Recent Submissions

  • Coupled Crust-Mantle Evolution for > 2 Gy in Southern Africa from Exceptionally Strong Crustal Anisotropy

    THYBO, Hans; YOUSSUF, Mohammad; ARTEMIEVA, Irina M. (Acta Geologica Sinica - English Edition, Wiley, 2021-11-27) [Article]
    An enigmatic feature of Precambrian continental lithosphere is its long-term stability, which depends on the degree of coupling between the crust and mantle since cratonisation. Earlier studies infer deformation of the lower lithosphere by mantle flow with fast direction of seismic anisotropy being parallel to present plate motion, and/or report anisotropy frozen into the lithospheric mantle. We demonstrate coupled crust-mantle evolution in southern African cratons for more than 2 billion years based on unexpectedly strong crustal azimuthal anisotropy (Thybo et al., 2019). The direction of the fast axis is uniform within tectonic units and parallel to orogenic strike in the Limpopo and Cape fold belts. It is further parallel to the strike of major dyke swarms which indicates that a large part of the observed anisotropy is controlled by lithosphere fabrics and macroscopic effects. Parallel fast axes in the crust and in the mantle indicate coupled crust-mantle evolution. These conclusions have implications for the rheology of the lower lithosphere and the effects of mantle flow on lithosphere deformation.
  • Perovskite-Nanosheet Sensitizer for Highly Efficient Organic X-ray Imaging Scintillator

    Wang, Jian-Xin; Wang, Xiaojia; Yin, Jun; Gutierrez Arzaluz, Luis; He, Tengyue; Chen, Cailing; Han, Yu; Zhang, Yuhai; Bakr, Osman; Eddaoudi, Mohamed; Mohammed, Omar F. (ACS Energy Letters, American Chemical Society (ACS), 2021-11-27) [Article]
    The weak X-ray capture capability of organic scintillators always leads to poor imaging resolution and detection sensitivity. Here, we realize an efficient and reabsorption-free organic scintillator at the interface of perovskite nanosheets using a very efficient energy transfer strategy. Our steady-state and ultrafast time-resolved experiments supported by density functional theory calculations demonstrate that an efficient interfacial energy transfer from the perovskite nanosheet to the organic chromophore with thermally activated delayed fluorescence (TADF) character can be achieved. Interestingly, we found that the direct harnessing of both singlet and triplet excitons of the TADF chromophores also contributed greatly to its remarkably enhanced radioluminescence intensity and X-ray sensitivity. A high X-ray imaging resolution of 135 μm and a low detection limit of 38.7 nGy/s were achieved in the fabricated X-ray imaging scintillator.
  • Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection

    Horn, Susanne; Schmid, Peter J.; Aurnou, Jonathan M. (EPL (Europhysics Letters), IOP Publishing, 2021-11-26) [Article]
    The large-scale circulation (LSC) is the most fundamental turbulent coherent flow structure in Rayleigh-B\'enard convection. Further, LSCs provide the foundation upon which superstructures, the largest observable features in convective systems, are formed. In confined cylindrical geometries with diameter-to-height aspect ratios of Γ ≅ 1, LSC dynamics are known to be governed by a quasi-two-dimensional, coupled horizontal sloshing and torsional (ST) oscillatory mode. In contrast, in Γ ≥ √2 cylinders, a three-dimensional jump rope vortex (JRV) motion dominates the LSC dynamics. Here, we use dynamic mode decomposition (DMD) on direct numerical simulation data of liquid metal to show that both types of modes co-exist in Γ = 1 and Γ = 2 cylinders but with opposite dynamical importance. Furthermore, with this analysis, we demonstrate that ST oscillations originate from a tilted elliptical mean flow superposed with a symmetric higher order mode, which is connected to the four rolls in the plane perpendicular to the LSC in Γ = 1 tanks.
  • Investigation on the formic acid evaporation and ignition of formic acid/octanol blend at elevated temperature and pressure

