196,043 research outputs found
Evaluation of the capacity of the APR-DRG classification system to predict hospital mortality [Valutazione della capacità del sistema di classificazione APR – DRG di predire la mortalità ospedaliera]
No full textInpatient mortality has increasingly been used as an hospital outcome measure. Comparing mortality rates across hospitals requires adjustment for patient risks before making inferences about quality of care based on patient outcomes. Therefore it is essential to dispose of well performing severity measures. The aim of this study is to evaluate the ability of the All Patient Refined DRG system to predict inpatient mortality for congestive heart failure, myocardial infarction, pneumonia and ischemic stroke. Administrative records were used in this analysis. We used two statistics methods to assess the ability of the APR-DRG to predict mortality: the area under the receiver operating characteristics curve (referred to as the c-statistic) and the Hosmer-Lemeshow test. The database for the study included 19,212 discharges for stroke, pneumonia, myocardial infarction and congestive heart failure from fifteen hospital participating in the Italian APR-DRG Project. A multivariate analysis was performed to predict mortality for each condition in study using age, sex and APR-DRG risk mortality subclass as independent variables. Inpatient mortality rate ranges from 9.7% (pneumonia) to 16.7% (stroke). Model discrimination, calculated using the c-statistic, was 0.91 for myocardial infarction, 0.68 for stroke, 0.78 for pneumonia and 0.71 for congestive heart failure. The model calibration assessed using the Hosmer-Leme-show test was quite good. The performance of the APR-DRG scheme when used on Italian hospital activity records is similar to that reported in literature and it seems to improve by adding age and sex to the model. The APR-DRG system does not completely capture the effects of these variables. In some cases, the better performance might be due to the inclusion of specific complications in the risk-of-mortality subclass assignment
Evoluzione dell'appropriatezza dei ricoveri nel Policlinico Senese dal 1994 al 1996
No full textSuppl.2 - Atti 38° Congr.Naz.S.It.I
Surface chemistry of Ni-free stainless steel
No full textNowadays there is a strong demand to replace Ni-Cr steels used for biomedical applications such as brackets in orthodoncy with a new generation of more biocompatible austenitic, nickel-free alloys. The aim of this work is the assessment of the substances that leach from the steel and the investigation of the growth and stability of the surface film formed on DIN 1.4456 Ni-free stainless steel in artificial saliva (pH 7.9) at 37°C by electrochemistry and XPS surface analyses. So far the data available in the literature refer to tests carried out at ambient temperature. Previous works of this research group [1] have shown that Ni-free stainless steel immersed into 0.1M NaOH solution form a passive film that changes its composition with immersion time. These results are confirmed in the present investigation: the corrosion current values decrease from 1 to 24 hours exposure time (see Table) to the solution and the passive film becomes more protective and thick. XPS provides evidence that the surface film formed is mainly composed of oxides and hydroxides of Fe (III), Cr(III) and Mn (see figure).
Fe (II) amount in the passive film decreases with immersion time in favor of Fe (III) oxide (Fe2O3) and hydroxide (FeOOH). Cr as well is first present as Cr2O3 and turns to Cr(OH)3 for longer contact time to artificial saliva.
The results will be discussed in comparison with those obtained on at ambient temperature [ref].
References.
1. T. H. Huang, Am. J. Orthod. Dentofac. (2001), 120, 1
2. C.T. Kao, Eur. J. Orthod. (2010), 32, 555-560
3. B. Elsener, Elec. Acta (2011), 56,4489-449
Stainless steel reinforcing bars – reason for their high pitting corrosion resistance
No full textIn harsh chloride bearing environments stainless steel reinforcing bars offer excellent corrosion resistance and very long service life for concrete structures, but the high costs limit a more widespread use. Manganese bearing nickel-free stainless steels could be a cost-effective alternative. Whereas the corrosion behavior of stainless steels in alkaline solutions, mortar and concrete is quite well established, only few information on the reasons for the high pitting resistance are available. This work reports the results of pitting potential measurements in solutions simulating alkaline and carbonated concrete on black steel, stainless steel DIN 1.4301, duplex steel DIN 1.4462 and nickel-free stainless steel DIN 1.4456. Duplex and nickel-free stainless steels are fully resistant even in 5 M NaCl solutions with pH 13 or higher, the lower grade DIN 1.4301 shows a wide scatter between fully resistant and pitting potentials as low as +0.2 V SCE. In carbonated solutions with pH 9 the nickel-free DIN 1.4456 shows pitting corrosion at chloride concentrations ≥ 3 M. This ranking of the pitting resistance can be rationalized based on XPS surface analysis results: both the increase of the Cr(III)oxy-hydroxide and Mo(VI) contents in the passive film and a marked nickel enrichment beneath the film improve the pitting resistance. The duplex DIN 1.4464 shows the highest pitting resistance, which can be attributed to the very high Cr(III)oxy-hydroxide, to a medium Mo(VI) content in the film and to a nickel enrichment beneath the film. Upon time, the protective properties of the surface film improve. This beneficial effect of ageing (transformation of the passive film to a less Fe2+ containing, more hydrated film) will lead to higher pitting potentials. It can be concluded that short-term solution experiments give conservative results in terms of resistance to chloride-induced corrosion in reinforced concrete structures
Nickel-free manganese bearing stainless steel in alkaline media - electrochemistry and surface chemistry
No full textThe use of austenitic nickel-containing stainless steels as concrete reinforcement offers excellent corrosion protection for concrete structures in harsh chloride bearing environments but is often limited due to the very high costs of these materials. Manganese bearing nickel-free stainless steels can be a cost-effective alternative for corrosion resistant reinforcements. Little, however, is known about the electrochemistry and even less on surface chemistry of these materials in alkaline media simulating concrete pore solutions. In this work a combined electrochemical (ocp = open circuit potential) and XPS (X-ray photoelectron spectroscopy) surface analytical investigation on the austenitic manganese bearing DIN 1.4456 (X8CrMnMoN18-18-2) stainless steel immersed into 0.1 M NaOH and more complex alkaline concrete pore solutions was performed. The results show that the passive film composition changes with immersion time, being progressively enriched in chromium oxy-hydroxide becoming similar to the conventional nickel-containing stainless steels. The composition of the metal interface beneath the passive film is strongly depleted in manganese and enriched in iron; chromium has nearly the nominal composition. The results are discussed regarding the film growth mechanism (ageing) of the new nickel-free stainless steel in alkaline solutions compared to traditional austenitic steels. Combining the results from pitting potential measurements with the composition of the passive film and the underlying metal interface, it can be concluded that the resistance against localized corrosion of the new nickel-free stainless steel relies on the strong chromium(III) and molybdenum (VI) oxy-hydroxide enrichment in the passive film
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