9,098 research outputs found
Rejection of human intestinal allografts: Alone or in combination with the liver
The current results of the present series demonstrate that intestinal allografts are more vulnerable to rejection and continue to be at a significantly higher risk long after transplantation compared with isolated liver allograft recipients. Unexpectedly, a combined liver allograft does not protect small bowel from rejection. The necessarily continuous heavy immunosuppression for these unique recipients is potentially self-defeating. This is clearly demonstrated by their high susceptibility to early and late infectious complications after transplantation as reported in this issue. With the minimal graft-versus-host disease threat in this clinical trial, our revised protocol for future intestinal transplantation is to maximize the passenger leukocyte traffic with supplementary bone marrow from the same intestinal donor in an attempt to augment the development of systemic chimerism and the gradual induction of donor-specific nonreactivity
Structural, Optical and Single-domain Magnetic Features of the Noncollinear Ferrimagnetic Nano-spinel Chromites ACrO (A = Ni, Co, and Mn)
Spinel chromites ACrO with inherent magnetic geometrical frustration
usually exhibit a noncollinear ferrimagnetic ground state when A are magnetic
ions, with possibly crystallite-size dependent intriguing magnetic features.
Here, we report single-domain magnetic properties of ACrO (A = Ni, Co,
and Mn) nanocrystals, with an average crystallite size of 18, 15 and 10 nm,
exhibiting an optical energy gap of 2.87, 3.05 and 2.9 eV, respectively. The
temperature dependence of magnetization indicates the main bulk magnetic
transitions with a commonly coexisting spin-glass-like state and finite-size
effects on the noncolinear ferrimagnetic transitions. An anomaly observed at Ts
= 15, 24 and 10 K is attributed to the bulk magnetic transition to a canted
antiferromagnetic state in NiCrO and incommensurate spiral orders in
CoCrO and MnCrO NCs, respectively. A further bulk magnetic
transition to a commensurate spiral order is observed for CoCrO NCs at
a lock-in temperature Tl = 5 K much lower than that reported using bulk
samples, while it is completely suppressed in the MnCrO NCs.
Finite-size effects and single-domain magnetic behaviors indicated by anomalous
temperature-dependences of the coercive field and the hysteresis-loop
squareness, mainly driven by a magnetocrystalline anisotropy, are discussed in
comparison to results reported using bulk counterparts
Final state interactions in B+- to K+ K- K+- decays
Charged B decays to three charged kaons are analysed in the framework of the
QCD factorization approach. The strong final state K+K-interactions are
described using the kaon scalar and vector form factors. The scalar non-strange
and strange form factors at low K+K- effective masses are constrained by chiral
perturbation theory and satisfy the two-body unitarity conditions. The latter
stem from the properties of the meson-meson amplitudes which describe all
possible S-wave transitions between three coupled channels consisting of two
kaons, two pions and four pions. The vector form factors are fitted to the data
on the electromagnetic kaon interactions. The model results are compared with
the Belle and BaBar data. Away from phi(1020) resonance, in the S-wave
dominated K+K- mass spectra, a possibility for a large CP asymmetry is
identified.Comment: 7 pages, 4 figures, modified version published in Physics Letters
Neural network modelling for shear strength of concrete members reinforced with FRP bars
yesThis paper investigates the feasibility of using artificial neural networks (NNs) to predict the shear capacity of concrete members reinforced longitudinally with fibre reinforced polymer (FRP) bars, and without any shear reinforcement. An experimental database of 138 test specimens failed in shear is created and used to train and test NNs as well as to assess the accuracy of three existing shear design methods. The created NN predicted to a high level of accuracy the shear capacity of FRP reinforced concrete members.
Garson index was employed to identify the relative importance of the influencing parameters on the shear capacity based on the trained NNs weightings. A parametric analysis was also conducted using the trained NN to establish the trend of the main influencing variables on the shear capacity. Many of the assumptions made by the shear design methods are predicted by the NN developed; however, few are inconsistent with the NN predictions
A Study of Meson Correlators at Finite Temperature
We present results for mesonic propagators in temporal and spatial directions
at T below and above the deconfining transition in quenched QCD. Anisotropic
lattices are used to get enough information in the temporal direction. We use
the Wilson fermion action for light quarks and Fermilab action for heavy
quarks.Comment: LATTICE 99 (finite temperature and density), 3 pages, LaTeX with 3
eps figures, espcrc2.sty, psfig.st
Size effect on shear strength of FRP reinforced concrete beams
yesThis paper presents test results of six concrete beams reinforced with longitudinal carbon fiber reinforced polymer (CFRP) bars and without vertical shear reinforcement. All beams were tested under a two-point loading system to investigate shear behavior of CFRP reinforced concrete beams. Beam depth and amount of CFRP reinforcement were the main parameters investigated. All beams failed due to a sudden diagonal shear crack at almost 45°. A simplified, empirical expression for the shear capacity of FRP reinforced concrete members accounting for most influential parameters is developed based on the design-by-testing approach using a large database of 134 specimens collected from the literature including the beams tested in this study. The equations of six existing design standards for shear capacity of FRP reinforced concrete beams have also been evaluated using the large database collected. The existing shear design methods for FRP reinforced concrete beams give either conservative or unsafe predictions for many specimens in the database and their accuracy are mostly dependent on the effective depth and type of FRP reinforcement. On the other hand, the proposed equation provides reasonably accurate shear capacity predictions for a wide range of FRP reinforced concrete beams
On the properties of massive Population III stars and metal-free stellar populations
We present realistic models for massive Population III stars and stellar
populations based on non-LTE model atmospheres, recent stellar evolution tracks
and up-to-date evolutionary synthesis models, to study their spectral
properties, including their dependence on age, star formation history, and IMF.
(..) The main results regarding integrated stellar populations are: * For young
bursts and the case of a constant SFR, nebular continuous emission - neglected
in previous studies - dominates the spectrum redward of Lyman-alpha (...).
Therefore predicted emission line equivalent widths are considerably smaller
than found in earlier studies, whereas the detection of the continuum is eased.
Nebular line and continuous emission strongly affect the broad band photometric
properties of Pop III objects. * Due to stellar evolution, the hardness of the
ionising spectrum decreases rapidly, leading to the disappearance of the
characteristic HeII 1640 recombination lines after ~ 3 Myr in instantaneous
bursts. * The relative efficiency of ionising photon energy to heavy element
rest mass production, eta, of metal-poor and metal-free populations is
increased by factors of ~ 4 to 18 with respect to solar metallicity and for
``standard'' IMFs. * The lowest values of eta ~ 1.6 - 2.2 % are obtained for
IMFs exclusively populated with high mass stars (M_low >~ 50 Msun). If correct,
the yields dominated by pair creation SNae then predict large overabundances of
O/C and Si/C compared to solar abundance ratios. Detailed results are given in
tabular form and as fit formulae for implementation in other calculations.
(abridged abstract)Comment: Accepted for publication in A&A. LaTeX, 15 pages including 8 figures.
Related models are available at http://webast.ast.obs-mip.fr/people/schaerer/
. SEDs will be available by request from the author
(mailto:[email protected]). Y-axis of Figs. 5 correcte
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