Metal-support spin orders: Crucial effect on electrocatalytic oxygen reduction.

Magnetic property (e.g. spin order) of support is of great importance in the rational design of heterogeneous catalysts. Herein, we have taken the Ni-supported ferromagnetic (FM) CrBr3 support (Nix/CrBr3) to thoroughly investigate the effect of spin-order on electrocatalytic oxygen reduction reaction (ORR) via spin-polarized density functional theory calculations. Specifically, Ni loading induces anti-FM coupling in Ni-Cr, leading to a transition from FM-to-ferrimagnetic (FIM) properties, while Ni-Ni metallic bonds create a robust FM direct exchange, benefiting the improvement of the phase transition temperature. Interestingly, with the increase in Ni loading, the easy magnetic axis changes from out-of-plane (2D-Heisenberg) to in-plane (2D-XY). The adsorption properties of Nix/CrBr3, involving O2 adsorption energy and configuration, are not governed by the d-band center but strongly correlate with magnetic anisotropy. It is noteworthy that the applied potential and electrolyte acidity triggers spin-order transition phenomena during the ORR and induces the catalytic pathway change from 4e- ORR to 2e- ORR with the excellent onset potential of 0.93 V/reversible hydrogen electrode, comparable to the existing most excellent noble-metal catalysts. Generally, these findings offer new avenues to understand and design heterogeneous catalysts with magnetic support.

Magnetic Order Transition of a Two-Dimensional Square-Lattice Electrocatalyst Assembled by Fe-N4 Units: Crucial Role on Oxygen Reduction.

Herein, we theoretically investigate the effect of magnetic orders on electrocatalytic oxygen reduction reaction (ORR) properties on the Fe-N4 site-embedded two-dimensional (2D) covalent organic framework (Fe-N4@COF-C3N2) under realistic environments. The Fe-N4@COF-C3N2 shows a 2D square-lattice (sql) topology with three magnetic order states: one ferromagnetic state (FM) and two antiferromagnetic states (AFM1 and AFM2). Specially, the electrocatalyst in the AFM2 state shows a remarkable onset potential of 0.80 V/reversible hydrogen electrode (RHE) at pH 1, superior to the existing most excellent noble-metal catalysts. Thermodynamically, the onset potential for the 4e- ORR is 0.64 V/RHE at pH 1, with a magnetic state transition process of FM → AFM1 → FM → FM → FM, while at pH 13, the onset potential for the 4e- ORR is 0.54 V/RHE, with the magnetic transition process of FM → FM → AFM1 → FM → FM. Generally, this finding will provide new avenues to rationally design the Fe-N4 electrocatalyst.

Visible-Light Photocatalytic Overall Water Splitting on a B4C3/CxNy Z-Scheme Heterojunction: Role of Ultrafast Carrier Recombination-Transfer Kinetics.

Herein, combining density functional theory (DFT) calculations with nonadiabatic molecular dynamics (NAMD), we built a computational framework to rationally screen from a series of 2D conjugated carbon nitrides (CNs) to match with B4C3, resulting in the excellent direct Z-scheme photocatalyst (B4C3/C6N6) for overall water splitting (OWS). Studies on interface engineering and ultrafast dynamics of carrier recombination-transfer show that in the B4C3/C6N6 system, compared with the slower interlayer migration process of carriers, strong nonadiabatic coupling and longer quantum decoherence time accelerates weak carrier interlayer recombination on a subpicosecond time scale, enabling simultaneous triggering of hydrogen evolution reaction (HER) with ΔG = -0.23 eV and spontaneous oxygen evolution reaction (OER) in the absence of sacrificial or cocatalysts. In general, our work will promote the design of efficient direct Z-scheme photocatalysts from an ultrafast dynamics perspective.

Correlation of the spin state and catalytic property of M-N4 single-atom catalysts in oxygen reduction reactions.

