イスラエル, ハイファ市から「シャローム(こんにちは)」

大学院自然科学研究科環境創成金沢大学工学

Determination of water-cement ratios of hardened cement pastes based on the estimation of under-pixel porosity in backscattered electron images

SEM-BSE image analysis technique is one of promising approaches to determine water/cement ratios in hardened cementitious materials. In this study, a method using under-pixel information in the BSE images is proposed. It is hypothesised that a grey level of each pixel reflects the under-pixel porosity. It is also assumed that the porosity smaller than the resolution results in the shifts in position of the grey levels of specific phases. The amounts of shifting are combined with the Powers and Brownyard model so that the degree of hydration is directly estimated from the BSE images. The method was applied to hardened cement pastes with different water/cement ratios. There was a good agreement between estimated and real water/cement ratios. An estimate within an error of ±0.02 was attained except an extremely low water/cement ratio. The shift in the grey level histogram is useful information on microstructure in cement pastes. Copyright © 2013 Inderscience Enterprises Ltd

Evaluation of capillary pore size characteristics in high-strength concrete at early ages

金沢大学工学部The quantitative scanning electron microscope-backscattered electron (SEM-BSE) image analysis was used to evaluate capillary porosity and pore size distributions in high-strength concretes at early ages. The Powers model for the hydration of cement was applied to the interpretation of the results of image analysis. The image analysis revealed that pore size distributions in concretes with an extremely low water/binder ratio of 0.25 at early ages were discontinuous in the range of finer capillary pores. However, silica-fume-containing concretes with a water/binder ratio of 0.25 had larger amounts of fine pores than did concretes without silica fume. The presence of larger amounts of fine capillary pores in the concretes with silica fume may be responsible for greater autogenous shrinkage in the silica-fume-containing concretes at early ages

Analysis of cement pastes and mortars by a combination of backscatter-based SEM image analysis and calculations based on the Powers model

Formation of microstructure in cement pastes and mortars were quantitatively analyzed by the SEM-BSE image analysis. Effects of water/cement ratio and of the addition of mineral admixtures on the contents of unhydrated cement particles and pores were discussed. The proportions of each phase obtained by the analyses were compared with proportions calculated on the Powers model. It was found from comparisons that the volume fractions of the residual cement and pores obtained by the image analysis did not contradict those estimated from the Powers model. Lower water/cement ratio pastes and those undergoing pozzolanic reaction showed less fine capillary pores. It was also found that large capillary pores still remained in the mixtures at long ages. The gel/space ratio in the Powers and Brownyard equation was calculated from the phase constituents determined by the image analysis. For mortars without mineral admixture, the gel/space ratio by the image analysis could be related to the strength

Comparison of observed and simulated cement microstructure using spatial correlation functions

金沢大学理工研究域環境デザイン学系The microstructure of cement pastes, as revealed by SEM-BSE image analysis, was compared with a simulated structure generated by the University of Twente version of the CEMHYD3D hydration simulation model. The spatial array of unhydrated cement particles was simulated by the model. However, spatial features in capillary pore structure obtained by the simulation are different from the observed microstructure. This disagreement in the spatial structure is to be expected since there are fundamental differences in porosity as represented by the two methods. Only coarse pores are detected in the SEM examination while the total capillary porosity and its whole spatial distribution are virtually simulated in the model. A subset of the visible pores must be different in spatial statistics from the universal set of total porosity. Care must therefore be taken in interpreting agreement between simulation output and microscopically observed microstructure in images. © 2009 Elsevier Ltd. All rights reserved

石炭灰原粉高含有吹付けコンクリートのフレッシュ特性と強度発現特性

金沢大学大学院自然科学研究科環境創成金沢大学工学

Targeted expression of stepfunction opsins in transgenic rats for optogenetic studies

Abstract Rats are excellent animal models for experimental neuroscience. However, the application of optogenetics in rats has been hindered because of the limited number of established transgenic rat strains. To accomplish cell-type specific targeting of an optimized optogenetic molecular tool, we generated ROSA26/CAG-floxed STOP-ChRFR(C167A)-Venus BAC rats that conditionally express the step-function mutant channelrhodopsin ChRFR(C167A) under the control of extrinsic Cre recombinase. In primary cultured cortical neurons derived from this reporter rat, only Cre-positive cells expressing ChRFR(C167A) became bi-stable, that is, their excitability was enhanced by blue light and returned to the baseline by yellow~red light. In bigenic pups carrying the Phox2B-Cre driver, ChRFR(C167A) was specifically expressed in the rostral parafacial respiratory group (pFRG) in the medulla, where endogenous Phox2b immunoreactivity was detected. These neurons were sensitive to blue light with an increase in the firing frequency. Thus, this transgenic rat actuator/reporter system should facilitate optogenetic studies involving the effective in vivo manipulation of the activities of specific cell fractions using light of minimal intensity

Distinctive nuclear zone for RAD51-mediated homologous recombinational DNA repair

Genome-based functions are inseparable from the dynamic higher-order architecture of the cell nucleus. In this context, the repair of DNA damage is coordinated by precise spatiotemporal controls that target and regulate the repair machinery required to maintain genome integrity. However, the mechanisms that pair damaged DNA with intact template for repair by homologous recombination (HR) without illegitimate recombination remain unclear. This report highlights the intimate relationship between nuclear architecture and HR in mammalian cells. RAD51, the key recombinase of HR, forms spherical foci in S/G2 phases spontaneously. Using super-resolution microscopy, we show that following induction of DNA double-strand breaks RAD51 foci at damaged sites elongate to bridge between intact and damaged sister chromatids; this assembly occurs within bundle-shaped distinctive nuclear zones, requires interactions of RAD51 with various factors, and precedes ATP-dependent events involved the recombination of intact and damaged DNA. We observed a time-dependent transfer of single-stranded DNA overhangs, generated during HR, into such zones. Our observations suggest that RAD51-mediated homologous pairing during HR takes place within the distinctive nuclear zones to execute appropriate recombination