scholarly journals The Dynamic Complexity of Acyclic Hypergraph Homomorphisms

2021 ◽  
pp. 232-244
Author(s):  
Nils Vortmeier ◽  
Ioannis Kokkinis
1984 ◽  
Vol 14 (2) ◽  
pp. 135-144
Author(s):  
Margaret Rodman ◽  
William Rodman

Who or what killed Sara Mata? During the hundred days of mourning that followed the young woman's “unnatural” death, residents of Aoba, an island in Vanuatu, sought to discover the cause of Sara's death. Alternative local explanations of the death highlight the ambiguity that characterizes Aoban beliefs about people's ability to cause death by supernatural means. We show the conventional anthropological categories of poison, sorcery, and witchcraft may misrepresent the dynamic complexity of such indigenous beliefs. Finally, we discuss a process of change in Aoban ideas concerning unnatural death, a shift from a belief in sorcery to a belief in self-destruction by supernatural means. The possibility that a society can “rewrite” a transitive process of sorcery into a reflexive mode raises new questions about the theoretical relations between witchcraft, sorcery, and structural principles of society.


2020 ◽  
Vol 49 (2) ◽  
pp. 18-29
Author(s):  
Thomas Schwentick ◽  
Nils Vortmeier ◽  
Thomas Zeume
Keyword(s):  

2017 ◽  
Vol 11 (4) ◽  
pp. 2018-2027 ◽  
Author(s):  
Jonathan Fischi ◽  
Roshanak Nilchiani ◽  
Jon Wade

Channels ◽  
2011 ◽  
Vol 5 (5) ◽  
pp. 424-431 ◽  
Author(s):  
Hwei Ling Ong ◽  
Indu S. Ambudkar
Keyword(s):  

2012 ◽  
Vol 153 (6) ◽  
pp. 214-221 ◽  
Author(s):  
Veronika Urbán S. ◽  
Elizabeta Benevolenskaya ◽  
Judit Kiss ◽  
Bernadett Sági ◽  
Beáta Hegyi ◽  
...  

Analysis of genomic sequences has clearly shown that the genomic differences among species do not explain the diversity of life. The genetic code itself serves as only a part of the dynamic complexity that results in the temporal and spatial changes in cell phenotypes during development. It has been concluded that the phenotype of a cell and of the organism as a whole is more influenced by environmentally-induced changes in gene activity than had been previously thought. The emerging field of epigenetics focuses on molecular marks on chromatin; called the epigenome, which serve as transmitters between the genome and the environment. These changes not only persist through multiple cell division cycles, but may also endure for multiple generations. Irregular alterations of the epigenome; called epimutations, may have a decisive role in the etiology of human pathologies such as malignancies and other complex human diseases. Epigenetics can provide the missing link between genetics, disease and the environment. Therefore, this field may have an increasing impact on future drug design and serve as a basis for new therapeutic/preventative approaches. Orv. Hetil., 2012, 153, 214–221.


2011 ◽  
Vol 2011 ◽  
pp. 1-19 ◽  
Author(s):  
Yakui Xue ◽  
Xiafeng Duan

We invest a predator-prey model of Holling type-IV functional response with stage structure and double delays due to maturation time for both prey and predator. The dynamical behavior of the system is investigated from the point of view of stability switches aspects. We assume that the immature and mature individuals of each species are divided by a fixed age, and the mature predator only attacks the mature prey. Based on some comparison arguments, sharp threshold conditions which are both necessary and sufficient for the global stability of the equilibrium point of predator extinction are obtained. The most important outcome of this paper is that the variation of predator stage structure can affect the existence of the interior equilibrium point and drive the predator into extinction by changing the maturation (through-stage) time delay. Our linear stability work and numerical results show that if the resource is dynamic, as in nature, there is a window in maturation time delay parameters that generate sustainable oscillatory dynamics.


2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Francesco M. Malvestuto

Given a connected hypergraph with vertex set V, a convexity space on is a subset of the powerset of V that contains ∅, V, and the singletons; furthermore, is closed under intersection and every set in is connected in . The members of are called convex sets. The convex hull of a subset X of V is the smallest convex set containing X. By a cluster of we mean any nonempty subset of V in which every two vertices are separated by no convex set. We say that a convexity space on is decomposable if it satisfies the following three axioms: (i) the maximal clusters of form an acyclic hypergraph, (ii) every maximal cluster of is a convex set, and (iii) for every nonempty vertex set X, a vertex does not belong to the convex hull of X if and only if it is separated from X by a convex cluster. We prove that a decomposable convexity space on is fully specified by the maximal clusters of in that (1) there is a closed formula which expresses the convex hull of a set in terms of certain convex clusters of and (2) is a convex geometry if and only if the subspaces of induced by maximal clusters of are all convex geometries. Finally, we prove the decomposability of some known convexities in graphs and hypergraphs taken from the literature (such as “monophonic” and “canonical” convexities in hypergraphs and “all-paths” convexity in graphs).


2021 ◽  
Vol 99 (2) ◽  
Author(s):  
Emma C Stephens

Abstract Worldwide, our collective research and policy institutions, including the American Society of Animal Science (ASAS), are calling for more systems-based research and analysis of society’s most pressing and complex problems. However, the use of systems analysis within animal science remains limited and researchers may not have the tools to answer this call. This review thus introduces important concepts in systems thinking methodology, such as policy resistance, feedback processes, and dynamic complexity. An overall rationale for systems thinking and analysis is presented, along with examples of the application of these concepts in current animal science research. In order to contrast systems approaches to more frequently employed event-oriented research frameworks, both frameworks are then applied to the ASAS’ identified “Grand Challenge” problem of antimicrobial resistance (AMR) in order to compare these two kinds of analyses. Systems thinking stresses the importance of underlying system structures that lead to persistent problem behaviors vs a focus on unidirectional cause-and-effect relationships. A potential systems framework for animal production decisions to use antimicrobials is shown that more explicitly accounts for AMR in a way that can lead to different animal production decisions than the event-oriented framework. Acknowledging and accounting for fundamental system structures that can explain persistent AMR will lead to different potential solutions to this problem than would be suggested from more linear approaches. The challenges and benefits of incorporating systems methods into animal science research are then discussed.


Sign in / Sign up

Export Citation Format

Share Document