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Integrin α2ÎČ1 in nonactivated conformation can induce focal adhesion kinase signaling.
Conformational activation of integrins is generally required for ligand binding and cellular signalling. However, we have previously reported that the nonactivated conformation of α2ÎČ1 integrin can also bind to large ligands, such as human echovirus 1. In this study, we show that the interaction between the nonactivated integrin and a ligand resulted in the activation of focal adhesion kinase (FAK) in a protein kinase C dependent manner. A loss-of-function mutation, α2E336A, in the α2-integrin did not prevent the activation of FAK, nor did EDTA-mediated inactivation of the integrin. Full FAK activation was observed, since phosphorylation was not only confirmed in residue Y397, but also in residues Y576/7. Furthermore, initiation of downstream signaling by paxillin phosphorylation in residue Y118 was evident, even though this activation was transient by nature, probably due to the lack of talin involvement in FAK activation and the absence of vinculin in the adhesion complexes formed by the nonactivated integrins. Altogether these results indicate that the nonactivated integrins can induce cellular signaling, but the outcome of the signaling differs from conventional integrin signaling
Optical quality assurance of GEM foils
An analysis software was developed for the high aspect ratio optical scanning
system in the Detec- tor Laboratory of the University of Helsinki and the
Helsinki Institute of Physics. The system is used e.g. in the quality assurance
of the GEM-TPC detectors being developed for the beam diagnostics system of the
SuperFRS at future FAIR facility. The software was tested by analyzing five
CERN standard GEM foils scanned with the optical scanning system. The
measurement uncertainty of the diameter of the GEM holes and the pitch of the
hole pattern was found to be 0.5 {\mu}m and 0.3 {\mu}m, respectively. The
software design and the performance are discussed. The correlation between the
GEM hole size distribution and the corresponding gain variation was studied by
comparing them against a detailed gain mapping of a foil and a set of six lower
precision control measurements. It can be seen that a qualitative estimation of
the behavior of the local variation in gain across the GEM foil can be made
based on the measured sizes of the outer and inner holes.Comment: 12 pages, 29 figure
Detection of Circular Polarization in the Galactic Center Black Hole Candidate Sagittarius A*
We report here the detection of circular polarization in the Galactic Center
black hole candidate, Sagittarius A*. The detection was made at 4.8 GHz and 8.4
GHz with the Very Large Array. We find that the fractional circular
polarization at 4.8 GHz is and that the spectral index of
the circular polarization is (). The systematic error in is less than 0.04% at both
frequencies. In light of our recent lower limits on the linear polarization in
Sgr A*, this detection is difficult to interpret with standard models. We
consider briefly whether scattering mechanisms could produce the observed
polarization. Detailed modeling of the source and the scattering medium is
necessary. We propose a simple model in which low energy electrons reduce
linear polarization through Faraday depolarization and convert linear
polarization into circular polarization. Circular polarization may represent a
significant new parameter for studying the obscured centimeter wavelength radio
source in Sgr A*.Comment: ApJL accepted, 11 pages including 1 figur
Habitat filtering determines spatial variation of macroinvertebrate community traits in northern headwater streams
Although our knowledge of the spatial distribution of stream organisms has been increasing rapidly in the last decades, there is still little consensus about trait-based variability of macroinvertebrate communities within and between catchments in near-pristine systems. Our aim was to examine the taxonomic and trait based stability vs. variability of stream macroinvertebrates in three high-latitude catchments in Finland. The collected taxa were assigned to unique trait combinations (UTCs) using biological traits. We found that only a single or a highly limited number of taxa formed a single UTC, suggesting a low degree of redundancy. Our analyses revealed significant differences in the environmental conditions of the streams among the three catchments. Linear models, rarefaction curves and beta-diversity measures showed that the catchments differed in both alpha and beta diversity. Taxon- and trait-based multivariate analyses also indicated that the three catchments were significantly different in terms of macroinvertebrate communities. All these findings suggest that habitat filtering, i.e., environmental differences among catchments, determines the variability of macroinvertebrate communities, thereby contributing to the significant biological differences among the catchments. The main implications of our study is that the sensitivity of trait-based analyses to natural environmental variation should be carefully incorporated in the assessment of environmental degradation, and that further studies are needed for a deeper understanding of trait-based community patterns across near-pristine streams
The Linear Polarization of Sagittarius A* I. VLA Spectro-polarimetry at 4.8 and 8.4 GHz
Synchrotron radiation from active galactic nuclei (AGN) is often highly
