A highly efficient homogeneous gold-catalyzed oxidative dimerization of propargylic acetates is described.
A highly efficient gold-catalyzed oxidative dimerization of propargylic acetates is ...developed. In this chemistry, Selectfluor oxidation of Au(I) to Au(III) is readily incorporated into Au-catalyzed tandem reactions of propargylic acetates, and transmetallation and reductive elimination on Au(III) intermediates are likely involved.
During the past two decades, one–dimensional (1D) metal–oxide nanowire (NW)-based molecular sensors have been witnessed as promising candidates to electrically detect volatile organic compounds ...(VOCs) due to their high surface to volume ratio, single crystallinity, and well-defined crystal orientations. Furthermore, these unique physical/chemical features allow the integrated sensor electronics to work with a long-term stability, ultra-low power consumption, and miniature device size, which promote the fast development of “trillion sensor electronics” for Internet of things (IoT) applications. This review gives a comprehensive overview of the recent studies and achievements in 1D metal–oxide nanowire synthesis, sensor device fabrication, sensing material functionalization, and sensing mechanisms. In addition, some critical issues that impede the practical application of the 1D metal–oxide nanowire-based sensor electronics, including selectivity, long-term stability, and low power consumption, will be highlighted. Finally, we give a prospective account of the remaining issues toward the laboratory-to-market transformation of the 1D nanostructure-based sensor electronics.
For mountain tunnels, ground heat exchangers can be integrated into the tunnel lining to extract geothermal energy for building heating and cooling via a heat pump. In recent decades, many ...researchers only focused on the thermal performance of tunnel lining Ground Heat Exchangers (GHEs), ignoring the energy efficiency of the heat pump. A numerical model combining the tunnel lining GHEs and heat pump was established to investigate the energy efficiency of the heat pump. The inlet temperature of an absorber pipe was coupled with the cooling load of GHEs in the numerical model, and the numerical results were calibrated using the in situ test data. The energy efficiency ratio (EER) of the heat pump was calculated based on the correlation of the outlet temperature and EER. The heat pump energy efficiencies under different pipe layout types, pipe pitches and pipe lengths were evaluated. The coupling effect of ventilation and groundwater flow on the energy efficiency of heat pump was investigated. The results demonstrate that (i) the absorber pipes arranged along the axial direction of the tunnel have a greater EER than those arranged along the cross direction; (ii) the EER increases exponentially with increasing absorber pipe pitch and length (the influence of the pipe pitch and length on the growth rate of EER fades gradually as wind speed and groundwater flow rate increase); (iii) the influence of groundwater conditions on the energy efficiency of heat pumps is more obvious compared with ventilation conditions. Moreover, abundant groundwater may lead to a negative effect of ventilation on the heat pump energy efficiency. Hence, the coupling effect of ventilation and groundwater flow needs to be considered for the tunnel lining GHEs design.
In this paper, the CdS/ZnO nanocomposite film with enhanced photoelectric response to UV or white lights at low bias was demonstrated. The pure ZnO film was firstly fabricated by the technology of ...screen printing, and the CdS/ZnO film was prepared by the subsequent successive ionic layer adsorption and reaction process. XRD, UV–vis DRS, FE-SEM and EDX analysis confirmed the successful growth of CdS on the surface of ZnO nanoparticles. The photoelectric responses of ZnO and CdS/ZnO were tested under different illumination and by application of a series low bias in the gas phase. The CdS/ZnO nanocomposite film exhibited a tremendous enhancement on the photocurrent amplitude by application of a 0.01V bias, which gave 13.3 and 153 times higher than that of the pure ZnO film under UV and white light irradiation, respectively. The mechanism for the enhanced response is attributed to the special interface between CdS and ZnO, which can efficiently suppress the recombination of photogenerated electron–hole pairs and in turn resulting in a large increase of the photocurrent in the external circuit.
An energy pile alters the ground temperature fields around it, which may lead to uneven settlements and a higher risk of failure. The thermomechanical behaviors of soils have been studied extensively ...in laboratory experiments, while in situ investigations are rare. In this research, flat dilatometer tests (DMTs) are first employed to investigate the thermomechanical behaviors of soil under in situ conditions. The soils were heated by a full-scale precast high-strength concrete (PHC) energy pile, and a series of DMTs were conducted. The results show that temperature changes had a substantial impact on the DMT data of the silt and clay layers. The measured pressures
p
0
and
p
1
of the silt and clay layers decreased with increasing ground temperature, and the measured pressure
p
2
of the silt and clay layers decreased at the beginning and then increased with increasing ground temperature. Although the silt and clay layers have similar variations in the measured pressures, the clay layer has a greater thermal response than the silt layer. Finally, the critical state soil mechanics theory is used to analyze the pore water pressure and thermomechanical properties of in situ overconsolidated soil. The results indicate that the elastic region (yield surface) and mean effective stress of in situ soil decrease with increasing ground temperature, potentially resulting in more irreversible deformation and a higher probability of failure.
