A general solution for the synthesis of various oxetan-3-ones is developed. This reaction uses readily available propargylic alcohols as substrates and proceeds without the exclusion of moisture or ...air (“open flask”). Notably, oxetan-3-one, a highly valuable substrate for drug discovery, can be prepared in one step from propargyl alcohol in a fairly good yield. The facile formation of the strained oxetane ring provides strong support for the intermediacy of α-oxo gold carbenes. This safe and efficient generation of gold carbenes via intermolecular alkyne oxidation offers a potentially general entry into α-oxo metal carbene chemistry without using hazardous diazo ketones.
Oxidizing gold? A gold(I)/gold(III) catalytic cycle is essential for the first oxidative cross-coupling reaction in gold catalysis. By using Selectfluor for gold(I) oxidation, this chemistry reveals ...the synthetic potential of incorporating gold(I)/gold(III) catalytic cycles into contemporary gold chemistry and promises a new area of gold research by merging powerful gold catalysis and oxidative metal-catalyzed cross-coupling reactions.
Shear failure of rock masses along pre-existing discontinuities is one of the predominant failure modes of rock slopes and underground tunnels. The monitoring and prediction of the impending shear ...failure is of great significance to ensure the stability of the rock structures and the safety of the workers. In this study, direct shear tests under normal stress ranging from 0.5 to 10 MPa are conducted on rock fractures (analogous to soft rock discontinuities), which are obtained by artificial splitting, during which the AE parameters are monitored. Test results show that the AE parameters (hit, energy and events) increase with the shear stress, and peak at or near the peak shear strength, after which the AEs gradually decay with the decrease of shear stress. The number of AE events first increases and then decreases with increasing normal stress, which may be associated with the ductile deformation of the porous structure of cement mortar under higher normal stress. The degradation of asperities on the fracture surface can be inferred from the accumulative AE hits and events, which are characterized by “S” shapes and can be divided into slow growth, fast growth and slow growth stages. Conceptual and mathematical asperity damage models are proposed respectively based on the temporal characteristics of AE events and the curve fitting, which can be used to predict the asperity damage for a given shear stress curve. The AE b-value fluctuates and remains high in the shear process. There is no strong correlation between the shear stress and the b-value, which indicates that the b-value may not be an effective index to predict the quasi-static shear failure of jointed rock masses possessing similar properties like cement mortar. Results of this study will not only contribute to a better understanding of the asperity degradation characteristics but also provide valuable knowledge for AE monitoring applications in jointed rock masses.
•Direct shear tests are performed on cement mortar splitting fractures.•The asperity damage characteristics are studied by acoustic emission monitoring.•Conceptual and mathematical asperity damage models are proposed.•The b-value is not effective to predict the shear failure of soft rock fractures.
Chiral rings made easy: Chiral azetidin‐3‐ones have been easily prepared from chiral N‐propargylsulfonamides, which in turn are readily accessible through chiral sulfinamide chemistry (see scheme). ...Using tert‐butylsulfonyl as the protecting group avoids unnecessary deprotection and reprotection steps, and allows its removal from the azetidine ring under acidic conditions.
Mimicking proton conduction mechanism of Nafion to construct novel proton-conducting materials with low cost and high proton conductivity is of wide interest. Herein, we have designed and synthesized ...a cationic covalent organic framework with high thermal and chemical stability by combining a cationic monomer, ethidium bromide (EB) (3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide), with 1,3,5-triformylphloroglucinol (TFP) in Schiff base reactions. This is the first time that the stable cationic crystalline frameworks allowed for the fabrication of a series of charged COFs (EB-COF:X, X = F, Cl, Br, I) through ion exchange processes. Exchange of the extra framework ions can finely modulate the COFs’ porosity and pore sizes at nanoscale. More importantly, by introducing PW12O40 3– into this porous cationic framework, we can greatly enhance the proton conductivity of ionic COF-based material. To the best of our knowledge, EB-COF:PW 12 shows the best proton conductivity at room temperature among ever reported porous organic materials.
•Yangtze and Hainan have akin detrital age peaks at 1.65 Ga, 1.45 Ga, and 1.15 Ga.•Precambrian Hainan was a part of the Yangtze, rather than the Cathaysia Block.•Yangtze located in interior of Nuna, ...and docked to India-Australia in Rodinia.•Cathaysia Block lay adjacent to northern India from Paleoproterozoic to Paleozoic.
