Graph inverse semigroups: their characterization and completion

Graph inverse semigroups generalize the polycyclic inverse monoids and play an important role in the theory of C*-algebras. This paper has two main goals: first, to provide an abstract characterization of graph inverse semigroups; and second, to show how they may be completed, under suitable conditions, to form what we call the Cuntz-Krieger semigroup of the graph. This semigroup is the ample semigroup of a topological groupoid associated with the graph, and the semigroup analogue of the Leavitt path algebra of the graph.Comment: Some minor corrections made and tangential material remove

Evaluating the Economic Impact of Countervailing Duties on United States Warm Water Shrimp Imports

Estimates of price and scale elasticities for U.S. consumed shrimp are derived using aggregate source country shrimp import data. It was assumed that supply was perfectly elastic and U.S. wholesalers determine the quantities imported from individual countries given the prices and preferences of U.S. consumers. Ex-ante analysis suggests that most countries levied with the countervailing duty experience declines in U.S. import demand while those countries not affected by the countervailing duty experience increases in import demand. Ex-post analysis shows the reverse to be true. Several countries impacted by the countervailing duty had increased import demand from the United States while Mexico, which was not affected by the countervailing duty, had decreased import demand. The results from aggregate level data suggest that imposing duties on specific companies within a country may not be effective if that company is not a monopoly producer or controls a significant share of the shrimp produced in that country.International Relations/Trade,

Commentary on Robert Riley's article "A personal account of the discovery of hyperbolic structures on some knot complements"

We give some background and biographical commentary on the postumous article that appears in this [journal issue | ArXiv] by Robert Riley on his part of the early history of hyperbolic structures on some compact 3-manifolds. A complete list of Riley's publications appears at the end of the article.Comment: 5 page

Using a fuzzy inference system to control a pumped storage hydro plant

The paper discusses the development of a fuzzy inference system (FIS) based governor control for a pumped storage hydroelectric plant. The First Hydro Company's plant at Dinorwig in North Wales is the largest of its kind in Europe and is mainly used for frequency control of the UK electrical grid. In previous investigations, a detailed model of the plant was developed using MATLAB(R)/SIMULINK(R) and this is now being used to compare FIS governor operation with the proportional-integral-derivative (PID) controller currently used. The paper describes the development of an FIS governor, and shows that its response to a step increase in load is superior to the PID under certain conditions of load. The paper proceeds to discuss the implications of these results in view of the possible practical application of an FIS governor at the Dinorwig plant

Deep learning extends de novo protein modelling coverage of genomes using iteratively predicted structural constraints

The inapplicability of amino acid covariation methods to small protein families has limited their use for structural annotation of whole genomes. Recently, deep learning has shown promise in allowing accurate residue-residue contact prediction even for shallow sequence alignments. Here we introduce DMPfold, which uses deep learning to predict inter-atomic distance bounds, the main chain hydrogen bond network, and torsion angles, which it uses to build models in an iterative fashion. DMPfold produces more accurate models than two popular methods for a test set of CASP12 domains, and works just as well for transmembrane proteins. Applied to all Pfam domains without known structures, confident models for 25% of these so-called dark families were produced in under a week on a small 200 core cluster. DMPfold provides models for 16% of human proteome UniProt entries without structures, generates accurate models with fewer than 100 sequences in some cases, and is freely available.Comment: JGG and SMK contributed equally to the wor

Polycyclic monoids and their generalisations

EPSRC Doctoral Training Account EP/P503647/