Direct Dioxygen Radical Coupling Driven by Octahedral Ruthenium-Oxygen-Cobalt Collaborative Coordination for Acidic Oxygen Evolution Reaction.

The acidic oxygen evolution reaction (OER) has long been the bottleneck of proton exchange membrane water electrolyzers given its harsh oxidative and corrosive environments. Herein, we suggest an effective strategy to greatly enhance both the acidic OER activity and stability of Co3O4 spinel by atomic Ru selective substitution on the octahedral Co sites. The resulting highly symmetrical octahedral Ru-O-Co collaborative coordination with strong electron coupling effect enables the direct dioxygen radical coupling OER pathway. Indeed, both experiments and theoretical calculations reveal a thermodynamically breakthrough heterogeneous diatomic oxygen mechanism. Additionally, the active Ru-O-Co units are well-maintained upon the acidic OER thanks to the electron transfer from surrounding electron-enriched tetrahedral Co atoms via bridging oxygen bonds that suppresses the overoxidation and thus dissolution of active Ru and Co species. Consequently, the prepared catalyst, even with a low Ru mass loading of ca. 42.8 µg cm-2, exhibits an attractive acidic OER performance with a low overpotential of 200 mV and a low potential decay rate of 0.45 mV h-1 at 10 mA cm-2. Our work suggests an effective strategy to significantly enhance both the acidic OER activity and stability of low-cost electrocatalysts.

Interface Density Engineering on Heterogeneous Molybdenum Dichalcogenides Enabling Highly Efficient Hydrogen Evolution Catalysis and Sodium Ion Storage.

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO2 /MoS2 heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO2 /MoS2 @NSC) by controllable sulfidation. MoO2 and MoS2 are coupled intimately at atomic level, forming the MoO2 /MoS2 heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO2 /MoS2 heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS2 nanorods counterpart (η10 : 156 mV vs 232 mV) and most of the MoS2 -based heterostructures reported recently. First-principles calculation deciphers that MoO2 /MoS2 heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O-Mo-S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant "ion reservoir"-like channels, and low Na+ diffusion barrier appended by high-density MoO2 /MoS2 heterointerfaces, the material delivers high specific capacity of 888 mAh g-1 , remarkable rate capability and cycling stability of 390 cycles at 0.1 A g-1 as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.

Characterization of antibiotic resistance genes and mobile elements in extended-spectrum ß-lactamase-producing Escherichia coli strains isolated from hospitalized patients in Guangdong, China.

AIM: This study aimed to investigate the high-resolution phenotypic and genotypic characterization of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli strains isolated from hospitalized patients to explore the resistance genes and mobile genetic elements (MGEs) involved in horizontal dissemination. METHODS: Between May and September 2021, a total of 216 ESBL-producing E. coli isolates were recovered from multiple departments. The identification of strains was performed using MALDI-TOF mass spectrometry and PCR, while antibiotic susceptibility testing was carried out using the Vitek 2 COMPACT system to determine resistance patterns, while PCR was used to detect different resistance genes and MGEs. In addition, a conjugation assay was performed to investigate the horizontal gene transfer of resistance genes. Selected isolates underwent whole-genome sequencing (WGS) using the Illumina MiSeq platform. RESULTS: A total of 216 out of 409 E. coli isolates recovered from a tertiary hospital were observed to be ESBL-producing, giving a carriage rate of 52.8%, as determined by phenotypic screening. The most frequent sources of ESBL-producing E. coli isolates were urine (129/216, 59.72%) and blood (50/216, 23.14%). The most prevalent ESBL genes identified were blaCTX-M (60.18%), blaTEM (40.27%), and blaSHV (18.05%). Three E. coli isolates were found to carry the genes blaNDM, mcr-1, and fosA3 genes. The most prevalent MGEs were IS26 (95.37%), Int (87.03%), and IncFIB (76.85%). WGS analysis of eight MDR E. coli strains revealed that these isolates belonged to eight different sequence types (STs) and serotypes and were found to harbor multiple plasmid replicons and virulence factors. CONCLUSION: This study highlights a high incidence of antibiotic resistance genes and MGEs associated with the dissemination of ESBLs and other resistance genes.

