Evaluation of the Fragility of East Bay Municipal Utility District (EBMUD) Mokelumne Aqueduct

The East Bay Municipal Utility District provides water to the eastern region of the San Francisco Bay Area. Water is delivered through the Mokelumne Aqueduct, which consists of three large diameter steel pipelines. Approximately 15 miles of the aqueducts cross the fragile Sacramento-San Joaquin Delta. A stability analysis has been conducted to evaluate how resilient the elevated aqueduct is in the Delta. Subsidence in the Delta considerably reduces the lateral support of piles. Based on previous studies, and available survey and LiDAR data, the amount of subsidence in the Delta has been predicted over time. In addition, site-specific seismic studies have been considered in order to estimate strong ground motion parameters. A series of axial single pile analyses, lateral single pile analyses, and pile group analyses have been performed to quantify the impact of ground loss due to subsidence on pile capacities along the 15-mile alignment. Results were compared with both the maximum expected lateral load at the pile cap occurring due to seismic ground motion (base shear) and the lateral capacity at the 1-inch horizontal displacement of the pile cap (threshold). Analysis shows a significant reduction in the piles’ lateral and axial capacities, caused by lack of soil shear strength. The analytical studies are presented and discussed in order to develop retrofit alternatives

Validating SSI Response of Buildings on Liquefiable Deposits using Centrifuge Testing and Numerical Modelling

The increasing shift towards performance based geotechnical earthquake engineering design requires an improved understanding of soil-structure interaction (SSI) for structures on liquefiable deposits. While a number of authors have used centrifuge tests and numerical modelling to study this phenomena, a limited number of studies have been undertaken where numerical models have been validated against well-instrumented physical model tests or centrifuge tests. As such, two of the centrifuge tests that were undertaken as part of the NEESR Seismic Performance Assessment in Dense Urban Environments project have been used to validate the ability of numerical simulations to model SSI for isolated structures on liquefiable deposits. The numerical simulations have been developed using FLAC and the PM4Sand constitutive soil model and OpenSees and PDMY02 constitutive soil model. The overall objective of the study is to validate the numerical model’s ability to capture both volumetric and deviatoric mechanisms by comparing against settlement, pore water pressure and accelerations measured, using a large array of instruments, in the centrifuge tests. This poster presents the validation of the numerical model’s ability to capture volumetric mechanisms by comparing 1D soil response simulations against free field measurements from the centrifuge tests. Additionally, an initial identification of the relative strengths and weaknesses of the two respective software packages and the two constitutive models is provided

Quantitative perfusion imaging of neoplastic liver lesions: A multi-institution study

Abstract We describe multi-institutional experience using free-breathing, 3D Spiral GRAPPA-based quantitative perfusion MRI in characterizing neoplastic liver masses. 45 patients (age: 48–72 years) were prospectively recruited at University Hospitals, Cleveland, USA on a 3 Tesla (T) MRI, and at Zhongshan Hospital, Shanghai, China on a 1.5 T MRI. Contrast-enhanced volumetric T1-weighted images were acquired and a dual-input single-compartment model used to derive arterial fraction (AF), distribution volume (DV) and mean transit time (MTT) for the lesions and normal parenchyma. The measurements were compared using two-tailed Student’s t-test, with Bonferroni correction applied for multiple-comparison testing. 28 hepatocellular carcinoma (HCC) and 17 metastatic lesions were evaluated. No significant difference was noted in perfusion parameters of normal liver parenchyma and neoplastic masses at two centers (p = 0.62 for AF, 0.015 for DV, 0.42 for MTT for HCC, p = 0.13 for AF, 0.97 for DV, 0.78 for MTT for metastases). There was statistically significant difference in AF, DV, and MTT of metastases and AF and DV of HCC compared to normal liver parenchyma (p < 0.5/9 = 0.0055). A statistically significant difference was noted in the MTT of metastases compared to hepatocellular carcinoma (p < 0.001*10-5). In conclusion, 3D Spiral-GRAPPA enabled quantitative free-breathing perfusion MRI exam provides robust perfusion parameters

Management of Compromised Ridges: A Case Report

Complete denture therapy is an age old form of dental treatment. Ridge atrophy poses a clinical challenge towards the fabrication of a successful prosthesis. Extreme resorption of the maxillary and mandibular denture bearing areas results in sunken appearance of cheeks, unstable and non retentive dentures with associated pain and discomfort. This article describes the step by step rehabilitation procedure of a patient with atrophic ridges using a hollow maxillary complete denture with cheek plumpers attached to it and the recording of neutral zone to ensure a stable mandibular denture