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Targeted delivery and labeling of single living cells in heterogeneous cell populations are of great importance to understand the molecular biology and physiological functions of individual cells. However, it remains challenging to perfuse fluorescence markers into single living cells with high spatial and temporal resolution without interfering neighboring cells. Here, we report a single cell perfusion and fluorescence labeling strategy based on nanoscale glass nanopipettes. With the nanoscale tip hole of 100 nm, the use of nanopipettes allows special perfusion and high-resolution fluorescence labeling of different subcellular regions in single cells of interest. The dynamic of various fluorescent probes has been studied to exemplify the feasibility of nanopipette-dependent targeted delivery. According to experimental results, the cytoplasm labeling of Sulfo-Cyanine5 and fluorescein isothiocyanate is mainly based on the Brownian movement due to the dyes themselves and does not have a targeting ability, while the nucleus labeling of 4',6-diamidino-2-phenylindole (DAPI) is originated from the adsorption between DAPI and DNA in the nucleus. From the finite element simulation, the precise manipulation of intracellular delivery is realized by controlling the electro-osmotic flow inside the nanopipettes, and the different delivery modes between nontargeting dyes and nucleus-targeting dyes were compared, showcasing the valuable ability of nanopipette-based method for the analysis of specially defined subcellular regions and the potential applications for single cell surgery, subcellular manipulation, and gene delivery.

BACKGROUND Frontotemporal lobar degeneration with tauopathy caused by MAPT (microtubule-associated protein tau) mutations is a highly heterogenous disorder. The ability to visualize and longitudinally monitor tau deposits may be beneficial to understand disease pathophysiology and predict clinical trajectories. OBJECTIVE The aim of this study was to investigate the cross-sectional and longitudinal 18 F-APN-1607 positron emission tomography/computed tomography (PET/CT) imaging findings in MAPT mutation carriers. METHODS Seven carriers of MAPT mutations (six within exon 10 and one outside of exon 10) and 15 healthy control subjects were included. All participants underwent 18 F-APN-1607 PET/CT at baseline. Three carriers of exon 10 mutations received follow-up 18 F-APN-1607 PET/CT scans. Standardized uptake value ratio (SUVR) maps were obtained using the cerebellar gray matter as the reference region. SUVR values observed in MAPT mutation carriers were normalized to data from healthy control subjects. A regional SUVR z score ≥ 2 was used as the criterion to define positive 18 F-APN-1607 PET/CT findings. RESULTS Although the seven study patients had heterogenous clinical phenotypes, all showed a significant 18 F-APN-1607 uptake characterized by high-contrast signals. However, the anatomical localization of tau deposits differed in patients with distinct clinical symptoms. Follow-up imaging data, which were available for three patients, demonstrated worsening trends in patterns of tau accumulation over time, which were paralleled by a significant clinical deterioration. CONCLUSIONS Our data represent a promising step in understanding the usefulness of 18 F-APN-1607 PET/CT imaging for detecting tau accumulation in MAPT mutation carriers. Our preliminary follow-up data also suggest the potential value of 18 F-APN-1607 PET/CT for monitoring the longitudinal trajectories of frontotemporal lobar degeneration caused by MAPT mutations. © 2021 International Parkinson and Movement Disorder Society.

