Cage Structure Research Articles

The Optical Corrector for the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) is currently measuring the spectra of 40 million galaxies and quasars, the largest such survey ever made to probe the nature of cosmological dark energy. The 4 m Mayall telescope at Kitt Peak National Observatory has been adapted for DESI, including the construction of a 3.°2 diameter prime focus corrector that focuses astronomical light onto a 0.8 m diameter focal surface with excellent image quality over the DESI bandpass of 360–980 nm. The wide-field corrector includes six lenses, as large as 1.1 m in diameter and as heavy as 237 kilograms, including two counterrotating wedged lenses that correct for atmospheric dispersion over zenith angles from 0° to 60°. The lenses, cells, and barrel assembly all meet precise alignment tolerances on the order of tens of microns. The barrel alignment is maintained throughout a range of observing angles and temperature excursions in the Mayall dome by use of a hexapod, which is itself supported by a new cage, ring, and truss structure. In this paper we describe the design, fabrication, and performance of the new corrector and associated structure, focusing on how they meet DESI requirements. In particular, we describe the prescription and specifications of the lenses, design choices and error budgeting of the barrel assembly, stray light mitigations, and integration and test at the Mayall telescope. We conclude with some validation highlights that demonstrate the successful corrector on-sky performance, and we list some lessons learned during the multiyear fabrication phase.

Strong Enhancement in Cobalt(II)-TPMA Aqueous Hydrogen Photosynthesis through Intramolecular Proton Relay.

Photosynthetic hydrogen generation by cobalt(II) tris(2-pyridylmethyl)amine (TPMA) complexes is mainly limited by protonation kinetics and decomposition routes involving demetallation. In the present work we have explored the effects of both proton shuttles and improved rigidity on the catalytic ability of cobalt(II) TPMA complexes. Remarkably, we demonstrate that, while a small enhancement in the catalytic performance is attained in a rigid cage structure, the introduction of ammonium groups as proton transfer relays in close proximity to the cobalt center allows to reach a 4-fold increase in the quantum efficiency of H2 formation, and a surprising 22-fold gain in the maximum turnover number, at low catalyst concentration. The beneficial role of the ammonium relays in promoting faster intramolecular proton transfer to the reduced cobalt center is documented by transient absorption spectroscopy, showcasing the great relevance of tuning the catalyst periphery to achieve efficient catalysis of solar fuel formation.

Failure Inducement Factor Analysis and Optimal Design Method of Ball Bearing Cage for Aviation Motor

In experiments of aviation motor bearings, when the deep-groove ball bearings are subjected to an overturning moment at high speed, it often happens that the rivet on the cage breaks and the debris invades the raceway, resulting in bearing failure. To address the problem of early failure of deep-groove ball bearing cages and rivets in aviation motors, the causes of early failure were analyzed from the aspect of cage design in this study. The influence of the raceway and cage structure parameters on the dynamic contact characteristics of the rolling element and cage under the action of overturning torque were analyzed, the weak link of the cage was determined, and the cage design parameters were optimized. The results show that with an increase in the cage width and pocket radius, the impact force between the ball and cage first decreases and then increases, and the tilt angle of the cage gradually decreases. A larger channel radius and smaller clearance can slow down the interaction between the cage and the rolling element and make the cage run more smoothly. Increasing the thickness of the cage can ensure that the rivet part of the cage is at a low stress level, and the risk of premature fatigue failure at the rivet part can be reduced by maintaining a small gap–fit relationship between the rivet and rivet holes. The research results indicate that the working condition adaptability of the bearing cage for aviation motors can be improved, and the design method for this type of bearing can be enhanced.

Decoupling of Rattling Mode and Superconductivity in Filled-Skutterudite BaxIr4Sb12

Abstract The rattling mode, an anharmonic vibrational phonon, is widely recognized as a critical factor in the emergence of superconductivity in caged materials. Here, we present a counterexample in a filled-skutterudite superconductor Ba x Ir4Sb12 (x = 0.8, 0.9, 1.0), synthesized via a high-pressure route. Transport measurements down to liquid 3He temperatures reveal a transition temperature (T c) of 1.2 K and an upper critical field (H c2) of 1.3 T. Unlike other superconductors with caged structures, the Ba x Ir4 X 12 (X = P, As, Sb) family exhibits a monotonic decreasing T c with the enhancement of the rattling mode, as indicated by fitting the Bloch–Grüneisen formula. Theoretical analysis suggests that electron doping from Ba transforms the direct bandgap IrSb3 into a metal, with the Fermi surface dominated by the hybridization of Ir 5d and Sb 5p orbitals. Our findings of decoupled rattling modes and superconductivity distinguish the Ba x Ir4Sb12 family from other caged superconductors, warranting further exploration into the underlying mechanism.

