Self-crack healing ability and strength recovery in ytterbium disilicate/silicon carbide nanocomposites

The SiO₂ volatility and SiC recession in hydrocarbon-rich combustion atmosphere is the main problem of SiC-reinforced ceramics when they are utilized as coating materials for gas turbine blades. The composite of Yb₂Si₂O₇-Yb₂SiO₅/SiC is expected as a self-crack healing material that can avoid this problem because the monosilicate can react with the SiO₂ glass to form disilicate and hence further reinforce the composite. In this study, the composites, fabricated with various morphology of SiC nanofillers, were precracked and then heat-treated in an oxidizing environment to activate their crack healing behavior. The healing effect as a function of filler morphology and annealing time was investigated. Healing mechanism and future applications of these composites were also discussed.     

Characterization of a GH Family 20 Exo-β-N-acetylhexosaminidase with Antifungal Activity from Streptomyces avermitilis

We characterized SaHEX, which is a glycoside hydrolase (GH) family 20 exo-β-N-acetylhexosaminidase found in Streptomyces avermitilis. SaHEX exolytically hydrolyzed chitin oligosaccharides from their non-reducing ends, and yielded N-acetylglucosamine (GlcNAc) as the end product. According to the initial rate of substrate hydrolysis, the rates of (GlcNAc)₃ and (GlcNAc)₅ hydrolysis were greater than the rates for the other oligosaccharides. The enzyme exhibited antifungal activity against Aspergillus niger, which was probably due to hydrolytic activity with regard to chitin in the hyphal tips. Therefore, SaHEX has potential for use in GlcNAc production and food preservation.     

Basic consideration of a nuclear power monitoring system using neutron-induced prompt gamma rays

ABSTRACT

Monitoring only neutron flux in a nuclear reactor core has an advantage of offering reactor power monitoring accuracy. We started the development of a new nuclear instrumentation based on the measurement of prompt gamma rays emitted from metals placed at the neutron flux monitoring positions. The thermal neutron flux at the position of each placed metal piece can be monitored by measuring the prompt gamma rays as the count rate of each energy. The gamma-ray energy range was limited from 6 to 10 MeV to mitigate the interference of environmental gamma rays. Four metals, Ti, V, Ni, and Cu, were chosen as candidates in consideration of their neutron emission rates and self-absorption. In an experiment with a high-purity germanium semiconductor detector, we considered the identification of individual peak energies in an assumed situation where prompt gamma rays were emitted from the four different metals at the same time. Energy resolutions of the peak with the largest energy gap from the nearest energy peak of the other candidate metals were smaller than the gap. Thus, we confirmed that at least one peak for each candidate metal was able to be separated from the peaks derived from other candidate metals.     

Cold Atmospheric Plasma Modification of Amyloid β

Cold atmospheric plasma (CAP) has attracted much attention in the fields of biotechnology and medicine owing to its potential utility in clinical applications. Recently accumulating evidence has demonstrated that CAP influences protein structures. However, there remain open questions regarding the molecular mechanisms behind the CAP-induced structural perturbations of biomacromolecules. Here, we investigated the potential effects of CAP irradiation of amyloid β (Aβ), an amyloidogenic protein associated with Alzheimer’s disease. Using nuclear magnetic resonance spectroscopy, we observed gradual spectral changes in Aβ after a 10 s CAP pretreatment, which also suppressed its fibril formation, as revealed by thioflavin T assay. As per mass spectrometric analyses, these effects were attributed to selective oxidation of the methionine residue (Met) at position 35. Interestingly, this modification occurred when Aβ was dissolved into a pre-irradiated buffer, indicating that some reactive species oxidize the Met residue. Our results strongly suggest that the H₂O₂ generated in the solution by CAP irradiation is responsible for Met oxidation, which inhibits Aβ amyloid formation. The findings of the present study provide fundamental insights into plasma biology, giving clues for developing novel applications of CAP.     

Magnetic-Pole Flip by Millimeter Wave

In the era of Big Data and the Internet of Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term data storage. To archive an enormous amount of data, further increase of the recording density is necessary. Herein a new magnetic recording methodology, “focused-millimeter-wave-assisted magnetic recording (F-MIMR),” is proposed. To test this methodology, magnetic films based on epsilon iron oxide nanoparticles are prepared and a focused-millimeter-wave generator is constructed using terahertz (THz) light. Irradiating the focused millimeter wave to epsilon iron oxide instantly switches its magnetic pole direction. The spin dynamics of F-MIMR are also calculated using the stochastic Landau–Lifshitz–Gilbert model considering all of the spins in an epsilon iron oxide nanoparticle. In F-MIMR, the heat-up effect of the recording media is expected to be suppressed. Thus, F-MIMR can be applied to high-density magnetic recordings.     

Enhanced early osteogenic differentiation by silicon-substituted hydroxyapatite ceramics fabricated via ultrasonic spray pyrolysis route

The influence of silicon-substituted hydroxyapatite (Si-HAp) on osteogenic differentiation was assessed by biological analysis. Si-HAp was prepared by ultrasonic spray pyrolysis (USSP) technique using various amounts of Si (0, 0.8, and 1.6 mass%). Chemical analysis revealed that Si was incorporated into the hydroxyapatite (HAp) lattice with no other crystalline phase and which caused the change of crystal structure. Biological analyses showed that the Si contents affected the cell proliferation and morphology, suggesting that there is an optimal Si content for cell culture. As for differentiation, alkaline phosphatase activity and osteocalcin production of Si-HAp were higher than those of HAp. Gene expression profiles also revealed that substitution of Si (0.8 mass%) up-regulated the expression levels of osteocalcin and especially Runx2, a master gene for osteoblast development. These results suggest that incorporating Si into the HAp lattice may enhance the bioactivity, particularly during early osteoblast development.     

