2,480 research outputs found
Asymmetry measures for QSOs and companions
An asymmetry index is derived from ellipse-fitting to galaxy images, that
gives weight to faint outer features and is not strongly redshift-dependent.
These measures are made on a sample of 13 2MASS QSOs and their neighbour
galaxies, and a control sample of field galaxies from the same wide-field
imaging data. The QSO host galaxy asymmetries correlate well with visual tidal
interaction indices previously published. The companion galaxies have somewhat
higher asymmetry than the control galaxy sample, and their asymmetry is
inversely correlated with distance from the QSO. The distribution of
QSO-companion asymmetry indices is different from that for matched control
field galaxies at the significance level. We present the data and
discuss this evidence for tidal and other disturbances in the vicinity of QSOs.Comment: 13 pages, 2 tables, 4 figures; to appear in A
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Matrix modification for enhancing the transport properties of the human cartilage endplate to improve disc nutrition.
Poor solute transport through the cartilage endplate (CEP) impairs disc nutrition and could be a key factor that limits the success of intradiscal biologic therapies. Here we demonstrate that treating the CEP with matrix metalloproteinase-8 (MMP-8) reduces the matrix constituents that impede solute uptake and thereby improves nutrient diffusion. Human CEP tissues harvested from four fresh cadaveric lumbar spines (age range: 38-66 years old) were treated with MMP-8. Treatment caused a dose-dependent reduction in sGAG, localized reductions to the amount of collagen, and alterations to collagen structure. These matrix modifications corresponded with 16-24% increases in the uptake of a small solute (376 Da). Interestingly, the effects of MMP-8 treatment depended on the extent of non-enzymatic glycation: treated CEPs with high concentrations of advanced glycation end products (AGEs) exhibited the lowest uptake compared to treated CEPs with low concentrations of AGEs. Moreover, AGE concentrations were donor-specific, and the donor tissues with the highest AGE concentrations appeared to have lower uptake than would be expected based on the initial amounts of collagen and sGAG. Finally, increasing solute uptake in the CEP improved cell viability inside diffusion chambers, which supports the nutritional relevance of enhancing the transport properties of the CEP. Taken together, our results provide new insights and in vitro proof-of-concept for a treatment approach that could improve disc nutrition for biologic therapy: specifically, matrix reduction by MMP-8 can enhance solute uptake and nutrient diffusion through the CEP, and AGE concentration appears to be an important, patient-specific factor that influences the efficacy of this approach
Fine-Structure FeII* Emission and Resonant MgII Emission in z = 1 Star-Forming Galaxies
We present a study of the prevalence, strength, and kinematics of ultraviolet
FeII and MgII emission lines in 212 star-forming galaxies at z = 1 selected
from the DEEP2 survey. We find FeII* emission in composite spectra assembled on
the basis of different galaxy properties, indicating that FeII* emission is
prevalent at z = 1. In these composites, FeII* emission is observed at roughly
the systemic velocity. At z = 1, we find that the strength of FeII* emission is
most strongly modulated by dust attenuation, and is additionally correlated
with redshift, star-formation rate, and [OII] equivalent width, such that
systems at higher redshifts with lower dust levels, lower star-formation rates,
and larger [OII] equivalent widths show stronger FeII* emission. We detect MgII
emission in at least 15% of the individual spectra and we find that objects
showing stronger MgII emission have higher specific star-formation rates,
smaller [OII] linewidths, larger [OII] equivalent widths, lower dust
attenuations, and lower stellar masses than the sample as a whole. MgII
emission strength exhibits the strongest correlation with specific
star-formation rate, although we find evidence that dust attenuation and
stellar mass also play roles in the regulation of MgII emission. Future
integral field unit observations of the spatial extent of FeII* and MgII
emission in galaxies with high specific star-formation rates, low dust
attenuations, and low stellar masses will be important for probing the
morphology of circumgalactic gas.Comment: 29 pages, 22 figures, 2 tables; accepted to Ap
New Image Statistics for Detecting Disturbed Galaxy Morphologies at High Redshift
Testing theories of hierarchical structure formation requires estimating the
distribution of galaxy morphologies and its change with redshift. One aspect of
this investigation involves identifying galaxies with disturbed morphologies
(e.g., merging galaxies). This is often done by summarizing galaxy images
using, e.g., the CAS and Gini-M20 statistics of Conselice (2003) and Lotz et
al. (2004), respectively, and associating particular statistic values with
disturbance. We introduce three statistics that enhance detection of disturbed
morphologies at high-redshift (z ~ 2): the multi-mode (M), intensity (I), and
deviation (D) statistics. We show their effectiveness by training a
machine-learning classifier, random forest, using 1,639 galaxies observed in
the H band by the Hubble Space Telescope WFC3, galaxies that had been
previously classified by eye by the CANDELS collaboration (Grogin et al. 2011,
Koekemoer et al. 2011). We find that the MID statistics (and the A statistic of
Conselice 2003) are the most useful for identifying disturbed morphologies.
We also explore whether human annotators are useful for identifying disturbed
morphologies. We demonstrate that they show limited ability to detect
disturbance at high redshift, and that increasing their number beyond
approximately 10 does not provably yield better classification performance. We
propose a simulation-based model-fitting algorithm that mitigates these issues
by bypassing annotation.Comment: 15 pages, 14 figures, accepted for publication in MNRA
Probabilistic Analysis of Power Network Susceptibility to GICs
As reliance on power networks has increased over the last century, the risk
of damage from geomagnetically induced currents (GICs) has become a concern to
utilities. The current state of the art in GIC modelling requires significant
geophysical modelling and a theoretically derived network response, but has
limited empirical validation. In this work, we introduce a probabilistic
engineering step between the measured geomagnetic field and GICs, without
needing data about the power system topology or the ground conductivity
profiles. The resulting empirical ensembles are used to analyse the TVA network
(south-eastern USA) in terms of peak and cumulative exposure to 5 moderate to
intense geomagnetic storms. Multiple nodes are ranked according to
susceptibility and the measured response of the total TVA network is further
calibrated to existing extreme value models. The probabilistic engineering step
presented can complement present approaches, being particularly useful for risk
assessment of existing transformers and power systems.Comment: 6 pages, 7 figures, accepted for PMAPS 202
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