Recent Submissions

  • Accelerating Geostatistical Modeling and Prediction With Mixed-Precision Computations: A High-Productivity Approach with PaRSEC

    Abdulah, Sameh; Cao, Qinglei; Pei, Yu; Bosilca, George; Dongarra, Jack; Genton, Marc G.; Keyes, David E.; Ltaief, Hatem; Sun, Ying (2021-05-06) [Technical Report]
    Geostatistical modeling, one of the prime motivating applications for exascale computing, is a technique for predicting desired quantities from geographically distributed data, based on statistical models and optimization of parameters. Spatial data is assumed to possess properties of stationarity or non-stationarity via a kernel fitted to a covariance matrix. A primary workhorse of stationary spatial statistics is Gaussian maximum log-likelihood estimation (MLE), whose central data structure is a dense, symmetric positive definite covariance matrix of dimension of the number of correlated observations. Two essential operations in MLE are the application of the inverse and evaluation of the determinant of the covariance matrix. These can be rendered through the Cholesky decomposition and triangular solution. In this contribution, we reduce the precision of weakly correlated locations to single- or half- precision based on distance. We thus exploit mathematical structure to migrate MLE to a three-precision approximation that takes advantage of contemporary architectures offering BLAS3-like operations in a single instruction that are extremely fast for reduced precision. We illustrate application-expected accuracy worthy of double-precision from a majority half-precision computation, in a context where uniform single precision is by itself insufficient. In tackling the complexity and imbalance caused by the mixing of three precisions, we deploy the PaRSEC runtime system. PaRSEC delivers on-demand casting of precisions while orchestrating tasks and data movement in a multi-GPU distributed-memory environment within a tile-based Cholesky factorization. Application-expected accuracy is maintained while achieving up to 1.59 by mixing FP64/FP32 operations on 1536 nodes of HAWK or 4096 nodes of Shaheen-II, and up to 2.64X by mixing FP64/FP32/FP16 operations on 128 nodes of Summit, relative to FP64-only operations, This translates into up to 4.5, 4.7, and 9.1 (mixed) PFlop/s sustained performance, respectively, demonstrating a synergistic combination of exascale architecture, dynamic runtime software, and algorithmic adaptation applied to challenging environmental problems.
  • Solubility and Stability of Some Pharmaceuticals in Natural Deep Eutectic Solvents-Based Formulations.

    Mustafa, Natali Rianika; Spelbos, Vincent Simon; Witkamp, Geert Jan; Verpoorte, Robert; Choi, Young Hae (Molecules (Basel, Switzerland), MDPI AG, 2021-05-05) [Article]
    Some medicines are poorly soluble in water. For tube feeding and parenteral administration, liquid formulations are required. The discovery of natural deep eutectic solvents (NADES) opened the way to potential applications for liquid drug formulations. NADES consists of a mixture of two or more simple natural products such as sugars, amino acids, organic acids, choline/betaine, and poly-alcohols in certain molar ratios. A series of NADES with a water content of 0-30% (w/w) was screened for the ability to solubilize (in a stable way) some poorly water-soluble pharmaceuticals at a concentration of 5 mg/mL. The results showed that NADES selectively dissolved the tested drugs. Some mixtures of choline-based NADES, acid-neutral or sugars-based NADES could dissolve chloral hydrate (dissociated in water), ranitidine·HCl (polymorphism), and methylphenidate (water insoluble), at a concentration of up to 250 mg/mL, the highest concentration tested. Whereas a mixture of lactic-acid-propyleneglycol could dissolve spironolacton and trimethoprim at a concentration up to 50 and 100 mg/mL, respectively. The results showed that NADES are promising solvents for formulation of poorly water-soluble medicines for the development of parenteral and tube feeding administration of non-water-soluble medicines. The chemical stability and bioavailability of these drug in NADES needs further studies.
  • D936Y and Other Mutations in the Fusion Core of the SARS-CoV-2 Spike Protein Heptad Repeat 1: Frequency, Geographical Distribution, and Structural Effect.

