2,090 research outputs found
Problems in extremal and probabilistic combinatorics
No full textIn this thesis we consider some problems in extremal and probabilistic combinatorics. In Chapter 2 we determine the maximum number of induced cycles that can be contained in a graph on n ≥ n0 vertices, and show that there is a unique graph that achieves this maximum. This answers a question of Tuza. Let Qd denote the hypercube of dimension d. Given d ≥ m, a spanning subgraph G of Qd is said to be (Qd,Qm)-saturated if it does not contain Qm as a subgraph but adding any edge of E(Qd) \ E(G) creates a copy of Qm in G. In Chapter 3, we show that for every fixed m ≥ 2 the minimum number of edges in a (Qd,Qm)-saturated graph is Θ(2d). This answers a question of Johnson and Pinto. We also answer another question of Johnson and Pinto about weak saturation. Given graphs F and H, a spanning subgraph G of F is said to be weakly (F,H)-saturated if the edges of E(F) \setminus E(G) can be added to G one at a time so that each additional edge creates a new copy of H. We determine the minimum number of edges in a weakly (Qd,Qm)-saturated graph for all d ≥ m ≥ 1. More generally, we determine the minimum number of edges in a subgraph of the d-dimensional grid Pk_d which is weakly saturated with respect to 'axis aligned' copies of a smaller grid Prm. In Chapter 4 we consider the r-neighbour bootstrap process in the hypercube. This process starts with an initial set A0 of infected vertices in a graph G and, at each step of the process, a healthy vertex becomes infected if it has at least r infected neighbours (once a vertex becomes infected, it remains infected forever). If every vertex of G eventually becomes infected, then we say that A0 percolates. We prove a conjecture of Balogh and Bollobás which says that, for fixed r and d tending to infinity, every percolating set in the d-dimensional hypercube has cardinality at least 1+o(1)/r (d choose r-1). We also prove an analogous result for multidimensional rectangular grids. Our proofs exploit a connection between bootstrap percolation and weak-saturation. In addition, we improve on the best known upper bound for the minimum size of a percolating set in the hypercube. In particular, when r=3, we determine the exact cardinality of a minimum percolating set in the d-dimensional hypercube, for all d ≥ 3. Finally, we consider a more general bootstrap process in a hypergraph setting. Given an r-uniform hypergraph , the -bootstrap process starts with an initial set of infected vertices of and, at each step, a healthy vertex becomes infected if there exists a hyperedge of in which it is the only healthy vertex. The initial set of infected vertices is said to percolate if every vertex of is eventually infected. In Chapter 5, for fixed r and large d, we obtain a sharp threshold for the probability that a p-random set of vertices in a q-random subhypergraph of percolates when p,q= Θ(d-1/(r-1)) and is any nearly d-regular r-uniform hypergraph with at most dO(1) vertices which satisfies certain 'codegree' conditions. As it turns out, for this wide class of hypergraphs, the threshold depends only on r and not on the underlying structure of the hypergraph. We apply this result to obtain a sharp threshold for a variant of the graph bootstrap process for strictly -balanced graphs. This result generalises a theorem of Korándi, Peled and Sudakov and the proof involves an application of the differential equations method
Il De gemitu Columbae del cardinale Roberto Bellarmino e lo jus publicum ecclesiasticum
No full textSOMMARIO: 1. Premessa - 2. Rilevanza del De gemitu per una “teologia politica” - 3. Il problema dell’appartenenza all’Ecclesia: il canto della “Colomba” - 4. Il can. I della Distinctio XCII del Decretum di Graziano - 5. Osservazioni conclusive.De gemitu Columbae by Cardinal Roberto Bellarmino and the jus publicum ecclesiasticumABSTRACT: One of the minor works of cardinal Roberto Bellarmino, De Gemitu Columbae sive De Bono lacrymarum (1617) is composed of three books: the first is dedicated to the "need for moans"; the second and third, respectively, to the sources and the fruits of the "tears". In investigating the origin of the moan, after quoting Isaiah and Nahum, the Author insists on a verse, particularly evocative, taken from the Song of Songs (6, 9). Therefore, the moan is not referred only to the animal in itself, but also to the whole Church: the work in question seems to be more connected to the textures of a "political theology" than to the classic counter-reformed edification readings. The present contribution aims to examine the relationships between De gemitu and the jus publicum ecclesiasticum, not only externum but also - and above all - internum. And, by this way, the highly debated theme of belonging to the Ecclesia, faced by the great Counter-reform theorist through the images of the dove and the chant
Correction for Sear et al., Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought.