Newly Developed Recombinant Antithrombin Protects the Endothelial Glycocalyx in an Endotoxin-Induced Rat Model of Sepsis

(1) Background: The endothelial glycocalyx is a primary target during the early phase of sepsis. We previously reported a newly developed recombinant non-fucosylated antithrombin has protective effects in vitro. We further evaluated the effects of this recombinant antithrombin on the glycocalyx damage in an animal model of sepsis. (2) Methods: Following endotoxin injection, in Wistar rats, circulating levels of hyaluronan, syndecan-1 and other biomarkers were evaluated in low-dose or high-dose recombinant antithrombin-treated animals and a control group (n = 7 per group). Leukocyte adhesion and blood flow were evaluated with intravital microscopy. The glycocalyx was also examined using side-stream dark-field imaging. (3) Results: The activation of coagulation was inhibited by recombinant antithrombin, leukocyte adhesion was significantly decreased, and flow was better maintained in the high-dose group (both p < 0.05). Circulating levels of syndecan-1 (p < 0.01, high-dose group) and hyaluronan (p < 0.05, low-dose group; p < 0.01, high-dose group) were significantly reduced by recombinant antithrombin treatment. Increases in lactate and decreases in albumin levels were significantly attenuated in the high-dose group (p < 0.05, respectively). The glycocalyx thickness was reduced over time in control animals, but the derangement was attenuated and microvascular perfusion was better maintained in the high-dose group recombinant antithrombin group (p < 0.05). (4) Conclusions: Recombinant antithrombin maintained vascular integrity and the microcirculation by preserving the glycocalyx in this sepsis model, effects that were more prominent with high-dose therapy.     

Heteroatom-doped reduced graphene oxide/polyaniline nanocomposites with improved n-type thermoelectric performance

Polyaniline (PANI) is a potential candidate for n-type thermoelectric (TE) materials owing to its intrinsic electrical conductivity, low thermal conductivity, and facile synthesis techniques. However, its low Seebeck coefficient and power factor have limited its widespread usage. In this study, nitrogen-doped, and sulfur-nitrogen co-doped reduced graphene oxide (rGO) were used for tuning the TE properties of PANI. Doped rGO and PANI/doped-rGO nanocomposites were prepared via hydrothermal technique and chemical oxidative polymerization respectively and thereafter characterized. The TE properties of the nanocomposites were also studied and an optimized Seebeck coefficient, power factor and zT value of −1.75 mV K⁻¹, 95 μW m⁻¹ K⁻² and 0.06, respectively were reported for the PANI nanocomposite containing 1 wt% sulfur-nitrogen co-doped rGO. These results suggest that PANI/heteroatom-doped rGO can serve as promising candidates for n-type based TE applications.     

The Multifaceted Role of Plasminogen in Cancer

Fibrinolytic factors like plasminogen, tissue-type plasminogen activator (tPA), and urokinase plasminogen activator (uPA) dissolve clots. Though mere extracellular-matrix-degrading enzymes, fibrinolytic factors interfere with many processes during primary cancer growth and metastasis. Their many receptors give them access to cellular functions that tumor cells have widely exploited to promote tumor cell survival, growth, and metastatic abilities. They give cancer cells tools to ensure their own survival by interfering with the signaling pathways involved in senescence, anoikis, and autophagy. They can also directly promote primary tumor growth and metastasis, and endow tumor cells with mechanisms to evade myelosuppression, thus acquiring drug resistance. In this review, recent studies on the role fibrinolytic factors play in metastasis and controlling cell-death-associated processes are presented, along with studies that describe how cancer cells have exploited plasminogen receptors to escape myelosuppression.     

Characterization and crystal structure of the thermophilic ROK hexokinase from Thermus thermophilus

We characterized and determined the crystal structure of a putative glucokinase/hexokinase from Thermus thermophilus that belongs to the ROK (bacterial repressors, uncharacterized open reading frames, and sugar kinases) family. The protein possessed significant enzymatic activity against glucose and mannose, with V(max) values of 260 and 68 μmol·min(-1)·mg(-1) protein, respectively. Therefore, we concluded that the enzyme is a hexokinase. However, the hexokinase showed little catalytic capacity for galactose and fructose. Circular dichroism measurements indicated that the enzyme was structurally stable at 90°C. The crystal structure of the enzyme was determined at a resolution of 2.02 ?, with R(cryst) and R(free) values of 18.1% and 22.6%, respectively. The polypeptide structure was divided into large and small domains. The ROK consensus sequences 1 and 2 were included in the large domain. The cysteine-rich consensus sequence 2 folded into a zinc finger, and the bound zinc was confirmed by both electron density and X-ray absorption fine structure (XAFS) spectrum. The overall structure was a homotetramer that consisted of a dimer of dimers. The accessible surface area buried by the association of the dimers into the tetrameric structures was significantly higher in the T. thermophilus enzyme than in a homologous tetrameric ROK sugar kinase.