The rational design of high-performance catalysts for oxygen reduction reactions (ORRs) is of great importance for large-scale applications in the field of proton-exchange membrane fuel cells and the green synthesis of H2O2. The effect of spin states of paramagnetic metal ions on the selectivity of ORRs is significant for single-atom catalysts (SACs). In this work, via spin-polarization density functional theory (DFT) calculations, we systematically investigated the popular paramagnetic metal-nitrogen graphene (M-N4-C, M = Mn, Fe, and Co) SACs to mainly focus on the correlation of spin states and catalytic performance (e.g. activity and selectivity). Both thermodynamically and kinetically, it was found that Co-N4-C (S = 1/2) has excellent 2e- oxygen reduction performance (hydrogen peroxide production) with an ultralow overpotential of 0.03 V, and the hydrogenation of OOH* is the rate-determining step (RDS) with an energy barrier of 1.20 eV. The 4e- ORR tends to occur along the OOH dissociation pathway (O* + OH*) on Co-N4-C (S = 3/2), in which OOH* decomposition is the RDS with an energy barrier of 1.01 eV. It is proved that the spin magnetic moment is the key factor to regulate the ORR property via multi-angle electronic analysis. The spin states of catalysts play a crucial role in the activity and selectivity of ORRs mainly by manipulating the bond strength between OOH and catalysts. This will provide new insights for the rational design of ORR catalysts with magnetic metals.

Rational design of bimetallic MXene solid solution with High-Performance electrocatalytic N2 reduction.

Electrocatalytic N2 reduction reaction (eNRR) was an effective alternative method for green synthesis of NH3. By combining the first-principal Density functional theory (DFT) calculations and Monte Carlo (MC) simulation, we systematacially investigated 24 types equal-ratio bimetallic MXene solid solution, involving 88 different catalysts. Our focus was on the catalytic performance of these materials in eNRR. The computational result indicate that MoW(3Mo) has high stability, selectivity (93.8 % against the hydrogen evolution reaction (HER)) and activity (UL = -0.26 V), which is significantly better than that of monometal Mo2CO2 and W2CO2. This improvement in catalytic properties is attributed to the unique electronic structure (e.g. d-band center, charge) of bimetallic MXene solid solution. In explicit solvent conditions, the microenvironment of hydrogen bond in aqueous liquid thermodynamically promotes the catalytic property for eNRR and reduce the catalytic property of HER side reaction, but the kinetic barrier is also increased due to the effect of the hydrogen-bond microenvironment on proton migration. Overall, the obtained bimetallic MXene solid solution MoW(3Mo) exhibits excellent catalytic performance in eNRR.

Cooperatively interface role of surface atoms and aqueous media on single atom catalytic property for H2O2 synthesis.

Direct electrosynthesis of hydrogen peroxide (H2O2) from H2 and O2 is a promising alternative to currently industrial Riedl-Pfleiderer route. Utilizing a combination of density functional theory (DFT) and ab-initio-molecular dynamic simulation (AIMD), we presented an effective computational framework to identify the cooperative role of surface atoms(e.g. O, N and S) and aqueous media on catalytic performance of single-atom catalysts (SACs) supported Nb2C MXenes. Computational results shown that both Ni/Nb2CN2 and Co/Nb2CS2 have low overpotentials of 0.17 V and 0.20 V, and the barrier of 0.89 eV and 0.67 eV for 2e- ORR under gas phase, respectively, while in aqueous phase, hydrogen bond framework on the surface promotes the transfer of proton, resulting in the lower 2e- ORR overpotential (0.05 V) in Co/Nb2CS2 and lower barrier (almost 0.01 eV) for rate-determining step (RDS) in Ni/Nb2CN2. Electronically, we found that the less-electronegativity N and S relative to O more benefit to mediate the activation degree of O2 on SACs and thereby improve catalytic selectivity. Thus, it is concluded that both surface atom and aqueous medium synergistically promote catalytic property for H2O2 synthesis.

