135 research outputs found
Broken phase effective potential in the two-loop Phi-derivable approximation and nature of the phase transition in a scalar theory
We study the phase transition of a real scalar phi^4 theory in the two-loop
Phi-derivable approximation using the imaginary time formalism, extending our
previous (analytical) discussion of the Hartree approximation. We combine Fast
Fourier Transform algorithms and accelerated Matsubara sums in order to achieve
a high accuracy. Our results confirm and complete earlier ones obtained in the
real time formalism [1] but which were less accurate due to the integration in
Minkowski space and the discretization of the spectral density function. We
also provide a complete and explicit discussion of the renormalization of the
two-loop Phi-derivable approximation at finite temperature, both in the
symmetric and in the broken phase, which was already used in the real-time
approach, but never published. Our main result is that the two-loop
Phi-derivable approximation suffices to cure the problem of the Hartree
approximation regarding the order of the transition: the transition is of the
second order type, as expected on general grounds. The corresponding critical
exponents are, however, of the mean-field type. Using a "RG-improved" version
of the approximation, motivated by our renormalization procedure, we find that
the exponents are modified. In particular, the exponent delta, which relates
the field expectation value phi to an external field h, changes from 3 to 5,
getting then closer to its expected value 4.789, obtained from accurate
numerical estimates [2].Comment: 54 pages, 16 figure
Copper-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes: Synthesis of cyclopropylboronates
This document is the accepted manuscript version of a Published Work that appeared in final form in Journal of American Chemical Society 136.45, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see DOI: 10.1021/ja510419zA novel Cu-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes to afford nonracemic cyclopropylboronates is described. Trapping the cyclopropylcopper intermediate with electrophilic amines allows for the synthesis of cyclopropylaminoboronic esters and demonstrates the potential of the approach for the synthesis of functionalized cyclopropanesWe thank the European Research Council (ERC-337776) and MINECO (CTQ2012-35957) for financial support. M. T. and A. P. thank MICINN for RyC and JdC contract
Antioxidant Defenses Predict Long-Term Survival in a Passerine Bird
Normal and pathological processes entail the production of oxidative substances that can damage biological molecules and harm physiological functions. Organisms have evolved complex mechanisms of antioxidant defense, and any imbalance between oxidative challenge and antioxidant protection can depress fitness components and accelerate senescence. While the role of oxidative stress in pathogenesis and aging has been studied intensively in humans and model animal species under laboratory conditions, there is a dearth of knowledge on its role in shaping life-histories of animals under natural selection regimes. Yet, given the pervasive nature and likely fitness consequences of oxidative damage, it can be expected that the need to secure efficient antioxidant protection is powerful in molding the evolutionary ecology of animals. Here, we test whether overall antioxidant defense varies with age and predicts long-term survival, using a wild population of a migratory passerine bird, the barn swallow (Hirundo rustica), as a model.Plasma antioxidant capacity (AOC) of breeding individuals was measured using standard protocols and annual survival was monitored over five years (2006-2010) on a large sample of selection episodes. AOC did not covary with age in longitudinal analyses after discounting the effect of selection. AOC positively predicted annual survival independently of sex. Individuals were highly consistent in their relative levels of AOC, implying the existence of additive genetic variance and/or environmental (including early maternal) components consistently acting through their lives.Using longitudinal data we showed that high levels of antioxidant protection positively predict long-term survival in a wild animal population. Present results are therefore novel in disclosing a role for antioxidant protection in determining survival under natural conditions, strongly demanding for more longitudinal eco-physiological studies of life-histories in relation to oxidative stress in wild populations
The instrument suite of the European Spallation Source
An overview is provided of the 15 neutron beam instruments making up the initial instrument suite of the
European Spallation Source (ESS), and being made available to the neutron user community. The ESS neutron
source consists of a high-power accelerator and target station, providing a unique long-pulse time structure
of slow neutrons. The design considerations behind the time structure, moderator geometry and instrument
layout are presented.
The 15-instrument suite consists of two small-angle instruments, two reflectometers, an imaging beamline,
two single-crystal diffractometers; one for macromolecular crystallography and one for magnetism, two powder
diffractometers, and an engineering diffractometer, as well as an array of five inelastic instruments comprising
two chopper spectrometers, an inverse-geometry single-crystal excitations spectrometer, an instrument for vibrational
spectroscopy and a high-resolution backscattering spectrometer. The conceptual design, performance
and scientific drivers of each of these instruments are described.
All of the instruments are designed to provide breakthrough new scientific capability, not currently
available at existing facilities, building on the inherent strengths of the ESS long-pulse neutron source of high
flux, flexible resolution and large bandwidth. Each of them is predicted to provide world-leading performance
at an accelerator power of 2 MW. This technical capability translates into a very broad range of scientific
capabilities. The composition of the instrument suite has been chosen to maximise the breadth and depth
of the scientific impact o
Recommended from our members
Combinatorial, additive and dose-dependent drug–microbiome associations
During the transition from a healthy state to cardiometabolic disease, patients become heavily medicated, which leads to an increasingly aberrant gut microbiome and serum metabolome, and complicates biomarker discovery. Here, through integrated multi-omics analyses of 2,173 European residents from the MetaCardis cohort, we show that the explanatory power of drugs for the variability in both host and gut microbiome features exceeds that of disease. We quantify inferred effects of single medications, their combinations as well as additive effects, and show that the latter shift the metabolome and microbiome towards a healthier state, exemplified in synergistic reduction in serum atherogenic lipoproteins by statins combined with aspirin, or enrichment of intestinal Roseburia by diuretic agents combined with beta-blockers. Several antibiotics exhibit a quantitative relationship between the number of courses prescribed and progression towards a microbiome state that is associated with the severity of cardiometabolic disease. We also report a relationship between cardiometabolic drug dosage, improvement in clinical markers and microbiome composition, supporting direct drug effects. Taken together, our computational framework and resulting resources enable the disentanglement of the effects of drugs and disease on host and microbiome features in multimedicated individuals. Furthermore, the robust signatures identified using our framework provide new hypotheses for drug–host–microbiome interactions in cardiometabolic disease
- …