Recent Submissions

  • Comment on “A periodic grain consolidation model of porous media” [Phys. Fluids A 1, 38 (1989)]

    Khirevich, Siarhei; Patzek, Tadeusz (Physics of Fluids, AIP Publishing, 2019-10-11) [Article]
    In this document, we correct the friction coefficient values presented in Table III in a study by Larson and Higdon [“A periodic grain consolidation model of porous media,” Phys. Fluids A 1, 38 (1989)]. The authors addressed the problem of Stokes flow through periodic arrays of (non)overlapping spheres and determined the friction coefficients. It appears that the volume of the overlapping region of spheres was not taken into account, which affected the total solid concentration and systematically biased the corresponding friction coefficient values. We correct the sphere concentration and friction coefficients, and validate our approach with lattice-Boltzmann simulations. The suggested correction is valid in the case of overlapping spheres only, when the volume of the overlapping region is positive.
  • Assessing the Range of Validity of Current Tube Models through Analysis of a Comprehensive Set of Star–Linear 1,4-Polybutadiene Polymer Blends

    Hall, Ryan; Desai, Priyanka S.; Kang, Beom-Goo; Huang, Qifan; Lee, Sanghoon; Chang, Taihyun; Venerus, David C.; Mays, Jimmy; Ntetsikas, Konstantinos; Polymeropoulos, George; Hadjichristidis, Nikolaos; Larson, Ronald G. (Macromolecules, American Chemical Society (ACS), 2019-10-10) [Article]
    We blend newly synthesized nearly monodisperse four-arm star 1,4-polybutadienes with various well-entangled linear polymers, confirming the conclusions in Desai et al. [ Macromolecules201649 (13)49644977] that advanced tube models, namely, the hierarchical 3.0 and branch-on-branch models [Wang, Z.; J. Rheol.201054 (2)223260], fail to predict the linear rheological data when the pure linear polymers have shorter relaxation times, but within 3–4 orders of magnitude of the star polymer. However, when the linear polymer has a longer relaxation time than the star, our new work, surprisingly, finds that non-monotonic dependence of terminal relaxation behavior on composition is both observed experimentally and captured by the models. Combined with previous data from the literature, we present results from over 50 1,4-polybutadiene star–linear blends, suitable for thorough testing of rheological models of entangled polymers.
  • Remotely sensing phytoplankton size structure in the Red Sea

    Gittings, John; Brewin, Robert J.W.; Raitsos, Dionysios E.; Kheireddine, Malika; Ouhssain, Mustapha; Jones, Burton; Hoteit, Ibrahim (Remote Sensing of Environment, Elsevier BV, 2019-10-09) [Article]
    Phytoplankton size structure impacts ocean food-web dynamics and biogeochemical cycling, and is thus an important ecological indicator that can be utilised to quantitatively evaluate the state of marine ecosystems. Potential alterations to size structure are predicted to occur in tropical regions under future scenarios of climate change. Therefore, there is an increasing requirement for the synoptic monitoring of phytoplankton size structure in marine systems. The Red Sea remains a comparatively unexplored tropical marine ecosystem, particularly with regards to its large-scale biological dynamics. Using an in situ pigment dataset acquired in the Red Sea, we parameterise a two-component, abundance-based phytoplankton size model and apply it to remotely-sensed observations of chlorophyll-a (Chl-a) concentration, to infer Chl-a in two size classes of phytoplankton, small cells <2 μm in size (picophytoplankton) and large cells >2 μm in size. Satellite-derived estimates of phytoplankton size structure are in good agreement with corresponding in situ measurements and also capture the spatial variability related to regional mesoscale dynamics. Our analysis reveals that, for the estimation of Chl-a in the two size classes, the model performs comparably or in some cases better, to validations in other oceanic regions. Our model parameterisation will be useful for future studies on the seasonal and interannual variability of phytoplankton size classes in the Red Sea, which may ultimately be relevant for understanding trophic linkages between phytoplankton size structure and fisheries, and the development of marine management strategies.
  • Ultraviolet-to-blue color-converting scintillating-fibers photoreceiver for 375-nm laser-based underwater wireless optical communication

