Recent Submissions

  • High summer temperatures amplify functional differences between coral- and algae-dominated reef communities

    Roth, Florian; Rädecker, Nils; Carvalho, Susana; Duarte, Carlos M.; Saderne, Vincent; Anton Gamazo, Andrea; Silva, Luis; Calleja Cortes, Maria de Lluch; Moran, Xose Anxelu G.; Voolstra, Christian R.; Kürten, Benjamin; Jones, Burton; Wild, Christian (Ecology, Wiley, 2020-10-17) [Article]
    Shifts from coral to algal dominance are expected to increase in tropical coral reefs as a result of anthropogenic disturbances. The consequences for key ecosystem functions such as primary productivity, calcification, and nutrient recycling are poorly understood, particularly under changing environmental conditions. We used a novel in situ incubation approach to compare functions of coral- and algae-dominated communities in the central Red Sea bi-monthly over an entire year. In situ gross and net community primary productivity, calcification, dissolved organic carbon fluxes, dissolved inorganic nitrogen fluxes, and their respective activation energies were quantified to describe the effects of seasonal changes. Overall, coral-dominated communities exhibited 30% lower net productivity and 10 times higher calcification than algae-dominated communities. Estimated activation energies indicated a higher thermal sensitivity of coral-dominated communities. In these communities, net productivity and calcification were negatively correlated with temperature (>40% and >65% reduction, respectively, with +5°C increase from winter to summer), while carbon losses via respiration and dissolved organic carbon release were more than doubled at higher temperatures. In contrast, algae-dominated communities doubled net productivity in summer, while calcification and dissolved organic carbon fluxes were unaffected. These results suggest pronounced changes in community functioning associated with phase shifts. Algae-dominated communities may outcompete coral-dominated communities due to their higher productivity and carbon retention to support fast biomass accumulation while compromising the formation of important reef framework structures. Higher temperatures likely amplify these functional differences, indicating a high vulnerability of ecosystem functions of coral-dominated communities to temperatures even below coral bleaching thresholds. Our results suggest that ocean warming may not only cause but also amplify coral-algal phase shifts in coral reefs.
  • Diatom modulation of select bacteria through use of two unique secondary metabolites

    Shibl, Ahmed A.; Isaac, Ashley; Ochsenkühn, Michael A.; Cardenas, Anny; Fei, Cong; Behringer, Gregory; Arnoux, Marc; Drou, Nizar; Santos, Miraflor P.; Gunsalus, Kristin C.; Voolstra, Christian R.; Amin, Shady A. (Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, 2020-10-17) [Article]
    Unicellular eukaryotic phytoplankton, such as diatoms, rely on microbial communities for survival despite lacking specialized compartments to house microbiomes (e.g., animal gut). Microbial communities have been widely shown to benefit from diatom excretions that accumulate within the microenvironment surrounding phytoplankton cells, known as the phycosphere. However, mechanisms that enable diatoms and other unicellular eukaryotes to nurture specific microbiomes by fostering beneficial bacteria and repelling harmful ones are mostly unknown. We hypothesized that diatom exudates may tune microbial communities and employed an integrated multiomics approach using the ubiquitous diatom Asterionellopsis glacialis to reveal how it modulates its naturally associated bacteria. We show that A. glacialis reprograms its transcriptional and metabolic profiles in response to bacteria to secrete a suite of central metabolites and two unusual secondary metabolites, rosmarinic acid and azelaic acid. While central metabolites are utilized by potential bacterial symbionts and opportunists alike, rosmarinic acid promotes attachment of beneficial bacteria to the diatom and simultaneously suppresses the attachment of opportunists. Similarly, azelaic acid enhances growth of beneficial bacteria while simultaneously inhibiting growth of opportunistic ones. We further show that the bacterial response to azelaic acid is numerically rare but globally distributed in the world’s oceans and taxonomically restricted to a handful of bacterial genera. Our results demonstrate the innate ability of an important unicellular eukaryotic group to modulate select bacteria in their microbial consortia, similar to higher eukaryotes, using unique secondary metabolites that regulate bacterial growth and behavior inversely across different bacterial populations.
  • Pan-regional marine benthic cryptobiome biodiversity patterns revealed by metabarcoding Autonomous Reef Monitoring Structures.

