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Annual cumulative nitrous oxide (N 2 O) emissions from soil have historically been calculated from intermittent data measured manually via the static chamber method. The temporal variability in emissions, both diurnally and between days, introduces uncertainty into the up-scaling of static chamber data. This study assessed the most appropriate time of the day to sample and the best sampling frequency to ensure reliable estimates of annual cumulative emissions. Sub-daily N 2 O emissions were measured using automatic gas sampling chambers over three years in a sub-tropical cereal crop system. The sub-daily dataset was divided into eight time periods per day to assess the best sampling time of the day. Daily mean N 2 O emissions were subsampled from the dataset to simulate different sampling frequencies, including pre-set and rainfall-based scenarios. Annual cumulative N 2 O emissions were calculated for these scenarios and compared to the ‘actual’ annual cumulative emissions. The results demonstrated that manual sampling between mid-morning (09:00) and midday (12:00), and late evening (21:00) and midnight (24:00) best approximated the daily mean N 2 O emission. Factoring in the need to sample during daylight hours, gas sampling from mid-morning to midday was the most appropriate sampling time. Overall, triweekly sampling provided the most accurate estimate (± 4% error) of annual cumulative N 2 O emissions, but was undesirable due to its labour intensive high sampling frequency. Weekly sampling with triweekly sampling in the two weeks following rainfall events was the most efficient sampling schedule, as it had similar accuracy (± 5% error) to the triweekly sampling, the smallest variability in outcomes and approximately half the sampling times of triweekly sampling. Inter-annual rainfall variability affected the accuracy and variability of estimations of annual cumulative emissions, but did not affect the overall trends in sampling frequency accuracy. This study demonstrated that intermittent samplings are capable of estimating the annual cumulative N 2 O emissions satisfactorily when timed appropriately. [ABSTRACT FROM AUTHOR]

Boundary line models for N2O emissions from agricultural soils provide a means of estimating emissions within defined ranges. Boundary line models partition a two-dimensional region of parameter space into sub-regions by means of thresholds based on relationships between N2O emissions and explanatory variables, typically using soil data available from laboratory or field studies. Such models are intermediate in complexity between the use of IPCC emission factors and complex process-based models. Model calibration involves characterizing the extent to which observed data are correctly forecast. Writing the numerical results from graphical two-threshold boundary line models as 3x3 prediction-realization tables facilitates calculation of expected mutual information, a measure of the amount of information about the observations contained in the forecasts. Whereas mutual information characterizes the performance of a forecaster averaged over all forecast categories, specific information and relative entropy both characterize aspects of the amount of information contained in particular forecasts. We calculate and interpret these information quantities for experimental N2O emissions data. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and fungicide iprodione on net nitrification rates and abundances of functional genes related to nitrification and denitrification in an agricultural soil. Single DMPP application or repeated iprodione applications decreased net nitrification rates in the test soil. However, when the DMPP and iprodione were applied together, they could generate antagonistic effects on the inhibitions of net nitrification rates. Repeated iprodione applications reduced ammonia-oxidizing archaea and bacteria (AOA and AOB) amo A gene abundances, while DMPP application decreased AOB amo A gene abundances only. The abundances of nar G and nir K genes were negatively affected by repeated iprodione applications. Our results demonstrated that combined applications of DMPP and iprodione could generate antagonistic effects on the inhibitions of net nitrification rates and discrepant impacts on the abundances of functional genes related to soil denitrification. [ABSTRACT FROM AUTHOR]

Understanding the change in chemical composition of crop residues during their decomposition is crucial to elucidate the mechanisms underlying the effects of residue retention on soil carbon (C) sequestration and nutrient cycling. Here a field experiment was carried out to investigate the decomposition process of maize, soybean, and wheat residues in a cultivated Mollisol in northeast China over a year. Using a litterbag method, we monitored the dynamics of residue mass loss, concentration of C and nitrogen (N), and C/N ratio, and evaluated the decomposition rates of residues and C functional groups. Chemical compositions of the crop residues were determined by solid-state 13 C nuclear magnetic resonance spectroscopy, and the cellulose crystallinity, lignin concentration, and syringyl to guaiacyl (S/G) ratio of lignin were estimated. After one year of incubation in field conditions, mass loss was 57% for soybean residues, significantly greater than 52% for maize and 45% for wheat. The decomposition rate of residues significantly decreased from 0.223 to 0.379 month −1 during the first month to 0.054–0.076 month −1 over the whole period. The proportion of decomposed C ranged at 57–63% among different residues, and had a positive relationship with the mass loss of O-alkyl C, di- O -alkyl C, and carbonyl C. The decomposition rates of these three C functional groups were greater in soybean than those in maize and wheat residues, which was also the case for lignin S/G ratio, possibly accounting for the higher decomposition extent of soybean residues. As decomposition progressed, the C chemistry of maize, soybean, and wheat residues exhibited an increasing divergence, which was mainly related to relative decreases in O-alkyl C and di- O -alkyl C contents, and relative increases in phenolic C and aromatic C contents in the residues. Net N release was observed for all residues after one-year decomposition, and was significantly related to the mass loss of alkyl C, O-alkyl C, and aromatic C. Overall, our study provides insight into chemical changes of crop residues over the degradation processes in the field, and highlights the significant effects of organic C chemistry on residue decomposition. [ABSTRACT FROM AUTHOR]

