ortho-Alkynyl aryl ketones as highly reactive and versatile synthons have been broadly applied in organic synthesis in the past decade considering their high reactivity and structural diversity. ...Among numerous transformations of ortho-alkynyl aryl ketones, four common intramolecular annulative patterns based on Baldwin's rule, including 5-exo-dig/6-endo-dig oxo-cyclization and 5/6-exo-dig/6-endo-dig carbocyclization, were often employed with the help of metal catalysts, organic oxidants, visible light photocatalysis or electrocatalysis. With great developments in recent years, ortho-alkynyl aryl ketones have become one of the most effective building blocks for the construction of furan, indenone, naphthalenone, isochromene and naphthalene scaffolds. For these reasons, this review provides an overview of the chemistry established with conversions of ortho-alkynyl aryl ketones by demonstrating their general and special reactivities, introducing and discussing their mechanisms as well as their applications.
Since its discovery in the 1970s, surface-enhanced Raman scattering (SERS) has been primarily associated with substrates composed of nanostructured noble metals. Here we investigate chemically ...synthesized nanocrystal aggregates of aluminum, an inexpensive, highly abundant, and sustainable metal, as SERS substrates. Al nanocrystal aggregates are capable of substantial near-infrared SERS enhancements, similar to Au nanoparticles. The intrinsic nanoscale surface oxide of Al nanocrystals supports molecule–substrate interactions that differ dramatically from noble metal substrates. The preferential affinity of the single-stranded DNA (ssDNA) phosphate backbone for the Al oxide surface preserves both the spectral features and nucleic acid cross sections relative to conventional Raman spectroscopy, enabling quantitative ssDNA detection and analysis.
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IJS, KILJ, NUK, PNG, UL, UM
The analytical solution of two magnetic-electro-elastic materials with hole-initiated cracks are investigated under anti-plane shearing. The modeling of the cracks is achieved by applying a pair of ...negative shear stresses in the region where the cracks occur. During this investigation, the fundamental solution of the displacement field is expressed by Green's function method. The expressions of the magneto-electric-elastic wave fields around the interface can be obtained by using the wave function expansion method and Sommerfeld radiation conditions. Then, combined with permeable electromagnetic boundary conditions, the crack problem is reduced to a system of the first kind of Fredholm's integral equations, from which the dynamic stress intensity factor (DSIF) at the crack tip is obtained. Finally, various examples are provided to illustrate the effects of the geometrical parameters, material properties, wave number, and incident angle on the DSIF. Compared with previous traditional numerical and analytical methods, the methods proposed in this article are more applicable in practical engineering and theoretical analysis.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Human-sensitive mechanosensation depends on ionic currents controlled by skin mechanoreceptors. Inspired by the sensory behavior of skin, we investigate zwitterionic hydrogels that generate ions ...under an applied force in a mobile-ion-free system. Within this system, water dissociates as the distance between zwitterions reduces under an applied pressure. Meanwhile, zwitterionic segments can provide migration channels for the generated ions, significantly facilitating ion transport. These combined effects endow a mobile-ion-free zwitterionic skin sensor with sensitive transduction of pressure into ionic currents, achieving a sensitivity up to five times that of nonionic hydrogels. The signal response time, which relies on the crosslinking degree of the zwitterionic hydrogel, was ~38 ms, comparable to that of natural skin. The skin sensor was incorporated into a universal throat-worn silent-speech recognition system that transforms the tiny signals of laryngeal mechanical vibrations into silent speech.
In this paper, dynamic anti-plane problem in graded non-homogeneous magnetic-electric-elastic material with a conductive cylindrical rigid inclusion is studied. Cracks are generated from the ...inclusion edge under the action of SH guided waves. By applying a pair of reversed shear stresses to the crack surface, the mechanical model of the crack is achieved, and Green's function method is used in this process. The scattering fields of displacement, electric potential and magnetic potential are constructed by the wave function expansion method. Numerical results clarified the factors that affect the dynamic stress intensity factor of the crack tips, including material parameters, inclusion parameters, wave number and incident angle. It is expected that the investigation of magnetic-electric-elastic material with inclusion-initiated crack defects can provide some references for the project designing, manufacture and application of non-homogeneous multi-fields coupling materials.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
A new electrochemical proton-coupled electron transfer method for the intermolecular CSP2–H amination of heteroarenes without oxidants, metal catalysts and external electrolytes has been developed. ...Various new N-containing heteroarenes were prepared in medium to high yields, and the indole-containing product could be converted into practical 2-oxindole by simple basic hydrolysis. Mechanistic investigation indicated that ester sulfonyl-substituted N-radicals could be formed by the combination of 2,6-lutidine and electrochemical oxidation, which is the key to achieve the desired chemoselectivity.
