Artykuły w czasopismach: „CORE VERTEX”

1

Fang, Qizhi, Liang Kong i Jia Zhao. "Core Stability of Vertex Cover Games". Internet Mathematics 5, nr 4 (styczeń 2008): 383–94. http://dx.doi.org/10.1080/15427951.2008.10129174.

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Wu, Tongsuo, Meng Ye, Dancheng Lu i Houyi Yu. "On Graphs Related to Comaximal Ideals of a Commutative Ring". ISRN Combinatorics 2013 (19.02.2013): 1–7. http://dx.doi.org/10.1155/2013/354696.

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We study the co maximal graph Ω(R), the induced subgraph Γ(R) of Ω(R) whose vertex set is R∖(U(R)∪J(R)), and a retract Γr(R) of Γ(R), where R is a commutative ring. For a graph Γ(R) which contains a cycle, we show that the core of Γ(R) is a union of triangles and rectangles, while a vertex in Γ(R) is either an end vertex or a vertex in the core. For a nonlocal ring R, we prove that both the chromatic number and clique number of Γ(R) are identical with the number of maximal ideals of R. A graph Γr(R) is also introduced on the vertex set {Rx∣x∈R∖(U(R)∪J(R))}, and graph properties of Γr(R) are studied.

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Green, D. G., i G. F. Gribakin. "Vertex enhancement of positron annihilation with core electrons". Journal of Physics: Conference Series 388, nr 7 (5.11.2012): 072018. http://dx.doi.org/10.1088/1742-6596/388/7/072018.

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P., Arun Kumar, i E. Rathakrishnan. "Triangular tabs for supersonic jet mixing enhancement". Aeronautical Journal 118, nr 1209 (listopad 2014): 1245–78. http://dx.doi.org/10.1017/s0001924000009969.

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AbstractThe mixing promoting capability of right-angled triangular tab with sharp and truncated vertex has been investigated by placing two identical tabs at the exit of a Mach 2 axi-symmetric nozzle. The mixing promoting efficiency of these tabs have been quantified in the presence of adverse and marginally favourable pressure gradients at the nozzle exit. It was found that, at all levels of expansion of the present study though the core length reduction caused by both the tabs are appreciable, but the mixing caused by the truncated tab is superior. The mixing promoting efficiency of the truncated tab is found to increase with increase of nozzle pressure ratio (that is, decrease of adverse pressure gradient). For all the nozzle pressure ratios of the present study, the core length reduction caused by the truncated vertex tab is more than that of sharp vertex tab. As high as 84% reduction in core length is achieved with truncated vertex right-angled triangular tabs at moderately overexpanded level, corresponding to expansion levelpe/pa= 0·90. The corresponding core length reduction for right-angled triangular tabs with sharp vertex and rectangular tabs are 65% and 31%, respectively. The present results clearly show that the mixing promoting capability of the triangular tab is best than that of rectangular tabs at identical blockage and flow conditions.

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Feng, Xiangnan, Wei Wei, Xing Li i Zhiming Zheng. "Core influence mechanism on vertex-cover problem through leaf-removal-core breaking". Journal of Statistical Mechanics: Theory and Experiment 2019, nr 7 (1.07.2019): 073401. http://dx.doi.org/10.1088/1742-5468/ab25e1.

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CUCURINGU, MIHAI, PUCK ROMBACH, SANG HOON LEE i MASON A. PORTER. "Detection of core–periphery structure in networks using spectral methods and geodesic paths". European Journal of Applied Mathematics 27, nr 6 (3.08.2016): 846–87. http://dx.doi.org/10.1017/s095679251600022x.

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We introduce several novel and computationally efficient methods for detecting “core–periphery structure” in networks. Core–periphery structure is a type of mesoscale structure that consists of densely connected core vertices and sparsely connected peripheral vertices. Core vertices tend to be well-connected both among themselves and to peripheral vertices, which tend not to be well-connected to other vertices. Our first method, which is based on transportation in networks, aggregates information from many geodesic paths in a network and yields a score for each vertex that reflects the likelihood that that vertex is a core vertex. Our second method is based on a low-rank approximation of a network's adjacency matrix, which we express as a perturbation of a tensor-product matrix. Our third approach uses the bottom eigenvector of the random-walk Laplacian to infer a coreness score and a classification into core and peripheral vertices. We also design an objective function to (1) help classify vertices into core or peripheral vertices and (2) provide a goodness-of-fit criterion for classifications into core versus peripheral vertices. To examine the performance of our methods, we apply our algorithms to both synthetically generated networks and a variety of networks constructed from real-world data sets.

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Zhao, Jianwen, i Yufei Tao. "Minimum vertex augmentation". Proceedings of the VLDB Endowment 14, nr 9 (maj 2021): 1454–66. http://dx.doi.org/10.14778/3461535.3461536.

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This paper introduces a class of graph problems named minimum vertex augmentation (MVA). Given an input graph G where each vertex carries a binary color 0 or 1, we want to flip the colors of the fewest 0-vertices such that the subgraph induced by all the (original and new) 1-vertices satisfies a user-defined predicate π. In other words, the goal is to minimally augment the subset of 1-vertices to uphold the property π. Different formulations of π instantiate the framework into concrete problems at the core of numerous applications. We first describe a suite of techniques for solving MVA problems with strong performance guarantees, and then present a generic algorithmic paradigm that a user can instantiate to deal with ad-hoc MVA problems. The effectiveness and efficiency of our solutions are verified with an extensive experimental evaluation.

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Bachrach, Y., E. Porat i J. S. Rosenschein. "Sharing Rewards in Cooperative Connectivity Games". Journal of Artificial Intelligence Research 47 (14.06.2013): 281–311. http://dx.doi.org/10.1613/jair.3841.

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We consider how selfish agents are likely to share revenues derived from maintaining connectivity between important network servers. We model a network where a failure of one node may disrupt communication between other nodes as a cooperative game called the vertex Connectivity Game (CG). In this game, each agent owns a vertex, and controls all the edges going to and from that vertex. A coalition of agents wins if it fully connects a certain subset of vertices in the graph, called the primary vertices. Power indices measure an agent's ability to affect the outcome of the game. We show that in our domain, such indices can be used to both determine the fair share of the revenues an agent is entitled to, and identify significant possible points of failure affecting the reliability of communication in the network. We show that in general graphs, calculating the Shapley and Banzhaf power indices is #P-complete, but suggest a polynomial algorithm for calculating them in trees. We also investigate finding stable payoff divisions of the revenues in CGs, captured by the game theoretic solution of the core, and its relaxations, the epsilon-core and least core. We show a polynomial algorithm for computing the core of a CG, but show that testing whether an imputation is in the epsilon-core is coNP-complete. Finally, we show that for trees, it is possible to test for epsilon-core imputations in polynomial time.

