Palaeomagnetism of Precambrian igneous rocks in Australia and East Antarctica: implications for the pre-Pangea supercontinents and supercontinent cycle

This thesis presents a series of new, high-quality palaeomagnetic data from Precambrian igneous rocks in Western Australia, South Australia and East Antarctica. The ages of the corresponding new palaeomagnetic poles range from late Archaean to late Mesoproterozoic. The new data improve significantly the Australian and East Antarctic palaeomagnetic database and shed lights on the tectonic evolution of Australia and global palaeogeographic reconstructions

Upregulation of AKAP12 by demethylation inhibits proliferation and increases chem osensitivity to adriamycin in leukemic cells

Purpose: To elucidate the role of AKAP12 in leukemia cells.Methods: Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting (WB) were employed to determine the expression of AKAP12 in leukocyte cell lines, while 5-azacytidine was used to treat the cells, followed by assessment of the expression of AKAP12. After constructing the overexpressing vector pc-AKAP12 and transfecting it into cells or treating the cells with 5-azacytidine, cell counting kit-8 assay (CCK-8) was used to determine cell proliferation. Cloning ability of the cells was evaluated by colony formation assay.  Furthermore, flow cytometry was employed to measure the degrees of cell cycle and cell apoptosis. The effect of AKAP12 on PI3K/AKT were determined by western blot.Results: The results showed that AKAP12 was lowly expressed in lymphocytic leukemia cell lines (p < 0.001), but was reversed by 5-azacytidine. Transfection of AKAP12 or 5-azacytidine treatment increased the expression of AKAP12 in the cells (p > 0.001), inhibited leukemia cell proliferation and clonality, and arrested cell cycle in G1 phase as well as induced apoptosis. In addition, PI3K/AKT signaling pathway was inhibited by AKAP12.Conclusion: AKAP12 is lowly expressed in leukemia cells, and may also play a role in inhibiting leukemia progression by suppressing the activity of PI3K/AKT pathway.Thus, targeting AKAP12 mght be a potential strategy in the management of lukemia

A quantum system control method based on enhanced reinforcement learning

Traditional quantum system control methods often face different constraints, and are easy to cause both leakage and stochastic control errors under the condition of limited resources. Reinforcement learning has been proved as an efficient way to complete the quantum system control task. To learn a satisfactory control strategy under the condition of limited resources, a quantum system control method based on enhanced reinforcement learning (QSC-ERL) is proposed. The states and actions in reinforcement learning are mapped to quantum states and control operations in quantum systems. By using new enhanced neural networks, reinforcement learning can quickly achieve the maximization of long-term cumulative rewards, and a quantum state can be evolved accurately from an initial state to a target state. According to the number of candidate unitary operations, the three-switch control is used for simulation experiments. Compared with other methods, the QSC-ERL achieves close to 1 fidelity learning control of quantum systems, and takes fewer episodes to quantum state evolution under the condition of limited resources.Comment: 10 pages, 3 figure

Archean geodynamics : Ephemeral supercontinents or long-lived supercratons

Many Archean cratons exhibit Paleoproterozoic rifted margins, implying they were pieces of some ancestral landmass(es). The idea that such an ancient continental assembly represents an Archean supercontinent has been proposed but remains to be justified. Starkly contrasting geological records between different clans of cratons have inspired an alternative hypothesis where cratons were clustered in multiple, separate "supercratons." A new ca. 2.62 Ga paleomagnetic pole from the Yilgarn craton of Australia is compatible with either two successive but ephemeral supercontinents or two long-lived supercratons across the Archean-Proterozoic transition. Neither interpretation supports the existence of a single, long-lived supercontinent, suggesting that Archean geodynamics were fundamentally different from subsequent times (Proterozoic to present), which were influenced largely by supercontinent cycles.Peer reviewe

Spermidine enhances heat tolerance of rice seeds during mid-filling stage and promote subsequent seed germination

IntroductionHeat stress is a vital factor which restricts rice seed quality and yield. However, the response mechanism to heat stress in the mid filling stage of rice seed is unclear.MethodsIn the present study we integrated phenotypic analysis with biochemical, hormone, and gene expression analysis in order to explore technologies for improving rice seeds heat tolerance and subsequent seed germination.ResultsSpermidine (Spd) application effectively alleviated the damage of heat stress treatment during mid-filling stage (HTM, 12-20 days after pollination) on seed development, promoted subsequent seed germination and seedlings establishment. Spd significantly increased seed dry weight, starch and amylose contents during seed development under heat stress, and improved seed germinate, seedlings establishment and seedling characteristics during germination time. Biochemical analysis indicated that, HTM significantly decreased the activities of several starch synthase enzymes and led to a decrease in starch content. While Spd treatment significantly enhanced the activities of ADP-glucose pyrophosphorylas and granule-bound starch synthase, as well as the corresponding-genes expressions in HTM rice seeds, resulting in the increases of amylose and total starch contents. In addition, Spd significantly increased the catalase and glutathione reductase activities together with corresponding-genes expressions, and lowered the overaccumulation of H2O2 and malondialdehyde in HTM seeds. In the subsequent seed germination process, HTM+Spd seeds exhibited dramatically up-regulated levels of soluble sugars, glucose, ATP and energy charges. Consistently, HTM+Spd seeds showed significantly increased of α-amylose and α-glucosidase activities as well as corresponding-genes expressions during early germination. Moreover, HTM evidently increased the abscisic acid (ABA) content, decreased the gibberellin (GA) content, and accordingly significantly declined the GA/ABA ratio during early rice seeds germination. However, Spd treatment did not significantly affect the metabolism of GA and ABA in seed germination stage.DiscussionThe present study suggested that Spd treatment could effectively alleviate the negative impact of HTM on seed development and the subsequent seed germination, which might be closely correlated with starch synthesis and antioxidant defense during seed filling period, starch decomposition and energy supply in seed germination period

