Influences of Hydrogen Blending on the Joule-Thomson Coefficient of Natural Gas.

Blending hydrogen into the natural gas pipeline is considered as a feasible way for large-scale and long-distance delivery of hydrogen. However, the blended hydrogen can exert major impacts on the Joule-Thomson (J-T) coefficient of natural gas, which is a significant parameter for liquefaction of natural gas and formation of natural gas hydrate in engineering. In this study, the J-T coefficient of natural gas at different hydrogen blending ratios is numerically investigated. First, the theoretical formulas for calculating the J-T coefficient of the natural gas-hydrogen mixture using the Soave-Redlich-Kwong (SRK) equation of state (EOS), Peng-Robinson EOS (PR-EOS), and Benedict-Webb-Rubin-Starling EOS (BWRS-EOS) are, respectively, derived, and the calculation accuracy is verified by experimental data. Then, the J-T coefficients of natural gas at six different hydrogen blending ratios and thermodynamic conditions are calculated and analyzed using the derived theoretical formulas and a widely used empirical formula. Results indicate that the J-T coefficient of the natural gas-hydrogen mixture decreases approximately linearly with the increase of the hydrogen blending ratio. When the hydrogen blending ratio reaches 30% (mole fraction), the J-T coefficient of the natural gas-hydrogen mixture decreases by 40-50% compared with that of natural gas. This work also provides a J-T coefficient database of a methane-hydrogen mixture with a hydrogen blending ratio of 5-30% at a pressure of 0.5-20 MPa and temperatures of 275, 300, and 350 K as a reference and a benchmark for interested readers.

Experimental Study on the Failure Mechanisms in Brittle Shales.

The brittle failure of Chengkou shale occurs throughout the exploration and development processes of hydrocarbons. To investigate the failure mechanisms of Chengkou shale and analyze the associated mechanical behavior such as crack initiation, propagation, and coalescence at different stress levels, a series of laboratory experiments were conducted on servo-controlled triaxial cells equipped with ultrasound monitoring. The experimental results show that key mechanical parameters such as peak stress σp, stress onset of dilation σci, and strain at peak stress εp exhibit nearly linear relationships at various confining pressures. In rock bodies, the wave velocity evolution at different stress levels very consistently reproduces the shape of stress-strain curves, while shear wave velocity v s is more sensitive to crack damage than compressional wave velocity v p. Furthermore, the Hoek-Brown failure criterion has an advantage over the Mohr-Coulomb fracture criterion due to the former's higher correlation coefficient r 2. The wing crack damage models with sandwiched multilayers help explain the mixed tensile and shear failure mechanisms of Chengkou shale. The experimental results provide significant guidance for optimizing the design of drilling and well completion jobs, especially hydraulic fracturing operations, both in Chengkou shale and in other brittle shales around the world.

Insights into the Effect of Spontaneous Fluid Imbibition on the Formation Mechanism of Fracture Networks in Brittle Shale: An Experimental Investigation.

In this paper, the high-temperature/high-pressure triaxial testing system of rocks is used to study the effect of spontaneous fluid imbibition on the formation mechanism of fracture networks, by means of acoustic emission (AE) monitoring and ultrasound measurement. After the water-shale interaction, the rock mechanical parameters such as rock strength, elastic modulus, cohesion, and internal friction angle of shales significantly decrease as the imbibition time increases, indicating that the fluid has a strong influence on the mechanical properties of brittle shales. The stress-strain curves of the wet and dry shales and their AE characteristics are quite different: (i) the stress-strain curve of wet shale samples shows multiple fluctuations before macroscopic failure, and its cumulative AE number curve presents a step-like jump many times that corresponds to the local microcracking; (ii) the stress-strain curve of dry shale samples mainly shows the characteristic of linear elastic deformation during early loading, which has less AE event number, and the step-like jump is not observed in all the AE curves. The dry shale only has a large number of AE events until it is close to macroscopic failure. Nuclear magnetic resonance, mineral composition, and microstructure analysis show that Chengkou shale generally develops micro-nanoscale pores with a small pore throat, and thus strong capillary spontaneous absorption occurs. The shale-water interaction includes both chemical and physical effects, which affect the key parameters such as acoustic velocity, frictional force on the surfaces of artificial fracture, fracability, and other mechanical properties. This paper provides new insights to the investigation on the formation mechanism of artificial fracture networks in brittle shales.

[Simultaneous determination of three antidepressant drugs in feces by HLPC-MS].

