1,170 research outputs found

    Enhancing Engine Block Quality by Reducing Metal Chips in Porosities - A Case Study

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    A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Santosh Kumar Kurella on March 25, 2009

    Laser Induced Hierarchical Coatings on Titanium Alloy

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    Biomaterials research is an exciting and challenging area. It is exciting because of its potential applications and need for improving the quality of life. It is challenging because of the complexity with which natural biomaterials function in their environments. The gap that exists in terms of maturity and sophistication of the currently used synthetic materials from natural biomaterials is huge. It is only in the last few decades with the evolution of advanced material analytical techniques that researchers are starting to understand the complexity of nature. One such particular feature that has attracted our interest is the hierarchical nature of the bioimplant surfaces. The present work is one small step in that direction where we tried to engineer a surface that is multi-scale in nature and biocompatible at these length scales. During a discovery phase a multi-scale textured zirconia coating was done on titanium alloy using a pulsed laser. Following proof of concept a bioactive calcium phosphate based coating was deposited on titanium alloy surface using a continuous wave laser. Based on detailed morphological and chemical analysis it was evident that the multi-phase coating had a multi-scale arrangement. Owing to the complexity of the coating a fractal based approach was used to interpret the morphology of the coatings. It appeared that at higher laser processing speeds star shaped calcium titanate features exist inside calcium phosphate and titania ring like structures. By tailoring a thermal model with current material system temperature calculations were made for various laser processing speeds. Using temperature predictions and knowledge of the phase constituents the series of self assembling steps that led to the formation of star and ring shaped arrangement are discussed. The biocompatibility of the coatings was evaluated by immersing in simulated body fluids. The morphological and chemical evolution of hydroxyapatite precipitation along the calcium phosphate rich ring like structures coupled with the porous structure supports the possibility of enhanced osteointegration. The presence of calcium titanate ensured an interaction between the substrate and the precursor coating material. Wear measurements indicated that the laser processed samples possessed better mechanical properties than unprocessed surfaces

    Validation of the Kidney Disease Quality of Life (KDQOL) Cognitive Function subscale

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    Validation of the Kidney Disease Quality of Life (KDQOL) Cognitive Function subscale.BackgroundFormal cognitive function testing is cumbersome, and no self-administered instruments for estimating cognitive function in persons with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have been validated. The goal of this study was to determine the validity of the Kidney Disease Quality of Life Cognitive Function scale (KDQOL-CF) for the assessment of cognitive impairment in persons with kidney disease.MethodsWe administered the KDQOL-CF to 157 subjects, 79 with ESRD and 78 with CKD participating in a cross-sectional study of cognitive function. Scores on the Modified Mini-Mental State Exam (3MS) were considered the gold standard measure of global cognitive function. Performance characteristics of the KDQOL-CF were assessed using correlation coefficients, Bland-Altman plots, and receiver operating characteristic curves.ResultsMedian scores on the KDQOL-CF were 73 (interquartile range 60–87) for subjects with ESRD and 87 (interquartile range 73–100) for subjects with CKD (P < 0.0001). Scores on the KDQOL-CF were directly correlated with scores on the 3MS (r = 0.31, P = 0.0001). Defining global cognitive impairment as a 3MS score <80, a cut-point of 60 on the KDQOL-CF accurately classified 76% of subjects, with 52% sensitivity and 81% specificity. On multivariable analysis, cerebral and peripheral vascular disease, benzodiazepine use, and higher serum phosphorus concentrations were associated with lower KDQOL-CF scores, while beta blocker use, education, and higher serum albumin concentrations were associated with higher KDQOL-CF scores.ConclusionThe KDQOL-CF is a valid instrument for estimating cognitive function in patients with CKD and ESRD. KDQOL-CF screening followed by 3MS testing in selected individuals may prove to be an effective and efficient strategy for identifying cognitive impairment in patients with kidney disease

    Anemia and risk for cognitive decline in chronic kidney disease

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    BACKGROUND: Anemia is common among patients with chronic kidney disease (CKD) but its health consequences are poorly defined. The aim of this study was to determine the relationship between anemia and cognitive decline in older adults with CKD. METHODS: We studied a subgroup of 762 adults age ≥55 years with CKD participating in the Chronic Renal Insufficiency Cohort (CRIC) study. Anemia was defined according to the World Health Organization criteria (hemoglobin <13 g/dL for men and <12 g/dL for women). Cognitive function was assessed annually with a battery of six tests. We used logistic regression to determine the association between anemia and baseline cognitive impairment on each test, defined as a cognitive score more than one standard deviation from the mean, and mixed effects models to determine the relation between anemia and change in cognitive function during follow-up after adjustment for demographic and clinical characteristics. RESULTS: Of 762 participants with mean estimated glomerular filtration rate of 42.7 ± 16.4 ml/min/1.73 m(2), 349 (46 %) had anemia. Anemia was not independently associated with baseline cognitive impairment on any test after adjustment for demographic and clinical characteristics. Over a median 2.9 (IQR 2.6–3.0) years of follow-up, there was no independent association between anemia and change in cognitive function on any of the six cognitive tests. CONCLUSIONS: Among older adults with CKD, anemia was not independently associated with baseline cognitive function or decline. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12882-016-0226-6) contains supplementary material, which is available to authorized users

    Fiber laser-microscope system for femtosecond photodisruption of biological samples

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    We report on the development of a ultrafast fiber laser-microscope system for femtosecond photodisruption of biological targets. A mode-locked Yb-fiber laser oscillator generates few-nJ pulses at 32.7 MHz repetition rate, amplified up to ∼125 nJ at 1030 nm. Following dechirping in a grating compressor, ∼240 fs-long pulses are delivered to the sample through a diffraction-limited microscope, which allows real-time imaging and control. The laser can generate arbitrary pulse patterns, formed by two acousto-optic modulators (AOM) controlled by a custom-developed field-programmable gate array (FPGA) controller. This capability opens the route to fine optimization of the ablation processes and management of thermal effects. Sample position, exposure time and imaging are all computerized. The capability of the system to perform femtosecond photodisruption is demonstrated through experiments on tissue and individual cells
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