The impact of the 1783-1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei

The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm<sup>−3</sup> at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions

Energy Flow in Acoustic Black Holes

We present the results of an analysis of superradiant energy flow due to scalar fields incident on an acoustic black hole. In addition to providing independent confirmation of the recent results in [5], we determine in detail the profile of energy flow everywhere outside the horizon. We confirm explicitly that in a suitable frame the energy flow is inward at the horizon and outward at infinity, as expected on physical grounds.Comment: 8 pages, 9 figures, Comments added to discussion of energy flow and introductory section abbreviate

The One Loop Effective Super-Potential and Non-Holomorphicity

We calculate the Kahlerian and the lowest order non-Kahlerian contributions to the one loop effective superpotential using super-Feynman graphs in the massless Wess-Zumino Model, the massive Wess-Zumino Model and N=1, U(1) gauge theory. We also calculate the Kahlerian term in Yang-Mills Theory for a general gauge group. Using this latter result we find the one loop Kahlerian contribution for N=2 Yang-Mills Theory in terms of N=1 superfields and we show that it can only come from non-holomorphic contributions to the N=2 effective potential.Comment: LaTeX, 10 pages, 7 figures, uses bezier.sty and ifthen.sty. First amendment. The results are extended to include the Kahlerian term for a general renormalisable N=1 supersymmetric theory, containing Wess-Zumino and Yang-Mills multiplets with a cubic superpotential. One reference has been changed and one has been added. Second amendment. One acknowledgment has been altered in the `note added in proof

Divergence in Dialogue

Copyright: 2014 Healey et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This work was supported by the Economic and Social Research Council (ESRC; http://www.esrc.ac.uk/) through the DynDial project (Dynamics of Conversational Dialogue, RES-062-23-0962) and the Engineering and Physical Sciences Research Council (EPSRC; http://www.epsrc.ac.uk/) through the RISER project (Robust Incremental Semantic Resources for Dialogue, EP/J010383/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Strengthening Indigenous Social Work in the Academy

This paper provides an account of the development of an Indigenous Social Work program in Sudbury, Ontario and how it was conceived, developed and implemented. It describes the transformational approaches that Aboriginal faculty, communities and academic allies engaged in to create a rightful space for Indigenous social work in mainstream academia. In its 25th year, this program has provided many transformational opportunities for students, faculty and Aboriginal communities. Incorporating resistance and proactive momentum, the program has become pivotal in expanding the visibility and legitimacy for Indigenous social work in practice, theory, research and pedagogies. This program is an example of how community-faculty collaborations can sustain a robust Indigenous social work program

Spiral Structure Based Limits on the Disk Mass of the Low Surface Brightness Galaxies UGC 6614 and F568-6

Upper limits for the disk mass-to-light ratios for the low surface brightness galaxies UGC 6614 and F568-6 (Malin 2) are estimated by considering the minimum velocity perturbations in the HI velocity field that should result from the spiral structure observed in the R band images. The weak observed response in the $\phi$ velocity component limits the mass-to-light ratios of the disk within a scale length to M/L <~ 3 and 6 for UGC 6614 for F568-6 respectively (in solar units) based upon azimuthal variations observed in the R band images. These limits are sufficiently strong to require a significant dark matter component even in the central regions of these galaxies. Our limits furthermore imply that this dark matter component cannot be in the form of a cold disk since a cold disk would necessarily be involved in the spiral structure. However, a more massive disk could be consistent with the observations because of a non-linear gas response or if the gas is driven by bar-like distortions instead of spiral structure. To produce the large observed arm/interarm HI density variations it is likely that the spiral arm potential perturbation is sufficiently strong to produce shocks in the gas. For a forcing that is greater than 2% of the axisymmetric force, M/L >~ 1 is required in both galaxies in the outer regions. These lower limits imply that the stellar surface density is at least of the same order as the gas surface density. This is consistent with the large scale morphology of the spiral structure, and the stability of the gas disk, both which suggest that a moderate stellar component is required to produce the observed spiral structure. (Shortened abstract)Comment: AAS Latex, Postscript and jpeg Figures, Accepted for publication in A