Elimination-Fusion Self-Assembly of a Nanometer-Scale 72-Nucleus Silver Cluster Caging a Pair of [EuW10 O36 ]9- Polyoxometalates.

The largest known polyoxometalate (POM)-templated silver-alkynyl cluster, [(EuW10 O36 )2 @Ag72 (tBuC≡C)48 Cl2 ⋅4 BF4 ] (SD/Ag20), was isolated under solvothermal conditions and structurally characterized. It was confirmed by single-crystal X-ray diffraction (SCXRD) as a {EuW10 }2 -in-{Ag72 } clusters-in-cluster rod-like compound. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) shows that such a double anion-templated cluster is assembled from a crucial single anion-templated Ag42 intermediate in the solution. The crystallization of Ag42 species (SD/Ag21), followed by SCXRD, gave an important clue about the assembly route of SD/Ag20 in solution: the Ag42 cluster eliminates six silver atoms laterally, then fuses together at the vacant face to form the final Ag72 cluster (elimination-fusion mechanism). The characteristic emission of [EuW10 O36 ]9- is well maintained in SD/Ag20. This work not only provides a new method for the synthesis of larger silver clusters as well as the functional integration of the silver cluster and POMs, but also gives deep insights about the high-nuclear silver cluster assembly mechanism.

The ionothermal synthesis, structure, and magnetism-structure relationship of two biphenyl tetracarboxylic acid-based metal-organic frameworks.

Two new metal-organic frameworks (1-2) were ionothermally obtained by the reaction of a biphenyltetracarboxylic sodium (Na4BPTC) ligand and M(OOCCH3)2 (M = Co(1) and Mn(2)). Crystal structure analysis reveals that 1 is a Co3Na6 unit-based three dimensional heterometallic MOF, while 2 exhibits a {Mn(COO)n} chain-based three-dimensional framework. Furthermore, the magnetic measurement shows that both of them have anti-ferromagnetic properties. A combination of Density Functional Theory (DFT) and Quantum Monte Carlo (QMC) simulation uncovers that in 2 the coupling parameters between two adjacent Mn(II) ions are J1 = -2.0 cm(-1) and J2 = -1.6 cm(-1), and the magnetism mainly originates from the propagation of Mn(II) ions by the super-exchange of carboxylates. Interestingly, the superexchange modes of J1 and J2 are different. Two spin nets of -/+/- dominate in the coupling for J1, while for J2 there are two spin nets of -/+/- and one spin net of +/-/+.

A novel La(III)-based metal-organic framework (MOF) with a new topology: poly[diaquabis(µ5-2,5-dioxopiperazine-1,4-diacetato)(µ2-oxalato)dilanthanum(III)].

In the title metal-organic framework (MOF), [La(C(8)H(8)N(2)O(6))(C(2)O(4))(0.5)(H(2)O)](n), the La(III) cation is coordinated by eight O atoms in a square antiprismatic configuration. Each La(III) cation is connected to adjacent La(III) cations by bridging 2,5-dioxopiperazine-1,4-diacetate (PODC(2-)) and oxalate (lying about an inversion centre) ligands, generating two-dimensional grid layers. The layers are further linked via the carboxylate groups of the PODC(2-) ligands in syn-syn and syn-anti modes, resulting in a three-dimensional framework with a short Schläfli vertex notation of {4(7).6(3)}{4(7).6(7).8}.

Production of bioactive exopolysaccharides from bitter medicinal mushroom, Antrodia camphorata (M. Zang et C.H. Su) Sh.H. Wu et al. (Aphyllophoromycetideae) in submerged cultivation.

