18,619 research outputs found
Effects of uncertainties and errors on Lyapunov control
Lyapunov control (open-loop) is often confronted with uncertainties and
errors in practical applications. In this paper, we analyze the robustness of
Lyapunov control against the uncertainties and errors in quantum control
systems. The analysis is carried out through examinations of uncertainties and
errors, calculations of the control fidelity under influences of the
certainties and errors, as well as discussions on the caused effects. Two
examples, a closed control system and an open control system, are presented to
illustrate the general formulism.Comment: 4 pages, 5 figure
On model selection criteria for climate change impact studies
Climate change impact studies inform policymakers on the estimated damages of
future climate change on economic, health and other outcomes. In most studies,
an annual outcome variable is observed, e.g. annual mortality rate, along with
higher-frequency regressors, e.g. daily temperature and precipitation.
Practitioners use summaries of the higher-frequency regressors in fixed effects
panel models. The choice over summary statistics amounts to model selection.
Some practitioners use Monte Carlo cross-validation (MCCV) to justify a
particular specification. However, conventional implementation of MCCV with
fixed testing-to-full sample ratios tends to select over-fit models. This paper
presents conditions under which MCCV, and also information criteria, can
deliver consistent model selection. Previous work has established that the
Bayesian information criterion (BIC) can be inconsistent for non-nested
selection. We illustrate that the BIC can also be inconsistent in our
framework, when all candidate models are misspecified. Our results have
practical implications for empirical conventions in climate change impact
studies. Specifically, they highlight the importance of a priori information
provided by the scientific literature to guide the models considered for
selection. We emphasize caution in interpreting model selection results in
settings where the scientific literature does not specify the relationship
between the outcome and the weather variables.Comment: Additional simulation results available from authors by reques
Entropy and specific heat for open systems in steady states
The fundamental assumption of statistical mechanics is that the system is
equally likely in any of the accessible microstates. Based on this assumption,
the Boltzmann distribution is derived and the full theory of statistical
thermodynamics can be built. In this paper, we show that the Boltzmann
distribution in general can not describe the steady state of open system. Based
on the effective Hamiltonian approach, we calculate the specific heat, the free
energy and the entropy for an open system in steady states. Examples are
illustrated and discussed.Comment: 4 pages, 7 figure
Tick-borne encephalitis virus induces chemokine RANTES expression via activation of IRF-3 pathway.
BACKGROUND: Tick-borne encephalitis virus (TBEV) is one of the most important flaviviruses that targets the central nervous system (CNS) and causes encephalitides in humans. Although neuroinflammatory mechanisms may contribute to brain tissue destruction, the induction pathways and potential roles of specific chemokines in TBEV-mediated neurological disease are poorly understood. METHODS: BALB/c mice were intracerebrally injected with TBEV, followed by evaluation of chemokine and cytokine profiles using protein array analysis. The virus-infected mice were treated with the CC chemokine antagonist Met-RANTES or anti-RANTES mAb to determine the role of RANTES in affecting TBEV-induced neurological disease. The underlying signaling mechanisms were delineated using RANTES promoter luciferase reporter assay, siRNA-mediated knockdown, and pharmacological inhibitors in human brain-derived cell culture models. RESULTS: In a mouse model, pathological features including marked inflammatory cell infiltrates were observed in brain sections, which correlated with a robust up-regulation of RANTES within the brain but not in peripheral tissues and sera. Antagonizing RANTES within CNS extended the survival of mice and reduced accumulation of infiltrating cells in the brain after TBEV infection. Through in vitro studies, we show that virus infection up-regulated RANTES production at both mRNA and protein levels in human brain-derived cell lines and primary progenitor-derived astrocytes. Furthermore, IRF-3 pathway appeared to be essential for TBEV-induced RANTES production. Site mutation of an IRF-3-binding motif abrogated the RANTES promoter activity in virus-infected brain cells. Moreover, IRF-3 was activated upon TBEV infection as evidenced by phosphorylation of TBK1 and IRF-3, while blockade of IRF-3 activation drastically reduced virus-induced RANTES expression. CONCLUSIONS: Our findings together provide insights into the molecular mechanism underlying RANTES production induced by TBEV, highlighting its potential importance in the process of neuroinflammatory responses to TBEV infection
Spectral properties of photon pairs generated by spontaneous four wave mixing in inhomogeneous photonic crystal fibers
The photonic crystal fiber (PCF) is one of the excellent media for generating
photon pairs via spontaneous four wave mixing. Here we study how the
inhomogeneity of PCFs affect the spectral properties of photon pairs from both
the theoretical and experimental aspects. The theoretical model shows that the
photon pairs born in different place of the inhomogeneous PCF are coherently
superposed, and a modulation in the broadened spectrum of phase matching
function will appear, which prevents the realization of spectral factorable
photon pairs. In particular, the inhomogeneity induced modulation can be
examined by measuring the spectrum of individual signal or idler field when the
asymmetric group velocity matching is approximately fulfilled. Our experiments
are performed by tailoring the spectrum of pulsed pump to satisfy the specified
phase matching condition. The observed spectra of individual signal photons,
which are produced from different segments of the 1.9 m inhomogeneous PCF,
agree with the theoretical predictions. The investigations are not only useful
for fiber based quantum state engineering, but also provide a dependable method
to test the homogeneity of PCF.Comment: to appear in Phys. Rev.
Atom-molecule conversion with particle losses
Based on the mean-field approximation and the phase space analysis, we study
the dynamics of an atom-molecule conversion system subject to particle loss.
Starting from the many-body dynamics described by a master equation, an
effective nonlinear Schr\"odinger equation is introduced. The classical phase
space is then specified and classified by fixed points. The boundary, which
separate different dynamical regimes have been calculated and discussed. The
effect of particle loss on the conversion efficiency and the self-trapping is
explored.Comment: 6 pages, 5 figure
Multiparticle Entanglement in the Lipkin-Meshkov-Glick Model
The multiparticle entanglement in the Lipkin-Meshkov-Glick model has been
discussed extensively in this paper. Measured by the global entanglement and
its generalization, our calculation shows that the multiparticle entanglement
can faithfully detect quantum phase transitions. For an antiferromagnetic case
the multiparticle entanglement reaches the maximum at the transition point,
whereas for ferromagnetic coupling, two different behaviors of multiparticle
entanglement can be identified, dependent on the anisotropic parameter in the
coupling.Comment: 7 pages and 5 figure
Effect of inter-subsystem couplings on the evolution of composite systems
The effect of inter-subsystem coupling on the adiabaticity of composite
systems and that of its subsystems is investigated. Similar to the adiabatic
evolution defined for pure states, non-transitional evolution for mixed states
is introduced; conditions for the non-transitional evolution are derived and
discussed. An example that describes two coupled qubits is presented to detail
the general presentation. The effects due to non-adiabatic evolution on the
geometric phase are also presented and discussed.Comment: 5 pages, 1 figur
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