A Hydrazine-Nitrate Flow Battery Catalyzed by a Bimetallic RuCo Precatalyst for Wastewater Purification along with Simultaneous Generation of Ammonia and Electricity.

The traditional technologies for industrial and agricultural effluent treatment are often energy-intensive. Herein, we suggest an electrochemical redox strategy for spontaneous and simultaneous decontamination of wastewater and generation of both fuels and electricity at low cost. Using hydrazine and nitrate effluents as a demonstration, we propose a hydrazine-nitrate flow battery (HNFB) that can efficiently purify the wastewater and meanwhile generate both ammonia fuel and electricity with the assistance of our developed bimetallic RuCo precatalyst. Specifically, the battery delivers a peak power density of 12 mW cm-2 and continuously operates for 20 h with an ammonia yield rate of ca. 0.38 mmol h-1 cm-2 under 100 mA cm-2 . The generated electricity can further drive a hydrazine electrolyzer to produce hydrogen fuel. Our work provides an alternative pathway to purify wastewater and generate high value-added fuels at low cost.

Population Pharmacokinetics of Caspofungin and Dose Simulations in Heart Transplant Recipients.

The effect of heart transplantation (HTx) on the pharmacokinetics (PK) of caspofungin is not well-characterized. The aim of this study was to investigate the population PK of caspofungin in HTx and non-HTx patients and to identify covariates that may affect the PK of caspofungin. Seven successive blood samples were collected before administration and at 1, 2, 6, 10, 16, and 24 h after the administration of caspofungin for at least 3 days. This study recruited 27 HTx recipients and 31 non-HTx patients with 414 plasma concentrations in total. A nonlinear mixed-effects model was used to describe the population PK of caspofungin. The PK of caspofungin was best described by a two-compartment model. The clearance (CL) and volume of the central compartment (Vc) of caspofungin were 0.385 liter/h and 4.27 liters, respectively. The intercompartmental clearance (Q) and the volume of the peripheral compartment (Vp) were 2.85 liters/h and 6.01 liters, respectively. In the final model, we found that albumin (ALB) affected the CL of caspofungin with an adjustment factor of -1.01, and no other covariates were identified. In this study, HTx was not found to affect the PK of caspofungin. Based on the simulations, the dose of caspofungin should be proportionately increased in patients with decreased ALB levels.

Surveillance of SARS-CoV-2 antibodies of patients in the local affected area during Wuhan lockdown.

BACKGROUND: Serosurveillance is crucial in estimating the range of SARS-CoV-2 infections, predicting the possibility of another wave, and deciding on a vaccination strategy. To understand the herd immunity after the COVID-19 pandemic, the seroprevalence was measured in 3062 individuals with or without COVID-19 from the clinic. METHODS: The levels of SARS-CoV-2 antibody IgM and IgG were measured by the immuno-colloidal gold method. A fusion fragment of nucleocapsid and spike protein was detected by a qualitative test kit with sensitivity (89%) and specificity (98%). RESULTS: The seroprevalence rate for IgM and IgG in all outpatients was 2.81% and 7.51%, respectively. The sex-related prevalence rate of IgG was significantly higher (P < 0.05) in women than men. The highest positive rate of IgM was observed in individuals < 20 years of age (3.57%), while the highest seroprevalence for IgG was observed in persons > 60 years of age (8.61%). Positive rates of IgM and IgG in the convalescent patients were 31.82% and 77.27%, respectively, which was significantly higher than individuals with suspected syndromes or individuals without any clinical signs (P < 0.01). Seroprevalence for IgG in medical staff was markedly higher than those in residents. No significant difference of seroprevalence was found among patients with different comorbidities (P > 0.05). CONCLUSIONS: The low positive rate of the SARS-CoV-2 IgM and nucleic acid (NA) test indicated that the SARS-CoV-2 outbreak is subsiding after 3 months, and the possibility of reintroduction of the virus from an unidentified natural reservoir is low. Seroprevalence provides information for humoral immunity and vaccine in the future.

