Now showing items 1-20 of 56854

    • Streamlining the estimation of kinetic parameters using periodic reaction conditions: the methanol-to-hydrocarbon reaction as a case study

      Vicente, Hector; Gayubo, Ana G.; Aguayo, Andres T.; Castaño, Pedro (Chemical Engineering Journal, Elsevier BV, 2022-01-25) [Article]
      Reducing the experimental time required to obtain a robust kinetic model with reliable kinetic parameters has been a long-standing objective in reaction engineering. In the present study, we compare the kinetic modeling of two sets of data obtained using periodic reaction conditions (PRC) and stationary reaction conditions (SRC). As a case study, we use the well-known methanol-to-hydrocarbon reaction on HZSM-5 zeolite. The SRC experiments are conducted with a temperature of 425−475 °C, a total pressure of 2.5 bar, a partial pressure for methanol of 1.125 bar, a space time of 0.1−1.5 gcat h molC-1, a initial molar ratio water:methanol of 0–0.66 and 16 h on stream. The PRC experiments involve sinusoidal variation in the methanol and water flowrates of 135 ± 88 µL min-1 and 20 ± 20 µL min-1, respectively, with a period of 16 h or sinusoidal variation in the temperature of 450 ± 25 °C with periods of 8 and 16 h. Several strategies are then used in fitting the kinetic parameters of five models. We obtain relatively similar results in terms of model discrimination, the parameters, and confidence intervals with a cumulative experimental time of 64 h on stream under the PRC compared with 192 h on stream under the SRC, a reduction of 67% in the experimental time.
    • Mechanical Reliability of Fullerene/Tin Oxide Interfaces in Monolithic Perovskite/Silicon Tandem Cells

      de Bastiani, Michele; Armaroli, Giovanni; Jalmood, Rawan S.; Ferlauto, Laura; Li, Xiaole; Tao, Ran; Harrison, George T.; Eswaran, Mathan Kumar; Azmi, Randi; Babics, Maxime; Subbiah, Anand Selvin; Aydin, Erkan; Allen, Thomas; Combe, Craig; Cramer, Tobias; Baran, Derya; Schwingenschlögl, Udo; Lubineau, Gilles; Cavalcoli, Daniela; De Wolf, Stefaan (ACS Energy Letters, American Chemical Society (ACS), 2022-01-25) [Article]
      High-efficiency perovskite-based solar cells comprise sophisticated stacks of materials which, however, often feature different thermal expansion coefficients and are only weakly bonded at their interfaces. This may raise concerns over delamination in such devices, jeopardizing their long-term stability and commercial viability. Here, we investigate the root causes of catastrophic top-contact delamination we observed in state-of-the-art p-i-n perovskite/silicon tandem solar cells. By combining macroscopic and microscopic analyses, we identify the interface between the fullerene electron transport layer and the tin oxide buffer layer at the origin of such delamination. Specifically, we find that the perovskite morphology and its roughness play a significant role in the microscopic adhesion of the top layers, as well as the film processing conditions, particularly the deposition temperature and the sputtering power. Our findings mandate the search for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells, as required for commercialization.
    • Inner-sphere electron transfer at the ruthenium-azo interface.