A regeneratively mode-locked erbium fiber laser was numerically investigated and experimentally demonstrated, which was able to generate a 583 fs pulse train at 10 GHz via intracavity pulse compression with nonlinear polarization evolution (NPE). To excite the NPE at such a high repetition rate, a dispersion map was intentionally introduced to obtain short pulses accompanied by high peaks through soliton-like pulse shaping. Numerical simulations indicated that steady-state oscillation with pulses below 1 ps can be successfully established using this laser configuration. Experimentally, we obtained a pulse duration of 583 fs and a 3 dB spectral width of 4.5 nm at an average output power of 15.6 mW. Simultaneously, supermode suppression of more than 80 dB was also obtained from the appropriate biased NPE.

The achievement of directly activating and utilizing bulk small molecules has remained a longstanding objective in the field of chemical synthesis. The present work reports a catalytic activation method for bulk chemical nitromethane (MeNO 2 ). This method combines homogeneous Lewis acid with recyclable heterogeneous Brønsted acid catalysis, featuring practicality, sustainability, and low cost, thus solving the inherent drawbacks of previous Nef processes where stoichiometric reductants or activators were required. By combining the advantages of both homo- and heterogeneous catalysts, this chemistry may not only offer new opportunities for the further development of MeNO 2 as a nitrogen source for organic synthesis, but also promote the catalysis design in synthetic chemistry., (© 2023 Wiley-VCH GmbH.)

Artificial (transfer) hydrogenases have been developed for organic synthesis, but they rely on precious metals. Native hydrogenases use Earth-abundant metals, but these cannot be applied for organic synthesis due, in part, to their substrate specificity. Herein, we report the design and development of manganese transfer hydrogenases based on the biotin-streptavidin technology. By incorporating bio-mimetic Mn(I) complexes into the binding cavity of streptavidin, and through chemo-genetic optimization, we have obtained artificial enzymes that hydrogenate ketones with nearly quantitative yield and up to 98 % enantiomeric excess (ee). These enzymes exhibit broad substrate scope and high functional-group tolerance. According to QM/MM calculations and X-ray crystallography, the S112Y mutation, combined with the appropriate chemical structure of the Mn cofactor plays a critical role in the reactivity and enantioselectivity of the artificial metalloenzyme (ArMs). Our work highlights the potential of ArMs incorporating base-meal cofactors for enantioselective organic synthesis., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Cyclometalated Ir(III) complexes as photosensitizers (PSs) have attracted widespread attention because of their good photostability and efficient 1 O 2 production ability. However, their strong absorption in the UV-vis region severely limits their applications in photodynamic therapy (PDT) because the short wavelength illuminating light can be easily absorbed by the skin and subcutaneous adipose tissue causing damage to the patient's normal tissue. Herein, mono- and tetra-nuclear Ir(III) complex-porphyrin conjugates are rationally designed and synthesized, especially [TPP-4Ir]4+ exhibits obvious aggregation-induced emission (AIE) characteristics. PSs comprising Ir(III) complex-porphyrin conjugates self-assembled as nanoparticles (NPs) are successfully achieved. The obtained [TPP-Ir]+ NPs and [TPP-4Ir]4+ NPs exhibit long wavelength absorption (500-700 nm) and near-infrared emission (635-750 nm), successfully overcoming the inherent defects of short wavelength absorption of traditional Ir(III) complexes. Moreover, [TPP-4Ir]4+ NPs exhibit good biocompatibility, high 1 O 2 generation ability, low half-maximal inhibitory concentration (IC 50 ) (0.47 × 10 -6 M), potent cytotoxicity toward cancer cells and superior cellular uptake under white light irradiation. This work extends the scope for transition metal complex PSs with promising clinical applications.

