199,568 research outputs found
Resonances, Unstable Systems and Irreversibility: Matter Meets Mind
The fundamental time-reversal invariance of dynamical systems can be broken
in various ways. One way is based on the presence of resonances and their
interactions giving rise to unstable dynamical systems, leading to well-defined
time arrows. Associated with these time arrows are semigroups bearing time
orientations. Usually, when time symmetry is broken, two time-oriented
semigroups result, one directed toward the future and one directed toward the
past. If time-reversed states and evolutions are excluded due to resonances,
then the status of these states and their associated backwards-in-time oriented
semigroups is open to question. One possible role for these latter states and
semigroups is as an abstract representation of mental systems as opposed to
material systems. The beginnings of this interpretation will be sketched.Comment: 9 pages. Presented at the CFIF Workshop on TimeAsymmetric Quantum
Theory: The Theory of Resonances, 23-26 July 2003, Instituto Superior
Tecnico, Lisbon, Portugal; and at the Quantum Structures Association Meeting,
7-22 July 2004, University of Denver. Accepted for publication in the
Internation Journal of Theoretical Physic
The Significance of William Augustus Bowles’s Seizure of Panton’s Apalachee Store in 1792
William Augustus Bowles accompanied by William Cunningham and a band of Indians made up of Cowitas, Broken Arrows, Hitchetas, Ufales, Chichas, and Ousutches captured the Apalachee trading post of Panton, Leslie and Company on the 16th day of January 1792. This event was one of the most important incidents in the commercial warfare waged by the merchants of New Providence against the house of Panton
In vivo analysis of NHPX reveals a novel nucleolar localization pathway involving a transient accumulation in splicing speckles
The NHPX protein is a nucleolar factor that binds directly to a conserved RNA target sequence found in nucleolar box C/D snoRNAs and in U4 snRNA. Using enhanced yellow fluorescent protein (EYFP)– and enhanced cyan fluorescent protein–NHPX fusions, we show here that NHPX is specifically accumulated in both nucleoli and Cajal bodies (CBs) in vivo. The fusion proteins display identical localization patterns and RNA binding specificities to the endogenous NHPX. Analysis of a HeLa cell line stably expressing EYFP–NHPX showed that the nucleolar accumulation of NHPX was preceded by its transient accumulation in splicing speckles. Only newly expressed NHPX accumulated in speckles, and the nucleolar pool of NHPX did not interchange with the pool in speckles, consistent with a unidirectional pathway. The transient accumulation of NHPX in speckles prior to nucleoli was observed in multiple cell lines, including primary cells that lack CBs. Inhibitor studies indicated that progression of newly expressed NHPX from speckles to nucleoli was dependent on RNA polymerase II transcription, but not on RNA polymerase I activity. The data show a specific temporal pathway involving the sequential and directed accumulation of NHPX in distinct subnuclear compartments, and define a novel mechanism for nucleolar localization
Homotopy classification of ribbon tubes and welded string links
Ribbon 2-knotted objects are locally flat embeddings of surfaces in 4-space
which bound immersed 3-manifolds with only ribbon singularities. They appear as
topological realizations of welded knotted objects, which is a natural quotient
of virtual knot theory. In this paper we consider ribbon tubes and ribbon
torus-links, which are natural analogues of string links and links,
respectively. We show how ribbon tubes naturally act on the reduced free group,
and how this action classifies ribbon tubes up to link-homotopy, that is when
allowing each component to cross itself. At the combinatorial level, this
provides a classification of welded string links up to self-virtualization.
This generalizes a result of Habegger and Lin on usual string links, and the
above-mentioned action on the reduced free group can be refined to a general
"virtual extension" of Milnor invariants. As an application, we obtain a
classification of ribbon torus-links up to link-homotopy.Comment: 33p. ; v2: typos and minor corrections ; v3: Introduction rewritten,
exposition revised, references added. Section 5 of the previous version was
significantly expanded and was separated into another paper
(arXiv:1507.00202) ; v4: typos and minor corrections ; to appear in Annali
della scuola Normale Superiore de Pisa (classe de scienze
Stable quasicrystalline ground states
We give a strong evidence that noncrystalline materials such as quasicrystals
or incommensurate solids are not exceptions but rather are generic in some
regions of a phase space. We show this by constructing classical lattice-gas
models with translation-invariant, finite-range interactions and with a unique
quasiperiodic ground state which is stable against small perturbations of
two-body potentials. More generally, we provide a criterion for stability of
nonperiodic ground states.Comment: 14 pages, Latex, 10 figures available upon request, completely
revised versio
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