The Effects of Grain Size and Precipitate on Strength of Nb-Treated Steels

Relationship between the strength and the change in grain size and precipitation behavior of NbC due to heat treatments was examined with 0.2% carbon steels containing 0.02 to 0.09% niobium. The results are summarized as follows. (1) Though NbC particles precipitated in niobium-treated steels tend to coalesce with the rise of austenitizing temperature, they remain in steel and prevent the austenite grain from coarsening because of its small solubility and low dissolving rate in austenite. (2) The highest strength is obtained when the cooling rate from austenitizing temperature to room temperature is 25℃/min. When niobium-treated steel is continuously cooled after a full solution treatment for a long time at sufficiently high temperatures such as 1250℃, NbC seems to precipitate not only at temperatures lower than A_3 point but also at temperatures of austenite range, and this precipitation from austenite will cause less strengthening than that from ferrite. (3) Strengthening effect by niobium-treatment may be explained on the assumption that both effects of the grain refinement and the precipitation of fine particles of NbC are additive to each other. An increase of strength in niobium-treated steels austenitized at temperatures lower than about 1050℃ is due mainly to refining of ferrite grain and that at higher temperatures is due mainly to fine precipitates of NbC

Isorhamnetin Promotes 53BP1 Recruitment through the Enhancement of ATM Phosphorylation and Protects Mice from Radiation Gastrointestinal Syndrome

Flavonoids are a subclass of polyphenols which are attractive, due to possessing various physiological activities, including a radioprotective effect. Tumor suppressor p53 is a primary regulator in the radiation response and is involved in the pathogenesis of radiation injuries. In this study, we revealed that isorhamnetin inhibited radiation cell death, and investigated its action mechanism focusing on DNA damage response. Although isorhamnetin moderated p53 activity, it promoted phosphorylation of ataxia telangiectasia mutated (ATM) and enhanced 53BP1 recruitment in irradiated cells. The radioprotective effect of isorhamnetin was not observed in the presence of ATM inhibitor, indicating that its protective effect was dependent on ATM. Furthermore, isorhamnetin-treated mice survived gastrointestinal death caused by a lethal dose of abdominal irradiation. These findings suggested that isorhamnetin enhances the ATM-dependent DNA repair process, which is presumably associated with the suppressive effect against GI syndrome

Regulation of lymphocyte proliferation by eosinophils via chymotrypsin-like protease activity and adhesion molecule interaction

1. We investigated the regulatory mechanisms responsible for release of eosinophil cationic protein (ECP) from eosinophils activated by platelet-activating factor (PAF) and monitored intra-cellular pH (pHi) changes using a pH-sensitive fluorescent probe. We also explored the mechanisms by which eosinophils suppress T-lymphocyte proliferation induced by phytohaemagglutinin (PHA). In these experiments, a separated culture to investigate the ECP-mediated pathway and a coculture to identify the adhesion molecules involved in eosinophil-lymphocyte interactions were employed. 2. Chymostatin (1×10(−6) M) inhibited ECP release by about 50% via stimulation by PAF or recombinant interleukin 5(rIL-5) plus IgG. 3. PAF (1×10(−7) M) raised eosinophil pHi from 6.9 to 7.3 within 20 s and pretreatment of these cells with chymostatin (1×10(−6) M), but not with leupeptin or E64-d, completely prevented this increase. 4. Calcium ionophore A23187 (1×10(−7) M) induced ECP release and raised pHi to within a range similar to that of PAF, however, chymostatin had no effect on either. 5. Chymostatin reversed ECP-mediated suppression of PHA-induced T-lymphocyte proliferation in separated cultures, but not in cocultures. 6. In coculture, eosinophils exhibited the same level of suppression of both CD4(+) and CD8(+) T-cell proliferation in response to PHA. 7. Monoclonal antibodies against CD11a, CD18 and CD54, but not CD11b, restored eosinophil suppression of T-lymphocyte proliferation which was chymostatin-resistant in coculture. 8. Eosinophils were unable to suppress the proliferative response to lymphocytes to anti-CD3 stimulation. 9. In conclusion, chymostatin specifically inhibited both the eosinophil pHi increase and ECP release induced by PAF. Eosinophils regulate PHA-induced T-lymphocyte proliferation via the ECP-mediation associated with chymotrypsin-like protease activity. These cells also control interactions with lymphocyte between adhesion molecules, CD11a, CD18 and CD54

Bond strength of resin-resin interfaces contaminated with saliva and submitted to different surface treatments

The purpose of this study was to investigate the effect of different surface treatments on shear bond strength of saliva-contaminated resin-resin interfaces. Flat resin surfaces were fabricated. In the control group, no contamination or surface treatment was performed. The resin surfaces of the experimental groups were contaminated with saliva and air-dried, and then submitted to: (G1) rinsing with water and drying; (G2) application of an adhesive system; (G3) rinsing and drying, abrasion with finishing disks, etching and application of adhesive system; (G4) rinsing and drying, etching, application of silane and adhesive system. Resin cylinders were placed over the treated surfaces. The specimens were stored in water or ethanol. Shear bond strength tests were performed and the mode of failure was evaluated. Data were submitted to two-way ANOVA and Dunnett T3 test. Contamination of resin-resin interfaces with saliva significantly reduced shear strength, especially after prolonged storage (p<0.05). Similar values to the original bond strength were obtained after abrasion and application of adhesive (G3) or etching and application of silane and adhesive (G4). If contamination occurs, a surface treatment is required to guarantee an adequate interaction between the resin increments