Aligned Carbon Nanotube Reinforcement of Aerospace Carbon Fiber Composites: Substructural Strength Evaluation for Aerostructure Applications

https://www.aiaa.org/ProceedingsDetail.aspx?id=5776Vertically aligned carbon nanotubes (VACNTs) are placed between all plies in an aerospace carbon fiber reinforced plastic laminate (unidirectional plies, [(0/90/±45)2]s) to reinforce the interlaminar region in the z-direction. Significant improvement in Mode I and II interlaminar toughness have been observed previously. In this work, several substructural in-plane strength tests relevant to aerostructures were undertaken: bolt/tension-bearing, open hole compression, and L-shape laminate bending. Improvements are observed for the nanostitched samples: critical bearing strength by 30%, open-hole compression ultimate strength by 10%, and L-shape laminate energy (via increased deflection) of 40%. The mechanism of reinforcement is not compliant interlayer creation, but rather is a fiberstitching mechanism, as no increase in interlayer thickness occurs with the nanostitches. Unlike traditional (large-fiber/tow/pin) stitching or z-pinning techniques that damage inplane fibers and reduce laminate in-plane strengths, the nano-scale CNT-based ‘stitches’ improve in-plane strength, demonstrating the potential of such an architecture for aerospace structural applications. The quality of VACNT transfer to the prepreg laminates has not been optimized and therefore the noted enhancement to strength may be considered conservative. Ongoing work has been undertaken to both improve VACNT transfer and expand the data set.Massachusetts Institute of Technology (Nano-Engineered Composite aerospace STructures (NECST) Consortium

抗アレルギー物質の探索を目的とする新規アッセイ法の開発と応用

卵白リゾチーム（HEL）を用いて感作したマウスのアレルギーインダクションフェーズでの血流量低下を指標とするアッセイ法を確立し、これを用いてこの血流量低下のメカニズムの解明を試みた。その結果、アナフィラキシー発症時に血流量あるいは血圧低下に関与するヒスタミン等のケミカルメディエーターは血流量低下に関与しないが、血管内皮細胞や血小板、好中球などが関与し、シクロオキシゲナーゼ（COX）-1および2、プロスタグランジン（PG）I2、トロンボキサン（TX）A2、エンドセリン（ET）-1、顆粒球エラスターゼ（GE）および誘導型NO合成酵素（iNOS）由来のNOが複雑に関連して関与していることを明らかにした。さらに天然資源から新規機能物質の探索を行う目的で、顕著な活性が認められたツリフネソウおよびスイフヨウに関して新規アッセイ法を用いてアレルギーインダクションフェーズ抑制物質の探索を行った結果、ツリフネソウ花弁の35% EtOHエキスよりluteolin（3）などに有意な改善効果を確認し、活性発現メカニズムについて検討した。次にスイフヨウ花弁MeOHエキスでは、活性成分としてquercetin-3-O- β-D-xylopyranosyl-(1→2)-β-D-galactopyranoside（12）、および新規化合物mutabiloside（11）を明らかにした。さらに本アッセイ法における末梢血流量低下の症状が、漢方における瘀血症状と類似していることに着目し、本アッセイ法が瘀血改善薬の探索に利用可能であることを明らかにし、新たな瘀血のアッセイ法として応用できることを示した。以上、本法はアレルギーのインダクションフェーズでの多数の因子による複雑な生体内反応を総合的にとらえたものであり、天然資源より新しいメカニズムによるアレルギー予防薬のシーズやリード化合物の探索に応用できる可能性を示すと考えられる。We discovered a phenomenon in which the blood flow in vein microcirculation markedly decreases in response to hen-egg white lysozyme (HEL)-sensitization without any change in blood pressure. Using this blood flow decrease as a guide, we developed an in vivo assay method to search for substances, which can prevent allergies. The blood flow decrease appears to be regulated by various factors such as nitric oxide (NO), thromboxane (TX) A2, prostacyclin (PGI2) and endothelin (ET)-1 together with cyclooxygenase (COX)-1, COX-2, inducible nitric oxide synthase (iNOS), and constitutive nitric oxide synthase (cNOS). Using this in vivo assay method, allergy-preventive activity was demonstrated for the 35% EtOH extract of flowers of Impatiens textori MIQ. and the MeOH extract of the petals of Hibiscus mutabilis L. \u27versicolor\u27 MAKINO in a continuing search for allergy-preventive substances from natural source. Among the principal compounds in IT, apigenin (1), apigenin 7-glucoside (2), luteolin (3) and luteolin 7-glucoside (10) showed significant allergy-preventive effects. Among the principal compounds in HM, quercetin-3-O- β-D-xylopyranosyl-(1→2)-β-D-galactopyranoside (12), and mutabiloside (11) showed significant allergy-preventiveeffects. “Oketsu”, or stagnant blood syndrome, is one of the important pathological concepts in therapy with Kampo formula and drugs. We showed the effectiveness of the method for screening drugs aimed at “oketsu” treatment

Aligned Carbon Nanotube Reinforcement of Aerospace Carbon Fiber Composites: Substructural Strength Evaluation for Aerostructure Applications

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Aligned carbon nanotube (A-CNT) arrays that were densified via patterning and mechanical instability are placed at the resin-rich ply-ply interface in aerospace-grade advanced composite laminates for z-direction reinforcement. The buckled A-CNT arrays display a wavelike folding shape and maintain such a shape after being transferred between the plies. The buckled A-CNT reinforced laminates were tested under short-beam shear (SBS) and double edge-notched tension (DENT) and are found to have a 7% increase in SBS strength and 25% increase in DENT strength, respectively. Both scanning electron microscope imaging and micro-computed tomography reveal that the buckled A-CNT arrays suppress delamination and force damage into the intralaminar region. Furthermore, they introduce multiscale and mixed mode reinforcement mechanisms. The findings demonstrate good potential for using mechanical instability in nanofiber arrays to densify them and tune their shapes, as well as the promising reinforcement effect from buckling-densified A-CNT arrays. Future work to change the pattern (e.g., patterning feature shape and interspacing between features), as well as synchrotron radiation computed tomography-based in situ testing is planned.National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award DMR-0819762

A survey of a functional amino acid of class Cβ-lactamase corresponding to Glu166 of class A β-lactamases

AbstractThe class C β-lactamase of Cltrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this β-lactamase were, respectively, previously shown not to be the counterpart of Glu166 (ABL166) in class A β-lactamases, even though sequence alignment of class A and C enzymes strongly suggested this possibility [(1990) FEBS Lett. 264, 211-214; (1990) J. Bacteriol. 172, 4348-4351]. We tried again to assign candidates for the counterpart of Glu166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C β-lactamase being selected. To investigate this possibility, these two glutamic acids were changed to glutamine, lysine or alanine, respectively. All the mutant enzymes showed more than 50% of the activity of the wild-type enzyme, indicating that the possibility was ruled out. These results strongly suggested the possibility that the class C β-lactamase lacks a functional acidic residue corresponding to Glu166 in class A enzymes