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                                                                    Exhibit 4.15

STATE OF DELAWARE
SECRETARY OF STATE
DIVISION OF CORPORATIONS
FILED 03:00 PM 06/28/1995
950145657 - 2520175

                          CERTIFICATE OF INCORPORATION

                                       of

                                    MDAS INC.

          The undersigned incorporator, in order to form a corporation under the
General Corporation Law of the State of Delaware, certifies as follows:

          1. Name. The name or the corporation is MDAS Inc. (the "Corporation").

          2. Address: Registered Office and Agent. The address of the
Corporation's registered office is 9 East Loockerman Street, City of Dover,
County of Kent, State of Delaware; and its registered agent at such address is
National Corporate Research, Ltd.

          3. Purposes. The purpose of the Corporation is to engage in, carry on
and conduct any lawful act or activity for which corporations may be organized
under the Delaware General Corporation Law.

          4. Number of Shares. The total number of shares of stock that the
Corporation shall have authority to issue is: One Thousand (1,000), all of which
shall be shares of Common Stock of the par value of one cent ($.01) each.

          5. Name and Address of Incorporator. The name and mailing address of
the incorporator are: Yvonne Y.F. Chan, Esq., 1285 Avenue of the Americas, New
York, New York 10019-6064.

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          6. Election of Directors. Members of the Board of Directors may be
elected either by written ballot or by voice vote.

          7. Limitation of Liability. No Director of the Corporation shall be
personally liable to the Corporation or its stockholders for monetary damages
for breach of fiduciary duty as a Director, except for liability (a) for any
breach of the Director's duty of loyalty to the Corporation or its stockholders,
(b) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (c) under Section 174 of the Delaware
General Corporation Law or (d) for any transaction from which the Director
derived any improper personal benefits.

          Any repeal or modification of the foregoing paragraph by the
stockholders of the Corporation shall not adversely affect any right or
protection of a Director of the Corporation existing at the time of such repeal
or modification.

          8. Indemnification.

8.1 To the extent not prohibited by law, the Corporation shall indemnify any
person who is or was made, or threatened to be made, a party to any threatened,
pending or completed action, suit or proceeding (a "Proceeding"), whether civil,
criminal, administrative or investigative,


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including, without limitation, an action by or in the right of the Corporation
to procure a judgment in its favor, by reason of the fact that such person, or a
person of whom such person is the legal representative, is or was a Director or
officer of the Corporation, or is or was serving in any capacity at the request
of the Corporation for any other corporation, partnership, joint venture, trust,
employee benefit plan or other enterprise (an "Other Entity"), against
judgments, fines, penalties, excise taxes, amounts paid in settlement and costs,
charges and expenses (including attorneys' fees and disbursements). Persons who
are not Directors or officers of the Corporation may be similarly indemnified in
respect of service to the Corporation or to an Other Entity at the request of
the Corporation to the extent the Board at any time specifies that such persons
are entitled to the benefits of this Section 8.

               8.2 The Corporation shall, from time to time, reimburse or
advance to any Director or officer or other person entitled to indemnification
hereunder the funds necessary for payment of expenses, including attorneys' fees
and disbursements, incurred in connection with any Proceeding, in advance of the
final disposition of such Proceeding; provided, however, that, if required by
the Delware General Corporation Law, such expenses incurred by or on behalf of


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any Director or officer or other person may be paid in advance of the final
disposition of a Proceeding only upon receipt by the Corporation of an
undertaking, by or on behalf of such Director or officer (or other person
indemnified hereunder), to repay any such amount so advanced if it shall
ultimately be determined by final judicial decision from which there is no
further right of appeal that such Director, officer or other person is not
entitled to be indemnified for such expenses.

               8.3 The rights to indemnification and reimbursement or
advancement of expenses provided by, or granted pursuant to, this Section 8
shall not be deemed exclusive of any other rights to which a person seeking
indemnification or reimbursement or advancement of expenses may have or
hereafter be entitled under any statute, this Certificate of Incorporation, the
By-laws of the Corporation (the "By-laws"), any agreement, any vote of
stockholders or disinterested Directors or otherwise, both as to action in his
or her official capacity and as to action in another capacity while holding such
office.

