FeSx@MoS2-x (FM-x, x implied real Mo/Fe content ratios) in which FeSx derived from MIL-88A deposited on the surface of MoS2 with a tight heterogeneous interface were synthesized for peroxymonosulfate (PMS) activation to degrade atrazine (ATZ). The catalytic performance of FM-0.96 was greatly improved due to the rapid regeneration of Fe2+ resulting from the interfacial interaction. FM-0.96 could completely degrade 10.0 mg/L ATZ within 1.0 min, and the toxicities for most of its intermediates were greatly reduced. The k value of FM-0.96 was 320 and 40 times higher than that of the MoS2 and FeSx, respectively. The SO4·−, ·OH and 1O2 were mainly responsible for ATZ degradation in FM-0.96/PMS system, and the conversion pathway of 1O2 was analyzed. Furthermore, the long-term continuous operation for ATZ degradation was achieved using a fixed membrane reactor. This work provides deep insights into metal sulfide composites derived from metal-organic frameworks for removing pollutants by activating PMS.
The compression of three-dimensional sound field signals has always been a very important issue. Recently, an Independent Component Analysis (ICA) based Higher Order Ambisonics (HOA) compression method introduces blind source separation to solve the shortcomings of discontinuity between frames in the existing Singular Value Decomposition (SVD) based methods. However, ICA is weak to model the reverberant environment, and its target is not to recover original signal. In this work, we replace ICA with autoencoder to further improve the above method’s ability to cope with reverberation conditions and ensure the unanimous optimization both in separation and recovery by reconstruction loss. We constructed a dataset with simulated and recorded signals, and verified the effectiveness of our method through objective and subjective experiments.
An accurate description of 2-D quantum transport in a double-gate metal oxide semiconductor field effect transistor (dgMOSFET) requires a high-resolution solver for a coupled system of the 4-D Wigner equation and 2-D Poisson equation. In this paper, we propose an operator-splitting spectral method to evolve such Wigner–Poisson (WP) system in 4-D phase space with high accuracy. After the operator splitting of the Wigner equation, the resulting two sub-equations can be solved analytically with spectral approximation in phase space. Meanwhile, we adopt a Chebyshev spectral method to solve the Poisson equation. Spectral convergence in phase space and a fourth-order accuracy in time are both numerically verified. Finally, we apply the proposed solver to the simulation of a dgMOSFET, develop the steady states via long-time simulations and obtain numerically converged current–voltage (I–V) curves.
Transient electronics is an emerging class of electronic devices that can physically degrade or disintegrate after a stable period of service, showing a vast prospect in applications of “green” consumer electronics, hardware-secure devices, medical implants, etc. Complementary metal-oxide–semiconductor (CMOS) technology is dominant in integrated circuit design for its advantages of low static power consumption, high noise immunity, and simple design layout, which also work and are highly preferred for transient electronics. However, the performance of complementary transient electronics is severely restricted by the confined selection of transient materials and compatible fabrication strategies. Here, we report the realization of high-performance transient complementary electronics based on carbon nanotube thin films via a reliable electrostatic doping method. Under a low operating voltage of 2 V, on a 1.5 μm-thick water-soluble substrate made of poly(vinyl alcohol), the width-normalized on-state currents of the p-type and n-type transient thin-film transistors (TFTs) reach 4.5 and 4.7 μA/μm, and the width-normalized transconductances reach 2.8 and 3.7 μS/μm, respectively. Meanwhile, these TFTs show small subthreshold swings no more than 108 mV/dec and current on/off ratios above 106 with good uniformity. Transient CMOS inverters, as basic circuit components, are demonstrated with a voltage gain of 24 and a high noise immunity of 67.4%. Finally, both the degradation of the active components and the disintegration of the functional system are continuously monitored with nontraceable remains after 10 and 5 h, respectively.
The overlooked role of high-valent cobalt-oxo species (Co(IV)) in the Co(II)/peroxymonosulfate (PMS) process was uncovered recently using methyl phenyl sulfoxide (PMSO) as the probe. Herein, we further interestingly found that Co(IV) could trigger hydroxyl radical (•OH) formation, resulting in the oxidized products distribution of PMSO heavily relied on the relative concentration of PMSO. More significantly, the generation of a series of 18O-labeled hydroxylated products (i.e., hydroxylated methyl phenyl sulfone, nitrobenzene and 4-nitrobenzoic acid) in H218O conclusively verified that •OH was triggered by Co(IV) species. Density functional theory calculation demonstrated that Co(IV) initiated •OH formation via oxo ligand protonation-induced valence tautomerization. Moreover, the oxidative contribution of Co(IV) and •OH on organic degradation was specifically dependent on the type and concentration of the substrate. This study provided deeper insights into the evolution pathway of •OH mediated by Co(IV) species and enriched the understandings on the collaborative oxidation mechanism in Co(IV)-involved processes.
The phenomenon of host-guest hydrogen bonding in clathrate hydrate crystal structures and its effect on physical and chemical properties have become subjects of extensive research. Hydrogen bonding has been studied for cubic (sI and sII) and hexagonal (sH) binary clathrates, while it has not been addressed for clathrate structures that exist at elevated pressures. Here, four acetone hydrate clathrates have been grown at high-pressure and low-temperature conditions. In situ single-crystal X-ray diffraction revealed that the synthesized phases possess already known trigonal (sTr), orthorhombic (sO), and tetragonal (sT) crystal structures as well as a previously unknown orthorhombic structure, so-called sO-II. Only sO and sII have previously been reported for acetone clathrates. Structural analysis suggests that acetone oxygens are hydrogen-bonded to the closest water oxygens of the host frameworks. Our discoveries show that clathrate hydrates hosting polar molecules are not as exotic as previously thought and could be stabilized at high-pressure conditions through hydrogen bonding.
