3,716 research outputs found

    The Optical - Infrared Colors of CORALS QSOs: Searching for Dust Reddening Associated With High Redshift Damped Lyman Alpha Systems

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    The presence of dust in quasar absorbers, such as damped Lyman alpha (DLA) systems, may cause the background QSO to appear reddened. We investigate the extent of this potential reddening by comparing the optical-to-infrared (IR) colors of QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio Absorption Line System (CORALS) survey of Ellison et al (2001). We have obtained near-simultaneous B and K band magnitudes for subset of the CORALS sample and supplemented our observations with further measurements published in the literature. To account for redshift-related color changes, the B-K colors are normalized using the Sloan Digital Sky Survey (SDSS) QSO composite. The mean normalized B-K color of the DLA sub-sample is +0.12, whereas the mean for the no-DLA sample is -0.10; both distributions have RMS scatters ~0.5. Neither a student's T-test nor a KS test indicate that there is any significant difference between the two color distributions. Based on simulations which redden the colors of QSOs with intervening DLAs, we determine a reddening limit which corresponds to E(B-V) < 0.04 (SMC-like extinction) at 99% confidence (3 sigma), assuming that E(B-V) is the same for all DLAs. Finally, we do not find any general correlation between absorber properties (such as [Fe/Zn] or neutral hydrogen column density) and B-K color. One of these two QSOs shows evidence for strong associated absorption from X-ray observations, an alternative explanation for its very red color. We conclude that the presence of intervening galaxies causes a minimal reddening of the background QSO.Comment: Accepted for publication in A

    Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor

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    The upgrade of the cold neutron triple-axis spectrometer FLEXX is described. We discuss the characterisation of the gains from the new primary spectrometer, including a larger guide and double focussing monochromator, and present measurements of the energy and momentum resolution and of the neutron flux of the instrument. We found an order of magnitude gain in intensity (at the cost of coarser momentum resolution), and that the incoherent elastic energy widths are measurably narrower than before the upgrade. The much improved count rate should allow the use of smaller single crystals samples and thus enable the upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table

    A Method to Distinguish Quiescent and Dusty Star-forming Galaxies with Machine Learning

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    Large photometric surveys provide a rich source of observations of quiescent galaxies, including a surprisingly large population at z > 1. However, identifying large, but clean, samples of quiescent galaxies has proven difficult because of their near-degeneracy with interlopers such as dusty, star-forming galaxies. We describe a new technique for selecting quiescent galaxies based upon t-distributed stochastic neighbor embedding (t-SNE), an unsupervised machine-learning algorithm for dimensionality reduction. This t-SNE selection provides an improvement both over UVJ, removing interlopers that otherwise would pass color selection, and over photometric template fitting, more strongly toward high redshift. Due to the similarity between the colors of high- and low-redshift quiescent galaxies, under our assumptions, t-SNE outperforms template fitting in 63% of trials at redshifts where a large training sample already exists. It also may be able to select quiescent galaxies more efficiently at higher redshifts than the training sample

    Human olfactory mesenchymal stromal cell transplants promote remyelination and earlier improvement in gait co-ordination after spinal cord injury

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    Autologous cell transplantation is a promising strategy for repair of the injured spinal cord. Here we have studied the repair potential of mesenchymal stromal cells isolated from the human olfactory mucosa after transplantation into a rodent model of incomplete spinal cord injury. Investigation of peripheral type remyelination at the injury site using immunocytochemistry for P0, showed a more extensive distribution in transplanted compared with control animals. In addition to the typical distribution in the dorsal columns (common to all animals), in transplanted animals only, P0 immunolabelling was consistently detected in white matter lateral and ventral to the injury site. Transplanted animals also showed reduced cavitation. Several functional outcome measures including end-point electrophysiological testing of dorsal column conduction and weekly behavioural testing of BBB, weight bearing and pain, showed no difference between transplanted and control animals. However, gait analysis revealed an earlier recovery of co-ordination between forelimb and hindlimb stepping in transplanted animals. This improvement in gait may be associated with the enhanced myelination in ventral and lateral white matter, where fibre tracts important for locomotion reside. Autologous transplantation of mesenchymal stromal cells from the olfactory mucosa may therefore be therapeutically beneficial in the treatment of spinal cord injury

    Analytical Model for Hook Anchor Pull-Out

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    Bilateral Breast Reconstruction with Extended Thoracodorsal Artery Perforator Propeller Flaps and Implants

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    We present our experience of bilateral total breast reconstruction using a double-sided extended thoracodorsal artery perforator propeller flap in a case series of 10 patients. Reconstruction was successfully achieved in all cases with few complications. The median time for surgery was 275 minutes (200–330), and the average implant size used was 350 cm(3) (195–650). We demonstrate how the extended thoracodorsal artery perforator propeller flap allows for a swift and reliable direct to implant bilateral total breast reconstruction in a simple setting and is a valuable adjunct to our armamentarium of techniques for single-stage bilateral breast reconstruction
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