      Panda, Sanjib; Singh, Aditi; Dey, Sanchaita; Huang, Kuo-Wei; Lahiri, Goutam Kumar (Dalton transactions (Cambridge, England : 2003), Royal Society of Chemistry (RSC), 2022-01-25) [Article]
      Metal complexes exhibiting multiple reversible redox states have drawn continuing research interest due to their electron reservoir features. In this context, the present article describes ruthenium-acac complexes (acac = acetylacetonate) incorporating redox-active azo-derived abim (azobis(1-methylbenzimidazole)) in mononuclear [RuII(acac)2(abim)] (1) and dinuclear [{RuIII(acac)2}2(μ-abim2−)] (2)/[{RuIII(acac)2}2(μ-abim˙−)]ClO4 ([2]ClO4) frameworks. Structural, spectroscopic, electrochemical, and theoretical analysis of the complexes revealed the varying redox states of the azo functionality of abim, i.e., [–N[double bond, length as m-dash]N–]0, [–NN–]˙−, and [–N–N–]2− in 1, [2]ClO4, and 2, respectively. Comparison between the calculated azo bond distances of analogous {Ru(acac)2}-coordinated azoheteroaromatics, i.e., abim and previously reported abbt (azobis(benzothiazole)) and abpy (azobis(pyridine)) examples, revealed the impact of varying amounts of intramolecular metal-to-azo electron transfer (i.e., the case of back-bonding) on stabilising radical anionic ([–NN–]˙−) and hydrazido ([–N–N–]2−) bridging modes in the complexes. An evaluation of the electronic forms of the complexes in accessible redox states via combined experimental and theoretical studies suggested a preferred resonance configuration rather than a precise description, primarily due to the severe mixing of metal-abim frontier orbitals. Moreover, the newly developed corresponding Cu-abim complex [CuI2(μ-abim)3](BF4)2 ([3](BF4)2) demonstrated the unique scenario of varying bridging modes of abim within the same molecular unit, involving both coordinated and non-coordinated azo functionalities. This also reemphasised the concept of the coordination-induced lengthening of the azo bond of abim (∼1.30 Å), via dπ(CuI) → π*(azo, abim) back-bonding, with reference to its non-coordinating counterpart (1.265(6) Å).
    • A computational study of thermally induced secondary atomization in multicomponent droplets

      Guida, Paolo; Ceschin, Alberto; Saxena, Saumitra; Im, Hong G.; Roberts, William L. (Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022-01-25) [Article]
      This study presents computational simulations of multicomponent and multiphase flows to reproduce the physical phenomena in the secondary atomization of a droplet induced by a hot temperature environment. The computational fluid dynamics model is based on the geometric volume of fluid method, with piecewise linear interface calculation reconstruction for accurate determination of the curvature and evaporation fluxes at the interface. The purpose of the model was to faithfully reproduce complex physical processes, such as internal gas cavity formation, liquid–vapour interface instability, cavity collapse and liquid jet ejection, and the pinch-off of a secondary droplet, leading to the microexplosion phenomenon that greatly enhances the evaporation rate of non-volatile liquid droplets. The solver was validated against the analytical solution in benchmark cases, and experimental data with bicomponent droplets reported in the literature. The developed model was used to predict the atomization of heavy fuel oil exposed at high temperatures under microgravity conditions. Different atomization regimes were identified, depending on the initial size of the internal bubbles. While small bubbles led to simple gas ejections, cavity collapse caused the larger bubbles to produce a jet formation. When the ratio between the bubble and droplet volumes was bigger than 0.7, microexplosions occurred. The results were found to be consistent with cases of bubble burst on flat surfaces, showing a strong dependence on the Ohnesorge number (Oh). Key observable quantities, particularly jet velocity and bubble cap drainage velocity, were found to agree with correlations reported in other studies. The similarities were also supported by studies extending over a wide range of simulations (4000 cases) at different Oh. An inversion in the dependence of the jet velocity on Oh (above a critical value Ohc) was observed.
    • Pieces in a global puzzle: Population genetics at two whale shark aggregations in the western Indian Ocean

