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Página 12 dos resultados de 20101 itens digitais encontrados em 0.007 segundos

## ‣ Only accessible information is useful: insights from gradient-mediated patterning

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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Information theory is gaining popularity as a tool to characterize
performance of biological systems. However, information is commonly quantified
without reference to whether or how a system could extract and use it; as a
result, information-theoretic quantities are easily misinterpreted. Here we
take the example of pattern-forming developmental systems which are commonly
structured as cascades of sequential gene expression steps. Such a multi-tiered
structure appears to constitute sub-optimal use of the positional information
provided by the input morphogen because noise is added at each tier. However,
the conventional theory fails to distinguish between the total information in a
morphogen and information that can be usefully extracted and interpreted by
downstream elements. We demonstrate that quantifying the information that is
_accessible_ to the system naturally explains the prevalence of multi-tiered
network architectures as a consequence of the noise inherent to the control of
gene expression. We support our argument with empirical observations from
patterning along the major body axis of the fruit fly embryo. Our results
exhibit the limitations of the standard information-theoretic characterization
of biological signaling and illustrate how they can be resolved.; Comment: Updated and refocused; 9 pages...

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## ‣ Conditions to the density of accessible sets

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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#Mathematics - Optimization and Control#60J60, 58E25 (Primary) 60J70, 37N35, 60J65, 60J35 (Secondary)

Given a control system $\dot{p} = X_0(p) + \sum_i u_i (t)X_i(p)$ on a compact
manifold M we study conditions for the foliation defined by the accessible sets
be dense in M . To do this we relate the control system to a stochastic
differential equation and, using the support theorem, we give a
characterization of the density in terms of the infinitesimal generator of the
diffusion and its invariant measures. Also we give a different proof of
Krener's theorem.; Comment: This paper has been withdrawn by the author due to crucial error in
theorem 3. The equivalence stated here is wrong. The gap in the proof is on
p. 5, paragraph starting with "On the other side"

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## ‣ Proposal of an experimentally accessible measure of many-fermion entanglement

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We propose a measure of interaction-induced ground state entanglement in
many-fermion systems that is experimentally accessible. It is formulated in
terms of cross-correlations of currents through resonant fermion levels weakly
coupled to the probed system. The proposed entanglement measure vanishes in the
absence of many-body interactions and it is related to measures of occupation
number entanglement. We evaluate it for two examples of interacting electronic
nanostructures.; Comment: 5 pages, 3 figures, published version

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## ‣ Locally Accessible Information of Multisite Quantum Ensembles Violates Monogamy

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 11/08/2011
Português

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Locally accessible information is a useful information-theoretic physical
quantity of an ensemble of multiparty quantum states. We find it has properties
akin to quantum as well as classical correlations of single multiparty quantum
states. It satisfies monotonicity under local quantum operations and classical
communication. However we show that it does not follow monogamy, an important
property usually satisfied by quantum correlations, and actually violates any
such relation to the maximal extent. Violation is obtained even for locally
indistinguishable, but globally orthogonal, multisite ensembles. The results
assert that while single multiparty quantum states are monogamous with respect
to their shared quantum correlations, ensembles of multiparty quantum states
may not be so. The results have potential implications for quantum
communication systems.; Comment: 6 pages, RevTeX4

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## ‣ Tight Bounds on the Accessible Information and the Informational Power

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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The accessible information quantifies the amount of classical information
that can be extracted from an ensemble of quantum states. Analogously, the
informational power quantifies the amount of classical information that can be
extracted by a quantum measurement. For both quantities, we provide upper and
lower bounds that depend only on the dimension of the system, and we prove
their tightness. In the case of symmetric informationally complete (SIC)
ensembles and measurements, stronger bounds are provided and their tightness
proved for qubits and qutrits. From our upper bounds, we notice, perhaps
surprisingly, that the statistics generated by SIC ensembles or measurements in
arbitrary dimension, though optimal for tomographic purposes, in fact never
contains more than just one bit of information, the rest being constituted by
completely random bits. On the other hand, from our lower bounds, we obtain an
explicit strategy beating the so-called "pretty-good" one for the extraction of
mutual information in the case of SIC ensembles and measurements.; Comment: 9 pages, 1 figure, updated references, published version

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## ‣ Chiral spin currents and spectroscopically accessible single merons in quantum dots

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Strongly Correlated Electrons#Physics - Computational Physics

We provide unambiguous theoretical evidence for the formation of
correlation-induced isolated merons in rotationally-symmetric quantum dots. Our
calculations rely on neither the lowest-Landau-level approximation, nor on the
maximum-density-droplet approximation, nor on the existence of a spin-polarized
state. For experimentally accessible system parameters, unbound merons condense
in the ground state at magnetic fields as low as $B^* = 0.2$ T and for as few
as N = 3 confined fermions. The four-fold degenerate ground-state at $B^*$
corresponds to four orthogonal merons $\ket{QC}$ characterized by their
topological chirality $C$ and charge $Q$. This degeneracy is lifted by the
Rashba and Dresselhaus spin-orbit interaction, which we include perturbatively,
yielding spectroscopic accessibility to individual merons. We further derive a
closed-form expression for the topological chirality in the form of a chiral
spin current and use it to both characterize our states and predict the
existence of other topological textures in other regions of phase space, for
example, at N=5. Finally, we compare the spin textures of our numerically exact
meron states to ansatz wave-functions of merons in quantum Hall droplets and
find that the ansatz qualitatively describes the meron states.; Comment: 4 pages...

