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                                                                    EXHIBIT 10.6

                          LICENSE REVOCATION AGREEMENT

THIS AGREEMENT, dated as of November 2, 1998, is between Paracelsian Inc.
     (hereinafter "PARACELSIAN"), a Delaware corporation having a principal
     place of business at the Cornell Technology Park in Ithaca, New York and
     The Dow Chemical Corporation (hereinafter "DOW"), a Delaware corporation
     having a principal place of business in Midland Michigan. PARACELSIAN and
     DOW are referred to individually as "Party" and collectively as "Parties."
     The parties agree as follows:

                                   1. RECITALS

1.1  In THE LICENSE between the Parties, dated January 19, 1995, DOW secured,
     for itself and its AFFILIATES (as defined in THE LICENSE), both a
     nonexclusive license to evaluate and practice PROPRIETARY INFORMATION
     (defined as in THE LICENSE), and Patent Applications and an exclusive
     option to acquire a worldwide, exclusive license, including a right to
     sublicense thereunder, to practice all aspects of PROPRIETARY INFORMATION
     related to environmental bioassay apparatus and testing, except for blood
     and blood component bioassays for indoor air and water quality applications
     for homes and office buildings under any claims of patents resulting from
     Patent Rights.

                                 2. DEFINITIONS

The  following definitions apply throughout this Agreement:

2.1  All terms in this agreement are, unless otherwise specifically noted, are
     used in accordance with the definitions provided in the in the agreement
     between the Parties dated January 19, 1995 (hereinafter "THE LICENSE").

                          3. MODIFICATION OF A LICENSE

This agreement modifies the entirety of THE LICENSE agreement reached between
     the parties dated January 19, 1995 as follows:

3.1  The Parties herein agree to a termination of any and all license,
     sublicense, or option provisions concerning the PROPRIETARY INFORMATION, as
     provided in part in paragraphs 2.1 through 3.3.3. of THE LICENSE.

3.2  PARACELSIAN hereby recovers from DOW all title and interest in the
     PROPRIETARY INFORMATION, or any products derived therefrom, which was the
     subject of THE LICENSE, as provided in part in paragraphs 2.1 through
     3.3.3. of THE LICENSE.

3.3  In consideration for DOW's agreement to terminate any and all license,
     sublicense, or option provisions concerning the PROPRIETARY INFORMATION,
     PARACELSIAN agrees to pay DOW 10% of all sublicensing fees generated
     through the sublicense of the PROPRIETARY INFORMATION provided by the
     Patent Applications which formed the basis of THE LICENSE, and 10% of any
     net sales of any products derived from the

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     PROPRIETARY INFORMATION which were the subject of THE LICENSE. The maximum
     total value for any and all such payments shall not exceed $250,000.

                       4. REPORTS, PAYMENTS AND ACCOUNTING

4.1  The parties hereby adopt all of the reporting and accounting terms present
     within THE LICENSE, except that PARACELSIAN shall report and account to
     DOW.

IN WITNESS WHEREOF the parties have executed this Agreement in duplicate
     originals by their respective duly authorized corporate officers or
     representatives.

PARACELSIAN INC.                          THE DOW CHEMICAL COMPANY


By:  /s/ Bernard Landes                   By:  /s/ Michael D. Parker
    ----------------------------------        ----------------------------------

Name:  Bernard Landes                     Name:  Michael D. Parker
      --------------------------------          --------------------------------

Title: President & CEO                    Title:  Executive Vice President
      --------------------------------          --------------------------------

Date:             10/15/98                Date:  NOVEMBER 2, 1998
     ---------------------------------         ---------------------------------

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                                    EXHIBIT A


                                    [Omitted]

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