N-Heterocyclic Carbene-Catalyzed [3 + 3] Annulation of 5-Aminopyrazoles with Enals: Enantioselective Synthesis of Pyrazolo[3,4-b]pyridones.

An enantioselective construction of pyrazolo[3,4-b]pyridones was achieved via N-heterocyclic carbene-catalyzed [3 + 3] annulation of enals with 5-aminopyrazoles. This protocol not only offers a highly efficient synthetic approach for the preparation of various substituted pyrazolo[3,4-b]pyridones but also provides an effective method for the rapid synthesis of enantiopure spirooxindone derivatives.

Highly Enantioselective Construction of the Polycyclic Piperazin-2-ones via NHC-Catalyzed [12 + 2] Cycloadditions.

NHC-catalyzed diastereoselective and enantioselective [12 + 2] higher-order cycloadditions of 5H-benzo[a]-pyrrolizine-3-carbaldehydes with cyclic sulfonic imines are described. Various optically pure polycyclic piperazin-2-ones were successfully constructed under mild reaction conditions with excellent diastereoselectivities and enantioselectivities. The generated chiral polycyclic piperazin-2-ones could be transformed to planar-chiral nine-membered cyclic amides via squaramide-catalyzed asymmetric ring-expansion reactions.

Atroposelective Access to Dihydropyridinones with C-N Axial and Point Chirality via NHC-Catalyzed [3 + 3] Annulation.

An N-heterocyclic carbene-catalyzed atroposelective [3 + 3] annulation of enals with 2-aminomaleate derivatives is described. A series of substituted dihydropyridones bearing both C-N axis and point chirality were synthesized with good diastereo- and enantioselectivity under mild conditions. This efficient strategy successfully superpositions an extra point chiral element with an axial backbone, and the generated structurally interesting atropisomers may have potential application in drug discovery.

Two-Dimensional Bimetallic Phthalocyanine Covalent-Organic-Framework-Based Chemiresistive Gas Sensor for ppb-Level NO2 Detection.

Two-dimensional (2D) phthalocyanine-based covalent organic frameworks (COFs) provide an ideal platform for efficient and rapid gas sensing-this can be attributed to their regular structure, moderate conductivity, and a large number of scalable metal active centers. However, there remains a need to explore structural modification strategies for optimizing the sluggish desorption process caused by the extensive porosity and strong adsorption effect of metal sites. Herein, we reported a 2D bimetallic phthalocyanine-based COF (COF-CuNiPc) as chemiresistive gas sensors that exhibited a high gas-sensing performance to nitrogen dioxide (NO2). Bimetallic COF-CuNiPc with an asymmetric synergistic effect achieves a fast adsorption/desorption process to NO2. It is demonstrated that the COF-CuNiPc can detect 50 ppb NO2 with a recovery time of 7 s assisted by ultraviolet illumination. Compared with single-metal phthalocyanine-based COFs (COF-CuPc and COF-NiPc), the bimetallic structure of COF-CuNiPc can provide a proper band gap to interact with NO2 gas molecules. The CuNiPc heterometallic active site expands the overlap of d-orbitals, and the optimized electronic arrangement accelerates the adsorption/desorption processes. The concept of a synergistic effect enabled by bimetallic phthalocyanines in this work can provide an innovative direction to design high-performance chemiresistive gas sensors.

Effect of breathing exercises on oxidative stress biomarkers in humans: A systematic review and meta-analysis.

Background: Breathing exercises improve oxidative stress in healthy young adults and patients with diabetes, hypertension, and chronic obstructive pulmonary disease. Furthermore, the mechanism of respiratory intervention is controversial. Therefore, in this meta-analysis, we aimed to systematically evaluate the effects of breathing exercises on oxidative stress biomarkers in humans and provide evidence for the clinical application of breathing exercises. Methods: The Embase, PubMed, Cochrane Library, Web of Science, CNKI, and WANFANG databases were searched for studies about the effects of breathing exercises on human oxidative stress levels, with no restraints regarding time, race, or language. The experimental group included various breathing exercises, and the outcome index included malondialdehyde, superoxide dismutase, and glutathione, nitric oxide, vitamin C, or total antioxidant capacity levels from a randomized controlled trial. Data were extracted by more than two authors and reviewed by one author. Results: Ten studies were included from five countries. Data from patients with no disease, chronic obstructive pulmonary disease, hypertension, or diabetes were included. Participants who performed breathing exercises had greater changes in the included biomarkers than those who did not, suggesting that these biomarkers can be used to evaluate oxidative stress after respiratory interventions. Conclusion: Breathing exercises increased SOD and GSH activities and decreased MDA content. Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022337119, identifier CRD42022337119.