Novel Reactive Polyhedral Oligomeric Silsesquioxane-Reinforced and Toughened Epoxy Resins for Advanced Composites.

Most toughening methods for epoxy resins are usually used at the expense of other properties. Some polyhedral oligomeric silsesquioxanes (POSSs) with both a rigid Si-O-Si structure and flexible organic chain segments could be expected to be effective toughening agents. In this study, three reactive polyhedral oligomeric silsesquioxanes with a thiol group (OMPPS), a carboxyl group (OCOPS), and an epoxy group (OGCPS) were synthesized and characterized. They were utilized as modifiers to toughen 3-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline (AFG-90MH)/4,4'-methylenebis(2-ethylaniline) (MOEA) (epoxy resin) with different molar ratios to obtain hybrid resins named OMPPS-EP-i, OCOPS-EP-j, and OGCPS-EP-k. The effects of the amount of modifier added and the length of the organic chain on the cage structure on various properties of the hybrid resins were investigated. The results show that all three modifiers show good compatibility with the epoxy resin. The hybrid resins have a low viscosity at 45~85 °C and can be cured at a low temperature (110 °C). The cured hybrid resins display improved toughness. Typically, the critical stress intensity factor (KIC) and impact strength of OGCPS-EP-0.6-C are 2.54 MPa∙m-1/2 and 19.33 kJ∙m-2, respectively, which increased by 58.75% and 22.48% compared with the pristine epoxy resin, respectively. In addition, the glass transition temperature and flexural strength of the hybrid resins are basically unchanged.

Structural Insights into the Roles of PARP4 and NAD + in the Human Vault Cage.

Vault is a massive ribonucleoprotein complex found across Eukaryota. The major vault protein (MVP) oligomerizes into an ovular cage, which contains several minor vault components (MVCs) and is thought to transport transiently bound "cargo" molecules. Vertebrate vaults house a poly (ADP-ribose) polymerase (known as PARP4 in humans), which is the only MVC with known enzymatic activity. Despite being discovered decades ago, the molecular basis for PARP4's interaction with MVP remains unclear. In this study, we determined the structure of the human vault cage in complex with PARP4 and its enzymatic substrate NAD + . The structures reveal atomic-level details of the protein-binding interface, as well as unexpected NAD + -binding pockets within the interior of the vault cage. In addition, proteomics data show that human vaults purified from wild-type and PARP4-depleted cells interact with distinct subsets of proteins. Our results thereby support a model in which PARP4's specific incorporation into the vault cage helps to regulate vault's selection of cargo and its subcellular localization. Further, PARP4's proximity to MVP's NAD + -binding sites could support its enzymatic function within the vault.

Adsorption and separation performance of tungsten and molybdenum on modified zirconium based metal organic frameworks UiO-66-CTAB

A modified zirconium (Zr)-based metal organic framework (UiO-66-CTAB) was synthesized by solvothermal method, and used for the adsorption and separation of molybdenum (Mo) and tungsten (W). Under the optimized conditions, UiO-66-CTAB with uniform pore size and containing particles with tetrahedral cage structure could be obtained. UiO-66-CTAB showed BET surface area and micropore volume of 873.848 m2·g−1 and 0.403 cm3·g−1, respectively, with the particle size range of 200–300 nm. It acquired positive charge at pH < 7, thus it could get easily connected with the negatively charged Mo species. The material shows excellent adsorption of Mo and its effective separation from W in acidic solution. It is beneficial for separation at room temperature under the optimal contact time of 3 h. The adsorption capacity for Mo (QMo) was 355 mg·g−1 and the highest separation factor (βMo/W) was 51.4. Comprehensive analysis of XRD, SEM, FT-IR spectroscopy, XPS, and thermodynamic results indicate that the adsorption mechanism involved the selectivity of the effect of pore size, stronger affinity of the metal point Zr for Mo, and coordination interaction between the N atom of CTAB and Mo element, which allowed more Mo-homopoly acid ions to enter the cage and significantly hindered the entrance of W-homopoly acid ions into the UiO-66-CTAB. The adsorbent UiO-66-CTAB can be considered as a potential candidate for new and green adsorbent materials for the separation and recovery of W and Mo in the treatment of ores, wastes, and wastewater, which is beneficial for environmental protection.

