Status Update and Interim Results from the Asymptomatic Carotid Surgery Trial-2 (ACST-2)

Objectives: ACST-2 is currently the largest trial ever conducted to compare carotid artery stenting (CAS) with carotid endarterectomy (CEA) in patients with severe asymptomatic carotid stenosis requiring revascularization. Methods: Patients are entered into ACST-2 when revascularization is felt to be clearly indicated, when CEA and CAS are both possible, but where there is substantial uncertainty as to which is most appropriate. Trial surgeons and interventionalists are expected to use their usual techniques and CE-approved devices. We report baseline characteristics and blinded combined interim results for 30-day mortality and major morbidity for 986 patients in the ongoing trial up to September 2012. Results: A total of 986 patients (687 men, 299 women), mean age 68.7 years (SD ± 8.1) were randomized equally to CEA or CAS. Most (96%) had ipsilateral stenosis of 70-99% (median 80%) with contralateral stenoses of 50-99% in 30% and contralateral occlusion in 8%. Patients were on appropriate medical treatment. For 691 patients undergoing intervention with at least 1-month follow-up and Rankin scoring at 6 months for any stroke, the overall serious cardiovascular event rate of periprocedural (within 30 days) disabling stroke, fatal myocardial infarction, and death at 30 days was 1.0%. Conclusions: Early ACST-2 results suggest contemporary carotid intervention for asymptomatic stenosis has a low risk of serious morbidity and mortality, on par with other recent trials. The trial continues to recruit, to monitor periprocedural events and all types of stroke, aiming to randomize up to 5,000 patients to determine any differential outcomes between interventions. Clinical trial: ISRCTN21144362. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved

Grand and White Lakes Flood Control Project: Numerical Model Investigation

Source: https://erdc-library.erdc.dren.mil/jspui/The Grand and White Lakes flood control project provides protection over a broad portion of the Louisiana coastline. The study area involves a wide variety of wetlands and complex canals and waterways. The area supports many economic interests with potentially conflicting desires for management of the water resources. The project required the capability of quantitatively estimating the relative performance of a large number of design alternatives. Numerical modeling techniques capable of addressing tbe flood routing and salinity intrusion processes required to evaluate project alternatives were developed. These techniques included the specification of control structures within the one-dimensional finite element formulation, utilization of marsh porosity, discretization of complex spatial geometric features of the wetlands, and the use of one-dimensional networking in conjunction with the two-dimensional finite element formulation. Numerical testing was performed for eighteen separate design alternatives for the system. Flood events with 2-, 5-, 10-, 25- and 50-year return intervals were simulated and stage exceedance curves generated. Salinity intrusion testing was performed for tbe influence of marine organism ingress structures on the upstream basin. The results of the testing showed that the marine ingress structures should be very modest in size if salinity intrusion problems are to be avoided. The flood control testing suggested that the optimum location of the increased flow capacity should be near the mouth of the primary tributary, tbe Mermentau River, or else extensive channelization would have to accompany an alternate location

The Atchafalaya River Delta. Report 3: Extrapolation of Delta Growth

Source: https://erdc-library.erdc.dren.mil/jspui/This study predicts the future delta growth of the Lower Atchafalaya River delta based on an extrapolation of historical deposition trends in Atchafalaya Bay. The prediction is made with a regression model developed by correlating deposition rates with river discharge, sediment yield, local water depth, and location relative to the delta mass centroid. The regression model is applied to a 50-yr hydrograph using the 1977 bathymetry as initial condition. The predicted delta condition at 10-yr increments is reported. Sensitivity tests were made with the regression model which determined that the sequencing of hydrologic events had no impact on the resultant 50-yr condition, provided the total water and sediment entering the bay remained unchanged by resequencing events. It was concluded that within 50 yr the delta should evolve gulfward of Eugene Island, the gulfward limit of the bay

The Atchafalaya River Delta. Report 13: Summary Report of Delta Growth Predictions

