• Biomimetic Coating-free Superomniphobicity.

      Das, Ratul; Ahmad, Zain; Nauruzbayeva, Jamilya; Mishra, Himanshu (Scientific reports, Springer Science and Business Media LLC, 2020-05-15) [Article]
      Superomniphobic surfaces, which repel droplets of  polar and apolar liquids, are used for reducing frictional drag, packaging electronics and foods, and separation processes, among other applications. These surfaces exploit perfluorocarbons that are expensive, vulnurable to physical damage, and have a long persistence in the environment. Thus, new approaches for achieving superomniphobicity from common materials are desirable. In this context, microtextures comprising "mushroom-shaped" doubly reentrant pillars (DRPs) have been shown to repel drops of polar and apolar liquids in air irrespective of the surface make-up. However, it was recently demonstrated that DRPs get instantaneously infiltrated by the same liquids on submersion because while they can robustly prevent liquid imbibition from the top, they are vulnerable to lateral imbibition. Here, we remedy this weakness through bio-inspiration derived from cuticles of Dicyrtomina ornata, soil-dwelling bugs, that contain cuboidal secondary granules with mushroom-shaped caps on each face. Towards a proof-of-concept demonstration, we created a perimeter of biomimicking pillars around arrays of DRPs using a two-photon polymerization technique; another variation of this design with a short wall passing below the side caps was investigated. The resulting gas-entrapping microtextured surfaces (GEMS) robustly entrap air on submersion in wetting liquids, while also exhibiting superomniphobicity in air. To our knowledge, this is the first-ever microtexture that confers upon intrinsically wetting materials the ability to simultaneously exhibit superomniphobicity in air and robust entrapment of air on submersion. These findings should advance the rational design of coating-free surfaces that exhibit ultra-repellence (or superomniphobicity) towards liquids.
    • Minimum Net Driving Temperature Concept for Membrane Distillation

      Blankert, Bastiaan; Vrouwenvelder, Johannes S.; Witkamp, Geert Jan; Ghaffour, NorEddine (Membranes, MDPI AG, 2020-05-14) [Article]
      <jats:p>In this study, we analyzed the heat requirement of membrane distillation (MD) to investigate the trade-off between the evaporation efficiency and driving force efficiency in a single effect MD system. We found that there exists a non-zero net driving temperature difference that maximizes efficiency. This is the minimum net driving temperature difference necessary for a rational operational strategy because below the minimum net driving temperature, both the productivity and efficiency can be increased by increasing the temperature difference. The minimum net driving temperature has a similar magnitude to the boiling point elevation (~0.5 °C for seawater), and depends on the properties of the membrane and the heat exchanger. The minimum net driving temperature difference concept can be used to understand the occurrence of optimal values of other parameters, such as flux, membrane thickness, and membrane length, if these parameters are varied in a way that consequently varies the net driving temperature difference.</jats:p>
    • Photovoltaic panel cooling by atmospheric water sorption–evaporation cycle

      Li, Renyuan; Shi, Yusuf; Wu, Mengchun; Hong, Seunghyun; Wang, Peng (Nature Sustainability, Springer Science and Business Media LLC, 2020-05-11) [Article]
      More than 600 GW of photovoltaic panels are currently installed worldwide, with the predicted total capacity increasing very rapidly every year. One essential issue in photovoltaic conversion is the massive heat generation of photovoltaic panels under sunlight, which represents 75–96% of the total absorbed solar energy and thus greatly increases the temperature and decreases the energy efficiency and lifetime of photovoltaic panels. In this report we demonstrate a new and versatile photovoltaic panel cooling strategy that employs a sorption-based atmospheric water harvester as an effective cooling component. The atmospheric water harvester photovoltaic cooling system provides an average cooling power of 295 W m–2 and lowers the temperature of a photovoltaic panel by at least 10 °C under 1.0 kW m–2 solar irradiation in laboratory conditions. It delivered a 13–19% increase in electricity generation in a commercial photovoltaic panel in outdoor field tests conducted in the winter and summer in Saudi Arabia. The atmospheric water harvester based photovoltaic panel cooling strategy has little geographical constraint in terms of its application and has the potential to improve the electricity production of existing and future photovoltaic plants, which can be directly translated into less CO2 emission or less land occupation by photovoltaic panels. As solar power is taking centre stage in the global fight against climate change, atmospheric water harvester based cooling represents an important step toward sustainability.
    • Superhydrophobicity and size reduction enabled Halobates (Insecta: Heteroptera, Gerridae) to colonize the open ocean

