155 research outputs found
Graviton Loop Corrections to Vacuum Polarization in de Sitter in a General Covariant Gauge
We evaluate the one-graviton loop contribution to the vacuum polarization on
de Sitter background in a 1-parameter family of exact, de Sitter invariant
gauges. Our result is computed using dimensional regularization and fully
renormalized with BPHZ counterterms, which must include a noninvariant owing to
the time-ordered interactions. Because the graviton propagator engenders a
physical breaking of de Sitter invariance two structure functions are needed to
express the result. In addition to its relevance for the gauge issue this is
the first time a covariant gauge graviton propagator has been used to compute a
noncoincident loop. A number of identities are derived which should facilitate
further graviton loop computations.Comment: 61 pages, 1 figure, 11 tables, version 2 (63 pages) revised for
publication in CQ
Graviton Propagator in a 2-Parameter Family of de Sitter Breaking Gauges
We formulate the graviton propagator on de Sitter background in a 2-parameter
family of simple gauges which break de Sitter invariance. Explicit results are
derived for the first order perturbations in each parameter. These results
should be useful in computations to check for gauge dependence of graviton loop
corrections.Comment: 23 pages, 1 table, uses LaTeX2e, version 2 slightly revised for
publicatio
One-loop Graviton Corrections to Conformal Scalars on a de Sitter Background
We exploit a recent computation of one graviton loop corrections to the
self-mass [1] to quantum-correct the field equation for a massless, conformally
coupled scalar on a de Sitter background. With the obvious choice for the
finite part of the counterterm, we find that neither plane wave
mode functions nor the response to a point source acquires large infrared
logarithms. However, we do find a decaying logarithmic correction to the mode
function and a short distance logarithmic running of the potential in addition
to the power-law effect inherited from flat space.Comment: 25 pages, 2 figures; published versio
Explaining Large Electromagnetic Logarithms from Loops of Inflationary Gravitons
Recent progress on nonlinear sigma models on de Sitter background has
permitted the resummation of large inflationary logarithms by combining a
variant of Starobinsky's stochastic formalism with a variant of the
renormalization group. We reconsider single graviton loop corrections to the
photon wave function, and to the Coulomb potential, in light of these
developments. Neither of the two 1-loop results have a stochastic explanation,
however, the flow of a curvature-dependent field strength renormalization
explains their factors of . We speculate that the factor of
in the Coulomb potential should not be considered as a leading logarithm
effect.Comment: 22 pages, uses LaTeX2e, slightly revised for publicatio
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Inflammation and Immune-Related Candidate Gene Associations with Acute Lung Injury Susceptibility and Severity: A Validation Study
Introduction: Common variants in genes related to inflammation, innate immunity, epithelial cell function, and angiogenesis have been reported to be associated with risks for Acute Lung Injury (ALI) and related outcomes. We tested whether previously-reported associations can be validated in an independent cohort at risk for ALI. Methods: We identified 37 genetic variants in 27 genes previously associated with ALI and related outcomes. We prepared allelic discrimination assays for 12 SNPs from 11 genes with MAF>0.05 and genotyped these SNPs in Caucasian subjects from a cohort of critically ill patients meeting criteria for the systemic inflammatory response syndrome (SIRS) followed for development of ALI, duration of mechanical ventilation, and in-hospital death. We tested for associations using additive and recessive genetic models. Results: Among Caucasian subjects with SIRS (n = 750), we identified a nominal association between rs2069832 in IL6 and ALI susceptibility (OR 1.61; 95% confidence interval [CI], 1.04–2.48, P = 0.03). In a sensitivity analysis limiting ALI cases to those who qualified for the Acute Respiratory Distress Syndrome (ARDS), rs61330082 in NAMPT was nominally associated with risk for ARDS. In terms of ALI outcomes, SNPs in MBL2 (rs1800450) and IL8 (rs4073) were nominally associated with fewer ventilator-free days (VFDs), and SNPs in NFE2L2 (rs6721961) and NAMPT (rs61330082) were nominally associated with 28-day mortality. The directions of effect for these nominal associations were in the same direction as previously reported but none of the associations survived correction for multiple hypothesis testing. Conclusion: Although our primary analyses failed to statistically validate prior associations, our results provide some support for associations between SNPs in IL6 and NAMPT and risk for development of lung injury and for SNPs in IL8, MBL2, NFE2L2 and NAMPT with severity in ALI outcomes. These associations provide further evidence that genetic factors in genes related to immunity and inflammation contribute to ALI pathogenesis
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Rapid fabrication of pressure-driven open-channel microfluidic devices in omniphobic RF paper
This paper describes the fabrication of pressure-driven, open-channel microfluidic systems with lateral dimensions of 45-300 microns carved in omniphobic paper using a craft-cutting tool. Vapor phase silanization with a fluorinated alkyltrichlorosilane renders paper omniphobic, but preserves its high gas permeability and mechanical properties. When sealed with tape, the carved channels form conduits capable of guiding liquid transport in the low-Reynolds number regime (i.e. laminar flow). These devices are compatible with complex fluids such as droplets of water in oil. The combination of omniphobic paper and a craft cutter enables the development of new types of valves and switches, such as “fold” valves and “porous switches,” which provide new methods to control fluid flow.Chemistry and Chemical Biolog
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