Aging and Economic Security Evaluation: Crosscutting Lessons Learned

This evaluation of Atlantic's grantmaking to support the economic security of low-income elders identifies elements most likely to help advance a policy agenda when working in a politically charged environment: Use a state-by-state approach and target multiple levels of government to show incremental progress for national resultsInvest in research to create the foundation for effective advocacy and communications strategiesUse strategic communications to change the narrativeEnsure the voices of the grassroots are heard in policy debatesSupport for capacity building should focus on filling gaps needed to achieve a goal rather than trying to bolster weak organizationsWork still needs to be done after winning a change in policy to help ensure implementation of a "new normal"The evaluation examined five projects that comprised a multi-pronged effort to improve the financial resources of retired adults. Goals included boosting enrollment in an array of social safety net programs and protecting and strengthening retirement policies. To achieve their goals, grantees used a mix of research and data, advocacy, communications, grassroots training and mobilization.Over the course of their work, grantees connected elders to available benefits, promoted state-level reforms to retirement programs, changed the narrative on social security, and exposed the gap between the cost of living and actual elder incomes

Non-Markovian out-of-equilibrium dynamics: A general numerical procedure to construct time-dependent memory kernels for coarse-grained observables

We present a numerical method to compute non-equilibrium memory kernels based on experimental data or molecular dynamics simulations. The procedure uses a recasting of the non-stationary generalized Langevin equation, in which we expand the memory kernel in a series that can be reconstructed iteratively. Each term in the series can be computed based solely on knowledge of the two-time auto-correlation function of the observable of interest. As a proof of principle, we apply the method to crystallization from a super-cooled Lennard Jones melt. We analyze the nucleation and growth dynamics of crystallites and observe that the memory kernel has a time extent that is about one order of magnitude larger than the typical timescale needed for a particle to be attached to the crystallite in the growth regime

Reconsidering the structure of nucleation theories

We discuss the structure of the equation of motion that governs nucleation processes at first order phase transitions. From the underlying microscopic dynamics of a nucleating system, we derive by means of a non-equilibrium projection operator formalism the equation of motion for the size distribution of the nuclei. The equation is exact, i.e. the derivation does not contain approximations. To assess the impact of memory, we express the equation of motion in a form that allows for direct comparison to the Markovian limit. As a numerical test, we have simulated crystal nucleation from a supersaturated melt of particles interacting via a Lennard-Jones potential. The simulation data show effects of non-Markovian dynamics

Extending the sample of core-collapse supernovae for searches of axion-like-particle induced gamma-ray bursts with the Fermi LAT

During a core-collapse supernova (SN), axion-like particles (ALPs) could be produced through the Primakoff process and subsequently convert into gamma rays in the magnetic field of the Milky Way. Using a sample of well studied extragalactic SNe at optical wavelengths, we estimate the time of the core collapse and search for a coincident gamma-ray burst with the Fermi Large Area Telescope (LAT). Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings within a factor of $\sim$5 of previous limits from SN1987A. With the increasing number of SNe observed with optical surveys, our results demonstrate the potential to probe ALP dark matter with combined optical and gamma-ray observations. We also provide preliminary results for the estimation of explosion times of 15 close-by SNe observed recently with ZTF. Our findings show that the explosion time can be estimated within one day (statistical uncertainty only) making them promising targets for a follow-up LAT analysis.Comment: Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021

Search for Axionlike-Particle-Induced Prompt Gamma-Ray Emission from Extragalactic Core-Collapse Supernovae with the Fermi Large Area Telescope

During a core-collapse supernova (SN), axionlike particles (ALPs) could be produced through the Primakoff process and subsequently convert into $\gamma$ rays in the magnetic field of the Milky Way. We do not find evidence for such a $\gamma$-ray burst in observations of extragalactic SNe with the Fermi Large Area Telescope (LAT). The SN explosion times are estimated from optical light curves and we find a probability of about $\sim$90% that the LAT observed at least one SN at the time of the core collapse. Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings $\gtrsim 2.6\times10^{-11}$GeV$^{-1}$ for ALP masses $m_a \lesssim 3\times 10^{-10}$ eV, within a factor of $\sim 5$ of previous limits from SN1987A.Comment: Published in Physical Review Letters. Includes Supplemental Material. 8+18 pages. Updated version fixes bug that overestimated the ALP flux. Constraints and conclusions have been updated (erratum is published). Version fixes typos in ArXiv versio

A mono-implicit Runge-Kutta-Nyström modification of the Numerov method

We present two two-parameter families of fourth-order mono-implicit Runge-Kutta-Nystrom methods. Each member of these families can be considered as a modification of the Numerov method. We analyze the stability and periodicity properties of these methods. It is shown that (i) within one of these families there exist A-stable (even L-stable) and P-stable methods, and (ii) in both families there exist methods with a phase lag of order six

