202 research outputs found
Cigarette Smoke, Airway Epithelial Cells and Host Defence
In COPD inflammation driven by exposure to tobacco smoke results in impaired innate immunity in the airway and ultimately to lung injury and remodeling. To understand the biological processes involved in host interactions with cigarette derived toxins submerged epithelial cell culture is widely accepted as a model for primary human airway epithelial cell culture research. Primary nasal and bronchial epithelial cells can also be cultured in models. Air liquid interface (ALI) and submerged culture models have their individual merits, and the decision to use either technique should primarily be determined by the research hypothesis. Cigarette smoke has gaseous and particulate matter, the latter constituent primarily represented in cigarette smoke extract (CSE). Although not ideal in order to facilitate our understanding of the responses of epithelial cells to cigarette smoke, CSE still has scientific merit in airway cell biology research. Using this model, it has been possible to demonstrate differences in levels of tight junction disruption after CSE exposure along with varied vulnerability to the toxic effects of CSE in cell cultures derived from COPD and control study groups. Primary nasal epithelial cells (PNECs) have been used as an alternative to bronchial epithelial cells (PBECs). However, at least in subjects with COPD, PNECs cannot consistently substitute for PBECs. Despite having a constitutional pro-inflammatory phenotype, bronchial epithelial cells retrieved from subjects with COPD have a relatively curtailed inflammatory response to CSE exposure when compared to epithelial cells from thei
Choptuik scaling in six dimensions
We perform numerical simulations of the critical gravitational collapse of a
spherically symmetric scalar field in 6 dimensions. The critical solution has
discrete self-similarity. We find the critical exponent \gamma and the
self-similarity period \Delta.Comment: 8 pages, 3 figures RevTe
Streambed organic matter controls on carbon dioxide and methane emissions from streams
Greenhouse
gas (GHG) emissions of carbon dioxide (CO2) and methane
(CH4) from streambeds are currently understudied.
There is a paucity of research exploring organic matter (OM) controls
on GHG production by microbial metabolic activity in streambeds, which
is a major knowledge gap given the increased inputs of allochthonous
carbon to streams, especially in agricultural catchments. This study
aims to contribute to closing this knowledge gap by quantifying how
contrasting OM contents in different sediments affect streambed GHG
production and associated microbial metabolic activity. We demonstrate,
by means of an incubation experiment, that streambed sediments have
the potential to produce substantial amounts of GHG, controlled by
sediment OM quantity and quality. We observed streambed CO2 production rates that can account for 35% of total stream evasion
estimated in previous studies, ranging between 1.4 and 86% under optimal
conditions. Methane production varied stronger than CO2 between different geologic backgrounds, suggesting OM quality controls
between streambed sediments. Moreover, our results indicate that streambed
sediments may produce much more CO2 than quantified to
date, depending on the quantity and quality of the organic matter,
which has direct implications for global estimates of C fluxes in
stream ecosystems
Scaling of curvature in sub-critical gravitational collapse
We perform numerical simulations of the gravitational collapse of a
spherically symmetric scalar field. For those data that just barely do not form
black holes we find the maximum curvature at the position of the central
observer. We find a scaling relation between this maximum curvature and
distance from the critical solution. The scaling relation is analogous to that
found by Choptuik for black hole mass for those data that do collapse to form
black holes. We also find a periodic wiggle in the scaling exponent.Comment: Revtex, 2 figures, Discussion modified, to appear in Phys. Rev.
Long-wavelength iteration scheme and scalar-tensor gravity
Inhomogeneous and anisotropic cosmologies are modeled withing the framework
of scalar-tensor gravity theories. The inhomogeneities are calculated to
third-order in the so-called long-wavelength iteration scheme. We write the
solutions for general scalar coupling and discuss what happens to the
third-order terms when the scalar-tensor solution approaches at first-order the
general relativistic one. We work out in some detail the case of Brans-Dicke
coupling and determine the conditions for which the anisotropy and
inhomogeneity decay as time increases. The matter is taken to be that of
perfect fluid with a barotropic equation of state.Comment: 13 pages, requires REVTeX, submitted to Phys. Rev.
Numerical evolution of Brill waves
We report a numerical evolution of axisymmetric Brill waves. The numerical
algorithm has new features, including (i) a method for keeping the metric
regular on the axis and (ii) the use of coordinates that bring spatial infinity
to the edge of the computational grid. The dependence of the evolved metric on
both the amplitude and shape of the initial data is found.Comment: added more discussion of results and several reference
Addendum:Thermal sensitivity of CO<sub>2</sub> and CH<sub>4</sub> emissions varies with streambed sediment properties
- …