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Action Contraction
The question we consider in this paper is: “When can a combination of fine-grain execution steps be contracted into an atomic action execution”? Our answer is basically: “When no observer can see the difference.” This is worked out in detail by defining a notion of coupled split/atomic simulation refinement between systems which differ in the atomicity of their actions, and proving that this collapses to Parrow and Sjödin’s coupled similarity when the systems are composed with an observer
筋収縮後の再酸素化実験に関する研究
博甲第38号生命システム科学博士県立広島大
Canonical decomposition of operators associated with the symmetrized polydisc
A tuple of commuting operators for which the closed
symmetrized polydisc is a spectral set is called a
-contraction. We show that every -contraction admits a
decomposition into a -unitary and a completely non-unitary
-contraction. This decomposition is an analogue to the canonical
decomposition of a contraction into a unitary and a completely non-unitary
contraction. We also find new characterizations for the set and
-contractions.Comment: Complex Analysis and Operator Theory, Published online on August 28,
2017. arXiv admin note: text overlap with arXiv:1610.0093
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Calcium-independent contraction in lysed cell models of teleost retinal cones: activation by unregulated myosin light chain kinase or high magnesium and loss of cAMP inhibition.
The retinal cones of teleost fish contract at dawn and elongate at dusk. We have previously reported that we can selectively induce detergent-lysed models of cones to undergo either reactivated contraction or reactivated elongation, with rates and morphology comparable to those observed in vivo. Reactivated contraction is ATP dependent, activated by Ca2+, and inhibited by cAMP. In addition, reactivated cone contraction exhibits several properties that suggest that myosin phosphorylation plays a role in mediating Ca2+-activation (Porrello, K., and B. Burnside, 1984, J. Cell Biol., 98:2230-2238). We report here that lysed cone models can be induced to contract in the absence of Ca2+ by incubation with trypsin-digested, unregulated myosin light chain kinase (MLCK) obtained from smooth muscle. This observation provides further evidence that MLCK plays a role in regulating cone contraction. We also report here that lysed cone models can be induced to contract in the absence of Ca2+ by incubation with high concentrations of MgCl2 (10-20 mM). Mg2+-induced reactivated contraction is supported by inosine triphosphate (ITP) just as well as by ATP. Because ITP will not serve as a substrate for MLCK, this finding suggests that Mg2+-activation of contraction does not require myosin phosphorylation. Although Ca2+-induced contraction is completely blocked by cAMP at concentrations less than 10 microM, cAMP has no effect on cone contraction activated by unregulated MLCK or by high Mg2+ in the absence of Ca2+. Because trypsin digestion of MLCK cleaves off not only the Ca2+/calmodulin-binding site but also the site phosphorylated by cAMP-dependent protein kinase, and because Mg2+ activation of cone contraction circumvents MLCK action altogether, both these observations would be expected if cAMP inhibits reactivated cone contraction by catalyzing the phosphorylation of MLCK and thus reducing its affinity for Ca2+, as has been described for smooth muscle. Together our results suggest that in lysed cone models, myosin phosphorylation is sufficient for activating cone contraction, even in the absence of other Ca2+-mediated events, that cAMP inhibition of contraction is mediated by cAMP-dependent phosphorylation of MLCK, and that 10-20 mM Mg2+ can activate actin-myosin interaction to produce contraction in the absence of myosin phosphorylation
Canonical decomposition of a tetrablock contraction and operator model
A triple of commuting operators for which the closed tetrablock
is a spectral set is called a tetrablock contraction or
an -contraction. The set is defined as We show that every -contraction can be
uniquely written as a direct sum of an -unitary and a completely
non-unitary -contraction. It is analogous to the canonical
decomposition of a contraction operator into a unitary and a completely
non-unitary contraction. We produce a concrete operator model for such a triple
satisfying some conditions.Comment: To appear in Journal of Mathematical Analysis and Application
Contraction groups and scales of automorphisms of totally disconnected locally compact groups
We study contraction groups for automorphisms of totally disconnected locally
compcat groups using the scale of the automorphism as a tool. The contraction
group is shown to be unbounded when the inverse automorphism has non-trivial
scale and this scale is shown to be the inverse value of the modular function
on the closure of the contraction group at the automorphism. The closure of the
contraction group is represented as acting on a homogenous tree and closed
contraction groups are characterised.Comment: revised version, 29 pages, to appear in Israel Journal of
Mathematics, please note that document starts on page
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