2,917 research outputs found
The Dynamics of T-Cell Receptor Repertoire Diversity Following Thymus Transplantation for DiGeorge Anomaly
T cell populations are regulated both by signals specific to the T-cell receptor
(TCR) and by signals and resources, such as cytokines and space, that act
independently of TCR specificity. Although it has been demonstrated that
disruption of either of these pathways has a profound effect on T-cell
development, we do not yet have an understanding of the dynamical interactions
of these pathways in their joint shaping of the T cell repertoire. Complete
DiGeorge Anomaly is a developmental abnormality that results in the failure of
the thymus to develop, absence of T cells, and profound immune deficiency. After
receiving thymic tissue grafts, patients suffering from DiGeorge anomaly develop
T cells derived from their own precursors but matured in the donor tissue. We
followed three DiGeorge patients after thymus transplantation to utilize the
remarkable opportunity these subjects provide to elucidate human T-cell
developmental regulation. Our goal is the determination of the respective roles
of TCR-specific vs. TCR-nonspecific regulatory signals in the growth of these
emerging T-cell populations. During the course of the study, we measured
peripheral blood T-cell concentrations, TCRβ V
gene-segment usage and CDR3-length spectratypes over two years or more for each
of the subjects. We find, through statistical analysis based on a novel
stochastic population-dynamic T-cell model, that the carrying capacity
corresponding to TCR-specific resources is approximately 1000-fold larger than
that of TCR-nonspecific resources, implying that the size of the peripheral
T-cell pool at steady state is determined almost entirely by TCR-nonspecific
mechanisms. Nevertheless, the diversity of the TCR repertoire depends crucially
on TCR-specific regulation. The estimated strength of this TCR-specific
regulation is sufficient to ensure rapid establishment of TCR repertoire
diversity in the early phase of T cell population growth, and to maintain TCR
repertoire diversity in the face of substantial clonal expansion-induced
perturbation from the steady state
Individual Physiological Adaptations Enable Selected Bacterial Taxa To Prevail during Long-Term Incubations
Enclosure experiments are frequently used to investigate the impact of
changing environmental conditions on microbial assemblages. Yet, how the incuba-
tion itself challenges complex bacterial communities is thus far unknown. In this
study, metaproteomic profiling, 16S rRNA gene analyses, and cell counts were com-
bined to evaluate bacterial communities derived from marine, mesohaline, and oli-
gohaline conditions after long-term batch incubations. Early in the experiment, the
three bacterial communities were highly diverse and differed significantly in their
compositions. Manipulation of the enclosures with terrigenous dissolved organic car-
bon resulted in notable differences compared to the control enclosures at this early
phase of the experiment. However, after 55 days, bacterial communities in the ma-
nipulated and the control enclosures under marine and mesohaline conditions were
all dominated by gammaproteobacterium Spongiibacter. In the oligohaline enclo-
sures, actinobacterial cluster I of the hgc group (hgc-I) remained abundant in the late
phase of the incubation. Metaproteome analyses suggested that the ability to use
outer membrane-based internal energy stores, in addition to the previously de-
scribed grazing resistance, may enable the gammaproteobacterium Spongiibacter to
prevail in long-time incubations. Under oligohaline conditions, the utilization of ex-
ternal recalcitrant carbon appeared to be more important (hgc-I). Enclosure experi-
ments with complex natural microbial communities are important tools to investi-
gate the effects of manipulations. However, species-specific properties, such as
individual carbon storage strategies, can cause manipulation-independent effects
and need to be considered when interpreting results from enclosures.This study was financially supported by the SAW-funded ATKiM project, which provided funds to D. P. R. Herlemann, C. Meeske, K. Jürgens, S. Markert, and T. Schweder. D. P. R. Herlemann was also supported by the European Regional Develop- ment Fund/Estonian Research Council funded Mobilitas Plus Top Researcher grant MOBTT24. We thank the crew and captain of the RV Meteor (M86, M87) for support during the research cruise. The computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at the PDC Centre for High Performance Computing (PDC-HPC) and Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX). We thank Jana Matulla for excellent technical assis- tance and Stephan Fuchs for his help and advice in MS database construction. We also thank Stefan E. Heiden for valuable help with the CDD BLAST analyses.This study was financially supported by the SAW-funded ATKiM project, which
provided funds to D. P. R. Herlemann, C. Meeske, K. Jürgens, S. Markert, and T.
Schweder. D. P. R. Herlemann was also supported by the European Regional Develop-
ment Fund/Estonian Research Council funded Mobilitas Plus Top Researcher grant
MOBTT24.
