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The corrosion behavior of the Xinjiang oil field (China) gathering pipeline steel was studied by a weight-loss technique, microscopic characterization, an X-ray diffractometer, and a three-dimensional microscope. When the CO2/O2/H2S system contains a low H2S concentration (100 ppm), the CO2 and O2 concentrations increase and the corrosion rate of 20# steel increases. When the CO2 concentration increases (10–30%), the corrosion rate increases by 8.84%, and the corrosion product film thickness increases significantly by 231.01%, while when the O2 concentration increases (0.5–2.5%), the corrosion rate increases by 29.24%, and the thickness of the product film increased by 29.21%. The two mechanisms that promote the increase in the corrosion rate are different. CO2 promotes the cathodic reaction to increase the corrosion rate, while O2 accelerates the corrosion process by destroying the structure of the corrosion film. The morphology of corrosion products is more complex. The increase in O2 concentration increases the number of corrosion defects, and the change in CO2 concentration has little effect on local corrosion. The corrosion products mainly include FeCO3, Fe2O3, and FeS2, but S and FeS are not formed. The reason is that CO2 controls the corrosion process, and a large amount of O2 is consumed, which weakens the interaction between H2S and O2. [ABSTRACT FROM AUTHOR]

Multi-component thermal fluid flooding is an efficient thermal technology for heavy oil recovery. However, the oil and gas transported by the gathering pipeline exhibit the large temperature difference along with high O2, H2S and CO2 contents, which may easily bring serious corrosion problems to the pipeline. In this article, the present work aims to study corrosion behavior and corrosion mechanisms in a CO2/H2S/O2 coexistence system using a Huning 4 block gathering pipeline material, particularly clarifying the influence of temperature on the corrosion behavior and localized corrosion mechanism. The high-temperature autoclave was used to simulate the corrosion environments. The corrosion products at various temperatures were examined via three-dimensional optical microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The maximum uniform corrosion rate of L245NS is 0.5149 mm/a (at 333 K), and the maximum local corrosion rate is 4.6258 mm/a (at 363 K). At lower temperatures (303–333 K), the corrosion product film possessed a double-layered membrane, where the bottom layer was enriched with S-based elements, mainly FeS or FeS2 and the upper layer was mainly covered by FeCO3 with the uniform corrosion state. Applying the higher temperatures (363–393 K) made the FeCO3 grain coverage more continuous and dense, leading to the formation of a dense double-layered film, where the uniform corrosion was suppressed, while localized corrosion emerged. The thermodynamics shows that an increase in the temperature was found to decrease the solubility product coefficient of FeS and FeCO3, inducing the appearance of a protective layer and inhibiting the corrosion process. [ABSTRACT FROM AUTHOR]

In this paper, the issue of fixed-time cluster synchronization is investigated for the directed community networks. We propose a new Lyapunov function method which leads to the settling time is not only independent of the initial value, but also unrelated to the number and dimensions of nodes in the networks. This means our estimated settling time is more accurate and much tighter than the one in the existing results. By designing the corresponding controllers and using the fixed-time stability theorem, some new criteria are derived to guarantee that the community networks achieve cluster synchronization in fixed time. Finally, an illustrative example with computer simulations is given to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

The aim of this work was to understand the synergistic effect of O2 and H2S on the corrosion behavior of N80 steel in a simulated high-pressure flue gas injection system. Weight loss measurements show that the presence of O2 and an increase in temperature significantly accelerated the general corrosion rate of the N80 steel. We calculated a gray relational grade between different impact factors and the general corrosion rate from the results of an orthogonal experimental corrosion rate. The grade ranking of impact factors was: O2 concentration (0.817) > temperature (0.706) > total pressure (0.689) > H2S concentration (0.665) > CO2 concentration (0.517). Surface characterization of corrosion scales was done using scanning electron microscopy, energy-dispersive spectroscopy, x-ray powder diffraction, and 3D optical microscope analysis. The results show that in the O2-H2S-CO2-H2O coexistence system the products were composed mainly of FeCO3, FeS, Fe2O3, Fe3O4, and elemental sulfur. The results of the corrosion rate test and the characterization show that the presence of O2 greatly accelerated the corrosion process and changed the corrosion mechanism. Elemental sulfur, which was generated by the reaction between the H2S and the O2, participated in the corrosion process of the N80 steel. It could be considered that the synergistic effect of O2 and H2S accelerated the corrosion of the N80 steel. In addition, the porous structures of the corrosion scales and the severe local pits show that the high content of O2 inhibited the formation of FeCO3 and aggravated the corrosion of N80 steel. [ABSTRACT FROM AUTHOR]

