As one of the most important energy sources in the world today, shale gas has attracted extensive research. Numerous scholars agreed that the organic matter (OM) pores in shale provide the main space ...which benefits effective gas occurrence. However, the connectivity provided by OM pores is more important in the development process than their reservoir properties. A comprehensive portrayal of the 3D connectivity of the OM pores is elaborated in this study. The Lower Silurian Longmaxi shale samples were selected as the research subject. The shale samples are subjected to focused ion beam scanning electron microscope, helium ion microscope observation experiments, 2D microscopic characterization of OM pores, and 3D segmentation extraction. The results indicate that the connectivity of shale is mainly contributed by OM pores. The OM pores have the advantageous structural characteristics of large number per unit area, evenly distributed, regular pore morphology, and large pore size relative to the mineral matrix pores. The OM pores structure in shale is complex with a network structure of small pores nested in large pores, which can increase the adsorption capacity of gas. Besides, the small pores nested in large pores can act as a throat to significantly improve the connectivity. OM pores in the pyrobitumen are interconnected in 3D space, providing the main channels for gas percolation in the shale reservoir.
Organic matter pores have a large number of pores per unit area and are characterized by uniform distribution, regular morphology, and large pore size. The organic matter pores of shale have a composite network structure, with large pores nested in small pores, improving the connectivity of the system. The large size organic matter pores in the pyrobitumen scorched bitumen are interconnected, providing the main channel for gas percolation in the shale reservoir.
Nucleoporins (Nups) assemble nuclear pores that form the permeability barrier between nucleoplasm and cytoplasm. Nucleoporins also localize in cytoplasmic foci proposed to function as pore ...pre‐assembly intermediates. Here, we characterize the composition and incidence of cytoplasmic Nup foci in an intact animal, C. elegans. We find that, in young non‐stressed animals, Nup foci only appear in developing sperm, oocytes and embryos, tissues that express high levels of nucleoporins. The foci are condensates of highly cohesive FG repeat‐containing nucleoporins (FG‐Nups), which are maintained near their solubility limit in the cytoplasm by posttranslational modifications and chaperone activity. Only a minor fraction of FG‐Nup molecules concentrate in Nup foci, which dissolve during M phase and are dispensable for nuclear pore assembly. Nucleoporin condensation is enhanced by stress and advancing age, and overexpression of a single FG‐Nup in post‐mitotic neurons is sufficient to induce ectopic condensation and organismal paralysis. We speculate that Nup foci are non‐essential and potentially toxic condensates whose assembly is actively suppressed in healthy cells.
Synopsis
Highly cohesive, phenylalanine/glycine repeat‐containing nucleoporins (FG‐Nups) form the central channel of nuclear pores and also concentrate in cytoplasmic foci proposed to function as pore pre‐assembly intermediates. This study in the C. elegans model shows that nucleoporin (Nup) foci are transient condensates that are not essential for pore assembly.
Cellular Nup foci arise when FG‐Nups accumulate at high levels in the cytoplasm exceeding their solubility limit, such as in oocytes and developing embryos.
FG‐Nup solubility is enhanced by posttranslational modifications, including GlcNAcylation and phosphorylation, as well as by chaperone activity.
FG‐Nup foci are transient structures that dissolve during M phase, when FG‐Nup solubility increases.
FG repeat‐containing nucleoporins form non‐essential, age‐ and stress‐enhanced cytoplasmic condensates in germ cells and developing embryos.
HIV-1 infection requires nuclear entry of the viral genome. Previous evidence suggests that this entry proceeds through nuclear pore complexes (NPCs), with the 120 × 60 nm capsid squeezing through an ...approximately 60-nm-wide central channel
and crossing the permeability barrier of the NPC. This barrier can be described as an FG phase
that is assembled from cohesively interacting phenylalanine-glycine (FG) repeats
and is selectively permeable to cargo captured by nuclear transport receptors (NTRs). Here we show that HIV-1 capsid assemblies can target NPCs efficiently in an NTR-independent manner and bind directly to several types of FG repeats, including barrier-forming cohesive repeats. Like NTRs, the capsid readily partitions into an in vitro assembled cohesive FG phase that can serve as an NPC mimic and excludes much smaller inert probes such as mCherry. Indeed, entry of the capsid protein into such an FG phase is greatly enhanced by capsid assembly, which also allows the encapsulated clients to enter. Thus, our data indicate that the HIV-1 capsid behaves like an NTR, with its interior serving as a cargo container. Because capsid-coating with trans-acting NTRs would increase the diameter by 10 nm or more, we suggest that such a 'self-translocating' capsid undermines the size restrictions imposed by the NPC scaffold, thereby bypassing an otherwise effective barrier to viral infection.
