1,765 research outputs found

    Discrete nonlinear Schrödinger equations for periodic optical systems : pattern formation in \chi(3) coupled waveguide arrays

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    Discrete nonlinear Schrödinger equations have been used for many years to model the propagation of light in optical architectures whose refractive index profile is modulated periodically in the transverse direction. Typically, one considers a modal decomposition of the electric field where the complex amplitudes satisfy a coupled system that accommodates nearest neighbour linear interactions and a local intensity dependent term whose origin lies in the χ (3) contribution to the medium's dielectric response. In this presentation, two classic continuum configurations are discretized in ways that have received little attention in the literature: the ring cavity and counterpropagating waves. Both of these systems are defined by distinct types of boundary condition. Moreover, they are susceptible to spatial instabilities that are ultimately responsible for generating spontaneous patterns from arbitrarily small background disturbances. Good agreement between analytical predictions and simulations will be demonstrated

    A revised checklist of Hawaiian mosses

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    A revised and updated literature-based checklist of Hawaiian mosses is presented. Geographic coverage includes the eight main Hawaiian Islands; the Northwestern Hawaiian Islands are excluded. The checklist is alphabetically ordered by scientific names; the family is noted for each genus. Synonyms and misapplied names are cross-referenced to the accepted names. A bibliography of supporting references is included

    Evolution of InAs branches in InAs/GaAs nanowire heterostructures

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    Branched nanowireheterostructures of InAs∕GaAs were observed during Au-assisted growth of InAs on GaAsnanowires. The evolution of these branches has been determined through detailed electron microscopy characterization with the following sequence: (1) in the initial stage of InAsgrowth, the Au droplet is observed to slide down the side of the GaAsnanowire, (2) the downward movement of Aunanoparticle later terminates when the nanoparticle encounters InAsgrowing radially on the GaAsnanowire sidewalls, and (3) with further supply of In and As vapor reactants, the Aunanoparticles assist the formation of InAs branches with a well-defined orientation relationship with GaAs∕InAs core/shell stems. We anticipate that these observations advance the understanding of the kink formation in axial nanowireheterostructures.The Australian Research Council is acknowledged for the financial support of this project. One of the authors M.P. acknowledges the support of an International Postgraduate Research Scholarship

    Unique Transcriptional Profile of Sustained Ligand-Activated Preconditioning in Pre- and Post-Ischemic Myocardium

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    BACKGROUND: Opioidergic SLP (sustained ligand-activated preconditioning) induced by 3–5 days of opioid receptor (OR) agonism induces persistent protection against ischemia-reperfusion (I-R) injury in young and aged hearts, and is mechanistically distinct from conventional preconditioning responses. We thus applied unbiased gene-array interrogation to identify molecular effects of SLP in pre- and post-ischemic myocardium. METHODOLOGY/PRINCIPAL FINDINGS: Male C57Bl/6 mice were implanted with 75 mg morphine or placebo pellets for 5 days. Resultant SLP did not modify cardiac function, and markedly reduced dysfunction and injury in perfused hearts subjected to 25 min ischemia/45 min reperfusion. Microarray analysis identified 14 up- and 86 down-regulated genes in normoxic hearts from SLP mice (≥1.3-fold change, FDR≤5%). Induced genes encoded sarcomeric/contractile proteins (Myh7, Mybpc3,Myom2,Des), natriuretic peptides (Nppa,Nppb) and stress-signaling elements (Csda,Ptgds). Highly repressed genes primarily encoded chemokines (Ccl2,Ccl4,Ccl7,Ccl9,Ccl13,Ccl3l3,Cxcl3), cytokines (Il1b,Il6,Tnf) and other proteins involved in inflammation/immunity (C3,Cd74,Cd83, Cd86,Hla-dbq1,Hla-drb1,Saa1,Selp,Serpina3), together with endoplasmic stress proteins (known: Dnajb1,Herpud1,Socs3; putative: Il6, Gadd45g,Rcan1) and transcriptional controllers (Egr2,Egr3, Fos,Hmox1,Nfkbid). Biological themes modified thus related to inflammation/immunity, together with cellular/cardiovascular movement and development. SLP also modified the transcriptional response to I-R (46 genes uniquely altered post-ischemia), which may influence later infarction/remodeling. This included up-regulated determinants of cellular resistance to oxidant (Mgst3,Gstm1,Gstm2) and other forms of stress (Xirp1,Ankrd1,Clu), and repression of stress-response genes (Hspa1a,Hspd1,Hsp90aa,Hsph1,Serpinh1) and Txnip. CONCLUSIONS: Protection via SLP is associated with transcriptional repression of inflammation/immunity, up-regulation of sarcomeric elements and natriuretic peptides, and modulation of cell stress, growth and development, while conventional protective molecules are unaltered

    Particle Swarm Transport in Porous Media

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    In recent years, interest in particulate transport in the subsurface has increased with the increased use of micro-particulates in consumer products. In this research, we study particulate swarm transport through porous media that depends on the complexity of the flow paths, on the size and shape of the particles and on the physical interactions among the particles, fluids, and matrix. Specifically, we investigate the effect of pore geometry and grain wettability on swarm evolution under gravity. Swarms were composed of 3 micron polystyrene beads in either water or water with KCL (%). Two types of grains are used to simulate a porous medium: (1) hydrogel spheres that are hydrophyllic and (2) 3D printed PMMA spheres that are hydrophobic. We found that a hydrophillic matrix resulted in a wider transport path and caused an increase in bifurcations when compared with the hydrophobic PMMA. We also observed that as the swarms increased in volume the number of bifurcations increased. Bifurcations occurred around the beads creating a more widespread dispersed transport path. The potential spread of particulate contaminants by swarms will depend on the hydrophobicity or hydrophilicity the grains, yielding either increased dispersion or more highly localized concentrations

    Ultrafast trapping times in ion implanted InP

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    As⁺ and P⁺implantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1×10¹⁶ cm⁻² and p-type InP was implanted with doses between 1×10¹² and 1×10¹⁶ cm⁻². Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implantedp-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity
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