Recent Submissions

  • Cloud resolving simulation of extremely heavy rainfall event over Kerala in August 2018 – Sensitivity to microphysics and aerosol feedback

    Thomas, Biyo; Viswanadhapalli, Yesubabu; Srinivas, C.V.; Dasari, Hari Prasad; Attada, Raju; Langodan, Sabique (Atmospheric Research, Elsevier BV, 2021-04-19) [Article]
    The state of Kerala located in the southwestern part of India experienced heavy to extremely heavy rainfall events from 07 to 17 August 2018 during the southwest monsoon, leading to a devastating flood and extensive infrastructure damage. Rainfall analysis suggests that the prolonged heavy rainfall event between 14 and 17 August 2018, was responsible for the major devastation. In this work, the sensitivity of prediction of heavy rainfall during 14–17 August 2018 to cloud microphysics parameterization (CMP) is investigated using the Weather Research and Forecasting (WRF) model. High resolution (1-km) cloud resolving simulations are conducted to study the sensitivity of rainfall to the cloud microphysics schemes and cloud-aerosol interactions. The model results are compared with observations such as Automatic Weather Station, Tropical Rainfall Measuring Mission, radiosonde, Global Precipitation Mission precipitation estimates and Doppler weather radar products. Comparisons of simulated hydrometeor structure with DWR estimates and thermodynamic stability indices with radiosonde reveal that the differences in microphysics formulations play a vital role on the thermodynamic profile that in turn influence the intensity of convection and hydrometeor structure responsible for the extremely heavy rainfall. Comparison of simulated rainfall with IMD observational estimates suggests that the Thomson aerosol aware scheme, followed by Goddard microphysics captured the spatial and temporal distributions of observed heavy rainfall. The Thomson aerosol aware scheme followed by Goddard produced strong convective instability conditions for heavy rainfall due to the simulation of a strong westerly jet and the formation of an offshore vortex.
  • Camera Calibration and Player Localization in SoccerNet-v2 and Investigation of their Representations for Action Spotting

    Cioppa, Anthony; Deliège, Adrien; Magera, Floriane; Giancola, Silvio; Barnich, Olivier; Ghanem, Bernard; Droogenbroeck, Marc Van (arXiv, 2021-04-19) [Preprint]
    Soccer broadcast video understanding has been drawing a lot of attention in recent years within data scientists and industrial companies. This is mainly due to the lucrative potential unlocked by effective deep learning techniques developed in the field of computer vision. In this work, we focus on the topic of camera calibration and on its current limitations for the scientific community. More precisely, we tackle the absence of a large-scale calibration dataset and of a public calibration network trained on such a dataset. Specifically, we distill a powerful commercial calibration tool in a recent neural network architecture on the large-scale SoccerNet dataset, composed of untrimmed broadcast videos of 500 soccer games. We further release our distilled network, and leverage it to provide 3 ways of representing the calibration results along with player localization. Finally, we exploit those representations within the current best architecture for the action spotting task of SoccerNet-v2, and achieve new state-of-the-art performances.
  • Controlling Electrochemically Induced Volume Changes in Conjugated Polymers by Chemical Design: from Theory to Devices

    Moser, Maximilian; Gladisch, Johannes; Ghosh, Sarbani; Hidalgo, Tania Cecilia; Ponder, James F.; Sheelamanthula, Rajendar; Thiburce, Quentin; Gasparini, Nicola; Wadsworth, Andrew; Salleo, Alberto; Inal, Sahika; Berggren, Magnus; Zozoulenko, Igor; Stavrinidou, Eleni; McCulloch, Iain (Advanced Functional Materials, Wiley, 2021-04-17) [Article]
    Electrochemically induced volume changes in organic mixed ionic-electronic conductors (OMIECs) are particularly important for their use in dynamic microfiltration systems, biomedical machinery, and electronic devices. Although significant advances have been made to maximize the dimensional changes that can be accomplished by OMIECs, there is currently limited understanding of how changes in their molecular structures impact their underpinning fundamental processes and their performance in electronic devices. Herein, a series of ethylene glycol functionalized conjugated polymers is synthesized, and their electromechanical properties are evaluated through a combined approach of experimental measurements and molecular dynamics simulations. As demonstrated, alterations in the molecular structure of OMIECs impact numerous processes occurring during their electrochemical swelling, with sidechain length shortening decreasing the number of incorporated water molecules, reducing the generated void volumes and promoting the OMIECs to undergo different phase transitions. Ultimately, the impact of these combined molecular processes is assessed in organic electrochemical transistors, revealing that careful balancing of these phenomena is required to maximize device performance.
  • Reimagining aquaculture in the Global South.

