Recent Submissions

  • Numerical methods for density driven groundwater ow with uncertain data

    Litvinenko, Alexander; Logashenko, Dmitry; Keyes, David E.; Wittum, Gabriel; Tempone, Raul (2019-02-20)
    Accurate modeling of contamination in subsurface flow and water aquifers is crucial for agriculture and environmental protection. We consider the density-driven subsurface flow and estimate how uncertainty from permeability and porosity propagates to the solution - mass fraction. We take an Elder-like problem as a numerical benchmark and we use random fields to model the limited knowledge on the porosity and permeability. We construct a low-cost generalized polynomial chaos expansion (gPCE) surrogate model, where the gPCE coefficients are computed by projection on sparse and full tensor grids. We parallelize both the numerical solver for the deterministic problem based on the multigrid method, and the quadrature over the parametric space.
  • Defect-free highly selective polyamide thin-film composite membranes for desalination and boron removal

    Ali, Zain; Al Sunbul, Yasmeen; Pacheco Oreamuno, Federico; Ogieglo, Wojciech; Wang, Yingge; Genduso, Giuseppe; Pinnau, Ingo (Elsevier BV, 2019-02-16)
    Removal of boron from saline water sources has presented a major challenge for commercially available reverse osmosis desalination membranes. In this work, we report the boron and sodium chloride separation properties of truly defect-free, highly selective, interfacially polymerized aromatic polyamide thin-film composite membranes. The fabricated membranes show potential for separating sodium chloride with a maximum rejection of 99.6% obtained for the optimized film-forming protocol under lab-scale brackish water desalination conditions. This translated into promising boron rejection performance with rejections of up to 99% at pH 10, higher than a number of commercially available reverse osmosis membranes tested in-house. Comprehensive characterization including X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, ellipsometry, and surface charge measurements revealed intimate insights on interfacially polymerized polyamide membrane structure-property relationships. Increased membrane crosslinking was shown to be the primary determining factor for membrane permselectivity performance. Furthermore, relationships were established between microstructural properties such as crosslinking and morphological characteristics like surface roughness, highlighting an intricate and complex structure formation mechanism.
  • The effect of Schiff base network on the separation performance of thin film nanocomposite forward osmosis membranes

    Akther, Nawshad; Lim, Sungil; Huy Tran, Van; Phuntsho, Sherub; Yang, Yanqin; Bae, Tae-Hyun; Ghaffour, NorEddine; Kyong Shon, Ho (Elsevier BV, 2019-02-16)
    In this study, Schiff base network-1 (SNW-1) nanoparticles, which are covalent organic frameworks (COFs), were used as fillers in the polyamide (PA) active layer to elevate the performance of thin-film nanocomposite (TFN) forward osmosis (FO) membranes. The TFN membranes were prepared by interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC), and the SNW-1 nanoparticles were dispersed in the MPD aqueous solution at various concentrations. The secondary amine groups of SNW-1 nanoparticles reacted with the acyl chloride groups of TMC during the IP reaction to form strong covalent/amide bonds, which facilitated better interface integration of SNW-1 nanoparticles in the PA layer. Additionally, the incorporation of amine-rich SNW-1 nanoparticles into the TFN membranes improved their surface hydrophilicity, and the porous structure of SNW-1 nanoparticles offered additional channels for transport of water molecules. The TFN0.005 membrane with a SNW-1 nanoparticle loading of 0.005 wt.% demonstrated a higher water flux than that of pristine TFC membrane in both AL-FS (12.0 vs. 9.3 Lm-2h-1) and AL-DS (25.2 vs. 19.4 Lm-2h-1) orientations when they were tested with deionized water and 0.5 M NaCl as feed and draw solution, respectively.
  • Directional Spectra-based Clustering for Visualizing Patterns of Ocean Waves and Winds

