GaAs(001)-(2×6)重构下的表面形貌及其重构原胞

采用RHEED与STM技术对GaAs(001)-(2×6)表面重构下的表面形貌进行研究,研究发现GaAs(001)-(2×6)重构表面是GaAs(001)-β2(2×4)重构表面经530℃,1.33μPa As BEP退火获得,在(2×6)重构下的GaAs(001)表面形貌已经进入表面存在系列单层岛和坑覆盖的无序平坦状态。为了进一步确定(2×6)重构的原胞结构,采用球棍模型对其原胞结构进行模拟,提出新的As表面覆盖率计算方法、结合STM图片分析对球棍模型进行验证和筛选,首次在实验上证实(2×6)重构原胞中存在2个As Dimers和2个Ga Dimers,并以此重构原胞结构构建理论下的(2×6)重构表面,获得结果与STM图片高度吻合。

Role of TGF-β1/Smads pathway in carotid artery remodeling in renovascular hypertensive rats and prevention by Enalapril and Amlodipine

Objective To investigate the role of transforming growth factor-β1 （TGF-β1）, Smad2/3 and Smad7 expressions in carotid artery remodeling in renovascular hypertensive rats, and also the therapeutic effect of Enalapril and Amlodipine. Methods The renovascular hypertensive rat （RHR） models with ＂two-kidney and one-clip＂ were established, including model group （n = 6）, sham-operated group （n = 6）, Enalapril group （10 mg/kg per day, n = 6）, Amlodipine group （5 mg/kg per day, n = 6） and combination group （Amlodipine 2.5 mg/kg per day ＋ Enalapril 5mg/kg per day, n = 6）. The medication were continuous administrated for six weeks. Carotid artery morphological and structural changes in the media were observed by HE staining, Masson staining and immuno histochemical staining. Media thickness （MT）, MT and lumen diameter ratio （MT/LD）, and the expression levels of media a-smooth muscle actin （α-actin）, proliferating cell nuclear antigen （PCNA）, TGF-β1, phosphorylated Smad2/3 （p-Smad2/3） and Smad7 in carotid arteries were measured. Results The media of carotid arteries in RHR model group was significantly thickened, the volume of smooth muscle cell was increased, and the array was in disorder; MT, MT/LD, the proliferation index of smooth muscle cell and collagen fiber area percentage of carotid arteries in the model group were significantly higher than those in the sham-operated group （P 〈 0.01）. Compared to sham-operated group, the model group had significantly higher expressions of TGF-β1 and p-Smad2/3 （P 〈 0.05） and lower Smad7 expression. Both Enalapril and Amlodipine improved smooth muscle hypertrophy and collagen deposition, reduced RHR carotid MT, MT/LD, proliferation index of smooth muscle cell, collagen fiber area percentage and the expressions of TGF-β1 and p-Smad2/3 （P 〈 0.05）, increased Smad7 expression （P 〈 0.05）. Moreover, the combination treatment of Enalapril and Amlodipine had significantly better effects than single Amlodipine group （P 〈 0.05）, but not single Enalapril group. Conclusions TGF-β1/Smads pathway may participate in the mechanism of carotid artery remodeling in RHR; the role of Amlodipine and Enalapril in inversing carotid artery remodeling may be related to the change of TGF-β1/Smads pathway, the combination treatment of Amlodipine and Enalapril had better effects than single administration of Amlodipine.