    Bank, Michael S; Swarzenski, Peter W; Bianchi, Gabriella; Metian, Marc; Ok, Yong Sik; Duarte, Carlos M. (Science (New York, N.Y.), American Association for the Advancement of Science (AAAS), 2021-04-16) [Article]
    Aquaculture has existed for millennia, reaching industrial scales in recent decades, and will play an increasingly important role in feeding the world (1–6). As this industry grows, we must ensure that it is ecologically and socially sustainable. However, the current production process for the food given to farmed fish still threatens coastal ecosystems and the livelihoods of local fishers, especially in the Global South (2–7). Before aquaculture is scaled up further, its global environmental and socioeconomic footprint should be carefully reimagined.
  • Covalent Assembly of Two-Dimensional COF-on-MXene Heterostructures Enables Fast Charging Lithium Hosts

    Guo, Dong; Ming, Fangwang; Shinde, Digambar; Cao, Li; Huang, Gang; Li, Chunyang; Li, Zhen; Yuan, Youyou; Hedhili, Mohamed N.; Alshareef, Husam N.; Lai, Zhiping (Advanced Functional Materials, Wiley, 2021-04-16) [Article]
    2D heterostructured materials combining ultrathin nanosheet morphology, defined pore configuration, and stable hybrid compositions, have attracted increasing attention for fast mass transport and charge transfer, which are highly desirable features for efficient energy storage. Here, the chemical space of 2D–2D heterostructures is extended by covalently assembling covalent organic frameworks (COFs) on MXene nanosheets. Unlike most COFs, which are generally produced as solid powders, ultrathin 2D COF-LZU1 grows in situ on aminated Ti3C2Tx nanosheets with covalent bonding, producing a robust MXene@COF heterostructure with high crystallinity, hierarchical porosity, and conductive frameworks. When used as lithium hosts in Li metal batteries, lithium storage and charge transport are significantly improved. Both spectroelectrochemical and theoretical analyses demonstrate that lithiated COF channels are important as fast Li+ transport layers, by which Li ions can be precisely nucleated. This affords dendrite-free and fast-charging anodes, which would be difficult to achieve using individual components.
  • Need for Rationally Designed SnWO4 Photo(electro)catalysts to Overcome the Performance Limitations for O2 and H2 Evolution Reactions

    Azofra Mesa, Luis; Cavallo, Luigi; Basset, Jean-Marie; Harb, Moussab (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2021-04-16) [Article]
    Although the α-SnWO4 material has recently been considered as a new good candidate for visible-light-driven photo(electro)chemical water splitting, the performance is still low and requires further improvement. Here, we present a deep fundamental work on the influence of the various possible facets exposed on this material for oxygen and hydrogen evolution reactions using hybrid density functional theory. The energetic, electronic, water redox, and charge carrier transport features of the four possible (100), (010), (001), and (110) facets (low-Miller index surfaces) are investigated, and significant anisotropic nature is revealed. The relevant properties of each facet to the water oxidation/reduction reactions are correlated with the surface W coordination number. Taking into account the stability and combining optoelectronic and water redox features together of each surface, our work demonstrates that the (110) facet is photocatalytically the best candidate for the OER, while the (100) facet is the best candidate for the HER. Their transport characteristics are found to be much better than those obtained for the three major (121), (210), and (111) facets of synthesized α-SnWO4 samples. Substitutional Ge at the Sn site and Mo at the W site on the two (110) and (100) facets are expected to increase the rates of the water oxidation/reduction reactions. An analysis of the reaction mechanism for the OER in (110)-oriented α-SnWO4 reveals a promising performance of this facet for electrocatalytic water oxidation. These outcomes will greatly motivate experimentalists for carefully designing (110)- and (100)-oriented α-SnWO4 samples to enhance the photo(electro)catalytic OER and photocatalytic HER performances.
  • Intriguing Ultrafast Charge Carrier Dynamics in Two-Dimensional Ruddlesden–Popper Hybrid Perovskites

