Synchronization of impulsively coupled complex systems with delay

This paper investigates the synchronization of complex systems with delay that are impulsively coupled at discrete instants only. Based on the comparison theorem of impulsive differential system, a distributed impulsive control scheme is proposed to achieve the synchronization for systems with delay. In the control strategy, the influence of all nodes to network synchronization relies on its weight. The proposed control scheme is applied to the chaotic delayed Hopfield neural networks and numerical simulations are presented to demonstrate the effectiveness of the proposed scheme.     

11B and constraints on neutrino oscillations and spectra from neutrino nucleosynthesis

We study the sensitivity to variations in the triple-alpha and 12C(α,γ)16O reaction rates, of the yield of the neutrino-process isotopes 7Li, 11B, 19F, 138La, and 180Ta in core-collapse supernovae. Compared to solar abundances, less than 15% of 7Li, about 25%-80% of 19F, and about half of 138La is produced in these stars. Over a range of ±2σ for each helium-burning rate, 11B is overproduced and the yield varies by an amount larger than the variation caused by the effects of neutrino oscillations. The total 11B yield, however, may eventually provide constraints on supernova neutrino spectra.     

Evidence for shape coexistence at medium spin in Rb

Four previously known rotational bands in ⁷⁶Rb have been extended to moderate spins using the Gammasphere and Microball γ ray and charged particle detector arrays and the ⁴⁰Ca(⁴⁰Ca, 3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g9/2 particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape coexisting structures at medium spins.     

On connected dominating sets of restricted diameter

A connected dominating set (CDS) is commonly used to model a virtual backbone of a wireless network. To bound the distance that information must travel through the network, we explicitly restrict the diameter of a CDS to be no more than s leading to the concept of a dominating s-club. We prove that for any fixed positive integer s it is NP-complete to determine if a graph has a dominating s  -club, even when the graph has diameter s+1$s+1$. As a special case it is NP-complete to determine if a graph of diameter two has a dominating clique. We then propose a compact integer programming formulation for the related minimization problem, enhance the approach with variable fixing rules and valid inequalities, and present computational results.     

Solving maximum clique in sparse graphs: an O(nm+n2^{d/4}) algorithm for d-degenerate graphs

We describe an algorithm for the maximum clique problem that is parameterized by the graph’s degeneracy \(d\) . The algorithm runs in \(O\left( nm+n T_d \right) \) time, where \(T_d\) is the time to solve the maximum clique problem in an arbitrary graph on \(d\) vertices. The best bound as of now is \(T_d=O(2^{d/4})\) by Robson. This shows that the maximum clique problem is solvable in \(O(nm)\) time in graphs for which \(d \le 4 \log _2 m + O(1)\) . The analysis of the algorithm’s runtime is simple; the algorithm is easy to implement when given a subroutine for solving maximum clique in small graphs; it is easy to parallelize. In the case of Bianconi-Marsili power-law random graphs, it runs in \(2^{O(\sqrt{n})}\) time with high probability. We extend the approach for a graph invariant based on common neighbors, generating a second algorithm that has a smaller exponent at the cost of a larger polynomial factor.     

Mechanistic aspects of biological redox reactions involving NADH 2: A combined semiempirical and ab initio study of hydride-ion transfer between the NADH analogue, 1-methyl-dihydronicotinamide,and folate and dihydrofolate analogue substrates of dihydrofolate reductase