Agriculture is the leading contributor to global nitrous oxide (N 2 O) emissions, mostly from soils. We examined the non-target impacts of four pesticides on N transformations, N cycling genes and N 2 O emissions from sugarcane-cropped soil. The pesticides, including a herbicide glyphosate (GLY), an insecticide imidacloprid (IMI), a fungicide methoxy ethyl mercuric chloride (MEMC) and a fumigant methyl isothiocyanate (MITC), were added to the soil and incubated in laboratory at 25 °C. The soil microcosms were maintained at two water contents, 55 % and 90 % water holding capacity (WHC), to simulate aerobic and partly anaerobic conditions, respectively. Half of the soil samples received an initial application of KNO 3 and were then maintained at 90 % WHC for 38 d, whilst the other half received (NH 4 ) 2 SO 4 and were maintained at 55 % WHC for 28 d followed by 10 d at 90 % WHC to favour denitrification. Responses of individual functional genes involved in nitrification and denitrification to the pesticides and their relationships to N 2 O emissions varied with time and soil water. Overall, MITC had pronounced repressive effects on AOA and AOB amoA gene abundances and gross nitrification. Under 55 % WHC during the initial 28 d, N 2 O emissions were low for all treatments (≤62 μg N kg -1 soil). However, under 90 % WHC (either during the first 28 d or the increase in water content from 55 to 90 % WHC after 28 d) the cumulative N 2 O emissions increased markedly. Overall, under 90 % WHC the cumulative N 2 O emissions were 19 (control) to 79-fold (MITC) higher than under 55% WHC; with the highest emissions observed in the MITC treatment (3140 μg N kg -1 soil). This was associated with increases in gross nitrate consumption rates and abundances of denitrifying genes (nirK, nirS and qnorB). Therefore, to minimise N 2 O emissions, MITC should not be applied to field under wet conditions favouring denitrification., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2022. Published by Elsevier B.V. All rights reserved.)

Carbon dioxide (CO 2 ) emissions from forest ecosystems originate largely from soil respiration, and microbial heterotrophic respiration plays a critical role in determining organic carbon (C) stock. This study investigated the impacts of successive nitrogen (N) and phosphorus (P) fertilization after 9 years on soil organic C stock; CO 2 emission; and microbial biomass, community, and function in a Chinese fir plantation. The annual fertilization rates were (1) CK, control without N or P fertilization; (2) N50, 50 kg N ha -1 ; (3) N100, 100 kg N ha -1 ; (4) P50, 50 kg P ha -1 ; (5) N50P50, 50 kg N ha -1  + 50 kg P ha -1 ; and (6) N100P50, 100 kg N ha -1  + 50 kg P ha -1 . The N100P50 treatment had the highest cumulative soil CO 2 emissions, but the CK treatment had the lowest cumulative soil CO 2 emissions among all treatments. The declines of soil organic C (SOC) after successive 9-year fertilization were in the order of 100 kg N ha -1  year -1  > 50 kg N ha -1  year -1  > CK. Compared to the CK treatment, successive N fertilization significantly changed soil microbial communities at different application rates and increased the relative gene abundances of glycoside hydrolases, glycosyl transferases, carbohydrate-binding modules, and polysaccharide lyases at 100 kg N ha -1  year -1 . Relative to P fertilization alone (50 kg P ha -1  year -1 ), combined N and P fertilization significantly altered the soil microbial community structure and favored more active soil microbial metabolism. Microbial community and metabolism changes caused by N fertilization could have enhanced CO 2 emission from heterotrophic respiration and eventually led to the decrease in organic C stock in the forest plantation soil. KEY POINTS: • N fertilization, alone or with P, favored more active microbial metabolism genes. • 100 kg N ha -1 fertilization significantly changed microbial community and function. • N fertilization led to a "domino effect" on the decrease of soil C stock., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Type 2 diabetes mellitus (T2DM) is an independent risk factor of Alzheimer's disease (AD), and populations with mild cognitive impairment (MCI) have high incidence to suffer from AD. Therefore, discerning who may be more vulnerable to MCI, among the increasing T2DM populations, is important for early intervention and eventually decreasing the prevalence rate of AD. This study was to explore whether the change of plasma β-amyloid (Aβ) could be a biomarker to distinguish MCI (T2DM-MCI) from non-MCI (T2DM-nMCI) in T2DM patients. Methods: Eight hundred fifty-two T2DM patients collected from five medical centers were assigned randomly to training and validation cohorts. Plasma Aβ, platelet glycogen synthase kinase-3β (GSK-3β), apolipoprotein E (ApoE) genotypes, and olfactory and cognitive functions were measured by ELISA, dot blot, RT-PCR, Connecticut Chemosensory Clinical Research Center (CCCRC) olfactory test based on the diluted butanol, and Minimum Mental State Examination (MMSE) test, respectively, and multivariate logistic regression analyses were applied. Results: Elevation of plasma Aβ1-42/Aβ1-40 is an independent risk factor of MCI in T2DM patients. Although using Aβ1-42/Aβ1-40 alone only reached an AUC of 0.631 for MCI diagnosis, addition of the elevated Aβ1-42/Aβ1-40 to our previous model (i.e., activated platelet GSK-3β, ApoE ε4 genotype, olfactory decline, and aging) significantly increased the discriminating efficiency of T2DM-MCI from T2DM-nMCI, with an AUC of 0.846 (95% CI: 0.794-0.897) to 0.869 (95% CI: 0.822-0.916) in the training cohort and an AUC of 0.848 (95% CI: 0.815-0.882) to 0.867 (95% CI: 0.835-0.899) in the validation cohort, respectively. Conclusion: A combination of the elevated plasma Aβ1-42/Aβ1-40 with activated platelet GSK-3β, ApoE ε4 genotype, olfactory decline, and aging could efficiently diagnose MCI in T2DM patients. Further longitudinal studies may consummate the model for early prediction of AD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Liu, Zhang, He, Chen, Ke, Zhao, Zhang, Wei, Xu, Xu, Yin, Mo, Li, Gao, Li, Wang, Yu, Wu, Pi, Jiang, Deng, Xiong, Lei, Tian, He, Sun, Zhou, Wang, Ye, Li, Hu, Song, Peng, Zheng, Zhang and Wang.)