METAGENOMIC NEXT-GENERATION SEQUENCING DETECTS PATHOGENS IN ENDOPHTHALMITIS PATIENTS.

PURPOSE: To investigate the utility of metagenomic next-generation sequencing (mNGS) in identifying the pathogens in endophthalmitis. METHODS: In this prospective study, 36 cases of endophthalmitis were recruited. All patients received surgical treatment and intraocular drug lavage. The samples of vitreous or aqueous humor were extracted for mNGS and microbiological culture. The diagnostic performance of pathogens was compared between mNGS and culture. RESULTS: The positive rates of mNGS and culture were 88.89% (32/36) and 27.78% (10/36), respectively. There was a statistically significant difference between mNGS and culture (Chi-square = 27.657; P < 0.01). Staphylococcus epidermidis, Streptococcus pneumoniae, and Klebsiella pneumoniae were the most pathogenic bacteria in traumatic, postoperative, and endogenous endophthalmitis, respectively. The concordance of pathogen identified by mNGS and culture was 70% for culture-positive cases. Antibiotic resistance genes were identified in 9 cases. There was a marginal correlation between the final visual acuity and the microbial sequence read (Spearman correlation coefficient = 0.498; P = 0.05). CONCLUSION: Metagenomic next-generation sequencing has a higher positive rate of identifying pathogens in endophthalmitis than in culture. It can also provide information on antibiotic resistance and visual prognosis. However, caution must be taken when interpreting the results of mNGS because they may not be concordant with culture.

Aberrant cytokine expression in COVID-19 patients: Associations between cytokines and disease severity.

Cytokines play pleiotropic, antagonistic, and collaborative in viral disease. The high morbidity and mortality of coronavirus disease 2019 (COVID-19) make it a significant threat to global public health. Elucidating its pathogenesis is essential to finding effective therapy. A retrospective study was conducted on 71 patients hospitalized with COVID-19. Data on cytokines, T lymphocytes, and other clinical and laboratory characteristics were collected from patients with variable disease severity. The effects of cytokines on the overall survival (OS) and event-free survival (EFS) of patients were analyzed. The critically severe and severe patients had higher infection indexes and significant multiple organ function abnormalities than the mild patients (P < 0.05). IL-6 and IL-10 were significantly higher in the critically severe patients than in the severe and mild patients (P < 0.05). IL-6 and IL-10 were closely associated with white blood cells, neutrophils, T lymphocyte subsets, D-D dimer, blood urea nitrogen, complement C1q, procalcitonin C-reactive protein. Moreover, the IL-6 and IL-10 levels were closely correlated to dyspnea and dizziness (P < 0.05). The patients with higher IL-10 levels had shorter OS than the group with lower levels (P < 0.05). The older patients with higher levels of single IL-6 or IL-10 tended to have shorter EFS (P < 0.05), while the patients who had more elevated IL-6 and IL-10 had shorter OS (P < 0.05). The Cox proportional hazard model revealed that IL-6 was the independent factor affecting EFS. IL-6 and IL-10 play crucial roles in COVID-19 prognosis.

A nomogram incorporating functional and tubular damage biomarkers to predict the risk of acute kidney injury for septic patients.

