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Abstract An analytical relation between burden velocity and ratio of burden to blasthole diameter is developed in this paper. This relation is found to be consistent with the measured burden velocities of all 37 full-scale blasts found from published articles. These blasts include single-hole blasts, multi-hole blasts, and simultaneously-initiated blasts with various borehole diameters such as 64 mm, 76 mm, 92 mm, 115 mm, 142 mm and 310 mm. All boreholes were fully charged. The agreement between measured and calculated burden velocities demonstrates that this relation can be used to predict the burden velocity of a wide range of full-scale blast with fully-coupled explosive charge and help to determine a correct delay time between adjacent holes or rows in various full-scale blasts involved in tunnelling (or drifting), surface and underground mining production blasts and underground opening slot blasts. In addition, this theoretical relation is found to agree with the measured burden velocities of 9 laboratory small-scale blasts to a certain extent. To predict the burden velocity of a small-scale blast, a further study or modification to the relation is necessary by using more small-scale blasts in the future.
Abstract The transcription factor USF2 is supposed to have an important role in tumor development. However, the regulatory mechanisms contributing to the function of USF2 are largely unknown. Cyclin-dependent kinase 5 (CDK5) seems to be of importance since high levels of CDK5 were found in different cancers associated with high USF2 expression. Here, we identified USF2 as a phosphorylation target of CDK5. USF2 is phosphorylated by CDK5 at two serine residues, serine 155 and serine 222. Further, phosphorylation of USF2 at these residues was shown to stabilize the protein and to regulate cellular growth and migration. Altogether, these results delineate the importance of the CDK5-USF2 interplay in cancer cells.
Abstract Two types of core–shell heterostructure TiO2 nanofibers (noted as core@shell TiO2 NFs) were synthesized by sequential hydrothermal, calcination, and impregnation processes. Rutile TiO2 nanofibers (R TiO2 NFs) core with anatase TiO2 nanoparticles (A TiO2 NPs) shell is denoted as R@A TiO2 NFs, and the reverse structure with anatase TiO2 NFs core (A TiO2 NFs) and rutile TiO2 nanoparticles shell (R TiO2 NPs) is denoted as A@R TiO2 NFs. In our study, the photodegradation of organic dyes and Kelvin probe force microscopy (KPFM) analysis were applied to shed light on the mechanism of the excited electron–hole pair separation. The results of photodegradation showed that the A@R TiO2 NFs have the highest activity under UV-B and UV-A irradiation, being nearly 3-fold higher as compared to AEROXIDE TiO2 P25. The results in conjunction with KPFM measurements indicated that, in the heterostructure, electron–hole pairs are efficiently separated, the excited electrons stay in the anatase phase, and holes are injected to the rutile phase. When the A@R TiO2 NFs heterostructures are decorated with Pt nanoparticles (Pt-A@R TiO2 NFs), the nanocomposite is particularly active in photocatalytic hydrogen evolution from ethanol–water mixtures with a production rate of ∼8,500 μmol/h·g. Our study not only explains the role of anatase–rutile junctions in photocarrier separation, but also projects the development of other efficient photocatalytic heterostructures for green energy production and conversion.
Abstract The objective of this study was to investigate granite responses to blasting. The focus was on the pressure and attenuation of shock waves in granite. Tests are reported on ten cylinders subjected to explosions from central pressed trinitrotoluene (TNT) charges with approximate density of 1.6 g/cm3. Three cylinders had dimensions Ø150 mm × 200 mm; seven, Ø240 mm × 300 mm. Specimens had concentric holes drilled from both ends: one 20-mm hole to position the explosive charge and one 50-mm hole to insert a granite plug equipped with Manganin gauges, which were applied to monitor the pressures of the shock waves. The configuration of the gauges was analyzed before testing to investigate how precisely they could measure shock waves in the granite. One or two gauges were used in each cylinder at distances of 7, 15, 22 or 35 mm from the explosive charge in the cylinder axis. At detonation of the charge, the measured peak pressure values ranged from 15.9–4.4 GPa depending on distance from the explosive, with pressure rise times of ∼0.5 μs. In one specimen, deflagration occurred, resulting in a low peak pressure of 1.35 GPa 11 mm from the explosive and a 16-μs pressure rise time. For specimens with two gauges, shock-wave velocities were found to depend strongly on the distance from the explosive. Fitting a curve to the experimental data, an exponential relation for the shock-wave peak pressure and its attenuation was obtained, expressing pressure (GPa) as a function of increasing distance (mm) from the explosive: p = 19.4exp(−0.04x). The findings, especially regarding the damping term, may for instance be useful for verification of numerical models for blasting simulation.
Abstract The thermal analysis of B2O3-Bi2O3-SiO2-ZnO (BBSZ) glass with different particle sizes and LiF addition was researched to study its temperature behavior. Next the composites with 50 wt% BaTiO3–50 wt% BBSZ glass were prepared for shrinkage, microstructures and dielectric properties investigations. The differently treated BBSZ glass showed that the smaller glass particles clearly decreased its softening and crystallization temperatures. LiF addition had the same but much weaker effect. The composites showed two-stage shrinkage related to the softening of the glass and new phase generation of Bi24Si2O40 at 385–450 °C, and Bi4BaTi4O15 over 680 °C. The microstructures of the composites sintered at 720 °C showed Bi4BaTi4O15, BaTiO3 and Bi24Si2O40 with residual ZnO phase. LiF addition increased the amount of Bi4BaTi4O15, thus increasing the loss value. However the particle size of the glass did not effect to the dielectric properties of the composites showing permittivity of 248–256 and loss of 0.013 at 100 kHz.