113 research outputs found
Self-affine Manifolds
This paper studies closed 3-manifolds which are the attractors of a system of
finitely many affine contractions that tile . Such attractors are
called self-affine tiles. Effective characterization and recognition theorems
for these 3-manifolds as well as theoretical generalizations of these results
to higher dimensions are established. The methods developed build a bridge
linking geometric topology with iterated function systems and their attractors.
A method to model self-affine tiles by simple iterative systems is developed
in order to study their topology. The model is functorial in the sense that
there is an easily computable map that induces isomorphisms between the natural
subdivisions of the attractor of the model and the self-affine tile. It has
many beneficial qualities including ease of computation allowing one to
determine topological properties of the attractor of the model such as
connectedness and whether it is a manifold. The induced map between the
attractor of the model and the self-affine tile is a quotient map and can be
checked in certain cases to be monotone or cell-like. Deep theorems from
geometric topology are applied to characterize and develop algorithms to
recognize when a self-affine tile is a topological or generalized manifold in
all dimensions. These new tools are used to check that several self-affine
tiles in the literature are 3-balls. An example of a wild 3-dimensional
self-affine tile is given whose boundary is a topological 2-sphere but which is
not itself a 3-ball. The paper describes how any 3-dimensional handlebody can
be given the structure of a self-affine 3-manifold. It is conjectured that
every self-affine tile which is a manifold is a handlebody.Comment: 40 pages, 13 figures, 2 table
Soluble Adenylyl Cyclase Is Localized to Cilia and Contributes to Ciliary Beat Frequency Regulation via Production of cAMP
Ciliated airway epithelial cells are subject to sustained changes in intracellular CO2/HCO3− during exacerbations of airway diseases, but the role of CO2/HCO3−-sensitive soluble adenylyl cyclase (sAC) in ciliary beat regulation is unknown. We now show not only sAC expression in human airway epithelia (by RT-PCR, Western blotting, and immunofluorescence) but also its specific localization to the axoneme (Western blotting and immunofluorescence). Real time estimations of [cAMP] changes in ciliated cells, using FRET between fluorescently tagged PKA subunits (expressed under the foxj1 promoter solely in ciliated cells), revealed CO2/HCO3−-mediated cAMP production. This cAMP production was specifically blocked by sAC inhibitors but not by transmembrane adenylyl cyclase (tmAC) inhibitors. In addition, this cAMP production stimulated ciliary beat frequency (CBF) independently of intracellular pH because PKA and sAC inhibitors were uniquely able to block CO2/HCO3−-mediated changes in CBF (while tmAC inhibitors had no effect). Thus, sAC is localized to motile airway cilia and it contributes to the regulation of human airway CBF. In addition, CO2/HCO3− increases indeed reversibly stimulate intracellular cAMP production by sAC in intact cells
Quantum erasure using entangled surface acoustic phonons
Using the deterministic, on-demand generation of two entangled phonons, we
demonstrate a quantum eraser protocol in a phononic interferometer where the
which-path information can be heralded during the interference process.
Omitting the heralding step yields a clear interference pattern in the
interfering half-quanta pathways; including the heralding step suppresses this
pattern. If we erase the heralded information after the interference has been
measured, the interference pattern is recovered, thereby implementing a
delayed-choice quantum erasure. The test is implemented using a closed
surface-acoustic-wave communication channel into which one superconducting
qubit can emit itinerant phonons that the same or a second qubit can later
re-capture. If the first qubit releases only half of a phonon, the system
follows a superposition of paths during the phonon propagation: either an
itinerant phonon is in the channel, or the first qubit remains in its excited
state. These two paths are made to constructively or destructively interfere by
changing the relative phase of the two intermediate states, resulting in a
phase-dependent modulation of the first qubit's final state, following
interaction with the half-phonon. A heralding mechanism is added to this
construct, entangling a heralding phonon with the signalling phonon. The first
qubit emits a phonon herald conditioned on the qubit being in its excited
state, with no signaling phonon, and the second qubit catches this heralding
phonon, storing which-path information which can either be read out, destroying
the signaling phonon's self-interference, or erased.Comment: 16 pages, 8 figure
- …