Recent Submissions

  • Controlling wave fronts with tunable disordered non-Hermitian multilayers.

    Novitsky, Denis V; Lyakhov, Dmitry; Michels, Dominik L.; Redka, Dmitrii; Pavlov, Alexander A; Shalin, Alexander S (Scientific reports, Springer Science and Business Media LLC, 2021-02-27) [Article]
    Unique and flexible properties of non-Hermitian photonic systems attract ever-increasing attention via delivering a whole bunch of novel optical effects and allowing for efficient tuning light-matter interactions on nano- and microscales. Together with an increasing demand for the fast and spatially compact methods of light governing, this peculiar approach paves a broad avenue to novel optical applications. Here, unifying the approaches of disordered metamaterials and non-Hermitian photonics, we propose a conceptually new and simple architecture driven by disordered loss-gain multilayers and, therefore, providing a powerful tool to control both the passage time and the wave-front shape of incident light with different switching times. For the first time we show the possibility to switch on and off kink formation by changing the level of disorder in the case of adiabatically raising wave fronts. At the same time, we deliver flexible tuning of the output intensity by using the nonlinear effect of loss and gain saturation. Since the disorder strength in our system can be conveniently controlled with the power of the external pump, our approach can be considered as a basis for different active photonic devices.
  • Vector Autoregressive Models with Spatially Structured Coefficients for Time Series on a Spatial Grid

    Yan, Yuan; Huang, Hsin-Cheng; Genton, Marc G. (Journal of Agricultural, Biological and Environmental Statistics, Springer Science and Business Media LLC, 2021-02-26) [Article]
    Motivated by the need to analyze readily available data collected in space and time, especially in environmental sciences, we propose a parsimonious spatiotemporal model for time series data on a spatial grid. In essence, our model is a vector autoregressive model that utilizes the spatial structure to achieve parsimony of autoregressive matrices at two levels. The first level ensures the sparsity of the autoregressive matrices using a lagged-neighborhood scheme. The second level performs a spatial clustering of the nonzero autoregressive coefficients such that within some subregions, nearby locations share the same autoregressive coefficients while across different subregions the coefficients may have distinct values. The model parameters are estimated using the penalized maximum likelihood with an adaptive fused Lasso penalty. The estimation procedure can be tailored to accommodate the need and prior knowledge of a modeler. Performance of the proposed estimation algorithm is examined in a simulation study. Our method gives reliable estimation results that are interpretable and especially useful to identify geographical subregions, within each of which, the time series have similar dynamical behavior with homogeneous autoregressive coefficients. We apply our model to a wind speed time series dataset generated from a climate model over Saudi Arabia to illustrate its power in explaining the dynamics by the spatially structured coefficients. Moreover, the estimated model can be useful for building stochastic weather generators as an approximation of the computationally expensive climate model.
  • The Importance of Thermal Treatment on Wet-Kneaded Silica–Magnesia Catalyst and Lebedev Ethanol-to-Butadiene Process

    Chung, Sang-Ho; Galilea, Adrian; Shoinkhorova, Tuiana; Mukhambetov, Ildar; Abou-Hamad, Edy; Telalovic, Selevedin; Gascon, Jorge; Ruiz-Martinez, Javier (Nanomaterials, MDPI AG, 2021-02-26) [Article]
    The Lebedev process, in which ethanol is catalytically converted into 1,3-butadiene, is an alternative process for the production of this commodity chemical. Silica–magnesia (SiO2–MgO) is a benchmark catalyst for the Lebedev process. Among the different preparation methods, the SiO2–MgO catalysts prepared by wet-kneading typically perform best owing to the surface magnesium silicates formed during wet-kneading. Although the thermal treatment is of pivotal importance as a last step in the catalyst preparation, the effect of the calcination temperature of the wet-kneaded SiO2–MgO on the Lebedev process has not been clarified yet. Here, we prepared and characterized in detail a series of wet-kneaded SiO2–MgO catalysts using varying calcination temperatures. We find that the thermal treatment largely influences the type of magnesium silicates, which have different catalytic properties. Our results suggest that the structurally ill-defined amorphous magnesium silicates and lizardite are responsible for the production of ethylene. Further, we argue that forsterite, which has been conventionally considered detrimental for the formation of ethylene, favors the formation of butadiene, especially when combined with stevensite.
  • The global network of ports supporting high seas fishing