This study examines the effects of various fructose concentrations in media on the production and quality of bioactive exopolysaccharides (EPS) from Bitter medicinal mushroom, Antrodia camphorata in submerged cultures. The fructose in media of submerged cultures of A. camphorata significantly affected the production, average molecular weight (Mn), and antioxidant activity of exopolysaccharides. The specific growth rate decreased monotonically from 0.33 to 0.25 1/day as the fructose concentration increased from 10 to 60 g/L; however, maximum production and productivity for EPS increased from 75.23 to 164.87 mg/L and 6.27 to 9.70 mg/L/day, respectively. In addition, the fed-batch culture used in this study significantly improved the production of EPS (2.43-fold enhancement, from 75.23 to 182.99 mg/L), number average molecular weights of EPS (1.47-fold enhancement, from 5.44 x 10, to 7.98 x 10(5) Da), protein/exopolysaccharide ratios (1.63-fold enhancement, from 16% to 26%), and antioxidant activity of EPS (1.32-fold enhancement, from 60% to 79%), as compared with corresponding properties of batch fermentation at 10 g/L fructose in an air-lift bioreactor. The antioxidant activity of EPS was highly correlated with number average molecular weights (R2 = 0.90) and protein/exopolysaccharide ratios (R2 = 0.96). The positive results of this research have successfully verified the promotion efficiency on the production and quality of EPS from the medicinal mushroom A. camphorata.

Temperature-dependent conductivity of Emim+ (Emim+ = 1-ethyl-3-methyl imidazolium) confined in channels of a metal-organic framework.

A 3D metal-organic framework, featuring three kinds of cation channels, was obtained through an ionothermal reaction. Investigation on its temperature-dependent conductivity indicates the contribution of order and disorder of the Emim(+) (Emim(+) = 1-ethyl-3-methyl imidazolium bromide) in the channel to its conductivity.

Magnetic and thermal properties of three ionothermally synthesized metal-carboxylate frameworks of [M3(ip)4][EMIm]2 (M = Co, Ni, Mn, H2ip = isophthalic acid, EMIm = 1-ethyl-3-methyl imidazolium).

Three metal-organic frameworks, [M(3)(ip)(4)][EMIm](2) (M = Co 1, Ni 2, Mn 3, H(2)ip = isophthalic acid, EMIm = 1-ethyl-3-methyl imidazolium) were prepared from an ionic liquid medium. All the compounds feature the same (4(24))(6(4)) topology based on linear trinuclear clusters as eight-connected nodes. Compounds 1 and 2 are isostructural, while compound 3 exhibits a different structure due to the slight difference in the arrangement of M(3)(OOCR)(8) SBUs. Magnetic property measurements reveal that all the compounds display anti-ferromagnetic coupling, where compounds 2 and 3 show isotropic exchange interactions of -0.10 cm(-1) for 2 and -1.6 cm(-1) for 3. Investigation of the thermal diffusivity shows that the thermal diffusivity of 1 is higher than that of 3, while that of 3 is higher than that of 2.

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a Ln6Cu24Na12 cluster as a node.

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a nanosized Ln(6)Cu(24)Na(12) (Ln = Gd, Dy) cluster as a node have been obtained under microwave irradiation conditions through the reaction of H(2)ANMA (H(2)ANMA = L-alanine-N-monoacetic acid), Cu(NO(3))(2), and Ln(NO(3))(3) (Ln = Gd for 1, Dy for 2) with NaOH in deionized water. Investigations on the magnetic properties show that 1 exhibits ferrimagnetic behavior. The electrical conductivity measurements reveal that 1 behaves as a proton conductor.

[A preliminary study on the preparation of perfusion-decellularized laryngeal scaffold and the feasibility of laryngeal muscle reconstruction].

