Document:

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                                                                   Exhibit 10.55

                             POST-CLOSING AGREEMENT

      This Post-Closing Agreement (this "Agreement") is entered into by and
among Drew Scientific, Inc. ("Borrower"), a Texas corporation, Keith Raymond
Drew ("Drew"), Drew Scientific Group, PLC ("Drew PLC") and Texas Mezzanine Fund
Inc. ("Lender"), a Texas corporation.

                                    RECITALS

      A. Reference is made to that certain loan transaction in the stated
principal amount of $558,000.00 (the "Loan") from Lender to Borrower as
evidenced by, among other things, (i) that certain Loan Agreement of even date
herewith between Borrower and Lender, and (ii) that certain Guaranty Agreement
dated of even date herewith, executed by Drew for the benefit of Lender. The
Loan Agreement and all documents and instruments executed in connection with the
Loan are hereinafter collectively referred to as the "Loan Documents".

      B. Lender has required that (i) Drew pledge all shares of Drew PLC owned
by Drew (the "Shares") to secure the obligations of Drew under the Guaranty
Agreement, (ii) Lender receive a perfected first lien security interest in the
Shares, and (iii) Lender receive a subordination of landlord's lien concerning
the premises located at 4230 Shilling Way, Dallas, Texas, in the form attached
hereto as Exhibit A (the "Landlord Waiver").

      C. Drew has advised Lender that Drew will be unable to deliver immediate
physical possession of the Shares to Lender in order to enable Lender to obtain
a perfected first lien security interest in said Shares. Borrower has also
advised Lender that it will be unable to deliver the Subordination to Lender by
the anticipated closing date. Borrower has requested that Lender disburse the
proceeds of the Loan to Borrower notwithstanding this circumstance. Subject to
the terms and conditions more particularly described herein, Lender has agreed
to disburse the proceeds of the Loan to Borrower.

      NOW, THEREFORE, for and in consideration of the covenants and agreements
contained herein, and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto hereby agree as
follows:

      1. Disbursement of the Loan. Lender hereby agrees to disburse the proceeds
of the Loan in the manner set forth in the Loan Agreement.

      2. Delivery of Shares. Drew shall deliver the Shares to Lender within
thirty (30) days of the date hereof. DREW, DREW PLC (COLLECTIVELY, "GUARANTORS")
AND BORROWER ACKNOWLEDGE AND AGREE THAT IN THE EVENT THE LENDER HAS NOT RECEIVED
THE SHARES WITHIN THIRTY (30) DAYS OF THE DATE HEREOF, SUCH FAILURE TO DELIVER
THE SHARES SHALL CONSTITUTE A DEFAULT UNDER THE LOAN AND LENDER MAY ELECT TO
PURSUE ITS RIGHTS AND REMEDIES UNDER THE LOAN DOCUMENTS OR OTHERWISE EXISTING AT
LAW OR IN EQUITY, INCLUDING, BUT NOT LIMITED TO, CEASING ANY FURTHER ADVANCES
UNDER THE LOAN.

      3. Delivery of the Landlord Waiver. Borrower shall deliver the Landlord
Waiver to Lender within thirty (30) days of the date hereof. GUARANTORS AND
BORROWER ACKNOWLEDGE AND AGREE THAT IN THE EVENT THE LENDER HAS NOT RECEIVED THE
LANDLORD WAIVER WITHIN THIRTY (30) DAYS OF THE DATE HEREOF, SUCH FAILURE TO
DELIVER THE LANDLORD WAIVER SHALL CONSTITUTE A DEFAULT UNDER THE LOAN AND LENDER
MAY ELECT TO PURSUE ITS RIGHTS AND REMEDIES UNDER THE LOAN DOCUMENTS OR
OTHERWISE EXISTING AT LAW OR IN EQUITY, INCLUDING, BUT NOT LIMITED TO, CEASING
ANY FURTHER ADVANCES UNDER THE LOAN.

      4. No Waiver. Borrower and Guarantors understand, acknowledge and agree
that any disbursement of the proceeds the Loan by Lender shall not, is not
intended to, nor shall it be construed as (a) a waiver of the obligation to
deliver the Shares and the Landlord Waiver, or (b) a waiver of Lender's right to
demand delivery of the Shares and the landlord Waiver.

