Distribution and characteristics of gas hydrates in shallow sediments of pockmarks and seepage sites

Cold seeps are regions where fluid migrates from deep subsurface and escapes to the water column through the sea floor. Such fluids are usually rich in low molecular weight hydrocarbons, mainly methane, with small amount of other gases, such as carbon dioxide and hydrogen sulfide. In areas of water depth greater than 300-600m, gas hydrate could form depending on the bottom water temperature and geothermal gradients. Formation and decomposition of gas hydrate potentially change the properties of marine sediment. Therefore, in order to understand the evolution and morphological changes of marine cold seeps, it is important to know the distribution of gas hydrate in shallow sediment. Gas enclathrated in hydrate also contains important information and is helpful to understand the source of the gas. One aim of the thesis is to understand the distribution of gas hydrate within the sediment of a pockmark field at the Nigerian continental margin by using infrared thermal scanning and pore water chloride concentration. Both methods show similar hydrate distribution with different resolutions. By using coring information, the seismic profiles obtained in 2008 were calibrated to show the overview of free gas accumulation and hydrate distribution in the whole pockmark field. Elevated geothermal gradients were observed in the center of a pockmark where gas flares in the water column were imaged by hydroacoustic method, indicating the pockmark was active. The interaction among the fluid flow, hydrate formation and dissolution, and the thermal regime governs the formation and evolution of the pockmarks in this area. Knowledge of gas composition and crystal structure of natural gas hydrates is important for determining the stability of hydrate, which is a key factor to understand the fate of methane gas bubbles and hydrate bulks in the water column and the size of the hydrate reservoir in marine sediment. Methane is the dominant gas of hydrate samples recovered from pockmarks at the Nigerian continental margin, indicating that the gas is mainly biogenic. Besides methane, hydrogen sulfide and carbon dioxide were also detected using both Raman spectroscopy and gas chromatography. The thickness of gas hydrate stability zone (GHSZ) increases significantly due to the existence of hydrogen sulfide and carbon dioxide although their contents are relatively low. Hydrogen sulfide containing hydrate has only been discovered at Hydrate Ridge and Niger delta. It is a big surprise to observe hydrogen sulfide within the samples from Nigerian continental margin. In order to know whether such type of hydrate is restricted only in specific areas, we did additional Raman spectroscopy analysis on the hydrate samples recovered at cold seeps from different areas, including the Black Sea and the Makran continental margin. Results show that both samples contain hydrogen sulfide. Therefore, we infer that hydrogen sulfide containing hydrate is not restricted to certain area, but widely occurs within seepage sites where intensive upward methane flux exists and sustains high activity of anaerobic methane oxidation that produces hydrogen sulfide. Sudden release of hydrogen sulfide from hydrate due to changes of the ambient condition might dramatically affect the distribution of chemosynthetic community

Evaluation of Biological Toxicity of CdTe Quantum Dots with Different Coating Reagents according to Protein Expression of Engineering Escherichia coli

The results obtained from toxicity assessment of quantum dots (QDs) can be used to establish guidelines for the application of QDs in bioimaging. This paper focused on the design of a novel method to evaluate the toxicity of CdTe QDs using engineering Escherichia coli as a model. The toxicity of mercaptoacetic acid (MPA), glutathione (GSH), and L-cysteine (Cys) capped CdTe QDs was analyzed according to the heterologous protein expression in BL21/DE3, engineering Escherichia coli extensively used for protein expression. The results showed that the MPA-CdTe QDs had more serious toxicity than the other two kinds of CdTe QDs. The microscopic images and SEM micrographs further proved that both the proliferation and the protein expression of engineering Escherichia coli were inhibited after treatment with MPA-CdTe QDs. The proposed method is important to evaluate biological toxicity of both QDs and other nanoparticles

Investigating the critical characteristics of thermal runaway process for LiFePO4/graphite batteries by a ceased segmented method

Lithium-ion batteries (LIBs) are widely used as the energy carrier in our daily life. However, the higher energy density of LIBs results in poor safety performance. Thermal runaway (TR) is the critical problem which hinders the further application of LIBs. Clarifying the mechanism of TR evolution is beneficial to safer cell design and safety management. In this paper, liquid nitrogen spray is proved to be an effective way to stop the violent reaction of LIBs during the TR process. Based on extended-volume accelerating rate calorimetry, the liquid nitrogen ceasing combined with non-atmospheric exposure analysis is used to investigate the TR evolution about LiFePO4/graphite batteries at critical temperature. Specifically, the geometrical shape, voltage, and impedance change are monitored during the TR process on the cell level. The morphologies/constitution of electrodes and separators are presented on the component level. Utilizing the gas analysis, the failure mechanism of the prismatic LiFePO4/graphite battery is studied comprehensively

Polymorphisms of TGFB1 and VEGF genes and survival of patients with gastric cancer

