Nitrogen and sulfur co-doped Ti3C2Tx MXenes for high-rate lithium-ion batteries.

The electrification of heavy-duty transport and aviation urgently requires new strategies to develop high-rate lithium-ion batteries (LIBs) whose performance fundamentally relies on electrode materials. However, commercially available graphite anodes still suffer from slow kinetics of lithium-ion diffusion and severe safety concerns of lithium plating when achieving the high-rate use goal. Herein, taking Ti3C2Tx as an example, it is demonstrated that N and S co-doping in Ti3C2Tx results in a high-rate MXene anode for LIBs. Nitrogen doping not only flattens the MXene layers and expands the interlayer spacing but also increases the Ti valence state change ability. As evidenced by density functional theory calculations, the diffusion barriers of S-containing Ti3C2Tx MXenes are lower than those of the S-free counterpart, suggesting that S plays an essential role in achieving high-rate performance. Therefore, the N and S co-doped Ti3C2Tx anode in LIBs exhibited excellent performance with a reversible capacity of 113.8 mA h g-1 at a rate of 3C and ∼89% capacity retention after 1000 charge/discharge cycles. The high capacity is attributed to the change in the oxidation states of both Ti and O elements, and the tiny volume change within ∼0.6% upon the stable charging/discharging process accounts for the good capacity retention. When paired up with a LiFe0.5Mn0.5PO4 cathode, the full cell delivers a reversible capacity of 134 mA h g-1 after 1000 cycles at a high rate of 1C. The demonstration of N and S co-doped Ti3C2Tx MXenes in this work may offer a feasible approach for high-rate intercalation anode materials.

Decontamination of mustard sulfur and VX by sodium percarbonate complexed with 1-acetylguanidine as a novel activator.

The peroxide-based decontaminants had attracted great attention for degradation of chemical warfare agents (CWAs) because of their high performance, non-corrosive and environmental-friendly merits. Hydrogen peroxide can be activated by some organic activators to enhance the oxidation ability. In this work, a novel formula based on sodium percarbonate (SPC) complexed with 1-acetylguanidine (ACG) was investigated for decontamination of sulfur mustard (HD) and VX as CWAs. In the experimental results, the active species acetyl peroxide imide acid in the formula aqueous solution was detected in situ by Raman and 13C NMR spectroscopy. The optimized conditions of the decontamination formula (SPC/ACG) were suggested that, the molar ratio of active oxygen and activator ([O]/[ACG]) was 1:1 while the pH value of the formula aqueous solution was about 9. To achieve the decontamination percentage over 99%, the molar ratio of active oxygen to CWA ((O)/(CWA)) needed to be at least 3 for HD and 7 for VX. Meanwhile, the degradation products detected by gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and ion chromatography (IC) indicated that the oxidation and elimination reactions should have occurred on HD molecule, while the degradation of VX mainly originate from the nucleophilic substitution and oxidation reactions.

sEMG-Based Continuous Hand Action Prediction by Using Key State Transition and Model Pruning.

Conventional classification of hand motions and continuous joint angle estimation based on sEMG have been widely studied in recent years. The classification task focuses on discrete motion recognition and shows poor real-time performance, while continuous joint angle estimation evaluates the real-time joint angles by the continuity of the limb. Few researchers have investigated continuous hand action prediction based on hand motion continuity. In our study, we propose the key state transition as a condition for continuous hand action prediction and simulate the prediction process using a sliding window with long-term memory. Firstly, the key state modeled by GMM-HMMs is set as the condition. Then, the sliding window is used to dynamically look for the key state transition. The prediction results are given while finding the key state transition. To extend continuous multigesture action prediction, we use model pruning to improve reusability. Eight subjects participated in the experiment, and the results show that the average accuracy of continuous two-hand actions is 97% with a 70 ms time delay, which is better than LSTM (94.15%, 308 ms) and GRU (93.83%, 300 ms). In supplementary experiments with continuous four-hand actions, over 85% prediction accuracy is achieved with an average time delay of 90 ms.

Zero Lithium Miscibility Gap Enables High-Rate Equimolar Li(Mn,Fe)PO4 Solid Solution.

