Thermal modification of collagen under biaxial isotonic loads /
There continues to be an ever-growing interest in the clinical use of thermal energy to treat a wide variety of diseases and injuries. Such usage is driven largely by technological advances in the design of the heat-delivery devices, not by a fundamental understanding of the underlying biothermomec...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765069701&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | There continues to be an ever-growing interest in the clinical use of thermal energy to treat a wide variety of diseases and injuries. Such usage is driven largely by technological advances in the design of the heat-delivery devices, not by a fundamental understanding of the underlying biothermomechanics. There is a pressing need to quantify the coupled effects of clinically controllable parameters such as temperature level, duration of heating, and mechanical loading imposed during heat-treatments. Prior uniaxial isothermal isotonic tests reveal that increasing temperature level hastens the rate of denaturation of tendons whereas increasing the mechanical load during heating delays this process. Moreover, a concept of time-temperature-load equivalency demonstrated that similar amounts of thermal damage (i.e., denaturation revealed through tissue shrinkage) could be attained through a wide range of time-temperature-load combinations for these collagenous tissues. Yet, because most tissues experience multiaxial loads in vivo and have a vastly different microstructure from tendons, there is a pressing need to evaluate the effects of multiaxial stresses on the kinetics of the denaturation process of other tissues. Herein, we describe a new experimental device and approach for performing biaxial isothermal isotonic tests on thin sheet-like specimens and report the effects of various multiaxial thermomechanical loads on the rate and amount of multiaxial shrinkage of bovine epicardium. Results from these tests reveal a much more complex behavior than that which revealed a time-temperature-load equivalency for tendons. There remains a need to delineate thermomechanical behaviors in much greater detail, and to correlate changes therein with the underlying microstructure. Toward this end, we also describe a new experimental approach for quantifying heat-induced changes in the multiaxial mechanical response of these specimens. Illustrative results are presented for nine different thermomechanical loading protocols. Among other results, it is shown that characteristic shrinkage times are the same for both principal directions and suggest an Arrhenius-type behavior, and overall changes in extensibility correlate well with the degree of thermal damage independent of the time-temperature-load combination used during heating. Multiaxial changes in behavior are nevertheless very complex, and there is a need for significantly more testing before constitutive relations can be formulated. |
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| Item Description: | Vita. "Major Subject: Biomedical Engineering". |
| Physical Description: | xiii, 136 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 118-129). |