Shared Edge Research Articles

Structure of Single-Crystal Rutile (TiO2) Prepared by High-Temperature Ultracentrifugation

We report the preparation of single-crystal rutile (TiO2) with a unique structure prepared by ultracentrifugation at high temperature (strong gravitational field). Single-crystal rutile was subjected along the c-axis direction to a gravitational field of 0.4 × 106 G at 400 °C, and the uniquely structured single-crystal rutile, which did not conform to Pauling’s third rule, was quenched at ambient conditions. The anisotropy (a/c ratio) of the tetragonal phase increased by 2%. The (Ti–Oa)/(Ti–Ob) and Os/Ou ratios increased by 1.6% and 3%, respectively, and approached 1; Ti–Oa and Ti–Ob are the two Ti–O interatomic distances, and Os and Ou are the shared edge Oa–Oa and the unshared edge Oa–Ob, respectively. This means that the TiO6 octahedral group became isotropic. Os was expanded from its normal size, in contradiction to the usual laws, by the strong gravitational force. Such a structural change has not previously been achieved under high-pressure or high-temperature conditions, and may be related to struc...

Geometry Clipmaps Terrain Rendering Using Hardware Tessellation

Due to heavy rendering load and unstable frame rate when rendering large terrain, this paper proposes a geometry clipmaps based algorithm. Triangle meshes are generated by few tessellation control points in GPU tessellation shader. ‘Cracks’ caused by different resolution between adjacent levels are eliminated by modifying outer tessellation level factor of shared edges between levels. Experimental results show the algorithm is able to improve rendering efficiency and frame rate stability in terrain navigation.

A Bayesian Approach for Learning Gene Networks Underlying Disease Severity in COPD.

In this paper, we propose a Bayesian hierarchical approach to infer network structures across multiple sample groups where both shared and differential edges may exist across the groups. In our approach, we link graphs through a Markov random field prior. This prior on network similarity provides a measure of pairwise relatedness that borrows strength only between related groups. We incorporate the computational efficiency of continuous shrinkage priors, improving scalability for network estimation in cases of larger dimensionality. Our model is applied to patient groups with increasing levels of chronic obstructive pulmonary disease severity, with the goal of better understanding the break down of gene pathways as the disease progresses. Our approach is able to identify critical hub genes for four targeted pathways. Furthermore, it identifies gene connections that are disrupted with increased disease severity and that characterize the disease evolution. We also demonstrate the superior performance of our approach with respect to competing methods, using simulated data.

Crystal chemistry and X-ray diffraction patterns for Co(NixZn1−x)Nb4O12(x= 0.2, 0.4, 0.6, 0.8)

X-ray reference powder patterns and structures have been determined for a series of cobalt-, nickel- and zinc-containing niobates, Co(NixZn1−x)Nb4O12(x= 0.2, 0.4, 0.6, 0.8). The Co(NixZn1−x)Nb4O12series crystallize in the space group ofPbcn, which is of the disordered columbite-type structure (α-PbO2). The lattice parameters range froma= 14.11190(13) to 14.1569(3) Å,b= 5.69965(6) to 5.71209(13) Å,c= 5.03332(5) to 5.03673(11) Å, andV= 404.844(8) to 407.296(17) Å3fromx= 0.8 to 0.2, respectively. Co(NixZn1−x)Nb4O12contains double zig-zag chains of NbO6octahedra and single chain of (Ni,Zn,Co)O6octahedra run parallel to thebc-plane. Within the same chain the NbO6octahedra share edges, while the adjacent NbO6chains are joined to each other through common oxygen corners. These double NbO6chains are further linked together along the [100]-direction through another (Co,Ni,Zn)O6units, via common oxygen corners. The edge-sharing (Co,Ni,Zn)O6also forms zig-zag chains along thec-axis. Powder X-ray diffraction patterns of this series of compounds have been submitted to be included in the Powder Diffraction File.

Crystal structure of Sr5Te4O12(OH)2, the first basic strontium oxotellurate(IV).

