9,527 research outputs found
Direct Counting Analysis on Network Generated by Discrete Dynamics
A detail study on the In-degree Distribution (ID) of Cellular Automata is
obtained by exact enumeration. The results indicate large deviation from
multiscaling and classification according to ID are discussed. We further
augment the transfer matrix as such the distributions for more complicated
rules are obtained. Dependence of In-degree Distribution on the lattice size
have also been found for some rules including R50 and R77.Comment: 8 pages, 11 figure
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
Quantum Teleportation of Light
Requirements for the successful teleportation of a beam of light, including
its temporal correlations, are discussed. Explicit expressions for the degrees
of first- and second-order optical coherence are derived. Teleportation of an
antibunched photon stream illustrates our results.Comment: 4 pages, 5 figure
Theory of ultrafast quasiparticle dynamics in high-temperature superconductors: Pump fluence dependence
We present a theory for the time-resolved optical spectroscopy of
high-temperature superconductors at high excitation densities with strongly
anisotropic electron-phonon coupling. A signature of the strong coupling
between the out-of-plane, out-of-phase O buckling mode () and
electronic states near the antinode is observed as a higher-energy peak in the
time-resolved optical conductivity and Raman spectra, while no evidence of the
strong coupling between the in-plane Cu-O breathing mode and nodal electronic
states is observed. More interestingly, it is observed that under appropriate
conditions of pump fluence, this signature exhibits a re-entrant behavior with
time delay, following the fate of the superconducting condensate.Comment: 5 pages, 3 embedded eps figures, to appear in PR
SUSY Hidden in the Continuum
We study models where the superpartners of the ordinary particles have
continuous spectra rather than being discrete states, which can occur when the
supersymmetric standard model is coupled to an approximately conformal sector.
We show that when superpartners that are well into the continuum are produced
at a collider they tend to have long decay chains that step their way down
through the continuum, emitting many fairly soft standard model particles along
the way, with a roughly spherical energy distribution in the center of mass
frame.Comment: 26 pages, 9 figures. Update of Fig.5 and added aknowledgement
Creation and pinning of vortex-antivortex pairs
Computer modeling is reported about the creation and pinning of a magnetic
vortex-antivortex (V-AV) pair in a superconducting thin film, due to the
magnetic field of a vertical magnetic dipole above the film, and two antidot
pins inside the film. For film thickness , , and no pins,
we find the film carries two V-AV pairs at steady state in the imposed flux
range , and no pairs below. With two antidot
pins suitably introduced into the film, a single V-AV pair can be stable in the
film for . At pin separation , we find the
V-AV pair remains pinned after the dipole field is removed, and, so can
represent a 1 for a nonvolatile memory.Comment: 8 pages, 6 figure
Observation of the spontaneous vortex phase in the weakly ferromagnetic superconductor ErNiBC: A penetration depth study
The coexistence of weak ferromagnetism and superconductivity in ErNiBC suggests the possibility of a spontaneous vortex phase (SVP) in which
vortices appear in the absence of an external field. We report evidence for the
long-sought SVP from the in-plane magnetic penetration depth of high-quality single crystals of ErNiBC. In addition to
expected features at the N\'{e}el temperature = 6.0 K and weak
ferromagnetic onset at K, rises to a maximum
at K before dropping sharply down to 0.1 K. We assign the
0.45 K-maximum to the proliferation and freezing of spontaneous vortices. A
model proposed by Koshelev and Vinokur explains the increasing as a consequence of increasing vortex density, and its subsequent decrease
below as defect pinning suppresses vortex hopping.Comment: 5 pages including figures; added inset to Figure 2; significant
revisions to tex
Entangled-State Cycles of Atomic Collective-Spin States
We study quantum trajectories of collective atomic spin states of
effective two-level atoms driven with laser and cavity fields. We show that
interesting ``entangled-state cycles'' arise probabilistically when the (Raman)
transition rates between the two atomic levels are set equal. For odd (even)
, there are () possible cycles. During each cycle the
-qubit state switches, with each cavity photon emission, between the states
, where is a Dicke state in a rotated
collective basis. The quantum number (), which distinguishes the
particular cycle, is determined by the photon counting record and varies
randomly from one trajectory to the next. For even it is also possible,
under the same conditions, to prepare probabilistically (but in steady state)
the Dicke state , i.e., an -qubit state with excitations,
which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure
Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces
Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from
high-temperature superconductivity and giant magnetoresistance to magnetism and
ferroelectricity. In addition, when TMOs are interfaced with each other, new
functionalities can arise, which are absent in individual components. Here, we
report results from first-principles calculations on the magnetism at the
BiFeO3/YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic
spin configurations inside BiFeO3, we are able to show that a metallic
ferromagnetism is induced near the interface. We further develop an interface
exchange-coupling model and place the extracted exchange coupling interaction
strengths, from the first-principles calculations, into a resultant generic
phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the
presence of a hysteresis loop in field-dependent magnetization data. The
emergence of interfacial ferromagnetism should have implications to electronic
and transport properties.Comment: 13 pages, 4 figure
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