Abstract：
:Instantaneous backflow through central clearance of bileaflet heart valves at the instant of closure is investigated. An Edwards-Duromedics valve in the mitral position is employed to measure the transient pressures near the entrance and exit region in an in vitro flow chamber. A region surrounding the clearance is modelled, and two-dimensional quasi-steady-state numerical simulations are performed, with the measured transient pressure difference across the clearance as a driving force for the flow. The results show that pressure difference several times larger than the driving pressure used to close the valve is established across the clearance for about 0.5 ms at the moment of closure. The resulting average wall shear stress is an order of magnitude larger than the turbulent Reynolds stresses reported distal to the valve during opening. A local jump in the shear stress distribution and fall in the pressure distribution are observed at the entrance region. Rounding of the corners in the channel entrance attenuates these spikes. The results of the study indicate that backflow through clearance at closure may be one reason for the haemolysis and thrombosis associated with mechanical heart valves, despite the short duration of the flow field.
journal_name
Med Biol Eng Computjournal_title
Medical & biological engineering & computingauthors
Lee CS,Chandran KBdoi
10.1007/BF02510497subject
Has Abstractpub_date
1995-05-01 00:00:00pages
257-63issue
3eissn
0140-0118issn
1741-0444journal_volume
33pub_type
杂志文章abstract：:Mammography is a widely used screening tool and is the gold standard for the early detection of breast cancer. The classification of breast masses into the benign and malignant categories is an important problem in the area of computer-aided diagnosis of breast cancer. A small dataset of 57 breast mass images, each wi...
journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/s11517-006-0077-6
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/s11517-007-0233-7
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/s11517-009-0464-x
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02349982
更新日期：2003-11-01 00:00:00
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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更新日期：1989-01-01 00:00:00
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章,评审
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02441963
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02345373
更新日期：2001-07-01 00:00:00
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02348134
更新日期：2002-03-01 00:00:00
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
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journal_title：Medical & biological engineering & computing
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journal_title：Medical & biological engineering & computing
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journal_title：Medical & biological engineering & computing
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章,评审
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02345290
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02447101
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
doi：10.1007/BF02446787
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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journal_title：Medical & biological engineering & computing
pub_type： 杂志文章
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