BACKGROUND: Combining tubular damage and functional biomarkers may improve prediction precision of acute kidney injury (AKI). Serum cystatin C (sCysC) represents functional damage of kidney, while urinary N-acetyl-ß-D-glucosaminidase (uNAG) is considered as a tubular damage biomarker. So far, there is no nomogram containing this combination to predict AKI in septic cohort. We aimed to compare the performance of AKI prediction models with or without incorporating these two biomarkers and develop an effective nomogram for septic patients in intensive care unit (ICU). METHODS: This was a prospective study conducted in the mixed medical-surgical ICU of a tertiary care hospital. Adults with sepsis were enrolled. The patients were divided into development and validation cohorts in chronological order of ICU admission. A logistic regression model for AKI prediction was first constructed in the development cohort. The contribution of the biomarkers (sCysC, uNAG) to this model for AKI prediction was assessed with the area under the receiver operator characteristic curve (AUC), continuous net reclassification index (cNRI), and incremental discrimination improvement (IDI). Then nomogram was established based on the model with the best performance. This nomogram was validated in the validation cohort in terms of discrimination and calibration. The decision curve analysis (DCA) was performed to evaluate the nomogram's clinical utility. RESULTS: Of 358 enrolled patients, 232 were in the development cohort (69 AKI), while 126 in the validation cohort (52 AKI). The first clinical model included the APACHE II score, serum creatinine, and vasopressor used at ICU admission. Adding sCysC and uNAG to this model improved the AUC to 0.831. Furthermore, incorporating them significantly improved risk reclassification over the predictive model alone, with cNRI (0.575) and IDI (0.085). A nomogram was then established based on the new model including sCysC and uNAG. Application of this nomogram in the validation cohort yielded fair discrimination with an AUC of 0.784 and good calibration. The DCA revealed good clinical utility of this nomogram. CONCLUSIONS: A nomogram that incorporates functional marker (sCysC) and tubular damage marker (uNAG), together with routine clinical factors may be a useful prognostic tool for individualized prediction of AKI in septic patients.

Co-existence of Citrobacter freundii exacerbated Pseudomonas aeruginosa infection in vivo.

The presence of bacterial species other than the pathogen at infection site can affect the progression of a bacterial infection. Based on the fact that Citrobacter freundii can coexist during Pseudomonas aeruginosa infection, this study aims to investigate the impact of the co-existing C. freundii on the pathogenesis of P. aeruginosa infection. A murine peritonitis model was used to compare the mortality rates and histopathology of P. aeruginosaPAO1 infection in the presence and absence of a C. freundii clinical isolate C9. We also investigated the intercellular interaction between PAO1 and C9 by examining pyocyanin production and comparing gene expression levels. The results demonstrate that co-infection with C9 significantly increased the mortality rate and tissue damages in PAO1 infected mice. At an inoculum of 106 CFU, no mortality was observed in the C9 infected group at three days post-infection, whereas the mortality rate in the PAO1-C9 co-infection group was 64%, compared with 24% in the PAO1 infected group. Pyocyanin production in P. aeruginosa PAO1 increased 8 folds approximately in the presence of C. freundii C9, and operons associated with phenazine synthesis, phzA1 and phzA2, were also upregulated. Disruption of the phzA1 and phzA2 eliminated the exacerbated pathogenicity in the co-infection group, indicating that the elevated pyocyanin production was the main contributing factor. The results suggest that co-existing C. freundii during P. aeruginosa infection can exacerbate the pathogenicity, which may have significant implications in patients infected with these bacteria.

Investigation of 4f-Related Electronic Transitions of Rare-Earth Doped ZnO Luminescent Materials: Insights from First-Principles Calculations.

Rare-earth (RE) doped zinc oxides (ZnO) are regarded as promising materials for application in versatile color-tuned devices. However, the understanding of underlying luminescence mechanism and the rule of 4 f-related electronic transition is still limited, which is full of significance for the exploration of advanced RE-based ZnO phosphors. Thus, a series of ZnO : RE (RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb) phosphors have been investigated by means of first-principles calculations. Meanwhile, we also consider the effect of native defects (VO , VZn ) on the luminescence of ZnO : RE phosphors. Accordingly, four types of electric-dipole allowed transition processes are figured out in ZnO : RE family. Additionally, we manifest that the VO can further improve the luminescent performance of ZnO : RE phosphors, and give insightful guidance to design desired RE-based ZnO materials with excellent luminescence.

Biosynthesis of the pyrrolidine protein synthesis inhibitor anisomycin involves novel gene ensemble and cryptic biosynthetic steps.

