EXHIBIT 10.43

                         CORNERSTONE ACQUISITION COMPANY
                                     BYLAWS

                                    ARTICLE I
                            MEETINGS OF SHAREHOLDERS

         1.1 Place and Time of Meetings.  Meetings of shareholders shall be held
at such place,  either within or without the  Commonwealth  of Virginia,  and at
such time,  as may be provided in the notice of the meeting and  approved by the
President or the Board of Directors.

         1.2 Annual Meeting.  The annual meeting of shareholders,  shall be held
on the  second  Tuesday  in July  of  each  year,  or on  such  date,  as may be
designated  by  resolution  of the Board of Directors  from time to time for the
purpose of electing directors and conducting such other business as may properly
come before the meeting.

         1.3  Special  Meetings.  Special  meetings of the  shareholders  may be
called by the  President  or the Board of  Directors  and shall be called by the
Secretary upon demand of  shareholders  as required by law. Only business within
the  purpose  or  purposes  described  in the  notice  for a special  meeting of
shareholders may be conducted at the meeting.

         1.4 Record Dates. The Board of Directors may fix, in advance,  a record
date to make a determination  of shareholders  entitled to notice of, or to vote
at, any meeting of  shareholders,  to receive any  dividend or for any  purpose,
such date to be not more than 70 days before the  meeting or action  requiring a
determination  of  shareholders.  If no such  record date is set then the record
date  shall be the close of  business  on the day  before  the date on which the
first notice is given.

         When a determination  of shareholders  entitled to notice of or to vote
at any  meeting of  shareholders  has been  made,  such  determination  shall be
effective for any adjournment of the

                                       1

<PAGE>

meeting unless the Board of Directors fixes a new record date, which it shall do
if the  meeting is  adjourned  to a date more than 120 days after the date fixed
for the original meeting.

         1.5 Notice of Meetings.  Written notice stating the place, day and hour
of each meeting of shareholders  and, in case of a special meeting,  the purpose
or purposes  for which the  meeting is called,  shall be given not less than ten
nor more than 60 days  before the date of the meeting  (except  when a different
time is  required  in these  Bylaws  or by law)  either  personally  or by mail,
telephone,  telegraph,  teletype,  telecopy  or other  form of wire or  wireless
communication,  or by private courier, to each shareholder of record entitled to
vote at such meeting and to such  nonvoting  shareholders  as may be required by
law. If mailed,  such notice shall be deemed to be effective  when  deposited in
first class United States mail with postage  thereon  prepaid,  addressed to the
shareholder  at his  address as it appears  on the share  transfer  books of the
Corporation.  If given in any other  manner,  such notice  shall be deemed to be
effective  (i)  when  given  personally  or by  telephone,  (ii)  when  sent  by
telegraph, teletype, telecopy or other form of wire or wireless communication or
(iii) when given to a private courier to be delivered.

         If a meeting is adjourned to a different  date,  time or place,  notice
need not be given if the new date,  time or place is  announced  at the  meeting
before  adjournment.  However,  if a new record date for an adjourned meeting is
fixed,  notice of the adjourned meeting shall be given to shareholders as of the
new record date, unless a court provides otherwise.

         1.6 Waiver of Notice;  Attendance at Meeting.  A shareholder  may waive
any notice required by law, the Articles of Incorporation or these Bylaws before
or after the date and time of the meeting  that is the  subject of such  notice.
The waiver  shall be in writing,  be signed by the  shareholder  entitled to the
notice,  and be delivered to the Secretary of the  Corporation  for inclusion in
the minutes or filing with the corporate records.

                                       2

<PAGE>


         A shareholder's attendance at a meeting (i) waives objection to lack of
notice or  defective  notice  of the  meeting,  unless  the  shareholder  at the
beginning of the meeting objects to holding the meeting or transacting  business
at the  meeting,  and (ii) waives  objection  to  consideration  of a particular
matter at the meeting  that is not within the purpose or purposes  described  in
the meeting  notice,  unless the  shareholder  objects to considering the matter
when it is presented.

