The purpose of this research was to improve the sorption ability of Pb and Cd by promoting the ion exchange and precipitation capacity of biochar. The adsorption performance and mechanisms of Pb and ...Cd in wastewater using coconut shell biochar modified with magnesium were investigated. After modification, the total adsorption capacity (Qt) of Pb and Cd on Mg-coated biochar (MgBC400) increased by 20 and 30 times compared with the unmodified biochar (BC400), respectively. The removal of Pb and Cd to biochar was attributed to ion exchange (Qe), mineral precipitation (Qp), interaction with oxygen functional groups (OFGs) (Qf), and metal-π electron coordination (Qπ). Compared with the BC400, the adsorption capacity of the four fractions of MgBC400 increased especially the ion exchange and precipitation. The Qe values of MgBC400 were almost 49 and 59 times that of BC400 in the adsorption of Pb and Cd, respectively. The Qp values of MgBC400 increased by 214.4 and 81.7 mg/g, respectively. Ion exchange and mineral precipitation dominated the adsorption of Pb and Cd by MgBC400.
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•The Qt of Pb2+/Cd2+ on MgB400 increased by 20/30 times, compared with B400.•The Qe of MgB400 was 49/59 times that of B400 in the adsorption of Pb2+/Cd2+.•MgB400 had a higher affinity for lead than cadmium.•Ion exchange and precipitation dominate the sorption of Pb2+/Cd2+ by MgB400.•MgO participated in ion exchange and precipitation processes.
This paper investigates the physical layer security of a satellite network, whose downlink spectral resource is shared with a terrestrial cellular network. We propose to employ a multi-antenna base ...station (BS) as a source of green interference to enhance secure transmission in the satellite network. By taking the mutual interference between these two networks into account, we first formulate a constrained optimization problem to maximize the instantaneous rate of the terrestrial user while satisfying the interference probability constraint of the satellite user. Then, with the assumption that imperfect channel state information (CSI) and statistical CSI of the link between the BS and satellite user are available at the BS, we present two beamforming (BF) schemes, namely, hybrid zero-forcing and partial zero-forcing to solve the optimization problem and obtain the BF weight vectors in a closed form. Moreover, we analyze the secrecy performance of primary satellite network by considering two practical scenarios, namely: Scenario I, the eavesdroppers CSI is unknown at the satellite and Scenario II, the eavesdroppers CSI is known at the satellite. Specifically, we derive the analytical expressions for the secrecy outage probability for Scenario I and the average secrecy rate for Scenario II. Finally, numerical results are provided to confirm the superiority of the proposed BF schemes and the validity of the performance analysis, as well as demonstrate the impacts of various parameters on the secrecy performance of the satellite network.
Linkage Chemistry of S(VI) Fluorides Zeng, Daming; Deng, Wei‐Ping; Jiang, Xuefeng
Chemistry : a European journal,
June 13, 2023, Letnik:
29, Številka:
33
Journal Article
Recenzirano
Sulfur(VI)‐fluoride exchange linkage as a next generation of click chemistry was introduced by Sharpless and coworkers in 2014. Distinguished from CuAAC, the SuFEx reaction proceeds under metal‐free ...conditions, and the reactive linkers are variable, enabling access to a diverse class of linkage compounds. Therein, a series of SuFEx linkers emerged has been widely prevalent in diverse fields. The SVI−F bond in comparison to SVI−Cl bond features excellent stability and chemoselectivity. The linkage chemistry primarily involves the formation of S−O and S−N bonds via commercially available phenols and amines, yet less study on C‐SuFEx linkage. This review will focus on three types of linkage for SuFEx linkers comprising S−O, S−N, and S−C bonds, and we hope to provide a practical guidance for SuFEx linkage chemistry.
Sulfur(VI)‐fluoride exchange: This review summarizes recent advances in the linkage chemistry of S(VI) fluorides since 2014, emphasizing the formation of S−O, S−N, and S−C bonds. The divergent SuFEx linkage is deployed in the assembly of S(VI)‐containing compounds library.
