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We investigate the charge density oscillations in a nanowire coupled asymmetrically to two leads. Depending on this asymmetry, the Friedel oscillations can either be characterized by a single wave-vector or become a superposition of oscillations with different wave-vectors. Using the formalism of nonequilibrium Keldysh Green functions, we derive a simple equation that determines bias voltage dependence of the wave-length of the oscillations. Finally, we discuss limitations of the commonly used formula that describes the spatial character of the Friedel oscillations. [ABSTRACT FROM AUTHOR]