Effect of Post-Heat Treatment Temperature on Interfacial Mechanical Properties of Cold-Rolled Ti/Al Clad Material.

Titanium and titanium alloys possess low density, high specific strength, and excellent corrosion resistance, but are expensive and have low formability at room temperature. Therefore, to reduce cost and achieve excellent properties, titanium and titanium alloys are jointed with aluminum and its alloys, which are inexpensive and have low density and excellent room temperature formability. Cladding is a widely used solid-state bonding technique, and the post-heat treatment of titanium/aluminum clad materials is required to improve their interfacial properties, which is important to ensure the reliability of Ti/Al-clad materials. The interfacial properties of Ti/Al-clad materials are significantly affected by changes in the microstructure and mechanical properties after the post-heat treatment. Thus, in this study, the relationship between the microstructure and mechanical properties at the interface of Ti/Al-clad materials was analyzed after the post-heat treatment at several different temperatures. The thick diffusion and intermetallic compound layer was formed with post-heat treatment owing to the active diffusion of Al atoms. As a result, their uniaxial and nanomechanical properties were varied with the interfacial characteristics of the Ti/Al-clad material.

Evaluation of the reliability of the dial test for posterolateral rotatory instability: a cadaveric study using an isotonic rotation machine.

PURPOSE: The purpose of our study was to evaluate the reliability of the dial test by assessing the correlation between the severity of posterolateral corner injuries and the amount of external rotation of the tibia. METHODS: Fourteen paired cadaveric legs were fixed into a custom-made isotonic rotation machine with the knee flexed at 30 degrees . For group I (7 right knees), the lateral collateral ligament, popliteofibular ligament, popliteus tendon, and posterior cruciate ligament (PCL) were cut serially. For group II (7 left knees), the PCL, lateral collateral ligament, popliteofibular ligament, and popliteus tendon were cut. The external rotation angles were measured with a 6-Nm rotational torque. RESULTS: For group I, the mean increase in the external rotation angle after cutting of the 3 posterolateral ligament structures was 17.9 degrees +/- 6.4 degrees. The additional increase in mean external rotation after cutting of the PCL was 4.7 degrees +/- 2.1 degrees. For group II, the mean increase in the external rotation angle after cutting of the PCL was 8 degrees +/- 4 degrees. Cutting the 3 posterolateral ligament structures increased the external rotation by 10.7 degrees +/- 5.3 degrees. The increase in external rotation was significant in group I after cutting of the 3 posterolateral structures and in group II after cutting of the PCL and 2 posterolateral structures (P = .05, Duncan test). CONCLUSIONS: The dial test may be a valuable diagnostic method in cases of injury to 3 posterolateral structures or combined injuries to the PCL and 2 posterolateral structures. However, posterolateral instability with injuries to only 1 or 2 posterolateral structures may not be clinically detected by the dial test. CLINICAL RELEVANCE: In the case of posterolateral instability with only 1 or 2 structure injuries, comprehensive diagnostic methods including the patient's history, other physical examinations, radiographs, and magnetic resonance imaging should be used to diagnose posterolateral rotatory instability.

Activation-Induced Cytidine Deaminase Induces DNA Demethylation of Pluripotency Genes in Bovine Differentiated Cells.

Activation-induced cytidine deaminase (AID) is the only enzyme that has been suggested as a putative DNA demethylase in mammals. However, very little is known about AID function as DNA demethylase of bovine differentiated cells toward pluripotent state. To investigate the effect of AID on DNA demethylation, bovine AID complementary DNAs were transfected into bovine differentiated cells, which were mostly methylated in the promoter regions of pluripotency genes. As a result, AID-transfected bovine cells started to transform into colonies at day 19 of transfection. The colonies derived from the transfected cells showed positive alkaline phosphatase (AP) staining and expression of pluripotency genes (OCT-3/4, NANOG, SOX2) and pluripotency-related antigens (SSEA-4, TRA1-60, TRA1-81), which have been widely used to characterize human embryonic stem cells. In particular, the levels of OCT-3/4 and NANOG expression were significantly increased in the AID-transfected cells when compared with the control and empty vector-transfected cells (p < 0.05). Finally, DNA demethylation in the promoter regions of pluripotency genes (OCT-3/4, NANOG) was significantly increased compared with the control (p < 0.05). These results demonstrate that the induction of the AID gene into bovine differentiated cells improves DNA demethylation and expression of pluripotency genes.

Time-dependent mechanical-electrical coupled behavior in single crystal ZnO nanorods.

Nanoscale time-dependent mechanical-electrical coupled behavior of single crystal ZnO nanorods was systematically explored, which is essential for accessing the long-term reliability of the ZnO nanorod-based flexible devices. A series of compression creep tests combined with in-situ electrical measurement was performed on vertically-grown single crystal ZnO nanorods. Continuous measurement of the current (I)-voltage (V) curves before, during, after the creep tests revealed that I is non-negligibly increased as a result of the time-dependent deformation. Analysis of the I-V curves based on the thermionic emission-diffusion theory allowed extraction of nanorod resistance, which was shown to decrease as time-dependent deformation. Finally, based on the observations in this study, a simple analytical model for predicting the reduction in nanorod resistance as a function of creep strain that is induced from diffusional mechanisms is proposed, and this model was demonstrated to be in an excellent agreement with the experimental results.