Solidified natural gas storage using gas hydrates is a promising technology for non-explosive, high capacity, and environmentally-friendly natural gas storage at mild storage conditions. Improvement ...in the kinetics of gas hydrate formation is essential for the further development of this novel technology. In this work, the use of graphite nanofluids for enhancing the CH4 hydrate formation was investigated. The experiments were conducted in a stirred tank reactor at 277.15 K and 6.0 MPa. The behavior of the CH4 hydrate nucleation and growth in graphite nanofluids was observed using a microscopy apparatus. The results indicate that compared to liquid water, the gas storage capacity obtained in graphite nanofluids increased by 3%, the induction time for the CH4 hydrate formation decreased by 89%, and the total time for hydrate formation decreased by 67%. Among the three graphite nanoparticles concentrations (0.2, 0.5, and 1.0 wt%) tested in this work, the concentration of 0.5 wt% was optimal for the enhancement of CH4 hydrate formation. The gas storage capacity obtained in the 0.5 wt% graphite nanofluids was higher than that obtained in other nanofluids such as the Fe3O4 and ZnO nanofluids. Thus, the use of graphite nanofluids is an effective approach to enhance hydrate formation for solidified natural gas storage, but the gas storage capacity should be further increased in future work.
•Graphite nanofluids was used to promote CH4 hydrate formation.•The effects of graphite nanoparticles on gas consumption and CH4 storage capacity were elucidated.•CH4 storage capacity obtained in graphite nanofluids was increased compared to other nanofluids.
A 2.5D PIC kinetic code is executed to simulate the excitation of electron whistlers and ion cyclotron whistler (L wave) during magnetic reconnection. Our simulation results suggest that ...quasi-parallel and anti-parallel whistler waves can be excited in the separatrix region near X-Line and in the outflow region, respectively. Electron whistlers play a crucial role in energy release and transfer, as the small mass of electrons allows them to move rapidly under the perturbation of a magnetic field during magnetic reconnection. The L wave excited near the separatrix region far from X-Line, it propagate obliquely to the local magnetic field. Velocity distribution functions (VDFs) indicate that these waves are associated with temperature anisotropy instabilities of electron-beams (ion-beam). The electron whistler in the separatrix region is excited by cyclotron resonance due to the electron beam. The electron whistler observed in the outflow region is generated by Landau resonance owing to beam-mode, where the v∥ is close to the phase speed vph of the wave. Regarding L wave, their excitation mechanism is attributed to significant perpendicular temperature anisotropy instability (Ti⊥>Ti∥) of ion-beam, and satisfies cyclotron resonance condition. Meanwhile, our simulation results illustrate that the existence of energy conversion between particles and waves during the wave excitation by using the Wave-Particle Interaction Analyzer (WPIA).
•The electron whistlers and ion cyclotron whistlers are excited in different regions of magnetic reconnection.•The excited waves exhibit interesting temperature anisotropy instabilities of electron-beam and ion-beam.•Wave-Particle Interaction Analyzer (WPIA) method confirms the efficient energy conversion between waves and particles.
To enhance the security of single-chaotic systems, we propose a novel image encryption cryptosystem based on true random numbers and chaotic systems. First, we select any one of several chaotic ...systems. Next, the hash function is used to calculate the initial value of the chaotic system using a plaintext image. Then, we obtain a solution of this chaotic system and use the k-medoids clustering machine-learning algorithm and chaotic sequence to scramble the original image. Finally, new random numbers obtained using a chaotic signal and true random numbers are used to perform the exclusive-OR operator on the scrambled results. To illustrate the effectiveness of our method, a one-dimensional (1D) logistic chaotic system is selected for image encryption. The simulation results show that compared with the existing models, such as image encryption based on chaos and image encryption based on the advanced encryption standar (AES), our method is simpler with a higher security and resists different classical attacks.
Double-node system is a typical end-face connector for spatial structures. It is found that the initial rotational stiffness of this connection is affected by the axial force of the member. This ...study aims to investigate the effect of the axial force-to-moment ratio λ on the initial rotational stiffness K0 of the double-node system. An analytical model composed of springs and a rigid plane is proposed according to the force transmission mechanism. The K0-λ curve first exhibits linear, then inverse proportional, and finally linear again, corresponding to the three mechanical states. Next, the component stiffnesses are illustrated by parametric studies, which are related to the geometrical parameters of the connection. And the component stiffnesses are used to derive the constant coefficients of the overall stiffness in the K0-λ formula through the component method. Finally, the process of determining the initial rotational stiffness is described, followed by some examples. Comparisons show that the proposed formulae are consistent with the numerical results, which are effective for predicting the initial rotational stiffness of the double-node system under different axial force-to-moment ratios.
