Island nucleation in the presence of step edge barriers: Theory and applications

We develop a theory of nucleation on top of two-dimensional islands bordered by steps with an additional energy barrier $\Delta E_S$ for descending atoms. The theory is based on the concept of the residence time of an adatom on the island,and yields an expression for the nucleation rate which becomes exact in the limit of strong step edge barriers. This expression differs qualitatively and quantitatively from that obtained using the conventional rate equation approach to nucleation [J. Tersoff et al., Phys. Rev. Lett.72, 266 (1994)]. We argue that rate equation theory fails because nucleation is dominated by the rare instances when two atoms are present on the island simultaneously. The theory is applied to two distinct problems: The onset of second layer nucleation in submonolayer growth, and the distribution of the sizes of top terraces of multilayer mounds under conditions of strong step edge barriers. Application to homoepitaxial growth on Pt(111) yields the estimate $\Delta E_S \geq 0.33$ eV for the additional energy barrier at CO-decorated steps.Comment: 13 pages, 3 figure

Single-Particle Diffusion-Coefficient on Surfaces with Ehrlich-Schwoebel-Barriers

The diffusion coefficient of single particles in the presence of Ehrlich-Schwoebel barriers (ESB)is considered. An exact expression is given for the diffusion coefficient on linear chains with random arrangements of ESB. The results are extended to surfaces having ESB with uniform extension in one or both directions. All results are verified by Monte Carlo simulations.Comment: 11 pages, LaTeX2e, 6 eps-figure

Leiomyosarcoma presenting as a spontaneously ruptured renal tumor-case report

BACKGROUND: Ruptured renal neoplasms can be a catastrophic clinical presentation. Angiomyolipoma is the commonest renal tumor which presents in this fashion. Renal sarcomas are rare renal neoplasms. Renal leiomyosarcomas are the most common histological subtype of renal sarcomas, accounting for approximately 50–60% of the reported cases. These tumors are usually peripherally located and appear to arise from either the renal capsule or smooth muscle tissue in the renal pelvic wall. CASE PRESENTATION: A 70 years old male, with hypertension and ischemic disease, developed acute left flank pain. The general physician evaluated this using ultrasound, which showed a solid left renal mass. Two weeks later, he presented in the emergency room in a state of shock with a palpable flank mass. CT scan of the abdomen showed a large heterogeneous mass lesion in the left perinephric space with minimal post contrast enhancement. Per-operatively, large retroperitoneal hematoma was found within Gerota's fascia along with spleen plastered to the upper limit of hematoma. Nephrectomy and splenectomy were performed. Postoperative course was uneventful and patient was discharged on the 10(th )post-operative day. Histopathological evaluation of the specimen showed high-grade leiomyosarcoma CONCLUSIONS: Spontaneous rupture of renal neoplasm is a rare clinical presentation. Angiomyolipoma is the commonest cause of spontaneous rupture of the kidney. Presentation of a leimyosarcoma as a ruptured renal neoplasm has not been previously reported in the English literature

遷移金属錯体のワルテン反転機構について

金沢大学理学部研究課題/領域番号:X43095-----84575, 研究期間(年度):1968出典：研究課題「遷移金属錯体のワルテン反転機構について」課題番号 X43095-----84575（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-X43095-----84575/）を加工して作

The process of irreversible nucleation in multilayer growth. II. Exact results in one and two dimensions

We study irreversible dimer nucleation on top of terraces during epitaxial growth in one and two dimensions, for all values of the step-edge barrier. The problem is solved exactly by transforming it into a first passage problem for a random walker in a higher-dimensional space. The spatial distribution of nucleation events is shown to differ markedly from the mean-field estimate except in the limit of very weak step-edge barriers. The nucleation rate is computed exactly, including numerical prefactors.Comment: 22 pages, 10 figures. To appear in Phys. Rev.