507 research outputs found

    The Debye-Waller Factor in solid 3He and 4He

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    The Debye-Waller factor and the mean-squared displacement from lattice sites for solid 3He and 4He were calculated with Path Integral Monte Carlo at temperatures between 5 K and 35 K, and densities between 38 nm^(-3) and 67 nm^(-3). It was found that the mean-squared displacement exhibits finite-size scaling consistent with a crossover between the quantum and classical limits of N^(-2/3) and N^(-1/3), respectively. The temperature dependence appears to be T^3, different than expected from harmonic theory. An anisotropic k^4 term was also observed in the Debye-Waller factor, indicating the presence of non-Gaussian corrections to the density distribution around lattice sites. Our results, extrapolated to the thermodynamic limit, agree well with recent values from scattering experiments.Comment: 5 figure

    Computer‐aided photo‐identification of a rare stingray, Megatrygon microps

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    We have defined protocol for photo‐identification to identify individual Megatrygon microps. 104 identification photographs were taken between 2005 and 2019. Spot patterns on the dorsal surface were used to identify individuals. Unique scarring on 8 re‐observed M. microps provided an independent confirmation of pattern stability of up to 761 days. Previously, studies have lacked statistical testing to validate photo‐identification approach. The I3S photo‐matching software was proven to successfully match images, identifying 69 individuals. A photo‐matching software facilitates an open‐source platform for identifying individual M. microps, allowing for better population assessments
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