3,915 research outputs found

    Boron nanobelts grown under intensive ion bombardment

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    High-quality α-tetragonal crystalline boronnanobelts with [001] growth axis were synthesized using a novel method combining e-beam evaporation and plasma ion bombardment techniques. Intensive ion bombardment of the growingboronnanobelts at a high substrate temperature (∼1200°C) was found to be effective in increasing the atomic density, reducing the crystal disorder, and improving the yield of the nanobelts.This work was supported by the Australian Research Council ARC

    Temperature Dependence of Droplet Nucleation in a Yukawa Fluid

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    We have studied the temperature dependence of gas-to-liquid nucleation in Yukawa fluids with gradient theory and density functional theory. Each of these nonclassical theories exhibits a weaker (i.e., better) temperature dependence than classical nucleation theory. At fixed temperature, the reversible work to form a critical nucleus found from gradient theory approaches the value given by density functional theory as the supersaturation increases. At high temperatures, the two theories remain quite close over a wide range of vapor densities. As the temperature is reduced, the difference between the two theories increases with decreasing vapor density. Compared to the classical theory we find that gradient theory can improve the predicted temperature dependence of the nucleation rate, although not always to the same degree as density functional theory. Finally, our results show that the scaling behavior of density functional theory proposed by McGraw and Laaksonen can be extended to higher temperatures if the incompressibility assumption is avoided when evaluating the classical reversible work

    Nucleation Near the Spinodal: Limitations of Mean Field Density Functional Theory

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    We investigate the diverging size of the critical nucleus near the spinodal using the gradient theory ~GT! of van der Waals and Cahn and Hilliard and mean field density functional theory ~MFDFT!. As is well known, GT predicts that at the spinodal the free energy barrier to nucleation vanishes while the radius of the critical fluctuation diverges. We show numerically that the scaling behavior found by Cahn and Hilliard for these quantities holds quantitatively for both GT and MFDFT. We also show that the excess number of molecules Dg satisfies Cahn-Hilliard scaling near the spinodal and is consistent with the nucleation theorem. From the latter result, it is clear that the divergence of Dg is due to the divergence of the mean field isothermal compressibility of the fluid at the spinodal. Finally, we develop a Ginzburg criterion for the validity of the mean field scaling relations. For real fluids with short-range attractive interactions, the near-spinodal scaling behavior occurs in a fluctuation dominated regime for which the mean field theory is invalid. Based on the nucleation theorem and on Wang\u27s treatment of fluctuations near the spinodal in polymer blends, we infer a finite size for the critical nucleus at the pseudospinodal identified by Wang

    The potential impacts of COVID-19 on the global value chains: GVC positioning and linkages

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    Long Narrative Songs from the Mongghul of Northeast Tibet: Texts in Mongghul, Chinese, and English

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    Containing ballads of martial heroism, tales of tragic lovers and visions of the nature of the world, Long Narrative Songs from the Mongghul of Northeast Tibet: Texts in Mongghul, Chinese, and English is a rich repository of songs collected amongst the Mongghul of the Seven Valleys, on the northeast Tibetan Plateau in western China. These songs represent the apogee of Mongghul oral literature, and they provide valuable insights into the lives of Mongghul people—their hopes, dreams, and worries. They bear testimony to the impressive plurilingual repertoire commanded by some Mongghul singers: the original texts in Tibetan, Mongghul, and Chinese are here presented in Mongghul, Chinese, and English. The kaleidoscope of stories told in these songs include that of Marshall Qi, a chieftain from the Seven Valleys who travels to Luoyang with his Mongghul army to battle rebels; Laarimbu and Qiimunso, a pair of star-crossed lovers who take revenge from beyond the grave on the families that kept them apart; and the Crop-Planting Song and the Sheep Song, which map the physical and spiritual terrain of the Mongghul people, vividly describing the physical and cosmological world in which they exist. This collection of songs is supported by an Introduction by Gerald Roche that provides an understanding of their traditional context, and shows that these works offer insights into the practices of multilingualism in Tibet. Long Narrative Songs from the Mongghul of Northeast Tibet is vital reading for researchers and others working on oral literature, as well as those who study Inner Asia, Tibet, and China’s ethnic minorities. Finally, this book is of interest to linguistic anthropologists and sociolinguists, particularly those working on small-scale multilingualism and pre-colonial multilingualism
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