<p>Abstract</p> <p>Background</p> <p>Some <it>TGFB1 </it>and <it>VEGF </it>polymorphisms are believed to be functional. Given that these genes are involved in tumor growth and progression including angiogenesis, dissemination, and invasiveness, we hypothesized that these polymorphisms would be associated with survival in patients with gastric cancer.</p> <p>Methods</p> <p>We genotyped <it>TGFB1 </it>-509 C>T, +1869 T>C, and +915 G>C and <it>VEGF </it>-1498T>C, -634G>C, and +936C>T in 167 patients with gastric cancer. Using the Kaplan and Meier method, log-rank tests, and Cox proportional hazard models, we evaluated associations among <it>TGFB1 </it>and <it>VEGF </it>variants with overall, 1-year, and 2-year survival rates.</p> <p>Results</p> <p>Although there were no significant differences in overall survival rates among all polymorphisms tested, patients with <it>TGFB1</it>+915CG and CC genotypes had a poorer 2-year survival (adjusted hazard ratio (HR), 3.06; 95% confidence interval (CI), 1.09–8.62; <it>P </it>= 0.034) than patients with the GG genotype had. In addition, patients heterozygous for <it>VEGF </it>-634CG also had a poorer 1-year survival (adjusted HR, 2.08; 95% CI, 1.03–4.22; <it>P </it>= 0.042) than patients with the -634GG genotype.</p> <p>Conclusion</p> <p>Our study suggested that <it>TGFB1</it>+915CG/CC and <it>VEGF </it>-634CG genotypes may be associated with short-term survival in gastric cancer patients. However, larger studies are needed to verify these findings.</p

A unified multi-step wind speed forecasting framework based on numerical weather prediction grids and wind farm monitoring data

Wind speed forecasting is the basis of wind farm operation, which provides a reference for the future operation status evaluation of wind farms. For the wind speed forecast of wind turbines in the whole wind farm, a strategy combining unified forecast and single site error correction is proposed in this paper. The unified forecast framework is composed of a unified forecast model and multiple single site error correction models, which combines the forecasted grids of numerical weather prediction (NWP) with the monitoring data of wind farms. The proposed unified forecast model is called spatiotemporal conversion deep predictive network (STC-DPN), which is composed of temporal convolution network (TCN) and 2D convolution long short-term memory network (ConvLSTM). Firstly, the NWP forecasted grids are interpolated to the fan location, and the sequence matrix is composed of the NWP data and the monitored data of each wind turbine according to the time series, which is entered into the TCN network for time sequence feature extraction. Then, the output of the TCN network is converted into a regular spatio-temporal data matrix, which is entered into the ConvLSTM network for joint learning of spatio-temporal features to obtain the wind speed sequence forecasted in the whole wind farm. Finally, an independent TCN-LSTM error correction model is added for each site. Variational modal decomposition (VMD) is used to process data series, and different processing methods are adopted in unified forecast and single site error correction. In the 96 steps forecast test of a wind farm from Jining City, China, the proposed method is superior to several baseline methods and has important practical application value

A method to prolong lithium-ion battery life during the full life cycle

Extended lifetime of lithium-ion batteries decreases economic costs and environmental burdens in achieving sustainable development. Cycle life tests are conducted on 18650-type commercial batteries, exhibiting nonlinear and inconsistent degradation. The accelerated fade dispersion is proposed to be triggered by the evolution of an additional potential of the anode during cycling as measured vs. Li$^+$/Li. A method to prolong the battery cycle lifetime is proposed, in which the lower cutoff voltage is raised to 3 V when the battery reaches a capacity degradation threshold. The results demonstrate a 38.1% increase in throughput at 70% of their beginning of life (BoL) capacity. The method is applied to two other types of lithium-ion batteries. A cycle lifetime extension of 16.7% and 33.7% is achieved at 70% of their BoL capacity, respectively. The proposed method enables lithium-ion batteries to provide long service time, cost savings, and environmental relief while facilitating suitable second-use applications

Data-driven capacity estimation of commercial lithium-ion batteries from voltage relaxation

Accurate capacity estimation is crucial for the reliable and safe operation of lithium-ion batteries. In particular, exploiting the relaxation voltage curve features could enable battery capacity estimation without additional cycling information. Here, we report the study of three datasets comprising 130 commercial lithium-ion cells cycled under various conditions to evaluate the capacity estimation approach. One dataset is collected for model building from batteries with LiNi$_{0.86}$Co$_{0.11}$Al$_{0.03}$O$_{2}$-based positive electrodes. The other two datasets, used for validation, are obtained from batteries with LiNi$_{0.83}$Co$_{0.11}$Mn$_{0.07}$O$_{2}$-based positive electrodes and batteries with the blend of Li(NiCoMn)O$_{2}$ - Li(NiCoAl)O$_{2}$ positive electrodes. Base models that use machine learning methods are employed to estimate the battery capacity using features derived from the relaxation voltage profiles. The best model achieves a root-mean-square error of 1.1% for the dataset used for the model building. A transfer learning model is then developed by adding a featured linear transformation to the base model. This extended model achieves a root-mean-square error of less than 1.7% on the datasets used for the model validation, indicating the successful applicability of the capacity estimation approach utilizing cell voltage relaxation