      Hardenstine, Royale; He, Song; Cochran, Jesse; Braun, Camrin D.; Cagua, Edgar Fernando; Pierce, Simon J.; Prebble, Clare E. M.; Rohner, Christoph A.; Saenz-Agudelo, Pablo; Sinclair-Taylor, Tane H.; Skomal, Gregory B.; Thorrold, Simon R.; Watts, Alexandra M.; Zakroff, Casey J.; Berumen, Michael L. (Ecology and Evolution, Wiley, 2022-01-25) [Article]
      The whale shark Rhincodon typus is found throughout the world's tropical and warm-temperate ocean basins. Despite their broad physical distribution, research on the species has been concentrated at a few aggregation sites. Comparing DNA sequences from sharks at different sites can provide a demographically neutral understanding of the whale shark's global ecology. Here, we created genetic profiles for 84 whale sharks from the Saudi Arabian Red Sea and 72 individuals from the coast of Tanzania using a combination of microsatellite and mitochondrial sequences. These two sites, separated by approximately 4500 km (shortest over-water distance), exhibit markedly different population demographics and behavioral ecologies. Eleven microsatellite DNA markers revealed that the two aggregation sites have similar levels of allelic richness and appear to be derived from the same source population. We sequenced the mitochondrial control region to produce multiple global haplotype networks (based on different alignment methodologies) that were broadly similar to each other in terms of population structure but suggested different demographic histories. Data from both microsatellite and mitochondrial markers demonstrated the stability of genetic diversity within the Saudi Arabian aggregation site throughout the sampling period. These results contrast previously measured declines in diversity at Ningaloo Reef, Western Australia. Mapping the geographic distribution of whale shark lineages provides insight into the species’ connectivity and can be used to direct management efforts at both local and global scales. Similarly, understanding historical fluctuations in whale shark abundance provides a baseline by which to assess current trends. Continued development of new sequencing methods and the incorporation of genomic data could lead to considerable advances in the scientific understanding of whale shark population ecology and corresponding improvements to conservation policy
    • Study on the effect of size on InGaN red micro-LEDs

      Horng, Ray-Hua; Ye, Chun-Xin; Chen, Po-Wei; Iida, Daisuke; Ohkawa, Kazuhiro; Wu, Yuh-Renn; Wuu, Dong-Sing (Scientific Reports, Springer Science and Business Media LLC, 2022-01-25) [Article]
      In this research, five sizes (100 × 100, 75 × 75, 50 × 50, 25 × 25, 10 × 10 µm$^{2}$) of InGaN red micro-light emitting diode (LED) dies are produced using laser-based direct writing and maskless technology. It is observed that with increasing injection current, the smaller the size of the micro-LED, the more obvious the blue shift of the emission wavelength. When the injection current is increased from 0.1 to 1 mA, the emission wavelength of the 10 × 10 μm$^{2}$ micro-LED is shifted from 617.15 to 576.87 nm. The obvious blue shift is attributed to the stress release and high current density injection. Moreover, the output power density is very similar for smaller chip micro-LEDs at the same injection current density. This behavior is different from AlGaInP micro-LEDs. The sidewall defect is more easily repaired by passivation, which is similar to the behavior of blue micro-LEDs. The results indicate that the red InGaN epilayer structure provides an opportunity to realize the full color LEDs fabricated by GaN-based LEDs.
    • Colloidal silica fouling mechanism in direct-contact membrane distillation

      Jang, Yongsun; Lee, Jung-Gil; Fortunato, Luca; Lee, Jieun; Lee, Yejin; An, Alicia Kyoungjin; Ghaffour, NorEddine; Lee, Sangho; Jeong, Sanghyun (Desalination, Elsevier BV, 2022-01-24) [Article]
      Membrane fouling limits the performance of membrane distillation (MD) and its application to seawater brine treatment. Silica fouling is considered one of the most complex type of fouling. In this study, we evaluated the flux decline and fouling ratio due to colloidal silica fouling in direct-contact MD and characterized the fouled membranes. We also tested the efficacy of high flow-rate water flushing for the restoration of flux after fouling. The formation and removal of silica scaling were monitored in real-time with optical coherence tomography (OCT). Our work demonstrated that fouling formation is influenced by silica particle size, feed temperature, salinity, and flow rate. Notably, silica formed cake-layer fouling on the MD membranes. Smaller silica particle size resulted in a higher flux decline and a denser cake layer. A higher feed temperature resulted in a higher flux, but more severe fouling. We also found that fouling was minimized at an optimal flow rate and salinity did not significantly affect fouling formation. OCT monitoring showed that silica fouling deposited on the membrane surface and evaluated the effect of each cleaning strategies on the cake layer. This comprehensive investigation provides valuable insights for the development of silica fouling control strategies in MD.
    • A variable fractional-order inductor design