    Euán, Carolina; Sun, Ying (Informa UK Limited, 2019-02-15)
    The energy distribution of wind-driven ocean waves is of great interest in marine science. Discovering the generating process of ocean waves is often challenging and the direction is the key for a better understanding. Typically, wave records are transformed into a directional spectrum which provides information about the wave energy distribution across different frequencies and directions. Here, we propose a new time series clustering method for a series of directional spectra in order to extract the spectral features of ocean waves and develop informative visualization tools to summarize identified wave clusters. We treat directional distributions as functional data of directions, and construct a directional functional boxplot to display the main directional distribution of the wave energy within a cluster. We also trace back when these spectra were observed, and we present color-coded clusters on a calendar plot to show their temporal variability. For each identified wave cluster, we analyze wind speed and wind direction hourly to investigate the link between wind data and wave directional spectra. The performance of the proposed clustering method is evaluated by simulations and illustrated by a real-world dataset from the red sea.
  • Computation of Electromagnetic Fields Scattered From Objects With Uncertain Shapes Using Multilevel Monte Carlo Method

    Litvinenko, Alexander; Yucel, Abdulkadir; Bagci, Hakan; Oppelstrup, Jesper; Tempone, Raul; Michielssen, Eric (2019-02-14)
    Computational tools for characterizing electromagnetic scattering from objects with uncertain shapes are needed in various applications ranging from remote sensing at microwave frequencies to Raman spectroscopy at optical frequencies. Often, such computational tools use the Monte Carlo (MC) method to sample a parametric space describing geometric uncertainties. For each sample, which corresponds to a realization of the geometry, a deterministic electromagnetic solver computes the scattered fields. However, for an accurate statistical characterization the number of MC samples has to be large. In this work, to address this challenge, the continuation multilevel Monte Carlo (CMLMC) method is used together with a surface integral equation solver. The CMLMC method optimally balances statistical errors due to sampling of the parametric space, and numerical errors due to the discretization of the geometry using a hierarchy of discretizations, from coarse to fine. The number of realizations of finer discretizations can be kept low, with most samples computed on coarser discretizations to minimize computational cost. Consequently, the total execution time is significantly reduced, in comparison to the standard MC scheme.
  • MXene-Derived Ferroelectric Crystals

    Tu, Shao Bo; Ming, Fangwang; Zhang, Junwei; Zhang, Xixiang; Alshareef, Husam N. (Wiley, 2019-02-14)
    This study demonstrates the first synthesis of MXene-derived ferroelectric crystals. Specifically, high-aspect-ratio potassium niobate (KNbO3 ) ferroelectric crystals is successfully synthesized using 2D Nb2 C, MXene, and potassium hydroxide (KOH) as the niobium and potassium source, respectively. Material analysis confirms that a KNbO3 orthorhombic phase with Amm2 symmetry is obtained. Additionally, ferroelectricity in KNbO3 is confirmed using standard ferroelectric, dielectric, and piezoresponse force microscopy measurements. The KNbO3 crystals exhibit a saturated polarization of ≈21 µC cm-2 , a remnant polarization of ≈17 µC cm-2 , and a coercive field of ≈50 kV cm-1 . This discovery illustrates that the 2D nature of MXenes can be exploited to grow ferroelectric crystals.
  • Chemical Stabilities of the Lowest Triplet State in Aryl Sulfones and Aryl Phosphine Oxides Relevant to OLED Applications