      Mahadik, G. A.; Hernandez Sanchez, Jose Federico; Arunachalam, Sankara; Gallo, A.; Cheng, L.; Farinha, A. S.; Thoroddsen, Sigurdur T; Mishra, Himanshu; Duarte, Carlos M. (Scientific Reports, Springer Science and Business Media LLC, 2020-05-08) [Article]
      Despite the remarkable evolutionary success of insects at colonizing every conceivable terrestrial and aquatic habitat, only five Halobates (Heteroptera: Gerridae) species (~0.0001% of all known insect species) have succeeded at colonizing the open ocean – the largest biome on Earth. This remarkable evolutionary achievement likely required unique adaptations for them to survive and thrive in the challenging oceanic environment. For the first time, we explore the morphology and behavior of an open-ocean Halobates germanus and a related coastal species H. hayanus to understand mechanisms of these adaptations. We provide direct experimental evidence based on high-speed videos which reveal that Halobates exploit their specialized and self-groomed body hair to achieve extreme water repellence, which facilitates rapid skating and plastron respiration under water. Moreover, the grooming behavior and presence of cuticular wax aids in the maintenance of superhydrophobicity. Further, reductions of their body mass and size enable them to achieve impressive accelerations (~400 ms−2) and reaction times (~12 ms) to escape approaching predators or environmental threats and are crucial to their survival under harsh marine conditions. These findings might also inspire rational strategies for developing liquid-repellent surfaces for drag reduction, water desalination, and preventing bio-fouling.
    • ECOSTRESS: NASA's Next Generation Mission to Measure Evapotranspiration From the International Space Station

      Fisher, Joshua B.; Lee, Brian; Purdy, Adam J.; Halverson, Gregory H.; Dohlen, Matthew B.; Cawse-Nicholson, Kerry; Wang, Audrey; Anderson, Ray G.; Aragon Solorio, Bruno Jose Luis; Arain, M. Altaf; Baldocchi, Dennis D.; Baker, John M.; Barral, Hélène; Bernacchi, Carl J.; Bernhofer, Christian; Biraud, Sébastien C.; Bohrer, Gil; Brunsell, Nathaniel; Cappelaere, Bernard; Castro-Contreras, Saulo; Chun, Junghwa; Conrad, Bryan J.; Cremonese, Edoardo; Demarty, Jérôme; Desai, Ankur R.; De Ligne, Anne; Foltýnová, Lenka; Goulden, Michael L.; Griffis, Timothy J.; Grünwald, Thomas; Johnson, Mark S.; Kang, Minseok; Kelbe, Dave; Kowalska, Natalia; Lim, Jong Hwan; Maïnassara, Ibrahim; McCabe, Matthew; Missik, Justine E.C.; Mohanty, Binayak P.; Moore, Caitlin E.; Morillas, Laura; Morrison, Ross; Munger, J. William; Posse, Gabriela; Richardson, Andrew D.; Russell, Eric S.; Ryu, Youngryel; Sanchez-Azofeifa, Arturo; Schmidt, Marius; Schwartz, Efrat; Sharp, Iain; Šigut, Ladislav; Tang, Yao; Hulley, Glynn; Anderson, Martha; Hain, Christopher; French, Andrew; Wood, Eric F.; Hook, Simon (Water Resources Research, American Geophysical Union (AGU), 2020-04-06) [Article]
      The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) was launched to the International Space Station on 29 June 2018 by the National Aeronautics and Space Administration (NASA). The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as Level-3 (L3) latent heat flux (LE) data products. These data are generated from the Level-2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear-sky ET product (L3_ET_PT-JPL, Version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear-sky instantaneous/time of overpass: r2 = 0.88; overall bias = 8%; normalized root-mean-square error, RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are overrepresented. The 70-m-high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1-km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data.
    • A molecular to macro level assessment of direct contact membrane distillation for separating organics from water

