The "Pull Effect" of a Hanging ZnII on Improving the Four-Electron Oxygen Reduction Selectivity with Co Porphyrin.

Due to the challenge of cleaving O-O bonds at single Co sites, mononuclear Co complexes typically show poor selectivity for the four-electron (4e-) oxygen reduction reaction (ORR). Herein, we report on selective 4e- ORR catalyzed by a Co porphyrin with a hanged ZnII ion. Inspired by Cu/Zn-superoxide dismutase, we designed and synthesized 1-CoZn with a hanging ZnII at the second sphere of a Co porphyrin. Complex 1-CoZn is much more effective than its Zn-lacking analogues to catalyze the 4e- ORR in neutral aqueous solutions, giving an electron number of 3.91 per O2 reduction. With spectroscopic studies, the hanging ZnII was demonstrated to be able to facilitate the electron transfer from CoII to O2, through an electronic "pull effect", to give CoIII-superoxo. Theoretical studies further suggested that this "pull effect" plays crucial roles in assisting O-O bond cleavage. This work is significant to present a new strategy of hanging a ZnII to improve O2 activation and O-O bond cleavage.

Switching Electrocatalytic Hydrogen Evolution Pathways through Electronic Tuning of Copper Porphyrins.

The electronic structure of metal complexes plays key roles in determining their catalytic features. However, controlling electronic structures to regulate reaction mechanisms is of fundamental interest but has been rarely presented. Herein, we report electronic tuning of Cu porphyrins to switch pathways of the hydrogen evolution reaction (HER). Through controllable and regioselective ß-oxidation of Cu porphyrin 1, we synthesized analogues 2-4 with one or two ß-lactone groups in either a cis or trans configuration. Complexes 1-4 have the same Cu-N4 core site but different electronic structures. Although ß-oxidation led to large anodic shifts of reductions, 1-4 displayed similar HER activities in terms of close overpotentials. With electrochemical, chemical and theoretical results, we show that the catalytically active species switches from a CuI species for 1 to a Cu0 species for 4. This work is thus significant to present mechanism-controllable HER via electronic tuning of catalysts.

Proton-Coupled Electron Transfer in Electrocatalytic Water Splitting.

Proton-coupled electron transfer (PCET) plays a crucial role in a diverse array of natural and artificial energy conversion processes. Herein, we will introduce the fundamentals of electrochemical PCET with a focus on its role in water splitting. Besides, perspectives of future development of PCET are presented with regard to the investigation of reaction mechanisms and the design of advanced electrocatalysts.

Coordination Tuning of Metal Porphyrins for Improved Oxygen Evolution Reaction.

The nucleophilic attack of water or hydroxide on metal-oxo units forms an O-O bond in the oxygen evolution reaction (OER). Coordination tuning to improve this attack is intriguing but has been rarely realized. We herein report on improved OER catalysis by metal porphyrin 1-M (M=Co, Fe) with a coordinatively unsaturated metal ion. We designed and synthesized 1-M by sterically blocking one porphyrin side with a tethered tetraazacyclododecane unit. With this protection, the metal-oxo species generated in OER can maintain an unoccupied trans axial site. Importantly, 1-M displays a higher OER activity in alkaline solutions than analogues lacking such an axial protection by decreasing up to 150-mV overpotential to achieve 10 mA/cm2 current density. Theoretical studies suggest that with an unoccupied trans axial site, the metal-oxo unit becomes more positively charged and thus is more favoured for the hydroxide nucleophilic attack as compared to metal-oxo units bearing trans axial ligands.

Energy consumption and pollutant emission of diesel-fired combustion from 2009 to 2018 in Beijing, China.

Diesel-fired combustion is one of the main sources of air pollution in the world. In this study, to better understand the energy consumption and main air pollutant emissions of diesel-fired combustion, a practical investigation and historical data analyses were conducted to determine the variations and driving forces of diesel consumption, the distribution of diesel consumption, and the contribution of emissions among various industries. Based on the results of this study, future control measures can be proposed for diesel-fired combustion. The results show that economic development led to an increase in the total volume of passengers and freight transportation, and the number of diesel vehicles increased from 0.16 million in 2009 to 0.25 million in 2018. However, diesel consumption in Beijing decreased from 2.4 Mt in 2009 to 1.8 Mt in 2018 due to the dominant driving forces, such as structural optimization of the diesel vehicle fleet and stricter limit standards for single-vehicle fuel consumption. The use of diesel vehicles in the logistics and transportation industries and the use of diesel-fired machinery in the construction industry were the two main sources of diesel consumption, accounting for 55% and 23% of the total, respectively. The main air pollutant emissions from diesel-fired combustion from 2009 to 2018 first increased and then decreased, while the NOX emissions peaked at 74,800 tons in 2014, which was affected by the structural optimization of the vehicle fleet and the elimination of old diesel trucks. The emissions finally decreased to 54,000 tons in 2018, which was approximately 89% of the amount in 2009. However, the continuously increasing contribution of diesel combustion to the total emissions requires more attention. The electrification of diesel vehicles and the structural upgrading of diesel vehicles have played important roles in mitigating the emissions of diesel combustion. Our study suggests that consumption control targets should be set, reduction plans for key industries such as the logistics and transportation, construction, and tourism industries should be developed, and low-emission zones should be created to promote the elimination and updating of low-emission diesel vehicles and machinery.

