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  • 1
    Online Resource
    Online Resource
    New York, NY :Springer,
    Keywords: Wave-motion, Theory of. ; Scattering (Mathematics). ; Inverse problems (Differential equations). ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (502 pages)
    Edition: 1st ed.
    ISBN: 9781461218784
    Series Statement: The IMA Volumes in Mathematics and Its Applications Series ; v.90
    DDC: 531/.1133/01515353
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 4813-4827 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We derive transport theoretic boundary conditions for acoustic wave reflection at a weakly rough boundary in an inhomogeneous half space. We use the Wigner distribution to go from waves to energy transport in the high frequency limit. We generalize known results on the reflection of acoustic plane waves in a homogeneous medium. We analyze higher order corrections, which include a enhanced backscattering effect in the back direction. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Probability theory and related fields 105 (1996), S. 279-334 
    ISSN: 1432-2064
    Keywords: Mathematics Subject Classification (1991):60J60, 76R50, 35R60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary. We prove long time diffusive behavior (homogenization) for convection-diffusion in a turbulent flow that it incompressible and has a stationary and square integrable stream matrix. Simple shear flow examples show that this result is sharp for flows that have stationary stream matrices.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Probability theory and related fields 105 (1996), S. 279-334 
    ISSN: 1432-2064
    Keywords: 60J60 ; 76R50 ; 35R60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We prove long time diffusive behavior (homogenization) for convection-diffusion in a turbulent flow that it incompressible and has a stationary and square integrable stream matrix. Simple shear flow examples show that this result is sharp for flows that have stationary stream matrices.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 95 (1999), S. 479-494 
    ISSN: 1572-9613
    Keywords: radiative transport ; waves in random media ; Wigner distribution ; semiclassical limits ; Bloch waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We derive radiative transport equations for solutions of a Schrödinger equation in a periodic structure with small random inhomogeneities. We use systematically the Wigner transform and the Bloch wave expansion. The streaming part of the radiative transport equations is determined entirely by the Bloch spectrum, and the scattering part by the random fluctuations.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Annals of vascular surgery 10 (1996), S. 347-355 
    ISSN: 1615-5947
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared the findings of intraoperative color duplex scanning and completion arteriography in patients undergoing infrainguinal vein bypasses to identify hemodynamic abnormalities that could result in a predisposition to early or late graft failure. We reviewed the records of 72 patients who underwent 81 vein bypass graft procedures. Three intraoperative diagnostic methods were used. In 28 procedures (group I) both color duplex and completion arteriography were used, in 21 procedures (group II) only color duplex was used, and in 26 procedures (group III) only completion arteriography was used. Grafts were followed using a duplex surveillance protocol for a mean interval of 16.1 months. Nine grafts in group I showed an abnormality on the duplex scan but not on the completion arteriogram. Seven grafts had a peak systolic velocity (PSV) greater than 200 cm/sec and two had a PSV less than 45 cm/sec. These findings led to six immediate repairs, one early revision, and two late revisions. Arteriography demonstrated additional defects in two procedures but repairs were not performed. In group II duplex scans showed an abnormality in eight procedures (seven grafts with PSV 200 to 250 cm/sec and one graft with a retained valve) resulting in three immediate repairs and five late revisions. In the remaining 13 procedures in group II, duplex scans were normal and no revisions were required during follow-up. In group II defects were detected by arteriography in four procedures (〉50% stenosis in three grafts and one arterial spasm) leading to three immediate repairs. In the remaining 22 studies arteriograms were interpreted as normal; however, seven of these grafts required late revisions. Our data suggest that grafts that appear normal on intraoperative duplex scans are not likely to develop a stenosis requiring revision. Intraoperative duplex ultrasound may be superior to completion arteriography.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1615-5947