The asymmetric unit of the title basic strontium oxotellurate(IV), Sr5Te4O12(OH)2 {systematic name penta-strontium tetra-kis-[oxotellurate(IV)] di-hydroxide}, comprises three SrII cations (one with site symmetry 2) and two TeIV atoms, as well as seven O atoms. The coordination numbers of the alkaline earth cations to nearby O atoms range from seven (2 ×) to eight, and the TeIV atoms are surrounded by three oxygen partners in the form of trigonal pyramids. The SrO x polyhedra share corners and edges to build up a three-dimensional framework structure encapsulating channels propagating along [010]. The TeIV atoms flank the framework O atoms and are situated at the outer array of the channels with the 5s2 lone electron pairs protruding into the empty space of the channels (diameter ≃ 4 Å). Although the H atom of the OH group could not be located, bond-valence-sum calculations and typical O⋯O distances (range 2.81-3.06 Å) clearly indicate hydrogen bonding of medium to weak strengths.

Identification of large disjoint motifs in biological networks.

BackgroundBiological networks provide great potential to understand how cells function. Network motifs, frequent topological patterns, are key structures through which biological networks operate. Finding motifs in biological networks remains to be computationally challenging task as the size of the motif and the underlying network grow. Often, different copies of a given motif topology in a network share nodes or edges. Counting such overlapping copies introduces significant problems in motif identification.ResultsIn this paper, we develop a scalable algorithm for finding network motifs. Unlike most of the existing studies, our algorithm counts independent copies of each motif topology. We introduce a set of small patterns and prove that we can construct any larger pattern by joining those patterns iteratively. By iteratively joining already identified motifs with those patterns, our algorithm avoids (i) constructing topologies which do not exist in the target network (ii) repeatedly counting the frequency of the motifs generated in subsequent iterations. Our experiments on real and synthetic networks demonstrate that our method is significantly faster and more accurate than the existing methods including SUBDUE and FSG.ConclusionsWe conclude that our method for finding network motifs is scalable and computationally feasible for large motif sizes and a broad range of networks with different sizes and densities. We proved that any motif with four or more edges can be constructed as a join of the small patterns.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-016-1271-7) contains supplementary material, which is available to authorized users.

Transformational Leadership, Psychological Capital and Front-line Sales Staffs’ Service Quality: Psychological Capital as a Mediator

Confronting diverse working pressure during office time, front-line sales staffs’ service quality will be threatened, which can affect customers’ satisfaction and loyalty degree, then influence market share and competitive edge of the company further. Thus, this paper focuses on the front-line sales staffs and aims at identifying the influence mechanism of transformational leadership on their service quality and the role of psychological capital among the triadic relationship. The result of hierarchy regression analysis about 250 sample data showed that both transformational leadership and psychological capital had significantly positive effect on front-line sales staffs’ service quality, while psychological capital acted as mediator between transformational leadership and front-line sales staffs’ service quality. Organizational management is advised to adopt transformational leadership and promote the employees’ level of psychological capital so as to improve the service quality of front-line sales staffs and the entire company.

Synthesis, crystal structure, and optical property of the quaternary chalcohalide Ba4Sb3S8Cl

The quaternary chalcohalide Ba4Sb3S8Cl has been prepared from stoichiometric mixtures of BaCl2, Ba, Sb, and S at 1093K in an evacuated silica tube. Ba4Sb3S8Cl crystallizes in the monoclinic P21/c space group and features a 0D structure containing totally isolated [SbS3]3− units and discrete SbS2Cl trigonal pyramids separated by Ba2+ cations. The [SbS3]3− units and SbS2Cl trigonal pyramids are further packed in a pseudolayer motif in bc plane, respectively. The [SbS3]3− units are built by dimeric Sb2S6 polyhedras and SbS3 trigonal pyramids. Within the dimeric Sb2S6 polyhedra, two SbS4 seesaws share edges, while two SbS3 trigonal pyramids share corners with dimeric Sb2S6 polyhedra. The optical gap of 2.09eV for Ba4Sb3S8Cl was deduced from the UV/Vis reflectance spectroscopy.

