Effects of degree of cross-links on adhesion curves of cross-linked polymers observed by a point-contact method.

The effects of degree of cross-links on the adhesion properties of polydimethylsiloxane (PDMS) were investigated with the use of a point-contact method in air at room temperature. The degree of cross-links, rho, was varied in a wide range, inducing changes in the rheology of the cross-linked PDMS from viscous solution to elastic gel, and the adhesion properties were examined by changing the separation velocity under a constant normal load and waiting period prior to separation. As a result, the adhesion force, F(A), strongly depended on rho and showed a maximum at a characteristic rho around the loss tangent (tan delta) = 1. In addition, the shapes of the adhesion curves were found to depend strongly on rho, and they were categorized into four types. The different states of cross-linked polymers, i.e., elastic-gel type, weak-gel type, and solution type, showed the different shapes. In the case of the weak gel, two types of characteristic adhesion curves were obtained, which resulted from the different separation mechanisms with and without cavitations near the surface due to the interface and cohesive failures. In the intermediate range of rho, viscous or elastic fingering was detected, which resulted in the characteristic shape of the adhesion curve. The factors determining the type of the adhesion curves are discussed in terms of the microscopic surface, bulk properties, and the different shapes of the adhesive front at the contact surface.

Polymorphism of SFBB-gamma and its use for S genotyping in Japanese pear (Pyrus pyrifolia).

Japanese pear (Pyrus pyrifolia) exhibits the S-RNase-based gametophytic self-incompatibility where the pollen-part determinant, pollen S, had long remained elusive. Recent identification of S locus F-box brothers (SFBB) in Japanese pear and apple suggested that the multiple F-box genes are the pollen S candidates as they exhibited pollen specific expression, S haplotype-specific polymorphisms and linkage to the S locus. In Japanese pear, three SFBBs were identified from a single S haplotype, and they were more homologous to other haplotype genes of the same group (i.e., alpha-, beta- and gamma-groups). In this study, we isolated new seven PpSFBB(-gamma) genes from different S genotypes of Japanese pear. These genes showed S haplotype-specific polymorphisms, however, sequence similarities among them were very high. Based on the sequence polymorphisms of the PpSFBB(-gamma) genes, we developed a CAPS/dCAPS system for S genotyping of the Japanese pear cultivars. This new S genotyping system was found to not only be able to discriminate the S(1)-S(9), but also be suitable for identification of the mutant S(4sm) haplotype for the breeding of self-compatible cultivars, and detection of new S haplotypes such as S(k).

[Development and evaluation of QA software for the monitor chamber of an accelerator].

The monitor chamber of a radiotherapy system needs to be calibrated once a week. Because the calibration procedure requires a large variety of complicated calculations, we have developed software that facilitates calculation and enables comparison and storage of data. According to the standard measurement of absorbed dose, we used Visual Basic 6.0 (Microsoft Corp.) to establish the calibration method. This new technique has simplified the conventional intricate calculation required for calibration of the monitor chamber and enabled automatic processing of calculated results. We have confirmed the usefulness of this software in calibrating the monitor chamber. In the routine inspection, we can compare the current data with former results. Because of this advantage, it is possible to eliminate serious accidents such as overdosing and underdosing.