    Oliva, Romina; Shaikh, Abdul Rajjak; Petta, Andrea; Vangone, Anna; Cavallo, Luigi (Molecules (Basel, Switzerland), MDPI AG, 2021-05-05) [Article]
    The crown of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is constituted by its spike (S) glycoprotein. S protein mediates the SARS-CoV-2 entry into the host cells. The "fusion core" of the heptad repeat 1 (HR1) on S plays a crucial role in the virus infectivity, as it is part of a key membrane fusion architecture. While SARS-CoV-2 was becoming a global threat, scientists have been accumulating data on the virus at an impressive pace, both in terms of genomic sequences and of three-dimensional structures. On 15 February 2021, from the SARS-CoV-2 genomic sequences in the GISAID resource, we collected 415,673 complete S protein sequences and identified all the mutations occurring in the HR1 fusion core. This is a 21-residue segment, which, in the post-fusion conformation of the protein, gives many strong interactions with the heptad repeat 2, bringing viral and cellular membranes in proximity for fusion. We investigated the frequency and structural effect of novel mutations accumulated over time in such a crucial region for the virus infectivity. Three mutations were quite frequent, occurring in over 0.1% of the total sequences. These were S929T, D936Y, and S949F, all in the N-terminal half of the HR1 fusion core segment and particularly spread in Europe and USA. The most frequent of them, D936Y, was present in 17% of sequences from Finland and 12% of sequences from Sweden. In the post-fusion conformation of the unmutated S protein, D936 is involved in an inter-monomer salt bridge with R1185. We investigated the effect of the D936Y mutation on the pre-fusion and post-fusion state of the protein by using molecular dynamics, showing how it especially affects the latter one.
  • Detailed nature of tire pyrolysis oil blended with light cycle oil and its hydroprocessed products using a NiW/HY catalyst

    Palos, Roberto; Kekäläinen, Timo; Duodu, Frank; Gutiérrez, Alazne; Arandes, José M.; Jänis, Janne; Castaño, Pedro (Waste Management, Elsevier BV, 2021-05-04) [Article]
    The pyrolysis of scrap tires is a very attractive strategy to valorize chemically these end-of-life wastes. The products of this step and any additional one, such as hydrotreating, are relatively complex in nature entangling the understanding and limiting the viability. In this work, we have investigated in detail the composition of a tire pyrolysis oil blended with light cycle oil (from a refinery) and its hydrotreated products using a bifunctional NiW/HY catalyst at 320–400 °C. We have applied a set of analytical techniques to assess the composition, namely simulated distillation, ICP, GC/FID-PFPD, GC × GC/MS, and APPI FT-ICR/MS. Our results show the strength of our analytical workflow to highlight the compositional similarities of this pyrolysis oil with the standard refinery streams. The main differences arise from the higher boiling point species (originated during the pyrolysis of tires) and relatively high concentration of oxygenates. These effects can be minimized by hydrotreating the feed which effectively removes heteroatomic compounds from the feed while boosting the quantity and quality of gasoline and diesel fractions.
  • Verification and runtime assurance for dynamical systems with uncertainty

    Abate, Matthew; Mote, Mark; Feron, Eric; Coogan, Samuel (ACM, 2021-05-04) [Conference Paper]
    In this work, we show how controlled robustly forward invariant sets for systems with disturbances are efficiently identified via the application of the mixed monotonicity property. A mixed monotone system can be embedded in a related deterministic embedding system with twice as many states but for which the dynamics are monotone; one can then apply the powerful theory of monotone dynamical systems to the embedding system to conclude useful properties of the initial mixed monotone system. Using this technique, we present a method for verifying state-feedback controllers against safety (set invariance) constraints, and our approach involves evaluating a control barrier function type condition that requires the vector field of the embedding system to point into a certain southeast cone. This approach also facilitates the construction of runtime assurance mechanisms for controlled systems with disturbances, and we study system safety in the presence of state uncertainty as well. The results and findings of this work are demonstrated through two numerical examples where we study (i) the verification of a controlled spacecraft system against a safety constraint, and (ii) the formation of a runtime assurance mechanism that functions in the presence of uncertain state measurements.
  • Cluster analysis with cellwise trimming and applications for the robust clustering of curves

