Protolith ages and timing of peak and retrograde metamorphism of the high-pressure granulites in the Shandong Peninsula,eastern North China Craton

High-pressure （HP） granulites widely occur as enclaves within tonalite-trondhjemite- granodiorite （TTG） gneisses of the Early Precambrian metamorphic basement in the Shandong Peninsula, southeast part of the North China Craton （NCC）. Based on cathodoluminescence （CL）, laser Raman spec- troscopy and in-situ U-Pb dating, we characterize the zircons from the HP granulites and group them into three main types： inherited （magmatic） zircon, HP metamorphic zircon and retrograde zircon. The inher- ited zircons with clear or weakly defined magmatic zoning contain inclusions of apatites, and 207pb/206pb ages of 2915--2890 Ma and 2763--2510 Ma, correlating with two magmatic events in the Archaean base- ment. The homogeneous HP metamorphic zircons contain index minerals of high-pressure metamor- phism including garnet, clinopyroxene, plagioclase, quartz, rutile and apatite, and yield 207pb/2066pb ages between 1900 and 1850 Ma, marking the timing of peak HP granulite facies metamorphism. The retrograde zircons contain inclusions of orthopyroxene, plagioclase, quartz, apatite and amphibole, and yield the youngest 207pb/206pb ages of 1840-1820 Ma among the three groups, which we correlate to the medium to low-pressure granulite facies retrograde metamorphism. The data presented in this study suggest subduction of Meso- and Neoarchean magmatic protoliths to lower crust depths where they were subjected to HP granulite facies metamorphism during Palaeoproterozoic （1900-1850 Ma）. Subse- quently, the HP granulites were exhumated to upper crust levels, and were ovel-printed by medium to low-pressure granulite and amphibolite facies retrograde event at ca. 1840--820 Ma.

ABA-mediated regulation of leaf and root hydraulic conductance in tomato grown at elevated CO2 is associated with altered gene expression of aquaporins

Elevated CO_(2)concentration in the air(e[CO_(2)])decreases stomatal density(SD)and stomatal conductance(gs)where abscisic acid(ABA)may play a role,yet the underlying mechanism remains largely elusive.We investigated the effects of e[CO_(2)](800 ppm)on leaf gas exchange and water relations of two tomato(Solanum lycopersicum)genotypes,Ailsa Craig(WT)and its ABA-deficient mutant(flacca).Compared to plants grown at ambient CO_(2)(400 ppm),e[CO_(2)]stimulated photosynthetic rate in both genotypes,while depressed the gs only in WT.SD showed a similar response to e[CO_(2)]as gs,although the change was not significant.e[CO_(2)]increased leaf and xylem ABA concentrations and xylem sap pH,where the increases were larger in WT than in flacca.Although leaf water potential was unaffected by CO_(2)growth environment,e[CO_(2)]lowered osmotic potential,hence tended to increase turgor pressure particularly for WT.e[CO_(2)]reduced hydraulic conductance of leaf and root in WT but not in flacca,which was associated with downregulation of gene expression of aquaporins.It is concluded that ABA-mediated regulation of gs,SD,and gene expression of aquaporins coordinates the whole-plant hydraulics of tomato grown at different CO_(2)environments.

Q-Learning-Based Adaptive Waveform Selection in Cognitive Radar

Cognitive radar is a new framework of radar system proposed by Simon Haykin recently. Adaptive waveform selection is an important problem of intelligent transmitter in cognitive radar. In this paper, the problem of adaptive waveform selection is modeled as stochastic dynamic programming model. Then Q-learning is used to solve it. Q-learning can solve the problems that we do not know the explicit knowledge of state-transition probabilities. The simulation results demonstrate that this method approaches the optimal wave-form selection scheme and has lower uncertainty of state estimation compared to fixed waveform. Finally, the whole paper is summarized.

The progressive onset and evolution of Precambrian subduction and plate tectonics

The regime of plate tectonics on early Earth is one of the fundamental problems in Earth sciences.Precambrian era takes the majority(ca.88%)of Earth’s history and thus plays a key role in understanding the onset of plate tectonics and the mechanism,distribution and process of Precambrian subduction zones.This paper presents a review on the progresses of subduction and subduction zones in different stages of Precambrian era,and sorts out some key issues and fields that merits further attention.We suggest that there was progressive onset and evolution of subduction and plate tectonics from Archean to Proterozoic eras.We emphasize the importance of comprehensive studies on subduction mechanism,metamorphic type,plate tectonics regime,the compositional evolution of continental crust,and petrogenesis of diverse granitoids formed in the Archean.It is proposed that innovative analytical techniques,big data,experimental petrology and numerical geodynamic modeling will facilitate future studies of Precambrian subduction zones.

Highly efficient photocatalytic Suzuki coupling reaction by Pd_(3)P/CdS catalyst under visible-light irradiation

Monodispersed palladium phosphide(Pd_(3)P)(5.2 ± 0.5 nm) was firstly applied to photocatalytic Suzuki coupling reaction under visible light irradiation with CdS nanoflake as a photo sensitizer.This heterogeneous system exhibited high yields to corresponding products and excellent stability in alcohol solvent at room temperature.

Experimental study of the metamorphic reaction involving melt under high temperature and high pressure

High P_T experiment with natural massive rock sample of garnet biotite plagioclase gneiss indicates that the metamorphic reaction involving melt (reaction between relic mineral phase and melt) is the most important reaction in granulite_facies metamorphism and accompanies anatexis process.