The protein synthesis inhibitor anisomycin features a unique benzylpyrrolidine system and exhibits diverse biological and pharmacologic activities. Its biosynthetic origin has remained obscure for more than 60 y, however. Here we report the identification of the biosynthetic gene cluster (BGC) of anisomycin in Streptomyces hygrospinosus var. beijingensis by a bioactivity-guided high-throughput screening method. Using a combination of bioinformatic analysis, reverse genetics, chemical analysis, and in vitro biochemical assays, we have identified a core four-gene ensemble responsible for the synthesis of the pyrrolidine system in anisomycin: aniQ, encoding a aminotransferase that catalyzes an initial deamination and a later reamination steps; aniP, encoding a transketolase implicated to bring together an glycolysis intermediate with 4-hydroxyphenylpyruvic acid to form the anisomycin molecular backbone; aniO, encoding a glycosyltransferase that catalyzes a cryptic glycosylation crucial for downstream enzyme processing; and aniN, encoding a bifunctional dehydrogenase that mediates multistep pyrrolidine formation. The results reveal a BGC for pyrrolidine alkaloid biosynthesis that is distinct from known bacterial alkaloid pathways, and provide the signature sequences that will facilitate the discovery of BGCs encoding novel pyrrolidine alkaloids in bacterial genomes. The biosynthetic insights from this study further set the foundation for biosynthetic engineering of pyrrolidine antibiotics.

S-type Anion Channels SLAC1 and SLAH3 Function as Essential Negative Regulators of Inward K+ Channels and Stomatal Opening in Arabidopsis.

Drought stress induces stomatal closure and inhibits stomatal opening simultaneously. However, the underlying molecular mechanism is still largely unknown. Here we show that S-type anion channels SLAC1 and SLAH3 mainly inhibit inward K+ (K+in) channel KAT1 by protein-protein interaction, and consequently prevent stomatal opening in Arabidopsis. Voltage-clamp results demonstrated that SLAC1 inhibited KAT1 dramatically, but did not inhibit KAT2. SLAH3 inhibited KAT1 to a weaker degree relative to SLAC1. Both the N terminus and the C terminuses of SLAC1 inhibited KAT1, but the inhibition by the N terminus was stronger. The C terminus was essential for the inhibition of KAT1 by SLAC1. Furthermore, drought stress strongly up-regulated the expression of SLAC1 and SLAH3 in Arabidopsis guard cells, and the over-expression of wild type and truncated SLAC1 dramatically impaired K+in currents of guard cells and light-induced stomatal opening. Additionally, the inhibition of KAT1 by SLAC1 and KC1 only partially overlapped, suggesting that SLAC1 and KC1 inhibited K+in channels using different molecular mechanisms. Taken together, we discovered a novel regulatory mechanism for stomatal movement, in which singling pathways for stomatal closure and opening are directly coupled together by protein-protein interaction between SLAC1/SLAH3 and KAT1 in Arabidopsis.

Strategy to Induce Multiferroic Property in (RTiO3 )n /(RVO3 )n Superlattices: A First-Principles Study.

By first-principles calculations, lanthanide contraction is applied on a 1/1 (with symmetric center) and a 2/2 (with non-centrosymmetric polar structure) RTiO3 /RVO3 superlattices to realize quasi-continuous structural distortion modulation. The strong correlations of microscopic structural distortion, magnetic coupling and charge disproportionation accompanying metal-insulator transition (MIT) are clarified. It is found that the effect of lanthanide contraction on the 1/1 and 2/2 RTiO3 /RVO3 superlattices can induce ferromagnetic to antiferromagnetic transition within ab VO2 plane and the MIT occurs within these superlattices. And the MIT phenomenon is attributed to the charge disproportionation on V sites caused by the magnetic coupling transition. More structural distortion in the 2/2 RTiO3 /RVO3 superlattice is necessary than that of the 1/1 RTiO3 /RVO3 superlattice to induce the similar magnetic and MIT transition originating from the smaller interface/volume ratio. Based on these results, combining lanthanide contraction and epitaxial strain effects, multiferroic property is realized on 2/2 YTiO3 /YVO3 superlattice. Among all the structural parameters, aspect ratio c/a and Ti-O-V bond angles along the [001] direction are found to play the vital roles in the relevant transition process. Therefore, our calculations provide a microscopic guidance to design and synthesize new multiferroic materials.

Comparison of non-volatile and volatile flavor compounds in six Pleurotus mushrooms.

