| Warrants outstanding | 
 We have the following shares of common stock
reserved for exercise of the warrants outstanding as of March 31, 2015: 
  
    |   | 
      | 
    March 31, 2015 | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Weighted | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Average | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Exercise | 
      | 
 
    |   | 
      | 
    Shares | 
      | 
      | 
    Price | 
      | 
 
    | Warrants outstanding  beginning of year | 
      | 
      | 
    20,709,845 | 
      | 
      | 
    $ | 
    0.23 | 
      | 
 
    | Warrants exercised | 
      | 
      | 
    - | 
      | 
      | 
      | 
    0.00 | 
      | 
 
    | Warrants granted | 
      | 
      | 
    1,118,068 | 
      | 
      | 
      | 
    0.16 | 
      | 
 
    | Warrants expired | 
      | 
      | 
    (3,886,800 | 
    ) | 
      | 
      | 
    (0.33 | 
    ) | 
 
    |   | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
 
    | Warrants outstanding  end of period | 
      | 
      | 
    17,941,113 | 
      | 
      | 
    $ | 
    0.20 | 
      | 
 
 
  
 | 
    |   | 
      | 
    December 31, 2014 | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Weighted | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Average | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    Exercise | 
      | 
 
    |   | 
      | 
    Shares | 
      | 
      | 
    Price | 
      | 
 
    | Warrants outstanding  beginning of year | 
      | 
      | 
    19,550,817 | 
      | 
      | 
    $ | 
    0.17 | 
      | 
 
    | Warrants exercised | 
      | 
      | 
    (10,332,199 | 
    ) | 
      | 
      | 
    0.19 | 
      | 
 
    | Warrants granted | 
      | 
      | 
    11,491,227 | 
      | 
      | 
      | 
    0.30 | 
      | 
 
    | Warrants expired | 
      | 
      | 
    - | 
      | 
      | 
      | 
    - | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
 
    | Warrants outstanding  end of period | 
      | 
      | 
    20,709,845 | 
      | 
      | 
    $ | 
    0.23 | 
      | 
 
 
 | 
| Weighted exercise price and weighted fair value of the warrants granted | 
 The weighted exercise price and weighted fair
value of the warrants granted by us as of March 31, 2015, are as follows: 
  
    |   | 
      | 
    March 31, 2015 | 
      | 
 
    |   | 
      | 
    Weighted | 
      | 
      | 
      | 
      | 
 
    |   | 
      | 
    Average | 
      | 
      | 
    Weighted | 
      | 
 
    |   | 
      | 
    Exercise | 
      | 
      | 
    Average | 
      | 
 
    |   | 
      | 
    Price | 
      | 
      | 
    Fair Value | 
      | 
 
    | Weighted average of warrants granted during the three months whose exercise price exceeded fair market value at the date of grant | 
      | 
    $ | 
    0.16 | 
      | 
      | 
    $ | 
    0.16 | 
      | 
 
 
 | 
    |   | 
      | 
    December
    31, 2014 | 
      | 
 
    |   | 
      | 
    Weighted | 
      | 
      | 
      | 
      | 
 
    |   | 
      | 
    Average | 
      | 
      | 
    Weighted | 
      | 
 
    |   | 
      | 
    Exercise | 
      | 
      | 
    Average | 
      | 
 
    |   | 
      | 
    Price
     | 
      | 
      | 
    Fair
    Value | 
      | 
 
    | Weighted average of warrants granted
    during the twelve months whose exercise price exceeded fair market value at the date of grant | 
      | 
    $ | 
    0.30 | 
      | 
      | 
    $ | 
    0.45 | 
      | 
 
 
 | 
| Summarizes information about fixed-price warrants outstanding | 
 The
following table summarizes information about fixed-price warrants outstanding: 
  
    |   | 
      | 
      | 
    Number | 
      | 
    Average | 
      | 
      | 
      | 
 
    | Range
    of | 
      | 
      | 
    Outstanding
    at | 
      | 
    Remaining | 
      | 
    Weighted | 
      | 
 
    | Exercise | 
      | 
      | 
    March 31, | 
      | 
    Contractual | 
      | 
    Average | 
      | 
 
    | Prices | 
      | 
      | 
    2015 | 
      | 
    Life | 
      | 
    Exercise
    Price | 
      | 
 