Biogenic methane in coastal unconsolidated sediment systems: A review.

Marine sediments are the world's largest known reservoir of methane. In many coastal regions, methane is trapped in sediments buried at depths ranging from centimeters to hundreds of meters below the seafloor, in the forms of gas pockets, dispersed gas bubbles and dissolved gas, also known as shallow gas (methane-dominated gas mixture). The existence of shallow gas affects the engineering geological environment and threatens the safety of artificial facilities. The escape of shallow gas from sediments into the atmosphere can even threaten ecosystem security and affect global climate change. However, until now, shallow gas has remained a mystery to the scientific community. For example, how it is generated, how it distributes and migrates in sediments, and what are the factors that influence these processes that are still unclear. In the context of increasingly intense offshore development and global warming, there is a huge gap between existing scientific understanding of shallow gas and the need to develop scientific solutions for related problems. Based on this, this paper systematically collects the information on all aspects of shallow gas mentioned above, comprehensively summarizes the current scientific understanding, and analyzes the existing shortcomings, which will provide systematic references for the research on environmental disaster prevention, engineering technology, climate change, and other fields.

N-Heterocyclic Carbene-Catalyzed [3 + 2] Annulation of 3,3'-Bisoxindoles with α-Bromoenals: Enantioselective Construction of Contiguous Quaternary Stereocenters.

An NHC-catalyzed enantio- and diastereoselective [3 + 2] annulation of α-bromoenals with bisoxindoles is developed, affording efficient access to various spirocyclic bisoxindole alkaloids. This protocol tolerates a broad substrates scope, with various spirocyclic bisoxindoles obtained in generally excellent enantioselectivities. More importantly, two contiguous sterically congested all-carbon quaternary stereocenters are successfully created during this process.

Distribution and environmental risk assessment of microplastics in continental shelf sediments in the southern East China Sea: A high-spatial-resolution survey.

We report a high-spatial-resolution study on the distributions, characteristics, and environmental risks of microplastics in surface sediments of the southern East China Sea. Microplastics were omnipresent in the sediments (concentration range: 53.3-246.7; mean: 138.4 particles/kg dry-weight sediment) and enriched in nearshore areas close to urban centers relative to lower offshore concentrations. The microplastics identified were dominated by polyethylene (41.2%) and polyethylene terephthalate (19.9%) in polymer type, fibers (45.8%) and fragments (40.3%) in shape, 0.1-0.5 mm (61.0%) in size, and black (52.0%) in color. The benthic environment experienced low to moderate microplastic pollution, with polyvinylchloride exhibiting the highest ecological risk index. The high-resolution sampling revealed highly diverse polymer types and strongly patchy distributions of microplastic abundance and pollution indices in sediments. Results from this study imply that complex physical, biological, and topographic interactions control the distribution of microplastics and the associated environmental risks in coastal sediments.

Highly Enantioselective Synthesis of Pyrroloindolones and Pyrroloquinolinones via an N-Heterocyclic Carbene-Catalyzed Cascade Reaction.

In this work, the NHC-catalyzed Michael/Mannich/lactamization cascade reaction of enals with either indole-2-carboxaldehyde-derived aldimines or indole-7-carboxaldehyde-derived aldimines is described. This protocol enables the rapid assembly of optically active pyrroloindolones and pyrroloquinolinones derivatives under mild conditions with high yields, excellent enantioselectivities, and a broad substrate scope.

