POPULATION AND THE ENVIRONMENT: FRAMEWORKS FOR ANALYSIS

This working paper is one of a series the EPAT/MUCIA Population and Environmental and Natural Resources team is producing. It examines major ways of thinking about the population-environment relationship over the past two centuries. The paper begins with Malthus and reviews developments to the present. Then it examines in detail six current frameworks or models for analyzing population-environment relationships. The six models include Bongaarts', Clark's, and Harrison's attempts to identify the relative impact of population growth on a limited number of forms of environmental degradation. It also examines the more complex Meadows, Meadows, and Randers WORLD3 dynamic model of the global system and International Institute of Applied Systems Analysis (IIASA) population-environment model now being applied to Mauritius. A basic finding of these models is that population growth can have a major impact on the environment. However, the impact is never simple and direct, and human organization always moderates its effect. Further, we cannot expect that slowing population growth will alleviate environmental pressures in the near term. Finally, achieving sustainable development will require a combined attack on population growth, consumption, and a variety of other human patterns of production.Resource /Energy Economics and Policy,

Planetary magnetospheres

A concise overview is presented of our understanding of planetary magnetospheres (and in particular, of that of the Earth), as of the end of 1981. Emphasis is placed on processes of astrophysical interest, e.g., on particle acceleration, collision-free shocks, particle motion, parallel electric fields, magnetic merging, substorms, and large scale plasma flows. The general morphology and topology of the Earth's magnetosphere are discussed, and important results are given about the magnetospheres of Jupiter, Saturn and Mercury, including those derived from the Voyager 1 and 2 missions and those related to Jupiter's satellite Io. About 160 references are cited, including many reviews from which additional details can be obtained

Modelling a Bistable System Strongly Coupled to a Debye Bath: A Quasiclassical Approach Based on the Generalised Langevin Equation

Bistable systems present two degenerate metastable configurations separated by an energy barrier. Thermal or quantum fluctuations can promote the transition between the configurations at a rate which depends on the dynamical properties of the local environment (i.e., a thermal bath). In the case of classical systems, strong system-bath interaction has been successfully modelled by the Generalised Langevin Equation (GLE) formalism. Here we show that the efficient GLE algorithm introduced in Phys. Rev. B 89, 134303 (2014) can be extended to include some crucial aspects of the quantum fluctuations. In particular, the expected isotopic effect is observed along with the convergence of the quantum and classical transition rates in the strong coupling limit. Saturation of the transition rates at low temperature is also retrieved, in qualitative, yet not quantitative, agreement with the analytic predictions. The discrepancies in the tunnelling regime are due to an incorrect sampling close to the barrier top. The domain of applicability of the quasiclassical GLE is also discussed.Comment: 21 pages, 5 figures. Presented at the NESC16 conference: Advances in theory and simulation of non-equilibrium system

Applications of the Generalised Langevin Equation: towards a realistic description of the baths

The Generalised Langevin Equation (GLE) method, as developed in Ref. [Phys. Rev. B 89, 134303 (2014)], is used to calculate the dissipative dynamics of systems described at the atomic level. The GLE scheme goes beyond the commonly used bilinear coupling between the central system and the bath, and permits us to have a realistic description of both the dissipative central system and its surrounding bath. We show how to obtain the vibrational properties of a realistic bath and how to convey such properties into an extended Langevin dynamics by the use of the mapping of the bath vibrational properties onto a set of auxiliary variables. Our calculations for a model of a Lennard-Jones solid show that our GLE scheme provides a stable dynamics, with the dissipative/relaxation processes properly described. The total kinetic energy of the central system always thermalises toward the expected bath temperature, with appropriate fluctuation around the mean value. More importantly, we obtain a velocity distribution for the individual atoms in the central system which follows the expected canonical distribution at the corresponding temperature. This confirms that both our GLE scheme and our mapping procedure onto an extended Langevin dynamics provide the correct thermostat. We also examined the velocity autocorrelation functions and compare our results with more conventional Langevin dynamics.Comment: accepted for publication in PR

