Mechanical Instability of Methane Hydrate–Mineral Interface Systems

Massive methane hydrates occur on sediment matrices in nature. Therefore, sediment-based methane hydrate systems play an essential role in the society and hydrate community, including energy resources, global climate changes, and geohazards. However, a fundamental understanding of mechanical properties of methane hydrate–mineral interface systems is largely limited due to insufficient experimental techniques. Herein, by using large-scale molecular simulations, we show that the mechanical properties of methane hydrate–mineral (silica, kaolinite, and Wyoming-type montmorillonite) interface systems are strongly dictated by the chemical components of sedimentary minerals that determine interfacial microstructures between methane hydrates and minerals. The tensile strengths of hydrate–mineral systems are found to decrease following the order of Wyoming-type montmorillonite- > silica- > kaolinite-based methane hydrate systems, all of which show a brittle failure at the interface between methane hydrates and minerals under tension. In contrast, upon compression, methane hydrates decompose into water and methane molecules, resulting from a large strain-induced mechanical instability. In particular, the failure of Wyoming-type montmorillonite-based methane hydrate systems under compression is characterized by a sudden decrease in the compressive stress at a strain of around 0.23, distinguishing it from those of silica- and kaolinite-based methane hydrate systems under compression. Our findings thus provide a molecular insight into the potential mechanisms of mechanical instability of gas hydrate-bearing sediment systems on Earth

Mechanical Instability of Methane Hydrate–Mineral Interface Systems

Massive methane hydrates occur on sediment matrices in nature. Therefore, sediment-based methane hydrate systems play an essential role in the society and hydrate community, including energy resources, global climate changes, and geohazards. However, a fundamental understanding of mechanical properties of methane hydrate–mineral interface systems is largely limited due to insufficient experimental techniques. Herein, by using large-scale molecular simulations, we show that the mechanical properties of methane hydrate–mineral (silica, kaolinite, and Wyoming-type montmorillonite) interface systems are strongly dictated by the chemical components of sedimentary minerals that determine interfacial microstructures between methane hydrates and minerals. The tensile strengths of hydrate–mineral systems are found to decrease following the order of Wyoming-type montmorillonite- > silica- > kaolinite-based methane hydrate systems, all of which show a brittle failure at the interface between methane hydrates and minerals under tension. In contrast, upon compression, methane hydrates decompose into water and methane molecules, resulting from a large strain-induced mechanical instability. In particular, the failure of Wyoming-type montmorillonite-based methane hydrate systems under compression is characterized by a sudden decrease in the compressive stress at a strain of around 0.23, distinguishing it from those of silica- and kaolinite-based methane hydrate systems under compression. Our findings thus provide a molecular insight into the potential mechanisms of mechanical instability of gas hydrate-bearing sediment systems on Earth

Mechanical Instability of Methane Hydrate–Mineral Interface Systems

Massive methane hydrates occur on sediment matrices in nature. Therefore, sediment-based methane hydrate systems play an essential role in the society and hydrate community, including energy resources, global climate changes, and geohazards. However, a fundamental understanding of mechanical properties of methane hydrate–mineral interface systems is largely limited due to insufficient experimental techniques. Herein, by using large-scale molecular simulations, we show that the mechanical properties of methane hydrate–mineral (silica, kaolinite, and Wyoming-type montmorillonite) interface systems are strongly dictated by the chemical components of sedimentary minerals that determine interfacial microstructures between methane hydrates and minerals. The tensile strengths of hydrate–mineral systems are found to decrease following the order of Wyoming-type montmorillonite- > silica- > kaolinite-based methane hydrate systems, all of which show a brittle failure at the interface between methane hydrates and minerals under tension. In contrast, upon compression, methane hydrates decompose into water and methane molecules, resulting from a large strain-induced mechanical instability. In particular, the failure of Wyoming-type montmorillonite-based methane hydrate systems under compression is characterized by a sudden decrease in the compressive stress at a strain of around 0.23, distinguishing it from those of silica- and kaolinite-based methane hydrate systems under compression. Our findings thus provide a molecular insight into the potential mechanisms of mechanical instability of gas hydrate-bearing sediment systems on Earth

