Layered Ferromagnetic Structure Caused by the Proximity Effect and Interlayer Charge Transfer for LaNiO3/LaMnO3 Superlattices.

Magnetic proximity-induced magnetism in paramagnetic LaNiO3 (LNO) has spurred intensive investigations in the past decade. However, no consensus has been reached so far regarding the magnetic order in LNO layers in relevant heterostructures. This paper reports a layered ferromagnetic structure for the (111)-oriented LNO/LaMnO3 (LMO) superlattices. It is found that each period of the superlattice consisted of an insulating LNO-interfacial phase (five unit cells in thickness, ∼1.1 nm), a metallic LNO-inner phase, a poorly conductive LMO-interfacial phase (three unit cells in thickness, ∼0.7 nm), and an insulating LMO-inner phase. All four of these phases are ferromagnetic, showing different magnetizations. The Mn-to-Ni interlayer charge transfer is responsible for the emergence of a layered magnetic structure, which may cause magnetic interaction across the LNO/LMO interface and double exchange within the LMO-interfacial layer. This work indicates that the proximity effect is an effective means of manipulating the magnetic state and associated properties of complex oxides.

Design and Implementation of C-Band Large-Power Planar Butler Matrix in SRS.

In satellite remote sensing (SRS), there is a demand for large-power microwave components. A Butler matrix is essential to a transmitting antenna array in SRS. This article illustrates the electrical and mechanical design, simulation, and test results of a large-power planar beamforming network for SRS at C-band. It is a 4 × 4 Butler matrix based on square coaxial lines. Short-ended stubs are used in the Butler matrix to broaden its bandwidth by 10%, support inner conductors, and enhance heat transfer in vacuum environments. The simulation results are consistent with the measured results. The reflection coefficient is less than -18 dB, and the isolation is more than 23 dB from 3.8 GHz to 4.2 GHz. The insertion losses are less than 0.6 dB, and the phase errors are better than ±6°. The measured peak microwave power of the proposed Butler matrix is 9 kW. Its size is 440 × 400 × 40 mm3. The proposed Butler matrix beamforming network can be applied to SRS systems.

Significantly Enhanced Room-Temperature Ferromagnetism in Multiferroic EuFeO3-δ Thin Films.

Regulating the magnetic properties of multiferroics lays the foundation for their prospective application in spintronic devices. Single-phase multiferroics, such as rare-earth ferrites, are promising candidates; however, they typically exhibit weak magnetism at room temperature (RT). Here, we significantly boosted the RT ferromagnetism of a representative ferrite, EuFeO3, by oxygen defect engineering. Polarized neutron reflectometry and magnetometry measurements reveal that saturation magnetization reaches 0.04 µB/Fe, which is approximately 5 times higher than its bulk phase. Combining the annular bright-field images with theoretical assessment, we unravel the underlying mechanism for magnetic enhancement, in which the decrease in Fe-O-Fe bond angles caused by oxygen vacancies (VO) strengthens magnetic interactions and tilts Fe spins. Furthermore, the internal relationship between magnetism and VO was established by illustrating how the magnetic structure and magnitude change with VO configuration and concentration. Our strategy for regulating magnetic properties can be applied to numerous functional oxide materials.

Association between perceived stress, loneliness and sleep disorders among breast cancer patients: the moderating roles of resilience.

Sleep disorders are prevalent and often neglected among breast cancer patients. This study aimed to identify the association among perceived stress, loneliness, resilience and sleep disorders and to further explore whether resilience could be a moderator in the association between them and sleep disorders. A cross-sectional study was conducted by 492 female breast cancer patients. Patients were asked in response to the questionnaires including the Pittsburgh Sleep Quality Index, Perceived Stress Scale-10, the Three-Item Loneliness Scale and Resilience Scale-14. The association among perceived stress, loneliness, resilience and perceived stress/loneliness × resilience interaction with sleep disorders were examined by hierarchical multiple regression analysis. The interaction was visualized by using simple slope analysis. 36.58% of the female breast cancer patients reported sleep disorders in our study. Perceived stress and loneliness were related to sleep disorders. Resilience could moderate the relationship between them and sleep disorders. When resilience was higher, perceived stress and loneliness had a weaker impact on sleep disorders. Medical staff should systematically evaluate the internal environmental factors related to patients' sleep quality and help patients relieve their emotional distress caused by the disease through positive psychological guidance.

