An in situ transmission electron microscopy study of the ion irradiation induced amorphisation of silicon by He and Xe

Transmission electron microscopy with in situ ion irradiation has been used to examine the ionbeam-induced amorphisation of crystalline silicon under irradiation with light (He) and heavy (Xe) ions at room temperature. Analysis of the electron diffraction data reveal the heterogeneous amorphisation mechanism to be dominant in both cases. The differences in the amorphisation curves are discussed in terms of intra-cascade dynamic recovery, and the role of electronic and nuclear loss mechanisms

Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure

Effect of He implantation on the microstructure of zircaloy-4 studied using in situ TEM

Highlights • Differences in the evolution of α and βZr microstructures under 6 keV He ion implantation have been analysed as a function of irradiation dose and temperature using in situ TEM. • Both thermal and irradiation stabilities of Zr hydrides particles were studied and were found to dissolve with increasing fluence. • It is suggested that the combination of two different mass-transport mechanisms for He in zircaloy-4 play a major rule in the Zr hydride irradiation-induced dissolution. • He bubble lattices were observed to form during irradiation at 473 K and 1148 K in both crystalline phases, α and βZr, at around the same fluence of 1.7×10^17 ions⋅cm−2 (3.2 dpa)

Changes in landscape and vegetation of coastal dunes in northwest Europe: a review

In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated with geomorphological stability. The historical development of dune woodland during these stable phases has been documented for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state. During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of stable, senescent dunes is an important challenge for dune management

Study of carbon nitride compounds synthesised by co-implantation of 13C and 14N in copper at different temperatures

Carbon nitride compounds have been synthesised in copper by simultaneous high fluence (1018 at. cm−2) implantation of 13C and 14N ions. During the implantation process, the substrate temperature was maintained at 25, 250, 350 or 450 °C. Depth profiles of 13C and 14N were determined using the non-resonant nuclear reactions (NRA) induced by a 1.05 MeV deuteron beam. The retained doses were deduced from NRA measurements and compared to the implanted fluence. The chemical bonds between carbon and nitrogen were studied as a function of depth and temperature by X-ray photoelectron spectroscopy (XPS). The curve fitting of C 1s and N 1s core level photoelectron spectra reveal different types of C–N bonds and show the signature of N2 molecules. The presence of nitrogen gas bubbles in copper was highlighted by mass spectroscopy. The structure of carbon nitride compounds was characterised by transmission electron microscopy (TEM). For that purpose, cross-sectional samples were prepared using a focused ion beam (FIB) system. TEM observations showed the presence of small amorphous carbon nitride “nano-capsules” and large gas bubbles in copper. Based on our observations, we propose a model for the growth of these nano-objects. Finally, the mechanical properties of the implanted samples were investigated by nano-indentation

The Impact of Gender and Department Climate on Job Satisfaction and Intentions to Quit for Faculty in Science and Engineering Fields

This study investigates whether gender and the perceptions of department climate affects faculty job satisfaction and intentions to quit (work outcomes) with surveys responses from 308 faculty members in science and engineering fields. The study finds that both gender and department climate are related to work outcomes and that two facets of department climate (affective and instrumental) mediate the relationship between gender and both job satisfaction and intention to quit. This finding suggests that universities can benefit from improving department climate, which then may improve the retention of both male and female faculty, but may have an even greater impact on improving job satisfaction and reducing intentions to quit of female faculty. Copyright Springer Science + Business Media, Inc. 2006gender, climate, work outcomes, regression and/or mediation analysis, faculty, D23, M14, I20, C42,