A novel approach to generate Au-containing all-carbon 1,3-dipoles is developed via an unprecedented migration−fragmentation of ketals/acetals. These in situ generated dipoles undergo rapid 3+2 ...cycloaddition under mild conditions with various enones/enals, electron-rich aromatic aldehydes, and N-benzylindole, leading to flexible formation of highly functionalized dihydrofurans and cyclopentenes.
Selectivity has been considered as one of the most significant performances to evaluate the practical application of the metal oxide semiconductor (MOS) gas sensor. Temperature modulation is now a ...commonly recognized method in enhancing the sensor selectivity as it can reflect more feature reaction information. In this paper, a novel method in the gas identification by using WO3 gas sensor based on the temperature-programmed modulation is reported. This method allows us to be capable of dynamically obtaining the temperature-dependent electrical conductivity (TEC) spectra in different atmospheres. In terms of the TEC of the WO3, a rigorous method for extracting the feature parameters is presented here, which are associated with the gas adsorption/desorption and defect reaction mechanisms, from the differential curve d{lnσT3/2}/dT−T. According to the feature parameters, we can clearly figure out the gas species that cannot be accomplished by the conventional methods. The temperature-programmed modulation thus provides a fundamental method for accurately identifying the gas species and is expected aid in opening up a new way to investigate the selectivity of the MOS gas sensors.
A rhodium-catalyzed tandem reaction of alkynyl cyclobutanols with salicylaldehydes has been developed. The reaction offers a new and atom-economical approach for the selective preparation of ...multisubstituted 2-(2-oxo-2-phenylethyl)cyclopentanone in high yields under mild reaction conditions with tolerance of a broad range of substituted alkynyl cyclobutanols and salicylaldehyes. The isolation of intermediate suggests that the reaction proceeds through a sequential process of intermolecular hydroacylation and semipinacol rearrangement.
The effect of pulsed electric current on the removal of MgO inclusions, which deteriorate mechanical and corrosion properties of magnesium alloys, was investigated. Through characterizing the number ...and size distribution of MgO inclusions, it’s found that the MgO inclusions were expelled to the surface (bottom and top) of the magnesium alloy melt and then absorbed by the coating agent, treated by the electropulsing. Besides, the electropulsing also promoted the aggregation of the inclusions, but the large size inclusion only exists on the surface of the sample. Based on the differences in electrical properties between the inclusions and the magnesium alloy melt, a force from electric current to electrically neutral MgO inclusion has been identified to drive the particles’ movement. Further, the results of numerical calculation show that under the action of pulse current, the migration of inclusions to the surface can reduce the system free energy, and the aggregation tendency between two inclusions with a relatively large radius is significantly stronger than the two inclusions with a smaller radius. The excellent agreement between numerical calculations and experimental data demonstrates that employing the electropulsing to separate the particles from the liquids is a fantastic new method in metal melt purification.
A novel concept of Au-containing all-carbon 1,n-dipoles is advanced. From 1-(1-alkynyl)cyclopropyl ketones, Au-containing all-carbon 1,4-dipoles are presumably generated in situ and can efficiently ...participate in 4 + 2 annulation with dipolarophiles including indoles, various carbonyl compounds, imines, and silyl enol ethers. Polycyclic, fully substituted furans are readily synthesized under mild reaction conditions.
•An innovative technology, tunnel lining GHEs was introduced.•The field test of tunnel lining GHEs was introduced.•The field test investigated the impact factors of heat transfer performance.
...Innovative tunnel lining ground heat exchangers (GHEs) were introduced in China for the first time and applied to Linchang Tunnel in Inner Mongolia. This paper is dedicated to studying this new technology based on a field experiment at Linchang Tunnel. The experiment investigated the heat transfer performance of tunnel lining GHEs and its impact factors, including the flow rate, inlet water temperature and pipe distance. The test results show that (i) the ground temperature at a pipe distance of 50cm cannot completely recover when the intermittent ratio is 1.1, but it can completely recover at a pipe distance of 100cm; (ii) the heat exchange rate presents a linear variation with the inlet temperature of the heat carrier liquid, and on average, the heat exchange rate increases 2.494W/m for every 1°C increase in the inlet temperature; (iii) the heat exchange rate increases exponentially as the flow rate increases; (iv) the heat exchange rate shows an exponential downward trend as the running time increases, and the heat exchange rate for a pipe distance of 50cm is always higher than that for a pipe distance of 100cm during the testing.
