Quantitative characterization of interfacial shear strength (IFSS), in multi-walled carbon nanotube (MWCNT)-reinforced Al matrix composites, has been carried out using an in-situ pull-out technique. ...The end of an MWCNT protruding out of the tensile fracture surface of the composite was bonded to the tip of an atomic force microscopy (AFM) cantilever using an electron-beam-induced deposition method. The MWCNT was pulled out from the Al matrix using a nanomanipulator system installed inside a scanning electron microscope (SEM). The effective embedded length of the MWCNT incorporated in the Al matrix was evaluated by observing the pulled out MWCNT under high-resolution transmission electron microscopy (HRTEM). Valid results were obtained for six MWCNTs with straight, visibly damage-free embedded parts nearly perpendicular to the fracture surface. The IFSS between the MWCNT and the Al matrix was 24.8 ± 3.2 MPa. The ultimate tensile strength (UTS) of the MWCNT/Al composites is in good agreement with that estimated by the shear lag model using these IFSS values, resulting in the realization of 60% load transfer efficiency at the directly contacted MWCNT-Al interface in the MWCNT/Al composites. No MWCNT failure was observed during the pullout in this study.
Due to their superior material properties, carbon nanotubes (CNTs) have many potential applications such as actuators, composites and electronic components. These CNT-based devices may experience ...high temperature during manufacture and operation. This leads to thermal expansion and residual stress in devices, and affects the device reliability. Therefore, the coefficient of thermal expansion (CTE) of CNTs is an important property for CNT-based devices. Although the CTE in radial direction of CNTs have been investigated using X-ray diffraction, there is no experimental determination for the axial CTE of CNTs and only numerical and theoretical predictions exit. Here, we investigated the CTE of aligned multi-walled CNT (MWCNT) reinforced epoxy composites in the MWCNT alignment direction in the temperature range of 30–60 °C. We demonstrated that the CTE of the composites in the MWCNT alignment direction became negative by addition of more than 10.4 vol.% MWCNTs, and the axial CTE of MWCNTs was deduced to be −1.2 × 10−5 K−1 using the rule of mixtures. In addition, the thermal contraction phenomenon was observed in thin sheets of MWCNTs alone. The negative CTE may be explained by out-of-plane atomic vibrations predicted by theoretical and numerical studies.
Feasibility of using multi-walled carbon nanotubes (MWCNTs) for the control of coefficients of thermal expansion (CTEs) of composite materials was evaluated, based on experimental data of CTEs and ...Young’s modulus newly obtained using a combined testing procedure. The axial CTE of the MWCNTs were evaluated over the temperature range −5°C to 85°C by using the MWCNT’s Young’s modulus and CTE of the aligned MWCNT reinforced epoxy composites in Turner’s model. The Young’s moduli of the MWCNTs were calculated by using Voigt model and the composite Young’s modulus measured by tensile tests. The MWCNTs were shown to possess negative CTEs, and the nanotube CTEs tended to become less negative with increasing temperature. Owing to their large Young’s modulus, aspect ratio and negative CTEs, the use of MWCNTs aligned axially was shown to be effective at controlling the CTE of polymer composites at lower volume fractions compared to conventional negative CTE materials.
Factors governing the tensile strength of unidirectional carbon fiber reinforced plastic (CFRP) composites were experimentally investigated by focusing on the mechanical characteristics of the epoxy ...matrix. Correlation analysis was conducted to reveal the mechanical characteristics of the matrix that affect the surface stress concentration of an intact fiber caused by a fracture site in an adjacent fiber. The stress concentration factors (SCFs) were evaluated by implementing double-fiber fragmentation tests in conjunction with spring element model simulations. From investigating six types of epoxy materials, a reasonable correlation was observed between the matrix crack tip opening displacement (CTOD) and the SCF; the SCF increased approximately linearly with increasing CTOD. The results reported here suggest that CTOD is one of the important tensile-strength-controlling factors to consider for the development of stronger CFRP composites.
Microsatellites are repeats of 1- to 6-bp units, and approximately 10 million microsatellites have been identified across the human genome. Microsatellites are vulnerable to DNA mismatch errors and ...have thus been used to detect cancers with mismatch repair deficiency. To reveal the mutational landscape of microsatellite repeat regions at the genome level, we analyzed approximately 20.1 billion microsatellites in 2717 whole genomes of pan-cancer samples across 21 tissue types. First, we developed a new insertion and deletion caller (MIMcall) that takes into consideration the error patterns of different types of microsatellites. Among the 2717 pan-cancer samples, our analysis identified 31 samples, including colorectal, uterus, and stomach cancers, with a higher proportion of mutated microsatellite (≥0.03), which we defined as microsatellite instability (MSI) cancers of genome-wide level. Next, we found 20 highly mutated microsatellites that can be used to detect MSI cancers with high sensitivity. Third, we found that replication timing and DNA shape were significantly associated with mutation rates of microsatellites. Last, analysis of mutations in mismatch repair genes showed that somatic SNVs and short indels had larger functional impacts than germline mutations and structural variations. Our analysis provides a comprehensive picture of mutations in the microsatellite regions and reveals possible causes of mutations, as well as provides a useful marker set for MSI detection.