      Pillai, Sreekiran; Santana, Adriano; Das, Ratul; Shrestha, Buddha R.; Manalastas, Edelberto; Mishra, Himanshu (Journal of Membrane Science, Elsevier BV, 2020-04-12) [Article]
      The removal of water-soluble organics from aqueous feeds is required in numerous practical applications, including bioresource processing, fermentation, and wastewater treatment. To this end, direct contact membrane distillation (DCMD) has been proposed as a separation technology. DCMD utilizes hydrophobic membranes – typically, comprising perfluorocarbons – which, when placed between a warm feed and a cold permeate, prevent mixing due to the robust entrapment of air inside the (membranes') pores. Thus, the membranes allow only pure water vapor to transport across, following the thermal gradient. Here, we assessed DCMD for separating organics from aqueous feeds in light of organic fouling by utilizing ethanol and perfluorodecyltrichlorosilane (FDTS) as the surrogate organic and hydrophobic coating, respectively. We investigated the adsorption of ethanol onto FDTS-grafted surfaces and membranes exposed to alcohol-water mixtures. Using the surface force apparatus, we found that the magnitude of hydrophobic forces between ultra-smooth FDTS-grafted mica surfaces in water-alcohol mixtures decreased with the increasing alcohol content. To simulate a practical DCMD scenario, we utilized FDTS-grafted polycarbonate membranes to separate a pure water reservoir from another containing 0.6 M NaCl and alcohol. For the 0% alcohol case, the membranes robustly separated the reservoirs for over a week, whereas even for ≥0.1% ethanol content, the membranes leaked within <5 h. After the leakage, the membranes’ hydrophobicity could not be recovered by rinsing them with pure water and blow-drying; a heat treatment at 363 K for 1 h proved to be successful, however. Our molecular dynamics simulations revealed that ethanol molecules in water got preferentially stabilized at the interfaces of water and hydrophobic surfaces. Furthermore, this stabilization is significantly enhanced at higher alcohol concentrations due to the emergence of II-D interfacial networks comprising adsorbed alcohol molecules. Thus, this micro to macro-scale assessment demonstrates that DCMD with hydrophobic membranes is not suitable for separating organics from water, even at low alcohol concentrations. We also compare the efficacies of apparent advancing and receding contact angles towards a reliable characterization of fouled surfaces.
    • The role of topography, soil, and remotely sensed vegetation condition towards predicting crop yield

      Franz, Trenton E.; Pokal, Sayli; Gibson, Justin P.; Zhou, Yuzhen; Gholizadeh, Hamed; Tenorio, Fatima Amor; Rudnick, Daran; Heeren, Derek; McCabe, Matthew; Ziliani, Matteo; Jin, Zhenong; Guan, Kaiyu; Pan, Ming; Gates, John; Wardlow, Brian (Field Crops Research, Elsevier BV, 2020-04-27) [Article]
      Foreknowledge of the spatiotemporal drivers of crop yield would provide a valuable source of information to optimize on-farm inputs and maximize profitability. In recent years, an abundance of spatial data providing information on soils, topography, and vegetation condition have become available from both proximal and remote sensing platforms. Given the wide range of data costs (between USD $0−50/ha), it is important to understand where often limited financial resources should be directed to optimize field production. Two key questions arise. First, will these data actually aid in better fine-resolution yield prediction to help optimize crop management and farm economics? Second, what level of priority should stakeholders commit to in order to obtain these data? Before fully addressing these questions a remaining challenge is the complex nature of spatiotemporal yield variation. Here, a methodological framework is presented to separate the spatial and temporal components of crop yield variation at the subfield level. The framework can also be used to quantify the benefits of different data types on the predicted crop yield as well to better understand the connection of that data to underlying mechanisms controlling yield. Here, fine-resolution (10 m) datasets were assembled for eight 64 ha field sites, spanning a range of climatic, topographic, and soil conditions across Nebraska. Using Empirical Orthogonal Function (EOF) analysis, we found the first axis of variation contained 60–85 % of the explained variance from any particular field, thus greatly reducing the dimensionality of the problem. Using Multiple Linear Regression (MLR) and Random Forest (RF) approaches, we quantified that location within the field had the largest relative importance for modeling crop yield patterns. Secondary factors included a combination of vegetation condition, soil water content, and topography. With respect to predicting spatiotemporal crop yield patterns, we found the RF approach (prediction RMSE of 0.2−0.4 Mg/ha for maize) was superior to MLR (0.3−0.8 Mg/ha). While not directly comparable to MLR and RF the EOF approach had relatively low error (0.5–1.7 Mg/ha) and is intriguing as it requires few calibration parameters (2–6 used here) and utilizes the climate-based aridity index, allowing for pragmatic long-term predictions of subfield crop yield.
    • Extracellular electron transfer-dependent anaerobic oxidation of ammonium by anammox bacteria

