It is well known that sediment internal loading can worsen lake water quality for many years even if effective measures have been taken to control external loading. In this study, a 12-month field ...study was carried out to reveal the relationship between sediment phosphorus (P) and nitrogen (N) forms as well as their fluxes across sediment-water interface from the most polluted area of Lake Chaohu, a large shallow eutrophication lake in China. The possible contribution of mobile fraction of P and N to lake eutrophication is also analyzed. The results indicate that the content of total P and N and their forms in water and sediment were rather dynamic during the year-long field investigation. Low concentrations of P and N from sediment and overlying water were observed in the winter but increased sharply in summer. The phosphate and ammonium fluxes showed evident seasonal variation, and higher fluxes can be observed in warmer seasons especially during the period of algal bloom with high sedimentation. The reduction of ferric iron and degradation of organic matter could be responsible for the increased P flux from sediment in algal bloom seasons, which is consistent with the seasonal variation of P forms in sediment. A comparison of the mole ratio of P flux:N flux to both the P:N mole ratio in sediments and the Redfield ratio was used to further distinguish the dominant sediment P forms’ release during seasonal variation. Moreover, the anoxic condition and enhanced microbial activity in warmer seasons contribute a lot to the ammonium release from sediment. Consequently, the nutrient fluxes seasonally influence their corresponding nutrient concentrations in the overlying water. The results of this study indicate that sediment internal loading plays an important role in the eutrophication of Lake Chaohu.
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•The relationship between nutrient fluxes and its sediment forms was studied.•P and N fluxes from sediment showed significant variation during 12-month study.•P fluxes across SWI showed positive correlation to sediment Al-P and Fe-P.•No relationship was found between N fluxes from sediment and sediment N forms.•N cycling in eutrophic lake could influence sediment internal P loading.
Sediment P release from sediment was controlled by different mechanisms during seasonal variation and substantially contributed to the eutrophication of Lake Chaohu.
Dissipative self-assembly is common in biological systems, where it serves to maintain a far-from-equilibrium functional state through fuel consumption. Synthetic dissipative systems have been ...prepared that can mimic some of the properties of biological systems, but they often show poor mechanical performance. Here, we report a shear-induced transient hydrogel that is highly stretchable. The system is constructed by adding Cu(II) into the aqueous solution of a pseudopolyrotaxane, which is itself formed by threading molecular tubes on polyethylene glycol chains. Vigorous shaking transforms the solution into a gel, which gradually relaxes back to the sol state over time. This cycle can be repeated at least five times. A mechanism is proposed that relies on a shear-induced transition from intrachain to interchain coordination and subsequent thermal relaxation. The far-from-equilibrium hydrogel is highly stretchable, which is probably due to 'frictional' sliding of the molecular tubes on the polyethylene glycol chains. On shaking, the hydrogel undergoes fast self-healing.
The rapid evolution of treatment for advanced lung cancer is a story of how scientists have struggled to move from nonselective cytotoxic chemotherapy to personalized precision medicine. In this ...century, extraordinary advances have been made in the management of advanced and metastatic non-small cell lung cancer, especially in the development of small molecules targeting specific tyrosine kinase receptors and immune checkpoint inhibitors. These developments have led to a significant improvement in survival for lung cancer patients with metastatic disease. Now, the core guidelines to treat non-small cell lung cancer are based on the identification of targetable driver mutations and immune checkpoints. Continued investigations of newly identified druggable genetic alterations, explorations of biomarkers of immune checkpoint inhibitors, development of next-generation immunotherapy, and optimization of combination therapy are necessary to provide better treatment outcomes for lung cancer patients in the future.
It is challenging to remove polar organic micropollutants from water through adsorption‐mediated processes. Macrocycle‐crosslinked polymers were recently shown to be effective adsorbents for nonpolar ...or charged organic micropollutants through specific host–guest binding, but are rarely used for the treatment of neutral and polar organic micropollutants. This is due to the challenge of recognizing polar molecules in water by macrocyclic hosts. In this research, we report two amide naphthotube‐crosslinked polymers which can effectively and rapidly adsorb a wide scope of polar organic micropollutants from water through biomimetic molecular recognition. Amide naphthotubes possess hydrogen bonding sites in their deep hydrophobic cavities and can effectively bind polar organic micropollutants in water through the hydrophobic effects and shielded hydrogen bonds. The cross‐linked polymers containing amide naphthotubes are even able to remove a complex mixture of organic micropollutants from water and the used materials can be easily regenerated through washing with MeOH or EtOH. This research provides a solution for the treatment of polar organic micropollutants by using biomimetic molecular recognition in water.
The cross‐linked polymers containing the biomimetic macrocyclic hosts, amide naphthotubes, are able to effectively and rapidly adsorb polar organic micropollutants from water by employing host–guest binding. The polymers can be readily regenerated through washing with MeOH or EtOH at room temperature.
The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been ...developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.