      Zhang, Li; Kartci, Aslihan; Bagci, Hakan; Salama, Khaled N. (International Journal of Circuit Theory and Applications, Wiley, 2022-01-24) [Article]
      Recently, interest in fractional-order inductors (FOIs) has increased since theyallow for accurate and robust models of dynamical systems to be designed.However, practical implementation of these models has not been possible dueto the lack of single FOI realizations. To address this challenge, in this work,we propose a simple-to-realize fractional-order inductor design with variableconstant phase angle (CPA). The design relies on characteristics of transverseelectromagnetic (TEM) mode propagating on a coaxial structure filled withconductive material, more specifically NaCl-water solution and flour-basedmixtures. The CPA of the resulting FOI can be tuned by changing the conduc-tivity of the dough mixture. Analysis of the proposed FOI design show that theCPA can vary in a range from 0 to 90 . Two of these CPA values are verifiedagainst experiments in the frequency band changing from 1 to 10 MHz
    • Forecasting high-frequency spatio-temporal wind power with dimensionally reduced echo state networks

      Huang, Huang; Castruccio, Stefano; Genton, Marc G. (Journal of the Royal Statistical Society: Series C (Applied Statistics), Wiley, 2022-01-23) [Article]
      Fast and accurate hourly forecasts of wind speed and power are crucial in quantifying and planning the energy budget in the electric grid. Modelling wind at a high resolution brings forth considerable challenges given its turbulent and highly nonlinear dynamics. In developing countries, where wind farms over a large domain are currently under construction or consideration, this is even more challenging given the necessity of modelling wind over space as well. In this work, we propose a machine learning approach to model the nonlinear hourly wind dynamics in Saudi Arabia with a domain-specific choice of knots to reduce spatial dimensionality. Our results show that for locations highlighted as wind abundant by a previous work, our approach results in an 11% improvement in the 2-h-ahead forecasted power against operational standards in the wind energy sector, yielding a saving of nearly one million US dollars over a year under current market prices in Saudi Arabia.
    • Study on the effects of narrow-throat pre-chamber geometry on the pre-chamber jet velocity using dual formaldehyde PLIF imaging

      Tang, Qinglong; Sampath, Ramgopal; Sharma, Priybrat; Marquez, Manuel Echeverri; Cenker, Emre; Magnotti, Gaetano (Combustion and Flame, Elsevier BV, 2022-01-22) [Article]
      The effects of narrow-throat pre-chamber geometry on the main chamber combustion were investigated on a heavy-duty optical engine fueled with methane. Simultaneous dual formaldehyde PLIF imaging and OH* chemiluminescence imaging were applied to characterize the early-stage formaldehyde jet and flame jet discharge process. The formaldehyde jet velocity on the jet boundary was quantified by dual formaldehyde PLIF for the first time. Three narrow-throat pre-chambers with two rows of orifices on the nozzle and with different pre-chamber volume and inner throat diameter were studied under the same pre-chamber to main chamber fuel ratio and global excess air ratio of 2.0. The results indicate that the narrow-throat pre-chamber performance is not very sensitive to the pre-chamber volume. The pre-chamber with a larger volume produces only slightly higher pressure buildup in the pre-chamber () and similar main chamber combustion phasing and engine efficiency. The inner throat diameter is the key dimension in the narrow-throat pre-chamber design. A larger inner throat diameter produces a smaller peak and a slower jet penetration, resulting in longer combustion duration and lower engine efficiency. The formaldehyde PLIF shows that the main chamber combustion can be generally classified into two stages: the initial flame ignition and the following flame propagation. The maximum local formaldehyde jet boundary velocity of the narrow-throat pre-chamber with an inner throat diameter of 3.3 mm is up to about 280 m/s and it decreases dramatically when the inner throat diameter is increased to 5.3 mm. The flame jet characteristics of lower and upper orifices can be significantly different due to the local pressure difference between them in the pre-chamber throat. A smaller inner throat diameter results in a larger pressure difference between the lower and upper row orifices and could lead to weak upper-row flame jets. The narrow-throat pre-chamber design with an optimized inner throat diameter can produce high, fast jet penetration, and short combustion duration, which favor the lean limit operation and high engine efficiency.
    • Silicon carbide in catalysis: from inert bed filler to catalytic support and multifunctional material

