1,478 research outputs found
Ex Vivo Expanded Hematopoietic Stem Cells Overcome the MHC Barrier in Allogeneic Transplantation
SummaryThe lack of understanding of the interplay between hematopoietic stem cells (HSCs) and the immune system has severely hampered the stem cell research and practice of transplantation. Major problems for allogeneic transplantation include low levels of donor engraftment and high risks of graft-versus-host disease (GVHD). Transplantation of purified allogeneic HSCs diminishes the risk of GVHD but results in decreased engraftment. Here we show that ex vivo expanded mouse HSCs efficiently overcame the major histocompatibility complex barrier and repopulated allogeneic-recipient mice. An 8-day expansion culture led to a 40-fold increase of the allograft ability of HSCs. Both increased numbers of HSCs and culture-induced elevation of expression of the immune inhibitor CD274 (B7-H1 or PD-L1) on the surface of HSCs contributed to the enhancement. Our study indicates the great potential of utilizing ex vivo expanded HSCs for allogeneic transplantation and suggests that the immune privilege of HSCs can be modulated
Is the Sun Embedded in a Typical Interstellar Cloud?
The physical properties and kinematics of the partially ionized interstellar
material near the Sun are typical of warm diffuse clouds in the solar vicinity.
The interstellar magnetic field at the heliosphere and the kinematics of nearby
clouds are naturally explained in terms of the S1 superbubble shell. The
interstellar radiation field at the Sun appears to be harder than the field
ionizing ambient diffuse gas, which may be a consequence of the low opacity of
the tiny cloud surrounding the heliosphere. The spatial context of the Local
Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at
International Space Sciences Institute, October 200
Degeneracy of Decadent Dyons
A quarter-BPS dyon in super Yang-Mills theory is generically
`decadent' in that it is stable only in some regions of the moduli space and
decays on submanifolds in the moduli space. Using this fact, and from the
degeneracy of the system close to the decay, a new derivation for the
degeneracy of such dyons is given. The degeneracy obtained from these very
simple physical considerations is in precise agreement with the results
obtained from index computations in all known cases. Similar considerations
apply to dyons in gauge theories. The relation between the
field theory dyons and those counted by the Igusa cusp form
in toroidally compactified heterotic string is elucidated.Comment: Some typos corrected and references adde
Carbon doping of superconducting magnesium diboride
We present details of synthesis optimization and physical properties of
nearly single phase carbon doped MgB2 with a nominal stoichiometry of
Mg(B{0.8}C{0.2})2 synthesized from magnesium and boron carbide (B4C) as
starting materials. The superconducting transition temperature is ~ 22 K (~ 17
K lower than in pure MgB2). The temperature dependence of the upper critical
field is steeper than in pure MgB2 with Hc2(10K) ~ 9 T. Temperature dependent
specific heat data taken in different applied magnetic fields suggest that the
two-gap nature of superconductivity is still preserved for carbon doped MgB2
even with such a heavily suppressed transition temperature. In addition, the
anisotropy ratio of the upper critical field for T/Tc ~ 2/3 is gamma ~ 2. This
value is distinct from 1 (isotropic) and also distinct from 6 (the value found
for pure MgB2).Comment: 11 pages, 13 figures, submitted to Physica
Supersymmetry and the LHC Inverse Problem
Given experimental evidence at the LHC for physics beyond the standard model,
how can we determine the nature of the underlying theory? We initiate an
approach to studying the "inverse map" from the space of LHC signatures to the
parameter space of theoretical models within the context of low-energy
supersymmetry, using 1808 LHC observables including essentially all those
suggested in the literature and a 15 dimensional parametrization of the
supersymmetric standard model. We show that the inverse map of a point in
signature space consists of a number of isolated islands in parameter space,
indicating the existence of "degeneracies"--qualitatively different models with
the same LHC signatures. The degeneracies have simple physical
characterizations, largely reflecting discrete ambiguities in electroweak-ino
spectrum, accompanied by small adjustments for the remaining soft parameters.
