction parameters such as the crosslinking agent concentration, media solvency (controlled by varying the amount of toluene addition), the initiator concentration, and the stabilizer concentration on the particle size and size distribution were investigated with reference particles with a monodisperse size distribution and crosslinked by 1.5 wt % divinylbenzene. The appropriate increase in media solvency was a prerequisite for preparing crosslinked particles without coagulated and/or odd‐shaped particles. The investigation of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with a monodisperse size distribution. The glass‐transition temperatures of the particles increased with increasing divinylbenzene concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4368–4377, 2002

A passive multiple-trailer system provides various practical advantages for multi-functional service robots. However, motion control is difficult because the kinematic model is highly nonlinear. The kinematic design of a trailer system was proposed in prior research of ours. In this paper, it is shown how the backward motion of a robot with n passive trailers can be controlled. Once the desired trajectory of the last trailer is computed, the control input of the pushing robot is obtained through the proposed control scheme. Some experimental issues on reversing the trailer system are addressed. This paper provides an answer to the following question: "Does the system work well even if there are sensing or modeling errors?" Although it is difficult to obtain general analytic solutions for the above research question, a practical answer will be explored though simplified analysis and experiments. Experimental verifications are carried out using a mobile robot with three passive trailers. The experimental results show that backward-motion control can be successfully carried out by applying the proposed control scheme.

Cognitive flexibility is an essential ability to adapt to changing environment and circumstances. NMDAR has long been implicated in cognitive flexibility, but the precise molecular and cellular mechanism is not well understood. Here, we report that astrocytes regulate NMDAR tone through Best1-mediated glutamate and D-serine release, which is critical for cognitive flexibility. Co-release of D-serine and glutamate is required for not only homosynaptic LTD but also heterosynaptic LTD, which is induced at unstimulated synapses upon release of norepinephrine and activation of astrocytic α1-AR during homosynaptic LTP. Remarkably, heterosynaptic LTD at unstimulated synapses during memory acquisition is required for later repotentiation LTP during reversal learning, laying a foundation for flexible memory and cognitive flexibility. Our study sheds light on the pivotal role of astrocytes in orchestrating multiple synapses during memory formation and determining the fate of consolidated memory to be retained as a flexible memory.