831 research outputs found
The extended Mathews stability graph: Quantifying case history requirements and site-specific effects
Electroweak Theory Without Higgs Bosons
A perturbative SU(2)_L X U(1)_Y electroweak theory containing W, Z, photon,
ghost, lepton and quark fields, but no Higgs or other fields, gives masses to
W, Z and the non-neutrino fermions by means of an unconventional choice for the
unperturbed Lagrangian and a novel method of renormalisation. The
renormalisation extends to all orders. The masses emerge on renormalisation to
one loop. To one loop the neutrinos are massless, the A -> Z transition drops
out of the theory, the d quark is unstable and S-matrix elements are
independent of the gauge parameter xi.Comment: 27 pages, LaTex, no figures; revised for publication; accepted by
Int. J. Mod. Phys. A; includes biographical note on A. F. Nicholso
Combining simulation modeling and stable isotope analyses to reconstruct the last known movements of one of Nature’s giants
The spatial ecology of rare, migratory oceanic animals is difficult to study directly. Where incremental tissues are available, their chemical composition can provide valuable indirect observations of movement and diet. Interpreting the chemical record in incremental tissues can be highly uncertain, however, as multiple mechanisms interact to produce the observed data. Simulation modeling is one approach for considering alternative hypotheses in ecology and can be used to consider the relative likelihood of obtaining an observed record under different combinations of ecological and environmental processes. Here we show how a simulation modeling approach can help to infer movement behaviour based on stable carbon isotope profiles measured in incremental baleen tissues of a blue whale (Balaenoptera musculus). The life history of this particular specimen, which stranded in 1891 in the UK, was selected as a case study due to its cultural significance as part of a permanent display at the Natural History Museum, London. We specifically tested whether measured variations in stable isotope compositions across the analysed baleen plate were more consistent with residency or latitudinal migrations. The measured isotopic record was most closely reproduced with a period of residency in sub-tropical waters for at least a full year followed by three repeated annual migrations between sub-tropical and high latitude regions. The latitudinal migration cycle was interrupted in the year prior to stranding, potentially implying pregnancy and weaning, but isotopic data alone cannot test this hypothesis. Simulation methods can help reveal movement information coded in the biochemical compositions of incremental tissues such as those archived in historic collections, and provides context and inferences that are useful for retrospective studies of animal movement, especially where other sources of individual movement data are sparse or challenging to validate.© 2019 Trueman et al.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited
An absolute polarimeter for high energy protons
A study of the spin asymmetries for polarized elastic proton proton
collisions in the electromagnetic hadronic interference (CNI) region of
momentum transfer provides a method of self calibration of proton polarization.
The method can be extended to non-identical spin half scattering so that, in
principle, the polarization of a proton may be obtained through an analysis of
its elastic collision with a different polarized particle, helium 3 for
instance. Sufficiently large CNI spin asymmetries provide enough information to
facilitate the evaluation of nearly all the helicity amplitudes at small t as
well as the polarization of both initial spin half fermions. Thus it can serve
equally well as a polarimeter for helium 3
Spin asymmetries for elastic proton scattering and the spin dependent couplings of the Pomeron
This paper serves as a report on the large amount of analysis done in
conjunction with the polarized proton program at RHIC. This comprises elastic
scattering data of protons on protons in colliding beam or fixed target mode
and proton beams on carbon targets. In addition to providing a model for the
energy dependence of the analyzing power of elastic scattering needed for
proton polarimetry, it also provides some significant information about the
spin dependence of dominant Regge poles. Most notably, the data indicates that
the Pomeron has a significant spin-flip coupling. This allows the exploration
of the double spin flip asymmetry A_{NN} for which some data over a wide energy
range is now available, along with a concrete realization of a proposed Odderon
search.Comment: final reference modife
A calculation of the Lepage-Mackenzie scale for the lattice axial and vector currents
We calculate the perturbative scales (q*) for the axial and vector currents
for the Wilson action, with and without tadpole improvement, using Lepage and
Mackenzie's formalism. The scale for the pseudoscalar density (times the mass)
is computed as well. Contrary to naive expectation, tadpole improvement reduces
q* by only a small amount for the operators we consider. We also discuss the
use of a nonperturbative coupling to calculate the perturbative scale.Comment: 13 pages. One postscript figur