Carbon defects-enriched NBC-C3N5@CoMn with ultrafast modulation of redox couples for efficient degradation of contaminant.

The inefficiency of catalysts in sulfate radical-based advanced oxidation processes (SR-AOPs) is primarily attributed to the sluggish circulation of redox couples. Herein, a carbon defects-enriched NBC-C3N5@CoMn (NCC) was synthesized through a self-assembly approach. The carbon defects within the NCC induce the electron trap effect, thereby facilitating the efficient cycling of redox couples in photo-Fenton-like processes during contaminant degradation. This effect enables the self-regeneration of the NCC catalyst. The reductive redox couples (Co (II) and Mn (II)) are continuously regenerated following the degradation process. Within the NCC, CoMn layered double hydroxides (LDHs) act as primary active sites, promoting the generation of hydroxyl radicals (•OH), sulfate radicals (SO4•-) and singlet oxygen (1O2) through continuous electron gain and loss. Additionally, the internal electric field established within the NCC further accelerates electron transfer. Density Functional Theory (DFT) calculations confirm that the carbon defects-enriched NCC exhibits lower adsorption energies and higher electron transfer efficiencies than carbon defect-deficient NCC. This study introduces a novel photocatalyst with self-regenerating capabilities, presenting an innovative approach to regulate redox couples in SR-AOPs for sustainable degradation.

[An analysis on clinical characteristics and prognosis-related risk factors in patients with drug-induced liver injury].

Objective: To explore the drugs and clinical characteristics causing drug-induced liver injury (DILI) in recent years, as well as identify drug-induced liver failure, and chronic DILI risk factors, in order to better manage them timely. Methods: A retrospective investigation and analysis was conducted on 224 cases diagnosed with DILI and followed up for at least six months between January 2018 and December 2020. Univariate and multivariate logistic regression analyses were used to identify risk factors for drug-induced liver failure and chronic DILI. Results: Traditional Chinese medicine (accounting for 62.5%), herbal medicine (accounting for 84.3% of traditional Chinese medicine), and some Chinese patent medicines were the main causes of DILI found in this study. Severe and chronic DILI was associated with cholestatic type. Preexisting gallbladder disease, initial total bilirubin, initial prothrombin time, and initial antinuclear antibody titer were independent risk factors for DILI. Prolonged time interval between alkaline phosphatase (ALP) and alanine aminotransferase (ALT) falling from the peak to half of the peak (T(0.5ALP) and T(0.5ALT)) was an independent risk factor for chronic DILI [area under the receiver operating characteristic curve (AUC) = 0.787, 95%CI: 0.697~0.878, P < 0.001], with cutoff values of 12.5d and 9.5d, respectively. Conclusion: Traditional Chinese medicine is the main contributing cause of DILI. The occurrence risk of severe DILI is related to preexisting gallbladder disease, initial total bilirubin, prothrombin time, and antinuclear antibodies. T(0.5ALP) and T(0.5ALT) can be used as indicators to predict chronic DILI.

Perceived Hospital Stress, Severe Acute Respiratory Syndrome Coronavirus 2 Activity, and Care Process Temporal Variance During the COVID-19 Pandemic.

