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Co2C nanoprisms were developed for the Fischer–Tropsch to olefins (FTO) reaction a few years ago, while to the best of our knowledge, the study of the electronic promoters were hardly reported due to the instability of the Co2C nanostructures with promoters. The absence of the promoters limited the performance modulation and industrial application of the Co2C-based FTO catalysts. The work reported here was aimed at developing a new strategy to synthesize the Zn-promoted Co2C nanoprisms and understanding the electronic effects of the Zn promoters on the Co2C facets without confusion over the geometric effects. Detailed characterizations of the carbonized and spent samples suggested that the Zn promoters lowered the stability of the Co2C nanostructures and led to the formation of the surface Co0species in the spent samples with high Zn contents, which was responsible for the decrease of the O/P ratios and the increase of the CH4selectivity. The XPS results showed that the electrons transferring from the Zn promoters to the Co2C facets enriched the density of the electron clouds of the Co species on the Co2C facets. Further evidence for the enhanced CO adsorption and dissociation routes were obtained from the measurements of the CO temperature-programmed desorption. The Zn promoters increased the strong adsorption sites, which were not active for the Boudouard reaction and the increase of the CO2selectivity originated from the Water–Gas Shift reaction. The activation route of the adsorbed CO species on the strong adsorption sites was H-assisted dissociation rather than direct dissociation, resulting in the inhibition of the carbene-mediated routes and the shifting of product selectivity toward light hydrocarbons.

Contemporary industries rely on instrumentation and control (I&C) systems to ensure their safe and efficient operation. In particular, shielded cables play a pivotal role in information transmission and signal control within I&C systems. Therefore, the diagnostic techniques of shielded cables for accurately locating faults and assessing their severity are required to ensure the safety and reliability of the I&C systems. This article proposes a new fault diagnosis technique for shielded cables in I&C systems. For fault localization, the multisynchrosqueezing transform (MSST) is introduced to enhance the energy aggregation of the existing localization spectrogram, thus effectively improving the range resolution. For fault severity detection, a novel approach for broadband impedance spectroscopy (BIS) signature interpretation is presented by incorporating the magnitude and phase of the BIS into a polar plot that captures more features of the measured signal than the single magnitude plot. Digital image processing (DIP) techniques are employed to automate the severity detection process. The simulation and experimental results of coaxial shielded cable show that the proposed method can effectively improve the positioning performance and detect the fault severity with relatively little interference from the locations.

Graphical abstract:

The effects of various alkali metal promoters on the structure–performance relationship of cobalt–manganese (CoMn) catalysts for the Fischer–Tropsch synthesis (FTS) reaction have been investigated. The electronic promotion effects are correlated with the ionic potential (IP) of the alkali metals, which represents their electronic polarizability. The presence of alkali metal promoters in the CoMn catalysts is beneficial for the formation and stabilization of the Co2C phase. With an increase in the IP of the alkali metal promoters, the active phase was found to transition from Co2C nanospheres to Co2C nanoprisms and then to a mixture of fcc Co0and Co2C nanospheres. In addition, the catalytic performance also changed with the transition in the active phase. For the Co2C nanospheres, high CH4selectivity and low activity were observed. A promising catalytic performance for Fischer–Tropsch to olefins (FTO) with low CH4selectivity and high C2–4=selectivity was achieved for the Co2C nanoprisms. However, low C2–4=selectivity with high activity was found for a mixture of fcc Co0and Co2C nanospheres. It is suggested that the alkali metal promoters in the CoMn catalysts have two different promotion effects that are enhanced with IP: (1) the electronic effect to enhance the CO dissociation probability and benefit the formation of Co2C and (2) the facet stabilization effect to stabilize the Co2C nanoprisms with specific exposed (101) and (020) facets under the FTO reaction conditions.

Lower olefins—generally referring to ethylene, propylene and butylene—are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The ‘Fischer–Tropsch to olefins’ (FTO) process has long offered a way of producing lower olefins directly from syngas—a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson–Schulz–Flory distribution, which is characterized by a maximum C2–C4hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2–C4products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

This study clarifies the ablation differences in air and in water for hard biological tissues, which are irradiated by fiber-guided long-pulsed holmium lasers. High-speed photography is used to record the dynamic characteristics of ablation plumes and vaporization bubbles induced by pulsed holmium lasers. The ablation morphologies and depth of hard tissues are quantitatively measured by optical coherence microscopy. Explosive vaporization effects in water play a positive role in the contact ablation process and are directly responsible for significant ablation enhancement. Furthermore, water layer depth can also contribute to ablation performance. Under the same laser parameters for fiber-tissue contact ablation in air and water, ablation performances are comparable for a single-laser pulse, but for more laser pulses the ablation performances in water are better than those in air. Comprehensive knowledge of ablation differences under various environments is important, especially in medical procedures that are performed in a liquid environment.

The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon (PyC) layer has been discussed. With rising reaction temperature, the thickness of SiC layer increases and the SiC grain is coarsening. The apparent activation energy for the synthesis of SiC layer is about 103.3 kJ/mol. The oxidation resistance of carbon fiber can be improved by the SiC/PyC layers significantly. The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 300°C higher than that of the uncoated carbon fiber. The oxidation of the SiC/PyC coated carbon fiber is owing to the diffusion of oxygen through the cracks generated by the mismatch of thermal expansion. [Copyright &y& Elsevier]

Low intensity irradiation of cells by laser was an effective method of biostimulation. Here, we have extended these actions to evaluate the apoptosis effects in red light emitting diode (RLED) exposure. Through morphological observation, flow cytometric analysis, intracellular calcium measurement and RT-PCR, we found that HeLa cells in 24 h RLED irradiation in in-vitro experiments would significantly affects the induction of cellular apoptosis, and morphological changes such as the loose arrangement of cells, the noticeable development of apoptotic bodies,and the accompaniment of arrested S phase and activated caspases-3,-6,-8. Moreover, intracellular calcium concentrations markedly increased 40.3 +/- 1.3% and 43.1 +/- 0.8% respectively, relative to an extracellular solution containing the Ca(2+) and Ca(2+) free unexposed group. In in-vivo tests, RLED irradiation decreased the growth of tumors on day 50 and attenuated the elevation of vascular endothelial growth factor (VEGF) expression in HeLa cell implanted BALB/c mice. Taken together, our results suggest that RLED could induce HeLa cell apoptosis and convey potential antitumor properties.

In the present paper, different annealing methods were performed on cross-linked polyethylene (XLPE) from three retired cables, the effects on thermal performance were discussed. The cables with length of 15 cm were prepared and the insulation layers were peeled, and the peels near the inner semi-conductive layer were used as the test samples. Isothermal treatment and heat recycling treatment were performed on the samples at temperatures of 85, 90, 95, and 100degC, and the temperature holding hour Th in the heat recycling treatment were 8, 16, and 24 h. Each kind of heat treatment was repeated 20 times, and the duration of the isothermal treatment was the same as that for the heat recycling treatment with 24 h temperature holding hour. Then, differential scanning calorimetry (DSC) were performed. The results show that the melting point, crystallinity, lamellar thickness increase and melting range decreases as the annealing temperature increases; the optimal values appear as the samples were annealed at 95degC. With longer Th , the cables annealed at 95degC exhibit decreased melting range and increased crystallinity, melting point, lamellar thickness.