Gradient cuts and extremal edges in relative depth and figure-ground perception.

Extremal edges (EEs) are borders consisting of luminance gradients along the projected edge of a partly self-occluding curved surface (e.g., a cylinder), with equiluminant contours (ELCs) that run approximately parallel to that edge. Gradient cuts (GCs) are similar luminance gradients with ELCs that intersect (are "cut" by) an edge that could be due to occlusion. EEs are strongly biased toward being seen as closer/figural surfaces (Palmer & Ghose, Psychological Science, 19(1), 77-83, 2008). Do GCs produce a complementary bias toward being seen as ground? Experiment 1 shows that, with EEs on the opposite side, GCs produce a ground bias that increases with increasing ELC angles between ELCs and the shared edge. Experiment 2 shows that, with flat surfaces on the opposite side, GCs do not produce a ground bias, suggesting that more than one factor may be operating. We suggest that two partially dissociable factors may operate for curved surfaces-ELC angle and 3-D surface convexity-that reinforce each other in the figural cues of EEs but compete with each other in GCs. Moreover, this figural bias is modulated by the presence of EEs and GCs, as specified by the ELC angle between ELCs and the shared contour.

Characterization of an inorganic-organic hybrid polyoxomolybdate (C6H18N2)2[H2Mo7O24]•7H2O

A novel inorganic-organic hybrid salt, hexanediammonium heptamolybdate (C6H18N2)2[H2Mo7O24]•7H2O has been synthesized and characterized by elemental analyses, IR, TGA, cyclic voltammetry, UV and X-ray single crystal diffraction. It crystallizes in triclinic space group P-1 with a = 10.0619(2) A, b = 12.059(2) A, c = 20.044(3) A, α = 97.06(1)°, β = 91.56(1)°, γ = 110.59(2)° and Z = 2. The crystal structure shows that seven MoO6 distorted octahedra share edges which have four ranges of Mo–O bond distances. The heptamolybdate anion of the crystal has approximate mm2 point symmetry and its structure is similar to that observed in other heptamolybdates. The titled compound consists of the protonated hexanediamine cations and the inorganic [H2Mo7O24]4– oxomolybdate anions, linked by hydrogen-bonding interactions.

Drawing Partially Embedded and Simultaneously Planar Graphs

We investigate the problem of constructing planar drawings with few bends for two related problems, the partially embedded graph problem-to extend a straight-line planar drawing of a subgraph to a planar drawing of the whole graph-and the simultaneous planarity problem-to find planar drawings of two graphs that coincide on shared vertices and edges. In both cases we show that if the required planar drawings exist, then there are planar drawings with a linear number of bends per edge and, in the case of simultaneous planarity, with a number of crossings between any pair of edges which is bounded by a constant. Our proofs provide efficient algorithms if the combinatorial embedding of the drawing is given. Our result on partially embedded graph drawing generalizes a classic result by Pach and Wenger which shows that any planar graph can be drawn with a linear number of bends per edge if the location of each vertex is fixed.

The minimum vulnerability problem on specific graph classes

Suppose that each edge e of an undirected graph G is associated with three nonnegative integers $$\mathsf{cost}(e)$$cost(e), $$\mathsf{vul}(e)$$vul(e) and $$\mathsf{cap}(e)$$cap(e), called the cost, vulnerability and capacity of e, respectively. Then, we consider the problem of finding $$k$$k paths in G between two prescribed vertices with the minimum total cost; each edge e can be shared without any cost by at most $$\mathsf{vul}(e)$$vul(e) paths, and can be shared by more than $$\mathsf{vul}(e)$$vul(e) paths if we pay $$\mathsf{cost}(e)$$cost(e), but cannot be shared by more than $$\mathsf{cap}(e)$$cap(e) paths even if we pay the cost for e. This problem generalizes the disjoint path problem, the minimum shared edges problem and the minimum edge cost flow problem for undirected graphs, and it is known to be NP-hard. In this paper, we study the problem from the viewpoint of specific graph classes, and give three results. We first show that the problem is NP-hard even for bipartite outerplanar graphs, 2-trees, graphs with pathwidth two, complete bipartite graphs, and complete graphs. We then give a pseudo-polynomial-time algorithm for bounded treewidth graphs. Finally, we give a fixed-parameter algorithm for chordal graphs when parameterized by the number $$k$$k of required paths.

