Depositional Processes of the Cenomanian-Turonian Reworked Carbonates in the Eastern Abu Dhabi, UAE

There are a limited number of studies and exploration cases for a "reworked carbonate" in Abu Dhabi, although these sediments are composed from some large oil and gas fields around the world (e.g. Poza Rica oil field in Mexico and Ruby gas field in Indonesia). In this study, we focused on Cenomanian-Turonian carbonates and considered the depositional processes of a "reworked carbonate" in the eastern part of Abu Dhabi. To understand the stacking pattern and/or depositional process of the Cenomanian-Turonian carbonate, we conducted a well-well correlation for total 16 wells, based on the core observations, wireline logs correlation (GR, Neutron, Density, Resistivity and Sonic), carbon and oxygen isotope analysis and trace elements analysis. Sampling was conducted for 8 wells and samples were taken approximately every 5 ft. In addition, to predict the spatiotemporal expansion of the reworked deposit, a 3D seismic interpretation was conducted. The result of the well-well correlation reveals that the depositional process and the stacking pattern of the Cenomanian-Turonian shoals around eastern Abu Dhabi are well consistent with the depositional model that proposed by Razin et al., 2010, and the reworked deposits are developed around the distal environment. 3D seismic interpretation represents that these reworked sediments were input from the north-west side and spread to the south-east like as a submarine-fan. Considering the core observation result, cohesive debris flow deposits are dominated at the depositional up-dip side and dilute flow deposits are dominated in the depositional down-dip side. In addition, an obvious erosional surface can be recognized in seismic sections and it truncates the top shoal sediments. The result of both, a combination of localized up-rift and global eustatic sea level fall in the early-middle Turonian triggered the regional erosion which is recognized as the middle Turonian unconformity. The result of this study suggests that the shoal sediments were eroded and reworked to a more distal environment at the early-middle Turonian.

Manipulating spatial alignment of donor and acceptor in host-guest MOF for TADF

Thermally activated delayed fluorescence (TADF) was achieved when electron-rich triphenylene (Tpl) donors (D) were confined to a cage-based porous MOF host (NKU-111) composed of electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (Tpt) acceptor (A) as the ligand. The spatially-separated D and A molecules in a face-to-face stacking pattern generated strong through-space charge transfer (CT) interactions with a small singlet-triplet excited states energy splitting (∼0.1 eV), which enabled TADF. The resulting Tpl@NKU-111 exhibited an uncommon enhanced emission intensity as the temperature increased. Extensive steady-state and time-resolved spectroscopic measurements and first-principles simulations revealed the chemical and electronic structure of this compound in both the ground and low-lying excited states. A double-channel (T1, T2) intersystem crossing mechanism with S1 was found and explained as single-directional CT from the degenerate HOMO-1/HOMO of the guest donor to the LUMO + 1 of one of the nearest acceptors. The rigid skeleton of the compound and effective through-space CT enhanced the photoluminescence quantum yield (PLQY). A maximum PLQY of 57.36% was achieved by optimizing the Tpl loading ratio in the host framework. These results indicate the potential of the MOFs for the targeted construction and optimization of TADF materials.

Molecular Determinants and Specificity of mRNA with Alternatively-Spliced UPF1 Isoforms, Influenced by an Insertion in the ‘Regulatory Loop’

The nonsense-mediated mRNA decay (NMD) pathway rapidly detects and degrades mRNA containing premature termination codons (PTCs). UP-frameshift 1 (UPF1), the master regulator of the NMD process, has two alternatively-spliced isoforms; one carries 353-GNEDLVIIWLR-363 insertion in the ‘regulatory loop (involved in mRNA binding)’. Such insertion can induce catalytic and/or ATPase activity, as determined experimentally; however, the kinetics and molecular level information are not fully understood. Herein, applying all-atom molecular dynamics, we probe the binding specificity of UPF1 with different GC- and AU-rich mRNA motifs and the influence of insertion to the viable control over UPF1 catalytic activity. Our results indicate two distinct conformations between 1B and RecA2 domains of UPF1: ‘open (isoform_2; without insertion)’ and ‘closed (isoform_1; with insertion)’. These structural movements correspond to an important stacking pattern in mRNA motifs, i.e., absence of stack formation in mRNA, with UPF1 isoform_2 results in the ‘open conformation’. Particularly, for UPF1 isoform_1, the increased distance between 1B and RecA2 domains has resulted in reducing the mRNA–UPF1 interactions. Lower fluctuating GC-rich mRNA motifs have better binding with UPF1, compared with AU-rich sequences. Except CCUGGGG, all other GC-rich motifs formed a 4-stack pattern with UPF1. High occupancy R363, D364, T627, and G862 residues were common binding GC-rich motifs, as were R363, N535, and T627 for the AU-rich motifs. The GC-rich motifs behave distinctly when bound to either of the isoforms; lower stability was observed with UPF1 isoform_2. The cancer-associated UPF1 variants (P533L/T and A839T) resulted in decreased protein–mRNA binding efficiency. Lack of mRNA stacking poses in the UPF1P533T system significantly decreased UPF1-mRNA binding efficiency and increased distance between 1B-RecA2. These novel findings can serve to further inform NMD-associated mechanistic and kinetic studies.