Source: https://erdc-library.erdc.dren.mil/jspui/Coastal Louisiana is experiencing dramatic and alarming land loss. The exception to this general trend is the Atchafalaya River delta, which has been experiencing dramatic deltaic growth during the past 20 years. This deltaic activity can be viewed as both a resource for development of coastal wetlands and as a threat for potentially aggravating flooding in communities upstream of the delta. In response to these concerns, the Corps of Engineers is conducting a thorough investigation to predict how the delta will evolve over the next 50 years, the impacts of the growth and the effectiveness of structures for controlling detrimental results. The investigation approach used several analytical and numerical techniques applied separately to arrive at independent predictions of delta growth. The approach was arranged to provide results from increasingly sophisticated techniques over the period 1980-1989. Each of the techniques are summarized and comparisons are made. The techniques included: analytical model, regression/extrapolation analysis of past behavior, generic analysis of similar deltas' growth patterns, a quasi-two-dimensional numerical model, and TABS two-dimensional numerical model. The results from these techniques indicated a wide possible range of 32 to 149 square miles of subaerial delta for year 2030. A regression analysis of all of these results predicted the subaerial delta area to peak at year 2035 with 89 square miles

TABS-MD Numerical Modeling Investigation of Shoaling in the Mississippi River-Gulf Outlet

Source: https://erdc-library.erdc.dren.mil/jspui/The combined effects of subsidence and erosion have caused encroachment of Lake Borgne toward the Mississippi River-Gulf Outlet (MR-GO) canal. The shoreline erosion poses the potential to alter the general circulation patterns in the area and increase the channel maintenance requirements in MR-GO. A numerical model was developed for the simulation of hydrodynamics and sediment transport to evaluate the potential changes in sedimentation. The numerical model was verified to hydrodynamics for three separate events, each with considerable degree of meteorological contamination. The sediment transport verification to the observed suspended sediment concentrations and the channel shoaling rates was initiated. The final sediment transport verification was not achieved as the project was terminated due to revised costs associated with the proposed bank line protection construction. This report documents the work performed toward the original study objectives

The Atchafalaya River Delta. Report 12: Two-Dimensional Modeling of Alternative Plans and Impacts on the Atchafalaya Bay and Terrebonne Marshes

Source: https://erdc-library.erdc.dren.mil/jspui/The Wax Lake Outlet and Atchafalaya River deltas in Louisiana have grown dramatically, and concern over the impact of this growth has led the US Army Corps of Engineers to conduct an investigation to predict how the deltas will evolve over the next 50 years. An additional task was to determine the impacts of that growth on navigation, flood control, salinity, and sedimentation in the bay area. The technical approach for this investigation builds upon the TABS-2 finite element numerical modeling system and is fully described in Report 11 of this series. Comparisons of the existing condition results with various alternatives are presented. In summary, the extension of the Avoca Island Levee to Beer Island (Reach 2) resulted in an approximate 8 percent increase in the predicted size of the 50-year delta evolution regardless of other constraints tested. For all alternatives tested, the size of the 50-year subaerial delta fell within the bounds of 56 to 144 square miles. The most extreme delta evolution simulation tested was the condition without the Wax Lake Outlet flow control project, no navigation channel dredging, and no levee extension. For all delta evolution simulations tested, the water surface elevations within areas east of the levee increased from 3.4 to 6.0 ft by year 2030. In each case tested, the Avoca Island Levee Extension to Reach 2 decreased the backwater effect of the 50-year delta by approximately 2 ft

U.S. Waterways Experiment Station Reports

Partial abstract: The purpose of this study is to define the reliability with which results of tests conducted in a physical model of the Delaware River Estuary can be used to predict the effects of modifications to the estuary. The Delaware River model at the Waterways Experiment Station was used to conduct tests to predict the effects of the navigation channel enlargement between Philadelphia and Trenton, and the results of the tests are compared with subsequent prototype data to determine the accuracy of the model predictions