      5. Representations and Warranties of Drew. As a material inducement to
Lender to disburse the proceeds of the Loan, Drew hereby represents and warrants
to Lender the following:

                                      - 1 -
<PAGE>

      a. Drew is the lawful owner of record of 3,178,984 shares of Drew PLC and
         has a beneficial interest in 1,400,000 shares of Drew PLC pursuant to
         Selbourne Limited.

      b. The Shares are duly authorized, validly issued and outstanding, fully
         paid and non-assessable.

      c. Drew owns the Shares free and clear of all security interests, liens,
         encumbrances and claims.

      d. There are no outstanding rights or options to acquire any of the
         Shares.

      e. There are no conditions or restrictions that prohibit the transfer of
         the Shares that have not been disclosed in writing to Lender.

      6. Covenants of Drew. As a material inducement to Lender to disburse the
proceeds of the Loan, Drew hereby covenants and agrees with Lender as follows:

      a. Drew shall diligently pursue the delivery of the Shares to Lender.

      b. Drew shall not sell, transfer, convey or assign the Shares to any party
         other than Lender.

      c. Drew shall not pledge, hypothecate or otherwise encumber the Shares for
         the benefit of any party other than Lender. .

      d. Drew shall take such actions with respect to Drew PLC as Lender deems
         reasonably necessary in order to evidence Lender's security interest in
         the Shares.

      7. Clerical Error. In the event Lender at any time discovers that this
Agreement or any document executed in connection herewith contains an error that
was caused by a unilateral mistake on the part of Lender, mutual mistake on the
part of Lender and Borrower and/or Guarantors, clerical mistake, calculation
error, computer malfunction, printing error or similar error, Borrower and
Guarantors respectively agree, upon notice from Lender, to re-execute any
documents that are necessary to correct any such error(s). Borrower and
Guarantors further agree that Lender shall not be liable to Borrower or
Guarantors for any damages incurred by Borrower or Guarantors that are directly
or indirectly caused by any such error.

      8. Costs and Expenses. All costs, fees and expenses incurred by Lender in
connection with the consummation of the transaction evidenced by this Agreement,
including, without limitation, all recording costs, reasonable fees and expenses
of Lender's counsel and any other costs and expenses referred to in this
Agreement, shall be paid by Borrower.

      9. Modification. This Agreement may not be modified or amended except by
an agreement in writing signed by the parties hereto. The parties may waive any
of the conditions contained herein or any of the obligations of the other
parties hereunder, but any such waiver shall be effective only if in writing and
signed by the party waiving such conditions or obligations.

      10. Headings and General Application. The article, paragraph and
subparagraph entitlements hereof are inserted for convenience of reference only
and shall in no way affect, modify or define, or be used in construing, the text
of such article, paragraph or subparagraph. If the text requires, words used in
the singular shall be read as including the plural, and pronouns of any gender
shall include all genders.

      11. Severability. If any provision of this Agreement is or may be held by
a court of competent jurisdiction to be invalid, void, or unenforceable to any
extent, the validity of the remaining parts, terms or provisions of this
Agreement shall not be affected thereby, and such illegal or invalid part,
terms, or provision shall be deemed not to be part of this Agreement. The
remaining provisions shall nevertheless survive and continue in full force and
effect without

                                      - 2 -
<PAGE>

being invalidated in any way to the extent the remaining provisions further
accomplish the goals and intents of this Agreement.

      12. Binding Effect. This agreement shall be binding upon and insure to the
benefit of the parties hereto and their respective heirs, legal representatives,
successors and assigns.

      13. Multiple Counterparts. This Agreement may be executed in an number of
identical counterparts, each of which for all purposes is deemed an original,
and all of which constitute collectively one agreement.

      14. Governing Law and Venue. This Agreement shall be governed by and
construed in accordance with the laws of the State of Texas. Venue of any suit
arising hereunder shall lie in Dallas County, Texas.

      15. ENTIRE AGREEMENT. THIS AGREEMENT EMBODIES AND CONSTITUTES THE FINAL
UNDERSTANDING AND AGREEMENT BETWEEN THE PARTIES HERETO WITH RESPECT TO THE
MATTERS CONTEMPLATED IN THIS AGREEMENT, AND MAY NOT BE CONTRADICTED BY EVIDENCE
OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT AGREEMENTS, UNDERSTANDINGS,
REPRESENTATION AND STATEMENTS, ORAL OR WRITTEN. THERE ARE NO UNWRITTEN ORAL
AGREEMENTS BETWEEN THE PARTIES HERETO.

      IN WITNESS WHEREOF, this Agreement is executed as of the 20th day of
November, 2003.

