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A low-bandgap polymer bearing the N-octyl-2,7-dithia-5-azacyclopenta[alpha]pentalene-4,6-dione electron-withdrawing unit
No full textA low-bandgap PBDTDTPD polymer is synthesized. It is a donor-acceptor-type polymer that consists of dialkylthiophenyl benzodithiophene (BDT) donor unit and N-octyl-2,7-dithia-5-aza-cyclopenta[a]pentalene-4,6-dione (DTPD) acceptor unit. The thienothiophene-fused strong-electron-withdrawing DTPD effectively reduces the bandgap of the resulting polymer and keeps its highest occupied molecular orbital low. Moreover, PBDTDTPD is thermally stable and dissolves well in typical organic solvents. PBDTDTPD:PC71BM(1:1) blend film showed a power conversion efficiency of 3.18% and a largely elevated open-circuit voltage of 0.75 V compared to that of well-known P3HT:PC61BM blend film. In this work, we prove that the DTPD moiety can be utilized to develop a future low-bandgap material that can absorb a broad wavelength of light and have high thermal stability, which are important characteristics for next-generation high-performance organic solar cells
Benchmarking integration of single-cell differential expression
No full textIntegration of single-cell RNA sequencing data between different samples has been a major challenge for analyzing cell populations. Here the authors benchmark 46 workflows for differential expression analysis of single-cell data with multiple batches and suggest several high-performance methods under different conditions based on simulation and real data analyses. Integration of single-cell RNA sequencing data between different samples has been a major challenge for analyzing cell populations. However, strategies to integrate differential expression analysis of single-cell data remain underinvestigated. Here, we benchmark 46 workflows for differential expression analysis of single-cell data with multiple batches. We show that batch effects, sequencing depth and data sparsity substantially impact their performances. Notably, we find that the use of batch-corrected data rarely improves the analysis for sparse data, whereas batch covariate modeling improves the analysis for substantial batch effects. We show that for low depth data, single-cell techniques based on zero-inflation model deteriorate the performance, whereas the analysis of uncorrected data using limmatrend, Wilcoxon test and fixed effects model performs well. We suggest several high-performance methods under different conditions based on various simulation and real data analyses. Additionally, we demonstrate that differential expression analysis for a specific cell type outperforms that of large-scale bulk sample data in prioritizing disease-related genes
Thermal transport experiment on the quasi-one-dimensional spin chain NiTe2O5
No full textThe thermal transport experiment is a unique method used to measure the transport properties of itinerant quasiparticles, both for charge-neutral as well as charged systems. It is known that one-dimensional magnetism prohibits long-range order but can lead to interesting bosonic and fermionic magnetic excitation. Recently, we reported a new quasi-one-dimensional spin chain NiTe2O5[1]. As decreasing temperature, archetypal antiferromagnetic phase transition happens across 30.5 K with an unconventional critical exponent of the order parameter. Beyond the ordering temperature, short-range spin correlation surprisingly survives up to room temperature[2]. In addition, it has been reported that the p-d hybridization induced magnetoelastic coupling and yields the high-order magneto-dielectric effect[3]. Thus, NiTe2O5 has an intriguing correlation for spin degree of freedom. In order to investigate a hindered magnetic excitation in NiTe2O5, we have developed the thermal transport experiment system for a relatively small specimen and studied thermal properties in NiTe2O5. In this presentation, we introduce our experiment setup and discuss the preliminary experimental results.
[1] J. H. Lee et al., Physical Review B 100, 144441 (2019).
[2] S-H Baek et al., Physical Review B 104, 214431 (2021).
[3] A. Tiwari et al., Physical Review Materials 6, 044409 (2022)
Laser-Assisted Nanotexturing for Flexible Ultrathin Crystalline Si Solar Cells
No full textUltrathin (UT) crystalline Si wafers, which are more flexible than conventional ones, can apply to curved surfaces, enabling a wide range of applications such as building-integrated photovoltaics, vehicle-integrated photovoltaics, and wearable devices. Thinner wafers require more effective light trapping; thus, surface texturing in microscale is a common approach to compensate for the reduced thickness by enhancing the light pathlength. Microscale textures, however, deteriorate the mechanical flexibility due to stress concentration in the valley of the microtextures. In this study, a laser-assisted nanotexturing process is proposed for enhanced flexibility of the UT Si solar cells with a 50 & mu;m thickness while maintaining light-trapping performances. A nanolens array is used to focus laser onto the Si wafers, inducing the formation of nanoparticle etch masks for nanopyramid texturing in an alkaline solution. The origin of the enhanced flexibility of the nanotextured Si wafers is discussed by a micromechanics simulation study. Herein, nanotexturing technique is applied to UT Si-based passivated emitter rear cells and the enhanced flexibility of the cells with a 26 mm critical bending radius is demonstrated. Also, it is shown that the nanotextured Si wafer provides a higher efficiency of 18.68%, whereas the microtextured one exhibits 18.10%
Mechanochemical Ammonia Synthesis: Old is New Again