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Dong, Zheng, Xin Huang, Guorui Yuan, Hengshu Zhu i Hui Xiong. "Butterfly-core community search over labeled graphs". Proceedings of the VLDB Endowment 14, nr 11 (lipiec 2021): 2006–18. http://dx.doi.org/10.14778/3476249.3476258.

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Community search aims at finding densely connected subgraphs for query vertices in a graph. While this task has been studied widely in the literature, most of the existing works only focus on finding homogeneous communities rather than heterogeneous communities with different labels. In this paper, we motivate a new problem of cross-group community search, namely Butterfly-Core Community (BCC), over a labeled graph, where each vertex has a label indicating its properties and an edge between two vertices indicates their cross relationship. Specifically, for two query vertices with different labels, we aim to find a densely connected cross community that contains two query vertices and consists of butterfly networks, where each wing of the butterflies is induced by a k-core search based on one query vertex and two wings are connected by these butterflies. We first develop a heuristic algorithm achieving 2-approximation to the optimal solution. Furthermore, we design fast techniques of query distance computations, leader pair identifications, and index-based BCC local explorations. Extensive experiments on seven real datasets and four useful case studies validate the effectiveness and efficiency of our BCC and its multi-labeled extension models.

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McCrabb, Andrew, i Valeria Bertacco. "Optimizing Vertex Pressure Dynamic Graph Partitioning in Many-Core Systems". IEEE Transactions on Computers 70, nr 6 (1.06.2021): 936–49. http://dx.doi.org/10.1109/tc.2021.3059386.

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He, Xiaocong, Lihua Feng i Dragan Stevanović. "The maximum spectral radius of graphs with a large core". Electronic Journal of Linear Algebra 39 (24.02.2023): 78–89. http://dx.doi.org/10.13001/ela.2023.7283.

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The $(k+1)$-core of a graph $G$, denoted by $C_{k+1}(G)$, is the subgraph obtained by repeatedly removing any vertex of degree less than or equal to $k$. $C_{k+1}(G)$ is the unique induced subgraph of minimum degree larger than $k$ with a maximum number of vertices. For $1\leq k\leq m\leq n$, we denote $R_{n, k, m}=K_k\vee(K_{m-k}\cup {I_{n-m}})$. In this paper, we prove that $R_{n, k, m}$ obtains the maximum spectral radius and signless Laplacian spectral radius among all $n$-vertex graphs whose $(k+1)$-core has at most $m$ vertices. Our result extends a recent theorem proved by Nikiforov [Electron. J. Linear Algebra, 27:250--257, 2014]. Moreover, we also present the bipartite version of our result.

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CARO, YAIR, i RAPHAEL YUSTER. "Dominating a Family of Graphs with Small Connected Subgraphs". Combinatorics, Probability and Computing 9, nr 4 (lipiec 2000): 309–13. http://dx.doi.org/10.1017/s0963548300004260.

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Let F = {G1, …, Gt} be a family of n-vertex graphs defined on the same vertex-set V, and let k be a positive integer. A subset of vertices D ⊂ V is called an (F, k)-core if, for each v ∈ V and for each i = 1, …, t, there are at least k neighbours of v in Gi that belong to D. The subset D is called a connected (F, k)-core if the subgraph induced by D in each Gi is connected. Let δi be the minimum degree of Gi and let δ(F) = minti=1δi. Clearly, an (F, k)-core exists if and only if δ(F) [ges ] k, and a connected (F, k)-core exists if and only if δ(F) [ges ] k and each Gi is connected. Let c(k, F) and cc(k, F) be the minimum size of an (F, k)-core and a connected (F, k)-core, respectively. The following asymptotic results are proved for every t < ln ln δ and k < √lnδ:formula hereThe results are asymptotically tight for infinitely many families F. The results unify and extend related results on dominating sets, strong dominating sets and connected dominating sets.

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Botea, Adi, Massimiliano Mattetti, Akihiro Kishimoto, Radu Marinescu i Elizabeth Daly. "Counting Vertex-Disjoint Shortest Paths in Graphs". Proceedings of the International Symposium on Combinatorial Search 12, nr 1 (21.07.2021): 28–36. http://dx.doi.org/10.1609/socs.v12i1.18548.

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Finding a shortest path in a graph is at the core of many combinatorial search problems. A closely related problem refers to counting the number of shortest paths between two nodes. Such problems are solvable in polynomial time in the size of the graph. However, more realistic problem formulations could additionally specify constraints to satisfy. We study the problem of counting the shortest paths that are vertex disjoint and can satisfy additional constraints. Specifically, we look at the problems of counting vertex-disjoint shortest paths in edge-colored graphs, counting vertex-disjoint shortest paths with directional constraints, and counting vertex-disjoint shortest paths between multiple source-target pairs. We give a detailed theoretical analysis, and show formally that all of these three counting problems are NP-complete in general.

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CAMERON, PETER J., i PRISCILA A. KAZANIDIS. "CORES OF SYMMETRIC GRAPHS". Journal of the Australian Mathematical Society 85, nr 2 (październik 2008): 145–54. http://dx.doi.org/10.1017/s1446788708000815.

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AbstractThe core of a graph Γ is the smallest graph Δ that is homomorphically equivalent to Γ (that is, there exist homomorphisms in both directions). The core of Γ is unique up to isomorphism and is an induced subgraph of Γ. We give a construction in some sense dual to the core. The hull of a graph Γ is a graph containing Γ as a spanning subgraph, admitting all the endomorphisms of Γ, and having as core a complete graph of the same order as the core of Γ. This construction is related to the notion of a synchronizing permutation group, which arises in semigroup theory; we provide some more insight by characterizing these permutation groups in terms of graphs. It is known that the core of a vertex-transitive graph is vertex-transitive. In some cases we can make stronger statements: for example, if Γ is a non-edge-transitive graph, we show that either the core of Γ is complete, or Γ is its own core. Rank-three graphs are non-edge-transitive. We examine some families of these to decide which of the two alternatives for the core actually holds. We will see that this question is very difficult, being equivalent in some cases to unsolved questions in finite geometry (for example, about spreads, ovoids and partitions into ovoids in polar spaces).