OBJECTIVE: To prepare a decellularized whole laryngeal scaffold by utilizing a perfusion-decellularized technique, reseed cells on it, and construct decellularized laryngeal muscles. METHODS: Perfusion decellularized larynxes were obtained by common carotid arterious perfusion with detergents. Then they were performed by macroscopic view, histological examination, scanning electron microscopy (SEM) and cartilage viability. Decellularized laryngeal scaffold were then reseeded with inducted mesenchymal stem cells (MSCs). Composites were transferred into greater omentums of rabbits after one day's adherence and harvested after eight weeks. Macroscopic view, histological examination and immunohistochemistry were performed. RESULTS: Perfusion larynxes became transparent after two hours. Histology and SEM indicated that perfusion method showed better decullularized effect. More vintages and collagen fibers but no intact cell or nuclei were retained in the decellularized matrix. Porosity measured by Image pro plus 6.0 was 80.4% +/- 3.2% (x +/- s). Chondrocyte vitality assay indicated chondrocyte vitality rate in the perfusion group was 86.9% +/- 1.5%. After eight weeks, vascularization formed and integrated cartilage frameworks still remained. Histological examination could clearly show the presence of muscle bundles and vessels. Immunohistochemical examination indicated that sarcomeric-alpha actin expressed positively in corresponding areas. CONCLUSIONS: It is feasible to reseed MSCs into the decellularized laryngeal muscle matrix for constructing tissue-engineered laryngeal muscles. This in vivo maturation into the omentum could be the first step before in situ implantation of the construct.

[An eight-year study on maternal and child health service utility in Sichuan province].

OBJECTIVE: To evaluate the effect of intervention on factors influencing the health service utility regarding Maternal and Child Health (MCH) under the 'Qinba Health Project' in Sichuan province. METHODS: 15 towns in 5 programmed counties were selected, using the method of 'random layer sampling' to be the trial group. With similar MCH status and comparable to the trial group, another 9 towns in 3 non-programmed counties were chosen as the control group, using the same sampling method. Indicators on MCH service utility were compared with that in the control group, and the influencing factors of MCH service utility analyzed by logistic model. RESULTS: The main characteristics of the two groups were quite similar at the baseline study, with the average annual family incomes and MCH service per 1000 people. Annual input on MCH services from the government had an distinct increase. The average annual rates of increase regarding the indicators as clean delivery, hospitalized delivery, systematic care on maternal and children, maternal and infant mortality rates were: 1.95%, 9.34%, 4.82%, 3.04%, -2.67%, -13.84% (P < 0.02) through chi2 trend tests. In the trial group, the changes seen in the 6 indicators were better in the control group than in the control group (P < 0.05). Data from the logistic regression model showed that the major influencing factors on the use of hospitalized delivery service were: age of the pregnant woman, average annual income of the family, health insurance status, number of pre-delivery visits, whether on poverty alleviate program, and on knowledge of MCH. CONCLUSION: The intervention project in this programmed area seemed effective and better than the non-programmed area, through an eight-year observation.

[Experience of diagnosis and treatment for cervical tracheoesophageal fistula complicated with laryngotracheal stenosis].

OBJECTIVE: To explore the treatment of cervical tracheoesophageal fistula (TEF) with complicated or remnant laryngotracheal stenosis (LTS) and anterior neck defect (AND). METHODS: From 1980 to 2007, 14 patients were diagnosed as TEF. Among them, 9 patients had complicated or remnant LTS, 3 patients had complicated AND, and 2 patients had TEF which were induced by Nickel-Titanium alloy mesh stent for treating benign esophageal stricture. All these patients were retrospectively studied in Tangdu Hospital. Treatment consisted of conservative therapy of TEF, staged surgical repair of TEF and laryngotracheal reconstruction according to the dimension (small or large) of TEF and complications. RESULTS: Four patients with small TEF (2 - 3 mm length) complicated LTS underwent laryngotracheal reconstruction stented with silicone T tube and TEF was adopted conservative treatment. The TEF and LTS were healed. Six patients with larger TEF (10 - 25 mm length) were repaired by staged surgical repair of TEF and laryngotracheal reconstruction. Among them, 3 cases had complicated LTS and AND, 2 cases had recent LTS and 1 case had TEF without complication. Two patients had TEF and LTS, whose TEF healed before laryngotracheal reconstruction, the remnant LTS were reconstructed and healed. During the follow-up ranged from one to ten years, 12 patients were successfully treated without complications. One patient with TEF and LTS was treated only LTS because of a segment of esophagus was closed and treated with esophagogastrostomy in the department of thoracic surgery after LTS was successfully reconstructed and cured. One patient died of bleeding and asphyxia induced by the Nickel-Titanium alloy stent because of the stent had not been taken out. CONCLUSION: The small cervical TEF complicated or remnant LTS can be treated by laryngotracheal reconstruction and conservative treatment of TEF at the same time. A larger TEF complicated LTS should be treated by staged repair of TEF and LTS.

