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Why donât pesticide applicators protect themselves? Exploring the use of personal protective equipment among Colombian smallholders
The misuse of personal protective equipment (PPE)
during pesticide application was investigated among
smallholders in Colombia. The integrative agent-centered
(IAC) framework and a logistic regression
approach were adopted. The results suggest that the
descriptive social norm was significantly influencing
PPE use. The following were also important: (1) having
experienced pesticide-related health problems; (2)
age; (3) the share of pesticide application carried out;
and (4) the perception of PPE hindering work. Interestingly,
the influence of these factors differed for different
pieces of PPE. Since conformity to the social
norm is a source of rigidity in the system, behavioral
change may take the form of a discontinuous transition.
In conclusion, five suggestions for triggering a
transition towards more sustainable PPE use are formulated:
(1) diversifying targets/tools; (2) addressing
structural aspects; (3) sustaining interventions in the
long-term; (4) targeting farmersâ learning-by-experience;
and (5) targeting PPE use on a collective level
Large-Scale Simulations of the Two-Dimensional Melting of Hard Disks
Large-scale computer simulations involving more than a million particles have
been performed to study the melting transition in a two-dimensional hard disk
fluid. The van der Waals loop previously observed in the pressure-density
relationship of smaller simulations is shown to be an artifact of finite-size
effects. Together with a detailed scaling analysis of the bond orientation
order, the new results provide compelling evidence for the
Halperin-Nelson-Young picture. Scaling analysis of the translational order also
yields a lower bound for the melting density that is much higher than
previously thought.Comment: 4 pages, 4 figure
A practical, unitary simulator for non-Markovian complex processes
Stochastic processes are as ubiquitous throughout the quantitative sciences
as they are notorious for being difficult to simulate and predict. In this
letter we propose a unitary quantum simulator for discrete-time stochastic
processes which requires less internal memory than any classical analogue
throughout the simulation. The simulator's internal memory requirements equal
those of the best previous quantum models. However, in contrast to previous
models it only requires a (small) finite-dimensional Hilbert space. Moreover,
since the simulator operates unitarily throughout, it avoids any unnecessary
information loss. We provide a stepwise construction for simulators for a large
class of stochastic processes hence directly opening the possibility for
experimental implementations with current platforms for quantum computation.
The results are illustrated for an example process.Comment: 12 pages, 5 figure
A New Monte Carlo Method and Its Implications for Generalized Cluster Algorithms
We describe a novel switching algorithm based on a ``reverse'' Monte Carlo
method, in which the potential is stochastically modified before the system
configuration is moved. This new algorithm facilitates a generalized
formulation of cluster-type Monte Carlo methods, and the generalization makes
it possible to derive cluster algorithms for systems with both discrete and
continuous degrees of freedom. The roughening transition in the sine-Gordon
model has been studied with this method, and high-accuracy simulations for
system sizes up to were carried out to examine the logarithmic
divergence of the surface roughness above the transition temperature, revealing
clear evidence for universal scaling of the Kosterlitz-Thouless type.Comment: 4 pages, 2 figures. Phys. Rev. Lett. (in press
The academic value of internships: benefits across disciplines and student backgrounds
While student benefits from internship experience have been frequently documented in research, the emphasis has been on internship effects on employment and career indicators. This work is concerned with effects on academic outcomes and focuses on the robustness of such effects across academic disciplines as well as for different achievement levels of students, student gender, and ethnicity. We present findings from a longitudinal sample (n > 15,000) that covers an extensive range of subjects and disciplines for large Undergraduate cohorts. Main effects and interactions for student background characteristics were investigated showing stable academic benefits for advantaged and disadvantaged students. Further, using ordinal logistic multi-level modelling, we explored the impact on the probability of attaining a higher degree classification for different student scenarios, thus illustrating the practical significance of these internship effects. Effects are less likely to stem from maturation or self-selection. Findings are therefore discussed against a background of motivational approaches suitable to integrate both direct and indirect paths from internship experience to academic outcomes to career indicators
Estimation and Inference in Short Panel Vector Autoregressions with Unit Roots and Cointegration
This paper considers estimation and inference in panel vector autoregressions (PVARs) with fixed effects when the time dimension of the panel is finite, and the cross-sectional dimension is large. A Maximum Likelihood (ML) estimator based on a transformed likelihood function is proposed and shown to be consistent and asymptotically normally distributed irrespective of the unit root and cointegrating properties of the underlying PVAR model. The transformed likelihood framework is also used to derive unit root and cointegration tests in panels with short time dimension; these tests have the attractive feature that they are based on standard chi-squared and normal distributed statistics. Examining Generalised Method of Moments (GMM) estimation as an alternative to our proposed ML estimator, it is shown that conventional GMM estimators based on standard orthogonality conditions break down if the underlying time series contain unit roots.Panel vector autoregressions, Fixed effects, Unit roots, Cointegration
Molecular-Dynamics Simulation of a Glassy Polymer Melt: Incoherent Scattering Function
We present simulation results for a model polymer melt, consisting of short,
nonentangled chains, in the supercooled state. The analysis focuses on the
monomer dynamics, which is monitored by the incoherent intermediate scattering
function. The scattering function is recorded over six decades in time and for
many different wave-vectors. The lowest temperatures studied are slightly above
the critical temperature of mode-coupling theory (MCT), which was determined
from a quantitative analysis of the beta- and alpha-relaxations. We find
evidence for the space-time factorization theorem in the beta-relaxation
regime, and for the time-temperature superposition principle in the
alpha-regime, if the temperature is not too close to the critical temperature.
The wave-vector dependence of the nonergodicity parameter, of the critical
amplitude, and the alpha-relaxation time are in qualitative agreement with
calculations for hard spheres. For wave-vectors larger than the maximum of the
structure factor the alpha-relaxation time already agrees fairly well with the
asymptotic MCT-prediction. The behavior of the relaxation time at small
wave-vectors can be rationalized by the validity of the Gaussian approximation
and the value of the Kohlrausch stretching exponent.Comment: 23 pages of REVTeX, 13 PostScript figures, submitted to Phys. Rev.
Phase transition at finite temperature in one dimension: Adsorbate ordering in Ba/Si(111)3x2
We demonstrate that the Ba-induced Si(111)3x2 reconstruction is a physical
realization of a one-dimensional antiferromagnetic Ising model with long-range
Coulomb interactions. Monte Carlo simulations performed on a corresponding
Coulomb-gas model, which we construct based on density-functional calculations,
reveal an adsorbate-ordering phase transition at finite temperature. We show
numerically that this unusual one-dimensional phase transition should be
detectable by low-energy electron diffraction.Comment: 11 pages + 4 figures. Surf. Sci. Lett. (in press
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