Spectroscopic ellipsometric investigation of the clean and oxygen exposed Ni(110) surface

Dynamical ellipsometric investigations of the initial oxidation of the Ni(110) surface have been performed. Ellipsometry appears to be well suited to distinguish between chemisorbed oxygen and nickel oxide on the surface. Annealing at 740 K causes the nucleation of nickel oxide to proceed faster than at 570 K. After equal exposures however, the nucleation is slower with an oxygen pressure of 2 × 10−7 Torr than with a pressure of 1.3 × 10−8 Torr. Spectroscopic ellipsometric measurements (400–800 nm) have been performed on clean and oxygen-exposed (at saturation) Ni(110) surfaces. The complex dielectric function of the clean surface has been determined. To explain the results of the oxygen exposed surface a model is discussed — a surface layer with a thickness of 6 Å and a mixture of 90% NiO and 10% Ni — in which changes with substrate optical properties are taken into account

Density Functional approach to Nonlinear Rheology

We present a density functional based closure of the pair Smoluchowski equation for Brownian particles under shear flow. Given an equilibrium free energy functional as input the theory provides first-principles predictions for the flow-distorted pair correlation function and associated rheological quantities over a wide range of volume fractions and flow rates. Taking two-dimensional hard-disks under shear flow as an illustrative model we calculate the pair correlation function, viscosity and normal stress difference under both steady and start-up shear

Dynamical density functional theory analysis of the laning instability in sheared soft matter

Using dynamical density functional theory (DDFT) methods we investigate the laning instability of a sheared colloidal suspension. The nonequilibrium ordering at the laning transition is driven by non-affine particle motion arising from interparticle interactions. Starting from a DDFT which incorporates the non-affine motion, we perform a linear stability analysis that enables identification of the regions of parameter space where lanes form. We illustrate our general approach by applying it to a simple one-component fluid of soft penetrable particles

Lateglacial to Holocene relative sea-level changes in the Stykkishólmur area, Snæfellsnes peninsula, Iceland

Until recently, relatively little scientific research has been undertaken to increase our understanding of relative sea-level (RSL) change in NW Iceland. This study presents the results of diatom, tephra and radiocarbon analyses on five isolation basin and two coastal lowland sediment cores from the Stykkishólmur area, northern Snæfellsnes. The analyses provide an accurate reconstruction of the postglacial RSL changes for the Snæfellsnes peninsula, through the generation of a RSL curve. In addition, the marine limit elevations established for northern Snæfellsnes allow the determination of areas of similar ice thickness within NW. Tephrochronological analyses from sediment cores have allowed the establishment of a potential signature for samples from the Snæfellsnes Volcanic Belt (SVB), as well as the determination of the extent of the Saksunarvatn tephra in Snæfellsnes and internal tephrostratigraphical correlations. In Snæfellsnes, the marine limit is measured at approximately 69 m above sea level, with its formation being estimated at ~ 14000 cal. yrs BP. Following the formation of the marine limit, the rate of RSL change was – 37 mm cal. yr-1 until the isolation of site Saurar 3 at 16.20 m asl in 12558 - 12646 cal. yrs BP, relating to a rate of crustal rebound of + 55 mm cal yr-1 over the same period. Following the isolation of Saurar 3, the rate of RSL fall reduced. During the mid- to late Holocene, RSL fell below present in northern Snæfellsnes, although poor chronological control means that this event can only be tentatively dated to~ 4800 cal. yrs BP. The results highlight the potential of isolation basin, coastal lowland and marine limit data in determining the RSL history for NW Iceland

Postglacial relative sea-level changes and the deglaciation of northwest Iceland

Iceland provides an important opportunity to investigate relative sea-level (RSL) changes and Last Glacial Maximum (LGM) glaciation in a sensitive area of the North Atlantic. This project employs new and existing RSL data, coupled with glacio-isostatic adjustment (GIA) modelling, to resolve the current debates surrounding the extent of the LGM Icelandic ice sheet (IIS). Robust understanding of the LGM IIS is important, because there are two markedly different maximum and minimum ice loading scenarios, with very different implications for global thermohaline circulation. Previous studies of glacial geomorphology and sedimentology have failed to differentiate between these scenarios. Reconstructing RSL changes in northwest Iceland can address this issue because the two LGM glaciation scenarios yield significantly contrasting RSL histories. Northwest Iceland is also an important location in which to determine Earth models for Iceland. In this study, a series of new sea-level index points (SLIPs) have been generated for northwest Iceland from isolation basin and coastal lowland sediment samples along two perpendicular transects. Diatom, tephrochronological and radiocarbon analyses have allowed the generation of new RSL curves for the region, showing higher marine limit elevations close to loading centres and differing influences of Younger Dryas ice re-advance. Mapping of the marine limit has shown differences in the pattern of deglaciation due to fjord width and morphology. The contrasting LGM glaciation scenarios have been tested using the GIA modelling, with the new and existing RSL dataset as a constraint. Both field data and GIA model outputs support the maximum glaciation hypothesis