Push-Pull Fatigue of Sintered Silicon Nitride Ceramics at Elevated Temperatures

The fatigue tests under push-pull completely reversed loading and pulsating loading were performed for silicon nitride ceramics at elevated temperatures. Then the effects of stress wave form, stress rate, and cyclic understressing on fatigue strength, and cyclic straining behavior, were examined. The cycle-number-based fatigue life is found to be shorter under trapezoidal stress wave loading than under triangular stress wave loading, and to become shorter with increasing hold time under the trapezoidal stress wave loading. Meanwhile, the equivalent time-based life curve, which is estimated from the concept of slow crack growth, almost agrees with the static fatigue life curve in the short and intermediate life regions, showing the small cyclic stress effect and the dominant stress-imposing period effect on cyclic fatigue life. The fatigue strength increased in stepwise stress amplitude increasing test, where stress amplitude is increased stepwise every given number of stress cycles, at 1100° and 1200°C. Occurrence of cyclic strengthening was proved through a gradual decrease in strain amplitude during a pulsating loading test at 1200°C in this material, corresponding to the above cyclic understressing effect on fatigue strength.     

Fracture Resistance Behavior of High‐Thermal‐Conductivity Silicon Nitride Ceramics

Silicon nitride ceramics were prepared from a high‐purity silicon powder doped with 2 mol% Y₂O₃ and 5 mol% MgO as sintering additives via a route of sintering of reaction‐bonded silicon nitride (SRBSN). The materials sintered at 1900°C for 3, 6, 12, and 24 h had thermal conductivities of 109, 125, 146, and 154 W/m/K, and four‐point bending strengths of 786, 676, 608, and 505 MPa, respectively. The fracture toughness values, determined by the single‐edge‐precracked‐beam (SEPB) method, were 8.4, 8.6, 9.7, and 10.7 MPa m^1/2 for the materials sintered for 3, 6, 12, and 24 h, respectively, which were similar to the results measured by the chevron‐notched‐beam (CNB) test method. The materials sintered for longer times (12 and 24 h) showed stronger R‐curve behaviors over longer range of crack extension, in comparison with the materials sintered for shorter times (3 and 6 h).     

Intestinal absorption and biological effects of orally administered amorphous silica particles

Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.     

A New Fluorogenic Probe for the Detection of endo‐β‐N‐Acetylglucosaminidase

We developed a fluorescence‐quenching‐based assay system to determine the hydrolysis activity of endo‐β‐N‐acetylglucosaminidases (ENGases). The pentasaccharide derivative 1 was labeled with an N‐methylanthraniloyl group as a reporter dye at the non‐reducing end and with a 2,4‐dinitrophenyl group as a quencher molecule at the reducing end. This derivative is hydrolyzed by ENGase, resulting in an increase in fluorescence intensity. Thus, the fluorescence signal is directly proportional to the amount of the tetrasaccharide derivative, hence allowing ENGase activity to be evaluated easily and quantitatively. Using this system, we succeeded in measuring the hydrolysis activities of ENGases and thus the inhibitory activities of known inhibitors. We confirmed that this assay system is suitable for high‐throughput screening for potential inhibitors of human ENGase that might serve as therapeutic agents for the treatment of N‐glycanase 1 (NGLY1) deficiency.     

Thermal conductivity analysis using three‐dimensional microstructures of gelation freezing derived cellular mullite

The relationship between thermal conductivity and unidirectional cellular mullite microstructures created with the freeze casting route is discussed using actual three‐dimensional (3D) images, in which a homogenization method was conducted with microscopic models created from 3D images, the temperature variation in macroscopic models by the finite element method (FEM), and local heat conduction in microscopic models. The simulation results were consistent with the experimental results. This image‐based modeling technique was thus confirmed to be a strong tool for the prediction of various thermal properties of porous ceramics.     

Impact of Serum Chemerin Levels on Liver Functional Reserves and Platelet Counts in Patients with Hepatocellular Carcinoma

Obesity-related metabolic abnormalities, including adipokine imbalance and chronic inflammation, are involved in liver carcinogenesis. Chemerin, a novel adipokine, plays a critical role in adipogenesis, energy metabolism, and inflammation. We evaluated the impact of serum chemerin levels on liver functional reserves in hepatocellular carcinoma (HCC) patients and on the recurrence and prognosis of HCC. This study included 44 patients with any stage of HCC who underwent curative treatment at Gifu Municipal Hospital (Gifu, Japan) between 2006 and 2007. Recurrence-free survival and overall survival were estimated using the Kaplan-Meier method. Serum albumin levels (Pearson’s correlation coefficient; r = 0.3110, p = 0.0399), platelet counts (r = 0.4159, p = 0.0050), and prothrombin times (r = 0.3775, p = 0.0115) were significantly correlated with serum chemerin levels in patients with HCC, and they were inversely correlated with Child-Pugh scores (r = −0.3732, p = 0.0126), serum alanine aminotransferase levels (r = −0.3864, p = 0.0105), and total bilirubin levels (r = −0.4023, p = 0.0068). Among these variables, a multiple comparison test identified that platelet counts and total bilirubin levels were associated with serum chemerin levels (p < 0.0083). No significant correlation was found between serum chemerin levels and recurrence-free survival (p = 0.3691) or overall survival (p = 0.7916). In HCC patients, serum chemerin concentrations were correlated with liver functional reserves and platelet counts, but not with recurrence or prognosis.     

