B(C6F5)3 has been found to be an effective catalyst for reduction of pyridines and other electron‐deficient N‐heteroarenes with hydrosilanes (or hydroboranes) and amines as the reducing reagents. The ...success of this development hinges upon the realization of a cascade process of dearomative hydrosilylation (or hydroboration) and transfer hydrogenation. The broad functional‐group tolerance (e.g. ketone, ester, unactivated olefins, nitro, nitrile, heterocycles, etc.) implies high practical utility.
Reduction cascade: An operationally simple B(C6F5)3‐catalyzed pyridine reduction method has been developed. The reaction occurs by a cascade process of dearomative hydrosilylation (or hydroboration) and transfer hydrogenation. The reduction features very broad functional‐group tolerance.
Particle swarm optimization (PSO) relies on its learning strategy to guide its search direction. Traditionally, each particle utilizes its historical best experience and its neighborhood's best ...experience through linear summation. Such a learning strategy is easy to use, but is inefficient when searching in complex problem spaces. Hence, designing learning strategies that can utilize previous search information (experience) more efficiently has become one of the most salient and active PSO research topics. In this paper, we proposes an orthogonal learning (OL) strategy for PSO to discover more useful information that lies in the above two experiences via orthogonal experimental design. We name this PSO as orthogonal learning particle swarm optimization (OLPSO). The OL strategy can guide particles to fly in better directions by constructing a much promising and efficient exemplar. The OL strategy can be applied to PSO with any topological structure. In this paper, it is applied to both global and local versions of PSO, yielding the OLPSO-G and OLPSO-L algorithms, respectively. This new learning strategy and the new algorithms are tested on a set of 16 benchmark functions, and are compared with other PSO algorithms and some state of the art evolutionary algorithms. The experimental results illustrate the effectiveness and efficiency of the proposed learning strategy and algorithms. The comparisons show that OLPSO significantly improves the performance of PSO, offering faster global convergence, higher solution quality, and stronger robustness.
Background
The impacts of chronic airway diseases on coronavirus disease 2019 (COVID‐19) are far from understood.
Objective
To explore the influence of asthma and chronic obstructive pulmonary ...disease (COPD) comorbidity on disease expression and outcomes, and the potential underlying mechanisms in COVID‐19 patients.
Methods
A total of 961 hospitalized COVID‐19 patients with a definite clinical outcome (death or discharge) were retrospectively enrolled. Demographic and clinical information were extracted from the medical records. Lung tissue sections from patients suffering from lung cancer were used for immunohistochemistry study of angiotensin‐converting enzyme II (ACE2) expression. BEAS‐2B cell line was stimulated with various cytokines.
Results
In this cohort, 21 subjects (2.2%) had COPD and 22 (2.3%) had asthma. After adjusting for confounding factors, COPD patients had higher risk of developing severe illness (OR: 23.433; 95% CI 1.525‐360.135; P < .01) and acute respiratory distress syndrome (OR: 19.762; 95% CI 1.461‐267.369; P = .025) than asthmatics. COPD patients, particularly those with severe COVID‐19, had lower counts of CD4+ T and CD8+ T cells and B cells and higher levels of TNF‐α, IL‐2 receptor, IL‐10, IL‐8, and IL‐6 than asthmatics. COPD patients had increased, whereas asthmatics had decreased ACE2 protein expression in lower airways, compared with that in control subjects without asthma and COPD. IL‐4 and IL‐13 downregulated, but TNF‐α, IL‐12, and IL‐17A upregulated ACE2 expression in BEAS‐2B cells.
Conclusion
Patients with asthma and COPD likely have different risk of severe COVID‐19, which may be associated with different ACE2 expression.
After adjusting for confounding factors, COVID‐19 patients with COPD have higher risks of developing severe illness and acute respiratory distress syndrome than COVID‐19 patients with asthma. COPD patients have increased, whereas asthmatics have decreased ACE2 protein expression in lower airways, compared with that in control subjects without asthma and COPD. IL‐17A, TNF‐α, and IL‐12 promote, while IL‐4 and IL‐13 suppress ACE2 expression in airway BEAS‐2B cells. Abbreviations: ACE2, angiotensin‐converting enzyme II; ARDS, acute respiratory distress syndrome; BEAS‐2B, adenovirus‐12 SV40 hybrid virus transformed bronchial epithelial cells; COPD, chronic obstructive pulmonary disease; COVID‐19, coronavirus disease 2019.
The aim of this work was to develop an easy-to-use food package label for pork shelf-life assessment. Meat samples were packaged in polyethylene terephthalate trays with on-package indicator labels ...and kept at 5 °C for 8 days. These indicators contained three groups of pH-sensitive dyes, i.e., bromocresol purple, bromothymol blue, and a mixture of bromothymol blue and methyl red. Results of pH, total volatile basic nitrogen (TVB-N) contents, aerobic plate counts and sensory scores of pork differentiated between fresh (on 0–3 days), medium fresh (on 4–5 days), and spoiled lean pork (on 6–8 days). Results of total color difference and principal components analysis carried out with colorimetric data of different indicator labels showed that the indicator label made by a mixture of bromothymol blue and methyl red at 3:2 proportion (at an initial pH of 5.0) was able to discriminate fresh (red), medium fresh (goldenrod), and spoiled (green) pork in cold storage. The statistical models obtained by partial least squares, with the color change of label, successfully predicted TVB-N contents and aerobic plate counts of pork. These results suggest the potential feasibility of this particular indicator system for monitoring freshness of packaged pork via color change detected directly using the naked eye.
•pH dye-based indicator labels were studied for lean pork meat spoilage assessment.•Indicator responds via visible color change to volatiles in the package headspace.•Indicator color change presents a similar tendency to microbial growth.•Indicator color change can discriminate fresh, medium fresh, and spoiled pork.