Managing not-so-small Numbers Between Comparative and Statistical Methods

The problem here is what to do with an N of 20? Comparative case studies effectively deal with up to five or so observations. Aggregate statistical studies can easily with hundreds and thousands of observations. But with an N of 20 is too large for detailed case com parisons and too small for the use of powerful statistical analyses. This article proposes a middle ground that weaves an argument from a combination of multiple regression equa tions and case histories. Multivariate outliers identify cases for historical analyses; and the exposure of data in bivariate scattergrams permits useful validity testing. The procedure is illustrated with analyses of modern Asian population policy changes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66541/2/10.1177_002071528502600101.pd

Non-equilibrium inelastic electronic transport: Polarization effects and vertex corrections to the self-consistent Born approximation

We study the effect of electron-vibron interactions on the inelastic transport properties of single-molecule nanojunctions. We use the non-equilibrium Green's functions technique and a model Hamiltonian to calculate the effects of second-order diagrams (double-exchange DX and dressed-phonon DPH diagrams) on the electron-vibration interaction and consider their effects across the full range of parameter space. The DX diagram, corresponding to a vertex correction, introduces an effective dynamical renormalization of the electron-vibron coupling in both the purely inelastic and the inelastic-resonant features of the IETS. The purely inelastic features correspond to an applied bias around the energy of a vibron, while the inelastic-resonant features correspond to peaks (resonance) in the conductance. The DPH diagram affects only the inelastic resonant features. We also discuss the circumstances in which the second-order diagrams may be approximated in the study of more complex model systems.Comment: To be published in PR

A Methodology to Assess the Air Force Materiel Command\u27s Exercise Support Program\u27s Weighting Scheme

This research performs analysis on the Air Force Materiel Command\u27s Exercise Support Program\u27s Weighting Scheme so that decision makers can create a more efficient and effective Resource Allocation - Integrated Process Team (RA-IPT) manpower allocation process. A linear programming (LP) model was derived from the Exercise Support Program (ESP) to assign manpower reductions throughout the Mission Element Board (MEB) organizational level in AFMC. Parametric analysis was performed on the LP model by simultaneously changing multiple objective function coefficients with the use of various direction vectors. These direction vectors were applied with the use of an incrementally increasing scalar step size and initiated from two initial states of objective function coefficient values. Throughout the analysis, multiple bounds on the LP model\u27s constraints and different scalar step sizes were applied. Results of the analysis indicated that there were specific situations in which changes in the relative weighting scheme did effect manpower allocations to the MEBs. These results also indicated that this analysis, along with the ESP model, could allow the decision makers in the RA-IPT to become more efficient in their manpower allocation process

Nonequilibrium processes from Generalised Langevin Equations: realistic nanoscale systems connected to two thermal baths

We extend the Generalised Langevin Equation (GLE) method [Phys. Rev. B 89, 134303 (2014)] to model a central classical region connected to two realistic thermal baths at two different temperatures. In such nonequilibrium conditions a heat flow is established, via the central system, in between the two baths. The GLE-2B (GLE two baths) scheme permits us to have a realistic description of both the dissipative central system and its surrounding baths. Following the original GLE approach, the extended Langevin dynamics scheme is modified to take into account two sets of auxiliary degrees of freedom corresponding to the mapping of the vibrational properties of each bath. These auxiliary variables are then used to solve the non-Markovian dissipative dynamics of the central region. The resulting algorithm is used to study a model of a short Al nanowire connected to two baths. The results of the simulations using the GLE-2B approach are compared to the results of other simulations that were carried out using standard thermostatting approaches (based on Markovian Langevin and Nose-Hoover thermostats). We concentrate on the steady state regime and study the establishment of a local temperature profile within the system. The conditions for obtaining a flat profile or a temperature gradient are examined in detail, in agreement with earlier studies. The results show that the GLE-2B approach is able to treat, within a single scheme, two widely different thermal transport regimes, i.e. ballistic systems, with no temperature gradient, and diffusive systems with a temperature gradient.Comment: present version accepted for publication in Phys. Rev. B (Apr 2016

Movie of the interplanetary magnetic field

Description of movie representing IMP-1 MAGNETOMETER observations of interplanetary magnetic fiel

Interplanetary magnetic field IMP-1, motion picture of the transverse components

Motion picture report of IMP-1 magnetometer observations of interplanetary magnetic fiel