3,341 research outputs found
Invariant expectations and vanishing of bounded cohomology for exact groups
We study exactness of groups and establish a characterization of exact groups
in terms of the existence of a continuous linear operator, called an invariant
expectation, whose properties make it a weak counterpart of an invariant mean
on a group. We apply this operator to show that exactness of a finitely
generated group implies the vanishing of the bounded cohomology of with
coefficients in a new class of modules, which are defined using the Hopf
algebra structure of .Comment: Final version, to appear in the Journal of Topology and Analysi
Adsorption of rare-gas atoms on Cu(111) and Pb(111) surfaces by van der Waals-corrected Density Functional Theory
The DFT/vdW-WF method, recently developed to include the Van der Waals
interactions in Density Functional Theory (DFT) using the Maximally Localized
Wannier functions, is applied to the study of the adsorption of rare-gas atoms
(Ne, Ar, Kr, and Xe) on the Cu(111) and Pb(111) surfaces, at three
high-symmetry sites. We evaluate the equilibrium binding energies and
distances, and the induced work-function changes and dipole moments. We find
that, for Ne, Ar, and Kr on the Cu(111) surface the different adsorption
configurations are characterized by very similar binding energies, while the
favored adsorption site for Xe on Cu(111) is on top of a Cu atom, in agreement
with previous theoretical calculations and experimental findings, and in common
with other close-packed metal surfaces. Instead, the favored site is always the
hollow one on the Pb(111) surface, which therefore represents an interesting
system where the investigation of high-coordination sites is possible.
Moreover, the Pb(111) substrate is subject, upon rare-gas adsorption, to a
significantly smaller change in the work function (and to a correspondingly
smaller induced dipole moment) than Cu(111). The role of the chosen reference
DFT functional and of different Van der Waals corrections, and their dependence
on different rare-gas adatoms, are also discussed
Market structure dynamics during COVID-19 outbreak
In this note, we discuss the impact of the COVID-19 outbreak from the
perspective of the market-structure. We observe that the US market-structure
has dramatically changed during the past four weeks and that the level of
change has followed the number of infected cases reported in the USA.
Presently, market-structure resembles most closely the structure during the
middle of the 2008 crisis but there are signs that it may be starting to evolve
into a new structure altogether. This is the first article of a series where we
will be analyzing and discussing market-structure as it evolves to a state of
further instability or, more optimistically, stabilization and recovery.Comment: 1 page, figure
Adaptive constraints for feature tracking
In this paper extensions to an existing tracking algorithm are described.
These extensions implement adaptive tracking constraints in the form
of regional upper-bound displacements and an adaptive track smoothness
constraint. Together, these constraints make the tracking algorithm
more flexible than the original algorithm (which used fixed tracking
parameters) and provide greater confidence in the tracking results.
The result of applying the new algorithm to high-resolution ECMWF
reanalysis data is shown as an example of its effectiveness
Constraining Torus Models for AGNs Using X-Ray Observations
In Unification Models, Active Galactic Nuclei (AGN) are believed to be
surrounded by an axisymmetric structure of dust and gas, which greatly
influences their observed properties according to the direction from which they
are observed. The main aim of this work is to constrain the properties of this
obscuring material using X-Ray observations. The distribution of column
densities observed by Chandra in the Chandra Deep Field South is used to
determine geometrical constraints for already proposed torus models. It is
found that the best torus model is given by a classical `donut shape' with an
exponential angular dependency of the density profile. The opening angle is
strongly constrained by the observed column densities. Other proposed torus
models are clearly rejected by the X-Ray observations.Comment: 10 pages, 4 figures, submitted to A&
Fish assemblages across the Mediterranean Sea and the effects of protection from fishing = I Popolamenti ittici nel Mediterraneo e gli effetti della protezione dall’impatto della pesca
Several studies have assessed the effectiveness of individual marine protected areas (MPAs) in protecting fish assemblages, but regional assessments of multiple parks are scarce. Here fish surveys using visual census were done in marine parks and fished areas at 31 locations across
the Mediterranean Sea. Fish species richness, diversity and biomass (especially of top predators) were higher in MPAs compared to fished areas, and community structure differed significantly between MPAs and fished areas. Results suggest that MPAs are generally effective means to protect and recover fish populations and assemblages
Does the use of playback affect the estimates of numbers of Red-legged Partridge Alectoris rufa?
The Benefits of Using XML Technologies in Astronomical Data Retrieval and Interpretation
This paper describes a solution found during recent research that could provide improvements in the efficiency, reliability and cost of retrieving stored astronomical data. This solution uses XML Technologies in showing that when querying a variety of astronomical data sources a standardised data structure can be output into an XML query results Document. This paper shows the astronomical XMLSchema that has been partially developed in conjunction with simple custom supporting system software. It also discusses briefly possible future implications
Development of hemostatic materials made of electrochemically oxidized bacterial cellulose
Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Cellulose is the most abundant polysaccharide in nature, being the main constituent of plant cell walls. It can undergo structural modification by oxidative methods, making it absorbable when implanted in the organism, contrarily to what happens with the non-oxidized cellulose. This way it can be used as raw material in medical devices, such as absorbable hemostatic materials and as a barrier to prevent postoperative adhesions. Cellulose can also be produced by bacteria (mainly from the species Glucanocetobacter xylinus), being this way known as bacterial cellulose (BC). With the increasing use of the hemostatic materials based on oxidized cellulose in surgical procedures, there has also been an increase in the number of case studies that describe post-operative complications associated with the use of these materials. BC has improved characteristics and unique properties compared with polysaccharide derived from plants, namely a higher biocompatibility. It has therefore been the subject of increased research over the past years allowing its application in various fields, especially in biomedical applications [1]. This project aims to develop a hemostatic material to reduce post-operative complications, based on the oxidized BC, using electrochemical oxidation methods [2]. These methods are based on the stable nitroxyl radicals commercially available. [...]info:eu-repo/semantics/publishedVersio
Highly Conductive Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate Polymer Coated Cathode for the Microbial Electrosynthesis of Acetate From Carbon Dioxide
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