To explore the effect of lenalidomide on human fibroblast-like synovial cells (HFLS) and the therapeutic efficacy on hemophilic arthropathy in hemophilia A mice model.In vitro, to remodel the inflammatory environment of synovial tissue after hemorrhage, ferric citrate and recombinant TNF-α were added into the cell culture medium of HFLS. Cell Counting Kit-8 (CCK-8), Enzyme-linked immunosorbent assay (ELISA), Quantitative Real-time PCR (RT-qPCR) and flow cytometry were employed for detection of the effects of lenalidomide on the proliferation ability, pro-inflammatory cytokines release and apoptosis of HFLS cells. In vivo, hemophilia arthropathy was remodeled in hemophilia A mice by induction of hemarthrosis. A series of doses of lenalidomide (0.1, 0.3 and 1.0 g/kg) was administrated intra-articularly. Tissues of knee joints were collected on the 14th day after administration, and the protective effect of lenalidomide on arthritis in hemophilia A mice were evaluated by RT-qPCR and histological grading.In vitro, compared with the untreated control group, lenalidomide could significantly inhibit the proliferation of HFLS cells (P0.05), and the effect was the most significant when the concentration was 0.01 μmol/L (P0.001). Compared with the control group, lenalidomide could significantly inhibit the expression levels of TNF-α, IL-1β, IL-6 and IFN-γ in HFLS cells (P0.05). The flow cytometry results showed that lenalidomide could enhance the apoptotis of HFLS cells (P0.05). The results of RT-qPCR showed that lenalidomide could significantly reduce the mRNA expression levels of TNF-α, IL-1β, IL-6,MCP-1 and VEGF in the joint tissues (P0.05). Histological results showed that compared with the injured group, lenalidomide could significantly reduce the pathological sequela after hemarthrosis induction, e.g. synovial thickening and neo-angiogenesis in the synovium. The protection displayed a dose-response pattern roughly.In vitro, lenalidomide can inhibit the proliferation of HFLS cells, promote their apoptosis, and inhibit the expression of pro-inflammatory cytokines. In vivo, lenalidomide can significantly decrease the expression of pro-inflammatory cytokines in the joints of mice, and prevent the development of inflammation and neo-angiogenesis. The results provide a theoretical and experimental basis for the clinical application of lenalidomide in the treatment of hemophilic arthropathy.来那度胺对血友病性关节炎的治疗作用研究.探讨来那度胺对人滑膜成纤维细胞（HFLS）增殖的影响以及对A型血友病小鼠血友病性关节炎（HA）的治疗效果。.以HFLS为模型细胞，在细胞培养基中添加柠檬酸铁和TNF-α重组蛋白，体外模拟炎性环境，加入不同浓度的来那度胺，通过CCK-8、ELISA、RT-qPCR、流式细胞术等方法检测HFLS的增殖能力、促炎细胞因子释放和细胞凋亡等功能的变化；构建小鼠HA模型，关节腔内注射不同浓度（0.1、0.3和1.0 g/kg）的来那度胺，在给药后d 14收集样本，通过RT-qPCR检测和组织学方法观察小鼠关节中滑膜增厚、新生血管形成等情况。.在体外，与未加药物的对照组相比，来那度胺0.001、0.01、0.1、1、10 μmol/L均能够显著抑制HFLS的增殖活力（P0.05），以浓度为0.01 μmol/L时作用最显著（P0.001）。与对照组相比，来那度胺能够显著抑制HFLS细胞TNF-α、IL-1β、IL-6和IFN-γ等炎性因子的表达水平（P0.05）。流式细胞术检测结果表明，来那度胺能够促进HFLS细胞的凋亡水平（P0.05)。RT-qPCR结果表明来那度胺能够显著降低小鼠关节组织中TNF-α、IL-1β、IL-6、MCP-1和VEGF的mRNA表达水平（P0.05)。组织学病理检测结果表明，来那度胺能够明显降低HA小鼠的关节滑膜厚度，减少新生血管生成，效果呈现剂量依赖性（r=-0.9129），以剂量为1 g/kg时保护作用最明显。.在体外，来那度胺能够有效抑制HFLS细胞增殖，促进其凋亡，并抑制其炎性因子的表达；在体内，能够缓解小鼠关节内炎症发展，显著降低小鼠关节中炎性因子的表达水平，为来那度胺将来应用于HA的临床治疗提供了理论和实验依据。.

Background 18 F-APN-1607 is a novel tau PET tracer characterized by high binding affinity for 3- and 4-repeat tau deposits. Whether 18 F-APN-1607 PET imaging is clinically useful in PSP remains unclear. Objectives The objective of this study was to investigate the clinical utility of 18 F-APN-1607 PET in the diagnosis, differential diagnosis, and assessment of disease severity in patients with PSP. Methods We enrolled 3 groups consisting of patients with PSP (n = 20), patients with α-synucleinopathies (MSA with predominant parkinsonism, n = 7; PD, n = 10), and age- and sex-matched healthy controls (n = 13). The binding patterns of 18 F-APN-1607 in PET/CT imaging were investigated. Regional standardized uptake ratios were compared across groups and examined in relation to their utility in the differential diagnosis of PSP versus α-synucleinopathies. Finally, the relationships between clinical severity scores and 18 F-APN-1607 uptake were investigated after adjustment for age, sex, and disease duration. Results Compared with healthy controls, patients with PSP showed increased 18 F-APN-1607 binding in several subcortical regions, including the striatum, putamen, globus pallidus, thalamus, subthalamic nucleus, midbrain, tegmentum, substantia nigra, pontine base, red nucleus, raphe nuclei, and locus coeruleus. We identified specific regions that were capable of distinguishing PSP from α-synucleinopathies. The severity of PSP was positively correlated with the amount of 18 F-APN-1607 uptake in the subthalamic nucleus, midbrain, substantia nigra, red nucleus, pontine base, and raphe nuclei. Conclusions 18 F-APN-1607 PET imaging holds promise for the diagnosis, differential diagnosis, and assessment of disease severity in patients with PSP. © 2021 International Parkinson and Movement Disorder Society.

