SiC Nanowires Synthesized by Rapidly Heating a Mixture of SiO and Arc-Discharge Plasma Pretreated Carbon Black

SiC nanowires have been synthesized at 1,600 °C by using a simple and low-cost method in a high-frequency induction furnace. The commercial SiO powder and the arc-discharge plasma pretreated carbon black were mixed and used as the source materials. The heating-up and reaction time is less than half an hour. It was found that most of the nanowires have core-shell SiC/SiO2nanostructures. The nucleation, precipitation, and growth processes were discussed in terms of the oxide-assisted cluster-solid mechanism

A transient liquid-like phase in the displacement cascades of zircon, hafnon and thorite

The study of radiation effects in solids is important for the development of 'radiation-resistant' materials for fission-reactor applications'. The effects of heavy-ion irradiation in the isostructural orthosilicates zircon (ZrSiO4), hafnon (HfSiO4) and thorite (ThSiO4) are particularly important because these minerals are under active investigation for use as a waste form for plutonium-239 resulting from the dismantling of nuclear weapons(2-4). During ion irradiation, localized 'cascades' of displaced atoms can form as a result of ballistic collisions in the target material, and the temperature inside these regions may for a short time exceed the bulk melting temperature. Whether these cascades do indeed generate a localized liquid state(5-8) has, however, remained unclear. Here we investigate the irradiation-induced decomposition of zircon and hafnon, and find evidence for formation of a liquidlike state in the displacement cascades. Our results explain the frequent occurrence of ZrO2 in natural amorphous zircong(9-12) Moreover, we conclude that zircon-based nuclear waste forms should be maintained within strict temperature Limits, to avoid potentially detrimental irradiation-induced amorphization or phase decomposition of the zircon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62853/1/395056a0.pd

Engineering self-organising helium bubble lattices in tungsten

The self-organisation of void and gas bubbles in solids into a superlattices is an intriguing nanoscale phenomenon. Despite the discovery of these lattices 30 years ago, the atomistics behind the ordering mechanisms responsible for the formation of these nanostructures are yet to be fully elucidated. Here we report on the direct observation via transmission electron microscopy of the formation of bubble lattices under He+ ion bombardment. By careful control of the irradiation conditions, it has been possible to engineer the bubble size and spacing of the superlattice leading to important conclusions about the significance of vacancy supply in determining the physical characteristics of the system. Furthermore, no bubble lattice alignment was observed in the directions pointing to a key driving mechanism for the formation of these ordered nanostructures being the two-dimensional diffusion of self-interstitial atoms

The genetic interaction network of CCW12, a Saccharomyces cerevisiae gene required for cell wall integrity during budding and formation of mating projections

<p>Abstract</p> <p>Background</p> <p>Mannoproteins construct the outer cover of the fungal cell wall. The covalently linked cell wall protein Ccw12p is an abundant mannoprotein. It is considered as crucial structural cell wall component since in baker's yeast the lack of <it>CCW12 </it>results in severe cell wall damage and reduced mating efficiency.</p> <p>Results</p> <p>In order to explore the function of <it>CCW12</it>, we performed a Synthetic Genetic Analysis (SGA) and identified genes that are essential in the absence of <it>CCW12</it>. The resulting interaction network identified 21 genes involved in cell wall integrity, chitin synthesis, cell polarity, vesicular transport and endocytosis. Among those are <it>PFD1</it>, <it>WHI3</it>, <it>SRN2</it>, <it>PAC10</it>, <it>FEN1 </it>and <it>YDR417C</it>, which have not been related to cell wall integrity before. We correlated our results with genetic interaction networks of genes involved in glucan and chitin synthesis. A core of genes essential to maintain cell integrity in response to cell wall stress was identified. In addition, we performed a large-scale transcriptional analysis and compared the transcriptional changes observed in mutant <it>ccw12</it>Δ with transcriptomes from studies investigating responses to constitutive or acute cell wall damage. We identified a set of genes that are highly induced in the majority of the mutants/conditions and are directly related to the cell wall integrity pathway and cell wall compensatory responses. Among those are <it>BCK1</it>, <it>CHS3</it>, <it>EDE1</it>, <it>PFD1</it>, <it>SLT2 </it>and <it>SLA1 </it>that were also identified in the SGA. In contrast, a specific feature of mutant <it>ccw12</it>Δ is the transcriptional repression of genes involved in mating. Physiological experiments substantiate this finding. Further, we demonstrate that Ccw12p is present at the cell periphery and highly concentrated at the presumptive budding site, around the bud, at the septum and at the tip of the mating projection.</p> <p>Conclusions</p> <p>The combination of high throughput screenings, phenotypic analyses and localization studies provides new insight into the function of Ccw12p. A compensatory response, culminating in cell wall remodelling and transport/recycling pathways is required to buffer the loss of <it>CCW12</it>. Moreover, the enrichment of Ccw12p in bud, septum and mating projection is consistent with a role of Ccw12p in preserving cell wall integrity at sites of active growth.</p> <p>The microarray data produced in this analysis have been submitted to NCBI GEO database and GSE22649 record was assigned.</p

Atomistic Modeling of Radiation Damage in Metallic Alloys

International audienceThe primary damage in metallic alloys, i.e., the point defect distribution resulting from the interaction between an energetic particle and a metallic matrix has been investigated for more than 60 years using atomistic simulations. In this chapter, we present an overview of the techniques used as well as the results achieved so far to conclude on the open questions and future directions