6,042 research outputs found
Proving Termination of Graph Transformation Systems using Weighted Type Graphs over Semirings
We introduce techniques for proving uniform termination of graph
transformation systems, based on matrix interpretations for string rewriting.
We generalize this technique by adapting it to graph rewriting instead of
string rewriting and by generalizing to ordered semirings. In this way we
obtain a framework which includes the tropical and arctic type graphs
introduced in a previous paper and a new variant of arithmetic type graphs.
These type graphs can be used to assign weights to graphs and to show that
these weights decrease in every rewriting step in order to prove termination.
We present an example involving counters and discuss the implementation in the
tool Grez
Correlations of projectile like fragments in heavy ion reactions at Fermi energy
Correlations between pairs of projectile-like fragments, emitted by the
system at the laboratory bombarding energy of 515 MeV,
have been studied under two stipulated conditions: (1) at least one member of
the pair is emitted at an angle less than the grazing angle for the system, (2)
both the members of the pair are emitted at angles larger than the grazing
angle. A surprisingly large difference, by more than an order of magnitude, is
found between the correlations for the two cases. This observation could be
explained on the basis of a simple semi-classical break up model. Further
analysis of the variation of the charge correlation function with the
difference in the nuclear charges of the correlated pair showed trends which
are consistent with an "inelastic break up process", in which the projectile
breaks up at the radius of contact, in such a way that, one fragment
(preferably the lighter) is emitted to one side within the grazing angle, while
the other orbits around the target nucleus for a while and emerges on the other
side, at a negative scattering angle, much like in a deep inelastic scattering.Comment: 19 pages, 12 figures accepted by Eurp. Physics Journal
Intolerant Democracies
International law is increasingly concerned with national transitions to democratic government. The holding of free and fair elections alone, however, provides no guarantee that a democratic system will become firmly established and capable of resisting challenges by anti-democratic actors. The question thus arises of how intolerant a democracy may become toward such actors in order to preserve itself without relinquishing the claim of being democratic. This problem has arisen on a number of occasions, perhaps the most dramatically upon the cancellation of the second round of the Algerian elections in early 1992.
This Article explores the legal issues raised by the presence of anti-democratic actors in an otherwise generally \u27free and fair electoral process. The Article first examines two models of democratic government- the procedural and the substantive-which take opposite perspectives on the permissibility of excluding anti-democratic actors. Using these models as organizing themes, it then examines the practice of a number of democratic states and the jurisprudence of international human rights regimes. The Article concludes that both national and international practice favor a substantive model of democracy, which holds that the long-term survival of democratic institutions outweighs short-term deprivation of political rights to anti-democratic actors. Having reached this general conclusion, the Article goes on to examine the standards required under international human rights law for the exclusion of such actors and the type of conduct that might justify a ban. Finally, the Article asks whether states that have obligations under human rights treaties to guarantee democratic government are now legally required to exclude anti-democratic actors if the integrity of their democratic institutions is at stake. The Article concludes that such a requirement does exist, though its concrete meaning will differ greatly from state to state
Attenuation of leukocyte sequestration by selective blockade of PECAM-1 or VCAM-1 in murine endotoxemia
Background: Molecular mechanisms regulating leukocyte sequestration into the tissue during endotoxemia and/or sepsis are still poorly understood. This in vivo study investigates the biological role of murine PECAM-1 and VCAM-1 for leukocyte sequestration into the lung, liver and striated skin muscle. Methods: Male BALB/c mice were injected intravenously with murine PECAM-1 IgG chimera or monoclonal antibody (mAb) to VCAM-1 ( 3 mg/kg body weight); controls received equivalent doses of IgG2a ( n = 6 per group). Fifteen minutes thereafter, 2 mg/kg body weight of Salmonella abortus equi endotoxin was injected intravenously. At 24 h after the endotoxin challenge, lungs, livers and striated muscle of skin were analyzed for their myeloperoxidase activity. To monitor intravital leukocyte-endothelial cell interactions, fluorescence videomicroscopy was performed in the skin fold chamber model of the BALB/c mouse at 3, 8 and 24 h after injection of endotoxin. Results: Myeloperoxidase activity at 24 h after the endotoxin challenge in lungs (12,171 +/- 2,357 mU/g tissue), livers ( 2,204 +/- 238 mU/g) and striated muscle of the skin ( 1,161 +/- 110 mU/g) was significantly reduced in both treatment groups as compared to controls, with strongest attenuation in the PECAM-1 IgG treatment group. Arteriolar leukocyte sticking at 3 h after endotoxin (230 +/- 46 cells x mm(-2)) was significantly reduced in both treatment groups. Leukocyte sticking in postcapillary venules at 8 h after endotoxin ( 343 +/- 69 cells/mm(2)) was found reduced only in the VCAM-1-mAb-treated animals ( 215 +/- 53 cells/mm(2)), while it was enhanced in animals treated with PECAM-1 IgG ( 572 +/- 126 cells/mm(2)). Conclusion: These data show that both PECAM-1 and VCAM-1 are involved in endotoxin-induced leukocyte sequestration in the lung, liver and muscle, presumably through interference with arteriolar and/or venular leukocyte sticking. Copyright (C) 2004 S. Karger AG, Basel
Estimation Of Nonorthogonal Shear Wave Polarizations And Shear Wave Velocities From Four-Component Dipole Logs
Polarizations of split shear waves and flexural borehole waves are most commonly estimated from four-component data using the rotation technique of Alford (1986). This
method is limited to the case of the two polarizations being orthogonal to each other.
We present a method that is able to handle the case of nonorthogonally polarized waves
and, moreover, is computationally more efficient than Alford's technique. Our method
is based on the eigenvalue decomposition of an asymmetric matrix and a least-squares
minimization of its off-diagonal components. In the case of orthogonally polarized waves,
our method will yield exactly the same results as the Alford rotation. We apply our
method to a cross-dipole shear-wave logging data set from the Powder River Basin in
Wyoming and find that independently rotated source-receiver sets are very consistent
with each other in anisotropic sections. After the rotation we compare two methods
for estimating the phase velocities of fast and slow waves-a semblance method and
homomorphic processing (Ellefsen et al., 1993). We find homomorphic processing to be
more reliable due to the dispersive nature of flexural waves.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumUnited States. Dept. of Energy (Contract DE-FG02-86ER13636
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