Metal-oxide nanowires have demonstrated excellent capability in the electrical detection of various molecules based on their material robustness in liquid and air environments. Although the surface ...structure of the nanowires essentially determines their interaction with adsorbed molecules, understanding the correlation between an oxide nanowire surface and an adsorbed molecule is still a major challenge. Herein, we propose a rational methodology to obtain this information for low-density molecules adsorbed on metal oxide nanowire surfaces by employing infrared p-polarized multiple-angle incidence resolution spectroscopy and temperature-programmed desorption/gas chromatography–mass spectrometry. As a model system, we studied the surface chemical transformation of an aldehyde (nonanal, a cancer biomarker in breath) on single-crystalline ZnO nanowires. We found that a slight surface reconstruction, induced by the thermal pretreatment, determines the surface chemical reactivity of nonanal. The present results show that the observed surface reaction trend can be interpreted in terms of the density of Zn ions exposed on the nanowire surface and of their corresponding spatial arrangement on the surface, which promotes the reaction between neighboring adsorbed molecules. The proposed methodology will support a better understanding of complex molecular transformations on various nanostructured metal-oxide surfaces.
Zebrafish have become an important alternative model for characterizing chemical bioactivity, partly due to the efficiency at which systematic, high-dimensional data can be generated. However, these ...new data present analytical challenges associated with scale and diversity. We developed a novel, robust statistical approach to characterize chemical-elicited effects in behavioral data from high-throughput screening (HTS) of all 1,060 Toxicity Forecaster (ToxCast™) chemicals across 5 concentrations at 120 hours post-fertilization (hpf). Taking advantage of the immense scale of data for a global view, we show that this new approach reduces bias introduced by extreme values yet allows for diverse response patterns that confound the application of traditional statistics. We have also shown that, as a summary measure of response for local tests of chemical-associated behavioral effects, it achieves a significant reduction in coefficient of variation compared to many traditional statistical modeling methods. This effective increase in signal-to-noise ratio augments statistical power and is observed across experimental periods (light/dark conditions) that display varied distributional response patterns. Finally, we integrated results with data from concomitant developmental endpoint measurements to show that appropriate statistical handling of HTS behavioral data can add important biological context that informs mechanistic hypotheses.
A rhodium-catalyzed intermolecular hydroacylation reaction of vinyl cyclobutanols with non-chelating aldehydes has been developed. This reaction offers a new and atom-economical approach for the ...selective preparation of 1,5-diketones in high yields. Experimental data suggest a sequential ring-opening, transfer hydrogenation, and hydroacylation mechanism. We propose that aldehyde decarbonylation is avoided by the formation of a novel rhodium enolate species that also accounts for the compatibility of a broad range of aldehydes and its anti-Markovnikov selectivity.
At present, the in-situ testing equipment used for measuring the thermophysical properties of rock and soil is scarce. Based on the working principle of the pressuremeter and ground heat exchanger, a ...pre-drilling thermal probe in-situ testing equipment is developed. This novel developed pre-drilling thermal probe in-situ testing equipment includes thermal probe, pressure control system, temperature control system, integrated conversion control device, and coaxial pressure pipe connection pipeline. A three-dimensional heat transfer model was established to simulate the heat transfer between the thermal probe and surrounding ground. Based on the principle of the temperature dissipation and numerical simulation, a calculation method for the thermal conductivity of rock and soil with pre-drilling thermal probe is proposed. Laboratory model tests of the sand under dry and saturated conditions were conducted. The deviation values for the thermal conductivities of sand under dry and saturated conditions measured by the designed pre-drilling thermal probe and thermal conductivity tester are 0.037 and 0.026 W/m·°C, respectively. Thus, the reliability of utilizing the new pre-drilling thermal probe testing equipment to measure the thermal conductivity of the soil is confirmed. The field test of utilizing this new pre-drilling thermal probe testing equipment to measure the thermal properties of the soil was performed. The results show that because the soil layers are in undisturbed state during the test process, the pre-drilling thermal probe testing equipment can truly reflect the inherent thermal properties of different soil layers.
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