X-ray tomographic analysis of the initial structure of the royal chamber and the nest-founding behavior of the drywood termite Incisitermes minor

The nesting biology of the drywood termite, Incisitermes minor, is poorly understood. To date, no published data are available regarding the in situ nest-gallery development of I. minor. Three naturally infested Sitka spruce (Picea sitchensis Bong. Carriere) timbers were analyzed by X-ray computer tomography to observe the structure of the first royal chamber and the termite’s nest-founding behavior. One timber was infested by a group of termites which emerged from their natal nest. The other two timbers were infested by dealate reproductives from the nuptial flight. The study revealed that the drywood termite engages in outside foraging activity and has great foraging flexibility. Computer tomographic images also revealed that I. minor reproductives showed anatomical selectivity in their nest-founding activity. The structure of the initial royal chambers varied to follow the anatomical texture of the timbers, which resembled either a European pear shape or a cashew nut shape

木造建築物におけるシロアリ食害の非破壊検出のためのアコースティック・エミッションおよびガスモニタリング法の開発

京都大学0048新制・論文博士博士(農学)乙第12762号論農博第2785号新制||農||1016(附属図書館)学位論文||H25||N4785(農学部図書室)30614(主査)教授 奥村 正悟, 教授 中野 隆人, 教授 吉村 剛学位規則第4条第2項該当Doctor of Agricultural ScienceKyoto UniversityDFA

Evaluation of larval growth process and bamboo consumption of the bamboo powder-post beetle Dinoderus minutus using X-ray computed tomography

The bamboo powder-post beetle Dinoderus minutus is a major pest of felled bamboo in Japan. In this study, X-ray computed tomography (CT) was utilized to non-destructively trace the movement of the larvae of D. minutus inside infested bamboo specimens and to evaluate the bamboo consumption of the larvae. The infested specimens, which had been enclosed with adult D. minutus beetles, were scanned using a microfocus X-ray CT system every 2 to 5 days. Larvae and other stages of the beetles were clearly recognizable in the CT images with a voxel size of 61.9 μm, and they were distinguishable from the bamboo, insect tunnels, and frass. The larvae were traced until pupation, and the length and volume of their tunnels were measured to evaluate their bamboo consumption. The tunnel length and volume bored by one larva was estimated to be 0.98 mm and 1.06 mm3 (0.70 mg of oven-dry mass) per day within the average observation period of 22 days, respectively, and the active larval period was estimated to be 39 days in our experimental conditions

Evaluation of the concentrations of hydrogen and methane emitted by termite using a semiconductor gas sensor

A gas detection apparatus equipped with a semiconductor gas sensor was employed for qualitative and quantitative measurement of hydrogen and methane emitted by termites. A gas sample of 2.5 ml was injected into the semiconductor gas sensor through the gas detection apparatus, and the maximum voltage of the sensor was converted into gas concentration. The gas samples were collected from three distinct experiments: (1) five combinations of workers and soldiers of Coptotermes formosanus with and without a wood specimen; (2) C. formosanus under six temperature conditions; and (3) four different termite species, C. formosanus, Reticulitermes speratus, Incisitermes minor, and Zootermopsis nevadensis. The hydrogen and methane concentrations increased with an increase in the number of termites. Concentrations were higher in samples with a wood specimen than without it. Both hydrogen and methane concentrations were the highest for the samples at 35 °C and were lowest at 15 and 5 °C. The concentrations were very low at 45 °C because all the termites had died in a few hours. The concentrations of hydrogen and methane were highest for Z. nevadensis, the dampwood termite, among the four species, and no methane was detected for I. minor, the drywood termite, at 28 °C and 75 % RH

Evaluation of increase in loss tangent from longitudinal vibration of wood log by considering apparent density difference between sapwood and heartwood caused by moisture content

Abstract This study confirmed that the loss tangent (or tangent loss, tan δ) obtained from the longitudinal vibration of a wood log increases with the apparent density difference between sapwood and heartwood, owing to moisture content difference. The reason for this was estimated to be the shear stress occurring when the longitudinal vibration is excited from the calculation of the longitudinal vibration equation for a cylindrical model with different sapwood and heartwood densities. According to the measurement of the vibrational properties of 35 sugi (Cryptomeria japonica) logs with large moisture content variation in the sapwood and heartwood, the tan δ for longitudinal vibration increased compared with that for flexural vibration when the apparent sapwood density exceeded apparent heartwood density, whereas the difference in the specific dynamic Young’s modulus (E/ρ) was small. To discover why tan δ increases, both the axial and shear strain energy were calculated from the numerical solution of the longitudinal vibration of a cylindrical model by only considering the apparent density difference between sapwood and heartwood. It was found that the shear strain energy increases with the apparent density difference. Because it is known from previous studies that tan δ from the shear strain (tan δ S) is larger than that from the axial strain (tan δ A), this study concluded that tan δ increases with the apparent density difference. The ratio of increase of tan δ calculated by the model adequately explaange of the measured tan δ caused by the longitudinal vibration of a sugi log

Moisture content estimation of green softwood logs of three species based on measurements of flexural vibration

Abstract The moisture contents of sugi (Cryptomeria japonica), todomatsu (Abies sachalinensis) and hinoki (Chamaecyparis obtusa) logs were estimated using a method of moisture content estimation proposed in our previous study. In the course of estimation, it was revealed that the regression line of the correlation between specific dynamic Young’s modulus (E/ρ) and tangent loss (tan δ) of green wood was different from that of moisture-conditioned wood and showed species dependency, both of which are not previously reported. Regression lines at the fiber saturation point (FSP) were constructed for each species by measuring E/ρ and tan δ from the flexural vibration of green small specimens and correcting the E/ρ values at their own moisture contents into E/ρ values at the FSP. The correlation of green wood in this study was different from that reported in previous studies of moisture-conditioned wood near the FSP. The correlations of sugi and hinoki were similar, whereas those of sugi and todomatsu were different despite no previous report of species dependency in air-dried wood. The moisture contents 86 logs (not those used to prepare small specimens) were estimated using regression lines of each species. The standard deviation of the difference between the estimated moisture content and the measured moisture content was 15.7%. A systematic error of 25.9% in moisture content was attributed to the different methods of specimen support used for small specimens and logs

Description and Analysis of Learning Strategy for Junior High School Students

本研究の目的は, 生徒が英語の基礎的な学力をどのようにつけているかを, 具体的に生徒の声を拾い上げることにより記述分析するものである。特に英単語を書くときの「綴りの覚え方」に着目し, 正確に書けない, 覚えられないといった生徒の声を聞き, 指導法改善に結びつけられるように分析を試みた。研究の実施学校および対象生徒は, 広島大学附属三原中学校2年生83名であった。単語の書き方に対するアンケートをとり, 生徒たちの覚え方の傾向を高得点群, 中得点群, 低得点群の3つに分類して分析した。文字と音を一致させることができる生徒ほど, 高得点群に位置しているが, その覚え方には独自の音のルールを作っているようであった。そして, 一部つまづきの見られる生徒に対してはインタビューを実施し, 記述形式でまとめた。文字と音を一致させることは困難で, そのままアルファベットの読み方で記憶するという課題が明らかになった。今回は, 生徒の傾向をまとめて, 分析したのみにとどまったので, 実際の対策を実施しするところまでに至ってないのが, 本研究を今後の書く指導の工夫改善に役立てたい