Anisotropic Magnetotransport and Exotic Longitudinal Linear Magnetoresistance in WTe2 Crystals

WTe2 semimetal, as a typical layered transition-metal dichalcogenide, has recently attracted much attention due to the extremely large, non-saturating parabolic magnetoresistance in perpendicular field. Here, we report a systematic study of the angular dependence of the magnetoresistance in WTe2 single crystal. The violation of the Kohler rule and a significant anisotropic magnetotransport behavior in different magnetic field directions are observed. Surprisingly, when the applied field is parallel to the tungsten chains of WTe2, an exotic large longitudinal linear magnetoresistance as high as 1200% at 15 T and 2 K is identified. Violation of the Kohler rule in transverse magnetoresistance can be understood based on a dual effect of the excitons formation and thermal activation, while large longitudinal linear magnetoresistance reflects perfectly the scattering and nesting of quasi-1D nature of this balanced hole-electron system. Our work will stimulate studies of such double-carrier correlated material and corresponding quantum physics

Electrospun ZnO Nanowires as Gas Sensors for Ethanol Detection

ZnO nanowires were produced using an electrospinning method and used in gas sensors for the detection of ethanol at 220 °C. This electrospinning technique allows the direct placement of ZnO nanowires during their synthesis to bridge the sensor electrodes. An excellent sensitivity of nearly 90% was obtained at a low ethanol concentration of 10 ppm, and the rest obtained at higher ethanol concentrations, up to 600 ppm, all equal to or greater than 90%

Attenuation of Vaccinia Tian Tan Strain by Removal of Viral TC7L-TK2L and TA35R Genes

Vaccinia Tian Tan (VTT) was attenuated by deletion of the TC7L-TK2L and TA35R genes to generate MVTT3. The mutant was generated by replacing the open reading frames by a gene encoding enhanced green fluorescent protein (EGFP) flanked by loxP sites. Viruses expressing EGFP were then screened for and purified by serial plaque formation. In a second step the marker EGFP gene was removed by transfecting cells with a plasmid encoding cre recombinase and selecting for viruses that had lost the EGFP phenotype. The MVTT3 mutant was shown to be avirulent and immunogenic. These results support the conclusion that TC7L-TK2L and TA35R deletion mutants can be used as safe viral vectors or as platform for vaccines

PIF4–Mediated Activation of YUCCA8 Expression Integrates Temperature into the Auxin Pathway in Regulating Arabidopsis Hypocotyl Growth

Higher plants adapt their growth to high temperature by a dramatic change in plant architecture. It has been shown that the transcriptional regulator phytochrome-interacting factor 4 (PIF4) and the phytohormone auxin are involved in the regulation of high temperature–induced hypocotyl elongation in Arabidopsis. Here we report that PIF4 regulates high temperature–induced hypocotyl elongation through direct activation of the auxin biosynthetic gene YUCCA8 (YUC8). We show that high temperature co-upregulates the transcript abundance of PIF4 and YUC8. PIF4–dependency of high temperature–mediated induction of YUC8 expression as well as auxin biosynthesis, together with the finding that overexpression of PIF4 leads to increased expression of YUC8 and elevated free IAA levels in planta, suggests a possibility that PIF4 directly activates YUC8 expression. Indeed, gel shift and chromatin immunoprecipitation experiments demonstrate that PIF4 associates with the G-box–containing promoter region of YUC8. Transient expression assay in Nicotiana benthamiana leaves support that PIF4 directly activates YUC8 expression in vivo. Significantly, we show that the yuc8 mutation can largely suppress the long-hypocotyl phenotype of PIF4–overexpression plants and also can reduce high temperature–induced hypocotyl elongation. Genetic analyses reveal that the shy2-2 mutation, which harbors a stabilized mutant form of the IAA3 protein and therefore is defective in high temperature–induced hypocotyl elongation, largely suppresses the long-hypocotyl phenotype of PIF4–overexpression plants. Taken together, our results illuminate a molecular framework by which the PIF4 transcriptional regulator integrates its action into the auxin pathway through activating the expression of specific auxin biosynthetic gene. These studies advance our understanding on the molecular mechanism underlying high temperature–induced adaptation in plant architecture

The effect of blockage and tunnel slope on smoke spread and ceiling temperature distribution in a natural-ventilated metro depot

The current research investigated the coupling effect of blockage and tunnel slope on spreading characteristics of the fire smoke and ceiling temperature distribution in a metro depot with one closed end. A series of 1/15 reduced scale experiments and full-scale numerical simulations were conducted to capture the global fire characteristics. The investigation addressed and compared the effect of tunnel slope on the fire plume behavior and ceiling temperature distribution in both uphill and downhill situations. The presence of the blockage upstream of the fire was further investigated to highlight the heat accumulation between the closed end and fire, and the associated effect on the pool fire mass burning rate. Comparison has been made between the ceiling temperature distribution of when the tunnel slope increases in both uphill and downhill tunnels. The coupling effect of blockage and tunnel slope was analyzed in relation to the maximum and extent of high temperature area at tunnel ceiling. Two empirical correlations have also been proposed to predict the maximum temperature and upstream temperature attenuation in a metro depot, accounting for the influence of blockage and tunnel slope. Comparison among the measurements, predicted values, literature models and data exhibit relatively good agreement

Effect of ceiling extraction on the smoke spreading characteristics and temperature profiles in a tunnel with one closed end

A series of fire tests in a 1/15 scaled-model tunnel with one closed end have been conducted. Analysis was carried out to explore temperature distribution and smoke propagation under the influence of ceiling extraction system. Five different heat release rates, three dimensions of exhaust outlet, and numerous extraction rates were considered. Experimental results led to some interesting findings about the relationships between smoke extraction rate, fuel mass burning rate, and ceiling temperature. Two distinctive ceiling temperature regions were identified according to their different responses to smoke extraction rate, i.e., ceiling temperature decay between the fire and outlet was almost independent of smoke extraction rate while temperature upstream of the outlet decreased sharply with the increase of smoke extraction rate. Analysis was also conducted about smoke back-layering length, revealing its strong dependence on heat release rate and induced air velocity. Based on the experimental results and dimensional analysis, three empirical formulas were proposed to capture ceiling temperature decay and smoke back-layering length for tunnels with one closed end utilizing ceiling smoke extraction