Structural and Na-ion diffusion behavior of O3/P3/P2-type NaNi1/3Mn1/3Fe1/3O2 cathode for Na-ion batteries from first-principles study.

A layered sodium-ion battery cathode, O3/P3/P2-type NaNi1/3Mn1/3Fe1/3O2, has been systematically investigated by first-principles density functional theory to explore the detailed structural and Na-ion diffusion behavior during desodiation. Our results suggest that the (NaO6) spacing is greatest in the P3 phase and lowest in the O3 phase, with the P2 phase exhibiting intermediate spacing. During desodiation, the intermediate stages have a greater (NaO6) spacing than the initial and final stages. The great (NaO6) spacing facilitates the formation of the P3 phase, resulting in the structural evolution of NaxNi1/3Mn1/3Fe1/3O2 from the O3 to the P3 phase at x ≈ 0.59, finally reaching the O3 structure again at x ≈ 0.12. The electronic structure clearly proves that both Ni and Fe are active in O3/P3/P2-type NaxNi1/3Mn1/3Fe1/3O2. Ni2+ is oxidized to Ni3+ as Na content decreases from x = 1 to x = 0.66, then further oxidized to Ni4+ at x = 0.33, and finally, Fe3+ → Fe4+ oxidation occurs at x = 0. In the Na ion diffusion behavior, the order of the barrier is O3 (0.82 eV) > P2 (0.53 eV) > P3 (0.35 eV) at the initial stage, whereas it is O3 (0.53 eV) > P3 (0.21 eV) > P2 (0.16 eV) at a highly desodiated stage. The former can be traced back to the (NaO6) spacing, but the latter is related to the different Na sites. Our results thus provide a factor of the structural evolution and Na ion diffusion barrier by considering (NaO6) width and Na site changes during desodiation.

TiB4 and SrB8 monolayers: high capacity and zero strain-like anode materials for Li/Na/K/Ca ion batteries.

Storage capacity, average open circuit voltage (OCV), diffusion barrier, lattice parameter changes, etc. are key indicators of whether a material would be suitable for use as a Li-ion or non-Li-ion battery (LIB or NLIB) anode. The rapid development of 2D materials over the past few decades has opened up new possibilities for these metrics. Using first-principles calculations, we prove that two 2D materials, TiB4 and SrB8, show excellent performance in terms of the above metrics when used as anodes for LIBs or NLIBs. As detailed, TiB4 has an Li\Na\K\Ca storage capacity of 588 mA h g-1, 588 mA h g-1, 588 mA h g-1, and 1176 mA h g-1, respectively, and SrB8 has an Li\Na\K\Ca storage capacity of 308 mA h g-1, 308 mA h g-1, 462 mA h g-1, and 616 mA h g-1, respectively, and they show good electrical conductivity whether existing Li, Na, K or Ca is adsorbed or not. The diffusion barriers on both surfaces are low, indicating good rate performance. The average OCV is also very low. In particular, the lattice parameters of the two materials change very little during the embedding of Li\Na\K\Ca. For Ti9B36 the corresponding values are about 0.37% (Li), 0.33% (Na), 0.64% (K) and 0.03% (Ca), and for Sr8B64 the corresponding values are about 0.70% (Li), 0.16% (Na), 0.13% (K) and 0.004% (Ca), which imply zero strain-like character and great cycling performance. All the above results show that TiB4 and SrB8 monolayers are very promising Li\Na\K\Ca ion battery anodes.

Automatic Segmentation and Assessment of Valvular Regurgitations with Color Doppler Echocardiography Images: A VABC-UNet-Based Framework.

This study investigated the automatic segmentation and classification of mitral regurgitation (MR) and tricuspid regurgitation (TR) using a deep learning-based method, aiming to improve the efficiency and accuracy of diagnosis of valvular regurgitations. A VABC-UNet model was proposed consisting of VGG16 encoder, U-Net decoder, batch normalization, attention block and deepened convolution layer based on the U-Net backbone. Then, a VABC-UNet-based assessment framework was established for automatic segmentation, classification, and evaluation of valvular regurgitations. A total of 315 color Doppler echocardiography images of MR and/or TR in an apical four-chamber view were collected, including 35 images in the test dataset and 280 images in the training dataset. In comparison with the classic U-Net and VGG16-UNet models, the segmentation performance of the VABC-UNet model was evaluated via four metrics: Dice, Jaccard, Precision, and Recall. According to the features of regurgitation jet and atrium, the regurgitation could automatically be classified into MR or TR, and evaluated to mild, moderate, moderate-severe, or severe grade by the framework. The results show that the VABC-UNet model has a superior performance in the segmentation of valvular regurgitation jets and atria to the other two models and consequently a higher accuracy of classification and evaluation. There were fewer pseudo- and over-segmentations by the VABC-UNet model and the values of the metrics significantly improved (p < 0.05). The proposed VABC-UNet-based framework achieves automatic segmentation, classification, and evaluation of MR and TR, having potential to assist radiologists in clinical decision making of the regurgitations in valvular heart diseases.

