Resonance tongues and patterns in periodically forced reaction-diffusion systems

Various resonant and near-resonant patterns form in a light-sensitive Belousov-Zhabotinsky (BZ) reaction in response to a spatially-homogeneous time-periodic perturbation with light. The regions (tongues) in the forcing frequency and forcing amplitude parameter plane where resonant patterns form are identified through analysis of the temporal response of the patterns. Resonant and near-resonant responses are distinguished. The unforced BZ reaction shows both spatially-uniform oscillations and rotating spiral waves, while the forced system shows patterns such as standing-wave labyrinths and rotating spiral waves. The patterns depend on the amplitude and frequency of the perturbation, and also on whether the system responds to the forcing near the uniform oscillation frequency or the spiral wave frequency. Numerical simulations of a forced FitzHugh-Nagumo reaction-diffusion model show both resonant and near-resonant patterns similar to the BZ chemical system

Effect of polymer concentration and length of hydrophobic end block on the unimer-micelle transition broadness in amphiphilic ABA symmetric triblock copolymer solutions

The effects of the length of each hydrophobic end block N_{st} and polymer concentration \bar{\phi}_{P} on the transition broadness in amphiphilic ABA symmetric triblock copolymer solutions are studied using the self-consistent field lattice model. When the system is cooled, micelles are observed, i.e.,the homogenous solution (unimer)-micelle transition occurs. When N_{st} is increased, at fixed \bar{\phi}_{P}, micelles occur at higher temperature, and the temperature-dependent range of micellar aggregation and half-width of specific heat peak for unimer-micelle transition increase monotonously. Compared with associative polymers, it is found that the magnitude of the transition broadness is determined by the ratio of hydrophobic to hydrophilic blocks, instead of chain length. When \bar{\phi}_{P} is decreased, given a large N_{st}, the temperature-dependent range of micellar aggregation and half-width of specific heat peak initially decease, and then remain nearly constant. It is shown that the transition broadness is concerned with the changes of the relative magnitudes of the eductions of nonstickers and solvents from micellar cores.Comment: 8 pages, 4 figure

Moduli Stabilization and Supersymmetry Breaking in Deflected Mirage Mediation

We present a model of supersymmetry breaking in which the contributions from gravity/modulus, anomaly, and gauge mediation are all comparable. We term this scenario "deflected mirage mediation," which is a generalization of the KKLT-motivated mirage mediation scenario to include gauge mediated contributions. These contributions deflect the gaugino mass unification scale and alter the pattern of soft parameters at low energies. In some cases, this results in a gluino LSP and light stops; in other regions of parameter space, the LSP can be a well-tempered neutralino. We demonstrate explicitly that competitive gauge-mediated terms can naturally appear within phenomenological models based on the KKLT setup by addressing the stabilization of the gauge singlet field which is responsible for the masses of the messenger fields. For viable stabilization mechanisms, the relation between the gauge and anomaly contributions is identical in most cases to that of deflected anomaly mediation, despite the presence of the Kahler modulus. Turning to TeV scale phenomenology, we analyze the renormalization group evolution of the supersymmetry breaking terms and the resulting low energy mass spectra. The approach sets the stage for studies of such mixed scenarios of supersymmetry breaking at the LHC.Comment: 33 pages, 8 figures. Published version in Journal of High Energy Physic

The effect of asymmetry of the coil block on self-assembly in ABC coil-rod-coil triblock copolymers

Using the self-consistent field approach, the effect of asymmetry of the coil block on the microphase separation is focused in ABC coil-rod-coil triblock copolymers. For different fractions of the rod block $f_{\text B}$, some stable structures are observed, i.e., lamellae, cylinders, gyroid, and core-shell hexagonal lattice, and the phase diagrams are constructed. The calculated results show that the effect of the coil block fraction $f_{\text A}$ is dependent on $f_{\text B}$. When $f_{\text B}=0.2$, the effect of asymmetry of the coil block is similar to that of the ABC flexible triblock copolymers; When $f_{\text B}=0.4$, the self-assembly of ABC coil-rod-coil triblock copolymers behaves like rod-coil diblock copolymers under some condition. When $f_{\text B}$ continues to increase, the effect of asymmetry of the coil block reduces. For $f_{\text B}=0.4$, under the symmetrical and rather asymmetrical conditions, an increase in the interaction parameter between different components leads to different transitions between cylinders and lamellae. The results indicate some remarkable effect of the chain architecture on self-assembly, and can provide the guidance for the design and synthesis of copolymer materials.Comment: 9 pages, 3 figure