               8.4 The rights to indemnification and reimbursement or
advancement of expenses provided by, or granted pursuant to, this Section 8
shall continue as to a person who has ceased to be a Director or officer (or
other person indemnified hereunder) and shall inure to the benefit of the


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executors, administrators, legatees and distributees of such person.

               8.5 The corporation shall have power to purchase and maintain
insurance on behalf of any person who is or was a Director, officer, employee or
agent of the Corporation, or is or was serving at the request of the Corporation
as a director, officer, employee or agent of an Other Entity, against any
liability asserted against such person and incurred by such person in any such
capacity, or arising out of such person's status as such, whether or not the
Corporation would have the power to indemnify such person against such liability
under the provisions of this Section 8, the By-laws or under Section 145 of the
Delaware General Corporation Law or any other provision of law.

               8.6 The provisions of this Section 8 shall be a contract between
the Corporation, on the one hand, and each Director and officer who serves in
such capacity at any time while this Section 8 is in effect and any other person
indemnified hereunder, on the other hand, pursuant to which the Corporation and
each such Director, officer, or other person intend to be legally bound. No
repeal or modification of this Section 8 shall affect any rights or obligations
with respect to any state of facts then or theretofore existing or thereafter
arising or any proceeding


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theretofore or thereafter brought or threatened based in whole or in part upon
any such state of facts.

               8.7 The rights to indemnification and reimbursement or
advancement of expenses provided by, or granted pursuant to, this Section 8
shall be enforceable by any person entitled to such indemnification or
reimbursement or advancement of expenses in any court of competent jurisdiction.
The burden of proving that such indemnification or reimbursement or advancement
of expenses is not appropriate shall be on the Corporation. Neither the failure
of the Corporation (including its Board of Directors, its independent legal
counsel and its stockholders) to have made a determination prior to the
commencement of such action that such indemnification or reimbursement or
advancement of expenses is proper in the circumstances nor an actual
determination by the Corporation (including its Board of Directors, its
independent legal counsel and its stockholders) that such person is not entitled
to such indemnification or reimbursement or advancement of expenses shall
constitute a defense to the action or create a presumption that such person is
not so entitled. Such a person shall also be indemnified for any expenses
incurred in connection with successfully establishing his or her right to such
indemnification or reimbursement or


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advancement of expenses, in whole or in part, in any such proceeding.

               8.8 Any Director or officer of the Corporation serving in any
capacity (a) another corporation of which a majority of the shares entitled to
vote in the election of its directors is held, directly or indirectly, by the
Corporation or (b) any employee benefit plan of the Corporation or any
corporation referred to in clause (a) shall be deemed to be doing so at the
request of the Corporation.

               8.9 Any person entitled to be indemnified or to reimbursement or
advancement of expenses as a matter of right pursuant to this Section 8 may
elect to have the right to indemnification or reimbursement or advancement of
expenses interpreted on the basis of the applicable law in effect at the time of
the occurrence of the event or events giving rise to the applicable Proceeding,
to the extent permitted by law, or on the basis of the applicable law in effect
at the time such indemnification or reimbursement or advancement of expenses is
sought. Such election shall be made, by a notice in writing to the Corporation,
at the time indemnification or reimbursement or advancement of expenses is
sought; provided, however, that if no such notice is given, the right to
indemnification or reimbursement or advancement of expenses shall be determined
by the law in


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effect at the time indemnification or reimbursement or advancement of expenses
is sought.

          9. Adoption, Amendment and/or Repeal of By-Laws. The Board or
Directors may from time to time (after adoption by the undersigned of the
original By-laws) make, alter or repeal the By-laws by a vote of two-thirds of
the entire Board of Directors that would be in office if no vacancy existed,
whether or not present at a meeting; provided, however, that any By-laws made,
amended or repealed by the Board of Directors may be amended or repealed, and
any By-laws may be made, by the stockholders of the Corporation by vote of a
majority of the holders of shares of stock of the Corporation entitled to vote
in the election of Directors of the Corporation.

          WITNESS the signature of this Certificate this 28th day of June, 1995.


                                        /s/ Yvonne Y.P. Chan
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                                        Yvonne Y.P. Chan, Incorporator


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