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                                                                    Exhibit 4.18

                                     BY-LAWS
                                       OF
                              MDAS ACQUISITION CO.

                             A Michigan Corporation

                                    ARTICLE I

                             Shareholders' Meetings

          Section 1. Annual Meeting. The annual meeting of shareholders shall be
held on the date during the third month of each fiscal year and at the time and
place as the Board of Directors shall fix, for the purpose of electing directors
and transacting such other business as may properly come before the meeting. Any
annual meeting not held on the designated day may be held on any day thereafter
to which it may be adjourned.

          Section 2. Special Shareholders' Meetings. Special meetings of
shareholders may be called by the Chairperson of the Board, the President, the
chief executive officer, or the Board of Directors. The chief executive officer
shall call a special shareholders' meeting whenever shareholders owning a
majority of the issued and outstanding shares of the Corporation's capital stock
entitled to vote at the special meeting shall so request in writing.

          Section 3. Place of Meeting. The Board of Directors may designate any
place either within or without Michigan as the meeting place for any
shareholders' meeting called by the Board of Directors. If no designation is
made or if some person other than the Board calls a special meeting, the meeting
shall be held at the Corporation's chief executive office in Michigan.

          Section 4. Notice of Meetings. written notice of the time, place and
purposes of a shareholders' meeting shall be given not less than ten (10) nor
more than sixty (60) days before the meeting date, either personally or by mail,
to each shareholder of record entitled to vote at the meeting. If mailed, the
notice shall be deemed to be given when deposited in the United States mail,
postage pre-paid, addressed to the shareholder at his or her address as it
appears on the Corporation's stock transfer books.

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          Section 5. Quorum. At all shareholders' meetings, except where
otherwise provided by law, the holders of a majority of the outstanding shares
entitled to vote, being present in person or by proxy, shall constitute a quorum
for all purposes. The shareholders present in person or by proxy at the meeting
may continue to do business until adjournment, notwithstanding the withdrawal of
enough shareholders to leave less than a quorum.

          Section 6. Voting. Each outstanding share of capital stock is entitled
to one vote on each matter submitted to a vote, except as otherwise provided in
the Articles of Incorporation or under law. A vote may be cast either orally or
in writing, at the discretion of the chairperson of the meeting.

          Section 7. Adjournments. Any annual or special shareholders' meeting,
whether or not a quorum is present, may be adjourned from time to time by a
majority vote of the shares present in person or by proxy. Unless the Board of
Directors fixes a new record date for the adjourned meeting, it is not necessary
to give notice of the adjourned meeting if the date, time and place to which the
meeting is adjourned are announced at the meeting at which the adjournment is
taken and only such business is transacted at the adjourned meeting as might
have been transacted at the original meeting.

                                   ARTICLE II

                                    Directors

          Section 1. Number and Term of Office. The number of directors of the
Corporation shall be not less than two (2) nor more than ten (10), the number to
be determined initially by the incorporator and thereafter by action by the
shareholders or by action of the Board of Directors. All directors shall be
elected at the annual meeting of shareholders and hold office until the
succeeding annual meeting and until their respective successors are elected and
have qualified, or until their earlier death, resignation or removal.

          Section 2. Removal. A director of the Corporation may be removed from
office for any reason by the vote of the holders of a majority of the capital
stock then outstanding and entitled to vote at a special meeting of the
shareholders called for that purpose.

          Section 3. Annual and Regular Meetings. The annual meeting of the
Board of Directors shall be held on the date of the Corporation's annual
shareholders meeting. Regular meetings of the Board of Directors may be held
without notice at such time and place as may be fixed by resolution of the
Board.


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          Section 4. Special Meetings. Special meetings of the Board of
Directors may be held whenever called by the Chairperson or the President, or
upon the written request of a majority of the Board of Directors. Notice thereof
shall be given personally or by telephone, mail, facsimile, or similar means of
communication to the last known address of each director at least one (1) day
before such meeting. Neither the business to be transacted at, nor the purpose
of, a special meeting need be specified in the notice of the meeting.

          Section 5. Quorum and Voting. A majority of the Directors then in
office shall constitute a quorum for transacting business, unless otherwise
provided by law or the Articles of Incorporation. A majority of Directors
present at any regular or special meeting, although less than a quorum, may
adjourn the meeting from time to time, without notice. The majority vote of
members present at a meeting at which a quorum is present constitutes the action
of the Board of Directors, unless the vote of a larger number is required by
law, the Articles of Incorporation, or the By-Laws.

