Nitrogen migration and transformation during re-suspension and photo-induction in landscape water replenished by reclaimed water.

Sediment re-suspension plays a crucial role in releasing endogenous nitrogen and greenhouse gases in shallow urban waters. However, the impacts of repeated re-suspension and photo-induced processes on migration and transformation from endogenous nitrogen, as well as the emission of greenhouse gases, remain unclear. This study simulated three conditions: re-suspension (Rs), re-suspension combined with ultravioletirradiation (Rs + UV), and ultraviolet irradiation (UV). The findings revealed that both repeated sediment re-suspension and exposure to UV light altered the characteristics of surface sediments. Decrease of convertible nitrogen in sediments, leading to the release of ion-exchangeable nitrogen (IEF-N) into NH4+-N and NO3--N, influenced greenhouse gas production differently under various conditions. The study observed the highest concentration of dissolved N2O in under UV irradiation, positively correlated with NO2--N and NO3--N. Re-suspension increased the turbidity of the overlying water and accelerated nitrification, resulting in the highest NO3--N concentration and the lowest dissolved N2O concentration. Additionally, in the Rs + UV dissolved N2O maintained the higher concentrations than in Rs, with greatest amount of N conversion in surface sediments, and a 59.45% reduction in IEF-N. The production of N2O during re-suspension was mainly positively correlated with NH4+-N in the overlying water. Therefore, this study suggest that repeated re-suspension and light exposure significantly influence nitrogen migration and transformation processes in sediment, providing a theoretical explanation for the eutrophication of water and greenhouse gas emissions.

Nonideal effects on ionization potential depression and ionization balance in dense Al and Au plasmas.

For low-density plasmas, the ionization balance can be properly described by the normal Saha equation in the chemical picture. For dense plasmas, however, nonideal effects due to the interactions between the electrons and ions and among the electrons themselves affect the ionization potential depression and the ionization balance. With the increasing of plasma density, the pressure ionization starts to play a more obvious role and competes with the thermal ionization. Based on a local-density temperature-dependent ion-sphere model, we develop a unified and self-consistent theoretical formalism to simultaneously investigate the ionization potential depression, the ionization balance, and the charge states distributions of the dense plasmas. In this work, we choose Al and Au plasmas as examples as Al is a prototype light element and Au is an important heavy element in many research fields such as in the inertial confinement fusion. The nonideal effect of the free electrons in the plasmas is considered by the single-electron effective potential contributed by both the bound electrons of different charge states and the free electrons in the plasmas. For the Al plasmas, we can reconcile the results of two experiments on measuring the ionization potential depression, in which one experiment can be better explained by the Stewart-Pyatt model while the other fits better with the Ecker-Kröll model. For dense Au plasmas, the results show that the double peak structure of the charge state distribution appears to be a common phenomenon. In particular, the calculated ionization balance shows that the two- and three-peak structures can appear simultaneously for denser Au plasmas above ∼30g/cm^{3}.

Improving water quality and mitigating CH4 and N2O production in urban landscape water simultaneously by optimizing calcium peroxide dosage.

Recent studies show that greenhouse gas (GHG) emissions from urban landscape water are significant and cannot be overlooked, underscoring the need to develop effective strategies for mitigating GHG production from global freshwater systems. Calcium peroxide (CaO2) is commonly used as an eco-friendly reagent for controlling eutrophication in water bodies, but whether CaO2 can reduce GHG emissions remains unclear. This study investigated the effects of CaO2 dosage on the production of methane (CH4) and nitrous oxide (N2O) in urban landscape water under anoxic conditions during summer. The findings reveal that CaO2 addition not only improved the physicochemical and organoleptic properties of simulated urban landscape water but also reduced N2O production by inhibiting the activity of denitrifying bacteria across various dosages. Moreover, CaO2 exhibited selective effects on methanogens. Specifically, the abundance of acetoclastic methanogen Methanosaeta and methylotrophic methanogen Candidatus_Methanofastidiosum increased whereas the abundance of the hydrogenotrophic methanogen Methanoregula decreased at low, medium, and high dosages, leading to higher CH4 production at increased CaO2 dosage. A comprehensive multi-objective evaluation indicated that an optimal dosage of 60 g CaO2/m2 achieved 41.21 % and 84.40 % reductions in CH4 and N2O production, respectively, over a 50-day period compared to the control. This paper not only introduces a novel approach for controlling the production of GHGs, such as CH4 and N2O, from urban landscape water but also suggests a methodology for optimizing CaO2 dosage, providing valuable insights for its practical application.

Electrocoagulation enhanced gravity driven membrane bioreactor for advanced treatment of rural sewage.

