Document:

EX-10.6

                  MODIFICATION AGREEMENT (THERMODYNETICS, INC.)
                  ---------------------------------------------

         THIS MODIFICATION AGREEMENT (THERMODYNETICS,  INC.) (this "AGREEMENT"),
dated as of April 25, 2006, is by and among:

         CITIZENS BANK OF  MASSACHUSETTS,  a Massachusetts  state chartered bank
with offices at 53 State Street, Boston,  Massachusetts,  as successor by merger
to USTrust (the "BANK");

         THERMODYNETICS,  INC., a Delaware  corporation having a principal place
of business at 651 Day Hill Road, Windsor, Connecticut 06095 (the "BORROWER");

         TURBOTEC PRODUCTS,  INC., a Connecticut  corporation having a principal
place of business at 651 Day Hill Road, Windsor, Connecticut ("TURBOTEC"); and

         VULCAN  INDUSTRIES,  INC.,  a Michigan  corporation  having a principal
place of  business  at of 1301  West  Dresser  Drive,  Sturgis,  Michigan  49091
("VULCAN" and collectively with Turbotec, the "GUARANTOR").

                              W I T N E S S E T H:
                              --------------------

         WHEREAS,   the  Bank  has  entered  into   certain  loan   arrangements
(collectively,   the  "LOAN   ARRANGEMENTS")  with  the  Borrower,   which  Loan
Arrangements  are  evidenced  by,  among  other  things,  each of the  following
documents, instruments and agreements:

         (a)      Security Agreement (Inventory,  Accounts,  Equipment and other
                  Personal Property) (the "SECURITY  AGREEMENT") dated September
                  4, 1992 between the Borrower and the Bank;

         (b)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "1999  ELOC") dated June 25, 1999 between the Borrower and the
                  Bank,  as  amended  by that  certain  Letter  Agreement  dated
                  September  29, 2000 and that certain  Letter  Agreement  dated
                  November 28, 2000;

         (c)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2001 ELOC")  dated  November 1, 2001 between the Borrower and
                  the Bank, as amended by that certain  Letter  Agreement  dated
                  January 23, 2002;

         (d)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2003 ELOC")  dated  January 14, 2003 between the Borrower and
                  the Bank, as amended by that certain  letter  agreement  dated
                  December 15, 2003;

         (e)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2004 ELOC")  dated  October 20, 2004 between the Borrower and
                  the Bank;

         (f)      Secured  Term Note (the "2002  NOTE")  dated  January 23, 2002
                  made by the  Borrower  payable  to the  Bank  in the  original
                  principal amount of $700,000.00;

<PAGE>

         (g)      Secured Term Note (the "REAL ESTATE  NOTE") dated  January 23,
                  2002 made by the Borrower  payable to the Bank in the original
                  principal amount of $2,025,000.00;

         (h)      Commercial  Promissory  Note  (the  "COMMERCIAL  NOTE")  dated
                  November 10, 2005 made by the Borrower and Turbotec payable to
                  the Bank in the original principal amount of $183,000.00;

         (i)      Open-End  Mortgage  (the  "MORTGAGE")  dated  January 23, 2002
                  granted by the  Borrower to the Bank and  encumbering  certain
                  property located on 651 Dayhill Road, Windsor, Connecticut, as
                  amended by that certain  Amendment to and Confirmation of Open
                  End Mortgage dated November 10, 2005; and

         (j)      Multi-Entity  Guaranty  (Unlimited)  dated  July 30,  2003 (as
                  amended  from  time to time  and in  effect,  the  "GUARANTY")
                  executed and delivered by each of the Borrower,  Turbortec and
                  Vulcan,  pursuant to which the Borrower,  Turbortec and Vulcan
                  each unconditionally guaranteed the payment and performance of
                  each  others'  obligations  to the Bank,  as  ratified by that
                  certain Ratification of Guaranty dated November 10, 2005.

         Hereinafter,   the  foregoing  documents,   instruments  and  agreement
         referred  to in items (a) through  (i) above,  together  with all other
         documents,   instruments   and  agreements   which  evidence  the  Loan
         Arrangements,  including without limitation,  this Agreement,  shall be
         referred to collectively  as the "LOAN  DOCUMENTS"  (Capitalized  terms
         used herein and not oterhwise defined herein shall have the meanings as
         in the Loan  Documents).  Hereinafter the 1999 ELOC, the 2001 ELOC, the
         2003 ELOC, and the 2004 ELOC shall be  collectively  referred to as the
         "ELOC NOTES".