First-Principles Study of Electronic and Optical Properties of Two-Dimensional WSSe/BSe van der Waals Heterostructure with High Solar-to-Hydrogen Efficiency

In this paper, the optical and electronic properties of WSSe/BSe heterostructure are investigated by first-principles calculations. The most stable stacking pattern of the WSSe/BSe compounds is formed by van der Waals interaction with a thermal stability proved by ab initio molecular dynamics simulation. The WSSe/BSe heterostructure exhibits a type-I band alignment with direct bandgap of 2.151 eV, which can improve the effective recombination of photoexcited holes and electrons. Furthermore, the band alignment of the WSSe/BSe heterostructure can straddle the water redox potential at pH 0–8, and it has a wide absorption range for visible light. In particular, the solar-to-hydrogen efficiency of the WSSe/BSe heterostructure is obtained at as high as 44.9% at pH 4 and 5. All these investigations show that the WSSe/BSe heterostructure has potential application in photocatalysts to decompose water.

Rolling the WSSe Bilayer into Double-Walled Nanotube for the Enhanced Photocatalytic Water-Splitting Performance

For the emerging Janus transition metal dichalcogenides (TMD) layered water-splitting photocatalysts, stacking the monolayers to form bilayers has been predicted to be an effective way to improve their photocatalytic performances. To achieve this, the stacking pattern plays an important role. In this work, by means of the density functional theory calculations, we comprehensively estimate energetical stability, light absorption and redox capacity of Janus WSSe bilayer with different stacking patterns. Unfortunately, the Janus WSSe bilayer with the most stable configuration recover the out-of-plane symmetry, which is not in favor of the photocatalytic reactions. However, rolling the Janus WSSe bilayer into double-walled nanotube could stabilize the appropriate stacking pattern with an enhanced instinct dipole moment. Moreover, the suitable band edge positions, high visible light absorbance, outstanding solar-to-hydrogen efficiency (up to 28.48%), and superior carrier separation promise the Janus WSSe double-walled nanotube the potential for the photocatalytic water-splitting application. Our studies not only predict an ideal water-splitting photocatalyst, but also propose an effective way to improve the photocatalytic performances of Janus layered materials.

Fringe or background: Characterizing deep-water mudstones beyond the basin-floor fan sandstone pinchout

ABSTRACT Mud dominates volumetrically the fraction of sediment delivered and deposited in deep-water environments, and mudstone is a major component of basin-floor successions. However, studies of basin-floor deposits have mainly focused on their proximal sandstone-prone part. A consequent bias therefore remains in the understanding of depositional processes and stratigraphic architecture in mudstone-prone distal settings beyond the sandstone pinchouts of basin-floor fans. This study uses macroscopic and microscopic descriptions of over 500 m of continuous cores from research boreholes from the Permian Skoorsteenberg Formation of the Karoo Basin, South Africa, to document the sedimentology, stratigraphy, and ichnology of a distal mudstone-prone basin-floor succession. Very thin- to thin-bedded mudstones, deposited by low-density turbidity currents, stack to form bedsets bounded by thin packages (< 0.7 m thick) of background mudstones. Genetically related bedsets stack to form bedset packages, which are bounded by thicker (> 0.7 m thick) background mudstones. Stratigraphic correlation between cores suggests that bedsets represent the distal fringes of submarine fan lobe elements and/or lobes, and bedset packages represent the distal fringes of lobe complexes and/or lobe complex sets. The internal stacking pattern of bedsets and bedset packages is highly variable vertically and laterally, which records dominantly autogenic processes (e.g., compensational stacking, avulsion of feeder channels). The background mudstones are characterized by remnant tractional structures and outsize particles, and are interpreted as deposited from low-density turbidity currents and debris flows before intense biogenic reworking. These observations challenge the idea that mud accumulates only from hemipelagic suspension fallout in distal basin-floor environments. Thin background mudstones separating bedsets (< 0.7 m thick) are interpreted to mainly represent autogenically driven lobe abandonment due to up-dip channel avulsion. The thicker background mudstones separating bedset packages (> 0.7 m thick) are interpreted to dominantly mark allogenically driven regional decrease of sand supply to the basin floor. The recognition of sandstone-prone basin-floor fans passing into genetically linked distal fringe mudstones suggests that submarine lobes are at least ∼ 20 km longer than previously estimated. This study provides sedimentological, stratigraphic, and ichnological criteria to differentiate mudstones deposited in different sub-environments in distal deep-water basin-floor settings, with implications for the accurate characterization of basin-floor fan architecture, and their use as archives of paleoenvironmental change.

Simultaneous interlayer and intralayer space control in two-dimensional metal−organic frameworks for acetylene/ethylene separation

Three-dimensional metal−organic frameworks (MOFs) are cutting-edge materials in the adsorptive removal of trace gases due to the availability of abundant pores with specific chemistry. However, the development of ideal adsorbents combining high adsorption capacity with high selectivity and stability remains challenging. Here we demonstrate a strategy to design adsorbents that utilizes the tunability of interlayer and intralayer space of two-dimensional fluorinated MOFs for capturing acetylene from ethylene. Validated by X-ray diffraction and modeling, a systematic variation of linker atom oxidation state enables fine regulation of layer stacking pattern and linker conformation, which affords a strong interlayer trapping of molecules along with cooperative intralayer binding. The resultant robust materials (ZUL-100 and ZUL-200) exhibit benchmark capacity in the pressure range of 0.001–0.05 bar with high selectivity. Their efficiency in acetylene/ethylene separation is confirmed by breakthrough experiments, giving excellent ethylene productivities (121 mmol/g from 1/99 mixture, 99.9999%), even when cycled under moist conditions.