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We present a detailed, three-dimensional hydrodynamic study of the neutrino-driven winds emerging from the remnant of a neutron star merger. Our simulations are performed with the Newtonian, Eulerian code FISH, augmented by a detailed, spectral neutrino leakage scheme that accounts for neutrino absorption. Consistent with earlier two-dimensional studies, a strong baryonic wind is blown out along the original binary rotation axis within approximate to 100 ms. From this model, we compute a lower limit on the expelled mass of 3.5 x 10(-3) M-circle dot, relevant for heavy element nucleosynthesis. Because of stronger neutrino irradiation, the polar regions show substantially larger electron fractions than those at lower latitudes. The polar ejecta produce interesting r-process contributions from A approximate to 80 to about 130, while the more neutron-rich, lower latitude parts produce elements up to the third r-process peak near A approximate to 195. We calculate the properties of electromagnetic transients powered by the radioactivity in the wind, in addition to the 'macronova' transient stemming from the dynamic ejecta. The polar regions produce ultraviolet/optical transients reaching luminosities up to 10(41) erg s(-1), which peak around 1 d in optical and 0.3 d in bolometric luminosity. The lower latitude regions, due to their contamination with high-opacity heavy elements, produce dimmer and more red signals, peaking after similar to 2 d in optical and infrared.