         WHEREAS,  the Borrower has  informed the Bank that  Turbotec  Products,
Plc,  a  subsidiary  of the  Borrower,  intends  to  conduct  a public  offering
(hereinafter, the "OFFERING") of its stock. In connection with the Offering, the
Borrower  intends  to sell a certain  amount  of the  stock it owns in  Turbotec
Products,  Plc and has requested that, in connection  therewith,  the Bank amend
certain terms and conditions of the Loan Documents; and

         WHEREAS,  the  Bank has  agreed  to do so,  subject  to the  terms  and
conditions set forth in this Agreement.

         NOW THEREFORE, in consideration of the mutual conditions and agreements
set forth in the Loan Documents and this Agreement,  and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto hereby agree as follows:

1.       ACKNOWLEDGMENT  OF OBLIGATIONS.  The Borrower hereby  acknowledges  and
         agrees that,  in accordance  with the terms and  conditions of the Loan
         Documents,  the Borrower is  unconditionally  liable to the Bank, as of
         April 25, 2006, in the following aggregate amounts:

<PAGE>

         (a)      ELOC Notes:

                           Principal: $461,326.18

         (b)      2002 Note:

                           Principal $104,983.00

         (c)      Real Estate Note:

                           Principal $1,594,687.50

         (d)      Commercial Note:

                           Principal $172,105.00

         (e)      Letters of Credit (aggregate face amount): $0.00

         (f)      For all amounts now or hereafter due pursuant to the Guaranty.

         (g)      In addition,  the  Borrower is and shall remain  liable to the
                  Bank for all accrued and unpaid interest as of April 25, 2006,
                  and all interest,  reasonable fees, costs, expenses, and costs
                  of  collection   (including  reasonable  attorneys'  fees  and
                  expenses)  heretofore or hereafter incurred in connection with
                  the  Loan  Documents,   including,   without  limitation,  all
                  reasonable attorney's fees and expenses incurred in connection
                  with the negotiation and preparation of this Agreement and all
                  documents, instruments, and agreements incidental hereto.

         (h)      Hereinafter  all amounts  due as set forth in this  Section 1,
                  and all amounts  payable  under the Loan  Documents,  shall be
                  referred to collectively as the "OBLIGATIONS".

2.       RATIFICATION OF LOAN DOCUMENTS; FURTHER ASSURANCES. The Borrower:

         (a)      Hereby  ratifies,  confirms,  and  reaffirms all the terms and
                  conditions  of  the  Loan  Documents.   The  Borrower  further
                  acknowledges  and agrees that except as specifically  modified
                  by this  Agreement,  all  terms  and  conditions  of the  Loan
                  Documents shall remain in full force and effect;

         (b)      Shall  cooperate  with the Bank and execute and deliver to the
                  Bank such further  instruments and documents as the Bank shall
                  reasonably  request  from  time to time  to  carry  out to its
                  satisfaction the  transactions  contemplated by this Agreement
                  and the Loan Documents.

3.       CONDITIONS  PRECEDENT.  This Agreement shall not become effective until
         the following  conditions  have been satisfied (or waived in writing by
         the  Bank),  all as  determined  by the Bank in its sole and  exclusive
         discretion:

         (a)      This Agreement, and all documents,  instruments and agreements
                  required  hereunder or related hereto shall have been executed
                  by the appropriate parties

<PAGE>

                  and original counterpart  signatures shall have been delivered
                  to the Bank (or its counsel).

         (b)      All  actions  on the part of the  Borrower  necessary  for the
                  valid execution, delivery and performance of the terms of this
                  Agreement  shall  have  been  duly and  effectively  taken and
                  evidence  thereof  satisfactory  to the Bank  shall  have been
                  provided to the Bank.

         (c)      The  Borrower  and  the  Turbotec   shall  have  executed  and
                  delivered to the Bank an Assignment and  Assumption  Agreement
                  with  regard  to the ELOC  Notes  and the 2002  Note in a form
                  attached hereto as EXHIBIT "A".

         (d)      The Borrower  shall have executed and delivered to the Bank an
                  Pledge  Agreement in connection with the pledge of $337,000.00
                  to  support  anticipated  debt  service  shortfalls  in a form
                  attached hereto as EXHIBIT "B".

         (e)      The Borrower  shall have caused all  obligations of Vulcan due
                  and owing,  (excluding the  indebtedness of Vulcan pursuant to
                  the   Guaranty)  to  the  Bank  as  referenced  in  a  certain
                  Modification  Agreement  dated  November 10, 2005 by and among
                  Vulcan, the Borrower and Turbotec to be paid in full.