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Hoepfner, K., i W. Schmidt-Parzefall. "Application of liquid-core fibres for a radiation-hard vertex detector". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 440, nr 1 (styczeń 2000): 46–56. http://dx.doi.org/10.1016/s0168-9002(99)00883-9.

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Liu, Qing, Xuliang Zhu, Xin Huang i Jianliang Xu. "Local algorithms for distance-generalized core decomposition over large dynamic graphs". Proceedings of the VLDB Endowment 14, nr 9 (maj 2021): 1531–43. http://dx.doi.org/10.14778/3461535.3461542.

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The distance-generalized core, also called ( k , h )-core, is defined as the maximal subgraph in which every vertex has at least k vertices at distance no longer than h. Compared with k -core, ( k , h )-core can identify more fine-grained subgraphs and, hence, is more useful for the applications such as network analysis and graph coloring. The state-of-the-art algorithms for ( k , h )-core decomposition are peeling algorithms, which iteratively delete the vertex with the minimum h -degree (i.e., the least number of neighbors within h hops). However, they suffer from some limitations, such as low parallelism and incapability of supporting dynamic graphs. To address these limitations, in this paper, we revisit the problem of ( k , h )-core decomposition. First, we introduce two novel concepts of pairwise h-attainability index and n-order H-index based on an insightful observation. Then, we thoroughly analyze the properties of n -order H-index and propose a parallelizable local algorithm for ( k , h )-core decomposition. Moreover, several optimizations are presented to accelerate the local algorithm. Furthermore, we extend the proposed local algorithm to address the ( k , h )-core maintenance problem for dynamic graphs. Experimental studies on real-world graphs show that, compared to the best existing solution, our proposed algorithms can reduce the ( k , h )-core decomposition time by 1--3 orders of magnitude and save the maintenance cost by 1--2 orders of magnitude.

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Liao, Xuankun, Qing Liu, Jiaxin Jiang, Xin Huang, Jianliang Xu i Byron Choi. "Distributed D-core decomposition over large directed graphs". Proceedings of the VLDB Endowment 15, nr 8 (kwiecień 2022): 1546–58. http://dx.doi.org/10.14778/3529337.3529340.

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Given a directed graph G and integers k and l , a D-core is the maximal subgraph H ⊆ G such that for every vertex of H , its in-degree and out-degree are no smaller than k and l , respectively. For a directed graph G , the problem of D-core decomposition aims to compute the non-empty D-cores for all possible values of k and l. In the literature, several peeling-based algorithms have been proposed to handle D-core decomposition. However, the peeling-based algorithms that work in a sequential fashion and require global graph information during processing are mainly designed for centralized settings, which cannot handle large-scale graphs efficiently in distributed settings. Motivated by this, we study the distributed D-core decomposition problem in this paper. We start by defining a concept called anchored coreness , based on which we propose a new H-index-based algorithm for distributed D-core decomposition. Furthermore, we devise a novel concept, namely skyline coreness , and show that the D-core decomposition problem is equivalent to the computation of skyline corenesses for all vertices. We design an efficient D-index to compute the skyline corenesses distributedly. We implement the proposed algorithms under both vertex-centric and block-centric distributed graph processing frameworks. Moreover, we theoretically analyze the algorithm and message complexities. Extensive experiments on large real-world graphs with billions of edges demonstrate the efficiency of the proposed algorithms in terms of both the running time and communication overhead.

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Wang, Xingyuan, i Junqiu Li. "Detecting communities by the core-vertex and intimate degree in complex networks". Physica A: Statistical Mechanics and its Applications 392, nr 10 (maj 2013): 2555–63. http://dx.doi.org/10.1016/j.physa.2013.01.039.

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Orlosky‐Novack, Jennifer A., i Susan M. Kline. "Nulliparous, Term, Singleton, Vertex Cesarean, Oh My! Deciphering the Perinatal Core Measures". Journal of Obstetric, Gynecologic & Neonatal Nursing 42 (czerwiec 2013): S54—S55. http://dx.doi.org/10.1111/1552-6909.12130.

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Holme, Petter, Josh Karlin i Stephanie Forrest. "Radial structure of the Internet". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, nr 2081 (13.02.2007): 1231–46. http://dx.doi.org/10.1098/rspa.2007.1820.

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The structure of the Internet at the autonomous system (AS) level has been studied by the physics, mathematics and computer science communities. We extend this work to include features of the core and the periphery, taking a radial perspective on AS network structure. New methods for plotting AS data are described, and they are used to analyse datasets that have been extended to contain edges missing from earlier collections. The average distance from one vertex to the rest of the network is used as the baseline metric for investigating radial structure. Common vertex-specific quantities are plotted against this metric to reveal distinctive characteristics of central and peripheral vertices. Two datasets are analysed using these measures as well as two common generative models (Barabási–Albert and Inet). We find a clear distinction between the highly connected core and a sparse periphery. We also find that the periphery has a more complex structure than that predicted by degree distribution or the two generative models.

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Anwar, Muhammad, Aboul Ella Hassanien, Václav Snás̃el i Sameh H. Basha. "Subgraph Query Matching in Multi-Graphs Based on Node Embedding". Mathematics 10, nr 24 (19.12.2022): 4830. http://dx.doi.org/10.3390/math10244830.

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This paper presents an efficient algorithm for matching subgraph queries in a multi-graph based on features-based indexing techniques. The KD-tree data structure represents these nodes’ features, while the set-trie index data structure represents the multi-edges to make queries effectively. The vertex core number, triangle number, and vertex degree are the eight features’ main features. The densest vertex in the query graph is extracted based on these main features. The proposed model consists of two phases. The first phase’s main idea is that, for the densest extracted vertex in the query graph, find the density similar neighborhood structure in the data graph. Then find the k-nearest neighborhood query to obtain the densest subgraph. The second phase for each layer graph, mapping the vertex to feature vector (Vertex Embedding), improves the proposed model. To reduce the node-embedding size to be efficient with the KD-tree, indexing a dimension reduction, the principal component analysis (PCA) method is used. Furthermore, symmetry-breaking conditions will remove the redundancy in the generated pattern matching with the query graph. In both phases, the filtering process is applied to minimize the number of candidate data nodes of the initiate query vertex. The filtering process is applied to minimize the number of candidate data nodes of the initiate query vertex. Finally, testing the effect of the concatenation of the structural features (orbits features) with the meta-features (summary of general, statistical, information-theoretic, etc.) for signatures of nodes on the model performance. The proposed model is tested over three real benchmarks, multi-graph datasets, and two randomly generated multi-graph datasets. The results agree with the theoretical study in both random cliques and Erdos random graph. The experiments showed that the time efficiency and the scalability results of the proposed model are acceptable.