Coalescence of Porous Coordination Cages into Crystalline and Amorphous Bulk Solids.

Discrete porous coordination cages are attractive as a solution processable material whose porosity is not predicated on a network structure. Here, we leverage the peripheral functionalization of these cage structures to obtain 12 novel, solution processable, porous coordination cages that afford crystalline and amorphous single-phase millimeter-scale monolithic bulk structures (six of each) upon solidification. These structures are based upon prototypal metal-organic polyhedra [Cu24(5-x-isophthalate)24] (where x = NH2, OH), wherein meta-substitution of linker ligands with acyl chloride or isocyanate moieties afforded amide and urethane functional groups, respectively. These porous cage structures were obtainable via direct synthesis between a metal salt and a ligand as well as postsynthetic modification of the cage and formed monoliths following centrifugation and drying of the product. We rationalize their self-assembly as colloidal packing of nanoscale cuboctahedral cages through weak interactions between their hydrophobic alkyl/aromatic surfaces. In general, amorphous solids were obtained via rapid precipitation from the mother liquor upon methanol addition, while crystalline solids could be obtained only following further chloroform and pyridine additions. The structure of the materials is confirmed via gas sorption and spectroscopic methods, while powder X-ray diffraction and transmission electron microscopy are used to determine the nature of these bulk solids.

HTR+: a novel algorithm for identifying type and polycrystal of gas hydrates

In this work, the hierarchical topology ring (HTR+) algorithm, an extension of the HTR algorithm, was developed for identifying gas hydrate types, cage structures, and grain boundaries (GBs) within polycrystalline structures. Utilizing molecular dynamics trajectories of polycrystalline hydrates, the accuracy of the HTR+ algorithm is validated in identifying sI, sII and sH hydrate types, hydrate grains, and GBs in multi-hydrate polycrystals, as well as clathrate cages at GBs. Additionally, during the hydrate nucleation and growth processes, clathrate cages, hydrate type, hydrate grains and ice structures are accurately recognized. Significantly, this algorithm demonstrates high efficiency, particularly for large hydrate systems. HTR+ algorithm emerges a powerful tool for identifying micro/mesoscopic structures of gas hydrates, enabling an in-depth understanding of the formation mechanisms and properties of gas hydrates.

Understanding shape selectivity effects of hydroisomerization using a reaction equilibrium model.

We study important aspects of shape selectivity effects of zeolites for hydroisomerization of linear alkanes, which produces a myriad of isomers, particularly for long chain hydrocarbons. To investigate the conditions for achieving an optimal yield of branched hydrocarbons, it is important to understand the role of chemical equilibrium in these reversible reactions. We conduct an extensive analysis of shape selectivity effects of different zeolites for the hydroisomerization of C7 and C8 isomers at chemical reaction equilibrium conditions. The reaction ensemble Monte Carlo method, coupled with grand-canonical Monte Carlo simulations, is commonly used for computing reaction equilibrium of heterogeneous reactions. The computational demands become prohibitive for a large number of reactions. We used a faster alternative in which reaction equilibrium is obtained by imposing chemical equilibrium in the gas phase and phase equilibrium between the gas phase components and the adsorbed phase counterparts. This effectively mimics the chemical equilibrium distribution in the adsorbed phase. Using Henry's law at infinite dilution and mixture adsorption isotherm models at elevated pressures, we calculate the adsorbed loadings in the zeolites. This study shows that zeolites with cage or channel-like structures exhibit significant differences in selectivity for alkane isomers. We also observe a minimal impact of pressure on the gas-phase equilibrium of these reactions at typical experimental reaction temperatures 400-700K. This study marks initial strides in understanding the reaction product distribution for long-chain alkanes.

Nature of partial sigma bond.