    Yin, Jun; Bakr, Osman; Mohammed, Omar F. (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2021-04-16) [Article]
    Two-dimensional (2D) Ruddlesden–Popper (RP) hybrid perovskites are among the most promising semiconductor candidates for next-generation highly efficient optoelectronic devices due to their impressive optical and transport properties. More importantly, 2D hybrid perovskites exhibit much higher structural and chemical stability against moisture and light radiation levels than their 3D counterparts, indicating a wide range of potential applications and commercialization. The highly ordered multiple-quantum-well structures of 2D RP perovskites give rise to several optoelectronic properties that can be effectively tuned by compositional engineering of organic spacers and inorganic layer thicknesses. In this Perspective, we review recent studies of charge carrier dynamics in 2D RP perovskites. More specifically, we focus on understanding how organic cations and the number of inorganic layers govern the ultrafast charge carrier dynamics in 2D RP perovskites. We also highlight our recent work on hot-carrier cooling dynamics, Rashba band splitting, and narrowband and broadband emissions in various 2D RP hybrid perovskites. We also provide a perspective on the future studies of 2D RP perovskites, including structure–property relationships, and remaining questions on the charge carrier dynamics, including hot-carrier extractions.
  • Dopant-Assisted Matrix Stabilization Enables Thermoelectric Performance Enhancement in n-Type Quantum Dot Films.

    Nugraha, Mohamad Insan; Sun, Bin; Kim, Hyunho; El Labban, Abdulrahman; Desai, Saheena; Chaturvedi, Neha; Hou, Yi; García de Arquer, F Pelayo; Alshareef, Husam N.; Sargent, E.; Baran, Derya (ACS applied materials & interfaces, American Chemical Society (ACS), 2021-04-15) [Article]
    Efficient thermoelectric generators require further progress in developing n-type semiconductors that combine low thermal conductivity with high electrical conductivity. By embedding colloidal quantum dots (CQDs) in a metal halide matrix (QDMH), the metal halide matrix can enhance phonon scattering, thus suppressing thermal transport; however, simultaneously achieving high electrical conductivity in such systems has previously been limited by the deleterious impact of a large density of interfaces on charge transport. Therefore, new strategies are needed to improve charge carrier transport without sacrificing matrix-enabled low thermal transport. Here, we report the use of chemical doping in the solution state to improve electron transport while maintaining low thermal transport in QDMH films. By incorporating cesium carbonate (Cs2CO3) salts as a dopant prior to matrix formation, we find that the dopant stabilizes the matrix in colloidal inks and enables efficient n-type doping in QDMH films. As a result, this strategy leads to an enhanced n-type thermoelectric behavior in solution-processed QDMH films near room temperature, with a thermal conductivity of 0.25 W m–1 K–1—significantly lower than in prior films based on organic-ligand-cross-linked CQD films (>0.6 W m–1 K–1) and spark-plasma-sintered CQD systems (>1 W m–1 K–1). This study provides a pathway to developing efficient n-type thermoelectric materials with low thermal conductivity using single-step deposition and low-temperature processing.
  • SeedQuant: A deep learning-based tool for assessing stimulant and inhibitor activity on root parasitic seeds.

    Braguy, Justine; Ramazanova, Merey; Giancola, Silvio; Jamil, Muhammad; Kountche, Boubacar Amadou; Zarban, Randa Alhassan Yahya; Felemban, Abrar; Wang, Jian You; Lin, Pei-Yu; Haider, Imran; Zurbriggen, Matias; Ghanem, Bernard; Al-Babili, Salim (Plant physiology, Oxford University Press (OUP), 2021-04-15) [Article]
    Witchweeds (Striga spp.) and broomrapes (Orobanchaceae and Phelipanche spp.) are root parasitic plants that infest many crops in warm and temperate zones, causing enormous yield losses and endangering global food security. Seeds of these obligate parasites require rhizospheric, host-released stimulants to germinate, which opens up possibilities for controlling them by applying specific germination inhibitors or synthetic stimulants that induce lethal germination in host's absence. To determine their effect on germination, root exudates or synthetic stimulants/inhibitors are usually applied to parasitic seeds in in vitro bioassays, followed by assessment of germination ratios. Although these protocols are very sensitive, the germination recording process is laborious, representing a challenge for researchers and impeding high-throughput screens. Here, we developed an automatic seed census tool to count and discriminate germinated from non-germinated seeds. We combined deep learning, a powerful data-driven framework that can accelerate the procedure and increase its accuracy, for object detection with computer vision latest development based on the Faster R-CNN algorithm. Our method showed an accuracy of 94% in counting seeds of Striga hermonthica and reduced the required time from ˜5 minutes to 5 seconds per image. Our proposed software, SeedQuant, will be of great help for seed germination bioassays and enable high-throughput screening for germination stimulants/inhibitors. ​SeedQuant is an open-source software that can be further trained to count different types of seeds for research purposes.
  • ENSO feedback drives variations in dieback at a marginal mangrove site

