763 research outputs found
A Broad 22 Microns Emission Feature in the Carina Nebula H II Region
We report the detection of a broad 22 microns emission feature in the Carina
nebula H II region by the Infrared Space Observatory (ISO) Short Wavelength
Spectrometer. The feature shape is similar to that of the 22 microns emission
feature of newly synthesized dust observed in the Cassiopeia A supernova
remnant. This finding suggests that both of the features are arising from the
same carrier, and that supernovae are probably the dominant production source
of this new interstellar grain. A similar broad emission dust feature is also
found in the spectra of two starburst galaxies from the ISO archival data. This
new dust grain could be an abundant component of interstellar grains and can be
used to trace the supernova rate or star formation rate in external galaxies.
The existence of the broad 22 microns emission feature complicates the dust
model for starburst galaxies and must be taken into account correctly in the
derivation of dust color temperature. Mg protosilicate has been suggested as
the carrier of the 22 microns emission dust feature observed in Cassiopeia A.
The present results provide useful information in studies on chemical
composition and emission mechanism of the carrier.Comment: 7 pages, 6 figures, to appear in ApJ Letter
Molecular and cellular responses to renal injury : a (phospho)-proteomic approach
Our kidneys play a major role in regulating the body__s internal environment, via transportation of water, salt, potassium and waste products. As a result of this transport function, cells within the kidney are relatively sensitive to injury. This injury can occur when the kidneys are exposed to anticancer drugs, antibiotics, toxic chemicals or as a result of a drop in blood flow during kidney transplantation (ischemia/reperfusion injury). As a consequence, renal function is rapidly lost. The primary targets for injury are epithelial cells lining the proximal tubule. These cells rest on a basement membrane via cell-matrix interactions and are connected to each other via cell-cell interactions. At these adhesion sites, several signalling complexes are located, which are linked to the F-actin cytoskeleton of the cell. When cells are damaged, they alter or may loose their cell-cell and cell-matrix adhesions in association with reorganization of the actin cytoskeleton. This is associated with changes in the activation status of several signal transduction pathways. The research described in this thesis was designed to identify __new__ signalling pathways involved in renal cell injury and understand their role in this process. The changes in protein expression and phosphorylation that occur in association with changes in cell adhesion and cytoskeletal organization prior to or during renal cell injury were analyzed using 2D-Difference In Gel Electrophoresis (DIGE) and 2D-phosphotyrosine blotting.the protein identifications that are described in this thesis point to a more common observation of alterations in the F-actin cytoskeleton that take place during the process of renal cell injury and regeneration. Assessing the precise role of these proteins and their phosphorylation status will increase our understanding of the events that take place during this process.LEI Universiteit LeidenLeiden/Amsterdam Center for Drug Research
J.E. Jurriaanse Stichting
Nierstichting Nederland
Tebu-bioLACD
ISOPHOT observations of 3CR quasars and radio galaxies
In order to check for consistency with the radio-loud AGN unification scheme, ISOPHOT data obtained for two small sets of intermediate redshift steep-spectrum 3CR radio galaxies and quasars are being examined. Supplementary submillimeter and centimeter radio data for the quasars are also taken into account, in order to assess the magnitude of any beamed nonthermal radiation. The fact that we find broad-lined objects to be somewhat more luminous in their far-infrared output than narrow-lined objects, hints at a contradiction to the unification scheme. However, as the sample objects are not particularly well matched, the sample size is small, and the FIR radiation may still be partly anisotropic, this evidence is, at the moment, weak
OH rotational lines as a diagnostic of the warm neutral gas in galaxies
We present Infrared Space Observatory (ISO) observations of several OH, CH
and H2O rotational lines toward the bright infrared galaxies NGC253 and
NGC1068. As found in the Galactic clouds in SgrB2 and Orion, the extragalactic
far-IR OH lines change from absorption to emission depending on the physical
conditions and distribution of gas and dust along the line of sight. As a
result, most of the OH rotational lines that appear in absorption toward NGC253
are observed in emission toward NGC1068. We show that the far-IR spectrum of OH
can be used as a powerful diagnostic to derive the physical conditions of
extragalactic neutral gas. In particular, we find that a warm (Tk~150 K, n(H2)<
5 10^4 cm^-3) component of molecular gas with an OH abundance of 10^{-7} from
the inner <15'' can qualitatively reproduce the OH lines toward NGC253. Similar
temperatures but higher densities (5 10^5 cm^-3) are required to explain the OH