Improving equivalence in fibrinogen evaluation between the prothrombin time-derived fibrinogen assay and Clauss method using a pooled plasma calibrator.

AIMS: Both the Clauss and prothrombin time-derived fibrinogen (PT-Fib) methods have widely been used in fibrinogen (Fib) evaluation. We aimed to improve the interchangeability between these two methods. METHODS: Thirty fresh plasmas of low, normal and high Fib concentration were mixed to prepare the pooled human plasma. The Fib concentration was assessed by the Clauss method. The PT-Fib values were further recalibrated by the assigned plasma pools and the precision, linearity and reference intervals were verified according to the guidelines of American Society for Clinical and Laboratory Standards (CLSI) EP15-A and EP6-A documents. Finally, the recalibrated PT-Fib method was compared with Clauss method by the simultaneous Fib test of total 5259 coagulation samples. RESULTS: The results indicated that the recalibrated PT-Fib method can detect the Fib concentration with clinically acceptable third-order linearity in the range of 1.27-8.00 g/L. Only one result out of 39 healthy people tested using the recalibrated PT-Fib method did not fall within the reference range defined by the manufacturer. We also found more than 99% of results between these two methods were interchangeable in the range of 1.51-8.00 g/L. The disagreement between these two methods was found only in patients with certain underlying conditions. CONCLUSIONS: After recalibration, the consistency between the PT-Fib and Clauss methods was enhanced and the interchangeability was improved. The application of the recalibrated PT-Fib method provided accurate and reliable results with the manufacturer-provided reagents and improved detection speed and cost-effectiveness.

Access to dihydropyrano[3,2-b]pyrrol-5-ones skeletons by N-heterocyclic carbene-catalyzed [3+3] annulations.

A novel and efficient NHC-catalyzed [3+3] annulation of enals with pyrrol-4-ones was developed, thus providing the dihydropyrano[3,2-b]pyrrol-5-one core structures with broad scope and good to excellent enantioselectivities. Notably, this strategy could also expand to the synthesis of axially chiral compounds and polysubstituted indoles.

Controlling factors for the distribution of typical organic pollutants in the surface sediment of a macrotidal bay.

Marine sediment is the final sink of polycyclic aromatic hydrocarbons (PAHs) from river input and atmospheric deposition. Such kind of pollutant cycles in the marine environment is usually controlled by hydrodynamic conditions. Many previous studies have explored how ocean currents influence pollutant distribution, but very few studies have focused on the relationships between the distribution patterns of pollutant and residual currents or sediment transport. In this study, 16 monomers of PAHs from 135 surface sediment samples collected in the Hangzhou Bay, a typical macrotidal bay, were systematically identified and their sources were analyzed. The sediment characteristics and distribution pattern were also comprehensively analyzed. The results showed the seabed sediments were moderately polluted by PAHs with a level of 38.58-1371.06 ng/g (median 186.70 ng/g). Most of the PAHs are composed of three to five rings, originated from combustion of coal and firewood. The combustion of oil also contributes to PAHs in seabed sediments for some areas. The PAHs are found to be concentrated within the estuary and the offshore areas, as well in coastal ocean. Fine-grained sediment transport is controlled by residual currents, which leads to PAH accumulation in the bay and the offshore areas, forming a high-value distribution pattern. Hence, we conclude that residual current is the main factors that control the long-term distribution of PAHs in the seabed sediments of the macrotidal bay. Temporal and spatial varying models of PAHs were needed in a further study to explore further the mechanisms how PAHs are transported in coastal areas.

Analysis of origin, change, and distribution of polycyclic aromatic hydrocarbons in the continental shelf of China Sea.

The sources and environmental fate of polycyclic aromatic hydrocarbons (PAHs) are closely related with anthropological activities and natural environmental conditions. The continental shelf of China Sea has the most intense land-ocean interactions. The PAHs' distribution in this region is of great significance for revealing the impact of human activities on the marine environment and the environmental fate of terrigenous substances input to the ocean. However, up to now, almost all the studies were confined to relatively small regions, such as estuaries. There was a lack of systematic understanding of PAHs in the whole continental shelf sea. In this study, the relevant research findings of PAHs in the continental shelf of China Sea in recent years were systematically summarized. The spatial and temporal variations of PAHs in sediments of China Sea were comprehensively displayed. The relationships between PAHs' distributions in different seas with regional economic development history were analyzed. These findings will play a guiding significance for improving marine environment research in large-scale areas.