    Hickey, S. M.; Radford, B.; Callow, J. N.; Phinn, S. R.; Duarte, Carlos M.; Lovelock, C. E. (Scientific Reports, Springer Nature, 2021-04-14) [Article]
    AbstractOcean–atmosphere climatic interactions, such as those resulting from El Niño Southern Oscillation (ENSO) are known to influence sea level, sea surface temperature, air temperature, and rainfall in the western Pacific region, through to the north-west Australian Ningaloo coast. Mangroves are ecologically important refuges for biodiversity and a rich store of blue carbon. Locations such as the study site (Mangrove Bay, a World Heritage Site within Ningaloo Marine Park and Cape Range National Park) are at the aridity range-limit which means trees are small in stature, forests small in area, and are potentially susceptible to climate variability such as ENSO that brings lower sea level and higher temperature. Here we explore the relationship between mangrove dieback, and canopy condition with climatic variables and the Southern Oscillation Index (SOI)—a measure of ENSO intensity, through remote sensing classification of Landsat satellite missions across a 29 year period at a north-west Australian site. We find that the SOI, and seasonal mean minimum temperature are strongly correlated to mangrove green canopy (as indicator of live canopy) area. This understanding of climate variations and mangrove temporal heterogeneity (patterns of abundance and condition) highlights the sensitivity and dynamics of this mangrove forest and recommends further research in other arid and semi-arid tropical regions at mangrove range-limits to ascertain the extent of this relationship.
  • Optimized Runge-Kutta Methods with Automatic Step Size Control for Compressible Computational Fluid Dynamics

    Ranocha, Hendrik; Dalcin, Lisandro; Parsani, Matteo; Ketcheson, David I. (arXiv, 2021-04-14) [Preprint]
    We develop error-control based time integration algorithms for compressible fluid dynamics (CFD) applications and show that they are efficient and robust in both the accuracy-limited and stability-limited regime. Focusing on discontinuous spectral element semidiscretizations, we design new controllers for existing methods and for some new embedded Runge-Kutta pairs. We demonstrate the importance of choosing adequate controller parameters and provide a means to obtain these in practice. We compare a wide range of error-control-based methods, along with the common approach in which step size control is based on the Courant-Friedrichs-Lewy (CFL) number. The optimized methods give improved performance and naturally adopt a step size close to the maximum stable CFL number at loose tolerances, while additionally providing control of the temporal error at tighter tolerances. The numerical examples include challenging industrial CFD applications.
  • Temporally-Aware Feature Pooling for Action Spotting in Soccer Broadcasts

    Giancola, Silvio; Ghanem, Bernard (arXiv, 2021-04-14) [Preprint]
    Toward the goal of automatic production for sports broadcasts, a paramount task consists in understanding the high-level semantic information of the game in play. For instance, recognizing and localizing the main actions of the game would allow producers to adapt and automatize the broadcast production, focusing on the important details of the game and maximizing the spectator engagement. In this paper, we focus our analysis on action spotting in soccer broadcast, which consists in temporally localizing the main actions in a soccer game. To that end, we propose a novel feature pooling method based on NetVLAD, dubbed NetVLAD++, that embeds temporally-aware knowledge. Different from previous pooling methods that consider the temporal context as a single set to pool from, we split the context before and after an action occurs. We argue that considering the contextual information around the action spot as a single entity leads to a sub-optimal learning for the pooling module. With NetVLAD++, we disentangle the context from the past and future frames and learn specific vocabularies of semantics for each subsets, avoiding to blend and blur such vocabulary in time. Injecting such prior knowledge creates more informative pooling modules and more discriminative pooled features, leading into a better understanding of the actions. We train and evaluate our methodology on the recent large-scale dataset SoccerNet-v2, reaching 53.4% Average-mAP for action spotting, a +12.7% improvement w.r.t the current state-of-the-art.
  • Flexible behaviour in a mesopelagic fish (Maurolicus muelleri)