•Longmaxi Shale is strongly controlled by the detachment belt in South China.•Structural deformation significantly influences the evolution of shale pore structure.•OM pore is poorly-developed in ...deformed shales.•Effect of tectonism on reservoir quality was discussed.
Pore types and pore size vary systematically across structural deformation in the shale gas reservoirs but lack a comprehensive study. Twelve Longmaxi Shale samples spanning a tectonism range from undeformed to deformed were formed in the structural deformation zone located in a field section of the Chuandong Thrust-Fold Belt, South China. Herein, pore structure investigations are performed using three types of organic-rich shale (undeformed shale, fault-related shale, and fold-related shale) with vitrinite reflectance (Ro value) ranging between 1.90 and 2.57% and total organic carbon (TOC) content ranging between 2.25 and 4.40%. Compared to the undeformed shales, deformed samples are quartz rich and carbonate poor. Total porosity from mercury intrusion porosimetry (MIP) ranges between 3.74 and 5.62% in undeformed shales, 2.66–6.83% in fold-related shales, and 2.55–13.92% in fault-related shales. Scanning electron microscopy (SEM) study of the pore type evolution reveals organic matter (OM) pores are dominant in undeformed shales whereas the interparticle (interP) pores, intraparticle (intraP) pores, micro-channels, and micro-fractures are more developed in both fold- and fault-related shales. A combination of low-pressure gas (N2 and CO2) adsorption and MIP techniques suggests that with increasing structural deformation, micropore volumes relatively increase in fold-related samples, while macropore volumes significantly increase in fault-related shales. These observations and experiments confirm that tectonism produces an open and interconnected pore network within organic-rich shale, which is not related to OM pores. The role of structural deformation during ductile folding and brittle sliding, both in changing the mineral composition and in the producing process of the new pore networks, may be critical to understanding tectonism on organic-rich shales. These data could provide important theoretical guidance and scientific basis for the exploration and development of shale gas and resources assessment in the complex tectonic area of South China.
Hydraulic fracturing is an effective method for producing coalbed methane. To better understand the evolution of the fracture and pore structure of coals that contain macro-fractures during hydraulic ...fracturing, we have performed a series of in-situ compression experiments under continuous injection liquid conditions and dynamically monitored the samples using nuclear magnetic resonance methods. The mechanism of fracture and pore structure dynamic evolution is identified in terms of spherical expansion theory. The total porosity increases dramatically within 10–120 min of the initial injection stage, and pore channels form. The number of micro-pores (<10 nm) and transition pores (10–100 nm) continues to increase during the injection pressure reduction stage or increasing confining pressure stage. Total porosity tends to initially decrease and then increase when the confining pressure remains either constant or increases. Continuous liquid injection leads to a constant change of coal pore pressure and effective stress, such that pores break, close, and continuously reorganize. The results presented here provide a reference for permeability calculations, coalbed methane productivity predictions, and improved hydraulic fracturing techniques.
Carbonaceous materials are attractive supercapacitor electrode materials due to their high electronic conductivity, large specific surface area, and low cost. Here, a unique hierarchical porous ...N,O,S‐enriched carbon foam (KNOSC) with high level of structural complexity for supercapacitors is reported. It is fabricated via a combination of a soft‐template method, freeze‐drying, and chemical etching. The carbon foam is a macroporous structure containing a network of mesoporous channels filled with micropores. It has an extremely large specific surface area of 2685 m2 g−1. The pore engineered carbon structure is also uniformly doped with N, O, and S. The KNOSC electrode achieves an outstanding capacitance of 402.5 F g−1 at 1 A g−1 and superior rate capability of 308.5 F g−1 at 100 A g−1. The KNOSC exhibits a Bode frequency at the phase angle of −45° of 18.5 Hz, which corresponds to a time constant of 0.054 s only. A symmetric supercapacitor device using KNOSC as electrodes can be charged/discharged within 1.52 s to deliver a specific energy density of 15.2 W h kg−1 at a power density of 36 kW kg−1. These results suggest that the pore and heteroatom engineered structures are promising electrode materials for ultrafast charging.