Forming olivine-structured Li(Mn,Fe)PO4 solid solution is theoretically a feasible way to improve the energy density of the solid solutions for lithium ion batteries. However, the Jahn-Teller active Mn3+ in the solid solution restricts their energy density and rate performance. Here, as demonstrated by operando X-ray diffraction, we show that equimolar LiMn0.5Fe0.5PO4 solid solution nanocrystals undergo a single-phase transition during the whole (de)lithiation process, with a feature of zero lithium miscibility gap, which endows the nanocrystals with excellent electrochemical properties. Specifically, the energy density of LiMn0.5Fe0.5PO4 reaches 625 Wh kg-1, which is 16% higher than that of LiFePO4. Moreover, the high-performance LiMn0.5Fe0.5PO4 nanocrystals are prepared by a microwave-assisted hydrothermal synthesis in pure water.

Understanding charge storage in Nb2CTx MXene as an anode material for lithium ion batteries.

MXenes represent an emerging family of two-dimensional materials of transition metal carbides/carbonitrides terminated with functional groups like -O, -OH, and -F on the chemically active surface of MX slabs. As a member of the family, Nb2CTx exhibits superior lithium storage capacity over most of the other MXenes as anode materials in lithium-ion batteries (LIBs). However, an in-depth understanding of the charge storage mechanism is still lacking so far. Here, through combining complementary experiments and density functional theory calculations, we provide insights into the (de)lithiation process. Specifically, Nb2CTx with dominant -O functional groups stores charge as a result of changes in the oxidation states of both transition metals Nb and O, which is supported by Bader charge analysis showing a significant change in the oxidation states of Nb and O upon lithiation. As monitored by ex situ X-ray diffraction, the interlayer spacing of Nb2CTx changes slightly upon lithium ion (de)intercalation, corresponding to a volume change of only 2.3% with a near zero-strain feature. By coupling with a LiFePO4/C cathode, the full cell presents superior rate capability and cycling stability as well. The insights into the charge storage mechanism of Nb2CTx in this work provide useful guidance for the rational design of MXene-based anode materials for high-performance LIBs.

Quantifying the rigidity of 2D carbides (MXenes).

MXenes represent a family of surface-functionalized two-dimensional (2D) carbides and nitrides with potential applications in the field of flexible electronics, which rely on their elasticity and flexibility. However, the knowledge on such aspects is rather limited. Here, taking the four most typical MXenes, namely, Ti2CTx, Ti3C2Tx, Nb2CTx and Nb4C3Tx (T = O, OH and F) as examples, we evaluate their intrinsic in-plane stiffness and out-of-plane rigidity at the nanoscale with respect to their functional groups, chemical components and thickness by first-principles calculations. We find that both the in-plane stiffness (C) and out-of-plane bending rigidity (D) of MXenes are highly dependent on the thickness of MX and the surface functional groups. Specifically, the thickness and surface functionalization increase C and D significantly. The Foppl-von Karman numbers per area (C/D), as the flexibility descriptor, of MXenes are comparable with that of the MoS2 monolayer, indicating MXenes as a class of strong yet bendable materials. The effective thickness, the critical parameter bridging C and D, of MXenes is determined to be only two-thirds of the average layer spacing. This study provides a fundamental basis for quantifying the rigidity of MXenes at the nanoscale.

Functional Reconstruction of Hindfoot With Total Calcaneus and Talus Loss by Ilizarov Technique: A Case Report.

Total calcaneus and talus loss in the hindfoot is an unusual but severe condition encountered in clinical settings. This condition affects lower-extremity function and poses a significant challenge to limb salvage. We present a case of a 43-year-old man with total calcaneus and talus loss in the right foot treated by Ilizarov technique. A staged treatment protocol was planned to reconstruct and optimize the heel for weightbearing and walking. During the 15-month postoperative follow-up, the patient reported no significant discomfort in the targeted foot and regained satisfactory function, including shoe wearing, walking, driving, and climbing stairs. The American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Scale score was 71, which was an improvement from a preoperative score of 40. This case is the first reported on the functional reconstruction by Ilizarov technique of hindfoot with total calcaneus and talus loss. This treatment protocol provides an effective approach to reconstructing the hindfoot with massive bone loss, although the long-term outcome remains unknown.

lncRNA DILC is downregulated in osteoarthritis and regulates IL-6 expression in chondrocytes.