    Rodríguez, J. P.; Fernández-Gracia, Juan; Duarte, Carlos M.; Irigoien, Xabier; Eguíluz, V. M. (Science Advances, American Association for the Advancement of Science (AAAS), 2021-02-26) [Article]
    Fisheries in waters beyond national jurisdiction (“high seas”) are difficult to monitor and manage. Their regulation for sustainability requires critical information on how fishing effort is distributed across fishing and landing areas, including possible border effects at the exclusive economic zone (EEZ) limits. We infer the global network linking harbors supporting fishing vessels to fishing areas in high seas from automatic identification system tracking data in 2014, observing a modular structure, with vessels departing from a given harbor fishing mostly in a single province. The top 16% of these harbors support 84% of fishing effort in high seas, with harbors in low- and middle-income countries ranked among the top supporters. Fishing effort concentrates along narrow strips attached to the boundaries of EEZs with productive fisheries, identifying a free-riding behavior that jeopardizes efforts by nations to sustainably manage their fisheries, perpetuating the tragedy of the commons affecting global fishery resources.
  • Superconductivity and High-Pressure Performance of 2D Mo2C Crystals

    Zhang, Junli; Cao, Zhen; He, Xin; Liu, Wenhao; Wen, Yan; Cavallo, Luigi; Ren, Wencai; Cheng, Huiming; Zhang, Xixiang (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2021-02-26) [Article]
    Two-dimensional (2D) materials have attracted significant attention for their ability to support novel magneto-electrical transport and their optical and magnetic properties, of which their superconductivity is particularly of interest. Here we report on the behavior of superconductivity in 2D Mo2C crystals when hydrostatic pressure is applied, which has not yet been described in the literature. We found that the localization of boundary atoms disorder-induced Cooper pairs can suppress the superconducting transition temperature (Tc) as effectively as a magnetic field and current. We observed that the Tc initially decreased as the pressure increased to 1.75 GPa but then began to increase as the pressure increased further to 2.5 GPa. Our density functional theory calculations revealed that this behavior was linked to the modulation of the strength of the electron-phonon coupling and the electron property, which was triggered by compression of the lattice under high pressure. We attributed the inflection point in the hydrostatic pressure-dependent Tc curve to the structural phase transition of Mo2C from a hexagonal to an orthorhombic structure. This work presents a new avenue for the study of the superconductivity of Mo2C, which can be extended to apply to other 2D superconductors to modulate their electronic states.
  • Layer number dependent ferroelasticity in 2D Ruddlesden–Popper organic-inorganic hybrid perovskites

    Xiao, Xun; Zhou, Jian; Song, Kepeng; Zhao, Jingjing; Zhou, Yu; Rudd, Peter Neil; Han, Yu; Li, Ju; Huang, Jinsong (Nature Communications, Springer Science and Business Media LLC, 2021-02-26) [Article]
    AbstractFerroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield.
  • Theoretical Insights into the Limitation of Photocatalytic Overall Water Splitting Performance of VIA Group Elements Doped Polymeric Carbon Nitride: A DFT Calculation Predicting Solar-to-Hydrogen Efficiency