    García-Escudero, L.A.; Rivera-García, D.; Mayo-Iscar, A.; Ortega, Alejandra (Information Sciences, Elsevier BV, 2021-05-04) [Article]
    In this work, we propose a robust cluster analysis methodology based on cellwise trimming as an extension to a robust version of Principal Component Analysis. This new approach is more reasonable than traditional casewise trimming when the dimension is not small. This type of trimming avoids an unnecessary loss of information when only a few cells of the entirely trimmed observations are atypical. We propose an algorithm to apply this approach. This algorithm is particularized to the case of functional cluster analysis. We provide simulations and applications using real data sets to illustrate the proposed methodology.
  • Structure of the full-length human Pannexin1 channel and insights into its role in pyroptosis

    Zhang, Sensen; Yuan, Baolei; Lam, Jordy Homing; Zhou, Jun; Zhou, Xuan; Ramos Mandujano, Gerardo; Tian, Xueyuan; Liu, Yang; Han, Renmin; Li, Yu; Gao, Xin; Li, Mo; Yang, Maojun (Cell Discovery, Springer Science and Business Media LLC, 2021-05-04) [Article]
    AbstractPannexin1 (PANX1) is a large-pore ATP efflux channel with a broad distribution, which allows the exchange of molecules and ions smaller than 1 kDa between the cytoplasm and extracellular space. In this study, we show that in human macrophages PANX1 expression is upregulated by diverse stimuli that promote pyroptosis, which is reminiscent of the previously reported lipopolysaccharide-induced upregulation of PANX1 during inflammasome activation. To further elucidate the function of PANX1, we propose the full-length human Pannexin1 (hPANX1) model through cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulation studies, establishing hPANX1 as a homo-heptamer and revealing that both the N-termini and C-termini protrude deeply into the channel pore funnel. MD simulations also elucidate key energetic features governing the channel that lay a foundation to understand the channel gating mechanism. Structural analyses, functional characterizations, and computational studies support the current hPANX1-MD model, suggesting the potential role of hPANX1 in pyroptosis during immune responses.
  • Halide Perovskites: A New Era of Solution-Processed Electronics

    Younis, Adnan; Lin, Chun-Ho; Guan, Xinwei; Shahrokhi, Shamim; Huang, Chien-Yu; Wang, Yutao; He, Tengyue; Singh, Simrjit; Hu, Long; Duran Retamal, Jose Ramon; He, Jr-Hau; Wu, Tao (Advanced Materials, Wiley, 2021-05-03) [Article]
    Organic–inorganic mixed halide perovskites have emerged as an excellent class of materials with a unique combination of optoelectronic properties, suitable for a plethora of applications ranging from solar cells to light-emitting diodes and photoelectrochemical devices. Recent works have showcased hybrid perovskites for electronic applications through improvements in materials design, processing, and device stability. Herein, a comprehensive up-to-date review is presented on hybrid perovskite electronics with a focus on transistors and memories. These applications are supported by the fundamental material properties of hybrid perovskite semiconductors such as tunable bandgap, ambipolar charge transport, reasonable mobility, defect characteristics, and solution processability, which are highlighted first. Then, recent progresses on perovskite-based transistors are reviewed, covering aspects of fabrication process, patterning techniques, contact engineering, 2D versus 3D material selection, and device performance. Furthermore, applications of perovskites in nonvolatile memories and artificial synaptic devices are presented. The ambient instability of hybrid perovskites and the strategies to tackle this bottleneck are also discussed. Finally, an outlook and opportunities to develop perovskite-based electronics as a competitive and feasible technology are highlighted.
  • Clinical and Genetic Characterization of Craniosynostosis in Saudi Arabia.

