9,907 research outputs found
Distributive inverse semigroups and non-commutative Stone dualities
We develop the theory of distributive inverse semigroups as the analogue of
distributive lattices without top element and prove that they are in a duality
with those etale groupoids having a spectral space of identities, where our
spectral spaces are not necessarily compact. We prove that Boolean inverse
semigroups can be characterized as those distributive inverse semigroups in
which every prime filter is an ultrafilter; we also provide a topological
characterization in terms of Hausdorffness. We extend the notion of the patch
topology to distributive inverse semigroups and prove that every distributive
inverse semigroup has a Booleanization. As applications of this result, we give
a new interpretation of Paterson's universal groupoid of an inverse semigroup
and by developing the theory of what we call tight coverages, we also provide a
conceptual foundation for Exel's tight groupoid.Comment: arXiv admin note: substantial text overlap with arXiv:1107.551
Characterizations of model sets by dynamical systems
It is shown how regular model sets can be characterized in terms of
regularity properties of their associated dynamical systems. The proof proceeds
in two steps. First, we characterize regular model sets in terms of a certain
map and then relate the properties of to ones of the underlying
dynamical system. As a by-product, we can show that regular model sets are, in
a suitable sense, as close to periodic sets as possible among repetitive
aperiodic sets.Comment: 41 pages, revised versio
Psychological pressure in competitive environments: Evidence from a randomized natural experiment: Comment
Apesteguia and Palacios-Huerta (forthcoming) report for a sample of 129 shootouts from various seasons in ten different competitions that teams kicking first in soccer penalty shootouts win significantly more often than teams kicking second. Collecting data for the entire history of six major soccer competitions we cannot replicate their result. Teams kicking first win only 53.4% of 262 shootouts in our data, which is not significantly different from random. Our findings have two implications: (1) Apesteguia and Palacios-Huertaâs results are not generally robust. (2) Using specific subsamples without a coherent criterion for data selection might lead to non-representative findings
Invariant means on Boolean inverse monoids
The classical theory of invariant means, which plays an important role in the
theory of paradoxical decompositions, is based upon what are usually termed
`pseudogroups'. Such pseudogroups are in fact concrete examples of the Boolean
inverse monoids which give rise to etale topological groupoids under
non-commutative Stone duality. We accordingly initiate the theory of invariant
means on arbitrary Boolean inverse monoids. Our main theorem is a
characterization of when a Boolean inverse monoid admits an invariant mean.
This generalizes the classical Tarski alternative proved, for example, by de la
Harpe and Skandalis, but using different methods
Psychological pressure in competitive environments: Evidence from a randomized natural experiment: Comment
Apesteguia and Palacios-Huerta (forthcoming) report for a sample of 129 shootouts from various seasons in ten different competitions that teams kicking first in soccer penalty shootouts win significantly more often than teams kicking second. Collecting data for the entire history of six major soccer competitions we cannot replicate their result. Teams kicking first win only 53.4% of 262 shootouts in our data, which is not significantly different from random. Our findings have two implications: (1) Apesteguia and Palacios-Huerta's results are not generally robust. (2) Using specific subsamples without a coherent criterion for data selection might lead to non-representative findings.Tournament, first-mover advantage, psychological pressure, field experiment, soccer, penalty shootouts
Psychological Pressure in Competitive Environments: Evidence from a Randomized Natural Experiment: Comment
Apesteguia and Palacios-Huerta (forthcoming) report for a sample of 129 shootouts from various seasons in ten different competitions that teams kicking first in soccer penalty shootouts win significantly more often than teams kicking second. Collecting data for the entire history of six major soccer competitions we cannot replicate their result. Teams kicking first win only 53.4% of 262 shootouts in our data, which is not significantly different from random. Our findings have two implications: (1) Apesteguia and Palacios-Huerta's results are not generally robust. (2) Using specific subsamples without a coherent criterion for data selection might lead to non-representative findings.tournament, first-mover advantage, psychological pressure, field experiment, soccer, penalty shootouts
Psychological pressure in competitive environments: Evidence from a randomized natural experiment: Comment
Apesteguia and Palacios-Huerta (forthcoming) report for a sample of 129 shootouts from various seasons in ten different competitions that teams kicking first in soccer penalty shootouts win significantly more often than teams kicking second. Collecting data for the entire history of six major soccer competitions we cannot replicate their result. Teams kicking first win only 53.4% of 262 shootouts in our data, which is not significantly different from random. Our findings have two implications: (1) Apesteguia and Palacios-Huerta?s results are not generally robust. (2) Using specific subsamples without a coherent criterion for data selection might lead to non-representative findings.Tournament, first-mover advantage, psychological pressure, field experiment, soccer, penalty shootouts
Psychological pressure in competitive environments: Evidence from a randomized natural experiment: Comment
Apesteguia and Palacios-Huerta (forthcoming) report for a sample of 129 shootouts from various seasons in ten different competitions that teams kicking first in soccer penalty shootouts win significantly more often than teams kicking second. Collecting data for the entire history of six major soccer competitions we cannot replicate their result. Teams kicking first win only 53.4% of 262 shootouts in our data, which is not significantly different from random. Our findings have two implications: (1) Apesteguia and Palacios-Huertaâs results are not generally robust. (2) Using specific subsamples without a coherent criterion for data selection might lead to non-representative findings.Tournament; first-mover advantage; psychological pressure; field experiment; soccer; penalty shootouts
Bioaugmentation of UASB reactors with immobilized Sulfurospirillum barnesii for simultaneous selenate and nitrate removal
Whole-cell immobilization of selenate-respiring Sulfurospirillum barnesii in polyacrylamide gels was investigated to allow the treatment of selenate contaminated (790¿”g SeÂżĂÂżL-1) synthetic wastewater with a high molar excess of nitrate (1,500 times) and sulfate (200 times). Gel-immobilized S. barnesii cells were used to inoculate a mesophilic (30°C) bioreactor fed with lactate as electron donor at an organic loading rate of 5 g chemical oxygen demand (COD)ÂżĂÂżL-1 day-1. Selenate was reduced efficiently (>97%) in the nitrate and sulfate fed bioreactor, and a minimal effluent concentration of 39¿”g SeÂżĂÂżL-1 was obtained. Scanning electron microscopy with energy dispersive X-ray (SEMâEDX) analysis revealed spherical bioprecipitates of =2¿”m diameter mostly on the gel surface, consisting of selenium with a minor contribution of sulfur. To validate the bioaugmentation success under microbial competition, gel cubes with immobilized S. barnesii cells were added to an Upflow Anaerobic Sludge Bed (UASB) reactor, resulting in earlier selenate (24 hydraulic retention times (HRTs)) and sulfate (44 HRTs) removal and higher nitrate/nitrite removal efficiencies compared to a non-bioaugmented control reactor. S. barnesii was efficiently immobilized inside the UASB bioreactors as the selenate-reducing activity was maintained during long-term operation (58 days), and molecular analysis showed that S. barnesii was present in both the sludge bed and the effluent. This demonstrates that gel immobilization of specialized bacterial strains can supersede wash-out and out-competition of newly introduced strains in continuous bioaugmented systems. Eventually, proliferation of a selenium-respiring specialist occurred in the non-bioaugmented control reactor, resulting in simultaneous nitrate and selenate removal during a later phase of operatio
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