268 research outputs found
THE INFLUENCE OF BACE1 EXPRESSION ON THE RECRUITMENT OF MACROPHAGES TO THE INJURED PERIPHERAL NERVE
Macrophages play a critical role in regeneration following peripheral nerve injury. Hematogenous macrophages are recruited to the distal nerve segment and shape the injured nerve microenvironment to be more conducive to regeneration through the clearance of cellular debris and the production of neurotrophic factors. Enhanced macrophage recruitment and debris clearance has been observed in BACE1 KO mice. This phenotype could be the result of BACE1 activity in macrophages, other nerve resident cells (neurons, Schwann cells), or it could also be the result of the hypomyelination phenotype that is also observed in BACE1 KO mice. To date it is uncertain what potential mechanisms may be driving this enhanced recruitment and debris clearance phenotype. Further, it is unknown which cell types in the peripheral microenvironment contribute most towards this phenotype when BACE1 is deleted. BACE1 is a promiscuous enzyme and has many substrates, thus may play a role in a variety pathways that could result in this enhanced macrophage recruitment and debris clearance phenotype. This thesis discusses several known BACE1 substrates and how they could impact macrophages in the context of peripheral nerve regeneration. Previous work done in our lab suggests that elimination of expression of BACE1 in cells derived from bone marrow may recapitulate the enhanced macrophage recruitment and activity phenotype. This thesis utilizes a mouse model with macrophage specific deletion of BACE1 to investigate whether BACE1 expression by macrophages mediates the immumodulatory phenotype observed in global BACE1 KO mice. This thesis demonstrates that there is not enhanced recruitment of macrophages to the injured peripheral nerve following injury. This suggests that the elimination of BACE1 expression by macrophages is not essential for the increased recruitment phenotype observed in global BACE1 KO mice
An Imprint of Molecular Cloud Magnetization in the Morphology of the Dust Polarized Emission
We describe a morphological imprint of magnetization found when considering
the relative orientation of the magnetic field direction with respect to the
density structures in simulated turbulent molecular clouds. This imprint was
found using the Histogram of Relative Orientations (HRO): a new technique that
utilizes the gradient to characterize the directionality of density and column
density structures on multiple scales. We present results of the HRO analysis
in three models of molecular clouds in which the initial magnetic field
strength is varied, but an identical initial turbulent velocity field is
introduced, which subsequently decays. The HRO analysis was applied to the
simulated data cubes and mock-observations of the simulations produced by
integrating the data cube along particular lines of sight. In the 3D analysis
we describe the relative orientation of the magnetic field with
respect to the density structures, showing that: 1.The magnetic field shows a
preferential orientation parallel to most of the density structures in the
three simulated cubes. 2.The relative orientation changes from parallel to
perpendicular in regions with density over a critical density in the
highest magnetization case. 3.The change of relative orientation is largest for
the highest magnetization and decreases in lower magnetization cases. This
change in the relative orientation is also present in the projected maps. In
conjunction with simulations HROs can be used to establish a link between the
observed morphology in polarization maps and the physics included in
simulations of molecular clouds.Comment: (16 pages, 11 figures, submitted to ApJ 05MAR2013, accepted
07JUL2013
Delayed crystallization of ultrathin Gd2O3 layers on Si(111) observed by in situ X-ray diffraction
We studied the early stages of Gd2O3 epitaxy on Si(111) in real time by synchrotron-based, high-resolution X-ray diffraction and by reflection high-energy electron diffraction. A comparison between model calculations and the measured X-ray scattering, and the change of reflection high-energy electron diffraction patterns both indicate that the growth begins without forming a three-dimensional crystalline film. The cubic bixbyite structure of Gd2O3 appears only after a few monolayers of deposition
Tracing H2 column density with atomic carbon (CI) and CO isotopologues
We present first results of neutral carbon ([CI], 3P1 - 3P0 at 492 GHz) and
carbon monoxide (13CO, J = 1 - 0) mapping in the Vela Molecular Ridge cloud C
(VMR-C) and G333 giant molecular cloud complexes with the NANTEN2 and Mopra
telescopes. For the four regions mapped in this work, we find that [CI] has
very similar spectral emission profiles to 13CO, with comparable line widths.
We find that [CI] has opacity of 0.1 - 1.3 across the mapped region while the
[CI]/13CO peak brightness temperature ratio is between 0.2 to 0.8. The [CI]
column density is an order of magnitude lower than that of 13CO. The H2 column
density derived from [CI] is comparable to values obtained from 12CO. Our maps
show CI is preferentially detected in gas with low temperatures (below 20 K),
which possibly explains the comparable H2 column density calculated from both
tracers (both CI and 12CO underestimate column density), as a significant
amount of the CI in the warmer gas is likely in the higher energy state
transition ([CI], 3P2 - 3P1 at 810 GHz), and thus it is likely that
observations of both the above [CI] transitions are needed in order to recover
the total H2 column density.Comment: accepted for publication in ApJ Letter
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