BACKGROUND: Non-volatile and volatile flavor compounds of six Pleurotus mushrooms including Pleurotus citrinopileatus, P. cornucopiae, P. djamor, P. floridanus, P. ostreatus and P. sapidus were studied. RESULTS: The content of total free amino acids ranged from 21.80 to 40.60 g kg-1 and the content of monosodium glutamate (MSG)-like amino acids ranged from 3.10 to 8.64 g kg-1 . The content of total 5'-nucleotides ranged from 4.16 to 8.80 g kg-1 while the content of flavor 5'-nucleotides ranged from 2.00 to 4.51 g kg-1 . Sixty-three volatile compounds were identified in six Pleurotus mushrooms, including 17 aldehydes, 10 ketones, 14 alcohols, 2 ethers, 5 acids, 5 hydrocarbons, 10 heterocyclic and aromatic compounds. 1-Octen-3-one and 1-octen-3-ol were the key odor compounds in P. citrinopileatus, P. djamor, P. ostreatus, P. floridanus and P. sapidus, while 1-octen-3-one, 1-octen-3-ol and 2-octenal were the key odor compounds in P. cornucopiae. CONCLUSION: Pleurotus citrinopileatus had highest content of total free amino acids (40.60 g kg-1 ), total 5'-nucleotides (8.80 g kg-1 ) and flavor 5'-nucleotides (4.51 g kg-1 ) than other Pleurotus mushrooms. Moreover, eight-carbon compounds were the most abundant compounds in six Pleurotus mushrooms. Our study should be helpful in promoting the cultivation and consumption of these Pleurotus mushrooms. © 2018 Society of Chemical Industry.

The S-Type Anion Channel ZmSLAC1 Plays Essential Roles in Stomatal Closure by Mediating Nitrate Efflux in Maize.

Diverse stimuli induce stomatal closure by triggering the efflux of osmotic anions, which is mainly mediated by the main anion channel SLAC1 in plants, and the anion permeability and selectivity of SLAC1 channels from several plant species have been reported to be variable. However, the genetic identity as well as the anion permeability and selectivity of the main S-type anion channel ZmSLAC1 in maize are still unknown. In this study, we identified GRMZM2G106921 as the gene encoding ZmSLAC1 in maize, and the maize mutants zmslac1-1 and zmslac1-2 harboring a mutator (Mu) transposon in ZmSLAC1 exhibited strong insensitive phenotypes of stomatal closure in response to diverse stimuli. We further found that ZmSLAC1 functions as a nitrate-selective anion channel without obvious permeability to chloride, sulfate and malate, clearly different from SLAC1 channels of Arabidopsis thaliana, Brassica rapa ssp. chinensis and Solanum lycopersicum L. Further experimental data show that the expression of ZmSLAC1 successfully rescued the stomatal movement phenotypes of the Arabidopsis double mutant atslac1-3atslah3-2 by mainly restoring nitrate-carried anion channel currents of guard cells. Together, these findings demonstrate that ZmSLAC1 is involved in stomatal closure mainly by mediating the efflux of nitrate in maize.

Density Functional Characterization of the 4f-Relevant Electronic Transitions of Lanthanide-Doped Lu2 O3 Luminescence Materials.

Herein, we present a theoretical study on trivalent-lanthanide-substituted luminescence materials (Lu2 O3 : Ln; with Ln=Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) by using first-principles calculations based on the Coulomb-corrected density functional theory (DFT+U). Large-scale calculations of electronic the structure are carried out with the goal of pinpointing the 4f-relevant electronic transition rule and optical features of Lu2 O3 : Ln systems. A characteristic double "zigzag" pattern for Ln3+ and Ln2+ energy levels is observed. Accordingly, four types of electric-dipole allowed transition modes are predicted in the lanthanide-doped Lu2 O3 family, with Lu2 O3 : Eu and Lu2 O3 : Yb showing superior absorption features. Finally, this 4f-controlled electronic transition image provides useful guidance for designing new luminescence materials with desired properties.

Insight into the Mechanism of the Ionic Conductivity for Ln-Doped Ceria (Ln = La, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, and Tm) through First-Principles Calculation.