In this paper, we investigate secrecy-energy efficient hybrid beamforming (BF) schemes for a satellite-terrestrial integrated network, wherein a multibeam satellite system shares the millimeter wave ...spectrum with a cellular system. Under the assumption of imperfect angles of departure for the wiretap channels, the hybrid beamformer at the base station and digital beamformers at the satellite are jointly designed to maximize the achievable secrecy-energy efficiency, while satisfying signal-to-interference-plus-noise ratio constraints of both the earth stations (ESs) and cellular users. Since the formulated optimization problem is nonconvex and mathematically intractable, we propose two robust BF schemes to obtain approximate solutions with low complexity. Specifically, for the case of a single ES, we integrate the Charnes-Cooper approach with an iterative search algorithm to convert the original nonconvex problem into a solvable one and obtain the BF weight vectors. In the case of multiple ESs, by exploiting the sequential convex approximation method, we convert the original problem into a linear one with multiple matrix inequalities and second-order cone constraints, for which we obtain a solution with satisfactory performance. The effectiveness and superiority of the proposed robust BF design schemes are validated via simulations using realistic satellite and terrestrial downlink channel models.
It is known that there exist two kinds of methods for direction-of-arrival (DOA) estimation in the literature: the subspace-based method and the sparsity-based method. However, pervious works reveal ...that the former method cannot address the case in which the number of signals is larger than that of sensors, whereas the latter one always suffers from the influence of basis mismatch. In this paper, to overcome these two shortcomings, we propose a new method called covariance matrix reconstruction approach (CMRA) for both uniform linear array and sparse linear array. In particular, by exploiting the Toeplitz structure of the covariance matrix of the array output, we formulate a low-rank matrix reconstruction (LRMR) problem for covariance matrix recovery. The nonconvex LRMR problem is then relaxed by replacing the rank norm with the nuclear norm and solved using the optimization toolbox. Next, we retrieve the DOAs from the recovered covariance matrix by using the subspace-based methods and obtain an estimated number of signals as a byproduct. We also provide two algorithm implementations for the LRMR problem based on duality and alternating direction method of multipliers, respectively. It is shown that CMRA can be regarded as an atomic norm minimization model or a gridless version of the sparsity-based methods and can recover more signals than sensors with a well-designed array. Numerical experiments are provided to validate the effectiveness of the proposed method, in comparison with some of the existing methods.
Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary tumor in the central nervous system. One of the most widely used chemotherapeutic drugs for GBM is temozolomide, ...which is a DNA-alkylating agent and its efficacy is dependent on MGMT methylation status. Little progress in improving the prognosis of GBM patients has been made in the past ten years, urging the development of more effective molecular targeted therapies. Hyper-activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway is frequently found in a variety of cancers including GBM, and it plays a central role in the regulation of tumor cell survival, growth, motility, angiogenesis and metabolism. Numerous PI3K inhibitors including pan-PI3K, isoform-selective and dual PI3K/mammalian target of rapamycin (mTOR) inhibitors have exhibited favorable preclinical results and entered clinical trials in a range of hematologic malignancies and solid tumors. Furthermore, combination of inhibitors targeting PI3K and other related pathways may exert synergism on suppressing tumor growth and improving patients' prognosis. Currently, only a handful of PI3K inhibitors are in phase I/II clinical trials for GBM treatment. In this review, we focus on the importance of PI3K/Akt pathway in GBM, and summarize the current development of PI3K inhibitors alone or in combination with other inhibitors for GBM treatment from preclinical to clinical studies.
Sulfur(VI) fluoride cleavage and exchanging linkage, a new generation of linkage chemistry, exhibits enormous potential for combining a range of functional molecules in an increasing number of ...fields. Herein, we established a metal‐free linkage of unactivated alkenes and sulfonimidoyl fluorides via hydrosulfonimidoylation to construct sulfoximines within minutes. An intermolecular hydride transfer process is the key step, and it occurs via overlap of the LUMO in the sulfonimidoyl cation and HOMO in the unactivated alkene, which was confirmed via control experiments with deuterated compounds. DFT calculations further demonstrated the concerted process involving formation of the S−C(sp3) bond and hydride transfer. Remarkably, abundant natural products and pharmaceuticals with multiple heteroatoms and sensitive functional groups have been subjected to the current linkage reaction to achieve various sulfoximine linkages, furnishing the basis for drug discovery and drug conjugation.