          Section 6. Compensation. The members of the Board of Directors of the
Corporation who are not full-time officers or employees of the Corporation shall
receive such reasonable compensation and reimbursement of expenses for their
services as determined by the Board of Directors.

                                   ARTICLE III

                                    Officers

          Section 1. Number. The officers of the Corporation shall be a
President, a Secretary, and a Treasurer. The Board of Directors may also elect a
Chairperson of the Board, one or more Vice Chairpersons of the Board, one or
more Vice Presidents (one or more of whom may be designated as Senior Vice
President or Executive Vice President), a Controller and one or more Assistant
Secretaries, Assistant Treasurers, and Assistant Controllers. The Board of
Directors shall have power to create such other offices as it may from time to
time deem expedient.

          Section 2. Election and Term of Office. The officers shall be elected
annually by the Board of Directors at its annual meeting. If the officers are
not elected at this meeting, they shall be elected as soon thereafter as
convenient. Each officer shall hold office until his or her successor shall have
been duly elected and qualified or until his or her death, resignation or
removal.


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          Section 3. Removal and Vacancies. Any officer elected or appointed by
the Board may be removed by the Board of Directors at any time with or without
cause. Vacancies among officers of the Corporation during the year may be filled
by the Board of Directors for the unexpired portion of the term.

          Section 4. Chief Executive and Chief Operating Officers. The Board of
Directors shall designate one of the Corporation's officers as the chief
executive officer and may, from time to time, but shall not be required to do
so, designate one of the officers as the chief operating officer. In the absence
of any designation, the President shall serve as the chief executive officer.
Subject to the direction of the Board of Directors, the chief executive officer
shall have general supervision of the Corporation's business, departments,
officers, and employees, and shall prescribe duties of other officers and
employees insofar as they are not specified by the By-Laws or by the Board of
Directors. The chief operating officer shall have such duties as may be
designated by the chief executive officer or by the Board of Directors.

          Section 5. Chairperson of the Board. The Chairperson of the Board
shall be appointed by the Board of Directors and shall perform such duties as
may be designated by the Board of Directors. The Chairperson shall preside at
meetings of the shareholders and Board of Directors.

          Section 6. Vice Chairperson of the Board. The Vice Chairperson of the
Board shall be appointed by the Board of Directors and shall perform such duties
as may be designated by the Board of Directors. In the Chairperson's absence or
disability, the Vice Chairperson shall preside at meetings of the shareholders
and Board of Directors.

          Section 7. President. The President shall perform such duties as may
be designated by the chief executive officer or by the Board of Directors.

          Section 8. Vice Presidents. The Vice Presidents shall perform such
duties and be vested with such powers as the Board of Directors or the chief
executive officer may prescribe.

          Section 9. Secretary. The Secretary shall keep a record in proper
books maintained for that purpose of all proceedings of the Board of Directors
and the shareholders. The Secretary shall keep all other records and shall
perform all other duties as the Board of Directors or the chief executive
officer shall designate. The Secretary shall give all notices required by law,
the Articles of Incorporation, the By-Laws, or the resolutions of the Board of
Directors. The Secretary shall


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in general perform all the duties appurtenant to the office of Secretary,
subject to the control of the Board of Directors and the chief executive
officer.

          Section 10. Treasurer. The Treasurer shall be responsible for all
funds and securities of the Corporation. The Treasurer shall deposit all the
Corporation's funds with such depositories as the Board of Directors may
designate. The Treasurer shall in general perform all duties incident to the
position of Treasurer, subject to the control of the Board of Directors and the
chief executive officer.

          Section 11. Other Officers. Other officers appointed by the Board of
Directors shall exercise those powers and perform those duties as may be
delegated to them by the Board of Directors or the chief executive officer.

          Section 12. Additional Duties and Authorities. The officers shall
have authority to execute on the Corporation's behalf any and all contracts,
agreements, bonds, deeds, mortgages, leases or other obligations of the
Corporation arising in its regular course of business other than where the
Corporation's Board of Directors designate one or more specific officers or
agents to act on the Corporation's behalf. All documents, instruments and
writings of any nature not arising in its regular course of business shall be
executed and delivered by the Corporation's officer or officers and in such
manner as the Board of Directors may, from time to time, determine.

                                   ARTICLE IV

                                   Committees

          The Board of Directors may establish such committees as it may deem
necessary or desirable to conduct the Corporation's business. Any committee
created shall consist of one or more directors and shall have the duties,
powers, and authority as the Board of Directors shall specify.