      Kulkarni, Shekhar Rajabhau; Velisoju, Vijay Kumar; Tavares, F.; Dikhtiarenko, Alla; Gascon, Jorge; Castaño, Pedro (Catalysis Reviews, Informa UK Limited, 2022-01-22) [Article]
      Silicon carbide (SiC) or carborundum has unparalleled thermal stability and conductivity compared with many other materials. This feature together with its unique photoelectrical properties (tunable band gap: 2.39–3.33 eV), low thermal expansion, high strength, and good chemical and thermal stability makes it an ideal inert solid in catalysis. The evolution of methods for synthesizing SiC has also progressively endowed it with additional features at the multiscale. This review tracks the development of SiC from a secondary to a leading role material in catalysis. First, the intrinsic properties of SiC are discussed and compared with other state-of-the-art catalytic materials. The synthetic methods are systematically reviewed and compared. Then, the applications of SiC in catalysis are assessed, paying particular attention to those that involve C1 chemistry (Fischer–Tropsch Synthesis and the valorization of CO2 and CH4), photocatalysis and biomass conversion. Finally, the potential future applications of SiC are also addressed and discussed.
    • Wall-resolved and wall-modelled large-eddy simulation of plane Couette flow

      Cheng, W.; Pullin, D.I.; Samtaney, Ravi (Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022-01-21) [Article]
      We describe wall-resolved and wall-modelled large-eddy simulation (LES) of plane Couette (PC) flow. Subgrid-scale (SGS) motion is represented using the stretched-spiral vortex SGS model and the virtual wall model is employed for wall-modelled LES. Cases studied include direct numerical simulation (DNS) at friction Reynolds numbers Reτ = 220, wall-resolved LES at Reτ ∼ 500–3600 and wall-modelled LES at Reτ ∼ 3600–2.8 × 105. All LES performed show the presence of approximately spanwise periodic sets of streamwise rolls. Averaged (including spanwise) wall-normal profiles of the mean streamwise velocity show a consistent log region across all Reynolds numbers. Two distinct measures of turbulent intensity are explored, one of which recognizes the roll structure and one that does not. The spanwise variation of turbulence flow metrics is investigated. Mean streamwise velocity profiles show substantial spanwise variation but collapse well when normalized by local skin-friction velocities. Similar collapse is found for streamwise turbulent intensities. For all present LES, the mean skin-friction variation with the plate Reynolds number is found to match a simple analytical form (Pirozzoli et al., J. Fluid Mech., vol. 758, 2014, pp. 327–343) while the scaled centre-plane, mean-velocity gradient exhibits an inverse ProductLog dependence. Both the mean-flow roll energy and circulation, scaled with outer variables, decrease monotonically for Reτ 500. At lower Reτ , the mean streamwise zero-velocity line follows a wavy form in the spanwise direction, while at our larger Reτ , a mushroom shape emerges which could potentially enhance local momentum transport in the spanwise direction and be responsible for the weakening of the spanwise rolls.
    • iSCAN-V2: A One-Pot RT-RPA–CRISPR/Cas12b Assay for Point-of-Care SARS-CoV-2 Detection

