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Quantifying stimulated emission in semiconductor nanocrystals (NCs) remains challenging due to masking of its effects on pump-probe spectra by excited state absorption and ground state bleaching signals. The absence of this defining photophysical parameter in turn impedes assignment of band edge electronic structure in many of these important fluorophores. Here we employ a generally applicable 3-pulse ultrafast spectroscopic method coined the "Spectator Exciton" (SX) approach to measure stimulated-emission efficiency in quantum confined inorganic perovskite CsPbBr3 NCs, the band edge electronic structure of which is the subject of lively ongoing debate. Our results show that in 5-6 nm CsPbBr3 NCs, a single exciton bleaches more than half of the intense band edge absorption band, while the cross section for stimulated emission from the same state is nearly 6 times weaker. Discussion of these findings in light of several recent electronic structure models for this material proves them unable to simultaneously explain both measures, proving the importance of this new input to resolving this debate. Along with femtosecond time-resolved photoluminescence measurements on the same sample, SX results also verify that biexciton interaction energy is intensely attractive with a magnitude of â¼80 meV. In light of this observation, our previous suggestion that biexciton interaction is repulsive is reassigned to hot phonon induced slowdown of carrier relaxation leading to direct Auger recombination from an excited state. The mechanism behind the extreme slowing of carrier cooling after several stages of exciton recombination remains to be determined.
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Zn deposition with a surface-preferred (002) crystal plane has attracted extensive attention due to its inhibited dendrite growth and side reactions. However, the nucleation and growth of the Zn(002) crystal plane are closely related to the interfacial properties. Herein, oriented growth of Zn(002) crystal plane is realized on Ag-modified surface that is directly visualized by in situ atomic force microscopy. A solid solution HCP-Zn (~1.10â at. % solubility of Ag, 30 °C) is formed on the Ag coated Zn foil (Zn@Ag) and possesses the same crystal structure as Zn to reduce its nucleation barrier caused by their lattice mismatch. It merits oriented Zn deposition and corrosion-resistant surface, and presents long cycling stability in symmetric cells and full cells coupled with V2O5 cathode. This work provides insights into interfacial regulation of Zn anodes for high-performance aqueous zinc metal batteries.
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Epigenomics and transcriptomics data from high-throughput sequencing techniques such as RNA-seq and ChIP-seq have been successfully applied in predicting gene transcript expression. However, the locations of chromatin loops in the genome identified by techniques such as Chromatin Interaction Analysis with Paired End Tag sequencing (ChIA-PET) have never been used for prediction tasks. Here, we developed machine learning models to investigate if ChIA-PET could contribute to transcript and exon usage prediction. In doing so, we used a large set of transcription factors as well as ChIA-PET data. We developed different Gradient Boosting Trees models according to the different tasks with the integrated datasets from three cell lines, including GM12878, HeLaS3 and K562. We validated the models via 10-fold cross validation, chromosome-split validation and cross-cell validation. Our results show that both transcript and splicing-derived exon usage can be effectively predicted with at least 0.7512 and 0.7459 of accuracy, respectively, on all cell lines from all kinds of validations. Examining the predictive features, we found that RNA Polymerase II ChIA-PET was one of the most important features in both transcript and exon usage prediction, suggesting that chromatin loop anchors are predictive of both transcript and exon usage.
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Montagem e Desmontagem da Cromatina/genética , Cromatina/genética , Biologia Computacional/métodos , Éxons , Transcrição Gênica , Metilação de DNA , Epigênese Genética , Epigenômica/métodos , Regulação da Expressão Gênica , Histonas/metabolismo , Modelos Biológicos , Reprodutibilidade dos TestesRESUMO
Li-O2 batteries with bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte are promising because TFSI-IL can stabilize O2 - to lower charge overpotential. However, slow Li+ transport in TFSI-IL electrolyte causes inferior Li deposition. Here we optimize weak solvating molecule (anisole) to generate anisole-doped ionic aggregate in TFSI-IL electrolyte. Such unique solvation environment can realize not only high Li+ transport parameters but also anion-derived solid electrolyte interface (SEI). Thus, fast Li+ transport is achieved in electrolyte bulk and SEI simultaneously, leading to robust Li deposition with high rate capability (3â mA cm-2 ) and long cycle life (2000â h at 0.2â mA cm-2 ). Moreover, Li-O2 batteries show good cycling stability (a small overpotential increase of 0.16â V after 120 cycles) and high rate capability (1â A g-1 ). This work provides an effective electrolyte design principle to realize stable Li deposition and high-performance Li-O2 batteries.