    Pearman, John K.; Chust, G; Aylagas, E; Villarino, E; Watson, J R; Chenuil, A; Borja, A; Cahill, A E; Carugati, L; Danovaro, R; David, R; Irigoien, X; Mendibil, I; Moncheva, S; Rodríguez-Ezpeleta, N; Uyarra, M C; Carvalho, Susana (Molecular ecology, Wiley, 2020-10-16) [Article]
    Autonomous Reef Monitoring Structures (ARMS) have been applied worldwide to characterize the critical yet frequently overlooked biodiversity patterns of marine benthic organisms. In order to disentangle the relevance of environmental factors in benthic patterns, here, through standardized metabarcoding protocols, we analyze sessile and mobile (
  • Total alkalinity production in a mangrove ecosystem reveals an overlooked Blue Carbon component

    Saderne, Vincent; Fusi, Marco; Thomson, Timothy; Dunne, Aislinn; Mahmud, Fatima; Roth, Florian; Carvalho, Susana; Duarte, Carlos M. (Limnology and Oceanography Letters, Wiley, 2020-10-16) [Article]
    Mangroves have the capacity to sequester organic carbon (Corg) in their sediments permanently. However, the carbon budget of mangroves is also affected by the total alkalinity (TA) budget. Principally, TA emitted from carbonate sediment dissolution is a perennial sink of atmospheric CO2. The assessment of the TA budget of mangrove carbonate sediments in the Red Sea revealed a large TA emission of 403 ± 17 mmol m−2 d−1, independent of light, seasons, or the presence of pneumatophores, compared to −36 ± 10 mmol m−2 d−1 in lagoon sediment. We estimate the TA emission from carbonate dissolution in Red Sea mangroves supported a CO2 uptake of 345 ± 15 gC m−2 yr−1, 23-fold the Corg burial rate of 15 gC m−2 yr−1. The focus on Corg burial in sediments may substantially underestimate the role of mangroves in CO2 removal. Quantifying the role of mangroves in climate change mitigation requires carbonate dissolution to be included in assessments.
  • Organic carbon export and loss rates in the Red Sea

    Kheireddine, Malika; Dall'Olmo, Giorgio; Ouhssain, Mustapha; Krokos, Georgios; Claustre, Hervé; Schmechtig, Catherine; Poteau, Antoine; Zhan, Peng; Hoteit, Ibrahim; Jones, Burton (Global Biogeochemical Cycles, American Geophysical Union (AGU), 2020-10-14) [Article]
    The export and fate of organic carbon in the mesopelagic zone are still poorly understood and quantified due to lack of observations. We exploited data from a BGC-Argo float that was deployed in the Red Sea to study how a warm and hypoxic environment can affect the fate of the organic carbon in the ocean’s interior. We observed that only 10% of the particulate organic carbon (POC) exported survived at depth due to remineralization processes in the upper mesopelagic zone. We also found that POC exported was rapidly degraded in a first stage and slowly in a second one, which may be dependent on the palatability of the organic matter. We observed that AOU-based loss rates (a proxy of the remineralization of total organic matter) were significantly higher than the POC-based loss rates, likely because changes in AOU are mainly attributed to changes in dissolved organic carbon. Finally, we showed that POC- and AOU-based loss rates could be expressed as a function of temperature and oxygen concentration. These findings advance our understanding of the biological carbon pump and mesopelagic ecosystem.
  • Interleukin-26 activates macrophages and facilitates killing of Mycobacterium tuberculosis