Accuracy of triage strategies for human papillomavirus DNA-positive women in low-resource settings: A cross-sectional study in China.

OBJECTIVE: CareHPV is a human papillomavirus (HPV) DNA test for low-resource settings (LRS). This study assesses optimum triage strategies for careHPV-positive women in LRS. METHODS: A total of 2,530 Chinese women were concurrently screened for cervical cancer with visual inspection with acetic acid (VIA), liquid-based cytology and HPV testing by physician- and self-collected careHPV, and physician-collected Hybrid Capture 2 (HC2). Screen-positive women were referred to colposcopy with biopsy and endocervical curettage as necessary. HPV-positivity was defined as ≥1.0 relative light units/cutoff (RLU/CO) for both careHPV and HC2. Primary physician-HC2, physician-careHPV and self-careHPV and in sequential screening with cytology, VIA, or increased HPV test-positivity performance, stratified by age, were assessed for cervical intraepithelial neoplasia (CIN) grade 2/3 or worse (CIN2/3+) detection. RESULTS: The sensitivities and specificities of primary HPV testing for CIN2+ were: 83.8%, 88.1% for physician-careHPV; 72.1%, 88.2% for self-careHPV; and 97.1%, 86.0% for HC2. Physician-careHPV test-positive women with VIA triage had a sensitivity of 30.9% for CIN2+ versus 80.9% with cytology triage. Self-careHPV test-positive women with VIA triage was 26.5% versus 66.2% with cytology triage. The sensitivity of HC2 test-positive women with VIA triage was 38.2% versus 92.6% with cytology triage. The sensitivity of physician-careHPV testing for CIN2+ decreased from 83.8% at ≥1.0 RLU/CO to 72.1% at ≥10.00 RLU/CO, while the sensitivity of self-careHPV testing decreased from 72.1% at ≥1.0 RLU/CO to 32.4% at ≥10.00 RLU/CO; similar trends were seen with age-stratification. CONCLUSIONS: VIA and cytology triage improved specificity for CIN2/3 than no triage. Sensitivity with VIA triage was unsuitable for a mass-screening program. VIA provider training might improve this strategy. Cytology triage could be feasible where a high-quality cytology program exists. Triage of HPV test-positive women by increased test positivity cutoff adds another LRS triage option.

[A prospective study on the prognosis of biopsy-confirmed cervical intraepithelial neoplasia grade 1 and the relationship with high-risk human papillomavirus].

OBJECTIVE: To evaluate the prognosis of cervical intraepithelial neoplasia grade 1 (CIN1) at different follow-up time points in Chinese women and the relationship with high-risk human papillomavirus (HR-HPV) infection. METHODS: Biopsy-confirmed CIN1 women were followed up from cervical cancer screening cohorts established during 1999 to 2008 in Xiangyuan county, Yangcheng county, Qinxian county and Wuxiang county, Shanxi Province.In each follow-up visit, participants were examined by visual inspection with acetic acid, liquid-based cytology and HR-HPV DNA testing. Those with any positive results received colposcope and biopsies. The cumulative incidence rates of CIN grade 2 or worse (CIN2+) and CIN grade 3 or worse (CIN3+), regression rates and persistent rates were calculated using pathological findings as a gold standard. The risks of progression related with HR-HPV were evaluated stratified by baseline and follow-up HR-HPV status. RESULTS: A total of 228, 224, 261 and 105 CIN1 women received the 1-year, 2-year, 6-year and 11-year follow-up exams, respectively. The cumulative incidence rate of CIN2+ among baseline HR-HPV positive women was 4.8% (6/126), 10.7% (16/150), 16.9% (29/172) and 35% (19/55) in the above follow-up visits, respectively, and their risk of progression was 2.7(95%CI:0.3-22.0), 2.9 (95%CI:0.7-12.1), 12.0 (95%CI:1.7-86.2) and 30.6 (95%CI:1.9-493.5) times higher than baseline HR-HPV negative women. Moreover, the cumulative incidence of CIN2+ among women with positive HR-HPV both at baseline and follow-up visit was 11% (6/55), 14% (6/42), 17% (10/60) and 50% (13/26) in the above follow-up visits, respectively.No new CIN2+ cases were found among those with negative HR-HPV both at baseline and follow-up visits. CONCLUSION: Given that CIN1 progression is related to HR-HPV infection, different follow-up intervals and strategies for CIN1 should be taken according to HR-HPV infection status.