Oxygen vacancy (VO) formation energy and its migration barrier are two determining factors for the effectiveness of solid electrolytes (SEs) in solid oxide fuel cells (SOFCs). In this work, a series of aliovalent rare-earth-doped ceria (Ln xCe1- xO2-δ, Ln = lanthanides) compounds serving as SEs are comprehensively and comparatively calculated, through which the determinant factors for oxygen vacancy formations and their migration activity are figured out at an atomistic level via the first-principles calculations with the consideration of electronic correlations. Initially, it is found that the oxygen vacancy formation energies of the Ln-doped ceria are largely reduced in contrast to the undoped ceria (CeO2-δ), which obviously agree with the literature. Then, the migration activity of an oxygen vacancy in Ln xCe1- xO2-δ is closely correlated to the association energies of Ln-VO, in which the different 4f5d bonding properties for different Ln ions should be taken into account. Additionally, the analysis of charge difference gradient (CDG) is revealed to be the intrinsic driving force for oxygen vacancy migration. We hope that our investigation provides a microscopic insight into the oxygen vacancy defect physics, and it is also a benefit for the design of more advanced relevant functional materials.

Theoretical Study on the Negative Thermal Expansion Perovskite LaCu3Fe4O12: Pressure-Triggered Transition of Magnetism, Charge, and Spin State.

The A-site ordered negative thermal expansion material LaCu3Fe4O12 (LaCFO) was comprehensively investigated by using first-principles calculations. A pressure-triggered crystal structural phase transition from space group Im3̅ (No. 204) to Pn3̅ (No. 201) and magnetic transformation from a G-type antiferromagnetic (G_AFM) ground state to ferrimagnetic (FerriM) coupling were observed in LaCFO via gradual compression of the equilibrium volume. Correspondingly, the Fe-Cu intersite charge transfer from Fe to Cu 3dxy orbital, expressed as 4Fe3+ + 3Cu3+ → 4Fe3.75+ + 3Cu2+, was simulated along with the magnetic phase transformation from the G_AFM configuration to the FerriM state. Intriguingly, the Fe charge disproportionation, formulated as 8Fe3.75+ → 5Fe3+ + 3Fe5+, appeared and was attributed to the strong hybridization between Fe 3d and O 2p orbitals in the FerriM state when the volumes were substantially compressed up to less than or equal to 80%V. Meanwhile, the external hydrostatic pressure also leads to a spin flip from a high-spin Fe3+ antiferromagnetically arranged LaCu3+3Fe3+4O12 Mott insulator at low pressure and goes through a FerriM LaCu2+3Fe3.75+4O12 half-metal to a low-spin FerriM coupled LaCu2+3Fe3+5/2Fe5+3/2O12 metal at high pressure. Therefore, the crossover from high spin to low spin is responsible for the charge disproportionation in LaCFO. Essentially, the charge transfer and spin flip originate from the discontinuous changes of metal-oxygen bond lengths and angles in the compressed atomic structure. Finally, the negative thermal expansion behavior and mechanism of LaCFO were theoretically examined and clearly revealed.

Regulation of DNA phosphorothioate modifications by the transcriptional regulator DptB in Salmonella.

DNA phosphorothioate (PT) modifications, with one non-bridging phosphate oxygen replaced with sulfur, are widely but sporadically distributed in prokaryotic genomes. Short consensus sequences surround the modified linkage in each strain, although each site is only partially modified. The mechanism that maintains this low-frequency modification status is still unknown. In Salmonella enterica serovar Cerro 87, PT modification is mediated by a four-gene cluster called dptBCDE. Here, we found that deletion of dptB led to a significant increase in intracellular PT modification level. In this deletion, transcription of downstream genes was elevated during rapid cell growth. Restoration of dptB on a plasmid restored wild-type levels of expression of downstream genes and PT modification. In vitro, DptB directly protected two separate sequences within the dpt promoter region from DNase I cleavage. Each protected sequence contained a direct repeat (DR). Mutagenesis assays of the DRs demonstrated that each DR was essential for DptB binding. The observation of two shifted species by gel-shift analysis suggests dimer conformation of DptB protein. These DRs are conserved among the promoter regions of dptB homologs, suggesting that this regulatory mechanism is widespread. These findings demonstrate that PT modification is regulated at least in part at the transcriptional level.