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Nasihatgozar, M., i SMR Khalili. "Vibration and buckling analysis of laminated sandwich conical shells using higher order shear deformation theory and differential quadrature method". Journal of Sandwich Structures & Materials 21, nr 4 (7.07.2017): 1445–80. http://dx.doi.org/10.1177/1099636217715806.

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Vibration and buckling analysis of laminated sandwich truncated conical shells with compressible or incompressible core are presented in this work considering curvature effects. The formulation uses the quadratic and cubic functions for transverse and in-plane displacements of the core and the first-order shear deformation theory for the face sheets. The motion equations of each individual layer are derived according to the principle of minimum total potential energy considering the continuity of the displacements and the internal stress fields at the interfaces. Differential quadrature method is applied in order to obtain the frequency and buckling load of the sandwich structure. The effects of different parameters such as core to face sheet stiffness ratio, number of layers of the face sheets, boundary condition, geometrical parameters of the core and the face sheets, semi vertex angle of the cone, trapezoidal shape, and in-plane stresses of the core are examined on the vibration and buckling response of sandwich truncated conical shells. Comparison of the present results with those reported in the literature confirms the accuracy of the proposed theory. Numerical results indicate that the effects of in-plane stresses of the core significantly affect the frequency with increasing the core to face sheet stiffness ratio.

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Matsuo, Shota, Seiji Yamazoe, Jing-Qiang Goh, Jaakko Akola i Tatsuya Tsukuda. "The electrooxidation-induced structural changes of gold di-superatomic molecules: Au23vs. Au25". Physical Chemistry Chemical Physics 18, nr 6 (2016): 4822–27. http://dx.doi.org/10.1039/c5cp06969f.

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Face-sharing bi-icosahedral Au₂₃ core of Au₃₈(SC₂H₄Ph)₂₄ retained its structure, whereas vertex-sharing bi-icosahedral Au₂₅ core of [Au₂₅(PPh₃)₁₀(SC₂H₄Ph)₅Cl₂]²⁺ underwent irreversible structural change upon electrooxidation.

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M R, Mr Rakesh. "Design and Implementation of Dual Core and Quad Core Processor in Vertex 6 FPGA Using Pipelined RISC Architecture". IJIREEICE 6, nr 11 (30.11.2018): 22–28. http://dx.doi.org/10.17148/ijireeice.2018.6114.

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Alinejad, M., i A. Erfanian. "Vertex and edge connectivity of non-normal graphs". Journal of Algebra and Its Applications 15, nr 06 (30.03.2016): 1650118. http://dx.doi.org/10.1142/s0219498816501188.

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Let [Formula: see text] be a finite group and [Formula: see text] be a subgroup of [Formula: see text]. The non-normal graph of [Formula: see text] in [Formula: see text], denoted by [Formula: see text], is defined as the bipartite graph with two parts [Formula: see text] and [Formula: see text], where [Formula: see text] and [Formula: see text] are the normalizer and the core of [Formula: see text] in [Formula: see text], respectively. Two vertices [Formula: see text] and [Formula: see text] are adjacent if [Formula: see text]. In this paper, we consider vertex and edge connectivity of [Formula: see text]. We show that [Formula: see text] and if [Formula: see text] is a positive integer such that [Formula: see text] and [Formula: see text], then the graph [Formula: see text] has a cycle of length [Formula: see text].

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Rakityansky, S. A., i I. M. Gopane. "Effective-range parameters and vertex constants for Λ-nuclear systems". International Journal of Modern Physics E 26, nr 04 (kwiecień 2017): 1750014. http://dx.doi.org/10.1142/s0218301317500148.

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For a wide range of the core-nuclei ([Formula: see text]), the scattering lengths, effective radii, and the other effective-range parameters (up to the order [Formula: see text]) for the angular momentum [Formula: see text] are calculated within a two-body [Formula: see text]-model. For the same hypernuclear systems, the [Formula: see text]-matrix residues as well as the corresponding Nuclear-Vertex and Asymptotic-Normalization constants (NVC’s and ANC’s) for the bound states are also found.

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Gozzini, Francesco. "A high-performance code for EPRL spin foam amplitudes". Classical and Quantum Gravity 38, nr 22 (27.10.2021): 225010. http://dx.doi.org/10.1088/1361-6382/ac2b0b.

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Abstract We present sl2cfoam-next, a high-performance software library for computing Lorentzian EPRL spin foam amplitudes. The library improves on previous codes by many orders of magnitude in single-core performance, can be parallelized on a large number of CPUs and on the GPU, and can be used interactively. We describe the techniques used in the code and provide many usage examples. As first applications, we use sl2cfoam-next to complete the numerical test of the Lorentzian single-vertex asymptotics and to confirm the presence of the ‘flatness problem’ of spin foam models in the BF and EPRL cases.

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Yuan, Long, i Wei Xin Tian. "A Parallel Subgraph Isomorphism Algorithm on Multi-Core Platform". Applied Mechanics and Materials 513-517 (luty 2014): 483–86. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.483.

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Subgraph isomorphism is an elemental issue in graph theory. Being the NP-hard problem overall, it is suitable for developing parallel algorithm to reduce the cost time. This paper presented an efficient isomorphism algorithm based on breadth first strategy and a scheme to decompose the matching task over multi-core platforms. The algorithm sorts the vertices of the two graphs by the the degree of outedge and inedge, then adds all the vertices to the feasible pair according to the connection relations of the current vertex. All the tasks distributed among the multi-cores share the same memory. The experiment shows that it has the better performance than current algorithm as the edges increase.

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Langford, Steven J., i Clint P. Woodward. "Six-Sided Heptaporphyrin Array: Towards a Nano-Sized Cube". Collection of Czechoslovak Chemical Communications 69, nr 5 (2004): 996–1008. http://dx.doi.org/10.1135/cccc20040996.

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A strategy in preparing a family of hexameric porphyrin cubes based on the interplay of Sn(IV)-O and Ru(II)-N interactions is described. In this first iteration, we have prepared the heptamer [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 (4 = (E)-(3-(4-pyridyl)acrylate)) constituting a 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) core and 5,10,15,20-tetraphenylporphyrin (TPP) faces and compared its formation by stepwise and "one-pot" strategies where up to nine components are assembled in a single step in a regiospecific manner. In one example, the heptamer is formed around the template [SnIV(TPyP)·(4)2] bearing pyridine groups in which the nitrogens radiate octahedrally along each vertex. The ability to modulate the axial vertex through choice of pyridine is also demonstrated. 1H NMR measurements on [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 indicate that the protons on the core template are extremely shielded as a result of the anisotropy of the peripheral porphyrin units. Various NMR techniques, including NOESY experiments, have been used to characterise the heptamer in solution.

