Association Of Gain Research Articles

Tectonic affinity and reworking of the Archaean Jiaodong Terrane in the Eastern Block of the North China Craton: evidence from LA-ICP-MS U–Pb zircon ages

AbstractThe Archaean Jiaodong Terrane is located in the southern segment of the Palaeoproterozoic Jiao-Liao-Ji Belt, which separates the Eastern Block of the North China Craton into the Longgang and Langrim blocks. Controversy has long surrounded the issue of whether the Jiaodong Terrane is part of the North China Craton or an exotic terrane. This study presents new zircon U–Pb ages for the major lithologies of the Jiaodong Terrane, and the results indicate that the terrane underwent two main magmatic events at ~2.89 Ga and 2.62–2.56 Ga and two metamorphic events at ~2.5 Ga and 1.9–1.8 Ga. These ages are consistent with those of other metamorphic complexes in the Eastern Block, suggesting that the Jiaodong Terrane was part of the Neoarchaean basement of the Eastern Block, which was reworked at 1.9–1.8 Ga in association with the development of the Palaeoproterozoic Jiao-Liao-Ji Belt.

The photoluminescence/excitation (PL/E) spectroscopy of Eu-implanted GaN

Several distinct luminescent centres form in GaN samples doped with Eu. One centre, Eu2, recently identified as the isolated, substitutional Eu impurity, Eu Ga, is dominant in ion-implanted samples annealed under very high pressures (1 GPa) of N 2. According to structural determinations, such samples exhibit an essentially complete removal of lattice damage caused by the implantation process. A second centre, Eu1, probably comprising Eu Ga in association with an intrinsic lattice defect, produces a more complex emission spectrum. In addition there are several unidentified features in the 5D 0 to 7F 2 spectral region near 620 nm. We can readily distinguish Eu1 and Eu2 by their excitation spectra, in particular through their different sensitivities to above-gap and below-gap excitation. The present study extends recent work on photoluminescence/excitation (PL/E) spectroscopy of Eu1 and Eu2 to arrive at an understanding of these mechanisms in terms of residual optically active defect concentrations. We also report further on the ‘host-independent’ excitation mechanism that is active in the case of a prominent minority centre. The relevance of this work to the operation of the red GaN:Eu light-emitting diode is discussed.

Nitrogenase and uptake hydrogenase activities of Rhizobium japonicum during the life cycle of Glycine max (L.) merr.

Uptake hydrogenase and nitrogenase activities of Rhizobium japonicum strains PJ 17.1 and GA in association with Glycine max cvs. Fengshou and Giessen were investigated throughout the life cycles of the hosts.The growth of the two cultivars was greater with PJ 17.1 than with GA. The nitrogenase specific activities were maximum at 37 days after sowing with GA and 48 days after sowing with PJ 17.1 and decreased thereafter, almost similarly on both the cultivars. However, the uptake hydrogenase actities of PJ 17.1 were found to be maximum at 30 days.The relative efficiencies of PJ 17.1 were 1.0 at all stages while those of GA varied similarly on both the cultivars. As plants inoculated with PJ 17.1 were aging, a similar decline was observed in the activities of nitrogenase and hydrogenase. Although relative efficiency of GA varied throughout the life cycle of soybean, no correlation was seen between it and the nitrogenase specific activity.