Neutron Ionization of Helium near the Neutron-Alpha Particle Collision Resonance

Neutron-impact single and double ionization cross sections of the He atom are calculated near the neutron-alpha particle collision resonance. Calculations using the time-dependent close-coupling method for total and differential cross sections are made at 8 incident neutron energies ranging from 250 to 2000 keV. At the resonance energy peak the double ionization cross sections unexpectedly become larger than the single ionization cross sections. This finding appears to be related to the high velocity of the recoiling alpha particle, which makes it unlikely that the atomic electrons can recombine with the alpha particle nucleus, enhancing the double ionization cross section.Peer ReviewedPostprint (author's final draft

BUDGET PERSPECTIVES 2016, PAPER 1. Exploring Tax and Welfare Options. June 2015

Budgetary policies on income-related taxes and welfare must find a balance between providing income support to those in need and maintaining a financial incentive to work which supports high employment. This paper focuses principally on the “cash” or “first round” impact of tax and welfare policy changes across the income distribution. Incentive issues are considered in Section 5 of this paper, and in a companion paper to this conference (Savage et al., 2015)

The Great Recession, Austerity and Inequality: Evidence from Ireland. ESRI WP499. April 2015

The advent of the Great Recession and the widespread adoption of fiscal austerity policies have heightened concern about inequality and its effects. We examine how the distribution of income in Ireland has evolved over the years 2008 to 2013, using data from the CSO’s Survey on Income and Living Conditions. Snapshots of the income distribution show that the greatest falls in income were for the bottom decile (poorest 10 per cent). Longitudinal analysis shows that these sharp falls were not due to decreasing income for those remaining in the bottom decile, but to falling income among those with somewhat higher incomes. Most of those falling into the bottom decile came from the bottom one third of the income distribution

BUDGET PERSPECTIVES 2016, PAPER 2. Making Work Pay More: Recent Initiatives. June 2015

This paper examines the financial incentives to work implicit in the Irish tax and benefit system, focusing in particular on incentives facing those who are unemployed and in receipt of Jobseeker’s Benefit or Jobseeker’s Assistance. The results, based on an analysis of current incomes, benefits and taxes, suggest that more than eight out of ten of these unemployed jobseekers would see their income increase by at least 40 per cent upon taking up employment. Fewer than 3 per cent of these individuals would, in the short-term, be financially better off not in work. The risk of facing weak financial incentives to work is higher for unemployed persons with a spouse and children, as the income support goal of the welfare system means that they tend to have higher welfare payments. However, even among that group, fewer than 1 in 15 would be financially better off not working. Our analysis shows that a recent policy initiative, the Back to Work Family Dividend, announced in Budget 2015, clearly improves the immediate financial incentives to work for this group

The hypoxic tissue microenvironment as a driver of mucosal inflammatory resolution

On the backdrop of all acute inflammatory processes lies the activation of the resolution response. Recent years have witnessed an emerging interest in defining molecular factors that influence the resolution of inflammation. A keystone feature of the mucosal inflammatory microenvironment is hypoxia. The gastrointestinal tract, particularly the colon, exists in a state of physiological hypoxia and during active inflammation, this hypoxic state is enhanced as a result of infiltrating leukocyte oxygen consumption and the activation of oxygen consuming enzymes. Most evidence suggests that mucosal hypoxia promotes the active resolution of inflammation through a variety of mechanisms, including extracellular acidification, purine biosynthesis/salvage, the generation of specialized pro-resolving lipid mediators (ie. resolvins) and altered chemokine/cytokine expression. It is now appreciated that infiltrating innate immune cells (neutrophils, eosinophils, macrophages) have an important role in molding the tissue microenvironment to program an active resolution response. Structural or functional dysregulation of this inflammatory microenvironment can result in the loss of tissue homeostasis and ultimately progression toward chronicity. In this review, we will discuss how inflammatory hypoxia drives mucosal inflammatory resolution and its impact on other microenvironmental factors that influence resolution

Inland dunes on the abandoned bed of Glacial Lake Chicago indicate eolian activity during the Pleistocene-Holocene transition, southwestern Michigan, USA

Inland dune fields have recently emerged as a source of data for reconstructing paleoenvironments and climate in the western Great Lakes region of North America during the Pleistocene-Holocene transition. We employ optically stimulated luminescence (OSL) methods, radiocarbon ages, soils, and landform relationships to determine the age of inland dunes in Ottawa County, Michigan. These dunes rest on the abandoned bed of Glacial Lake Chicago, which is thought to have been exposed after ~13.6 ka. OSL analyses from two inland dunes yield ages ranging from 13.3±1.1 to 11.6±0.9 ka (uncertainty = 2 σ). Fine sand in the parabolic dunes suggests deflation of exposed glaciolacustrine nearshore sand by northwesterly and westerly winds. These new data add to a growing number of studies that demonstrate widespread eolian activity in the western Great Lakes region during the Pleistocene-Holocene transition. OSL ages from dune fields in the western Great Lakes indicate peak eolian activity and dune stabilization occurred during or following the Younger Dryas and Preboreal events. Northwesterly and westerly winds suggest the limited effect of hypothesized easterly anticyclonic winds during the Pleistocene-Holocene transition. Rapidly changing climate and newly deglaciated surfaces provided an ideal environment for dune formation

Treatment of Ion-Atom Collisions using a Partial-Wave Expansion of the Projectile Wavefunction

We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge scattering quantities. Here we show that such calculations are possible using modern high-performance computing. We demonstrate the utility of our method by examining elastic scattering of protons by hydrogen and helium atoms, problems familiar to undergraduate students of atomic scattering. Application to ionization of helium using partial-wave expansions of the projectile wavefunction, which has long been desirable in heavy-ion collision physics, is thus quite feasible

Compact acceleration of energetic neutral atoms using high intensity laser-solid interaction

Recent advances in high-intensity laser-produced plasmas have demonstrated their potential as compact charge particle accelerators. Unlike conventional accelerators, transient quasi-static charge separation acceleration fields in laser produced plasmas are highly localized and orders of magnitude larger. Manipulating these ion accelerators, to convert the fast ions to neutral atoms with little change in momentum, transform these to a bright source of MeV atoms. The emittance of the neutral atom beam would be similar to that expected for an ion beam. Since intense laser-produced plasmas have been demonstrated to produce high-brightness-low-emittance beams, it is possible to envisage generation of high-flux, low-emittance, high energy neutral atom beams in length scales of less than a millimeter. Here, we show a scheme where more than 80% of the fast ions are reduced to energetic neutral atoms and demonstrate the feasibility of a high energy neutral atom accelerator that could significantly impact applications in neutral atom lithography and diagnostics