A self-assembly technique was used for fabrication of a Si/metal interface in nanometer scale. Fine particles of gold of nanometer-order diameter were generated by a gas-phase condensation method and deposited on a Si substrate. Through a heat treatment and a cooling process, a nanoscopic Si–Au composite structure was formed on the surface of the Si substrate. Then, surface diffusing Si atoms played an important role for fabrication of the Si–Au structure which were epitaxially grown projecting onto the substrate. Furthermore, the Si/Au interface was atomically flat with no mixed-layer formation, and the Au nanoparticles also had the same crystal orientation as that of the Si dots in spite of a large lattice constant mismatch between them. This structure was considered to be fabricated as a result of minimization of the total surface and interface energy of the Si/Au system.

The retinoblastoma tumor suppressor (Rb) gene product plays an essential role in cell-cycle regulation. However, its role in terminal differentiation of hematopoietic cells is speculative. Here we show a model of 12-o-tetradecanoylphorbol-13-acetate (TPA)-induced hematopoietic differentiation and growth arrest with a defective Rb-mediated pathway. TPA treatment arrested the cell cycle of a human hematopoietic cell line, MEG-01s, at the G1-S boundary and induced expression of p21/SDI1/WAF1/CIP1 and p27/KIP1. Both of these proteins were present in cyclin E-associated complexes, the histone H1 and Rb kinase activities of which were then inactivated. However, MEG-01s cells lacked the intact Rb protein and the Rb-mediated pathway was defective. This model raises a question about the role for Rb in terminal differentiation of hematopoietic cells.

固体表面 の構造,電 子状態は,表 面敏感 な測定手法の 発展に よ り理解が進んだのに対 し,表 面 直下 の界面は非 破 壊 で調 べ るこ との困難 さか ら理 解が進 んでい ない. w. J. KaiserとLD.Beuに よ り1988年 に提案 され た弾 道電子放射顕微鏡(BEEM: Ballistic Electron Emission Microscopy)1)は,走 査 型 トンネル顕微 鏡(STM)か ら 派生 した手法で,表 面 直下の界面の情報 を原子 レベルで 表面最外層の情報 と一体 に得 ることが出来る. BEEMで は シ ョッ トキー障壁 を形成 す る金属/半 導体 界面を対象 と し,STM探 針 か ら金属薄膜 に注 入 された トンネル電子の うち,散 乱を受 けず に弾道的に薄膜基板 界面 に到達 し障壁を通過 して半導体側に流入 した電子を コレクター電流(BEEM電 流)と して検出す る. STM 同様 に探針を走査す るこ とによ りSTM像 と表面直下 の 界面 のBEEM電 流像を 同時 に得 るこ とが 出来 る.探 針 の位 置を固 定 し探針 電圧 を変 え るこ とに よ り,BEEM 電流 の探針 電圧 依存性,す なわちBEEMス ペ ク トルを 得 ることが 出来,こ のスペ ク トルの電流立 ち上が り位置 か らシ ョッ トキ ー障壁 高 さが求 まる.BEEM電 流 は, シ ョッ トキ ー障壁 高 さ,探 針電圧,探 針か らの トンネル 電流だけでな く,金 属 薄膜 の構造や形状に依存す る.従 って,界 面 の電子状態 の知見を得 るだけでな く,薄 膜の 形成過程 を表面のみな らず基板 との界面 と関連付けて明 らか にす ることが可能である. 金属薄膜表面の汚染 や界面 への不純物の混入は,試 料 のBEEM像 に与え る影響 が大 きい.そ こで,試 料作製 は分子 線エ ピタキ シー法(MBE)に よ り行 い,超 高真 空中 でBEEM測 定 まで行 った.試 料 系 と しては シ ョッ トキ ー障壁 形成 の代 表例 であ り,BEEMで の報告 がな されてい るが2-4),障 壁の形成機 構や界面 の形成過程 に つ いては不 明な点 が多 いAu/Si系 を取 り上げ た.本 研 究 では,BEEMを 用 いて,Si上Au薄 膜 の成 長過 程 を 界面に着 目して明らか にす ることを 目的 とした.

Cyclin D1 is one of the key regulators in G1 progression in the cell cycle and is also a candidate oncogene (termed PRAD1 or bcl-1) in several types of human tumors, We report a collaboration of the cyclin D1 gene with ras and a mutated form of p53 (p53-mt) in neoplastic transformation, Transfection of cyclin D1 alone or in combination with ras or with p53-mt was not sufficient for focus formation of rat embryonic fibroblasts. However, focus formation induced by co-transfection of ras and p53-mt was enhanced in the presence of the cyclin D1-expression plasmid, Co-transfection of ras- and p53-mt-transformants with the cyclin D1-expression plasmid resulted in reduced serum dependency in vitro. Furthermore, the transformants expressing exogenous cyclin D1 grew faster than those without the cyclin D1 plasmid when injected into nude mice, These observations strengthen the significance of cyclin D1 overexpression through gene rearrangement or gene amplification observed in human tumors as a step in multistep oncogenesis; deregulated expression of cyclin D1 may reduce the requirement for growth factors and may stimulate in vivo growth.