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•Interfacial tension in n-decane + methane + water system was measured.•Interfacial tension in this system decreases linearly with increasing temperature.•Methane has little influence ...on temperature dependence of interfacial tension.•Pressure dependence of interfacial tension in this system changes at around 2.00 MPa.•The change of pressure dependence of interfacial tension is caused by methane.
Interfacial tension is one of the most important physical properties for high-precision simulations to develop the methods of preventing plugging of pipelines in the oil and natural gas industry. This paper reports experimental data with the pendant drop method for the interfacial tension of a decane + methane + water system at temperatures between 278.2 K to 298.2 K and pressures up to 10 MPa. The data show that in this temperature range the interfacial tension in the decane + methane + water system decreases almost linearly with increasing temperature. The results also show that by increasing the pressure of methane, the interfacial tension decreases from 53.98 mN m−1 to 50.23 mN m−1 at 283.2 K and 52.23 mN m−1 to 49.74 mN m−1 at 288.2 K. The nature of the methane pressure dependence of the interfacial tension changes for pressures above around 2.00 MPa. The interfacial tension decreases with the pressure up to 2.00 MPa, but has no pressure dependence above 2.00 MPa. It may be inferred that the decane/water interface is saturated with methane at pressures around 2.00 MPa and at higher pressure the interfacial tension is no longer affected by the presence of methane.
•Four-phase (H2 + CO2) + water + THP + hydrate equilibrium conditions was measured.•THP acts as the hydrate thermodynamic promoter in this system.•The equilibrium conditions in this system can be ...estimated from CO2 partial pressure.•H2 might scarcely influences the stability of the hydrate with H2 + CO2 + THP.•The structure of the hydrate in this system was identified to be structure II.
This paper reports the thermodynamic and crystallographic characterization of the clathrate hydrate formed in H2 + CO2 + tetrahydropyran (THP) + water system by phase equilibrium measurements and powder X-ray diffraction measurements with a goal of developing a hydrate-based carbon capture technology in an integrated coal gasification combined cycle. The four-phase (H2 + CO2) gas + water liquid + THP liquid + hydrate equilibrium conditions were measured with two series of gas compositions (around H2:CO2 = 0.7:0.3 and 0.9:0.1 in mole fractions) in the range of 2.64 MPa to 7.51 MPa. At around H2:CO2 = 0.7:0.3 in gas phase, the equilibrium temperatures in (H2 + CO2) gas + THP + water system are always higher by approximately 9 to 10 K compared to the equilibrium temperatures of H2 + CO2 + water system. This means that THP acts as the hydrate thermodynamic promoter. The equilibrium conditions in (H2 + CO2) gas + THP + water system, which is only considered with CO2 partial pressure, greatly agree with those in CO2 + THP + water system. Therefore, the equilibrium conditions in (H2 + CO2) gas + THP + water system would only depend on the partial pressure of CO2. Moreover, the crystallographic structure of the hydrate formed in H2 + CO2 + THP + water system was identified to be structure II, which is the same structure as the hydrate formed in H2 + CO2 + water system. These results can contribute to the study of a hydrate-based gas separation and carbon capture.
This paper reports the thermodynamic and crystallographic properties of the binary clathrate hydrate with methane + 1,1,1,3,3-pentafluoropropane (HFC-245fa) by phase equilibrium measurements, powder ...X-ray diffraction (PXRD) measurements, and first-principles and thermodynamic calculations. The four-phase (methane gas + water liquid + HFC-245fa liquid + hydrate) equilibrium conditions are lower in pressure by approximately 2–3 MPa than those of the methane + trans-1,3,3,3-tetrafluoropropene HFO-1234ze(E) hydrates at each temperature from 274.5 to 282.17 K, in spite of the similar molecular structure of HFC-245fa and HFO-1234ze(E). The crystallographic structure of the hydrate with methane + HFC-245fa was identified to be structure II by the PXRD measurement; although because of its molecular length, HFC-245fa would be expected to be encapsulated into a 51268 cage of structure H hydrate. First-principles calculations revealed that these thermodynamic and crystallographic phenomena are the result of two physical factors. First, the total HFC-245fa–water interactions in the cages are stronger than the HFO-1234ze(E)–water interactions due to the presence of more fluorine atoms at the two edge groups in the HFC-245fa molecule and the resulting higher dipole moment of HFC-245fa, and second, the HFC-245fa–HFC-245fa interaction is more greatly enhanced by the presence of methane compared to the HFO-1234ze(E)–HFO-1234ze(E) interactions.
Blockages in natural gas and oil pipelines can be caused by the aggregation of clathrate hydrate crystals which form at the oil-water-gas interfaces. Knowledge of interfacial tensions between ...components are crucial to understanding the interface physical chemistry and numerically simulating pipeline multiphase flow. This study measures the effect of the presence of natural gas components on the oil-water interfacial tension and its potential implications on flow assurance in oil-gas pipelines. Decane is used to mimic oil and is saturated with the gaseous mixture of methane, ethane, and propane as is consistent with simulations of multiphase dynamics. Water droplets were generated in decane and photographed through a window using pendant drop method in order to determine the oil-water interfacial tension. This study examined both mechanical and thermodynamic phenomena by considering interfacial tension under different pressure/temperature conditions covering the natural gas hydrate formation region. The effect of the gas mixture composition and pressure on the interfacial tension was determined at different temperatures in the range of pipeline operating conditions. The behavior was explained from both experimental and theoretical points of view. At lower pressures, the presence of the C2 and C3 natural gas components lowers the decane-water interfacial tension compared to the case of the decane-water-methane system. In particular, the pressure dependence of the interfacial tension was found to be almost five times higher than that in the absence of C2 and C3. By decreasing the interfacial tension, the presence of ethane and propane may facilitate the mixing of the water and oil phases in pipelines, therefore affecting the rate of hydrate formation.