OBJECTIVES: The COVID-19 pandemic threatened standard hospital operations. We sought to understand how this stress was perceived and manifested within individual hospitals and in relation to local viral activity. DESIGN: Prospective weekly hospital stress survey, November 2020-June 2022. SETTING: Society of Critical Care Medicine's Discovery Severe Acute Respiratory Infection-Preparedness multicenter cohort study. SUBJECTS: Thirteen hospitals across seven U.S. health systems. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We analyzed 839 hospital-weeks of data over 85 pandemic weeks and five viral surges. Perceived overall hospital, ICU, and emergency department (ED) stress due to severe acute respiratory infection patients during the pandemic were reported by a mean of 43% ( sd , 36%), 32% (30%), and 14% (22%) of hospitals per week, respectively, and perceived care deviations in a mean of 36% (33%). Overall hospital stress was highly correlated with ICU stress (ρ = 0.82; p < 0.0001) but only moderately correlated with ED stress (ρ = 0.52; p < 0.0001). A county increase in 10 severe acute respiratory syndrome coronavirus 2 cases per 100,000 residents was associated with an increase in the odds of overall hospital, ICU, and ED stress by 9% (95% CI, 5-12%), 7% (3-10%), and 4% (2-6%), respectively. During the Delta variant surge, overall hospital stress persisted for a median of 11.5 weeks (interquartile range, 9-14 wk) after local case peak. ICU stress had a similar pattern of resolution (median 11 wk [6-14 wk] after local case peak; p = 0.59) while the resolution of ED stress (median 6 wk [5-6 wk] after local case peak; p = 0.003) was earlier. There was a similar but attenuated pattern during the Omicron BA.1 subvariant surge. CONCLUSIONS: During the COVID-19 pandemic, perceived care deviations were common and potentially avoidable patient harm was rare. Perceived hospital stress persisted for weeks after surges peaked.

An Axially Chiral Styrene-Phosphine Ligand for Pd-Catalyzed Asymmetric N-Alkylation of Indoles.

An efficient palladium-catalyzed enantioselective direct N-alkylation of indoles using a novel type of axially chiral styrene-phosphine ligand SJTU-PHOS-1 was developed. This reaction demonstrated good functional group compatibility and a wide range scope of substrates in mild conditions. Moreover, the DFT calculations expounded the coordination mode of the metal catalyst and the axially chiral styrene-phosphine ligand in the enantioselectivity control.

Inhibition of the BNIP3/NIX-dependent mitophagy aggravates copper-induced mitochondrial dysfunction in duck renal tubular epithelial cells.

The accumulation of copper (Cu) in the organisms could lead to kidney damage by causing mitochondrial dysfunction. Given that mitochondria are one of the targets of Cu poisoning, this study aimed to investigate the role of mitophagy in Cu-induced mitochondrial dysfunction in renal tubular epithelial cells to understand the mechanism of Cu nephrotoxicity. Hence, the cells were treated with different concentrations of Cu sulfate (CuSO4 ) (0, 100, and 200 µM), and mitophagy inhibitor (Cyclosporine A, 0.5 µM) and/or 200 µM CuSO4 in the combination for 12 h. Results showed that Cu caused mitochondrial swelling, vacuoles, and cristae fracture; increased the number of mitochondrial and lysosome fluorescent aggregation points; upregulated the mRNA levels of mitophagy-associated genes (LC3A, LC3B, P62, BNIP3, NIX, OPTN, NDP52, Cyp D LAMP1, and LAMP2) and protein levels of LC3II/LC3I, BNIP3, and NIX, downregulated the mRNA and protein levels of P62; reduced the mitochondrial membrane potential (MMP), ATP content, mitochondrial respiratory control rate (RCR), mitochondrial respiratory control rate (OPR), and the mRNA and protein levels of PGC-1α, TOMM20, and Mfn2, but increased the mRNA and protein levels of Drp1. Besides, cotreatment with Cu and CsA dramatically decreased the level of mitophagy, but increased mitochondrial division, further reduced MMP, ATP content, RCR, and OPR, mitochondrial fusion and thereby reduced mitochondrial biogenesis. Taken together, these data indicated that Cu exposure induced BNIP3/NIX-dependent mitophagy in duck renal tubular epithelial cells, and inhibition of mitophagy aggravated Cu-induced mitochondrial dysfunction.