The integration of a tri‐doping and pore engineering method to prepare a unique hierarchical macroporous structure for ultrafast supercapacitors is demonstrated. This N,O,S tri‐doped structure offers an ultrahigh specific surface area and a network of multiple scale channels helping to improve capacitance performance of carbon structures including electric double layer capacitance, pseudocapacitance, and rate capability.
•Effects of salt precipitation on the properties of the shale matrix are studied.•The 3D porous structure reconstructions of the shale matrix are conducted.•Petrophysical properties are simulated ...based on the reconstructed pore networks.•The methane adsorption capacities at different temperatures are predicted.•The method complements laboratory measurements or empirical rock property models.
The study of salt precipitation and its effect on the reservoir physical properties and hydrocarbon adsorption capacity is important to the development of the shale reservoir with high salinity brine. In this study, a brine evaporation (static salting-out) is conducted on the shale matrix sample extracted from the Eocene Qianjiang inter-salt hypersaline lacustrine shale formation located in the Qianjiang Depression, Jianghan Basin, mid-eastern China, to prompt the salt precipitation to reach the exacerbation stage. The porous structure reconstruction technology is applied to study the effect of salt precipitation on the petrophysical properties of the shale matrix. The 3D pore networks of the shale matrix before and after brine evaporation are reconstructed based on 2D high-resolution nanoscale focused ion beam scanning electron microscopy (FIB-SEM) images. Pore-throat structural analyses and fluid flow simulations are carried out on the reconstructed pore networks to generate the physical and fluid flow properties. The density function theory (DFT) and the adsorption potential theory (APT) are combined to predict the CH4 adsorption isotherms of shale matrix with salt precipitation at different temperatures based on the pore size distribution (PSD) obtained from the reconstructed pore networks. The results show that salt precipitation can cause a 23.0% reduction in the porosity and a 47.0% reduction in the absolute permeability of the shale matrix. Salt precipitation has a stronger effect on larger pores and throats, which will cause the destruction of the reservoir fluid flow channels and a large change in the pore size distribution. The CH4 adsorption isotherms that are predicted based on the pore size distribution by the density function theory and the adsorption potential theory show that salt precipitation could cause a reduction of approximately 20.4% in the adsorption capacity, and the absolute adsorption capacity could be even smaller when the temperature is increased from the lab temperature to higher temperatures.
•PFPs are fundamental defense and virulence factors in bacteria and as executors of regulated cell death in eukaryotic cells.•Proteins and lipids cooperate to form different types of pores in ...membranes.•State-of-art single-particle techniques have allowed getting insight into the mechanism of pore formation by different PFPs.
Pore-forming proteins (PFPs) and small antimicrobial peptides (AMPs) represent a large family of molecules with the common ability to punch holes in cell membranes to alter their permeability. They play a fundamental role as infectious bacteria’s defensive tools against host’s immune system and as executors of endogenous machineries of regulated cell death in eukaryotic cells. Despite being highly divergent in primary sequence and 3D structure, specific folds of pore-forming domains have been conserved. In fact, pore formation is considered an ancient mechanism that takes place through a general multistep process involving: membrane partitioning and insertion, oligomerization and pore formation. However, different PFPs and AMPs assemble and form pores following different mechanisms that could end up either in the formation of protein-lined or protein-lipid pores. In this review, we analyze the current findings in the mechanism of action of different PFPs and AMPs that support a wide role of membrane pore formation in nature. We also provide the newest insights into the development of state-of-art techniques that have facilitated the characterization of membrane pores. To understand the physiological role of these peptides/proteins or develop clinical applications, it is essential to uncover the molecular mechanism of how they perforate membranes.