This study investigates the formation of partial sigma (σ) covalent bonds in experimentally synthesizable biradicals formed from hydrogenated and fluorinated C8, C20, and C60 cage structures, by assessing their stability, geometry, and bonding character in singlet and triplet states using restricted B3LYP-D3/6-31+G(d,p) theory, natural bond orbital (NBO) analysis, and complete active space self-consistent field (CASSCF) method. The results show that these partial σCC bonds have Wiberg bond orders of 0.38 to 0.48 and bond lengths ranging from 2.62 Å to 5.93 Å. Cage size influences the characteristics of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), with electrons favoring more antibonding orbitals in smaller cages where electrons reside more on the exterior of the cage and favoring bonding orbitals in larger ones where electrons are more in the interior. Fluorination enhances electron density on bonding orbitals. The analysis further clarified that the differentiation between antibonding and bonding features of HOMOs and LUMOs extends beyond merely electron transfer from s- to p-atomic orbitals, also noting possible interactions of the same symmetry repel. The study also introduces hyperconjugation from α-position CH bonds as a factor in stabilizing partial σ-bond formation. The results also caution against the use of broken symmetry methodology in unrestricted SCF wavefunctions for biradicals, such as those in this study as it may cause large spin contamination and thus errors in the calculated electronic properties results.

Homochiral metalated tetraphenylethylene‐based organic cages: Unusual chiral and luminescent behavior depending on thermodynamic and kinetic aggregation

AbstractChirality and luminescence are important for both chemistry and biology, which are highly influenced by aggregation. In this work, a pair of metalated tetraphenylethylene(TPE)‐based organic cage enantiomers are reported, which feature a quadrangular prismatic cage structure. These homochiral cages exhibit concentration‐dependent chiral behaviors alongside a propensity for thermodynamic aggregation. Aggregation caused quench effect is found for these cages accompanying the increasing of the concentrations. When a poor solvent is added to produce a kinetical aggregation, the aggregation‐annihilation circular dichroism and aggregation‐induced emission behaviors are observed for these enantiomeric cages. By comparing these observations with the photophysical behaviors of a pair of structurally similar organic molecular enantiomers, the unique photophysical properties observed are intricately linked to the metal‐integrated TPE‐functionalized cage structures.

Low density phases of TiO2 by cluster self-assembly

The interest in titanium dioxide (TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}) phases is growing due to the number of applications in cosmetics, food industry and photocatalysis, an increase that is driven by its exceptional properties when engineered at the nanoscale like in the form of nanoparticles. Our goal is to discover unknown low-density phases of TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, with potential for applications in various fields. We then use well-known TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} clusters as fundamental building blocks to be self-assembled into unique structures to study their distinct characteristics. Density functional calculations are employed to relax the structures and identify the most stable TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} structures within an energy range of 0.1 eV per atom from the rutile and anatase phases, which are confirmed, validating our methodology. Going beyond conventional phases, we found two-dimensional TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} structures, previously explored in separate studies, and showing typical structures of transition metal dichalcogenide layers, that forge a bridge between different TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} structures. It is noteworthy that our investigation uncovered an entirely novel class of TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} structures featuring hexagonal cages like beehive channels, opening novel phases with huge potential. These discovered low-density phases are interesting, particularly the hexagonal cage structures with remarkable large gaps, because they introduce other dimensions for uncharted applications in the ever-growing TiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} landscape.

In situ measurements and simulations of a net cage in currents

Accurate predictions of net cages’ deformation under current loads are vitally important for the welfare of stocked fish and the safety of cage structures. In this study, a scaled cage model was deployed at a fish farm. The incoming flow profile was measured through an Acoustic Doppler Current Profiler (ADCP) with high resolution in the depth direction, and the flow inside the cage was measured through an Acoustic Doppler Vector (ADV). Pressure tags were applied to capture the lifting of the cage under varying current conditions. The incoming flow velocity shows a good correlation with the lifting of the cage, and in general the rate of the cage being lifted by the flow increases with flow speed. However, the flow speed measured inside the cage is much less correlated to the upstream flow and cage deformation. Numerical cage models consisting of truss elements were developed; two flow reduction factors r = 0.9 and 0.8 derived from empirical formulas and measurements inside cages in previous studies were applied. The numerical model with r = 0.8 can predict the cage deformation well, with most relative deviations in the depth directions being less than 15%. The study indicates the feasibility of applying pressure tags with high precision to estimate current-induced cage deformation in situ, especially when a cage is experiencing obvious deformation.