    Wang, Yiqing; Zhao, Daming; Deng, Hao; Li, Mingtao; Chen, Jie; Shen, Shaohua (Solar RRL, Wiley, 2021-02-26) [Article]
    Polymeric carbon nitride (p-C3N4) is thermodynamically feasible for photocatalytic overall water splitting. Element doping has been proved effective in enhancing the photocatalytic performance of p-C3N4. The effect of doping is usually interpreted from the angle of electronic structures by first-principles density functional theory (DFT) calculations. However, the information on electronic structures is insufficient for understanding and predicting the ultimate criterion of solar-to-hydrogen (STH) efficiency. Herein, we provided a DFT calculation method to investigate and predict the STH of VIA group elements doped p-C3N4 by calculating the efficiencies of both light absorption and carrier utilization. Particularly, significant efforts were made to calculating the energy barriers for surface hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to determine the carrier utilization efficiency. Moreover, the chemisorption energies of the reactant intermediates were calculated to quantify the intermediates affinity for HER and OER on the surface. Among the VIA elements, oxygen was discovered as the most effective dopant in promoting the STH because that oxygen-doped p-C3N4 has the lowest energy barriers for OER and the largest chemisorption energy for intermediates absorption. The calculation results highlight the importance of the surface reaction properties for efficient photocatalytic overall water splitting.
  • Surrogate formulation and molecular characterization of sulfur species in vacuum residues using APPI and ESI FT-ICR mass spectrometry

    Abdul Jameel, Abdul Gani; Alquaity, Awad B.S.; Campuzano, Felipe; Emwas, Abdul-Hamid M.; Saxena, Saumitra; Sarathy, Mani; Roberts, William L. (Fuel, Elsevier BV, 2021-02-26) [Article]
    Vacuum residues (VR) are the bottom of the barrel products left after vacuum distillation of crude oils. VR are primarily used as feedstock for production of syn-gas and hydrogen via gasification; and heavy fuel oil (HFO) for use as fuel in power generation and shipping. However, VR contain relatively large amounts of sulfur (upto 8% by mass) and require the removal of varying amounts depending on the emission norms (eg. International Maritime Organization 2020 sulfur regulations). Understanding the fuel molecular structure and, in particular, the structure of sulfur species enables the adoption and optimization of suitable desulfurization strategies. In the present work, detailed molecular characterization of the sulfur species in VR was performed using positive ion atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) coupled to Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Ions possessing mass to charge (m/z) in the range of 100 to 1200 were detected using the ultra-high resolution instrument and were resolved into unique chemical formulas (CcHhSsNnOo). The assigned masses were then divided into molecular classes based on the presence of heteroatoms, and plots of carbon number versus double bond equivalency (DBE) were made for each molecular class. The molecular classes were further sub-divided based on the presence of sulfur families like sulfides (Su), thiophenes (Th), benzothiophenes (BT), dibenzothiophenes (DBT) and benzonaphthothiophene (BNT) and their derivatives. A single surrogate molecule that represents the average structure of the VR sample was then designed based on the average molecular parameters (AMP) obtained from APPI and ESI FT-ICR MS. Plausible core skeletal structures of VR were drawn from the average DBE value, and then a symmetrical, alkylated, polyaromatic sulfur heterocycles (PASH) molecule was formulated as the VR surrogate. A number of physical and thermo-chemical properties of the VR surrogate were then predicted using quantitative structure property relationships (QSPR). The VR surrogate proposed here will enable high-fidelity computational studies, including chemical kinetic modeling, property estimation, and emissions modeling.
  • All-Solution-Processed Quantum Dot Electrical Double-Layer Transistors Enhanced by Surface Charges of Ti3C2Tx MXene Contacts

