Characterization of Mechanical Properties for Creep-fatigued Ferritic Heat-resisting Steel by Nano-indentation

AbstractCreep-fatigue test was conducted for a ferritic heat-resisting steel that contained 12mass%chromium and 2mass% tungsten. The creep-fatigue fracture originated from prior austenite grain boundaries. Subgrains neighboring the prior austenite grain boundaries became coarse during creep-fatigue testing. Nano-indentation tests were performed on the coarse subgrains neighboring grain boundaries and finer subgrains inner grains. As the results, the nano scale-hardness of the coarse subgrains were markedly lower than those of the finer subgrains inner grains. Therefore, it is suggested that the coarse subgrains neighboring grain boundaries play an important role of creep-fatigue fracture mechanism

MC3T3-E1 Cells on Titanium Surfaces with Nanometer Smoothness and Fibronectin Immobilization

The present study was aimed to evaluate the viability and total protein contents of osteoblast-like cells on the titanium surface with different surface mechanical treatment, namely, nanometer smoothing (Ra: approximately 2.0 nm) and sandblasting (Ra: approximately 1.0 μm), and biochemical treatment, namely, with or without fibronectin immobilization. Fibronectin could be easily immobilized by tresyl chloride-activation technique. MC3T3-E1 cells were seeded on the different titanium surfaces. Cell viability was determined by MTT assay. At 1 day of cell culture, there were no significant differences in cell viability among four different titanium surfaces. At 11 days, sandblasted titanium surface with fibronectin immobilization showed the significantly highest cell viability than other titanium surface. No significant differences existed for total protein contents among four different titanium surfaces at 11 days of cell culture. Scanning electron microscopy observation revealed that smoothness of titanium surface produced more spread cell morphologies, but that fibronectin immobilization did not cause any changes of the morphologies of attached cells. Fibronectin immobilization provided greater amount of the number of attached cells and better arrangement of attached cells. In conclusion, the combination of sandblasting and fibronectin immobilization enhanced the cell viability and fibronectin immobilization providing better arrangements of attached cells

Missense Mutation in the Alternative Splice Region of the PAX6 Gene in Eye Anomalies

SummaryThe PAX6 gene is involved in ocular morphogenesis, and PAX6 mutations have been detected in various types of ocular anomalies, including aniridia, Peters anomaly, corneal dystrophy, congenital cataract, and foveal hypoplasia. The gene encodes a transcriptional regulator that recognizes target genes through its paired-type DNA-binding domain. The paired domain is composed of two distinct DNA-binding subdomains, the N-terminal subdomain (NTS) and the C-terminal subdomain (CTS), which bind respective consensus DNA sequences. The human PAX6 gene produces two alternative splice isoforms that have the distinct structure of the paired domain. The insertion, into the NTS, of 14 additional amino acids encoded by exon 5a abolishes the DNA-binding activity of the NTS and unmasks the DNA-binding ability of the CTS. Thus, exon 5a appears to function as a molecular switch that specifies target genes. We ascertained a novel missense mutation in four pedigrees with Peters anomaly, congenital cataract, Axenfeldt anomaly, and/or foveal hypoplasia, which, to our knowledge, is the first mutation identified in the splice-variant region. A T→A transition at the 20th nucleotide position of exon 5a results in a Val→Asp (GTC→GAC) substitution at the 7th codon of the alternative splice region. Functional analyses demonstrated that the V54D mutation slightly increased NTS binding and decreased CTS transactivation activity to almost half

Electronic structure and electrical properties of amorphous OsO2

The valence-band spectrum of an amorphous OsO2 film deposited by glow discharge of OsO4 vapor can be predicted well with calculated electronic band structure of crystalline OsO2 from first principles using the liner-muffin-tin-orbital method with the local-density approximation. Resistivity of the amorphous OsO2 was less than 631023 V cm at 80 K, and it was almost temperature independent, but the temperature coefficient of resistivity was negative. The Hall coefficient of the amorphous OsO2 increased with temperature, and was saturated at around 220 K. Temperature dependence of the Hall mobility was proportional to T3/2, and it implies that the scattering of charged carriers by ionized atoms is dominant below 220 K

N2O production characteristics of strain stabilized premixed laminar ammonia/hydrogen/air premixed flames in lean conditions

Product gas characteristics of ammonia/hydrogen/air laminar premixed flames stabilized in stagnation flows were experimentally and numerically studied. Although the maximum value of NO mole fraction increased compared with pure ammonia/air flames, the trade-off relationship between NO and unburnt NH3 were also observed. In addition, N2O production for very lean conditions were observed. To clarify the N2O production mechanism in detail, numerical simulation modelling was employed using CHEMKIN software. Sensitivity analysis suggested that the reactions of (R58) NH+NO = N2O+H, (R105) N2O+H = N2+OH, and (R106) N2O(+M) = N2+O(+M) play an important role in N2O production. Product gas characteristics of N2O were numerically investigated for various stagnation plane temperatures and the equivalence ratios. The reaction rate of R106 decreases for low stagnation plane temperature cases and small equivalence ratios. It was considered that the decrease in the reaction rate of R106 decreased the reduction rate of N2O to N2, and thus large amount of N2O were detected. Also, the N2O amount decreased when the stagnation plane temperatures were sufficiently high. This also suggested that the N2O production may be restricted by a decrease in the heat loss in an ammonia-fueled combustor

Study on N2O production mechanisms of lean ammonia/hydrogen/air premixed laminar flames

Application of ammonia as fuel is a potential candidate to achieve carbon neutrality. As laminar burning velocity of ammonia is slow, hydrogen addition is also considered to improve combustion characteristics with no carbon emission. In this study, we experimentally investigated product gas characteristics of strain stabilized ammonia/hydrogen/air premixed laminar flames under atmospheric pressure for various equivalence ratios. In a lean condition, large amount of N2O production was observed. To clarify N2O production mechanisms, numerical simulations were conducted using a reaction mechanism developed by Gotama et al. In the Gotama reaction mechanism, major N2O production path was NH+NO=N2O+H and major N2O consumption paths were N2O+H=N2+OH and N2O(+M)=N2+O(+M). It was clarified that a decrease in N2O consumption via N2O(+M)=N2+O(+M) increases N2O emission for lean and strained conditions

18. asırda "Hırkai şerif" ziyareti

Taha Toros Arşivi, Dosya No: 120-Saraylar. Not: Gazetenin "Tarihten Sahifeler" köşesinde yayımlanmıştır.İstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033