No full textCorrection for "Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought," byDavid A. Sear,Melinda S. Allen, JonathanD. Hassall, Ashley E. Maloney, Peter G. Langdon, Alex E. Morrison, Andrew C. G. Henderson, Helen Mackay, Ian W. Croudace, Charlotte Clarke, Julian P. Sachs, Georgiana Macdonald, Richard C. Chiverrell, Melanie J. Leng, L. M. Cisneros-Dozal, and Thierry Fonville, which was first published April 6, 2020; 10.1073/pnas.1920975117 (Proc. Natl. Acad. Sci. U.S.A. 117, 8813-8819). The authors note that Emma Pearson should be added to the author list after Thierry Fonville. Emma Pearson should be credited with performing research and analyzing data. The corrected author line, affiliation line, and author contributions appear below. The author line, affiliations, and contributions sections have been corrected online. The authors note that the following statement should be added to the Acknowledgments: "E.P. acknowledges NERC grant BRIS/ 81/0415"
Imaginary futures: from thinking machines to the global village
No full text16 commissioned artworks by Alex Veness to accompany text by Richard Barbrook, coordinator of the Hypermedia Research Centre at the University of Westminster. About the bookThis book is a history of the future. It shows how our contemporary understanding of the Net is shaped by visions of the future that were assembled in the 1950s and 1960s.Richard Barbrook argues that at the height of the Cold War the Americans invented the only working model of communism in human history, the Internet. Yet, for all of its libertarian potential, the goal of this high-tech project was geopolitical dominance. The ownership of time was control over the destiny of humanity. The potentially subversive theory of cybernetics was transformed into the military-friendly project of "artificial intelligence." Capitalist growth became the fastest route to the "information society." The rest of the world was expected to follow America's path into the networked future.Today, we're still being told that the Net is creating the information society---and that America today is everywhere else tomorrow. Barbrook shows how this idea serves a specific geopolitical purpose. Thankfully, at the beginning of the twenty-first century, the DIY ethic of the Net shows that people can resist these authoritarian prophecies by shaping information technologies in their own interest. Ultimately, if we don't want the future to be what it used to be, we must invent our own improved and truly revolutionary future.Richard Barbrook is the author of a number of highly influential essays on the clash between commerce and cooperation within the Net, including "The Hi-Tech Gift Economy," "Cyber-communism," and (with Andy Cameron) "The Californian Ideology." He has recently published a book on the social groups shaping the information society, The Class of the New. Barbrook is Senior Lecturer in the School of Media, Art and Design at the University Westminster and is a trustee of cybersalon.org/
Erratum: Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought (Proceedings of the National Academy of Sciences of the United States of America(2020)117(8813-8819)DOI: 10.1073/pnas.1920975117)
No full textCorrection for "Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought," byDavid A. Sear,Melinda S. Allen, JonathanD. Hassall, Ashley E. Maloney, Peter G. Langdon, Alex E. Morrison, Andrew C. G. Henderson, Helen Mackay, Ian W. Croudace, Charlotte Clarke, Julian P. Sachs, Georgiana Macdonald, Richard C. Chiverrell, Melanie J. Leng, L. M. Cisneros-Dozal, and Thierry Fonville, which was first published April 6, 2020; 10.1073/pnas.1920975117 (Proc. Natl. Acad. Sci. U.S.A. 117, 8813-8819). The authors note that Emma Pearson should be added to the author list after Thierry Fonville. Emma Pearson should be credited with performing research and analyzing data. The corrected author line, affiliation line, and author contributions appear below. The author line, affiliations, and contributions sections have been corrected online. The authors note that the following statement should be added to the Acknowledgments: "E.P. acknowledges NERC grant BRIS/ 81/0415"
Heat risk exacerbation potential for neurology patients during the COVID-19 pandemic and related isolation