A host–guest cooperative protection strategy has been developed for constructing single‐atom catalysts (SACs), extending the range of available precursors from nitrogenous to non‐nitrogenous MOFs. The obtained Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) at different pyrolysis temperatures feature varying nitrogen coordination numbers. The best of these catalysts, NiSA‐N2‐C, shows superior activity and selectivity in CO2 electroreduction.
Bromide is naturally present in source waters worldwide. Chlorination of drinking water can generate a variety of chlorinated and brominated disinfection byproducts (DBPs). Although substantial ...efforts have been made to examine the effect of bromide concentration on the formation and speciation of halogenated DBPs, almost all previous studies have focused on trihalomethanes and haloacetic acids. Given that about 50% of total organic halogen formed in chlorination remains unknown, it is still unclear how bromide concentration affects the formation and speciation of the new/unknown halogenated DBPs. In this study, chlorinated drinking water samples with different bromide concentrations were prepared, and a novel approachprecursor ion scan using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometrywas adopted for the detection and identification of polar halogenated DBPs in these water samples. With this approach, 11 new putative aromatic halogenated DBPs were identified, and they were classified into four groups: dihalo-4-hydroxybenzaldehydes, dihalo-4-hydroxybenzoic acids, dihalo-salicylic acids, and trihalo-phenols. A mechanism for the formation of the four groups of new aromatic halogenated DBPs was proposed. It was found that increasing the bromide concentration shifted the entire polar halogenated DBPs as well as the four groups of new DBPs from being less brominated to being more brominated; these new aromatic halogenated DBPs might be important intermediate DBPs formed in drinking water chlorination. Moreover, the speciation of the four groups of new DBPs was modeled: the speciation patterns of the four groups of new DBPs well matched those determined from the model equations, and the reactivity differences between HOBr and HOCl in reactions forming the four groups of new DBPs were larger than those in reactions forming trihalomethanes and haloacetic acids.
Phenol‐based macrocyclic arenes have been widely used in supramolecular chemistry, significantly enriching the toolbox of the field. In contrast, naphthol‐based macrocyclic arenes are rather ...underdeveloped. Very recently, Gaeta and co‐workers successfully synthesized such macrocycles (referred to as prismnarenes) with good guest‐binding ability by reacting 2,6‐dimethoxynaphthalene with paraformaldehyde under optimized conditions. In view of the simple synthesis and good host–guest chemistry, we anticipate that this macrocycle will find similar success and wide applications as the phenol‐based macrocyclic arenes.
New macrocyclic arenes, so‐called prismnarenes, are readily synthesized from 2,6‐dimethoxynaphthalene and paraformaldehyde in the presence of templates. They adopt a prism‐like structure with an electron‐rich cavity and show excellent binding affinities towards organic cations. In view of the simple synthesis and good host–guest chemistry, they should find many uses in supramolecular chemistry.
The new development trends including Internet of Things (IoT), smart city, enterprises digital transformation and world's digital economy are at the top of the tide. The continuous growth of data ...storage pressure drives the rapid development of the entire storage market on account of massive data generated. By providing data storage and management, cloud storage system becomes an indispensable part of the new era. Currently, the governments, enterprises and individual users are actively migrating their data to the cloud. Such a huge amount of data can create magnanimous wealth. However, this increases the possible risk, for instance, unauthorized access, data leakage, sensitive information disclosure and privacy disclosure. Although there are some studies on data security and privacy protection, there is still a lack of systematic surveys on the subject in cloud storage system. In this paper, we make a comprehensive review of the literatures on data security and privacy issues, data encryption technology, and applicable countermeasures in cloud storage system. Specifically, we first make an overview of cloud storage, including definition, classification, architecture and applications. Secondly, we give a detailed analysis on challenges and requirements of data security and privacy protection in cloud storage system. Thirdly, data encryption technologies and protection methods are summarized. Finally, we discuss several open research topics of data security for cloud storage.
Macrocyclic hosts with a well‐defined cavity are particularly appealing for supramolecular chemistry, but they are still rare. In this research, we reported a new class of macrocyclic hosts, namely ...methylene‐bridged naphthotubes, with well‐defined cavities. They were synthesized through TFA‐catalyzed Friedel–Crafts reactions between alkoxy‐substituted bisnaphthalenes and paraformaldehyde. A configurational selection was observed. Three‐membered macrocycles possess a single cavity, while four‐membered macrocycles adopt a double‐cavity conformation or a self‐filling conformation depending on the alkoxy length. The small homologue shows quite strong binding affinities (up to 108 M−1) to organic cations, which is better than structurally similar but flexible macrocycles. This demonstrates the advantage of a well‐defined cavity in molecular recognition. Moreover, these naphthotubes can be used as chirality sensors for chiral organic cations through different chirality transfer mechanisms.
Methylene‐bridged naphthotubes have been successfully developed. The three‐membered naphthotubes possess a rigid and well‐defined cavity, while four‐membered naphthotubes possess a double‐cavity conformation or a self‐filling conformation depending on the alkoxy length. They show quite strong binding affinities (up to 108 M−1) to organic cations and can be used as chirality sensors for chiral organic cations.
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