390 research outputs found
Is tagging with visual implant elastomer a reliable technique for marking earthworms?
Visual implant elastomer (VIE) has recently been employed to investigate different aspects of earthworm ecology. However, a number of fundamental questions relating to the detection and positioning of the tag, its persistence and potential effects on earthworms remain unknown. Seven earthworm species belonging to three ecological groupings, with different pigmentation and burrowing behaviour, were tagged using different coloured VIE. External inspection after two days, one week and 1, 10 and 27 months were followed by preservation, dissection and internal inspection. Tags could be seen in living specimens to 27 months, and dissection revealed that in most cases they were lodged in the coelomic cavity, held in place by septa. However, over longer time periods (more than two years), the chlorogogenous tissue tended to bind to the tags and made external observation increasingly difficult. Migration of the VIE material towards the posterior of the earthworm and potential loss of the tag were only observed on rare occasions, and a recovery rate in excess of 98% was recorded. By introducing a reasonable amount of VIE into segments, just after the clitellum, this technique can become a valuable tool in earthworm ecology and life history studies, particularly in short-medium term laboratory and field experiments
An overview of research activities and achievement in Geotechnics from the Scottish Universities Geotechnics Network (SUGN)
ABSTRACT: Design of geotechnical systems is often challenging as it requires the understanding of complex soil behaviour and its influence on field-scale performance of geo-structures. To advance the scientific knowledge and the technological development in geotechnical engineering, a Scottish academic community, named Scottish Universities Geotechnics Network (SUGN), was established in 2001, composing of eight higher education institutions. The network gathers geotechnics researchers, including experimentalists as well as centrifuge, constitutive, and numerical modellers, to generate multiple synergies for building larger collaboration and wider research dissemination in and beyond Scotland. The paper will highlight the research excellence and leading work undertaken in SUGN emphasising some of the contribution to the geotechnical research community and some of the significant research outcomes. RĂSUMĂ: Conception de systĂšmes gĂ©otechniques est souvent difficile car elle nĂ©cessite la comprĂ©hension du comportement des sols complexes et son influence sur la performance Ă©chelle du champ de gĂ©o-structures. Pour faire avancer la connaissance scientifique et le dĂ©veloppement technologique en ingĂ©nierie gĂ©otechnique, une communautĂ© universitaire Ă©cossais, nommĂ© Ă©cossais universitĂ©s GĂ©otechnique rĂ©seau (SUGN), a Ă©tĂ© crĂ©Ă© en 2001, la composition des huit Ă©tablissements d'enseignement supĂ©rieur. Le rĂ©seau rĂ©unit gĂ©otechnique chercheurs, y compris les expĂ©rimentateurs ainsi que centrifugeuse, constitutif, et les modĂ©lisateurs numĂ©riques, de gĂ©nĂ©rer des synergies multiples pour la construction de plus grande collaboration et une plus large diffusion de la recherche en Ecosse et au-delĂ . Le document mettra l'accent sur l'excellence de la recherche et de diriger le travail entrepris dans SUGN soulignant certains de la contribution Ă la communautĂ© de recherche en gĂ©otechnique et certains des rĂ©sultats importants de la recherche
Increasing source to image distance for AP pelvis imaging â impact on radiation dose and image quality
Aim: A quantative primary study to determine whether increasing source to image distance (SID), with
and without the use of automatic exposure control (AEC) for antero-posterior (AP) pelvis imaging, reduces
dose whilst still producing an image of diagnostic quality.
Methods: Using a computed radiography (CR) system, an anthropomorphic pelvic phantom was positioned
for an AP examination using the table bucky. SID was initially set at 110 cm, with tube potential set
at a constant 75 kVp, with two outer chambers selected and a fine focal spot of 0.6 mm. SID was then
varied from 90 cm to 140 cm with two exposures made at each 5 cm interval, one using the AEC and
another with a constant 16 mAs derived from the initial exposure. Effective dose (E) and entrance surface
dose (ESD) were calculated for each acquisition. Seven experienced observers blindly graded image
quality using a 5-point Likert scale and 2 Alternative Forced Choice software. Signal-to-Noise Ratio (SNR)
was calculated for comparison. For each acquisition, femoral head diameter was also measured for
magnification indication.