The daily discharge of rural sewage in China occupies 30 % of the national wastewater discharge, and developing an energy-efficient, easy to operate, and decentralized rural sewage treatment technology becomes an important task. In this work, a novel rural sewage treatment technology, Electrocoagulation enhanced Gravity-Driven Membrane Bioreactor (EC-GDMBR) was exploited for the rural sewage treatment under long-term operation (160 days). Two EC-GDMBRs with various module structures of ceramic membrane (horizontal module and side module) not only displayed the desirable effluent quality, but also sustained the stable flux (8-13 LMH). The electrocoagulation, electrooxidation, biodegradation, and separation in EC-GDMBRs were able to synergistically remove the particle matter, organic (CODCr effluent <11.6 ± 1.2 mg/L) and nutrients (NH3-N effluent <0.1 mg/L, TN effluent <8.5 mg/L, TP effluent <0.05 mg/L). Besides, the high permeability of ceramic membrane and large porosity of biofilm on its surface improved the sustainability of stable flux during the long-term operation. Moreover, by analyzing bacterial abundance, Extracellular Polymeric Substances, Adenosine Tri-Phosphate and Confocal Laser Scanning Microscopy, a large number of microorganisms grew and accumulated on the carrier, as well as formed the biofilm (23.46-659.9 µm), while Nitrobacteria (1.6-4.1 %) and Nitrate (0.01-0.06 %) exited in the carrier biofilms, promoting the nitrogen removal. Compared with EC-GDMBR with side module of ceramic membrane, EC-GDMBR with horizontal module of ceramic membrane has advantages in flux behavior, organic/nutrient removal, microbial abundance/activity, abundance of nitrogen removal functional bacteria and water permeability of biofilm, because the ceramic membrane of horizontal module can promote the uniform growth of biofilm and improve the uniformity of flow penetration distribution. In general, the findings of this work verify the reliability of EC-GDMBR for the sustainable operation of wastewater treatment and improve its application value of rural sewage treatment.

A Facile Route for the Formation of Complex Nitrogen-Containing Prebiotic Molecules in the Interstellar Medium.

Prebiotic molecules have often been identified in the interstellar medium and meteorite samples. However, we still have only a fragmentary knowledge of the mechanism of the evolutionary process of these prebiotic molecules. With the aid of state-of-the-art vacuum ultraviolet (VUV)-infrared (IR) spectroscopy and ab initio calculations, we reveal a new pathway leading to the formation of the biorelevant molecules carrying amine groups or peptide bonds via the single-photon ionization induced Michael/cyclization reaction of acrylonitrile (AN)-alcohol heterodimer complexes in the gas phase. In the reactions, not only N-H nitrilium cations with H+-N≡C-R Lewis structure but also cyclic amine cations with a peptide bond can be formed when the AN reacts with alcohols of increasing molecular size (such as ethanol, propanol, or butanol). This study suggests the possibility of unsaturated nitriles being reduced by ionized alcohols in space, which can further drive sequential Michael addition/cyclization reactions to form more complex biorelevant molecules.

Bioorthogonal Light-Up Fluorescent Probe Enables Wash-Free Real-Time Dynamic Monitoring of Cellular Glucose Uptake.

As a significant energy source for living systems, the aberrant cellular glucose uptake is seriously implicated in numerous metabolic diseases. Unfortunately, current shortage of robust tools leaves the limitation to understand its precise biology. Herein we presented a bioorthogonal light-up fluorescent probe consist of two reagents, Glu-HT-Me+AzGlu2, for rapidly responsive (within 25 min), highly specific and sensitive (20-folds enhancement) detection of live-cell glucose uptake based on arylphosphine-induced a-PET effect and Staudinger ligation. Especially, taking the advantage of wash-free characteristic, the probe displayed the real-time dynamic monitoring of cellular glucose uptake. Furthermore, it was successfully capable of not only differentiating cancer cells from normal cells, but also allowing evaluation of anticancer/glycolysis/transport mediated glucose flux. Importantly, it was employed to monitor the fluctuations of glucose uptake in a doxycycline-inducible K-rasG12 V expression oncogenic cell system, implying its potential as a valuable tool to explore glucose uptake biology.

A ratiometric ESIPT fluorescent probe for detection of anticancer-associated H2O2 level in vitro and in vivo.

ROS is a significant factor in the cancer treatment mechanism. The monitoring anticancer-associated H2O2 level plays a vital role in the anticancer mechanistic exploration in pathology and physiology. Herein we synthesized a ratiometric fluorescent probe (HBQ-L) to detect and image H2O2 based on excited-state intramolecular proton transfer. HBQ-L had a high sensitivity (231-fold) with a low detection limit (28.5 nM) for monitoring H2O2 in solution. HBQ-L showed good mitochondrial-targeting and successfully detected both exo-/endogenous H2O2 in A549 cells. Furthermore, HBQ-L was used to ratiometric monitor H2O2 level in anticancer reagent DOX-treated cells or zebrafish. Importantly, it was employed to access the monitoring H2O2 in the A549 tumor-bearing mice.

An ESIPT-Dependent AIE Fluorophore Based on HBT Derivative: Substituent Positional Impact on Aggregated Luminescence and its Application for Hydrogen Peroxide Detection.

