170 research outputs found
Population dynamics of two sympatric intertidal fish species (the shanny, Lipophrys pholis, and long-spined scorpion fish,Taurulus bubalis) of Great Britain
The shanny/common blenny (Lipophrys pholis) and long-spined scorpionfish/bullhead (Taurulus bubalis) are commonly encountered, sympatric species within much of Great Britain’s rocky intertidal zones. Despite being prey items of the cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) respectively, and both contributors to the diet of the near-threatened European otter (Lutra lutra), little is known on the population dynamics of the temperate specimens of Great Britain. It is further less known of the degrees of sympatricy between the two fish species and to what extent they are able to coexist. The current study examines spatio-temporal distributions and abundances at various resolutions: monthly population dynamics of both species along England’s Yorkshire coast and seasonal population dynamics along the Yorkshire coast and around the Isle of Anglesey, Wales. Studies of their abundances, sizes, degrees of rock pool co-occurrence and diel activities are further examined, which indicate coexistence is maintained when interspecific co-occurrence takes place only between specimens of similar sizes, thus demoting size-related dominance hierarchies
Area metric gravity and accelerating cosmology
Area metric manifolds emerge as effective classical backgrounds in quantum
string theory and quantum gauge theory, and present a true generalization of
metric geometry. Here, we consider area metric manifolds in their own right,
and develop in detail the foundations of area metric differential geometry.
Based on the construction of an area metric curvature scalar, which reduces in
the metric-induced case to the Ricci scalar, we re-interpret the
Einstein-Hilbert action as dynamics for an area metric spacetime. In contrast
to modifications of general relativity based on metric geometry, no continuous
deformation scale needs to be introduced; the extension to area geometry is
purely structural and thus rigid. We present an intriguing prediction of area
metric gravity: without dark energy or fine-tuning, the late universe exhibits
a small acceleration.Comment: 52 pages, 1 figure, companion paper to hep-th/061213
The holonomy of the supercovariant connection and Killing spinors
We show that the holonomy of the supercovariant connection for M-theory
backgrounds with Killing spinors reduces to a subgroup of SL(32-N,\bR)\st
(\oplus^N \bR^{32-N}). We use this to give the necessary and sufficient
conditions for a background to admit Killing spinors. We show that there is
no topological obstruction for the existence of up to 22 Killing spinors in
eleven-dimensional spacetime. We investigate the symmetry superalgebras of
supersymmetric backgrounds and find that their structure constants are
determined by an antisymmetric matrix. The Lie subalgebra of bosonic generators
is related to a real form of a symplectic group. We show that there is a
one-one correspondence between certain bases of the Cartan subalgebra of
sl(32, \bR) and supersymmetric planar probe M-brane configurations. A
supersymmetric probe configuration can involve up to 31 linearly independent
planar branes and preserves one supersymmetry. The space of supersymmetric
planar probe M-brane configurations is preserved by an SO(32,\bR) subgroup of
SL(32, \bR).Comment: 27 pages, a key reference was added. v3: minor change
Properties of hyperkahler manifolds and their twistor spaces
We describe the relation between supersymmetric sigma-models on hyperkahler
manifolds, projective superspace, and twistor space. We review the essential
aspects and present a coherent picture with a number of new results.Comment: 26 pages. v2: Sign mistakes corrected; Kahler potential explicitly
calculated in example; references added. v3: Published version--several small
clarifications per referee's reques
Colorectal polyp outcomes after participation in the seAFOod polyp prevention trial: Evidence of rebound elevated colorectal polyp risk after short-term aspirin use
Background
The seAFOod polyp prevention trial was a randomised, placebo-controlled, 2 × 2 factorial trial of aspirin 300 mg and eicosapentaenoic acid (EPA) 2000 mg daily in individuals who had a screening colonoscopy in the English Bowel Cancer Screening Programme (BCSP). Aspirin treatment was associated with a 20% reduction in colorectal polyp number at BCSP surveillance colonoscopy 12 months later. It is unclear what happens to colorectal polyp risk after short-term aspirin use.
Aim
To investigate colorectal polyp risk according to the original trial treatment allocation, up to 6 years after trial participation.