    Kang, Chun Hong; Trichili, Abderrahmen; Alkhazragi, Omar; Zhang, Huafan; Subedi, Ram Chandra; Guo, Yujian; Mitra, Somak; Shen, Chao; Roqan, Iman S.; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S. (Optics Express, The Optical Society, 2019-10-08) [Article]
    Underwater wireless optical communication (UWOC) can offer reliable and secure connectivity for enabling future internet-of-underwater-things (IoUT), owing to its unlicensed spectrum and high transmission speed. However, a critical bottleneck lies in the strict requirement of pointing, acquisition, and tracking (PAT), for effective recovery of modulated optical signals at the receiver end. A large-area, high bandwidth, and wide-angle-of-view photoreceiver is therefore crucial for establishing a high-speed yet reliable communication link under non-directional pointing in a turbulent underwater environment. In this work, we demonstrated a large-area, of up to a few tens of cm2, photoreceiver design based on ultraviolet(UV)-to-blue color-converting plastic scintillating fibers, and yet offering high 3-dB bandwidth of up to 86.13 MHz. Tapping on the large modulation bandwidth, we demonstrated a high data rate of 250 Mbps at bit-error ratio (BER) of 2.2 × 10−3 using non-return-to-zero on-off keying (NRZ-OOK) pseudorandom binary sequence (PRBS) 210-1 data stream, a 375-nm laser-based communication link over the 1.15-m water channel. This proof-of-concept demonstration opens the pathway for revolutionizing the photodetection scheme in UWOC, and for non-line-of-sight (NLOS) free-space optical communication.
  • New Insight on the Role of Electrolyte Additives in Rechargeable Lithium Ion Batteries

    Ming, Jun; Cao, Zhen; Wu, Yingqiang; Wahyudi, Wandi; Wang, Wenxi; Guo, Xianrong; Cavallo, Luigi; Hwang, Jang-Yeon; Shamim, Atif; Li, Lain-Jong; Sun, Yang-Kook; Alshareef, Husam N. (ACS Energy Letters, American Chemical Society (ACS), 2019-10-08) [Article]
    Solid electrolyte interphase (SEI)-forming agents such as vinylene carbonate, sulfone, and cyclic sulfate are commonly believed to be film-forming additives in lithium-ion batteries that help to enhance graphite anode stability. However, we find that the film-forming effect and the resultant SEI may not be the only reasons for the enhanced graphite stability. This is because the as-formed SEI cannot inhibit Li+–solvent co-intercalation once the additive is removed from the electrolyte. Instead, we show that the Li+ solvation structure, which is modified by these additives, plays a critical role in achieving reversible Li+ (de)intercalation within graphite. This discovery is confirmed in both carbonate and ether-based electrolytes. We show that the problem of graphite exfoliation caused by Li+–solvent co-intercalation can be mitigated by adding ethene sulfate to tune the Li+ coordination structure. This work brings new insight into the role of additives in electrolytes, expanding the prevailing thinking over the past 2 decades. In addition, this finding can guide the design of more versatile electrolytes for advanced rechargeable metal-ion batteries.
  • Understanding Ostwald Ripening and Surface Charging Effects in Solvothermally-Prepared Metal Oxide–Carbon Anodes for High Performance Rechargeable Batteries