         (f)      The Borrower shall have delivered to the Bank an executed copy
                  of the  "Commercial  Lease"  between the Borrower and Turbotec
                  acceptable to the Bank and its counsel in connection  with the
                  property located at 651 Dayhill Road, Windsor, Connecticut. In
                  connection  therewith,  the Borrower  shall have  executed and
                  delivered  to the Bank a  Landlord  Waiver in a form  attached
                  hereto as EXHIBIT "C".

4.       PAYMENT IN REDUCTION OF OBLIGATIONS.  The Borrower hereby covenants and
         agrees that upon  consummation of the Offering,  the Borrower shall pay
         to the Bank, in good and collected  funds,  a minimum of $625,000.00 to
         be applied by the Bank in  reduction of the  Obligations  in any manner
         the Bank deems appropriate in its sole and exclusive discretion.

5.       PAYDOWN OF COMMERCIAL  NOTE. The Borrower  hereby  covenants and agrees
         that upon  consummation of the Offering,  the Borrower shall pay to the
         Bank, in good and collected  funds,  an amount to cause the obligations
         under the  Commercial  Note to have a principal  balance of not greater
         than $37,000.00 (the "REMAINING OBLIGATIONS").  The Bank hereby agrees,
         that the Remaining  Obligations  shall be paid in  accordance  with the
         terms and conditions of the Commercial Note.

6.       AMENDMENTS  TO THE  LOAN  DOCUMENTS.  From and  after  the date of this
         Agreement,  and  satisfaction  of all the  conditions  precedent to the
         effectiveness of this Agreement as described herein, the Loan Documents
         shall be amended as follows:

         (a)      The Real Estate Note shall be amended as follows:

<PAGE>

                  (i)      Paragraphs  three  (3)  through  six (6)  are  hereby
                           deleted  in  their   entirety,   and  the   following
                           paragraph shall be inserted in its place:

                           "IN  THE  EVENT  OF  PREPAYMENT  OF  THE   BORROWER'S
                           OBLIGATIONS UNDER THIS SECURED TERM NOTE TO THE BANK,
                           EITHER  AT THE  BORROWER'S  INITIATIVE  OR  UPON  THE
                           EXERCISE  BY THE BANK OF ITS  RIGHTS  IN THE EVENT OF
                           THE   BORROWER'S   DEFAULT,   OTHER  THEN   FINANCING
                           FURNISHED BY THE BANK,  THE BORROWER  AGREES TO PAY A
                           PREPAYMENT  FEE IN THE  AMOUNT  EQUAL TO ONE  PERCENT
                           (1%) OF THE  PRINCIPAL  BALANCE  WHICH  IS SO PAID OR
                           PAYABLE PRIOR TO JANUARY 1, 2007."

                  (ii)     Paragraph   eight  (8)  is  hereby   deleted  in  its
                           entirety.

         (b)      Section  2.01 of the  Security  Agreement  shall be amended to
                  read as follows:

                           "LIABILITIES  SHALL  MEAN  ANY AND  ALL  LIABILITIES,
                           DEBTS, AND OBLIGATIONS OF THE BORROWER TO THE SECURED
                           PARTY,  WHETHER  OR NOT ANY OF SUCH  ARE  LIQUIDATED,
                           UNLIQUIDATED, PRIMARY, SECONDARY, SECURED, UNSECURED,
                           DIRECT,  INDIRECT,  ABSOLUTE,  CONTINGENT,  OR OF ANY
                           OTHER TYPE,  NATURE, OR DESCRIPTION,  OR BY REASON OF
                           ANY CAUSE OF ACTION WHICH THE SECURED  PARTY MAY HOLD
                           AGAINST  THE   BORROWER,   WHETHER  NOW  EXISTING  OR
                           HEREAFTER ARISING, INCLUDING, WITHOUT LIMITATION, ALL
                           LIABILITIES  AND  OBLIGATIONS  OF BORROWER TO SECURED
                           PARTY   PURSUANT  TO  (I)  THAT  CERTAIN   COMMERCIAL
                           PROMISSORY  NOTE DATED  NOVEMBER 10, 2005 MADE BY THE
                           BORROWER PAYABLE THAT CERTAIN TO THE SECURED PARTY IN
                           THE ORIGINAL  PRINCIPAL  AMOUNT OF  $183,000.00;  AND
                           (II) THAT CERTAIN SECURED TERM NOTE DATED JANUARY 23,
                           2002  MADE BY THE  BORROWER  PAYABLE  TO THE  SECURED
                           PARTY   IN   THE   ORIGINAL   PRINCIPAL   AMOUNT   OF
                           $2,025,000.00."