Genome-wide investigation of sucrose synthase gene family in pineapple: Characterization and expression profile analysis during fruit development

Sucrose content influences the flavour and quality of fruits. Sucrose synthase (SUS; EC 2.4.1.13) mediates the reversible conversion of uridine diphosphate and sucrose to uridine diphosphate-glucose and fructose. Although genome-wide analyses of SUS gene families exist for various species, such studies are lacking for pineapple. The specific SUS gene(s) involved in sucrose metabolism during pineapple development remain unknown. This study identified six SUS genes (AcSUS1–6) and analysed their chromosomal locations, synteny, structure, motif composition, sequence alignments, and phylogenetic relationships. Gene promoter analysis revealed a predominance of light-response elements in the AcSUS gene family. AcSUS1 was predominantly expressed in the peduncle, pericarp, and core, whereas AcSUS4 was highly expressed in the flesh. The levels of sucrose, glucose, and fructose increase during pineapple fruit development. Further gene expression analysis indicated that AcSUS2, AcSUS3, and AcSUS5 were down-regulated during this period. These results suggest that AcSUS2, AcSUS3, and AcSUS5 may modulate sucrose breakdown in pineapple. This study contributes to our understanding of SUS gene function in regulating sucrose metabolism and offers valuable theoretical guidance for the genetic improvement of pineapples.</p

Mechanical Instability of Methane Hydrate–Mineral Interface Systems

Massive methane hydrates occur on sediment matrices in nature. Therefore, sediment-based methane hydrate systems play an essential role in the society and hydrate community, including energy resources, global climate changes, and geohazards. However, a fundamental understanding of mechanical properties of methane hydrate–mineral interface systems is largely limited due to insufficient experimental techniques. Herein, by using large-scale molecular simulations, we show that the mechanical properties of methane hydrate–mineral (silica, kaolinite, and Wyoming-type montmorillonite) interface systems are strongly dictated by the chemical components of sedimentary minerals that determine interfacial microstructures between methane hydrates and minerals. The tensile strengths of hydrate–mineral systems are found to decrease following the order of Wyoming-type montmorillonite- > silica- > kaolinite-based methane hydrate systems, all of which show a brittle failure at the interface between methane hydrates and minerals under tension. In contrast, upon compression, methane hydrates decompose into water and methane molecules, resulting from a large strain-induced mechanical instability. In particular, the failure of Wyoming-type montmorillonite-based methane hydrate systems under compression is characterized by a sudden decrease in the compressive stress at a strain of around 0.23, distinguishing it from those of silica- and kaolinite-based methane hydrate systems under compression. Our findings thus provide a molecular insight into the potential mechanisms of mechanical instability of gas hydrate-bearing sediment systems on Earth

Electric Field-Controlled Structural Instability and Mechanical Properties of Methane Hydrates

Gas hydrates play a significant role in the broad areas of energy applications and climate changes. Furthermore, externally applied fields by charged sediments and artificial activities are of paramount importance for transitions between disordered and ordered gas hydrate systems on the Earth. Herein, the role of external static electric fields in the structural instability and mechanical properties of methane hydrates are explored using molecular dynamics simulation methods. Our simulation results show that mechanical characteristics of methane hydrates such as Young’s modulus, strengths, and failure modes are greatly affected by strengths and imposed directions of external electric fields. Interestingly, strong electric fields can result in the distortion and dissociation of local water cages in methane hydrates mainly due to realignments of water molecules, thereby weakening their mechanical properties. Moreover, instability failure modes of methane hydrates can be attributed to notable reorientations of water molecules and molecular diffusions of water and methane molecules in methane hydrates. This work provides new insights into mechanics of natural crystalline gas hydrates, which is also helpful for understanding the mechanical instability of charged sediment–host natural gas hydrates

