5,024 research outputs found
Canopy structural modeling using object-oriented image classification and laser scanning
A terrestrial laser scanning (TLS) experiment was carried out in the EAGLE 2006 campaign to characterize and model
the canopy structure of the Speulderbos forest. Semi-variogram analysis was used to describe spatial variability of the
surface. The dependence of the spatial variability on the applied grid size showed, that in this forest spatial details of the
digital surface model are lost in the case of larger than 0.3-0.4 m grid size. Voxel statistics was used for describing the
density of the canopy structure. Five zones of the canopy were identified according to their density distribution. Basic
geometric structures were tested for modeling the forest at the individual tree level. The results create a firm basis for
modeling physical processes in the canopy
Lorentz violation in neutron and allowed nuclear beta decay
We explore the possibility that the weak interaction violates Lorentz, and in
particular rotational, invariance in neutron and allowed nuclear beta decay. A
broad class of Lorentz-violating effects is considered, in which the standard
propagator of the W-boson acquires an additional Lorentz-violating tensor. The
general decay rate for allowed beta decay that incorporates such a modified
propagator is derived. The resulting Lorentz-violating signals are discussed
for the different types of beta-decay transitions, Fermi, Gamow-Teller, and
mixed. We study the implications of our formalism for dedicated beta-decay
experiments. We give a short overview of the few relevant experiments that have
been performed or are ongoing.Comment: 23 pages; added reference
Nuclear beta decay with Lorentz violation
We consider the possibility of Lorentz-invariance violation in weak-decay
processes. We present a general approach that entails modifying the W-boson
propagator by adding a Lorentz-violating tensor to it. We describe the effects
of Lorentz violation on nuclear beta decay in this scenario. In particular we
show the expression for a first-forbidden transition with a spin change of two.
Using data from an old experiment on the rotational invariance of yttrium-90,
we derive several bounds on the Lorentz-violating parameters of the order of
10^(-6)-10^(-8).Comment: 4 pages; presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 2013; Added reference
Multidimensional Sequence Alignment Methods for Activity Pattern Analysis: A comparison of dynamic programming and genetic algorithms
Exploration of Lorentz violation in neutral-kaon decay
The KLOE collaboration recently reported bounds on the directional dependence
of the lifetime of the short-lived neutral kaon with respect to the
dipole anisotropy of the cosmic microwave background. We interpret their
results in an effective field theory framework developed to probe the violation
of Lorentz invariance in the weak interaction and previously applied to
semileptonic processes, in particular decay. In this approach a general
Lorentz-violating tensor is added to the standard propagator of
the boson. We perform an exploratory study of the prospects to search for
Lorentz violation in nonleptonic decays. For the kaon, we find that the
sensitivity to Lorentz violation is limited by the velocity of the kaons and by
the extent to which hadronic effects can be calculated. In a simple model we
derive the decay rate and calculate the asymmetry for the lifetime.
Using the KLOE data, limits on the values of are determined.Comment: accepted for publication in Physics Letters
Deuteron Magnetic Quadrupole Moment From Chiral Effective Field Theory
We calculate the magnetic quadrupole moment (MQM) of the deuteron at leading
order in the systematic expansion provided by chiral effective field theory. We
take into account parity and time-reversal violation which, at the quark-gluon
level, results from the QCD vacuum angle and dimension-six operators that
originate from physics beyond the Standard Model. We show that the deuteron MQM
can be expressed in terms of five low-energy constants that appear in the
parity- and time-reversal-violating nuclear potential and electromagnetic
current, four of which also contribute to the electric dipole moments of light
nuclei. We conclude that the deuteron MQM has an enhanced sensitivity to the
QCD vacuum angle and that its measurement would be complementary to the
proposed measurements of light-nuclear EDMs
Bulk de novo mitogenome assembly from pooled total DNA elucidates the phylogeny of weevils (Coleoptera: Curculionoidea)
Complete mitochondrial genomes have been shown to be reliable markers for phylogeny reconstruction among diverse animal groups. However, the relative difficulty and high cost associated with obtaining de novo full mitogenomes have frequently led to conspicuously low taxon sampling in ensuing studies. Here, we report the successful use of an economical and accessible method for assembling complete or near-complete mitogenomes through shot-gun next-generation sequencing of a single library made from pooled total DNA extracts of numerous target species. To avoid the use of separate indexed libraries for each specimen, and an associated increase in cost, we incorporate standard polymerase chain reaction-based âbaitâ sequences to identify the assembled mitogenomes. The method was applied to study the higher level phylogenetic relationships in the weevils (Coleoptera: Curculionoidea), producing 92 newly assembled mitogenomes obtained in a single Illumina MiSeq run. The analysis supported a separate origin of wood-boring behavior by the subfamilies Scolytinae, Platypodinae, and Cossoninae. This finding contradicts morphological hypotheses proposing a close relationship between the first two of these but is congruent with previous molecular studies, reinforcing the utility of mitogenomes in phylogeny reconstruction. Our methodology provides a technically simple procedure for generating densely sampled trees from whole mitogenomes and is widely applicable to groups of animals for which bait sequences are the only required prior genome knowledge
Schiff Theorem and the Electric Dipole Moments of Hydrogen-Like Atoms
The Schiff theorem is revisited in this work and the residual - and
-odd electron--nucleus interaction, after the shielding takes effect, is
completely specified. An application is made to the electric dipole moments of
hydrogen-like atoms, whose qualitative features and systematics have important
implication for realistic paramagnetic atoms.Comment: 3 pages. Contribution to PANIC05, Particles and Nuclei International
Conference, Santa Fe, New Mexico, Oct. 24-28, 200
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