    Zhou, Lin; Zhang, Jiao; Wu, Yingqiang; Wang, Wenxi; Ming, Hai; Sun, Qujiang; Wang, Limin; Ming, Jun; Alshareef, Husam N. (Advanced Energy Materials, Wiley, 2019-10-08) [Article]
    Metal oxides synthesized by the solvothermal approach have widespread applications, while their nanostructure control remains challenging because their reaction mechanism is still not fully understood. Herein, it is demonstrated how the competitive relation between Ostwald ripening and surface charging during solvothermal synthesis is crucial to engineering high-quality metal (oxide)–carbon nanomaterials. Using SnO2 as a case study, a new type of hollow SnO2–C hybrid nanoparticles is synthesized consisting of core–shell structured SnO2@C nanodots (which has not been previously reported). This new anode material exhibits extremely high lithium storage capacity of 1225 and 955 mAh g−1 at 200 and 500 mA g−1, respectively, and excellent cycling stability. In addition, full-battery cells are constructed combining SnO2–C anode with Ni-rich cathode, which can be charged to a higher voltage compared to commercial graphite anode and still demonstrate extraordinary rate performance. This study provides significant insight into the largely unexplored reaction mechanism during solvothermal synthesis, and demonstrates how such understanding can be used to achieve high-performance metal (oxide)–C anodes for rechargeable batteries.
  • Proteome-level assessment of origin, prevalence and function of Leucine-Aspartic Acid (LD) motifs.

    Alam, Tanvir; Alazmi, Meshari; Naser, Rayan Mohammad Mahmoud; Huser, Franceline; Momin, Afaque Ahmad Imtiyaz; Astro, Veronica; Hong, Seungbeom; Walkiewicz, Katarzyna Wiktoria; Canlas, Christian G; Huser, Raphaël; Ali, Amal J.; Merzaban, Jasmeen; Adamo, Antonio; Jaremko, Mariusz; Jaremko, Lukasz; Bajic, Vladimir B.; Gao, Xin; Arold, Stefan T. (Bioinformatics (Oxford, England), Oxford University Press (OUP), 2019-10-05) [Article]
    MOTIVATION:Leucine-aspartic acid (LD) motifs are short linear interaction motifs (SLiMs) that link paxillin family proteins to factors controlling cell adhesion, motility and survival. The existence and importance of LD motifs beyond the paxillin family is poorly understood. RESULTS:To enable a proteome-wide assessment of LD motifs, we developed an active-learning based framework (LDmotif finder; LDMF) that iteratively integrates computational predictions with experimental validation. Our analysis of the human proteome revealed a dozen new proteins containing LD motifs. We found that LD motif signalling evolved in unicellular eukaryotes more than 800 Myr ago, with paxillin and vinculin as core constituents, and nuclear export signal (NES) as a likely source of de novo LD motifs. We show that LD motif proteins form a functionally homogenous group, all being involved in cell morphogenesis and adhesion. This functional focus is recapitulated in cells by GFP-fused LD motifs, suggesting that it is intrinsic to the LD motif sequence, possibly through their effect on binding partners. Our approach elucidated the origin and dynamic adaptations of an ancestral SLiM, and can serve as a guide for the identification of other SLiMs for which only few representatives are known. AVAILABILITY:LDMF is freely available online at; Source code is available at SUPPLEMENTARY INFORMATION:Supplementary data are available at Bioinformatics online.
  • Ultralong cycle stability of aqueous zinc-ion batteries with zinc vanadium oxide cathodes

    Wang, Lulu; Huang, Kuo-Wei; Chen, Jitao; Zheng, Junrong (Science Advances, American Association for the Advancement of Science (AAAS), 2019-10-04) [Article]
    Rechargeable aqueous zinc-ion batteries are promising candidates for large-scale energy storage but are plagued by the lack of cathode materials with both excellent rate capability and adequate cycle life span. We overcome this barrier by designing a novel hierarchically porous structure of Zn-vanadium oxide material. This Zn0.3V2O5·1.5H2O cathode delivers a high specific capacity of 426 mA·h g−1 at 0.2 A g−1 and exhibits an unprecedented superlong-term cyclic stability with a capacity retention of 96% over 20,000 cycles at 10 A g−1. Its electrochemical mechanism is elucidated. The lattice contraction induced by zinc intercalation and the expansion caused by hydronium intercalation cancel each other and allow the lattice to remain constant during charge/discharge, favoring cyclic stability. The hierarchically porous structure provides abundant contact with electrolyte, shortens ion diffusion path, and provides cushion for relieving strain generated during electrochemical processes, facilitating both fast kinetics and long-term stability.
  • Modeling and Experimental Study of the Vibration Effects in Urban Free-Space Optical Communication Systems