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Metallic Na is a promising anode for rechargeable batteries, however, it is plagued by an unstable solid electrolyte interphase (SEI) and Na dendrites. Herein, a robust anion-derived SEI is constructed on Na anode in a high-concentration 1,2-dimethoxyethane (DME) based electrolyte with a cosolvent hydrofluoroether, which effectively restrains Na dendrite growth. The hydrofluoroether can tune the solvation configuration of the electrolyte from three-dimensional network aggregates to solvent-cation-anion clusters, enabling more anions to enter and reinforce the inner solvation sheath and their stepwise decomposition. The gradient inorganic-rich SEI leads to a reduced energy barrier of Na+ migration and enhanced interfacial kinetics. These render the Na||Na3 V2 (PO4 )3 battery with an excellent rate capability of 79.9â mAh g-1 at 24â C and a high capacity retention of 94.2 % after 6000â cycles at 2â C. This highlights the modulation of the electrode-electrolyte interphase chemistry for advanced batteries.
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Bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte could endow Li-O2 batteries with low charging overpotential. However, their weak Li+ transport ability (LTA) leads to non-uniform Li deposition. Herein, guided by Sand formula, the LTA of TFSI-IL electrolyte is greatly enhanced to realize robust Li deposition through introducing hydrofluoroether (HFE) and optimizing electrolyte component ratios to regulate solvation environment. The solvation environment changes from Li(TFSI)2 - ion pair into ionic aggregate clusters in the optimal electrolyte thanks to the slicing function of HFE toward ionic aggregate network. The transport parameters of Sand formula are synchronously enhanced, resulting in highly robust Li deposition behavior with greatly improved Coulombic efficiency (ca. 97.5 %) and cycling rate (1â mA cm-2 ). Cycling stability of Li-O2 batteries was greatly improved (a tiny overpotential rise of 64â mV after 75â cycles).
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Metal K-CO2 batteries suffer from large polarization and safety hazards, which mainly result from the difficult decomposition of K2 CO3 and dendrite growth. Moreover, the battery redox mechanism remains not fully understood. Here we report K-CO2 batteries with KSn alloy as the anode and carboxyl-containing multi-walled carbon nanotubes (MWCNTs-COOH) as the cathode catalyst, proving the redox mechanism to be 4 KSn + 3 CO2 â 2 K2 CO3 + C + 4 Sn. Compared with K metal, the less active and dendrite-free KSn anode effectively enhances the safety and stability of CO2 batteries. More importantly, the strong electrostatic interaction between MWCNTs-COOH and K2 CO3 weakens the C=O bond in K2 CO3 and thus facilitates K2 CO3 decomposition. As a result, the K-CO2 batteries show excellent cycling stability (an overpotential increase of 0.89â V after 400â cycles) and good rate performance (up to 2000â mA g-1 ). This work paves a way to develop highly stable and safe CO2 -based batteries.
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Sodium metal is a promising anode, but uneven Na deposition with a dendrite growth seriously impedes its application. Herein, a fibrous hydroxylated MXene/carbon nanotubes (h-Ti3 C2 /CNTs) composite is designed as a scaffold for dendrite-free Na metal electrodes. This composite displays fast Na+ /electron transport kinetics and good thermal conductivity and mechanical properties. The h-Ti3 C2 contains abundant sodiophilic functional groups, which play a significant role in inducing homogeneous nucleation of Na. Meanwhile, CNTs provide high tensile strength and ease of film-forming. As a result, h-Ti3 C2 /CNTs exhibit a high average Coulombic efficiency of 99.2 % and no dendrite after 1000â cycles. The h-Ti3 C2 /CNTs/Na based symmetric cells show a long lifespan over 4000â h at 1.0â mA cm-2 with a capacity of 1.0â mAh cm-2 . Furthermore, Na-O2 batteries with a h-Ti3 C2 /CNTs/Na anode exhibit a low potential gap of 0.11â V after an initial 70 cycles.
