Social dominance modifies behavioral rhythm in a queenless ant

Social insects provide an intriguing model system in chronobiology. Typically, an egg-laying queen exhibits arrhythmicity in activity while foraging worker has clear rhythmicity. In the queenless ant, Diacamma sp., from Japan, colony members lack morphological caste, and reproductive differentiation occurs as a consequence of dominance hierarchy formation. Their specialized dominance interaction “gemmae mutilation”, provide us a fascinating model system to investigate the effect of social dominance on rhythmic ontogeny. Measurement of individual rhythms revealed that they have clear circadian rhythm at eclosion but it is diminished by social mutilation of gemmae. Moreover, unlike highly eusocial species, mated egg-layer (i.e., gamergate) possessed a circadian rhythm even after mating in Diacamma. Measurement of colony-level rhythms revealed that gemmae mutilations are performed in the limited time of the day, but foraging occurs around-the-clock. The above finding is a novel form of temporal organization in social insects, providing a new insight in morphologically casteless species. We discuss the causes and consequences of rhythmic variability in social organization.     

Synthesis of novel polymer type sulfoxide solid phase combined with the porogen imprinting for enabling selective separation of polychlorinated biphenyls

We developed a novel polymer type sulfoxide-modified solid phase enabling to achieve selective separation of polychlorinated biphenyls (PCBs) from insulation oil. In this study, firstly we prepared base-polymer based on the concept of the molecular imprinting to capture PCBs in selectively, then, the sulfoxide groups were modified on the pore surface of base-polymers by changing preparation methods. As results of liquid chromatographic analyses for the polymers as columns, the base-polymer prepared by xylene as a porogenic solvent showed selective retention ability for chlorinated aromatic compounds by the porogen imprinting effect. Additionally, the polymer-type sulfoxide solid phases showed highly retention ability for PCBs by increasing amount of introduced sulfoxide groups. Consequently, the results of separation of PCBs comparing to insulation oil suggested that the prepared solid phase can be used for the selective separation of PCBs at the same level as a commercially available media utilized for the regulated method.     

Nucleophilic substitution of poly(vinyl chloride) with iminoacetic acid and n-dodecanethiol

The modification of poly(vinyl chloride) was carried out with iminodiacetic acid (IDA, C₄H₇NO₄) and iminodiacetic acid dimethylester (IDADM, C₆H₁₁NO₄), as well as with n-dodecanethiol (DT, C₁₂H₂₆S) in the presence of K₂CO₃. The reaction was carried out at different temperatures below 100 °C with dimethyl formamide (DMF) and cyclohexanone as solvents. IDA did not show any reactivity, probably due to the dipolar character of the molecule. IDADM caused the elimination of HCl, while only substitution ratios of about 3 % were observed. However, the modification of PVC with DT resulted in a substitution rate of 18 % without elimination. DT-PVC showed excellent thermal properties, comparable with those of the unmodified polymer.     

Effect of losing on male fights of broad-horned flour beetle, Gnatocerus cornutus

Experience-dependent tactics of males trying to gain access to females were examined in the beetle Gnatocerus cornutus, which engages in male–male fighting for mates. In male fights, subsequent behavior is modified by winning and losing experiences. Males, therefore, may choose between several behavioral tactics to obtain a mate, based on his previous fighting experience. In G. cornutus, we examined for how long aggressive behaviors were modified by experiences of winning or losing, i.e., the duration of the prior experience effect. Losing decreased a male's frequency of fighting for 4 days, and few defeated males fought any male regardless of the opponent's size. By the fifth day, this effect disappeared. No modulation of male behavior due to winning was observed. Furthermore, the experience of losing not only decreased a male's aggressiveness but also switched the male behavior from fighting to dispersal from the fight site to another site. In future, it is necessary to clarify why the optimal term of the losing experience is 4 days in this beetle.     

PSA application for a PCB detoxification plant

 Polychlorinated biphenyls (PCBs), a type of persistent organic pollutants (POPs), are considered to be endocrine disrupters. According to the Stockholm Convention on POPs, PCB detoxification is being accelerated globally. We have developed an environmentally sound chemical PCB detoxification plant using the ultraviolet ray/catalyst method. The purpose of this paper is to check the design methodology for the PCB detoxification plant by the application of probabilistic safety analysis. First, possible hazardous events were determined; second, the weakest points in these hazardous events were established; and third, the impact when failures arise at the weak points in the system were studied. We clarified the preventive measures as follows. To prevent PCBs leaking into the environment, select leak-tight valves for the piping containing PCBs, and reduce the number of valves. To prevent fire or explosions due to leaks of an inflammable mixture, select leak-tight valves, reduce the number of valves installed in the piping, and improve the reliability of the suppression tank in the isopropyl alcohol (IPA) recovery unit. Received: February 27, 2001 / Accepted: June 17, 2002