7.       RELEASE OF MULTI-ENTITY GUARANTY  (UNLIMITED).  From and after the date
         of this Agreement,  and satisfaction of all the conditions precedent to
         the effectiveness of this Agreement as described  herein,  the Borrower
         and  Turbotec  are  hereby   released  from  all  its  liabilities  and
         obligations under the Guaranty. In connection therewith,  Vulcan hereby
         ratifies,  confirms and reaffirms,  all and singular, each of the terms
         and  conditions  of  the  Guaranty  and  each  of  the  warranties  and
         representations  made in the  Guaranty,  and confirms and reaffirms the
         indebtedness represented by the Guaranty, and that the Guaranty remains
         in full force and  effect.  Furthermore,  Vulcan  hereby  acknowledges,
         confirms  and agrees  that,  in addition to all other  Obligations  (as
         defined in the Guaranty)  guaranteed by the undersigned pursuant to the
         Guaranty,  the Guaranty expressly  includes,  without  limitation,  all
         liabilities and obligations arising under the $183M Note, together with
         any  future  modifications,   amendments,   substitutions  or  renewals
         thereof.

8.       AMENDMENTS  TO  COLLATERAL;  SUPPLEMENTAL  GRANT OF SECURITY  INTEREST.
         Notwithstanding any terms of the Security Agreement or any of the other
         Loan  Documents to the  contrary,  the Borrower  hereby  covenants  and
         agrees as follows:

         (a)      The  security  interests  and liens  granted  by the  Borrower
                  pursuant to the Security  Agreement  and any other of the Loan
                  Documents  shall  secure all of the  Obligations,  whether now
                  existing or hereafter incurred.

<PAGE>

         (b)      The term "Uniform Commercial Code" shall be deemed to mean and
                  refer to the "Uniform Commercial Code as may be amended and in
                  effect from time to time".

         (c)      The collateral granted to the Bank by the Borrower pursuant to
                  Section 1 of the Security Agreement is intended to include all
                  assets of the Borrower.  In order to secure the prompt payment
                  and performance of any and all Obligations  (whether now owing
                  or  hereafter  incurred)  of the  Borrower  to the  Bank,  the
                  Borrower  hereby  grants (and confirms and reaffirms all prior
                  grants) to the Bank, a continuing  security interest in and to
                  all "Collateral" which term includes,  without limitation, and
                  in  addition  to all  collateral  set  forth  in the  Security
                  Agreement,  the  following  categories of assets as defined in
                  the  Uniform  Commercial  Code:  goods  (including  inventory,
                  equipment and any accessions thereto),  instruments (including
                  promissory    notes),    documents,     accounts    (including
                  health-care-insurance  receivables, and license fees), chattel
                  paper  (whether  tangible or  electronic),  deposit  accounts,
                  letter-of-credit  rights  (whether or not the letter of credit
                  is evidenced by a writing), commercial tort claims, securities
                  and  all  other  investment   property,   general  intangibles
                  (including  payment  intangibles  and  software),   supporting
                  obligations and any and all proceeds of any thereof,  wherever
                  located,  whether now owned, or now due, in which the Borrower
                  has an interest or the power to transfer rights,  or hereafter
                  acquired,  arising, or to become due, or in which the Borrower
                  obtains an  interest,  or the power to  transfer  rights.  The
                  Borrower acknowledges and agrees that the foregoing grant of a
                  security  interest is in addition to, and is supplemental  of,
                  all other security  interests and liens previously  granted to
                  the Bank by the Borrower.

         (d)      The Borrower  hereby:  ratifies,  confirms and  reaffirms  the
                  effectiveness  of any previously  filed financing  statements,
                  and  authorizes the Bank (and any agent or  representative  of
                  the Bank) to prepare and file such financing  statements (and,
                  if appropriate,  amendments to existing financing  statements)
                  as the Bank may deem  necessary or  appropriate  to perfect or
                  protect its  interests  in the  Collateral  granted  under the
                  terms of the Security Agreement, this Agreement, or any of the
                  other Loan Documents, including, without limitation, financing
                  statements  which describe the  Collateral  with generic terms
                  such as "all assets" and/or "all personal  property" (or words
                  of similar import) of the Borrower.

9.       ADDITIONAL  OPERATING  ACCOUNT.  Upon the consummation of the Offering,
         and upon the Borrower's satisfaction of all the conditions precedent to
         the  effectiveness of this Agreement,  as determined by the Bank in the
         Bank's  sole and  exclusive  discretion,  the  Borrower  shall  deposit
         certain funds into an operating account (the "OPERATING ACCOUNT") to be
         maintained  by  the  Bank.  The  Operating  Account  shall  secure  all
         Obligations of the Borrower to the Bank.  Prior to the occurrence of an
         Event of Default,  the  Borrower  shall use the funds in the  Operating
         Account as it determines in its  discretion.  Upon the occurrence of an
         Event of Default, the Bank may use any remaining funds in the Operating
         Account to reduce the  Obligations  in manner  determined in the Bank's
         sole and exclusive discretion.