    Kim, Hyunho; Nugraha, Mohamad Insan; Guan, Xinwei; Wang,Zhenwei; Hota, Mrinal Kanti; Xu, Xiangming; Wu, Tao; Baran, Derya; Anthopoulos, Thomas D.; Alshareef, Husam N. (ACS Nano, American Chemical Society (ACS), 2021-02-26) [Article]
    Fully solution-processed, large-area, electrical double-layer transistors (EDLTs) are presented by employing lead sulfide (PbS) colloidal quantum dots (CQDs) as active channels and Ti3C2Tx MXene as electrical contacts (including gate, source, and drain). The MXene contacts are successfully patterned by standard photolithography and plasma-etch techniques and integrated with CQD films. The large surface area of CQD film channels is effectively gated by ionic gel, resulting in high performance EDLT devices. A large electron saturation mobility of 3.32 cm2 V-1 s-1 and current modulation of 1.87 × 104 operating at low driving gate voltage range of 1.25 V with negligible hysteresis are achieved. The relatively low work function of Ti3C2Tx MXene (4.42 eV) compared to vacuum-evaporated noble metals such as Au and Pt makes them a suitable contact material for n-type transport in iodide-capped PbS CQD films with a LUMO level of ∼4.14 eV. Moreover, we demonstrate that the negative surface charges of MXene enhance the accumulation of cations at lower gate bias, achieving a threshold voltage as low as 0.36 V. The current results suggest a promising potential of MXene electrical contacts by exploiting their negative surface charges.
  • NMR-based metabolomics with enhanced sensitivity

    Chandra, Kousik; Al-Harthi, Samah; Sukumaran, Sujeesh; Almulhim, Fatimah F.; Emwas, Abdul-Hamid M.; Atreya, Hanudatta S.; Jaremko, Lukasz; Jaremko, Mariusz (RSC Advances, Royal Society of Chemistry (RSC), 2021-02-25) [Article]
    NMR-based metabolomics, which emerged along with mass spectrometry techniques, is the preferred method for studying metabolites in medical research and food industries. However, NMR techniques suffer from inherently low sensitivity, regardless of their superior reproducibility. To overcome this, we made two beneficial modifications: we detuned the probe to reach a position called “Spin Noise Tuning Optimum” (SNTO), and we replaced the conventional cylindrical 5 mm NMR tube with an electric field component-optimized shaped tube. We found that concerted use of both modifications can increase the sensitivity (signal to noise ratio per unit volume) and detection of metabolites and decrease the measurement time by order of magnitude. In this study, we demonstrate and discuss the achieved signal enhancement of metabolites on model non-human (bovine serum, amino acid standard mixture) and human urine samples.
  • Effect of Zinc-doping on the Reduction of the Hot-carrier Cooling Rate in Halide Perovskites

    Xing, Guichuan; WEI, Qi; Yin, Jun; Bakr, Osman; Wang, Ze; Wang, Chenhao; Mohammed, Omar F.; Li, Mingjie (Angewandte Chemie, Wiley, 2021-02-25) [Article]
    Fast hot-carrier cooling process in the solar-absorbers fundamentally limits the photon-energy conversion efficiencies. It is highly desirable to develop the solar absorber with long-lived hot-carriers at sun-illumination level, which can be used to develop the hot-carrier solar cells with enhanced efficiency. Herein, we reveal that zinc-doped (0.34%) halide perovskites have the slower hot-carrier cooling compared with the pristine sample through the transient absorption spectroscopy measurements and theoretical calculations. The hot-carrier energy loss rate at the low photoexcitation level of 10 17 cm -3 is found to be ~3 times smaller than that of un-doped perovskites for 500-K hot carriers, and up to ten times when the hot-carrier temperature approaching the lattice temperature. The incorporation of zinc-dopant into perovskites can reduce the nonadiabatic couplings between conduction bands, which retards the photogenerated hot-carriers relaxation process. Our findings present a practical strategy to slow down the hot-carrier cooling in perovskites at low carrier densities, which are valuable for the further development of practical perovskite hot-carrier photovoltaics .
  • Toward Electrically Pumped Organic Lasers: A Review and Outlook on Material Developments and Resonator Architectures