Abstract Vegetation community complexity is a critical factor influencing terrestrial ecosystem stability. China, the country leading the world in vegetation greening resulting from human activities, has experienced dramatic changes in vegetation community composition during the past 30 years. However, how China's vegetation community complexity varies spatially and temporally remains unclear. Here, we examined the spatial pattern of China's vegetation community complexity and its temporal changes from the 1980s to 2015 using two vegetation maps of China as well as more than half a million field samples. Spatially, China's vegetation community complexity distribution is primarily dominated by elevation, although temperature and precipitation can be locally more influential than elevation when they become the factors limiting plant growth. Temporally, China's vegetation community complexity shows a significant decreasing trend during the past 30 years, despite the observed vegetation greening trend. Prevailing climate warming across China exhibits a significant negative correlation with the decrease in vegetation community complexity, but this correlation varies with biogeographical regions. The intensity of human activities have an overall negative influence on vegetation community complexity, but vegetation conservation and restoration efforts can have a positive effect on maintaining vegetation composition complexity, informing the critical role of vegetation management policies in achieving the sustainable development goal.
Increasing energy and environmental demands raise intensive interests on cleaner but challenging resource explorations, where unconventional tight reservoirs attract attentions due to its huge reserves but complex reservoir conditions. As commonly-used gas solvents for enhancing tight oil recovery, CO2 and N2 show their superb capabilities in each single usage, while their combinations, particularly utilizing of huff-n-puff (HnP) strategy, has been rarely investigated. In this paper, novel gas solvents, hybrid CO2-N2 gases with six molar ratios were synthesized and applied for a series of laboratory HnP tests using artificial cores. The proposed technology was specifically evaluated by analysing relevant properties, optimising production strategy, and examining the post-production residual oil saturation by means of nuclear magnetic resonance (NMR). Overall, our experiments validate the first three HnP cycles usually have higher oil recovery, while the subsequently further cycles would only be mildly beneficial. In this case, the hybrid CO2-N2 HnP simultaneously takes advantages of CO2-induced viscosity reduction and N2-induced elastic energy increase. The optimum proportion of CO2-N2 in the hybrid gas solvent is found to be 1:2, with the best HnP oil recovery of 39.0%. The NMR-assisted coreflood tests indicate largely uneven residual oil distributions. The effectivities of CO2 and N2 HnP are determined to be different in variation of pore scale in production tight oil, where the N2 HnP has better oil extraction ability in small pores.
The Devonian Antrim Shale is an unconventional biogenic gas accumulation with a technical recoverable resource of 19.9 Tcf. However, major knowledge gaps remain regarding understanding of the source rock potential, organic facies assemblages and paleo-depositional conditions of the Antrim Shale members. This work utilized Rock-Eval pyrolysis, reflected light microscopy and solid bitumen reflectance to characterize the source rock quality, organo-facies assemblages, and thermal maturity of the various Antrim Shale members at three different localities in the Michigan Basin. Results showed that the Lachine and Norwood members are richer in organic matter (up to 24 wt%) than the Upper and Paxton members (<8 wt%). Organic matter is mainly dominated by marine Type II kerogen in the black shales of the Lachine and Norwood members, and by Type II and Type II/III in the Paxton Member. Telalginite, which is represented mainly by Tasmanites and Leiosphaeridia cysts, is the dominant organic matter in the black shale members where they account for about two-thirds of the organic matter composition. Solid bitumen, which accounts for less than one-third of the organic matter composition, is second after alginite. Both alginite and solid bitumen populations decline in abundance progressively in the Upper and Paxton members at the expense of inertinite and vitrinite. The dominant organofacies groups in the studied Antrim Shale members can be assigned to the BP type B and type D/E. Organic matter maturity determined from Rock-Eval Tmax and bitumen reflectance varies from immature to marginally mature across the Michigan Basin. The results confirmed that sediment burial depth and lateral position in the basin controlled organic facies assemblages within the Antrim Shale members.
Peracetic acid (PAA) has been widely used as an alternative disinfectant in wastewater treatment, and PAA-based advanced oxidation processes (AOPs) have drawn increasing attention recently. Among the generated reactive species after PAA activation, acetylperoxyl radical (CH3CO3•) plays an important role in organic compounds degradation. However, little is known about the reaction mechanism on CH3CO3• attack due to the challenging of experimental analysis. In this study, a homogeneous PAA activation system was built up using Co(II) as an activator at neutral pH to generate CH3CO3• for phenol degradation. More importantly, reaction mechanism on CH3CO3•-driven oxidation of phenol is elucidated at the molecular level. CH3CO3• with lower electrophilicity index but much larger Waals molecular volume holds different phenol oxidation route compared with the conventional •OH. Direct evidences on CH3CO3• formation and attack mechanism are provided through integrated experimental and theoretical results, indicating that hydrogen atom abstraction (HAA) is the most favorable route in the initial step of CH3CO3•-driven phenol oxidation. HAA reaction step is found to produce phenoxy radicals with a low energy barrier of 4.78 kcal mol−1 and free energy change of -12.21 kcal mol−1. The generated phenoxy radicals will undergo further dimerization to form 4-phenoxyphenol and corresponding hydroxylated products, or react with CH3CO3• to generate catechol and hydroquinone. These results significantly promote the understanding of CH3CO3•-driven organic pollutant degradation and are useful for further development of PAA-based AOPs in environmental applications.