    Christiansen, Svenja; Klevjer, Thor A; Røstad, Anders; Aksnes, Dag L; Kaartvedt, Stein (ICES Journal of Marine Science, Oxford University Press (OUP), 2021-04-14) [Article]
    Abstract Variability of mesopelagic scattering layers is often attributed to environmental conditions or multi-species layer composition. Yet, little is known about variation in behaviour among the individuals forming scattering layers. Based on a 10 months high-resolution dataset from stationary echosounders in a Norwegian fjord, we here assess short-term and long-term behaviour of a single mesopelagic fish species, the pearlside Maurolicus muelleri. The daytime vertical extension of the monospecific pearlside scattering layers spanned four orders of magnitude ambient light in the autumn and winter and less than one order of magnitude in summer. While the main layers tracked relatively stable light levels over daytime, some individuals actively crossed light gradients of up to 1.5 orders of magnitude. This included individuals that moved between scattering layers, and apparently bold individuals that made regular upward excursions beyond the main population distribution. During the daytime, M. muelleri mitigated the risk of predation by forming tight groups in the upper scattering layer and, at light levels >10−6 µmol m−2 s−1, by instantly diving into deeper waters upon encounters with predators. Our observations suggest that individual, and probably state-dependent, decisions may extend the pearlsides’ vertical distribution, with implications for predator–prey interactions.
  • Significant variants of type 2 diabetes in the Arabian Region through an Integration of exome databases.

    Goto, Kosuke; Mineta, Katsuhiko; Miyazaki, Satoru; Gojobori, Takashi (PloS one, Public Library of Science (PLoS), 2021-04-13) [Article]
    Type 2 diabetes (T2D) is a major global health issue, and it has also become one of the major diseases in Arab countries. In addition to the exome databases that have already been established, whole exome sequencing data for the Greater Middle East are now available. To elucidate the genetic features of T2D in the Arabian Peninsula, we integrated two exome databases (gnomAD exome and the Greater Middle East Variome Project) with clinical information from the ClinVar. After the integration, we obtained 18 single nucleotide polymorphisms and found two statistically and clinically significant variants in two genes, SLC30A8 rs13266634 and KCNJ11 rs5219. Interestingly, the two genes are linked to the uptake of the metals, Zn and K respectively, which indicating the regional features of the genetic variants. The frequency of the risk allele of rs13266634 among individuals in the Arabian Peninsula was higher than among individuals in other regions. On the other hand, the frequency of the risk allele of rs5219 in the Arabian Peninsula was lower than that in other regions. We identified and characterized T2D-related variants that show unique tendencies in the Arabian Peninsula. Our analyses contribute to and provide guidance for the clinical research of T2D in the Arabian Peninsula.
  • Improved characterisation of clinical text through ontology-based vocabulary expansion.

    Slater, Luke T; Bradlow, William; Ball, Simon; Hoehndorf, Robert; Gkoutos, Georgios V (Journal of biomedical semantics, Springer Nature, 2021-04-13) [Article]
    BackgroundBiomedical ontologies contain a wealth of metadata that constitutes a fundamental infrastructural resource for text mining. For several reasons, redundancies exist in the ontology ecosystem, which lead to the same entities being described by several concepts in the same or similar contexts across several ontologies. While these concepts describe the same entities, they contain different sets of complementary metadata. Linking these definitions to make use of their combined metadata could lead to improved performance in ontology-based information retrieval, extraction, and analysis tasks.ResultsWe develop and present an algorithm that expands the set of labels associated with an ontology class using a combination of strict lexical matching and cross-ontology reasoner-enabled equivalency queries. Across all disease terms in the Disease Ontology, the approach found 51,362 additional labels, more than tripling the number defined by the ontology itself. Manual validation by a clinical expert on a random sampling of expanded synonyms over the Human Phenotype Ontology yielded a precision of 0.912. Furthermore, we found that annotating patient visits in MIMIC-III with an extended set of Disease Ontology labels led to semantic similarity score derived from those labels being a significantly better predictor of matching first diagnosis, with a mean average precision of 0.88 for the unexpanded set of annotations, and 0.913 for the expanded set.ConclusionsInter-ontology synonym expansion can lead to a vast increase in the scale of vocabulary available for text mining applications. While the accuracy of the extended vocabulary is not perfect, it nevertheless led to a significantly improved ontology-based characterisation of patients from text in one setting. Furthermore, where run-on error is not acceptable, the technique can be used to provide candidate synonyms which can be checked by a domain expert.
  • Seagrass (Halophila stipulacea) invasion enhances carbon sequestration in the Mediterranean Sea.