         1.7 Quorum and Voting Requirements. Unless otherwise required by law, a
majority of the votes  entitled to be cast on a matter  constitutes a quorum for
action on that matter. Once a share is represented for any purpose at a meeting,
it is deemed  present for quorum  purposes for the  remainder of the meeting and
for any  adjournment of that meeting unless a new record date is or shall be set
for that adjourned meeting. If a quorum exists,  action on a matter,  other than
the  election of  directors,  is approved if the votes cast  favoring the action
exceed  the  votes  cast  opposing  the  action,  unless  a  greater  number  of
affirmative votes is required by law.  Directors shall be elected by a plurality
of the votes cast by the shares entitled to vote in the election at a meeting at
which a quorum is present. Less than a quorum may adjourn a meeting.

         1.8 Action Without Meeting. Action required or permitted to be taken at
a meeting of the  shareholders may be taken without a meeting and without action
by the  Board of  Directors  if the  action  is  taken  by all the  shareholders
entitled to vote on the action.  The action  shall be  evidenced  by one or more
written consents describing the action taken, signed by all the shareholders and
delivered to the  Secretary of the  Corporation  for inclusion in the minutes or
filing with the corporate  records.  Action taken by unanimous  consent shall be
effective  according to its terms when all consents are in the possession of the
Corporation,  unless the consent specifies a different  effective date, in which
event the action  taken  shall be  effective  as of the date  specified  therein
provided that the consent  states the date of execution by each

                                       3

<PAGE>


shareholder.  A shareholder  may withdraw a consent only by delivering a written
notice of withdrawal to the Corporation  prior to the time that all consents are
in the possession of the Corporation.

         If not otherwise  fixed  pursuant to the provisions of Section 1.5, the
record date for  determining  shareholders  entitled  to take  action  without a
meeting is the date the first  shareholder  signs the consent  described  in the
preceding paragraph.

                                   ARTICLE II
                                    DIRECTORS

         2.1 General Powers.  The  Corporation  shall have a Board of Directors.
All  corporate  powers shall be exercised by or under the  authority of, and the
business and affairs of the  Corporation  managed  under the  direction  of, its
Board of  Directors,  subject to any  limitation  set forth in the  Articles  of
Incorporation.

         2.2  Number,  Term  and  Election.  The  number  of  directors  of  the
Corporation  shall be not less than one nor more than three.  This number may be
changed  from time to time by  amendment to these Bylaws to increase or decrease
by 30 percent or less the number of directors last elected by the  shareholders,
but only the  shareholders  may  increase or decrease the number by more than 30
percent.  No decrease in number shall have the effect of shortening  the term of
any  incumbent  director.  Each  director  shall  hold  office  until his death,
resignation, retirement or removal or until his successor is elected.

         Except as provided in Section 2.3 of this Article, the directors (other
than initial  directors) shall be elected by the holders of the Common Shares at
the annual meeting of  shareholders,  and those persons who receive the greatest
number of votes  shall be  deemed  elected  even  though  they do not  receive a
majority  of the  votes  cast.  No  individual  shall be named or  elected  as a
director without his prior consent.

                                       4

<PAGE>


         2.3  Removal;  Vacancies.  The  shareholders  may  remove  one or  more
directors,  with or  without  cause,  if the  number of votes cast to remove him
constitutes  a  majority  of the votes  entitled  to be cast at an  election  of
directors.  A  director  may be removed  by the  stockholders  only at a meeting
called for the  purpose of removing  him and the meeting  notice must state that
the purpose, or one of the purposes of the meeting, is removal of the director.

         A vacancy on the Board of Directors, including a vacancy resulting from
the  removal of a director or an  increase  in the number of  directors,  may be
filled  by (i) the  shareholders,  (ii) the  Board of  Directors,  or (iii)  the
affirmative  vote of a majority of the  remaining  directors  though less than a
quorum of the Board of  Directors,  and may, in the case of a  resignation  that
will become  effective at a specified  later date,  be filled before the vacancy
occurs but the new director may not take office until the vacancy occurs.