    Maharjan, Sumit; Elbaz, Ayman M.; Roberts, William L. (Fuel, Elsevier BV, 2021-11-25) [Article]
    With the growing advancements in new energy sources, formic acid has become a subject of interest as a hydrogen carrier. Apart from being a hydrogen carrier source, to explore the possibility of formic acid being used as a potential fuel in engines, the combustion of formic acid is yet to be explored fully. Few studies have been conducted to determine its laminar burning velocity. The study of droplet combustion and evaporation is also critical if formic acid is to be deployed as a potential fuel. Therefore, the evaporation of formic acid with a droplet diameter of ∼1.00 mm is investigated in a constant volume combustion chamber for pressures ranging from 5 bar to 20 bar at a wide temperature range (150–300 °C). A model was developed to get a fundamental understanding of the experimental results. The D2 plot from experimental data exhibited the presence of two zones for evaporation. Zone 1 showed a slower evaporation rate compared to zone 2. Due to a thin layer of formic acid remaining on the thermocouple, the surface area of the droplet increased in zone 2, resulting in faster evaporation of the droplet. The steeper decline in droplet evaporation occurred at the point of complete loss of sphericity of the droplet. Even so, the trend for total evaporation time from the model and experiments was consistent. Formic acid is a low reactive fuel, and it did not ignite at the ambient temperature and pressure of 300 °C and 20 bar, respectively. So, to determine the auto-ignition behavior of formic acid, a separate experimental setup that could exceed the ambient temperature higher than the auto-ignition temperature of formic acid was used. When pure formic acid did not ignite, it was mixed with octanol at different concentrations and further investigated. The mixture droplet’s ignition probability slightly decreased to 65 vol% of formic acid addition in the octanol. Further addition of formic acid in octanol significantly decreased the ignition probability of the mixture droplet. Lastly, a polynomial equation is proposed to extrapolate the auto-ignition time of pure formic acid droplets with a droplet diameter of ∼0.7 mm.
  • Transistors based on two-dimensional materials for future integrated circuits

    Das, Saptarshi; Sebastian, Amritanand; Pop, Eric; McClellan, Connor J.; Franklin, Aaron D.; Grasser, Tibor; Knobloch, Theresia; Illarionov, Yury; Penumatcha, Ashish V.; Appenzeller, Joerg; Chen, Zhihong; Zhu, Wenjuan; Asselberghs, Inge; Li, Lain-Jong; Avci, Uygar E.; Bhat, Navakanta; Anthopoulos, Thomas D.; Singh, Rajendra (Nature Electronics, Springer Science and Business Media LLC, 2021-11-25) [Article]
    Field-effect transistors based on two-dimensional (2D) materials have the potential to be used in very large-scale integration (VLSI) technology, but whether they can be used at the front end of line or at the back end of line through monolithic or heterogeneous integration remains to be determined. To achieve this, multiple challenges must be overcome, including reducing the contact resistance, developing stable and controllable doping schemes, advancing mobility engineering and improving high-κ dielectric integration. The large-area growth of uniform 2D layers is also required to ensure low defect density, low device-to-device variation and clean interfaces. Here we review the development of 2D field-effect transistors for use in future VLSI technologies. We consider the key performance indicators for aggressively scaled 2D transistors and discuss how these should be extracted and reported. We also highlight potential applications of 2D transistors in conventional micro/nanoelectronics, neuromorphic computing, advanced sensing, data storage and future interconnect technologies.
  • Numerical investigation of the effect of injection strategy on a high-pressure isobaric combustion engine

    Liu, Xinlei; Aljabri, Hammam H.; Al-lehaibi, Moaz; AlRamadan, Abdullah S; Badra, Jihad; Im, Hong G. (International Journal of Engine Research, SAGE Publications, 2021-11-25) [Article]
    High-pressure isobaric combustion adopted in the double compression expansion engine (DCEE) has the prospect to achieve higher thermal efficiency compared to conventional diesel combustion. This work numerically explored the effects of various injection strategies on the combustion and emission characteristics of isobaric combustion. The study developed a mathematical model to predict the injection rate profile. After validations, extensive simulations were conducted with a peak pressure of up to 300 bar – mimicking the high-pressure unit of DCEE. Several major engine design parameters such as the exhaust recirculation gas (EGR) rate, engine speed, injection strategy, and intake pressure were varied and evaluated. The results demonstrated that a higher EGR rate resulted in a higher exhaust loss but a lower heat transfer loss owing to the lower combustion temperature, so the thermal efficiency exhibited a firstly growing and then declining trend. Besides, a higher engine speed generated a higher thermal efficiency due to the shorter combustion duration and thus lower heat transfer loss. Consequently, a peak thermal efficiency of 47.5% was achieved at EGR = 50% and 1800 rpm. The high-pressure cylinder performance can also be improved with an appropriate introduction of the isochoric combustion, but its impact on the whole DCEE setup needs further investigation.
  • The barley immune receptor Mla recognizes multiple pathogens and contributes to host range dynamics