      Aman, Rashid; Marsic, Tin; Sivakrishna Rao, Gundra; Mahas, Ahmed; Ali, Zahir; Alsanea, Madain; Al-Qahtani, Ahmed; Alhamlan, Fatimah; Mahfouz, Magdy (Frontiers in Bioengineering and Biotechnology, Frontiers Media SA, 2022-01-21) [Article]
      Rapid, specific, and sensitive detection platforms are prerequisites for early pathogen detection to efficiently contain and control the spread of contagious diseases. Robust and portable point-of-care (POC) methods are indispensable for mass screening of SARS-CoV-2. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-based nucleic acid detection technologies coupled with isothermal amplification methods provide a straightforward and easy-to-handle platform for detecting SARS-CoV-2 at POC, low-resource settings. Recently, we developed iSCAN, a two-pot system based on coupled loop-mediated isothermal amplification (LAMP) and CRISPR/Cas12a reactions. However, in two-pot systems, the tubes must be opened to conduct both reactions; two-pot systems thus have higher inherent risks of cross-contamination and a more cumbersome workflow. In this study, we developed and optimized iSCAN-V2, a one-pot reverse transcription-recombinase polymerase amplification (RT-RPA)-coupled CRISPR/Cas12b-based assay for SARS-CoV-2 detection, at a single temperature in less than an hour. Compared to Cas12a, Cas12b worked more efficiently in the iSCAN-V2 detection platform. We assessed and determined the critical factors, and present detailed guidelines and considerations for developing and establishing a one-pot assay. Clinical validation of our iSCAN-V2 detection module with reverse transcription-quantitative PCR (RT-qPCR) on patient samples showed 93.75% sensitivity and 100% specificity. Furthermore, we coupled our assay with a low-cost, commercially available fluorescence visualizer to enable its in-field deployment and use for SARS-CoV-2 detection. Taken together, our optimized iSCAN-V2 detection platform displays critical features of a POC molecular diagnostic device to enable mass-scale screening of SARS-CoV-2 in low-resource settings.
    • Dye tracing and concentration mapping in coastal waters using unmanned aerial vehicles

      Johansen, Kasper; Dunne, Aislinn F.; Tu, Yu-Hsuan; Almashharawi, Samir; Jones, Burton; McCabe, Matthew (Scientific Reports, Springer Science and Business Media LLC, 2022-01-21) [Article]
      AbstractCoastal water flows facilitate important nutrient exchanges between mangroves, seagrasses and coral reefs. However, due to the complex nature of tidal interactions, their spatiotemporal development can be difficult to trace via traditional field instrumentations. Unmanned aerial vehicles (UAVs) serve as ideal platforms from which to capture such dynamic responses. Here, we provide a UAV-based approach for tracing coastal water flows using object-based detection of dye plume extent coupled with a regression approach for mapping dye concentration. From hovering UAV images and nine subsequent flight surveys covering the duration of an ebbing tide in the Red Sea, our results show that dye plume extent can be mapped with low omission and commission errors when assessed against manual delineations. Our results also demonstrated that the interaction term of two UAV-derived indices may be employed to accurately map dye concentration (coefficient of determination = 0.96, root mean square error = 7.78 ppb), providing insights into vertical and horizontal transportation and dilution of materials in the water column. We showcase the capabilities of high-frequency UAV-derived data and demonstrate how field-based dye concentration measurements can be integrated with UAV data for future studies of coastal water flow dynamics.
    • Myo-Inositol Limits Kainic Acid-Induced Epileptogenesis in Rats

      Kandashvili, Manana; Gamkrelidze, Georgi; Tsverava, Lia; Lordkipanidze, Tamar; Lepsveridze, Eka; Lagani, Vincenzo; Burjanadze, Maia; Dashniani, Manana; Kokaia, Merab; Solomonia, Revaz (International Journal of Molecular Sciences, MDPI AG, 2022-01-21) [Article]
      Epilepsy is a severe neurological disease characterized by spontaneous recurrent seizures (SRS). A complex pathophysiological process referred to as epileptogenesis transforms a normal brain into an epileptic one. Prevention of epileptogenesis is a subject of intensive research. Cur-rently, there are no clinically approved drugs that can act as preventive medication. Our previous studies have revealed highly promising antiepileptogenic properties of a compound–myo-inositol (MI) and the present research broadens previous results and demonstrates the long-term disease-modifying effect of this drug, as well as the amelioration of cognitive comorbidities. For the first time, we show that long-term treatment with MI: (i) decreases the frequency and duration of elec-trographic SRS in the hippocampus; (ii) has an ameliorating effect on spatial learning and memory deficit associated with epileptogenesis, and (iii) attenuates cell loss in the hippocampus. MI treatment also alters the expression of the glial fibrillary acidic protein, LRRC8A subunit of volume-regulated anion channels, and protein tyrosine phosphatase receptor type R, all expected to coun-teract the epileptogenesis. All these effects are still present even 4 weeks after MI treatment ceased. This suggests that MI may exert multiple actions on various epileptogenesis-associated changes in the brain and, therefore, could be considered as a candidate target for prevention of epileptogenesis.
    • Hybrid architecture based on two-dimensional memristor crossbar array and CMOS integrated circuit for edge computing

