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  • International Union of Crystallography (IUC)  (21)
  • Oxford University Press  (12)
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  • 1
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    International Union of Crystallography (IUC)
    Publication Date: 2015-08-13
    Description: In the title compound, C10H4Cl2O3, a dichlorinated 3-formylchromone, the non-H atoms of the 4H-chromene ring are essentially coplanar (r.m.s. = 0.0188 Å), with the largest deviation from the least-squares plane [0.043 (2) Å] being for the pyran C=O C atom. The α,β-unsaturated carbonyl O atom deviates from the least-square plane by 0.124 (2) Å. The dihedral angle between the chromone and formyl least-square planes is 6.76 (3)°. In the crystal, molecules are linked through C—H...O hydrogen bonds between the translation-symmetry and inversion-symmetry equivalents to form tetrads, which are further assembled by stacking interactions [centroid–centroid distance between the benzene rings = 3.769 (2) Å]. van der Waals contacts are found between the Cl atoms at the 6-position and the Cl atoms at 7-position of the glide-reflection-symmetry equivalents [Cl...Cl = 3.4785 (16) Å, C—Cl...Cl = 160.23 (7)° and Cl...Cl—C = 122.59 (7)°].
    Keywords: crystal structurechromonehydrogen bondinghalogen–halogen contactstacking interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 2
    Publication Date: 2016-06-24
    Description: Climate-driven changes in the marine ecosystem largely influence the distribution, abundance, and the consequent availability of marine resources to the fishery. In this study, we examined the potential habitat distributions of the neon flying squid ( Ommastrephes bartramii ) under the projected impacts of ocean warming. We used the sea surface temperature (SST) from the three CMIP5 climate scenarios (RCP4.5, RCP6.0, and RCP8.5) with the low to high future emissions. Based on the squid habitat models, SST showed the highest effect on the present potential squid habitat distribution that accounted for at least 60% of the predicted spatial patterns from May to July 2000–2010. This result underpinned the species' high sensitivity to the temperature changes in its feeding environments. Moreover, the projected future potential squid habitats revealed pronounced differences in the spatial and temporal patterns relative to the present habitat distributions across the different regions of the western and central North Pacific. The future squid habitat predictions revealed a net reduction in the suitable squid habitat coupled with the corresponding northward habitat retreat. Moreover, the magnitude of the predicted habitat changes was proportional to the levels of warming for the representative periods from May to July 2025, 2050, and 2100. The highest decrease in the spatial extent and poleward retreat of the potential squid habitat were observed from May to July 2100 under the RCP 8.5 scenario. These trends could translate to shorter squid fishing periods and offshore shifts of the squid fishing grounds. Thus, insights into the future spatio-temporal patterns and trajectories of the potential squid habitats could lend important implications on the availability of squid resources to the fishery and subsequent evaluation of squid fishery management options under climate change.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 3
    Publication Date: 2016-07-27
    Description: Neon flying squid ( Ommastrephes bartramii ) is a large pelagic squid internationally harvested in the North Pacific. Here, we examined its potential habitat in the central North Pacific using an ensemble modelling approach. Initially, ten statistical models were constructed by combining the squid fishing points, selected vertical layers of the sea temperature and salinity, sea surface height (SSH), and SSH gradient from the multi-variate ocean variational estimation system for the western North Pacific from June to July 1999–2011. The variable selection analyses have captured the importance of vertical temperature and salinity layers at the upper 300 and 440 m, respectively, coinciding with the reported vertical ranges of diel migration for the squid's primary prey species in the North Pacific. The evaluation of the habitat predictions using the independent sets of the presence data from 2012 to 2014 showed significant variability in the predictive accuracy, which is likely reflective of the interannual differences in environmental conditions across the validation periods. Our findings from ensemble habitat model approach using three-dimensional oceanographic data were able to characterize the near- and subsurface habitats of the neon flying squid. Moreover, our results underpinned the possible link between interannual environmental variability and spatio-temporal patterns of potential squid habitats. As such, these further suggest that an ensemble model approach could present a promising tool for operational fishery application and squid resource management.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 4
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    International Union of Crystallography (IUC)
    Publication Date: 2015-06-28
    Description: In the title compound, C10H4BrFO3, a brominated and fluorinated 3-formylchromone derivative, all atoms are essentially coplanar (r.m.s. deviation of 0.025 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.050 (6) Å] being for a benzene-ring C atom. In the crystal, molecules are linked through stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.912 (4) Å], C—H...O hydrogen bonds and short C...O contacts [2.865 (7) Å]. Unsymmetrical halogen...halogen interactions between the bromine and fluorine atoms [Br...F = 3.116 (4) Å, C—Br...F = 151.8 (2), C—F...Br = 154.1 (4)°] are also formed, giving a meandering two-dimensional network propagating in the (041) plane. A comparison with related structures is made and the various types of weak interactions are ranked in importance.
