45 research outputs found

    Soliton Turbulence in Shallow Water Ocean Surface Waves

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    We analyze shallow water wind waves in Currituck Sound, North Carolina and experimentally confirm, for the first time, the presence of solitonsoliton turbulenceturbulence in ocean waves. Soliton turbulence is an exotic form of nonlinear wave motion where low frequency energy may also be viewed as a densedense solitonsoliton gasgas, described theoretically by the soliton limit of the Korteweg-deVries (KdV) equation, a completelycompletely integrableintegrable solitonsoliton systemsystem: Hence the phrase "soliton turbulence" is synonymous with "integrable soliton turbulence." For periodic/quasiperiodic boundary conditions the ergodicergodic solutionssolutions of KdV are exactly solvable by finitefinite gapgap theorytheory (FGT), the basis of our data analysis. We find that large amplitude measured wave trains near the energetic peak of a storm have low frequency power spectra that behave as ω1\sim\omega^{-1}. We use the linear Fourier transform to estimate this power law from the power spectrum and to filter denselydensely packedpacked solitonsoliton wavewave trainstrains from the data. We apply FGT to determine the solitonsoliton spectrumspectrum and find that the low frequency ω1\sim\omega^{-1} region is solitonsoliton dominateddominated. The solitons have randomrandom FGTFGT phasesphases, a solitonsoliton randomrandom phasephase approximationapproximation, which supports our interpretation of the data as soliton turbulence. From the probabilityprobability densitydensity ofof thethe solitonssolitons we are able to demonstrate that the solitons are densedense inin timetime and highlyhighly nonnon GaussianGaussian.Comment: 4 pages, 7 figure

    Asymmetric leaves1 mediates leaf patterning and stem cell function in Arabidopsis

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    Meristem function in plants requires both the maintenance of stem cells and the specification of founder cells from which lateral organs arise. Lateral organs are patterned along proximodistal, dorsoventral and mediolateral axes (1,2). Here we show that the Arabidopsis mutant asymmetric leaves1 (as1) disrupts this process. AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2 in maize, both of which negatively regulate knotted-class homeobox genes. AS1 negatively regulates the homeobox genes KNAT1 and KNAT2 and is, in turn, negatively regulated by the meristematic homeobox gene SHOOT MERISTEMLESS. This genetic pathway defines a mechanism for differentiating between stem cells and organ founder cells within the shoot apical meristem and demonstrates that genes expressed in organ primordia interact with meristematic genes to regulate shoot morphogenesi

    A Strawberry KNOX Gene Regulates Leaf, Flower and Meristem Architecture

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    The KNOTTED-LIKE HOMEODOMAIN (KNOX) genes play a central role in maintenance of the shoot apical meristem. They also contribute to the morphology of simple and compound leaves. In this report we characterize the FaKNOX1 gene from strawberry (Fragaria spp.) and demonstrate its function in trasgenic plants. The FaKNOX1 cDNA was isolated from a cultivated strawberry (F.×ananassa) flower EST library. The sequence is most similar to Class I KNOX genes, and was mapped to linkage group VI of the diploid strawberry genome. Unlike most KNOX genes studied, steady-state transcript levels were highest in flowers and fruits. Transcripts were also detected in emerging leaf primordia and the apical dome. Transgenic strawberry plants suppressing or overexpressing FaKNOX1 exhibited conspicuous changes in plant form. The FaKNOX1 RNAi plants presented a dwarfed phenotype with deeply serrated leaflets and exaggerated petiolules. They also exhibited a high level of cellular disorganization of the shoot apical meristem and leaves. Overexpression of FaKNOX1 caused dwarfed stature with wrinkled leaves. These gain- and loss-of-function assays in strawberry functionally demonstrate the contributions of a KNOX domain protein in a rosaceous species

    The James Webb Space Telescope Mission

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    Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4m4m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5m6.5m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure
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