Privacy Enhancing Technologies

The sixth annual Workshop on Privacy Enhancing Technologies (PET) was held in Cambridge, England, from 28-30 June 2006.     

Mechanism of N-acetylgalactosamine binding to a C-type animal lectin carbohydrate-recognition domain

The mammalian hepatic asialoglycoprotein receptor, a member of the C-type animal lectin family, displays preferential binding to N-acetylgalactosamine compared with galactose. The structural basis for selective binding to N-acetylgalactosamine has been investigated. Regions of the carbohydrate-recognition domain of the receptor believed to be important in preferential binding to N-acetylgalactosamine have been inserted into the homologous carbohydrate-recognition domain of a mannose-binding protein mutant that was previously altered to bind galactose. Introduction of a single histidine residue corresponding to residue 256 of the hepatic asialoglycoprotein receptor was found to cause a 14-fold increase in the relative affinity for N-acetylgalactosamine compared with galactose. The relative ability of various acyl derivatives of galactosamine to compete for binding to this modified carbohydrate-recognition domain suggest that it is a good model for the natural N-acetylgalactosamine binding site of the asialoglycoprotein receptor. Crystallographic analysis of this mutant carbohydrate-recognition domain in complex with N-acetylgalactosamine reveals a direct interaction between the inserted histidine residue and the methyl group of the N-acetyl substituent of the sugar. Evidence for the role of the side chain at position 208 of the receptor in positioning this key histidine residue was obtained from structural analysis and mutagenesis experiments. The corresponding serine residue in the modified carbohydrate-recognition domain of mannose-binding protein forms a hydrogen bond to the imidazole side chain. When this serine residue is changed to valine, loss in selectivity for N-acetylgalactosamine is observed. The structure of this mutant reveals that the beta-branched valine side chain interacts directly with the histidine side chain, resulting in an altered imidazole ring orientation.     

Analysis of electromigration effects within various types of aluminum test structures

Advances in integrated circuit fabrication technology over the past two decades have resulted in integrated circuits with smaller device dimensions and larger area and complexity. This evolution of technology highlights electromigration as a major reliability problem in silicon VLSI circuits. Emphasis is placed on the scope and detail of the electromigration test structures themselves, and on the analysis of electromigration effects within various types of aluminum test structures.     

Visualization of anisotropic pulsations in extraembryonic compartments of incubated quail eggs by NMR microimaging

Multi-plane tagging time-of-flight and bipolar gradient phase-encoding and amplitude-weighting NMR microimaging techniques have been employed to study transport in extraembryonic compartments of fertilized quail eggs during the first seven days of incubation. After the fourth day coherent and incoherent motions became visible in certain regions, in particular in the upper part of the albumen. Coherent motions as visualized by deformations of multiplane tagging grids were specified by local velocities less than 1 mm/s at most. On the other hand, incoherent motions led to much more pronounced phenomena. The multiplane tagging grid completely faded in a region comprising the upper third of the albumen after 4.5 incubation days. Images weighted by signal attenuation owing to incoherent displacements indicate motions in the same region. The fact that a reproducible localization of the motions is only possible when signals from different transients are averaged indicates that the incoherence at least partly is temporal in nature. The signal intensity of a volume selected in the incoherent-motion region consequently fluctuates with time. The Fourier analysis of these fluctuations revealed a distinct pulsation with a frequency of 0.4 Hz.     

Metrology and microscopic picture of the integer quantum Hall effect

Since 1990, the integer quantum Hall effect has provided the electrical resistance standard, and there has been a firm belief that the measured quantum Hall resistances are described only by fundamental physical constants--the elementary charge e and the Planck constant h. The metrological application seems not to rely on detailed knowledge of the microscopic picture of the quantum Hall effect; however, technical guidelines are recommended to confirm the quality of the sample to confirm the exactness of the measured resistance value. In this paper, we give our present understanding of the microscopic picture, derived from systematic scanning force microscopy investigations on GaAs/(AlGa)As quantum Hall samples, and relate these to the technical guidelines.     

14 Thesen zum Datenschutz im Smart Grid

In den folgenden Thesen sind die wesentlichen Anmerkungen und Anregungen der Verfasser zum Datenschutz im Smart Grid und in der Elektromobilit?t zusammengefasst. Dem Dokument liegen Untersuchungen der Verfasser aus dem Dokument „Datenschutz im Smart Grid“, das im Rahmen der gemeinsamen Begleitforschung der F?rderprogramme „E-Energy — IKT-basiertes Energiesystem der Zukunft“ und „IKT für Elektromobilit?t“ entstanden ist, zugrunde.     

Formation of Metallic Nanowires by Laser Ablation in Liquid Helium

Laser ablation of metals in liquid helium results in the formation of metal filaments with diameters on the order of 2?C10 nanometres and of spherical nanoparticles. In superfluid helium these nanowires aggregate into centimeter-sized networks. We study the morphology and the electric conductivity of these large aggregates, as well as extinction spectra and the crystalline structure of the individual nanofragments. We discuss the effect of superfluidity on the mechanisms of coalescence processes at the nanometer and centimeter scales.