Jointly optimized QoS-aware virtualization and routing in software defined networks

Software Defined Networks (SDNs) have been recognized as the next-generation networking paradigm that decouples the network control plane from the data forwarding plane. A logically centralized controller is responsible for all the control decisions and communication among the forwarding switches. However, current traffic engineering techniques and state-of-the-art routing algorithms do not effectively use the merits of SDNs, such as global centralized visibility, control and data plane decoupling, network management simplification and great computation capability. In this paper, a multi-tenancy management framework is proposed to enable the jointly optimized design of quality-of-services (QoSs)-aware virtualization and routing by tenant isolation and prioritization as well as flow allocation, fulfilling QoS requirements of tenants’ applications. Specifically, a fine-grained network virtualization is first proposed to isolate and prioritize tenants through the design of network and switch hypervisors. Furthermore, a QoS-aware dynamic flow allocation is proposed to enable optimal flow routes selection upon the given network slicing with QoS provisioning. Finally, an adaptive feedback management tool, called QoS-aware Virtualization-enabled Routing (QVR), is proposed to combine virtualization with flow allocation and supports reliable and efficient transmissions with regards of time-varying QoS requirements, network topologies, and traffic statistics. Simulations confirm that QVR achieves much less shared edges, congestion latency, and traffic delay for multiple tenants, thus facilitating virtualization-enabled traffic engineering for multi-tenancy SDNs.

Crystal structure of post-perovskite-type CaIrO3 reinvestigated: new insights into atomic thermal vibration behaviors.

Single crystals of the title compound, the post-perovskite-type CaIrO3 [calcium iridium(IV) trioxide], have been grown from a CaCl2 flux at atmospheric pressure. The crystal structure consists of an alternate stacking of IrO6 octa-hedral layers and CaO8 hendeca-hedral layers along [010]. Chains formed by edge-sharing of IrO6 octa-hedra (point-group symmetry 2/m..) run along [100] and are inter-connected along [001] by sharing apical O atoms to build up the IrO6 octa-hedral layers. Chains formed by face-sharing of CaO8 hendeca-hedra (point-group symmetry m2m) run along [100] and are inter-connected along [001] by edge-sharing to build up the CaO8 hendeca-hedral layers. The IrO6 octa-hedral layers and CaO8 hendeca-hedral layers are inter-connected by sharing edges. The present structure refinement using a high-power X-ray source confirms the atomic positions determined by Hirai et al. (2009 ▸) [Z. Kristallogr. 224, 345-350], who had revised our previous report [Sugahara et al. (2008 ▸). Am. Mineral. 93, 1148-1152]. However, the displacement ellipsoids of the Ir and Ca atoms based on the present refinement can be approximated as uniaxial ellipsoids elongating along [100], unlike those reported by Hirai et al. (2009 ▸). This suggests that the thermal vibrations of the Ir and Ca atoms are mutually suppressed towards the Ir⋯Ca direction across the shared edge because of the dominant repulsion between the two atoms.

One-dimensional decavanadate chains in the crystal structure of Rb4[Na(H2O)6][HV10O28]·4H2O.

