3,672 research outputs found
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
Recommended from our members
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 CuO
A resonant inelastic x-ray scattering study of the electronic structure of
the semiconductor cuprous oxide, , 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 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 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
- …