•An analytical model of the double-node system is proposed.•The relationship between the initial rotational stiffness K0 and the axial force-to-moment ratio λ is investigated.•An energy-based method for determining the rotation of connection is proposed.•The formulae for component stiffnesses and overall stiffnesses are developed.
The kinetics of semiclathrate hydrates formation with CO2 in the presence of tetra-n-butyl ammonium bromide (TBAB), tetra-n-butyl phosphonium bromide (TBPB), and TBAB + TBPB were investigated. The ...experiments were conducted at the stoichiometric concentration of TBAB hydrate (2.57 mol%) and three subcoolings (ΔT = 6 K, 9 K, and 12 K) with the initial pressure fixed at 2.8 MPa. It was found that adding TBPB into the TBAB solution can promote hydrate nucleation, and this promotion effect at a lower subcooling (ΔT = 6 K) was stronger compared to that at higher subcoolings (ΔT = 9 K and 12 K). The gas consumption obtained in TBAB, TBPB, and TBAB + TBPB solutions decreased with the increase of subcooling, despite the increase of the rate of hydrate growth. At a given subcooling, gas consumption (CO2 uptake) in TBAB + TBPB solutions was greater than that in TBAB and TBPB solutions, indicating that hydrate formation kinetics and the CO2 storage capacity were improved in the TBAB + TBPB solution. The largest gas consumption was obtained at ΔT = 6 K in the TBAB + TBPB solution, which was 28.7% and 17.2% larger than those obtained in TBAB and TBPB solutions, respectively. Therefore, a mixture of TBAB + TBPB is a promising option to improve the kinetics of semiclathrate hydrate formation with CO2.
•The images of TBAB, TBPB, and TBAB + TBPB semiclathrate hydrates formed with CO2 were reported.•CO2 consumption decreased with the increase of subcooling from 6 to 12 K.•The kinetics and CO2 storage capacity of semiclathrare hydrate was improved in TBAB + TBPB solutions.•A mixture of TBAB + TBPB is preferable for the design of a hydrate-based gas separation process of CO2 capture.
Accumulating evidence indicates that the long non-coding RNA HOTAIR plays a critical role in cancer progression and metastasis. However, the overall biological role and clinical significance of ...HOTAIR in gastric carcinogenesis remains largely unknown.
HOTAIR expression was measured in 78 paired cancerous and noncancerous tissue samples by real-time PCR. The effects of HOTAIR on gastric cancer cells were studied by overexpression and RNA interference approaches in vitro and in vivo. Insights of the mechanism of competitive endogenous RNAs (ceRNAs) were gained from bioinformatic analysis, luciferase assays and RNA binding protein immunoprecipitation (RIP). The positive HOTAIR/HER2 interaction was identified and verified by immunohistochemistry assay and bivariate correlation analysis.
HOTAIR upregulation was associated with larger tumor size, advanced pathological stage and extensive metastasis, and also correlated with shorter overall survival of gastric cancer patients. Furthermore, HOTAIR overexpression promoted the proliferation, migration and invasion of gastric carcinoma cells, while HOTAIR depletion inhibited both cell invasion and cell viability, and induced growth arrest in vitro and in vivo. In particular, HOTAIR may act as a ceRNA, effectively becoming a sink for miR-331-3p, thereby modulating the derepression of HER2 and imposing an additional level of post-transcriptional regulation. Finally, the positive HOTAIR/HER2 correlation was significantly associated with advanced gastric cancers.
HOTAIR overexpression represents a biomarker of poor prognosis in gastric cancer, and may confer malignant phenotype to tumor cells. The ceRNA regulatory network involving HOTAIR and the positive interaction between HOTAIR and HER2 may contribute to a better understanding of gastric cancer pathogenesis and facilitate the development of lncRNA-directed diagnostics and therapeutics against this disease.