Multi-Context Attention for Human Pose Estimation

In this paper, we propose to incorporate convolutional neural networks with a multi-context attention mechanism into an end-to-end framework for human pose estimation. We adopt stacked hourglass networks to generate attention maps from features at multiple resolutions with various semantics. The Conditional Random Field (CRF) is utilized to model the correlations among neighboring regions in the attention map. We further combine the holistic attention model, which focuses on the global consistency of the full human body, and the body part attention model, which focuses on the detailed description for different body parts. Hence our model has the ability to focus on different granularity from local salient regions to global semantic-consistent spaces. Additionally, we design novel Hourglass Residual Units (HRUs) to increase the receptive field of the network. These units are extensions of residual units with a side branch incorporating filters with larger receptive fields, hence features with various scales are learned and combined within the HRUs. The effectiveness of the proposed multi-context attention mechanism and the hourglass residual units is evaluated on two widely used human pose estimation benchmarks. Our approach outperforms all existing methods on both benchmarks over all the body parts.Comment: The first two authors contribute equally to this wor

Development of polymeric hollow fiber membranes containing catalytic metal nanoparticules.

Metal nanoparticles (MNPs) have unique physico-chemical properties advantageous for catalytic applications which differ from bulk material. However, the main drawback of MNPs is their insufficient stability due to a high trend for aggregation. To cope with this inconvenience, the stabilization of MNPs in polymeric matrices has been tested. This procedure is a promising strategy to maintain catalytic properties. The aim of this work is the synthesis of polymer-stabilized MNPs inside functionalized polymeric membranes in order to build catalytic membrane reactors. First, the polymeric support must have functional groups capable to retain nanoparticle precursors (i.e. sulfonic), then, nanoparticles can grow inside the polymeric matrix by chemical reduction of metal ions. Two different strategies have been used in this work. Firstly, polyethersulfone microfiltration hollow fibers have been modified by applying polyelectrolyte multilayers. Secondly, polysulfone ultrafiltration membranes were modified by UV-photografting using sodium p-styrene sulfonate as a vinyl monomer. The catalytic performance of developed hollow fibers has been evaluated by using the reduction of nitrophenol to aminophenol by sodium borohydride. Hollow fiber modules with Pd MNPs have been tested in dead-end and cross-flow filtration. Complete nitrophenol degradation is possible depending on operation parameters such as applied pressure and permeate flux

Catalytic hollow fiber membranes prepared using layer-by-layer adsorption of polyelectrolytes and metal nanoparticles

Immobilization of metalnanoparticles in hollowfibermembranes via alternating adsorption of polyelectrolytes and negatively charged Au nanoparticles yields catalytic reactors with high surface areas. SEM images show that this technique deposits a high density of unaggregated metalnanoparticles both on the surfaces and in the pores of the hollowfibers. Catalytic reduction of 4-nitrophenol with NaBH4, which can be easily monitored by UV–vis spectrophotometry, demonstrates that the nanoparticles in the hollowfibermembrane are highly catalytically active. In a single pass through the membrane, >99% of the 4-nitrophenol is reduced to 4-aminophenol, but this conversion decreases over time. The conversion decline may stem from catalyst fouling caused by by-products of 4-aminophenol oxidation

Defect turbulence in inclined layer convection

We report experimental results on the defect turbulent state of undulation chaos in inclined layer convection of a fluid withPrandtl number $\approx 1$. By measuring defect density and undulation wavenumber, we find that the onset of undulation chaos coincides with the theoretically predicted onset for stable, stationary undulations. At stronger driving, we observe a competition between ordered undulations and undulation chaos, suggesting bistability between a fixed-point attractor and spatiotemporal chaos. In the defect turbulent regime, we measured the defect creation, annihilation, entering, leaving, and rates. We show that entering and leaving rates through boundaries must be considered in order to describe the observed statistics. We derive a universal probability distribution function which agrees with the experimental findings.Comment: 4 pages, 5 figure