Methods
All seAFOod trial participants were scheduled for further BCSP surveillance and provided informed consent for the collection of colonoscopy outcomes. We linked BCSP colonoscopy data to trial outcomes data.
Results
In total, 507 individuals underwent one or more colonoscopies after trial participation. Individuals grouped by treatment allocation were well matched for clinical characteristics, follow-up duration and number of surveillance colonoscopies. The polyp detection rate (PDR; the number of individuals who had ≥1 colorectal polyp detected) after randomization to placebo aspirin was 71.1%. The PDR was 80.1% for individuals who had received aspirin (odds ratio [OR] 1.13 [95% confidence interval 1.02, 1.24]; p = 0.02). There was no difference in colorectal polyp outcomes between individuals who had been allocated to EPA compared with its placebo (OR for PDR 1.00 [0.91, 1.10]; p = 0.92).
Conclusion
Individuals who received aspirin in the seAFOod trial demonstrated increased colorectal polyp risk during post-trial surveillance. Rebound elevated neoplastic risk after short-term aspirin use has important implications for aspirin cessation driven by age-related bleeding risk. ISRCTN05926847
Effect of Intralipid infusion on peripheral blood T cells and plasma cytokines in women undergoing assisted reproduction treatment
Objectives: Intravenous infusion of Intralipid is an adjunct therapy in assisted reproduction treatment (ART) when immune-associated infertility is suspected. Here, we evaluated the effect of Intralipid infusion on regulatory T cells (Treg cells), effector T cells and plasma cytokines in peripheral blood of women undertaking IVF. Methods: This prospective, observational pilot study assessed Intralipid infusion in 14 women exhibiting recurrent implantation failure, a clinical sign of immune-associated infertility. Peripheral blood was collected immediately prior to and 7Â days after intravenous administration of Intralipid. Plasma cytokines were measured by Luminex, and T-cell subsets were analysed by flow cytometry. Results: A small increase in conventional CD8+ T cells occurred after Intralipid infusion, but no change was seen in CD4+ Treg cells, or naĂŻve, memory or effector memory T cells. Proliferation marker Ki67, transcription factors Tbet and RORÎłt, and markers of suppressive capacity CTLA4 and HLA-DR were unchanged. Dimensionality-reduction analysis using the tSNE algorithm confirmed no phenotype shift within Treg cells or other T cells. Intralipid infusion increased plasma CCL2, CCL3, CXCL8, GM-CSF, G-CSF, IL-6, IL-21, TNF and VEGF. Conclusion: Intralipid infusion elicited elevated pro-inflammatory cytokines, and a minor increase in CD8+ T cells, but no change in pro-tolerogenic Treg cells. Notwithstanding the limitation of no placebo control, the results do not support Intralipid as a candidate intervention to attenuate the Treg cell response in women undergoing ART. Future placebo-controlled studies are needed to confirm the potential efficacy and clinical significance of Intralipid in attenuating cytokine induction and circulating CD8+ T cells.Kerrie L Foyle, David J Sharkey, Lachlan M Moldenhauer, Ella S Green, Jasmine J Wilson, Cassandra J Roccisano ... et al
Interactions between propagating cracks and bioinspired self-healing vascules embedded in glass fibre reinforced composites
International audienceThis study considers the embedment of a bioinspired vasculature within a composite structure that is capable of delivering functional agents from an external reservoir to regions of internal damage. Breach of the vascules, by propagating cracks, is a crucial pre-requisite for such a self-healing system to be activated. Two segregated vascule fabrication techniques are demonstrated, and their interactions with propagating Mode I and II cracks determined. The vascule fabrication route adopted played a significant role on the resulting laminate morphology which in-turn dictated the crack-vascule interactions. Embedment of the vascules did not lower the Mode I or II fracture toughness of the host laminate, with vascules orientated transverse to the crack propagation direction leading to significant increases in G and G through crack arrest. Large resin pockets were found to redirect the crack around the vascules under Mode II conditions, therefore, it is recommended to avoid this configuration for self-healing applications
