With the development of faults in many coalfields, many large faults will form a relatively independent area, forming regional tectonic stress concentration. Under the influence of mining, it is easy ...to induce fault activation, produce mine tremor, and then induce rock burst. Through field investigation, theoretical analysis, numerical simulation, and engineering verification, the overburden movement model of No. 3504 working face square and fault activation in Liangbaosi Coal Mine was established. The stress variation and energy release law of working face advance and fault area were analyzed, and the mechanism of rock burst under the coupling action of working face square and regional tectonic stress was revealed. The results show that the regional stress adjustment and fault activation are caused by the large-scale overall movement of overburden during the working face square, and there is a peak value of elastic energy release during the fault activation, which is easy to produce large energy mine earthquake. The energy level of the daily maximum energy event is higher than that of the initial mining stage in the square period, and the location of on-site large energy microseismic event is basically consistent with the predicted fault strike. The study provides a theoretical basis for the prevention and control of rock burst during the working face square under the condition of regional tectonic stress.
Four copper-based catalysts were prepared by co-precipitation method. The catalysts were characterized by scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction ...process (H2-TPR), X-ray diffraction (XRD) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) to explore the effects of different components on catalyst activity. The performance of different catalysts for hydrogen production via methanol steam reforming was evaluated on a fixed-bed reactor. The effects of different components, reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance were investigated. The results exhibited that among the investigated catalysts, 1# and 2# catalysts had the higher catalytic activity and stability. Under the conditions of 280 °C, a molar ratio of methanol to water of 1:1.3, and a GHSV of 13.3 L/(g·h), the methanol conversion rate reached 99.9%, the CO concentration was as low as 0.29%, and the selectivity was only 1.16%. The H2 production flow rate per unit mass of catalyst was 270 mL/(min·g). After 60 h of start-stop experiments, the methanol conversion rate remained above 98.4%, the CO concentration was always lower than 0.5%, and the start-up speed was significantly faster than that of the commercial catalyst M650. This study provided an effective method for the preparation of catalysts for methanol steam reforming.
A series of copper-based methanol reforming catalysts with different components were prepared by co-precipitation method on a ZnO–CeO2–ZrO2 support. The catalytic performance was evaluated on a fixed-bed reactor. At the same time, the mechanism of methanol steam reforming was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy. Display omitted
•The addition of Fe can improve the structure and reduction performance of CuO–ZnO–CeO2–ZrO2 catalyst.•The introduction of Fe can significantly reduce the CO concentration in the reforming gas, even at high temperatures.•The self-prepared catalyst has good stability, and the start-up speed is significantly faster than that of commercial catalyst.
Amorphous magnetic core has been widely used in pulsed power technology with applications including plasma science research, high-power microwave generation, and material surface treatment. For ...different applications, dynamic properties of the magnetic core will vary with stimulated magnetic field which determines by magnetization time and waveform of the driving voltage. In this paper, toroidal amorphous magnetic core (<inline-formula> <tex-math notation="LaTeX">\Phi ~540 </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">740\times25 </tex-math></inline-formula> mm) was investigated theoretically, numerically, and experimentally. Specifically, the circuit is analyzed. A high-voltage test stand, which can generate different driving voltages with same components, was designed and developed in our laboratory. Dynamic properties, including magnetic induction change, coercive force and losses, were studied under three different typical waveforms with the same magnetic flux. Driving voltages of the pulses were 12, 12, and 6 kV and the magnetization rates were 0.6, 1.2, and 0.6 T/<inline-formula> <tex-math notation="LaTeX">\mu \text{s} </tex-math></inline-formula>, respectively. Experimental results show reasonable agreement with the numerical analysis.