The Role of microRNAs in Cholangiocarcinoma

Cholangiocarcinoma (CCA), an aggressive malignancy, is typically diagnosed at an advanced stage. It is associated with dismal 5-year postoperative survival rates, generating an urgent need for prognostic and diagnostic biomarkers. MicroRNAs (miRNAs) are a class of non-coding RNAs that are associated with cancer regulation, including modulation of cell cycle progression, apoptosis, metastasis, angiogenesis, autophagy, therapy resistance, and epithelial–mesenchymal transition. Several miRNAs have been found to be dysregulated in CCA and are associated with CCA-related risk factors. Accumulating studies have indicated that the expression of altered miRNAs could act as oncogenic or suppressor miRNAs in the development and progression of CCA and contribute to clinical diagnosis and prognosis prediction as potential biomarkers. Furthermore, miRNAs and their target genes also contribute to targeted therapy development and aid in the determination of drug resistance mechanisms. This review aims to summarize the roles of miRNAs in the pathogenesis of CCA, their potential use as biomarkers of diagnosis and prognosis, and their utilization as novel therapeutic targets in CCA.     

Rubber‐toughened polyamide‐6 with a low thermal expansion coefficient: effect of preferential distribution of rubber and inorganic filler

The effects of morphological changes on the thermal expansion, toughness and heat resistance of polyamide‐6 (PA)/styrene–ethylene–butylene–styrene (SEBS)/polyphenylene ether (PPE) blends were investigated. Compared with the typical ‘sea (PA matrix)–island (PPE domain)–lake (SEBS in PPE domain)’ morphology, an injection‐molded ternary blend with a preferential distribution of SEBS component at the interface between PA and PPE exhibited a low coefficient of linear thermal expansion (CLTE) in the flow direction. This low CLTE was ascribed to the deformation of SEBS and PA into a co‐continuous microlayer network structure during injection molding. Consequently, the expansion preferentially occurred towards the thickness direction. Further CLTE reduction either by a change in PA viscosity or by the selective location of an inorganic filler was examined, and its influences on impact strength and heat resistance are discussed based on transmission electron microscopy observations. © 2015 Society of Chemical Industry     

Contribution of Invariant Natural Killer T Cells to the Clearance of Pseudomonas aeruginosa from Skin Wounds

Chronic infections are considered one of the most severe problems in skin wounds, and bacteria are present in over 90% of chronic wounds. Pseudomonas aeruginosa is frequently isolated from chronic wounds and is thought to be a cause of delayed wound healing. Invariant natural killer T (iNKT) cells, unique lymphocytes with a potent regulatory ability in various inflammatory responses, accelerate the wound healing process. In the present study, we investigated the contribution of iNKT cells in the host defense against P. aeruginosa inoculation at the wound sites. We analyzed the re-epithelialization, bacterial load, accumulation of leukocytes, and production of cytokines and antimicrobial peptides. In iNKT cell–deficient (Jα18KO) mice, re-epithelialization was significantly decreased, and the number of live colonies was significantly increased, when compared with those in wild-type (WT) mice on day 7. IL-17A, and IL-22 production was significantly lower in Jα18KO mice than in WT mice on day 5. Furthermore, the administration of α-galactosylceramide (α-GalCer), a specific activator of iNKT cells, led to enhanced host protection, as shown by reduced bacterial load, and to increased production of IL-22, IL-23, and S100A9 compared that of with WT mice. These results suggest that iNKT cells promote P. aeruginosa clearance during skin wound healing.     

A method for testing the interface toughness of ceramic environmental barrier coatings (EBCs) on ceramic matrix composites (CMCs)

A simple interface fracture test for ceramic environmental barrier coatings (EBCs) on ceramic matrix composites (CMCs) was developed. A variation on the asymmetric double cantilever beam (ADCB) test was proposed so that the interface toughness could be measured in a small specimen of simple shape without applying interlaminar loading to the CMC substrate. The proposed test was applied to an EBC consisting of a mullite layer and Si bond coat on a monolithic SiC substrate. A pre-crack was introduced by pop-in cracking, and then a notch overlapping the pre-crack was machined. The pre-crack was opened by inserting a wedge into the notch. From the critical notch opening displacement the crack starts to propagate, interface toughness is calculated. The measured interface toughness was 4.1?J/m2. Finally, the application range of the test was discussed and suggestions were made for introduction of the notch and pre-crack.