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The benefit of preoperative cardiac evaluation in the diabetic patient undergoing peripheral vascular surgery is uncertain. To investigate this issue we performed a retrospective review of 192 procedures performed in diabetic patients for chronic lower extremity arterial occlusive disease. The incidence of adverse postoperative cardiac events was determined, as well as its association with several preoperative factors including symptoms of coronary artery disease (CAD), extent and results of preoperative noninvasive cardiac evaluation, and operative site (aorta vs. lower extremity). The overall death and cardiac complication rates were 10.2% for lower extremity and 25.7% for aortic procedures (p=0.02). For myocardial infarction and cardiac death alone, the rates were 5.1% and 5.7%, respectively (p〉0.10). Although a history of symptomatic CAD predicted the occurrence of any cardiac complication (28.3% vs. 8.2% [p〈0.01] for the aortic and lower extremity revascularization groups combined), no factor was found to be associated with the occurrence of myocardial infarction and cardiac death alone. In patients with a history of symptomatic CAD, there was no significant difference in the incidence of complications whether or not preoperative noninvasive cardiac testing was performed (28.1% vs. 28.6%,p〉0.10) or, if testing was performed, if the results were abnormal or normal (35.3% vs. 20.0%,p〉0.10). Similar results were obtained in patients with no history of symptomatic CAD. In summary, this retrospective review of our experience with noninvasive evaluation to detect CAD in diabetic patients undergoing peripheral vascular surgery failed to show any benefit in terms of reducing the incidence of postoperative cardiac events.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1615-5947
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1615-5947
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We developed a theoretic model of arterial stenosis to study the relationship between perfusion pressure and regional hemodynamics in stenotic infrainguinal vein grafts in an attempt to identify grafts at high risk for failure. Our model was based on the concept of energy and mass conservation of the flowing blood. We used the modified Bernoulli equation (ΔP=4ΔV2) to calculate the maximum possible intrastenotic peak systolic velocity (PSV) from the systolic blood pressure. PSV was measured by means of duplex ultrasonography in infrainguinal bypasses up to the time of revision (nine grafts) or spontaneous thrombosis (two grafts). We related arm systolic blood pressure, intrastenotic PSV, and prestenotic PSV obtained from duplex examinations conducted prior to graft thrombosis or revision and applied our model to these stenotic vein grafts. Intrastenotic PSV was consistently lower than maximum PSV predicted from the Bernoulli equation. The highest measured intrastenotic PSV of 600 cm/sec would require a minimum perfusion pressure of 144 mm Hg. The lowest measured PSV (20 cm/sec) was considered the minimum “thrombotic threshold velocity.” This model predicts that for parabolic profile flow in an 80% diameter-reducing axisymmetric stenosis (96% cross-sectional area reduction), a prestenotic PSV of 20 cm/sec would produce an intrastenotic PSV of 500 cm/sec requiring the equivalent potential energy of 100 mm Hg systolic blood pressure. Our theory implies that in patients with nocturnal hypotension thrombosis of stenotic vein grafts may occur.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1615-5947
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During a 62-month period, carbon dioxide was used to supplement or completely replace iodinated contrast agents in performing 27 transluminal angioplasties in 26 patients. The arterial segments addressed included the following: renal in two cases, iliac in five, femoral/popliteal in 15, infrapopliteal in two, and combined in three. Indications for intervention included lower extremity gangrene in 11 cases, ischemic ulceration in 10, rest pain in three, claudication in one, and ischemic nephropathy in two. Contraindications to iodinated contrast agents included renal insufficiency resulting from diabetes (n = 20) or ischemic nephropathy (n = 2) and congestive heart failure (n = 4). Eight procedures used carbon dioxide as the sole contrast agent, whereas 19 required supplementation of carbon dioxide with a mean of 39 ml of nonionic contrast medium. Technical success was achieved in 25 procedures with significant hemodynamic improvement in 20 patients. Complications included transient deterioration in renal function in two patients and myocardial infarctions in two. At 30 days 18 patients had demonstrated significant clinical improvement. Patients at high risk for iodinated contrast-related complications may undergo transluminal angioplasty using carbon dioxide/digital subtraction arteriography to reduce or eliminate the need for iodinated contrast agents.
    Type of Medium: Electronic Resource
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