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Environment perception is one of the major issues in autonomous driving systems. In particular, effective and robust drivable road region detection still remains a challenge to be addressed for autonomous vehicles in multi-lane roads, intersections and unstructured road environments. In this paper, a computer vision and neural networks-based drivable road region detection approach is proposed for fixed-route autonomous vehicles (e.g., shuttles, buses and other vehicles operating on fixed routes), using a vehicle-mounted camera, route map and real-time vehicle location. The key idea of the proposed approach is to fuse an image with its corresponding local route map to obtain the map-fusion image (MFI) where the information of the image and route map act as complementary to each other. The information of the image can be utilized in road regions with rich features, while local route map acts as critical heuristics that enable robust drivable road region detection in areas without clear lane marking or borders. A neural network model constructed upon the Convolutional Neural Networks (CNNs), namely FCN-VGG16, is utilized to extract the drivable road region from the fused MFI. The proposed approach is validated using real-world driving scenario videos captured by an industrial camera mounted on a testing vehicle. Experiments demonstrate that the proposed approach outperforms the conventional approach which uses non-fused images in terms of detection accuracy and robustness, and it achieves desirable robustness against undesirable illumination conditions and pavement appearance, as well as projection and map-fusion errors.
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Organic carbonyl electrode materials have shown great prospects for rechargeable batteries in view of their high capacity, flexible designability, and sustainable production. However, organic carbonyl electrode materials still suffer from unsatisfactory electrochemical performance, which is highly relevant to their redox processes. Herein, an in-depth understanding on redox processes and the correlated electrochemical performance of organic carbonyl electrode materials is provided. The redox processes discussed mainly involve molecular structure evolution (intermediates), crystal structure evolution (phase transition), and charge storage mechanisms. The properties of intermediates can affect voltage, cycling stability, reversible capacity, and rate performance of batteries. Moreover, the reversible capacity/cycling stability and rate performance would be also influenced by phase transition and charge storage mechanisms (diffusion- or surface-controlled), respectively. To accelerate the practical applications of organic carbonyl electrode materials, future work should focus on developing more in situ or operando characterization techniques and further understanding the intrinsic relationships between redox processes and performance. It is hoped that the work discussed herein will stimulate more attention to the detailed redox processes and their correlations with the performance of organic carbonyl electrode materials in rechargeable batteries.
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All-solid-state sodium batteries with poly(ethylene oxide) (PEO)-based electrolytes have shown great promise for large-scale energy storage applications. However, the reported PEO-based electrolytes still suffer from a low Na+ transference number and poor ionic conductivity, which mainly result from the simultaneous migration of Na+ and anions, the high crystallinity of PEO, and the low concentration of free Na+. Here, we report a high-performance PEO-based all-solid-state electrolyte for sodium batteries by introducing Na3SbS4 to interact with the TFSI- anion in the salt and decrease the crystallinity of PEO. The optimal PEO/NaTFSI/Na3SbS4 electrolyte exhibits a remarkably enhanced Na+ transference number (0.49) and a high ionic conductivity of 1.33 × 10-4 S cm-1 at 45 °C. Moreover, we found that the electrolyte can largely alleviate Na+ depletion near the electrode surface in symmetric cells and, thus, contributes to stable and dendrite-free Na plating/stripping for 500 h. Furthermore, all-solid-state Na batteries with a 3,4,9,10-perylenetetracarboxylic dianhydride cathode exhibit a high capacity retention of 84% after 200 cycles and superior rate performance (up to 10C). Our work develops an effective way to realize a high-performance all-solid-state electrolyte for sodium batteries.
