RESUMO
Laser surface treatment was carried out on AISI 416 machinable martensitic stainless steel containing 0.225 wt.% sulfur. Nd:YAG laser with a 2.2-KW continuous wave was used. The aim was to compare the physical and chemical properties achieved by this type of selective surface treatment with those achieved by the conventional treatment. Laser power of different values (700 and 1000 W) with four corresponding different laser scanning speeds (0.5, 1, 2, and 3 mâ¢min-1) was adopted to reach the optimum conditions for impact toughness, wear, and corrosion resistance for laser heat treated (LHT) samples. The 0 °C impact energy of LHT samples indicated higher values compared to the conventionally heat treated (CHT) samples. This was accompanied by the formation of a hard surface layer and a soft interior base metal. Microhardness was studied to determine the variation of hardness values with respect to the depth under the treated surface. The wear resistance at the surface was enhanced considerably. Microstructure examination was characterized using optical and scanning electron microscopes. The corrosion behavior of the LHT samples was also studied and its correlation with the microstructures was determined. The corrosion data was obtained in 3.5% NaCl solution at room temperature by means of a potentiodynamic polarization technique.
RESUMO
PURPOSE: To document published utilities for health states associated with Chronic Kidney Disease (CKD) and End Stage Renal Disease (ESRD) and determine the most appropriate values for use in economic models to evaluate renal treatments in the UK. METHODS: A structured literature review was conducted (MEDLINE, EMBASE, NHS EED and HTA) in order to identify relevant articles published between January 1990 and January 2006. In addition searches were conducted on websites of Health Technology Assessment (HTA) organizations and the Cost Effectiveness Analysis Registry. Articles were reviewed and those not containing utilities excluded. Results were assessed on the quality of the elicitation studies and their relevance to the UK HTA environment. RESULTS: Thirty-five studies satisfied the inclusion criteria. Most studies were conducted in Canada (13), the US (10) and the Netherlands (4). Utilities were identified for all/most of the necessary states, but scores for individual states differed widely between studies and very few studies met the quality criteria. The majority of studies used the time trade-off (23) and standard gamble (11) to elicit utilities, while only six used EQ-5D. Seven studies provided community preferences. Two studies were judged to be directly relevant to economic evaluations in the UK. CONCLUSIONS: Many studies have estimated utilities in ESRD patients, but only a few have estimated utilities based upon public preferences. Further empirical research is needed to produce more reliable utilities for economic modelling in the UK, especially in chronic kidney disease patients who do not require dialysis.
