648 research outputs found
Some Properties of Distal Actions on Locally Compact Groups
We consider the actions of (semi)groups on a locally compact group by
automorphisms. We show the equivalence of distality and pointwise distality for
the actions of a certain class of groups. We also show that a compactly
generated locally compact group of polynomial growth has a compact normal
subgroup such that is distal and the conjugacy action of on
is ergodic; moreover, if itself is (pointwise) distal then is Lie
projective. We prove a decomposition theorem for contraction groups of an
automorphism under certain conditions. We give a necessary and sufficient
condition for distality of an automorphism in terms of its contraction group.
We compare classes of (pointwise) distal groups and groups whose closed
subgroups are unimodular. In particular, we study relations between distality,
unimodularity and contraction subgroups.Comment: 27 pages, main results are revised and improved, some preliminary
results are removed and some new results are added, some proofs are revised
and some are made shorte
Linear semigroups with coarsely dense orbits
Let be a finitely generated abelian semigroup of invertible linear
operators on a finite dimensional real or complex vector space . We show
that every coarsely dense orbit of is actually dense in . More
generally, if the orbit contains a coarsely dense subset of some open cone
in then the closure of the orbit contains the closure of . In the
complex case the orbit is then actually dense in . For the real case we give
precise information about the possible cases for the closure of the orbit.Comment: We added comments and remarks at various places. 14 page
Existence of Weak Solutions for a Diffuse Interface Model for Two-Phase Flows of Incompressible Fluids with Different Densities
We prove existence of weak solutions for a diffuse interface model for the
flow of two viscous incompressible Newtonian fluids in a bounded domain in two
and three space dimensions. In contrast to previous works, we study a new model
recently developed by Abels, Garcke, and Gr\"un for fluids with different
densities, which leads to a solenoidal velocity field. The model is given by a
non-homogeneous Navier-Stokes system with a modified convective term coupled to
a Cahn-Hilliard system. The density of the mixture depends on an order
parameter.Comment: 33 page
Coercivity and stability results for an extended Navier-Stokes system
In this article we study a system of equations that is known to {\em extend}
Navier-Stokes dynamics in a well-posed manner to velocity fields that are not
necessarily divergence-free. Our aim is to contribute to an understanding of
the role of divergence and pressure in developing energy estimates capable of
controlling the nonlinear terms. We address questions of global existence and
stability in bounded domains with no-slip boundary conditions. Even in two
space dimensions, global existence is open in general, and remains so,
primarily due to the lack of a self-contained energy estimate. However,
through use of new coercivity estimates for the linear equations, we
establish a number of global existence and stability results, including results
for small divergence and a time-discrete scheme. We also prove global existence
in 2D for any initial data, provided sufficient divergence damping is included.Comment: 29 pages, no figure
Peptide Presentation Is the Key to Immunotherapeutical Success
Positive and negative selection in the thymus relies on T-cell receptor recognition of peptides presented by HLA molecules and determines the repertoire of T cells. Immune competent T-lymphocytes target cells display nonself or pathogenic peptides in complex with their cognate HLA molecule. A peptide passes several selection processes before being presented in the peptide binding groove of an HLA molecule; here the sequence of the HLA moleculeâs heavy chain determines the mode of peptide recruitment. During inflammatory processes, the presentable peptide repertoire is obviously altered compared to the healthy state, while the peptide loading pathway undergoes modifications as well. The presented peptides dictate the fate of the HLA expressing cell through their (1) sequence, (2) topology, (3) origin (self/nonself). Therefore, the knowledge about peptide competition and presentation in the context of alloreactivity, infection or pathogenic invasion is of enormous significance. Since in adoptive cellular therapies transferred cells should exclusively target peptide-HLA complexes they are primed for, one of the most crucial questions remains at what stage of viral infection viral peptides are presented preferentially over self-peptides. The systematic analyzation of peptide profiles under healthy or pathogenic conditions is the key to immunological success in terms of personalized therapeutics
Overexpression of melanoma inhibitory activity (MIA) enhances extravasation and metastasis of A-mel 3 melanoma cells in vivo
The secreted MIA protein is strongly expressed by advanced primary and metastatic melanomas but not in normal melanocytes. Previous studies have shown that MIA serum levels correlate with clinical tumour progression in melanoma patients. To provide direct evidence that MIA plays a role in metastasis of malignant melanomas, A-mel 3 hamster melanoma cells were transfected with sense- and antisense rhMIA cDNA and analysed subsequently for changes in their tumorigenic and metastatic potential. Enforced expression of MIA in A-mel 3 cells significantly increased their metastatic potential without affecting primary tumour growth, cell proliferation or apoptosis rate in hamsters, compared with control or antisense transfected cells. Additionally, MIA overexpressing transfectants showed a higher rate of both tumour cell invasion and extravasation. Cells transfected with MIA antisense generally exerted an opposite response. The above changes in function attributed to the expression of MIA may underlie the contribution of MIA to the malignant phenotype. Š 2000 Cancer Research Campaig
Boundedness of Pseudodifferential Operators on Banach Function Spaces
We show that if the Hardy-Littlewood maximal operator is bounded on a
separable Banach function space and on its associate space
, then a pseudodifferential operator
is bounded on whenever the symbol belongs to the
H\"ormander class with ,
or to the the Miyachi class
with ,
. This result is applied to the case of
variable Lebesgue spaces .Comment: To appear in a special volume of Operator Theory: Advances and
Applications dedicated to Ant\'onio Ferreira dos Santo
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