Results: Results demonstrated that when increasing SID from 110 cm to 140 cm, both E and ESD reduced
by 3.7% and 17.3% respectively when using AEC and 50.13% and 41.79% respectively, when the constant
mAs was used. No significant statistical (T-test) difference (p Œ 0.967) between image quality was
detected when increasing SID, with an intra-observer correlation of 0.77 (95% confidence level). SNR
reduced slightly for both AEC (38%) and no AEC (36%) with increasing SID.
Conclusion: For CR, increasing SID significantly reduces both E and ESD for AP pelvis imaging without
adversely affecting image quality
Probing for the host galaxies of the fast X-ray transients XRTÂ 000519 and XRTÂ 110103
Over the past few years, âŒ30 extragalactic fast X-ray transients (FXRTs) have been discovered, mainly in Chandra and XMM-Newton data. Their nature remains unclear, with proposed origins, including a double neutron star merger, a tidal disruption event involving an intermediate-mass black hole and a white dwarf, or a supernova shock breakout. A decisive differentiation between these three promising mechanisms for their origin requires an understanding of the FXRT energetics, environments, and/or host properties. We present optical observations obtained with the Very Large Telescope for the FXRTs XRT 000519 and XRT 110103 and Gran Telescopio Canarias observations for XRT 000519 designed to search for host galaxies of these FXRTs. In the gs, rs, and R-band images, we detect an extended source on the north-west side of the âŒ1âČâČ (68 perâcent confidence) error circle of the X-ray position of XRT 000519 with a Kron magnitude of gs = 26.29 ± 0.09 (AB magnitude). We discuss the XRT 000519 association with the probable host candidate for various possible distances, and we conclude that if XRT 000519 is associated with the host candidate a supernova shock breakout scenario is likely excluded. No host galaxy is found near XRT 110103 down to a limiting magnitude of R > 25.8
Isospin dependence of electromagnetic transition strengths among an isobaric triplet
Electric quadrupole matrix elements, M, for the J=2â0, ÎT=0, T=1 transitions across the A=46 isobaric multiplet Cr-V-Ti have been measured at GSI with the FRS-LYCCA-AGATA setup. This allows direct insight into the isospin purity of the states of interest by testing the linearity of M with respect to T. Pairs of nuclei in the T=1 triplet were studied using identical reaction mechanisms in order to control systematic errors. The M values were obtained with two different methodologies: (i) a relativistic Coulomb excitation experiment was performed for Cr and Ti; (ii) a âstretched targetâ technique was adopted here, for the first time, for lifetime measurements in V and Ti. A constant value of M across the triplet has been observed. Shell-model calculations performed within the fp shell fail to reproduce this unexpected trend, pointing towards the need of a wider valence space. This result is confirmed by the good agreement with experimental data achieved with an interaction which allows excitations from the underlying sd shell. A test of the linearity rule for all published data on complete T=1 isospin triplets is presented.Peer Reviewe
Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus
A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 Ă 10-20), ER-negative BC (P=1.1 Ă 10-13), BRCA1-associated BC (P=7.7 Ă 10-16) and triple negative BC (P-diff=2 Ă 10-5). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 Ă 10-3) and ABHD8 (P<2 Ă 10-3). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3âČ-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk
Measurement of the cross section for isolated-photon plus jet production in pp collisions at âs=13 TeV using the ATLAS detector
The dynamics of isolated-photon production in association with a jet in protonâproton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fbâ1. Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- algorithm with radius parameter and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photonâjet invariant mass and the scattering angle in the photonâjet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements
A search for resonances decaying into a Higgs boson and a new particle X in the XH â qqbb final state with the ATLAS detector
A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fbâ1 of protonâproton collision data at collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle X is assumed to decay to a pair of light quarks, and the fully hadronic final state is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the resonance
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
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