The number of degeneracies falls in the range 1<d<100, depending on whether or
not sleptons are copiously produced in cascade decays. This number is large
enough to represent a clear challenge but small enough to encourage looking for
new observables that can further break the degeneracies and determine at the
LHC most of the SUSY physics we care about. Degeneracies occur because
signatures are not independent, and our approach allows testing of any new
signature for its independence. Our methods can also be applied to any other
theory of physics beyond the standard model, allowing one to study how model
footprints differ in signature space and to test ways of distinguishing
qualitatively different possibilities for new physics at the LHC.Comment: 55 pages, 30 figure
Understorey plant community and light availability in conifer plantations and natural hardwood forests in Taiwan
Questions: What are the effects of replacing mixed species natural forests with Cryptomeria japonica plantations on understorey plant functional and species diversity? What is the role of the understorey light environment in determining understorey diversity and community in the two types of forest?
Location: Subtropical northeast Taiwan.
Methods: We examined light environments using hemispherical photography, and diversity and composition of understorey plants of a 35âyr C. japonica plantation and an adjacent natural hardwood forest.
Results: Understorey plant species richness was similar in the two forests, but the communities were different; only 18 of the 91 recorded understorey plant species occurred in both forests. Relative abundance of plants among different functional groups differed between the two forests. Relative numbers of shadeâtolerant and shadeâintolerant seedling individuals were also different between the two forest types with only one shadeâintolerant seedling in the plantation compared to 23 seedlings belonging to two species in the natural forest. In the natural forest 11 species of tree seedling were found, while in the plantation only five were found, and the seedling density was only one third of that in the natural forest. Across plots in both forests, understorey plant richness and diversity were negatively correlated with direct sunlight but not indirect sunlight, possibly because direct light plays a more important role in understorey plant growth.
Conclusions: We report lower species and functional diversity and higher light availability in a natural hardwood forest than an adjacent 30âyr C. japonica plantation, possibly due to the increased dominance of shadeâintolerant species associated with higher light availability. To maintain plant diversity, management efforts must be made to prevent localized losses of shadeâadapted understorey plants
QGP flow fluctuations and the characteristics of higher moments
The dynamical development of expanding Quark-gluon Plasma (QGP) flow is
studied in a 3+1D fluid dynamical model with a globally symmetric, initial
condition. We minimize fluctuations arising from complex dynamical processes at
finite impact parameters and from fluctuating random initial conditions to have
a conservative fluid dynamical background estimate for the statistical
distributions of the thermodynamical parameters. We also avoid a phase
transition in the equation of state, and we let the matter supercool during the
expansion.
Then central Pb+Pb collisions at TeV are studied in an
almost perfect fluid dynamical model, with azimuthally symmetric initial state
generated in a dynamical flux-tube model. The general development of
thermodynamical extensives are also shown for lower energies.
We observe considerable deviations from a thermal equilibrium source as a
consequence of the fluid dynamical expansion arising from a least fluctuating
initial state
The Influences of Diesel Particulate Filter Installation on Air Pollutant Emissions for Used Vehicles
Three kinds of diesel particulate filters (DPFs) were installed on used diesel-powered vehicles to investigate their influences on air pollutant emissions. The air pollutant emissions were measured before, after and running for specific distances to assess the deterioration effect. The emission measurement was performed on a chassis dynamometer. The results show that emissions of smoke, CO and HC are all reduced after DPF installation. After 20000 km driving, the emission concentrations of the above 3 criteria air pollutants do not increase in comparison with that right after installation. When DPFs are installed, the emissions of PAHs (polycyclic aromatic hydrocarbons) are reduced by 85.6-89.4% and 69.0-89.2% for heavy-duty diesel vehicles (HDVs) and light-duty diesel vehicles (LDVs), respectively. After driving 20000 km for HDVs and 2500 km for LDVs, PAH emissions do not increase in comparison with that right after installation, indicating that the DPFs do not deteriorate after driving for the test mileages. The lower molecular weight PAHs predominates in the exhaust both before and after DPF installation. The results also show the reduction rate is higher for higher molecular weight PAHs due to their tendency to adsorb on particulate
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