Catalytic asymmetric acetalization of carboxylic acids for access to chiral phthalidyl ester prodrugs.

Carboxylic acids are common moieties in medicines. They can be converted to phthalidyl esters as prodrugs. Unfortunately, phthalidyl esters are now mostly prepared in racemic forms. This is not desirable because the two enantiomers of phthalidyl esters likely have different pharmacological effects. Here we address the synthetic challenges in enantioselective modification of carboxylic acids via asymmetric acetalizations. The key reaction step involves asymmetric addition of a carboxylic acid to the catalyst-bound intermediate. This addition step enantioselectively constructs a chiral acetal unit that lead to optically enriched phthalidyl esters. A broad range of carboxylic acids react effectively under mild and transition metal-free conditions. Preliminary bioactivity studies show that the two enantiomers of chlorambucil phthalidyl esters exhibit different anti-cancer activities to inhibit the growth of Hela cells. Our catalytic strategy of asymmetric acetalizations of carboxylic acids shall benefit future development of chiral phthalidyl ester prodrugs and related molecules.

The effect of hydrodynamic forcing on the transport and deposition of polybrominated diphenyl ethers (PBDEs) in Hangzhou Bay.

Surface sediment samples (n = 92) were collected from Hangzhou Bay to investigate the transport and deposition of polybrominated diphenyl ethers (PBDEs) and to assess the ecological risks in Hangzhou Bay. The concentrations of ∑7PBDEs (sum of BDE-28, 47, 99, 100, 153, 154, 183) and BDE-209 ranged from 3.61 to 91.09 pg g-1 and from non-detectable to 2007.52 pg g-1 (dry weight), respectively. The high values of ∑7PBDEs and BDE-209 were commonly occurred at the northeast of Hangzhou Bay and the Nanhui Spit coast of Shanghai. Compared with the south part of the bay, the dominance of BDE-209 was more prominent and the linear correlations between PBDEs concentrations and TOCs as well as median grain size were more significant in the northern Hangzhou Bay. Hydrodynamic forcing on the transport and deposition of PBDEs is primarily responsible for the discrepancy of this spatial distribution in these two parts. In addition to BDE-209, BDEs-153, 99, 47, and 100 were also the abundant congeners. Three principal components were extracted using principal component analysis (PCA), mainly attributed to human activities, erosion of polluted soils via surface runoff and release from products for PC1, PC2 and PC3, respectively. The calculation results of mass inventories, hazard quotients (HQs) and risk quotients (RQs) indicated that the ecological risk of PBDEs in Hangzhou Bay was low. The multiple effect of hydrodynamic forcing with complicated and large-scope tidal currents made it hard to deposit for organic matters and contaminants in Hangzhou Bay.

Three-Dimensional Framework of Graphene Nanomeshes Shell/Co3O4 Synthesized as Superior Bifunctional Electrocatalyst for Zinc-Air Batteries.

The synthesis of durable and low-cost electrocatalyst is crucial but challenging. Here, we developed a one-pot pyrolysis approach toward the preparation of heteroatom-doped hierarchical porous three-dimensional (3D) graphene frameworks decorated with multilayer graphene shell-coated cobalt oxide nanocrystal. Large literal sheet size of graphene nanomeshes may stimulate rapid thermolysis with cobalt-oleate complex to form Co3O4 nanocrystals and in situ growth of multilayer graphene coating co-doped by boron and nitrogen with controlling heating rate up to 600 °C. This new material worked as superior bifunctional electrocatalyst on oxygen reduction reaction and oxygen evolution reaction to commercial Pt/C with better onset potential/half-wave potentials, larger current density, better stability, and stronger methanol tolerance. The heteroatom co-doping into porous/curved graphene confined nanocrystals in 3D porous walls provided adequate accessibility of created catalytic active sites and ideal mass transport route for the excellent catalytic activity on redox reaction of oxygen. The synthesized material-based Zn-air battery further confirmed its superior electrolytic activity with high specific capacity and smaller overpotential. This one-pot pyrolysis method shows a great potential of scalable synthesis of high-performance practical electrocatalyst for metal-air batteries and fuel cells at a low cost.