Designing Anion-Derived Solid Electrolyte Interphase in a Siloxane-Based Electrolyte for Lithium-Metal Batteries

The rational electrolyte design with weak solvation is regarded as an effective way to regulate the electrolyte/electrode interface (SEI) that profoundly affects the performance of Li-metal batteries. Herein, we propose a newly developed siloxane-based weakly solvating electrolyte (SiBE) with contact ion pairs (CIPs) or aggregates (AGGs) dominating the solution structure, which enables the dendrite-free Li deposition and long cycle stability of Li-metal batteries. By altering the combination of Li salts, the SiBE leads to the formation of an inorganic anion-derived solid electrolyte interphase, which is highly stable and Li+-conductive. Based on SiBE, the Li||LiFePO4 (LFP) full cell can stably cycle for 1000 cycles at a 2C rate with a capacity retention of 76.9%. Even with a limited Li-metal anode, it can maintain a capacity retention of 80% after 110 cycles with a high average Coulombic efficiency of 99.8%. This work reveals that siloxane can be a promising solvent to obtain weakly solvating electrolytes, which opens a new avenue for SEI composition regulation of Li-metal batteries

Giant Stretchability and Reversibility of Tightly Wound Helical Carbon Nanotubes

There is a surging interest in 3D graphitic nanostructures which possess outstanding properties enabling them to be prime candidates for a new generation of nanodevices and energy-absorbing materials. Here we study the stretching instability and reversibility of tightly wound helical carbon nanotubes (HCNTs) by atomistic simulations. The intercoil van der Waals (vdW) interaction-induced flattening of HCNT walls prior to loading is constrained by the defects coordinated for the curvature formation of helices. The HCNTs exhibit extensive stretchability in the range from 400% to 1000% as a result of two distinct deformation mechanisms depending on the HCNT size. For small HCNTs tremendous deformation is achieved by domino-type partial fracture events, whereas for large HCNTs this is accomplished by stepwise buckling of coils. The formation and fracture of edge-closed graphene ribbons occur at lower temperatures, while at elevated temperatures the highly distributed fracture realizes a phenomenal stretchability. The results of cyclic stretching-reversing simulations of large HCNTs display pronounced hysteresis loops, which produce large energy dissipation via full recovery of buckling and vdW bondings. This study provides physical insights into the origins of high ductility and superior reversibility of hybrid CNT structures

Table_4_Metabolomic and transcriptomic analyses reveal the mechanism of sweet-acidic taste formation during pineapple fruit development.XLSX

Pineapple (Ananas comosus L.) is one of the most valuable subtropical fruit crop in the world. The sweet-acidic taste of the pineapple fruits is a major contributor to the characteristic of fruit quality, but its formation mechanism remains elusive. Here, targeted metabolomic and transcriptomic analyses were performed during the fruit developmental stages in two pineapple cultivars (“Comte de Paris” and “MD-2”) to gain a global view of the metabolism and transport pathways involved in sugar and organic acid accumulation. Assessment of the levels of different sugar and acid components during fruit development revealed that the predominant sugar and organic acid in mature fruits of both cultivars was sucrose and citric acid, respectively. Weighted gene coexpression network analysis of metabolic phenotypes and gene expression profiling enabled the identification of 21 genes associated with sucrose accumulation and 19 genes associated with citric acid accumulation. The coordinated interaction of the 21 genes correlated with sucrose irreversible hydrolysis, resynthesis, and transport could be responsible for sucrose accumulation in pineapple fruit. In addition, citric acid accumulation might be controlled by the coordinated interaction of the pyruvate-to-acetyl-CoA-to-citrate pathway, gamma-aminobutyric acid pathway, and tonoplast proton pumps in pineapple. These results provide deep insights into the metabolic regulation of sweetness and acidity in pineapple.</p