    Cai, Wenqi; Ndoye, Ibrahima; Ooi, Boon S.; Alouini, Mohamed-Slim; Laleg-Kirati, Taous-Meriem (IEEE Photonics Journal, IEEE, 2019-10-04) [Article]
    Free-space optical (FSO) communication, considered as a last-mile technology, is widely used in many urban scenarios. However, the performance of urban free-space optical (UFSO) communication systems fades in the presence of system vibration caused by many factors in the chaotic urban environment. In this paper, we develop a dedicated indoor vibration platform and atmospheric turbulence to estimate the Bifurcated-Gaussian (B-G) distribution model of the receiver optical power under different vibration levels and link distances using nonlinear iteration method. Mean square error (MSE) and coefficient of determination ($R^2$) metrics have been used to show a good agreement between the PDFs of the experimental data with the resulting B-G distribution model. Besides, the UFSO channel under the effects of both vibration and atmospheric turbulence is also explored under three atmospheric turbulence conditions. Our proposed B-G distribution model describes the vibrating UFSO channels properly and can easily help to perform and evaluate the link performance of UFSO systems, e.g., bit-error-rate (BER), outage probability. Furthermore, this work paves the way for constructing completed auxiliary control subsystems for robust UFSO links and contributes to more extensive optical communication scenarios, such as underwater optical communication, etc.
  • Disruption of the coordination between host circadian rhythms and malaria parasite development alters the duration of the intraerythrocytic cycle

    Subudhi, Amit; O'Donnell, Aidan John; Ramaprasad, Abhinay; Abkallo, Hussein M.; Kaushik, Abhinav; Ansari, Hifzur Rahman; Abdel-Haleem, Alyaa M.; Rached, Fathia Ben; Kaneko, Osamu; Culleton, Richard; Reece, Sarah E.; Pain, Arnab (Cold Spring Harbor Laboratory, 2019-10-03) [Preprint]
    Malaria parasites complete their intra-erythrocytic developmental cycle (IDC) in multiples of 24 hours (depending on the species), suggesting a circadian basis to the asexual cell cycle, but the mechanism controlling this periodicity is unknown. Combining in vivo and in vitro approaches using rodent and human malaria parasites, we reveal that: (i) 57% of Plasmodium chabaudi genes exhibit 24 h circadian periodicity in transcription; (ii) 58% of these genes lose transcriptional rhythmicity when the IDC is out-of-synchrony with host rhythms; (iii) 9% of Plasmodium falciparum genes show circadian transcription under free-running conditions; (iv) Serpentine receptor 10 (SR10) has a circadian transcription profile and disrupting it in rodent malaria parasites shortens the IDC by 2-3 hours; (v) Multiple processes including DNA replication and the ubiquitin and proteasome pathways are affected by loss of coordination with host rhythms and by disruption of SR10. Our results show that malaria parasites are at least partly responsible for scheduling their IDCs explaining the fitness benefits of coordination with host rhythms.
  • Can Fish and Cell Phones Teach Us about Our Health?

    Lee, Michael A; Duarte, Carlos M.; Eguíluz, V. M.; Heller, Daniel A; Langer, Robert; Meekan, Mark G; Sikes, Hadley D; Srivastava, Mani; Strano, Michael S; Wilson, Rory P (ACS sensors, American Chemical Society (ACS), 2019-10-03) [Article]
    Biologging is a scientific endeavor that studies the environment and animals within it by outfitting the latter with sensors of their dynamics as they roam freely in their natural habitats. As wearable technologies advance for the monitoring of human health, it may be instructive to reflect on the successes and failures of biologging in field biology over the past few decades. Several lessons may be of value. Physiological sensors can
  • Deciphering photocarrier dynamics for tuneable high-performance perovskite-organic semiconductor heterojunction phototransistors

