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Host plant recognition by the root feeding clover weevil, Sitona lepidus (Coleoptera: Curculionidae)
This study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae
Agriproduct supply-chain management in developing countries. Proceedings of a workshop held in Bali, Indonesia, 19â22 August 2003.
Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence
Energies of 5l_j (l= s, p, d, f, g) and 4f_j states in neutral Ag and Ag-like
ions with nuclear charges Z = 48 - 100 are calculated using relativistic
many-body perturbation theory. Reduced matrix elements, oscillator strengths,
transition rates and lifetimes are calculated for the 17 possible 5l_j-5l'_{j'}
and 4f_j-5l_{j'} electric-dipole transitions. Third-order corrections to
energies and dipole matrix elements are included for neutral Ag and for ions
with Z60. Comparisons are made
with available experimental data for transition energies and lifetimes.
Correlation energies and transition rates are shown graphically as functions of
nuclear charge Z for selected cases. These calculations provide a theoretical
benchmark for comparison with experiment and theory.Comment: 8 page
Hadron mass corrections in semi-inclusive deep inelastic scattering
We derive mass corrections for semi-inclusive deep inelastic scattering of
leptons from nucleons using a collinear factorization framework which
incorporates the initial state mass of the target nucleon and the final state
mass of the produced hadron. The formalism is constructed specifically to
ensure that physical kinematic thresholds for the semi-inclusive process are
explicitly respected. A systematic study of the kinematic dependencies of the
mass corrections to semi-inclusive cross sections reveals that these are even
larger than for inclusive structure functions, especially at very small and
very large hadron momentum fractions. The hadron mass corrections compete with
the experimental uncertainties at kinematics typical of current facilities, and
will be important to efforts at extracting parton distributions or
fragmentation functions from semi-inclusive processes at intermediate energies.Comment: 22 pages, 6 figures; expanded discussion of kinematics and new
scaling variable; appendix comparing collinear frames included; version to
appear in JHE
Evaluation of the low-lying energy levels of two- and three-electron configurations for multi-charged ions
Accurate QED evaluations of the one- and two-photon interelectron interaction
for low lying two- and three-electron configurations for ions with nuclear
charge numbers are performed. The three-photon interaction is
also partly taken into account. The Coulomb gauge is employed. The results are
compared with available experimental data and with different calculations. A
detailed investigation of the behaviour of the energy levels of the
configurations , near
the crossing points Z=64 and Z=92 is carried out. The crossing points are
important for the future experimental search for parity nonconserving (PNC)
effects in highly charged ions
Finite nuclear size and Lamb shift of p-wave atomic states
We consider corrections to the Lamb shift of p-wave atomic states due to the
finite nuclear size (FNS). In other words, these are radiative corrections to
the atomic isotop shift related to FNS. It is shown that the structure of the
corrections is qualitatively different from that for s-wave states. The
perturbation theory expansion for the relative correction for a -state
starts from -term, while for -states it starts
from term. Here is the fine structure constant and is
the nuclear charge. In the present work we calculate the -terms for
-states, the result for -state reads
. Even more interesting are
-states. In this case the ``correction'' is by several orders of
magnitude larger than the ``leading'' FNS shift.Comment: 4 pages, 2 figure
Forbidden transitions in the helium atom
Nonrelativistically forbidden, single-photon transition rates between low
lying states of the helium atom are rigorously derived within quantum
electrodynamics theory. Equivalence of velocity and length gauges, including
relativistic corrections is explicitly demonstrated. Numerical calculations of
matrix elements are performed with the use of high precision variational wave
functions and compared to former results.Comment: 11 pages, 1 figure, submitted to Phys. Rev.
A rigorous evaluation of crossover and mutation in genetic programming
The role of crossover and mutation in Genetic Programming (GP) has been the subject of much debate since the emergence of the field. In this paper, we contribute new empirical evidence to this argument using a rigorous and principled experimental method applied to six problems common in the GP literature. The approach tunes the algorithm parameters to enable a fair and objective comparison of two different GP algorithms, the first using a combination of crossover and reproduction, and secondly using a combination of mutation and reproduction. We find that crossover does not significantly outperform mutation on most of the problems examined. In addition, we demonstrate that the use of a straightforward Design of Experiments methodology is effective at tuning GP algorithm parameters
Lightweighting of railway axles for reduction of unsprung mass and track access charges
The potential for lightweighting of railway axles was investigated to primarily reduce the unsprung mass of rail vehicles. The reduction of unsprung mass equates to an overall lighter train, which will help to reduce track damage, energy consumption and total operating costs. Two approaches were considered for the lightweighting of railway axles, which include a hollow axle design and material substitution using advanced composite materials, to offer a more track-friendly design. The first approach showed that if the outer diameter of a hollow axle is increased by 30% over that of the solid axle diameter, a mass reduction of 56% is achievable for a hollow steel axle design. The second approach explored further mass savings that could be achieved through material substitution of a hollow axle. A systematic approach to material selection for the design requirements and constraints of a railway axle was considered to identify the candidate materials for the application. The optimum material identified was a âbismaleimide matrixâ+âcarbon fibre composite.â A hollow axle manufactured from this composite material offered 64% savings in mass when compared to a hollow steel axle, and 84% savings in mass when compared to a solid steel axle. Estimates for the cost savings of lightweighting of an axle were quantified by utilising Network Railâs variable usage charge calculator, to assess the track access charge savings that can be achieved. For the scenario described in this paper, a potential ÂŁ5.58 million per year could be saved for an intercity 220/M Voyager train, in terms of variable usage charges, over the entire fleet of 34 trains (four carriages per train) by implementing hollow composite axles. This is an example of a costing approach to support the decision making of lightweighting of rail vehicles
Finite nuclear size effect on Lamb shift of s1/2, p1/2, and p3/2 atomic states
We consider one-loop self-energy and vacuum polarization radiative
corrections to the shift of atomic energy level due to finite nuclear size.
Analytic expressions for vacuum polarization corrections are derived. For the
self-energy of p1/2 and p3/2 states in addition to already known terms we
derive next-to-leading nonlogarithmic Z\alpha-terms. Together with
contributions obtained earlier the terms derived in the present work give
explicit analytic expressions for s1/2 and p1/2 corrections which agree with
results of previous numerical calculations up to Z=100 (Z is the nuclear charge
number). We also show that the finite nuclear size radiative correction for a
p3/2 state is not small compared to the similar correction for a p1/2 state at
least for small Z.Comment: 12 pages, 7 figure
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