Facing the increasing demand of atmosphere pollutant control, selective catalytic reduction (SCR) technology has been widely applied in various industries for NO

Herein, we report a method for C3-selective C-H tri- and difluoromethylthiolation of pyridines. The method relies on borane-catalyzed pyridine hydroboration for generation of nucleophilic dihydropyridines; these intermediates react with trifluoromethylthio and difluoromethylthio electrophiles to form functionalized dihydropyridines, which then undergo oxidative aromatization. The method can be used for late-stage functionalization of pyridine drugs for the generation of new drug candidates.

Heavy metal pollutants generated from municipal solid waste (MSW) incineration are mainly concentrated in the fly ash, among which lead species have received considerable attention due to their high content and biotoxicity. CaO is an active component in fly ash to adsorb heavy metal species. In this study, based on density functional theory (DFT) calculations, the migration and transformation mechanisms of lead species over the CaO (100) surface were investigated by calculating the adsorption configurations, energies, and electronic structures, etc. The results indicate that the adsorption of lead species over the CaO (100) surface is dominated by chemisorption, and PbCl2 molecule exhibits a stronger affinity to the CaO surface than Pb0. The dissociation of HCl molecule on the CaO (100) surface facilitates the adsorption and chemical reactivity of lead species. The chlorination of Pb0 to PbCl2 is a two-stage route. In the first stage, two HCl molecules are exothermically adsorbed on the surface without an energy barrier, and Pb0 is directly bonded to the active Cl atom, which is controlled by the Eley-Rideal mechanism. In the second stage, PbCl intermediate bonds with another Cl atom over the surface to form the PbCl2 molecule, following the Langmuir-Hinshelwood mechanism, which is also the rate-determining step. Compared with the homogeneous chlorination, CaO catalyzes the heterogeneous process to greatly reduce the oxidation energy barrier and promotes the formation of PbCl2. Consequently, CaO is able to accelerate the lead enrichment in fly ash, which is favorable for lead species purification.

Background There was a paucity of follow-up studies in the disease progression of early-onset PD patients with Parkin mutations (Parkin-EOPD). Here we conducted a longitudinal study to investigate the progression of motor and cognitive features of Parkin-EOPD patients. Methods Genetic analysis was performed via target sequencing and multiplex ligation-dependent probe amplification. Thirty patients carrying homozygous or compound heterozygous Parkin mutations with at least 2 follow-up revisions were investigated as the Parkin-EOPD group. Fifty-two patients with at least 2 follow-up revisions, who did not have any known causative PD mutations, GBA or LRRK2 risk variants, a heterozygous Parkin mutation or 2 Parkin mutations without a segregation test, were defined as the genetically undefined EOPD (GU-EOPD) group. A linear mixed-effect model was implemented to evaluate longitudinal changes in motor symptoms and cognition. Results At baseline, the Parkin-EOPD group had a lower Unified Parkinson's Disease Rating Scale score (UPDRS-III) (off-medication) than the GU-EOPD group, without significant differences in cognition. A longitudinal study showed the estimated progression rate per year (standard error) of the UPDRS-III score (off-medication) was lower in the Parkin-EOPD group (0.203 [0.3162] points per year) than in the GU-EOPD group (1.056 [0.3001] points per year). The difference in the UPDRS-III score rate between the 2 groups was 0.853 (0.4183) (P = 0.042). The Parkin-EOPD group showed better maintenance of spatial processing ability compared with the GU-EOPD group (P = 0.027). Conclusion Parkin-EOPD patients showed a slower deterioration of motor symptoms and a better spatial processing ability than GU-EOPD patients, which suggests that subtyping according to genetic features can help predict PD progression. © 2020 International Parkinson and Movement Disorder Society.