    Lin, Yen-Hung; Huang, Wentao; Pattanasattayavong, Pichaya; Lim, Jongchul; Li, Ruipeng; Sakai, Nobuya; Panidi, Julianna; Hong, Min Ji; Ma, Chun; Wei, Nini; Wehbe, Nimer; Fei, Zhuping; Heeney, Martin; Labram, John G.; Anthopoulos, Thomas D.; Snaith, Henry J. (Nature Communications, Springer Science and Business Media LLC, 2019-10-02) [Article]
    Looking beyond energy harvesting, metal-halide perovskites offer great opportunities to revolutionise large-area photodetection technologies due to their high absorption coefficients, long diffusion lengths, low trap densities and simple processability. However, successful extraction of photocarriers from perovskites and their conversion to electrical signals remain challenging due to the interdependency of photogain and dark current density. Here we report hybrid hetero-phototransistors by integrating perovskites with organic semiconductor transistor channels to form either “straddling-gap” type-I or “staggered-gap” type-II heterojunctions. Our results show that gradual transforming from type-II to type-I heterojunctions leads to increasing and tuneable photoresponsivity with high photogain. Importantly, with a preferential edge-on molecular orientation, the type-I heterostructure results in efficient photocarrier cycling through the channel. Additionally, we propose the use of a photo-inverter circuitry to assess the phototransistors’ functionality and amplification. Our study provides important insights into photocarrier dynamics and can help realise advanced device designs with “on-demand” optoelectronic properties.
  • Tuning the Electrochemical Performance of Titanium Carbide MXene by Controllable in situ Anodic Oxidation.

    Tang, Jun; Mathis, Tyler; Kurra, Narendra; Sarycheva, Asia; Xiao, Xu; Hedhili, Mohamed N.; Jiang, Qiu; Alshareef, Husam N.; Xu, Baomin; Pan, Feng; Gogotsi, Yury (Angewandte Chemie (International ed. in English), Wiley, 2019-10-02) [Article]
    MXenes are a class of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides that have shown promise for high-rate pseudocapacitive energy storage. However, the effects that irreversible oxidation have on the surface chemistry and electrochemical properties of MXenes are still not understood. Here we report on a controlled anodic oxidation method which improves the rate performance of titanium carbide MXene (Ti 3 C 2 T x, T x refers to -F, =O, -Cl and -OH) electrodes in acidic electrolytes. The capacitance retention at 2000 mV/s (with respect to the lowest scan rate of 5 mV/s) increases gradually from 38% to 66% by tuning the degree of anodic oxidation. At the same time, a loss in the redox behavior of Ti 3 C 2 is evident at high anodic potentials after oxidation. Several analysis methods were employed to reveal that preserving the structure and surface chemistry while simultaneously introducing defects, without compromising electrochemically active sites, are key factors for improving the rate performance of Ti 3 C 2 T x . This study demonstrates improvement of the electrochemical performance of MXene electrodes by controlling the surface chemistry and transition metal stoichiometry.
  • Iodine-transfer polymerization and CuAAC “click” chemistry: A versatile approach toward poly(vinylidene fluoride)-based amphiphilic triblock terpolymers

    Patil, Yogesh Raghunath; Zapsas, Georgios; Gnanou, Yves; Hadjichristidis, Nikolaos (Journal of Polymer Science Part A: Polymer Chemistry, Wiley, 2019-10-01) [Article]
    This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C6F13I) serving as chain-transfer agent (CTA) to afford C6F13-PVDF-I, (b) ITP of styrene with the C6F13-PVDF-I macromolecular-CTA to obtain C6F13-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C6F13-PVDF-b-PS-b-PEO triblock terpolymers. The 1H and 19F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019
  • A new tricrystalline triblock terpolymer by combining polyhomologation and ring-opening polymerization. synthesis and thermal properties