    Bettgenhaeuser, Jan; Hernández-Pinzón, Inmaculada; Dawson, Andrew M.; Gardiner, Matthew; Green, Phon; Taylor, Jodie; Smoker, Matthew; Ferguson, John N.; Emmrich, Peter; Hubbard, Amelia; Bayles, Rosemary; Waugh, Robbie; Steffenson, Brian J.; Wulff, Brande B. H.; Dreiseitl, Antonín; Ward, Eric R.; Moscou, Matthew J. (Nature Communications, Springer Science and Business Media LLC, 2021-11-25) [Article]
    Crop losses caused by plant pathogens are a primary threat to stable food production. Stripe rust (Puccinia striiformis) is a fungal pathogen of cereal crops that causes significant, persistent yield loss. Stripe rust exhibits host species specificity, with lineages that have adapted to infect wheat and barley. While wheat stripe rust and barley stripe rust are commonly restricted to their corresponding hosts, the genes underlying this host specificity remain unknown. Here, we show that three resistance genes, Rps6, Rps7, and Rps8, contribute to immunity in barley to wheat stripe rust. Rps7 cosegregates with barley powdery mildew resistance at the Mla locus. Using transgenic complementation of different Mla alleles, we confirm allele-specific recognition of wheat stripe rust by Mla. Our results show that major resistance genes contribute to the host species specificity of wheat stripe rust on barley and that a shared genetic architecture underlies resistance to the adapted pathogen barley powdery mildew and non-adapted pathogen wheat stripe rust.
  • Clownfish hosting anemones (Anthozoa, Actiniaria) of the Red Sea: new associations and distributions, historical misidentifications, and morphological variability

    Bennett-Smith, Morgan; Majoris, John E.; Titus, Benjamin M.; Berumen, Michael L. (Marine Biodiversity Records, Springer Science and Business Media LLC, 2021-11-25) [Article]
    Background: The Red Sea contains thousands of kilometers of fringing reef systems inhabited by clownfish and sea anemones, yet there is no consensus regarding the diversity of host anemone species that inhabit this region. We sought to clarify a historical record and recent literature sources that disagree on the diversity of host anemone species in the Red Sea, which contains one endemic anemonefish, Amphiprion bicinctus Rüppell 1830. Results: We conducted 73 surveys spanning ~ 1600 km of coastline from the northern Saudi Arabian Red Sea to the Gulf of Aden and encountered seven species of host anemones, six of which hosted A. bicinctus. We revise the list of symbionts for A. bicinctus to include Stichodactyla haddoni (Saville-Kent, 1893) and Stichodactyla mertensii Brandt, 1835 which were both observed in multiple regions. We describe Red Sea phenotypic variability in Heteractis crispa (Hemprich & Ehrenberg in Ehrenberg, 1834) and Heteractis aurora (Quoy & Gaimard, 1833), which may indicate that these species hybridize in this region. We did not encounter Stichodactyla gigantea (Forsskål, 1775), although the Red Sea is the type locality for this species. Further, a thorough review of peer-reviewed literature, occurrence records, and misidentified basis of record reports dating back to the early twentieth century indicate that it is unlikely that S. gigantea occurs in the Red Sea. Conclusions: In sum, we present a new guide for the host anemones of the Red Sea, revise the host specificity of A. bicinctus, and question whether S. gigantea occurs in the central and western Indian Ocean.
  • Influences of ALD Al2O3 on the surface band-bending of c-plane, Ga-face GaN