The 1.24–1.21 Ga Licheng large igneous province in the North China Craton: Implications for paleogeographic reconstruction

Detailed geochronological, geochemical, and paleomagnetic studies of mafic dyke swarms, often associated with mantle plumes, can provide unique constraints on paleogeographic reconstructions. Mafic dykes with baddeleyite U-Pb ages of 1,233 27 Ma (SIMS), 1,206.7 1.7 Ma (TIMS), 1,214.0 4.9 Ma (TIMS), and 1,236.3 5.4 Ma (TIMS) have been identified in the eastern North China Craton. Geochemical data indicate subalkaline to alkaline basalt compositions with OIB-like trace element signatures and an intraplate tectonic setting. In addition to these geochemical signatures, the radiating geometry of these dykes also suggests a 1.24-1.21 Ga large igneous province caused by a mantle plume event. A new similar to 1.24 Ga paleomagnetic pole at 2.0 degrees N, 165.1 degrees E, A(95) = 11.0 degrees, N = 9 and an similar to 1.21 Ga VGP at -23.0 degrees N, 92.5 degrees E, dp/dm = 4.7 degrees/7.8 degrees have been obtained from these dykes, with the 1.24 Ga pole supported by positive baked contact test. Our paleomagnetic analyses suggest that the North China Craton and the proto-Australian continent could have been separated by 1.24-1.21 Ga from an established Nuna connection at ca. 1.32 Ga. By comparison with Laurentia paleopoles, we present the paleogeography of dispersing North China, proto-Australian, and Laurentia cratons in the late Mesoproterozoic during the breakup of the supercontinent Nuna.Peer reviewe

Weak orogenic lithosphere guides the pattern of plume-triggered supercontinent break-up

The importance of nonrigid geological features (such as orogens) inside tectonic plates on Earth’s dynamic evolution lacks thorough investigation. In particular, the influence of continent-spanning orogens on (super)continental break-up remains unclear. Here we reconstruct global orogens and model their controlling effects on Pangea break-up. We show that while loci of Pangea break-up are linked to mantle plumes, development of continental rifts is guided by orogens. Rifting at Central Atlantic is driven by the modelled plume responsible for the Central Atlantic Magmatic Province (CAMP) within Pangea-forming orogens. South Atlantic rifting is controlled by necking between Pangea- and Gondwana-forming orogens with the assistance of plume-induced lithospheric weakening. Without CAMP-induced weakening, South Atlantic rifting fails between the West African and Amazonian cratons, but occurs between the West African and Saharan cratons instead. Our modeling on Pangea break-up is able to recreate present-day continental geometry through the combined effect of orogens and plume center-locations

Palaeomagnetic field intensity measurements from the 2.6 Ga Yandinilling dyke swarm (Western Australia)

SUMMARY Precambrian palaeointensity measurements provide fundamental constraints on the evolution of the deep Earth. Core evolution models predict trends in dipole moment on billion-year timescales that can be tested by palaeomagnetic records. Here, we report new palaeointensity results from the recently identified ∼2.62 Ga Yandinilling dyke swarm of the Yilgarn Craton, Western Australia, and consider them alongside published measurements spanning 500 Myr across the late Archaean to earliest Proterozoic. Rock magnetic and scanning electron microscopy analysis confirm that the magnetic mineralogy is fine-grained magnetite, appearing mostly as exsolved lamellae with ilmenite. Six sites produced acceptable palaeointensity estimates from thermal and microwave IZZI protocol Thellier experiments and from double-heating technique Shaw experiments. These site mean values of 9–26 µT translate to virtual dipole moments of 11–44 ZAm2 that are considerably lower than today's dipole moment of ∼80 ZAm2 and the value predicted for this time period by some thermal evolution models. Their average (median = 41 ZAm2) is, however, similar to the long-term average during both of the intervals 2300–2800 Ma (median = 44 ZAm2; N = 103) and 10–500 Ma (median 41 ZAm2; N = 997). While there is little evidence for a substantial net change in average dipole moment between the late Archaean and Phanerozoic, there is preliminary evidence that its variance has increased between the two intervals. This lower variance more than two billion years ago supports the idea that the geodynamo, even while not producing a stronger magnetic field, was more stable on average at the Archaean–Proterozoic transition than it is today.</jats:p

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure