Cross-border diversification in bank asset portfolios

Taking the mean-variance portfolio model as a benchmark, we compute the optimally diversified portfolio for banks located in France, Germany, the U.K., and the U.S. under different assumptions about currency hedging. We compare these optimal portfolios to the actual cross-border assets of banks from 1995-1999 and try to explain the deviations. We find that banks over-invest domestically to a considerable extent and that cross-border diversification entails considerable gain. Banks underweight countries which are culturally less similar or have capital controls in place. Capital controls have a strong impact on the degree of underinvestment whereas less political risk increases the degree of over-investment. JEL Classification: G21, G11, E44, F40International banking, international integration, portfolio diversification

Cross-Border Diversification in Bank Asset Portfolios

Taking the mean-variance portfolio model as a benchmark, we compute the optimally diversified portfolio for banks located in France, Germany, the U.K., and the U.S. under different assumptions about currency hedging. We compare these optimal portfolios to the actual cross-border assets of banks from 1995-1999 and try to explain the deviations. We find that banks over-invest domestically to a considerable extent and that cross-border diversification entails considerable gain. Banks underweight countries which are culturally less similar or have capital controls in place. Capital controls have a strong impact on the degree of underinvestment whereas less political risk increases the degree of over-investment.international banking, portfolio diversification, international integration

Multiple layer local oxidation for fabricating semiconductor nanostructures

Coupled semiconductor nanostructures with a high degree of tunability are fabricated using local oxidation with a scanning force microscope. Direct oxidation of the GaAs surface of a Ga[Al]As heterostructure containing a shallow two-dimensional electron gas is combined with the local oxidation of a thin titanium film evaporated on top. A four-terminal quantum dot and a double quantum dot system with integrated charge readout are realized. The structures are tunable via in-plane gates formed by isolated regions in the electron gas and by mutually isolated regions of the Ti film acting as top gates. Coulomb blockade experiments demonstrate the high quality of this fabrication process.Comment: 3 pages, 3 figure

In Situ Treatment of a Scanning Gate Microscopy Tip

In scanning gate microscopy, where the tip of a scanning force microscope is used as a movable gate to study electronic transport in nanostructures, the shape and magnitude of the tip-induced potential are important for the resolution and interpretation of the measurements. Contaminations picked up during topography scans may significantly alter this potential. We present an in situ high-field treatment of the tip that improves the tip-induced potential. A quantum dot was used to measure the tip-induced potential.Comment: 3 pages, 1 figure, minor changes to fit published versio

Local oxidation of Ga[Al]As heterostructures with modulated tip-sample voltages

Nanolithography based on local oxidation with a scanning force microscope has been performed on an undoped GaAs wafer and a Ga[Al]As heterostructure with an undoped GaAs cap layer and a shallow two-dimensional electron gas. The oxide growth and the resulting electronic properties of the patterned structures are compared for constant and modulated voltage applied to the conductive tip of the scanning force microscope. All the lithography has been performed in non-contact mode. Modulating the applied voltage enhances the aspect ratio of the oxide lines, which significantly strengthens the insulating properties of the lines on GaAs. In addition, the oxidation process is found to be more reliable and reproducible. Using this technique, a quantum point contact and a quantum wire have been defined and the electronic stability, the confinement potential and the electrical tunability are demonstrated to be similar to the oxidation with constant voltage.Comment: 7 pages, 7 figures, accepted by J. Appl. Phy

Frequency-selective single photon detection using a double quantum dot

We use a double quantum dot as a frequency-tunable on-chip microwave detector to investigate the radiation from electron shot-noise in a near-by quantum point contact. The device is realized by monitoring the inelastic tunneling of electrons between the quantum dots due to photon absorption. The frequency of the absorbed radiation is set by the energy separation between the dots, which is easily tuned with gate voltages. Using time-resolved charge detection techniques, we can directly relate the detection of a tunneling electron to the absorption of a single photon

Letter to the Editor: 1H, 15N, and 13C chemical shift assignments of the resuscitation promoting factor domain of Rv1009 from Mycobacterium tuberculosis

International audienceNo abstract availabl

Measurement of the Tip-Induced Potential in Scanning Gate Experiments

We present a detailed experimental study on the electrostatic interaction between a quantum dot and the metallic tip of a scanning force microscope. Our method allowed us to quantitatively map the tip-induced potential and to determine the spatial dependence of the tip's lever arm with high resolution. We find that two parts of the tip-induced potential can be distinguished, one that depends on the voltage applied to the tip and one that is independent of this voltage. The first part is due to the metallic tip while we interpret the second part as the effect of a charged dielectric particle on the tip. In the measurements of the lever arm we find fine structure that depends on which quantum state we study. The results are discussed in view of scanning gate experiments where the tip is used as a movable gate to study nanostructures.Comment: 7 pages, 5 figures, minor changes to fit published versio