Search

The coordination of tBuNC and CO with the diarsenido complexes (C5 Me5 )2 An(η2 -As2 Mes2 ), An=Th, U, has been investigated. For the first time, a comparison between isostructural complexes of ThIV and UIV has been possible with CO; density functional calculations indicated an appreciable amount of π backbonding that originates from charge transfer from an actinide-arsenic sigma bond. The calculated CO stretching frequencies in the ThIV and UIV diarsenido complexes are consistent with the experimental measurements, both show large shifts to lower frequency. We demonstrate that the π backbonding is crucial to explaining the red shifts of CO frequency upon AnIV complex formation. Interestingly, this interaction essentially correlates to the parallel orientation of π*(C-O) orbitals relative to the An-As bond.

The growth of ZnO clusters supported by ZnO‐bilayers on Ag(111) and the interaction of these oxide nanostructures with water have been studied by a multi‐technique approach combining temperature‐dependent infrared reflection absorption spectroscopy (IRRAS), grazing‐emission X‐ray photoelectron spectroscopy, and density functional theory calculations. Our results reveal that the ZnO bilayers exhibiting graphite‐like structure are chemically inactive for water dissociation, whereas small ZnO clusters formed on top of these well‐defined, yet chemically passive supports show extremely high reactivity ‐ water is dissociated without an apparent activation barrier. Systematic isotopic substitution experiments using H2 16O/D2 16O/D2 18O allow identification of various types of acidic hydroxyl groups. We demonstrate that a reliable characterization of these OH‐species is possible via co‐adsorption of CO, which leads to a red shift of the OD frequency due to the weak interaction via hydrogen bonding. The theoretical results provide atomic‐level insight into the surface structure and chemical activity of the supported ZnO clusters and allow identification of the presence of under‐coordinated Zn and O atoms at the edges and corners of the ZnO clusters as the active sites for H2O dissociation., Chemical nature of small ZnO clusters: The combined infrared reflection absorption spectroscopy (IRRAS) and theoretical results reveal that the Ag(111)‐supported graphitic ZnO bilayers are chemically inactive. Significant activity is observed when small ZnO clusters are supported by these bilayers. This apparently barrier‐free water dissociation takes place at under‐coordinated Zn and O atoms at the edges and corners of the ZnO nanostructures. Various acidic hydroxyl species are identified by isotopic substitution experiments and the formation of weak H bonds to coadsorbed CO molecules.

Potential underlying molecular mechanisms for uric acid-induced lipid metabolic disturbances had not been elucidated clearly. This study investigated the effects and underlying mechanisms of uric acid on the development of lipid metabolic disorders. We collected blood samples from 100 healthy people and 100 patients with hyperuricemia for whom serum lipid analysis was performed. Meanwhile, a mouse model of hyperuricemia was generated, and lipidomics was performed on liver tissues, comparing control and hyperuricemia groups, to analyze lipid profiles and key metabolic enzymes. Uric acid directly induced serum lipid metabolic disorders in both humans and mice based on triglycerides, total cholesterol, and low-density lipoprotein cholesterol. Through lipidomic analysis, 46 lipids were differentially expressed in hyperuricemic mouse livers, and the phosphatidylcholine composition was altered, which was mediated by LPCAT3 upregulation. High-uric acid levels-induced p-STAT3 inhibition and SREBP-1c activation in vivo and in vitro. Moreover, LPCAT3-knockdown significantly attenuated uric acid-induced p-STAT3 inhibition, SREBP-1c activation, and lipid metabolic disorders in L02 cells. In conclusion, uric acid induces lipid metabolic disturbances through LPCAT3-mediated p-STAT3 inhibition and SREBP-1c activation. LPCAT3 could be a key regulatory factor linking hyperuricemia and lipid metabolic disorders. These results might provide novel insights into the clinical treatment of hyperuricemia.

Aim Renal thrombotic microangiopathy (TMA) is a common pathological manifestation of Castleman's disease (CD)-associated renal lesions. Increased level of plasma vascular endothelial growth factor (VEGF) has been shown in single-case reports. We aimed to investigate the dysregulation of VEGF in the pathogenesis of CD-associated TMA-like lesions (CD-TMA) in a larger cohort. Methods Nineteen patients with clinico-pathologically diagnosed CD with renal involvement were enrolled. Ten patients with pregnancy TMA or TMA of unknown reasons were enrolled as TMA control group. The plasma levels of VEGF, soluble Flt-1 and interleukin-6 (IL-6) were detected using enzyme-linked immunosorbent assay kits. The expression of VEGF in the kidney biopsied tissue sections and the lymph node specimens were detected by immunostaining. Results The plasma levels of VEGF and IL-6 levels were the highest in CD-TMA group compared to TMA control group and healthy controls. The levels of plasma VEGF was positively correlated with that of IL-6, and increased expression of VEGF and IL-6 was also observed in the lymph nodes from CD-TMA patients. However, the expression of VEGF in the glomerular podocytes was significantly decreased in CD-TMA group as well as in the TMA control. Conclusion Our findings suggest that renal VEGF expression might be important in the pathogenetic mechanism of CD-associated TMA-like lesions.

