216 research outputs found
Chapter 14: Vulnerability of seabirds on the Great Barrier Reef to climate change
Seabirds are highly visible, charismatic predators in marine ecosystems that are defined as feeding
exclusively at sea, in either nearshore, offshore or pelagic waters. At a conservative estimate there
are approximately 0.7 billion individuals of 309 species of seabirds globally. Such high population
abundance means that in all ecosystems where seabirds occur the levels of marine resources they
consume are significant. Such high consumption rates also mean that seabirds play a number of
important functional roles in marine ecosystems, including the transfer of nutrients from offshore and
pelagic areas to islands and reefs, seed dispersal and the distribution of organic matter into lower parts
of the developing soil profile (eg burrow-nesting species such as shearwaters).This is Chapter 14 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13
Nuclear transparencies in relativistic A(e,e'p) models
Relativistic and unfactorized calculations for the nuclear transparency
extracted from exclusive A(e,e'p) reactions for 0.3 \leq Q^2 \leq 10 (GeV/c)^2
are presented for the target nuclei C, Si, Fe and Pb. For Q^2 \geq 0.6
(GeV/c)^2, the transparency results are computed within the framework of the
recently developed relativistic multiple-scattering Glauber approximation
(RMSGA). The target-mass and Q^2 dependence of the RMSGA predictions are
compared with relativistic distorted-wave impulse approximation (RDWIA)
calculations. Despite the very different model assumptions underlying the
treatment of the final-state interactions in the RMSGA and RDWIA frameworks,
they predict comparable nuclear transparencies for kinematic regimes where both
models are applicable.Comment: 15 pages, 4 figure
Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron
The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2]
for the proton and neutron have been determined from measurements of polarised
cross section asymmetries in deep inelastic scattering of 27.5 GeV
longitudinally polarised positrons from polarised 1H and 3He internal gas
targets. The data were collected in the region above the nucleon resonances in
the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the
proton the contribution to the generalised Gerasimov-Drell-Hearn integral was
found to be substantial and must be included for an accurate determination of
the full integral. Furthermore the data are consistent with a QCD
next-to-leading order fit based on previous deep inelastic scattering data.
Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte
Measurement of the Proton Spin Structure Function g1p with a Pure Hydrogen Target
A measurement of the proton spin structure function g1p(x,Q^2) in
deep-inelastic scattering is presented. The data were taken with the 27.6 GeV
longitudinally polarised positron beam at HERA incident on a longitudinally
polarised pure hydrogen gas target internal to the storage ring. The kinematic
range is 0.021<x<0.85 and 0.8 GeV^2<Q^2<20 GeV^2. The integral
Int_{0.021}^{0.85} g1p(x)dx evaluated at Q0^2 of 2.5 GeV^2 is
0.122+/-0.003(stat.)+/-0.010(syst.).Comment: 7 pages, 3 figures, 1 table, RevTeX late
Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction
Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H,
3He, and 14N targets has been studied by the HERMES experiment at squared
four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20
GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the
nuclear transparency, was found to decrease with increasing coherence length of
quark-antiquark fluctuations of the virtual photon. The data provide clear
evidence of the interaction of the quark- antiquark fluctuations with the
nuclear medium.Comment: RevTeX, 5 pages, 3 figure
Double-Spin Asymmetry in the Cross Section for Exclusive rho^0 Production in Lepton-Proton Scattering
Evidence for a positive longitudinal double-spin asymmetry = 0.24
+-0.11 (stat) +-0.02 (syst) in the cross section for exclusive diffractive
rho^0(770) vector meson production in polarised lepton-proton scattering was
observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA
positron beam was scattered off a longitudinally polarised pure hydrogen gas
target. The average invariant mass of the photon-proton system has a value of
= 4.9 GeV, while the average negative squared four-momentum of the virtual
photon is = 1.7 GeV^2. The ratio of the present result to the
corresponding spin asymmetry in inclusive deep-inelastic scattering is in
agreement with an early theoretical prediction based on the generalised vector
meson dominance model.Comment: 10 pages, 4 embedded figures, LaTe
Measurement of the Neutron Spin Structure Function with a Polarized ^3He Target
Results are reported from the HERMES experiment at HERA on a measurement of
the neutron spin structure function in deep inelastic scattering
using 27.5 GeV longitudinally polarized positrons incident on a polarized