South China, consisting of the Yangtze and Cathaysia blocks (including Hainan Island), is characterized by episodic magmatism and lithospheric-scale tectonism during 1.7–1.0 Ga, and is important in the Nuna and Rodinia reconstruction. Three newly identified Mesoproterozoic magmatic intervals at 1.76–1.60 Ga, 1.53–1.37 Ga, and 1.25–1.05 Ga, were accompanied by three mineralization events at 1.65 Ga, 1.45 Ga, and 1.05 Ga. These events are also recorded by detrital zircon from ca. 1.05 Ga equivalent sedimentary sequences in both western Yangtze and central Hainan Island. These findings indicate a common Proterozoic tectonic history shared by central Hainan and Yangtze, contradicting models invoking Grenvillian-aged tectonism in South China. The Yangtze Block occupied an intracratonic position (between Laurentia and Australia) in Nuna, before it drifted away and docked to Western Australia and northern India in the reconfigured Rodinia. The Cathaysia was located close to northern India during the Proterozoic.
Background Psoriasis has been linked to cardiovascular disease (CVD), including coronary artery disease (CAD), myocardial infarction (MI), and heart failure (HF). However, available studies regarding ...this relationship have shown inconsistent results. Therefore, in this report, we performed a comprehensive review of the literature to assess the effects of psoriasis on risk of these CVDs. Methods A search of literature until 24 December 2021 was done in PubMed, the Cochrane Library, Web of Science, Google Scholar, and Embase. Within European and East Asian populations, meta-analyses of observational studies assessing correlations between psoriasis and various CVD risk factors were conducted. Mendelian randomization (MR) was then employed to assess the causative impact of genetic pre-disposition for psoriasis on these CVD risk factors. Results The results of the meta-analyses indicated that, in both the European and East Asian populations, psoriasis was significantly linked to an elevated risk in the incidence of CAD (RR = 1.51, 95% confidence interval (CI): 1.04-2.18, p = 0.028 and RR = 1.91, 95% CI: 1.62-2.25, p < 0.001) and MI (RR = 1.23, 95% CI: 1.04-1.46, p = 0.017 and RR = 2.17, 95% CI: 1.44-3.28, p < 0.001). A positive genetic relationship of psoriasis with CAD was found in European individuals (IVW OR:1.03; 95% CI: 1.01-1.06, p = 0.005) and in East Asian individuals (IVW OR:1.18; 95% CI: 1.03-1.32, p = 0.031). We also established that psoriasis was causally linked with an elevated risk of MI (IVW OR:1.05; 95% CI: 1.01-1.09, p = 0.026) in the European population as determined using an MR approach. Moreover, our MR results were congruent with the null findings from the meta-analysis assessing associations of psoriasis with HF risk. Conclusions This research work provides preliminary evidence that psoriasis and CVD have a common genetic origin and that targeted psoriasis treatment might improve cardiovascular outcomes. These results not only increase our knowledge of the genetic underpinnings linking a comorbidity of psoriasis with CVD but also suggests a novel approach for CVD prevention. Keywords: Cardiovascular disease, Psoriasis, Mendelian randomization
The two‐step: Chroman‐3‐ones are important intermediates for organic synthesis and medicinal chemistry. However, their syntheses require multiple steps and are not efficient. By using gold‐catalyzed ...alkyne oxidation, this versatile heterocycle can be prepared in only two steps from readily available phenols and with mostly high efficiencies (see scheme).
Formation of composites of dextran-coated Fe3O4 nanoparticles (NPs) and graphene oxide (Fe3O4-GO) and their application as T 2-weighted contrast agent for efficient cellular magnetic resonance ...imaging (MRI) are reported. Aminodextran (AMD) was first synthesized by coupling reaction of carboxymethyldextran with butanediamine, which was then chemically conjugated to meso-2,3-dimercaptosuccinnic acid-modified Fe3O4 NPs. Next, the AMD-coated Fe3O4 NPs were anchored onto GO sheets via formation of amide bond in the presence of 1-ethyl-3-(3-dimethyaminopropyl) carbodiimide (EDC). It is found that the Fe3O4-GO composites possess good physiological stability and low cytotoxicity. Prussian Blue staining analysis indicates that the Fe3O4-GO nanocomposites can be internalized efficiently by HeLa cells, depending on the concentration of the composites incubated with the cells. Furthermore, compared with the isolated Fe3O4 NPs, the Fe3O4-GO composites show significantly enhanced cellular MRI, being capable of detecting cells at the iron concentration of 5 μg mL–1 with cell density of 2 × 105 cells mL–1, and at the iron concentration of 20 μg mL–1 with cell density of 1000 cells mL–1.
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