No full textCOVID-19 may increase the risk of heat-related symptoms during hot weather since vulnerable populations, including the elderly
and those with neurological disabilities, must continue to self-isolate, often indoors. Within the chronic neurological patient
population, indoor conditions in summer months present a hazard because of impaired and/or altered thermoregulation, including
poor hydration status due to both autonomic and behavioral dysfunction(s). To address this increased risk, telemedicine protocols
should include an assessment of the patient’s environmental parameters, and when combined with physiological data from
wearable devices, identify those with neurological diseases who are at higher risk of heat illness. Personalized medicine during
times of self-isolation must be encouraged, and using smart technology in ambient assisted living solutions, including e-health to
monitor physiological parameters are highly recommended, not only during extreme weather conditions but also during times of
increased isolation and vulnerability
Multi-Objective Calibration For Agent-Based Models
No full textAgent-based modelling is already proving to be an immensely useful tool for scientific and industrial modelling applications. Whilst the building of such models will always be something between an art and a science, once a detailed model has been built, the process of parameter calibration should be performed as precisely as possible. This task is often made difficult by the proliferation of model parameters with non-linear interactions. In addition to this, these models generate a large number of outputs, and their ‘accuracy’ can be measured by many different, often conflicting, criteria. In this paper we demonstrate the use of multi-objective optimisation tools to calibrate just such an agent-based model. We use an agent-based model of a financial market as an exemplar and calibrate the model using a multi-objective genetic algorithm. The technique is automated and requires no explicit weighting of criteria prior to calibration. The final choice of parameter set can be made after calibration with the additional input of the domain expert
Imaginary Futures: From Thinking Machines to the Global Village
No full text16 commissioned artworks by Alex Veness to accompany text by Richard Barbrook, coordinator of the Hypermedia Research Centre at the University of Westminster. In the book: "Imaginary Futures From Thinking Machines to the Global Village". About the bookThis book is a history of the future. It shows how our contemporary understanding of the Net is shaped by visions of the future that were put together in the 1950s and 1960s.Richard Barbrook argues that at the height of the Cold War the Americans invented the only working model of communism in human history, the Internet. Yet, for all of its libertarian potential, the goal of this high-tech project was geopolitical dominance. The ownership of time was control over the destiny of humanity. The potentially subversive theory of cybernetics was transformed into the military-friendly project of "artificial intelligence." Capitalist growth became the fastest route to the "information society." The rest of the world was expected to follow America's path into the networked future.Today, we're still being told that the Net is creating the information society---and that America today is everywhere else tomorrow. Barbrook shows how this idea serves a specific geopolitical purpose. Thankfully, at the beginning of the twenty-first century, the DIY ethic of the Net shows that people can resist these authoritarian prophecies by shaping information technologies in their own interest. Ultimately, if we don't want the future to be what it used to be, we must invent our own improved and truly revolutionary future.Richard Barbrook is the author of a number of highly influential essays on the clash between commerce and cooperation within the Net, including "The Hi-Tech Gift Economy," "Cyber-communism," and (with Andy Cameron) "The Californian Ideology." He has recently published a book on the social groups shaping the information society, The Class of the New. Barbrook is Senior Lecturer in the School of Media, Art and Design at the University Westminster and is a trustee of cybersalon.org/
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