115,525 research outputs found

    Photoreactions in Phycomyes: growth and tropic responses to the stimulation of narrow test areas

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    Sporangiophores of Phycomyces in stage IV b have been stimulated by parallel light in test areas 0.2 mm. wide. The growth responses to large stimuli are very large, owing probably to light scattered within the specimen. For medium stimuli the sensitive zone coincides with the growth response zone obtained previously and excludes the region of maximum stretch. Sustained stimulations were used to elicit tropic responses. The bends formed travel away from the sporangium at a speed equal to the growth speed. Thus they remain very close to the stimulus when this is held at a constant level relative to ground but separate from it for stimuli programmed differently. The existence of a protoplasmic structure, the "inner wall," with the following properties is postulated: it is attached to the lower, non-growing part of the sporangiophore and grows by addition above the sensitive zone. It neither stretches nor twists in the sensitive zone. It is the seat of the light receptors and gives growth and tropic responses. The cell wall follows its bends by elastic stretch

    Despite Regulatory Changes, Hospitals Cautious in Helping Physicians Purchase Electronic Medical Records

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    Examines hospitals' strategies to aid physicians' adoption of electronic medical records (EMRs) following regulatory changes facilitating hospital-subsidized EMRs. Looks at factors determining support for physicians' EMR adoption and their implications

    Phase boundaries in deterministic dense coding

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    We consider dense coding with partially entangled states on bipartite systems of dimension d×dd\times d, studying the conditions under which a given number of messages, NN, can be deterministically transmitted. It is known that the largest Schmidt coefficient, λ0\lambda_0, must obey the bound λ0≤d/N\lambda_0\le d/N, and considerable empirical evidence points to the conclusion that there exist states satisfying λ0=d/N\lambda_0=d/N for every dd and NN except the special cases N=d+1N=d+1 and N=d2−1N=d^2-1. We provide additional conditions under which this bound cannot be reached -- that is, when it must be that λ0<d/N\lambda_0<d/N -- yielding insight into the shapes of boundaries separating entangled states that allow NN messages from those that allow only N−1N-1. We also show that these conclusions hold no matter what operations are used for the encoding, and in so doing, identify circumstances under which unitary encoding is strictly better than non-unitary.Comment: 7 pages, 1 figur

    Spin Waves in Ferromagnetic Metals and the Dynamical Form of the Landau Quasi-particle Theory

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    Spin waves in ferromagnetic metals dynamical form of Landau quasi-particle theor

    Percolation Critical Exponents in Scale-Free Networks

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    We study the behavior of scale-free networks, having connectivity distribution P(k) k^-a, close to the percolation threshold. We show that for networks with 3<a<4, known to undergo a transition at a finite threshold of dilution, the critical exponents are different than the expected mean-field values of regular percolation in infinite dimensions. Networks with 2<a<3 possess only a percolative phase. Nevertheless, we show that in this case percolation critical exponents are well defined, near the limit of extreme dilution (where all sites are removed), and that also then the exponents bear a strong a-dependence. The regular mean-field values are recovered only for a>4.Comment: Latex, 4 page

    Standardized Pearson type 3 density function area tables

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    Tables constituting extension of similar tables published in 1936 are presented in report form. Single and triple parameter gamma functions are discussed. Report tables should interest persons concerned with development and use of numerical analysis and evaluation methods

    Enhancing efficiency of single, large-aperture antennas

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    Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed

    The structure of Herbig-Haro object 43 and Orion dark cloud extinction

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    New ultraviolet and optical observations of Herbig-Haro Object No. 43 are reported. Continuum and emission line fluxes in the range 1250 A equal to or less than lambda equal to less than 7350A have been measured. The continuum fluxes are best matched by an enhanced H two photon component added to H free bound emission, assuming theta Ori extinction curve with E(B-V) = 0.2, R = 5. The strucutre and dynamics of three components within the object are discussed. The object has a radiative output of equal to or greater than 0.23 infrared luminosity in ultraviolet and optical radiation combined. The energy requirements are discussed in terms of the production of shock waves by a collimated, supersonic mass outflow from a nearby infrared source

    Life and death of a hero - Lessons learned from modeling the dwarf spheroidal Hercules: an incorrect orbit?

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    Hercules is a dwarf spheroidal satellite of the Milky Way, found at a distance of about 138 kpc, and showing evidence of tidal disruption. It is very elongated and exhibits a velocity gradient of 16 +/- 3 km/s/kpc. Using this data a possible orbit of Hercules has previously been deduced in the literature. In this study we make use of a novel approach to find a best fit model that follows the published orbit. Instead of using trial and error, we use a systematic approach in order to find a model that fits multiple observables simultaneously. As such, we investigate a much wider parameter range of initial conditions and ensure we have found the best match possible. Using a dark matter free progenitor that undergoes tidal disruption, our best-fit model can simultaneously match the observed luminosity, central surface brightness, effective radius, velocity dispersion, and velocity gradient of Hercules. However, we find it is impossible to reproduce the observed elongation and the position angle of Hercules at the same time in our models. This failure persists even when we vary the duration of the simulation significantly, and consider a more cuspy density distribution for the progenitor. We discuss how this suggests that the published orbit of Hercules is very likely to be incorrect.Comment: accepted by MNRAS; 19 pages, 19 figures, 2 table
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