Aiming to develop the facile organic fluorophore possessing excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE), we designed and synthesized two isomers with different linkage site between hydroxyl of 2-(2-hydroxyphenyl) benzothiazole (HBT) and a benzothiazole substituent (para position refers to p-BHBT and ortho position refers to o-BHBT). Fluorescence emission properties of p-BHBT and o-BHBT in THF/water mixtures with different water volume fractions indicated an opposite luminescence in aggregates, in which p-BHBT showed an ESIPT-dependent AIE properties while o-BHBT displayed ESIPT effect and aggregation-caused quenching (ACQ) qualities. A possible mechanism for molecular actions to illustrate the aggregating luminescence alteration of these two isomers had been proposed and verified by theoretical and experimental studies. More importantly, Probe-1, generated from dual ESIPT-AIE fluorophore p-BHBT, was successfully used as a ratiometric fluorescent chemosensor for highly selective (above 15-fold over other ROS) and sensitive (69-fold fluorescence enhancement with 0.22 µM of detection limit) detection of hydrogen peroxide in aqueous solution and living cells, respectively.

A ratiometric ESIPT probe based on 2-aza-Cope rearrangement for rapid and selective detection of formaldehyde in living cells.

Formaldehyde (FA) is a crucial reactive signaling molecule participating in epigenetic and metabolic pathways. However, abnormally elevated levels of FA are implicated in various diseases spanning from tumors to neurodegenerative disorders. Despite being highly selective for FA, current 2-aza-Cope-based fluorescent probes leave room for improvement because their relatively slow reaction kinetics (1-9 hours response time) hinder their capability to track transient biological FA. Herein, we present a ratiometric fluorescent probe, FormAFP, based on excited state intramolecular photon transfer (ESIPT) for rapid (within 10 min), selective (above 70-fold over other RCS) and sensitive (240-times fluorescence enhancement with 66 nM detection limit) detection of FA via 2-aza-Cope rearrangement. The probe also displayed a fast response (<20 min) to both exogenous and endogenous FA in living cells. Besides, FormAFP was capable of monitoring FA released by folate degradation in living MCF7 cells. More importantly, FormAFP successfully detected fluctuations of endogenous FA levels in oxidative stress stimulation, demonstrating its potential as an ideal tool to explore FA biology.

Impact of Nrf2 on tumour growth and drug sensitivity in oncogenic K-ras-transformed cells in vitro and in vivo.

K-ras is one of the most common oncogenes in human cancers, and its aberrant activation may lead to malignant transformation associated with oxidative stress and activation of the transcription factor Nrf2 that regulates multiple detoxification enzymes. The purpose of this research was to use gene editing technology to evaluate the role of Nrf2 in affecting tumour growth and drug sensitivity of K-rasG12V-transformed cells. We showed that induction of K-rasG12V caused a significant activation of Nrf2 associated with increased expression of its target genes NAD(P)H:quinone oxidoreductase 1 (NQO1) and haem oxygenase-1 (HO-1). Interestingly, knock-out of Nrf2 by CRISPR/Cas9 in K-rasG12V-expressing cells only impacted the expression of NQO1 but not HO-1. We also found that Nrf2 knock-out caused high reactive oxygen species (ROS) stress, suppression of cell proliferation, increased apoptosis in vitro, and a decrease of tumour growth in vivo. Furthermore, abrogation of Nrf2 significantly increased the sensitivity of K-rasG12V cells to multiple anticancer agents including phenethyl isothiocyanate (PEITC), doxorubicin, etoposide, and cisplatin. These results show that genetic abrogation of Nrf2 impairs the malignant phenotype of K-RasG12V-transformed cells in vitro and in vivo, and demonstrates the critical role of Nrf2 in promoting cell survival and drug resistance in cells harbouring oncogenic K-ras. As such, inhibition of Nrf2 would be an attractive strategy to increase the therapeutic effect and overcome drug resistance in cancer with oncogenic K-ras activation.

A smart "off-on" gate for the in situ detection of hydrogen sulphide with Cu(ii)-assisted europium emission.

A water-soluble and emissive Eu-complex (EuL1) bearing a DO3A(Eu3+)-pyridine-aza-crown motif has been prepared and its Cu2+ complex has been demonstrated to be a smart luminescence "off-on" gate for H2S detection in water with a nano-molar detection limit (60 nM). EuL1 binds to Cu2+ ions selectively (KB = 1.2 × 105 M-1) inducing 17-fold luminescence quenching and forming a 1 : 1 stoichiometric complex (EuL1-Cu2+), which responds to H2S selectively with restoration of the original Eu emission of EuL1 followed by a further 40-fold luminescence enhancement, forming a 1 : 1 stoichiometric complex (EuL1-Na2S, KB = 1.5 × 104 M-1). Without Cu2+ ions, EuL1 showed non-specific binding towards H2S with only a 5-fold luminescence enhancement.

Enantioselective Synthesis of the ABC-Tricyclic Core of Phomactin A by a γ-Hydroxylation Strategy.

An enantioselective synthesis of the ABC-tricyclic furanochroman core of phomactin A has been accomplished by a γ-hydroxylation approach. The C ring was established by γ-hydroxylation of an α-enone. The regioselectivity was optimized by using a strong base with an oxophilic cation (t-BuLi) and a bulky oxygen donor (Davis reagent), which afforded the γ-hydroxylation product selectively in 63% yield.