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Broussonetia papyrifera has a high lignocellulose content leading to poor palatability and low digestion rate of ruminants. Thus, dynamic profiles of fermentation lignocellulose characteristics, microbial community structure, potential function, and interspecific relationships of B. papyrifera mixing with wheat bran in different ratios: 100:0 (BP100), 90:10 (BP90), 80:20 (BP80), and 65:35 (BP65) were investigated on ensiling days 5, 15, 30, and 50. The results showed that adding bran increased the degradation rate of hemicellulose, neutral detergent fiber, and the activities of filter paper cellulase, endoglucanase, acid protease, and neutral protease, especially in the ratio of 65:35. Lactobacillus, Pediococcus, and Weissella genus bacteria were the dominant genera in silage fermentation, and Pediococcus and Weissella genus bacteria regulated the process of silage fermentation. Compared with monospecific B. papyrifera silage, adding bran significantly increased the abundance of Weissella sp., and improved bacterial fermentation potential in BP65 (p < 0.05). Distance-based redundancy analysis showed that lactic acid bacteria (LAB) were significantly positive correlated with most lignocellulose content and degrading enzymes activities, while Monascus sp. and Syncephalastrum sp. were opposite (p < 0.05). Co-occurrence network analysis indicated that there were significant differences in microbial networks among different mixing ratios of B. papyrifera silage prepared with bran. There was a more complex, highly diverse and less competitive co-occurrence network in BP65, which was helpful to silage fermentation. In conclusion, B. papyrifera ensiled with bran improved the microbial community structure and the interspecific relationship and reduced the content of lignocellulose.
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Covalent organic frameworks (COFs) have shown great potential as high-performance electrode materials for metal-ion batteries in view of their relatively high capacity, flexibly designable structure, ordered porous structure, and limited solubility in electrolyte. To develop more attractive COF electrode materials, it is necessary to understand their structure-performance relationships. This Perspective focuses on discussing the relationships between structure (molecular structure, micro structure, and electrode structure) and performance (voltage, capacity, cycling stability, and rate performance) of COF electrode materials in metal-ion batteries. Among the reported COF electrode materials, those with all linkages being redox active based on CâO and CâN groups would be the most promising cathode materials because of their high capacity (â¼500 mAh g-1), moderate working voltage (â¼2 V vs Li+/Li), and good cycling stability. To accelerate practical application of COF electrode materials in metal-ion batteries, future work should pay more attention to function-oriented molecular structure design via theoretical simulations, as well as full-cell fabrication and evaluation. This Perspective will stimulate high-quality research that might lead to future commercialization.
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It is difficult to achieve higher energy density with the existing system of lithium (Li)-ion batteries. As a powerful candidate, Li metal batteries are in the renaissance. Unfortunately, the uncontrolled growth process of Li dendrites has limited their actual application. Hence, inhibiting the formation and spread of Li dendrites has become an enormous challenge. Herein, a novel composite separator is developed with functionalized boron nitride nanosheet modification layer as a Li-ion regulator to regulate Li-ion fluxes. The composite separator contains abundant polar groups and nanoscale channels and could achieve uniform electrochemical deposition via the lithiophilic effect and shunting action. Under the synergy influence of the lithiophilic effect and shunting action, Li dendrites are effectively suppressed. As proof, the Li||Li symmetrical cells with composite separators can circulate steadily for a long time under high current densities (10 mA cm-2, 800 h). Moreover, the LiFePO4||Li full cells display excellent long cycling performance (82% retention after 800 cycles).
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Chromatin interactions play important roles in regulating gene expression. However, the availability of genome-wide chromatin interaction data is limited. We develop a computational method, chromatin interaction neural network (ChINN), to predict chromatin interactions between open chromatin regions using only DNA sequences. ChINN predicts CTCF- and RNA polymerase II-associated and Hi-C chromatin interactions. ChINN shows good across-sample performances and captures various sequence features for chromatin interaction prediction. We apply ChINN to 6 chronic lymphocytic leukemia (CLL) patient samples and a published cohort of 84 CLL open chromatin samples. Our results demonstrate extensive heterogeneity in chromatin interactions among CLL patient samples.
