5 research outputs found

    Quantum Monte Carlo calculations of spectroscopic overlaps in A7A \leq 7 nuclei

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    We present Green's function Monte Carlo calculations of spectroscopic overlaps for A7A \leq 7 nuclei. The realistic Argonne v18 two-nucleon and Illinois-7 three-nucleon interactions are used to generate the nuclear states. The overlap matrix elements are extrapolated from mixed estimates between variational Monte Carlo and Green's function Monte Carlo wave functions. The overlap functions are used to obtain spectroscopic factors and asymptotic normalization coefficients, and they can serve as an input for low-energy reaction calculations

    Asymptotic normalization coefficients from ab initio calculations

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    We present calculations of asymptotic normalization coefficients (ANCs) for one-nucleon removals from nuclear states of mass numbers 3 to 9. Our ANCs were computed from variational Monte Carlo solutions to the many-body Schroedinger equation with the combined Argonne v18 two-nucleon and Urbana IX three-nucleon potentials. Instead of computing explicit overlap integrals, we applied a Green's function method that is insensitive to the difficulties of constructing and Monte Carlo sampling the long-range tails of the variational wave functions. This method also allows computation of the ANC at the physical separation energy, even when it differs from the separation energy for the Hamiltonian. We compare our results, which for most nuclei are the first ab initio calculations of ANCs, with existing experimental and theoretical results and discuss further possible applications of the technique.Comment: 5 pages, 3 figures; minor changes to match published version, and minor additional corrections to Fig.

    Optimizing the rate and timing of phosphogypsum application to magnesium-affected soils for crop yield and water productivity enhancement

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    The levels of magnesium (Mg2+) in irrigation waters and soils are increasing in several irrigation schemes worldwide. Excess levels of Mg2+ in irrigation waters and/or in soils negatively affect soil physical properties (infiltration rate and hydraulic conductivity) and ultimately crop growth and yield. Although few studies have been undertaken on productivity enhancement of magnesium-affected soils by adding a source of calcium (Ca2+) to mitigate the effects of excess Mg2+, there is no information available on optimizing the rate and time of the Ca2+-amendments. A 2-year field study was undertaken in southern Kazakhstan by applying phosphogypsum (PG), a source of Ca2+ and a byproduct of the phosphorous fertilizer industry, to a magnesium-affected soil. There were five treatments with four replications: (1) control (without PG application); (2) PG application in January (before snowfall) equivalent to PG requirement for 0.3m soil depth (3.3tha-1); (3) PG application in January equivalent to PG requirement for 0.6m soil depth (8.0tha-1); (4) PG application in April (after snowmelt) at 3.3tha-1; and (5) PG application in April (after snowmelt) at 8.0tha-1. All treatment plots were grown with cotton (Gossypium hirsutum L.), which is the most important summer crop in the region. The PG treatments performed significantly better than the control in terms of (1) improved soil quality with a reduction in exchangeable magnesium percentage (EMP) levels; (2) enhanced water movement into and through the soil vis-à-vis increased moisture storage in the root zone for use by the plant roots; (3) increased irrigation efficiency; (4) increased cotton yield and water productivity; and (5) greater financial benefits. In terms of the best rate and time of application, PG applied before the snowfall improved the soil properties to a greater extent than its application in spring after snowmelt. The economic benefits from the amendment application at 3.3tha-1 were double those from the treatments where it was applied at 8.0tha-1, suggesting that the lower rate was economically optimal. In addition to improving crop productivity, the study demonstrated the beneficial use of an industrial waste material in agriculture.Magnesium to calcium ratio Exchangeable magnesium percentage Salt-affected soils Phosphogypsum Water quality Central Asia Kazakhstan Cotton
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