Excessive production of interleukin 6 (IL-6) is involved in the pathogenesis of osteoarthritis. It has been reported that long noncoding RNA (lncRNA) DILC inhibited IL-6 to regulate liver cancer stem cells. Therefore, lncRNA DILC may also participate in osteoarthritis. We found that lncRNA DILC was downregulated, while IL-6 was upregulated in plasma of osteoarthritis patients comparing to the control group. Levels of plasma lncRNA DILC and IL-6 were significantly and inversely correlated only in patients with osteoarthritis. Downregulation of lncRNA DILC effectively distinguished patients with osteoarthritis from the control group. Overexpression of lncRNA DILC resulted in inhibited IL-6 expression in chondrocytes, while treatment with exogenous IL-6 did not affect lncRNA DILC expression. However, lncRNA DILC overexpression did not affect the proliferation and apoptosis of chondrocytes. Therefore, lncRNA DILC is downregulated in osteoarthritis and regulates IL-6 expression in chondrocytes.

Carbon vacancies in Ti2CT2 MXenes: defects or a new opportunity?

Carbon vacancies are commonly present in two-dimensional (2D) MXenes that hold promise in a variety of applications whereas their behavior remains unknown. Here we report on the influence of carbon vacancies on the structural stability, electronic properties and stiffness of MXenes by taking Ti2CT2 (T = O, F, and OH) as an example. According to the first-principles calculations, the formation energies of carbon vacancies in MXenes are lower than those in other typical 2D materials including graphene and MoS2, in combination with high migration energies. These two features mean that carbon-vacant MXenes are thermodynamically and dynamically stable as further evidenced by the absence of structural reconstruction both in the ground state and at ambient temperature. Interestingly, carbon vacancies that are usually considered as defects substantially offer a new opportunity on at least two aspects: enhanced electronic conduction and reduced stiffness corresponding to improved flexibility. The localized states in the vicinity of the Fermi level introduced by carbon vacancies account for the prominent metallic characteristics in carbon-vacant Ti2CT2 MXenes.

Isolation and genetic characterization of avian influenza virus H4N6 from ducks in China.

An avian influenza virus (AIV) strain belonging to the H4 subtype and provisionally designated as A/duck/China/J1/2012(H4N6) was isolated from diseased ducks with respiratory disease at a commercial poultry farm in Shandong, China, in 2012. The genomic coding sequences of all eight segments of this J1 isolate were determined and used for subsequent analysis. Phylogenetic analysis of all eight segments showed that this duck H4N6 virus was of Eurasian lineage and not American lineage. The results show that the virus probably emerged because of a reassortment event involving other avian H4N6 and H6N1 viruses. Interestingly, this H4N6 virus had all the conserved features common to low-pathogenic AIVs, including the HA cleavage sequence, receptor-binding sequences for the 2,3-linked sialic acid receptor in avian species, and the PB2 627E motif. These results suggest that the duck H4N6 isolate could not cross the species barrier to infect and replicate in mammals, including humans. In addition, screening of the duck serum samples showed that only 0.57 % (2/352) of the individuals had weak but measurable hemagglutination inhibition (HI) antibody titers. The low antibody prevalence data were also supported by the failure to detect H4N6 virus (0/56) in clinical nasal swabs of the ducks. These data indicate an alternate reservoir for the H4N6 virus.

KIF15 promotes the development and progression of chordoma via activating PI3K-AKT signalling pathway.

