Al/GaSb Contact with Slow Positron Beam

Annealing study of the Al/GaSb system was performed by using a slow positron beam and the measurement of X-ray diffraction. The S parameter against positron energy data were fitted by a three layer model （Al/interface/GaSb）. It was found there was a ～5 nm interfacial at the region between the Al layer and bulk in the sample of as-deposited. After the 400 ℃ annealing, this interfacial region extends to over 40 nm and S parameter dramatically drops. This is possibly due to a new phase formation induced by the atoms＇inter-diffusion at the interface. The annealing out of the open volume defects in the Al layer was revealed by the decrease of the S parameter and the increase of the effective diffusion length of the Al layer. Annealing behaviors of Sb and Lb of the GaSb bulk showed the annealing out of positron traps at 250 ℃. However,further annealing at 400 ℃ induces formation of positron traps, which are possibly another kind of VGarelated defect and the positron shallow trap GaSb anti-site. The results of the X-ray diffraction experiment verified the conclusion of obtained by using positron technology.

γ射线诱发大鼠胚胎细胞转化与N－ras的激活

以γ射线诱发转化的大鼠胚胎细胞（ＲＥＣ：ｍｙｃ：γ３３）的ＤＮＡ构建粘粒基因库，用总基因库ＤＮＡ转染ＮＩＨ／３Ｔ３细胞，产生转化灶的ＤＮＡ作二轮转染，二轮转化的ＮＩＨ／３Ｔ３细胞内有大鼠ＲＥＣ：ｍｙｃ：γ３３ＤＮＡ中具转化活性的Ｎ－ｒａｓ基因，用不对称ＰＣＲ和ＤＮＡ序列分析法证明，ＲＥＣ：ｍｙｃ：γ３３细胞中鼠Ｎ－ｒａｓ的活化是由于第６１位密码子的Ａ→Ｇ点突变。ＮＩＨ／３Ｔ３转化灶中鼠Ｎ－ｒａｓ也有同样点突变，但ＮＩＨ／３Ｔ３细胞的内源性Ｎ－ｒａｓ基因则无此突变。