    Alghamdi, Malak; Alhumsi, Taghreed R; Altweijri, Ikhlass; Alkhamis, Waleed H; Barasain, Omar; Cardona-Londoño, Kelly J; Ramakrishnan, Reshmi; Guzmán-Vega, Francisco J.; Arold, Stefan T.; Ali, Ghaida; Adly, Nouran; Ali, Hebatallah; Basudan, Ahmed; Bakhrebah, Muhammed A (Frontiers in pediatrics, Frontiers Media SA, 2021-05-03) [Article]
    Background: Craniosynostosis (CS) is defined as pre-mature fusion of one or more of the cranial sutures. CS is classified surgically as either simple or complex based on the number of cranial sutures involved. CS can also be classified genetically as isolated CS or syndromic CS if the patient has extracranial deformities. Currently, the link between clinical and genetic patterns of CS in the Saudi population is poorly understood. Methodology: We conducted a retrospective cohort study among 28 CS patients, of which 24 were operated and four were not. Clinical and genetic data were collected between February 2015 and February 2019, from consenting patient’s families. The electronic chart data were collected and analyzed including patient demographics, craniofacial features, other anomalies and dysmorphic features, operative data, intra cranial pressure (ICP), parent consanguinity and genetic testing results. Results: The most common deformity in our population was trigonocephaly. The most performed procedure was cranial vault reconstruction with fronto-orbital advancement, followed by posterior vault distraction osteogenesis and suturectomy with barrel staving. Genetics analysis revealed pathogenic mutations in FGFR2 (6 cases), TWIST1 (3 cases), ALPL (2 cases), and TCF12 (2 cases), and FREM1 (2 case). Conclusion: Compared to Western countries, our Saudi cohort displays significant differences in the prevalence of CS features, such as the types of sutures and prevalence of inherited CS. The genomic background allows our phenotype-genotype study to reclassify variants of unknown significance. Worldwide, the sagittal suture is the most commonly affected suture in simple CS, but in the Saudi population, the metopic suture fusion was most commonly seen in our clinic. Further studies are needed to investigate the characteristics of CS in our population in a multicenter setting.
  • Nonvolatile magnetic half adder combined with memory writing

    Lu, Ziyao; Xiong, Chengyue; Mou, Hongming; Luo, Zhaochu; Fang, Chi; Wan, Caihua; Wu, Huaqiang; Zhang, Xixiang; Zhang, Xiaozhong (Applied Physics Letters, AIP Publishing, 2021-05-03) [Article]
    With the rapid development of modern computers, problems caused by the performance gap between processor and memory in von-Neumann architecture have become significant. Spintronic devices, benefitting from the potential of achieving in-memory computing, have become one of the most competitive candidates to bridge the performance gap. Great efforts have been made to realize the functions of modern computers using spintronic devices. Here, a nonvolatile magnetic arithmetic logic device working at room temperature based on coupling of anomalous Hall effect of Ta/CoFeB/MgO multilayers with perpendicular magnetic anisotropy and elements with negative differential resistance characteristics has been proposed. Logic function of half adder has been experimentally demonstrated. This device could perform the arithmetic logic function of half adder and simultaneously write the computation result in storage bits in the process of performing logic operation. It has the potential to bridge the gap between arithmetic logic units and memory in modern computers.
  • Clinical and Genetic Characterization of Craniosynostosis in Saudi Arabia.

    Alghamdi, Malak; Alhumsi, Taghreed R; Altweijri, Ikhlass; Alkhamis, Waleed H; Barasain, Omar; Cardona-Londoño, Kelly J; Ramakrishnan, Reshmi; Guzmán-Vega, Francisco J.; Arold, Stefan T.; Ali, Ghaida; Adly, Nouran; Ali, Hebatallah; Basudan, Ahmed; Bakhrebah, Muhammed A (Frontiers in pediatrics, Frontiers Media SA, 2021-05-03) [Article]
    Background: Craniosynostosis (CS) is defined as pre-mature fusion of one or more of the cranial sutures. CS is classified surgically as either simple or complex based on the number of cranial sutures involved. CS can also be classified genetically as isolated CS or syndromic CS if the patient has extracranial deformities. Currently, the link between clinical and genetic patterns of CS in the Saudi population is poorly understood. Methodology: We conducted a retrospective cohort study among 28 CS patients, of which 24 were operated and four were not. Clinical and genetic data were collected between February 2015 and February 2019, from consenting patient’s families. The electronic chart data were collected and analyzed including patient demographics, craniofacial features, other anomalies and dysmorphic features, operative data, intra cranial pressure (ICP), parent consanguinity and genetic testing results. Results: The most common deformity in our population was trigonocephaly. The most performed procedure was cranial vault reconstruction with fronto-orbital advancement, followed by posterior vault distraction osteogenesis and suturectomy with barrel staving. Genetics analysis revealed pathogenic mutations in FGFR2 (6 cases), TWIST1 (3 cases), ALPL (2 cases), and TCF12 (2 cases), and FREM1 (2 case). Conclusion: Compared to Western countries, our Saudi cohort displays significant differences in the prevalence of CS features, such as the types of sutures and prevalence of inherited CS. The genomic background allows our phenotype-genotype study to reclassify variants of unknown significance. Worldwide, the sagittal suture is the most commonly affected suture in simple CS, but in the Saudi population, the metopic suture fusion was most commonly seen in our clinic. Further studies are needed to investigate the characteristics of CS in our population in a multicenter setting.
  • Investigation of flux stability and fouling mechanism during simultaneous treatment of different produced water streams using forward osmosis and membrane distillation.