      Shaw, Dario R.; Ali, Muhammad; Katuri, Krishna; Gralnick, Jeffrey A.; Reimann, Joachim; Mesman, Rob; van Niftrik, Laura; Jetten, Mike S. M.; Saikaly, Pascal (Nature Communications, Island Press, 2020-04-28) [Article]
      Anaerobic ammonium oxidation (anammox) bacteria contribute significantly to the global nitrogen cycle and play a major role in sustainable wastewater treatment. Anammox bacteria convert ammonium (NH4+) to dinitrogen gas (N2) using intracellular electron acceptors such as nitrite (NO2−) or nitric oxide (NO). However, it is still unknown whether anammox bacteria have extracellular electron transfer (EET) capability with transfer of electrons to insoluble extracellular electron acceptors. Here we show that freshwater and marine anammox bacteria couple the oxidation of NH4+ with transfer of electrons to insoluble extracellular electron acceptors such as graphene oxide or electrodes in microbial electrolysis cells. 15N-labeling experiments revealed that NH4+ was oxidized to N2 via hydroxylamine (NH2OH) as intermediate, and comparative transcriptomics analysis revealed an alternative pathway for NH4+ oxidation with electrode as electron acceptor. Complete NH4+ oxidation to N2 without accumulation of NO2− and NO3− was achieved in EET-dependent anammox. These findings are promising in the context of implementing EET-dependent anammox process for energy-efficient treatment of nitrogen.
    • Habitat maps to enhance monitoring and management of the Great Barrier Reef

      Roelfsema, Chris M.; Kovacs, Eva M.; Ortiz, Juan Carlos; Callaghan, David P.; Hock, Karlo; Mongin, Mathieu; Johansen, Kasper; Mumby, Peter J.; Wettle, Magnus; Ronan, Mike; Lundgren, Petra; Kennedy, Emma V.; Phinn, Stuart R. (Coral Reefs, Springer Science and Business Media LLC, 2020-04-09) [Article]
      The Great Barrier Reef (GBR) is of immense biological, cultural and economic importance, but has also rapidly degraded over the last 30 years. Improved spatial information on reef geomorphic zonation and benthic cover type (including coral type) is critical to support scientific work to understand how the GBR is changing, and to support resource management decisions that enable conservation of the reef and its essential ecosystem services. Yet, no comprehensive maps exist that detail the geomorphic zonation or benthic cover for the GBR’s ~ 3000 reefs. This study presents three new types of shallow reef maps for 237 reefs in the central Cairns Management Region of the GBR Marine Park (GBRMP), explores how the detailed habitat maps created compared to current maps and posits how the new maps may support and refine current critical key science outputs and management challenges. Geomorphic Zonation, Benthic Cover and Coral Type habitat maps were created using a unique combined object-based image analysis and ecological modelling approach that incorporated satellite imagery, limited field data and key reef physical attributes (depth, slope, waves) using a previously peer-reviewed mapping approach developed for the Capricorn Bunker Group reefs, Southern GBR. The mapping approach was consistent and repeatable, suggesting applicability to mapping all 3000 reefs in the GBRMP. Compared to existing maps that only outline each reef, the increase in detail provided by these new habitat maps enabled discrete characterisation of each reef’s geomorphology and benthic composition. With the new habitat maps, areas within each reef can be identified as either coral habitat or not coral habitat. This has not been possible previously. As such, a model of coral ecological and biophysical processes that depends on bottom reflectance of sand and coral areas can be fine-tuned. Similarly, for reef restoration, nursery structures are commonly placed in non-coral habitats, and/or coral larvae are dispersed in areas of known coral habitat. The new habitat maps presented permit more accurate identification of these areas such that restoration projects can be targeted more effectively. These findings confirm the need to now apply this mapping approach to the full extent of the GBR.
    • Evaluating the effect of hydraulic retention time on fouling development and biomass characteristics in an algal membrane photobioreactor treating a secondary wastewater effluent.

      Novoa, Andres Felipe; Fortunato, Luca; Rehman, Zahid Ur; Leiknes, TorOve (Bioresource technology, Elsevier BV, 2020-04-19) [Article]
      Coupling algal biomass growth to wastewater treatment is a promising alternative for the simultaneous removal and recovery of nutrients. This study aims to evaluate the effects of the Hydraulic Retention Time (HRT) on the fouling behavior and biomass characteristics of C. Vulgaris in a Membrane Photobioreactor (MPBR), fed with a secondary synthetic wastewater effluent. The changes in the algal cell characteristics and in their metabolic products were assessed at three different HRTs (12 h, 24 h and 36 h). Experimental results showed that higher loading rates led to a broader Particle Size Distribution (PSD) resulting from looser and less stable algal flocs. In contrast, bigger and homogeneously distributed particles observed at lower loading rates, led to a porous layer with lower fouling rates and organic removal. The presence of smaller particles and dissolved organics resulted in a more compact and less porous layer that increased the removal of small-MW organics.
    • Water Pass: The Aquaporin ZmPIP2:5 Contributes to Water Transport at the Gatekeeper Cells.