Achieving C3-selective pyridine functionalization is a longstanding challenge in organic chemistry. The existing methods, including electrophilic aromatic substitution and C-H activation, often require harsh reaction conditions and excess pyridine and generate multiple regioisomers. Herein, we report a method for borane-catalyzed tandem reactions that result in exclusively C3-selective alkylation of pyridines. These tandem reactions consist of pyridine hydroboration, nucleophilic addition of the resulting dihydropyridine to an imine, an aldehyde, or a ketone, and subsequent oxidative aromatization. Because the pyridine is the limiting reactant and the reaction conditions are mild, this method constitutes a practical tool for late-stage functionalization of structurally complex pharmaceuticals bearing a pyridine moiety.

The aim of this study was to evaluate the performance of the four scoring tools in predicting mortality in pediatric intensive care units (PICUs) in western China.This was a multicenter, prospective, cohort study conducted in six PICUs in western China. The performances of the scoring systems were evaluated based on both discrimination and calibration. Discrimination was assessed by calculating the area under the receiver operating characteristic curve (AUC) for each model. Calibration was measured across defined groups based on mortality risk using the Hosmer-Lemeshow goodness-of-fit test.A total of 2034 patients were included in this study, of whom 127 (6.2%) died. For the entire cohort, AUCs for Pediatric Risk of Mortality Score (PRISM) I, Pediatric Index of Mortality 2 (PIM2), Pediatric Logistic Organ Dysfunction Score-2 (PELOD-2) and PRISM IV were 0.88 [95% confidence interval (CI) 0.85-0.92], 0.84 (95% CI 0.80-0.88), 0.80 (95% CI 0.75-0.85), and 0.91 (95% CI 0.88-0.94), respectively. The Hosmer-Lemeshow goodness-of-fit Chi-square value was 12.71 (P = 0.12) for PRISM I, 4.70 (P = 0.79) for PIM2, 205.98 (P 0.001) for PELOD-2, and 7.50 (P = 0.48) for PRISM IV [degree of freedom (df) = 8]. The standardized mortality ratios obtained with the PRISM I, PIM2, PELOD-2, and PRISM IV models were 0.87 (95% CI, 0.75-1.01), 0.97 (95% CI, 0.85-1.12), 1.74 (95% CI, 1.58-1.92), and 1.05 (95% CI, 0.92-1.21), respectively.PRISM IV performed best and can be used as a prediction tool in PICUs in Western China. However, PRISM IV needs to be further validated in NICUs.

The V

Improvement of quality-of-life (QoL) has been termed as a primary objective in initiating therapy in both Parkinson’s disease (PD) and multiple system atrophy Parkinsonian subtype (MSA-P). We aimed to compare the determinants of life quality in drug naive PD and MSA-P patients. Eighty-six drug-naive PD patients and thirty-five drug-naive MSA-P patients were included to explore the determinants of QoL. Demographic information, motor deficits, and non-motor symptoms were included in the clinical assessment. Both motor and non-motor functions were more severely impaired in the drug-naive MSA-P patients, with higher PDQ-39 scores indicating poorer QoL. Physical discomfort and stigma were the main affected sub-domains in PD, while mobility and activity of daily life were the main affected ones in MSA-P. BECK depressive scores and UPDRS-III scores were independent variables of PDQ-39 in MSA-P patients. Age, depression, disease stages and non-motor scores were independent variables of PDQ-39 in PD patients. Drug-naive MSA-P patients suffered from more severe motor and non-motor disability, as well as poorer QoL. Depression and non-motor symptoms were proved to be the most critical determinants for QoL in PD, while motor function was supposed to be the major determinant for MSA-P. When initiating therapy, physicians need to focus more on motor functions in drug-naive MSA-P patients, but on depression in PD patients.