    Li, Huifang; Hong, Minki; Scarpaci, Annabelle; He, Xuyang; Risko, Chad; Sears, John S.; Barlow, Stephen; Winget, Paul; Marder, Seth R.; Kim, Dongwook; Bredas, Jean-Luc (American Chemical Society (ACS), 2019-02-14)
    Aryl sulfones and phosphine oxides are widely used as molecular building blocks for host materials in the emissive layers of organic light-emitting diodes. In this context, the chemical stability of such molecules in the triplet state is of paramount concern to long-term device performance. Here, we explore the triplet excited-state (T1) chemical stabilities of aryl sulfonyl and aryl phosphoryl molecules by means of UV absorption spectroscopy and density functional theory calculations. Both the sulfur–carbon bonds of the aryl sulfonyl molecules and the phosphorus–carbon bonds of aryl phosphoryl derivatives are significantly more vulnerable to dissociation in the T1 state when compared to the ground (S0) state. Although the vertical S0→T1 transitions correspond to non-bonding→π-orbital transitions, geometry relaxations in the T1 state lead to -* character over the respective sulfur–carbon or phosphorus–carbon bond, a result of significant electronic state mixing, which facilitates bond dissociation. Both the activation energy for bond dissociation and the bond dissociation energy in the T1 state are found to vary linearly with the adiabatic T1-state energy. Specifically as T1 becomes more energetically stable, the activation energy becomes larger, and dissociation becomes less likely, i.e., more endothermic or less exothermic. While substitutions of electron-donating or accepting units onto the aryl sulfones and aryl phosphine oxides have only marginal influence on the dissociation reactions, extension of the -conjugation of the aryl groups leads to a significant reduction in the triplet energy and a considerable enhancement in the T1-state chemical stabilities.
  • Three-dimensional Signature of the Red Sea Eddies and Eddy-induced Transport

    Zhan, Peng; Krokos, George; Guo, Daquan; Hoteit, Ibrahim (American Geophysical Union (AGU), 2019-02-14)
    Mesoscale eddies are a dominant feature of the Red Sea circulation, yet their three-dimensional characteristics remain largely unexplored. This hinders our understanding of about eddy-induced transport in the basin. This study analyzes 14-year outputs from a high-resolution eddy-resolving model to investigate the three-dimensional signature of the Red Sea eddies, their contribution to the air-sea flux, and the eddy-induced transport of heat and salt. Eddies are mostly active and energetic in the central and northern Red Sea. Their associated variability explains ∼8% of the total variance in the surface heat flux, and particularly, ∼39% in the salt flux. The asymmetric eddy structure and meridional gradient drive significant transport of heat and salt across the basin. A negative feedback mechanism is identified that relates the eddy intensity and the meridional steepness of the mixed layer depth in the basin.
  • Unmatched level of molecular convergence among deeply divergent complex multicellular fungi

    Merenyi, Zsolt; Prasanna, Arun N; Zheng, Wang; Kovacs, Karoly; Hegedus, Botond; Balint, Balazs; Papp, Balazs; Townsend, Jeffrey P; Nagy, Laszlo G (Cold Spring Harbor Laboratory, 2019-02-14)
    Convergent evolution is pervasive in nature, but it is poorly understood how various constraints and natural selection limit the diversity of evolvable phenotypes. Here, we report that, despite >650 million years of divergence, the same genes have repeatedly been co-opted for the development of complex multicellularity in the two largest clades of fungi-the Ascomycota and Basidiomycota. Co-opted genes have undergone duplications in both clades, resulting in >81% convergence across shared multicellularity-related families. This convergence is coupled with a rich repertoire of multicellularity-related genes in ancestors that predate complex multicellular fungi, suggesting that the coding capacity of early fungal genomes was well suited for the repeated evolution of complex multicellularity. Our work suggests that evolution may be predictable not only when organisms are closely related or are under similar selection pressures, but also if the genome biases the potential evolutionary trajectories organisms can take, even across large phylogenetic distances.
  • Advanced Hepatitis C Virus Replication PDE Models within a Realistic Intracellular Geometric Environment