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30

Callelero, Marcielow J., i Danilo M. Yanga. "Mobility of spin polarons with vertex corrections". International Journal of Modern Physics B 33, nr 18 (20.07.2019): 1950195. http://dx.doi.org/10.1142/s0217979219501959.

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The mobility of holes in the spin polaron theory is discussed in this paper using a representation where holes are described as spinless fermions and spins as normal bosons. The hard-core bosonic operator is introduced through the Holstein–Primakoff transformation. Mathematically, the theory is implemented in the finite temperature (Matsubara) Green’s function method. The expressions for the zeroth-order term of the hole mobility is determined explicitly for hole occupation factor taking the form of Fermi–Dirac distribution and the classical Maxwell–Boltzmann distribution function. These are proportional to the relaxation time and the square of the renormalization factor. In the Ising limit, we showed that the mobility is zero and the holes are localized. The calculation of the hole mobility is generalized by considering the vertex corrections, which included the ladder diagrams. One of the vertex functions in the hole mobility can be evaluated using the Ward identity for hole-spin wave weak interaction. We also derived an expression for the hole mobility with vertex corrections in the low-temperature limit and vanishing self-energy effects. Our calculation is made up to second-order correction in the case where the hole occupation factor follows the Fermi–Dirac distribution.

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31

Meng, Zheng, Ying Lin, Yan Kang i Qian Yu. "A Parallel Programming Pattern Based on Directed Acyclic Graph". Applied Mechanics and Materials 303-306 (luty 2013): 2165–69. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.2165.

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With the development of computer technology, multi-core programming is now becoming hot issues. Based on directed acyclic graph, this paper gives definition of a number of executable operations and establishes a parallel programming pattern. Using verticies to represent tasks and edges to represent communication between vertex, this parallel programming pattern let the programmers easily to identify the available concurrency and expose it for use in the algorithm design. The proposed pattern can be used for large-scale static data batch processing in multi-core environments and can bring lots of convenience when deal with complex issues.

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32

Gudmundsson, Joachim, John Pfeifer i Martin P. Seybold. "On Practical Nearest Sub-Trajectory Queries under the Fréchet Distance". ACM Transactions on Spatial Algorithms and Systems 9, nr 2 (2.05.2023): 1–24. http://dx.doi.org/10.1145/3587426.

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We study the problem of sub-trajectory nearest-neighbor queries on polygonal curves under the continuous Fréchet distance. Given an n vertex trajectory P and an m vertex query trajectory Q , we seek to report a vertex-aligned sub-trajectory P ′ of P that is closest to Q , i.e., P′ must start and end on contiguous vertices of P . Since in real data P typically contains a very large number of vertices, we focus on answering queries, without restrictions on P or Q , using only precomputed structures of 𝒪(n) size. We use three baseline algorithms from straightforward extensions of known work; however, they have impractical performance on realistic inputs. Therefore, we propose a new Hierarchical Simplification Tree (HST) data structure and an adaptive clustering-based query algorithm that efficiently explores relevant parts of P . The core of our query methods is a novel greedy-backtracking algorithm that solves the Fréchet decision problem using 𝒪(n+m) space and 𝒪O(nm) time in the worst case. Experiments on real and synthetic data show that our heuristic effectively prunes the search space and greatly reduces computations compared to baseline approaches.

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33

Requerey, Iker S., Basilio Ruiz Cobo, Milan Gošić i Luis R. Bellot Rubio. "Persistent magnetic vortex flow at a supergranular vertex". Astronomy & Astrophysics 610 (luty 2018): A84. http://dx.doi.org/10.1051/0004-6361/201731842.

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Context. Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial scales. Their interplay with magnetic fields is poorly characterized, however. Aims. We study the relation between a persistent photospheric vortex flow and the evolution of a network magnetic element at a supergranular vertex. Methods. We used long-duration sequences of continuum intensity images acquired with Hinode and the local correlation-tracking method to derive the horizontal photospheric flows. Supergranular cells are detected as large-scale divergence structures in the flow maps. At their vertices, and cospatial with network magnetic elements, the velocity flows converge on a central point. Results. One of these converging flows is observed as a vortex during the whole 24 h time series. It consists of three consecutive vortices that appear nearly at the same location. At their core, a network magnetic element is also detected. Its evolution is strongly correlated to that of the vortices. The magnetic feature is concentrated and evacuated when it is caught by the vortices and is weakened and fragmented after the whirls disappear. Conclusions. This evolutionary behavior supports the picture presented previously, where a small flux tube becomes stable when it is surrounded by a vortex flow.

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Lin, Zhe, Fan Zhang, Xuemin Lin, Wenjie Zhang i Zhihong Tian. "Hierarchical core maintenance on large dynamic graphs". Proceedings of the VLDB Endowment 14, nr 5 (styczeń 2021): 757–70. http://dx.doi.org/10.14778/3446095.3446099.

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The model of k -core and its decomposition have been applied in various areas, such as social networks, the world wide web, and biology. A graph can be decomposed into an elegant k -core hierarchy to facilitate cohesive subgraph discovery and network analysis. As many real-life graphs are fast evolving, existing works proposed efficient algorithms to maintain the coreness value of every vertex against structure changes. However, the maintenance of the k -core hierarchy in existing studies is not complete because the connections among different k -cores in the hierarchy are not considered. In this paper, we study hierarchical core maintenance which is to compute the k -core hierarchy incrementally against graph dynamics. The problem is challenging because the change of hierarchy may be large and complex even for a slight graph update. In order to precisely locate the area affected by graph dynamics, we conduct in-depth analyses on the structural properties of the hierarchy, and propose well-designed local update techniques. Our algorithms significantly outperform the baselines on runtime by up to 3 orders of magnitude, as demonstrated on 10 real-world large graphs.

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35

Liaw, Sy-Sang. "Transition amplitudes in the Dirac–Fock approximation". Canadian Journal of Physics 70, nr 8 (1.08.1992): 644–51. http://dx.doi.org/10.1139/p92-104.

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Transition amplitudes for several iso-electronic sequences are computed on the frozen-core Dirac–Fock approximation using the B-spline method. The length and velocity forms of the oscillator strengths are shown to be equal numerically if the nonlocal effective vertex is used. These gauge-invariant values, when compared with other theoretical results aiming for the exact values of the oscillate strengths, show satisfactory quality. We also find a peculiar feature for some transitions.