Objective: To establish a high performance liquid chromatography tandem mass spectrometry (HPLC / MS) method for the simultaneous determination of three antidepressant drugs in feces. Methods: Samples were pretreated with n-hexane isopropanol (95:5, v/v). Gradient elution was carried out with mixed liquid of ultrapure water and acetonitrile as mobile phase and separated by Agilent ZORBAX SB-C18 liquid chromatography column (2.1 mm×100 mm, 3.5 m). The samples were detected by electrospray ionization tandem mass spectrometry and quantified by internal standard method. Results: The recoveries of duloxetine, fluoxetine and escitalopram in fecal samples were 61.6% - 116.5%, with precision of 2.80% - 12.9% (n=5). The correlation coefficients (r) of linear equations were all greater than 0.995. The detection limits were 0.1, 1, and 0.001 µg/g, and the limits of quantification were 0.5, 2 and 0.005 µg/g, respectively. Conclusion: The method is simple and accurate to detect the contents of three antidepressants in feces, such as duloxetine, fluoxetine and escitalopram.

The effect of oestrogen on mandibular condylar cartilage via hypoxia-inducible factor-2α during osteoarthritis development.

Oestrogen and hypoxia inducible factor-2α (HIF2α) are key regulators in the pathogenesis of osteoarthritis (OA). However, the cellular interaction between oestrogen and HIF2α in articular cartilage during OA process remains unknown. Our previous study has revealed that high-physiological level of oestrogen aggravates the degradation of condylar cartilage in the early stage of temporomandibular joint osteoarthritis (TMJ OA). Here, we hypothesize that HIF2α involves the effect of oestrogen on mandibular condylar cartilage in the progression of TMJ OA. Our experiment in vivo found that the degeneration of condylar cartilage caused by unilateral anterior crossbite (UAC) model, characterized by obvious degenerative morphology, loss of cartilage extracellular matrix, up-regulation of TNF-α, HIF2α and its' down-stream OA-related cytokines (MMP-13, VEGF and Col X), could be alleviated by lack of oestrogen while aggravated by high level of oestrogen in rats. Meanwhile, our in vitro study found that 17ß-estradiol stimulation resulted in the loss of extracellular matrix, increased expression of TNF-α, IL-1, HIF2α and its' down-stream OA-related cytokines (MMP-13, VEGF and Col X) in primary condylar chondrocytes via oestrogen receptor beta (ERß), which could be reversed by ER antagonist, selective estrogen receptor modulators (SERMs) and HIF2α translation inhibitor. Our results reveal that high level of oestrogen can aggravate the degenerative changes of mandibular condylar cartilage, while lack of oestrogen can alleviate it via oestrogen-ERß-HIF2α pathway during TMJ OA progression.

Migration behaviors of leaky dielectric droplets with electric and hydrodynamic forces.

The external electric field enables separation and transport of droplets effectively in microfluidic devices. Herein, a volume-of-fluid (VOF) + level-set (LS) + smoothed physical parameters (SPP) method associated with the dynamically adaptive grid technique is extended to simulate three-dimensional leaky dielectric droplets in the electric field. The effects of electric and hydrodynamic forces on droplet behaviors are investigated. It is demonstrated that the electric force could act toward the outside or inside of a droplet and produce different droplet deformations. For the dielectrophoretic migration of droplets in the nonuniform electric field, the electric force has a dominant effect. It is found that when the electric conductivity ratio is greater than 1, an unbalanced electric force toward a stronger electric field is generated, bringing about the migration toward a stronger electric field. In contrast, when the electric conductivity ratio is smaller than 1, the unbalanced electric force direction is reversed and the droplet migrates toward a weaker electric field. The hydrodynamic force produces little promotion or hindrance to droplet migration. A greater permittivity ratio usually produces greater electric force and migration velocity. The droplet migrates along one direction in a symmetric nonuniform electric field but tends to migrate along the normal direction of electric potential profiles in an asymmetric nonuniform electric field.

Nanoscale Study of Bubble Nucleation on a Cavity Substrate Using Molecular Dynamics Simulation.

In this paper, the molecular dynamics simulation method is utilized to investigate the phase transition behavior of an argon film placed on cavity substrates with different wettability conditions. A simple Lennard-Jones liquid is heated by a metal platinum substrate at different temperatures, and a complete process of bubble nucleation is successfully visualized on the cavity substrate at temperatures of 150 and 160 K. Moreover, the bubble nucleation behavior shows dependence on cavity wettability. A layer of liquid atom is attracted to the strongly hydrophilic cavity and obtains more energy to nucleate first. In contrast, the liquid atom suffers a large repulsive force from the metal atom in the hydrophobic cavity, thus an original small bubble nucleus stably stays inside before the incipient boiling time. With an increase in the heating time, the original bubble nucleus grows up from the hydrophobic cavity. This bubble nucleation behavior on a hydrophobic cavity is in agreement with macro theory, which states that a cavity provides an original nucleus for bubble formation and growth. Besides, cavity wettability plays a crucial role in the incipient boiling temperature of an argon film. The incipient boiling temperature increases with the weakening of the cavity hydrophobicity, and this trend is in accordance with macro experiments, which show that liquid is easier to boil on a more hydrophobic substrate.

