Diagnostic and Prognostic Value Analysis of miR-206 in Asymptomatic Carotid Artery Stenosis.

Introduction: To investigate the expression level of miR-206 in serum of patients with asymptomatic carotid artery stenosis (CAS) and estimate the value of miR-206 in the diagnosis and prognosis of asymptomatic CAS. Methods: A total of 206 individuals enrolled in this study, including 105 CAS patients and 101 controls. RT-qPCR technology was applied to measure the relative level of miR-206, and Pearson's correlation coefficient was performed to analyze the relationship between carotid artery stenosis degree and miR-206 level. An ROC curve was drawn to assess the diagnostic value of miR-206 in asymptomatic CAS. The 5-year prognosis of asymptomatic CAS patients was tested using multivariate Cox regression analysis and Kaplan-Meier survival curve. Results: MiR-206 expression was reduced in asymptomatic CAS patients. The AUC of the ROC curve of miR-206 was 0.939, with a sensitivity of 86.70% and a specificity of 86.14%. The amount of CAS gradually increased with the decrease of miR-206 level. Seven-teen patients in the low miR-206 expression group developed CIEs, and 3 patients in the high miR-206 expression group developed CIEs during the 5-year follow-up. miR-206 and the amount of CAS were independent factors for the occurrence of CIEs within 5 years in asymptomatic CAS patients. Conclusion: Serum miR-206 has high diagnostic accuracy for asymptomatic CAS and has predictive value for the incidence of CIEs in patients within 5 years.

Formation and Combustion Heat Release of Naphthenic-Based Crude Oil Cokes at Different Reaction Temperatures.

Petroleum cokes prepared from naphthenic crude oil differ significantly in terms of the oxygen content and hydrogen/carbon (H/C) ratio, which mainly depend on the different coking temperatures. Thermogravimetric-differential scanning calorimetry was applied to study the heat release and combustion weight loss of petroleum cokes prepared at 350 and 500 °C, respectively. The effect of different coke formation temperatures on the combustion properties of the coke formed during air injection in situ combustion (ISC) was also investigated. The results showed that the petroleum coke formed under oxygen exhibited an H/C ratio of 0.895 and an O/C ratio of 0.109 at 350 °C and an H/C ratio of 0.395 and an O/C ratio of 0.054 at 500 °C. As the temperature rises, the hydrogen atoms on the petroleum coke molecules intensify to separate and form water molecules and thus giving off heat. It can be further inferred that under the combustion temperature of air injection ISC, the coke at 350 °C can release more heat in the lower combustion temperature range, and the combustion weight loss is faster; however, the formation temperature continues to rise due to combustion at 500 °C, coke begins to release massive heat, and the combustion weight loss is as high as 97.95%. The combustion residuals of both temperature cokes and the residual solid content of the formation after combustion in porous media are both little, which can be used as fire flooding fuels at different formation temperatures to provide heat energy for oil displacement.

13C Solid-State NMR Analysis of the Chemical Structure in Petroleum Coke during Idealized In Situ Combustion Conditions.

Petroleum cokes with different chemical structures and oxygen-containing functional groups were obtained from two kinds of naphthenic- and paraffin-base crude oils by simulating an in situ combustion (ISC) process with the same reaction atmosphere and different reaction temperatures. 13C wide-cavity solid-state nuclear magnetic resonance (13C NMR) spectroscopy was used to identify and investigate the oxygen-containing functional groups of petroleum cokes obtained under different compositions and reaction temperatures. This study demonstrated that with the increase of coking temperature, the content of alkyl side chain and active oxygen-containing functional groups in naphthenic-base crude coke decreased obviously, while the content of aromatic carbon increased. The 13C NMR analysis of the two kinds of petroleum cokes obtained at 500 °C further revealed that the paraffin-base petroleum coke retained a high content of oxygen- and nitrogen-rich functional groups, while the naphthenic-base petroleum coke had a lower amount of carbonyl groups and oxygen-containing functional groups.

New and little known species of Nemouridae (Plecoptera) from Inner Mongolia of China.

Four species of the family Nemouridae, Amphinemura helanshana sp. n., A. didyma Zhu & Yang, Nemoura geei Wu, and Nemoura cf. securigera Klapálek were collected during a two years survey of the Helan Mountains of Inner Mongolia, China. Nemoura cf. securigera has not been collected for more than one hundred years.