Aims: Despite its implication in various human cancers, the expression and functional significance of Kinesin family member 15 (KIF15) in chordomas remain unexplored. Main methods: The evaluation of KIF15 protein levels was conducted through immunohistochemistry (IHC) staining and Western blot analysis. Cell proliferation was quantified using MTT and CCK8 assays, whereas cell migration was examined using wound healing and Transwell assays. Furthermore, flow cytometric analysis was utilized to assess cell apoptosis and the cell cycle. Additionally, in vivo experiments were performed using a mouse xenograft model. Key findings: Our study revealed significantly higher expression of KIF15 in stage III chordoma tissues compared to stage II tissues. Knockdown of KIF15 led to notable inhibition of cell proliferation and migration, along with enhanced apoptosis and cell cycle arrest. In vivo studies further confirmed the inhibitory effects of KIF15 knockdown on chordoma tumour growth. In terms of mechanism, we identified the involvement of the PI3K-AKT signalling pathway mediated by KIF15 in chordomas. Notably, the anti-tumour effects of KIF15 deficiency on chordomas were partially reversed by the addition of an AKT activator. Significance: KIF15 promotes chordoma development and progression through the activation of the PI3K-AKT signalling pathway. Thus, targeting KIF15 might be a promising therapeutic strategy for treating chordomas.

Duration perception in peripheral vision: Underestimation increases with greater stimuli eccentricity.

Duration perception plays a fundamental role in our daily visual activities; however, it can be easily distorted, even in the retinal location. While this topic has been extensively investigated in central vision, similar exploration in peripheral vision is still at an early stage. To investigate the influence of eccentricity, a commonly used indicator for quantifying retinal location, on duration perception in peripheral vision, we conducted two psychophysical experiments. In Experiment 1, we observed that the retinal location influenced the Point of Subjective Equality (PSE) but not the Weber Fraction (WF) of stimuli appearing at eccentricities ranging from 30° to 70°. Except at 30°, the PSEs were significantly longer than 416.7 ms (25 frames), which was the duration of standard stimuli. This suggested that participants underestimated duration, and this underestimation increased with greater distance from the central fixation point on the retina. To eliminate the potential interference of the central task used in Experiment 1, we conducted a supplementary experiment (Experiment 2) that demonstrated that this central task did not change the underestimation (PSE) but did influence the sensitivity (WF) at an eccentricity of 50°. In summary, our findings revealed a compressive effect of eccentricity on duration perception in peripheral vision: as stimuli appeared more peripheral on the retina, there was an increasing underestimation of subjective duration. Reasons and survival advantages of this underestimation are discussed. Findings provide new insight on duration perception in peripheral vision, highlighting an expanding compressive underestimation effect with greater eccentricity.

Scanning the active center of formolase to identify key residues for enhanced C1 to C3 bioconversion.

BACKGROUND: Formolase (FLS) is a computationally designed enzyme that catalyzes the carboligation of two or three C1 formaldehyde molecules into C2 glycolaldehyde or C3 dihydroxyacetone (DHA). FLS lays the foundation for several artificial carbon fixation and valorization pathways, such as the artificial starch anabolic pathway. However, the application of FLS is limited by its low catalytic activity and product promiscuity. FINDINGS: FLS, designed and engineered based on benzoylformate decarboxylase from Pseudomonas putida, was selected as a candidate for modification. To evaluate its catalytic activity, 25 residues located within an 8 Å distance from the active center were screened using single-point saturation mutagenesis. A screening approach based on the color reaction of the DHA product was applied to identify the desired FLS variants. After screening approximately 5,000 variants (approximately 200 transformants per site), several amino acid sites that were not identified by directed evolution were found to improve DHA formation. The serine-to-phenylalanine substitution at position 236 improved the activity towards DHA formation by 7.6-fold. Molecular dynamics simulations suggested that the mutation increased local hydrophobicity at the active site, predisposing the cofactor-C2 intermediate to nucleophilic attack by the third formaldehyde molecule for subsequent DHA generation. CONCLUSIONS: This study provides improved FLS variants and valuable information into the influence of residues adjacent to the active center affecting catalytic efficiency, which can guide the rational engineering or directed evolution of FLS to optimize its performance in artificial carbon fixation and valorization.

Surveillance and molecular characterization of Newcastle disease virus in seafowl from coastal areas of China in 2011.