<PAGE>

10.      FEES AND EXPENSES.

         (a)      Upon  execution of this  Agreement,  the Borrower shall pay to
                  the  Bank an  amount  equal to any and all  reasonable  costs,
                  fees,  or expenses  (including  attorneys'  fees and expenses)
                  incurred by the Bank in  connection  with the Loan  Documents,
                  whether directly or indirectly, including (but not limited to)
                  all reasonable legal fees and expenses  incurred in connection
                  with the  negotiation  and the  preparation of this Agreement.
                  From and after the execution of this  Agreement,  the Borrower
                  shall pay all of such costs,  fees and expenses to the Bank on
                  demand.

         (b)      The Borrower  hereby  covenants and agrees that the Bank shall
                  be  entitled  (but  not  required)  to  debit  or  charge  any
                  operating  account of the Borrower to collect any fees,  costs
                  or expenses to which the Bank may be entitled pursuant to this
                  Agreement  or any of the other  Loan  Documents,  all  without
                  prior notice to the Borrower.

11.      WAIVERS.

         (a)      JURY TRIAL. The Borrower makes the following waiver knowingly,
                  voluntarily, and intentionally,  and understand that the Bank,
                  in  entering  into this  Agreement,  is relying  thereon.  THE
                  BORROWER,  TO THE EXTENT OTHERWISE  ENTITLED  THERETO,  HEREBY
                  IRREVOCABLY WAIVES ANY PRESENT OR FUTURE RIGHT OF THE BORROWER
                  TO A JURY IN ANY TRIAL OF ANY CASE OR CONTROVERSY IN WHICH THE
                  BANK IS OR BECOMES A PARTY  (WHETHER SUCH CASE OR  CONTROVERSY
                  IS  INITIATED  BY OR AGAINST  THE BANK OR IN WHICH THE BANK IS
                  JOINED AS A PARTY LITIGANT),  WHICH CASE OR CONTROVERSY ARISES
                  OUT OF, OR IS IN RESPECT  OF,  ANY  RELATIONSHIP  BETWEEN  THE
                  BORROWER, OR ANY SUCH PERSON AND THE BANK.

         (b)      WAIVER OF CLAIMS. The Borrower hereby  acknowledges and agrees
                  that it does  not  have  any  offsets,  defenses,  claims,  or
                  counterclaims  against the Bank, or any of its affiliates,  or
                  their respective officers, directors,  employees,  affiliates,
                  attorneys,  representatives,   predecessors,   successors,  or
                  assigns with respect to the Loan Documents,  the  Obligations,
                  or  otherwise,  and that if the  Borrower now had, or ever did
                  have, any such offsets,  defenses,  claims,  or  counterclaims
                  against  the  Bank,  or  any  of  its  affiliates,   or  their
                  respective   officers,   directors,   employees,   affiliates,
                  attorneys,  representatives,   predecessors,   successors,  or
                  assigns,  whether known or unknown,  at law or in equity, from
                  the  beginning of the world  through this date and through the
                  time of  execution of this  Agreement,  all of them are hereby
                  expressly  WAIVED,  and the Borrower hereby RELEASES the Bank,
                  its  affiliates,  and their  respective  officers,  directors,
                  employees,     affiliates,     attorneys,     representatives,
                  predecessors,  successors,  and  assigns  from  any  liability
                  therefore.

<PAGE>

12.      REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby  represents and
         warrants to the Bank as follows:

         (a)      The Loan Documents, as amended hereby, constitute legal, valid
                  and  binding  obligations  of  the  Borrower,  enforceable  in
                  accordance with their respective terms.

         (b)      No approval or consent of, or filing  with,  any  governmental
                  agency or  authority  is  required  to make valid and  legally
                  binding the execution, delivery or performance by the Borrower
                  of this Agreement or the Loan Documents as amended hereby.

         (c)      The  representations  and  warranties  contained  in the  Loan
                  Documents  are true and correct at and as of the date made and
                  as of the  date  hereof,  except  to  the  extent  of  changes
                  resulting  from  transactions   specifically  contemplated  or
                  specifically  permitted by the Loan  Documents,  changes which
                  have been  disclosed  in writing to the Bank prior to the date
                  hereof  and  changes  occurring  in  the  ordinary  course  of
                  business that singly or in the  aggregate  are not  materially
                  adverse,  and to the  extent  that  such  representations  and
                  warranties relate expressly to an earlier date.

