Author/Authors :
Soleimani, S Laboratory of Biological Structure Mechanics - Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy , Pennati, G Laboratory of Biological Structure Mechanics - Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy , Dubini, G Laboratory of Biological Structure Mechanics - Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy
Abstract :
In this study, the rheology of blood clot is measured with the help of rotational rheometer.
Several shear strains (0.5, 1 and 2%) are applied with two frequencies (5 and 10 Hz) from the
incipient time of clot formation and the response of the sample is measured in the form of shear
stress and the phase lag which is interpreted with storage and loss moduli. In this study the ratio
of loss to storage modulus is studied and the blood clot gel-point as the transition from
viscoelastic fluid to viscoelastic solid is investigated. By increasing the frequency, “tan delta”
decreases before the gel-point and increases after the gel-point which indicates the viscoelastic
fluid and viscoelastic solid behaviour,respectively. Moreover, by increasing the shear strain, “tan
delta” varies with lower rate at luidic stage (Ra1 and Ra3) and with higher rate at solid stage
(Ra2 and Ra4). It is also shown that increasing the shear strain causes a delay on gel-point
formation.
Farsi abstract :
در اين مطالعه، رئولوژي لخته خون با استفاده از دستگاه رئومتر چرخشي اندازه گرفته مي شود. تنش هاي برشي متعددي (0/5، 1 و 2 درصد) در دو فركانس (5 و 10 هرتز) از زمان اوليه تشكيل لخته به كار گرفته مي شود و پاسخ نمونه به شكل تنش برشي و تاخير فاز اندازه گيري مي گردد كه با مدول ذخيره سازي وكاهش تفسير مي شود. در اين تحقيق، نسبت مدول كاهش به ذخيره سازي مورد مطالعه قرار گرفته و نقطه-ژل لخته خون به عنوان گذار ازسيال ويسكوالاستيك به جامد ويسكوالاستيك بررسي شده است. با افزايش فركانس، "دلتا تن" قبل ازنقطه-ژل كاهش و بعد از نقطه-ژل افزايش مي يابد كه به ترتيب رفتار سيال ويسكوالاستيك و جامد ويسكوالاستيك را نشان مي دهد. علاوه بر اين،با افزايش تنش برشي، "دلتا تن" با نرخ پايين تري در حالت سيال (Ra1وRa3) وبا نرخ بالاتري در حالت جامد (Ra2 وRa4) تغيير مي كند. همچنين نشان داده مي شود كه افزايش فشار برشي باعث تاخير در تشكيل نقطه-ژل مي گردد.