Four Newcastle disease virus (NDV) isolates were obtained from 997 fecal and tissue samples were collected in 2011 from seafowl that included seagull, sea duck, and swan from the coastal areas of Guangdong, Jiangsu, and Shandong in China. These isolates (SD1, SD2, GD1, and JS1) were characterized for their pathogenicity according to their mean death time, intracerebral pathogenicity index and intravenous pathogenicity index. Full-length fusion protein genes containing the cleavage site were sequenced, and amino-acid sequences around the cleavage site were deduced. One isolate (SD2) was virulent to poultry as indicated by its mean death time, intracerebral pathogenicity index, and fusion gene cleavage site sequence, which was specific for virulent NDV ((112)R-R-Q-K-R-F(117)). The phylogenic analysis indicated that three of the isolates (SD1, GD1, and JS1) belonged to genotype II and the virulent isolate (SD2) belonged to genotype VIId. These findings suggest that some seafowl NDVs in the coastal areas of China have different virulences and molecular characterizations, and these NDVs have some similarity with vaccine- or poultry-adapted isolates.

Directed evolution of a neutrophilic and mesophilic methanol dehydrogenase based on high-throughput and accurate measurement of formaldehyde.

Methanol is a promising one-carbon feedstock for biomanufacturing, which can be sustainably produced from carbon dioxide and natural gas. However, the efficiency of methanol bioconversion is limited by the poor catalytic properties of nicotinamide adenine dinucleotide (NAD+)-dependent methanol dehydrogenase (Mdh) that oxidizes methanol to formaldehyde. Herein, the neutrophilic and mesophilic NAD+-dependent Mdh from Bacillus stearothermophilus DSM 2334 (MdhBs) was subjected to directed evolution for enhancing the catalytic activity. The combination of formaldehyde biosensor and Nash assay allowed high-throughput and accurate measurement of formaldehyde and facilitated efficient selection of desired variants. MdhBs variants with up to 6.5-fold higher Kcat/KM value for methanol were screened from random mutation libraries. The T153 residue that is spatially proximal to the substrate binding pocket has significant influence on enzyme activity. The beneficial T153P mutation changes the interaction network of this residue and breaks the α-helix important for substrate binding into two short α-helices. Reconstructing the interaction network of T153 with surrounding residues may represent a promising strategy to further improve MdhBs, and this study provides an efficient strategy for directed evolution of Mdh.

Development of a growth-coupled selection platform for directed evolution of heme biosynthetic enzymes in Corynebacterium glutamicum.

Heme is an important tetrapyrrole compound, and has been widely applied in food and medicine industries. Although microbial production of heme has been developed with metabolic engineering strategies during the past 20 years, the production levels are relatively low due to the multistep enzymatic processes and complicated regulatory mechanisms of microbes. Previous studies mainly adopted the strategies of strengthening precursor supply and product transportation to engineer microbes for improving heme biosynthesis. Few studies focused on the engineering and screening of efficient enzymes involved in heme biosynthesis. Herein, a growth-coupled, high-throughput selection platform based on the detoxification of Zinc-protoporphyrin IX (an analogue of heme) was developed and applied to directed evolution of coproporphyrin ferrochelatase, catalyzing the insertion of metal ions into porphyrin ring to generate heme or other tetrapyrrole compounds. A mutant with 3.03-fold increase in k cat/K M was selected. Finally, growth-coupled directed evolution of another three key enzymes involved in heme biosynthesis was tested by using this selection platform. The growth-coupled selection platform developed here can be a simple and effective strategy for directed evolution of the enzymes involved in the biosynthesis of heme or other tetrapyrrole compounds.

Engineering allosteric inhibition of homoserine dehydrogenase by semi-rational saturation mutagenesis screening.

