Piezoresistive effect of plain-weave CFRP fabric subjected to cyclic loading

The present study deals with electrical resistance changes in woven-fabric CFRP during loading. Four kinds of plain weave woven-fabric CFRP laminated specimens are prepared and subjected to cyclic tensile loading that does not cause any damages, and the electrical resistance changes of the specimens are measured experimentally by the four-probe method. As a result, the present study shows that the electrical resistance of a specimen comprised of six ±45° plies decreases remarkably with increasing number of loading cycles. The decrease is caused by shear plastic deformation of ±45° plies. The thickness shrinkage caused by shear plastic deformation increases the number of fiber contacts, and this decreases the interlaminar contact resistance between the plies. For a single ±45° ply, the same electrical resistance decrease caused by the shear plastic deformation is observed, and the magnitude of the decrease is smaller than that of the six-ply laminate tested. This is because the effect of interlaminar contact resistance decrease does not exist for a single ±45° ply. For the six 0°/90° plies, the present study shows that electrical resistance in the through-thickness direction is decreased by out-of-plane plastic deformation of carbon fiber and misalignment of the plies.     

Physicochemical interaction mechanism between nanoparticles and tetrasaccharides (stachyose) during freeze-drying

Nanoparticle suspensions are thermodynamically unstable and subject to aggregation. Freeze-drying on addition of saccharides is a useful method for preventing aggregation. In the present study, tetrasaccharides (stachyose) was employed as an additive. In addition, we hypothesize the interactive mechanism between stachyose and the nanoparticles during freeze-drying for the first time. The mean particle size of the rehydrated freeze-dried stachyose-containing nanoparticles (104.7?nm) was similar to the initial particle size before freeze-drying (76.8?nm), indicating that the particle size had been maintained. The mean particle size of the rehydrated normal-dried stachyose-containing nanoparticles was 222.2?nm. The powder X-ray diffraction of the freeze-dried stachyose-containing nanoparticles revealed a halo pattern. The powder X-ray diffraction of the normally dried stachyose-containing nanoparticles produced mainly a halo pattern and a partial peak. These results suggest an interaction between the nanoparticles and stachyose, and that this relationship depends on whether the mixture is freeze-dried or dried normally. In the case of normal drying, although most molecules cannot move rapidly thereby settling irregularly, some stachyose molecules can arrange regularly leading to some degree of crystallization and potentially some aggregation. In contrast, during freeze-drying, the moisture sublimed, while the stachyose molecules and nanoparticles were immobilized in the ice. After sublimation, stachyose remained in the space occupied by water and played the role of a buffer material, thus preventing aggregation.     

Inhibition of Autophagy at Different Stages by ATG5 Knockdown and Chloroquine Supplementation Enhances Consistent Human Disc Cellular Apoptosis and Senescence Induction rather than Extracellular Matrix Catabolism

The intervertebral disc is the largest avascular organ. Autophagy is an important cell survival mechanism by self-digestion and recycling damaged components under stress, primarily nutrient deprivation. Resident cells would utilize autophagy to cope with the harsh disc environment. Our objective was to elucidate the roles of human disc cellular autophagy. In human disc cells, serum deprivation and pro-inflammatory interleukin-1β (IL-1β) stimulation increased autophagy marker microtubule-associated protein 1 light chain 3 (LC3)-II and decreased autophagy substrate p62/sequestosome 1 (p62/SQSTM1), indicating enhanced autophagy. Then, RNA interference (RNAi) of autophagy-related gene 5 (ATG5), essential for autophagy, showed decreases in ATG5 protein (26.8%–27.4%, p < 0.0001), which suppressed early-stage autophagy with decreased LC3-II and increased p62/SQSTM1. Cell viability was maintained by ATG5 RNAi in serum-supplemented media (95.5%, p = 0.28) but reduced in serum-free media (80.4%, p = 0.0013) with IL-1β (69.9%, p = 0.0008). Moreover, ATG5 RNAi accelerated IL-1β-induced changes in apoptosis and senescence. Meanwhile, ATG5 RNAi unaffected IL-1β-induced catabolic matrix metalloproteinase release, down-regulated anabolic gene expression, and mitogen-activated protein kinase pathway activation. Lysosomotropic chloroquine supplementation presented late-stage autophagy inhibition with apoptosis and senescence induction, while catabolic enzyme production was modest. Disc-tissue analysis detected age-related changes in ATG5, LC3-II, and p62/SQSTM1. In summary, autophagy protects against human disc cellular apoptosis and senescence rather than extracellular matrix catabolism.     