      Julkowska, Magdalena M. (Plant physiology, American Society of Plant Biologists (ASPB), 2020-04-08) [Article]
      Water transport is essential for many physiological processes in vascular plants. One of the forces driving water transport across roots is provided by the tension created by transpiration from the shoot, which extends to the root xylem. On the cellular level, water can be transported between cells through plasmodesmata (symplastic path), intercellular spaces (apoplastic path), or across membranes (transcellular path). Water follows the path of least resistance, which often means flowing through the apoplast and usually hydrophilic cell walls (Steudle and Frensch, 1996). When the water arrives at the exodermal or endodermal layer, where the Casparian strip makes the cell wall hydrophobic, it is forced to move through the transcellular path, which relies on the membrane-localized aquaporins. Aquaporins are small membrane proteins that form channels permeable to water and other small uncharged molecules. Plant aquaporins are a large family of proteins that vary in their subcellular localization and site of expression (Deshmukh et al., 2016). While aquaporin abundance in the membrane is regulated through posttranscriptional modifications (Santoni, 2017), it is still unclear how individual aquaporins contribute to the overall hydraulic conductivity of the plant. Ding et al. (2020) explored how the most abundant maize (Zea mays) root aquaporin, ZmPIP2;5, affects hydraulic conductance at the cell, root, and leaf levels using knockout and overexpression lines. Overexpression of ZmPIP2;5 increased hydraulic conductivity of individual cells (cortical cells and mesophyll protoplasts) but did not increase hydraulic conductivity of the entire root (Ding et al., 2020). This discrepancy between cell and tissue hydraulic conductivity was hypothesized to be due to the nonuniform water permeability of individual cell layers. While ZmPIP2;5 is expressed in all root cells, its expression is enriched in the gatekeeper cells of endodermis and exodermis (Hachez et al., 2006). Assuming that the aquaporin abundance at these gatekeeper cells is the limiting factor for radial water conductivity, the increased expression in other cell types is not likely to contribute to the overall root conductivity. The above hypothesis was examined using the model of explicit cross-section hydraulic architecture (MECHA; Couvreur et al., 2018), which integrates, among others, root anatomy and plasma membrane conductivity to predict the root’s radial hydraulic conductivity. A MECHA where the aquaporin abundance is already saturated in the gatekeeper cells, but not in other cell types, predicted that overexpression of the aquaporins in the entire root will not additionally increase the root conductivity. Interestingly, MECHA also predicted a significant reduction in the overall root conductivity, which was observed for the knockout lines. Because hydraulic conductivity changes in response to external factors, the plant’s water use efficiency can be compromised under stress conditions. Therefore, Ding et al. (2020) examined the leaf elongation rate under moderate water deficit conditions. Interestingly, overexpression lines showed increased leaf elongation rate compared with wild-type plants, suggesting increased leaf water permeability. This effect on leaf elongation rate was not observed in knockout lines, possibly because ZmPIP2;5 is not expressed in shoot tissue under normal conditions. The gatekeeper cells in the leaf are the suberized cells around the vasculature, which usually express different aquaporin genes, not ZmPIP2;5 (Hachez et al., 2008). Although vascular aquaporins have previously been associated with increased water use efficiency (Sade and Moshelion, 2017), experimental evidence for fine-tuned expression of aquaporins in stress tolerance under controlled or field conditions has yet to be demonstrated. The work by Ding et al. (2020) opens up new possibilities, suggesting the importance of tissue-specific overexpression of aquaporins in gatekeeper cells for more fine-tuned modification of hydraulic conductance and more crop per drop.
    • Tuning to the Signal of Stress: Subcellular Regulation of Abscisic Acid Receptor Abundance by E3 Ubiquitin Ligases.

