542 research outputs found
A novel hepatitis C virus (HCV) subtype from Somalia and its classification into HCV clade 3.
Hepatitis C virus (HCV) sequences from throughout the world have been grouped into six clades, based on recently proposed criteria. Here, the partial sequences and clade assignment are reported for three HCV isolates from chronic hepatitis C patients from Somalia, for whom conventional assays failed to identify the genotype. Phylogenetic analysis of the sequences of the core, envelope 1 and part of the non- structural 5b regions suggests that all three isolates belong to a distinct HCV genetic group, tentatively classified as subtype 3h. This novel HCV subtype shows the highest sequence similarity with HCV isolates from Indonesia. Despite the fact that these patients were infected with HCV clade 3, none of them responded to standard interferon treatment
Lack of in vivo blockade of Fas- and TNFR1-mediated hepatocyte apoptosis by the hepatitis C virus.
In vitro data have shown that the hepatitis C virus (HCV) core protein binds to protein members of the tumour necrosis factor receptor (TNFR) superfamily. Since this interaction could be relevant to HCV persistence and oncogenesis, this study assessed whether HCV may interfere with the apoptotic cascade in vivo. Apoptosis (by TUNEL) and Fas and TNFR1 expression (by immunohistochemistry) were scored in the liver of 60 chronic hepatitis C patients. Results were compared with the liver disease grading and staging scores and the HCV replication level in serum and liver. Apoptotic hepatocytes were stained in 29 cases. Fas was expressed in 35 cases and TNFR1 in 21, 15 patients (25%) being negative for both receptors. Overall, the numbers of TUNEL-, Fas- and TNFR-positive hepatocytes did not correlate with the extent of intrahepatic CD8+ T-lymphocyte infiltration, the grading and staging of liver disease, or the serum or liver HCV RNA levels. Furthermore, when patients expressing either Fas or TNFR1 were stratified according to serum HCV RNA levels, cases with detectable hepatocyte apoptosis had higher HCV viraemias. In conclusion, an HCV-mediated, in vivo blockade of hepatocyte apoptosis via the Fas- or TNFR1-dependent pathways seems unlikely
Flow measurements across an automotive catalyst monolith situated downstream of a planar wide-angled diffuser
Slavnov-Taylor Parameterization for the Quantum Restoration of BRST Symmetries in Anomaly-Free Gauge Theories
It is shown that the problem of the recursive restoration of the
Slavnov-Taylor (ST) identities at the quantum level for anomaly-free gauge
theories is equivalent to the problem of parameterizing the local approximation
to the quantum effective action in terms of ST functionals, associated with the
cohomology classes of the classical linearized ST operator. The ST functionals
of dimension <=4 correspond to the invariant counterterms, those of dimension
>4 generate the non-symmetric counterterms upon projection on the action-like
sector. At orders higher than one in the loop expansion there are additional
contributions to the non-invariant counterterms, arising from known lower order
terms. They can also be parameterized by using the ST functionals. We apply the
method to Yang-Mills theory in the Landau gauge with an explicit mass term
introduced in a BRST-invariant way via a BRST doublet. Despite being
non-unitary, this model provides a good example where the method devised in the
paper can be applied to derive the most general solution for the action-like
part of the quantum effective action, compatible with the fulfillment of the ST
identities and the other relevant symmetries of the model, to all orders in the
loop expansion. The full dependence of the solution on the normalization
conditions is given.Comment: 23 pages. Final version published in the journa
The Role of Bulge Formation in the Homogenization of Stellar Populations at as revealed by Internal Color Dispersion in CANDELS
We use data from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy
Survey to study how the spatial variation in the stellar populations of
galaxies relate to the formation of galaxies at . We use the
Internal Color Dispersion (ICD), measured between the rest-frame UV and optical
bands, which is sensitive to age (and dust attenuation) variations in stellar
populations. The ICD shows a relation with the stellar masses and morphologies
of the galaxies. Galaxies with the largest variation in their stellar
populations as evidenced by high ICD have disk-dominated morphologies (with
S\'{e}rsic indexes ) and stellar masses between . There is a marked decrease in the ICD as the stellar mass and/or
the S\'ersic index increases. By studying the relations between the ICD and
other galaxy properties including sizes, total colors, star-formation rate, and
dust attenuation, we conclude that the largest variations in stellar
populations occur in galaxies where the light from newly, high star-forming
clumps contrasts older stellar disk populations. This phase reaches a peak for
galaxies only with a specific stellar mass range, , and prior to the formation of a substantial bulge/spheroid. In contrast,
galaxies at higher or lower stellar masses, and/or higher S\'{e}rsic index () show reduced ICD values, implying a greater homogeneity of their stellar
populations. This indicates that if a galaxy is to have both a quiescent bulge
along with a star forming disk, typical of Hubble Sequence galaxies, this is
most common for stellar masses and when the
bulge component remains relatively small ().Comment: 15 pages, 14 figure
CLEAR I: Ages and Metallicities of Quiescent Galaxies at Derived from Deep Hubble Space Telescope Grism Data
We use deep \textit{Hubble Space Telescope} spectroscopy to constrain the
metallicities and (\editone{light-weighted}) ages of massive () galaxies selected to have quiescent stellar
populations at . The data include 12--orbit depth coverage with the
WFC3/G102 grism covering ~\AA\, at a spectral
resolution of taken as part of the CANDELS Lyman- Emission
at Reionization (CLEAR) survey. At , the spectra cover important
stellar population features in the rest-frame optical. We simulate a suite of
stellar population models at the grism resolution, fit these to the data for
each galaxy, and derive posterior likelihood distributions for metallicity and
age. We stack the posteriors for subgroups of galaxies in different redshift
ranges that include different combinations of stellar absorption features. Our
results give \editone{light-weighted ages of ~Gyr,
~Gyr, ~Gyr, and
~Gyr, \editone{for galaxies at , 1.2,
1.3, and 1.6. This} implies that most of the massive quiescent galaxies at
\% of their stellar mass by a redshift of }. The
posteriors give metallicities of \editone{~, ~, ~, and ~}. This is evidence
that massive galaxies had enriched rapidly to approximately Solar metallicities
as early as .Comment: 32 pages, 23 figures, Resubmited to ApJ after revisions in response
to referee repor
An Approach to the Equivalence Theorem by the Slavnov-Taylor Identities
We discuss the Equivalence Theorem (ET) in the BRST formalism. The existence
of a local inverse of the field transformation (at least as a formal power
expansion) suggests a formulation of the ET, which allows a nilpotent BRST
symmetry. This strategy cannot be implemented at the quantum level if the
inverse is non-local. In this case we propose an alternative formulation of the
ET, where, by using Faddeev-Popov fields, this difficulty is circumvented. We
study the quantum deformation of the associated ST identity, which turns out to
be anomaly free, and show that a selected set of Green functions, which in some
cases can be identified with the physical observables of the model, does not
depend on the choice of the transformation of the fields. In general the
transformation of the fields yields a non-renormalizable theory. When the
equivalence is established between a renormalizable and a non-renormalizable
theory, the ET provides a way to give a meaning to the last one by using the
resulting ST identity. In this case the Quantum Action Principle cannot be of
any help in the discussion of the ET. We assume and discuss the validity of a
Quasi Classical Action Principle, which turns out to be sufficient for the
present work. As an example we study the renormalizability and unitarity of
massive QED in Proca's gauge by starting from a linear Lorentz-covariant gauge.Comment: 26 page
- …