GPX4 utilization by selenium is required to alleviate cadmium-induced ferroptosis and pyroptosis in sheep kidney.

Cadmium (Cd), a persistent and harmful heavy metal in the environment, can accumulate in the kidneys and cause nephrotoxicity. Selenium (Se) is a beneficial natural element that alleviates the toxicity of Cd. To ascertain the relationship between the protective mechanism of Se against Cd nephrotoxicity and ferroptosis and pyroptosis, we randomly divided 48 sheep into four groups and treated them with Cd chloride and/or sodium selenite for 50 days. The data confirmed that Cd apparently resulted in impaired kidney histology and function, depletion of GSH and nicotinamide adenine dinucleotide phosphate contents and CAT and SOD activities, elevation of MDA level, as well as the reduction in selenoprotein mRNA (GPX1, GPX4, TXNRD1, SELP) levels and GPX4 protein level and immunofluorescence intensity. Meanwhile, Cd induced ferroptosis by causing iron overload, up-regulating PTGS2, NCOA4, TFR1, and LC3B mRNA levels and PTGS2 and LC3B-II/LC3B-I protein levels, reducing SLC7A11 and FTH1 mRNA and protein levels, and enhancing the immunofluorescence co-localization of FTH1/LC3B. Moreover, it was also found that Cd triggered pyroptosis, which was evidenced by the increase of NLRP3 immunohistochemical positive signal, GSDMD-N immunofluorescence intensity, IL-1ß and IL-18 release and the levels of pyroptosis-related mRNA (NLRP3, ASC, Caspase-1, GSDMD, IL-1ß and IL-18) and proteins (NLRP3, Caspase-1p20, GSDMD-N, IL-1ß and IL-18). Notably, Se increased the expression level of GPX4 and the transcription factors TFAP2c and SP1, and ameliorated Cd-induced changes in aforementioned factors. In conclusion, GPX4 utilization by Se might be required to alleviate Cd-induced ferroptosis and pyroptosis in sheep kidney.

Review on the degradation of chlorinated hydrocarbons by persulfate activated with zero-valent iron-based materials.

Chlorinated hydrocarbons (CHCs) are often used in industrial processes, and they have been found in groundwater with increasing frequency in recent years. Several typical CHCs, including trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride (CT), etc., have strong cytotoxicity and carcinogenicity, posing a serious threat to human health and ecological environment. Advanced persulfate (PS) oxidation technology based on nano zero-valent iron (nZVI) has become a research hotspot for CHCs degradation in recent years. However, nZVI is easily oxidized to form the surface passivation layer and prone to aggregation in practical application, which significantly reduces the activation efficiency of PS. In order to solve this problem, various nZVI modification solutions have been proposed. This review systematically summarizes four commonly used modification methods of nZVI, and the theoretical mechanisms of PS activated by primitive and modified nZVI. Besides, the influencing factors in the engineering application process are discussed. In addition, the controversial views on which of the two (SO4·- and ·OH) is dominant in the nZVI/PS system are summarized. Generally, SO4·- predominates in acidic conditions while ·OH prefers neutral and alkaline environments. Finally, challenges and prospects for practical application of CHCs removal by nZVI-based materials activating PS are also analyzed.

Quantifying the Dzyaloshinskii-Moriya Interaction Induced by the Bulk Magnetic Asymmetry.