Objective
To investigate systematically previous studies on the accuracy of artificial intelligence (AI)‐assisted diagnostic models in detecting esophageal neoplasms on endoscopic images so as to ...provide scientific evidence for the effectiveness of these models.
Methods
A literature search was conducted on the PubMed, EMBASE and Cochrane Library databases for studies on the AI‐assisted detection of esophageal neoplasms on endoscopic images published up to December 2020. A bivariate mixed‐effects regression model was used to calculate the pooled diagnostic efficacy of AI‐assisted system. Subgroup analyses and meta‐regression analyses were performed to explore the sources of heterogeneity. The effectiveness of AI‐assisted models was also compared with that of the endoscopists.
Results
Sixteen studies were included in the systematic review and meta‐analysis. The pooled sensitivity, specificity, positive and negative likelihood ratios, diagnostic odds ratio and area under the summary receiver operating characteristic curve regarding AI‐assisted detection of esophageal neoplasms were 94% (95% confidence interval CI 92%‐96%), 85% (95% CI 73%‐92%), 6.40 (95% CI 3.38‐12.11), 0.06 (95% CI 0.04‐0.10), 98.88 (95% CI 39.45‐247.87) and 0.97 (95% CI 0.95‐0.98), respectively. AI‐based models performed better than endoscopists in terms of the pooled sensitivity (94% 95% CI 84%‐98% vs 82% 95% CI 77%‐86%, P < 0.01).
Conclusions
The use of AI results in increased accuracy in detecting early esophageal cancer. However, most of the included studies have a retrospective study design, thus further validation with prospective trials is required.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Forging and welding are common necessary procedures for AA6××× alloys, and recrystallization is an inevitable process. However, it is still difficult to realize the control of the recrystallization ...behavior, while realizing the strengthening of mechanical properties of the base metal and welded joint. In this study, we overcome this problem through 0.5 wt% TiC–TiB2 nanoparticles, and fully reveal the influence of the nanoparticles on the recrystallization behavior of the base metal and nugget zone of a friction-stir-welded (FSW)-ed joint from the perspectives of dislocation rearrangement and grain boundary motion. The strengthening mechanisms of the base metal and FSW-ed joint are clarified. The recrystallization driving force of the base metal and nugget zone was increased. Dislocations with a higher density rearranged and formed more grain boundaries in the nugget zone. Besides, nanoparticles distributed on the grain boundaries restrained the vanishing of low-angle grain boundaries. The nugget zone microstructures were refined from 3.1 to 2.3 μm, and the recrystallization ratio was increased from 7.2% to 10.4% at 800 rpm. The grains in the nugget zone were refined from 2.2 to 1.9 μm, and the recrystallization ratio was increased from 16.1% to 18.4% at 1200 rpm. The promoted recrystallization in the nugget zone accelerated the release of stress. Nanoparticles weakened the precipitate coarsening in the nugget zone. After strengthening, the ultimate tensile strength and plastic strain of the FSW-ed joint at 800 rpm were increased by 4.7% and 18.8%, respectively. This study provides new approaches for a systematic microstructure evolution control in FSW-ed 6061 Al alloys.
•Trace nanoparticles double the recrystallization driving force of base metal.•More dislocation tangles promoted recrystallization of nugget zone.•Nanoparticle also inhibited grain coarsening of nugget zone.•Precipitate coarsening in the nugget zone was weakened.•FSW-ed joint softening was alleviated and the mechanical properties were enhanced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Developing a highly efficient and cost-effective catalyst for the oxygen evolution is urgent for the application of water splitting. Herein, we report a Co-based nanocubes (NBs) containing an low ...amount of ruthenium oxide RuO2/Co3O4 as an efficient electrocatalyst synthesized via a facile ion impregnation and calcine approach with Co3(Co(CN)6) precursor. Owing to the close combination between Ru ions and Co3(Co(CN)6), the good dispersion and small size of RuO2 nanoparticle can be achieved on the surface of Co3O4 nanotubes after calcination, suggesting the more active sites and better utilization of RuO2. The synergistic effect of RuO2/Co3O4 hybrid can provide the faster charge transfer process and the structural stability. The as-synthesized RuO2/Co3O4 NBs show the promising electrocatalytic performance for oxygen evolution reaction (OER) with lower overpotential (302 mV to reach 10 mA cm−2) and higher current density than state of the commercial RuO2 samples. The long-term stability of RuO2/Co3O4 NBs is obtained. Therefore, designing the ions impregnation into precursor may present a facile strategy for cost-effective electrocatalysts for OER.
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•RuO2/Co3O4 nanotube is synthesized using ion impregnation and calcine approach.•The good dispersion and low loading of RuO2 on Co3O4 can be achieved.•The interface and synergistic effect between RuO2 and Co3O4 are responsible for the better OER properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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