Metal-organic frameworks with optimal pore cages for high Xe adsorption and efficient Xe/Kr separation

Separation of Xe/Kr mixtures obtained from the by-products of air separation is a paramount industrial process but still a formidable challenge due to the inherent inertness and close physicochemical properties of Xe and Kr. Herein we present two isostructural metal–organic frameworks (MOF), MIL-88B-tpt and MIL-88B-tpt-F, which were found to have high Xe uptake capacities and efficient Xe/Kr separation resulted from the suitable pore caged structures and pore sizes. Remarkably, MIL-88B-tpt exhibits a record-high Xe sorption capacity of 210.2 cm3 g−1 at 273 K and 1 bar. The highest Xe uptake and moderate Xe/Kr separation selectivity endow MIL-88B-tpt with high-performance Xe/Kr separation, ranking it among the best-performing MOF. The comparable Xe/Kr separation performance observed for the fluorinated version of MIL-88B-tpt-F and MIL-88B-tpt indicates the fluorine groups have a negligible effect on the Xe/Kr separation. Thus the efficient Xe/Kr separation for both MOF is mainly resulted from the optimal pore cages for Xe trapping and the well-matched pore sizes for Xe atom. The extensive Xe···framework interactions unveiled by computational simulations facilitate a strong binding affinity to Xe, thus leading to the highest Xe uptakes and efficient separation ability for both MOF.

Experimental study of multiscale dynamic characterization of the gas-solid phase in a disturbing rotary centrifugal air classifier using pressure signal testing and analysis methods

This study investigates the complex dynamic characteristics of the flow field inside a disturbing rotary centrifugal air classifier through experimental analysis. To this end, micro-pressure sensors are employed to measure pressure signals in different spatial regions under various operating conditions. The analysis includes time-frequency characterization, complexity assessment, and multi-scale energy analysis. The time-domain fluctuation characteristics of the air classifier's pressure signal are closely tied to operating parameters, with the most intense pressure fluctuations occurring in the middle and back region of the air classifier. The loaded condition intensifies the fluctuations, with particle presence exacerbating low-frequency pressure variations and affecting the cyclone's vortex stability. Additionally, the internal installation of the screen cage structure exhibits maximum complexity and randomness in the internal flow field when Rf = 45 Hz, f = 0.4 kg/s, and β = 0°, showing higher randomness and reflecting fine-scale interactions between gas and particles. Conversely, larger scale characteristics are revealed by DET values in higher detail signal levels. Changes in operational parameters, such as perturbation frequency and feeding time, significantly affect the axial distribution of multi-scale energy in the air classifier, with a greater influence on pressure fluctuation at the macroscopic scale, indicating intensified turbulent behavior between gas and particles. This study reveals the influencing mechanisms of various operating parameters on the multiscale dynamic characteristics and complexity of the flow field inside the rotary centrifugal air classifier.

In Silico Design and Characterization of a New Molecular Electride: Li@Calix[3]Pyrrole.

Electrides, in which anionic electrons are localized independently of the atoms in the compound, have shown promise, especially as catalysts and optoelectronic materials. Here, we present a new computationally designed molecular electride, Li@calix[3]pyrrole (Li@C3P). Electron density and electron localization function analyses unequivocally confirm the existence of localized electride electron density, outside the system, independent of any specific atoms. Non-covalent interaction plots further validate the character of the isolated localized electron, suggesting that the system can be accurately represented by Li+@calix[3]pyrrole ⋅ e-, denoting its distinct charge separation. The remarkable non-linear optical properties of Li@C3P, including average polarizability, =412.4 au, first hyperpolarizability, β=4.46×104 au, and second hyperpolarizability, =18.40×106 au, are unparalleled in the previously reported and similar Li@C4P molecular electride. Furthermore, energy decomposition analysis in combination with natural orbital for chemical valence theory sheds light on the mechanism of electron density transfer from Li to the C3P cage, yielding the charge-separated Li@C3P complex. In addition to the electron transfer, a key factor to its electride nature is the electronic structure of the CnP cage, which has its lowest unoccupied molecular orbital located in the void adjacent to the N-H groups at the back of the bowl-shaped CnP cage.