    Zhang, Qi; Tao, Wenwen; Huang, Jingsong; Xia, Ruidong; Cabanillas-Gonzalez, Juan (Advanced Photonics Research, Wiley, 2021-02-25) [Article]
    Organic lasers have undergone decades of development. A myriad of materials with excellent optical gain properties, including small molecules, dendrimers, and polymers, have been demonstrated. Various resonator geometries have also been applied. While sharing the advantages of the solution processability and mechanical flexibility features of organic materials, organic optical gain media also offer interesting optical properties, such as emission tunability through chemical functionalization and inherent large optical gain coefficients. They offer prospects for different applications in the fields of bioimaging, medicine, chemo- and biosensing, anticounterfeit applications, or displays. However, the realization of electrically pumped organic lasers still remains a challenge due to the inherent drawbacks of organic semiconductors, e.g., modest carrier mobility, long-lived excited-state absorption, and extra losses which originate in the device (e.g., absorption from metal electrodes). Herein, the past developments of organic lasers are discussed, highlighting the importance of materials and cavities with regard to the goal of electrically pumped organic lasers. The latest progress and the possible ways to address the challenge are discussed.
  • One-step conversion of crude oil to light olefins using a multi-zone reactor

    Alabdullah, Mohammed A.; Rodriguez Gomez, Alberto; Shoinkhorova, Tuiana; Dikhtiarenko, Alla; Chowdhury, Abhishek Dutta; Hita, Idoia; Kulkarni, Shekhar Rajabhau; Vittenet, Jullian; Sarathy, Mani; Castaño, Pedro; Bendjeriou-Sedjerari, Anissa; Abou-Hamad, Edy; Zhang, Wen; Ali, Ola S.; Morales-Osorio, Isidoro; Xu, Wei; Gascon, Jorge (Nature Catalysis, Springer Science and Business Media LLC, 2021-02-25) [Article]
    With the demand for gasoline and diesel expected to decline in the near future, crude-to-chemicals technologies have the potential to become the most important processes in the petrochemical industry. This trend has triggered intense research to maximize the production of light olefins and aromatics at the expense of fuels, which calls for disruptive processes able to transform crude oil to chemicals in an efficient and environmentally friendly way. Here we propose a catalytic reactor concept consisting of a multi-zone fluidized bed that is able to perform several refining steps in a single reactor vessel. This configuration allows for in situ catalyst stripping and regeneration, while the incorporation of silicon carbide in the catalyst confers it with improved physical, mechanical and heat-transport properties. As a result, this reactor–catalyst combination has shown stable conversion of untreated Arabian Light crude into light olefins with yields per pass of over 30 wt% with a minimum production of dry gas.
  • Imbalance deep multi-instance learning for predicting isoform–isoform interactions

    Yu, Guoxian; Zeng, Jie; Wang, Jun; Zhang, Hong; Zhang, Xiangliang; Guo, Maozu (International Journal of Intelligent Systems, Wiley, 2021-02-25) [Article]
    Multi-instance learning (MIL) can model complex bags (samples) that are further made of diverse instances (subsamples). In typical MIL, the labels of bags are known while those of individual instances are unknown and to be specified. In this paper we propose an imbalanced deep multi-instance learning approach (IDMIL-III) and apply it to predict genome-wide isoform–isoform interactions (IIIs). This prediction task is crucial for precisely understanding the interactome between proteoforms and to reveal their functional diversity. The current solutions typically formulate the prediction of IIIs as a MIL problem by pairing two genes as a “bag” and any two isoforms spliced from these two genes as “instances.” The key instances (interacting isoform pairs) trigger the label of the positive (interacting) gene bags, which is important for identifying the IIIs. Furthermore, the prediction task was simplified as a balanced classification problem, which in practice is a rather imbalanced one. To address these issues, IDMIL-III fuses RNA-seq, nucleotide sequence, amino acid sequence and exon array data, and further introduces a novel loss function to separately model the loss of positive pairs and of negative pairs, and thus to avoid the expected loss dominated by majority negative pairs. In addition, it includes an attention strategy to identify positive isoform pairs from a positive gene bag. Extensive experimental results prove the effectiveness of IDMIL-III on predicting IIIs. Particularly, IDMIL-III achieves an F1 value as 95.4%, at least 3.8% higher than those of competitive methods at the gene-level; and obtains an F1 as 29.8%, at least 2.4% higher than the state-of-the-art methods at the isoform-level. The code of IDMIL-III is available at
  • Towards Detecting Red Palm Weevil Using Machine Learning and Fiber Optic Distributed Acoustic Sensing

