def MAE_dust_caponi(wavelengths, formulation='libya25'):
    """class defining dust Mass Absorption Efficiency (MAE) for several dust sources according to
       Caponi et al. 2017 """
    MAE400_AAE = {'libya25': (110.0, 4.1), 'marocco25': (90.0, 2.6),
        'algeria25': (73.0, 2.8), 'mali25': (630.0, 3.4), 'saudi_arabia25':
        (130.0, 4.5), 'kuwait25': (310.0, 3.4), 'namibia25': (135.0, 5.1),
        'china25': (180.0, 3.2), 'australia25': (293.0, 2.9), 'libya10': (
        77.0, 3.2), 'algeria10': (82.0, 2.5), 'bodele10': (27.0, 3.3),
        'saudi_arabia10': (81.0, 4.1), 'namibia10': (50.0, 4.7), 'china10':
        (59.0, 3.0), 'arizona10': (103.0, 3.1), 'patagonia10': (83.0, 2.9),
        'australia10': (124.0, 2.9)}
    if formulation not in MAE400_AAE.keys():
        formulation = 'libya25'
        raise ValueError('Bad caponi formulaion')
    MAE400, AAE = MAE400_AAE[formulation]
    MAE = MAE400 * (wavelengths / 4e-07) ** -AAE
    return MAE
