Split-off dimer defects on the Si(001)2x1 surface

Dimer vacancy (DV) defect complexes in the Si(001)2x1 surface were investigated using high-resolution scanning tunneling microscopy and first principles calculations. We find that under low bias filled-state tunneling conditions, isolated 'split-off' dimers in these defect complexes are imaged as pairs of protrusions while the surrounding Si surface dimers appear as the usual 'bean-shaped' protrusions. We attribute this to the formation of pi-bonds between the two atoms of the split-off dimer and second layer atoms, and present charge density plots to support this assignment. We observe a local brightness enhancement due to strain for different DV complexes and provide the first experimental confirmation of an earlier prediction that the 1+2-DV induces less surface strain than other DV complexes. Finally, we present a previously unreported triangular shaped split-off dimer defect complex that exists at SB-type step edges, and propose a structure for this defect involving a bound Si monomer.Comment: 8 pages, 7 figures, submitted to Phys. Rev.

Reconceptualising adaptation to climate change as part of pathways of change and response

The need to adapt to climate change is now widely recognised as evidence of its impacts on social and natural systems grows and greenhouse gas emissions continue unabated. Yet efforts to adapt to climate change, as reported in the literature over the last decade and in selected case studies, have not led to substantial rates of implementation of adaptation actions despite substantial investments in adaptation science. Moreover, implemented actions have been mostly incremental and focused on proximate causes; there are far fewer reports of more systemic or transformative actions. We found that the nature and effectiveness of responses was strongly influenced by framing. Recent decision-oriented approaches that aim to overcome this situation are framed within a "pathways" metaphor to emphasise the need for robust decision making within adaptive processes in the face of uncertainty and inter-temporal complexity. However, to date, such "adaptation pathways" approaches have mostly focused on contexts with clearly identified decision-makers and unambiguous goals; as a result, they generally assume prevailing governance regimes are conducive for adaptation and hence constrain responses to proximate causes of vulnerability. In this paper, we explore a broader conceptualisation of "adaptation pathways" that draws on 'pathways thinking' in the sustainable development domain to consider the implications of path dependency, interactions between adaptation plans, vested interests and global change, and situations where values, interests, or institutions constrain societal responses to change. This re-conceptualisation of adaptation pathways aims to inform decision makers about integrating incremental actions on proximate causes with the transformative aspects of societal change. Case studies illustrate what this might entail. The paper ends with a call for further exploration of theory, methods and procedures to operationalise this broader conceptualisation of adaptation

Hydrophobic and ionic-interactions in bulk and confined water with implications for collapse and folding of proteins

Water and water-mediated interactions determine thermodynamic and kinetics of protein folding, protein aggregation and self-assembly in confined spaces. To obtain insights into the role of water in the context of folding problems, we describe computer simulations of a few related model systems. The dynamics of collapse of eicosane shows that upon expulsion of water the linear hydrocarbon chain adopts an ordered helical hairpin structure with 1.5 turns. The structure of dimer of eicosane molecules has two well ordered helical hairpins that are stacked perpendicular to each other. As a prelude to studying folding in confined spaces we used simulations to understand changes in hydrophobic and ionic interactions in nano droplets. Solvation of hydrophobic and charged species change drastically in nano water droplets. Hydrophobic species are localized at the boundary. The tendency of ions to be at the boundary where water density is low increases as the charge density decreases. Interaction between hydrophobic, polar, and charged residue are also profoundly altered in confined spaces. Using the results of computer simulations and accounting for loss of chain entropy upon confinement we argue and then demonstrate, using simulations in explicit water, that ordered states of generic amphiphilic peptide sequences should be stabilized in cylindrical nanopores

Snipe taxonomy based on vocal and non-vocal sound displays: the South American Snipe is two species