    Nawaz, Muhammad Saqib; Son, Hyuk Soo; Jin, Yong; Kim,Youngjin; Soukane, Sofiane; Al-Hajji, Mohammed Ali; Abu-Ghdaib, Muhannad; Ghaffour, NorEddine (Water research, Elsevier BV, 2021-05-02) [Article]
    Forward osmosis-membrane distillation (FO-MD) hybrids were recently found suitable for produced water treatment. Exclusion of synthetic chemical draw solutions, typically used for FO, can reduce FO-MD operational costs and ease its onsite application. This study experimentally validates a novel concept for the simultaneous treatment of different produced water streams available at the same industrial site using an FO-MD hybrid system. The water oil separator outlet (WO) stream was selected as FO draw solution and it generated average fluxes ranging between 8.30 LMH and 26.78 LMH with four different feed streams. FO fluxes were found to be governed by the complex composition of the feed streams. On the other hand, with WO stream as MD feed, an average flux of 14.41 LMH was achieved. Calcium ions were found as a main reason for MD flux decline in the form of CaSO4 scaling and stimulating the interaction between the membrane and humic acid molecules to form scale layer causing reduction in heat transfer and decline in MD flux (6%). Emulsified oil solution was responsible for partial pore clogging resulting in further 2% flux decline. Ethylenediaminetetraaceticacid (EDTA) was able to mask a portion of calcium ions and resulted in a complete recovery of the original MD flux. Under hybrid FO-MD experiments MD fluxes between 5.62 LMH and 11.12 LMH were achieved. Therefore, the novel concept is validated to produce fairly stable FO and MD fluxes, with few streams, without severe fouling and producing excellent product water quality.
  • Hierarchically Structured Ti3C2T MXene Paper for Li-S Batteries with High Volumetric Capacity

    zhao, Wenli; Lei, Yongjiu; Zhu, Yunpei; Wang, Qian; Zhang, Fan; Dong, Xiaochen; Alshareef, Husam N. (Nano Energy, Elsevier BV, 2021-05-02) [Article]
    Due to the Low density of sulfur as well as the large portion of carbon-based materials used as conducting network and lithium polysulfide (LiPS) host, the practical volumetric energy density of lithium–sulfur (Li–S) batteries barely rivals the Li-ion batteries. Here, MXene (Ti3C2Tx)-based membrane with unique 3D hierarchical structure, high electronic conductivity, abundent active binding sites, fast ion transport ability, and high affinity for lithium polysulfides has been developed as a new host material to improve the electrochemical performance of Li-S batteries. With a density of 2.2 g cm−3, a MXene-based cathode containing 4.0 mg cm−2 sulfur delivers a high volumetric capacity of 2.7 Ah cm−3 after 200 cycles. Based on operando XRD and ex-situ XPS results, we find that the Ti-OH bonds present on the surface of MXene membrane can effectively trigger the LiPS transformation. Furthermore, α-S8, as the stable charge product, is first reported in MXene-based host along with its possible important role in curtailing active mass loss and enhancing cycling capability. Our results reveal that 2D MXene with rationally-designed architecture enable high volumetric capacity Li-S batteries for practical applications.
  • Enzyme catalysis with artificial membranes towards process intensification in biorefinery- A review

    Mazzei, Rosalinda; Yihdego Gebreyohannes, Abaynesh; Papaioannou, Emmaouil; Nunes, Suzana Pereira; Vankelecom, Ivo F.J.; Giorno, Lidietta (Bioresource Technology, Elsevier BV, 2021-05) [Article]
    In this review, for the first time, the conjugation of the major types of enzymes used in biorefineries and the membrane processes to develop different configurations of MBRs, was analyzed for the production of biofuels, phytotherapics, food ingredients, etc. In particular, the aim is to critically review all the works related to the application of MBR in biorefinery, highlighting the advantages and the main drawbacks which can interfere with the development of this system at industrial scale. Alternatives strategies to overcome main limits will be also described in the different application fields, such as the use of biofunctionalized magnetic nanoparticles associated with membrane processes for enzyme re-use and membrane cleaning or the membrane fouling control by the use of integrated membrane process associated with MBR.
  • Topological Data Analysis of COVID-19 Virus Spike Proteins

