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Low-temperature sintering to fabricate MgB2 is considered a promising method because it reduces the formation of MgO and reduces the grain size, thereby increasing the critical current density. Chemical doping, ball milling of precursor and modifying the Mg source in precursor for low-temperature sintering have all been carefully investigated. However, the threshold of sintering temperature have been kept near 500 °C. A new in-situ method to low-temperature sintering using Mg(BH4)2 as a precursor is presented in this paper. Mg(BH4)2 decomposes into highly reactive nanoscale Mg and B in a molar ratio of 1:2 without impurities. In this method, only 2 h of sintering at 400 °C is required to completely react Mg with B to produce MgB2, and after 54 h sintering, the sample has comparable JC to the normal MgB2 from solid-state reaction method sintered at 800 °C. The sample sintered at 500 °C give better JC than normal MgB2 under both high and low magnetic field. [ABSTRACT FROM AUTHOR]

Daily average temperature data from 48 meteorological stations in Chinese oases that are within the distribution area of Populus euphratica were analyzed to determine the spatiotemporal responses of this tree to climate change. Specifically, the start and end date as well as the number of days that comprised the growing season were analyzed with a multi-year trend line and using the Mann-Kendall mutation test, inverse distance weighted interpolation (IDW) in the software ArcGIS, a Morlet wavelet power spectrum, and correlation analysis. The results of this study show that, over the last 56 years, the start date of the P. euphratica growing season has advanced, while the end date has been postponed, and the number of days that comprise the growing season have gradually increased. The changing trend rates recovered in this analysis for these three time slices are -1.34 d/10 a, 1.33 d/10a, and 2.66 d/10a (α ⩾ 0.001), respectively. Data show that while spatial disparity is extremely significant, it is nevertheless the case that along a southwest-to-northeast transect of Chinese oases, the later the start date of the P. euphratica season, the sooner the end data and the shorter the growing season. Mutations points in start and end date, as well as for the growing season overall were observed in 2001, 1989, and 1996, respectively, and the data presented in this paper show that, in particular, the date of this end of this period is most sensitive to climate warming. Growing season cycles for P. euphratica are between 3.56 years and 7.14 years, consistent with the periodicity of El Niño events, while a start date cycle between 3.56 years and 4.28 years is consistent with atmospheric circulation cyclicity. The causal analysis presented in this paper shows that the Asian polar vortex area index (APVAI), the Qinghai- Tibet Plateau index (TPI), the westerly circulation index (WCI), and carbon dioxide emissions (CDE) are the main factors influencing spatiotemporal changes in the growth of P. euphratica, the effect of latitude during the growing season is more significant than altitude, and the start date of the growing season is more significantly influenced by these factors than end date. In addition, data show that the start date, end date, and length of the growing season are all significantly correlated with their average corresponding monthly temperature (correlation coefficients are -0.875, 0.770, and 0.897; α⩾0.001). Thus, if the average temperature in March increases by 1°C, the start date of the growing season will advance by 2.21 days, while if the average temperature in October increases by the same margin then the seasonal end date will be delayed by 2.76 days. Similarly, if the average temperature between March and October increases by 1°C, the growing season will be extended by 7.78 days. The results of this study corroborate the fact that changes in the P. euphratica growing are sensitive to regional warming and are thus of considerable theoretical significance to our understanding of the responses of Chinese vegetation to climate change as well as to ecological restoration. [ABSTRACT FROM AUTHOR]

MgB 2 has shown great potential in making medium strength superconducting magnet using electronic refrigeration without liquid helium. One of the major problem in building the MgB 2 superconducting magnet is the joints in the coils. An effective method of building a superconducting joint is crucial. In this work, we have demonstrated a novel process of building a superconducting joint utilizing sol-gel method. Two HPCVD MgB 2 thin film on SiC substrate is pasted face-to-face with Mg(BH 4 ) 2 •Et 2 O gel. After annealing in Mg vapor, Mg(BH 4 ) 2 •Et 2 O gel decomposed and turned to MgB 2 superconducting joint. The joint showed good connectivity between the two films and has a good T C of 34 K. Infield measurement of the joint showed that the joint work well at 20 K with the applied magnetic field up to 4 T. [ABSTRACT FROM AUTHOR]