A broken interfacial inversion symmetry in ultrathin ferromagnet/heavy metal (FM/HM) bilayers is generally believed to be a prerequisite for accommodating the Dzyaloshinskii-Moriya interaction (DMI) and for stabilizing chiral spin textures. In these bilayers, the strength of the DMI decays as the thickness of the FM layer increases and vanishes around a few nanometers. In the present study, through synthesizing relatively thick films of compositions CoPt or FePt, CoCu or FeCu, FeGd and FeNi, contributions to DMI from the composition gradient-induced bulk magnetic asymmetry (BMA) and spin-orbit coupling (SOC) are systematically examined. Using Brillouin light scattering spectroscopy, both the sign and amplitude of DMI in films with controllable direction and strength of BMA, in the presence and absence of SOC, are experimentally studied. In particular, we show that a sizable amplitude of DMI (±0.15 mJ/m^{2}) can be realized in CoPt or FePt films with BMA and strong SOC, whereas negligible DMI strengths are observed in other thick films with BMA but without significant SOC. The pivotal roles of BMA and SOC are further examined based on the three-site Fert-Lévy model and first-principles calculations. It is expected that our findings may help to further understand the origin of chiral magnetism and to design novel noncollinear spin textures.

Room-Temperature Ferromagnetism at an Oxide-Nitride Interface.

Heterointerfaces have led to the discovery of novel electronic and magnetic states because of their strongly entangled electronic degrees of freedom. Single-phase chromium compounds always exhibit antiferromagnetism following the prediction of the Goodenough-Kanamori rules. So far, exchange coupling between chromium ions via heteroanions has not been explored and the associated quantum states are unknown. Here, we report the successful epitaxial synthesis and characterization of chromium oxide (Cr_{2}O_{3})-chromium nitride (CrN) superlattices. Room-temperature ferromagnetic spin ordering is achieved at the interfaces between these two antiferromagnets, and the magnitude of the effect decays with increasing layer thickness. First-principles calculations indicate that robust ferromagnetic spin interaction between Cr^{3+} ions via anion-hybridization across the interface yields the lowest total energy. This work opens the door to fundamental understanding of the unexpected and exceptional properties of oxide-nitride interfaces and provides access to hidden phases at low-dimensional quantum heterostructures.

Activation of endoplasmic reticulum-mitochondria coupling drives copper-induced autophagy in duck renal tubular epithelial cells.

Copper (Cu) as a transition metal can be toxic to public and ecosystem health at high level, but the specific mechanism of Cu-evoked nephrotoxicity remains elusive. Here, we first revealed the crosstalk between mitofusin2 (Mfn2)-dependent mitochondria-associated endoplasmic reticulum membrane (MAM) dynamics and autophagy in duck renal tubular epithelial cells under Cu exposure. Primary duck renal tubular epithelial cells were treated with 100 and 200 µM Cu sulfate for 12 h and exposed to lentivirus to deliver mitofusin2 (Mfn2). We found that excessive Cu disrupted MAM integrity, decreased the mitochondrial calcium level, co-localization of IP3R and VDAC1, the mRNA levels of PACS2, Mfn2, IP3R and MCU, and Mfn2 and VDAC1 protein levels, causing MAM dysfunction. Furthermore, Mfn2 overexpression ameliorated Cu-induced MAM dysfunction, and increased Cu-evoked autophagy in duck renal tubular epithelial cells accompanied with the elevation of autophagosomes number, ROS level, LC3 puncta, Atg5 and LC3B mRNA levels, and Beclin1, Atg14, LC3BII/LC3BI protein levels. Accordingly, our data proved that excessive Cu could trigger MAM dysfunction and autophagy in duck renal tubular epithelial cells, and Cu-induced autophagy could be activated through Mfn2-dependent MAM, providing evidence on the toxicological exploration mechanisms of Cu.

A Ratiometric Photoacoustic Probe with a Reversible Response to Hydrogen Sulfide and Hydroxyl Radicals for Dynamic Imaging of Liver Inflammation.