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The effect of aspirin and eicosapentaenoic acid on urinary biomarkers of prostaglandin E2 synthesis and platelet activation in participants of the seAFOod polyp prevention trial
Urinary prostaglandin (PG) E metabolite (PGE-M) and 11-dehydro (d)-thromboxane (TX) B2 are biomarkers of cyclooxygenase-dependent prostanoid synthesis. We investigated (1) the effect of aspirin 300 mg daily and eicosapentaenoic acid (EPA) 2000 mg daily, alone and in combination, on urinary biomarker levels and, (2) whether urinary biomarker levels predicted colorectal polyp risk, during participation in the seAFOod polyp prevention trial. Urinary PGE-M and 11-d-TXB2 were measured by liquid chromatography-tandem mass spectrometry. The relationship between urinary biomarker levels and colorectal polyp outcomes was investigated using negative binomial (polyp number) and logistic (% with one or more polyps) regression models. Despite wide temporal variability in PGE-M and 11-d-TXB2 levels within individuals, both aspirin and, to a lesser extent, EPA decreased levels of both biomarkers (74% [P ≤ .001] and 8% [P ≤ .05] reduction in median 11-d-TXB2 values, respectively). In the placebo group, a high (quartile [Q] 2-4) baseline 11-d-TXB2 level predicted increased polyp number (incidence rate ratio [IRR] [95% CI] 2.26 [1.11,4.58]) and risk (odds ratio [95% CI] 3.56 [1.09,11.63]). A low (Q1) on-treatment 11-d-TXB2 level predicted reduced colorectal polyp number compared to placebo (IRR 0.34 [0.12,0.93] for combination aspirin and EPA treatment) compared to high on-treatment 11-d-TXB2 values (0.61 [0.34,1.11]). Aspirin and EPA both inhibit PGE-M and 11-d-TXB2 synthesis in keeping with shared in vivo cyclooxygenase inhibition. Colorectal polyp risk and treatment response prediction by 11-d-TXB2 is consistent with a role for platelet activation during early colorectal carcinogenesis. The use of urinary 11-d-TXB2 measurement for a precision approach to colorectal cancer risk prediction and chemoprevention requires prospective evaluation
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Plasma and rectal mucosal oxylipin levels during aspirin and eicosapentaenoic acid treatment in the seAFOod polyp prevention trial
Background
Aspirin and eicosapentaenoic acid (EPA) have colorectal polyp prevention activity, alone and in combination. This study measured levels of plasma and rectal mucosal oxylipins in participants of the seAFOod 2 Ă— 2 factorial, randomised, placebo-controlled trial, who received aspirin 300 mg daily and EPA 2000 mg free fatty acid, alone and in combination, for 12 months.
Methods
Resolvin (Rv) E1, 15-epi-lipoxin (LX) A4 and respective precursors 18-HEPE and 15-HETE (with chiral separation) were measured by ultra-high performance liquid chromatography-tandem mass spectrometry in plasma taken at baseline, 6 months and 12 months, as well as rectal mucosa obtained at trial exit colonoscopy at 12 months, in 401 trial participants.
Results
Despite detection of S- and R- enantiomers of 18-HEPE and 15-HETE in ng/ml concentrations, RvE1 or 15‑epi-LXA4 were not detected above a limit of detection of 20 pg/ml in plasma or rectal mucosa, even in individuals randomised to both aspirin and EPA. We have confirmed in a large clinical trial cohort that prolonged (12 months) treatment with EPA is associated with increased plasma 18-HEPE concentrations (median [inter-quartile range] total 18-HEPE 0.51 [0.21–1.95] ng/ml at baseline versus 0.95 [0.46–4.06] ng/ml at 6 months [P<0.0001] in those randomised to EPA alone), which correlate strongly with respective rectal mucosal 18-HEPE levels (r = 0.82; P<0.001), but which do not predict polyp prevention efficacy by EPA or aspirin.
Conclusion
Analysis of seAFOod trial plasma and rectal mucosal samples has not provided evidence of synthesis of the EPA-derived specialised pro-resolving mediator RvE1 or aspirin-trigged lipoxin 15‑epi-LXA4. We cannot rule out degradation of individual oxylipins during sample collection and storage but readily measurable precursor oxylipins argues against widespread degradation
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