The equation of the curve seen when brooms are stacked in a school classroom is derived. The curve obtained is identified to be the tractrix, which is often obtained as the locus of a moving point. Unlike what is usually seen, the tractrix derived in this paper is a static one.

We observed inhibitory syn e rgism of the combinations of two kinds of monoterpenes containing ℓ- menthol on the growth of six strains of dematiaceous fungi ( Cladosporium spp. and Aureo basi- dium spp.) using direct contact experiment based on an agar medium dilution method.The mono- terpenes except ℓ- menthol are menthone, (R)-pulegone, linalool, (-)-carveol and citral. All of t he m are included in herb As for 0.02% (w/v) of ℓ- menthol concentration, the other mono- terpenes concentration was adjusted in 0.02-0.1% (v/v). For some strains, multiplier effects of antifungal activity to the fungi were observed in 0.05-0.1% (v/v) of (R)-pulegone, 0.1% (v/v) of linalool, 0.02% (v/v) of (-)-carveol, and 0.02% (v/v) of citral at 25° C. In other most combinations ,it was equal to the independent antifungal activity of ℓ-menthol, (-)- carveol or citral.

The preservation of four strains of Trichoderma spp. using mycelium agar disks (5 mm in diameter) soaked in four kinds of cryoprotectants (i.e. 40% (w/w) maltose aqueous solution, 40% (w/w) glucose one, 10% (w/w) glycerol one, and pure water) at 20°C of an experimental freezer and at around 19°C of a domestic freezer was investigated. The results obtained were as follows:

(1) The survival rate of the four strains (NBRC 33016, 93130Tr, ANCT-05011, ANCT-05138) was 100% soaked in the maltose aqueous solution, the glucose one, and the glycerol one at -20°C for 133 days.

(2) Using the maltose aqueous solution for the cryoprotectant, the survival rate of all two strains tested (NBRC 33016, ANCT-05011) was 100% at 20°C and at around -19°C for 240 days.

(3) Using pure water for the cryoprotectant, the survival rate of the two strains tested (NBRC 33016, ANCT-05011) was 100% at -20°C and at around -19°C for 84 days. Therefore, it was revealed that the cryopreserving of Trichoderma spp. strains using mycelium agar disks at around -20°C had a potential.

Inhibitory effects of charcoal particles immobilized Trichoderma spp. on wood degradation by a psychrophilic-house fungus, Serpula lacrymans were examined. Japanese white birch (Betula platyphylla var. japonica) blocks were covered with three kinds of the particles immobilized Trichoderma spp. (ANCT-05013, ANCT-05103 and NBRC 33016) and exposed to S. lacrymans (HFPR 0301 and HFPR 0502) at 20℃ for 12 weeks to measure mass losses. ANCT-05013 and ANCT-05103 showed superior inhibition effects on wood degradation compared to NBRC 33016. The mass losses were 0% in the particles immobilized ANCT-05013 and ANCT-05103, 9-10% in the ones immobilized NBRC 33016, and 11-18% in the absence of the particles (control). Furthermore, S. lacrymans mycelial growth (HFPR 0301 and HFPR 0502) did not occur at the charcoal surface mobilized ANCT-05013 and ANCT-05103. This study revealed that the charcoal particles mobilized ANCT-05013 and ANCT-05103 had superior inhibition performance to brown rot by S. lacrymans. The two strains of ANCT-05013 and ANCT-05103 were accepted as NBRC 113097 and NBRC 113098 in January 2018, respectively.

About four strains of wild type yeast that were obtained from some fruits and a flower in Asahikawa-city and Asahikawa neighbor areas, and in North Tohoku area, we observed their cell length, quantity of propagation at 5-35°C and performance of alcohol fermentation (the gas yield) at 15-35°C. The results obtained were as follows:

(1) The cell length of ANCT-06051 isolated from a mountain ash fruit was 4.7 μm, which was the longest in the four wild type yeasts. The quantity of propagation of ANCT-06051 was the most in the four strains at 5-35°C. The gas yield of ANCT 06051 became the maximum at 25°C, and decreased at 15°C and 35°C.

(2) The cell length of ANCT-07017 isolated from an azalea petal was 3.7 μm. The quantity of propagation of ANCT-07017 was a lot next to ANCT-06051 at 5-25°C. The gas yield of ANCT-07017 which was incubated for seven days at 15-35°C was the highest in the four strains.

(3) The cell length of ANCT-07018 isolated from an apple peel was 3.5 μm, which was the smallest in the four strains. The quantity of propagation of ANCT-07018 increased with temperature at 5-35°C. There was a little quantity of gas yield at 25°C and 35°C, but the yield was not confirmed at 15°C.

(4) The cell length of ANCT-07023 isolated from a cherry fruit was 3.7 μm. The quantity of propagation of ANCT-07023 was less than that of ANCT-07018 at 5-25°C. The gas yield of ANCT-07023 was approximately similar to ANCT-07018 at 15-35°C.

(5) The cell lengths of NBRC 0308 (a sake yeast) and ANCT-07009 (a commercial dry yeast) were longer than the four wild type yeasts, and were superior in the quantity of propagation to the four yeasts at 10-25°C. Although the gas yields of NBRC 0308 and ANCT-07009 at 15°C showed a tendency to decrease, the gas yields of them at 15-35°C for 7 days were higher than that of the three wild type yeasts (ANCT-06051, ANCT-07018, ANCT-07023) .

(6) In ANCT-06051 and NBRC 0308, there was not the significant difference to the quantity of propagation and the gas yield on YM-media of pH=4.2-7.8 at 25°C.

We tested the inhibitory effects of nine kinds of essential oil and ethanol on the growth of four strains of fungi (i.e. Cladosporium cladosporides NBRC 4459, C. sphaerospermum NBRC 6348, Aureobasidium pullulans NBRC 6353, Aspergillus oryzae ANCT-07058) using direct contact experiment based on potato-dextrose-agar medium dilution method. The essential oils were a bergamot oil, a cedar one, a clove one, a eucalyptus one, a heliotrope one, a lavender one, a lemon one, a peppermint one, and a rose one. The minimal inhibitory concentration (MIC) of the bergamot oil, the cedar one, the eucalyptus one, and the lemon one to NBRC 6348 and ANCT-07058 were over 2% (v/v) at 25°C. MIC of the lavender oil and the peppermint oil were 0.3-0.5% (v/v) to the four strains. MIC of the clove oil, the heliotrope one and the rose one were 0.025-0.1% (v/v) to all strains. MIC of the rose oil and ethanol was 0.05-0.1% (v/v) and over 2% (v/v), respectively. On the other hand, MIC of the rose oil combined with 2% (v/v) ethanol was 0.025% (v/v) to the four strains.

In experiments, students are training design and assembl y combinational logic circuits . These circuits use for decode BCD (Binary Code Decimal) to 7 segment LED display. Since this assembling requires a lot of wiring, there is a high possibility that connections will be mistaken. It is difficult for students to repair circuits , because they can’t detect the incorrect wiring. The purpose of this study was to develo p device s that assist students with incorrect wiring detection.