Propargylic pivalates with electronically unbiased internal alkynes are selectively transformed into (1Z,3E)-2-pivaloxy-1,3-dienes containing various functionalities. The unusual selectivity of ...1,2-acyloxy migration over the structurally preferred 3,3-rearrangement is realized. This reaction is highly stereoselective and offers rapid access to dienes for one-pot intra-/intermolecular Diels−Alder reactions either under thermal conditions or with Lewis acid catalysis.
► Conducting the first field experiment of heat exchangers in diaphragm wall. ► Finding the difference between heat exchanger in diaphragm wall and in borehole. ► Investigating the influence of 4 ...factors on heat exchange rate in diaphragm wall.
To bury absorber tubes in diaphragm wall as heat exchanger is a new energy saving technology. This paper is dedicated to study this new technology based on the field experiment at Shanghai Museum of Nature History. By the experiment, the heat transfer performance of heat exchanger in diaphragm wall and its impact factors including heat exchanger type, water velocity, inlet water temperature and operation mode were investigated. The test results show that (i) the heat exchange rate of W-shaped heat exchanger reached to 66.3 and 73.7W/m for tube type (a) and (b) at the inlet temperature of 35°C, which are approximately 1.2–1.4 times higher than that of single U-shaped type (c); (ii) under the experimental condition, the reasonable water velocity is 0.6–0.9m/s; (iii) the exchange rate reached to 40.3, 66.3 and 85.0W/m at the inlet temperature of 32, 35 and 38°C, respectively, for tube type (a), every 1°C rise of inlet water will promote 15% heat exchange rate; (iv) in intermittent operation mode, the average heat exchange rate is 82.8W/m while 72.7W/m for continuous mode under the experimental condition, i.e., 14.7% higher than that in continuous mode.
Herein, two-ligand nickel-based MOF (JUC-85Ni) have been prepared by choosing high N-containing and S-containing ligand. On this basis of the research, the NiS2 nanoparticles dispersed N and S ...co-doped carbon materials (NiS2@NSC) are fabricated through the sulfidation of JUC-85Ni precursors with thioacetamide (TAA). The rationally designed NiS2@NSC catalysts are conducted a test for catalytically reducing 4-nitrophenol (4-NP) to environment friendly 4-aminophenol (4-AP) under NaBH4 alkaline condition. The superior features endows the catalyst with outstanding catalytic activity and recycling performance, and support it great potential for wastewater treatment.
The N, S-codoped carbon-coated NiS2nanoparticle composites (NiS2@NSC) are accurately synthesized by using two-ligand MOF as precursors through sulfidation with thioacetamide. Synergetic effect endow NiS2@NSC with excellent catalytic activity and stability for 4-nitrophenol reduction. Display omitted
•The NiS2 nanoparticles dispersed N, S co-doped carbon nanocomposites are rationally synthesized.•Synergetic effect endows catalyst with unusual catalytic activity in 4-NP reduction.•The proposal catalytic mechanism for NiS2@NSC is proposed in detail.•The high stability stems from the thin carbon around NiS2 nanoparticles.
A total synthesis of the highly strained natural product aquatolide has been achieved. The synthesis featured a photoinduced Wolff ring contraction reaction for the construction of ...bicyclo2.1.1hexane from diazo compound with a bicyclo2.2.1heptane skeleton. The eight-membered enone was built by a late-stage intramolecular Nozaki–Hiyama–Kishi vinylation reaction of steric bulky vinyl iodide and aldehyde.
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