         2.4  Annual and  Regular  Meetings.  An annual  meeting of the Board of
Directors,   which  shall  be  considered  a  regular  meeting,  shall  be  held
immediately  following each annual meeting of  shareholders,  for the purpose of
electing  officers  and  carrying on such other  business as may  properly  come
before  the  meeting.  The  Board of  Directors  may also  adopt a  schedule  of
additional meetings which shall be considered regular meetings. Regular meetings
shall  be  held  at such  times  and at  such  places,  within  or  without  the
Commonwealth  of Virginia,  as the  President  or the Board of  Directors  shall
designate from time to time. If no place is designated,  regular  meetings shall
be held at the principal office of the Corporation.

         2.5 Special Meetings. Special meetings of the Board of Directors may be
called by the President or a majority of the directors of the  Corporation,  and
shall  be  held  at such  times  and at  such  places,  within  or  without  the
Commonwealth  of Virginia,  as the person or persons  calling

                                       5

<PAGE>

the meetings shall designate.  If no such place is designated in the notice of a
meeting, it shall be held at the principal office of the Corporation.

         2.6 Notice of Meetings.  No notice need be given of regular meetings of
the Board of  Directors.  Notices of special  meetings of the Board of Directors
shall be given to each  director  in person or  delivered  to his  residence  or
business  address (or such other place as he may have  directed in writing)  not
less  than  twenty-four  (24)  hours  before  the  meeting  by mail,  messenger,
telecopy,  telegraph,  or other means of written communication or by telephoning
such notice to him.  Any such  notice  shall set forth the time and place of the
meeting and state the purpose for which it is called.

         2.7 Waiver of Notice;  Attendance at Meeting.  A director may waive any
notice required by law, the Articles of Incorporation, or these Bylaws before or
after  the  date  and time  stated  in the  notice,  and  such  waiver  shall be
equivalent  to the  giving  of such  notice.  Except  as  provided  in the  next
paragraph  of this  section,  the  waiver  shall be in  writing,  signed  by the
director entitled to the notice and filed with the minutes or corporate records.

         A director's  attendance at or  participation  in a meeting  waives any
required  notice to him of the meeting  unless the director at the  beginning of
the  meeting or  promptly  upon his  arrival  objects to holding  the meeting or
transacting  business at the meeting and does not thereafter  vote for or assent
to action taken at the meeting.

         2.8  Quorum;  Voting.  A majority of the number of  directors  fixed in
these Bylaws  shall  constitute  a quorum for the  transaction  of business at a
meeting of the Board of Directors.  If a quorum is present when a vote is taken,
the  affirmative  vote of a majority of the directors  present is the act of the
Board of  Directors.  A  director  who is  present  at a meeting of the Board of
Directors  or a committee  of the Board of Directors  when  corporate  action is
taken is deemed to

                                       6

<PAGE>

have  assented to the action taken unless (i) he objects at the beginning of the
meeting,  or promptly upon his arrival,  to holding it or transacting  specified
business at the meeting;  or (ii) he votes against, or abstains from, the action
taken.

         2.9 Telephonic  Meetings.  The Board of Directors may permit any or all
directors  to  participate  in a regular or special  meeting  by, or conduct the
meeting  through the use of, any means of  communication  by which all directors
participating may simultaneously  hear each other during the meeting. A director
participating  in a meeting  by this  means is deemed to be present in person at
the meeting.

         2.10 Action Without  Meeting.  Action required or permitted to be taken
at a meeting  of the Board of  Directors  may be taken  without a meeting if the
action is taken by all members of the Board.  The action  shall be  evidenced by
one or more written consents  stating the action taken,  signed by each director
either  before or after the action  taken,  and included in the minutes or filed
with the corporate records reflecting the action taken.  Action taken under this
section shall be effective  when the last director  signs the consent unless the
consent specifies a different effective date, in which event the action taken is
effective as of the date specified  therein provided the consent states the date
of execution by each director.

         2.11  Compensation.  The Board of Directors may fix the compensation of
directors  and may provide for the payment of all  expenses  incurred by them in
attending meetings of the Board of Directors.

