3,923 research outputs found

    Surveys of the earth's resources and environment by satellites

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    The potential and promise of observing the earth from the vantage point of space is discussed. The systematic surveying of processes and phenomena occurring on the surface of the earth by Landsat 1 and Nimbus 5 is considered to be useful in the following areas: assessment of water resources; mineral and petroleum exploration; land use planning; crop, forest, and rangeland inventory; assessment of flood, earthquake, and other environmental hazards; monitoring coastal processes; environmental effects of industrial effluents and of air pollution; mapping the distribution and types of ice covering the earth's polar caps and global soil moisture distributions

    Universal resonant ultracold molecular scattering

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    The elastic scattering amplitudes of indistinguishable, bosonic, strongly-polar molecules possess universal properties at the coldest temperatures due to wave propagation in the long-range dipole-dipole field. Universal scattering cross sections and anisotropic threshold angular distributions, independent of molecular species, result from careful tuning of the dipole moment with an applied electric field. Three distinct families of threshold resonances also occur for specific field strengths, and can be both qualitatively and quantitatively predicted using elementary adiabatic and semi-classical techniques. The temperatures and densities of heteronuclear molecular gases required to observe these univeral characteristics are predicted. PACS numbers: 34.50.Cx, 31.15.ap, 33.15.-e, 34.20.-bComment: 4 pages, 5 figure

    Radial and angular rotons in trapped dipolar gases

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    We study Bose-Einstein condensates with purely dipolar interactions in oblate (pancake) traps. We find that the condensate always becomes unstable to collapse when the number of particles is sufficiently large. We analyze the instability, and find that it is the trapped-gas analogue of the ``roton-maxon'' instability previously reported for a gas that is unconfined in two dimensions. In addition, we find that under certain circumstances, the condensate wave function attains a biconcave shape, with its maximum density away from the center of the gas. These biconcave condensates become unstable due to azimuthl excitation - an angular roton.Comment: 4 pages, 3 figure

    Tuning p-wave interactions in an ultracold Fermi gas of atoms

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    We have measured a p-wave Feshbach resonance in a single-component, ultracold Fermi gas of potassium atoms. We have used this resonance to enhance the normally suppressed p-wave collision cross-section to values larger than the background s-wave cross-section between potassium atoms in different spin-states. In addition to the modification of two-body elastic processes, the resonance dramatically enhances three-body inelastic collisional loss.Comment: 4 pages, 5 figure
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