polarized. We present a search for linear polarization with the Very Large
Array (VLA) at 4.8 GHz and 8.4 GHz from the nearest AGN, Sagittarius A*. As a
part of this study we used spectro-polarimetric data that were sensitive to a
rotation measure (RM) as large as 3.5 x 10^6 rad m^-2 at 4.8 GHz and 1.5 x 10^7
rad m^-2 at 8.4 GHz. The upper limit to the linear polarization of Sgr A* over
a broad range of RM is 0.2% at both frequencies. We also present continuum
observations with the VLA at 4.8 GHz which give an upper limit of 0.1% for RMs
less than 10^4 rad m^-2. We conclude that depolarization is unlikely to occur
in the Galacter Center scattering medium. However, it is possible for
depolarization to occur in the accretion region of Sgr A* if the outer scale of
turbulence is small enough. We also consider the implications of a very low
intrinsic polarization for Sgr A*.Comment: 16 pages, 3 figures, accepted for publication in the Astrophysical
Journal, August 20, 1999, Vol 521 #
Molecular Hydrogen and Paschen-alpha Emission in Cooling Flow Galaxies
We present near-infrared spectra obtained to search for Pa-alpha and
molecular hydrogen lines in edge-darkened (FR I-type) radio galaxies with
bright Halpha emission in the redshift range 0.0535<z<0.15. We find that all
three galaxies in our sample (PKS 0745-191, PKS 1346+26, & PKS2322-12) which
are associated with strong cooling flows also have strong Pa-alpha and H_2
(1-0) S(1) through S(5) emission, while other radio galaxies do not. Together
with earlier observations this confirms claims that cooling flow galaxies are
copious emitters of molecular hydrogen with large H_2 (1-0) S(3)/Pa-alpha
ratios in the range 0.5 to 2. The emission is centrally concentrated within the
inner few kiloparsec and could come from warm (T ~ 1000-1500 K) molecular
material which is being deposited by the cooling flow. We speculate that the
H_2 emission could be related to the interaction between the jets and this
molecular gas.Comment: ApJ Letters, in press, AAS LaTex, preprint also available at
http://www.astro.umd.edu/~hfalcke/publications.html#nirga
The Linear Polarization of Sagittarius A* II. VLA and BIMA Polarimetry at 22, 43 and 86 GHz
We present a search for linear polarization at 22 GHz, 43 GHz and 86 GHz from
the nearest super massive black hole candidate, Sagittarius A*. We find upper
limits to the linear polarization of 0.2%, 0.4% and 1%, respectively. These
results strongly support the conclusion of our centimeter wavelength
spectro-polarimetry that Sgr A* is not depolarized by the interstellar medium
but is in fact intrinsically depolarized.Comment: Accepted for publication in ApJ, 13 pages, 2 figure
The influence of emotional reaction on help seeking by victims of school bullying
Research has started to focus on how victims of school bullying cope, but there is still very little understanding if why pupils cope in one way and not another. This paper aimed to examine the effects of gender, school-stage, frequency of victimization and different emotions (anger, vengeance, self-pity, indifference, and helplessness) upon the choice of social support that children report using. Questionnaires were completed by 6282 Maltese schoolchildren aged between 9 and 14 years old. Analyses revealed that specific patterns of emotion and victimization predict whether pupils report using certain sources of social support. Results are discussed in relation to their relevance for possible intervention, future research needs and implications for the theoretical framework used
A comparative analysis reveals weak relationships between ecological factors and beta diversity of stream insect metacommunities at two spatial levels
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted by insect group, latitude, spatial extent, altitudinal range, and dataset properties across multiple drainage basins throughout the world. Second, we assessed the relative roles of environmental and spatial factors in driving variation in assemblage composition within each drainage basin. Our analyses were based on a dataset of 95 stream insect metacommunities from 31 drainage basins distributed around the world. We used dissimilarity-based indices to quantify beta diversity for each metacommunity and, subsequently, regressed beta diversity on insect group, latitude, spatial extent, altitudinal range, and dataset properties (e.g., number of sites and percentage of presences). Within each metacommunity, we used a combination of spatial eigenfunction analyses and partial redundancy analysis to partition variation in assemblage structure into environmental, shared, spatial, and unexplained fractions. We found that dataset properties were more important predictors of beta diversity than ecological and geographical factors across multiple drainage basins. In the within-basin analyses, environmental and spatial variables were generally poor predictors of variation in assemblage composition. Our results revealed deviation from general biodiversity patterns because beta diversity did not show the expected decreasing trend with latitude. Our results also call for reconsideration of just how predictable stream assemblages are along ecological gradients, with implications for environmental assessment and conservation decisions. Our findings may also be applicable to other dynamic systems where predictability is low
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