The VEGF -634G>C promoter polymorphism is associated with risk of gastric cancer

<p>Abstract</p> <p>Background</p> <p>Both TGF-β1 and VEGF play a critic role in the multiple-step process of tumorgenesis of gastric cancer. Single nucleotide polymorphisms (SNPs) of the <it>TGFB1 </it>and <it>VEGF </it>genes have been associated with risk and progression of many cancers. In this study, we investigated the association between potentially functional SNPs of these two genes and risk of gastric cancer in a US population.</p> <p>Methods</p> <p>The risk associated with genotypes and haplotypes of four <it>TGFB1 </it>SNPs and four <it>VEGF </it>SNPs were determined by multivariate logistic regression analysis in 171 patients with gastric cancer and 353 cancer-free controls frequency-matched by age, sex and ethnicity.</p> <p>Results</p> <p>Compared with the <it>VEGF</it>-634GG genotype, the -634CG genotype and the combined -634CG+CC genotypes were associated with a significantly elevated risk of gastric cancer (adjusted OR = 1.88, 95% CI = 1.24-2.86 and adjusted OR = 1.56, 95% CI = 1.07-2.27, respectively). However, none of other <it>TGFB1 </it>and <it>VEGF </it>SNPs was associated with risk of gastric cancer.</p> <p>Conclusion</p> <p>Our data suggested that the <it>VEGF</it>-634G>C SNP may be a marker for susceptibility to gastric cancer, and this finding needs to be validated in larger studies.</p

Verteilung und Eigenschaften von Gashydraten im flachen Sedimenten des Pockennarben und kalten Quellen

Cold seeps are regions where fluid migrates from deep subsurface and escapes to the water column through the sea floor. Such fluids are usually rich in low molecular weight hydrocarbons, mainly methane, with small amount of other gases, such as carbon dioxide and hydrogen sulfide. In areas of water depth greater than 300-600m, gas hydrate could form depending on the bottom water temperature and geothermal gradients. Formation and decomposition of gas hydrate potentially change the properties of marine sediment. Therefore, in order to understand the evolution and morphological changes of marine cold seeps, it is important to know the distribution of gas hydrate in shallow sediment. Gas enclathrated in hydrate also contains important information and is helpful to understand the source of the gas. One aim of the thesis is to understand the distribution of gas hydrate within the sediment of a pockmark field at the Nigerian continental margin by using infrared thermal scanning and pore water chloride concentration. Both methods show similar hydrate distribution with different resolutions. By using coring information, the seismic profiles obtained in 2008 were calibrated to show the overview of free gas accumulation and hydrate distribution in the whole pockmark field. Elevated geothermal gradients were observed in the center of a pockmark where gas flares in the water column were imaged by hydroacoustic method, indicating the pockmark was active. The interaction among the fluid flow, hydrate formation and dissolution, and the thermal regime governs the formation and evolution of the pockmarks in this area. Knowledge of gas composition and crystal structure of natural gas hydrates is important for determining the stability of hydrate, which is a key factor to understand the fate of methane gas bubbles and hydrate bulks in the water column and the size of the hydrate reservoir in marine sediment. Methane is the dominant gas of hydrate samples recovered from pockmarks at the Nigerian continental margin, indicating that the gas is mainly biogenic. Besides methane, hydrogen sulfide and carbon dioxide were also detected using both Raman spectroscopy and gas chromatography. The thickness of gas hydrate stability zone (GHSZ) increases significantly due to the existence of hydrogen sulfide and carbon dioxide although their contents are relatively low. Hydrogen sulfide containing hydrate has only been discovered at Hydrate Ridge and Niger delta. It is a big surprise to observe hydrogen sulfide within the samples from Nigerian continental margin. In order to know whether such type of hydrate is restricted only in specific areas, we did additional Raman spectroscopy analysis on the hydrate samples recovered at cold seeps from different areas, including the Black Sea and the Makran continental margin. Results show that both samples contain hydrogen sulfide. Therefore, we infer that hydrogen sulfide containing hydrate is not restricted to certain area, but widely occurs within seepage sites where intensive upward methane flux exists and sustains high activity of anaerobic methane oxidation that produces hydrogen sulfide. Sudden release of hydrogen sulfide from hydrate due to changes of the ambient condition might dramatically affect the distribution of chemosynthetic community