    Hawerkamp, Heike C.; van Geelen, Lasse; Korte, Jan; Di Domizio, Jeremy; Swidergall, Marc; Momin, Afaque Ahmad Imtiyaz; Guzmán-Vega, Francisco J.; Arold, Stefan T.; Ernst, Joachim; Gilliet, Michel; Kalscheuer, Rainer; Homey, Bernhard; Meller, Stephan (Scientific Reports, Springer Science and Business Media LLC, 2020-10-14) [Article]
    Abstract Tuberculosis-causing Mycobacterium tuberculosis (Mtb) is transmitted via airborne droplets followed by a primary infection of macrophages and dendritic cells. During the activation of host defence mechanisms also neutrophils and T helper 1 (TH1) and TH17 cells are recruited to the site of infection. The TH17 cell-derived interleukin (IL)-17 in turn induces the cathelicidin LL37 which shows direct antimycobacterial effects. Here, we investigated the role of IL-26, a TH1- and TH17-associated cytokine that exhibits antimicrobial activity. We found that both IL-26 mRNA and protein are strongly increased in tuberculous lymph nodes. Furthermore, IL-26 is able to directly kill Mtb and decrease the infection rate in macrophages. Binding of IL-26 to lipoarabinomannan might be one important mechanism in extracellular killing of Mtb. Macrophages and dendritic cells respond to IL-26 with secretion of tumor necrosis factor (TNF)-α and chemokines such as CCL20, CXCL2 and CXCL8. In dendritic cells but not in macrophages cytokine induction by IL-26 is partly mediated via Toll like receptor (TLR) 2. Taken together, IL-26 strengthens the defense against Mtb in two ways: firstly, directly due to its antimycobacterial properties and secondly indirectly by activating innate immune mechanisms.
  • Biofilm removal efficacy using direct electric current in cross-flow ultrafiltration processes for water treatment

    Kerdi, Sarah; Qamar, Adnan; Vrouwenvelder, Johannes S.; Ghaffour, NorEddine (Journal of Membrane Science, Elsevier BV, 2020-10-14) [Article]
    Biofouling of membranes in water treatment is considered as one of the major practical problems. A novel and an efficient approach for cleaning biofilm grown on the membrane surface is proposed by applying a direct electric current (124 mA, 90 s) through platinum electrodes inside a cross-flow ultrafiltration channel. Depending on the electrochemical reactions occurring at the electrodes, either chlorine or hydrogen-producing configuration is realized by interchanging the current polarity. Baseline determination of the amount of chlorine generated and change in pH is assessed as a function of current intensity, linear cross-flow velocity, and duration of applied current. The efficiency of the proposed method is determined by investigating electrically treated biofilm through bacterial inactivation using Confocal Laser Scanning Microscopy (CLSM), bacterial cell structure changes through Scanning Electron Microscopy (SEM), and by estimating the amount of biomass removal through Optical Coherence Tomography (OCT). When a chlorine-producing electrode is placed at the inlet of the flow cell, 68% of bacterial inactivation is achieved without any modification of bacterial cell shape. Furthermore, a high and near-complete biomass removal is achieved (99%) after a subsequent forward flush of the electrically treated biofilm. However, placing a hydrogen-producing electrode at the inlet reveals a slightly lower bacterial inactivation (65%) and lower biomass removal (77%). Additional systematic experiments using individually sodium hydroxide (NaOH), sodium hypochlorite (NaOCl), or gas microbubbles enabled to elucidate the cause of biofilm removal, synergic effect of caustic agent NaOH and microbubbles.
  • Semantic similarity and machine learning with ontologies.

    Kulmanov, Maxat; Smaili, Fatima Z.; Gao, Xin; Hoehndorf, Robert (Briefings in bioinformatics, Oxford University Press (OUP), 2020-10-13) [Article]
    Ontologies have long been employed in the life sciences to formally represent and reason over domain knowledge and they are employed in almost every major biological database. Recently, ontologies are increasingly being used to provide background knowledge in similarity-based analysis and machine learning models. The methods employed to combine ontologies and machine learning are still novel and actively being developed. We provide an overview over the methods that use ontologies to compute similarity and incorporate them in machine learning methods; in particular, we outline how semantic similarity measures and ontology embeddings can exploit the background knowledge in ontologies and how ontologies can provide constraints that improve machine learning models. The methods and experiments we describe are available as a set of executable notebooks, and we also provide a set of slides and additional resources at https://github.com/bio-ontology-research-group/machine-learning-with-ontologies.
  • Metal Halide Perovskites for High-Energy Radiation Detection

    Kakavelakis, George; Gedda, Murali; Panagiotopoulos, Apostolis; Kymakis, Emmanuel; Anthopoulos, Thomas D.; Petridis, Konstantinos (Advanced Science, Wiley, 2020-10-12) [Article]
    Metal halide perovskites (MHPs) have emerged as a frontrunner semiconductor technology for application in third generation photovoltaics while simultaneously making significant strides in other areas of optoelectronics. Photodetectors are one of the latest additions in an expanding list of applications of this fascinating family of materials. The extensive range of possible inorganic and hybrid perovskites coupled with their processing versatility and ability to convert external stimuli into easily measurable optical/electrical signals makes them an auspicious sensing element even for the high-energy domain of the electromagnetic spectrum. Key to this is the ability of MHPs to accommodate heavy elements while being able to form large, high-quality crystals and polycrystalline layers, making them one of the most promising emerging X-ray and γ-ray detector technologies. Here, the fundamental principles of high-energy radiation detection are reviewed with emphasis on recent progress in the emerging and fascinating field of metal halide perovskite-based X-ray and γ-ray detectors. The review starts with a discussion of the basic principles of high-energy radiation detection with focus on key performance metrics followed by a comprehensive summary of the recent progress in the field of perovskite-based detectors. The article concludes with a discussion of the remaining challenges and future perspectives.
  • Evolution and biogeography of the Zanclea-Scleractinia symbiosis

    Maggioni, Davide; Arrigoni, Roberto; Seveso, Davide; Galli, Paolo; Berumen, Michael L.; Denis, Vianney; Hoeksema, Bert W.; Huang, Danwei; Manca, Federica; Pica, Daniela; Puce, Stefania; Reimer, James D.; Montano, Simone (Coral Reefs, Springer Science and Business Media LLC, 2020-10-12) [Article]
    Abstract Scleractinian corals provide habitats for a broad variety of cryptofauna, which in turn may contribute to the overall functioning of coral symbiomes. Among these invertebrates, hydrozoans belonging to the genus Zanclea represent an increasingly known and ecologically important group of coral symbionts. In this study, we analysed 321 Zanclea colonies associated with 31 coral genera collected from 11 localities across the Indo-Pacific and Caribbean regions, and used a multi-disciplinary approach to shed light on the evolution and biogeography of the group. Overall, we found high genetic diversity of hydrozoans that spans nine clades corresponding to cryptic or pseudo-cryptic species. All but two clades are associated with one or two coral genera belonging to the Complex clade, whereas the remaining ones are generalists associated with both Complex and Robust corals. Despite the observed specificity patterns, no congruence between Zanclea and coral phylogenies was observed, suggesting a lack of coevolutionary events. Most Zanclea clades have a wide distribution across the Indo-Pacific, including a generalist group extending also into the Caribbean, while two host-specific clades are possibly found exclusively in the Red Sea, confirming the importance of this peripheral region as an endemicity hotspot. Ancestral state reconstruction suggests that the most recent common ancestor of all extant coral-associated Zanclea was a specialist species with a perisarc, occurring in what is now known as the Indo-Pacific. Ultimately, a mixture of geography- and host-related diversification processes is likely responsible for the observed enigmatic phylogenetic structure of coral-associated Zanclea.
  • Innovative concentrated photovoltaic thermal (CPV/T) system with combined hydrogen and MgO based storage

    Burhan, Muhammad; Chen, Qian; Shahzad, Muhammad Wakil; Ybyraiymkul, Doskhan; Akhtar, Faheem; Ng, Kim Choon (International Journal of Hydrogen Energy, Elsevier BV, 2020-10-10) [Article]
    The intermittency of renewable energy resources which only have localized availability with low energy density, is the main reasons for our reliance on conventional fossil fuels. If steady supply and high energy quality can be achieved then solar energy potential is enough to meet the global energy demand. Heat and electricity both are equally important forms of derived energies. In this paper, an innovative configuration of solar energy system for simultaneous need of electricity and high grade thermal energy, is presented and discussed along with the long term energy storage solution. The proposed CPV/T system, with hydrogen based electrical and MgO based thermal storage, can produce electricity and high-temperature thermal energies at efficiency of 30% and 70% respectively. The CPV-Hydrogen configuration achieved Solar to Hydrogen efficiency of 19%. On the other hand, the MgO based TES system obtained 80% material storage efficiency at 400 °C which can be easily achieved with the concentrated thermal energy density of 240 Suns.
  • Investigating the Catalytic Active Sites of Mo/HZSM-5 and Their Deactivation During Methane Dehydroaromatization