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## ‣ Approximations of superstability in concrete accessible categories

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/05/2015
Português

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We generalize the constructions and results of Chapter 10 in Baldwin's
"Categoricity" to coherent accessible categories with concrete directed
colimits and concrete monomorphisms. In particular, we prove that if any
category of this form is categorical in a successor, directed colimits of
saturated objects are themselves saturated.; Comment: 17 pages

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## ‣ Tradeoff between extractable mechanical work, accessible entanglement, and ability to act as a reference system, under arbitrary superselection rules

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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Superselection rules (SSRs) limit the mechanical and quantum processing
resources represented by quantum states. However SSRs can be violated using
reference systems to break the underlying symmetry. We show that there is a
duality between the ability of a system to do mechanical work and to act as a
reference system. Further, for a bipartite system in a globally symmetric pure
state, we find a triality between the system's ability to do local mechanical
work, its ability to do ``logical work'' due to its accessible entanglement,
and its ability to act as a shared reference system.; Comment: 5 pages, no figures. Extended resubmitted version. Slightly modified
title. Transferred to PRA

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## ‣ Buried and accessible surface area control intrinsic protein flexibility

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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Proteins experience a wide variety of conformational dynamics that can be
crucial for facilitating their diverse functions. How is the intrinsic
flexibility required for these motions encoded in their three-dimensional
structures? Here, the overall flexibility of a protein is demonstrated to be
tightly coupled to the total amount of surface area buried within its fold. A
simple proxy for this, the relative solvent accessible surface area (Arel),
therefore shows excellent agreement with independent measures of global protein
flexibility derived from various experimental and computational methods.
Application of Arel on a large scale demonstrates its utility by revealing
unique sequence and structural properties associated with intrinsic
flexibility. In particular, flexibility as measured by Arel shows little
correspondence with intrinsic disorder, but instead tends to be associated with
multiple domains and increased {\alpha}- helical structure. Furthermore, the
apparent flexibility of monomeric proteins is found to be useful for
identifying quaternary structure errors in published crystal structures. There
is also a strong tendency for the crystal structures of more flexible proteins
to be solved to lower resolutions. Finally, local solvent accessibility is
shown to be a primary determinant of local residue flexibility. Overall this
work provides both fundamental mechanistic insight into the origin of protein
flexibility and a simple...

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## ‣ The $B_{s}\to K$ Form Factor in The Whole Kinematically Accessible Range

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 16/06/2001
Português

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A systematic analysis is presented of the $B_{s}\to K$ form factor $f(q^{2})
$ in the whole range of momentum transfer $q^{2}$, which would be useful to
analyzing the future data on $B_{s}\to K$ decays and extracting $| V_{ub}|$.
With a modified QCD light cone sum rule (LCSR) approach, in which the
contributions cancel out from the twist 3 wavefunctions of $K$ meson, we
investigate in detail the behavior of $f(q^{2})$ at small and intermediate
$q^{2}$ and the nonperturbative quantity $f_{B^{\ast}}g_{B^{\ast}B_{s}K}$
$(f_{B^{\ast}}$ is the decay constant of $B^{\ast}$ meson and
$g_{B^{\ast}B_{s}K}$ the $B^{\ast}B_{s}K$ strong coupling), whose numerical
result is used to study $q^{2}$ dependence of $f(q^{2})$ at large $q^{2}$ in
the single pole approximation. Based on these findings, a form factor model
from the best fit is formulated, which applies to the calculation on $f(q^{2})$
in the whole kinematically accessible range. Also, a comparison is made with
the standard LCSR predictions.; Comment: 11 pages, Latex, 1 eps figure, Final version to appear in Phys.Rev.D

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## ‣ Non-Markovianity through accessible information

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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The degree of non-Markovianity of quantum processes has been characterized in
several different ways in the recent literature. However, the relationship
between the non-Markovian behavior and the flow of information between the
system and the environment through an entropic measure has not been yet
established. We propose an entanglement-based measure of non-Markovianity by
employing the concept of assisted knowledge, where the environment E, acquires
information about a system S, by means of its measurement apparatus A. The
assisted knowledge, based on the accessible information in terms of von-Neumann
entropy, monotonically increases in time for all Markovian quantum processes.
We demonstrate that the signatures of non-Markovianity can be captured by the
nonmonotonic behaviour of the assisted knowledge. We explore this scenario for
a two-level system undergoing a relaxation process, through an experimental
implementation using an optical approach that allows full access to the state
of the environment.; Comment: Final Version

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## ‣ Non-accessible critical points of Cremer polynomials

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 11/02/1995
Português

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It is shown that a polynomial with a Cremer periodic point has a
non-accessible critical point in its Julia set provided that the Cremer
periodic point is approximated by small cycles.