    Ladelta, Viko; Zapsas, Georgios; Gnanou, Yves; Hadjichristidis, Nikolaos (Journal of Polymer Science Part A: Polymer Chemistry, Wiley, 2019-10-01) [Article]
    New tricrystalline triblock terpolymers, polyethylene-block-poly(ε-caprolactone)-block-poly(L-lactide) (PE-b-PCL-b-PLLA), were synthesized by ROP of ε-caprolactone (CL) and L-lactide (LLA) from linear ω-hydroxyl polyethylene (PE-OH) macroinitiators. The linear PE-OH macroinitiators were prepared by C1 polymerization of methylsulfoxonium methylide (polyhomologation). Tin(II) 2-ethylhexanoate was used as the catalyst for the sequential ROP of CL and LLA in one-pot polymerization at 85 °C in toluene (PE-OH macroinitiators are soluble in toluene at 80 °C). 1H NMR spectra confirmed the formation of PE-b-PCL-b-PLLA triblock terpolymers through the appearance of the characteristic proton peaks of each block. GPC traces showed the increase in the number average molecular weight from PE-OH macroinitiator to PE-b-PCL, and PE-b-PCL-b-PLLA corroborating the successful synthesis. The existence of three crystalline blocks was proved by DSC and XRD spectroscopy. © 2019 The Authors. Journal of Polymer Science Part A: Polymer Chemistry published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019
  • Tunable Dual-Wavelength Self-injection Locked InGaN/GaN Green Laser Diode

    Shamim, Md. Hosne Mobarok; Alkhazragi, Omar; Ng, Tien Khee; Ooi, Boon S.; Khan, Mohammed Zahed Mustafa (IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2019-10-01) [Article]
    We implemented a tunable dual-longitudinal-mode spacing InGaN/GaN green (521–528 nm) laser diode by employing a self-injection locking scheme that is based on an external cavity configuration and utilizing either a high-or partial-reflecting mirror. A tunable longitudinal-mode spacing of 0.20 – 5.96 nm was accomplished, corresponding to a calculated frequency difference of 0.22–6.51 THz, as a result. The influence of operating current and temperature on the system performance was also investigated with a measured maximum side-mode-suppression ratio of 30.4 dB and minimum dual-mode peak optical power ratio of 0.03 dB. To shed light on the operation of the dual-wavelength device arising from the tunable longitudinal-mode spacing mechanism, the underlying physics is qualitatively described. To the best of our knowledge, this tunable longitudinal-mode-spacing dual-wavelength device is novel, and has potential applications as an alternative means in millimeter wave and THz generation, thus possibly addressing the terahertz technology gap. The dual-wavelength operation is also attractive for high-resolution imaging and broadband wireless communication.
  • Poly(2-alkyl-2-oxazoline) electrode interlayers for improved n-type organic field effect transistor performance

    Nam, Sungho; de la Rosa, Victor R.; Cho, Yuljae; Hamilton, Rick; Cha, SeungNam; Hoogenboom, Richard; Bradley, Donal (Applied Physics Letters, AIP Publishing, 2019-10-01) [Article]
    Thin film interlayer materials inserted at the metal/semiconductor interface provide an effective means to improve charge injection and reduce the threshold voltage for organic field-effect transistors. Here, we report the use of poly(2-alkyl-2-oxazoline) interlayers for gold electrodes within n-type poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] field-effect transistors. We specifically show that the use of poly(2-ethyl-2-oxazoline) yields a reduction in the work function from 5.07 to 4.73 eV (ΔE = 0.34 eV), an increase in the electron mobility from 0.04 to 0.15 cm2/V s (3.75 times), and a reduction in the threshold voltage from 27.5 to 16.5 V (ΔV = 11 V) relative to bare gold. The alkyl side chain of the poly(2-alkyl-2-oxazoline) has a significant influence on the film microstructure and, as a consequence, also device performance.
  • 17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS2 as a Replacement for PEDOT:PSS