    Keywords: crystal structurechromonehydrogen bondinghalogen interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 5
    Publication Date: 2016-08-31
    Description: Graph is an increasingly popular way to model complex data, and the size of single graphs is growing toward massive. Nonetheless, executing graph algorithms efficiently and at scale is surprisingly challenging. As a consequence, distributed programming frameworks have emerged to empower large graph processing. Pregel, as a popular computational model for processing billion-vertex graphs, has been employed to improve the scalability of many algorithms. In this paper, we investigate frequent subgraph mining on single large graphs using Pregel. We present the first distributed algorithm based on Pregel for single massive graphs. In addition, two optimizations are proposed to enhance the algorithm, reducing communication cost and distribution overhead. Extensive experiments conducted on real-life data confirm the effectiveness and efficiency of the proposed algorithm and techniques.
    Print ISSN: 0010-4620
    Electronic ISSN: 1460-2067
    Topics: Computer Science
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  • 6
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    International Union of Crystallography (IUC)
    Publication Date: 2015-06-20
    Description: In the title compound, C10H8O3 (systematic name 3-hydroxymethyl-4H-chromen-4-one), the fused-ring system is slightly puckered [dihedral angle between the rings = 3.84 (11)°]. The hydroxy O atom deviates from the heterocyclic ring by 1.422 (1) Å. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate R22(12) loops. The dimers are linked by aromatic π–π stacking [shortest centroid–centroid distance = 3.580 (3) Å], and C—H...O hydrogen bonds, generating a three-dimensional network.
    Keywords: crystal structurechromonehydrogen bondingπ–π stacking
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 7
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    International Union of Crystallography (IUC)
    Publication Date: 2015-07-18
    Description: In the title compound, C10H6O4, also known as 3-carboxychromone, the non-H atoms of the chromone ring are essentially coplanar (r.m.s. deviation = 0.0057 Å), with the maximum deviation from their least-squares plane [0.011 (2) Å] being for a pyran C atom. The dihedral angle between the fused ring and plane of the carboxy group is 3.06 (2)°. An intramolecular hydrogen bond is formed between the ring carbonyl O atom and the carboxy O—H atom, closing an S(6) loop. In the crystal, molecules are assembled by stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.844 (3) Å] and C—H...O hydrogen bonds, generating a three-dimensional network. Short contacts are also observed between the carboxy O and C atoms [C=O...C=O = 3.002 (3) Å].
    Keywords: crystal structurechromonehydrogen bondingstacking interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 8
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    International Union of Crystallography (IUC)
    Publication Date: 2015-07-16
    Description: In the title compound, C10H5BrO3, a brominated 3-formylchromone, all atoms are essentially coplanar (r.m.s. = 0.0104 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.028 (5) Å] being for one of the benzene C atoms. In the crystal, molecules are linked through C—H...O hydrogen bonds, which are further assembled by face-to-face π–π stacking interactions [centroid–centroid distance between the pyran rings = 3.854 (4) Å]. Shorter contacts than the sum of van der Waals radii are observed between the Br and formyl O atoms [Br...O = 3.046 (4) Å, C—Br...O = 175.23 (18)° and Br...O—C = 132.6 (3)°], features that do indicate halogen bonding.
    Keywords: crystal structurechromonehydrogen bondinghalogen bondingπ–π stacking
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 9
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    International Union of Crystallography (IUC)
    Publication Date: 2015-07-09
    Description: In the title compound, C10H4Cl2O3, a dichlorinated 3-formylchromone derivative, the fused-ring system is slightly puckered [dihedral angle between the benzene and pyran rings = 3.66 (10)°]. The dihedral angle between the pyran ring and the formyl plane is 8.64 (7)°. In the crystal, molecules are linked through π–π stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.727 (2) Å], C—H...O hydrogen bonds and short C...O contacts [2.838 (4) Å]. Halogen bonds between the formyl O atoms and the Cl atoms at the 7-position [Cl...O = 2.984 (3) Å, C—Cl...O = 170.83 (12)° and Cl...O—C = 116.05 (19)°] are also formed along the a axis, resulting in helical structures constructed by C—H...O hydrogen bonds and Cl...O halogen bonds along the b axis. In addition, type II halogen–halogen contacts between the chlorine atoms at the 7- and 8-positions [Cl...Cl = 3.519 (2) Å, C–Cl...Cl = 171.24 (10)° and 88.74 (11)°] are observed.
    Keywords: crystal structureπ–π stackinghydrogen bondhalogen bondhalogen–halogen interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 10
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    International Union of Crystallography (IUC)
    Publication Date: 2015-07-01
    Description: In the title compound, C11H8O3, the fused-ring system is almost planar (r.m.s. deviation = 0.020 Å), with the largest deviation from the least-squares plane [0.0462 (17) Å] being for a pyran C atom. The dihedral angle between the plane of the fused-ring system and acetyl plane is 5.149 (16)°. In the crystal, the fused rings are linked by aromatic π–π stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.643 (6) Å] and C—H...O hydrogen bonds, generating a three-dimensional network.
    Keywords: crystal structurechromonehydrogen bondπ–π stacking
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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