13 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"
Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices
Interplay between Kondo effect and trends to antiferromagnetic and spin glass
ordering in perfect and disordered bipartite Kondo lattices is considered.
Ginzburg-Landau equation is derived from the microscopic effective action
written in three mode representation (Kondo screening, antiferromagnetic
correlations and spin liquid correlations). The problem of local constraint is
resolved by means of Popov-Fedotov representation for localized spin operators.
It is shown that the Kondo screening enhances the trend to a spin liquid
crossover and suppresses antiferromagnetic ordering in perfect Kondo lattices
and spin glass ordering in doped Kondo lattices. The modified Doniach's diagram
is constructed, and possibilities of going beyond the mean field approximation
are discussed.Comment: 18 pages, RevTeX, 7 EPS figures include
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
Wüstite: electric, thermodynamic and optical properties of FeO
We report on a systematic optical investigation of w\"ustite. In addition,
the sample under consideration, Fe0.93O, has been characterized in detail by
electrical transport, dielectric, magnetic and thermodynamic measurements. From
infrared reflectivity experiments, phonon properties, Drude-like conductivity
contributions and electronic transitions have been systematically investigated.
The phonon modes reveal a clear splitting below the antiferromagnetic ordering
temperature, similar to observations in other transition-metal monoxides and in
spinel compounds which have been explained in terms of a spin-driven
Jahn-Teller effect. The electronic transitions can best be described assuming a
crystal-field parameter Dq = 750 cm-1 and a spin-orbit coupling constant
\lambda = 95 cm-1. A well defined crystal field excitation at low temperatures
reveals significant broadening on increasing temperature with an overall
transfer of optical weight into dc conductivity contributions. This fact seems
to indicate a melting of the on-site excitation into a Drude behavior of
delocalized charge carriers. The optical band gap in w\"ustite is close to 1.0
eV at room temperature. With decreasing temperatures and passing the magnetic
phase transition we have detected a strong blue shift of the
correlation-induced band edge, which amounts more than 15% and has been rarely
observed in antiferromagnets.Comment: 13 pages, 10 figure
Tying SUMO modifications to dynamic behaviors of chromosomes during meiotic prophase of Saccharomyces cerevisiae
Investigation of nonlinear effects in glassy matter using dielectric methods
We summarize current developments in the investigation of glassy matter using
nonlinear dielectric spectroscopy. This work also provides a brief introduction
into the phenomenology of the linear dielectric response of glass-forming
materials and discusses the main mechanisms that can give rise to nonlinear
dielectric response in this material class. Here we mainly concentrate on
measurements of the conventional dielectric permittivity at high fields and the
higher-order susceptibilities characterizing the 3-omega and 5-omega components
of the dielectric response as performed in our group. Typical results on
canonical glass-forming liquids and orientationally disordered plastic crystals
are discussed, also treating the special case of supercooled monohydroxy
alcohols.Comment: 26 pages, 20 figure