11,650 research outputs found

    Evaluation of Transgenic ‘Chardonnay' ( Vitis vinifera ) Containing Magainin Genes for Resistance to Crown Gall and Powdery Mildew

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    Magainins, short peptides with broad-spectrum antimicrobial activity in vitro, were assayed for their ability to confer resistance to pathogens in transgenic grapevines. Embryogenic cell suspensions of ‘Chardonnay' (Vitis vinifera L.) were co-transformed by microprojectile bombardment with a plasmid carrying the npt-II gene and a second plasmid harboring either a natural magainin-2 (mag2) or a synthetic derivative (MSI99) gene. Magainin genes and the marker gene were driven by Arabidopsis ubiquitin-3 and ubiquitin-11 promoters, respectively. A total of 10 mag2 and 9 MSI99 regenerated lines were studied by Southern blot hybridization, which showed 1-6 transgene integration events into the plant genome. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed a variable range in transcription levels among mag2 and MSI99 lines. A positive correlation between number of integration events and transcription level was observed (p<0.05). Plants were acclimated and challenged in the greenhouse with either Agrobacterium vitis strains (bacterial crown gall pathogen) at 108cfu/ml or Uncinula necator (fungal powdery mildew pathogen) at 105 conidia/ml for evaluation of disease resistance. A total of 6 mag2 and 5 MSI99 lines expressing the antimicrobial genes exhibited significant reductions of crown gall symptoms as compared to non-transformed controls. However, only two mag2 lines showed measurable symptom reductions in response to U. necator, but not strong resistance. Our results suggest that the expression of magainin-type genes in grapevines may be more effective against bacteria than fungi. Additional strategies to enhance transgene expression and the spectrum of resistance to grape diseases are suggeste

    Searching for Far-Ultraviolet Auroral/Dayglow Emission from HD209458b

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    We present recent observations from the HST-Cosmic Origins Spectrograph aimed at characterizing the auroral emission from the extrasolar planet HD209458b. We obtained medium-resolution (R~18-20,000) far-ultraviolet (1150-1700A) spectra at both the Phase 0.25 and Phase 0.75 quadrature positions as well as a stellar baseline measurement at secondary eclipse. This analysis includes a catalog of stellar emission lines and a star-subtracted spectrum of the planet. We present an emission model for planetary H2 emission, and compare this model to the planetary spectrum. No unambiguously identifiable atomic or molecular features are detected, and upper limits are presented for auroral/dayglow line strengths. An orbital velocity cross-correlation analysis finds a statistically significant (3.8 sigma) feature at +15 (+/- 20) km/s in the rest frame of the planet, at 1582 A. This feature is consistent with emission from H2 B-X (2-9) P(4) (lambda_{rest} = 1581.11 A), however the physical mechanism required to excite this transition is unclear. We compare limits on relative line strengths seen in the exoplanet spectrum with models of ultraviolet fluorescence to constrain the atmospheric column density of neutral hydrogen between the star and the planetary surface. These results support models of short period extrasolar giant planets with weak magnetic fields and extended atomic atmospheres.Comment: Accepted to ApJ. 12 pages, 5 figures, 4 table

    Computational requirements of the virtual patient

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    Medical visualization in a hospital can be used to aid training, diagnosis, and pre- and intra-operative planning. In such an application, a virtual representation of a patient is needed that is interactive, can be viewed in three dimensions (3D), and simulates physiological processes that change over time. This paper highlights some of the computational challenges of implementing a real time simulation of a virtual patient, when accuracy can be traded-off against speed. Illustrations are provided using projects from our research based on Grid-based visualization, through to use of the Graphics Processing Unit (GPU)

    Observations of Mass Loss from the Transiting Exoplanet HD 209458b

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    Using the new Cosmic Origins Spectrograph (COS) on the {\it Hubble Space Telescope (HST)}, we obtained moderate-resolution, high signal/noise ultraviolet spectra of HD 209458 and its exoplanet HD 209458b during transit, both orbital quadratures, and secondary eclipse. We compare transit spectra with spectra obtained at non-transit phases to identify spectral features due to the exoplanet's expanding atmosphere. We find that the mean flux decreased by 7.8±1.37.8\pm 1.3% for the C II 1334.5323\AA\ and 1335.6854\AA\ lines and by 8.2±1.48.2\pm 1.4% for the Si III 1206.500\AA\ line during transit compared to non-transit times in the velocity interval --50 to +50 km s1^{-1}. Comparison of the C II and Si III line depths and transit/non-transit line ratios shows deeper absorption features near --10 and +15 km s1^{-1} and less certain features near --40 and +30--70 km s1^{-1}, but future observations are needed to verify this first detection of velocity structure in the expanding atmosphere of an exoplanet. Our results for the C II lines and the non-detection of Si IV 1394.76\AA\ absorption are in agreement with \citet{Vidal-Madjar2004}, but we find absorption during transit in the Si III line contrary to the earlier result. The 8±18\pm 1% obscuration of the star during transit is far larger than the 1.5% obscuration by the exoplanet's disk. Absorption during transit at velocities between --50 and +50 km s1^{-1} in the C II and Si III lines requires high-velocity ion absorbers, but models that assume that the absorbers are high-temperature thermal ions are inconsistent with the COS spectra. Assuming hydrodynamic model values for the gas temperature and outflow velocity at the limb of the outflow as seen in the C II lines, we find mass-loss rates in the range (8--40)×1010\times 10^{10} g s1^{-1}.Comment: 25 pages, 4 figures, Astrophysical Journal in pres

    Nonadditivity of Bipartite Distillable Entanglement follows from Conjecture on Bound Entangled Werner States

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    Assuming the validity of a conjecture in quant-ph/9910026 and quant-ph/9910022 we show that the distillable entanglement for two bipartite states, each of which individually has zero distillable entanglement, can be nonzero. We show that this also implies that the distillable entanglement is not a convex function. Our example consists of the tensor product of a bound entangled state based on an unextendible product basis with a Werner state which lies in the class of conjectured undistillable states.Comment: 4 pages RevTex, 1 figure, to appear in Phys. Rev. Lett. Title changed and small paragraph adde
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