Kazushi Yoshida

Caenorhabditis elegans shows chemotaxis to various odorants and water-soluble chemoattractants such as NaCl. Previous studies described the pirouette mechanism for chemotaxis, in which C. elegans quickly changes the direction of locomotion by using a set of stereotyped behaviors, a pirouette, in response to a decrease in the concentration of the chemical. Here, we report the discovery of a second mechanism for chemotaxis, called the weathervane mechanism. In this strategy animals respond to a spatial gradient of chemoattractant and gradually curve toward higher concentration of the chemical. By computer simulation, we find that both of these mechanisms contribute to chemotaxis and both mechanisms need to act in parallel for efficient chemotaxis. Using laser ablation of individual neurons to examine the underlying neural circuit, we find the ASE sensory neurons and AIZ interneurons are essential for both the pirouette and weathervane mechanisms in chemotaxis to NaCl. Salt-conditioned animals show reversed responses in both of these behaviors, leading to avoidance of NaCl. These results provide a platform for detailed molecular and cellular analyses of chemotaxis and its plasticity in this model organism.

Abstract Macromolecules at the surface of a polymeric solid have considerable mobility, and the specific arrangement of functional groups of macromolecules at the surface is dictated by the environmental conditions in which the surface is placed. Consequently, the change of environmental conditions, such as immersion in water or placement in a biological surrounding, could cause a cosiderable degree of change in the surface characteristics of a polymer from those evaluated in the laboratory against ambient air. The mobile nature of a polymer surface can be investigated by surface‐implanting fluorine‐containing moieties, mainly—CF 3 , by the plasma implantation technique and following the disappearance and reappearance of fluorine atoms on the surface. The disappearance rates (based on the immersion time in water at room temperature) of ESCA F 1 s signals, the decay rates of (advancing) contact angle of water, and the recovery of these values on heat treatment of water‐immersed samples were measured as a function of crystallinity of polymer samples (at three levels of crystallinity) for poly(ethylene terephthalate) and nylon 6.

This paper describes the components and system of a thermoelectric (TE) generator with a catalytic butane combustor. The combustion chamber with a size of 8 mm/spl times/8 mm/spl times/0.4 mm is etched in a 0.65-mm-thick silicon substrate, and bonded to both sides of a 0.77-mm-thick glass substrate with a thin-film ignition heater. A set of 34 couples of BiTe TE elements, each with a size of 0.65 mm/spl times/0.65 mm/spl times/2 mm, are directly bonded to both sides of the combustor. The combustor without the TE modules was tested using butane as fuel, and self-sustaining combustion and electrical ignition were achieved. Also, nearly 100% combustion efficiency and a uniform temperature distribution were confirmed by gas chromatography and infrared thermoimaging, respectively. When the TE modules were attached to the combustor, however, butane combustion was impossible. The characteristics of TE generation were measured using hydrogen as fuel. When a theoretical combustion power was 6.6 W, the maximum output power of 184 mW was obtained with a load of 5.68 /spl Omega/. The total efficiency in this experiment was 2.8% (184 mW/6.6 W).

S. Ueno, K. Yoshida, K. Ebitani and K. Kaneda, Chem. Commun., 1998, 295 DOI: 10.1039/A707655J