Journal of Oceanology and Limnology - In this study, a programmable freezing technique has been developed for strip spawned sperm in the blue mussel, Mytilus galloprovincialis. The optimized key... 相似文献
Oil from the Oligocene oil sands of the Lower Ganchaigou Formation in the Northern Qaidam Basin and the related asphaltenes was analyzed using bulk and organic geochemical methods to assess the organic matter source input, thermal maturity, paleo-environmental conditions, kerogen type, hydrocarbon quality, and the correlation between this oil and its potential source rock in the basin. The extracted oil samples are characterized by very high contents of saturated hydrocarbons (average 62.76%), low contents of aromatic hydrocarbons (average 16.11%), and moderate amounts of nitrogen–sulfur–oxygen or resin compounds (average 21.57%), suggesting that the fluid petroleum extracted from the Oligocene oil sands is of high quality. However, a variety of biomarker parameters obtained from the hydrocarbon fractions (saturated and aromatic) indicate that the extracted oil was generated from source rocks with a wide range of thermal maturity conditions, ranging from the early to peak oil window stages, which are generally consistent with the biomarker maturity parameters, vitrinite reflectance (approximately 0.6%), and Tmax values of the Middle Jurassic carbonaceous mudstones and organic-rich mudstone source rocks of the Dameigou Formation, as reported in the literature. These findings suggest that the studied oil is derived from Dameigou Formation source rocks. Furthermore, the source- and environment-related biomarker parameters of the studied oil are characterized by relatively high pristane/phytane ratios, the presence of tricyclic terpanes, low abundances of C27 regular steranes, low C27/C29 regular sterane ratios, and very low sterane/hopane ratios. These data suggest that the oil was generated from source rocks containing plankton/land plant matter that was mainly deposited in a lacustrine environment and preserved under sub-oxic to oxic conditions, and the data also indicate a potential relationship between the studied oil and the associated potential source rocks. The distribution of pristane, phytane, tricyclic terpanes, regular steranes and hopane shows an affinity with the studied Oligocene Lower Ganchaigou Formation oil to previously published Dameigou Formation source rocks. In support of this finding, the pyrolysis–gas chromatography results of the analyzed oil asphaltene indicate that the oil was primarily derived from type II organic matter, which is also consistent with the organic matter of the Middle Jurassic source rocks. Thus, the Middle Jurassic carbonaceous mudstones and organic rock mudstones of the Dameigou Formation could be significantly contributing source rocks to the Oligocene Lower Ganchaigou Formation oil sand and other oil reservoirs in the Northern Qaidam Basin.
Due to high gas content, high geo-stress and complex geological conditions, gas disasters occur frequently in deep coal mining. The hard thick roof (HTR) greatly increases the difficulty of coalbed gas control besides causing dynamic disasters. In this paper, the effects of HTR on gas migration were numerically analyzed based on a multi-field coupling model. Results indicated that the hanging arch leads to remarkable stress concentration and induces a “cap-shaped” low-permeable zone above the gob, which greatly prevents gas from migrating upwards. Meanwhile, HTR hinders the subsidence movements of the upper rock strata, contributing to very few roof fractures and bed-separated fractures. Without the formation of roof-fractured zone, coalbed gas completely loses the possibility of upward concentration and will accumulate in the gob, forming a major safety hazard. To overcome these problems, borehole artificially guided pre-splitting (BAGP) technology was proposed. Three different pre-splitting boreholes were constructed as a group to generate artificial fractures in advance in HTR via deep-hole blasting, promoting the evolution of roof fractures. With the effects of mining stress, a fracture network is eventually formed in HTR, which provides a preferential passage for the upward flow of coalbed gas. Moreover, the controllable breaking of HTR was achieved and the roof strata could deform and subside regularly, forming an “O-shaped” roof-fractured zone above the gob which greatly improves the gas extraction efficiency of roof high-level boreholes. In addition, after BAGP, several extraction measures can be applied in the gob-side entry to drain the gas in different concentrated areas. In the field experiment, the roof periodic breaking length was reduced by half, and the average gas extraction rate was increased by 4 times to 67.7%. The synergetic controls of HTR and coalbed gas were effectively realized. This study provides valuable insight into gas control in other deep coal mines with similar geological conditions.
ABSTRACT Cellular automata (CA) models are in growing use for land-use change simulation and future scenario prediction. It is necessary to conduct model assessment that reports the quality of simulation results and how well the models reproduce reliable spatial patterns. Here, we review 347 CA articles published during 1999–2018 identified by a Scholar Google search using ‘cellular automata’, ‘land’ and ‘urban’ as keywords. Our review demonstrates that, during the past two decades, 89% of the publications include model assessment related to dataset, procedure and result using more than ten different methods. Among all methods, cell-by-cell comparison and landscape analysis were most frequently applied in the CA model assessment; specifically, overall accuracy and standard Kappa coefficient respectively rank first and second among all metrics. The end-state assessment is often criticized by modelers because it cannot adequately reflect the modeling ability of CA models. We provide five suggestions to the method selection, aiming to offer a background framework for future method choices as well as urging to focus on the assessment of input data and error propagation, procedure, quantitative and spatial change, and the impact of driving factors. 相似文献
To overcome the fast or burst release of hydrophilic drugs from hydrophilic alginate-based carriers, hydrophobic molecule(vinyl acetate, VAc) was grafted on alginate(Alg), which was further used to prepare drug carriers. Amphiphilic Alg-g-PVAc hydrogel beads were firstly prepared by emulsification/internal gelation technique for the loading of bovine serum albumin(BSA). Then, chitosan was coated on the surface of beads to form novel amphiphilic Alg-g-PVAc/chitosan(Alg-g-PVAc/CS) microcapsules.The BSA-loading amphiphilic Alg-g-PVAc/chitosan(Alg-g-PVAc/CS) microcapsules display similar morphology and size to the hydrophilic alginate/chitosan(AC) microcapsules. However, the drug loading and loading efficiency of BSA in Alg-g-PVAc/CS microcapsules are higher, and the release rate of BSA from Alg-g-PVAc/CS microcapsules is slower. The results demonstrate that the introduction of hydrophobic PVAc on alginate can effectively help retard the release of BSA, and the higher degree of substitution is,the slower the release rate is. In addition, the complex membrane can also be adjusted to delay the release of BSA. As a whole, amphiphilic sodium alginate-vinyl acetate/CS microparticles could be developed for macromolecular drug delivery. 相似文献
Journal of Geographical Sciences - Land use and cover change (LUCC) is an important indicator of the human-earth system under climate/environmental change, which also serves as a key impact factor... 相似文献