Allosteric regulation by pathway products plays a vital role in amino acid metabolism. Homoserine dehydrogenase (HSD), the key enzyme for the biosynthesis of various aspartate family amino acids, is subject to feedback inhibition by l-threonine and l-isoleucine. The desensitized mutants with the potential for amino acid production remain limited. Herein, a semi-rational approach was proposed to relieve the feedback inhibition. HSD from Corynebacterium glutamicum (CgHSD) was first characterized as a homotetramer, and nine conservative sites at the tetramer interface were selected for saturation mutagenesis by structural simulations and sequence analysis. Then, we established a high-throughput screening (HTS) method based on resistance to l-threonine analog and successfully acquired two dominant mutants (I397V and A384D). Compared with the best-ever reported desensitized mutant G378E, both new mutants qualified the engineered strains with higher production of CgHSD-dependent amino acids. The mutant and wild-type enzymes were purified and assessed in the presence or absence of inhibitors. Both purified mutants maintained >90% activity with 10 mM l-threonine or 25 mM l-isoleucine. Moreover, they showed >50% higher specific activities than G378E without inhibitors. This work provides two competitive alternatives for constructing cell factories of CgHSD-related amino acids and derivatives. Moreover, the proposed approach can be applied to engineering other allosteric enzymes in the amino acid synthesis pathway.

Genetic and biological characterizations of a Newcastle disease virus from swine in China.

BACKGROUND: Newcastle Disease Virus (NDV) has been considered to only infect avian species. However, one paramyxovirus named as Xiny10 was isolated from swine. The differences of Xiny10, another previous swine NDV (JL01) and vaccine strain La Sota were compared on the basis of sequences of the whole-lengthen Fusion (F) gene and biological characteristics. FINDINGS: Through serologic tests and sequence alignment, Xiny10 was proved as NDV. It has great differences with JL01 in virulence, biological characteristics, genotype and amino acid homology of F gene. The sequence alignment showed Xiny10 and La Sota both belonged to genotype II. It shared 97.3% to 98.7% identities with genotype II NDVs, which was higher than these strains from the other genotypes. CONCLUSIONS: These above data suggested that the swine virus was NDV and it might be generated from La Sota.

High fraction of soluble trace metals in fine particles under heavy haze in central China.

Atmospheric trace metals are a key component of particulate matter and significantly influence the atmospheric process and human health. The dissolved fraction of trace metals represents their bioavailability and exhibits high chemical activity. However, the optimum measurement method for detecting the soluble fraction of trace metals is still undetermined. The impact of variations in pollution on the soluble fraction is largely unrevealed. Therefore, in this work, a one-month field observation was conducted in Central China and different extraction solvents were used to determine the proper measurement method for the soluble fraction of trace metals and investigate the variation pattern under different pollution conditions. The findings show that solvents with acidity near that of aerosol water can better reflect the actual soluble fraction of trace metals in fine particulate matter. The soluble fraction of trace metals tends to increase with pollution level increased, demonstrating unexpectedly high health risks and chemical activity under heavy haze conditions. Our results indicate that remediation and trace metal pollution control are urgently needed.

Rapid detection of newly isolated Tembusu-related Flavivirus by reverse-transcription loop-mediated isothermal amplification assay.

BACKGROUND: From April 2010 to January 2011, a severe new viral disease had devastated most duck-farming regions in China. This disease affected not only laying ducks but also meat ducks, causing huge economic losses for the poultry industry. The objective of this study is to develop a one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of the new virus related to Tembusu-related Flavivirus. RESULTS: The RT-LAMP assay is very simple and rapid, and the amplification can be completed within 50 min under isothermal conditions at 63°C by a set of 6 primers targeting the E gene based on the sequences analysis of the newly isolated viruses and other closely related Flavivirus.The monitoring of gene amplification can also be visualized by using SYBR green I fluorescent dye. In addition, the RT-LAMP assay for newly isolated Tembusu-related Flavivirus showed higher sensitivity with an RNA detection-limit of 2 copies/µL compared with 190 copies/µL of the conventional RT-PCR method. The specificity was identified without cross reaction to other common avian pathogens. By screening a panel of clinical samples this method was more feasible in clinical settings and there was higher positive coincidence rate than conventional RT-PCR and virus isolation. CONCLUSION: The RT-LAMP assay for newly isolated Tembusu-related Flavivirus is a valuable tool for the rapid and real-time detection not only in well-equipped laboratories but also in general conditions.