catena-Poly[[tetra­aqua­zinc(II)]-μ-2,2′-dihydr­oxy-5,5′-diazenediyldibenzoato]

In the title compound, [Zn(C14H8N2O6)(H2O)4]n, the 2,2′-dihydr­oxy-5,5′-diazenediyldibenzoate ligand acts as a carboxyl­ate bridge, leading to the formation of a polymeric chain running along the [10] direction. The ZnII atom is hexa-coordinated in a distorted octa­hedral geometry by six O atoms [Zn—O = 2.055 (4)–2.132 (3) Å] from two carboxylate ligands and four water mol­ecules. The crystal packing is stabilized by inter­molecular O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, and two π–π inter­actions. The centroid–centroid distances are 3.803 (16) and 3.804 (17) Å

Off-diagonal low-rank preconditioner for difficult PageRank problems

PageRank problem is the cornerstone of Google search engine and is usually stated as solving a huge linear system. Moreover, when the damping factor approaches 1, the spectrum properties of this system deteriorate rapidly and this system becomes difficult to solve. In this paper, we demonstrate that the coefficient matrix of this system can be transferred into a block form by partitioning its rows into special sets. In particular, the off-diagonal part of the block coefficient matrix can be compressed by a simple low-rank factorization, which can be beneficial for solving the PageRank problem. Hence, a matrix partition method is proposed to discover the special sets of rows for supporting the low rank factorization. Then a preconditioner based on the low-rank factorization is proposed for solving difficult PageRank problems. Numerical experiments are presented to support the discussions and to illustrate the effectiveness of the proposed methods. (C) 2018 Elsevier B.V. All rights reserved

Geographical Origin Traceability of Red Wines Based on Chemometric Classification via Organic Acid Profiles

A preliminary study on the chemometric classification of red wines produced from different grape varieties and geographical origins was performed based on their chromatographic profiles of organic acids. Tartaric, malic, citric, lactic, acetic, and succinic acids in wines were detected via high performance liquid chromatography (HPLC). Employing multivariate statistical methods including principal component analysis (PCA) and linear discriminant analysis (LDA), pattern recognition models were built for the classification of the investigated wines regarding the grape varieties and geographical origins. The PCA clearly grouped the wines according to variety, and the LDA further offered 100% classification ability toward geographical identification of the wines and the leave-one-out cross-validated assignments were 100%, 86.7%, and 100% correct for Cabernet Sauvignon, Merlot, and Pinot Noir wines, respectively. The results reveal the potential of using chromatographic profiles of organic acid as the characteristic indices for chemometric classification of red wines

Bee-hawking by the wasp, Vespa velutina, on the honeybees Apis cerana and A. mellifera

The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively

Structure of the Macrobrachium rosenbergii nodavirus: a new genus within the Nodaviridae?

Macrobrachium rosenbergii nodavirus (MrNV) is a pathogen of freshwater prawns that poses a threat to food security and causes significant economic losses in the aquaculture industries of many developing nations. A detailed understanding of the MrNV virion structure will inform the development of strategies to control outbreaks. The MrNV capsid has also been engineered to display heterologous antigens, and thus knowledge of its atomic resolution structure will benefit efforts to develop tools based on this platform. Here, we present an atomic-resolution model of the MrNV capsid protein (CP), calculated by cryogenic electron microscopy (cryoEM) of MrNV virus-like particles (VLPs) produced in insect cells, and three-dimensional (3D) image reconstruction at 3.3 Å resolution. CryoEM of MrNV virions purified from infected freshwater prawn post-larvae yielded a 6.6 Å resolution structure, confirming the biological relevance of the VLP structure. Our data revealed that unlike other known nodavirus structures, which have been shown to assemble capsids having trimeric spikes, MrNV assembles a T = 3 capsid with dimeric spikes. We also found a number of surprising similarities between the MrNV capsid structure and that of the Tombusviridae: 1) an extensive network of N-terminal arms (NTAs) lines the capsid interior, forming long-range interactions to lace together asymmetric units; 2) the capsid shell is stabilised by 3 pairs of Ca2+ ions in each asymmetric unit; 3) the protruding spike domain exhibits a very similar fold to that seen in the spikes of the tombusviruses. These structural similarities raise questions concerning the taxonomic classification of MrNV

Green synthesis of biogenetic Te(0) nanoparticles by high tellurite tolerance fungus Mortierella sp. AB1 with antibacterial activity

Tellurite [Te(IV)] is a high-toxicity metalloid. In this study, a fungus with high Te(IV) resistance was isolated. Strain AB1 could efficiently reduce highly toxic Te(IV) to less toxic Te(0). The reduced products formed rod-shaped biogenetic Te(0) nanoparticles (Bio-TeNPs) intracellularly. Further TEM-element mapping, FTIR, and XPS analysis showed that the extracted Bio-TeNPs ranged from 100 to 500 nm and consisted of Te(0), proteins, lipids, aromatic compounds, and carbohydrates. Moreover, Bio-TeNPs exhibited excellent antibacterial ability against Shigella dysenteriae, Escherichia coli, Enterobacter sakazakii, and Salmonella typhimurium according to inhibition zone tests. Further growth and live/dead staining experiments showed that E. coli and S. typhimurium were significantly inhibited by Bio-TeNPs, and cells were broken or shriveled after treatment with Bio-TeNPs based on SEM observation. Additionally, the antioxidant and cytotoxicity tests showed that the Bio-TeNPs exhibited excellent antioxidant capacity with no cytotoxicity. All these results suggested that strain AB1 showed great potential in bioremediation and Bio-TeNPs were excellent antibacterial nanomaterials with no cytotoxicity.Peer reviewe