By utilizing wave velocity imaging technology, the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture. Based on the time series ...parameters of acoustic emissions (AE), joint response characteristics of the velocity field and AE during rock fracture were analyzed. Moreover, the localization effect of damage during rock fracture was explored by applying wave velocity imagings. The experimental result showed that the wave velocity imagings enable three-dimensional (3-D) visualization of the extent and spatial position of damage to the rock. A damaged zone has a low wave velocity and a zone where the low wave velocity is concentrated tends to correspond to a severely damaged zone. AE parameters and wave velocity imagings depict the changes in activity of cracks during rock fracture from temporal and spatial perspectives, respectively: the activity of cracks is strengthened, and the rate of AE events increases during rock fracture; correspondingly, the low-velocity zones are gradually aggregated and their area gradually increases. From the wave velocity imagings, the damaged zones in rock were divided into an initially damaged zone, a progressively damaged zone, and a fractured zone. During rock fracture, the progressively damaged zone and the fractured zone both develop around the initially damaged zone, showing a typical localization effect of the damage. By capturing the spatial development trends of the progressively damaged zone and fractured zone in wave velocity imagings, the development of microfractures can be predicted, exerting practical significance for determining the position of the main fracture.
The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering. Therefore, a new method and concept of deep rock mechanics testing ...are proposed to reveal the mechanical behavior evolution mechanism of deep roadway surrounding rock after excavation with a depth over 1000 m. High stress-seepage coupling experiments of deep sandstone under various confining pressures are conducted using GCTS. Stress — strain and permeability curves are obtained. The three-stage mechanical behavior of deep sandstone is better characterized. A platform and secondary compaction phenomena are observed. With the confining pressure increasing, the platform length gradually decreases, even disappears. In the stade I, the rigid effect of deep sandstone is remarkable. In the stage II, radial deformation of deep sandstone dominates. The transient strain of confining pressure compliance is defined, which shows three-stage evolution characteristics. In the stage III, the radial deformation is greater than the axial deformation in the pre-peak stage, but the opposite trend is observed in the post-peak stage. It is found that the dynamic permeability can be more accurately characterized by the radial strain. The relations between the permeability and stress-strain curves in various stages are revealed.
The phosphorylation of the ortho C-H bonds in benzamides containing an 8-aminoquinoline moiety as a bidentate directing group with H-phosphonates using copper as a catalyst under mild temperature ...conditions is described. This method shows high functional group compatibility and selectively gives mono-substituted products.
In this work, the Mn-doped copper (II) oxide (CuO) nanoflower spheres (CuO-1% Mn nanoflower spheres) are synthesized through a facile low-temperature hydrothermal method. The as-prepared sample is ...characterized by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman and Brunauer-Emmett-Teller (BET) analysis. The results indicate that the nanoflower spheres with diameters of 5-<inline-formula> <tex-math notation="LaTeX">10 \mu \text{m} </tex-math></inline-formula> are assembled by a huge number of nanosheets. In addition, Mn ions are uniformly doped into the CuO nanoflower spheres. The surface area of the CuO-1% Mn nanoflower spheres is 33.079 <inline-formula> <tex-math notation="LaTeX">\text{m}^{{2}} </tex-math></inline-formula>/g. Under the optimized temperature of 235 °C, when the Mn doping amount is 1%, the CuO-1% Mn nanoflower spheres exhibit the best sensing property toward isopropanol, the response of which is almost 11.5 times higher than that of pure CuO. In a wide range of 1-100 ppm, the CuO-1% Mn nanoflower spheres exhibit linear response in isopropanol detection. The doped sample also exhibits excellent selectivity, repeatability, and durability. It is believed that the doping of Mn ions would be the reason of the improvement of sensing properties. Due to the doping introduced more defects and spillover effect, more oxygen anions would be generated and more isopropanol molecules can be oxidized on the surface of the CuO-1% Mn nanoflower spheres. It is believed that the product has great application potential in isopropanol detection.
Electromagnetic signals may be a promising precursor to seismic activity which has been observed in many case studies in past decades. However, the correlation and causation between the ...electromagnetic signals and the seismic activity are still unclear without intensive observation network. In order to find seismoelectromagnetic phenomenon, we deployed AETA (acoustic and electromagnetic testing all-in-one system), a high-density multi-component seismic monitoring system in the China Earthquake Science Experiment site (CESE, in Sichuan Province and Yunnan Province, China) and the capital circle (areas with a distance which is ≤200 km from Beijing), to record electromagnetic and geo-acoustic data across 0.1 Hz–10 kHz. In the course of data collection, we discovered an electromagnetic waveform that occurs on a daily basis. Because the signal generally coincides with sunrise and sunset, we named this phenomenon the SRSS (Sunrise-Sunset) waveform. After conducting three statistical tests based on seismicity and SRSS, we determined that the SRSS waveform is roughly correlated with the onset of seismic activity. It generally occurs at the regions where seismicity occurs. This discovery might have significant implications with respect to the future of earthquake prediction.
