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The shear behaviors of grain boundaries are investigated using molecular dynamics simulations. The Σ5〈001〉310 symmetric tilt grain boundary (GB) of body-centered cubic (bcc) Nb is investigated and the simulations are conducted under a series of shear directions at a wide range of temperatures. The results show that the GB shearing along [13¯0], which is perpendicular to the tilt axis, has a coupled motion behavior. The coupling factor is predicted using Cahn's model. The critical stress of the coupling motion is found to decrease exponentially with increasing temperature. The GB under shear deformation along the [001¯] direction, which is parallel to the tilt axis, has a pure sliding behavior at most of the temperatures investigated. The critical stress of sliding is found to be much larger than that of the coupled motion at the same temperature. At very low temperatures, pure sliding is not observed, and dislocation nucleating and extending is found on GBs. We observed mixed behaviors when the shear direction is between [13¯0] and [001¯]. The transition region between GB coupled motion and pure sliding is determined. If the shear angles between the shear direction and the tilt axis are larger than a certain value, the GB has a coupled motion behavior similar to the [13¯0] direction. A GB with a shear angle smaller than the critical angle exhibits mixed mechanisms at low temperatures, such as dislocation, atomic shuffle and GB distortion, whereas for the [001¯]-like GB pure sliding is the dominating mechanism at high temperatures. The stresses to activate the coupling and gliding motions are analyzed for shear deformations along different directions at various temperatures. [ABSTRACT FROM AUTHOR]

A high performance CoO/carbon nanofibers (CNF) composite catalyst was synthesized for Li-O2batteries. For comparison, CoO/BP2000 and CoO/MWNTs were also prepared and investigated to study the influence of carbon supports on the electrochemical performance of the composite catalysts. Electrochemical tests showed that the Li-O2battery with CoO/CNF demonstrated obviously enhanced electrochemical performance than the batteries with CoO/BP2000 and CoO/MWNTs catalysts, which delivered a first discharge capacity of 3882.5mAhgcat-1and remained about 3302.8mAhgcat-1after 8 cycles in the voltage range from 2.0 to 4.2V. More importantly, the cycle stability of the Li-O2battery with CoO/CNF could maintain over 50 cycles when cycled at a fixed capacity of 1000mAhgcat-1. The unique porous nanofiberous structure of CoO/CNF greatly contributed to its high electrocatalytic performance. [ABSTRACT FROM AUTHOR]

A nanofibrous MnNi/CNF (carbon nanofiber) composite electrocatalyst with diameter of 50-200 nm was synthesized via electrospinning technique and followed by a carbonization process using polyacrylonitrile (PAN), manganese acetate and nickel acetate as raw materials. XRD analysis indicated that the manganese and nickel in the composite were presented as MnO and metallic Ni respectively. The oxygen electrode using the prepared MnNi/CNF catalyst showed high electrochemical performance due to its special microstructure as mesoporous carbon nanofibers embedded with 10-20 nm particles of MnO-Ni catalyst. TEM observation and BET analysis indicated that the MnNi/CNF nanofibers possessed larger specific surface area and larger mesopore size than that of pure carbon nanofibers apparently due to the effects of the metal components on the rapid gas release during polymer carbonization. The mesoporous nanofiber structure benefited the heterophase reaction on the oxygen electrode. In addition, the presence of Ni in the nanofibers improved the electrical conductivity of the composite catalyst thus benefited the cycling and rate performances of the Li/O2 cell. [ABSTRACT FROM AUTHOR]

The natural variation in stable water isotope ratio data, also known as water isoscape, is a spatiotemporal fingerprint and a powerful natural tracer that has been widely applied in disciplines as diverse as hydrology, paleoclimatology, ecology and forensic investigation. Although much effort has been devoted to developing a predictive water isoscape model, it remains a central challenge for scientists to generate high accuracy, fine scale spatiotemporal water isoscape prediction. Here we develop a novel approach of using the MODIS-EVI (the Moderate Resolution Imagining Spectroradiometer-Enhanced Vegetation Index), to predict δ18O in precipitation at the regional scale. Using a structural equation model, we show that the EVI and precipitated d O are highly correlated and thus the EVI is a good predictor of precipitated δ18O. We then test the 18 predictability of our EVI-δ18O model and demonstrate that our approach can provide high accuracy with fine spatial 18 (250x250 m) and temporal (16 days) scale δ18O predictions (annual and monthly predictabilities [r] are 0.96 and 0.80, 18 respectively). We conclude the merging of the EVI and δ18O in precipitation can greatly extend the spatial and temporal data availability and thus enhance the applicability for both the EVI and water isoscape. [ABSTRACT FROM AUTHOR]

ATF1 (activating transcription factor 1), a stimulus-induced CREB family transcription factor, plays important roles in cell survival and proliferation. Phosphorylation of ATF1 at Ser63 by PKA (cAMP-dependent protein kinase) and related kinases was the only known post-translational regulatory mechanism of ATF1. Here, we found that HIPK2 (homeodomain-interacting protein kinase 2), a DNA-damage-responsive nuclear kinase, is a new ATF1 kinase that phosphorylates Ser198 but not Ser63. ATF1 phosphorylation by HIPK2 activated ATF1 transcription function in the GAL4-reporter system. ATF1 is a transcriptional repressor of ferritin H, the major intracellular iron storage gene, through an ARE (antioxidant-responsive element). HIPK2 overrode the ATF1-mediated ARE repression in a kinase-activity-dependent manner in HepG2 cells. Furthermore, DNA-damage-inducing agents doxorubicin, etoposide and sodium arsenite induced ferritin H mRNA expression in HIPK2+/+ MEF cells, whereas it was significantly impaired in HIPK2-/- MEF cells. Induction of other ARE-regulated detoxification genes such as NQO1 (NADPH quinone oxidoreductase 1), GST (glutathione Stransferase) and HO1 (heme oxygenase 1) by genotoxic stress was also decreased in HIPK2-deficient cells. Taken together, these results suggest that HIPK2 is a new ATF1 kinase involved in the regulation of ferritin H and other antioxidant detoxification genes in genotoxic stress conditions. [ABSTRACT FROM AUTHOR]