    Wang, Ning; Dong, Xinglong; Liu, Lingmei; Cai, Dali; Wang, Jianjian; Hou, Yilin; Emwas, Abdul-Hamid M.; Gascon, Jorge; Han, Yu (SSRN Electronic Journal, Elsevier BV, 2020-10-09) [Article]
    Molybdenum supported on zeolite HZSM-5 (Mo/HZSM-5) is the most studied catalyst for methane dehydroaromatization (MDA). However, the nature of its catalytic active sites and their deactivation mechanisms remain unclear and controversial. Here we report new insights into this system, on the basis of advanced characterization and a rational design of experiments. We find that it is the size of the HZSM-5 crystal that determines the form and location of the catalytic active molybdenum carbide (MoCx) species, and thus the performance of Mo/HZSM-5; we also find that MoCx sites are preferentially deactivated over acid sites, when supported on nano-sized HZSM-5. These findings lead us to develop an “encapsulation” strategy, which effectively reconciles the deactivation rates at the MoCx sites and the acid sites, enabling a full utilization of both sites, and consequently leading to a 10-fold increase in catalyst lifetime and aromatics yield. Our results indicate that MoCx particles formed outside the micropores of HZSM-5, which are traditionally considered detrimental to the reaction, can serve as active sites for MDA, provided that they are properly protected from direct exposure to coke deposition. These findings allow us to design control experiments to answer an open question whether the acid sites, in addition to promoting the dispersion of Mo species, play a catalytic role in the MDA reaction, and the results show that acid sites are indeed essential for the conversion of methane.
  • Optimising sample sizes for animal distribution analysis using tracking data

    Shimada, Takahiro; Thums, Michele; Hamann, Mark; Limpus, Colin J.; Hays, Graeme C.; FitzSimmons, Nancy; Wildermann, Natalie E.; Duarte, Carlos M.; Meekan, Mark G. (Methods in Ecology and Evolution, Wiley, 2020-10-09) [Article]
    1. Knowledge of the spatial distribution of populations is fundamental to management plans for any species. When tracking data are used to describe distributions, it is sometimes assumed that the reported locations of individuals delineate the spatial extent of areas used by the target population. 2. Here, we examine existing approaches to validate this assumption, highlight caveats, and propose a new method for a more informative assessment of the number of tracked animals (i.e. sample size) necessary to identify distribution patterns. We show how this assessment can be achieved by considering the heterogeneous use of habitats by a target species using the probabilistic property of a utilisation distribution. Our methods are compiled in the R package SDLfilter. 3. We illustrate and compare the protocols underlying existing and new methods using conceptual models and demonstrate an application of our approach using a large satellite tracking data-set of flatback turtles, Natator depressus, tagged with accurate Fastloc-GPS tags (n = 69). 4. Our approach has applicability for the post-hoc validation of sample sizes required for the robust estimation of distribution patterns across a wide range of taxa, populations and life history stages of animals.
  • Laser induced fluorescence investigation of the chemical impact of nanosecond repetitively pulsed glow discharges on a laminar methane-air flame

    Del Cont-Bernard, Davide; Guiberti, Thibault; Lacoste, Deanna (Proceedings of the Combustion Institute, Elsevier BV, 2020-10-08) [Article]
    This paper reports on an experimental investigation of the chemical impact of nanosecond repetitively pulsed (NRP) glow discharges on a laminar methane-air flame. The chosen configuration was a lean wall stabilized flame where NRP discharges were generated across the flame front. After careful selection of the excitation lines, planar laser induced fluorescence of OH and CH was conducted. Comparisons between the OH and CH fluorescence of a base flame (without plasma actuation), and those obtained during the steady state and the transient regimes of plasma actuation, were performed. First it is shown that during the steady state regime, the intensity of OH and CH fluorescence in the flame could be increased by up to 40% and 10%, respectively. In addition, the life time of OH fluorescence in the discharge channel was estimated to be between 3 and 4.5 µs. The transient regime at the beginning of plasma actuation showed that the flame began to be affected by the discharges long before OH fluorescence could be detected in the discharge channel, upstream of the flame. After 40 ms of plasma actuation, OH intensity began to increase simultaneously in both the flame and the discharge area. Based on current knowledge of nanosecond discharge chemistry, explanations for these results are proposed.
  • Diels-Alder Polymer Networks with Temperature-Reversible Cross-Linking-Induced Emission Yu Jiang*, and Nikos Hadjichristidis*