         (d)      After giving effect to this Agreement,  the Borrower will have
                  performed and complied in all material respects with all terms
                  and conditions of the Loan Documents  required to be performed
                  or complied with by them prior to or at the time hereof.

13.      NOTICES.  Any  communication  between  the Bank and  Borrower  shall be
         forwarded  via  certified  mail,  return  receipt  requested,   or  via
         recognized overnight courier, addressed as follows:

         If to the Bank:            Citizens Bank of Massachusetts
                                    53 State Street
                                    Boston, Massachusetts 02109
                                    Attention: James Herzog, Vice President

                  With a copy via telecopier to:

                                    Robert E. Paul, Esquire
                                    Riemer & Braunstein LLP
                                    Three Center Plaza
                                    Boston, Massachusetts 02108
                                    Telecopier No. (617) 880-3456

         If to the Borrower:        Thermodynetics, Inc.
                                    651 Day Hill Road
                                    Windsor, Connecticut 06095
                                    Attention: Robert I. Lieberman, President

<PAGE>

                  With a copy via telecopier to:

                                    Kenneth B. Lerman, Esquire
                                    Kenneth B. Lerman, P.C.
                                    Attorney at Law
                                    651 Day Hill Road
                                    Windsor, Connecticut 06095
                                    Telecopier No. (860) 285-0139

14.      GENERAL.

         (a)      This  Agreement  shall be binding  upon the  Borrower  and its
                  respective  successors  and  assigns  and  shall  inure to the
                  benefit of the Bank and its successors and assigns.

         (b)      Any determination  that any provision of this Agreement or any
                  application  thereof is invalid,  illegal, or unenforceable in
                  any  respect in any  instance  shall not affect the  validity,
                  legality,  or  enforceability  of such  provision in any other
                  instance, or the validity,  legality, or enforceability of any
                  other provision of this Agreement.

         (c)      This Agreement, together with the agreements,  instruments and
                  other documents executed in connection herewith,  incorporates
                  all  discussions and  negotiations  among the Borrower and the
                  Bank,  either  express  or  implied,  concerning  the  matters
                  included  herein and in such other  instruments,  any  custom,
                  usage, or course of dealings to the contrary  notwithstanding.
                  No such discussions, negotiations, custom, usage, or course of
                  dealings  shall  limit,   modify,   or  otherwise  affect  the
                  provisions hereof.

         (d)      It is declared  and agreed by each of the parties  hereto that
                  the Loan Documents,  as amended hereby, shall continue in full
                  force and effect.  The Borrower  shall continue to comply with
                  all of the  terms and  conditions  of the Loan  Documents,  as
                  modified hereby.

         (e)      All rights and  obligations  hereunder,  including  matters of
                  construction,  validity, and performance, shall be governed by
                  and construed in accordance  with the law of the  Commonwealth
                  of  Massachusetts  and are  intended  to take effect as sealed
                  instruments.

         (f)      The captions of this  Agreement are for  convenience  purposes
                  only,  and shall not be used in  construing  the intent of the
                  parties hereto.

         (g)      In the event of any  inconsistency  between the  provisions of
                  this  Agreement  and the other  Loan  Documents  (or any other
                  documents,  instruments  and agreements  which may evidence or
                  relate  to the  Loan  Arrangements),  the  provisions  of this
                  Agreement shall govern and control.

         (h)      This Agreement may be executed in several  counterparts and by
                  each  party on a separate  counterpart,  each of which when so
                  executed and delivered shall be an original,  and all of which
                  together shall constitute one instrument.

                            [Signature Page Follows]

<PAGE>

         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this  Agreement  to be duly  executed  and  delivered as of the date and year
first above written.

                                     "BORROWER"

                                     THERMODYNETICS, INC.

                                     By:_______________________________
                                     Name:
                                     Title:

                                     "BANK"

                                     CITIZENS BANK OF MASSACHUSETTS

                                     By:    ________________________________
                                     Name:  James Herzog
                                     Title: Vice President

                                     ACKNOWLEDGED AND AGREED:

                                     TURBOTEC PRODUCTS, INC.

                                     By:    _______________________________
                                     Name:
                                     Title:

                                     VULCAN INDUSTRIES, INC.