Reengineering of an Artificial Protein Cage for Efficient Packaging of Active Enzymes.

Protein cages that readily encapsulate active enzymes of interest present useful nanotools for delivery and catalysis, wherein those with programmable disassembly characteristics serve as particularly attractive platforms. Here, a general guest packaging system based on an artificial protein cage, TRAP-cage, the disassembly of which can be induced by the addition of reducing agents, is established. In this system, TRAP-cage with SpyCatcher moieties in the lumen is prepared using genetic modification of the protein building block and assembled into a cage structure with either monovalent gold ions or molecular crosslinkers. The resulting protein cage can efficiently capture guest proteins equipped with a SpyTag by simply mixing them in an aqueous solution. This post-assembly loading system, which circumvents the exposure of guests to thiol-reactive crosslinkers, enables the packaging of enzymes possessing a catalytic cysteine or a metal cofactor while retaining their catalytic activity.

Degradation of Bisphenol A by Nitrogen-Rich ZIF-8-Derived Carbon Materials-Activated Peroxymonosulfate.

Bisphenol A (BPA), representing a class of organic pollutants, finds extensive applications in the pharmaceutical industry. However, its widespread use poses a significant hazard to both ecosystem integrity and human health. Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) via heterogeneous catalysts are frequently proposed for treating persistent pollutants. In this study, the degradation performance of BPA in an oxidation system of PMS activated by transition metal sites anchored nitrogen-doped carbonaceous substrate (M-N-C) materials was investigated. As heterogeneous catalysts targeting the activation of peroxymonosulfate (PMS), M-N-C materials emerge as promising contenders poised to overcome the limitations encountered with traditional carbon materials, which often exhibit insufficient activity in the PMS activation process. Nevertheless, the amalgamation of metal sites during the synthesis process presents a formidable challenge to the structural design of M-N-C. Herein, employing ZIF-8 as the precursor of carbonaceous support, metal ions can readily penetrate the cage structure of the substrate, and the N-rich linkers serve as effective ligands for anchoring metal cations, thereby overcoming the awkward limitation. The research results of this study indicate BPA in water matrix can be effectively removed in the M-N-C/PMS system, in which the obtained nitrogen-rich ZIF-8-derived Cu-N-C presented excellent activity and stability on the PMS activation, as well as the outstanding resistance towards the variation of environmental factors. Moreover, the biological toxicity of BPA and its degradation intermediates were investigated via the Toxicity Estimation Software Tool (T.E.S.T.) based on the ECOSAR system.

Molecular dynamics study on roles of surface mixed hydrate in the CH4/CO2 replacement mechanisms

The CH4/CO2 replacement method is a promising approach for the exploitation of natural gas hydrates, offering dual benefits of extracting CH4 and sequestering CO2. This technique not only facilitates the extraction process but also mitigates the greenhouse effect and maintains geological stability, thereby contributing to sustainable energy utilization and environmental preservation. Currently, there are multiple viewpoints about the replacement mechanism. Furthermore, mixed hydrates can form on the surface during the replacement process. The unclear mechanism of CH4/CO2 replacement and the obstruction of mass transfer caused by the mixed hydrate impede its practical applicability. Clarifying the effects of surface mixed hydrate in replacement mechanisms can offer valuable insights for identifying optimal operating conditions in practical exploitation applications. Therefore, the present study aims to reveal the significant roles of surface mixed hydrates in the replacement mechanism by employing the molecular dynamics simulation methodology. The results showed that under the mechanism of cage complete rupture, the surface mixed hydrate decomposes rapidly to form a thickening water zone. Additionally, each layer of the hydrate cage structure undergoes a process from deformation or partial rupture to sudden complete disintegration, which is concomitant with an abrupt change of potential energy. Under the mechanism of cage incomplete rupture, the surface mixed hydrates hinder mass transfer and decelerate the reaction rate. A similar situation arises when the number of the surface mixed hydrate layers is increased. Therefore, the key to distinguishing the replacement mechanism lies in whether the environmental conditions are sufficient to break the potential energy barrier of the surface mixed hydrate and disrupt its cage structure.