    | $ | 
    0.33 | 
      | 
      | 
      | 
    1,284,000 | 
      | 
    1
    Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    | $ | 
    0.33 | 
      | 
      | 
      | 
    120,000 | 
      | 
    2 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    | $ | 
    0.33 | 
      | 
      | 
      | 
    249,600 | 
      | 
    3 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    | $ | 
    0.46 | 
      | 
      | 
      | 
    600,000 | 
      | 
    5 Months | 
      | 
    $ | 
    0.46 | 
      | 
 
    | $ | 
    0.46 | 
      | 
      | 
      | 
    150,000 | 
      | 
    10 Months | 
      | 
    $ | 
    0.46 | 
      | 
 
    | $ | 
    0.85 | 
      | 
      | 
      | 
    40,000 | 
      | 
    13 Months | 
      | 
    $ | 
    0.85 | 
      | 
 
    | $ | 
    0.40 | 
      | 
      | 
      | 
    333,333 | 
      | 
    17 Months | 
      | 
    $ | 
    0.40 | 
      | 
 
    | $ | 
    0.33 | 
      | 
      | 
      | 
    439,637 | 
      | 
    22 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    | $ | 
    0.16 | 
      | 
      | 
      | 
    750,000 | 
      | 
    24 Months | 
      | 
    $ | 
    0.16 | 
      | 
 
    | $ | 
    0.30 | 
      | 
      | 
      | 
    964,912 | 
      | 
    40 Months | 
      | 
    $ | 
    0.30 | 
      | 
 
    | $ | 
    0.30 | 
      | 
      | 
      | 
    4,824,561 | 
      | 
    41 Months | 
      | 
    $ | 
    0.30 | 
      | 
 
    | $ | 
    0.06 | 
      | 
      | 
      | 
    7,067,002 | 
      | 
    43 Months | 
      | 
    $ | 
    0.06 | 
      | 
 
    | $ | 
    0.16 | 
      | 
      | 
      | 
    1,118,068 | 
      | 
    47 Months | 
      | 
    $ | 
    0.16 | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
    17,941,113 | 
      | 
      | 
      | 
      | 
      | 
      | 
 
 
 | 
    |   | 
      | 
      | 
      | 
    Number | 
      | 
    Average | 
      | 
      | 
      | 
 
    |   | 
    Range of | 
      | 
      | 
    Outstanding at | 
      | 
    Remaining | 
      | 
    Weighted | 
      | 
 
    |   | 
    Exercise | 
      | 
      | 
    December 31, | 
      | 
    Contractual | 
      | 
    Average | 
      | 
 
    |   | 
      | 
    Prices | 
      | 
      | 
    2014 | 
      | 
    Life | 
      | 
    Exercise Price | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    3,154,800 | 
      | 
    1 Month | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    564,000 | 
      | 
    2 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    264,000 | 
      | 
    3 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    1,188,000 | 
      | 
    4 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    120,000 | 
      | 
    5 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    249,600 | 
      | 
    6 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.46 | 
      | 
      | 
      | 
    600,000 | 
      | 
    8 Months | 
      | 
    $ | 
    0.46 | 
      | 
 
    |   | 
    $ | 
    0.46 | 
      | 
      | 
      | 
    150,000 | 
      | 
    13 Months | 
      | 
    $ | 
    0.46 | 
      | 
 
    |   | 
    $ | 
    0.85 | 
      | 
      | 
      | 
    40,000 | 
      | 
    16 Months | 
      | 
    $ | 
    0.85 | 
      | 
 
    |   | 
    $ | 
    0.40 | 
      | 
      | 
      | 
    333,333 | 
      | 
    20 Months | 
      | 
    $ | 
    0.40 | 
      | 
 
    |   | 
    $ | 
    0.33 | 
      | 
      | 
      | 
    439,637 | 
      | 
    25 Months | 
      | 
    $ | 
    0.33 | 
      | 
 
    |   | 
    $ | 
    0.16 | 
      | 
      | 
      | 
    750,000 | 
      | 
    27 Months | 
      | 
    $ | 
    0.16 | 
      | 
 
    |   | 
    $ | 
    0.30 | 
      | 
      | 
      | 
    964,912 | 
      | 
    43 Months | 
      | 
    $ | 
    0.30 | 
      | 
 
    |   | 
    $ | 
    0.30 | 
      | 
      | 
      | 
    4,824,561 | 
      | 
    44 Months | 
      | 
    $ | 
    0.30 | 
      | 
 
    |   | 
    $ | 
    0.06 | 
      | 
      | 
      | 
    7,067,002 | 
      | 
    46 Months | 
      | 
    $ | 
    0.06 | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
      | 
    20,709,845  | 
      | 
      | 
      | 
      | 
      | 
      | 
 
 
 |