ABSTRACT
Computational modeling and experimental measurements on metal samples subject to a laser-driven, ablative Richtmyer-Meshkov instability showed differences between viscosity and strength effects. In particular, numerical and analytical solutions, coupled with measurements of fed-through perturbations, generated by perturbed shock fronts onto initially flat surfaces, show promise as a validation method for models of deviatoric response in the postshocked material. Analysis shows that measurements of shock perturbation amplitudes at low sample thickness-to-wavelength ratios are not enough to differentiate between strength and viscosity effects, but that surface displacement data of the fed-through perturbations appears to resolve the ambiguity. Additionally, analytical and numerical results show shock front perturbation evolution dependence on initial perturbation amplitude and wavelength is significantly different in viscous and materials with strength, suggesting simple experimental geometry changes should provide data supporting one model or the other.
ABSTRACT
OBJECTIVE: Previous reparative valvular surgical options directed at reconstructing damaged common femoral vein (CFV) valves associated with pathological chronic venous insufficiency (CVI) have not succeeded in reliably managing CVI. In consequence, venous valvuloplasty is rare and most patients are managed conservatively. As a result, monocusp surgery was identified as an optional surgical solution for this large underserved patient group. METHODS: Ulcer patients appear at wound clinics and often experience disappointing results. Monocusp valves were constructed utilizing viable vein wall in 14 operations on 11 patients. These patients were observed for four years to see if such an autogenous vein wall valve might control aggressive symptomatic CVI when faced with unusable valves. RESULTS: Long-term follow-up showed that the monocusp valves remained competent at four years. Symptomatic failures have not appeared at this time. Pain, swelling, ulcers and leg congestion were reliably reversed. VEnous INsufficiency Epidemiologic and Economic Study (VEINES) classification (see Abenhaim L, Krux X, VIENES Study collaborators. Angiology 1997;48:59 and Kurz X, Kahn SR, Abenhaim L, et al. Int Angiol 1999;18:83-102) improved over four years from 2.7 +/- 0.9 to 0 (P < 0.001); CEAP classifications (see Kistner RL, Eklof B, Masuda EM. Mayo Clin Proc 1996;71:338-45) improved from grade 4-6 to 0-1 (CEAP is not generally a postoperative grading system, but it can be used to develop some form of qualitative analyses as to intervention effectiveness, i.e. what existed preoperatively no longer exists postoperatively. Its postsurgery use is limited by (C5) classification - history of ulcer, which by definition cannot go below that with a history of ulcer even if the ulcer has been cured). Mean venous reflux scores decreased from 3.8 +/- 0.4 to 0.3 +/- 0.5 (P < 0.001). CONCLUSION: Monocusp implantation reliably resolved patient symptoms when unusable CFV valves were encountered. Postoperative CFV reflux is usually undetectable. The monocusp valve exhibits minimal thrombogenicity related to its viability with attendant antithrombotic hormone production capacity and has markedly improved the patient's quality of life. Full thickness monocusp surgery could become widespread with the difficult dysplastic/aplastic CVI patient subset because of its simplicity, repeatability, durability, low complication rate, effectiveness, persistent availability and viability providing nitric oxide synthase and thymomodulin hormone production capacity. The full thickness of vein wall has distinct advantages over other partial thickness valve creation methods because of its long-term vitality. Postoperative coumadin is recommended for six months to minimize risks of deep vein thrombosis and/or pulmonary embolism.