Frontotemporal lobar degeneration with tauopathy caused by MAPT (microtubule-associated protein tau) mutations is a highly heterogenous disorder. The ability to visualize and longitudinally monitor tau deposits may be beneficial to understand disease pathophysiology and predict clinical trajectories.The aim of this study was to investigate the cross-sectional and longitudinalSeven carriers of MAPT mutations (six within exon 10 and one outside of exon 10) and 15 healthy control subjects were included. All participants underwentAlthough the seven study patients had heterogenous clinical phenotypes, all showed a significantOur data represent a promising step in understanding the usefulness of

Lead (Pb) species trigger serious poisoning of selective catalytic reduction (SCR) catalysts. To improve the Pb resistance ability, revealing the impact mechanism of Pb species on the commercial SCR catalysts from a molecular level is of great significance. Herein, first-principles calculations were applied to unveil the Pb adsorption mechanism on the vanadium-based catalysts, the results were also compared with the previous experimental findings. The intrinsic interaction mechanism between Pb and catalyst components was interpreted by clarifying the change of the catalyst electronic structures (including charge transfer, bond formation situations, and active sites reactivities). It is found that the adsorption of Pb species belongs to chemisorption, evident electron transfer with the catalyst surface is inspected and intense charge transfer indicates strong adsorption. A remarkable interaction with the V = O active sites occurs and stable Pb-O bonds are formed, which significantly changes the electronic structures of the V = O sites and inhibits the NH3 adsorption, thus suppressing the SCR activity. Finally, thermodynamic analysis was applied to elucidate the temperature influence on Pb adsorption. It is found that Pb adsorption on catalysts cannot proceed spontaneously over 500 K. At higher temperatures the adsorption is inhibited and the Pb species become less stable, which partially explains why the Pb-poisoning effect at high temperatures is relatively moderate than that at low temperatures.

The objective of this study was to investigate the clinical utility ofWe enrolled 3 groups consisting of patients with PSP (n = 20), patients with α-synucleinopathies (MSA with predominant parkinsonism, n = 7; PD, n = 10), and age- and sex-matched healthy controls (n = 13). The binding patterns ofCompared with healthy controls, patients with PSP showed increased

Selenium (Se) species can deposit in selective catalytic reduction (SCR) system during the denitrification process, which is harmful to the catalyst. To improve the Se-poisoning resistance of SCR catalysts, the influence mechanism of Se species on vanadium-titanium-based catalysts should be elucidated from an atomic scale. In this paper, theoretical calculations were conducted to reveal the adsorption and interaction mechanism of Se species on V2O5-WO3(MoO3)/TiO2 surface based on the first-principles. The impact of Se species on the electronic structure of the catalyst was investigated from electron transfer, bond formation, and V O site activity. The results show that the adsorption of elementary Se (Se0) belongs to chemisorption, while SeO2 can undergo both physisorption and chemisorption. For the chemisorption of Se species, obvious charge transfer with the catalyst is observed and Se–O bond is formed, which enhances the oxidation activity of the catalyst, triggers the reaction of Se0 and SeO2 with the catalyst components to generate SeVOx and SeW(Mo)Ox. The active sites are thereby damaged and the SCR performance is reduced. The above conclusions are mutually confirmed with the previous experimental research. By studying the correlation with the adsorption energies of Se species, descriptors manifesting the Se species adsorption were initially investigated to unveil the relationship between the electronic structure and the adsorption energy. Finally, the influence of temperature on Se adsorption was investigated. The adsorption can only proceed spontaneously below 500 K and is inhibited at high temperatures.

A comprehensive understanding of the effect of N doping on CO oxidation over FeS2 is prominently meaningful for fabricating a low-cost heteroatom catalyst with an optimum structure and satisfactory activity. Herein, periodic density functional theory (DFT) calculations were performed to investigate possible reaction mechanisms for CO oxidation over FeS2 and N doped FeS2 (N-FeS2). Two kinds of active oxygen species are observed on the catalyst surfaces, including the adsorbed O2 and atomic O. The results show that the CO first prefers to react with the atomic O formed by O2 dissociation (FeS2) and the adsorbed O2 (N-FeS). Comparing to FeS2, the energy barriers of CO oxidation over N-FeS2 are lower, which indicates that N doping can improve the activity for CO oxidation. The analyses of electronic structure evidence that N doping can modify the electronic density of the adjacent Fe atoms and thus form favorable electronic configurations for O2 adsorption, which facilitates O2 activation and the succeeding CO oxidation. The whole favorable CO oxidation cycle for N-FeS2 consists of three stages: O2 adsorption → first CO oxidation → second CO oxidation. Our findings can provide a fundamental understanding to develop N doped catalysts with high activity for CO abatement.