The hydrate-based solidified natural gas (SNG) technology is a promising approach for natural gas storage and transportation. One challenge of this technology is to enhance the hydrate formation ...kinetics and achieve mild storage conditions. This work employed a biomass surfactant sulfonated lignin (SL) to enhance CH4 hydrate formation. Meanwhile, the self-preservation effect of CH4 hydrate formed in the presence of SL was investigated using a high-pressure micro-differential scanning calorimeter (HP μ-DSC). The results indicate that 500 ppm SL is an optimum concentration for improving CH4 hydrate formation kinetics among the five SL concentrations (300, 500, 700, 900, and 1000 ppm) tested. At 500 ppm SL, the CH4 hydrate formation rate was increased significantly, and the largest gas consumption was obtained, which was 2.7 times larger than that obtained in pure water under the same temperature and pressure conditions. The gas consumption was also larger than that obtained in the presence of other surfactants (sodium dodecyl sulfate, silicone surfactant, and ethylene diamine tetraacetamide). CH4 hydrate formed in the presence of SL can be stably preserved at 0.1 MPa and 268.15 K due to the self-preservation effect. Therefore, the energy costs, such as system cooling and gas compression, for SNG using SL are lower than conventional natural gas storage and transport technologies.
•The kinetics of CH4 hydrate formation was enhanced in the presence of SL.•500 ppm SL is an optimum concentration to promote CH4 hydrate formation.•CH4 consumption at 500 ppm SL is larger than that using pure water or other surfactants.•The self-preservation effect of CH4 hydrate formed in the presence of SL was found.•CH4 hydrate formed at 500 ppm SL can be stably preserved at 0.1 MPa and 268.15 K.
In this work, the formation of tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate for CO2 capture was studied by conducting experiments in a kinetic setup coupled with high-pressure in situ ...Raman spectroscopy. The impacts of TBAB concentration and operating temperature on CO2 incorporation into TBAB semiclathrate hydrates were investigated from the macroscopic and microscopic perspectives. It was found that the structure transition of TBAB semiclathrates from type A to type B occurred in the presence of CO2 and could be identified by the splitting of the Raman peak at 1447 and 1465 cm–1 (C–C stretching vibration mode in TBA+). CO2 consumption increased substantially upon the occurrence of hydrate structure transition, indicating that a larger amount of CO2 is incorporated into the TBAB semiclathrate of type B. The structure transition of the TBAB semiclathrate occurring at 2.57 mol % TBAB is faster than that at 0.29 and 3.72 mol % TBAB, and CO2 consumption obtained at 2.57 mol % TBAB is greater. When the temperature is reduced from 282.15 to 279.15 K, the structure transition of the TBAB semiclathrate occurs faster, but the amount of CO2 trapped in the hydrate is reduced. Therefore, the TBAB semiclathrate formed at 2.57 mol % TBAB and 282.15 K is a suitable system for CO2 capture using TBAB semiclathrate hydrates.
Objective:
To investigate the effect of different bladder filling states on positioning errors in radiotherapy for cervical cancer and obtain the reference range of bladder filling consistency during ...radiotherapy.
Methods:
Patients who underwent postoperative radiotherapy for cervical cancer in Nantong Tumor Hospital from October 2018 to December 2019 were selected. According to the bladder filling deviation, they were divided into group A1 (deviation < 20%) and group B1 (deviation ≥ 20%). The bladder filling variations of the two groups were compared with different positioning errors. Group A2 has a positioning error of <0.4 cm, and group B2 has a positioning error of ≥0.4 cm. The reference range of bladder filling consistency during radiotherapy is obtained by analyzing the composition ratio of different positioning errors of bladder filling deviation.
Results:
This study included 195 patients with cervical cancer. The error of longitudinal and vertical position in group B1 was significantly higher than that in group A1 (0.50 ± 0.34 vs. 0.26 ± 0.22 cm,
p
< 0.001, and 0.22 ± 0.17 vs. 0.16 ± 0.12 cm,
p
< 0.001). Compared with group B2, the absolute deviation of bladder filling in group A2 (54.1% ± 54.4% vs. 25.6% ± 22.7%,
p
< 0.001) was slight. The chi-square test showed significant differences in the proportion of the positioning state of different bladder filling forms (
χ
2
= 31.006,
p
< 0.001). In addition, there was a significant difference in the proportion of stability errors in patients with poor stability in different directions (
χ
2
= 118.551,
p
< 0.001).
Conclusion:
In patients with cervical cancer fixed in the supine position, a bladder capacity deviation <20% is easier to achieve excellent positioning with, and it can better control the positioning error of radiotherapy and ensure the positioning accuracy of dose distribution to the target area. It can also achieve good tumor treatment effects. This range can be used as a reference for bladder filling consistency in patients with cervical cancer undergoing radiotherapy.
PDF
