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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Warming the phycosphere: differential effect of temperature on the use of diatom-derived carbon by two copiotrophic bacterial taxa.(Environmental microbiology, Wiley, 2020-02-25) [Article]Heterotrophic bacteria associated with microphytoplankton, particularly those colonizing the phycosphere, are major players in the remineralization of algal-derived carbon. Ocean warming might impact DOC uptake by microphytoplankton-associated bacteria with unknown biogeochemical implications. Here, by incubating natural seawater samples at 3 different temperatures we analyzed the effect of experimental warming on the abundance and C and N uptake activity of Rhodobacteraceae and Flavobacteria, two bacterial groups typically associated with microphytoplankton. Using NanoSIMS single-cell analysis we quantified the temperature-sensitivity of these two taxonomic groups to the uptake of algal-derived DOC in the microphytoplankton-associated fraction with 13 C-bicarbonate and 15 N-leucine as tracers. We found that cell-specific 13 C uptake was similar for both groups (~0.42 fg C h-1 μm-3 ), but Rhodobacteraceae were more active in 15 N-leucine uptake. Due to the higher abundance of Flavobacteria associated with microphytoplankton, this group incorporated 4-fold more carbon than Rhodobacteraceae. Cell-specific 13 C uptake was influenced by temperature, but no significant differences were found for 15 N-leucine uptake. Our results show that the contribution of Flavobacteria and Rhodobacteraceae to C assimilation increased up to 6-fold and 2-fold, respectively, with an increase of 3°C above ambient temperature, suggesting that warming may differently affect the contribution of distinct copiotrophic bacterial taxa to carbon cycling. This article is protected by copyright. All rights reserved.
Molecular enhancement of heterogeneous CO2 reduction(Nature Materials, Springer Science and Business Media LLC, 2020-02-25) [Article]The electrocatalytic carbon dioxide reduction reaction (CO2RR) addresses the need for storage of renewable energy in valuable carbon-based fuels and feedstocks, yet challenges remain in the improvement of electrosynthesis pathways for highly selective hydrocarbon production. To improve catalysis further, it is of increasing interest to lever synergies between heterogeneous and homogeneous approaches. Organic molecules or metal complexes adjacent to heterogeneous active sites provide additional binding interactions that may tune the stability of intermediates, improving catalytic performance by increasing Faradaic efficiency (product selectivity), as well as decreasing overpotential. We offer a forward-looking perspective on molecularly enhanced heterogeneous catalysis for CO2RR. We discuss four categories of molecularly enhanced strategies: molecular-additive-modified heterogeneous catalysts, immobilized organometallic complex catalysts, reticular catalysts and metal-free polymer catalysts. We introduce present-day challenges in molecular strategies and describe a vision for CO2RR electrocatalysis towards multi-carbon products. These strategies provide potential avenues to address the challenges of catalyst activity, selectivity and stability in the further development of CO2RR.
Biocompatible 3D Printed Microneedles for Transdermal, Intradermal, and Percutaneous Applications(Advanced Engineering Materials, Wiley, 2020-02-25) [Article]Microneedles (MNs) are playing an increasingly important role in biomedicalapplications, where minimally invasive methods are being developed that requireimperceptible tissue penetration and drug delivery. To improve the integration ofMNs in microelectromechanical devices, a high-resolution 3D printing techniqueis implemented. A reservoir with an array of hollow MNs is produced. Theflowrate through the MNs is simulated and measured experimentally. The mechan-ical properties of the 3D printed material, such as elasticity modulus and yieldstrength, are investigated as functions of printing parameters, reaching maxi-mum values of 1750.7 and 101.8 MPa, respectively. Analytical estimation of theMN buckling, fracture, and skin penetration forces is presented. Penetration testsof MNs into a skin-like material are conducted, where the piercing force rangesfrom 0.095 to 0.115 N, confirming sufficient stability of MNs. Furthermore, 200and 400μm-long MN arrays are used to successfully pierce and deliver intomouse skin with an average penetration depth of 100 and 180μm, respectively.A biocompatibility assessment is performed, showing a high viability of HCT 116cells cultured on top of the MN’s material, making the developed MNs a veryattractive solution for many biomedical applications
Extended preclinical investigation of lactate for neuroprotection after ischemic stroke(Clinical and Translational Neuroscience, SAGE Publications, 2020-02-24) [Article]Lactate has been shown to have beneficial effect both in experimental ischemia–reperfusion models and in human acute brain injury patients. To further investigate lactate’s neuroprotective action in experimental in vivo ischemic stroke models prior to its use in clinics, we tested (1) the outcome of lactate administration on permanent ischemia and (2) its compatibility with the only currently approved drug for the treatment of acute ischemic stroke, recombinant tissue plasminogen activator (rtPA), after ischemia–reperfusion. We intravenously injected mice with 1 µmol/g sodium l-lactate 1 h or 3 h after permanent middle cerebral artery occlusion (MCAO) and looked at its effect 24 h later. We show a beneficial effect of lactate when administered 1 h after ischemia onset, reducing the lesion size and improving neurological outcome. The weaker effect observed at 3 h could be due to differences in the metabolic profiles related to damage progression. Next, we administered 0.9 mg/kg of intravenous (iv) rtPA, followed by intracerebroventricular injection of 2 µL of 100 mmol/L sodium l-lactate to treat mice subjected to 35-min transient MCAO and compared the outcome (lesion size and behavior) of the combined treatment with that of single treatments. The administration of lactate after rtPA has positive influence on the functional outcome and attenuates the deleterious effects of rtPA, although not as strongly as lactate administered alone. The present work gives a lead for patient selection in future clinical studies of treatment with inexpensive and commonly available lactate in acute ischemic stroke, namely patients not treated with rtPA but mechanical thrombectomy alone or patients without recanalization therapy.
Improving the Thermodynamic Energy Efficiency of Battery Electrode Deionization Using Flow-Through Electrodes(Environmental Science & Technology, American Chemical Society (ACS), 2020-02-24) [Article]Ion intercalation electrodes are being investigated for use in mixed capacitive deionization (CDI) and battery electrode deionization (BDI) systems because they can achieve selective ion removal and low energy deionization. To improve the thermodynamic energy efficiency (TEE) of these systems, flow-through electrodes were developed by coating porous carbon felt electrodes with a copper hexacyanoferrate composite mixture. The TEE for ion separation using flow-through electrodes was compared to a system using flow-by electrodes with the same materials. The flow-through BDI system increased the recoverable energy nearly threefold (0.009 kWh m−3, compared to a 0.003 kWh m−3), which increased the TEE from ~6% to 8% (NaCl concentration reduction from 50 mM to 42 mM; 10 A m−2, 50% water recovery, and 0.5 mL min−1). The TEE was further increased to 12% by decreasing the flow rate from 0.50 mL min−1 to 0.25 mL min−1. These findings suggest that under similar operational conditions and materials, flow-through battery electrodes could achieve better energy recovery and TEE for desalination than flow-by electrodes.