We analysed breeding sounds of the two subspecies of South American Snipe Gallinago paraguaiae paraguaiae and Gallinago paraguaiae magellanica to determine whether they might be different species: loud vocalizations given on the ground, and the tail‐generated Winnow given in aerial display. Sounds of the two taxa differ qualitatively and quantitatively. Both taxa utter two types of ground call. In G. p. paraguaiae, the calls are bouts of identical sound elements repeated rhythmically and slowly (about five elements per second (Hz)) or rapidly (about 11 Hz). One call of G. p. magellanica is qualitatively similar to those of G. p. paraguaiae but sound elements are repeated more slowly (about 3 Hz). However, its other call type differs strikingly: it is a bout of rhythmically repeated sound couplets, each containing two kinds of sound element. The Winnow of G. p. paraguaiae is a series of sound elements that gradually increase in duration and energy; by contrast, that of G. p. magellanica has two or more kinds of sound element that roughly alternate and are repeated as sets, imparting a stuttering quality. Sounds of the related Puna Snipe (Gallinago andina) resemble but differ quantitatively from those of G. p. paraguaiae. Differences in breeding sounds of G. p. paraguaiae and G. p. magellanica are strong and hold throughout their geographical range. Therefore we suggest that the two taxa be considered different species: G. paraguaiae east of the Andes in much of South America except Patagonia, and G. magellanica in central and southern Chile, Argentina east of the Andes across Patagonia, and Falklands/Malvinas.Fil: Miller, Edward H.. Memorial University Of Newfoundland; CanadáFil: Areta, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Jaramillo, Alvaro. San Francisco Bay Bird Observatory; Estados UnidosFil: Imberti, Santiago. Asociación Ambiente Sur, Rio Gallegos; ArgentinaFil: Matus, Ricardo. Kilómetro 7 Sur; Chil

Hepatitis B virus and hepatitis D virus infection in women with or at risk for HIV infection in the United States

Hepatitis D virus (HDV) requires co-infection with hepatitis B virus (HBV). Human immunodeficiency virus (HIV) shares transmission routes with these viruses. Among 4,932 US women infected with or at-risk for HIV during 1994–2015, HBV surface antigen (HBsAg) positivity was more common in women with HIV (2.8% vs. 1.2%; p = 0.001); HDV was more common among participants enrolled during 2013–2015 (p = 0.0004) and those with resolved rather than active hepatitis C (1.9% vs. 0.5%; p = 0.02). Among HBsAg-positive women (n = 117), HDV antibody prevalence was 22% and did not vary by HIV status; HDV infection was associated with the presence of advanced fibrosis/cirrhosis at enrollment (adjusted odds ratio, 5.70; 95% confidence interval, 1.46–22.29). Our results demonstrate the importance of HDV testing in HBV-infected US women

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

Reflexive adaptation for resilient water services: lessons for theory and practice

‘Adaptive management’ concern attempts to manage complex social-ecological and socio-technical systems in nimble ways to enhance their resilience. In this paper, three forms of adaptive management are identified, ‘scientific’ forms focused on collation of scientific data in response to management experiments, but more recent developments adding processes of collaboration as well as emphasising the need for reflexivity, that is, conscious processes of opening up debates to different perspectives and values. While reflexive adaptive management has been increasingly discussed in theory, there is a lack of examples of what its application means in practice. As a response, this paper examines an ‘Adaptive Planning Process’ (APP), seeking to apply reflexive adaptive management as a means to improve climate resilience in the UK water sector. The APP’s three inter linked workshops – Aspiration, Scenario and Roadmapping – were co-developed and trialled in a water utility. By describing and justifying the choices made in the development of the APP, the paper aims to reveal some of the challenges that arise when trying to design processes that achieve reflexive adaptation. The paper concludes that, if applied to planning for climate change, reflexive adaptation has the potential to explore multiple value positions, highlight different potential futures and acknowledge (and hence, partly address) power differentials, and therefore to offer the possibility of real change. On the basis of the trial, we argue that through tapping the depth and breadth of internal knowledge the APP process created the potential for decision making to be joined up across different parts of the utility, and hence offering new strategies and routes for addressing uncertainties and delivering more resilient water services