    Wang, Biwei; Mao, Yuan; Ashry, Islam; Al-Fehaid, Yousef; Al-Shawaf, Abdulmoneim; Ng, Tien Khee; Yu, Changyuan; Ooi, Boon S. (Sensors, MDPI AG, 2021-02-25) [Article]
    Red palm weevil (RPW) is a detrimental pest, which has wiped out many palm tree farms worldwide. Early detection of RPW is challenging, especially in large-scale farms. Here, we introduce the combination of machine learning and fiber optic distributed acoustic sensing (DAS) techniques as a solution for the early detection of RPW in vast farms. Within the laboratory environment, we reconstructed the conditions of a farm that includes an infested tree with ∼12 day old weevil larvae and another healthy tree. Meanwhile, some noise sources are introduced, including wind and bird sounds around the trees. After training with the experimental time- and frequency-domain data provided by the fiber optic DAS system, a fully-connected artificial neural network (ANN) and a convolutional neural network (CNN) can efficiently recognize the healthy and infested trees with high classification accuracy values (99.9% by ANN with temporal data and 99.7% by CNN with spectral data, in reasonable noise conditions). This work paves the way for deploying the high efficiency and cost-effective fiber optic DAS to monitor RPW in open-air and large-scale farms containing thousands of trees.
  • Evidence of Carrier Localization in AlGaN/GaN based Ultraviolet Multiple Quantum Wells with Opposite Polarity Domains Provided by Nanoscale Imaging

    Cui, Mei; Guo, Wei; Xu, Houqiang; Jiang, Jie'an; Chen, Li; Mitra, Somak; Roqan, Iman S.; Jiang, Haibo; Li, Xiaohang; Ye, Jichun (physica status solidi (RRL) – Rapid Research Letters, Wiley, 2021-02-25) [Article]
    AlGaN based multiple-quantum-wells (MQWs) incorporating opposite polarity domains was grown by MOCVD. A direct demonstration of carrier localization effect was provided by a combination analysis of space-resolved luminescence peak position and Ga/Al composition distribution. Furthermore, through Raman spectroscopy, it is found that compressive strain plays a key role in improving the optical properties of UV-MQWs despite of the inferior crystalline quality in the N-polar domains. This suggests that incorporating sub-micrometer scale polarity domains in the MQWs is a promising perspective for the development of efficient UV emitters.
  • Reporting Device Performance of Emerging Photovoltaic Materials (Version 1)

    Almora, Osbel; Baran, Derya; Bazan, Guillermo C; Cabrera, Carlos I; Catchpole, Kylie R; Erten-Ela, Sule; Guo, Fei; Hauch, Jens; Ho-Baillie, Anita W Y; Jacobsson, T Jesper; Janssen, Rene A J; Kirchartz, Thomas; Kopidakis, Nikos; Li, Yongfang; Loi, Maria A; Lunt, Richard R; Mathew, Xavier; Mcgehee, Michael D; Min, Jie; Mitzi, David B; Nazeeruddin, Mohammad K; Nelson, Jenny; Nogueira, Ana F; Paetzold, Ulrich W; Park, Nam-Gyu; Rand, Barry P; Rau, Uwe; Snaith, Henry J; Unger, Eva; Vaillant-Roca, Lídice; Yip, Hin-Lap; Brabec, Christoph J (Advanced Energy Materials, Authorea, Inc., 2021-02-24) [Preprint]
    Emerging photovoltaics (PVs), focuses on a variety of applications complementing large scale electricity generation. For instance, organic, dye-sensitized and some perovskite solar cells are considered in building integration, greenhouses, wearable and indoors, thereby motivating research on flexible, transparent, semitransparent, and multi-junction PVs. Nevertheless, it can be very time consuming to find or develop an up-to-date overview over the state-of-the-art performance for these systems and applications. Two important resources for record research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley-Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield (STEY) is included as an analysis parameter among state-of-the-art emerging PVs.
  • Flight safety during Covid-19: A study of Charles de Gaulle airport atypical energy approaches.