Effects of Strain and Electric Field on Molecular Doping in MoSSe.

Recently, synthesized Janus MoSSe monolayers have attracted tremendous attention in science and technology due to their novel properties and promising applications. In this work, we investigate their molecular adsorption-induced structural and electronic properties and tunable doping effects under biaxial strain and external electric field by first-principles calculations. We find an effective n-type or p-type doping in the MoSSe monolayer caused by noncovalent tetrathiafulvalene (TTF) or tetracyanoquinodimethane (TCNQ) molecular adsorption. Moreover, the concentration of doping carrier with respect to the S or Se side also exhibits Janus characteristics because of the electronegativity difference between S and Se atoms and the intrinsic dipole moment in the MoSSe monolayer. In particular, this n-type or p-type molecular doping effect can be flexibly tuned by biaxial strain or under external electric field. By analyzing the valence band maximum (VBM) and conduction band minimum (CBM) in the band structure of MoSSe/TTF under strain, the strain-tunable band gap of MoSSe and the n-type molecular doping effect is revealed. Further explanation of charge transfer between TTF or TCNQ and the MoSSe monolayer by an equivalent capacitor model shows that the superimposition of external electric field and molecular adsorption-induced internal electric field plays a crucial role in achieving a controllable doping concentration in the MoSSe monolayer.

Efficient potential-tuning strategy through p-type doping for designing cathodes with ultrahigh energy density.

Designing new cathodes with high capacity and moderate potential is the key to breaking the energy density ceiling imposed by current intercalation chemistry on rechargeable batteries. The carbonaceous materials provide high capacities but their low potentials limit their application to anodes. Here, we show that Fermi level tuning by p-type doping can be an effective way of dramatically raising electrode potential. We demonstrate that Li(Na)BCF2/Li(Na)B2C2F2 exhibit such change in Fermi level, enabling them to accommodate Li+(Na+) with capacities of 290-400 (250-320) mAh g-1 at potentials of 3.4-3.7 (2.7-2.9) V, delivering ultrahigh energy densities of 1000-1500 Wh kg-1. This work presents a new strategy in tuning electrode potential through electronic band structure engineering.

Composition and Dynamics of Bacterial Communities in a Full-Scale Mineral Water Treatment Plant.

The aim of this study was to gain insight into the bacterial composition and dynamics in a mineral water treatment system (MWTS). The bacterial community of a full-scale mineral water treatment plant in the Maofeng Mountain, South China, was studied using high-throughput sequencing combined with cultivation-based techniques in both the dry and wet season. Overall, adenosine tri-phosphate (ATP) concentration (6.47 × 10-11 - 3.32 × 10-8 M) and heterotrophic plate counts (HPC) (3 - 1.29 × 103 CFU/mL) of water samples in the wet season were lower than those (ATP concentration 5.10 × 10-11 - 6.96 × 10-8 M, HPC 2 - 1.97 × 103 CFU/mL) in the dry season throughout the whole MWTS. The microbial activity and biomass of water samples obviously changed along with treatment process. All 300 isolates obtained using cultivation-based techniques were distributed in 5 phyla, 7 classes, and 19 genera. Proteobacteria accounted for 55.7% (167) of the total isolates, among which predominant genus was Pseudomonas (19.3%). Illumina sequencing analysis of 16s rRNA genes revealed 15 bacterial phyla (relative abundance >0.1%) as being identified in all water samples. Among these, Proteobacteria constituted the dominant bacteria microbiota in all water samples. A large shift in the proportion of Bacteroidetes, Actinobacteria, and Firmicutes was obtained during the treatment process, with the proportion of Bacteroidetes, Actinobacteria decreasing sharply, whereas that of Firmicutes increased and predominated in the final water product. The core microbiome, which was still present in whole MWTS comprised several genera including Pseudomonas, Acinetobacter, Clostridium, and Mycobacterium, that contain species that are opportunistic pathogens, suggesting a potential threat for mineral water microbiology safety. This study is the first to investigate the bacterial community of a full-scale mineral water treatment plant in China. The results provided data regarding the bacteria composition and dynamics in an MWTS, which will contribute to the beneficial manipulation of the mineral water microbiome.

First Principles Study of Penta-siligraphene as High-Performance Anode Material for Li-Ion Batteries.