[Historical succour of poverty and medical assistance in rural China.].

There was considerable attention paid to the succour of poverty with widespread practice in China's history. Succour of poverty and medical assistance in rural areas were closely connected with famine relief carried out by the rulers. The mutual assistance of emotional and moral support long-term in rural communities is the most important form of medical assistance. A succour of poverty and medical assistance system in the modern sense should inherit and learn from the past consideration of poverty assistance and bring in the fine tradition of multiple forces to participate, in order to establish a succour of poverty and medical assistance system compatible with economic and social development. This is not only an important component of anti-poverty strategy in rural areas but also an inevitable requirement of historical development.

[An evaluation of the maternal and child health services in Qinba Health Project in Sichuan province].

OBJECTIVES: To evaluate the effectiveness of interventions taken by Qinba Health Project on the Maternal and Child Health (MCH) services in Sichuan province. METHODS: Stratified random sampling was undertaken to select participants for the evaluation. Eighty one villages in 27 towns in the nine project counties and 27 villages in nine towns in three non-project counties with similar social economic backgrounds were selected. A questionnaire survey was undertaken in all of the selected health facilities and 462 women who received maternal services during the project time. Multiple variable regression analysis was performed to identify determinants of the change of services. RESULTS: The project MCH services reached the expected targets. The project towns improved their MCH services more significantly than the non-project towns. The logistic regression analysis identified project intervention, maternal age, average family income, health insurance, numbers of pre-natal examinations, eligibility to poverty alleviation, and knowledge as key determinants of the improvement of MCH services. CONCLUSION: The project intervention is effective in improving MCH services. However, more attentions to poverty alleviation and health promotion need to be paid.

[Anteroposterior cricoid split interposition grafting for severe glottic and subglottic stenosis].

OBJECTIVE: To study the effect of anterior and posterior cricoid splitting interposition grafting for severe glottic and subglottic stenosis. METHODS: This is a retrospective study, from 1991 to 2001 years, 25 patients (male 15, female 10, aged 9 to 46 years) with severe glottic and subglottic stenosis were operated with anterior and posterior cricoid splitting interposition grafting method at Tangdu Hospital. All of 25 patients were tracheostomy dependent before reconstruction. 19 patients had previously undergone 1 to 7 (average 2) surgical procedures. The surgical technique consisted of laryngotracheostomy, cricoid lamina midline vertical incision; rib cartilage graft (17 cases), muscular fasciae, perichondrium or split-thickness skin graft (15 cases), pedicle arytenoid cartilage graft (2 cases) and thyroid cartilage graft (1 case) interposition and silicon T-tube stenting for 3 to 6 months. RESULTS: Twenty-four patients (96%) were successfully decannulated and got an effective phonation. One patient failed decannulation. The follow-up period ranged from 1 to 10 years. All of the 24 patients had a stable airway and effective phonation. CONCLUSIONS: The anteroposterior cricoid split interposition graft technique was a safe and effective method for the treatment of severe glottic and subglottic stenosis. Careful split of the cricoid, avoiding injury of esophageal musculature, careful hemostasis, a tight suture graft and using stent were the keys of successful operation.