    Chung, Moo K.; Ombao, Hernando (arXiv, 2021-05-01) [Preprint]
    Topological data analysis, including persistent homology, has undergone significant development in recent years. However, due to heterogenous nature of persistent homology features that do not have one-to-one correspondence across measurements, it is still difficult to build a coherent statistical inference procedure. The paired data structure in persistent homology as birth and death events of topological features add further complexity to conducting inference. To address these current problems, we propose to analyze the birth and death events using lattice paths. The proposed lattice path method is implemented to characterize the topological features of the protein structures of corona viruses. This demonstrates new insights to building a coherent statistical inference procedure in persistent homology.
  • Atomistic simulations of syngas oxy-combustion in supercritical CO2

    Grajales Gonzalez, Edwing; Monge Palacios, Manuel; Sarathy, Mani (Journal of CO2 Utilization, Elsevier BV, 2021-04-30) [Article]
    The growing energy demand worldwide is currently supplied by the direct use of fossil fuels, which are limited in nature and represent an environmental concern. Syngas/oxy-combustion technologies have become popular due to recent advances in carbon capture and storage and the possibility to avoid NOX formation by replacing N2 with supercritical CO2. However, the successful implementation of these systems faces several drawbacks: variability in syngas composition and lack of understanding of the chemical kinetics at elevated temperature and pressures in the presence of CO2. In this work, we carried out a molecular dynamics study of syngas oxy-combustion using ReaxFF force field. Three main initiation reactions were identified: H2 + O2 → HO2 + H, H2 → H + H, and CO2 → CO + O, with the last being dominant at high temperatures and high concentrations of CO2. We also found that increasing the initial CO2 concentration and decreasing that of O2 delays ignition. However, for enriched CO2 mixtures, this substrate exerts a catalytic effect in the reactions H2 → H + H and H2O → OH + H by forming the intermediate HCO2. In the absence of initial CO2, formyl radical (HCO) chemistry is lacking due to the prominent consumption of H species by molecular oxygen via O2 + H → OH + O and H + O2 (+M) → HO2 (+M). However, we observed the association between HCO and OH radicals to form stable formic acid, a reaction not implemented in syngas mechanisms.
  • Efficient Hybrid Amorphous Silicon/Organic Tandem Solar Cells Enabled by Near-Infrared Absorbing Nonfullerene Acceptors

    Troughton, Joel; Neubert, Sebastian; Gasparini, Nicola; Villalva, Diego Rosas; Bertrandie, Jules; Seitkhan, Akmaral; Paleti, Sri Harish Kumar; Sharma, Anirudh; de Bastiani, Michele; Aydin, Erkan; Anthopoulos, Thomas D.; De Wolf, Stefaan; Schlatmann, Rutger; Baran, Derya (Advanced Energy Materials, Wiley, 2021-04-30) [Article]
    Monolithically stacked tandem solar cells present opportunities to absorb more of the sun's radiation while reducing the degree of energetic loss through thermalization. In these applications, the bandgap of the tandem's constituent subcells must be carefully adjusted so as to avoid competition for photons. Organic photovoltaics based on nonfullerene acceptors (NFAs) have recently exploded in popularity owing to the ease with which their electrical and optical properties can be tuned through chemistry. Here, highly complementary and efficient 2-terminal tandem solar cells are reported based on a wide bandgap amorphous silicon absorber, and a narrow bandgap NFA bulk-heterojunction with power conversion efficiencies (PCEs) exceeding 15%. Interface engineering of this tandem device allows for high PCEs across a wide range of light intensities both above and below “1 sun.” Furthermore, the addition of an inorganic silicon subcell enhances the operational stability of the tandem by reducing the light-stress experienced by the bulk heterojunction, resolving a long-standing stumbling block in organic photovoltaic research.
  • Solitary water waves created by variations in bathymetry

