A sample of kerogen isolated from Huadian oil shale was studied using a combination of solid-state 13 C NMR, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) techniques to evaluate its structural characteristics. 13 C NMR results indicate that the carbon skeletal structure of this kerogen is mainly composed of a fairly high fraction of aliphatic carbon (86.1%), with a very low aromaticity (f a ) of 9.7%; methylene (CH 2 ) carbons dominate in all types of aliphatic carbons and the majority of them exist as many long straight chains but not saturated alicyclics. The average methylene carbon chain length (C n ) is between 12 and 24. There are only one fused aromatic ring (e.g., naphthalene) or two single aromatic rings (one benzene ring and one penta-heterocycle) per 100 carbon atoms. However, aromatic rings in this kerogen have a very high value of substitutive degree (δ = 0.42À0.75). Furthermore, XRD analysis suggests that most methylene straight chains and aromatic carbons can not form crystalline but amorphous structure and are linked to each other by various bridge bonds and methylene (CH 2 ) chains. FT-IR, XPS, and 13 C NMR results show that organic oxygen in the kerogen exists as mainly three types of oxygen functional groups. Both XPS and 13 C NMR results agree on the same ordering of their respective contents: CÀO and CÀOH groups are dominant, followed by OdCÀO, and CdO or OÀCÀO groups. The 13 C NMR results further suggest that more oxygen of CÀO and CÀOH groups is bound to aromatic carbons. XPS shows that over half the total amount of organic nitrogen in Huadian kerogen exists as aromatic heterocycles, which concludes pyrrolic nitrogen richest in total organic nitrogen, pyridinic, and protonated-pyridinic forms. A relatively high content of amino nitrogen over 30 mol % also is present in this kerogen, which is much higher than that of other same type kerogens. Organic sulfur is distributed in this kerogen as aromatic and aliphatic sulfur, sulfone, and sulfoxide in the order of the relative mole fraction.

MC is a common disease process. Female gender, increased age, and the use of PPIs and SSRIs are associated with a significantly increased risk of developing MC. Further work is needed to evaluate reported data from developing countries and to elucidate the biologic mechanisms behind the risk factors for MC.

The endogenous vasodilator nitric oxide (NO) is metabolized in tissues in an O2-dependent manner. In skeletal and cardiac muscle, high concentrations of myoglobin (Mb) function as a potent NO scavenger. However, Mb concentration is very low in vascular smooth muscle where low concentrations of cytoglobin (Cygb) may play a major role in metabolizing NO. Questions remain regarding how low concentrations of Cygb and Mb differ in their NO metabolism and the basis for their different cellular roles and functions. In this study, electrode techniques were applied to perform comparative measurements of the kinetics of NO consumption by Mb and Cygb. UV/Vis spectroscopic methods and computer simulations were performed to study the reaction of Mb and Cygb with ascorbate (Asc) and the underlying mechanism. It was observed that the initial rate of Cygb3+ reduction by Asc was 415-fold greater than that of Mb3+. In the low [O2] range (0-50 μM), Cygb-mediated NO consumption rate is ~500 times more sensitive to changes in O2 concentration than that of Mb. The reduction of Cygb3+ by Asc follows a reversible kinetic model while its reduction of Mb3+ is irreversible. A reaction mechanism for Cygb3+ reduction by Asc was proposed and the reaction equilibrium constants determined. Our results suggest that the rapid reduction of Cygb by cellular reductants enables Cygb to efficiently regulate NO metabolism in the vascular wall in an oxygen-dependent manner, while the slow rate of Mb reduction does not provide this oxygen dependence.