    Lin, Yuanbao; Adilbekova, Begimai; Firdaus, Yuliar; Yengel, Emre; Faber, Hendrik; Sajjad, Muhammad; Zheng, Xiaopeng; Yarali, Emre; Seitkhan, Akmaral; Bakr, Osman; El Labban, Abdulrahman; Schwingenschlögl, Udo; Tung, Vincent; McCulloch, Iain; Laquai, Frédéric; Anthopoulos, Thomas D. (Advanced Materials, Wiley, 2019-10-01) [Article]
    The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short-circuit current (JSC), and lower series resistance than devices based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and MoS2. Cells based on the ternary bulk-heterojunction PBDB-T-2F:Y6:PC71BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open-circuit voltage of 0.84 V, and a JSC of 26 mA cm−2. Analysis of the cells' optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2-based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high-efficiency organic photovoltaics.
  • An improved indirect evaporative cooler experimental investigation

    Shahzad, Muhammad Wakil; Burhan, Muhammad; Ybyraiymkul, Doskhan; Oh, Seung Jin; Ng, Kim Choon (Applied Energy, Elsevier BV, 2019-10-01) [Article]
    Air conditioning has enhanced the work efficiency and improved life style by maintaining comfortable environment. The growing demand of air conditioning has negative impact on energy and environment. In 2015, air conditioning consumed 6% of total global electricity produced and it is expected to increase to 20% by 2050. The leveling-off conventional chiller’s efficiency at 0.85 ± 0.03 kW/Rton due to pairing of dehumidification and cooling processes in one machine is not only the major reason of high energy consumption but also the key limitation in efficiency improvement. The de-coupling of dehumidification and cooling processes can be one of the solution to achieve the quantum jump in the performance, 0.6 ± 0.03 kW/Rton, by improving individual processes. We proposed an improved indirect evaporative cooler system for sensible cooling that can be combined with dehumidification processes to achieve sustainable cooling goals. The experimentation on 800 mm long and 280 mm wide generic cell showed that it can produce temperature differential up to 10 °C with small area of heat transfer. It was showed that the proposed vertical heat exchanger configuration with multi point injection of working air is the best configuration of the indirect evaporative cooler, achieving coefficient of performance level of 78 for cooling alone. We expect that overall coefficient of performance level of 7–8 is achievable by incorporating efficient dehumidification processes. We also presented detailed design parameters that can be used as a reference for commercial system design.
  • CDPath: Cooperative driver pathways discovery using integer linear programming and Markov clustering

    Yang, Ziying; Yu, Guoxian; Guo, Maozu; Yu, Jiantao; Zhang, Xiangliang; Wang, Jun (IEEE/ACM Transactions on Computational Biology and Bioinformatics, Institute of Electrical and Electronics Engineers (IEEE), 2019-10-01) [Article]
    Discovering driver pathways is an essential task to understand the pathogenesis of cancer and to design precise treatments for cancer patients. Increasing evidences have been indicating that multiple pathways often function cooperatively in carcinogenesis. In this study, we propose an approach called CDPath to discover cooperative driver pathways. CDPath firstly uses Integer Linear Programming to explore driver core modules from mutation profiles by enforcing co-occurrence and functional interaction relations between modules, and by maximizing the mutual exclusivity and coverage within modules. Next, to enforce cooperation of pathways and help the follow-up exact cooperative driver pathways discovery, it performs Markov clustering on pathway-pathway interaction network to cluster pathways. After that, it identifies pathways in different modules but in the same clusters as cooperative driver pathways. We apply CDPath on two TCGA datasets: breast cancer (BRCA) and endometrial cancer (UCEC). The results show that CDPath can identify known (i.e., TP53) and potential driver genes (i.e., SPTBN2). In addition, the identified cooperative driver pathways are related with the target cancer, and they are involved with carcinogenesis and several key biological processes. CDPath can uncover more potential biological associations between pathways (over 100%) and more cooperative driver pathways (over 200%) than competitive approaches.

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