The Pd-catalyzed carbon-carbon bond formation pioneered by Heck in 1969 has dominated medicinal chemistry development for the ensuing fifty years. As the demand for more complex three-dimensional active pharmaceuticals continues to increase, preparative enzyme-mediated assembly, by virtue of its exquisite selectivity and sustainable nature, is poised to provide a practical and affordable alternative for accessing such compounds. In this minireview, we summarize recent state-of-the-art developments in practical enzyme-mediated assembly of carbocycles. When appropriate, background information on the enzymatic transformation is provided and challenges and/or limitations are also highlighted., (© 2021 Wiley-VCH GmbH.)

Electrophilic halogenation reactions have been a reliable approach to accessing organohalides. During the past decades, various catalytic systems have been developed for the activation of haleniums. However, there is still a short of effective catalysts, which could cover various halogenation reactions and broad scope of unsaturated compounds. Herein, TEMPO (2,2,6,6-tetramethylpiperidine nitroxide) and its derivatives are disclosed as active catalysts for electrophilic halogenation of olefins, alkynes, and aromatics. These catalysts are stable, readily available, and reactive enough to activate haleniums including Br + , I + and even Cl + reagents. This catalytic system is applicable to various halogenations including haloarylation of olefins or dibromination of alkynes, which were rarely realized in previous Lewis base catalysis or Lewis acid catalysis. The high catalytic ability is attributed to a synergistic activation model of electrophilic halogenating reagents, where the carbonyl group and the halogen atom are both activated by present TEMPO catalysis.

In this study, TiO 2 /Ag 3 PO 4 composites based on anatase TiO 2 nanocrystals with co-exposed {101}, {010}/{100}, {001} and [111]-facets and Ag 3 PO 4 microcrystals with irregular and cubic-like polyhedron morphologies were successfully synthesized by combining hydrothermal and ion-exchange methods. The anatase TiO 2 nanocrystals with different high-energy facets were controllably prepared via hydrothermal treatment of the exfoliated [Ti 4 O 9 ] 2- /[Ti 2 O 5 ] 2- nanosheet solutions at desired pH values. The Ag 3 PO 4 microcrystal with different morphologies was prepared via the ion-exchange method in the presence of AgNO 3 and NH 4 H 2 PO 4 at room temperature, which was used as a substrate to load the as-prepared anatase TiO 2 nanocrystals on its surface and to form TiO 2 /Ag 3 PO 4 heterostructures. The apparent rate constant of the pH 3.5-TiO 2 /Ag 3 PO 4 composite was the highest at 12.0 × 10 -3 min -1 , which was approximately 1.1, 1.2, 1.4, 1.6, 13.3, and 24.0 fold higher than that of pH 0.5-TiO 2 /Ag 3 PO 4 (10.5 × 10 -3 min -1 ), pH 7.5-TiO 2 /Ag 3 PO 4 (10.2 × 10 -3 min -1 ), pH 11.5-TiO 2 (8.8 × 10 -3 min -1 ), Ag 3 PO 4 (7.7 × 10 -3 min -1 ), blank sample (0.9 × 10 -3 min -1 ), and the commercial TiO 2 (0.5 × 10 -3 min -1 ), respectively. The pH 3.5-TiO 2 /Ag 3 PO 4 composite exhibited the highest visible-light photocatalytic activity which can be attributed to the synergistic effects of its heterostructure, relatively small crystal size, large specific surface area, good crystallinity, and co-exposed high-energy {001} and [111]-facets. The as-prepared TiO 2 /Ag 3 PO 4 composites still exhibited good photocatalytic activity after three successive experimental runs, indicating that they had remarkable stability. This study provides a new way for the preparation of TiO 2 /Ag 3 PO 4 composite semiconductor photocatalysts with high energy crystal surfaces and high photocatalytic activity., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