                                      BORROWER:

                                      DREW SCIENTIFIC, INC.,
                                      a Texas corporation

                                      By: /s/ Keith Drew
                                          --------------------------------------
                                      Name:  Keith Drew
                                      Title: President

                                      GUARANTORS:

                                      /s/ Keith Raymond Drew
                                      ------------------------------------------
                                      KEITH RAYMOND DREW

                                      DREW SCIENTIFIC GROUP,  PLC,
                                      a public limited company organized under
                                      the laws of England and Wales

                                      By: /s/ K.R. Drew
                                          --------------------------------------
                                      Name:  K.R. DREW
                                      Title: DIRECTOR

                                      LENDER:

                                      TEXAS MEZZANINE FUND INC.,
                                      a Texas corporation

                                      BY: /s/ Theresa Lee
                                          --------------------------------------
                                      Name:  Theresa Lee
                                      Title: Vice-President

                                       -3-
<PAGE>

                                    Exhibit A

Ms. Theresa Lee
Texas Mezzanine Fund Inc.
351 West Jefferson Blvd., Suite 800
Dallas, Texas 75208

      Re:   Commercial Lease Agreement (the "Lease") between Echometer Profit
            Sharing Trust, Jerry B. West and Rebecca Ann West (collectively,
            "Landlord"), as landlord, and Drew Scientific, Inc. ("Tenant"), a
            Texas corporation f/k/a MWI, Inc. d/b/a/ Danam Electronics, as
            tenant, relating to certain property located at 4230 Shilling Way,
            Dallas, Texas (the "Property")

      Pursuant to that certain Landlord's Subordination Agreement dated as of
April 27, 1997, by and between Landlord and Tenant (the "Subordination
Agreement"), a true and correct copy of which is attached hereto as Exhibit "A",
Landlord has subordinated all of Landlord's right, title and interest in and to
the Equipment (as defined in the Subordination Agreement) that may exist as a
result of the Lease, to the right, title and interest of any lender in and to
the Equipment.

      Landlord has been advised that Tenant has entered into a certain loan
transaction with Texas Mezzanine Fund Inc. ("Lender") pursuant to which Tenant
shall give as security for the payment of such indebtedness a security interest
or other lien upon the Equipment. Accordingly:

      1. The Lease is in full force and effect and Tenant is paying the full
rent stipulated in the Lease with no offsets, defenses or claims.

      2. The renewal term of the Lease will terminate on March 31, 2007.

      3. Landlord specifically acknowledges and agrees that the Subordination
Agreement has not been modified or terminated and agrees that any and all
presently existing or future liens that may exist as a result of the lease or
rental of the Property by Tenant from Landlord (including, without limitation,
any contractual landlord's lien or any lien existing pursuant to the Texas
Property Code or the Constitution of Texas), are and shall be subordinate,
subject and inferior to any security interest or liens now or hereafter held by
Lender upon any of the Equipment;

      4. Landlord agrees to provide Lender with (a) written notice of a default
under the Lease concurrently with or immediately after the occurrence of such
default, and (b) written notice of the commencement of any action to enforce the
provisions of the Lease concurrently with or immediately after the commencement
of any such action; and

      5. Landlord agrees that in the event Lender becomes entitled to possession
of any of the Equipment, Lender shall have the right to enter the Property upon
five (5) days written notice to Landlord in order to remove the Equipment during
normal business hours. Landlord shall allow Lender such time as is reasonably
necessary (and in no eventless than three (3) business days) to remove the
Equipment from the Property, and any Equipment so removed shall be free of any
liens or claims of Landlord. Lender shall not be liable for any rental
whatsoever doing such period of removal.

      Landlord acknowledges, understands and agrees that Lender is relying upon,
and is entitled to rely upon, the terms, conditions and representations set
forth in the Subordination Agreement and this letter.

ECHOMETER PROFIT SHARING TRUST                /s/ Jerry B. West
                                              ----------------------------------
                                              JERRY B. WEST

By:________________________________
Name:______________________________           __________________________________
Title: Trustee                                REBECCA ANN WEST<PAGE>
                                                                   Exhibit 10.56

                               FIRST AMENDMENT TO
                             POST-CLOSING AGREEMENT

      This First Amendment to Post-Closing Agreement (this "First Amendment"),
is executed on the respective dates set forth below effective as of December 20,
2003 (the "Effective Date"), and is entered into by and among Drew Scientific,
Inc., Texas corporation ("Borrower "), Keith Drew, individually ("Drew"), Drew
Scientific Group, PLC, a public limited company organized under the laws of
England and Wales ("Drew PLC"), and Texas Mezzanine Fund Inc., a Texas
corporation ("Lender") for the purpose of amending and modifying that certain
Post-Closing Agreement executed as of November 20, 2003 (the "Original
Agreement"). Borrower, Drew, Drew PLC and Lender are collectively referred to
herein as the "Parties". All capitalized terms used in this First Amendment and
not otherwise defined herein shall have the meanings assigned to such terms in
the Original Agreement, unless the context specifically requires otherwise