    Knodel, Markus; Targett-Adams, Paul; Grillo, Alfio; Herrmann, Eva; Wittum, Gabriel (MDPI AG, 2019-02-13)
    The hepatitis C virus (HCV) RNA replication cycle is a dynamic intracellular process occurring in three-dimensional space (3D), which is difficult both to capture experimentally and to visualize conceptually. HCV-generated replication factories are housed within virus-induced intracellular structures termed membranous webs (MW), which are derived from the Endoplasmatic Reticulum (ER). Recently, we published 3D spatiotemporal resolved diffusion–reaction models of the HCV RNA replication cycle by means of surface partial differential equation (sPDE) descriptions. We distinguished between the basic components of the HCV RNA replication cycle, namely HCV RNA, non-structural viral proteins (NSPs), and a host factor. In particular, we evaluated the sPDE models upon realistic reconstructed intracellular compartments (ER/MW). In this paper, we propose a significant extension of the model based upon two additional parameters: different aggregate states of HCV RNA and NSPs, and population dynamics inspired diffusion and reaction coefficients instead of multilinear ones. The combination of both aspects enables realistic modeling of viral replication at all scales. Specifically, we describe a replication complex state consisting of HCV RNA together with a defined amount of NSPs. As a result of the combination of spatial resolution and different aggregate states, the new model mimics a cis requirement for HCV RNA replication. We used heuristic parameters for our simulations, which were run only on a subsection of the ER. Nevertheless, this was sufficient to allow the fitting of core aspects of virus reproduction, at least qualitatively. Our findings should help stimulate new model approaches and experimental directions for virology.
  • Beyond the visual: using metabarcoding to characterize the hidden reef cryptobiome

    Carvalho, Susana; Aylagas, Eva; Villalobos, Rodrigo; Kattan, Yasser; Berumen, Michael L.; Pearman, John K. (The Royal Society, 2019-02-13)
    In an era of coral reef degradation, our knowledge of ecological patterns in reefs is biased towards large conspicuous organisms. The majority of biodiversity, however, inhabits small cryptic spaces within the framework of the reef. To assess this biodiverse community, which we term the ‘reef cryptobiome’, we deployed 87 autonomous reef monitoring structures (ARMS), on 22 reefs across 16 degrees latitude of the Red Sea. Combining ARMS with metabarcoding of the mitochondrial cytochrome oxidase I gene, we reveal a rich community, including the identification of 14 metazoan phyla within 10 416 operational taxonomic units (OTUs). While mobile and sessile subsets were similarly structured along the basin, the main environmental driver was different (particulate organic matter and sea surface temperature, respectively). Distribution patterns of OTUs showed that only 1.5% were present in all reefs, while over half were present in a single reef. On both local and regional scales, the majority of OTUs were rare. The high heterogeneity in community patterns of the reef cryptobiome has implications for reef conservation. Understanding the biodiversity patterns of this critical component of reef functioning will enable a sound knowledge of how coral reefs will respond to future anthropogenic impacts.
  • Plant Genome Engineering for Targeted Improvement of Crop Traits

    Sedeek, Khalid E. M.; Mahas, Ahmed; Mahfouz, Magdy M. (Frontiers Media SA, 2019-02-12)
    To improve food security, plant biology research aims to improve crop yield and tolerance to biotic and abiotic stress, as well as increasing the nutrient contents of food. Conventional breeding systems have allowed breeders to produce improved varieties of many crops; for example, hybrid grain crops show dramatic improvements in yield. However, many challenges remain and emerging technologies have the potential to address many of these challenges. For example, site-specific nucleases such as TALENs and CRISPR/Cas systems, which enable high-efficiency genome engineering across eukaryotic species, have revolutionized biological research and its applications in crop plants. These nucleases have been used in diverse plant species to generate a wide variety of site-specific genome modifications through strategies that include targeted mutagenesis and editing for various agricultural biotechnology applications. Moreover, CRISPR/Cas genome-wide screens make it possible to discover novel traits, expand the range of traits, and accelerate trait development in target crops that are key for food security. Here, we discuss the development and use of various site-specific nuclease systems for different plant genome-engineering applications. We highlight the existing opportunities to harness these technologies for targeted improvement of traits to enhance crop productivity and resilience to climate change. These cutting-edge genome-editing technologies are thus poised to reshape the future of agriculture and food security.
  • A Novel Error Performance Analysis Methodology for OFDM-IM