A metal‐free linkage chemistry of unactivated alkenes and sulfonimidoyl fluorides via hydrosulfonimidoylation to construct sulfoximines within minutes is presented. An intermolecular hydride transfer process is the key step in the reaction.
Air pollution has become an extremely serious problem, with particulate matter having a significantly greater impact on human health than other contaminants. The small diameter of fine particulate ...matter (PM2.5) allows it to penetrate deep into the alveoli as far as the bronchioles, interfering with a gas exchange within the lungs. Long-term exposure to particulate matter has been shown to cause the cardiovascular disease, respiratory disease, and increase the risk of lung cancers. Therefore, forecasting air quality has also become important to help guide individual actions. This paper aims to forecast air quality for up to 48 h using a combination of multiple neural networks, including an artificial neural network, a convolutional neural network, and a long-short-term memory to extract spatial-temporal relations. The proposed predictive model considers various meteorology data from the previous few hours as well as information related to the elevation space to extract terrain impact on air quality. The model includes trends from multiple locations, extracted from correlations between adjacent locations, and among similar locations in the temporal domain. Experiments employing Taiwan and Beijing data sets show that the proposed model achieves excellent performance and outperforms current state-of-the-art methods.
This paper investigates the secure communication of a cognitive satellite terrestrial network with software-defined architecture, where a gateway is acting as a control center to offer the resource ...allocation for the wireless systems. Specifically, we propose beamforming (BF) schemes to utilize the interference from the terrestrial network as a green source to enhance the physical-layer security for the satellite network, provided that the two networks share the portion of millimeter-wave frequencies. Supposing that the satellite employs multibeam antenna while the base station is equipped with a uniform planar array, we first formulate a constrained joint optimization problem to minimize the total transmit power while satisfying both the quality-of-service requirement of the terrestrial user and the secrecy rate (SR) requirements of the satellite users. Since the formulated optimization problem is nonconvex and mathematically intractable, we then propose two BF schemes to obtain the optimal solutions with high computational efficiency. For the case of one eavesdropper (Eve), we present a method to convert the nonconvex SR constraint to a second-order cone one and then adopt a penalty function approach to obtain the BF weight vectors. In the case of multiple Eves, by introducing a list of auxiliary variables, we propose a two-layer iterative BF scheme using penalty function approach together with gradient-based method to calculate the BF weight vectors. Finally, simulation results are given to demonstrate the effectiveness and superiority of the proposed BF schemes.
Oxidative dehydrogenation of propane to olefins is a promising alternative route to industrialized direct dehydrogenation, but encounters the difficulty in selectivity control for olefins because of ...the overoxidation reactions that produce a substantial amount of undesired CO2. Here we report edge‐hydroxylated boron nitride, a metal‐free catalyst, that efficiently catalyzed dehydrogenation of propane to propylene with superior selectivity (80.2 %) but with only negligible CO2 formation (0.5 %) at a given propane conversion of 20.6 %. Remarkable stability was evidenced by the operation of a 300 h test with steady conversion and product selectivity. The active BNO. site, generated dynamically through hydrogen ion of B−OH groups by molecular oxygen, triggered propane dehydrogenation by selectively breaking the C−H bond but simultaneously shut off the pathway of propylene overoxidation towards CO2.
Olefin generation without a metal: Edge‐hydroxylated boron nitride shows superior selectivity for the oxidative dehydrogenation of propane to propylene with only negligible CO2 formation. The dynamically generated active BNO. site triggers propane dehydrogenation by selectively breaking the C−H bond by concomitantly avoiding propylene oxidation to CO2.
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