The intramolecular Csp 3 -H and/or C-C bond amination is very important in modern organic synthesis due to its efficiency in the construction of diversified N-heterocycles. Herein, we report a novel intramolecular cyclization of alkyl azides for the synthesis of cyclic imines and tertiary amines through selective Csp 3 -H and/or C-C bond cleavage. Two C-N single bonds or a C[double bond, length as m-dash]N double bond are efficiently constructed in these transformations. The carbocation mechanism differs from the reported metal nitrene intermediates and therefore enables metal-free and new transformation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Nitrous oxide (N 2 O) emissions from soil contribute to global warming and are in turn substantially affected by climate change. However, climate change impacts on N 2 O production across terrestrial ecosystems remain poorly understood. Here, we synthesized 46 published studies of N 2 O fluxes and relevant soil functional genes (SFGs, that is, archaeal amoA, bacterial amoA, nosZ, narG, nirK and nirS) to assess their responses to increased temperature, increased or decreased precipitation amounts, and prolonged drought (no change in total precipitation but increase in precipitation intervals) in terrestrial ecosystem (i.e. grasslands, forests, shrublands, tundra and croplands). Across the data set, temperature increased N 2 O emissions by 33%. However, the effects were highly variable across biomes, with strongest temperature responses in shrublands, variable responses in forests and negative responses in tundra. The warming methods employed also influenced the effects of temperature on N 2 O emissions (most effectively induced by open-top chambers). Whole-day or whole-year warming treatment significantly enhanced N 2 O emissions, but daytime, nighttime or short-season warming did not have significant effects. Regardless of biome, treatment method and season, increased precipitation promoted N 2 O emission by an average of 55%, while decreased precipitation suppressed N 2 O emission by 31%, predominantly driven by changes in soil moisture. The effect size of precipitation changes on nirS and nosZ showed a U-shape relationship with soil moisture; further insight into biotic mechanisms underlying N 2 O emission response to climate change remain limited by data availability, underlying a need for studies that report SFG. Our findings indicate that climate change substantially affects N 2 O emission and highlights the urgent need to incorporate this strong feedback into most climate models for convincing projection of future climate change., (© 2019 John Wiley & Sons Ltd.)

Soil biogeochemical cycles are largely mediated by microorganisms, while fire significantly modifies biogeochemical cycles mainly via altering microbial community and substrate availability. Majority of studies on fire effects have focused on the surface soil; therefore, our understanding of the vertical distribution of microbial communities and the impacts of fire on nitrogen (N) dynamics in the soil profile is limited. Here, we examined the changes of soil denitrification capacity (DNC) and denitrifying communities with depth under different burning regimes, and their interaction with environmental gradients along the soil profile. Results showed that soil depth had a more pronounced impact than the burning treatment on the bacterial community size. The abundance of 16S rRNA and denitrification genes (narG, nirK, and nirS) declined exponentially with soil depth. Surprisingly, the nosZ-harboring denitrifiers were enriched in the deeper soil layers, which was likely to indicate that the nosZ-harboring denitrifiers could better adapt to the stress conditions (i.e., oxygen deficiency, nutrient limitation, etc.) than other denitrifiers. Soil nutrients, including dissolved organic carbon (DOC), total soluble N (TSN), ammonium (NH(4)(+)), and nitrate (NO(3)(-)), declined significantly with soil depth, which probably contributed to the vertical distribution of denitrifying communities. Soil DNC decreased significantly with soil depth, which was negligible in the depths below 20 cm. These findings have provided new insights into niche separation of the N-cycling functional guilds along the soil profile, under a varied fire disturbance regime.