      Julkowska, Magdalena M. (Plant physiology, American Society of Plant Biologists (ASPB), 2020-04-08) [Article]
      Developmental and environmental changes are communicated systemically throughout the plant by various signals, ranging from electric currents to plant hormones. As the responses elicited by the systemic signals depend on the tissue and subcellular context, the signal needs to be adjusted at every scale, which can be achieved by regulating the abundance of receptor proteins (Guerra and Callis 2012). Regulation of hormone receptor abundance controls the magnitude of the response to hormones. Numbers of hormone receptors are reduced by tagging with ubiquitin residues, which targets the receptor proteins for degradation (Kelley and Estelle 2012). Once the protein is ubiquitinylated, degradation can proceed either through the 26S proteasome (Stone 2014) or the endosomal sorting complex required for transport (Gao et al., 2017). The ubiquitin tag is added to the substrate protein through the coordinated action of E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme, and E3 ubiquitin ligase (Shu and Yang, 2017). The perception of the stress-related abscisic acid (ABA) hormone was previously found to be regulated by the E3 ligase RING FINGER OF SEED LONGEVITY (RSL1; Belda-Palazon et al., 2016). RSL1 protein carries a C-terminal transmembrane domain, which tethers the E3 ligase to the plasma membrane, where it decorates ABA receptors PYR1 and PYL1 with ubiquitin tags (Bueso et al., 2014), initiating degradation in the vacuole mediated by the endosomal sorting complex required for transport (Belda-Palazon et al., 2016). While the Arabidopsis (Arabidopsis thaliana) genome contains 10 members of the RSL1/RFA (RING finger ABA-related) family, their contribution to the regulation of ABA receptor abundance is unknown. In the current issue of Plant Physiology, Fernandez et al. (2020) examine other members of RSL1/RFA family for their potential roles in regulating ABA perception. The group examined five members of the family (RFA1–RFA5), which lacked the C-terminal transmembrane domain. The in silico study of transcript abundance revealed that RFA1 and RFA4 were expressed in the same tissues and conditions as the ABA receptors, suggesting possible interactions between the RFAs and PYR/PYL. Fernandez et al. (2020) showed that both E3 ligases were interacting with ABA receptors using split yellow fluorescent protein/luciferase and pull-down assays. While RFA4 interacted with ABA receptors exclusively in the nucleus, the interaction between ABA receptors and RFA1 was observed in the nucleus and the cytosol. The yeast two-hybrid screen for the partner E2 ligase revealed that UBIQUITIN CONJUGATING ENZYME 26 (UBC26) interacts with RFA4 and ABA receptors in the nucleus. As expected, the ubc26 and rfl1/4 mutant lines showed higher levels of the PYR/PYL receptor proteins and were hypersensitive to ABA. However, ABA treatment still induced the degradation of ABA receptors in rfl1/4 mutant lines, revealing that the receptor level is regulated by multiple pathways working in parallel. The work by Fernandez et al. (2020) shows that ABA receptor turnover is regulated by multiple E3 ubiquitin ligases: RSL1 targets the ABA receptors at the plasma membrane, RFA1 targets the nuclear and cytosolic PYL/PYR proteins, and RFA4 exclusively targets nuclear ABA receptors. The interactions between hormone receptors, E3, and E2 ligases illustrate the complexity of hormone signaling cascades, where the hormone perception can be modulated not only at the tissue level but at the subcellular level, by regulating the receptor abundance. Tapping into this complexity between the ABA receptors and the E3 ubiquitin ligases might be an exciting target in future breeding programs for increased resilience of plants to biotic and abiotic stressors, finetuning the plant’s stress response without compromising plant performance under nonstress conditions
    • Aquaponics water use and nutrient cycling in a seawater-cooled controlled environment agriculture system

      Lefers, Ryan; Alam, A.; Scarlett, F.; Leiknes, TorOve (International Society for Horticultural Science (ISHS), 2020-03-18) [Conference Paper]
      To demonstrate the water use efficiency and nutrient cycling of an aquaponics system in combination with a seawater based evaporative cooling system, a pilot-scale aquaponics unit was installed and operated for one year inside a controlled environment agriculture building cooled by the evaporation of seawater on the campus of King Abdullah University of Science and Technology in Thuwal, Saudi Arabia. Results collected from the operation included crop water use, water quality parameters, dissolved ion concentrations, outdoor/indoor climate data and crop output. Seawater-based evaporative cooling did not provide adequate indoor temperatures for the cultivation of lettuce during the hot and humid summer season. However, the combined aquaponics with seawater evaporative cooling was effective for fall, winter, and spring cultivation with a mixed crop of lettuce and tomatoes. Opposite to the vegetable production cycle, higher water temperature in the summer favored the production of Sabaki tilapia during the warm summer season rather than the cool winter season. Because of this dichotomy, the system showed promise for management and nutrient balancing on an annual basis rather than on seasonal or daily basis. From a fresh water use perspective, the average daily fresh water use by plants totaled only 4.6 L day-1 m-2 or 19 L kg-1 of crop harvested during the peak winter/spring growing season. Results demonstrated that an aquaponics system in combination with seawater-based evaporative cooling is capable of saving ~90% of fresh water as compared with traditional forms of agriculture in the region.
    • Membrane filtration performance enhancement and biofouling mitigation using symmetric spacers with helical filaments

