1,212 research outputs found
A Myelin Proteolipid Protein-LacZ Fusion Protein Is Developmentally Regulated and Targeted to the Myelin Membrane in Transgenic Mice
Transgenic mice were generated with a fusion gene carrying a portion of the murine myelin proteolipid protein (PLP) gene, including the first intron, fused to the E. coli LacZ gene. Three transgenic lines were derived and all lines expressed the transgene in central nervous system white matter as measured by a histochemical assay for the detection of β-galactosidase activity. PLP-LacZ transgene expression was regulated in both a spatial and temporal manner, consistent with endogenous PLP expression. Moreover, the transgene was expressed specifically in oligodendrocytes from primary mixed glial cultures prepared from transgenic mouse brains and appeared to be developmentally regulated in vitro as well. Transgene expression occurred in embryos, presumably in pre- or nonmyelinating cells, rather extensively throughout the peripheral nervous system and within very discrete regions of the central nervous system. Surprisingly, beta-galactosidase activity was localized predominantly in the myelin in these transgenic animals, suggesting that the NH_2-terminal 13 amino acids of PLP, which were present in the PLP-LacZ gene product, were sufficient to target the protein to the myelin membrane. Thus, the first half of the PLP gene contains sequences sufficient to direct both spatial and temporal gene regulation and to encode amino acids important in targeting the protein to the myelin membrane
The s Process: Nuclear Physics, Stellar Models, Observations
Nucleosynthesis in the s process takes place in the He burning layers of low
mass AGB stars and during the He and C burning phases of massive stars. The s
process contributes about half of the element abundances between Cu and Bi in
solar system material. Depending on stellar mass and metallicity the resulting
s-abundance patterns exhibit characteristic features, which provide
comprehensive information for our understanding of the stellar life cycle and
for the chemical evolution of galaxies. The rapidly growing body of detailed
abundance observations, in particular for AGB and post-AGB stars, for objects
in binary systems, and for the very faint metal-poor population represents
exciting challenges and constraints for stellar model calculations. Based on
updated and improved nuclear physics data for the s-process reaction network,
current models are aiming at ab initio solution for the stellar physics related
to convection and mixing processes. Progress in the intimately related areas of
observations, nuclear and atomic physics, and stellar modeling is reviewed and
the corresponding interplay is illustrated by the general abundance patterns of
the elements beyond iron and by the effect of sensitive branching points along
the s-process path. The strong variations of the s-process efficiency with
metallicity bear also interesting consequences for Galactic chemical evolution.Comment: 53 pages, 20 figures, 3 tables; Reviews of Modern Physics, accepte
In Situ Contaminated Sediments Project – Work Package 1A Report
Project aims
Defra is seeking to understand the magnitude of risks (e.g. to aquatic ecology and human health) or
impacts (e.g. on the way that water bodies are managed) posed by contaminated sediment in England,
as part of its work towards meeting its environmental objectives.
In the context of this project, in-situ contaminated sediment is defined as:
Chemically contaminated sediment within the water column, bed, banks and floodplain of a surface
water body that has been transported alongside the normal sediment load and deposited by fluvial
or coastal processes.
This project considers the risk posed by non-agricultural diffuse pollution sources in England that result
in the contamination of in-situ sediments (for example, contamination from toxic metals, hydrocarbons
and surfactants). The scope encompasses both freshwater and marine sediments in England and
extends to one nautical mile off-shore (the seaward limit of coastal waters under the Water Framework
Directive (WFD) in England).
Previous national strategies, including the 2007 Defra UK Strategy for Managing Contaminated Marine
Sediments (CDMS), focussed on characterising the risks associated with contaminated sediments in
the marine environment. However, while extensive research has been carried out in many locations
(including as part of WFD implementation studies) and for particular sources of contamination (e.g.
historical metal mining; Environment Agency, 2008) there has not been a comprehensive overview of
sediment contamination on a national scale. This project seeks to build on the existing evidence base,
drawing together information on the freshwater environment to complement that already gathered for
marine waters. This project’s overall aim is to provide a sound evidence base on the contamination of
in-situ sediments, which can underpin the development of tools and methods that will help Defra, the
Environment Agency and other bodies engaged in regulation and protection of water quality
The social geography of unmarried cohabitation in the USA, 2007-2011
US studies of marriage and cohabitation have mainly highlighted the social and racial differentials as they were observed in cross-sections, and have as a result essentially focused on the "pattern of disadvantage". The evolution of such social differentials over time and space reveals that this pattern of disadvantage has clearly persisted, but that it is far from covering the whole story. Historically, there has been a major contribution to the rise of cohabitation by white college students, and later on young white adults with higher education continued to start unions via cohabitation to ever increasing degrees. Only, they seem to move into marriage to a greater extent later on in life than other population segments. Also, the religious affiliation matters greatly: Mormons and evangelical Christians have resisted the current trends. Furthermore this effect is not only operating at the individual but at the contextual level as well. Conversely, even after controls for competing socio-economic explanations, residence in areas (either counties or PUMA-areas) with a Democratic voting pattern is related to higher cohabitation probabilities. And, finally, different legal contexts at the level of States also significantly contributed to the emergence of strong spatial contrasts. Hence, there is a concurrence of several factors shaping the present differentiations, and the rise of secular and liberal attitudes, i.e. the "ethics revolution", is equally a part of the explanation
Disk-Jet Connection in Cygnus X-3
We present the results of a detailed correlation study between the soft
X-ray, hard X-ray, and radio emission (obtained from RXTE ASM, BATSE, and GBI
observations, respectively) of the bright radio emitting Galactic X-ray binary
Cygnus X-3. We detect a very strong positive correlation between the soft X-ray
and radio emission during the low-hard and minor flaring periods of the source,
and an anti-correlation between the soft and hard X-ray emissions. We present
statistical arguments to suggest that the anti-correlation between the radio
and hard X-ray emission, reported earlier, is primarily due to their
correlation and anti-correlation, respectively, with the soft X-ray emission.
We make a wide band X-ray spectral study using the pointed RXTE observations
and detect a pivotal behaviour in the X-ray spectrum. We argue that this X-ray
spectral pivoting is responsible for the anti-correlation between the soft and
hard X-ray emissions. The strong correlation between the soft X-ray and radio
emission suggests a close link between the accreting mechanism, plasma cloud
surrounding the compact object and the radio emission.Comment: Accepted in A&A Letters. Major revioson of discussion, minor revision
of tables and figure
A generalized Cahn-Hilliard equation for biological applications
Recently we considered a stochastic discrete model which describes fronts of
cells invading a wound \cite{KSS}. In the model cells can move, proliferate,
and experience cell-cell adhesion. In this work we focus on a continuum
description of this phenomenon by means of a generalized Cahn-Hilliard equation
(GCH) with a proliferation term. As in the discrete model, there are two
interesting regimes. For subcritical adhesion, there are propagating "pulled"
fronts, similarly to those of Fisher-Kolmogorov equation. The problem of front
velocity selection is examined, and our theoretical predictions are in a good
agreement with a numerical solution of the GCH equation. For supercritical
adhesion, there is a nontrivial transient behavior, where density profile
exhibits a secondary peak. To analyze this regime, we investigated relaxation
dynamics for the Cahn-Hilliard equation without proliferation. We found that
the relaxation process exhibits self-similar behavior. The results of continuum
and discrete models are in a good agreement with each other for the different
regimes we analyzed.Comment: 11 figures, submitted to PR
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