Strength of carbon nanotubes depends on their chemical structures

引っ張りに強いカーボンナノチューブの構造を特定 --軽量で高強度な究極の構造材料の実現に一歩近づく--. 京都大学プレスリリース. 2019-07-11.Single-walled carbon nanotubes theoretically possess ultimate intrinsic tensile strengths in the 100–200 GPa range, among the highest in existing materials. However, all of the experimentally reported values are considerably lower and exhibit a considerable degree of scatter, with the lack of structural information inhibiting constraints on their associated mechanisms. Here, we report the first experimental measurements of the ultimate tensile strengths of individual structure-defined, single-walled carbon nanotubes. The strength depends on the chiral structure of the nanotube, with small-diameter, near-armchair nanotubes exhibiting the highest tensile strengths. This observed structural dependence is comprehensively understood via the intrinsic structure-dependent inter-atomic stress, with its concentration at structural defects inevitably existing in real nanotubes. These findings highlight the target nanotube structures that should be synthesized when attempting to fabricate the strongest materials

Evaluation of chromID strepto B as a screening media for Streptococcus agalactiae

BACKGROUND: Streptococcus agalactiae (Group B Streptococcus, GBS), a leading cause of sepsis and meningitis in infants, can be transmitted vertically from mother to infant during passage through the birth canal. Detection of GBS colonization in perinatal women is a major strategy for the prevention of postpartum neonatal disease. The U.S. Centers for Disease Control and Prevention recommends that all women undergo vaginal-rectal screening for GBS colonization at 35-37 weeks of gestation. ChromID Strepto B (STRB) is a chromogenic GBS screening media on which GBS colonies appear pink or red, while other bacteria are either inhibited or form colonies in other colors. In this study, we compared STRB with a conventional GBS detection method using 5% sheep blood agar (BA) followed by a selective enrichment broth. METHODS: Anovaginal swabs were collected from 1425 women during weeks 35 to 37 of their pregnancies. The swabs were used to inoculate both STRB and BA plates after enrichment with selective Todd Hewitt Broth (THB). A GBS latex agglutination test was used to confirm the identity of isolates from each plate. RESULTS: GBS was recovered from 319 (22.4%) samples with one or both media: 318 on STRB compared to 299 using BA. One false negative was observed on STRB, and 20 false negatives were observed on BA. In addition, non-hemolytic GBS was recovered from 19 (6.0%) samples using STRB. CONCLUSIONS: STRB offers effectiveness and convenience over BA for GBS screening in clinical laboratories. STRB produces fewer false negatives, has a higher detection rate and uses a simple color screen that is ideal for technician-level applications. We recommend STRB as the media of choice for GBS screening