    Gong, Jiarui; Lu, Kuangye; Kim, Jisoo; Ng, Tien Khee; Kim, Donghyeok; Zhou, Jie; Liu, Dong; Kim, Jeehwan; Ooi, Boon S.; Ma, Zhenqiang (Japanese Journal of Applied Physics, IOP Publishing, 2021-11-25) [Article]
    The recently demonstrated approach of grafting n-type GaN with p-type Si or GaAs, by employing ultrathin Al2O3 at the interface, has shown the feasibility to overcome the poor p-type doping challenge of GaN. However, the surface band-bending of GaN that could be influenced by the Al2O3 has been unknown. In this work, the band-bending of c-plane, Ga-face GaN with ultrathin Al2O3 deposition at the surface of GaN was studied using X-ray photoelectron spectroscopy (XPS). The study shows that the Al2O3 can help suppress the upward band-bending of the c-plane, Ga-face GaN with a monotonic reduction trend from 0.48 eV down to 0.12 eV as the number of Al2O3 deposition cycles increases from 0 to 20. The study further shows that the band-bending can be mostly recovered after removing the Al2O3 layer, concurring that the introduction of ultrathin Al2O3 is the main reason for the surface band-bending modulation.
  • Exploring the Structure and Performance of Cd–Chalcogenide Photocatalysts in Selective Trifluoromethylation

    Muralirajan, Krishnamoorthy; Kancherla, Rajesh; Bau, Jeremy; Taksande, Mayur Rahul; Qureshi, Muhammad; Takanabe, Kazuhiro; Rueping, Magnus (ACS Catalysis, American Chemical Society (ACS), 2021-11-24) [Article]
    The field of heterogeneous photoredox catalysis has grown substantially and impacted organic synthesis because of the affordability and reusability of catalysts. This study reports radical trifluoromethylation with Cd–chalcogenide semiconductors. Cd semiconductors, particularly CdSe, are readily available, commercial, visible-light-responsive, heterogeneous photocatalysts. The potential of readily available Cd semiconductors, particularly CdSe, is confirmed by their increased photocatalytic activity toward trifluoromethylation with various substrates, such as (hetero)arenes and vinylic amides/acids, via addition, cyclization, and decarboxylation under visible light. The economic significance of this strategy is also highlighted through the scalable synthesis of biologically active molecules followed by catalyst reuse. Moreover, these catalysts are relatively inexpensive compared with transition metal-based homogeneous photocatalysts, presently used in organic synthesis.
  • A Homozygous Missense Variant in PPP1R1B/DARPP-32 Is Associated With Generalized Complex Dystonia

    Khan, Amjad; Molitor, Anne; Mayeur, Sylvain; Zhang, Gaoqun; Rinaldi, Bruno; Lannes, Béatrice; Lhermitte, Benoît; Umair, Muhammad; Arold, Stefan T.; Friant, Sylvie; Rastegar, Sepand; Anheim, Mathieu; Bahram, Seiamak; Carapito, Raphael (Movement Disorders, Wiley, 2021-11-24) [Article]
    Background The dystonias are a heterogeneous group of hyperkinetic disorders characterized by sustained or intermittent muscle contractions that cause abnormal movements and/or postures. Although more than 200 causal genes are known, many cases of primary dystonia have no clear genetic cause. Objectives To identify the causal gene in a consanguineous family with three siblings affected by a complex persistent generalized dystonia, generalized epilepsy, and mild intellectual disability. Methods We performed exome sequencing in the parents and two affected siblings and characterized the expression of the identified gene by immunohistochemistry in control human and zebrafish brains. Results We identified a novel missense variant (c.142G>A (NM_032192); p.Glu48Lys) in the protein phosphatase 1 regulatory inhibitor subunit 1B gene (PPP1R1B) that was homozygous in all three siblings and heterozygous in the parents. This gene is also known as dopamine and cAMP-regulated neuronal phosphoprotein 32 (DARPP-32) and has been involved in the pathophysiology of abnormal movements. The uncovered variant is absent in public databases and modifies the conserved glutamate 48 localized close to the serine 45 phosphorylation site. The PPP1R1B protein was shown to be expressed in cells and regions involved in movement control, including projection neurons of the caudate-putamen, substantia nigra neuropil, and cerebellar Purkinje cells. The latter cells were also confirmed to be positive for PPP1R1B expression in the zebrafish brain. Conclusions We report the association of a PPP1R1B/DARPP-32 variant with generalized dystonia in man. It might be relevant to include the sequencing of this new gene in the diagnosis of patients with otherwise unexplained movement disorders. © 2021 International Parkinson and Movement Disorder Society
  • Simple and Precision Approach to Polythioimidocarbonates and Hybrid Block Copolymer Derivatives