                                    RECITALS

      A.    Pursuant to Section 2 of the Original Agreement, Drew was required
            to deliver to Lender, on or prior to the Effective Date, all of the
            Shares owned by Drew;

      B.    As of the Effective Date, Lender had received share certificates
            issued by Drew PLC to Drew evidencing ownership of 2,600,000 Shares;

      C.    Since the Effective Date, Lender has received share certificates
            issued by Drew PLC to Drew evidencing ownership of an additional
            573,984 Shares;

      D.    Drew has determined that he does not control Selbourne Limited
            ("Selbourne"), either directly or indirectly, and cannot either (i)
            pledge or cause the pledge of the 1,400,000 shares of Drew PLC
            issued to Selbourne ("Selbourne Shares") or (ii) cause to be
            delivered to Lender certificates evidencing such shares;

      E.    It has been determined that Paragraph 5a that the Original Agreement
            incorrectly slated the number of shares of Drew PLC of which Drew is
            the lawful owner as being 3,178,984 and that the correct number is
            3,173,984;

      F.    The Parties desire to correct the typographical error referenced in
            Recital D; and

      G.    The Parties desire to clarify that (since Drew does not own such
            shares) the Selbourne Shares are not collateral for the Loan and
            that certificates evidencing such shares need not be delivered to
            Lender.

<PAGE>

                                    AGREEMENT

      NOW THEREFORE, in consideration of the premises and the mutual agreements
contained herein, the parties agree to amend the Original Agreement on the
following terms and conditions:

      1.    Delivery of Shares. There is hereby added at the end of Paragraph 2
of the Original Agreement the following:

            Notwithstanding the foregoing, if certificates have not been issued
            by Drew PLC to evidence any portion of the Shares, failure to
            deliver such Shares shall not constitute a default under this
            Paragraph.

      2.    Shares Owned; Selbourne Shares. Section 5(a) of the Original
Agreement is hereby amended to in its entirety to read: "Drew is the lawful
owner of record of 3,173,984 shares of Drew PLC".

      3.    Representation and Warranty. Section 6 of the Original Agreement is
hereby amended by adding a new Subsection 5.1 that reads as follows:

            Drew hereby represents and warrants that he has determined that he
            does not control Selbourne Limited ("Selbourne"), either directly or
            indirectly, and cannot either (i) pledge or cause the pledge of the
            1,400,000 shares of Drew PLC issued to Selbourne ("Selbourne
            Shares") or (ii) cause to be delivered to Lender certificates
            evidencing such shares.

      4.    Limitation. Except as expressly modified and amended by this First
Amendment, the terms, conditions and provisions of the Original Agreement shall
remain in full force and effect in all respects.

      5.    Counterparts. The Parties may execute this First Amendment in any
number of counterparts. Each such counterpart shall be deemed to be an original,
but all such counterparts shall together constitute one and the same agreement.

      6.    Amendment And Waiver. No amendment of this First Amendment, and no
waiver of any one or more of the provisions hereof shall be effective unless set
forth in a writing and signed by the parties hereto.

      7.    Governing Law. This First Amendment shall be governed by and
construed in accordance with the internal laws of the State of Texas without
reference to conflict of law principles.

      8.    Severability. Any provision of this First Amendment that is held to
be inoperative, unenforceable, voidable or invalid in any jurisdiction shall, as
to that jurisdiction, be ineffective, unenforceable, void or invalid without
affecting the remaining provisions in that or

<PAGE>

any other jurisdiction, and to this end the provisions of this First Amendment
are declared to be severable.

      IN WITNESS WHEREOF, the parties hereto have executed this First Amendment
effective as of the date first above written.

                                        BORROWER:

                                        DREW SCIENTIFIC, INC.,
                                        a Texas corporation

Mar 8 '04                               By: /s/ K.R. DREW
----------------                            -------------------------
Date signed                             Name: K.R. DREW
                                        Title: President.

                                        DREW:

Mar 8 '04                               /s/ Keith Drew
----------------                        -----------------------------
Date signed                             Keith Drew, individually

                                        DREW PLC:

                                        DREW SCIENTIFIC GROUP, PLC
                                        a public limited company organized under
                                        the laws of England and Wales.

Mar 8 '04                               By: /s/ K.R. DREW
----------------                            -------------------------
Date signed                             Name: K.R. DREW
                                        Title: President

                                        LENDER:

                                        TEXAS MEZZANINE FUND, INC.,
                                        a Texas corporation

                                        By:
                                            -------------------------------
                                        Name:
----------------------                        -----------------------------
Date signed                             Title:
                                               ----------------------------

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