    Wesselmann, Marlene; Geraldi, Nathan; Duarte, Carlos M.; Garcia-Orellana, Jordi; Diaz Rua, Ruben; Arias-Ortiz, Ariane; Hendriks, Iris E; Apostolaki, Eugenia T; Marbà, Núria (Global change biology, Wiley, 2021-04-12) [Article]
    The introduction and establishment of exotic species often result in significant changes in recipient communities and their associated ecosystem services. However, usually the magnitude and direction of the changes are difficult to quantify because there is no pre-introduction data. Specifically, little is known about the effect of marine exotic macrophytes on organic carbon sequestration and storage. Here, we combine dating sediment cores (210Pb) with sediment eDNA fingerprinting to reconstruct the chronology of pre- and post-arrival of the Red Sea seagrass Halophila stipulacea spreading into the Eastern Mediterranean native seagrass meadows. We then compare sediment organic carbon storage and burial rates before and after the arrival of H. stipulacea and between exotic (H. stipulacea) and native (C. nodosa and P. oceanica) meadows since the time of arrival following a Before-After-Control-Impact (BACI) approach. This analysis revealed that H. stipulacea arrived at the areas of study in Limassol (Cyprus) and West Crete (Greece) in the 1930s and 1970s, respectively. Average sediment organic carbon after the arrival of H. stipulacea to the sites increased in the exotic meadows twofold, from 8.4 ± 2.5 g Corg m−2 year−1 to 14.7 ± 3.6 g Corg m−2 year−1, and, since then, burial rates in the exotic seagrass meadows were higher than in native ones of Cymodocea nodosa and Posidonia oceanica. Carbon isotopic data indicated a 50% increase of the seagrass contribution to the total sediment Corg pool since the arrival of H. stipulacea. Our results demonstrate that the invasion of H. stipulacea may play an important role in maintaining the blue carbon sink capacity in the future warmer Mediterranean Sea, by developing new carbon sinks in bare sediments and colonizing areas previously occupied by the colder thermal affinity P. oceanica.
  • Vigilant: An Engineered VirD2-Cas9 Complex for Lateral Flow Assay-Based Detection of SARS-CoV2

    Marsic, Tin; Ali, Zahir; Tehseen, Muhammad; Mahas, Ahmed; Hamdan, Samir; Mahfouz, Magdy M. (Nano Letters, American Chemical Society (ACS), 2021-04-12) [Article]
    Rapid, sensitive, and specific point-of-care testing for pathogens is crucial for disease control. Lateral flow assays (LFAs) have been employed for nucleic acid detection, but they have limited sensitivity and specificity. Here, we used a fusion of catalytically inactive SpCas9 endonuclease and VirD2 relaxase for sensitive, specific nucleic acid detection by LFA. In this assay, the target nucleic acid is amplified with biotinylated oligos. VirD2-dCas9 specifically binds the target sequence via dCas9 and covalently binds to a FAM-tagged oligonucleotide via VirD2. The biotin label and FAM tag are detected by a commercially available LFA. We coupled this system, named Vigilant (<u>Vi</u>rD2-dCas9 <u>g</u>u<u>i</u>ded and <u>L</u>FA-coupled <u>n</u>ucleic acid <u>t</u>est), to reverse transcription-recombinase polymerase amplification to detect SARS-CoV2 in clinical samples. Vigilant exhibited a limit of detection of 2.5 copies/μL, comparable to CRISPR-based systems, and showed no cross-reactivity with SARS-CoV1 or MERS. Vigilant offers an easy-to-use, rapid, cost-effective, and robust detection platform for SARS-CoV2.
  • Snapshot space-time holographic three-dimensional particle tracking velocimetry

    Chen, Ni; Wang, Congli; Heidrich, Wolfgang (Laser & Photonics Reviews, Wiley-VCH, 2021-04-12) [Article]
    Digital inline holography is an amazingly simple and effective approach for three-dimensional imaging, to which particle tracking velocimetry is of particular interest. Conventional digital holographic particle tracking velocimetry techniques are computationally separated in particle and flow reconstruction, plus the expensive computations. Usually, the particle volumes are recovered firstly, from which fluid flows are computed. Without iterative reconstructions, This sequential spacetime process lacks accuracy. This paper presents a joint optimization framework for digital holographic particle tracking velocimetry: particle volumes and fluid flows are reconstructed jointly in a higher space-time dimension, enabling faster convergence and better reconstruction quality of both fluid flow and particle volumes within a few minutes on modern GPUs. Synthetic and experimental results are presented to show the efficiency of the proposed technique.
  • Iso-anchorene is an endogenous metabolite that inhibits primary root growth in Arabidopsis.

