Critical behavior of colloid-polymer mixtures in random porous media

We show that the critical behavior of a colloid-polymer mixture inside a random porous matrix of quenched hard spheres belongs to the universality class of the random-field Ising model. We also demonstrate that random-field effects in colloid-polymer mixtures are surprisingly strong. This makes these systems attractive candidates to study random-field behavior experimentally.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let

Paradigm change in hydrogel sensor manufacturing: from recipe-driven to specification-driven process optimization

The volume production of industrial hydrogel sensors lacks a quality-assuring manufacturing technique for thin polymer films with reproducible properties. Overcoming this problem requires a paradigm change from the current recipe-driven manufacturing process to a specification-driven one. This requires techniques to measure quality-determining hydrogel film properties as well as tools and methods for the control and optimization of the manufacturing process. In this paper we present an approach that comprehensively addresses these issues. The influence of process parameters on the hydrogel film properties and the resulting sensor characteristics have been assessed by means of batch manufacturing tests and the application of several measurement techniques. Based on these investigations, we present novel methods and a tool for the optimization of the cross-linking process step, with the latter being crucial for the sensor sensitivity. Our approach is applicable to various sensor designs with different hydrogels. It has been successfully tested with a sensor solution for surface technology based on PVA/PAA hydrogel as sensing layer and a piezoelectric thickness shear resonator as transducer. Finally, unresolved issues regarding the measurement of hydrogel film parameters are outlined for future research

Paradigm change in hydrogel sensor manufacturing: From recipe-driven to specification-driven process optimization

The volume production of industrial hydrogel sensors lacks a quality-assuring manufacturing technique for thin polymer films with reproducible properties. Overcoming this problem requires a paradigm change from the current recipe-driven manufacturing process to a specification-driven one. This requires techniques to measure quality-determining hydrogel film properties as well as tools and methods for the control and optimization of the manufacturing process. In this paper we present an approach that comprehensively addresses these issues. The influence of process parameters on the hydrogel film properties and the resulting sensor characteristics have been assessed by means of batch manufacturing tests and the application of several measurement techniques. Based on these investigations, we present novel methods and a tool for the optimization of the cross-linking process step, with the latter being crucial for the sensor sensitivity. Our approach is applicable to various sensor designs with different hydrogels. It has been successfully tested with a sensor solution for surface technology based on PVA/PAA hydrogel as sensing layer and a piezoelectric thickness shear resonator as transducer. Finally, unresolved issues regarding the measurement of hydrogel film parameters are outlined for future research

Astronomical Data Management

We present a summary of the major contributions to the Special Session on Data Management held at the IAU General Assembly in Prague in 2006. While recent years have seen enormous improvements in access to astronomical data, and the Virtual Observatory aims to provide astronomers with seamless access to on-line resources, more attention needs to be paid to ensuring the quality and completeness of those resources. For example, data produced by telescopes are not always made available to the astronomical community, and new instruments are sometimes designed and built with insufficient planning for data management, while older but valuable legacy data often remain undigitised. Data and results published in journals do not always appear in the data centres, and astronomers in developing countries sometimes have inadequate access to on-line resources. To address these issues, an 'Astronomers Data Manifesto' has been formulated with the aim of initiating a discussion that will lead to the development of a 'code of best practice' in astronomical data management.Comment: Proceedings of Special Session SPS6 (Astronomical Data Management) at the IAU GA 2006. To appear in Highlights of Astronomy, Volume 14, ed. K.A. van der Huch

Crystallographically oriented magnetic ZnFe2O4 nanoparticles synthesized by Fe implantation into ZnO

In this paper, a correlation between structural and magnetic properties of Fe implanted ZnO is presented. High fluence Fe^+ implantation into ZnO leads to the formation of superparamagnetic alpha-Fe nanoparticles. High vacuum annealing at 823 K results in the growth of alpha-Fe particles, but the annealing at 1073 K oxidized the majority of the Fe nanoparticles. After a long term annealing at 1073 K, crystallographically oriented ZnFe2O4 nanoparticles were formed inside ZnO with the orientation relationship of ZnFe2O4(111)[110]//ZnO(0001)[1120]. These ZnFe2O4 nanoparticles show a hysteretic behavior upon magnetization reversal at 5 K.Comment: 21 pages, 7 figures, accepted by J. Phys. D: Appl. Phy