DNA barcoding identifies a cosmopolitan diet in the ocean sunfish
The ocean sunfish (Mola mola) is the world’s heaviest bony fish reaching a body mass of up to 2.3 tonnes. However, the prey M. mola consumes to fuel this prodigious growth remains poorly known. Sunfish were thought to be obligate gelatinous plankton feeders, but recent studies suggest a more generalist diet. In this study, through molecular barcoding and for the first time, the diet of sunfish in the north-east Atlantic Ocean was characterised. Overall, DNA from the diet content of 57 individuals was successfully amplified, identifying 41 different prey items. Sunfish fed mainly on crustaceans and teleosts, with cnidarians comprising only 16% of the consumed prey. Although no adult fishes were sampled, we found evidence for an ontogenetic shift in the diet, with smaller individuals feeding mainly on small crustaceans and teleost fish, whereas the diet of larger fish included more cnidarian species. Our results confirm that smaller sunfish feed predominantly on benthic and on coastal pelagic species, whereas larger fish depend on pelagic prey. Therefore, sunfish is a generalist predator with a greater diversity of links in coastal food webs than previously realised. Its removal as fisheries’ bycatch may have wider reaching ecological consequences, potentially disrupting coastal trophic interactions
Developing Mn-doped lead sulfide quantum dots for MRI labels
Magnetic interactions of Mn2+ions in lead sulfide (PbS) nanocrystals with protons in water are probed by NMR and MRI. A thin layer of capping molecules enables free solvent diffusion to the nanocrystal surface resulting in a decrease of proton relaxation times. Magnetic resonance imaging of neuronal cell pellets exposed to (PbMn)S at non-toxic concentrations demonstrates their prospects as MRI-labels
The analytical singlet QCD contributions into the -annihilation Adler function and the generalized Crewther relations
The generalized Crewther relations in the channels of the non-singlet and
vector quark currents are considered. They follow from the double application
of the operator product expansion approach to the same axial
vector-vector-vector triangle amplitude in two regions, adjoining to the angle
sides (or ). We assume that the generalized Crewther relations
in these two kinematic regimes result in the existence of the same perturbation
expression for two products of the coefficient functions of annihilation and
deep-inelastic scattering processes in the non-singlet and vector channels.
Taking into account the 4-th order result for and the perturbative
effects of the violation of the conformal symmetry in the generalized Crewther
relation, we obtain the analytical contribution to the singlet
correction to the -function. Its a-posteriori comparison with the
recent result of direct diagram-by-diagram evaluation of the singlet 4-th order
corrections to - function demonstrates the coincidence of the
predicted and obtained -contributions to the singlet term. They can
be obtained in the conformal invariant limit from the original Crewther
relation. On the contrary to previous belief, the appearance of -terms
in perturbative series in gauge models does not contradict to the property of
conformal symmetry and can be considered as ragular feature. The Banks-Zaks
motivated relation between our predicted and obtained 4-th order corrections is
mentioned. This confirms Baikov-Chetyrkin-Kuhn expectation that the generalized
Crewther relation in the channel of vector currents receives additional singlet
contribution, which in this order of perturbation theory is proportional to the
first coefficient of the QCD -function.Comment: Concrete new foundations explained, abstract updated, presentation
improved, 2 references added, extra acknowledgements added. This work is
dedicated to K. G. Chetyrkin on the occasion of his 60th anniversary, to be
published in Jetp. Lett supposedly in vol.94, issue 1
Dilepton production in proton-proton collisions at BEVALAC energies
The dilepton production in elementary reactions at
BEVALAC energies GeV is investigated. The calculations
include direct decays of the vector mesons , , and , Dalitz decays of the -, -, -, -, and -mesons, and of the baryon resonances
. The subthreshold vector meson production cross sections in
collisions are treated in a way sufficient to avoid double counting with the
inclusive vector meson production. The vector meson dominance model for the
transition form factors of the resonance Dalitz decays is
used in an extended form to ensure correct asymptotics which are in agreement
with the quark counting rules. Such a modification gives an unified and
consistent description of both radiative decays and meson decays.
The effect of multiple pion production on the experimental efficiency for the
detection of the dilepton pairs is studied. We find the dilepton yield in
reasonable agreement with the experimental data for the set of intermediate
energies whereas at the highest energy GeV the number of
dilepton pairs is likely to be overestimated experimentally in the mass range
MeV.Comment: 25 pages (IOP style), 5 figures, revised manuscript accepted for
publication in JP
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