Cadmium (Cd) pollutants from the incineration of municipal solid waste (MSW) has drawn considerable attention due to their high volatility and biological toxicity. Current experimental results have revealed the strong interaction between SiO2 and Cd species, which provides an insight for the removal of Cd species, but the detailed mechanism is still unclear. Thus, with the density functional theory (DFT) calculations, the interaction mechanisms of Cd species over the SiO2(0 0 1) surface were investigated, considering the effect of HCl in MSW incineration flue gas. It is found that the adsorption manners of Cd0 and CdO are chemisorption over the SiO2 surface and the active sites are O sites, while the interaction between CdCl2 and the surface is dominated by weak chemisorption. HCl plays a dual role in the interaction of Cd0 and CdO with the surface. The introduction of HCl can promote the fixation of CdO and Cd0, but also promote their chlorination into CdCl2 whose adsorption on SiO2 is too weak to be captured. The chlorination of Cd0 can be achieved by two-step and one-step routes, both following the Eley-Rideal mechanism. Whereas, CdO can only be chloridized through a two-step pathway, in which the first step follows the Eley-Rideal mechanism and the second step follows the Langmuir-Hinshelwood mechanism. Compared with Cd0, the chlorination of CdO has a higher reaction energy barrier and is more difficult to proceed. Therefore, CdO is the most effortless cadmium pollutant for SiO2 to control.

Background Spinocerebellar ataxias (SCAs) are the autosomal dominant cerebellar ataxia (ADCA) with great clinical and genetic heterogeneity. Genetic testing will contribute to the final diagnosis. Methods A total of 204 Chinese ADCA patients were recruited and 190 had genetic testing. Dynamic mutations of SCA1, 2, 3, 6, 7, 8, 10, 12, 17 and dentatorubral-pallidoluysian atrophy (DRPLA) were screened firstly. For the patients with negative results, the dynamic mutations of HTT of Huntington Disease (HD), SCA31, 36 and even the whole exome sequencing (WES) were further performed. We investigated the genetic results and clinical characteristics retrospectively. Results Among these 190 index cases, 177(93.16%) were identified SCA dynamic mutations. SCA3 was the commonest, accounting for 70.06%, followed by SCA1 (9.6%), 2 (9.05%), 12 (3.39%), 6 (2.26%), DRPLA (2.26%), 7(1.13%), 8 (1.13%) and 17(0.56%). One patient carried a compound dynamic mutation of SCA6 and SCA17 (SCA6/17). No SCA10 or SCA36 was found. Among the remaining 13 patients, three were diagnosed with HD (1.58%) and one with Episodic Ataxia 2 (EA2). WES did reveal several variants with uncertain significance (VUS) in the remaining nine patients, but failed to detect causative mutations. Conclusion We illustrated the approach and challenge of genetic testing in Chinese ADCA patients. Dynamic mutations of SCAs should be screened firstly. When the results were negative, dynamic mutation of HTT would better be screened consequently. In early-onset ADCA patients, WES might be effective to identify causative mutations, but in adult-onset cases, WES might be less effective.

Quantum chemistry calculations were performed to reveal the roles of the active oxygen species in the CO oxidation and the interactions between the gaseous molecules (CO, O2, CO2, etc.) and the active sites to design a highly active and low-temperature Mn/TiO2 catalyst. The results show that the Ti5a-O2b-Mn5c (TOM) coordination structure is the active center for the chemisorption of CO and O2. The dominant cycles were proposed over the TOM structure, which consist of three reaction stages, i.e., first CO oxidation → surface re-oxidation → second CO oxidation. Two kinds of active oxygen species, i.e., the lattice oxygen of TOM and the two atomic oxygen formed during the surface re-oxidation process, play critical roles in the dominant CO oxidation cycles. The energy barriers of the dominant oxidation cycles are lower than 50 kJ/mol, which explain well the high low-temperature activity of Mn/TiO2 catalyst for CO abatement.