He internal gas target. The data cover the kinematic range
and . The integral evaluated at a fixed of is . Assuming Regge behavior at low , the first
moment is .Comment: 4 pages TEX, text available at
http://www.krl.caltech.edu/preprints/OAP.htm
Flavor Decomposition of the Polarized Quark Distributions in the Nucleon from Inclusive and Semi-inclusive Deep-inelastic Scattering
Spin asymmetries of semi-inclusive cross sections for the production of
positively and negatively charged hadrons have been measured in deep-inelastic
scattering of polarized positrons on polarized hydrogen and 3He targets, in the
kinematic range 0.023<x<0.6 and 1 GeV^2<Q^2<10 GeV^2. Polarized quark
distributions are extracted as a function of x for up $(u+u_bar) and down
(d+d_bar) flavors. The up quark polarization is positive and the down quark
polarization is negative in the measured range. The polarization of the sea is
compatible with zero. The first moments of the polarized quark distributions
are presented. The isospin non-singlet combination Delta_q_3 is consistent with
the prediction based on the Bjorken sum rule. The moments of the polarized
quark distributions are compared to predictions based on SU(3)_f flavor
symmetry and to a prediction from lattice QCD.Comment: 14 pages, 6 figures (eps format), 10 tables in Latex New version
contains tables of asymmetries and correlation matri
An ultrafast system for signaling mechanical pain in human skin.
The canonical view is that touch is signaled by fast-conducting, thickly myelinated afferents, whereas pain is signaled by slow-conducting, thinly myelinated ("fast" pain) or unmyelinated ("slow" pain) afferents. While other mammals have thickly myelinated afferents signaling pain (ultrafast nociceptors), these have not been demonstrated in humans. Here, we performed single-unit axonal recordings (microneurography) from cutaneous mechanoreceptive afferents in healthy participants. We identified A-fiber high-threshold mechanoreceptors (A-HTMRs) that were insensitive to gentle touch, encoded noxious skin indentations, and displayed conduction velocities similar to A-fiber low-threshold mechanoreceptors. Intraneural electrical stimulation of single ultrafast A-HTMRs evoked painful percepts. Testing in patients with selective deafferentation revealed impaired pain judgments to graded mechanical stimuli only when thickly myelinated fibers were absent. This function was preserved in patients with a loss-of-function mutation in mechanotransduction channel PIEZO2. These findings demonstrate that human mechanical pain does not require PIEZO2 and can be signaled by fast-conducting, thickly myelinated afferents
Identification of new susceptibility loci for osteoarthritis (arcOGEN):a genome-wide association study
To access publisher's full text version of this article. Please click on the hyperlink in Additional Links field.Osteoarthritis is the most common form of arthritis worldwide and is a major cause of pain and disability in elderly people. The health economic burden of osteoarthritis is increasing commensurate with obesity prevalence and longevity. Osteoarthritis has a strong genetic component but the success of previous genetic studies has been restricted due to insufficient sample sizes and phenotype heterogeneity. We undertook a large genome-wide association study (GWAS) in 7410 unrelated and retrospectively and prospectively selected patients with severe osteoarthritis in the arcOGEN study, 80% of whom had undergone total joint replacement, and 11,009 unrelated controls from the UK. We replicated the most promising signals in an independent set of up to 7473 cases and 42,938 controls, from studies in Iceland, Estonia, the Netherlands, and the UK. All patients and controls were of European descent. We identified five genome-wide significant loci (binomial test p≤5·0×10(-8)) for association with osteoarthritis and three loci just below this threshold. The strongest association was on chromosome 3 with rs6976 (odds ratio 1·12 [95% CI 1·08-1·16]; p=7·24×10(-11)), which is in perfect linkage disequilibrium with rs11177. This SNP encodes a missense polymorphism within the nucleostemin-encoding gene GNL3. Levels of nucleostemin were raised in chondrocytes from patients with osteoarthritis in functional studies. Other significant loci were on chromosome 9 close to ASTN2, chromosome 6 between FILIP1 and SENP6, chromosome 12 close to KLHDC5 and PTHLH, and in another region of chromosome 12 close to CHST11. One of the signals close to genome-wide significance was within the FTO gene, which is involved in regulation of bodyweight-a strong risk factor for osteoarthritis. All risk variants were common in frequency and exerted small effects. Our findings provide insight into the genetics of arthritis and identify new pathways that might be amenable to future therapeutic intervention.Arthritis Research UK
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