An atomic-level understanding of dioxygen activation on metal oxides remains one of the major challenges in heterogeneous catalysis. By performing a thorough surface-science study of all three low-index single-crystal surfaces of ceria, probably the most important redox catalysts, we provide a direct spectroscopic characterization of reactive dioxygen species at defect sites on the reduced ceria (110) and (100) surfaces. Surprisingly, neither of these superoxo and peroxo species was found on ceria (111), the thermodynamically most stable surface of this oxide. Applying density functional theory, we could relate these apparently inconsistent findings to a sub-surface diffusion of O-vacancies on (111) substrates, but not on the less closely packed surfaces. These observations resolve a long standing debate concerning the location of O-vacancies on ceria surfaces and the activation of O2 on ceria powders.

The adsorption of CO₂ on the surface of a CeO₂(110) bulk single crystal was studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The high-quality XPS and C K-edge NEXAFS data show that CO₂ adsorbs as a carbonate species on both fully oxidized CeO₂(110) and partially reduced CeO₂-x(110). No evidence for the formation of a carboxylate intermediate could be found. On the fully oxidized CeO₂(110) substrate, the carbonate decomposes upon heating to above 400 K, leading to the desorption of CO₂. The NEXAFS data reveal the presence of a minor amount of formate (or carboxylate) and bicarbonate species, which are related to reactions of CO₂ with surface hydroxyl groups. In case of the reduced CeO₂-x(110), the carbonate species completely disappear upon heating to temperatures above 500 K. In contrast to conclusions presented in earlier works, the oxidation state of the surface is unchanged, i.e. CO₂ does not re-oxidize the reduced CeO₂-x(110) surface.

Developing the environment-friendly insulation gases to replace sulfur hexafluoride (SF6 ) has attracted considerable experimental and theoretical attentions but without success. A computational methodology was presented herein for prediction on dielectric strength and boiling point of arbitrary gaseous molecules in the purpose of molecular design and screening. New structure-activity relationship (SAR) models have been established by combining the density-dependent properties of the electrostatic potential surface, including surface area and the statistical variance of the surface potentials, with the molecular properties including polarizability, electronegativity, and hardness. All the descriptors in the SAR models were calculated using density functional theory. The substitution effect of SF6 by various functional groups was studied systematically. It was found that CF3 is the most effective functional group to improve the dielectric strength due to the large surface area and polarizability. However, all the substitutes exhibit higher boiling points than SF6 because the molecular hardness decreases. The balance between Er and Tb could be achieved by minimizing the local polarity of the molecules. SF5 CN and SF5 CFO were found to be the potent candidates to replace SF6 in view of their large dielectric strengths and low boiling points. © 2017 Wiley Periodicals, Inc.

The surface atomic arrangement of metal oxides determines their physical and chemical properties, and the ability to control and optimize structural parameters is of crucial importance for many applications, in particular in heterogeneous catalysis and photocatalysis. Whereas the structures of macroscopic single crystals can be determined with established methods, for nanoparticles (NPs), this is a challenging task. Herein, we describe the use of CO as a probe molecule to determine the structure of the surfaces exposed by rod-shaped ceria NPs. After calibrating the CO stretching frequencies using results obtained for different ceria single-crystal surfaces, we found that the rod-shaped NPs actually restructure and expose {111} nanofacets. This finding has important consequences for understanding the controversial surface chemistry of these catalytically highly active ceria NPs and paves the way for the predictive, rational design of catalytic materials at the nanoscale.

Anal cancer is primarily caused by human papillomavirus (HPV) infection in both men and women. However, little is known about the sex differences in the natural history of anal HPV infection in a heterosexual population. From May 2014 to March 2016, perianal/anal canal (PA) swab samples were collected semiannually from 2,302 heterosexual men and 2,371 heterosexual women aged 18-55 years old in Liuzhou, China. The specimens were genotyped for HPV DNA by polymerase chain reaction. The incidence rate ratio (IRR) and clearance rate ratio (CRR) were used to analyze the sex differences of incidence and clearance by Poisson regression, respectively. The incidences of PA oncogenic HPV in men and women were 3.4 per 1,000 person-months and 8.6 per 1,000 person-months, respectively, with an IRR of 0.39 (95% confidence interval (CI), 0.29-0.54 for men versus women) (p < 0.0001). The CRR of PA oncogenic HPV infection for men versus women was 1.54 (95% CI, 1.17-2.03) (p = 0.0022). At 12 months, 44% (20/45) of HPV 16/18 infections among women remained positive, whereas no (0/7) infections persisted among men (p = 0.0350). Both the higher incidence and slower clearance of anal carcinogenic HPV infection among women may lead to a higher burden of anal cancer among women than among men in a heterosexual population.