A series of Zn-modified HBeta (Zn/HBeta) catalysts were prepared via the wetness impregnation method with different zinc precursors such as ZnSO4·7H2O, ZnCl2, C4H6O4Zn·2H2O and Zn(NO3)2·6H2O, and ...their catalytic performance in the conversion of ethanol to propylene reaction was evaluated. Results indicate that the amount and strength distribution of the acid sites of the Zn/HBeta catalysts were easily tuned by employing different types of zinc precursors. More importantly, when the zinc species were introduced to the HBeta, the propylene yield was significantly enhanced, whereas the yields of ethylene and C2–C4 alkanes were remarkably suppressed. For the catalyst prepared by using the ZnCl2 precursor, a higher propylene yield of up to 43.4% for Zn/HBeta-C was achieved as a result of the moderate amount and strength distribution of acid sites. The average coking rate of the used Zn/HBeta catalysts strongly depended on the amount of total acid sites, especially the strong acid sites, i.e., the higher the amount of total acid sites of the catalyst, the greater the average coking rate. For the catalyst prepared by using the ZnSO4·7H2O precursor, Zn/HBeta-S exhibited a better stability even after depositing more coke, which was due to the higher amount of strong acid sites.
In this work, amorphous silica-alumina composite (ASA) with varied compositions was synthesized via the complex-decomposition method with different complex agents. The XRD characterization revealed ...the amorphous nature of ASA composites regardless of the synthesis conditions. However, the acidity and the textural properties of ASA composites characterized by BET, Py-FTIR and NH3-TPD were significantly affected by the specific complex agent and amount, Si/Al molar ratio and calcination temperature. Among the investigated complex agents, the optimal amount of ammonium carbonate was the most efficient in tailoring both the textural and acidic properties of ASA. The hybrid of the synthesized ASA and a commercial Cu/ZnO/Al2O3 was studied for the steam reforming of dimethyl ether (SRD), and ASA synthesized by using ammonium carbonate as the complexing agent showed the optimal activity. Importantly, the synergetic effect between ASA and Cu/ZnO/Al2O3 was found to play a crucial role in determining the activity and stability of the bifunctional catalyst, and the partial oxidation of Cu0 to Cu+ induced from the ASA acidity had a great contribution to the deactivation of the bifunctional catalyst. These understandings are favorable for developing a more efficient solid acid for SRD.
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•ASA was prepared by complex-decomposition method with different complexing agents.•ASA obtained with ammonium carbonate as complexing agent was more effective for SRD.•Over 80% DME conversion and H2 yield were achieved at 300 ℃ over optimal catalyst.•ASA-induced Oxidation of Cu0 to Cu+ was one reason for deactivating SRD catalyst.
Genome of the Chinese tree shrew Fan, Yu; Huang, Zhi-Yong; Cao, Chang-Chang ...
Nature communications,
2013, Letnik:
4, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Chinese tree shrews (Tupaia belangeri chinensis) possess many features valuable in animals used as experimental models in biomedical research. Currently, there are numerous attempts to employ tree ...shrews as models for a variety of human disorders: depression, myopia, hepatitis B and C virus infections, and hepatocellular carcinoma, to name a few. Here we present a publicly available annotated genome sequence for the Chinese tree shrew. Phylogenomic analysis of the tree shrew and other mammalians highly support its close affinity to primates. By characterizing key factors and signalling pathways in nervous and immune systems, we demonstrate that tree shrews possess both shared common and unique features, and provide a genetic basis for the use of this animal as a potential model for biomedical research.
Alkenylation of unactivated arenes and 6-arylpurines with terminal alkynes in high yields using Cp*Co(CO)I2 as catalyst under mild conditions is described. This method shows outstanding functional ...group compatibility and can be applied in the design of a mitochondria-targeted imaging dye.
This study was designed to improve the absorption and hypoglycemic efficacy of berberine (BBR), which is a substrate of P-glycoprotein (P-gp), by combination with a P-gp inhibitor tetrandrine (Tet). ...Flow cytometry and LC-MS/MS were used to determine the cellular efflux or retention of chemicals. Pharmacokinetic study was performed in ICR mice following oral administration of the study compounds. The hypoglycemic efficacies of the compounds were evaluated in diabetic KK-Ay mice. In the in vitro experiments, Tet significantly inhibited the efflux and increased the uptake of P-gp substrates rhodamine-123 as well as BBR in MCF7/DOX cells and Caco-2 intestinal cells. Meanwhile, Tet greatly reduced the expression of P-gp in Caco-2 cells. The inhibition of BBR efflux by Tet was translated into improved pharmacokinetics in vivo. When co-administered, Tet dose-dependently increased the average maximum concentration (Cmax) and area under concentration–time curve (AUC0–24) of BBR in mice. Tet itself had no impact on glucose metabolism. However, it greatly potentiated the hypoglycemic efficacy of BBR in diabetic KK-Ay mice. In addition, we found that Tet had moderate inhibitory effect on the catalytic activity of CYP3A4, which played a role in the bio-transformation of BBR, and this may also take part in the improvement of the pharmacokinetics of BBR. In summary, combination with P-gp inhibitors such as Tet can improve the pharmacokinetics and hypoglycemic efficacy of BBR greatly; this implicates a feasible strategy for exploring the therapeutic effects of BBR and other pharmaceuticals which are substrates of P-gp.
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