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36

Wu, Yanping, Jun Zhao, Renjie Sun, Chen Chen i Xiaoyang Wang. "Efficient Personalized Influential Community Search in Large Networks". Data Science and Engineering 6, nr 3 (29.04.2021): 310–22. http://dx.doi.org/10.1007/s41019-021-00163-3.

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AbstractCommunity search, which aims to retrieve important communities (i.e., subgraphs) for a given query vertex, has been widely studied in the literature. In the recent, plenty of research is conducted to detect influential communities, where each vertex in the network is associated with an influence value. Nevertheless, there is a paucity of work that can support personalized requirement. In this paper, we propose a new problem, i.e., maximal personalized influential community search. Given a graph G, an integer k and a query vertex u, we aim to obtain the most influential community for u by leveraging the k-core concept. To handle larger networks efficiently, two algorithms, i.e., top-down algorithm and bottom-up algorithm, are developed. In real-life applications, there may be a lot of queries issued. Therefore, an optimal index-based approach is proposed in order to meet the online requirement. In many scenarios, users may want to find multiple communities for a given query. Thus, we further extend the proposed techniques for the top-r case, i.e., retrieving r communities with the largest influence value for a given query. Finally, we conduct extensive experiments on 6 real-world networks to demonstrate the advantage of proposed techniques.

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37

Androsov, Alexey, Vera Fofonova, Ivan Kuznetsov, Sergey Danilov, Natalja Rakowsky, Sven Harig, Holger Brix i Karen Helen Wiltshire. "FESOM-C v.2: coastal dynamics on hybrid unstructured meshes". Geoscientific Model Development 12, nr 3 (21.03.2019): 1009–28. http://dx.doi.org/10.5194/gmd-12-1009-2019.

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Abstract. We describe FESOM-C, the coastal branch of the Finite-volumE Sea ice – Ocean Model (FESOM2), which shares with FESOM2 many numerical aspects, in particular its finite-volume cell-vertex discretization. Its dynamical core differs in the implementation of time stepping, the use of a terrain-following vertical coordinate, and the formulation for hybrid meshes composed of triangles and quads. The first two distinctions were critical for coding FESOM-C as an independent branch. The hybrid mesh capability improves numerical efficiency, since quadrilateral cells have fewer edges than triangular cells. They do not suffer from spurious inertial modes of the triangular cell-vertex discretization and need less dissipation. The hybrid mesh capability allows one to use quasi-quadrilateral unstructured meshes, with triangular cells included only to join quadrilateral patches of different resolution or instead of strongly deformed quadrilateral cells. The description of the model numerical part is complemented by test cases illustrating the model performance.

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38

Suo, Lina, Haimiao Zhou, Ya-Pei Peng, Fan Yang, Hsiang-Chen Chui i Nan-Kuang Chen. "High Sensitivity Fiber Refractive Index Sensors Based on Asymmetric Supermodes Interference in Tapered Four Core Fiber". Photonics 9, nr 1 (14.01.2022): 45. http://dx.doi.org/10.3390/photonics9010045.

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We demonstrate high sensitivity fiber refractive index (RI) sensor based on asymmetric supermode interferences in tapered four core fiber (TFCF). To make TFCF-based RI sensors, the whitelight was launched into any one of the cores to define the excitation orientation and is called a vertex-core excitation scheme. When the four-core fiber (FCF) was gradually tapered, the four cores gathered closer and closer. Originally, the power coupling occurred between its two neighboring cores first and these three cores are grouped to produce supermodes. Subsequently, the fourth diagonal core enters the evanescent field overlapping region to excite asymmetric supermodes interferences. The output spectral responses of the two cores next to the excitation core are mutually in phase whereas the spectral responses of the diagonal core are in phase and out of phase to that of the excitation core at the shorter and longer wavelengths, respectively. Due to the lowest limitation of the available refractive index of liquids, the best sensitivity can be achieved when the tapered diameter is 10 μm and the best RI sensitivity S is 3249 nm/RIU over the indices ranging from 1.41–1.42. This is several times higher than that at other RI ranges due to the asymmetric supermodes.

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39

Yao, Hai-Jun, Chun-Hua hu, Jie Sun, Ruo-Shui Jin, Pei-Ju Zheng, Jonathan Bould, Robert Greatrex, John D. Kennedy, Daniel L. Ormsby i Mark Thornton-Pett. "Isolation and Structure of [(PPh3)3(PPh2)2Pd4B20H16]. A Possible Prognostic for New Globular Borane-Based Cluster Architectures". Collection of Czechoslovak Chemical Communications 64, nr 6 (1999): 927–37. http://dx.doi.org/10.1135/cccc19990927.

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A novel metallaborane compound, [(PPh3)3(PPh2)2Pd4B20H16], prepared from [PdCl2(PPh3)2] and [B10H10]2- in EtOH, exhibits a globular cluster architecture consisting of two twelve-vertex closo {PdB11} cluster units fused to generate a condensed globular {PdB20} assembly that has a tetrahedral {B4} borons-only core. There is dynamic bonding between this borane-based assembly and an unusual exopolyhedral palladium-based domain consisting of a {(PPh3)Pd(PPh2)Pd(PPh2)Pd(PPh3)} string. The central tetrahedral borons-only core suggests a new type of globular "megaloborane" architectural principle for higher condensed boron hydrides, which is assessed by ab initio studies at the STO-3G level on protonated [B28H18]2- and related structures: results suggest energetic minimisation at neutral [B27H21].

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40

Cacciapuoti, Claudio. "Scale Invariant Effective Hamiltonians for a Graph with a Small Compact Core". Symmetry 11, nr 3 (9.03.2019): 359. http://dx.doi.org/10.3390/sym11030359.

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We consider a compact metric graph of size ε and attach to it several edges (leads) of length of order one (or of infinite length). As ε goes to zero, the graph G ε obtained in this way looks like the star-graph formed by the leads joined in a central vertex. On G ε we define an Hamiltonian H ε , properly scaled with the parameter ε . We prove that there exists a scale invariant effective Hamiltonian on the star-graph that approximates H ε (in a suitable norm resolvent sense) as ε → 0 . The effective Hamiltonian depends on the spectral properties of an auxiliary ε -independent Hamiltonian defined on the compact graph obtained by setting ε = 1 . If zero is not an eigenvalue of the auxiliary Hamiltonian, in the limit ε → 0 , the leads are decoupled.