Reversible imaging probes that allow for the dynamic visualization of the redox cycle between hydroxyl radical (⋅OH) and hydrogen sulfide (H2 S) are vital to probe the redox imbalance-involved pathological process in vivo. Herein, we report a reversible ratiometric photoacoustic (PA) imaging nanoprobe (1-PAIN) for the real-time imaging of ⋅OH/H2 S redox cycle in vivo. 1-PAIN displays a low PA ratio between 690 and 825 nm (PA690 /PA825 ), which significantly increases by ≈5-fold upon oxidation by ⋅OH, and is switched back to the initially low PA690 /PA825 value upon reduction by H2 S. 1-PAIN could dynamically report on the hepatic ⋅OH production in mice during the lipopolysaccharide (LPS)-induced liver inflammation process, and visualize hepatic H2 S generation during the N-acetyl cysteine (NAC)-induced anti-inflammation process. 1-PAIN can act as a useful tool to probe the redox state in living biology, beneficial for the study of redox imbalance-related diseases.

Tailoring a Near-Infrared Macrocyclization Scaffold Allows the Control of In Situ Self-Assembly for Photoacoustic/PET Bimodal Imaging.

Enzyme-triggered macrocyclization and in situ self-assembly of small molecules into nanoparticles has shown promise to design activatable probes for molecular imaging. However, controlling macrocyclization and self-assembly to concurrently augment positron emission tomography (PET) and photoacoustic (PA) signals for bimodality imaging is challenging. Herein, we report the engineering of a triazole-IR780 fluorophore as a versatile macrocyclization scaffold for controlling in situ self-assembly and design a caspase-3-activatable PA/PET bimodal probe ([18 F]-IR780-1) for in vivo imaging of tumor apoptosis. By leveraging the high-sensitivity whole-body imaging signals offered by PET with the high-resolution imaging signals offered by PA, [18 F]-IR780-1 can provide a promising tool for the early evaluation of antitumor efficacy, helpful for optimizing the therapeutic protocol for patients. This scaffold may be adopted to design other activatable bimodal probes for in vivo imaging.

Prognostic significance of occult lymph node metastases in breast cancer: a meta-analysis.

BACKGROUND: Occult metastases in axillary lymph nodes have been reported to be associated with poor prognosis in patients with breast cancer. However, studies on the prognostic value of occult metastases have shown controversial results. This meta-analysis aimed to evaluate the prognostic significance of occult lymph node metastases in breast cancer. METHODS: Studies published until May, 2020, which retrospectively examined negative lymph nodes by stepsectioning and/or immunohistochemistry, were retrieved from MEDLINE, EMBASE, CNKI, and Cochrane Library databases. The pooled Relative Risk (RR) with 95% confidence interval (95% CI) for overall survival (OS) and disease-free survival (DFS) were calculated to examine the associations between occult metastases and prognosis. RESULTS: Patients with occult metastases in axillary lymph nodes had poorer five-year DFS (RR = 0.930; 95% CI = 0.907-0.954) and OS (RR = 0.972; 95% CI = 0.954-0.990). Furthermore, the DFS (RR = 0.887; 95% CI = 0.810-0.972) and OS (RR = 0.896; 95% CI = 0.856-0.939) of patients with occult metastases were significantly lower after a ten-year follow-up. CONCLUSIONS: Occult metastases in the axillary lymph nodes are associated with poorer DFS andOS of patients with breast cancer. Occult metastases might serve as a predictive factor of survival outcomes in patients with breast cancer.

Molybdenum and cadmium co-induce mitophagy and mitochondrial dysfunction via ROS-mediated PINK1/Parkin pathway in Hepa1-6 cells.

