Exhibit 24

POWERS OF ATTORNEY

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 25, 2007	/s/ PATRICK B. COLLINS
	Patrick B. Collins

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 21, 2007	/s/ JAMES R. CRANE
	James R. Crane

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 20, 2007	/s/ J. ROBERT DICKERSON
	J. Robert Dickerson

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 22, 2007	/s/ WALTER M. DUER
	Walter M. Duer

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 22, 2007	/s/ JAMES C. FLAGG
	James C. Flagg, Ph.D.

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 21, 2007	/s/ ALLAN W. FULKERSON
	Allan W. Fulkerson

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 21, 2007	/s/ JOHN N. MOLBECK, JR.
	John N. Molbeck, Jr.

POWER OF ATTORNEY

     Know all men by these presents, that the undersigned constitutes and appoints Frank J. Bramanti and Edward H. Ellis, Jr. and each of them, his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and in his name, place, and stead, in any and all capacities, to sign this Annual Report on Form 10-K and any and all amendments thereto, and to file same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

February 26, 2007	/s/ MICHAEL A. F. ROBERTS
	Michael A. F. Roberts