988 research outputs found
Role of endothelial permeability hotspots and endothelial mitosis in determining age-related patterns of macromolecule uptake by the rabbit aortic wall near branch points
AbstractBackground and aimsTransport of macromolecules between plasma and the arterial wall plays a key role in atherogenesis. Scattered hotspots of elevated endothelial permeability to macromolecules occur in the aorta; a fraction of them are associated with dividing cells. Hotspots occur particularly frequently downstream of branch points, where lesions develop in young rabbits and children. However, the pattern of lesions varies with age, and can be explained by similar variation in the pattern of macromolecule uptake. We investigated whether patterns of hotspots and mitosis also change with age.MethodsEvans’ Blue dye-labeled albumin was injected intravenously into immature or mature rabbits and its subsequent distribution in the aortic wall around intercostal branch ostia examined by confocal microscopy and automated image analysis. Mitosis was detected by immunofluorescence after adding 5-bromo-2-deoxiuridine to drinking water.ResultsHotspots were most frequent downstream of branches in immature rabbits, but a novel distribution was observed in mature rabbits. Neither pattern was explained by mitosis. Hotspot uptake correlated spatially with the much greater non-hotspot uptake (p < 0.05), and the same pattern was seen when only the largest hotspots were considered.ConclusionsThe pattern of hotspots changes with age. The data are consistent with there being a continuum of local permeabilities rather than two distinct mechanisms. The distribution of the dye, which binds to elastin and collagen, was similar to that of non-binding tracers and to lesions apart from a paucity at the lateral margins of branches that can be explained by lower levels of fibrous proteins in those regions
Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study
The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, these transport processes and their dependence on transmural pressure remain incompletely understood. Here, we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media and the geometry of medial smooth muscle cells (SMCs) and extracellular matrix (ECM). Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was identified that modulates pressure-induced changes in medial transport properties: compaction of the ECM leading to spatial reorganization of SMCs. This is summarized in an empirical constitutive law for permeability and volumetric strain. It led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above approximately 93 mmHg in this vessel
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The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines
We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field
spectroscopy to probe the morphology and kinematics of the ionized gas in four
velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky
Survey. These objects possess optical emission lines that are offset in
velocity from systemic as measured from stellar absorption features. At a
resolution of ~0.18", OSIRIS allows us to distinguish which velocity offset
emission lines are produced by the motion of an AGN in a dual supermassive
black hole system, and which are produced by outflows or other kinematic
structures. In three galaxies, J1018+2941, J1055+1520 and J1346+5228, the
spectral offset of the emission lines is caused by AGN-driven outflows. In the
remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that
contains the peak of Pa emission 0.2" from the center of the galaxy.
The most plausible explanation for the origin of this spatially and
kinematically offset peak is that it is a region of enhanced Pa
emission located at the intersection zone between the nuclear disk and the bar
of the galaxy. In all four objects, the peak of ionized gas emission is not
spatially coincident with the center of the galaxy as traced by the peak of the
near-IR continuum emission. The peaks of ionized gas emission are spatially
offset from the galaxy centers by 0.1"-0.4" (0.1-0.7 kpc). We find that the
velocity offset originates at the location of this peak of emission, and the
value of the offset can be directly measured in the velocity maps. The
emission-line ratios of these four velocity-offset AGNs can be reproduced only
with a mixture of shocks and AGN photoionization. Shocks provide a natural
explanation for the origin of the spatially and spectrally offset peaks of
ionized gas emission in these galaxies.Comment: 14 pages, 12 figures, accepted for publication in Ap
Recommendations for a Cockpit Display that Integrates Weather Information with Traffic Information
This effort was supported by the System-Wide Accident Prevention element of NASA s Aviation Safety Program. This document may serve as a first step toward the goal of integrating traffic, weather, and terrain information; it provides recommendations for a cockpit display that integrates weather information with traffic information. While some of the recommendations are general enough to be used for any type of operations, these recommendations are targeted for Federal Aviation Regulations Part 121 Operations. The document is organized in the following manner. First, weather information is discussed as an independent subject matter, and recommendations are presented for presenting weather in the cockpit. Second, traffic is discussed independently, but this discussion essentially reviews work on the display of traffic in the cockpit. Third, recommendations for the cockpit integration of weather and traffic information are discussed. Fourth, several research groups are recognized for their efforts in developing systems that are relevant to the current discussion. Finally, closing remarks provide suggestions for future efforts
Die-by Framing both Lengthens and Shortens Life: Further Evidence on Constructed Beliefs in Life Expectancy
Decisions regarding consumption over the lifespan require some estimate of how long that lifespan is likely to be. Payne et al. (2013) found that respondents' estimates of their own life expectancy are on average 8.6 years shorter when elicited using a die-by frame than when elicited by a live-to frame. If decision makers act on these life expectancies, then an arbitrary detail of framing will lead to drastically different choices. We propose that the framing effect is sensitive to the iterative probabilistic elicitation procedure employed by the previous literature. Study 1 compares the framing effect across the iterative probabilistic procedure and a point estimate procedure that simply asks respondents the age they will live to/die by. The iterative probabilistic procedure implies a life expectancy six years shorter in the die-by frame than in the live-to frame, replicating the results of Payne et al. (2013). With the point estimate procedure, however, the framing effect reverses: the die-by frame increases life expectancy by three years. In Study 2, we test for the framing effect using a point estimate procedure on a representative sample of 2000 Britons. Again, and in contrast with the previous literature, we find that the die-by frame implies longer life. Our results reinforce the previous literature that beliefs around life expectancy are constructed. We recommend caution when attempting to debias life expectancy estimates or using life expectancies in choice architecture
Proof of concept that requiring energy labels for dwellings can induce retrofitting
How to induce households to install energy efficient technology remains a puzzle. Could an energy labeling requirement for residential real estate help? We propose that the salient color-letter grades on the English Energy Performance Certificate (EPC) served as targets, motivating vendors to invest in energy efficiency. To test our hypothesis we look to a random sample of over 16,000 homes in England. In the post-EPC data we find a cluster of homes with energy efficiency scores just above the D-grade threshold. This cluster was not present prior to the requirement, replicates in an independently-drawn random sample and is significantly larger amongst properties that can be identified as treated by the EPC requirement. We conclude that the EPC requirement induced investment, and hence that energy efficiency labels have potential to green the housing stock. We infer from our analysis how the design of the EPC could be altered to motivate greater investment in energy efficiency
Accounting for decarbonisation and reducing capital at risk in the S&P500
This document is the Accepted Manuscript version of the following article: Colin Haslam, Nick Tsitsianis, Glen Lehman, Tord Andersson, and John Malamatenios, ‘Accounting for decarbonisation and reducing capital at risk in the S&P500’, Accounting Forum, Vol. 42 91): 119-129, March 2018. Under embargo until 7 August 2019. The final, definitive version is available online at doi: https://doi.org/10.1016/j.accfor.2018.01.004.This article accounts for carbon emissions in the S&P 500 and explores the extent to which capital is at risk from decarbonising value chains. At a global level it is proving difficult to decouple carbon emissions from GDP growth. Top-down legal and regulatory arrangements envisaged by the Kyoto Protocol are practically redundant given inconsistent political commitment to mitigating global climate change and promoting sustainability. The United Nations Environment Programme (UNEP) and European Commission (EC) are promoting the role of financial markets and financial institutions as drivers of behavioural change mobilising capital allocations to decarbonise corporate activity.Peer reviewe
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