emission in NGC1068.Comment: 5 pages, 4 figures, accepted in ApJ Part I (2004, October 6
Spitzer-IRS high resolution spectroscopy of the 12\mu m Seyfert galaxies: I. First results
The first high resolution Spitzer IRS 9-37um spectra of 29 Seyfert galaxies
(about one quarter) of the 12um Active Galaxy Sample are presented and
discussed. The high resolution spectroscopy was obtained with corresponding
off-source observations. This allows excellent background subtraction, so that
the continuum levels and strengths of weak emission lines are accurately
measured. The result is several new combinations of emission line ratios,
line/continuum and continuum/continuum ratios that turn out to be effective
diagnostics of the strength of the AGN component in the IR emission of these
galaxies. The line ratios [NeV]/[NeII], [OIV]/[NeII], already known, but also
[NeIII]/[NeII] and [NeV]/[SiII] can all be effectively used to measure the
dominance of the AGN. We extend the analysis, already done using the 6.2um PAH
emission feature, to the equivalent width of the 11.25um PAH feature, which
also anti-correlates with the dominance of the AGN. We measure that the 11.25um
PAH feature has a constant ratio with the H_2 S(1) irrespective of Seyfert
type, approximately 10 to 1. Using the ratio of accurate flux measurements at
about 19um with the two spectrometer channels, having aperture areas differing
by a factor 4, we measured the source extendness and correlated it with the
emission line and PAH feature equivalent widths. The extendness of the source
gives another measure of the AGN dominance and correlates both with the EWs of
[NeII] and PAH emission. Using the rotational transitions of H we were able
to estimate temperatures (200-300K) and masses (1-10 x 10^6 M_sun), or
significant limits on them, for the warm molecular component in the galaxies
observed.Comment: submitted to ApJ, Aug.2007, revised, in the refereeing proces
Water in Emission in the ISO Spectrum of the Early M Supergiant Star mu Cephei
We report a detection of water in emission in the spectrum of the M2
supergiant atar mu Cep (M2Ia) observed by the Short Wavelength Spectrometer
(SWS) aboard Infrared Space Observatory (ISO) and now released as the ISO
Archives. The emission first appears in the 6 micron region (nu2 fundamental)
and then in the 40 micron region (pure rotation lines) despite the rather
strong dust emission. The intensity ratios of the emission features are far
from those of the optically thin gaseous emission. Instead, we could reproduce
the major observed emission features by an optically thick water sphere of the
inner radius about two stellar radii (1300Rsun), Tex = 1500K, and Ncol (H2O) =
3.0E+20/cm2. This model also accounts for the H2O absorption bands in the near
infrared (1.4, 1.9, and 2.7 micron) as well. The detection of water in emission
provides strong constraints on the nature of water in the early M supergiant
stars, and especially its origin in the outer atmosphere is confirmed against
other models such as the large convective cell model. We finally confirm that
the early M supergiant star is surrounded by a huge optically thick sphere of
the warm water vapor, which may be referred to as MOLsphere for simplicity.
Thus, the outer atmosphere of M supergiant stars should have a complicated
hierarchical and/or hybrid structure with at least three major constituents
including the warm MOLsphere (T about 1.0E+3K) together with the previously
known hot chromosphere (T about 1.0E+4K) and cool expanding gas-dust envelope
(T about 1.0E+2K).Comment: 14 pages, 5 postscript figures, to appear in ApJ
Annexin A2 phosphorylation mediates cell scattering and branching morphogenesis via cofilin Activation
Dynamic remodeling of the actin cytoskeleton is required for cell spreading, motility, and migration and can be regulated by tyrosine kinase activity. Phosphotyrosine proteomic screening revealed phosphorylation of the lipid-, calcium-, and actin-binding protein annexin A2 (AnxA2) at Tyr23 as a major event preceding ts-v-Src kinase-induced cell scattering. Expression of the phospho-mimicking mutant Y23E-AnxA2 itself was sufficient to induce actin reorganization and cell scattering in MDCK cells. While Y23E-AnxA2, but not Y23A-AnxA2, enhanced Src- or hepatocyte growth factor (HGF)-induced cell scattering, short hairpin RNA-mediated knockdown of AnxA2 inhibited both v-Src- and HGF-induced cell scattering. Three-dimensional branching morphogenesis was induced in wild-type-AnxA2-expressing cells only in the presence of HGF, while Y23E-AnxA2 induced HGF-independent branching morphogenesis. Knockdown of AnxA2 prevented lumen formation during cystogenesis. The Y23E-AnxA2-induced scattering was associated with dephosphorylation/activation of the actin-severing protein cofilin. Likewise, inactive S3E-cofilin and constitutively active LIM kinase, a direct upstream kinase of cofilin, inhibited Y23E-AnxA2-induced scattering. Together, our studies indicate an essential role for AnxA2 phosphorylation in regulating cofilin-dependent actin cytoskeletal dynamics in the context of cell scattering and branching morphogenesis
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