      Kerdi, Sarah; Qamar, Adnan; Alpatova, Alla; Vrouwenvelder, Johannes S.; Ghaffour, NorEddine (Desalination, Elsevier BV, 2020-04-02) [Article]
      Optimization of the feed spacer geometry is one of the key challenges for improved ultrafiltration performance in water treatment and desalination. Novel feed spacers with different number of helices (1-3) along the spacer filament are proposed. To elucidate the intrinsic ability of the helical feature on filtration process improvement, experiments were conducted at two different fluid inlet velocities (U0 = 0.166 m/s and 0.182 m/s). The presence of micro-helices in the filaments aids significantly in increasing the specific permeate flux when compared to the standard spacer (without helices). The highest improvement was observed in the case of 3-helical spacer (291% specific permeate flux increase at U0 = 0.182 m/s). Furthermore, Optical Coherence Tomography OCT) imaging demonstrated less (bio)fouling amount developed on membrane surface equipped with helical spacers, whereas, a thicker and more dense cake fouling layer appeared in the case of standard spacer. Moreover, novel helical design spacers reduce the pressure drop inside the channel. The 3-helical spacer was found to have the least feed-channel pressure drop (65% of decrease relative to standard spacer). Numerical analysis was simultaneously realized by the Direct Numerical Simulation (DNS) technique to understand the hydrodynamic behavior at an elemental level inside the filtration channel. Low shear stress and high local velocity magnitudes were observed in presence of helical spacers resulting in (bio)fouling mitigation on filtration membrane surface.
    • Online characterization of bacterial processes in drinking water systems

      Farhat, Nadia; Kim, Lan Hee; Vrouwenvelder, Johannes S. (npj Clean Water, Springer Science and Business Media LLC, 2020-03-27) [Article]
      The use of traditional drinking water microbial quality monitoring methods, including heterotrophic plate counts (HPCs) and total coliform counts, are not only laborious and time-consuming but also do not readily allow identification of risk areas in the network. Furthermore, if areas of concern are identified, and mitigation measures are taken, it takes days before the effectiveness of these measures is known. This study identified flow cytometry (FCM) as an online sensor technology for bacterial water quality monitoring in the distribution network. We monitored the total bacterial cell numbers and biodiversity in a drinking water distribution system (DWDS) using an online FCM. Two parallel online FCM monitoring systems were installed on two different locations at a drinking water treatment plant (DWTP; Saudi Arabia) supplying chlorinated water to the distribution and in the network 3.6 km away from the DWTP. The FCMs were operated at the same time in parallel to assess the biological stability in DWDSs. The flow cytometric data was compared with the conventional water quality detection methods (HPC and total coliforms). HPC and total coliforms were constantly below the detection limits, while the FCM provided detectable total cell count data and enabled the quantification of changes in the drinking water both with time and during distribution. Results demonstrate the value of FCM as a tool for compliance monitoring and risk assessment of DWDSs.
    • Nanoparticles applied in membrane bioreactors: Potential impact on reactor performance and microbial communities

      Cheng, Hong; Hong, Pei-Ying (Elsevier, 2019-11-03) [Book Chapter]
      Both aerobic and anaerobic membrane bioreactors (MBRs) are able to remove contaminants of emerging concern from wastewater at high efficiencies. However, the main bottleneck of this technology is membrane biofouling. Coating heavy metal nanoparticles on the surface of membrane has been proposed as an effective antifouling strategy. Nevertheless, metal nanoparticles can potentially result in detrimental impact on the overall functionality of the MBRs. This book chapter aims to understand how nanoparticles impact MBRs. To achieve this aim, the chapter starts off by illustrating the antibacterial mechanisms of nanoparticles. The chapter then critically reviews past studies that illustrate the antibacterial effect of nanoparticles against pure bacterial cultures and biofilm-associated populations. Finally, the chapter evaluates if the presence of nanoparticles would affect the overall performance of aerobic and anaerobic biological processes. Specifically, the impact of heavy metal nanoparticles on nitrogen and phosphorus removal process was discussed. The effect on anaerobic fermentation, which is comprised of hydrolysis, acidogenesis, acetogenesis, and methanogenesis, was also reviewed.
    • Mitigating cavitation erosion using biomimetic gas-entrapping microtextured surfaces (GEMS)

