417 research outputs found
Isospectral potentials and conformally equivalent isospectral metrics on spheres, balls and Lie groups
We construct pairs of conformally equivalent isospectral Riemannian metrics
and on spheres and balls for certain
dimensions , the smallest of which is , and on certain compact simple
Lie groups. In the case of Lie groups, the metric is left-invariant. In the
case of spheres and balls, the metric is not the standard metric but may be
chosen arbitrarily close to the standard one. For the same manifolds we
also show that the functions and are isospectral potentials
for the Schr\"odinger operator . To our knowledge, these
are the first examples of isospectral potentials and of isospectral conformally
equivalent metrics on simply connected closed manifolds.Comment: 34 pages, AMS-TeX; revised subsection 5.
Isospectral deformations of closed Riemannian manifolds with different scalar curvature
We construct the first examples of continuous families of isospectral
Riemannian metrics that are not locally isometric on closed manifolds, more
precisely, on , where is a torus of dimension and
is a sphere of dimension . These metrics are not locally
homogeneous; in particular, the scalar curvature of each metric is nonconstant.
For some of the deformations, the maximum scalar curvature changes during the
deformation.Comment: amstex, 10 pages, no figure
THE PREPARATION AND PROPERTIES OF MACROPHAGE-L CELL HYBRIDS
The plasma membrane of the mouse peritoneal macrophage has specific receptors which enable the cell to bind IgG or complement-coated sheep red cells and is also rich in a divalent cation-dependent adenosine triphosphatase (ATPase) activity. L cells lack these macrophage membrane markers. The question of macrophage membrane receptor expression was investigated in DBA/2 mouse macrophage x mouse LMTK- cell hybrids produced with the aid of Sendai virus. Three independent clones and one mass culture were isolated by their ability to grow in hypoxanthine, aminopterin, and thymidine (HAT) selection medium. These hybrids retained 85–100% of the sum of two parent cells' chromosomes and expressed several genes derived from both parents, including glucose phosphate isomerase isozymes and H-2 antigens. The hybrids displayed ATPase activity which was intermediate between that of the macrophage and L cell. The macrophage specific receptors for antibody or complement-coated red cells could not be demonstrated on hybrid cells. The selective absence of these receptors is probably because of a failure in gene expression rather than to loss of genes
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