Crystalline Ni nanoparticles as the origin of ferromagnetism in Ni implanted ZnO crystals

We report the structural and magnetic properties of ZnO single crystals implanted at 623 K with up to 10 at. % of Ni. As revealed by X-ray diffraction, crystalline fcc-Ni nanoparticles were formed inside ZnO. The magnetic behavior (magnetization with field reversal and with different temperature protocol) of all samples is well explained by a magnetic Ni-nanoparticle system. Although the formation of Ni:ZnO based diluted magnetic semiconductor cannot be ruled out, the major contribution to the magnetic properties stems from crystalline nanoparticles synthesized under these implantation conditions.Comment: 15 pages, 4 figures, to be published at J. Appl. Phy

Evolutionary multi-stage financial scenario tree generation

Multi-stage financial decision optimization under uncertainty depends on a careful numerical approximation of the underlying stochastic process, which describes the future returns of the selected assets or asset categories. Various approaches towards an optimal generation of discrete-time, discrete-state approximations (represented as scenario trees) have been suggested in the literature. In this paper, a new evolutionary algorithm to create scenario trees for multi-stage financial optimization models will be presented. Numerical results and implementation details conclude the paper

Resonant inelastic x-ray scattering study of the electronic structure of Cu2_2O

A resonant inelastic x-ray scattering study of the electronic structure of the semiconductor cuprous oxide, $\rm Cu_2O$, is reported. When the incident x-ray energy is tuned to the Cu K-absorption edge, large enhancements of the spectral features corresponding to the electronic transitions between the valence band and the conduction band are observed. A feature at 6.5 eV can be well described by an interband transition from occupied states of mostly Cu 3d charactor to unoccupied states with mixed 3d, 4s and 2p character. In addition, an insulating band gap is observed, and the momentum dependence of the lower bound is measured along the $\Gamma-R$ direction. This is found to be in good agreement with the valence band dispersion measured with angle-resolved photoemission spectroscopy.Comment: 7 pages, 6 figure

The Fourth VLBA Calibrator Survey - VCS4

This paper presents the fourth extension to the Very Long Baseline Array (VLBA) Calibrator Survey, containing 258 new sources not previously observed with very long baseline interferometry (VLBI). This survey, based on three 24 hour VLBA observing sessions, fills remaining areas on the sky above declination -40 degrees where the calibrator density is less than one source within a 4 degree radius disk at any given direction. The share of these area was reduced from 4.6% to 1.9%. Source positions were derived from astrometric analysis of group delays determined at 2.3 and 8.6 GHz frequency bands using the Calc/Solve software package. The VCS4 catalogue of source positions, plots of correlated flux density versus projected baseline length, contour plots and fits files of naturally weighted CLEAN images, as well as calibrated visibility function files are available on the Web at http://gemini.gsfc.nasa.gov/vcs4 .Comment: 8 pages, 8 figures, 3 tables, accepted for publication in the Astronomical Journal; minor changes to the text are made, table 2 in electronic form is added and can be extracted from the preprint sourc

Infrared fixed point in quantum Einstein gravity

We performed the renormalization group analysis of the quantum Einstein gravity in the deep infrared regime for different types of extensions of the model. It is shown that an attractive infrared point exists in the broken symmetric phase of the model. It is also shown that due to the Gaussian fixed point the IR critical exponent $\nu$ of the correlation length is 1/2. However, there exists a certain extension of the model which gives finite correlation length in the broken symmetric phase. It typically appears in case of models possessing a first order phase transitions as is demonstrated on the example of the scalar field theory with a Coleman-Weinberg potential.Comment: 9 pages, 7 figures, final version, to appear in JHE