THE KAUST Repository is an initiative of the University Library to expand the impact of conference papers, technical reports, peer-reviewed articles, preprints, theses, images, data sets, and other research-related works of King Abdullah University of Science and Technology (KAUST). 

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  • Remobilization of Heavy Metals by Mangrove Leaves

    Almahasheer, Hanan; Serrano, Oscar; Duarte, Carlos M.; Irigoien, Xabier (Frontiers Media SA, 2018-12-13)
    Several studies have been carried out on heavy metal pollution in mangrove ecosystems. However, the role of mangroves in heavy metal remobilization is still relatively unknown. On one side, mangrove woody organs and soils sequester heavy metals for long time periods, but on the other hand, senescence of mangrove leaves may return these metals collected by roots to the upper layers of the soil. Here, we analyzed the concentration of chemical elements (Al, As, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sr, V, and Zn) as a function of age in mangrove leaves to understand heavy metals retention by the plant and to quantify the amounts shed with senescing leaves. In addition, we estimated metal concentrations and stocks in mangrove soils. Our results revealed that the concentration of most metals increased with leaf age, resulting in the remobilization of metals stored in soil, thereby returning metals to the upper layers of the soil during senescence of mangrove leaves. Only Cu was reabsorbed prior to shedding of leaves, a mechanism similar to that described for nutrients in mangroves globally. These results provide key data to understand mangroves role in the dynamics of heavy metals.
  • Enhanced Reactivity of Aluminum Complexes Containing P-Bridged Biphenolate Ligands in Ring-Opening Polymerization Catalysis

    Zou, Xue-Ru; Chang, Yu-Ning; Huang, Kuo-Wei; Liang, Lan-Chang (Frontiers Media SA, 2018-12-13)
    Aluminum complexes containing [RP(O)(2-O-3,5-tBu2C6H2)2]2− [R = tBu (3a), Ph (3b)] have been synthesized, structurally characterized, and their reactivity studied in comparison with those of their [RP(2-O-3,5-tBu2C6H2)2]2− [R = tBu (2a), Ph (2b)] analogs. Treating AlMe3 with one equiv of H2[3a-b] in THF at 0°C affords quantitatively [3a-b]AlMe, subsequent reactions of which with benzyl alcohol in THF at 25°C generate {[3a-b]Al(μ2-OCH2Ph)}2. The methyl [3a-b]AlMe and the benzyloxide {[3a-b]Al(μ2-OCH2Ph)}2 are all active for catalytic ring-opening polymerization (ROP) of ε-caprolactone and rac-lactide (rac-LA). Controlled experiments reveal that {[3a]Al(μ2-OCH2Ph)}2 is competent in living polymerization. Kinetic studies indicate that [3a]AlMe, in the presence of benzyl alcohol, catalyzes ROP of rac-LA at a rate faster than [3b]AlMe and [2a]AlMe(THF) by a factor of 1.8 and 23.6, respectively, highlighting the profound reactivity enhancement in ROP catalysis by varying the P-substituents of these biphenolate complexes of aluminum.
  • Multiscale and Multimodal Analysis for Computational Biology

    Gao, Xin; Chen, Jake Y.; Zaki, Mohammed J. (Institute of Electrical and Electronics Engineers (IEEE), 2018-12-13)
    The papers in this special section were presented at the 16th International Workshop on Data Mining in Bioinformatics (BIOKDD17). The BIOKDD17 Workshop was organized in conjunction with the ACM SIGKDD International Conference on Knowledge Discovery and Data Mining on August 14, 2017 in Halifax, Canada. It brought together international researchers in the interacting disciplines of data mining, medical informatics, and bioinformatics at the World Trade and Convention Centre venue. The goal of this workshop is to encourage Knowledge Discovery and Data mining (KDD) researchers to take on the numerous challenges that bioinformatics offers. Bioinformatics is the science of managing, mining, and interpreting information from biological data. Various genome projects have contributed to an exponential growth in DNA and protein sequence databases. Rapid advances in high-throughput technologies, such as microarrays, mass spectrometry, and new/next-generation sequencing, can monitor quantitatively the presence or activity of thousands of genes, RNAs, proteins, metabolites, and compounds in a given biological state. The ongoing influx of these data, the pressing need to address complex biomedical challenges, and the gap between the two have collectively created exciting opportunities for data mining researchers.
  • Intra-Season Crop Height Variability at Commercial Farm Scales Using a Fixed-Wing UAV

    Ziliani, Matteo; Parkes, Stephen; Hoteit, Ibrahim; McCabe, Matthew (MDPI AG, 2018-12-12)
    Monitoring the development of vegetation height through time provides a key indicator of crop health and overall condition. Traditional manual approaches for monitoring crop height are generally time consuming, labor intensive and impractical for large-scale operations. Dynamic crop heights collected through the season allow for the identification of within-field problems at critical stages of the growth cycle, providing a mechanism for remedial action to be taken against end of season yield losses. With advances in unmanned aerial vehicle (UAV) technologies, routine monitoring of height is now feasible at any time throughout the growth cycle. To demonstrate this capability, five digital surface maps (DSM) were reconstructed from high-resolution RGB imagery collected over a field of maize during the course of a single growing season. The UAV retrievals were compared against LiDAR scans for the purpose of evaluating the derived point clouds capacity to capture ground surface variability and spatially variable crop height. A strong correlation was observed between structure-from-motion (SfM) derived heights and pixel-to-pixel comparison against LiDAR scan data for the intra-season bare-ground surface (R2 = 0.77 − 0.99, rRMSE = 0.44% − 0.85%), while there was reasonable agreement between canopy comparisons (R2 = 0.57 − 0.65, rRMSE = 37% − 50%). To examine the effect of resolution on retrieval accuracy and processing time, an evaluation of several ground sampling distances (GSD) was also performed. Our results indicate that a 10 cm resolution retrieval delivers a reliable product that provides a compromise between computational cost and spatial fidelity. Overall, UAV retrievals were able to accurately reproduce the observed spatial variability of crop heights within the maize field through the growing season and provide a valuable source of information with which to inform precision agricultural management in an operational context.
  • Desert plant bacteria reveal host influence and beneficial plant growth properties

    Eida, Abdul Aziz; Ziegler, Maren; Lafi, Feras Fawzi; Michell, Craig; Voolstra, Christian R.; Hirt, Heribert; Saad, Maged (Public Library of Science (PLoS), 2018-12-12)
    Deserts, such as those found in Saudi Arabia, are one of the most hostile places for plant growth. However, desert plants are able to impact their surrounding microbial community and select beneficial microbes that promote their growth under these extreme conditions. In this study, we examined the soil, rhizosphere and endosphere bacterial communities of four native desert plants Tribulus terrestris, Zygophyllum simplex, Panicum turgidum and Euphorbia granulata from the Southwest (Jizan region), two of which were also found in the Midwest (Al Wahbah area) of Saudi Arabia. While the rhizosphere bacterial community mostly resembled that of the highly different surrounding soils, the endosphere composition was strongly correlated with its host plant phylogeny. In order to assess whether any of the native bacterial endophytes might have a role in plant growth under extreme conditions, we analyzed the properties of 116 cultured bacterial isolates that represent members of the phyla Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. Our analysis shows that different strains have highly different biochemical properties with respect to nutrient acquisition, hormone production and growth under stress conditions. More importantly, eleven of the isolated strains could confer salinity stress tolerance to the experimental model plant Arabidopsis thaliana suggesting some of these plant-associated bacteria might be useful for improving crop desert agriculture.

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