Evaluation of smear zone extent surrounding mandrel driven vertical drains using the cavity expansion theory

In this study, an attempt is made to analyse the extent of the smear zone caused by mandrel driven vertical drains, employing the cavity expansion theory for soft clay obeying the modified Cam-clay model. The predictions are verified by large-scale laboratory tests, where the extent of the smear zone was estimated based on the indications such as the pore pressure generated during mandrel driving, change in lateral permeability and the water content reduction. This study reveals that the radius of smear zone is about 4-6 times the equivalent vertical drain radius, and the lateral permeability (inside the smear zone) is 61-92% of that of the outer undisturbed zone. Finally, the predicted size of the smear zone using the undrained cavity expansion solution is incorporated in the finite element code PLAXIS to study the performance of a test embankment selected from the Sunshine Motorway, Queensland, Australia. A good agreement between the predicted values and field measurements was found

Analytical and numerical solutions for a single vertical drain including the effects of vacuum preloading

A system of vertical drains combined with vacuum preloading is an effective method to accelerate soil consolidation by promoting radial flow. This study presents the analytical modeling of vertical drains incorporating vacuum preloading in both axisymmetric and plane strain conditions. The effectiveness of the applied vacuum pressure along the drain length is considered. The exact solutions applied on the basis of the unit cell theory are supported by finite element analysis using ABAQUS software. Subsequently, the details of an appropriate matching procedure by transforming permeability and vacuum pressure between axisymmetric and equivalent plane strain conditions is described through analytical and numerical schemes. The effects of the magnitude and distribution of vacuum pressure on soft clay consolidation are examined through average excess pore pressure, consolidation settlement and time analyses. Finally, the practical implications of this study are discussed

Development and Assessment of a Soda Lime Glass Model for Ballistic Impact

Transparent armour (more commonly known as bullet-resistant glass) is used in armoured land vehicles to provide increased visibility while maintaining adequate levels of protection for the occupants. Soda-lime glass is commonly used in transparent armour due to the ease of manufacture and relatively low cost. Computational impact models of soda-lime glass can be used to aid in the development and optimization of transparent armour systems, but require experimental data to provide input parameters and must be assessed against independent impact data for model validation. In this study, a robust computation model of soda-lime glass was developed and successfully validated against a wide range of experimental data from coupon level dynamic tensile testing to full-scale ballistic impact experiments. To support the development and validation of the computational model, three experimental tests were conducted: a dynamic diametral compression test to measure the tensile strength of the soda lime glass; a sphere ballistic impact test on glass tiles to characterize the dynamic failure of soda-lime glass over a range of impact velocities; and a depth of penetration test to validate the ballistic performance of the soda-lime glass model. Three discretization methods commonly used to model impact problems were investigated including smooth particle hydrodynamics (SPH), element free Galerkin (EFG) and the finite element method (FEM). A first set of models were used to assess common numerical modelling techniques using the sphere on glass tile impact tests and material parameters from the literature. The Johnson Holmquist (JH-2) ceramic constitutive model, accounting for strength dependence on pressure and material damage, was used to model the response and failure of the glass. The SPH method predicted projectile residual velocities with some success (difference in residual velocities as low as 15% at lower impact speeds) but had poor convergence tendencies (p = 1.1). The EFG method demonstrated higher rates of convergence (p = 2.1) but did not predict residual velocities well (differences as high as 348% using literature parameters). Lastly, the FEM showed acceptable convergence tendencies (p = 1.88). Although other solution methods predicted ballistic performance more accurately using literature parameters, the methods were prone to numerical error (SPH) or computationally expensive (EFG) to use effectively. The FEM with failure treated using erosion provided a good balance between simulation accuracy and runtimes, provided that a sufficiently fine mesh, 0.5 mm in this study, was used. In a second set of simulations, the material parameters for the JH-2 constitutive model were determined by fitting strength curves to experimental data and improved using sphere on glass impact test data. It was determined that the fractured strength of the material (B) had a significant effect on the residual velocities of the sphere on glass impact simulations, and the damage coefficient (D1) had an effect on the mode of failure predicted. There was some interaction between the fractured strength (B) and damage coefficient (D1) on the projectile velocities, so B and D1 were determined such that they minimized the error in the residual velocity prediction in the sphere on glass tests. The performance of the updated FEM JH-2 material model was assessed using three sets of experimental data: dynamic Brazilian test, sphere on glass tile test, and preliminary assessment using depth of penetration (DOP) tests. The proposed new material parameters in the JH-2 constitutive model predicted the failure strain and mode of failure in diametral compression samples, within the range of experimental results, demonstrating the ability to predict complex tensile failure of soda-lime glass. Although the model parameters were determined in part using the projectile kinematics of the sphere on glass tile dataset, the measured damage progression and damage propagation velocities in the tiles were used separately for partial model validation. The FEM model with updated JH-2 parameters predicted the projectile penetration in the DOP tests with a 12% difference on average. The predicted difference was as low as 6% at higher impact velocities (930 m/s), and as high 95% associated with lower impact velocities and cases where the experimental projectile path veered off-axis relative to the target. The model used quarter symmetry and did not account for this aspect of projectile motion. This was considered a preliminary assessment since variable such as friction and the projectile material properties require further investigation. The FEM and JH-2 constitutive model with updated material properties predicted a wide range of soda-lime glass impact behaviour demonstrating improved response over a range of load cases

Theoretical and numerical perspectives and field observations for the design and performance evaluation of embankments constructed on soft marine clay

