Assessment of water quality in small agricultural ponds in Nara,Japan

Paddy and Water Environment - In Japan, since ancient times, numerous small- to medium-size agricultural ponds have been constructed to irrigate paddy rice fields. Economic growth and urbanization...     

Criterion for estimating humidity control capacity of materials in a room

As a measure of estimating humidity control capacity of materials in an airtight room under sinusoidal temperature variation, we used the Cb value, which is the ratio of the range of variation in relative humidity in a steel box lined with the material of interest to the range in an empty steel box. In order to clarify the factors that affect the Cb value, we focused on both the temperature variation rate and the area that is lined in the box. It was found that changing the rate of temperature variation over one period strongly affected the Cb value, although the amplitude of temperature variation did not. We further noticed that the difference between the time when peak temperature was reached and the time when peak absolute humidity was reached (peak time difference), was found to be useful for estimating the humidity control capacity of materials. Knowing the difference between the phase when peak temperature was reached and the phase when peak absolute humidity was reached (phase angle difference) was also useful. Because the Cb value was affected by both the variation period and the lined area in the box, we can draw a contour diagram of the period and the lined area for materials to give an overview of the humidity control capacity of a material. The materials of primary interest in this study were Japanese cedar and porous ceramics.     

Assessment of wood surface roughness: comparison of tactile roughness and three-dimensional parameters derived using a robust Gaussian regression filter

Japanese oak and Japanese beech were sanded by hand with abrasive papers of varying grit number. Two three-dimensional parameters selected to characterize their surface roughness – one parameter for the distribution of roughness-profile peaks and the other for the relative area of the roughness-profile peaks above the threshold height – were compared against tactile roughness. The parameters were obtained from roughness profiles as determined by a robust Gaussian regression filter (RGRF) using seven cutoffs. The RGRF filtering process was adjusted specifically for the evaluation of wood surface roughness. Except for a cutoff wavelength of 0.25mm, the RGRF lent itself well to the determination of roughness profiles. No distortion of roughness profiles occurred around deep valleys, and there was a good correlation between the parameters and tactile roughness.Part of this study was presented at the 2002 Kansai Branch Office lecture meeting of the Japan Society for Precision Engineering, Kyotanabe, August 2002     

Acoustic emission monitoring during partial compression to detect early stages of decay

Summary The acoustic emissions (AEs) under partially compression were monitored with two softwood and one hardwood specimens in very eary stages of decay by a brown- and a white-rot fungus. Even slightly decayed specimens emitted AEs immediately after beginning of loading, typically when partial compression stress was applied to brown-rotted wood with the flat-headed attachment. With sound specimens of three wood species, only a few AEs were generated until the load reached at the proportional limit. These results suggest that AE monitoring will be one of the feasible means to detect the incipient stages of decay in a field test.The authors thank the Weyerhaeuser Research Grants Program for its aid in this investigation     

Lignin-degrading activity of edible mushroom <Emphasis Type="Italic">Strobilurus ohshimae</Emphasis> that forms fruiting bodies on buried sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) twigs

Strobilurus ohshimae is an edible mushroom, and it specifically forms its fruiting bodies on buried sugi (Cryptomeria japonica) twigs. In this research, we studied lignindegrading activity of S. ohshimae. We isolated 18 strains of S. ohshimae from various regions of Japan, and determined their lignin degradation rates on sugi wood meal medium. All the strains of S. ohshimae degraded approximately 6%–12% of sugi lignin in 30 days, and these lignin degradation rates were 1.5–3 times higher than those of Trametes versicolor, which is a typical lignin-degrading fungus. Among the three main lignin-degrading enzymes, activity of lignin peroxidase and manganese peroxidase was not observed, while 4340U/g of laccase was produced in 30 days. To investigate the effect of wood species on lignin degradation by S. ohshimae, the lignin degradation rate and laccase productivity on sugi wood meal medium were compared with those on beech (Fagus crenata). In T. versicolor, both lignin degradation rate and laccase productivity were higher on beech than on sugi. Conversely, in S. ohshimae, lignin degradation rate and laccase productivity were higher on sugi than on beech. Therefore, it was suggested that coniferous lignin is not always difficult to degrade for the fungi that inhabit softwood. Part of this article presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004     

Hydration behavior and compressive strength of cement mixed with exploded wood fiber strand obtained by the water-vapor explosion process

Poor compatibility was found between exploded wood fiber strand (WFS) and cement due to the excessive presence of water-soluble degraded polysaccharides in extractives of exploded WFS obtained from weathered wood waste treated by the water-vapor explosion process (WVEP). This study presents some comparative results from a continuing investigation on the compressive strengths of exploded WFS–cement mixtures. Based on results previously obtained with the hydration test, the relation between hydration behavior and compressive strength of the mixture was explored. In addition, the effect of the curing age on compressive strength development of the mixture with selected additive chemicals was examined. The results supported the results of early studies with hydration tests indicating that adding MgCl₂ to the mixtures of exploded WFS mixed with quick-curing cement or ordinary Portland cement and a composite of MgCl₂ + CaO added to the mixture of exploded WFS and furnace-slag cement effectively improved the hydration behaviors; it greatly enhanced the compressive strengths of mixtures as well. Compressive strengths were strongly correlated to maximum hydration temperatures (T_max) of wood–cement mixtures influenced by the cement type, wood wastes (treated or not with WVEP), additive chemicals, and their content levels. The results also indicated that adding selected chemicals had no significant effect on compressive strength among the mixtures of exploded WFS mixed, respectively, with three types of cement at a curing age of 180 days. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to identify the hydration products and to probe the element distribution of the mixture in the wood–cement interface zone from a fractured surface.Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

Effect of cropping systems and crop successions on fumonisin levels in corn from Northern Paraná State,Brazil

In this study the effect of different cropping systems and crop successions was evaluated on natural Fusarium sp. contamination and fumonisin levels in corn. The cropping systems consisted of a conventional and no-tillage area cultivated with corn in the summer following either oats or fallow in the winter (2006 and 2007 growing seasons). In addition, the effect of applying nitrogen fertilizer (0, 22.5, 45.0, 90.0 and 90.0 kg ha⁻¹ nitrogen supplemented with potassium oxide) on fumonisin contamination was evaluated in the 2006 growing season. Fusarium sp. was detected in 90% samples in 2006 and in 100% samples in 2007. In both growing seasons, no-till corn following oats showed the highest mean fumonisin levels and differed significantly (P < 0.05) from all the others (2006) and from conventional till corn following either oats or fallow in the winter (2007). Fumonisin levels ranged from 0.13 to 19.52 μg g⁻¹ (mean 6.97 μg g⁻¹) and from 3.70 to 7.75 μg g⁻¹ (mean 6.29 μg g⁻¹) in no-till corn following oats from the 2006 and 2007 growing seasons, respectively. Plots treated with 0 kg ha⁻¹ and 22.5 kg ha⁻¹ nitrogen showed the highest mean fumonisin levels and differed significantly from those with 45.0 and 90 kg ha⁻¹ nitrogen. Fumonisin levels correlated negatively (P < 0.05) with the nitrogen fertilization rates. Although no-till is advantageous from a soil conservation standpoint, it may enhance the potential for fumonisin contamination in corn.