4,723 research outputs found

    Seven Steps Towards the Classical World

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    Classical physics is about real objects, like apples falling from trees, whose motion is governed by Newtonian laws. In standard Quantum Mechanics only the wave function or the results of measurements exist, and to answer the question of how the classical world can be part of the quantum world is a rather formidable task. However, this is not the case for Bohmian mechanics, which, like classical mechanics, is a theory about real objects. In Bohmian terms, the problem of the classical limit becomes very simple: when do the Bohmian trajectories look Newtonian?Comment: 16 pages, LaTeX, uses latexsy

    Entrapment of Bacteria in Fluid Inclusions in Laboratory-Grown Halite

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    This is the publisher's version, also available electronically from "http://online.liebertpub.com".Cells of the bacterium Pseudomonas aeruginosa, which were genetically modified to produce green fluorescent protein, were entrapped in fluid inclusions in laboratory-grown halite. The bacteria were used to inoculate NaCl-saturated aqueous solutions, which were allowed to evaporate and precipitate halite. The number, size, and distribution of fluid inclusions were highly variable, but did not appear to be affected by the presence of the bacteria. Many of the inclusions in crystals from inoculated solutions contained cells in populations ranging from two to 20. Microbial attachment to crystal surfaces was neither evident nor necessary for entrapment. Cells occurred exclusively within fluid inclusions and were not present in the crystal matrix. In both the inclusions and the hypersaline solution, the cells fluoresced and twitched, which indicates that the bacteria might have remained viable after entrapment. The fluorescence continued up to 13 months after entrapment, which indicates that little degradation of the bacteria occurred over that time interval. The entrapment, fluorescence, and preservation of cells were independent of the volume of hypersaline solution used or whether the solutions were completely evaporated prior to crystal extraction. The results of this study have a wide range of implications for the long-term survival of microorganisms in fluid inclusions and their detection through petrography. The results also demonstrate the preservation potential for microbes in hypersaline fluid inclusions, which could allow cells to survive harsh conditions of space, the deep geologic past, or burial in sedimentary basins

    Scaling of the electron dissipation range of solar wind turbulence

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    Electron scale solar wind turbulence has attracted great interest in recent years. Clear evidences have been given from the Cluster data that turbulence is not fully dissipated near the proton scale but continues cascading down to the electron scales. However, the scaling of the energy spectra as well as the nature of the plasma modes involved at those small scales are still not fully determined. Here we survey 10 years of the Cluster search-coil magnetometer (SCM) waveforms measured in the solar wind and perform a statistical study of the magnetic energy spectra in the frequency range [1,1801, 180]Hz. We show that a large fraction of the spectra exhibit clear breakpoints near the electon gyroscale ρe\rho_e, followed by steeper power-law like spectra. We show that the scaling below the electron breakpoint cannot be determined unambiguously due to instrumental limitations that will be discussed in detail. We compare our results to recent ones reported in other studies and discuss their implication on the physical mechanisms and the theoretical modeling of energy dissipation in the SW.Comment: 10 pages, submitte

    Ecosystem Services in Decision Making: Time to Deliver

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    Over the past decade, efforts to value and protect ecosystem services have been promoted by many as the last, best hope for making conservation mainstream – attractive and commonplace worldwide. In theory, if we can help individuals and institutions to recognize the value of nature, then this should greatly increase investments in conservation, while at the same time fostering human well-being. In practice, however, we have not yet developed the scientific basis, nor the policy and finance mechanisms, for incorporating natural capital into resource- and land-use decisions on a large scale. Here, we propose a conceptual framework and sketch out a strategic plan for delivering on the promise of ecosystem services, drawing on emerging examples from Hawai‘i. We describe key advances in the science and practice of accounting for natural capital in the decisions of individuals, communities, corporations, and governments

    A New Geographic Locality and Three New Host Records for Neobenedenia melleni (MacCallum) (Monogenea: Capsalidae)

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    A new geographic locality record and three new host records for Neobenedenia melleni (MacCallum, 1921) (Monogenea: Capsalidae) are provided. Specimens of N. melleni were collected from the skin of three Florida pompano, Trachinotus carolinus (Linnaeus, 1166)(Carangidae),caught in the northern Gulf of Mexico off Horn Island, Mississippi; from the skin of a bluering angelfish, Pomacanthus annularis (Bloch, 1157) (Pomacanthidae), in the Shark Reef Aquarium at Mandalay Bay, Las Vegas, Nevada; from the skin of a rock greenling, Hexagrammos lagocephalus (Pallas, 1810) (Hexagrammidae), in the Alaska SeaLife Center, Seward, Alaska; and from the skin of two blue-barred ribbon gobies, Oxymetopon cyanoctenosum Klausewitz and Condé, 1981 (Microdesmidae), in a tropical fish clearinghouse in Hayward, California. This is the first published record of the parasite from a microdesmid or wild carangid. Prior to this report, no specimen of N. melleni had been reported from a wild-caught fish in the Gulf of Mexico. The presence of N. melleni in the Gulf of Mexico is particularly noteworthy because this monogenean is a known pathogen of cultured fishes in netpens and recirculating seawater systems

    Ecosystem Services in Decision Making: Time to Deliver

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    Over the past decade, efforts to value and protect ecosystem services have been promoted by many as the last, best hope for making conservation mainstream – attractive and commonplace worldwide. In theory, if we can help individuals and institutions to recognize the value of nature, then this should greatly increase investments in conservation, while at the same time fostering human well-being. In practice, however, we have not yet developed the scientific basis, nor the policy and finance mechanisms, for incorporating natural capital into resource- and land-use decisions on a large scale. Here, we propose a conceptual framework and sketch out a strategic plan for delivering on the promise of ecosystem services, drawing on emerging examples from Hawai‘i. We describe key advances in the science and practice of accounting for natural capital in the decisions of individuals, communities, corporations, and governments

    Generation of Laminar Vortex Rings by an Impulsive Body Force

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    It is shown that laminar vortex rings can be generated by impulsive body forces having particular spatial and temporal characteristics. The method produces vortex rings in a fluid initially at rest, and once generated, the flow field automatically satisfies the boundary conditions and is divergence-free. Numerical simulations and analytical models show that the strength of these rings can be accurately predicted by considering diffusion alone, despite the nonlinear nature of the generation process. A particularly simple model, which approximates the source of vorticity within vertical slabs, is proposed. This model predicts the ring circulation almost as accurately as a model which uses the exact geometry of the source of vorticity. It is found that when the duration of the force is less than a time scale based on the force radius and fluid viscosity, the ring circulation can be predicted accurately using an inviscid model.Comment: 37 pages, 11 figure
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