As part of a study of factors controlling biological redox reactions of nicotinamide cofactors [nicotinamide adenine dinucleotide (phosphate) NAD(P)H], we have investigated the effect on a model reaction of the conformational state (cis or trans) of the carboxamide side chain, using quantum chemical methods. The reaction is that for the enzyme dihydrofolate reductase between the NADPH analogue, 1-methyl-dihydronicotinamide, and the protonated forms of the folate and dihydrofolate substrate analogues, pyrazine and dihydropyrazine. Some calculations on pterin and dihydropterin substrate analogues were also carried out in order to gauge the effects of inter-ring coupling. The influence of carboxamide side-chain conformation of nicotinamide on the energetics of the hydride-ion transfer, and on the structures of the transition states and stable intermolecular-interaction complexes, are examined as a function of the orientation of approach of the reactants. These approach geometries include those corresponding to the observed binding of cofactor and either substrate or inhibitor in the enzyme active site. Reactant, product, reactants-complex, and transition-state geometries were optimized at the semiempirical AM1 level, while ab initio SCF/STO-3G and SCF/3-21G single-point calculations were carried out at the AM1 optimized geometries for all species, as well as full geometry optimizations for isolated reactants and products. The results show that reactants-complex and transition-state energies are lower for the trans conformer of dihydronicotinamide than for the cis conformer, due to more favorable H-bonding or electrostatic interactions with the protonated substrate. Also, consideration of the structural parameters, including reaction coordinate bond lengths, ring geometries, and charge distributions, indicate that the trans transition states are more product-like than those for the cis. For the (trans) approaches corresponding to the enzymic orientation for substrate, the intermolecular interaction for the folate reaction lacks the stabilizing influence of the formal H-bond which is present for the dihydrofolate reaction, and consequently the reactants-complex and transition state are less stable.     

Ionic conductivity in hydrogels for contact lens applications

Biphasic hydrogel polymers are in the forefront of new extended wear contact lens development. In the biphasic hydrogel the objective is to produce co-continuous domains of siloxane units for high oxygen permeability, coupled with hydrophilic units forming aqueous channels for hydraulic and ion mobility. These are distributed in phase separated nano-scale regions such that the material is optically clear while achieving the required properties to maintain corneal health and lens movement. This paper describes how Impedance Spectroscopy permits a rapid measurement of ion conductivity in a range of silicone and non-silicone hydrogel materials with water contents ranging from 18% to 75% equilibrium water content. For non-silicone hydrogels relative sodium ion conductivity follows a typical percolation curve. However, for silicone hydrogels ion mobility is three orders of magnitude higher than conventional hydrogels of the same equilibrium water content. The influence of electrolyte concentration, interfacial electrode sample contact pressure and temperature are also reported. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Molecular structural analysis of 55mol% CuI-45mol% Ag2MoO4 solid electrolyte using XPS and laser raman techniques

The solid electrolyte 55 mol% CuI - 45 mol% Ag₂MoO₄ has been analyzed structurally by employing X-ray photoelectron spectroscopic (XPS) and laser Raman studies. The core level Ag 3d, Cu 2p, Mo 3d, I 3d and O1s XPS spectra of the constituent elements were recorded. The presence of both bridging (BO) and non-bridging (NBO) oxygen atoms in the oxyanion framework has been identified through the deconvolution of the O 1s spectrum. Laser Raman spectroscopic studies tend to reveal that the oxyanion framework is constructed with [MoO ₄ ²⁻ ]-tetrahedral and [MoO₆]-octahedral units as in the case of CuI - Cu₂MoO₄ and AgI - Ag₂O - MoO₃ glasses.     

Movement of the velum during speech and singing in classically trained singers

The present study addresses two questions: (a) Is the action and/orposture of the velopharyngeal valve conducive to allow significant resonance during Western tradition classical singing? (b) How do the actions of the velo-pharyngeal valve observed in this style of singing compare with normal speech? A photodetector system was used to observe the area function of the velopharyngeal port during speech and classical style singing. Identical speech samples were produced by each subject in a normal speaking voice and then in the low, medium, and high singing ranges. Results indicate that in these four singers the velopharyngeal port was closed significantly longer in singing than in speaking samples. The amount of time the velopharyngeal port was opened was greatest in speech and diminished as the singer ascended in pitch. In the high voice condition, little or no opening of the velopharyngeal port was measured.     

On imposing connectivity constraints in integer programs

We study an extension of the classical graph cut problem, wherein we replace the modular (sum of edge weights) cost function by a submodular set function defined over graph edges. Special cases of this problem have appeared in different applications in signal processing, machine learning, and computer vision. In this paper, we connect these applications via the generic formulation of “cooperative graph cuts”, for which we study complexity, algorithms, and connections to polymatroidal network flows. Finally, we compare the proposed algorithms empirically.