                                   ARTICLE III
                                    OFFICERS

         3.1 Officers. The officers of the Corporation shall be a President, and
a Secretary,  and, in the discretion of the Board of Directors, one or more Vice
Presidents  and such other  officers

                                       7

<PAGE>

as may be  deemed  necessary  or  advisable  to  carry  on the  business  of the
Corporation. Any two or more offices may be held by the same person.

         3.2 Election;  Term. Officers shall be elected at the annual meeting of
the Board of  Directors  and may be  elected  at such other time or times as the
Board of Directors  shall  determine.  They shall hold office,  unless  removed,
until  the next  annual  meeting  of the  Board  of  Directors  or  until  their
successors  are elected.  Any officer may resign at any time upon written notice
to the Board of Directors,  and such resignation  shall be effective when notice
is delivered unless the notice specifies a later effective date.

         3.3 Removal of Officers.  The Board of Directors may remove any officer
at any time, with or without cause.

         3.4 Duties of  Officers.  The  President  shall be the Chief  Executive
Officer of the Corporation. He and the other officers shall have such powers and
duties as generally  pertain to their respective  offices as well as such powers
and  duties  as may be  delegated  to them  from  time to time by the  Board  of
Directors.  The Chief Executive Officer, if he is present,  shall be chairman of
all  meetings of the  shareholders  and the Board of  Directors,  as well as any
committee of which he is a member.

                                   ARTICLE IV
                               SHARE CERTIFICATES

         4.1  Form.  Shares  of the  Corporation  shall,  when  fully  paid,  be
evidenced by certificates  containing such information as is required by law and
approved  by the  Board  of  Directors.  Certificates  shall  be  signed  by the
President  and the  Secretary  and may (but need not) be sealed with the seal of
the  Corporation.  The seal of the  Corporation  and any or all  signatures on a
share  certificate  may be  facsimile.  If any  officer  who has signed or whose
facsimile  signature has been placed upon a certificate  shall have ceased to be
such  officer  before  such  certificate  is  issued  it

                                       8

<PAGE>

may be issued by the Corporation with the same effect as if he were such officer
on the date of issue.

         4.2  Transfer.  The Board of Directors  may make rules and  regulations
concerning the issue, registration and transfer of certificates representing the
shares  of  the  Corporation.  Transfers  of  shares  and  of  the  certificates
representing  such  shares  shall be made upon the books of the  Corporation  by
surrender of the certificates  representing  such shares  accompanied by written
assignments given by the owners or their attorneys-in-fact.

         4.3 Restrictions on Transfer.  A lawful  restriction on the transfer or
registration of transfer of shares is valid and  enforceable  against the holder
or a transferee of the holder if the restriction  complies with the requirements
of law and its  existence  is noted  conspicuously  on the  front or back of the
certificate  representing  the  shares.  Unless  so noted a  restriction  is not
enforceable against a person without knowledge of the restriction.

         4.4 Lost or Destroyed Share  Certificates.  The Corporation may issue a
new share certificate in the place of any certificate  theretofore  issued which
is  alleged to have been lost or  destroyed  and may  require  the owner of such
certificate,  or his legal representative,  to give the Corporation a bond, with
or without surety, or such other agreement, undertaking or security as the Board
of Directors  shall  determine is  appropriate,  to  indemnify  the  Corporation
against any claim that may be made  against it on account of the alleged loss or
destruction or the issuance of any such new certificate.

                                    ARTICLE V
                            MISCELLANEOUS PROVISIONS

         5.1 Fiscal Year. The fiscal year of the Corporation shall be set by the
Board of Directors.

                                       9

<PAGE>

         5.2 Amendments. These Bylaws may be amended or repealed, and new Bylaws
may be made at any regular or special meeting of the Board of Directors.  Bylaws
made by the Board of Directors  may be repealed or changed and new Bylaws may be
made by the shareholders, and the shareholders may prescribe that any Bylaw made
by them shall not be altered, amended or repealed by the Board of Directors.






                                       10