In this chapter, a two-demensional plane strain solution is adopted for the embankment analysis, which includes the effects of smear zone caused by mandrel driven vertical drains. The equivalent (transformed) permeability coefficients are incorporated in finite element codes, employing modified Cam-clay theory. Selected numerical studies have been carried out to study the effect of embankment slope, construction rate, and drain spacing on the failure of the soft clay foundation. Finally, the observed and predicted performances of well-instrumented full-scale trial embankments built on soft Malaysian marine clay have been discussed in detail. The predicted results agree with the field measurements

Histopathological Types of Operable Early Breast Cancer in the Elderly: Is there a Special Pattern? – a Retrospective, Multicentre Study

Introduction: The aim of this study was to determine the pattern of histopathological types of breast cancer in women aged 70 years or more with operable early breast cancer, and its implication on the potential prognosis. Methodology & Material: A retrospective cohort study included 170 patients hospitalised for breast cancer treatment in departments of surgery of two teaching hospitals (Basildon University Hospital, Basildon, United Kingdom, and Greater Poland Oncology Centre, Poznan, Poland). Material and methods: All 170 patients underwent surgical management for breast cancer. Invasive ductal carcinoma (IDC) was the most common histopathological type in the study group (74%). The mucinous carcinoma was seen in 1.7% of cases, invasive lobular carcinoma in only 1% of patients, while the ductal carcinoma in situ was present in 6.5% of subjects. Lympho-vascular invasion was detected in 23% of cases. Conclusion: Less aggressive histological pattern was predominantly detected in the elderly patients with breast cancers

Access to Long Acting Reversible Contraceptives in Northeast TN: A Study of Reproductive Care in Hawkins County, TN

Unintended pregnancy leads to many public health consequences like lower educational attainment and diminished career opportunities, with higher rates of unintended pregnancies occurring in lower income communities and among women with drug addiction. Beyond preventing unintended pregnancies, effective contraception helps prevent poor birth spacing, thereby reducing the risk of both premature and low-weight births and maternal mortality and morbidity during the peripartum period. Long acting reversible contraceptives (LARCs), such as intrauterine devices (IUDs) and implants, are considered the birth control of choice for women of reproductive potential as they possess a number of advantages: cost-effectiveness, minimal maintenance for 3 to 10 years, reversibility, and high efficacy and continuation rates. Despite these benefits, LARCs have been widely underused in rural communities as a result of many factors including hospital and gynecology department closures, workforce shortages, provider knowledge, and access to care challenges that arise from complex social determinants of health specific to rural US communities. We therefore investigated the knowledge and current practice of clinical providers regarding LARCs counseling and provision in Hawkins County of Northeast Tennessee. Hawkins County is a primarily rural county with clinics serving a large lower income population with a high prevalence of substance use, therefore making it at risk for higher rates of unintended pregnancies. An online survey was sent to all consenting medical providers (NPs, PAs, and physicians) (n=7) to collect information on their practices related to contraception, including LARCs. Following completion of online surveys, semi-structured interviews (n=2) were planned to qualitatively explore providers’ perspectives. Quantitative analysis of survey data and thematic analysis of interviews were conducted. Analysis of survey data shows that though non-OB/GYN primary care providers reported on being somewhat comfortable to comfortable in their ability to counsel patients on LARCs, they reported low levels of actually counseling on LARCs, compared with oral contraception. Furthermore, the survey data also shows low levels of LARC insertion/removal among non-OB/GYN primary care providers, with most noting preference to refer patients to a private OB/GYN provider within the community or the health department. Additionally, non-OB/GYN primary care providers reported little to no interest in including insertion/removal of LARCs within their scope of practice, citing clinic supply, no time for procedures, and low patient desire as reasons. All providers reported believing that there are little to no barriers to obtaining LARCs by patients within Hawkins County.The semi-structured interviews, including one with the county’s main OB/GYN provider, indicated that though there is access to LARCs within Hawkins County, there may still be multiple barriers including possible poor quality of counseling on LARCs by non-OB/GYN primary care providers and preference for counseling specific populations on LARCs rather than all patients of reproductive potential, both of which may contribute to low patient desire for LARCs. This work is a useful starting place for increasing utilization of LARCs within Hawkins County. By exploring current knowledge and practices of primary care providers, we can better address potential systematic barriers to improve access to and utilization of LARCs in rural communities

Transcatheter aortic valve resection: new mechanical devices

Background To improve periprocedural outcomes of transcatheter aortic valve implantation (TAVI), transcatheter mechanical resection devices were tested for prior ablation of the aortic cusps. Methods Three mechanical transcatheter resection devices were tested in a series of native porcine (n=30) and reassembled calcified human valves (n=54). The resection time, the resected valve area, the number of released cusps, and the degree of surrounding tissue damage were measured. Afterwards, postmortem transapical-transcatheter-resections of the aortic valve in two humans were performed. Results In the native porcine hearts, the Aesculap II device demonstrated significantly shorter resection time compared to the R&R II and the Randstad devices (6.5±2.0 vs. 28.6±24.1 vs. 23.3±14.4 sec; P=0.001). However, it created more lesions in the surrounding tissue (P=0.002). The R&R II achieved a smaller number of resected cusps than the other two devices (2.7±0.7 vs. 1.1±0.7 vs. 2.4±0.5; P<0.001, respectively). It also resected a smaller area of the aortic valve (306.5±149.2 vs. 106.7±29.6 vs. 256.8±81.3 mm2; P=0.09) but a larger mean area of the resected fragments (110.3±41.5 vs. 160.7±29.6 vs. 111.5±43.9 mm2; P=0.01). The resection of the reassembled human valves demonstrated the same results between the devices regarding resection time (P=0.001) and resected area (P=0.016), but not fragment sizes (P=0.610). Finally, transapical-transcatheter-resection of aortic valve was performed in two cadavers. Conclusions Transcatheter aortic valve resection is feasible with variable aortic leaflet resection times and mild risk of lesions of the surrounding tissue