Excessive molybdenum (Mo) and Cadmium (Cd) can adversely affect health status. However, the correlation between mitophagy and mitochondrial dysfunction caused by Mo and Cd and the underlying mechanisms are still unknown. The aim of this study was to investigate the relationship between mitophagy and mitochondrial dysfunction via the ROS-mediated PINK1/Parkin pathway caused by Mo and Cd. Here, Hepa1-6 cells were incubated with (NH4)6Mo7O24.4 H2O (600.0 µM Mo), CdCl2 (10.0 µM Cd), and the combination of reactive oxygen species (ROS) scavenger (N-acetyl-L-cysteine, NAC, 100.0 µM), or mitophagy inhibitor (Cyclosporin A, CsA, 1.0 µM) for 24 h. Results revealed that Mo or/and Cd elevated the level of intracellular ROS and malondialdehyde (MDA) content, reduced superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities. Additionally, Mo or/and Cd could observably increase the percentage of cells with low membrane potential and decrease the content of ATP, elevate the number of autophagosomes and LC3 puncta, upregulate the mRNA and protein levels of LC3II/LC3I, Parkin, Pink1, VDAC1, downregulate mRNA and protein levels of P62. Moreover, treatments with NAC could significantly alleviate the changes of the above factors co-induced by Mo and Cd, and CsA intensify the changes of the above factors. In summary, our results reveal that Mo and Cd co-exposure can cause oxidative stress and mitophagy via the ROS-mediated PINK1/Parkin pathway in Hepa1-6 cells, and inhibition of mitophagy aggravates Mo and Cd co-induced mitochondrial dysfunction.

Synthesis of a perovskite-type catalyst from Cr electroplating sludge for effective catalytic oxidization of VOC.

Chromium-containing electroplating sludge usually lacked proper disposal and recycling. High-temperature melting was a technology aiming to form glass-phase slag for the stabilizations of heavy metals. This work investigated the possibility of forming perovskite-like phase by chromium-containing sludge using high-temperature melting. The formed material was applied in catalytic oxidization of volatile organic compound. As a result, Ca2+-doped LaCrO3 was formed according to XRD and HRTEM. When Ca2+ doping reached 33%, i.e., La0.67Ca0.33CrO3, surface oxygen species of the obtained catalyst was increased to 65.7%, which was detected by XPS, resulting in a toluene removal of 50% at 302 °C. Besides, the activity was stable for over 50 h. In addition, the doping amount was as high as 40 mol% of Cr in the catalyst. Based on these results, a high-value-added catalyst was produced by the hazardous waste, which was in favor of hazardous-waste recycling as well as high-temperature-melting development.

Formation and Oxidation Reactivity of MnO2+(HCO3-)n in the MnII(HCO3-)-H2O2 System.

The MnII(HCO3-)-H2O2 (MnII-BAP) system shows high reactivity toward oxidation of electron-rich organic substrates; however, the predominant oxidizing species and its formation pathways involved in the MnII-BAP system are still under debate. In this study, we used the MnII-BAP system to oxidize As(III) in that As(III), Mn2+, and HCO3- are common components in As(III)-contaminated groundwater. Kinetic results show that MnII(HCO3-)n [including MnII(HCO3)+ and MnII(HCO3)2] is a key factor in the MnII-BAP system to oxidize As(III). Quenching experiments rule out contributions of OH• and 1O2 to As(III) oxidation and reveal that O2•- and the oxidizing species generated from O2•- play predominant roles in the oxidation of As(III). We further reveal that the MnO2+(HCO3-)n intermediate generated in the reaction between MnII(HCO3-)n and O2•-, instead of O2•-, is the predominant oxidizing species. Although CO3•- also contributes to As(III) oxidation, the high reaction rate constant between CO3•- and O2•- indicates that CO3•- is not the predominant oxidizing species in the As(III)-MnII-BAP system. In addition, the presence of Mn(III) further indicates the important Mn(II)-Mn(III) cycling in the MnII-BAP system. We therefore suggest two important roles of MnII(HCO3-)n in the MnII-BAP system: (i) MnII(HCO3-)n reacts with H2O2 to form the MnIII(HCO3)3 intermediate, followed by a subsequent reaction between MnIII(HCO3)3 and H2O2 to produce O2•-; (ii) MnII(HCO3-)n can also stabilize O2•- with the formation of MnO2+(HCO3-)n. MnO2+(HCO3-)n is an electrophilic reagent and plays the predominant role in the oxidation of As(III) to As(V).