      Gonzalez-Avila, Silvestre Roberto; Nguyen, Dang Minh; Arunachalam, Sankara; Domingues, Eddy; Mishra, Himanshu; Ohl, Claus-Dieter (Science Advances, American Association for the Advancement of Science (AAAS), 2020-03-27) [Article]
      Cavitation refers to the formation and collapse of vapor bubbles near solid boundaries in high-speed flows, such as ship propellers and pumps. During this process, cavitation bubbles focus fluid energy on the solid surface by forming high-speed jets, leading to damage and downtime of machinery. In response, numerous surface treatments to counteract this effect have been explored, including perfluorinated coatings and surface hardening, but they all succumb to cavitation erosion eventually. Here, we report on biomimetic gas-entrapping microtextured surfaces (GEMS) that robustly entrap air when immersed in water regardless of the wetting nature of the substrate. Crucially, the entrapment of air inside the cavities repels cavitation bubbles away from the surface, thereby preventing cavitation damage. We provide mechanistic insights by treating the system as a potential flow problem of a multi-bubble system. Our findings present a possible avenue for mitigating cavitation erosion through the application of inexpensive and environmentally friendly materials.
    • Electroactive biofilms on surface functionalized anodes: the anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens

      Katuri, Krishna; Kamireddy, Sirisha; Kavanagh, Paul; Ali, Mohammad; Peter, Connolly; Kumar, Amit; Saikaly, Pascal; Leech, Donal (Cold Spring Harbor Laboratory, 2020-03-06) [Preprint]
      Surface chemistry is known to influence the formation, composition and electroactivity of electron-conducting biofilms with however limited information on the variation of microbial composition and electrochemical response during biofilm development to date. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (-NH2, -COOH and -OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (-C2H5). In addition, early-stage films formed on hydrophilic electrodes were dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominated on -C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential induced growth (~19 h followed by inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters.
    • Current Practices in UAS-based Environmental Monitoring

      Tmušić, Goran; Manfreda, Salvatore; Aasen, Helge; James, Mike R.; Gonçalves, Gil; Ben-Dor, Eyal; Brook, Anna; Polinova, Maria; Arranz, Jose Juan; Mészáros, János; Zhuang, Ruodan; Johansen, Kasper; Malbeteau, Yoann; de Lima, Isabel Pedroso; Davids, Corine; Herban, Sorin; McCabe, Matthew (Remote Sensing, MDPI AG, 2020-03-20) [Article]
      With the increasing role that unmanned aerial systems (UAS) are playing in data collection for environmental studies, two key challenges relate to harmonizing and providing standardized guidance for data collection, and also establishing protocols that are applicable across a broad range of environments and conditions. In this context, a network of scientists are cooperating within the framework of the Harmonious Project to develop and promote harmonized mapping strategies and disseminate operational guidance to ensure best practice for data collection and interpretation. The culmination of these efforts is summarized in the present manuscript. Through this synthesis study, we identify the many interdependencies of each step in the collection and processing chain, and outline approaches to formalize and ensure a successful workflow and product development. Given the number of environmental conditions, constraints, and variables that could possibly be explored from UAS platforms, it is impractical to provide protocols that can be applied universally under all scenarios. However, it is possible to collate and systematically order the fragmented knowledge on UAS collection and analysis to identify the best practices that can best ensure the streamlined and rigorous development of scientific products.
    • Thermo-economic analysis and optimization of a vacuum multi-effect membrane distillation system

      Chen, Qian; Muhammad, Burhan; Akhtar, Faheem; Ybyraiymkul, Doskhan; Muhammad, Wakil Shahzad; Li, Yong; Ng, Kim Choon (Desalination, Elsevier BV, 2020-03-12) [Article]
      Vacuum multi-effect membrane distillation is an advanced system that possesses the features and merits of vacuum membrane distillation and multi-effect distillation. It has low operating pressure and temperature, high levels of non-volatile rejection and high energy efficiency. This study presents a thermo-economic analysis and optimization of this novel system. A thermodynamic analysis is firstly conducted to evaluate the productivity and the energy consumption under varying design and operational conditions. Special emphases are placed on the impacts of the system configuration, including the number of effects and the overall membrane area, which are rarely covered in the literature. Results reveal that there is a trade-off between the production rate and the energy consumption with respect to most of the operating parameters, e.g. the feed flowrate and the cooling water flowrate. An increase in the number of effects and the membrane area will reduce the energy consumption, but the specific permeate flux for the unit membrane area also becomes lower. To obtain the optimal parameters that minimize the desalination cost, an economic study is then carried out considering a wide range of thermal energy prices. It is observed that a higher feed flowrate, more numbers of effects and larger membrane areas are preferable when the energy price is higher. However, when thermal energy with low prices is available, lower feed flowrates and smaller membrane areas are recommended. The derived results will provide useful information on the vacuum multi-effect membrane distillation system for its future design and operation.