Differential effects of high-physiological oestrogen on the degeneration of mandibular condylar cartilage and subchondral bone.

The striking predilection of temporomandibular disorders (TMD) in women, especially during gonad-intact puberty or reproductive years, indicates that oestrogen plays an important role in the progression of TMD, but the underlying mechanism remains unclear. In this study, unilateral anterior crossbite (UAC) was used to create temporomandibular joint osteoarthritis (TMJ OA) models in rats, while 17ß-estradiol (E2) injections were applied to mimic patients with high-physiological levels of oestrogen. Micro-CT scanning, histological staining and real-time PCR assays were preformed to observe the degenerative changes in the mandibular condylar cartilage and subchondral bone. The results showed that obvious degradation was found in the condylar cartilage and subchondral bone of rats with UAC procedure, including decreased cartilage thickness, loss of extracellular matrix, increased apoptotic chondrocytes and expression of pro-inflammatory and catabolic factors, decreased bone mineral density and increased osteoclast activity. E2 supplements aggravated the condylar cartilage degradation but reversed the abnormal bone resorption in the subchondral bone induced by UAC. Our results revealed that high-physiological oestrogen plays a destructive role in condylar cartilage but a protective role in subchondral bone at the early stage of TMJ OA. These dual and distinct effects should be given serious consideration in future OA treatments.

The effect of methamphetamine abuse on dental caries and periodontal diseases in an Eastern China city.

BACKGROUND: Dental diseases are among the most frequently reported health problems in drug abusers. However, few studies have been conducted on oral health of methamphetamine (meth) abusers in China. The aim of the present study was to investigate the caries and periodontal health profile of former meth abusers in Eastern China. METHODS: A cross-sectional study was conducted on 162 former meth abusers in the male Zhoushan Compulsory Detoxification Center. A standardized questionnaire, which collected information about age, drug-use duration / pattern, oral hygiene habit and systemic diseases, was administered. Then, a dental examination was performed to investigate the severity of dental caries and periodontal diseases. In evaluating dental caries, the prevalence of dental caries, the scores of decayed teeth (DT), missing teeth (MT), filled teeth (FT), and decayed, missing, filled teeth (DMFT) were recorded. In evaluating periodontal diseases, community periodontal index (CPI), and the prevalence of gingival bleeding, dental calculus, periodontal pocket and loose teeth, were recorded. Additionally, the non-parametric test was adopted to analyze the potential risk factors via SPSS. RESULTS: All the participants abused meth by inhalation. The mean scores of DT, MT, FT and DMFT in the former meth users were 2.72 ± 2.78, 3.07 ± 3.94, 0.33 ± 1.03 and 6.13 ± 5.20 respectively. The prevalence of gingival bleeding, dental calculus, periodontal pocket and loose teeth was 97.53%, 95.68%, 51.23% and 9.26% respectively. The DT, DMFT and CPI scores in those who had abused meth for longer than 4 years were significantly higher than those who abused for less than 4 years (P = 0.039, 0.045, P < 0.001, respectively). The DT score in those who brushed their teeth more than twice a day were significantly lower than those who brushed less (P = 0.018). CONCLUSIONS: The status of caries and periodontal diseases among former male meth users in Eastern China was poor. Prolonged drug abuse and lower frequency of tooth brushing may be the risk factors of their poor status of caries and periodontal diseases.

A method for simulating the release of natural gas from the rupture of high-pressure pipelines in any terrain.

The rupture of a high-pressure natural gas pipeline can pose a serious threat to human life and environment. In this research, a method has been proposed to simulate the release of natural gas from the rupture of high-pressure pipelines in any terrain. The process of gas releases from the rupture of a high-pressure pipeline is divided into three stages, namely the discharge, jet, and dispersion stages. Firstly, a discharge model is established to calculate the release rate of the orifice. Secondly, an improved jet model is proposed to obtain the parameters of the pseudo source. Thirdly, a fast-modeling method applicable to any terrain is introduced. Finally, based upon these three steps, a dispersion model, which can take any terrain into account, is established. Then, the dispersion scenarios of released gas in four different terrains are studied. Moreover, the effects of pipeline pressure, pipeline diameter, wind speed and concentration of hydrogen sulfide on the dispersion scenario in real terrain are systematically analyzed. The results provide significant guidance for risk assessment and contingency planning of a ruptured natural gas pipeline.