No full textHydrogen is a promising clean energy source, an alternative to fossil fuels, and can potentially play a crucial role in reducing carbon emissions. The transportation and storage of hydrogen are the biggest hurdles to realizing a hydrogen economy. Ammonia is considered to be one of the most promising hydrogen carriers, because of its high hydrogen content and easy liquefaction in mild conditions. To date, ammonia is mostly produced by the 'thermocatalytic' Haber-Bosch process, which requires high temperature and pressure. As a result, it can only produce ammonia in 'centralized' manufacturing systems. Mechanochemistry, a newly emerging method for efficient ammonia synthesis, offers potential advantages over the Haber-Bosch process. Mechanochemical ammonia synthesis under near ambient conditions can be connected with 'localized' sustainable energy systems. In this perspective, the state-of-the-art mechanochemical ammonia synthesis processes will be introduced. Challenges and opportunities are also discussed in relation to its role in a hydrogen economy
Olefin-Linked Covalent Organic Frameworks with Electronegative Channels as Cationic Highways for Sustainable Lithium Metal Battery Anodes
No full textDespite the enormous interest in Li metal as an ideal anode material, the uncontrollable Li dendrite growth and unstable solid electrolyte interphase have plagued its practical application. These limitations can be attributed to the sluggish and uneven Li+ migration towards Li metal surface. Here, we report olefin-linked covalent organic frameworks (COFs) with electronegative channels for facilitating selective Li+ transport. The triazine rings and fluorinated groups of the COFs are introduced as electron-rich sites capable of enhancing salt dissociation and guiding uniform Li+ flux within the channels, resulting in a high Li+ transference number (0.85) and high ionic conductivity (1.78 mS cm(-1)). The COFs are mixed with a polymeric binder to form mixed matrix membranes. These membranes enable reliable Li plating/stripping cyclability over 700 h in Li/Li symmetric cells and stable capacity retention in Li/LiFePO4 cells, demonstrating its potential as a viable cationic highway for accelerating Li+ conduction
Commercialisation time and licensing performance of university inventions: the moderating role of university inventors
No full textThis paper examines the relationship between time and performance in the commercialisation of university-originated inventions. Focusing on the commercialisation time, defined as the time taken for a lab-scale invention to be developed for commercial sale, we investigate whether there is any systematic association between commercialisation time and the licensing revenue generated by university-originated inventions. Analysing a sample of inventions from Stanford University, we find that both pre- and postlicensing time of commercialisation are negatively associated with its licensing revenue. We also find that the negative relationship between the postlicensing time of commercialisation and licensing revenue is contingent on the inventor???s orientation towards university-industry collaboration. We discuss theoretical and practical implications of our findings as well as future avenues of research in technolog
Cerium guided site-selective crystal disorder engineering of MIL-88B(Ni) frameworks for electrocatalysis offering high-performance water oxidation
No full textEngineering the degree of crystallinity is an attractive route to expose unsaturated coordinative metal nodes that act as active electrocatalytic sites in metal-organic frameworks (MOFs). Herein, we develop a novel strategy to induce site-selective disordering of the crystalline structure of MIL88B(Ni) frameworks via Ce-doping, resulting crystalline/amorphous heterostructures. X-ray diffraction and electron microscopy analyses reveal that Ce-rich spherical regions in the framework are amorphous while Ce-deficient flat sheets are crystalline. Comparatively, an optimally Ce-doped MIL-88B(Ni)/NF(nickel foam) anode exhibits significantly lower overpotentials (eta) of 205, 290, 410 and 450 mV to drive the oxygen evolution reaction (OER) under current densities of 10, 100, 1000 and 2000 mAcm(-2), respectively with a superior kinetic of 46.09 mVdec(-1) and a larger turnover frequency (TOF@eta = 330 mV) of 0.36 s(-1). DFT calculations support the experimentally observed Ce3+ ion doping effect in inducing site-selective crystal disorder on MIL-88B(Ni) framework structure, and hence on the OER electrocatalytic activity enhancement. In addition to the remarkably high OER performance, the optimized Ce-doped MIL-88B(Ni)/NF anode exhibits superbly enhanced electrochemical durability over 146 h against industrially relevant high biases of up to 1000 mAcm(-2) in 1.0 M KOH solution, thus demonstrating that Ce-doped MIL88B (Ni)/NF is a highly promising industrially relevant high-performance anode material for electrocatalyzing the OER
Sensing of sound pressure gradients by C. elegans drives phonotaxis behavior
No full textDespite lacking ears, the nematode C. elegans senses airborne sound and engages in phonotaxis behavior, enabling it to locate and avoid sound sources.1 How worms sense sound, however, is not well understood. Here, we report an interesting observation that worms respond only to sounds emitted by small but not large speakers, indicating that they preferentially respond to localized sound sources. Notably, sounds emitted by small speakers form a sharp sound pressure gradient across the worm body, while sounds from large speakers do not, suggesting that worms sense sound pressure gradients rather than absolute sound pressure. Analysis of phonotaxis behavior, sound-evoked skin vibration, and sound-sensitive neuron activities further support this model. We suggest that the ability to sense sound pressure gradients provides a potential mechanism for worms to distinguish sounds generated by their predators, which are typically small animals, from those produced by large animals or background noise. As vertebrate cochlea and some insect ears can also detect sound pressure gradients, our results reveal that sensing of sound pressure gradients may represent a common mechanism in auditory sensation across animal phyla