    Dang, Shuping; Ma, Guoqing; Shihada, Basem; Alouini, Mohamed-Slim (Institute of Electrical and Electronics Engineers (IEEE), 2019-02-12)
    Orthogonal frequency-division multiplexing with index modulation (OFDM-IM) has become a high-profile candidate for the modulation scheme in next generation networks, and many works have been published to analyze it in recent years. Error performance is one of the most important and interesting aspects of OFDM-IM, which has been analyzed in most works. However, most of them employ two key approximations to derive the closed-form expressions of block error rate (BLER) and/or average bit error rate (BER). The first one is to utilize the union bound assisted by the pairwise error probability (PEP) analysis, and the second one is to employ an exponential approximation of Q-function. In this letter, we apply Craig’s formula to analyze the error performance for OFDM-IM in place of the exponential approximation. Because Craig’s formula is the exact expression of Q-function, the accuracy of analytical results regarding error performance for OFDM-IM can be improved. We examine the proposed error performance analysis methodology based on Craig’s formula by investigating both average BLER and BER.
  • Accurate 3D Shape, Displacement and Deformation Measurement Using a Smartphone

    Yu, Liping; Tao, Ran; Lubineau, Gilles (MDPI AG, 2019-02-12)
    The stereo-digital image correlation technique using two synchronized industrial-grade cameras has been extensively used for full-field 3D shape, displacement and deformation measurements. However, its use in resource-limited institutions and field settings is inhibited by the need for relatively expensive, bulky and complicated experimental set-ups. To mitigate this problem, we established a cost-effective and ultra-portable smartphone-based stereo-digital image correlation system, which only uses a smartphone and an optical attachment. This optical attachment is composed of four planar mirrors and a 3D-printed mirror support, and can split the incoming scene into two sub-images, simulating a stereovision system using two virtual smartphones. Although such a mirror-based system has already been used for stereo-image correlation, this is the first time it has been combined with a commercial smartphone. This publication explores the potential and limitations of such a configuration. We first verified the effectiveness and accuracy of this system in 3D shape and displacement measurement through shape measurement and in-plane and out-of-plane translation tests. Severe thermal-induced virtual strains (up to 15,000 με) were found in the measured results due to the smartphone heating. The mechanism for the generation of the temperature-dependent errors in this system was clearly and reasonably explained. After a simple preheating process, the smartphone-based system was demonstrated to be accurate in measuring the strain on the surface of a loaded composite specimen, with comparable accuracy to a strain gauge. Measurements of 3D deformation are illustrated by tracking the deformation on the surface of a deflating ball. This cost-effective and ultra-portable smartphone-based system not only greatly decreases the hardware investment in the system construction, but also increases convenience and efficiency of 3D deformation measurements, thus demonstrating a large potential in resource-limited and field settings.
  • SymPortal: a novel analytical framework and platform for coral algal symbiont next-generation sequencing ITS2 profiling

    Hume, B C C; Smith, E G; Ziegler, Maren; Warrington, H J M; Burt, J A; LaJeunesse, T C; Wiedenmann, J; Voolstra, Christian R. (Wiley, 2019-02-11)
    We present SymPortal (SymPortal.org), a novel analytical framework and platform for genetically resolving the algal symbionts of reef corals using next-generation sequencing (NGS) data of the ITS2 rDNA. Although the ITS2 marker is widely used to genetically characterise taxa within the family Symbiodiniaceae (formerly the genus Symbiodinium), the multi-copy nature of the marker complicates its use. Commonly, the intragenomic diversity resultant from this multi-copy nature is collapsed by analytical approaches thereby focusing on only the most abundant sequences. In contrast, SymPortal employs logic to identify within-sample informative intragenomic sequences, which we have termed 'defining intragenomic variants' (DIVs), to identify ITS2 type profiles representative of putative Symbiodiniaceae taxa. By making use of this intragenomic ITS2 diversity, SymPortal is able to resolve genetic delineations using the ITS2 at a level that was previously only possible by using additional genetic markers. We demonstrate this by comparing this novel approach to the most commonly used alternative approach for NGS ITS2 data, the 97% similarity clustering to operational taxonomic units (OTUs). The SymPortal platform accepts NGS raw sequencing data as input to provide an easy to use, standardisation-enforced, and community-driven framework that integrates with a database to gain resolving power with increased use. We consider that SymPortal, in conjunction with ongoing large-scale sampling and sequencing efforts, should play an instrumental role in making future sampling efforts more comparable and in maximizing their efficacy in working towards the classification of a global Symbiodiniaceae diversity. This article is protected by copyright. All rights reserved.
  • A Decomposition of Total Variation Depth for Understanding Functional Outliers