From first principles calculations, a novel pentagonal Si/C complexity is predicted to have potential applications as a promising anode material for Li-ion batteries. It is found that the structural and thermal stability of the penta-siligraphene (P-Si2C4) is better than penta-graphene that is composed of C atoms only. Electronic band structure analysis shows that the empty C-2pz state in the P-Si2C4 provides space to accommodate and stabilize electrons from Li, which makes Li storage energetically favorable. As a result, four Li atoms can be stored by one formula unit of the P-Si2C4, corresponding to a theoretical gravimetric Li storage capacity of 1028.7 mAhg-1. The metallic electronic structures of the Li-adsorbed P-LixSi2C4 as well as very small Li migration energy barriers are beneficial for fast charge/discharge performance of the battery. The mechanism on the Li adsorption interaction on the P-Si2C4 is discussed. These results demonstrate a novel strategy to design two-dimensional Si/C complex anode materials for high-performance Li-ion batteries.

New insights into Li diffusion in Li-Si alloys for Si anode materials: role of Si microstructures.

Li ion transport is very important to the rate capability of electrode materials in Li ion batteries. For Si anodes, due to huge structural changes of Si structures during the process of charging and discharging, Li ion transport is essentially affected by the Si internal microstructures. Herein, we studied the effect of Si microstructures on Li ion diffusion in Li-Si alloys using first-principles molecular dynamics calculations. Our results demonstrate that the Li diffusion coefficients are closely related to the aggregation degree of Si atoms, regardless of whether it is the low Li concentration phase LiSi or the high Li concentration phase Li2Si under consideration. Furthermore, through counting the number of Si microstructures, such as rings, chains and small clusters, the relationship between the aggregation degree of Si atoms and the number of Si microstructures is established. A large number of Si microstructures corresponds to the low aggregation degree of Si atoms, thus resulting in small Li diffusion coefficients due to the strong interaction between Li and Si atoms. Conversely, a small number of Si microstructures originates from the high aggregation degree of Si atoms, consequently leading to large Li diffusion coefficients. Our study provides a deep insight into the relationship between the Li ion diffusion and the Si distribution, which facilitates the performance improvement of future Si anode materials.

Density functional theory prediction of Mg3N2 as a high-performance anode material for Li-ion batteries.

Two dimensional (2D) materials have great potential for application in energy storage due to their unique structural characteristics. Here we propose for the first time a density functional theory study into the scientific feasibility of using g-Mg3N2, which is a novel graphene-like 2D material, as a high-capacity anode material for Li-ion batteries (LIBs). The favorable Li-adsorption geometries and the Li adsorption thermodynamics are explored in detail. It is found that monolayer g-Mg3N2 can be lithiated up to Li7Mg3N2 that offers a super high theoretical capacity of 1858 mA h g-1 and the average intercalation potential ranging from 0.2 to 0.7 V is suitable for anode applications. The metallic electronic structures of LixMg3N2, in combination with the low Li-ion diffusion energy barriers on the honeycomb structure, promote high electron and Li-ion conductivity to ensure fast charge/discharge cycling. The excellent structural stability of Mg3N2 is good for the cycling performance. These results predict that g-Mg3N2 can serve as a high-performance anode material for LIBs.

Phosphorus-Mediated MoS2 Nanowires as a High-Performance Electrode Material for Quasi-Solid-State Sodium-Ion Intercalation Supercapacitors.

Molybdenum disulfide (MoS2 ) is a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacity and fascinating 2D layered structure. However, its sluggish kinetics for ionic diffusion and charge transfer limits its practical applications. Here, a promising strategy is reported for enhancing the Na+ -ion charge storage kinetics of MoS2 for supercapacitors. In this strategy, electrical conductivity is enhanced and the diffusion barrier of Na+ ion is lowered by a facile phosphorus-doping treatment. Density functional theory results reveal that the lowest energy barrier of dilute Na-vacancy diffusion on P-doped MoS2 (0.11 eV) is considerably lower than that on pure MoS2 (0.19 eV), thereby signifying a prominent rate performance at high Na intercalation stages upon P-doping. Moreover, the Na-vacancy diffusion coefficient of the P-doped MoS2 at room temperatures can be enhanced substantially by approximately two orders of magnitude (10-6 -10-4 cm2 s-1 ) compared with pure MoS2 . Finally, the quasi-solid-state asymmetrical supercapacitor assembled with P-doped MoS2 and MnO2 , as the positive and negative electrode materials, respectively, exhibits an ultrahigh energy density of 67.4 W h kg-1 at 850 W kg-1 and excellent cycling stability with 93.4% capacitance retention after 5000 cycles at 8 A g-1 .

DNA Demethylation by DNMT3A and DNMT3B in vitro and of Methylated Episomal DNA in Transiently Transfected Cells.