We thank the crew and captain of the RV Meteor (M86, M87) for support during the
research cruise. The computations were performed on resources provided by the
Swedish National Infrastructure for Computing (SNIC) at the PDC Centre for High
Performance Computing (PDC-HPC) and Uppsala Multidisciplinary Center for Advanced
Computational Science (UPPMAX). We thank Jana Matulla for excellent technical assis-
tance and Stephan Fuchs for his help and advice in MS database construction. We also
thank Stefan E. Heiden for valuable help with the CDD BLAST analyses
VHMPID: a new detector for the ALICE experiment at LHC
This article presents the basic idea of VHMPID, an upgrade detector for the
ALICE experiment at LHC, CERN. The main goal of this detector is to extend the
particle identification capabilities of ALICE to give more insight into the
evolution of the hot and dense matter created in Pb-Pb collisions. Starting
from the physics motivations and working principles the challenges and current
status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference
Prevention and early detection of prostate cancer
This Review was sponsored and funded by the International Society of Cancer Prevention (ISCaP), the European Association of Urology (EAU), the National Cancer Institute, USA (NCI) (grant number 1R13CA171707-01), Prostate Cancer UK, Cancer Research UK (CRUK) (grant number C569/A16477), and the Association for International Cancer Research (AICR
Study of dielectron production in C+C collisions at 1 AGeV
The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV
per nucleon has been investigated. The measured production probabilities,
spanning from the pi0-Dalitz to the rho/omega! invariant-mass region, display a
strong excess above the cocktail of standard hadronic sources. The
bombarding-energy dependence of this excess is found to scale like pion
production, rather than like eta production. The data are in good agreement
with results obtained in the former DLS experiment.Comment: submitted to Physics Letters
Azimuthal anisotropy and correlations in the hard scattering regime at RHIC
Azimuthal anisotropy () and two-particle angular correlations of high
charged hadrons have been measured in Au+Au collisions at
=130 GeV for transverse momenta up to 6 GeV/c, where hard
processes are expected to contribute significantly. The two-particle angular
correlations exhibit elliptic flow and a structure suggestive of fragmentation
of high partons. The monotonic rise of for GeV/c is
consistent with collective hydrodynamical flow calculations. At \pT>3 GeV/c a
saturation of is observed which persists up to GeV/c.Comment: As publishe
Elliptic flow from two- and four-particle correlations in Au + Au collisions at sqrt{s_{NN}} = 130 GeV
Elliptic flow holds much promise for studying the early-time thermalization
attained in ultrarelativistic nuclear collisions. Flow measurements also
provide a means of distinguishing between hydrodynamic models and calculations
which approach the low density (dilute gas) limit. Among the effects that can
complicate the interpretation of elliptic flow measurements are azimuthal
correlations that are unrelated to the reaction plane (non-flow correlations).
Using data for Au + Au collisions at sqrt{s_{NN}} = 130 GeV from the STAR TPC,
it is found that four-particle correlation analyses can reliably separate flow
and non-flow correlation signals. The latter account for on average about 15%
of the observed second-harmonic azimuthal correlation, with the largest
relative contribution for the most peripheral and the most central collisions.
The results are also corrected for the effect of flow variations within
centrality bins. This effect is negligible for all but the most central bin,
where the correction to the elliptic flow is about a factor of two. A simple
new method for two-particle flow analysis based on scalar products is
described. An analysis based on the distribution of the magnitude of the flow
vector is also described.Comment: minor text change
Disappearance of back-to-back high hadron correlations in central Au+Au collisions at = 200 GeV
Azimuthal correlations for large transverse momentum charged hadrons have
been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and
p+p collisions at = 200 GeV. The small-angle correlations
observed in p+p collisions and at all centralities of Au+Au collisions are
characteristic of hard-scattering processes already observed in elementary
collisions. A strong back-to-back correlation exists for p+p and peripheral Au
+ Au. In contrast, the back-to-back correlations are reduced considerably in
the most central Au+Au collisions, indicating substantial interaction as the
hard-scattered partons or their fragmentation products traverse the medium.Comment: submitted to Phys. Rev. Let
Six Years of Chandra Observations of Supernova Remnants
We present a review of the first six years of Chandra X-ray Observatory
observations of supernova remnants. From the official "first-light" observation
of Cassiopeia A that revealed for the first time the compact remnant of the
explosion, to the recent million-second spectrally-resolved observation that
revealed new details of the stellar composition and dynamics of the original
explosion, Chandra observations have provided new insights into the supernova
phenomenon. We present an admittedly biased overview of six years of these
observations, highlighting new discoveries made possible by Chandra's unique
capabilities.Comment: 82 pages, 28 figures, for the book Astrophysics Update
- …