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Cromatina , Aprendizado de Máquina , Redes Neurais de Computação , Sequência de Bases , Biologia Computacional , Genoma , Humanos , Leucemia/genéticaRESUMO
The mechanisms underlying gene repression and silencers are poorly understood. Here we investigate the hypothesis that H3K27me3-rich regions of the genome, defined from clusters of H3K27me3 peaks, may be used to identify silencers that can regulate gene expression via proximity or looping. We find that H3K27me3-rich regions are associated with chromatin interactions and interact preferentially with each other. H3K27me3-rich regions component removal at interaction anchors by CRISPR leads to upregulation of interacting target genes, altered H3K27me3 and H3K27ac levels at interacting regions, and altered chromatin interactions. Chromatin interactions did not change at regions with high H3K27me3, but regions with low H3K27me3 and high H3K27ac levels showed changes in chromatin interactions. Cells with H3K27me3-rich regions knockout also show changes in phenotype associated with cell identity, and altered xenograft tumor growth. Finally, we observe that H3K27me3-rich regions-associated genes and long-range chromatin interactions are susceptible to H3K27me3 depletion. Our results characterize H3K27me3-rich regions and their mechanisms of functioning via looping.
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Cromatina/metabolismo , Repressão Epigenética , Histonas/genética , Neoplasias/genética , Elementos Silenciadores Transcricionais/genética , Animais , Linhagem Celular Tumoral , Cromatina/genética , Sequenciamento de Cromatina por Imunoprecipitação , Feminino , Fatores de Crescimento de Fibroblastos/genética , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Técnicas de Inativação de Genes , Histonas/metabolismo , Humanos , Fator de Crescimento Insulin-Like II/genética , Camundongos , RNA-Seq , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
All-solid-state sodium batteries have great potential for large-scale energy storage applications. However, constructing a compatible Na anode/solid-state electrolyte (SSE) interface is still challenging because most SSEs are unstable toward Na metal. A succinonitrile (SN) SSE shows high room-temperature ionic conductivity (10-3 S cm-1) but easily deteriorates if in contact with Na metal, leading to continuously increased interfacial resistance. Here we present an extremely simple approach to introduce a compact NaF-rich interphase on a Na surface via chemical reactions between fluoroethylene carbonate-Na+ and Na metal, resulting in a compatible Na anode/SN-based electrolyte interface. The in situ formed NaF-rich interphase can not only prevent side reactions between the SN-based electrolyte and Na anode but also regulate the uniform deposition of dendrite-free Na. As a result, the symmetric cells show a low overpotential of 150 mV after cycling for 4000 h. Furthermore, all-solid-state Na-CO2 batteries (4Na + 3CO2 â 2Na2CO3 + C) with the compatible interface can run for 50 cycles with a small overpotential increase of 0.33 V. This work provides a promising method to build a stable interface that enables the use of an SSE which is unstable toward Na in Na metal batteries.
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Despite advancements in treatment regimens, the mortality rate of patients with oral tongue squamous cell carcinoma (OTSCC) is high. In addition, the signaling pathways and oncoproteins involved in OTSCC progression remain largely unknown. Therefore, the aim of the present study was to identify specific prognostic marker for patients at a high risk of developing OTSCC. The present study used four original microarray datasets to identify the key candidate genes involved in OTSCC pathogenesis. Expression profiles of 93 OTSCC tissues and 76 normal tissues from GSE9844, GSE13601, GSE31056 and GSE75538 datasets were investigated. Differentially expressed genes (DEGs) were determined, and gene ontology enrichment and gene interactions were analyzed. The four GSE datasets reported five upregulated and six downregulated DEGs. Five upregulated genes (matrix metalloproteinase 1, 3, 10 and 12 and laminin subunit gamma 2) were localized in the extracellular region of cells and were associated with extracellular matrix disassembly. Furthermore, analysis for The Cancer Genome Atlas database revealed that the aforementioned five upregulated genes were also highly expressed in OTSCC and head and neck squamous cell carcinoma tissues. These results demonstrated that the five upregulated genes may be considered as potential prognostic biomarkers of OTSCC and may serve at understanding OTSCC progression. Upregulated DEGs may therefore represent valuable therapeutic targets to prevent or control OTSCC pathogenesis.