    Jia, Kunpeng; Mi, Jianing; Ablazov, Abdugaffor; Ali, Shawkat; Yang, Yu; Balakrishna, Aparna; Berqdar, Lamis; Feng, Qitong; Blilou, Ikram; Al-Babili, Salim (The Plant journal : for cell and molecular biology, Wiley, 2021-04-10) [Article]
    Carotenoid-derived regulatory metabolites and hormones are generally known to arise through the oxidative cleavage of a single double bond in the carotenoid backbone, which yields mono-carbonyl products called apocarotenoids. However, the extended conjugated double bond system of these pigments predestines them also to repeated cleavage forming di-aldehyde products, diapocarotenoids, which have been less investigated due to their instability and low abundance. Recently, we reported on the short diapocarotenoid anchorene as an endogenous Arabidopsis metabolite and specific signaling molecule that promotes anchor root formation. In this work, we investigated the biological activity of a synthetic isomer of anchorene, iso-anchorene, which can derive from repeated carotenoid cleavage. We show that iso-anchorene is a growth inhibitor that specifically inhibits primary root growth by reducing cell division rates in the root apical meristem. Using auxin efflux transporter marker lines, we also show that the effect of iso-anchorene on primary root growth involves the modulation of auxin homeostasis. Moreover, by using liquid chromatography mass spectrometry (LC-MS) analysis, we demonstrate that iso-anchorene is a natural Arabidopsis metabolite. Chemical inhibition of carotenoid biosynthesis led to a significant decrease in the iso-anchorene level, indicating that it originates from this metabolic pathway. Taken together, our results reveal a further carotenoid-derived regulatory metabolite with a specific biological function that affects root growth, manifesting the biological importance of diapocarotenoids.
  • Statistical study on engine knock oscillation and heat release using multiple spark plugs and pressure sensors

    Shi, Hao; Uddeen, Kalim; An, Yanzhao; Pei, Yiqiang; Johansson, Bengt (Fuel, Elsevier BV, 2021-04-10) [Article]
    Engine knock has been an inherent problem that limits engine efficiency improvement and threatens engine service life. To trigger the controllable knock, a specialized liner with installing four side spark plugs mounted on the cylinder head are used in this study to produce various in-cylinder flame propagation. Various spark strategies (e.g., spark timing, spark number, spark location) are applied to generate different auto-ignition sites and knock characteristics. Up to five channels of pressure signal are collected to analyze the knock intensities regarding different spark strategies. To investigate the knock-induced fluctuations and heat release, we use the multiple correlations to evaluate the maximum amplitude of pressure oscillation (MAPO) respecting different influential factors and building a multiple linear regression (MLR) model for MAPO prediction and validate it against the experiment results. Besides, the Wiebe function and curve-fitting techniques are applied to estimate the energy released by auto-ignition in each cycle, and its relations with knock intensity are assessed. The results show that the average growth of pre-oscillation plays an important role in MAPO value (correlation coefficient, r_s = 0.965), the established MLR model possesses high accuracy for MAPO prediction. The pressure oscillation regarding the 1st resonance mode is extracted from the band-pass filtered signal, representing the main pressure oscillating process. Compared with the single spark ignition, triggering more spark plugs could boost the fuel consumption rate, while shortening the knocking combustion duration and reducing the heat release fraction contributed by auto-ignition. At the same CA50 (9 CAD aTDC), the four spark ignition leads to the least heat release fluctuations than other spark strategies. With advancing the CA50, the heat release fraction produced by knock increases at first then reduces due to the thermodynamic conditions and the flame propagation. Activating two or three spark plugs, the rising rate of the heat release rate goes up, but the knock-induced heat release fraction decreases. Moreover, the primary acoustic resonance mode (1, 0) gives more regular knock vibrations than the mixing form (including mode (1, 0), (0, 1), (2, 0), etc.), the average traveling distance of acoustic wave in the time gap of receiving two continuous signals is very close to the cylinder bore. The results give insights into the pressure wave propagation during knock and the relations between knock conditions, pressure oscillations, and heat release.

View more