    Lai, Tao; Zhang, Pengfei; Zhao, Junpeng; Zhang, Guangzhao (Macromolecules, American Chemical Society (ACS), 2021-11-24) [Article]
    The advancement of polymeric materials relies heavily on the innovation in polymerization reactions. In this study, we have discovered alternating copolymerization of isothiocyanate (ITC) and epoxide, which results in a nearly unexploited sulfur-containing polymer, polythioimidocarbonate (PTC). Provided with a simple two-component catalyst, i.e., a Lewis pair consisting of triethylborane (Et3B) and excess phosphazene base (PB), the copolymerization starts from an alcohol and proceeds in a strictly alternating and highly chemoselective manner, yielding PTC with controlled molar mass and low dispersity, free of cyclic byproducts and ether linkages. The method applies well to a variety of ITCs and epoxides. It is also found with great excitement that the reaction on ITC is fully inhibited when the catalyst composition is inverted to have Et3B in excess, while homopolymerization of epoxide occurs selectively in this case. Density functional theory (DFT) calculation reveals that Et3B-alkoxide complexation is the key to suppressing the back-biting reaction during the copolymerization ([Et3B] < [PB]) and inhibiting the copolymerization ([Et3B] > [PB]). This unique “biased” feature is harnessed to develop a catalyst switch strategy for one-pot block copolymerization from the mixture of ITC and epoxide with either copolymerization or homopolymerization conducted first, resulting in tailor-made PTC-polyether block copolymers with reversible sequence structures. On the other hand, sequence-selective terpolymerization occurs from a mixture of phthalic anhydride, ITC, and epoxide, allowing the one-step synthesis of polyester-PTC block terpolymer. These results have highlighted the versatility of the method for exploring this uncharted area of polymers.
  • Selective Separation of Lithium Chloride by Organogels Containing Strapped Calix[4]pyrroles

    Wang, Hu; Jones, Leighton O.; Hwang, Inhong; Allen, Marshall J.; Tao, Daliao; Lynch, Vincent M.; Freeman, Benny D.; Khashab, Niveen M.; Schatz, George C; Page, Zachariah A.; Sessler, Jonathan L. (Journal of the American Chemical Society, American Chemical Society (ACS), 2021-11-23) [Article]
    Reported herein are two functionalized crown ether strapped calix[4]pyrroles, H1 and H2. As inferred from competitive salt binding experiments carried out in nitrobenzene-d5 and acetonitrile-d3, these hosts capture LiCl selectively over four other test salts, viz. NaCl, KCl, MgCl2, and CaCl2. Support for the selectivity came from density functional theory (DFT) calculations carried out in a solvent continuum. These theoretical analyses revealed a higher innate affinity for LiCl in the case of H1, but a greater selectivity relative to NaCl in the case of H2, recapitulating that observed experimentally. Receptors H1 and H2 were outfitted with methacrylate handles and subject to copolymerization with acrylate monomers and cross-linkers to yield gels, G1 and G2, respectively. These two gels were found to adsorb lithium chloride preferentially from an acetonitrile solution containing a mixture of LiCl, NaCl, KCl, MgCl2, and CaCl2 and then release the lithium chloride in methanol. The gels could then be recycled for reuse in the selective adsorption of LiCl. As such, the present study highlights the use of solvent polarity switching to drive separations with potential applications in lithium purification and recycling.
  • Green Synthesis of Silver-Peptide Nanoparticles Generated by the Photoionization Process for Anti-Biofilm Application