The nitrides and carbides of transition metals are highly favored due to their excellent physical and chemical properties, among which MXene is a hot research topic for microwave absorption. Herein, ...the controlled preparation of 3D Mo
TiC
T
-based microspheres toward microwave absorption is reported for the first time. With the merits of the performances of both reduced graphite oxide (RGO) and MXene sufficiently considered, the influence of carbonization temperature on the internal crystal structure and the effective microwave-material interaction surface of the prepared Mo
TiC
T
/RGO is systematically investigated. The structure-activity relationships relating the apparent morphology and crystal structure to the microwave absorption performance are deeply explored, and the wave absorption mechanism is put forward as well. The results show that the Mo
TiC
T
/RGO-700 product obtained after heating treatment at 700 °C exhibits excellent microwave absorption performance, with the RL
being up to -55.1 dB@2.1 mm@13.8 GHz, and the corresponding effective absorption bandwidth covering 5.7 GHz. The outstanding microwave absorption characteristics are attributed to the appropriate impedance matching, high specific surface area, rich intrinsic defects, desirable conductivity, and strong multipolarization capabilities. This work enriches the types of MXene-based composite absorbers and provides a new strategy for controlled preparation of high-performance 3D composite absorbers.
The nitrides and carbides of transition metals are highly favored due to their excellent physical and chemical properties, among which MXene is a hot research topic for microwave absorption. Herein, ...the controlled preparation of 3D Mo2 TiC2 Tx -based microspheres toward microwave absorption is reported for the first time. With the merits of the performances of both reduced graphite oxide (RGO) and MXene sufficiently considered, the influence of carbonization temperature on the internal crystal structure and the effective microwave-material interaction surface of the prepared Mo2 TiC2 Tx /RGO is systematically investigated. The structure-activity relationships relating the apparent morphology and crystal structure to the microwave absorption performance are deeply explored, and the wave absorption mechanism is put forward as well. The results show that the Mo2 TiC2 Tx /RGO-700 product obtained after heating treatment at 700 °C exhibits excellent microwave absorption performance, with the RLmin being up to -55.1 dB@2.1 mm@13.8 GHz, and the corresponding effective absorption bandwidth covering 5.7 GHz. The outstanding microwave absorption characteristics are attributed to the appropriate impedance matching, high specific surface area, rich intrinsic defects, desirable conductivity, and strong multipolarization capabilities. This work enriches the types of MXene-based composite absorbers and provides a new strategy for controlled preparation of high-performance 3D composite absorbers.
The design and fabrication of efficient catalysts for ammonium perchlorate (AP) decomposition is crucial for the performance of composite solid propellants. Herein, a novel hierarchical structure ...material of Cu-WO 3 nanowire arrays on a nanoflower flake (Cu-WO 3 NANF) was synthesized by a facile hydrothermal reaction. The negatively charged (001) polar facets of hexagonal WO 3 and the action of Cu 2+ induced growth were two important factors for the formation of hierarchical structures. The Cu-WO 3 NANF exhibited remarkable catalytic activity for the thermal decomposition of AP. The temperature and activation energy of high temperature AP decomposition were significantly decreased to 378.3 °C and 147.01 kJ mol −1 , respectively, which are attributed to the more oxygen vacancies and lower band gap energy of the Cu-WO 3 NANF. Thus, it was excited at a lower heat to produce activated species. Under the strong adsorption of Cu-WO 3 NANF surface Lewis acid, the activated species can react with NH 3 quickly and deeply to produce N 2 , N 2 O, NO 2 and NO gases, accompanied by a heat release of up to 1118 J g −1 . The proposed catalytic mechanism was further corroborated by the in situ TG-MS result. This facile strategy provided a new idea for the design of hierarchical catalysts, and our research opened up a new field for WO 3 applications.
