Quantized Conductance of a Single Magnetic Atom

A single Co atom adsorbed on Cu(111) or on ferromagnetic Co islands is contacted with non-magnetic W or ferromagnetic Ni tips in a scanning tunneling microscope. When the Co atom bridges two non-magnetic electrodes conductances of 2e^2/h are found. With two ferromagnetic electrodes a conductance of e^2/h is observed which may indicate fully spin-polarized transport.Comment: 3 pages, 2 figure

Kondo effect of a Co atom on Cu(111) in contact with an Fe tip

Single Co atoms, which exhibit a Kondo effect on Cu(111), are contacted with Cu and Fe tips in a low-temperature scanning tunneling microscope. With Fe tips, the Kondo effect persists with the Abrikosov-Suhl resonance significantly broadened. In contrast, for Cu-covered W tips, the resonance width remains almost constant throughout the tunneling and contact ranges. The distinct changes of the line width are interpreted in terms of modifications of the Co d state occupation owing to hybridization with the tip apex atoms.Comment: 4 pages, 3 figure

Theoretical analysis of STM-derived lifetimes of excitations in the Shockley surface state band of Ag(111)

We present a quantitative many-body analysis using the GW approximation of the decay rate $\Gamma$ due to electron-electron scattering of excitations in the Shockley surface state band of Ag(111), as measured using the scanning tunnelling microscope (STM). The calculations include the perturbing influence of the STM, which causes a Stark-shift of the surface state energy $E$ and concomitant increase in $\Gamma$. We find $\Gamma$ varies more rapidly with $E$ than recently found for image potential states, where the STM has been shown to significantly affect measured lifetimes. For the Shockley states, the Stark-shifts that occur under normal tunnelling conditions are relatively small and previous STM-derived lifetimes need not be corrected.Comment: 4 pages, 3 figure

Differentiated integration as a fair scheme of cooperation (working paper)

This is the final version. Available from the European University Institute via the link in this recordIn the past few years, there have been few discussions about the future of the European Union (EU) that did not involve the topic of differentiated integration (DI), the process whereby some member states integrate further, while others temporarily or permanently opt out of specific policies. Pragmatically, DI has allowed European integration to proceed by both widening and deepening. Normatively, it has allowed for diverging national capacities and preferences to be accommodated. However, the growing acceptance that the EU’s future may lie in more institutional diversity leaves unanswered the question of the conditions under which DI could be accepted as a fair scheme of cooperation. This is the question addressed by this paper. Why is this an important question? First, if DI is perceived as unfair, it will not generate the support it needs to work and, to the contrary, might further nourish hard forms of Euroscepticism. Second, if the institutional design of DI is perceived to be unfair, it will fail in its purpose of reconciling member states who want to integrate to different degrees, and at different speeds. Third, it has often been suggested that DI allows member states to leave their fundamental disagreements about the nature and the finalité of the EU unresolved by recognising that they may proceed separately, with some moving forward whilst others hold back. However, DI can in fact contribute to creating new divisions and is itself an expression of divisions. Therefore, it is important to develop a more explicit understanding of the different notions of fairness that are involved in different designs of DI. Overall, fair design in DI matters because it ensures that DI contributes to greater acceptance of the EU rather than creating additional divisions. The paper explores two main approaches of international cooperation – statism and cosmopolitanism – and relates them to fairness in institutional design in DI

Differentiated integration as a fair scheme of cooperation

Differentiated integration (DI), whereby some MS opt out or are excluded from certain common EU policies for sovereignty or capacity reasons, may be thought to undermine the EU’s functioning as what John Rawls called a fair scheme of cooperation, grounded in norms of impartiality and reciprocity. However, we argue that different forms of DI can be compatible with either fair cooperation between states on the model of Rawls’ Law of Peoples or cooperation among citizens on the model of Rawls’ two principles of domestic justice. Meanwhile, the EU has features of both, being an international Union of states and a supra- and trans-national Union of citizens. We defend the coherence of this combination and contend that DI can provide a justified mechanism for ensuring fairness between states remains compatible with fairness between citizens both within and across states. Indeed it offers a potential model for other forms of international cooperation

Optimization of the indications for allogeneic stem cell transplantation in Acute Myeloid Leukemia based on interactive diagnostic strategies

The indications for allogeneic stem cell transplantation (SCT) in Acute Myeloid Leukemia (AML) represent a real challenge due to the clinical and genetic heterogeneity of the disorder. Therefore, an optimized indication for SCT in AML first requires the determination of the individual relapse risk based on diverse chromosomal and molecular prognosis-defining aberrations. A broad panel of diagnostic methods is needed to allow such subclassification and prognostic stratification: cytomorphology, cytogenetics, molecular genetics, and immunophenotyping by multiparameter flow cytometry. These methods should not be seen as isolated techniques but as parts of an integral network with hierarchies and interactions. Examples for a poor risk constellation as a clear indication for allogeneic SCT are provided by anomalies of chromosome 7, complex aberrations, or FLT3-length mutations. In contrast, the favorable reciprocal translocations such as the t(15;17)/PML-RARA or t(8;21)/AML1-ETO are not indications for SCT in first remission due to the rather good prognosis after standard therapy. Further, the indication for SCT should include the results of minimal residual disease (MRD) diagnostics by polymerase chain reaction (PCR) or flow cytometry. New aspects for a safe and fast risk stratification as basis for an optimized indication for SCT in AML might be provided by novel technologies such as microarray-based gene expression profiling. Keywords: Acute Myeloid Leukemia (AML), Allogeneic Stem Cell Transplantation (SCT), Indication, Cytogenetics, Polymerase Chain Reaction (PCR

Defect distribution in a-plane GaN on Al2O3

The authors studied the structural and point defect distributions of hydride vapor phase epitaxial GaN film grown in the [11−20] a direction on (1−102) r-plane sapphire with metal-organic vapor phase deposited a-GaN template using transmission electron microscopy, secondary ion mass spectrometry, and positron annihilation spectroscopy. Grown-in extended and point defects show constant behavior as a function of thickness, contrary to the strong nonuniform defect distribution observed in GaN grown along the [0001] direction. The observed differences are explained by orientation-dependent and kinetics related defect incorporation.Peer reviewe

Atom Transfer and Single-Adatom Contacts

The point contact of a tunnel tip approaching towards Ag(111) and Cu(111) surfaces is investigated with a low temperature scanning tunneling microscope. A sharp jump-to-contact, random in nature, is observed in the conductance. After point contact, the tip-apex atom is transferred to the surface, indicating that a one-atom contact is formed during the approach. In sharp contrast, the conductance over single silver and copper adatoms exhibits a smooth and reproducible transition from tunneling to contact regime. Numerical simulations show that this is a consequence of the additional dipolar bonding between the homoepitaxial adatom and the surface atoms.Comment: 4 pages, 4 figure

Scanning tunneling microscopy and kinetic Monte Carlo investigation of Cesium superlattices on Ag(111)

Cesium adsorption structures on Ag(111) were characterized in a low-temperature scanning tunneling microscopy experiment. At low coverages, atomic resolution of individual Cs atoms is occasionally suppressed in regions of an otherwise hexagonally ordered adsorbate film on terraces. Close to step edges Cs atoms appear as elongated protrusions along the step edge direction. At higher coverages, Cs superstructures with atomically resolved hexagonal lattices are observed. Kinetic Monte Carlo simulations model the observed adsorbate structures on a qualitative level.Comment: 8 pages, 7 figure