    Hadjichristidis, Nikos; Jiang, Yu (Angewandte Chemie, Wiley, 2020-10-08) [Article]
    A novel synthetic strategy toward reversible cross-linked polymeric materials with tunable fluorescence properties is presented. Dimaleimide-substituted tetraphenylethene (TPE-2MI), which is nonemissive due to the photo-induced electron transfer (PET) between maleimide (MI) and tetraphenylethene (TPE) groups, was used to cross-link random copolymers of methyl (MM), decyl (DM) or lauryl (LM) with furfuryl methacrylate (FM). The mixture of copolymer and TPE-2MI in DMF showed reversible fluorescence with “on/off” behavior depending on the Diels-Alder (DA)/retro-DA process, which is easily adjusted by temperature. At high temperatures, the retro-DA reaction of polymer networks is dominant, and the fluorescence is quenched by the PET mechanism. In contrast, at low temperatures, the emission recovers as the DA reaction takes over. Based on these results, a transparent PMFM/TPE-2MI film was prepared, and the emission behavior was investigated. It was found that the polymer film shows an accurate response to the external temperature and exhibited tunable fluorescent “turn on/off” behavior. These excitingresults suggest the possible application of this type of reversible cross-linked materials in many areas, including information security and transmission. An example of invisible/visible writing is given.
  • Impact of data preprocessing on cell-type clustering based on single-cell RNA-seq data.

    Wang, Chunxiang; Gao, Xin; Liu, Juntao (BMC bioinformatics, Springer Science and Business Media LLC, 2020-10-08) [Article]
    BACKGROUND:Advances in single-cell RNA-seq technology have led to great opportunities for the quantitative characterization of cell types, and many clustering algorithms have been developed based on single-cell gene expression. However, we found that different data preprocessing methods show quite different effects on clustering algorithms. Moreover, there is no specific preprocessing method that is applicable to all clustering algorithms, and even for the same clustering algorithm, the best preprocessing method depends on the input data. RESULTS:We designed a graph-based algorithm, SC3-e, specifically for discriminating the best data preprocessing method for SC3, which is currently the most widely used clustering algorithm for single cell clustering. When tested on eight frequently used single-cell RNA-seq data sets, SC3-e always accurately selects the best data preprocessing method for SC3 and therefore greatly enhances the clustering performance of SC3. CONCLUSION:The SC3-e algorithm is practically powerful for discriminating the best data preprocessing method, and therefore largely enhances the performance of cell-type clustering of SC3. It is expected to play a crucial role in the related studies of single-cell clustering, such as the studies of human complex diseases and discoveries of new cell types.
  • Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make-Up, Hydrostatic Pressure, and Cavity Aspect Ratio

    Arunachalam, Sankara; Ahmad, Zain; Das, Ratul; Mishra, Himanshu (Advanced Materials Interfaces, Wiley, 2020-10-07) [Article]
    Surfaces that entrap air underwater serve numerous practical applications, such as mitigating cavitation erosion and reducing frictional drag. These surfaces typically rely on perfluorinated coatings. However, the non-biodegradability and fragility of the coatings limit practical applications. Thus, coating-free, sustainable, and robust approaches are desirable. Recently, a microtexture comprising doubly reentrant cavities (DRCs) has been demonstrated to entrap air on immersion in wetting liquids. While this is a promising approach, insights into the effects of surface chemistry, hydrostatic pressure, and cavity dimensions on wetting transitions in DRCs remain unavailable. In response, Cassie-to-Wenzel transitions into circular DRCs submerged in water are investigated and compared with those in cylindrical “simple” cavities (SCs). It is found that at low hydrostatic pressures (≈50 Pa), DRCs with hydrophilic (θo ≈ 40°) and hydrophobic (θo ≈ 112°) make-ups fill within 105 and 107 s, respectively, while SCs with hydrophilic make-up fill within <10−2 s. Under elevated hydrostatic pressure (P ≤ 90 kPa), counterintuitively, DRCs with hydrophobic make-up fill dramatically faster than the commensurate SCs. This comprehensive report should provide a rational framework for harnessing microtexturing and surface chemistry toward coating-free liquid repellency.
  • Effect of localized hydrodynamics on biofilm attachment and growth in a cross-flow filtration channel