The design and fabrication of efficient catalysts for ammonium perchlorate (AP) decomposition is crucial for the performance of composite solid propellants. Herein, a novel hierarchical structure ...material of Cu-WO
3
nanowire arrays on a nanoflower flake (Cu-WO
3
NANF) was synthesized by a facile hydrothermal reaction. The negatively charged (001) polar facets of hexagonal WO
3
and the action of Cu
2+
induced growth were two important factors for the formation of hierarchical structures. The Cu-WO
3
NANF exhibited remarkable catalytic activity for the thermal decomposition of AP. The temperature and activation energy of high temperature AP decomposition were significantly decreased to 378.3 °C and 147.01 kJ mol
−1
, respectively, which are attributed to the more oxygen vacancies and lower band gap energy of the Cu-WO
3
NANF. Thus, it was excited at a lower heat to produce activated species. Under the strong adsorption of Cu-WO
3
NANF surface Lewis acid, the activated species can react with NH
3
quickly and deeply to produce N
2
, N
2
O, NO
2
and NO gases, accompanied by a heat release of up to 1118 J g
−1
. The proposed catalytic mechanism was further corroborated by the
in situ
TG-MS result. This facile strategy provided a new idea for the design of hierarchical catalysts, and our research opened up a new field for WO
3
applications.
Cu-WO
3
hierarchical structures are rapidly prepared and they exhibit excellent catalytic activity in AP decomposition due to their rich oxygen vacancies and Lewis acid sites.
Roundup-Ready soybeans have been genetically modified to resist the effects of the herbicidal glyphosate and have become the most prevalent transgenic crop in the world. In this work, Roundup-Ready ...soybeans were used as raw material to study the effects of critical processing procedures such as grinding, cooking, blending, homogenization, sterilization, and spray-drying on the length of DNA fragments of an endogenous gene (lectin) and an exogenous gene (epsps) examined in material from three soybean foods of bean curd, soy milk, and soy powder and from samples taken during their processing. The results showed that various processing procedures caused degradations of both the endogenous and exogenous genes to different degrees. In the grinding procedure, endogenous gene DNA was degraded from 1883 to ∼836 bp, and exogenous gene DNA was degraded from 1512 to ∼408 bp. In the blending and squeeze-molding procedures, exogenous gene DNA was also degraded from about 408 to 190 bp, but there was no obvious action on the endogenous gene. After the endogenous and exogenous genes had been degraded to some degree, such as 836 and 408 bp, respectively, they were not evidently affected by cooking procedure at 100 °C for 15 min. However, the endogenous gene was further considerably degraded from around 836 to 162 bp in the sterilization procedure at 121 °C for 30 s. The effect of the homogenization step on endogenous and exogenous genes was similar to that of the cooking procedure. The coagulation procedure, principally a biochemical reaction, did not greatly affect the exogenous gene but did affect endogenous gene, reducing DNA size from about 836 to 407 bp. Furthermore, the spray-drying procedure, a process of physical shearing, high temperature, and sudden high pressure, distinctly caused degradation of both the lectin and epsps genes, rapidly decreasing the sizes from about 836 to 162 bp for the endogenous gene and from about 408 to 190 bp for the exogenous gene. Keywords: Roundup-Ready soybean; processing procedures; endogenous gene; exogenous gene; degradation
Abstract
Sterol-regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) is a rapid feedback regulatory mechanism by which cells employ to control the cholesterol ...biosynthesis. This process is initiated by the sterol-induced interaction between HMGCR and Insig-1/gp78, a membrane-bound ubiquitin ligase complex. There are two Lys residues (Lys89 and Lys248) facing cytosol in the membrane domain of HMGCR, and Lys248 is the major ubiquitination site. In this study, we investigated the mechanism of ubiquitination site selection in HMGCR. We find that the distance of Lys248 to membrane is dispensable for its ubiquitination. However, the conserved tetra-glutamic acid residues adjacent to Lys248 in HMGCR are essential. Replacement of these negatively charged residues with tetra-arginine causes the resistance of HMGCR to sterol-induced ubiquitination and degradation, albeit this mutant HMGCR can still binds to Insig-1. We further find that the tetra-glutamic acid residues are necessary but not sufficient for the modification on their adjacent Lys, since they are not functional on Lys89 of HMGCR or in SCAP. UBE2G2, a previously known E2 of gp78, is demonstrated to be involved in the sterol-regulated ubiquitination and degradation of HMGCR. In summary, these results identify the tetra-glutamic acid residues as a critical motif in HMGCR for the ubiquitination reaction mediated by gp78 and UBE2G2.
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