    Huang, Huang; Sun, Ying (Informa UK Limited, 2019-02-11)
    There has been extensive work on data depth-based methods for robust multivariate data analysis. Recent developments have moved to infinite-dimensional objects such as functional data. In this work, we propose a notion of depth, the total variation depth, for functional data, which has many desirable features and is well suited for outlier detection. The proposed depth is in the form of an integral of a univariate depth function. We show that the novel formation of the total variation depth leads to useful decomposition associated with shape and magnitude outlyingness of functional data. Compared to magnitude outliers, shape outliers are often masked among the rest of samples and more difficult to identify. We then further develop an effective procedure and visualization tools for detecting both types of outliers, while naturally accounting for the correlation in functional data. The outlier detection performance is investigated through simulations under various outlier models. Finally, the proposed methodology is demonstrated using real datasets of curves, images, and video frames.
  • Seasonal modulation of mesoscale processes alters nutrient availability and plankton communities in the Red Sea

    Kürten, Benjamin; Zarokanellos, Nikolaos; Devassy, Reny P.; El-Sherbiny, Mohsen M.; Struck, Ulrich; Capone, Douglas G.; Schulz, Isabelle Katharina; Al-Aidaroos, Ali M.; Irigoien, Xabier; Jones, Burton (Elsevier BV, 2019-02-10)
    Hydrographic and atmospheric forcing set fundamental constraints on the biogeochemistry of aquatic ecosystems and manifest in patterns of resource (nutrient) availability and recycling, species composition of communities, trophic dynamics, and ecosystem metabolism. In the Red Sea, gradients in environmental conditions and primary production have been ascribed to fluctuations in Gulf of Aden Water inflow, upwelling/mixing, and regenerated nutrient utilization i.e. rapidly recycled nitrogen in upper layers. However, the understanding of upper layer dynamics and related changes in plankton communities, metabolism and carbon and nitrogen export is limited. We surmised that stratification and mesoscale eddies modulate the nutrient availability and taxonomic identity of plankton communities in the central Red Sea. Based on remote-sensing data of sea level anomalies and high resolution in situ profiling (ScanFish) we selected stations for hydrographic CTD profiles, water sampling (nutrients, seawater stable oxygen isotopes [δ18OSW]), phytoplankton and zooplankton collections. In fall 2014, strong stratification subjected the plankton community to an overall nitrogen and phosphorus shortage. The nutrient deficiency increased numbers of heterotrophic dinoflagellates, microzooplankton, and diazotrophs (Trichodesmium, diatom-diazotroph associations [DDAs]), albeit largely decreased phytoplankton and mesozooplankton abundances. In spring 2015, mesoscale eddies increased the nutrient availability, and the thermohaline characteristics and low δ18OSW point to the interaction of eddies with Gulf of Aden Surface Water (GASW). Cyclonic eddies and, most likely, the availability of nutrients associated with the GASW, increased the abundances of autotrophs (diatoms, Prasinophytes) and supported larger numbers of zooplankton and their larvae. We demonstrate that the interplay of stratification, advection of Gulf of Aden water and mesoscale eddies are key to better understand changes in plankton community composition, ecosystem metabolism, and macronutrient export in the Red Sea in space and time.
  • Rapid photonic curing of solution-processed In2O3 layers on flexible substrates