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41

Alam, Md Tanvir, Chowdhury Farhan Ahmed i Md Samiullah. "A Vertex-extension based Algorithm for Frequent Pattern Mining from Graph Databases". Dhaka University Journal of Applied Science and Engineering 7, nr 1 (1.02.2023): 58–65. http://dx.doi.org/10.3329/dujase.v7i1.62887.

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Frequent pattern mining is a core problem in data mining. Algorithms for frequent pattern mining have been proposed for itemsets, sequences, and graphs. However, existing graph mining frameworks follow an edge-growth approach to building patterns which limits many applications. Motivated by real-life problems, in this work, we define a novel graph mining framework that incorporates vertex-based extensions along with the edge-growth approach. We also propose an efficient algorithm for mining frequent subgraphs. To deal with the exploding search space, we introduce a canonical labeling technique for isomorphic candidates as well as downward closure property-based search space pruning. We present an experimental analysis of our algorithm on real-life benchmark graph datasets to demonstrate the performance in terms of runtime. DUJASE Vol. 7(1) 58-65, 2022 (January)

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42

Kapoor, R. C., i C. S. Shukre. "A Geometrical origin of the Pulsar Core and Conal Emissions". International Astronomical Union Colloquium 160 (1996): 229–30. http://dx.doi.org/10.1017/s0252921100041579.

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We have analysed the dipole magnetic field geometry for the general case of an oblique rotator and have found that open field lines which define the polar cap divide into two branches (Kapoor and Shukre 1996) which appear naturally relevant for distinguishing the core and conal emissions. The polar cap shape is actually determined by a quadratic equation having two roots leading to two values of the polar angle,θ+andθ−with respect to the magnetic axis for a given azimuth φ. For the north pole bothθ+andθ−branches are shown as polar plots in Fig. 1 for various inclination angles α and a typical pulsar period. The discussion of pulsar polar caps hitherto (e.g. Biggs 1990) had not distinguished between theθ+and theθ−solutions. The region defined by theθ+solution is completely contained inside the polar cap. It has a peculiar triangular shape whose lowest vertex is always on the magnetic axis. This naturally suggests an identification of theθ+and theθ−regions with the core and conal emission zones.

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43

Klose, Thomas, i Michael G. Rossmann. "Structure of large dsDNA viruses". Biological Chemistry 395, nr 7-8 (1.07.2014): 711–19. http://dx.doi.org/10.1515/hsz-2014-0145.

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Abstract Nucleocytoplasmic large dsDNA viruses (NCLDVs) encompass an ever-increasing group of large eukaryotic viruses, infecting a wide variety of organisms. The set of core genes shared by all these viruses includes a major capsid protein with a double jelly-roll fold forming an icosahedral capsid, which surrounds a double layer membrane that contains the viral genome. Furthermore, some of these viruses, such as the members of the Mimiviridae and Phycodnaviridae have a unique vertex that is used during infection to transport DNA into the host.

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44

Brentano, Liana, Diana L. Noah, Earl G. Brown i Barbara Sherry. "The Reovirus Protein μ2, Encoded by the M1 Gene, Is an RNA-Binding Protein". Journal of Virology 72, nr 10 (1.10.1998): 8354–57. http://dx.doi.org/10.1128/jvi.72.10.8354-8357.1998.

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ABSTRACT The reovirus M1, L1, and L2 genes encode proteins found at each vertex of the viral core and are likely to form a structural unit involved in RNA synthesis. Genetic analyses have implicated the M1 gene in viral RNA synthesis and core nucleoside triphosphatase activity, but there have been no direct biochemical studies of μ2 function. Here, we expressed μ2 in vitro and assessed its RNA-binding activity. The expressed μ2 binds both poly(I-C)- and poly(U)-Sepharose, and binding activity is greater in Mn2+ than in Mg2+. Heterologous RNA competes for μ2 binding to reovirus RNA transcripts as effectively as homologous reovirus RNA does, providing no evidence for sequence-specific RNA binding by μ2. Protein μ2 is now the sixth reovirus protein demonstrated to have RNA-binding activity.

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45

GAO, PU. "The Firstk-Regular Subgraph is Large". Combinatorics, Probability and Computing 23, nr 3 (7.04.2014): 412–33. http://dx.doi.org/10.1017/s0963548314000169.

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Let$(G_m)_{0\le m\le \binom{n}{2}}$be the random graph process starting from the empty graph on vertex set [n] and with a random edge added in each step. Letmkdenote the minimum integer such thatGmkcontains ak-regular subgraph. We prove that for all sufficiently largek, there exist two constants εk≥ σk> 0, with εk→ 0 ask→ ∞, such that asymptotically almost surely anyk-regular subgraph ofGmkhas size between (1 − εk)|${\mathcal C}_k$| and (1 − σk)|${\mathcal C}_k$|, where${\mathcal C}_k$denotes thek-core ofGmk.

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46

Stockinger, G., H.-T. Janka, D. Kresse, T. Melson, T. Ertl, M. Gabler, A. Gessner i in. "Three-dimensional models of core-collapse supernovae from low-mass progenitors with implications for Crab". Monthly Notices of the Royal Astronomical Society 496, nr 2 (15.06.2020): 2039–84. http://dx.doi.org/10.1093/mnras/staa1691.

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ABSTRACT We present 3D full-sphere supernova simulations of non-rotating low-mass (∼9 M⊙) progenitors, covering the entire evolution from core collapse through bounce and shock revival, through shock breakout from the stellar surface, until fallback is completed several days later. We obtain low-energy explosions (∼0.5–1.0 × 1050 erg) of iron-core progenitors at the low-mass end of the core-collapse supernova (LMCCSN) domain and compare to a super-AGB (sAGB) progenitor with an oxygen–neon–magnesium core that collapses and explodes as electron-capture supernova (ECSN). The onset of the explosion in the LMCCSN models is modelled self-consistently using the vertex-prometheus code, whereas the ECSN explosion is modelled using parametric neutrino transport in the prometheus-HOTB code, choosing different explosion energies in the range of previous self-consistent models. The sAGB and LMCCSN progenitors that share structural similarities have almost spherical explosions with little metal mixing into the hydrogen envelope. A LMCCSN with less second dredge-up results in a highly asymmetric explosion. It shows efficient mixing and dramatic shock deceleration in the extended hydrogen envelope. Both properties allow fast nickel plumes to catch up with the shock, leading to extreme shock deformation and aspherical shock breakout. Fallback masses of $\mathord {\lesssim }\, 5\, \mathord {\times }\, 10^{-3}$ M⊙ have no significant effects on the neutron star (NS) masses and kicks. The anisotropic fallback carries considerable angular momentum, however, and determines the spin of the newly born NS. The LMCCSN model with less second dredge-up results in a hydrodynamic and neutrino-induced NS kick of >40 km s−1 and a NS spin period of ∼30 ms, both not largely different from those of the Crab pulsar at birth.