Memory effects in the Fermi-Pasta-Ulam Model

We study the Intermediate Scattering Function (ISF) of the strongly-nonlinear Fermi-Pasta Ulam Model at thermal equilibrium, using both numerical and analytical methods. From the molecular dynamics simulations we distinguish two limit regimes, as the system behaves as an ideal gas at high temperature and as a harmonic chain for low excitations. At intermediate temperatures the ISF relaxes to equilibrium in a nontrivial fashion. We then calculate analytically the Taylor coefficients of the ISF to arbitrarily high orders (the specific, simple shape of the two-body interaction allows us to derive an iterative scheme for these.) The results of the recursion are in good agreement with the numerical ones. Via an estimate of the complete series expansion of the scattering function, we can reconstruct within a certain temperature range its coarse-grained dynamics. This is governed by a memory-dependent Generalized Langevin Equation (GLE), which can be derived via projection operator techniques. Moreover, by analyzing the first series coefficients of the ISF, we can extract a parameter associated to the strength of the memory effects in the dynamics

Percolation in suspensions of polydisperse hard rods : quasi-universality and finite-size effects

We present a study of connectivity percolation in suspensions of hard spherocylinders by means of Monte Carlo simulation and connectedness percolation theory. We focus attention on polydispersity in the length, the diameter and the connectedness criterion, and invoke bimodal, Gaussian and Weibull distributions for these. The main finding from our simulations is that the percolation threshold shows quasi universal behaviour, i.e., to a good approximation it depends only on certain cumulants of the full size and connectivity distribution. Our connectedness percolation theory hinges on a Lee-Parsons type of closure recently put forward that improves upon the often-used second virial approximation [ArXiv e-prints, May 2015, 1505.07660]. The theory predicts exact universality. Theory and simulation agree quantitatively for aspect ratios in excess of 20, if we include the connectivity range in our definition of the aspect ratio of the particles. We further discuss the mechanism of cluster growth that, remarkably, differs between systems that are polydisperse in length and in width, and exhibits non-universal aspects.Comment: 7 figure

Agrobacterium tumefaciens-mediated transformation of Fusarium oxysporum f. sp. cubense for pathogenicity gene analysis

Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive plant diseases in recorded history. The disease was first discovered in Australia in 1874 but became renowned for the severe losses it caused to export banana plantations during the 1960s in Central America. The banana export industry was saved only by replacing Gros Michel bananas, the dessert banana grown for the export market, with highly resistant Cavendish banana cultivars. Despite this apparent solution, the fungus was found to attack Cavendish bananas in the sub-tropics, where plants were believed to be predisposed to the disease by the cool winter climate. Good management practices and conventional disease management strategies have not been sufficient to reduce losses and stop the disease from spreading, and today Fusarium wilt can be found in almost all banana-producing countries of the world. Since 1988, Foc has been responsible for significant losses of Cavendish bananas in tropical Asia. The only sustainable control measure, the use of resistant varieties, is not always popular as people prefer to eat locally adopted varieties that, unfortunately, are susceptible to Foc. Sustainable Fusarium wilt management in banana depends on the improvement of existing banana cultivars or the development of novel disease management strategies. Molecular biology and biotechnology provide opportunities to introduce foreign resistance genes into existing cultivars and to develop new, environmentally friendly products that can protect susceptible bananas from Foc. Better knowledge of the Fusarium wilt pathogen, its diversity, and its mechanisms of pathogenesis will contribute significantly to developing these novel approaches for control of the disease. Molecular information on the pathogenicity of Foc, however, is limited, whereas other formae speciales of F. oxysporum have been better studied. In this thesis, Agrobacterium tumefaciens-mediated transformation of (ATMT) was employed to investigate genes responsible for pathogenicity of Foc to banana. Chapter 1 provides an overview of pathogenicity in F. oxysporum. Pathogenic and non-pathogenic forms of the fungus are first introduced to the reader, and then the biology, epidemiology and etiology of pathogenic forms of F. oxysporum are discussed. The genetic make-up and ability of the Fusarium wilt fungus to cause disease in plants concludes the first part of the review. In recent years, there has been a noted increase in the number of techniques available to study hostpathogen interactions. The second part of the review concentrates on these techniques and their applications in studying pathogenicity of the Fusarium wilt pathogen. In Chapter 2, an ATMT and screening system for Foc was developed. Five A. tumefaciens strains were evaluated for their efficiency to transform Foc with a randomly integrating vector that confers hygromycin B resistance and expression of green fluorescent protein (GFP). A small insertion mutant library of Foc was created, and a subset of transformants was characterized by determining the number of T-DNA inserts present, the location and identity of predicted genes disrupted by T-DNA insertion, and whether transformants of Foc were altered in their virulence against susceptible banana plants. In Chapter 3, the role of a known pathogenicity gene, Frp1, of the tomato pathogen F. oxysporum f. sp. lycopersici (Fol) was investigated in Foc. The first objective was to isolate and characterize the Frp1 gene in Foc, and to compare it to the homologous gene in Fol. A vector containing a modified Fol Frp1 gene was then obtained and used for targeted disruption of the gene in Foc via ATMT. Mutants in which the Frp1 gene was disrupted were then analyzed for GFP expression, culture morphology, and alterations in pathogenicity to banana.Dissertation (MSc)--University of Pretoria, 2008.Microbiology and Plant Pathologyunrestricte