    Jarry, Gabriel; Delahaye, Daniel; Feron, E. (Transportation research interdisciplinary perspectives, Elsevier BV, 2021-02-24) [Article]
    During the COVID-19 period and particularly during lockdown, deviations from nominal operations have shown to become more frequent. To confirm this observation this paper proposes to evaluate the impact of COVID-19, and more generally of crises that lead to a sharp drop in traffic, on the pilot/controller system, especially during the critical approach and landing phases. To study the influence of this type of crisis on flight operations at Charles De Gaulle airport, an existing energy atypicality metric is applied on a reference period before COVID-19 and compared to the COVID-19 period. Whereas the traffic at Charles De Gaulle airport has decreased by around 90% on April 2020, the obtained statistics underlined an increase in the atypical flight ratio of around 50%. This trend can be explained in part by the appearance of glide interceptions from above as a result of trajectory shortenings, and an increase in the proportion of high speed approaches.
  • A Brief Review of Solar Indoor Lighting System Integrated with Optofluidic Technologies

    Chen, Qian; Burhan, Muhammad; Oh, Seung Jin (Energy Technology, Wiley, 2021-02-23) [Article]
    Indoor lighting system incorporating daylighting effectively provides potential energy savings as well as meaningful spatial and temporal variation in illuminance beneficial to human well-being and performance. Integration of the tunable liquid prisms driven by optofluidic technologies will further improve the solar indoor lighting systems to achieve better illumination performance and higher solar energy utilization efficiency. This paper provides an overview of the state-of-the-art investigations over different aspects of the solar indoor lighting system enhanced by optofluidic liquid prisms, including (1) theoretical background, design, fabrication, and operation of liquid prisms, (2) advances in solar collectors and solar trackers, and (3) major tools for indoor lighting simulation and ray-tracing simulation. These studies form a solid foundation for future solar indoor lighting systems integrated with optofluidic technologies. The prospective study will focus on laboratory and on-site testing of the integrated system.
  • Replacing Thymine with a Strongly Pairing Fifth Base: a Combined Quantum Mechanics and Molecular Dynamics Study

    Chawla, Mohit; Gorle, Suresh; Shaikh, Abdul Rajjak; Oliva, Romina; Cavallo, Luigi (Computational and Structural Biotechnology Journal, Elsevier BV, 2021-02-23) [Article]
    The non-natural ethynylmethylpyridone C-nucleoside (W), a thymidine (T) analogue that can be incorporated in oligonucleotides by automated synthesis, has recently been reported to form a high fidelity base pair with adenosine (A) and to be well accommodated in B-DNA duplexes. The enhanced binding affinity for A of W, as compared to T, makes it an ideal modification for biotechnological applications, such as efficient probe hybridization for the parallel detection of multiple DNA strands. In order to complement the experimental study and rationalize the impact of the non-natural W nucleoside on the structure, stability and dynamics of DNA structures, we performed quantum mechanics (QM) calculations along with molecular dynamics (MD) simulations. Consistently with the experimental study, our QM calculations show that the A:W base pair has an increased stability as compared to the natural A:T pair, due to an additional CH-π interaction. Furthermore, we show that mispairing between W and guanine (G) causes a distortion in the planarity of the base pair, thus explaining the destabilization of DNA duplexes featuring a G:W pair. MD simulations show that incorporation of single or multiple consecutive A:W pairs in DNA duplexes causes minor changes to the intra- and inter-base geometrical parameters, while a moderate widening/shrinking of the major/minor groove of the duplexes is observed. QM calculations applied to selected stacks from the MD simulations also show an increased stacking energy for W, over T, with the neighboring bases.

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