The aim of this study is to clarify the characteristics of gram-negative bacteremia (GNB), including extended-spectrum β-lactamase (ESBL)-producing pathogens, among allogeneic hematopoietic stem cell ...transplant (allo-HSCT) recipients on levofloxacin (LVFX) prophylaxis. A retrospective analysis on GNB at the first episode of febrile neutropenia (FN) was conducted among allo-HSCT recipients (age ≥ 20 years) on 500 mg/day of oral LVFX prophylaxis. Epidemiological and microbiological features of GNB were investigated and compared between the inappropriate and appropriate empiric therapy groups. In total, FN occurred in 414 allo-HSCT cases, and bacteremia at the first episode of FN occurred in 169 cases. Overall, 29 GNB cases were documented, and the causative organisms identified were
Escherichia coli
in 21 cases (including 10 ESBLs),
Klebsiella pneumoniae
in 2,
Pseudomonas aeruginosa
in 2, and other in 4. The crude 30-day mortality rate was not significantly different among cases of GNB (6.9%), gram-positive bacteremia (GPB) (7.1%), or non-bacteremia (5.4%;
P
= 0.78). Cefepime (CFPM) was administered in all cases in the inappropriate empiric therapy group, and all causative organisms were ESBL-producing
E. coli
(ESBL-EC). All patients in the inappropriate empiric therapy group had a low Pitt bacteremia score (≤ 2). Thirty-day mortality did not differ significantly between the inappropriate and appropriate empiric therapy groups (1/10 vs. 1/15,
P
= 0.61). In conclusion, GNB was not a significant cause of death. In LVFX breakthrough ESBL-EC bacteremia among allo-HSCT recipients, the administration of CFPM as empiric therapy did not lead to significantly poor prognosis. Empiric CFPM administration might be an acceptable strategy.
The tensile strengths of unidirectional carbon fiber-reinforced plastic (CFRP) were predicted by using a spring element model that considers the surface stress concentration on fibers caused by a ...fracture site in an adjacent fiber. The surface stress concentration on the fibers was experimentally evaluated by implementing multi-fiber fragmentation tests in conjunction with a spring element model simulation. Four types of epoxy materials were utilized to explore the effects of matrix polymer properties on the surface stress concentration of the fibers. The size scaling results, coupled with the results of the spring element model simulation, designed to take into account the surface stress concentration, were reasonably consistent with the experimental data on the tensile strengths of the unidirectional CFRP composites, regardless of the differences in the matrix mechanical properties. Possible mechanisms by which additional stress concentration is generated on an intact fiber surface were analyzed numerically using the finite element method.
Clostridium butyricum, a probiotic commonly prescribed in Asia, most notably as MIYA-BM (Miyarisan Pharmaceutical Co., Ltd.; https://www.miyarisan.com), occasionally leads to bacteremia. The ...prevalence and characteristics of C. butyricum bacteremia and its bacteriologic and genetic underpinnings remain unknown. We retrospectively investigated patients admitted to Osaka University Hospital during September 2011-February 2023. Whole-genome sequencing revealed 5 (0.08%) cases of C. butyricum bacteremia among 6,576 case-patients who had blood cultures positive for any bacteria. Four patients consumed MIYA-BM, and 1 patient consumed a different C. butyricum-containing probiotic. Most patients had compromised immune systems, and common symptoms included fever and abdominal distress. One patient died of nonocclusive mesenteric ischemia. Sequencing results confirmed that all identified C. butyricum bacteremia strains were probiotic derivatives. Our findings underscore the risk for bacteremia resulting from probiotic use, especially in hospitalized patients, necessitating judicious prescription practices.
An 84-year-old man in Japan who had undergone endovascular aortic repair 9 years earlier had an infected aneurysm develop. We detected Desulfovibrio desulfuricans MB at the site. The patient ...recovered after surgical debridement, artificial vessel replacement, and appropriate antimicrobial therapy. Clinicians should suspect Desulfovibrio spp. infection in similar cases.
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