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47

COUDERT, DAVID, FREDERIC GIROIRE i IGNASI SAU. "CIRCUITS IN GRAPHS THROUGH A PRESCRIBED SET OF ORDERED VERTICES". Journal of Interconnection Networks 11, nr 03n04 (wrzesień 2010): 121–41. http://dx.doi.org/10.1142/s0219265910002763.

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A circuit in a simple undirected graph G = (V, E) is a sequence of vertices {v1, v2, …, vk+1} such that v1 = vk+1 and {vi, vi+1} ∈ E for i = 1, …, k. A circuit C is said to be edge-simple if no edge of G is used twice in C. In this article we study the following problem: which is the largest integer k such that, given any subset of k ordered vertices of a graph G, there exists an edge-simple circuit visiting the k vertices in the prescribed order? We first study the case when G has maximum degree at most 3, establishing the value of k for several subcases, such as when G is planar or 3-vertex-connected. Our main result is that k = 10 in infinite square grids. To prove this, we introduce a methodology based on the notion of core graph, in order to reduce the number of possible vertex configurations, and then we test each one of the resulting configurations with an Integer Linear Program (ILP) solver.

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48

Melson, Tobias, Hans-Thomas Janka, Alexander Summa, Robert Bollig, Andreas Marek i Bernhard Müller. "Exploring the explosion mechanism of core-collapse supernovae in three dimensions". Proceedings of the International Astronomical Union 12, S329 (listopad 2016): 424. http://dx.doi.org/10.1017/s1743921317001181.

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AbstractWe present the first successful simulations of neutrino-driven supernova explosions in three dimensions (3D) using the Vertex-Prometheus code including sophisticated energy-dependent neutrino transport. The simulated models of 9.6 and 20 solar-mass iron-core stars demonstrate that successful explosions can be obtained in self-consistent 3D simulations, where previous models have failed. New insights into the supernova mechanism can be gained from these explosions. The first 3D model (Melson et al. 2015a) explodes at the same time but more energetically than its axially symmetric (2D) counterpart. Turbulent energy cascading reduces the kinetic energy dissipation in the cooling layer and therefore suppresses neutrino cooling. The consequent inward shift of the gain radius increases the gain layer mass, whose recombination energy provides the surplus for the explosion energy.The second explosion (Melson et al. 2015b) is obtained through a moderate reduction of the neutral-current neutrino opacity motivated by strange-quark contributions to the nucleon spin. A corresponding reference model without these corrections failed, which demonstrates how close current 3D models are to explosion. The strangeness adjustment is meant as a prototype for remaining neutrino opacity uncertainties.

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49

Silvestry, Mariena, Steffen Lindert, Jason G. Smith, Oana Maier, Christopher M. Wiethoff, Glen R. Nemerow i Phoebe L. Stewart. "Cryo-Electron Microscopy Structure of Adenovirus Type 2 Temperature-Sensitive Mutant 1 Reveals Insight into the Cell Entry Defect". Journal of Virology 83, nr 15 (20.05.2009): 7375–83. http://dx.doi.org/10.1128/jvi.00331-09.

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ABSTRACT The structure of the adenovirus type 2 temperature-sensitive mutant 1 (Ad2ts1) was determined to a resolution of 10 Å by cryo-electron microscopy single-particle reconstruction. Ad2ts1 was prepared at a nonpermissive temperature and contains the precursor forms of the capsid proteins IIIa, VI, and VIII; the core proteins VII, X (mu), and terminal protein (TP); and the L1-52K protein. Cell entry studies have shown that although Ad2ts1 can bind the coxsackievirus and Ad receptor and undergo internalization via αv integrins, this mutant does not escape from the early endosome and is targeted for degradation. Comparison of the Ad2ts1 structure to that of mature Ad indicates that Ad2ts1 has a different core architecture. The Ad2ts1 core is closely associated with the icosahedral capsid, a connection which may be mediated by preproteins IIIa and VI. Density within hexon cavities is assigned to preprotein VI, and membrane disruption assays show that hexon shields the lytic activity of both the mature and precursor forms of protein VI. The internal surface of the penton base in Ad2ts1 appears to be anchored to the core by interactions with preprotein IIIa. Our structural analyses suggest that these connections to the core inhibit the release of the vertex proteins and lead to the cell entry defect of Ad2ts1.

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50

Thakral, Preston P., Kevin P. Madore, Sarah E. Kalinowski i Daniel L. Schacter. "Modulation of hippocampal brain networks produces changes in episodic simulation and divergent thinking". Proceedings of the National Academy of Sciences 117, nr 23 (26.05.2020): 12729–40. http://dx.doi.org/10.1073/pnas.2003535117.

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Prior functional magnetic resonance imaging (fMRI) studies indicate that a core network of brain regions, including the hippocampus, is jointly recruited during episodic memory, episodic simulation, and divergent creative thinking. Because fMRI data are correlational, it is unknown whether activity increases in the hippocampus, and the core network more broadly, play a causal role in episodic simulation and divergent thinking. Here we employed fMRI-guided transcranial magnetic stimulation (TMS) to assess whether temporary disruption of hippocampal brain networks impairs both episodic simulation and divergent thinking. For each of two TMS sessions, continuous θ-burst stimulation (cTBS) was applied to either a control site (vertex) or to a left angular gyrus target region. The target region was identified on the basis of a participant-specific resting-state functional connectivity analysis with a hippocampal seed region previously associated with memory, simulation, and divergent thinking. Following cTBS, participants underwent fMRI and performed a simulation, divergent thinking, and nonepisodic control task. cTBS to the target region reduced the number of episodic details produced for the simulation task and reduced idea production on divergent thinking. Performance in the control task did not statistically differ as a function of cTBS site. fMRI analyses revealed a selective and simultaneous reduction in hippocampal activity during episodic simulation and divergent thinking following cTBS to the angular gyrus versus vertex but not during the nonepisodic control task. Our findings provide evidence that hippocampal-targeted TMS can specifically modulate episodic simulation and divergent thinking, and suggest that the hippocampus is critical for these cognitive functions.

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