Synthesis of Cycloparaphenylenes and Related Carbon Nanorings: A Step toward the Controlled Synthesis of Carbon Nanotubes

Since their discovery in 1991, carbon nanotubes (CNTs) have attracted significant attention because of their remarkable mechanical, electronic, and optical properties. Structural uniformity of the CNT is critically important because the sidewall structures (armchair, zigzag, and chiral) determine many of the significant properties of CNTs. Ideally researchers would synthesize CNTs with a defined target sidewall structure and diameter, but the current synthetic methods, such as arc discharge and chemical vapor deposition, only provide CNTs as the mixtures of various structures. Purification of these mixtures does not allow researchers to isolate a structurally uniform CNT, which is the bottleneck for fundamental studies and advanced applications of these materials. Therefore, the selective and predictable synthesis of structurally uniform CNTs would represent a critical advance in both nanocarbon science and synthetic chemistry. This Account highlights our efforts toward the bottom-up synthesis of structurally uniform carbon nanotubes (CNTs). We envisioned a bottom-up synthesis of structurally uniform CNTs through a controlled growth process from a short carbon nanoring (template) that corresponds to the target structure of CNTs. Our simple retrosynthetic analysis led to the identification of cycloparaphenylenes (CPPs), acene-inserted CPPs, and cyclacenes as the shortest sidewall segments of armchair, chiral, and zigzag CNTs, respectively. With this overall picture in mind, we initiated our synthetic studies of aromatic rings/belts as an initial step toward structurally uniform CNTs in 2005. This research has led to (i) a general strategy for the synthesis of CPPs and related carbon nanorings using cyclohexane derivatives as a benzene-convertible L-shaped unit, (ii) a modular, size-selective, and scalable synthesis of [n]CPPs (a shortest segment of armchair CNTs), (iii) the X-ray crystal structure analysis of CPPs, (iv) the design and synthesis of acene-inserted CPPs as the shortest segment of chiral CNTs, and (v) the first synthesis of cyclo-1,4-naphthylene, a π-extended CPP. We believe this work will serve as important initial steps toward a controlled synthesis of CNTs.     

New analytical method for electric current and multiple delamination cracks for thin CFRP cross-ply laminates using equivalent electric conductance

Carbon fiber reinforced polymer (CFRP) composites have low inter-lamina strength. One of the monitoring technologies is a self-sensing method that uses the electrical resistance change of a CFRP structure for detecting damage. The electric current distribution is vital information for the self-sensing method when optimizing the arrangement of probes to measure electric potential changes. We have developed a new orthotropic electric potential function analysis approach using affine transformation for unidirectional CFRP. In this study, the orthotropic electric potential function analysis method is improved to calculate the electric current of a thin cross-ply CFRP. Two types of stacking sequences for the beam-type cross-ply laminates were calculated to confirm the effectiveness of the improved method. The electrical voltage changes caused by multiple delamination cracks of a cross-ply laminate are new outcomes of this study. The analytical results were compared with computed results using the finite difference method. Consequently, the new equivalent electric conductance method proved to be effective for calculations of the electric current density of a cross-ply CFRP laminate. Furthermore, the new method for calculating the electric potential difference changes caused by multiple delamination cracks using orthotropic distributed doublet analysis, with the equivalent electric conductance, has also proved to be effective.     

Supply amount and marginal price of renewable electricity under the renewables portfolio standard in Japan

The Renewables Portfolio Standard (RPS) in Japan requires that approximately 1.35% of each retail supplier's electricity sales in FY2010 come from renewable energy sources (RES), for example, photovoltaics, wind, biomass, geothermal, and small hydropower. To help retail suppliers and renewable generators develop effective strategies, this study provides a quantitative analysis of the impact of this measure. We assume the supply conditions for electricity generation from renewable energy sources (RES-E) based on regional resource endowments, and we derive the cost-effective compositions of renewable portfolios, RES-E certificate prices, and additional costs to retail suppliers. The future prospects of RES-E are assessed based on technology, region, and year up to FY2010. The analysis reveals that wind power and biomass power generated from municipal waste will provide the majority of the total supply of RES-E under the RPS. It also indicates that the marginal price of RES-E certificates will be approximately 5.8 JPY/kWh (5.2 USc/kWh) in FY2010, in the case wherein the marginal price of electricity is assumed to be 4 JPY/kWh (3.6 USc/kWh). In order to elaborate on this further, sensitivity analyses for some parameters of RES and the price of electricity are provided. The dynamic supply curves of RES-E certificates are also indicated.     

Micrococcus luteus K-3-type glutaminase from Aspergillus oryzae RIB40 is salt-tolerant

Aspergillus oryzae RIB40 possesses the gene of glutaminase (Micrococcus luteus K-3-type glutaminase; AoGls), which has 40% homology with the salt-tolerant glutaminase from M. luteus K-3 (Micrococcus glutaminase). It was found that AoGls is a salt-tolerant enzyme, and its properties are similar to those of Micrococcus glutaminase.     

Artificial lightning testing on graphite/epoxy composite laminate

This study examines the evolution of damage in graphite/epoxy composite laminates due to lightning strikes. To clarify the influence of lightning parameters and specimen size, artificial lightning testing was performed on a series of laminated composite specimens. Damage was assessed using visual inspection, ultrasonic testing, micro X-ray inspection, and sectional observation. The results showed that the damage modes can be categorized into fiber damage, resin deterioration, and internal delamination modes. Damage progression is governed by the strong electrical orthotropic properties of the laminates, and the lightning parameters defining impulse waveform show strong relationship with certain damage modes, though specimen size and thickness variation barely affect damage size.