Robust stability conditions for feedback interconnections of distributed-parameter negative imaginary systems

Sufficient and necessary conditions for the stability of positive feedback interconnections of negative imaginary systems are derived via an integral quadratic constraint (IQC) approach. The IQC framework accommodates distributed-parameter systems with irrational transfer function representations, while generalising existing results in the literature and allowing exploitation of flexibility at zero and infinite frequencies to reduce conservatism in the analysis. The main results manifest the important property that the negative imaginariness of systems gives rise to a certain form of IQCs on positive frequencies that are bounded away from zero and infinity. Two additional sets of IQCs on the DC and instantaneous gains of the systems are shown to be sufficient and necessary for closed-loop stability along a homotopy of systems.Comment: Submitted to Automatica, A preliminary version of this paper appeared in the Proceedings of the 2015 European Control Conferenc

Fluctuation and localization of acoustic waves in bubbly water

Here the fluctuation properties of acoustic localization in bubbly water is explored. We show that the strong localization can occur in such a system for a certain frequency range and sufficient filling fractions of air-bubbles. Two fluctuating quantities are considered, that is, the fluctuation of transmission and the fluctuation of the phase of acoustic wave fields. When localization occurs, these fluctuations tend to vanish, a feature able to uniquely identify the phenomenon of wave localization.Comment: 10 pages, 4 figure

Asymmetric TP and TN completion problems

We first give a complete list of polynomial conditions on the data for TP (TN) completability of partial TP (TN) matrices with just one or two unspecified entries in either or both of the upper right or lower left entries. These results are used to identify which such patterns, and related patterns, are TP (TN) completable. Then, the TN completable echelon and TP completable jagged patterns are characterized. This generalizes earlier work on combinatorially symmetric TN completable patterns. (C) 2012 Elsevier Inc. All rights reserved

Formation of regular spatial patterns in ratio-dependent predator-prey model driven by spatial colored-noise

Results are reported concerning the formation of spatial patterns in the two-species ratio-dependent predator-prey model driven by spatial colored-noise. The results show that there is a critical value with respect to the intensity of spatial noise for this system when the parameters are in the Turing space, above which the regular spatial patterns appear in two dimensions, but under which there are not regular spatial patterns produced. In particular, we investigate in two-dimensional space the formation of regular spatial patterns with the spatial noise added in the side and the center of the simulation domain, respectively.Comment: 4 pages and 3 figure

Aspiring to the fittest and promotion of cooperation in the prisoner's dilemma game

Strategy changes are an essential part of evolutionary games. Here we introduce a simple rule that, depending on the value of a single parameter $w$, influences the selection of players that are considered as potential sources of the new strategy. For positive $w$ players with high payoffs will be considered more likely, while for negative $w$ the opposite holds. Setting $w$ equal to zero returns the frequently adopted random selection of the opponent. We find that increasing the probability of adopting the strategy from the fittest player within reach, i.e. setting $w$ positive, promotes the evolution of cooperation. The robustness of this observation is tested against different levels of uncertainty in the strategy adoption process and for different interaction network. Since the evolution to widespread defection is tightly associated with cooperators having a lower fitness than defectors, the fact that positive values of $w$ facilitate cooperation is quite surprising. We show that the results can be explained by means of a negative feedback effect that increases the vulnerability of defectors although initially increasing their survivability. Moreover, we demonstrate that the introduction of $w$ effectively alters the interaction network and thus also the impact of uncertainty by strategy adoptions on the evolution of cooperation.Comment: 7 two-column pages, 5 figures; accepted for publication in Physical Review

Thick branes with a nonminimally coupled bulk-scalar field

In this paper, we investigate thick branes with a nonminimally coupled background scalar field, whose solution is a single-kink or a double-kink. The effects of the nonminimal coupling constant $\xi$ on the structure of the thick branes and the localization of gravity, fermions, scalars and vectors are discussed. It is shown that each brane will split into two sub-branes as increasing the nonminimal coupling constant $\xi$. By investigating the tensor perturbation equations of gravity and the general covariant Dirac equation of fermions, we find that both the gravity zero mode and left-chiral fermion zero mode are localized at the center of the single-kink branes and localized between the two sub-branes generated by the double-kink, which indicates that the constant $\xi$ does not effect the localization of these zero modes. However, the zero mode of scalars is localized on each sub-brane (for both single-kink and double-kink branes) when $\xi$ is larger than its critical value $\xi_0$. The effects of the nonminimal coupling constant $\xi$ on the resonances of gravity and fermions with finite lifetime on the branes are also discussed.Comment: V2: 33 pages, 17 figures, 3 tables, published versio

Simulated Quantum Computation of Global Minima

Finding the optimal solution to a complex optimization problem is of great importance in practically all fields of science, technology, technical design and econometrics. We demonstrate that a modified Grover's quantum algorithm can be applied to real problems of finding a global minimum using modest numbers of quantum bits. Calculations of the global minimum of simple test functions and Lennard-Jones clusters have been carried out on a quantum computer simulator using a modified Grover's algorithm. The number of function evaluations $N$ reduced from O(N) in classical simulation to $O(\sqrt{N})$ in quantum simulation. We also show how the Grover's quantum algorithm can be combined with the classical Pivot method for global optimization to treat larger systems.Comment: 6 figures. Molecular Physics, in pres

Withania somnifera Root Extract Inhibits Mammary Cancer Metastasis and Epithelial to Mesenchymal Transition

Though clinicians can predict which patients are at risk for developing metastases, traditional therapies often prove ineffective and metastatic disease is the primary cause of cancer patient death; therefore, there is a need to develop anti-metastatic therapies that can be administered over long durations to specifically inhibit the motility of cancer cells. Withania somnifera root extracts (WRE) have anti-proliferative activity and the active component, Withaferin A, inhibits the pro-metastatic protein, vimentin. Vimentin is an intermediate filament protein and is part of the epithelial to mesenchymal transition (EMT) program to promote metastasis. Here, we determined whether WRE standardized to Withaferin A (sWRE) possesses anti-metastatic activity and whether it inhibits cancer motility via inhibition of vimentin and the EMT program. Several formulations of sWRE were created to enrich for Withaferin A and a stock solution of sWRE in EtOH could recover over 90% of the Withaferin A found in the original extract powder. This sWRE formulation inhibited breast cancer cell motility and invasion at concentrations less than 1μM while having negligible cytotoxicity at this dose. sWRE treatment disrupted vimentin morphology in cell lines, confirming its vimentin inhibitory activity. To determine if sWRE inhibited EMT, TGF-β was used to induce EMT in MCF10A human mammary epithelial cells. In this case, sWRE prevented EMT induction and inhibited 3-D spheroid invasion. These studies were taken into a human xenograft and mouse mammary carcinoma model. In both models, sWRE and Withaferin A showed dose-dependent inhibition of tumor growth and metastatic lung nodule formation with minimal systemic toxicity. Taken together, these data support the hypothesis that low concentrations of sWRE inhibit cancer metastasis potentially through EMT inhibition. Moreover, these doses of sWRE have nearly no toxicity in normal mouse organs, suggesting the potential for clinical use of orally administered WRE capsules. © 2013 Yang et al

Polarization and Charge Transfer in the Hydration of Chloride Ions

A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation, and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The Quantum Theory of Atoms in Molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared with the estimated quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2 level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.Comment: Slight revision, in press at J. Chem. Phy