Star formation triggered by non-head-on cloud-cloud collisions, and clouds with pre-collision sub-structure

In an earlier paper, we used smoothed particle hydrodynamics (SPH) simulations to explore star formation triggered by head-on collisions between uniform-density 500 M clouds, and showed that there is a critical collision velocity, vCRIT. At collision velocities below vCRIT, a hub-and-spoke mode operates and delivers a monolithic cluster with a broad mass function, including massive stars (M 10 M) formed by competitive accretion. At collision velocities above vCRIT, a spider’s-web mode operates and delivers a loose distribution of small sub-clusters with a relatively narrow mass function and no massive stars. Here we show that,if the head-on assumption is relaxed, vCRIT is reduced. However, if the uniform-density assumption is also relaxed, the collision velocity becomes somewhat less critical: a low collision velocity is still needed to produce a global hub-and-spoke system and a monolithic cluster, but, even at high velocities, large cores – capable of supporting competitive accretion and thereby producing massive stars – can be produced. We conclude that cloud–cloud collisions may be a viable mechanism for forming massive stars – and we show that this might even be the major channel for forming massive stars in the Galaxy

Direct nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation

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The Kirkendall effect and nanoscience: hollow nanospheres and nanotubes

Hollow nanostructures are ranked among the top materials for applications in various modern technological areas including energy storage devices, catalyst, optics and sensors. The last years have witnessed increasing interest in the Kirkendall effect as a versatile route to fabricate hollow nanostructures with different shapes, compositions and functionalities. Although the conversion chemistry of nanostructures from solid to hollow has reached a very advanced maturity, there is still much to be discovered and learned on this effect. Here, the recent progress on the use of the Kirkendall effect to synthesize hollow nanospheres and nanotubes is reviewed with a special emphasis on the fundamental mechanisms occurring during such a conversion process. The discussion includes the oxidation of metal nanostructures (i.e., nanospheres and nanowires), which is an important process involving the Kirkendall effect. For nanospheres, the symmetrical and the asymmetrical mechanisms are both reviewed and compared on the basis of recent reports in the literature. For nanotubes, in addition to a summary of the conversion processes, the unusual effects observed in some particular cases (e.g., formation of segmented or bamboo-like nanotubes) are summarized and discussed. Finally, we conclude with a summary, where the prospective future direction of this research field is discussed

Interface Engineering in CuInSe 2 Solar Cells Using Ammonium Sulfide Vapors

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Sponge-like carbon thin films: The dealloying concept applied to copper/carbon nanocomposite

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Impact of the morphology and composition on the dealloying process of co-sputtered silver-aluminum alloy thin films

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Synthesis of nickel-filled carbon nanotubes at 350 degrees C

International audienceThe deposition of nickel/amorphous carbon (Ni/a-C) films by a hybrid plasma process combining magnetron sputtering of a Ni target and plasma enhanced chemical vapor deposition using methane gas has been investigated. The formation of nickel nanowires encapsulated by a-C matrix has been demonstrated by transmission electron microscopy (TEM). The obtained nanowires array can be easily dispersed or can be simply converted to a Ni-filled CNTarray by annealing at 350 C as confirmed by TEM analysis. The developed fabrication method of Ni-filled CNT array is a low temperature technique compatible with substrates of low melting point

Effect of ammonium sulfide treatments on the surface properties of Cu 2 ZnSnSe 4 thin films

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Micro-sensors nano-functionalized for chemical detection

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