Compositional dependence of serrated flow in nickel binary solid solutions during high-temperature microindentation

At 450?°C, pure nickel and nickel binary solid solutions, containing Ru, Rh, W, Re, Ir and Pt, have a smooth load–depth curves. In contrast, the alloying addition of Nb, Mo, Pd and Ta results in the occurrence of serrations in their load–depth profiles. Analyses show the load increment of the quasi-elastic segments scales linearly with the load at their starting point. The slope of such linear relationships was normalized by the solute concentration and then plotted against the diffusion rate of transition metal solutes within the nickel lattice and along dislocation cores. Linear relationships were observed in both cases. Results suggest that the solute diffusion along dislocation cores coupled with the atomic size misfit are mainly responsible for such serrations.     

Oxidized Xanthan Gum Crosslinked NOCC: Hydrogel System and Their Biological Stability from Oxidation Levels of the Polymer

Dynamic hydrogel systems from N,O-carboxymethyl chitosan (NOCC) are investigated in the past years, which has facilitated their widespread use in many biomedical engineering applications. However, the influence of the polymer's oxidation levels on the hydrogel biological properties is not fully investigated. In this study, chitosan is converted into NOCC and introduced to react spontaneously with oxidized xanthan gum (OXG) to form several injectable hydrogels with controlled degradability. Different oxidation levels of xanthan gum, as well as NOCC/OXG volume ratios, are trialed. The infrared spectroscopy spectra verify chemical modification on OXG and successful crosslinking. With increasing oxidation levels, more dialdehyde groups are introduced into the OXG, resulting in changes in physical properties including gelation, swelling, and self-healing efficiency. Under different volume ratios, the hydrogel shows a stable structure and rigidity with higher mechanical properties, and a slower degradation rate. The shear-thinning and self-healing properties of the hydrogels are confirmed. In vitro assays with L929 cells show the biocompatibility of all formulations although the use of a high amount of OXG15 and OXG25 limited the cell proliferation capacity. Findings in this study suggested a suitable amount of OXG at different oxidation levels in NOCC hydrogel systems for tissue engineering applications.     

Model-based clustering for random hypergraphs

Advances in Data Analysis and Classification - A probabilistic model for random hypergraphs is introduced to represent unary, binary and higher order interactions among objects in real-world...     

Adaptive variable step-size neural controller for nonlinear feedback active noise control systems

Adaptive filter techniques and the filtered-x least mean square (FxLMS) algorithm have been used in Active Noise Control (ANC) systems. However, their effectiveness may degrade due to the nonlinearities and modeling errors in the system. In this paper, a new feedback ANC system with an adaptive neural controller and variable step-size learning parameters (VSSP) is proposed to improve the performance. A nonlinear adaptive controller with the FxLMS algorithm is first designed to replace the traditional adaptive FIR filter; then, a variable step-size learning method is developed for online updating the controller parameters. The proposed control is implemented without any offline learning phase, while faster convergence and better noise elimination can be achieved. The main contribution is that we show how to analyze the stability of the proposed closed-loop ANC systems, and prove the convergence of the presented adaptations. Moreover, the computational complexities of different methods are compared. Comparative simulation results demonstrate the validity of the proposed methods for attenuating different noise sources transferred via nonlinear paths, and show the improved performance over classical methods.     

Cyclopropane derivatives from the lithium aluminium hydride reduction of methoxyalkynols

Lithium aluminium hydride reduction of methoxyalkynol(1) yields cyclopropane derivatives (2) and (3), both formed by loss of a methoxy group; a reaction scheme for their formation is presented.     

Effective spin spin interactions in the damped ferromagnets

Simanek's theory is extended by taking into account the nuclear spin excitations due to the motion of the electronic system. Damping of the magnons is found to be an extra criteria for having a finite interaction range for the nuclear spin system. The resonance excitation of Simanek's theory is due to the neglect of the second order in the hyperfine interaction.     

Noncoplanar correlation spectra from the 2H(p, 2p)n reaction at Einc = 44.9 MeV

The differential cross section $\text{d}{}^3\text{σ/}\text{d}\text{Ω}{}_3\text{d}\text{Ω}{}_4\text{d}\text{E}{}_3$ for the ²H(p, 2p)n reaction at E_inc = 44.9 MeV is measured in noncoplanar geometry. The Amado model in general gives a good fit to the absolute cross section. The dependence of the cross section on the momentum of the undetected particle Q₅, on the scattering angle θ₃₄, as well as on the angle of the undetected particle is investigated.     

A Melnikov Method for Homoclinic Orbits with Many Pulses

We present an extension of the Melnikov method which can be used for ascertaining the existence of homoclinic and heteroclinic orbits with many pulses in a class of near‐integrable systems. The Melnikov function in this situation is the sum of the usual Melnikov functions evaluated with some appropriate phase delays. We show that a nonfolding condition which involves the logarithmic derivative of the Melnikov function must be satisfied in addition to the usual transversality conditions in order for homoclinic orbits with more than one pulse to exist. (Accepted December 2, 1996)     

Natural Product Rottlerin Derivatives Targeting Quorum Sensing

Rottlerin is a natural product consisting of chalcone and flavonoid scaffolds, both of which have previously shown quorum sensing (QS) inhibition in various bacteria. Therefore, the unique rottlerin scaffold highlights great potential in inhibiting the QS system of Pseudomonas aeruginosa. Rottlerin analogues were synthesised by modifications at its chalcone- and methylene-bridged acetophenone moieties. The synthesis of analogues was achieved using an established five-step synthetic strategy for chalcone derivatives and utilising the Mannich reaction at C6 of the chromene to construct morpholine analogues. Several pyranochromene chalcone derivatives were also generated using aldol conditions. All the synthetic rottlerin derivatives were screened for QS inhibition and growth inhibition against the related LasR QS system. The pyranochromene chalcone structures displayed high QS inhibitory activity with the most potent compounds, 8b and 8d, achieving QS inhibition of 49.4% and 40.6% and no effect on bacterial growth inhibition at 31 µM, respectively. Both compounds also displayed moderate biofilm inhibitory activity and reduced the production of pyocyanin.     

Ionic peptide aggregation: exploration of conformational dynamics in aqueous solution by computational techniques

The effects of end groups on KEK peptide conformational characteristics and self-assembling properties in water solution are investigated by using long lasting all-atom molecular dynamics simulations. The analysis of the structural macroscopic and microscopic properties and the examination of intra- and intermolecular interactions suggest, in agreement with experimental observations, the role played by side chains and terminal regions in determining the characteristic features of the assemblages. Competition between intra- and interchain interactions greatly affects the diffusivity of peptide molecules and the conformational space that they can sample, ultimately controlling the shape, size, and distribution of the aggregate configurations. Different peptide end groups influence peptide flexibility and seem to play a crucial role in determining the aggregates' supramolecular architectures.