480 research outputs found
Improvement of Thymopoiesis after Hematopoietic Stem Cell Transplantation by Cytokines: Translational studies in experimental animal models
Allogeneic hematopoietic stem cell transplantation (AlloHSCT) is a powerful treatment
modality that is frequently applied as part of treatment of hematological malignancies,
aplastic anemia and inborn errors of hematopoietic progenitor cells. A major drawback of
alloHSCT is the treatment related morbidity and treatment related mortality (TRM), which
are largely accounted for by opportunistic infections. Those infections occur during a
prolonged period (1-2 years), characterized by an impaired reconstitution of the adaptive
immune system. Especially, the recovery of naïve T cells and thymopoiesis are protracted
after transplantation, but are considered pivotal for restoration of anti-infectious immunity.
This thesis has experimentally addressed new strategies that may improve thymopoiesis,
including the post-transplant administration of cytokines that are physiologically involved in
the differentiation and proliferation of thymocytes
All conformally flat pure radiation metrics
The complete class of conformally flat, pure radiation metrics is given,
generalising the metric recently given by Wils.Comment: 7 pages, plain Te
Scientific Expertise in Child Protection Policies and Juvenile Justice Practices in Twentieth-Century Belgium
Modern society cannot function without experts and yet we increasingly question the authority of those who advise us. The essays in this collection explore our reliance on experts within a historical context and across a wide range of fields, including agriculture, engineering, health sciences and labour management. Contributors argue that experts were highly aware of their audiences and used performance to gain both scientific and popular support
Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574
While following up L dwarf candidates selected photometrically from the Two
Micron All Sky Survey, we uncovered an unusual object designated 2MASS
J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium
oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium.
Morphologically such spectroscopic characteristics fall intermediate between
old, field early-L dwarfs (log(g)~5) and very late M giants (log(g)~0), leading
us to favor low gravity as the explanation for the unique spectral signatures
of this L dwarf. Such a low gravity can be explained only if this L dwarf is
much lower in mass than a typical old field L dwarf of similar temperature and
is still contracting to its final radius. These conditions imply a very young
age. Further evidence of youth is found in the near-infrared spectrum,
including a triangular-shaped H-band continuum reminiscent of young brown dwarf
candidates discovered in the Orion Nebula Cluster. Using the above information
along with comparisons to brown dwarf atmospheric and interior models, our
current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of
6-25 M_Jupiter. The location of 2MASS 0141-4633 on the sky coupled with a
distance estimate of ~35 pc and the above age estimate suggests that this
object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium
Association or the ~12-Myr-old beta Pic Moving Group.Comment: Accepted for publication in the 10 March 2006 issue (volume 639) of
the Astrophysical Journa
Interpreting a conformally flat pure radiation space-time
A physical interpretation is presented of the general class of conformally
flat pure radiation metrics that has recently been identified by Edgar and
Ludwig. It is shown that, at least in the weak field limit, successive wave
surfaces can be represented as null (half) hyperplanes rolled around a
two-dimensional null cone. In the impulsive limit, the solution reduces to a
pp-wave whose direction of propagation depends on retarded time. In the general
case, there is a coordinate singularity which corresponds to an envelope of the
wave surfaces. The global structure is discussed and a possible vacuum
extension through the envelope is proposed.Comment: 9 pages, Plain TeX, 2 figures. To appear in Class. Quantum Grav.
Reference adde
Cataclysmic Variables from the Catalina Real-time Transient Survey
We present 855 cataclysmic variable candidates detected by the Catalina
Real-time Transient Survey (CRTS) of which at least 137 have been
spectroscopically confirmed and 705 are new discoveries. The sources were
identified from the analysis of five years of data, and come from an area
covering three quarters of the sky. We study the amplitude distribution of the
dwarf novae CVs discovered by CRTS during outburst, and find that in quiescence
they are typically two magnitudes fainter compared to the spectroscopic CV
sample identified by SDSS. However, almost all CRTS CVs in the SDSS footprint
have ugriz photometry. We analyse the spatial distribution of the CVs and find
evidence that many of the systems lie at scale heights beyond those expected
for a Galactic thin disc population. We compare the outburst rates of newly
discovered CRTS CVs with the previously known CV population, and find no
evidence for a difference between them. However, we find that significant
evidence for a systematic difference in orbital period distribution. We discuss
the CVs found below the orbital period minimum and argue that many more are yet
to be identified among the full CRTS CV sample. We cross-match the CVs with
archival X-ray catalogs and find that most of the systems are dwarf novae
rather than magnetic CVs.Comment: 15 pages, 17 figures, accepted MNRA
On the Symmetries of the Edgar-Ludwig Metric
The conformal Killing equations for the most general (non-plane wave)
conformally flat pure radiation field are solved to find the conformal Killing
vectors. As expected fifteen independent conformal Killing vectors exist, but
in general the metric admits no Killing or homothetic vectors. However for
certain special cases a one-dimensional group of homotheties or motions may
exist and in one very special case, overlooked by previous investigators, a
two-dimensional homethety group exists. No higher dimensional groups of motions
or homotheties are admitted by these metrics.Comment: Plain TeX, 7 pages, No figure
The Orbital Period and Negative Superhumps of the Nova-Like Cataclysmic Variable V378 Pegasi
A radial velocity study is presented of the cataclysmic variable V378 Pegasi
(PG 2337+300). It is found to have an orbital period of 0.13858 +/- 0.00004 d
(3.32592 +/- 0.00096 hours). Its spectrum and long-term light curve suggest
that V378 Peg is a nova-like variable, with no outbursts. We use the
approximate distance and position in the Galaxy of V378 Peg to estimate E(B-V)
= 0.095, and use near-infrared magnitudes to calculate a distance of 680 +/- 90
pc and M_V = 4.68 +/- 0.70, consistent with V378 Peg being a nova-like.
Time-resolved photometry taken between 2001 and 2009 reveals a period of 0.1346
+/- 0.0004 d (3.23 +/- 0.01 hours). We identify this photometric variability to
be negative superhumps, from a precessing, tilted accretion disk. Our repeated
measurements of the photometric period of V378 Peg are consistent with this
period having been stable between 2001 and 2009, with its negative superhumps
showing coherence over as many as hundreds or even thousands of cycles.Comment: 24 pages, 19 figures, accepted for publication in New Astronom
Explicit Kundt type II and N solutions as gravitational waves in various type D and O universes
A particular yet large class of non-diverging solutions which admits a
cosmological constant, electromagnetic field, pure radiation and/or general
non-null matter component is explicitly presented. These spacetimes represent
exact gravitational waves of arbitrary profiles which propagate in background
universes such as Minkowski, conformally flat (anti-)de Sitter, Edgar-Ludwig,
Bertotti-Robinson, and type D (anti-)Nariai or Plebanski-Hacyan spaces, and
their generalizations. All possibilities are discussed and are interpreted
using a unifying simple metric form. Sandwich and impulsive waves propagating
in the above background spaces with different geometries and matter content can
easily be constructed. New solutions are identified, e.g. type D pure radiation
or explicit type II electrovacuum waves in (anti-)Nariai universe. It is also
shown that, in general, there are no conformally flat Einstein-Maxwell fields
with a non-vanishing cosmological constant.Comment: 17 pages, LaTeX 2e. v2: added two references concerning generalized
Kerr-Schild transformations, minor changes in the tex
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