    Twyman, Nicholas M.; Tetzner, Kornelius; Anthopoulos, Thomas D.; Payne, David J.; Regoutz, Anna (Elsevier BV, 2019-02-10)
    In2O3 is one of the most important semiconducting metal oxides primarily because of its wide band gap, high electron mobility and processing versatility. To this end, high-quality thin films of In2O3 can be prepared using scalable and inexpensive solution-based deposition methods, hence making it attractive for application in a number of emerging electronic applications. However, traditional solution processing often requires high temperature and lengthy annealing steps, making it impossible to use in combination with temperature-sensitive plastic substrates, which would be desired for numerous emerging flexible device applications. Here, rapid photonic curing of In2O3 layers is explored as an alternative to thermal annealing. Oxide thin films are successfully prepared on a range of substrates, including glass, polyimide, and polyethylene naphthalate. The effect of substrate and post-processing treatment on the morphology, surface chemistry, and electronic properties is investigated by atomic force microscopy and X-ray photoelectron spectroscopy. Systematic trends are identified, particularly in the degree of conversion of the precursor and its influence on the electronic structure.
  • Microstructural Peculiarities of Al-Rich Al-La-Ni-Fe Alloys

    Vasiliev, A. L.; Bakhteeva, N. D.; Presniakov, M. Yu.; Lopatin, Sergei; Kolobylina, N. N.; Ivanova, A. G.; Todorova, E. V. (Springer Nature, 2019-02-08)
    The results of a comprehensive microstructural study of the ternary and quaternary phases in air-cast Al85Ni11−xFexLa4 (where x = 2 and 4 at. pct) polycrystalline alloys by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray microanalysis, and X-ray diffraction are presented. It was found that these alloys contain several phases, namely, fcc-Al, Al11La3, Al3Ni1−xFex, Al9Ni2−xFex, Al8Fe2−xNixLa, and Al3.2Fe1−xNix, in the form of δ-layers in Al8Fe2−xNixLa particles. A high density of other defects in the quaternary Al8Fe2−xNixLa particles was found, and the formation of these defects could be caused by the dendritic type of growth of this phase. The crystal structures of all these defects were revealed by high-resolution scanning transmission electron microscopy together with atomic-resolution energy-dispersive X-ray microanalysis. The thermal stability of the ternary and quaternary phases was also studied. The Al8Fe2−xNixLa phase is metastable and undergoes an irreversible transformation: Al8Fe2−xNixLa → Al9Ni2−xFex + Al11La3. Based on these data, a sequence of solid-phase reactions in these alloys during cooling and heating is proposed.
  • Catalytic degradation of O-cresol using H2 O2 onto Algerian Clay-Na

    Herbache, Hayat; Ramdani, Amina; Taleb, Zoubida; Ruiz-Rosas, Ramiro; Taleb, Safia; Morallón, Emilia; Pirault-Roy, Laurence; Ghaffour, NorEddine (Wiley, 2019-02-08)
    Clay material is used as a catalyst to degrade an organic pollutant. This study focused on the O-cresol oxidative degradation in aqueous solution by adding H2 O2 and Mont-Na. The catalytic tests showed a high catalytic activity of Mont-Na, which made it possible to achieve more than 84.6% conversion after 90 min of reaction time at 55°C in 23.2 mM H2 O2 . The pH value was found to be negatively correlated with the degradation rate of O-cresol. UV-Vis spectrophotometry revealed that the increase of degradation rate at low pH is related to the formation of 2-methylbenzoquinone as intermediate product. In addition, the content of iron in Mont-Na decreased after the catalytic test, bringing further evidence about the O-cresol catalytic oxidation. The mineralization of O-cresol is also confirmed by the different methods of characterization of Mont-Na after the catalytic oxidation test. The effect of the O-cresol oxidation catalyzed by natural clay is significant. PRACTITIONER POINTS: Algerian Montmorillonite-Na is used as a catalyst to degrade an organic pollutant: O-cresol. It shows a great potential for catalyst properties in the presence of the oxidizing reagent H2 O2 . It proved to be an effective means for the degradation of O-cresol contained in wastewaters.

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