                                     By:_______________________________
                                     Name:
                                     Title:

                    Signature Page to Modification Agreement

<PAGE>

                                    Exhibit A
                                    ---------

<PAGE>

                                    Exhibit B
                                    ---------

<PAGE>

                                    Exhibit CEX-10.7

                       ASSIGNMENT AND ASSUMPTION AGREEMENT
                       -----------------------------------

         This ASSIGNMENT AND ASSUMPTION AGREEMENT (this "AGREEMENT") is made and
entered into as of the 25th day of April, 2006, by and among:

         CITIZENS BANK OF MASSACHUSETTS, a Massachusetts state chartered bank
with offices at 53 State Street, Boston, Massachusetts, as successor by merger
to USTrust (the "BANK");

         TURBOTEC PRODUCTS,  INC., a Connecticut  corporation having a principal
place of business at 651 Day Hill Road,  Windsor,  Connecticut (the "TURBOTEC");
and

         THERMODYNETICS,  INC., a Delaware  corporation having a principal place
of business at 651 Day Hill Road, Windsor, Connecticut 06095 ("THERMO").

                              W I T N E S S E T H:
                              --------------------

         WHEREAS, the Bank has entered into certain loan arrangements
(collectively, the "LOAN ARRANGEMENTS") with the Thermo, which Loan Arrangements
are evidenced by, among other documents, instruments and agreements, the
following:

         (a)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "1999 ELOC") dated June 25, 1999 between Thermo and the Bank,
                  as amended by that certain Letter Agreement dated September
                  29, 2000 and that certain Letter Agreement dated November 28,
                  2000;

         (b)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2001 ELOC") dated November 1, 2001 between Thermo and the
                  Bank, as amended by that certain Letter Agreement dated
                  January 23, 2002;

         (c)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2003 ELOC") dated January 14, 2003 between Thermo and the
                  Bank, as amended by that certain letter agreement dated
                  December 15, 2003;

         (d)      Line of Credit Agreement for the Acquisition of Equipment (the
                  "2004 ELOC") dated October 20, 2004 between Thermo and the
                  Bank; and

         (e)      Secured Term Note dated January 23, 2002 (the "TERM NOTE")
                  made by Thermo payable to the Bank in the original principal
                  amount of $700,000.00.

         Hereinafter, the foregoing documents, instruments and agreement
         referred to in items (a) through (e) above, together with all other
         documents, instruments and agreements which evidence the Loan
         Arrangements, including without limitation, this Agreement, shall be
         referred to collectively as the "LOAN DOCUMENTS"). Hereinafter the 1999
         ELOC, the 2001 ELOC, the 2003 ELOC, and the 2004 ELOC shall be
         collectively referred to as the "ELOC NOTES".

                                   Page 1 of 5

<PAGE>

         WHEREAS, Thermo and Turbotec have informed the Bank that a subsidiary
Thermo intends to conduct a public offering (hereinafter, the "OFFERING") of its
stock and has requested that, in connection therewith, the Bank consent to
Turbotec's assumption of certain obligations of Thermo to the Bank; and

         WHEREAS, Turbotec has determined that it is in its best interest to
assume and repay certain obligations of the Thermo under the Loan Documents to
the Bank; and

         WHEREAS, the Bank is willing to consent to the assumption of the
obligations of Thermo by Turbotec, but only in accordance with the terms and
conditions set forth herein;

         NOW, THEREFORE, in consideration of the mutual conditions and
agreements set forth in the Loan Documents and this Agreement, and other good
and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto hereby agree as follows:

1.       ACKNOWLEDGMENT OF INDEBTEDNESS. Turbotec hereby acknowledge and agree
         that, in accordance with the terms and conditions of the Loan
         Documents, Turbotec shall be liable as of the date of execution of this
         Agreement, to the Bank as follows:

         (a) ELOC Notes:

                  i.       Principal: $461,326.18

         (b) Term Note:

                  i.       Principal $104,983.00

         (c)      In addition, the Borrower is and shall remain liable to the
                  Bank for all accrued and unpaid interest as of April 25, 2006,
                  and all interest, reasonable fees, costs, expenses, and costs
                  of collection (including reasonable attorneys' fees and
                  expenses) heretofore or hereafter incurred in connection with
                  the Loan Documents, including, without limitation, all
                  reasonable attorney's fees and expenses incurred in connection
                  with the negotiation and preparation of this Agreement and all
                  documents, instruments, and agreements incidental hereto.

2.       ASSUMPTION OF THE OBLIGATIONS. Turbotec hereby assumes the payment and
         performance of the obligations and liabilities of Thermo under the Loan
         Documents, including, without limitation, the repayment of the
         principal and interest due under the ELOC Notes and the Term Note, as
         if Turbotec were the borrower thereunder. Turbotec hereby agrees to
         comply with all of the terms and conditions of the Loan Documents, and
         further agrees that in all respects, the terms "BORROWER" in the Loan
         Documents shall mean and refer to Turbotec as fully and as effectually
         as if Turbotec was named "BORROWER" therein. The parties hereto
         acknowledge that this transaction is in the nature of an assumption.

