Fetal umbilical vein transplantation for the repair of middle cerebral artery injury

It is necessary to investigate the longitudinal tensile mechanical characteristics of the middle cere- bral artery and the fetal umbilical vein prior to applying fetal umbilical vein transplantation for repair of injured middle cerebral artery. Fifteen fresh fetal umbilical vein specimens and 15 normal human fresh cadaver middle cerebral artery specimens were collected for longitudinal tensile testing at the speed of 0.5 mm/min and at normal human temperature. The results showed that under 16.0 kPa physiological stress, the strain value of fetal umbilical vein specimens was larger, while the maximal stress and elastic modulus values were less than those of middle cerebral artery specimens. Our findings indicate that fetal umbilical vein has good elastic properties and the stress-strain curve of the fetal umbilical vein is similar to that of the middle cerebral artery. Fetal umbilical vein transplan- tation can, therefore, potentially repair the injured middle cerebral artery.

A linear elastic Ni_(50)Mn_(25)Ga_9Cu_(16) martensitic alloy

The linear elasticity was studied in a martens- tic alloy NisoMn25Ga9Cu16. A 0.4 % linear elastic strain is btained in the polycrystalline sample under compressive stress of 745 MPa. The elastic modulus is 186 GPa. The obtained linear elastic strain and elastic modulus are much higher than that of ternary Ni-Mn-Ga martensitic alloys.~.bstract The linear elasticity was studied in a martens- tic alloy NisoMn25Ga9Cu16. A 0.4 % linear elastic strain is ~btained in the polycrystalline sample under compressive stress of 745 MPa. The elastic modulus is 186 GPa. The obtained linear elastic strain and elastic modulus are much higher than that of ternary Ni-Mn-Ga martensitic alloys.

Scale dependence of tensile strength of micromachined polysilicon MEMS structures due to microstructural and dimensional constraints

The success of microelectromechanical systems (MEMS) as a key technology in the 21st century depends in no small part on the solution of materials issues associated with the design and fabrication of complex MEMS devices. The reliable mechanical properties of these thin films are critical to the safety and functioning of these microdevices and should be accurately determined. In order to accomplish a reliable mechanical design of MEMS, a new microtensile test device using a magnetic-solenoid force actuator was developed to evaluate the mechanical properties of microfabricated polysilicon thin films with dimensions of 100—660 mm length, 20—200 mm width, and 2.4 mm thickness. It was found that the measured average value of Young抯 modulus, 164±1.2 GPa, falls within the theoretical bounds. The average fracture strength is 1.36 GPa with a standarddeviation of 0.14 GPa, and the Weibull modulus is 10.4—11.7, respectively. Statistical analysis of the specimen size effect on the tensile strength predicated the size effect on the length, the surface area and the volume of the specimens due tomicrostructural and dimensional constraints. The fracturestrength increases with the increase of the ratio of surfacearea to volume. In such cases the size effect can be tracedback to the ratio of surface area to volume as the governing parameter. The test data account for the uncertainties inmechanical properties and may be used in the future reliability design of polysilicon MEMS. The testing of 40specimens to failure results in a recommendation for design that the nominal strain be maintained below 0.0057.