Microstructure and Texture Evolution During Hot-Pack Rolling of Nickel-Base Superalloys to Thin Sheet and Foil

Microstructure evolution during hot-pack rolling of nickel-base superalloys to ~1-mm-thick sheet and ~200-μm-thick foil was investigated with electron backscatter diffraction. The microstructure was observed at increasing levels of strain, which revealed the progressive formation of an unrecrystallized, banded microstructure at sheet gage. The bands contained large orientation gradients, sometimes spanning multiple texture components considered to be stable with respect to the imposed plane-strain compression. After reaching stable orientations, grain-scale shear bands were observed within individual unrecrystallized bands that resulted in local subgrain rotations that formed new bands of different orientation. This phenomenon, which is known as band splitting in the literature, was shown to be the result of continuous dynamic recrystallization as opposed to discontinuous dynamic recrystallization or classical static recrystallization. The unrecrystallized bands were eliminated by unidirectional rolling to foil but not by cross rolling.     

The use of composite materials in modern orthopaedic medicine and prosthetic devices: A review

The use of fibre reinforced composite materials for biomedical purposes is reviewed. The development of polymer composite materials has, in recent years, led to technological advances across a wide range of applications in modern orthopaedic medicine and prosthetic devices. Composites typically possess a superior strength to weight characteristic compared to monolithic materials and offer excellent biocompatibility. They are, therefore, favourable for both hard- and soft-tissue applications as well as the design of prostheses. In particular, the development of specifically designed carbon fibre sports prostheses now allows lower-limb amputees to actively participate in competitive sports. Sensory feedback systems, porous composite materials for tissue engineering and functional coatings for metallic implants are further developments anticipated to be introduced in next generation orthopaedic medicine.     

Hot working of platinum group metal-modified Ni-base superalloys for thermal protection system applications

Platinum group metal-modified nickel-base superalloys are being investigated for use in thin gage applications, such as thermal protection systems, due to their strength and inherent oxidation resistance at temperatures in excess of 1000 °C. This paper summarizes deformation behavior and microstructure evolution during multi-hit hot forging and subsequent hot rolling of an experimental two phase γ-Ni + γ′-Ni₃Al alloy with a composition of Ni–15Al–5Cr–3Pt–2Ir–0.3Hf (atomic %) with C, B, and Zr additions for grain-boundary refinement and strengthening. The feasibility of hot rolling this material to a final thickness of 250 μm and obtaining a nearly fully recrystallized microstructure was demonstrated. However, an anomalous grain-growth behavior was also observed at the surface in the intermediate and final rolled product.     

Double-strand break repair by Ku70 requires heterodimerization with Ku80 and DNA binding functions

Heterodimers of the 70 and 80 kDa Ku autoantigens (Ku70 and Ku80) activate the DNA-dependent protein kinase (DNA-PK). Mutations in any of the three subunits of this protein kinase (Ku70, Ku80 and DNA-PKcs) lead to sensitivity to ionizing radiation (IR) and to DNA double-strand breaks, and V(D)J recombination product formation defects. Here we show that the IR repair, DNA end binding and DNA-PK defects in Ku70-/- embryonic stem cells can be counteracted by introducing epitope-tagged wild-type Ku70 cDNA. Truncations and chimeras of Ku70 were used to identify the regions necessary for DNA end binding and IR repair. Site-specific mutational analysis revealed a core region of Ku70 responsible for DNA end binding and heterodimerization. The propensity for Ku70 to associate with Ku80 and to bind DNA correlates with the ability to activate DNA-PK, although two mutants showed that the roles of Ku70 in DNA-PK activation and IR repair are separate. Mutation of DNA-PK autophosphorylation sites and other structural motifs in Ku70 showed that these sites are not necessary for IR repair in vivo. These studies reveal Ku70 features required for double-strand break repair.     

N-methyl-D-aspartate-stimulated increases in intracellular calcium exhibit brain regional differences in sensitivity to inhibition by ethanol

To determine what effect ovariectomy and the accompanying sudden loss of circulating gonadal hormones has on spatial learning performance in the adult rat, two groups of rats were tested on the Lashley III simple alley maze following surgery. Ovariectomized animals were compared with a control group of animals that underwent laparotomy at the same time. The ovariectomized group evidenced superior performance on the maze task, as measured by latency to reach goal (running times) and error scores. It is suggested that this finding provides further evidence for the role of gonadal steroid hormones in the manipulation of functions related to learning and memory, especially in the hippocampus.     

TNK-tissue plasminogen activator compared with front-loaded alteplase in acute myocardial infarction: results of the TIMI 10B trial. Thrombolysis in Myocardial Infarction (TIMI) 10B Investigators

BACKGROUND: Bolus thrombolytic therapy is a simplified means of administering thrombolysis that facilitates rapid time to treatment. TNK-tissue plasminogen activator (TNK-tPA) is a highly fibrin-specific single-bolus thrombolytic agent. METHODS AND RESULTS: In TIMI 10B, 886 patients with acute ST-elevation myocardial infarction presenting within 12 hours were randomized to receive either a single bolus of 30 or 50 mg TNK-tPA or front-loaded tPA and underwent immediate coronary angiography. The 50-mg dose was discontinued early because of increased intracranial hemorrhage and was replaced by a 40-mg dose, and heparin doses were decreased. TNK-tPA 40 mg and tPA produced similar rates of TIMI grade 3 flow at 90 minutes (62.8% versus 62.7%, respectively, P=NS); the rate for the 30-mg dose was significantly lower (54.3%, P=0.035) and was 65. 8% for the 50-mg dose (P=NS). A prespecified analysis of weight-based TNK-tPA dosing using median TIMI frame count demonstrated a dose response (P=0.001). Similar dose responses were observed for serious bleeding and intracranial hemorrhage, but significantly lower rates were observed for both TNK-tPA and tPA after the heparin doses were lowered and titration of the heparin was started at 6 hours. CONCLUSIONS: TNK-tPA, given as a single 40-mg bolus, achieved rates of TIMI grade 3 flow similar to those of the 90-minute bolus and infusion of tPA. Weight-adjusting TNK-tPA appears to be important in achieving optimal reperfusion; reduced heparin dosing appears to improve safety for both agents. Together with the safety results from the parallel Assessment of the Safety of a New Thrombolytic: TNK-tPA (ASSENT I) trial, an appropriate dose of this single-bolus thrombolytic agent has been identified for phase III testing.