Vanadium‑titanium based selective catalytic reduction (SCR) catalysts are commercially applied for the denitrification of nitrogen oxides (NOx) in flue gas. Meanwhile, they are also catalytically effective to the abatements of many contaminants including carbon monoxide (CO) catalytic oxidation. Understanding the catalytic performance on CO oxidation is of great significance to develop modified SCR catalysts for the synergetic control of nitrogen oxides and CO. Two SCR catalyst models were constructed, i.e., V2O5/TiO2(001) and V2O5-WO3/TiO2(001). The mechanisms of CO oxidation over the above two catalyst surfaces were analyzed by density functional theory (DFT) calculations. The results show that the whole oxidation cycle of CO includes two reaction stages. In the first stage, CO reacts with terminal oxygen of V O site, following MvK mechanism, which is also the rate-determining step of the whole reaction process. In the second stage, the redundant oxygen Oe of the absorbed O2 molecule reacts with another CO molecule, which follows E-R mechanism. The activation energy barriers of the CO oxidation on V2O5/TiO2 surface are lower than those on V2O5-WO3/TiO2, indicating that WO3 doping inhibits CO oxidation. Moreover, the established reaction kinetics of elementary reactions would be helpful to model CO catalytic oxidation over the real SCR catalysts.

The arsenic oxides in flue gas can cause severe poisoning and deactivation of the vanadium-titanium-based denitrification catalyst. Investigation of the interaction mechanism between arsenic oxides and denitrification catalyst can provide theoretical guidance for the development of anti-arsenic poisoning catalyst. To this end, the periodic V2O5-TiO2 (0 0 1) models were constructed to represent the actual vanadium-titanium-based catalyst in this study. Density functional theory (DFT) calculations were applied to explore the interaction mechanism between the catalyst surface and typical arsenic oxide (As2O3) in flue gas. Stable adsorption configurations and adsorption energies for As2O3 and NH3 adsorption were calculated, the detailed interaction pathways and reaction barriers were also obtained. The results indicate that As2O3 is chemisorbed on the catalyst surface, strong interaction and electron transfer occur after As2O3 adsorption. The adsorption strength of NH3 on Lewis and Bronsted sites are decreased after As2O3 adsorption and the inhibition effect on the Lewis acid sites is much stronger. As2O3 is oxidized to As2O5 on catalyst surface, the Lewis acid sites (V = O) are destroyed and the valence of vanadium is decreased, which should be responsible for the catalyst deactivation. The analysis of the interaction pathway shows that As2O3 inclines to react with two adjacent V2O5 clusters to produce V2O4 because of the lowest energy barrier. Therefore, when the catalyst is poisoned by As2O3 in flue gas, the active component V2O5 inclines to generate V2O4, which is consistent with previous experimental researches.

WO3 and MoO3 are widely used as the additives for the V2O5-based selective catalytic reduction (SCR) catalysts, which have different anti-arsenic poisoning performances. To clarify their different influence mechanism on the interaction between arsenic oxide (As2O3) and the V2O5-based catalyst, WO3 and MoO3 doped V2O5/TiO2 catalyst models were built, density functional theory (DFT) method was employed to explore the interaction mechanism for As2O3 with V2O5, WO3 and MoO3 from a theoretical level. As2O3 adsorption configurations, adsorption energies and electronic structures were obtained, along with the detailed inter-reaction pathways and relevant energy barriers. The results indicate that strong interaction and electron transfer occur after As2O3 adsorption, the MoO3 doped catalyst has higher reactivity and stronger charge transfer with As2O3 than the WO3 doped catalyst. Moreover, on V2O5-WO3/TiO2 catalyst, the reactivity of WO3 with As2O3 is lower than that of V2O5, hence As2O3 is inclined to react with V2O5, resulting in the catalyst deactivation. Whereas for V2O5-MoO3/TiO2 catalyst, As2O3 tends to react with the more active MoO3, thus protecting the V2O5 from arsenic poisoning. In summary, MoO3 doping provides better anti-arsenic poisoning effect than WO3, which agrees well with previous experimental results.

Background The risk factors of duodenal injury from distal migrated biliary plastic stents remain uncertain. The aim of this study was to determine the risk factors of distal migration and its related duodenal injury in patients who underwent placement of a single biliary plastic stent for biliary strictures. Methods We retrospectively reviewed all patients with biliary strictures who underwent endoscopic placement of a single biliary plastic stent from January 2006 to October 2017. Results Two hundred forty-eight patients with 402 endoscopic retrograde cholangiopancreatography procedures were included. The incidence of distal migration was 6.2%. The frequency of duodenal injury was 2.2% in all cases and 36% in cases with distal migration. Benign biliary strictures (BBS), length of the stent above the proximal end of the stricture (> 2 cm), and duration of stent retention (