    Quezada de Luna, Manuel; Ketcheson, David I. (Journal of Fluid Mechanics, Cambridge University Press (CUP), 2021-04-30) [Article]
    We study the flow of water waves over bathymetry that varies periodically along one direction. We derive a linearized, homogenized model and show that the periodic bathymetry induces an effective dispersion, distinct from the dispersion inherently present in water waves. We relate this dispersion to the well-known effective dispersion introduced by changes in the bathymetry in non-rectangular channels. Numerical simulations using the (non-dispersive) shallow water equations reveal that a balance between this effective dispersion and nonlinearity can create solitary waves. We derive a Korteweg–de Vries-type equation that approximates the behaviour of these waves in the weakly nonlinear regime. We show that, depending on geometry, dispersion due to bathymetry can be much stronger than traditional water wave dispersion and can prevent wave breaking in strongly nonlinear regimes. Computational experiments using depth-averaged water wave models confirm the analysis and suggest that experimental observation of these solitary waves is possible.
  • A Roadmap to Sorption-Based Atmospheric Water Harvesting: From Molecular Sorption Mechanism to Sorbent Design and System Optimization

    Yang, Kaijie; Pan, Tingting; Lei, Qiong; Dong, Xinglong; Cheng, Qingpeng; Han, Yu (Environmental Science & Technology, American Chemical Society (ACS), 2021-04-29) [Article]
    Sorption-based atmospheric water harvesting (SAWH), which uses sorbents to capture water vapor from the air and low-grade energy to produce fresh liquid water, has been recognized as a promising strategy for decentralized water supply in arid areas. This review aims to summarize the latest progress in this field and provide perspectives for the further development of SAWH, focusing on the design of sorbent materials and the optimization of the entire system. We first introduce the water sorption mechanisms on different sorbent materials. Next, we discuss the properties and performances of various sorbents developed for SAWH by categorizing them into specific groups: nanoporous solids, hygroscopic polymers, salt-based composites, and liquid sorbents; for each type of sorbent materials, we have analyzed its advantages and limitations, as well as design strategies. In addition, we discuss the influences of the mass and heat transport of the SAWH system on its overall performance in actual operations, and introduce different types of water harvesters developed for SAWH. In the last section, we outline the challenges in this field from fundamental research and practical application aspects, and describe roadmaps for the future development of this technology.
  • 18.4% Organic Solar Cells Using a High Ionization Energy Self-Assembled Monolayer as Hole Extraction Interlayer

    Lin, Yuanbao; Magomedov, Artiom; Firdaus, Yuliar; Kaltsas, Dimitris; El Labban, Abdulrahman; Faber, Hendrik; Naphade, Dipti R; Yengel, Emre; Zheng, Xiaopeng; Yarali, Emre; Chaturvedi, Neha; Loganathan, Kalaivanan; Gkeka, Despoina; Alshammari, Sanaa Hayel Nazil; Bakr, Osman; Laquai, Frédéric; Tsetseris, Leonidas; Getautis, Vytautas; Anthopoulos, Thomas D. (ChemSusChem, Wiley, 2021-04-29) [Article]
    Self-assembled monolayers (SAMs) based on Br-2PACz and MeO-2PACz molecules are investigated as hole-extracting interlayers in organic photovoltaics (OPVs). The highest occupied molecular orbital (HOMO) energies of these SAMs were measured at -6.01 and -5.30 eV for Br-2PACz and MeO-2PACz, respectively, and found to induce significant changes in the work function (WF) of indium-tin-oxide (ITO) electrodes upon chemical functionalization. OPV cells based on PM6:BTP-eC9:PC 71 BM using ITO/Br-2PACz anodes exhibit a maximum power conversion efficiency (PCE) of 18.4%, outperforming devices with ITO/MeO-2PACz (14.5%) and ITO/PEDOT:PSS (17.5%). The higher PCE is found to originate from the much higher WF of ITO/Br-2PACz (-5.81 eV) compared to ITO/MeO-2PACz (4.58 eV) and ITO/PEDOT:PSS (4.9 eV), resulting in lower interface resistance, improved hole transport/extraction, lower trap-assisted recombination, and longer carrier lifetimes. Importantly, the ITO/Br-2PACz electrode is chemically stable and after removal of the SAM it can be recycled and reused to construct fresh OPVs with equally impressive performance.

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