1,321 research outputs found
The potential use of lures for thrips biological control in greenhouses: practice and theory
Exploiting the response of thrips pest species to odours has long been a goal for improving thrips pest management including biological control. Applications of attractants could include improved monitoring, push-pull (in conjunction with a repellent odour), lure and kill, and lure and infect technologies, and surveillance for invasive organisms. We have recently discovered that 4-pyridyl carbonyl compounds can elicit responses from a range of thrips species (Thrips tabaci, T. major, T. obscuratus and Frankliniella occidentalis) in the laboratory, in glasshouses and in open field bioassays. Some of these compounds can increase the trap capture of these thrips species in both commercial greenhouses and broad acre commercial crops where these species are considered pests. However, our understanding of the mechanisms eliciting this response in thrips is still only rudimentary. Greater knowledge of the underlying behavioural mechanisms, including the intrinsic and extrinsic factors that may affect these responses, as well as optimal trap design and configuration, and odour formulation, will be essential if semiochemical-based approaches are to be integrated into thrips management programme
Validation of multi-body modelling methodology for reconfigurable underwater robots
This paper investigates the problem of employing reconfigurable robots in an underwater setting. The main results presented is the experimental validation of a modelling methodology for a system consisting of N dynamically connected robots with heterogeneous dynamics. Two distinct types of experiments are performed, a series of hydrostatic free-decay tests and a series of open-loop trajectory tests. The results are compared to a simulation based on the modelling methodology. The modelling methodology shows promising results for usage with systems composed of reconfigurable underwater modules. The purpose of the model is to enable design of control strategies for cooperative reconfigurable underwater systems
A finite continuation algorithm for bound constrained quadratic programming
The dual of the strictly convex quadratic programming problem with unit bounds is posed as a linear ℓ1 minimization problem with quadratic terms. A smooth approximation to the linear ℓ1 function is used to obtain a parametric family of piecewise-quadratic approximation problems. The unique path generated by the minimizers of these problems yields the solution to the original problem for finite values of the approximation parameter. Thus, a finite continuation algorithm is designed. Results of extensive computational experiments are reported
Enriquecimiento cognoscitivo: el hombre visto como sistema abierto
Texto sobre las aportaciones y los beneficios de la perspectiva psicológica del enriquecimiento cognoscitivo para la intervención educativa y terapéutica con personas que demuestran desempeño retardado y otros tipos de desviación emocional o conductual. Se incluye también texto sobre el Primer Coloquio Internacional de Psicología Comunitaria y la Décima Semana de Psicología en el ITESO
SU(N) Quantum Antiferromagnets and the Phase Structure of QED in the Strong Coupling Limit
We examine the strong coupling limit of both compact and non compact QED on a
lattice with staggered fermions. We show that every SU(N) antiferromagnet with
spins in a particular fundamental representation of the SU(N) Lie Algebra and
with nearest neighbor couplings on a bipartite lattice is exactly equivalent to
the infinite coupling limit of lattice QED with the numbers of flavors of
electrons related to N and the dimension of spacetime D+1. We find that,for
both compact and noncompact QED,when N is odd the ground state of the strong
coupling limit breaks chiral symmetry in any dimensions and for any N and the
condensate is an isoscalar mass operator. When N is even,chiral symmetry is
broken if D is bigger or equal to 2 and N is small enough and the order
parameter is an isovector mass operator. We also find the exact ground state of
the lattice Coulomb gas as well as a variety of related lattice statistical
systems with long ranged interactions.Comment: latex, 45 pages, DFUPG 69/9
Structural Relaxation and Frequency Dependent Specific Heat in a Supercooled Liquid
We have studied the relation between the structural relaxation and the
frequency dependent thermal response or the specific heat, , in a
supercooled liquid.
The Mode Coupling Theory (MCT) results are used to obtain
corresponding to different wavevectors. Due to the two-step
relaxation process present in the MCT, an extra peak, in addition to the low
frequency peak, is predicted in specific heat at high frequency.Comment: 14 pages, 13 Figure
Models of Neutrino Masses: Anarchy versus Hierarchy
We present a quantitative study of the ability of models with different
levels of hierarchy to reproduce the solar neutrino solutions, in particular
the LA solution. As a flexible testing ground we consider models based on
SU(5)xU(1)_F. In this context, we have made statistical simulations of models
with different patterns from anarchy to various types of hierachy: normal
hierarchical models with and without automatic suppression of the 23
(sub)determinant and inverse hierarchy models. We find that, not only for the
LOW or VO solutions, but even in the LA case, the hierarchical models have a
significantly better success rate than those based on anarchy. The normal
hierachy and the inverse hierarchy models have comparable performances in
models with see-saw dominance, while the inverse hierarchy models are
particularly good in the no see-saw versions. As a possible distinction between
these categories of models, the inverse hierarchy models favour a maximal solar
mixing angle and their rate of success drops dramatically as the mixing angle
decreases, while normal hierarchy models are far more stable in this respect.Comment: v1: 28 pages, 12 figures; v2: 34 pages, 14 figures, updated previous
analysis with the inclusion of recent SNO result
Accelerating cycle expansions by dynamical conjugacy
Periodic orbit theory provides two important functions---the dynamical zeta
function and the spectral determinant for the calculation of dynamical averages
in a nonlinear system. Their cycle expansions converge rapidly when the system
is uniformly hyperbolic but greatly slowed down in the presence of
non-hyperbolicity. We find that the slow convergence can be associated with
singularities in the natural measure. A properly designed coordinate
transformation may remove these singularities and results in a dynamically
conjugate system where fast convergence is restored. The technique is
successfully demonstrated on several examples of one-dimensional maps and some
remaining challenges are discussed
Semiclassical Quantization of Effective String Theory and Regge Trajectories
We begin with an effective string theory for long distance QCD, and evaluate
the semiclassical expansion of this theory about a classical rotating string
solution, taking into account the the dynamics of the boundary of the string.
We show that, after renormalization, the zero point energy of the string
fluctuations remains finite when the masses of the quarks on the ends of the
string approach zero. The theory is then conformally invariant in any spacetime
dimension D. For D=26 the energy spectrum of the rotating string formally
coincides with that of the open string in classical Bosonic string theory.
However, its physical origin is different. It is a semiclassical spectrum of an
effective string theory valid only for large values of the angular momentum.
For D=4, the first semiclassical correction adds the constant 1/12 to the
classical Regge formula.Comment: 65 pages, revtex, 3 figures, added 2 reference
First Principles Calculation of Elastic Properties of Solid Argon at High Pressures
The density and the elastic stiffness coefficients of fcc solid argon at high
pressures from 1 GPa up to 80 GPa are computed by first-principles
pseudopotential method with plane-wave basis set and the generalized gradient
approximation (GGA). The result is in good agreement with the experimental
result recently obtained with the Brillouin spectroscopy by Shimizu et al.
[Phys. Rev. Lett. 86, 4568 (2001)]. The Cauchy condition was found to be
strongly violated as in the experimental result, indicating large contribution
from non-central many-body force. The present result has made it clear that the
standard density functional method with periodic boundary conditions can be
successfully applied for calculating elastic properties of rare gas solids at
high pressures in contrast to those at low pressures where dispersion forces
are important.Comment: 4 pages, 5 figures, submitted to PR
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