104 research outputs found
Electrode Polarization Effects in Broadband Dielectric Spectroscopy
In the present work, we provide broadband dielectric spectra showing strong
electrode polarization effects for various materials, belonging to very
different material classes. This includes both ionic and electronic conductors
as, e.g., salt solutions, ionic liquids, human blood, and
colossal-dielectric-constant materials. These data are intended to provide a
broad data base enabling a critical test of the validity of phenomenological
and microscopic models for electrode polarization. In the present work, the
results are analyzed using a simple phenomenological equivalent-circuit
description, involving a distributed parallel RC circuit element for the
modeling of the weakly conducting regions close to the electrodes. Excellent
fits of the experimental data are achieved in this way, demonstrating the
universal applicability of this approach. In the investigated ionically
conducting materials, we find the universal appearance of a second dispersion
region due to electrode polarization, which is only revealed if measuring down
to sufficiently low frequencies. This indicates the presence of a second
charge-transport process in ionic conductors with blocking electrodes.Comment: 9 pages, 6 figures, experimental data are provided in electronic form
(see "Data Conservancy"
The Flux-Line Lattice in Superconductors
Magnetic flux can penetrate a type-II superconductor in form of Abrikosov
vortices. These tend to arrange in a triangular flux-line lattice (FLL) which
is more or less perturbed by material inhomogeneities that pin the flux lines,
and in high- supercon- ductors (HTSC's) also by thermal fluctuations. Many
properties of the FLL are well described by the phenomenological
Ginzburg-Landau theory or by the electromagnetic London theory, which treats
the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft
mainly because of the large magnetic penetration depth: The shear modulus of
the FLL is thus small and the tilt modulus is dispersive and becomes very small
for short distortion wavelength. This softness of the FLL is enhanced further
by the pronounced anisotropy and layered structure of HTSC's, which strongly
increases the penetration depth for currents along the c-axis of these uniaxial
crystals and may even cause a decoupling of two-dimensional vortex lattices in
the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause
thermally activated depinning of the flux lines or of the 2D pancake vortices
in the layers. Various phase transitions are predicted for the FLL in layered
HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to
interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do
not exist as postscript file
Age-hardening characteristics of Cuâ2.4Niâ0.6Si alloy produced by the spray forming process
The microstructural features and heat treatment response of a spray formed Cuâ2.4Niâ0.6Si (wt.%) alloy have been investigated. The alloy was aged at 450 âŠC either in the as spray formed condition or after a cold deformation of 40% reduction in original thickness. Some of the samples were subjected to a solution treatment at 900 âŠC for 1 h prior to their cold deformation to 40% of original thickness and subsequent ageing. The variation in hardness and electrical conductivity of the alloys wasmeasured as a function of ageing time. The results indicated the highest peak hardness value of approximately 250 kgfmmâ2 for the alloy aged after the solution treatment and cold rolling,
compared to the maximum hardness of 220 kgfmmâ2 for samples aged directly in as spray formed condition. However, the electrical conductivity was observed to be a maximum of 62% IACS in samples which had only been cold rolled. This behaviour is discussed in the light of microstructural characteristics associated with different processing conditions of this alloy
Fusarium head blight and associated mycotoxin occurrence on winter wheat in Luxembourg in 2007/2008
Fusarium head blight (FHB) is among the major causes of reduced quality in winter wheat and its products.
In addition, the causal fungi produce a variety of toxins. A relatively high FHB infection rate in winter wheat was
observed in 2007 and 2008 in Luxembourg. A fusariotoxin survey was carried out in 17 different geographical
locations. Three groups of Fusarium mycotoxins (trichothecenes A and B and zearalenone) were analysed by a
multi-detection HPLCâMS/MS method. Fusarium strains were also investigated by morphological and molecular
methods. In addition, questionnaires relating to cultural practices were sent to the farmers managing the 17 fields
investigated. FHB prevalence ranged from 0.3 to 65.8% (mean: 8.5%) in 2007 and from 0 to 24.5% (mean: 8.3%)
in 2008. Results of morphological and molecular identification showed that the most common species isolated
from diseased wheat spikes was F. graminearum (33.1%), followed by F. avenaceum (20.3%) and F. poae (17.8%).
The chemical analysis revealed that 75% of the investigated fields were contaminated by deoxynivalenol (DON,
range 0â8111 mg/kg). The preceding crop was highly and significantly correlated to the number of grains infected
and had a significant impact on disease prevalence ( pÂŒ0.025 and 0.017, respectively, Fisherâs F-test). A trend
was found for maize as the preceding crop ( pÂŒ0.084, Tukeyâs test) to predict the amount of DON in the fields.
This is the first report on the occurrence of DON and ZON in naturally infected wheat grains sampled from
Luxembourg
A novel approach to prevent the interference of protein A in immunoassays of enterotoxins
Semantic challenges for sensor plug and play
Abstract. The goal of the Sensor Web Enablement (SWE) initiative of the Open Geospatial Consortium (OGC) is the definition of web service interfaces and data encodings to make sensors discoverable, taskable and accessible on the World Wide Web. The SWE specifications enable a standardized communication and interaction with arbitrary types of sensors and sensor systems. The central concepts within OGCâs Sensor Web architecture are sensors, observations and features of interest. Sensors and their observations can be registered and stored through the Sensor Observation Service (SOS) to make them accessible for clients. So far, mechanisms are missing which support a semantic matching between features of interest stored in a database and referred to by an observation. The same applies for the matching between observations as sensor outputs and the properties of the features of interest. By taking a use case from disaster management, we outline the challenges and demonstrate how semantically annotated SWE data models and service interfaces support semantic matching. The result is a roadmap towards a semantically enabled sensor plug & play within the Sensor Web.
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