New decavanadate minerals, the products of the leaching or metasomatic processes, are possible in nature via Na/Rb removal/inclusion reactions. As part of our search for novel vanadate phases with varying functionalities, a new phase, tetrarubidium hexaaquasodium hydrogen decavanadate tetrahydrate, Rb4[Na(H2O)6][HV10O28]·4H2O, has been synthesized by the hydrothermal technique at 553 K. Ten shared edges of V-centred octahedra form monoprotonated decavanadate cages, which are joined together via hydrogen bonds into one-dimensional chains parallel to the [101] direction. Within these chains, H atoms are sandwiched between neighbouring polyanions. Na and Rb atoms and H2O molecules occupy interstices flanked by the anionic chains providing additional crosslinking in the structure. This compound is the second decavanadate with P2/n symmetry. Structural relationships among protonated and deprotonated decavanadates with inorganic cations, including minerals of the pascoite group, are discussed.

Cyclic Diamondoid Structures with Shared Vertices, Edges, or 6-membered Rings

Cyclic Diamondoid Structures with Shared Vertices, Edges, or 6-membered Rings

ChemInform Abstract: Thermal Expansion in C2/C Pyroxenes: A Review and New High‐Temperature Structural Data for a Pyroxene of Composition (Na0.53Ca0.47) (Al0.53Fe0.47)Si2O6 (Jd53Hd47)

AbstractReview: 40 refs.

Joint reconstruction of PET-MRI by exploiting structural similarity

Recent advances in technology have enabled the combination of positron emission tomography (PET) with magnetic resonance imaging (MRI). These PET-MRI scanners simultaneously acquire functional PET and anatomical or functional MRI data. As function and anatomy are not independent of one another the images to be reconstructed are likely to have shared structures. We aim to exploit this inherent structural similarity by reconstructing from both modalities in a joint reconstruction framework. The structural similarity between two modalities can be modelled in two different ways: edges are more likely to be at similar positions and/or to have similar orientations. We analyse the diffusion process generated by minimizing priors that encapsulate these different models. It turns out that the class of parallel level set priors always corresponds to anisotropic diffusion which is sometimes forward and sometimes backward diffusion. We perform numerical experiments where we jointly reconstruct from blurred Radon data with Poisson noise (PET) and under-sampled Fourier data with Gaussian noise (MRI). Our results show that both modalities benefit from each other in areas of shared edge information. The joint reconstructions have less artefacts and sharper edges compared to separate reconstructions and the ℓ2-error can be reduced in all of the considered cases of under-sampling.

Identifying common components across biological network graphs using a bipartite data model.

The GeneWeaver bipartite data model provides an efficient means to evaluate shared molecular components from sets derived across diverse species, disease states and biological processes. In order to adapt this model for examining related molecular components and biological networks, such as pathway or gene network data, we have developed a means to leverage the bipartite data structure to extract and analyze shared edges. Using the Pathway Commons database we demonstrate the ability to rapidly identify shared connected components among a diverse set of pathways. In addition, we illustrate how results from maximal bipartite discovery can be decomposed into hierarchical relationships, allowing shared pathway components to be mapped through various parent-child relationships to help visualization and discovery of emergent kernel driven relationships. Interrogating common relationships among biological networks and conventional GeneWeaver gene lists will increase functional specificity and reliability of the shared biological components. This approach enables self-organization of biological processes through shared biological networks.

Preface Algorithms and Computation (ISAAC 2012)

This special issue ofAlgorithmica contains extended versions of selected contributions to The 23rd International Symposium on Algorithms and Computation (ISAAC 2012) held in Taipei, Taiwan, on December 19–21, 2012. The mission of the ISAAC series is to provide a top-notch forum for researchers working in algorithms and theory of computation. The ISAAC 2012 Program Committee selected 68 papers for oral presentation out of 174 high-quality submissions from 33 countries. Among those presented papers, the following three papers in Algorithms have been selected in this special issue. They went through a standard review process of Algorithmica. The paper “A framework for succinct labeled ordinal trees over large alphabets” considers succinct representations of labeled ordinal trees that are able to handle large alphabets. The new representations also provide a much broader collection of operations than previous work. The paper “The minimum vulnerability problem” considers the problem of finding k paths with a minimum number of shared edges between two vertices of a graph. The authors present several interesting algorithms including a k/2-approximation algorithm, improving the best previous approximation factor of k − 1.