Cost Effectiveness of Primary Total Hip Arthroplasty for Varying Levels of BMI

The demand for hip arthroplasty is increasing rapidly due to a combination of an aging population as well as an increasing level of obesity in the country. The purpose of this study is to evaluate the risks and benefits of arthroplasty for patients of different obesity classes. The first two parts were to use a systematic review with meta-analysis and retrospective chart review to quantify the risks and benefits in different obesity classes. The third part was to perform a cost-effectiveness analysis to weight the balance between the two. We found that higher obesity classes are at higher risk of complications and comparable improvement after an arthroplasty. Our cost-effectiveness analysis determined that greater obesity levels had a higher incremental cost-effectiveness ratio than lower obesity levels, but was within generally used willingness-to-pay thresholds. In conclusion, patients of all obesity levels have a greater benefit to cost ratio for total hip arthroplasty

Nano-structured morphological features of pulsed direct current magnetron sputtered Mo films for photovoltaic applications

Historically, molybdenum thin films have been used as the back contact for Cu(In,Ga)Se2 based solar cells and as such the properties of these layers play an important role in the overall cell structure. This paper describes the production of molybdenum films using pulsed d.c magnetron sputtering from compressed molybdenum powder targets. The films were deposited at different substrate temperatures under constant power and constant current modes, and analysed using X-ray diffraction, scanning electron microscopy, atomic force microscopy and four point resistance probe. Mechanical strain and resistivity were found to decrease with substrate temperature together with a shift in the (110) crystallographic plane towards higher diffraction angles. All films were well adhered to the glass substrates irrespective of their high tensile strain. Surface morphology analysis revealed the presence of nano-structured stress relief patterns which can enhance the nucleation sites for subsequent CuInSe2 deposition. A high-resolution cross sectional image showed the columnar growth of the films. Surface roughness analysis revealed that roughness increased with increase in substrate temperature

Thermal Model for a Li-Ion Cell

A thermal model for a lithium-ion cell is presented and used to predict discharge performance at different operating temperatures. The results from the simulations are compared to experimental data obtained from lithium-ion pouch cells. The model includes a set of parameters (and their concentration and temperature dependencies) that has been obtained for a lithium-ion cell composed of a mesocarbon microbead anode, LiCoO2 cathode in 1 M LiPF6 salt, in a mixture of ethylene carbonate, propylene carbonate, ethyl-methyl carbonate, and diethyl carbonate electrolyte. The parameter set was obtained by comparing the model predictions to the experimental discharge profiles obtained at various temperatures and rates. The concentration and temperature dependence of the extracted parameters were correlated through empirical expressions. Also, the effect of including the thermal dependence of various parameters in the model on the simulated discharge profiles is discussed

Optimization of a horizontal axis marine current turbine via surrogate models

Flow through a scaled horizontal axis marine current turbine was numerically simulated after validation and the turbine design was optimized. The computational fluid dynamics (CFD) code Ansys-CFX 16.1 for numerical modeling, an in-house blade element momentum (BEM) code for analytical modeling and an in-house surrogate-based optimization (SBO) code were used to find an optimal turbine design. The blade-pitch angle (θ) and the number of rotor blades (NR) were taken as design variables. A single objective optimization approach was utilized in the present work. The defined objective function was the turbine’s power coefficient (CP). A 3x3 full-factorial sampling technique was used to define the sample space. This sampling technique gave different turbine designs, which were further evaluated for the objective function by solving the Reynolds-Averaged Navier–Stokes equations (RANS). Finally, the SBO technique with search algorithm produced an optimal design. It is found that the optimal design has improved the objective function by 26.5%. This article presents the solution approach, analysis of the turbine flow field and the predictability of various surrogate based techniques

Parameter Estimation and Life Modeling of Lithium-Ion Cells

Lithium-ion pouch cells were cycled at five different temperatures (5, 15, 25, 35, and 45°C ), and rate capability studies were performed after every hundred cycles. The data were used with a simple physics-based model to estimate parameters that capture the capacity fade in the cell, with cycling. The weight of active material within each electrode was estimated as a function of time, using rate capability data at the C/33 rate. The C-rate for these cells is 1.656 A. The capacity fade due to the loss of active material and that due to the loss of cyclable lithium were quantified. It was found that while the loss of cyclable lithium is the limiting cause for the capacity decay of the cell during the first 200 cycles, the loss of active carbon, which is the anode material, becomes limiting for these cells. The loss of active material leads to a drastic decrease in cell capacity at higher temperatures

Identification of synergistic interactions among microorganisms in biofilms by digital image analysis

Digital image analysis showed that reductions in biofilm plating efficiency were due to the loss of protection provided by two benzoate-degrading strains of Pseudomonas fluorescens. This loss in protection was due to the spatial separation of the protective organisms from benzoate-sensitive organisms during the dilution process. Communities were cultivated in flow cells irrigated with trypticase soy broth. When the effluent from these flow cells was plated on 0.15% benzoic acid, satellite colonies formed only in the vicinity of primary colonies. A digital image analysis procedure was developed to measure the size and spatial distribution of these satellites as a function of distance from the primary colony. The size of satellites served as a measure of growth, and the number per unit area served as a measure of survival. At the three dilutions tested, the size and concentration of satellite colonies varied inversely with distance from the primary colonies. When these measurements were plotted, the slopes were used to quantify the effect of bacterial association on the growth and survivability of the satellites. In the absence of the primary colonies, satellites grew in axenic culture only at low benzoate concentrations. Thus benzoate-degrading organisms are capable of creating a protective microenvironment for other members of biofilm communities

Assessing Traceability of Software Engineering Artifacts

The generation of traceability links or traceability matrices is vital to many software engineering activities. It is also person-power intensive, time-consuming, error-prone, and lacks tool support. The activities that require traceability information include, but are not limited to, risk analysis, impact analysis, criticality assessment, test coverage analysis, and verification and validation of software systems. Information Retrieval (IR) techniques have been shown to assist with the automated generation of traceability links by reducing the time it takes to generate the traceability mapping. Researchers have applied techniques such as Latent Semantic Indexing (LSI), vector space retrieval, and probabilistic IR and have enjoyed some success. This paper concentrates on examining issues not previously widely studied in the context of traceability: the importance of the vocabulary base used for tracing and the evaluation and assessment of traceability mappings and methods using secondary measures. We examine these areas and perform empirical studies to understand the importance of each to the traceability of software engineering artifacts