Research on Damage Evolution Law of Glazed Hollow Beads-Cement/Sodium Silicate Grouting Materials under Different Cycles of Loading and Unloading.

With the depletion of shallow resources, deep resource mining has become a trend. However, the high temperature and complex stress environment in deep mines make resource extraction extremely challenging. This paper developed a thermal insulation grouting material made of glazed hollow beads, sodium silicate, and cement and tested the compressive strength, gelation time, and stone rate under various curing days in light of the issue of high temperature heat damage in high ground temperature mines and the impact of mining on roadway grouting bolt support. Fatigue strength, fatigue deformation, load-residual strain, energy evolution and microscopic features were studied and analyzed in relation to the damage law of graded cyclic loading and unloading under the number of varying cycles. The findings demonstrate that cyclic loading and unloading strength is lower than uniaxial compressive strength. The fatigue strength is significantly decreased when the number of cycles reaches its limit. Residual strain is less sensitive to changes in stress than load strain. The fitting correlation coefficients of total output energy and elastic energy are higher than 0.71.

Electrocatalytic hydrogen evolution with a copper porphyrin bearing meso-(o-carborane) substituents.

A newly designed copper complex of 5,15-bis(pentafluorophenyl)-10,20-bis(o-carborane)porphyrin (1) was synthesized and tested for the electrocatalytic hydrogen evolution reaction (HER). In acetonitrile, 1 was much more efficient than Cu 5,15-bis(pentafluorophenyl)-10,20-diphenylporphyrin (2) for electrocatalytic HER by shifting the catalytic wave to the anodic direction by 190 mV. In aqueous media, 1 also outperformed 2 by achieving higher current densities under smaller overpotentials. This enhancement was attributed to the aromatic and the strong electron-withdrawing properties of o-carborane groups. This work is significant to address the crucial effects of meso-(o-carborane) substituents of metal porphyrins on boosting the electrocatalytic HER.

Non-negligible Axial Ligand Effect on Electrocatalytic CO2 Reduction with Iron Porphyrin Complexes.

Iron(III) porphyrin complexes have been demonstrated as one of the efficient molecular catalysts for the electrochemical reduction of CO2. However, the role of axial ligands coordinated with a metal center in the complex on the electrochemical CO2 reduction activity has not been fully explored yet. Herein, iron(III) tetraphenylporphyrin thiocyanate (FeTPP-SCN) is synthesized from a commercially available catalyst of FeTPP-Cl by a counteranion exchanging reaction. Cyclic voltammetry measurements showed that the catalytic activity of FeTPP-SCN is noticeably suppressed in the DMF solutions. The structural dynamics of the axial ligand in FeTPP-SCN are further examined by the FTIR and ultrafast IR spectroscopies, where the SCN ligand is employed as the local vibrational probe. Vibrational relaxation measurements showed that the reorientational dynamics of SCN ligands was strongly restricted in DMF solution, suggesting that the subtle electrostatic interaction between the ligands and metal center in the complex can have a non-negligible effect on its catalytic activity.

GATA-4-expressing mouse bone marrow mesenchymal stem cells improve cardiac function after myocardial infarction via secreted exosomes.

This study aimed to investigate whether exosomes secreted by mouse GATA-4-expressing bone marrow mesenchymal stem cells (BMSCs) could induce BMSC differentiation into myocyte precursors, decrease cardiomyocyte apoptosis, and improve cardiac function following myocardial infarction (MI). BMSCs were transduced with a lentivirus carrying a doxycycline (DOX)-inducible GATA-4 or control lentivirus, and secreted exosomes from these BMSCs were collected and co-cultured with BMSCs or cardiomyocytes under hypoxic and serum free conditions. Furthermore, exosomes were injected into mice 48 h after MI. Cardiac function was evaluated by echocardiography at 48, 72, and 96 h after exosome treatment. Quantitative PCR showed that co-culture of BMSCs with GATA-4-BMSC exosomes increased cardiomyocyte-related marker expression. Co-culture of GATA-4-BMSC exosomes with cardiomyocytes in anoxic conditions decreased apoptosis as detected by flow cytometry. Injection of GATA-4-BMSC exosomes in mice 48 h after MI increased cardiac function over the next 96 h; increased cardiac blood vessel density and number of c-kit-positive cells and decreased apoptotic cardiomyocyte cells were also observed. Differential expression of candidate differentiation- and apoptosis-related miRNAs and proteins that may mediate these effects was also identified. Exosomes isolated from GATA-4-expressing BMSCs induce differentiation of BMSCs into cardiomyocyte-like cells, decrease anoxia-induced cardiomyocyte apoptosis, and improve myocardial function after infarction.