24,184 research outputs found
Inequalities Detecting Quantum Entanglement for Systems
We present a set of inequalities for detecting quantum entanglement of
quantum states. For and systems, the
inequalities give rise to sufficient and necessary separability conditions for
both pure and mixed states. For the case of , these inequalities are
necessary conditions for separability, which detect all entangled states that
are not positive under partial transposition and even some entangled states
with positive partial transposition. These inequalities are given by mean
values of local observables and present an experimental way of detecting the
quantum entanglement of quantum states and even multi-qubit pure
states.Comment: 6 page
On Holographic Dual of the Dyonic Reissner-Nordstr\"om Black Hole
It is shown that the hidden conformal symmetry, namely symmetry, of the non-extremal dyonic
Reissner-Nordstr\"om black hole can be probed by a charged massless scalar
field at low frequencies. The existence of such hidden conformal symmetry
suggests that the field theory holographically dual to the 4D
Reissner-Nordstr\"om black hole indeed should be a 2D CFT. Although the
associated AdS structure does not explicitly appear in the near horizon
geometry, the primary parameters of the dual CFT can be exactly obtained
without the necessity of embedding the 4D Reissner-Nordstr\"om black hole into
5D spacetime. The duality is further supported by comparing the absorption
cross sections and real-time correlators obtained from both the CFT and the
gravity sides.Comment: 18 pages, no figure, typos correcte
Normalized Information Distance
The normalized information distance is a universal distance measure for
objects of all kinds. It is based on Kolmogorov complexity and thus
uncomputable, but there are ways to utilize it. First, compression algorithms
can be used to approximate the Kolmogorov complexity if the objects have a
string representation. Second, for names and abstract concepts, page count
statistics from the World Wide Web can be used. These practical realizations of
the normalized information distance can then be applied to machine learning
tasks, expecially clustering, to perform feature-free and parameter-free data
mining. This chapter discusses the theoretical foundations of the normalized
information distance and both practical realizations. It presents numerous
examples of successful real-world applications based on these distance
measures, ranging from bioinformatics to music clustering to machine
translation.Comment: 33 pages, 12 figures, pdf, in: Normalized information distance, in:
Information Theory and Statistical Learning, Eds. M. Dehmer, F.
Emmert-Streib, Springer-Verlag, New-York, To appea
Twofold Hidden Conformal Symmetries of the Kerr-Newman Black Hole
In this paper, we suggest that there are two different individual 2D CFTs
holographically dual to the Kerr-Newman black hole, coming from the
corresponding two possible limits --- the Kerr/CFT and Reissner-Nordstr\"om/CFT
correspondences, namely there exist the Kerr-Newman/CFTs dualities. A probe
scalar field at low frequencies turns out can exhibit two different 2D
conformal symmetries (named by - and -pictures, respectively) in its
equation of motion when the associated parameters are suitably specified. These
twofold dualities are supported by the matchings of entropies, absorption cross
sections and real time correlators computed from both the gravity and the CFT
sides. Our results lead to a fascinating "microscopic no hair conjecture" ---
for each macroscopic hair parameter, in additional to the mass of a black hole
in the Einstein-Maxwell theory, there should exist an associated holographic
CFT description.Comment: 21 pages, 1 figure, typos correcte
echinus, required for interommatidial cell sorting and cell death in the Drosophila pupal retina, encodes a protein with homology to ubiquitin-specific proteases
Background: Programmed cell death is used to remove excess cells between ommatidia in the Drosophila pupal retina. This death is required to establish the crystalline, hexagonal packing of ommatidia that characterizes the adult fly eye. In previously described echinus mutants, interommatidial cell sorting, which precedes cell death, occurred relatively normally. Interommatidial cell death was partially suppressed, resulting in adult eyes that contained excess pigment cells, and in which ommatidia were mildly disordered. These results have suggested that echinus functions in the pupal retina primarily to promote interommatidial cell death.
Results: We generated a number of new echinus alleles, some of which are likely null mutants. Analysis of these alleles provides evidence that echinus has roles in cell sorting as well as cell death. echinus encodes a protein with homology to ubiquitin-specific proteases, which cleave ubiquitin-conjugated proteins at the ubiquitin C-terminus. The echinus locus encodes multiple splice forms, including two proteins that lack residues thought to be critical for deubiquitination activity. Surprisingly, ubiquitous expression in the eye of versions of Echinus that lack residues critical for ubiquitin specific protease activity, as well as a version predicted to be functional, rescue the echinus loss-of-function phenotype. Finally, genetic interactions were not detected between echinus loss and gain-of-function and a number of known apoptotic regulators. These include Notch, EGFR, the caspases Dronc, Drice, Dcp-1, Dream, the caspase activators, Rpr, Hid, and Grim, the caspase inhibitor DIAP1, and Lozenge or Klumpfuss.
Conclusions: The echinus locus encodes multiple splice forms of a protein with homology to ubiquitin-specific proteases, but protease activity is unlikely to be required for echinus function, at least when echinus is overexpressed. Characterization of likely echinus null alleles and genetic interactions suggests that echinus acts at a novel point(s) to regulate interommatidial cell sorting and/or cell death in the fly eye
Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations
A correct general formula for the spin current through an interacting quantum
dot coupled to ferromagnetic leads with magnetization at an arbitrary angle
is derived within the framework of the Keldysh formalism. Under
asymmetric conditions, the spin current component J_{z} may change sign for
. It is shown that the spin current and spin tunneling
magnetoresistance exhibit different angle dependence in the free and Coulomb
blockade regimes. In the latter case, the competition of spin precession and
the spin-valve effect could lead to an anomaly in the angle dependence of the
spin current.Comment: 7 pages, 4 figures; some parts of the text has been revised in this
version accepted by J. Phys.: Condens. Matte
Investigation of Structural Dynamics of Enzymes and Protonation States of Substrates Using Computational Tools.
This review discusses the use of molecular modeling tools, together with existing experimental findings, to provide a complete atomic-level description of enzyme dynamics and function. We focus on functionally relevant conformational dynamics of enzymes and the protonation states of substrates. The conformational fluctuations of enzymes usually play a crucial role in substrate recognition and catalysis. Protein dynamics can be altered by a tiny change in a molecular system such as different protonation states of various intermediates or by a significant perturbation such as a ligand association. Here we review recent advances in applying atomistic molecular dynamics (MD) simulations to investigate allosteric and network regulation of tryptophan synthase (TRPS) and protonation states of its intermediates and catalysis. In addition, we review studies using quantum mechanics/molecular mechanics (QM/MM) methods to investigate the protonation states of catalytic residues of β-Ketoacyl ACP synthase I (KasA). We also discuss modeling of large-scale protein motions for HIV-1 protease with coarse-grained Brownian dynamics (BD) simulations
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