Summary
Visual pH‐sensing films were fabricated using cellulose nanofibrils (CNF) reinforced polyvinyl alcohol (PVA) and alizarin. The relationships between the ratio of PVA: CNF hydrogel (2:1, 1:1, ...1:2) and the physical properties and colour response efficiency of indicator films were investigated. Fourier transform infrared spectroscopy of films evidenced alizarin and CNF was properly incorporated by physical interaction. A new weak X‐ray diffraction peak appeared at 2θ = 22.4°, which was affected by the incorporation of CNF. The increase in the CNF content induced enhancements of thermal stability, tensile strength, water contact angle and colour sensitivity of the indicator films. The colourimetric films had a higher sensitivity to discolouration when exposed to acidic vapours than alkaline vapours. The films presented a remarkable colour change varied from purple in alkaline condition to yellow in acidic condition. Therefore, this colourimetric film can be used as a volatile acid sensor for intelligent packaging.
Visual pH‐sensing films were fabricated using cellulose nanofibrils (CNF) reinforced polyvinyl alcohol (PVA) and alizarin. The relationships between the ratio of PVA: CNF hydrogel and the physical properties and colour response efficiency of indicator films were investigated.
In this study, using coconut fibers as raw material, activated carbon fibers were prepared
via
carbonization and KOH activation processes. The morphology, composition, specific surface area, pore ...structure and thermal stability of the resulting activated carbon fibers were systematically characterized. It was found that the activation process increases the specific surface area of carbon fibers to a greater extent
via
formation of a large number of micropores (0.7-1.8 nm) and a certain amount of slit-shaped mesopores (2-9 nm). The specific surface area and the pore volume of the activated carbon fibers reach 1556 m
2
g
−1
and 0.72 cm
3
g
−1
, respectively. The activation process can also decompose the tar deposits formed after the carbonization process by pyrolysis, making the surface of the activated carbon fibers smoother. To study the adsorption properties of the as-prepared activated carbon fibers, the adsorption capacities and adsorption kinetics of various organic dyes including methylene blue, Congo red and neutral red were investigated. The adsorption capacities of the dyes increased with the increasing initial dye concentrations, and varied greatly with the pH value of the system. In methylene blue and neutral red systems, the adsorption capacities reach the maximum at pH 9, and in the Congo red system, it reaches the maximum at pH 3. The adsorption capacities of the activated carbon fibers in methylene blue, Congo red and neutral red systems reached equilibrium at 150, 120, and 120 min, and the maximum adsorption capacities were 21.3, 22.1, and 20.7 mg g
−1
, respectively. The kinetics of the adsorption process was investigated using three models including pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results indicated that the dynamic adsorption processes of coconut-based activated carbon fibers to methylene blue, Congo red and neutral red were all in accordance with the second-order kinetic model, and the equations are as follows:
t
/
Q
t
= 0.1028 +
t
/21.3220,
t
/
Q
t
= 0.1128 +
t
/21.5982 and
t
/
Q
t
= 0.0210 +
t
/20.6612.
Activated carbon fibers with high micropore volume and large specific surface area were prepared from abundant and low-cost coconut fibers, which show excellent adsorption performances towards various dyes.
Nacre is an ultratough natural nanocomposite found in mollusc shells. It consists of hard aragonite nanocrystals and a soft biopolymer matrix. Apart from maintaining the integrity of nacre's ...brick‐and‐mortar nanoarchitecture, the biopolymer plays a critical role in the strengthening and toughening of nacre. By directly probing the biopolymer strands using atomic force microscopy, it is revealed that the biopolymer in nacre has the capability to strengthen itself during deformation. This remarkable deformation–strengthening mechanism contributes significantly to the ultrahigh toughness of nacre, and can be explained by a coiled‐spring model. The findings explain the mystery of nacre's toughening mechanisms, provide additional design guidelines for developing biomimetic nanomaterials, and lay a constitutive foundation for modeling the deformation behavior of nacre.
Directly testing nacre biopolymer strands using atomic force microscopy reveals that nacre biopolymer can strengthen itself during deformation, a phenomenon that can be explained by a coiled spring model. The findings advance the understanding of nacre's toughening mechanisms, provide additional design guidelines for developing biomimetic nanomaterials, and lay a constitutive foundation for modeling the deformation behavior of nacre.
Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal ...catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites.
Palladium and CO.: The title reaction proceeds in the presence of CO, thus providing a synthesis for 1,3‐oxazin‐6‐ones (see scheme; DABCO=1,4‐diazabicyclo2.2.2octane, DMF=N,N‐dimethylformamide). The ...reaction tolerates a variety of functional groups on both the aryl ring and the amide of the substrate. Initial mechanistic studies suggest the activation of the alkenyl CH bond to be a key step.
Most two-dimensional (2D) covalent organic frameworks (COFs) are non-fluorescent in the solid state even when they are constructed from emissive building blocks. The fluorescence quenching is usually ...attributed to non-irradiative rotation-related or π-π stacking-caused thermal energy dissipation process. Currently there is a lack of guiding principle on how to design fluorescent, solid-state material made of COF. Herein, we demonstrate that the eclipsed stacking structure of 2D COFs can be used to turn on, and tune, the solid-state photoluminescence from non-emissive building blocks by the restriction of intramolecular bond rotation via intralayer and interlayer hydrogen bonds among highly organized layers in the eclipse-stacked COFs. Our COFs serve as a platform whereby the size of the conjugated linkers and side-chain functionalities can be varied, rendering the emission colour-tuneable from blue to yellow and even white. This work provides a guide to design new solid-state emitters using COFs.
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