The DNA methylation program in vertebrates is an essential part of the epigenetic regulatory cascade of development, cell differentiation, and progression of diseases including cancer. While the DNA methyltransferases (DNMTs) are responsible for the in vivo conversion of cytosine (C) to methylated cytosine (5mC), demethylation of 5mC on cellular DNA could be accomplished by the combined action of the ten-eleven translocation (TET) enzymes and DNA repair. Surprisingly, the mammalian DNMTs also possess active DNA demethylation activity in vitro in a Ca2+- and redox conditions-dependent manner, although little is known about its molecular mechanisms and occurrence in a cellular context. In this study, we have used LC-MS/MS to track down the fate of the methyl group removed from 5mC on DNA by mouse DNMT3B in vitro and found that it becomes covalently linked to the DNA methylation catalytic cysteine of the enzyme. We also show that Ca2+ homeostasis-dependent but TET1/TET2/TET3/TDG-independent demethylation of methylated episomal DNA by mouse DNMT3A or DNMT3B can occur in transfected human HEK 293 and mouse embryonic stem (ES) cells. Based on these results, we present a tentative working model of Ca2+ and redox conditions-dependent active DNA demethylation by DNMTs. Our study substantiates the potential roles of the vertebrate DNMTs as double-edged swords in DNA methylation-demethylation during Ca2+-dependent physiological processes.

Bandgap tuning in MoSSe bilayers: synergistic effects of dipole moment and interlayer distance.

From first principles calculations, the lowest energy structures of bilayer MoSSe with different combination patterns (S-S, Se-Se, and S-Se bilayers) have been confirmed. The results demonstrate that the band gap of bilayer MoSSe can be tuned by interlayer distance and dipole moment. A larger interlayer distance increases the band gap, while a larger dipole moment reduces the band gap. That is, the gap is affected by the synergistic effects of dipole moment and interlayer distance in a MoSSe bilayer. Our results provide a new way to realize band gap modulation by changing the dipole moment or the interlayer distance. Impressively, another important finding is that the S-Se bilayer has a type-II band alignment, which makes it a good candidate for applications in optoelectronics.

Electron-donor doping enhanced Li storage in electride Ca2N monolayer: a first-principles study.

It was reported by Hu et al (2015 ACS Appl. Mater. Interfaces 7 24016) that Li adsorption on the Ca2N monolayer is energetically unfavorable, although it was found to be a good candidate for Na storage. In this paper, from first-principles calculations, it is shown that compressive stain can greatly enhance the interactions between Li adsorbate and the Ca2N host, which is beneficial to prevent Li from clustering on the surface and thus Li storage becomes possible. Charge distribution analysis further shows that the enhanced Li-adsorption is a result of the increased surface charge density and the more confined charge distribution under compressive strain. Inspired by this observation, several electron-donor-doped Ca2N materials are considered as anode materials for Li-ion batteries. Results show that the O and F doped Ca2N have the best performance, with predicted Li storage capacity reaching about 567.9 and 565.9 mAh g-1 for O and F doped cases, respectively. It is also demonstrated that electron-donor doping does not change the metallic electronic structures and the low Li-ion migration energy barriers on the surface of the Ca2N monolayer, and thus the rate performance of the doped Ca2N can be as good as the undoped case. Our study offers a deep understanding of the Li interactions with 2D materials and provides an approach of material modification to 2D electrides for battery applications.

Gene therapy for human glioblastoma using neurotropic JC virus-like particles as a gene delivery vector.

Glioblastoma multiforme (GBM), the most common malignant brain tumor, has a short period of survival even with recent multimodality treatment. The neurotropic JC polyomavirus (JCPyV) infects glial cells and oligodendrocytes and causes fatal progressive multifocal leukoencephalopathy in patients with AIDS. In this study, a possible gene therapy strategy for GBM using JCPyV virus-like particles (VLPs) as a gene delivery vector was investigated. We found that JCPyV VLPs were able to deliver the GFP reporter gene into tumor cells (U87-MG) for expression. In an orthotopic xenograft model, nude mice implanted with U87 cells expressing the near-infrared fluorescent protein and then treated by intratumoral injection of JCPyV VLPs carrying the thymidine kinase suicide gene, combined with ganciclovir administration, exhibited significantly prolonged survival and less tumor fluorescence during the experiment compared with controls. Furthermore, JCPyV VLPs were able to protect and deliver a suicide gene to distal subcutaneously implanted U87 cells in nude mice via blood circulation and inhibit tumor growth. These findings show that metastatic brain tumors can be targeted by JCPyV VLPs carrying a therapeutic gene, thus demonstrating the potential of JCPyV VLPs to serve as a gene therapy vector for the far highly treatment-refractory GBM.