diff --git a/Modules/Biophotonics/python/iMC/mc/tissuemodels.py b/Modules/Biophotonics/python/iMC/mc/tissuemodels.py
index 0e330566f5..4b35c1a42e 100644
--- a/Modules/Biophotonics/python/iMC/mc/tissuemodels.py
+++ b/Modules/Biophotonics/python/iMC/mc/tissuemodels.py
@@ -1,132 +1,135 @@
 '''
 Created on Sep 9, 2015
 
 @author: wirkert
 '''
 
 import numpy as np
 
 from mc.sim import MciWrapper
 from mc.usuag import Ua, UsgJacques
 
 
 class AbstractTissue(object):
     '''
     Initializes a abstract tissue model"
     '''
 
     def set_nr_photons(self, nr_photons):
         self._mci_wrapper.set_nr_photons(nr_photons)
 
     def set_mci_filename(self, mci_filename):
         self._mci_wrapper.set_mci_filename(mci_filename)
 
     def set_mco_filename(self, mco_filename):
         self._mci_wrapper.set_mco_filename(mco_filename)
 
     def set_wavelength(self, wavelength):
         self.wavelength = wavelength
 
     def create_mci_file(self):
         # set layers
         for i, ua in enumerate(self.uas):
             self._mci_wrapper.set_layer(i,  # layer nr
                                         self.ns[i],  # refraction index
                                         self.uas[i](self.wavelength),  # ua
                                         self.usgs[i](self.wavelength)[0],  # us
                                         self.usgs[i](self.wavelength)[1],  # g
                                         self.ds[i])  # d
         # now that the layers have been updated: create file
         self._mci_wrapper.create_mci_file()
 
     def __str__(self):
         """ Overwrite this method!
         print the current model"""
         model_string = ""
         return model_string
 
     def __init__(self, ns, uas, usgs, ds):
         self._mci_wrapper = MciWrapper()
 
         self.wavelength = 500.*10**9 # standard wavelength, should be set.
         self.uas = uas
         self.usgs = usgs
         self.ds = ds
         self.ns = ns
         # initially create layers. these will be overwritten as soon
         # as create_mci_file is called.
         for i in enumerate(uas):
             self._mci_wrapper.add_layer()
 
 
 class GenericTissue(AbstractTissue):
     '''
     Initializes a 3-layer generic tissue model
     '''
 
     def set_dataframe_element(self, df, element):
         """take the element element of the batch and set the tissue to
         resemble the structure specified by this"""
         layers = [l for l in df.columns.levels[0] if "layer" in l]
         for i, l in enumerate(layers):
             self.set_layer(i,
                            df[l, "vhb"][element],
                            df[l, "sao2"][element],
                            df[l, "a_mie"][element],
                            df[l, "b_mie"][element],
                            df[l, "d"][element],
                            df[l, "n"][element],
                            df[l, "g"][element])
 
     def set_layer(self, layer_nr=0,
                   bvf=None, saO2=None, a_mie=None, b_mie=None, d=None,
                   n=None, g=None):
         """Helper function to set one layer."""
         if bvf is None:
             bvf = 0.02
         if saO2 is None:
             saO2 = 0.7
         if a_mie is None:
             a_mie = 10. * 100
         if d is None:
             d = 500. * 10 ** -6
         if b_mie is None:
             b_mie = 1.286
         if n is None:
             n = 1.38
         if g is None:
             g = 0.
         # build obejct for absorption coefficient determination
         self.uas[layer_nr].bvf = bvf
         self.uas[layer_nr].saO2 = saO2
         # and one for scattering coefficient
         self.usgs[layer_nr].a_mie = a_mie
         self.usgs[layer_nr].a_ray = 0.
         self.usgs[layer_nr].b_mie = b_mie
         self.usgs[layer_nr].g = g
         self.ds[layer_nr] = d
         self.ns[layer_nr] = n
 
     def __str__(self):
         """print the current model"""
         model_string = ""
         for i, ua in enumerate(self.uas):
             layer_string = "layer " + str(i) + \
                      "    - vhb: " + "%.1f" % (self.uas[i].bvf * 100.) + \
                     "%; sao2: " + "%.1f" % (self.uas[i].saO2 * 100.) + \
                     "%; a_mie: " + "%.2f" % (self.usgs[i].a_mie / 100.) + \
                     "cm^-1; a_ray: " + "%.2f" % (self.usgs[i].a_ray / 100.) + \
                     "cm^-1; b_mie: " + "%.3f" % self.usgs[i].b_mie + \
                     "; d: " + "%.0f" % (self.ds[i] * 10 ** 6) + "um" + \
                     "; n: " + "%.2f" % (self.ns[i]) + \
-                    "; g: " + "%.2f" % (self.usgs[i].g) + "\n"
+                    "; g: " + "%.2f" % self.usgs[i].g + "\n"
             model_string += layer_string
         return model_string
 
     def __init__(self, nr_layers=3):
-        uas = [Ua()] * nr_layers
-        usgs = [UsgJacques()] * nr_layers
+        uas = []
+        usgs = []
+        for i in range(nr_layers):
+            uas.append(Ua())
+            usgs.append(UsgJacques())
         ds = np.ones(nr_layers, dtype=float) * 500.*10 ** -6
         ns = np.ones(nr_layers, dtype=float) * 1.38
         super(GenericTissue, self).__init__(ns, uas, usgs, ds)