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## ‣ Random Generation and Enumeration of Accessible Determinisitic Real-time Pushdown Automata

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 18/12/2015
Português

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This papers presents a general framework for the uniform random generation of
deterministic real-time accessible pushdown au-tomata. A polynomial time
algorithm to randomly generate a pushdown automaton having a fixed stack
operations total size is proposed. The influence of the accepting condition
(empty stack, final state) on the reachability of the generated automata is
investigated.; Comment: Frank Drewes. CIAA 2015, Aug 2015, Umea, Sweden. Springer, 9223,
pp.12, 2015, Implementation and Application of Automata - 20th International
Conference

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## ‣ Accessible Banking: Experiences and Future Directions

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 16/07/2015
Português

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This is a short position paper drawing on experience working with the UK
banking industry and their disabled and ageing customers in the Business
Disability Forum, a UK non-profit member organisation funded by a large body of
UK private and public sector businesses. We describe some commonly reported
problems of disabled customers who use modern banking technologies, relating
them to UK law and best practice. We describe some of the recent banking
industry innovations and the hope they may offer for improved inclusive and
accessible multi-channel banking.; Comment: 3 pages, presented at Workshop on Inclusive Privacy and Security
(WIPS): Privacy and Security for Everyone, Anytime, Anywhere, held as part of
Symposium on Usable Privacy and Security (SOUPS) 2015, July 22-24, 2015,
Ottawa, Canada

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## ‣ Iterative procedure for computing accessible information in quantum communication

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/08/2004
Português

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We present an iterative algorithm that finds the optimal measurement for
extracting the accessible information in any quantum communication scenario.
The maximization is achieved by a steepest-ascent approach toward the extremal
point, following the gradient uphill in sufficiently small steps. We apply it
to a simple ad-hoc example, as well as to a problem with a bearing on the
security of a tomographic protocol for quantum key distribution.; Comment: REVTeX, 4 pages, 1 figure, 1 table

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## ‣ Final coalgebras in accessible categories

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 29/05/2009
Português

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We give conditions on a finitary endofunctor of a finitely accessible
category to admit a final coalgebra. Our conditions always apply to the case of
a finitary endofunctor of a locally finitely presentable (l.f.p.) category and
they bring an explicit construction of the final coalgebra in this case. On the
other hand, there are interesting examples of final coalgebras beyond the realm
of l.f.p. categories to which our results apply. We rely on ideas developed by
Tom Leinster for the study of self-similar objects in topology.; Comment: 23 pages

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## ‣ New Types of Accessible Environmental Influence on Neutrino Oscillation

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 13/11/1997
Português

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To describe possible effects of medium, besides the hamiltonian introduced by
Mikheev, Smirnov and Wolfenstein (MSW), in principle, there may exist new terms
in the evolution equation for the neutrino oscillation due to the environment.
Considering a two-energy-level quantum system: $\nu_1-\nu_2$, two-species
neutrino system which is embedded in a matter environment, we solve the
neutrino evolution equation precisely with the possible extra terms,
especially, those cause alternations between pure and mixed states of the
neutrino quantum system. We obtain some remarkable features for the neutrino
oscillations, which are different from that of MSW and accessible to be
observed in solar neutrino observation and/or in the planned long-baseline
neutrino experiments.; Comment: Latex file, 12pages, no figures

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## ‣ Route to nonlocality and observation of accessible solitons

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/08/2003
Português

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We develop a general theory of spatial solitons in a liquid crystalline
medium exhibiting a nonlinearity with an arbitrary degree of effective
nonlocality. The model accounts the observability of "accessible solitons" and
establishes an important link with parametric solitons.; Comment: 4 pages, 2 figures

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## ‣ Nonlinear optical magnetometry with accessible in situ optical squeezing

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/09/2014
Português

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We demonstrate compact and accessible squeezed-light magnetometry using
four-wave mixing in a single hot rubidium vapor cell. The strong intrinsic
coherence of the four wave mixing process results in nonlinear magneto-optical
rotation (NMOR) on each mode of a two mode relative-intensity squeezed state.
This framework enables 4.7 dB of quantum noise reduction while the opposing
polarization rotation signals of the probe and conjugate fields add to increase
the total signal to noise ratio.

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## ‣ Algebraic weak factorisation systems I: accessible AWFS

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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Algebraic weak factorisation systems (AWFS) refine weak factorisation systems
by requiring that the assignations sending a map to its first and second
factors should underlie an interacting comonad--monad pair on the arrow
category. We provide a comprehensive treatment of the basic theory of
AWFS---drawing on work of previous authors---and complete the theory with two
main new results. The first provides a characterisation of AWFS and their
morphisms in terms of their double categories of left or right maps. The second
concerns a notion of cofibrant generation of an AWFS by a small double
category; it states that, over a locally presentable base, any small double
category cofibrantly generates an AWFS, and that the AWFS so arising are
precisely those with accessible monad and comonad. Besides the general theory,
numerous applications of AWFS are developed, emphasising particularly those
aspects which go beyond the non-algebraic situation.; Comment: 46 pages, final journal version

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