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•Interfacial tension data covering natural gas hydrate formation area.•Recreate a natural gas transportation pipeline and measure the interfacial tensions.•Measurement was conducted using a ternary system, natural gas-decane-water.•Effect of gas mixture and its each gas components on interfacial tension.•Understanding multiphase dynamics and gas hydrate formation in the pipeline.
Background
Although peritoneal lavage cytology often serves as a sensitive method to detect free cancer cells in the abdominal cavity, some patients experience peritoneal recurrence despite negative ...cytology. The aim of this study was to evaluate mRNAs in peritoneal lavage fluid as potential markers for predicting the peritoneal recurrence of gastric cancer (GC).
Methods
Peritoneal lavage fluid samples were obtained during surgery conducted on 187 patients with GC and from 30 patients with non-malignant disease (controls). The mRNA levels of nine candidate markers were quantified, and analysis of a receiver-operating characteristic curve compared their accuracies. The cutoff was defined as the highest value of the controls.
Results
Synaptotagmin XIII (
SYT13
) and carcinoembryonic antigen (
CEA
) mRNA levels were analyzed further.
SYT13
levels were significantly associated with shorter peritoneal recurrence-free survival (PRFS) and overall survival. Among patients with negative peritoneal lavage cytology, those positive for either
SYT13
or
CEA
mRNA experienced significantly shorter peritoneal recurrence-free survival compared with those with negative fluid (hazards ratio HR 4.21,
P
= 0.0114; HR 3.53;
P
= 0.0426, respectively). Univariate analysis revealed that
SYT13
and
CEA
mRNA levels were significant predictors of peritoneal recurrence. Positive levels of both
SYT13
and
CEA
mRNA demonstrated the highest HR for peritoneal recurrence (HR 12.27,
P
= 0.0064). Multivariable analysis revealed that
SYT1
3 positivity was a significant independent prognostic factor (HR 3.69; 95% confidence interval, 1.18–12.74;
P
= 0.0246).
Conclusions
Combined measurement of
SYT13
and
CEA
mRNA levels in peritoneal lavage fluid could serve as a promising approach to predict peritoneal recurrence of GC.
Background
Metastatic gastric cancer (GC) has a poor prognosis, and elucidating the molecular mechanisms involved in metastasis may lead to the development of novel therapeutic modalities.
Methods
...Transcriptome analysis of surgically resected metastatic tissue from GC patients and noncancerous tissue was performed to identify novel metastasis-related genes. Analyses of in vitro cell function, apoptosis, the cell cycle and cancer stemness were performed using GC cell lines with a stable knockout of a candidate gene. In vivo percutaneous, peritoneal dissemination and liver metastasis xenograft models were also generated. PCR array and proteome analyses were performed. Expression of the candidate gene was analyzed in GC tissues from 300 patients.
Results
Lysosomal Associated Membrane Protein Family Member 5 (
LAMP5
) was upregulated in the metastatic tissues.
LAMP5
knockout significantly suppressed proliferation, invasion, and migration of GC cells and increased apoptosis, cell cycle arrest and cancer stemness.
LAMP5
knockout virtually suppressed tumor growth in in vivo percutaneous, peritoneal dissemination and liver metastasis models. EMT- and autophagy-related genes were associated with
LAMP5
. High
LAMP5
mRNA levels were significantly associated with a worse prognosis.
Conclusion
LAMP5
plays a vital role in metastasis formation and may be a promising novel target of drug development for metastatic GC in the future.
Background
Squamous cell carcinoma antigen (SCC-Ag) and carcinoembryonic antigen (CEA) are widely used in clinical practice to predict the prognosis of patients with esophageal squamous cell ...carcinoma (ESCC). However, their predictive values for prognosis are controversial. This study determined optimal cutoff values of serum SCC-Ag and CEA concentrations for predicting postoperative recurrence of ESCC, which enabled selection of high-risk patients.
Methods
The study retrospectively analyzed 427 patients who underwent curative resection for ESCC. The optimal cutoff values of preoperative SCC-Ag and CEA concentrations for predicting postoperative recurrence were determined using combined analysis of hazard ratios and sensitivities for recurrence. Using the optimal cutoff value, the study evaluated survival, recurrence patterns, and temporal changes in marker concentrations.
Results
The preoperative SCC-Ag concentration of 1.1 ng/ml was the optimal cutoff value for predicting postoperative recurrence, whereas precise cutoff values could not be determined for preoperative CEA concentrations. High preoperative SCC-Ag concentrations (> 1.1 ng/ml), which were significantly associated with more aggressive tumor phenotypes and shorter disease-free survival, were identified as an independent prognostic factor in the multivariable analysis. High preoperative SCC-Ag concentrations were significantly associated with greater prevalence of lung/pleura and local recurrences. Normalization of serum SCC-Ag concentrations after neoadjuvant treatment or esophagectomy was not associated with a decreased risk of postoperative recurrence.
Conclusions
The optimal cutoff value of preoperative SCC-Ag concentrations that predicted recurrence of ESCC was 1.1 ng/ml, illuminating the utility of serum SCC-Ag concentrations as an easily measurable tool for selecting a perioperative management strategy.
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