      Kumar, Pratik; Zhu, Kaichen; Gao, Xu; Wang, Sui-Dong; Lanza, Mario; Thakur, Chetan Singh (npj 2D Materials and Applications, Springer Science and Business Media LLC, 2022-01-21) [Article]
      AbstractThe fabrication of integrated circuits (ICs) employing two-dimensional (2D) materials is a major goal of semiconductor industry for the next decade, as it may allow the extension of the Moore’s law, aids in in-memory computing and enables the fabrication of advanced devices beyond conventional complementary metal-oxide-semiconductor (CMOS) technology. However, most circuital demonstrations so far utilizing 2D materials employ methods such as mechanical exfoliation that are not up-scalable for wafer-level fabrication, and their application could achieve only simple functionalities such as logic gates. Here, we present the fabrication of a crossbar array of memristors using multilayer hexagonal boron nitride (h-BN) as dielectric, that exhibit analog bipolar resistive switching in >96% of devices, which is ideal for the implementation of multi-state memory element in most of the neural networks, edge computing and machine learning applications. Instead of only using this memristive crossbar array to solve a simple logical problem, here we go a step beyond and present the combination of this h-BN crossbar array with CMOS circuitry to implement extreme learning machine (ELM) algorithm. The CMOS circuit is used to design the encoder unit, and a h-BN crossbar array of 2D hexagonal boron nitride (h-BN) based memristors is used to implement the decoder functionality. The proposed hybrid architecture is demonstrated for complex audio, image, and other non-linear classification tasks on real-time datasets.
    • MXene-Coated Membranes for Autonomous Solar-Driven Desalination

      Mustakeem, Mustakeem; El Demellawi, Jehad K.; Obaid, M.; Ming, Fangwang; Alshareef, Husam N.; Ghaffour, NorEddine (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-01-21) [Article]
      Clean water supply in off-grid locations remains a stumbling stone for socio-economic development in remote areas where solar energy is abundant. In this regard, several technologies have already introduced various solutions to the off-grid freshwater predicament; however, most of them are either costly or complex to operate. Nonetheless, photothermal membrane distillation (PMD) has emerged as a promising candidate with great potential to be autonomously driven by solar energy. Instead of using energy-intensive bulk feed heating in conventional MD systems, PMD membranes can directly harvest the incident solar light at the membrane interface as an alternative driving energy resource for the desalination process. Because of its excellent photothermal properties and stability in ionic environments, herein, Ti3C2Tx MXene was coated onto commercial polytetrafluoroethylene (PTFE) membranes to allow for a self-heated PMD process. An average water vapor flux of 0.77 kg/m2 h with an excellent temporal response under intermitting lighting and a photothermal efficiency of 65.3% were achieved by the PMD membrane under one-sun irradiation for a feed salinity of 0.36 g/L. Naturally, the efficiency of the process decreased with higher feed concentrations due to the reduction of the evaporation rate and the scattering of incident sunlight toward the membrane photothermal surface, especially at rates above 10 g/L. Notably, with such performance, 1 m2 of the MXene-coated PMD membrane can fulfill the recommended daily potable water intake for a household, that is, ca. 6 L/day.
    • Fuel flexibility potential for isobaric combustion in a compression ignition engine: A computational study