                                    ARTICLE V

                                  Capital Stock

          Section 1. Certificates. The interest of the Corporation's
shareholders may be evidenced by stock certificates, certifying the number of
shares represented thereby and in such form not inconsistent with law and the
Articles of Incorporation as the Board of Directors may from time to time
prescribe. The Board of Directors may authorize that some or all of the
Corporation's shares shall be issued without certificates in the manner
prescribed by law.


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          The stock certificates shall be signed by the Chairperson of the
Board, the President, or a Vice President and may also be signed by the
Secretary or the Treasurer. The Corporation's seal may be affixed to the
certificates, and may be either printed or manually affixed. The officers'
signatures may be facsimiles if the certificate is countersigned by a transfer
agent or registered by a registrar other than the Corporation itself. If any
officer who has signed or whose facsimile signature has been placed upon any
certificate ceases to hold that office before the certificate is issued, the
Corporation may issue the certificate with the same effect as if he or she held
that office at its issuance.

          All certificates of stock surrendered to the Corporation for transfer
shall be cancelled and, except in the case of lost or destroyed certificates as
provided below, no new certificate shall be issued until the former certificate
or certificates for the shares represented thereby shall have been surrendered
and cancelled.

          Section 2. Lost Certificates. When a stock or other certificate
previously issued is alleged to have been lost or destroyed, a replacement
certificate may be issued upon such terms and indemnity to the Corporation as
the Board of Directors or the chief executive officer may prescribe.

          Section 3. Transfer of Shares. Transfer of the Corporation's stock
shall be made only on the stock transfer books, and the Corporation may decline
to recognize the holder of any certificate as a shareholder until the shares
represented by such certificate are transferred into his or her name on the
Corporation's stock transfer books. The Corporation shall be entitled to treat
the record holder of any shares as the absolute owner thereof, and shall not be
bound to recognize any equitable or other claim to or interest in those shares
on the part of any other person, whether or not it has express or other notice
thereof, except as otherwise provided by law. The Board of Directors may appoint
one or more stock transfer agents and registrars (which functions may be
combined), and may require all stock certificates to bear the signature of the
transfer agent and registrar.

          Section 4. Fixing Record Dates. For the purpose of determining
shareholders entitled to notice of and to vote at a shareholders' meeting or any
adjournment thereof, or for any other purpose, the Board of Directors may fix in
advance a date as the record date. The date shall not be more than sixty (60)
nor less than ten (10) days before the date of the meeting, nor more than sixty
(60) days before any other action.


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                                   ARTICLE VI

                                  Miscellaneous

          Section 1. Seal. The Corporation's seal shall consist of the
Corporation's name and state of incorporation around the periphery of a circle,
with the words "Seal" or "Corporate Seal" within the circle.

          Section 2. Fiscal Year. The Corporation's fiscal year shall begin on
the first day of January in each year and end on the last day of December in
each year.

          Section 3. Indemnification of Directors, Officers, Employees, and
Agents. The Corporation shall indemnify any person who was or is a party, or is
threatened to be made a party, to any threatened, pending or completed action,
suit or proceeding, whether civil, criminal, administrative or investigative, by
reason of the fact that he or she is or was a director or officer of the
Corporation, or is or was serving another organization or entity (whether for
profit or not) at the Corporation's request. Such indemnification shall be to
the fullest extent, and shall be determined in such manner, as now or hereafter
permitted by law. The indemnification shall continue as to a person who has
ceased to be a director or officer and shall inure to the benefit of the heirs,
executors and administrators of the person.

          The Corporation may, by action of its Board of Directors, indemnify
its employees and agents to the same extent as the indemnification of directors
and officers.

          Notwithstanding the foregoing, the indemnification and advancement of
expenses provided by or granted under the Michigan Business Corporation Act
shall not be considered exclusive of any other rights to which those seeking
indemnification or advancement of expenses may be entitled under the Articles of
Incorporation, By-Laws, insurance, or a contractual agreement.

                                  ARTICLE VII

                                   Amendments

          These By-Laws may be amended, altered or repealed and new By-Laws may
be adopted by the shareholders or, unless prohibited or restricted by the
Corporation's Articles of Incorporation, the Board of Directors.


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                                  ARTICLE VIII

                                Scope of By-Laws

          These By-Laws govern the regulation and management of the
Corporation's affairs to the extent they are consistent with applicable law and
the Articles of Incorporation. To the extent of any inconsistency, applicable
law and the Articles of Incorporation shall govern the Corporation's affairs.


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