Distributions and sources of heavy metals in sediments of the Bohai Sea, China: a review.

This paper summarizes the recent research results from studies concerning heavy metals in the Bohai Sea in recent decades. The temporal and spatial variations and potential sources of the heavy metals in the surface sediments were analyzed. Based on these obtained data, the average concentrations in surface sediments collected in recent years (summarized 3171 samples) were 0.31, 87.0, 25.7, 25.8, 0.11, 16.9, 52.2, and 27.7 µg/g for Cd, Zn, Cu, Pb, Hg, As, Cr, and Ni, respectively. In the samples collected in the 1980s, the concentrations were 22.6, 21.3, 69.13, 0.26, and 57.5 µg/g (summarized 218 samples) for Cu, Pb, Zn, Cd, and Cr. The concentrations of Cu, Pb, Zn, and Cd increased slightly. Generally, higher concentrations were measured in the Bohai Bay and central Bohai Sea. The distribution patterns of heavy metals were significantly different between samples collected after the year of 2000 and those in the 1980s. In the 1980s and recent years, higher concentrations of Zn, Cd, and Pb were measured in the samples collected from Bohai Bay and Liaodong Bay, respectively. This indicated that the sources of heavy metals in Bohai Sea were changed significantly during the past decades.

Hydrazonyl Radical-Participated Tandem Reaction: A Strategy for the Synthesis of Pyrazoline-Functionalized Oxindoles.

An efficient and practical tandem cyclization/addition/cyclization strategy is developed for the initial generated hydrazonyl radicals derived from the oxidation of ß,γ-unsaturated hydrazones. By using this protocol, structurally novel pyrazoline-functionalized oxindoles are prepared by the reaction of easily accessible ß,γ-unsaturated hydrazones with N-aryl acrylamides under the metal- and solvent-free conditions of DTBP (di-tert-butyl peroxide) via a tandem intra/intermolecular C-N/C-C/C-C bond formation.

Polycyclic aromatic hydrocarbons in sediments of China Sea.

Increasing pollution pressures were placed in the coastal and estuarine ecosystems in China because of the elevated pollutants discharged from various sources. Polycyclic aromatic hydrocarbons (PAHs) in the environment were closely linked to human activities, which have been intensively studied for their geochemical interest as markers. In this review, the status of PAH contamination in China Sea was assessed by comprehensive reviews of the concentrations, sources, and fates of PAHs in sediments of China Sea. PAH concentrations in China Sea sediments decreased from north to south due to the higher emissions in North China. Atmosphere was probably the main carrier of PAHs in the north due to the higher contents of atmospheric fine particles and higher wind speeds. However, riverine inputs were probably the most important sources of PAHs in the coastal sediments of South China due to higher rainfall.

An assessment of human influences on sources of polycyclic aromatic hydrocarbons in the estuarine and coastal sediments of China.

Sediments collected from the coastal area of China, embracing west coast of Bohai Sea, south coast of Shandong Peninsula, and the Changjiang estuary (listed in order of decreasing north latitude), were analyzed for polycyclic aromatic hydrocarbons (PAHs). ∑PAH (Sixteen US EPA priority PAHs) were 2.7-350.9ng/g. Petroleum residue was the major contributor of PAHs in the coastal sediments of China due to oil leakage from ships and offshore oil fields. The contribution of vehicular emissions in coast of North China was significantly lower than that in the Changjiang Estuary, and the reverse was true for coal combustion. PAH concentrations in the sediment core of the Changjiang estuary steadily increased upward and the variation was primarily due to economic development and severe floods. The impact on PAHs by vehicular emissions (37.2%) and petrogenic sources (45.8%) overwhelmed combustion sources (17.0%).