                                  Page 2 of 5
<PAGE>

3.       RELEASE OF THERMO. The parties hereto acknowledge and agree that Thermo
         shall be released from all obligations and liabilities under the Loan
         Documents, including, without limitation, the repayment of the
         principal and interest due under the ELOC Notes and the Term Note.

4.       RELEASE OF TURBOTEC. The parties hereto acknowledge and agree that
         Turbotec shall be released from all obligations and liabilities under
         the Commercial Note.

5.       ACKNOWLEDGEMENT OF THERMO'S OBLIGATIONS. The parties hereto acknowledge
         and agree that Turbotec is not assuming any obligations of Thermo
         pursuant to the following documents, instruments and agreements:

         (d)      Security Agreement (Inventory, Accounts, Equipment and other
                  Personal Property) dated September 4, 1992 between Thermo and
                  the Bank;

         (e)      Secured Term Note dated January 23, 2002 made by Thermo
                  payable to the Bank in the original principal amount of
                  $2,025,000.00;

         (f)      Commercial Promissory Note dated November 10, 2005 made by
                  Thermo and Turbotec payable to the Bank in the original
                  principal amount of $183,000.00; and

         (g)      Open-End Mortgage dated January 23, 2002 granted by Thermo to
                  the Bank and encumbering certain property located on 651
                  Dayhill Road, Windsor, Connecticut, as amended by that certain
                  Amendment to and Confirmation of Open End Mortgage dated
                  November 10, 2005.

6.       FURTHER ASSURANCES. At the request of the Bank, Turbotec agrees to
         endorse the ELOC Notes and the Commercial Note and to execute and
         deliver, or cause to be executed and delivered, all other documentation
         as the Bank shall reasonably require to effectuate the provisions
         hereof.

7.       RATIFICATION OF LOAN DOCUMENTS. Turbotec hereby ratifies and confirms
         all and singular the terms and conditions of the Loan Documents,
         including, without limitation, the terms and conditions of the ELOC
         Notes and the Term Note, and each acknowledges, confirms, and agrees
         that, except as specifically modified herein, the ELOC Notes and the
         Term Note, and all of the terms and conditions of the Loan Documents
         shall remain in full force and effect as originally written and
         Turbotec hereby ratify and confirm all terms and conditions thereof.

8.       WAIVER OF CLAIMS. Turbotec and Thermo each hereby acknowledge and agree
         that they have no offsets, defenses, claims, or counterclaims against
         the Bank with respect to the Loan Documents or otherwise and that, to
         the extent that each of Turbotec and Thermo has or ever had any such
         offsets, defenses, claims, or counterclaims, Turbotec and Thermo each
         hereby specifically WAIVES AND RELEASES any and all rights to such
         offsets, defenses, or counterclaims.

                                  Page 3 of 5
<PAGE>

7.       MISCELLANEOUS.

         (a)      This Agreement may be executed in several counterparts and by
                  each party on a separate counterpart, each of which when so
                  executed and delivered shall be an original, and all of which
                  together shall constitute one instrument.

         (b)      This Agreement expresses the entire understanding of the
                  parties with respect to the transactions contemplated hereby.
                  No prior negotiations or discussions shall limit, modify, or
                  otherwise affect the provisions hereof.

         (c)      Any determination that any provision of this Agreement or any
                  application hereof is invalid, illegal or unenforceable in any
                  respect and in any instance shall not effect the validity,
                  legality, or enforceability of such provision in any other
                  instance, or the validity, legality or enforceability of any
                  other provisions of this Agreement.

         (d)      Turbotec is liable for and shall pay on demand all costs and
                  expenses of the Bank previously incurred, or to be incurred,
                  including, without limitation, attorneys' fees and costs in
                  connection with the preparation, negotiation, execution and
                  delivery of this Agreement.

         (e)      This Agreement shall be construed in accordance with and
                  governed by the laws of the Commonwealth of Massachusetts and
                  shall take effect as a sealed instrument.

         (f)      This Agreement shall be deemed to be a Loan Document.

                            {Signature Page Follows]

                                  Page 4 of 5
<PAGE>

         IN WITNESS WHEREOF, the parties have caused this Assumption Agreement
to be executed as of the 25th day of April, 2006.

                                     TURBOTEC PRODUCTS, INC.

                                     By:______/s/_________________________
                                     Name:
                                     Title:

                                     THERMODYNETICS, INC.

                                     By:    ____/s/___________________________
                                     Name:
                                     Title:

                                     CITIZENS BANK OF MASSACHUSETTS

                                     By:    _____/s/__________________________
                                     Name:  James Herzog
                                     Title: Vice President

                                  Page 5 of 5

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