      Aljabri, Hammam H.; Liu, Xinlei; Al-lehaibi, Moaz; Cabezas, Kevin Moreno; AlRamadan, Abdullah S.; Badra, Jihad; Im, Hong G. (Fuel, Elsevier BV, 2022-01-21) [Article]
      This work numerically explored the potential of using various kinds of fuels for the isobaric combustion concept in a compression ignition engine. Primary reference fuels (PRFs) including PRF0, PRF20, PRF40, PRF60, PRF80, and PRF100 were employed at the same middle engine load. Different injection strategies ranging from single to four injections were studied. The results demonstrated that the tested PRFs showed significant differences when using a single injection method, due to the different fuel auto-ignition characteristics: the lower fuel reactivity led to the longer ignition delay and thus more premixed combustion heat release. Fuel flexibility was achieved by utilizing at least two injection events, under which condition various fuels shared similar engine combustion performance and emissions. Predicted in-cylinder distribution of temperature revealed that the first injection event generated initial high-temperature pockets downstream of the nozzle, which helped to ignite the upstream air–fuel mixture from the following injection events and resulted in a relatively stable spray-controlled heat release process. To reduce soot emissions, various amounts of three shorter-chain alcohols (methanol, ethanol, and n-butanol) were blended with the baseline fuel (n-heptane). The methanol-blended fuels yielded the lowest soot emissions, but the fuel economy suffered due to the highest heat transfer losses. By increasing the nozzle number and introducing an adequate amount of isochoric combustion, the fuel economy for pure methanol combustion was effectively improved.
    • MXenes for Energy Harvesting

      Wang, Yizhou; Guo, Tianchao; Tian, Zhengnan; Bibi, Khadija; Zhang, Yi-Zhou; Alshareef, Husam N. (Advanced Materials, Wiley, 2022-01-20) [Article]
      Energy-harvesting modules play an increasingly important role in the development of autonomous self-powered microelectronic devices. MXenes (i.e., two-dimensional transition metal carbide/nitride) have recently emerged as promising candidates for energy applications due to their excellent electronic conductivity, large specific surface area, and tunable properties. In this review, we present a perspective on using MXenes to harvest energy from various sources in the environment. First, we systematically introduce the characteristics of MXenes that facilitate energy capturing and summarize the preparation strategies of MXenes and their derived nanostructures tailored towards such applications. Subsequently, we discuss the harvesting mechanism of different energy sources (e.g., solar energy, thermoelectric energy, triboelectric energy, piezoelectric energy, salinity gradient energy, electrokinetic energy, ultrasound energy, and humidity energy). Then we introduce the recent progress of MXene-based nanostructures in energy harvesting, as well as their applications. Finally, we present our opinions on the existing challenges and future directions of MXene-based nanostructure for energy harvesting.
    • Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis

      Rahmani, Jamal; Montesanto, Alberto; Giovannucci, Edward; Zand, Hamid; Barati, Meisam; Kopchick, John J.; Mirisola, Mario G.; Lagani, Vincenzo; Bawadi, Hiba; Vardavas, Raffaele; Laviano, Alessandro; Christensen, Kaare; Passarino, Giuseppe; Longo, Valter D. (Aging Cell, Wiley, 2022-01-20) [Article]
      The association between IGF-1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta-analysis investigates this complex relationship between IGF-1 and all-cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta-analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF-1 and were conducted among adults. A random-effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all-cause mortality. Nineteen studies involving 30,876 participants were included. Meta-analysis of the 19 eligible studies showed that with respect to the low IGF-1 category, higher IGF-1 was not associated with increased risk of all-cause mortality (HR = 0.84, 95% CI = 0.68–1.05). Dose–response analysis revealed a U-shaped relation between IGF-1 and mortality HR. Pooled results comparing low vs. middle IGF-1 showed a significant increase of all-cause mortality (HR = 1.33, 95% CI = 1.14–1.57), as well as comparing high vs. middle IGF-1 categories (HR = 1.23, 95% CI = 1.06–1.44). Finally, we provide data on the association between IGF-1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF-1 increase mortality risk, with a specific 120–160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF-1 levels and mortality.