    Seferji, Kholoud; Susapto, Hepi Hari; Khan, Babar Khalid; Rehman, Zahid Ur; Abbas, Manzar; Emwas, Abdul-Hamid M.; Hauser, Charlotte (ACS Applied Bio Materials, American Chemical Society (ACS), 2021-11-23) [Article]
    An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.
  • Oriented Two-Dimensional Covalent Organic Framework Membranes with High Ion Flux and Smart Gating Nanofluidic Transport

    Cao, Li; Liu, Xiaowei; Shinde, Digambar; Chen, Cailing; Chen, I-Chun; Li, Zhen; Zhou, Zongyao; Yang, Zhongyu; Han, Yu; Lai, Zhiping (Angewandte Chemie, Wiley, 2021-11-23) [Article]
    Nanofluidic ion transport holds high promise in bio-sensing and energy conversion applications. However, smart nanofluidic devices with high ion flux and modulable ion transport capabilities remain to be realised. Herein, we demonstrate smart nanofluidic devices based on oriented two-dimensional covalent organic framework (2D COF) membranes with vertically aligned nanochannel arrays that achieved a 2–3 orders of magnitude higher ion flux compared with that of conventional single-channel nanofluidic devices. The surface-charge-governed ion conductance is dominant for electrolyte concentration up to 0.01 M. Moreover, owing to the customisable pH-responsivity of imine and phenol hydroxyl groups, the COF-DT membranes attained an actively modulable ion transport with a high pH-gating on/off ratio of ~100. The customisable structure and rich chemistry of COF materials will offer a promising platform for manufacturing nanofluidic devices with modifiable ion/molecular transport features.
  • Synthesis and Characterization of Asymmetric A1BA2 Supramolecular Triblock Copolymers via Noncovalent Interactions: A Solution and Solid-State Study

    Bhaumik, Saibal; Shan, Wenpeng; Thomas, Edwin L.; Hadjichristidis, Nikos (Macromolecules, American Chemical Society (ACS), 2021-11-22) [Article]
    We present the design, synthesis, and characterization of triple hydrogen-bond-forming precursors and their supramolecular triblock copolymers. Thymine end-functionalized polystyrene-b-polyisoprene (PS-b-PI-Thy) and diaminotriazine end-functionalized polystyrene (PS-DAT) were successfully synthesized via anionic polymerization followed by suitable organic reactions and then solution-mixed to form supramolecular triblocks via hydrogen-bonding interactions. Three different types of asymmetric A1-b-B-sb-A2 supramolecular triblock copolymers were prepared by varying the molecular weight of the A1-b-B diblock copolymers and A2 homopolymers. Proton nuclear magnetic resonance spectroscopy was used for the detailed structural characterization of the polymers in solution, and gel permeation chromatography was used to determine the molecular weight and polydispersity index of all homopolymers and block copolymers. Additionally, transmission electron microscopy and small-angle X-ray scattering measurements were employed to assess the solid-state morphological structures of the supramolecular triple hydrogen-bond triblocks, the diblocks, and single hydrogen-bond mixtures of diblocks with homopolymers.
  • The development of integrated circuits based on two-dimensional materials

    Zhu, Kaichen; Wen, Chao; Aljarb, Areej A.; Xue, Fei; Xu, Xiangming; Tung, Vincent; Zhang, Xixiang; Alshareef, Husam N.; Lanza, Mario (Nature Electronics, Springer Science and Business Media LLC, 2021-11-22) [Article]
    Two-dimensional (2D) materials could potentially be used to develop advanced monolithic integrated circuits. However, despite impressive demonstrations of single devices and simple circuits—in some cases with performance superior to those of silicon-based circuits—reports on the fabrication of integrated circuits using 2D materials are limited and the creation of large-scale circuits remains in its infancy. Here we examine the development of integrated circuits based on 2D layered materials. We assess the most advanced circuits fabricated so far and explore the key challenges that need to be addressed to deliver highly scaled circuits. We also propose a roadmap for the future development of integrated circuits based on 2D layered materials.
  • Dual Mode Sensing of Binding and Blocking of Cancer Exosomes to Biomimetic Human Primary Stem Cell Surfaces

