40 research outputs found
Morphological effects on IR band profiles: Experimental spectroscopic analysis with application to observed spectra of oxygen-rich AGB stars
To trace the source of the unique 13, 19.5, and 28 m emission features
in the spectra of oxygen-rich circumstellar shells around AGB stars, we have
compared dust extinction spectra obtained by aerosol measurements. We have
measured the extinction spectra for 19 oxide powder samples of eight different
types, such as Ti-compounds (TiO, TiO, TiO, TiO,
AlTiO, CaTiO), -, -,
---AlO, and MgAlO in the infrared region
(10 - 50 m) paying special attention to the morphological (size, shape,
and agglomeration) effects and the differences in crystal structure. Anatase
(TiO) particles with rounded edges are the possible 13, 19.5 and 28 m
band carriers as the main contributor in the spectra of AGB stars, and
spherically shaped nano-sized spinel and AlTiO dust grains are possibly
associated with the anatase, enhancing the prominence of the 13 m feature
and providing additional features at 28 m. The extinction data sets
obtained by the aerosol and CsI pellet measurements have been made available
for public use at http://elbe.astro.uni-jena.deComment: 17 pages, 8 figures, Accepted 24 March 2009 for publication in A&
Lipopolysaccharide-induced expression of cell surface receptors and cell activation of neutrophils and monocytes in whole human blood
Lipopolysaccharide (LPS) activates neutrophils and monocytes, inducing a wide array of biological activities. LPS rough (R) and smooth (S) forms signal through Toll-like receptor 4 (TLR4), but differ in their requirement for CD14. Since the R-form LPS can interact with TLR4 independent of CD14 and the differential expression of CD14 on neutrophils and monocytes, we used the S-form LPS from Salmonella abortus equi and the R-form LPS from Salmonella minnesota mutants to evaluate LPS-induced activation of human neutrophils and monocytes in whole blood from healthy volunteers. Expression of cell surface receptors and reactive oxygen species (ROS) and nitric oxide (NO) generation were measured by flow cytometry in whole blood monocytes and neutrophils. The oxidative burst was quantified by measuring the oxidation of 2',7'-dichlorofluorescein diacetate and the NO production was quantified by measuring the oxidation of 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate. A small increase of TLR4 expression by monocytes was observed after 6 h of LPS stimulation. Monocyte CD14 modulation by LPS was biphasic, with an initial 30% increase followed by a 40% decrease in expression after 6 h of incubation. Expression of CD11b was rapidly up-regulated, doubling after 5 min on monocytes, while down-regulation of CXCR2 was observed on neutrophils, reaching a 50% reduction after 6 h. LPS induced low production of ROS and NO. This study shows a complex LPS-induced cell surface receptor modulation on human monocytes and neutrophils, with up- and down-regulation depending on the receptor. R- and S-form LPS activate human neutrophils similarly, despite the low CD14 expression, if the stimulation occurs in whole blood