    Kerdi, Sarah; Qamar, Adnan; Vrouwenvelder, Johannes S.; Ghaffour, NorEddine (Water Research, Elsevier BV, 2020-10-07) [Article]
    Biofilm attachment and growth in membrane filtration systems are considerably influenced by the localized flow inside the feed channel. The present work aims to map the biofilm attachment/growth mechanism under varying flow conditions. Effect of varying clearance region (space between the spacer filament and membrane surface) on biofouling pattern is investigated by using three 3D-printed pillar spacers having different filament diameters of 340, 500, and 1000 µm while maintaining the same pillar orientation, diameter and height. Direct Numerical Simulations (DNS) and Optical Coherence Tomography (OCT) were carried out to accurately predict the local hydrodynamics behavior and in-situ monitor the biofilm formation. On spacer filaments, biofouling attachment is primarily observed in the regions where low and non-fluctuating shear stresses are present. Conversely, on membrane surface, highest biofouling attachment was observed under spacer filaments where high shear stresses are prevalent along with low clearance height. Furthermore, as filtration time progresses, the biofilm grows faster on the membrane in the center of spacer cells where low shear stress with steady hydrodynamics conditions are prevalent. The proposed hydrodynamics approach envisages a full spectrum of spacer design constraints that can lead to intrinsic biofilm mitigation while improving filtration performance of membranes based water treatment.
  • In silico design of novel NRR electrocatalysts: cobalt-molybdenum alloys.

    Castellano-Varona, Blanca; Harb, Moussab; Araña, Javier; Cavallo, Luigi; Azofra Mesa, Luis (Chemical communications (Cambridge, England), Royal Society of Chemistry (RSC), 2020-10-07) [Article]
    Metals are amongst the most efficient developed electrocatalysts for nitrogen reduction reaction (NRR) with iron and ruthenium presenting the best catalytic indicators. However, the potential use of metal alloys as NRR electrocatalysts is still underdeveloped. While Co has demonstrated poor electrocatalytic activity for NRR, alloying Co with Mo exhibits an improvement in both N2 physisorption and the stabilisation of the elusive N2H as the first reduced intermediate species. This stabilisation occurs on surface Mo or Co atoms with a high connectivity with Mo. Herein, we report a complete DFT study analysing the potential application of CoMo alloys as catalysts for N2-into-NH3 conversion given the low theoretical overpotentials that they present.
  • Optical frequency metrology in the bending modes region

    Lamperti, Marco; Gotti, Riccardo; Gatti, Davide; Shakfa, Mohammad Khaled; Cané, E.; Tamassia, F.; Schunemann, P.; Laporta, P.; Farooq, Aamir; Marangoni, M. (Communications Physics, Springer Science and Business Media LLC, 2020-10-06) [Article]
    Abstract Optical metrology and high-resolution spectroscopy, despite impressive progress across diverse regions of the electromagnetic spectrum from ultraviolet to terahertz frequencies, are still severely limited in the region of vibrational bending modes from 13 to 20 µm. This long-wavelength part of the mid-infrared range remains largely unexplored due to the lack of tunable single-mode lasers. Here, we demonstrate bending modes frequency metrology in this region by employing a continuous-wave nonlinear laser source with tunability from 12.1 to 14.8 µm, optical power up to 110 µW, MHz-level linewidth and comb calibration. We assess several CO2-based frequency benchmarks with uncertainties down to 30 kHz and we provide an extensive study of the v11 band of benzene, a significant testbed for the resolution of the spectrometer. These achievements pave the way for long-wavelength infrared metrology, rotationally-resolved studies and astronomic observations of large molecules such as aromatic hydrocarbons.

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