    Uribe, Johana; Traberg, Walther C.; Hama, Adel; Druet, Victor; Mohamed, Zeinab; Ooi, Amanda Siok Lee; Pappa, Anna-Maria; Huerta, Miriam; Inal, Sahika; Owens, R. M.; Daniel, Susan (ACS Biomaterials Science & Engineering, American Chemical Society (ACS), 2021-11-21) [Article]
    Cancer-derived exosomes (cEXOs) facilitate transfer of information between tumor and human primary stromal cells, favoring cancer progression. Although the mechanisms used during this information exchange are still not completely understood, it is known that binding is the initial contact established between cEXOs and cells. Hence, studying binding and finding strategies to block it are of great therapeutic value. However, such studies are challenging for a variety of reasons, including the need for human primary cell culture, the difficulty in decoupling and isolating binding from internalization and cargo delivery, and the lack of techniques to detect these specific interactions. In this work, we created a supported biomimetic stem cell membrane incorporating membrane components from human primary adipose-derived stem cells (ADSCs). We formed the supported membrane on glass and on multielectrode arrays to offer the dual option of optical or electrical detection of cEXO binding to the membrane surface. Using our platform, we show that cEXOs bind to the stem cell membrane and that binding is blocked when an antibody to integrin β1, a component of ADSC surface, is exposed to the membrane surface prior to cEXOs. To test the biological outcome of blocking this interaction, we first confirm that adding cEXOs to cultured ADSCs leads to the upregulation of vascular endothelial growth factor, a measure of proangiogenic activity. Next, when ADSCs are first blocked with anti-integrin β1 and then exposed to cEXOs, the upregulation of proangiogenic activity and cell proliferation are significantly reduced. This biomimetic membrane platform is the first cell-free label-free in vitro platform for the recapitulation and study of cEXO binding to human primary stem cells with potential for therapeutic molecule screening as it is compatible with scale-up and multiplexing.
  • Adversarial attack and defense methods for neural network based state estimation in smart grid

    Tian, Jiwei; Wang, Buhong; Li, Jing; Konstantinou, Charalambos (IET Renewable Power Generation, Institution of Engineering and Technology (IET), 2021-11-21) [Article]
    Deep learning has been recently used in safety-critical cyber-physical systems (CPS) such as the smart grid. The security assessment of such learning-based methods within CPS algorithms, however, is still an open problem. Despite existing research on adversarial attacks against deep learning models, only few works are concerned about safety-critical energy CPS, especially the state estimation routine. This paper investigates security issues of neural network based state estimation in the smart grid. Specifically, the problem of adversarial attacks against neural network based state estimation is analysed and an efficient adversarial attack method is proposed. To thwart this attack, two defense methods based on protection and adversarial training, respectively, are proposed further. The experiments demonstrate that the proposed attack method poses a major threat to neural network based state estimation models. In addition, our results present that defense methods can improve the ability of neural network models to defend against such adversarial attacks.
  • Machine Learning-Evolutionary Algorithm Enabled Design for 4D-Printed Active Composite Structures

    Sun, Xiaohao; Yue, Liang; Yu, Luxia; Shao, Han; Peng, Xirui; Zhou, Kun; Demoly, Frédéric; Zhao, Ruike; Qi, H. Jerry (Advanced Functional Materials, Wiley, 2021-11-21) [Article]
    Active composites consisting of materials that respond differently to environmental stimuli can transform their shapes. Integrating active composites and 4D printing allows the printed structure to have a pre-designed complex material or property distribution on numerous small voxels, offering enormous design flexibility. However, this tremendous design space also poses a challenge in efficiently finding appropriate designs to achieve a target shape change. Here, a novel machine learning (ML) and evolutionary algorithm (EA) based approach is presented to guide the design process. Inspired by the beam deformation characteristics, a recurrent neural network (RNN) based ML model whose training dataset is acquired by finite element simulations is developed for the forward shape-change prediction. EA empowered with ML is then used to solve the inverse problem of finding the optimal design. For multiple target shapes with different complexities, the ML-EA approach demonstrates high efficiency. Combining the ML-EA with computer vision algorithms, a new paradigm is presented that streamlines design and 4D printing process where active straight beams can be designed based on hand-drawn lines and be 4D printed that transform into the drawn profiles under the stimulus. The approach thus provides a highly efficient tool for the design of 4D-printed active composites.

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