Macrolide antibiotics are lipophilic drugs with some limitations including low solubility, limited cellular permeation, patients discomfort, etc. With amphiphilic methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-PCL) copolymer and azithromycin (AZT) as drug carrier and model drug, AZT-loaded micelles were prepared via thin-membrane hydration method in order to overcome these limitations. Encapsulation efficiency of AZT-loaded micelles was 94.40% with good storage stability for 28 days, and AZT’s water solubility was enhanced to 944 μg/mL. Fourier transform infrared spectrum and x-ray diffraction analysis indicated that AZT was enveloped into the micelles in amorphous form due to its interaction with the copolymer. AZT’s in vitro release from the AZT-loaded micelles demonstrated a slow and continuous behavior when compared with raw AZT. The release dynamics was accorded with Weibull equation, meaning that release amount of AZT lowered with time and was proportional to remaining amount of drug in the AZT-loaded micelles. Korsmeyer-Peppas fitting result suggested that drug release process was a classical Fickian diffusion-controlled manner. With Staphylococcus aureus as bacterial strain, antibacterial activity of the AZT-loaded micelles displayed was comparable with raw AZT. In conclusion, MPEG-PCL should be a promising carrier for macrolide antibiotic delivery in treatment of bacterial infections. [ABSTRACT FROM AUTHOR]

Apple-derived porous carbon (denoted as APC) is successfully prepared and analyzed as a potential carbon material by hydrothermal carbonization and pyrolysis, which exhibits a high specific surface area and porous structure. Furthermore, nickel-cobalt double hydroxide (Ni-Co DH) is synthesized by design of hybrid nanowires on APC for supercapacitors via a simple hydrothermal process. The fabricated electrode produces a capacitance of 1519 F g at 1 A g, and 90.2% of the capacitance is retained after 2000 cycles at a high current density. An asymmetric supercapacitor (ASC) is assembled using the Ni-Co DH@APC as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 61.2 Wh kg and high power density of 14,400 W kg at 5 A g. The desirable electrochemical performance can be attributed to the suitability of APC as a support and the Ni-Co nanostructure constructed on the surface of APC as an effective active material for high-energy and long-life cycling supercapacitor applications. The fabricated composite provides a potential design of low-cost functional carbon materials that can be produced in large scale by using biomass as starting materials. [ABSTRACT FROM AUTHOR]

Curcumin (CUR) is a hydrophobic polyphenol with anti-inflammatory activity. However, its low water-solubility and poor skin permeation limited its application in the treatment of dermititis. CUR-loaded micelles were prepared using thin membrane hydration method with methoxy poly (ethylene glycol)-block-poly (ε-caprolactone) (MPEG-PCL) as carrier material. The drug loading capacity and encapsulation efficiency were 12.14 ± 0.33 and 93.57 ± 1.67%, respectively. CUR-loaded micelles increased CUR's water-solubility to 1.87 mg/mL, being 1.87 × 106-folds higher than native CUR. CUR-loaded supramolecular hydrogels (CUR-H) were prepared through mixing the CUR-loaded micelles solution with α-cyclodextrin (α-CD) solution. The CUR-H presented continuous dissolution behaviour in aqueous medium for 4.5 h. The ex vivo skin permeation test and confocal fluorescence microscopy evaluation confirmed that CUR-H obviously enhanced skin deposition of CUR without drug flux from skin. In vivo experimental results confirmed that the CUR-H was more effective than dexamethasone ointments against croton oil-induced ear edema. The CUR-H composed of MPEG-PCL and α-CD is a promising formulation for skin inflammatory treatment. [ABSTRACT FROM AUTHOR]

To overcome honokiol’s poor water solubility and investigate its antifungal activity and pharmacokinetic property, Pluronic® F-127 (F127)-cyclodextrin conjugate was synthesized and employed to prepare honokiol-loaded micelles through emulsion-solvent evaporation method. The drug-loaded micelles were obtained with 92.30 ± 3.28% of encapsulation efficiency being higher than that obtained from F127 due to additional cyclodextrin inclusion. Fourier transformation infrared spectrometry and diffraction scanning calorimetry analysis tests demonstrated that honokiol was successfully encapsulated into the conjugate micelles in the amorphous or solid solution state because of their interactions. Meanwhile, in vitro antifungal activity experiment indicated that the MIC90 of drug-loaded micelles was 64 μg/mL, showing the same antifungal activity as pure honokiol although it obviously retarded honokiol’s release. In vivo pharmacokinetic results confirmed that in vivo area under curve and apparent distribution volume of honokiol in drug-loaded micelles were 2- and 1.69-folds higher than that for pure honokiol, with its obvious prolonged mean retention time and half-life period, respectively. The clearance rate of honokiol was also shortened about 2-fold in comparison with pure honokiol when encapsulated into the micelles. These results suggest that the developed F127-cyclodextrin micellar formulation is a promising drug delivery system for antifungal drugs.ᅟ [ABSTRACT FROM AUTHOR]