Ag-coverage-dependent symmetry of the electronic states of the Pt(111)-Ag-Bi interface: The ARPES view of a structural transition

We studied by angle-resolved photoelectron spectroscopy the strain-related structural transition from a pseudomorphic monolayer (ML) to a striped incommensurate phase in an Ag thin film grown on Pt(111). We exploited the surfactant properties of Bi to grow ordered Pt(111)-xMLAg-Bi trilayers with 0 < x < 5 ML, and monitored the dispersion of the Bi-derived interface states to probe the structure of the underlying Ag film. We find that their symmetry changes from threefold to sixfold and back to threefold in the Ag coverage range studied. Together with previous scanning tunneling microscopy and photoelectron diffraction data, these results provide a consistent microscopic description of the coverage-dependent structural transition.Comment: 10 pages, 9 figure

Single 3dd transition metal atoms on multi-layer graphene systems: electronic configurations, bonding mechanisms and role of the substrate

The electronic configurations of Fe, Co, Ni, and Cu adatoms on graphene and graphite have been studied by x-ray magnetic circular dichroism and charge transfer multiplet theory. A delicate interplay between long-range interactions and local chemical bonding is found to influence the adatom equilibrium distance and magnetic moment. The results for Fe and Co are consistent with purely physisorbed species having, however, different 3$d$-shell occupancies on graphene and graphite ($d^{n+1}$ and $d^n$, respectively). On the other hand, for the late 3$d$ metals Ni and Cu a trend towards chemisorption is found, which strongly quenches the magnetic moment on both substrates.Comment: 7 pages, 4 figure

Microsurgical Technique of Simultaneous Pancreas/Kidney Transplantation in the Rat: Clinical Experience and Review of the Literature

Background: For experimental basic research, standardized transplantation models reflecting technical and immunologic aspects are necessary. This article describes an experimental model of combined pancreas/kidney transplantation (PKTx) in detail. Materials and Methods: Donor rats underwent en bloc pancreatectomy and nephrectomy. Revascularization was performed using the aorta with the superior mesenteric artery and the inferior vena cava with the portal vein. Exocrine drainage of the pancreas took place over a segment of the duodenum which was transplanted side-to-side to the jejunum. The kidney vessels were transplanted end-to-side. The ureter was anastomosed by patch technique. Postoperatively, serum parameters were monitored daily. Biopsies for histopathology were taken on days 5, 8 and 12. Results: All 12 recipients survived the combined PKTx without serious surgical complications. One thrombosis of the portal vein led to organ failure. Blood glucose levels were normal by the 3rd postoperative day. The transplanted duodenal segment showed slight villous atrophy, and the kidneys were well perfused without vascular complications. The anastomosis between ureter and bladder was leakproof. Conclusions: Excellent graft function and survival rates can be achieved due to simplified operation technique and short operation time. It may thus have high clinical relevance to immunologic issues within the scope of basic research. Copyright (C) 2009 S. Karger AG, Base

Structural phase transitions of vortex matter in an optical lattice

We consider the vortex structure of a rapidly rotating trapped atomic Bose-Einstein condensate in the presence of a co-rotating periodic optical lattice potential. We observe a rich variety of structural phases which reflect the interplay of the vortex-vortex and vortex-lattice interactions. The lattice structure is very sensitive to the ratio of vortices to pinning sites and we observe structural phase transitions and domain formation as this ratio is varied.Comment: 4 pages, 3 figure

A study of the vortex flow over 76/40-deg double-delta wing

A low-speed wind-tunnel study of the flow about a 76/40-deg double-delta wing is described for angles of attack ranging from -10 to 25 deg and Reynolds numbers ranging from 0.5 to 1.5 Million. The study was conducted to provide data for the purpose of understanding the vortical flow behavior and for validating Computational Fluid Dynamics methods. Flow visualization tests have provided insight into the effect of the angle of attack and Reynolds number of the vortex-dominated flow both on and off of the surface of the double-delta wing. Upper surface pressure recordings from pressure orifices and Pressure Sensitive Paint have provided data on the pressures induced by the vortices. Flowfield surveys were carried out at an angle of attack of 10 deg by using a thin 5-hole probe. Numerical solutions of the compressible thin-layer Navier-Stokes equations were conducted and compared to the experimental data