Elucidating the Mechanistic Origin of a Spin State-Dependent FeNx-C Catalyst toward Organic Contaminant Oxidation via Peroxymonosulfate Activation.

Atomically dispersed metals on nitrogen-doped carbon matrices have attracted extensive interest in the removal of refractory organic pollutants. However, a thorough exploration of the particular structure for each active site and specific effects of these sites still remains elusive. Herein, an Fe-pyridinic N4 structure in a single-atom catalyst (FeNx-C) was constructed using a facile pyrolysis strategy, and it exhibited superior catalytic activity in peroxymonosulfate (PMS) activation toward organic contaminant oxidation. The various Fe species and relative amounts of each Fe site in the FeNx-C catalyst were validated using X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy, which showed critical dependencies on the precursor ratio and calcination temperature. The positive correlations between relative content of high-spin state species (FeII and FeIII) and catalytic performance were found to determine the reactive species generation and electron transfer pathway in the FeNx-C/PMS system. Moreover, catalytic performance and theoretical calculation results revealed that FeII-N4 in the high-spin state (S = 2) tends to activate PMS to form sulfate and hydroxyl radicals via a one-electron transfer process, while the FeIII-N4 moiety (S = 5/2) is prone to high-valent iron species generation with lower free energy. Benefiting from finely tuned active sites, a single-atom FeNx-C catalyst achieved favorable applicability in actual wastewater treatment with efficient resistance of the common water matrix. The present work advances the mechanistic understanding of spin state-dependent persulfate activation in single-atom catalysts and provides guidance to design a superior catalyst based on spin state descriptions.

Highly active and stable Ir nanoclusters derived from Ir1/MgAl2O4 single-atom catalysts.

Single-atom catalysts (SACs) prepared by the atom trapping method often possess high stability yet have limited advantages regarding catalytic performance due to the strong metal-support interaction. Using these SACs as seeds to develop supported nanoclusters or nanoparticles has, however, been proven to be effective in improving the catalysts' intrinsic activity. Herein, we have prepared extremely stable Ir SACs supported by MgAl2O4 via atomic trapping and used them as seeds to fabricate highly active and stable Ir nanocluster catalysts by high-temperature reduction. The activity toward N2O decomposition increased by more than ten times compared with that of the parent Ir SACs. This study provides a new avenue to design and develop highly active and stable catalysts for industrial use.

Islet microvasculature in islet hyperplasia and failure in a model of type 2 diabetes.

Gene expression profiling of islets from pre-diabetic male Zucker diabetic fatty (ZDF) rats showed increased expression of hypoxia-related genes, prompting investigation of the vascular integrity of the islets. The islet microvasculature was increased approximately twofold in young male ZDF rats by both morphometric analysis and quantifying mRNA levels of endothelial markers. ZDF rats at 12 weeks of age showed a significant reduction in the number of endothelial cells, which was prevented by pretreatment with pioglitazone. Light and electron microscopy of normoglycemic 7-week-old ZDF rats showed thickened endothelial cells with loss of endothelial fenestrations. By 12 weeks of age, there was disruption of the endothelium and intra-islet hemorrhage. Islets from 7- and 12-week-old ZDF rats showed an approximate three- and twofold increase in vascular endothelial growth factor (VEGF)-A mRNA and VEGF protein secretion, respectively, compared with lean controls. Thrombospondin-1 mRNA increased in 7- and 12-week-old rats by 2- and 10-fold, respectively, and was reduced by 50% in 12-week-old rats pretreated with pioglitazone. Islets from young male control rats induced migration of endothelial cells in a collagen matrix only after pretreatment with matrix metalloproteinase (MMP)-9. Islets from 7-week-old ZDF rats showed a fivefold increase in migration score compared with wild-type controls, even without MMP-9 treatment. Islets from 15-week-old ZDF rats did not induce migration; rather, they caused a significant rounding up of the duct-derived cells, suggesting a toxic effect. These data suggest that in the ZDF rat model of type 2 diabetes, an inability of the islet to maintain vascular integrity may contribute to beta-cell failure.

Long-term results of patients with head injuries treated in different hospitals after the Wenchuan, China, earthquake.

OBJECTIVE: To present an overview of mortality, disability, and depression among patients with head injuries admitted to multiple center hospitals after the 2008 Wenchuan earthquake in China. METHODS: A retrospective analysis was done of the medical records of earthquake victims with head traumas admitted to three different area hospitals; analysis included 18 months of follow-up. Demographic data, causes of injury, diagnosis, clinical classification, treatment, and prognosis were reviewed. RESULTS: This analysis included 1299 victims with craniocerebral injuries admitted to eight hospitals in or near the disaster zone. The victims were divided into three main groups. Group A comprised 68 victims treated in the local hospital; all 68 (100%) were hospitalized during the 24 hours after the earthquake, and 38 (55.88%) victims died 18 months later. Group B comprised 600 victims treated in regional hospitals; 264 (44%) were admitted within 72 hours after the earthquake, and 109 (18.17%) died. Group C comprised 631 victims transported to territory hospitals; 39 (6.18%) were dead at 18 months. Among survivors, 409 (31.48%) victims sustained a disability, and 879 (80.35%) have depression. CONCLUSIONS: In the first 72 hours after this major earthquake, the local and regional hospital neurosurgery departments were flooded with numerous victims with craniocerebral injuries. Most of these patients died or were disabled. The territory hospitals with expert neurosurgeons and advanced equipment did not effectively contribute to successful treatment of victims. The mobile hospital played an important role in initial triage and treatment.