The use of webcams to monitor the prolonged autumn attendance of guillemots on the Isle of May in 2015

Although Guillemots at the southern edge of the range are known to return to the colonies in autumn, usually only opportunistic observations of this behaviour are available. In the autumn of 2015 we took advantage of the live interactive cameras on the Isle of May, Fife to make systematic checks of Guillemot colony attendance. Birds were recorded at dawn on 59 consecutive mornings between 23 October and 20 December after which webcam images ceased due to lack of power on the island. This prolonged period of attendance covered several periods of stormy weather and appears unprecedented at this colony. Presumably local feeding conditions must have been extremely favourable to enable the birds to spend so much time ashore

The status of the gannet in Scotland in 2013-14

All 16 Gannet colonies in Scotland were counted in 2013–14. Combined colony totals indicated that Scotland currently holds 243,505 apparently occupied sites (58% and 46% of the east Atlantic and world populations, respectively). Numbers were divided very unevenly between the colonies with Bass Rock (now the world’s largest colony), St Kilda and Ailsa Craig together holding 70% of the Scottish population. Gannets started to nest on Barra Head, Berneray in 2007 and breeding may now be regular on Rockall. Numbers at St Kilda, Sule Stack and Scar Rocks were stable, but all other colonies had increased, some spectacularly. Overall the Scottish population increased by 33% between 2003–04 and 2013–14 at an average rate of increase of 2.9% per annum. Although the Gannet appears less vulnerable to climate change than many other UK seabirds, the proposed construction of major offshore wind farms close to colonies in the North Sea and the imminent ban on fishery discards, could pose future threats to this species

Gannet surveys in north-west Scotland in 2013

A photographic survey of the Gannet colonies off the north-west coast of Scotland in 2013 found 60,290 Apparently Occupied Sites (AOS) on St Kilda, 11,230 AOS on Sula Sgeir, 5,280 AOS on the Flannan Islands, 4,550 AOS on Sule Stack and 1,870 AOS on Sule Skerry. Since 2004, numbers had increased rapidly at Sule Skerry and the Flannan Islands (47.4% per annum (pa) and 7.5% pa respectively), but had changed little at Sule Stack and St Kilda. The harvested colony on Sula Sgeir increased by 2.2% pa, reversing the trend over the previous 10 years during which the population declined at 1.2% pa

Dome growth, collapse, and valley fill at Soufrière Hills Volcano, Montserrat, from 1995 to 2013: Contributions from satellite radar measurements of topographic change

Frequent high-resolution measurements of topography at active volcanoes can provide important information for assessing the distribution and rate of emplacement of volcanic deposits and their influence on hazard. At dome-building volcanoes, monitoring techniques such as LiDAR and photogrammetry often provide a limited view of the area affected by the eruption. Here, we show the ability of satellite radar observations to image the lava dome and pyroclastic density current deposits that resulted from 15 years of eruptive activity at Soufrière Hills Volcano, Montserrat, from 1995 to 2010. We present the first geodetic measurements of the complete subaerial deposition field on Montserrat, including the lava dome. Synthetic aperture radar observations from the Advanced Land Observation Satellite (ALOS) and TanDEM-X mission are used to map the distribution and magnitude of elevation changes. We estimate a net dense-rock equivalent volume increase of 108 ± 15M m3 of the lava dome and 300 ± 220M m3 of talus and subaerial pyroclastic density current deposits. We also show variations in deposit distribution during different phases of the eruption, with greatest on-land deposition to the south and west, from 1995 to 2005, and the thickest deposits to the west and north after 2005. We conclude by assessing the potential of using radar-derived topographic measurements as a tool for monitoring and hazard assessment during eruptions at dome-building volcanoes

On the nature of progress

15th International Conference, OPODIS 2011, Toulouse, France, December 13-16, 2011. ProceedingsWe identify a simple relationship that unifies seemingly unrelated progress conditions ranging from the deadlock-free and starvation-free properties common to lock-based systems, to non-blocking conditions such as obstruction-freedom, lock-freedom, and wait-freedom. Properties can be classified along two dimensions based on the demands they make on the operating system scheduler. A gap in the classification reveals a new non-blocking progress condition, weaker than obstruction-freedom, which we call clash-freedom. The classification provides an intuitively-appealing explanation why programmers continue to devise data structures that mix both blocking and non-blocking progress conditions. It also explains why the wait-free property is a natural basis for the consensus hierarchy: a theory of shared-memory computation requires an independent progress condition, not one that makes demands of the operating system scheduler

On the magnetic stability at the surface in strongly correlated electron systems

The stability of ferromagnetism at the surface at finite temperatures is investigated within the strongly correlated Hubbard model on a semi-infinite lattice. Due to the reduced surface coordination number the effective Coulomb correlation is enhanced at the surface compared to the bulk. Therefore, within the well-known Stoner-picture of band ferromagnetism one would expect the magnetic stability at the surface to be enhanced as well. However, by taking electron correlations into account well beyond the Hartree-Fock (Stoner) level we find the opposite behavior: As a function of temperature the magnetization of the surface layer decreases faster than in the bulk. By varying the hopping integral within the surface layer this behavior becomes even more pronounced. A reduced hopping integral at the surface tends to destabilize surface ferromagnetism whereas the magnetic stability gets enhanced by an increased hopping integral. This behavior represents a pure correlation effect and can be understood in terms of general arguments which are based on exact results in the limit of strong Coulomb interaction.Comment: 6 pages, RevTeX, 4 eps figures, accepted (Phys. Rev. B), for related work and info see http://orion.physik.hu-berlin.d

A Study of the S=1/2 Alternating Chain using Multiprecision Methods

In this paper we present results for the ground state and low-lying excitations of the $S=1/2$ alternating Heisenberg antiferromagnetic chain. Our more conventional techniques include perturbation theory about the dimer limit and numerical diagonalization of systems of up to 28 spins. A novel application of multiple precision numerical diagonalization allows us to determine analytical perturbation series to high order; the results found using this approach include ninth-order perturbation series for the ground state energy and one magnon gap, which were previously known only to third order. We also give the fifth-order dispersion relation and third-order exclusive neutron scattering structure factor for one-magnon modes and numerical and analytical binding energies of S=0 and S=1 two-magnon bound states.Comment: 16 pages, 9 figures. for submission to Phys.Rev.B. PICT files of figs available at http://csep2.phy.ornl.gov/theory_group/people/barnes/barnes.htm

Atomic layering at the liquid silicon surface: a first- principles simulation

We simulate the liquid silicon surface with first-principles molecular dynamics in a slab geometry. We find that the atom-density profile presents a pronounced layering, similar to those observed in low-temperature liquid metals like Ga and Hg. The depth-dependent pair correlation function shows that the effect originates from directional bonding of Si atoms at the surface, and propagates into the bulk. The layering has no major effects in the electronic and dynamical properties of the system, that are very similar to those of bulk liquid Si. To our knowledge, this is the first study of a liquid surface by first-principles molecular dynamics.Comment: 4 pages, 4 figures, submitted to PR