Abstract The effect of increased total knee arthroplasty (TKA) surgical volume on the incidence of knee complications within a single surgeon's practice was determined. Data were collected ...prospectively on 600 primary TKAs. Major complications required knee reoperation. Minor complications were wound concerns requiring increased surveillance or oral antibiotics. Twelve major (2.0%) and 40 minor (6.7%) complications occurred at minimum 2-year follow-up. Surgical volume increased from 57 to 150 procedures per 6 months through the course of the study. Multivariate analysis determined that increased surgical volume was associated with lower rates of both major and minor complications, adjusted odds ratio 0.62 (95% confidence interval CI, 0.40-0.96) and 0.56 (95% CI, 0.43-0.73), respectively. For each additional 50 procedures performed within a 6-month interval, major complications were reduced by 38% ( P = .03), and minor complications were reduced by 44% ( P < .0001). All complications were significantly decreased when the surgeon was performing 112 ± 44 TKAs compared with 85 ± 49 TKAs per 6-month interval.
Objectives: To investigate whether there is a relationship between fatigue and sickness absence. Two additional hypotheses were based on the theoretical distinction between involuntary, health ...related absence and voluntary, attitudinal absence. In the literature, the former term is usually used to describe long term sickness absence, the latter relates to short term sickness absence. In line with this, the first additional hypothesis was that higher fatigue would correspond with a higher risk of long term, primarily health related absence. The second additional hypothesis was that higher fatigue would correspond with a higher risk of short term, primarily motivational absence. Methods: A multidimensional fatigue measure, as well as potential sociodemographic and work related confounders were assessed in the baseline questionnaire of the Maastricht cohort study on fatigue at work. Sickness absence was objectively assessed on the basis of organisational absence records and measured over the six months immediately following the baseline questionnaire. In the first, general hypothesis the effect of fatigue on time-to-onset of first sickness absence spell during follow up was investigated. For this purpose, a survival analysis was performed. The effect of fatigue on long term sickness absence was tested by a logistic regression analysis. The effect of fatigue on short term sickness absence was investigated by performing a survival analysis with time-to-onset of first short absence spell as an outcome. Results: It was found that higher fatigue decreased the time-to-onset of the first sickness absence spell. Additional analyses showed that fatigue was related to long term as well as to short term sickness absence. The effect of fatigue on the first mentioned outcome was stronger than the effect on the latter outcome. Potential confounders only weakened the effect of fatigue on long term absence. Conclusions: Fatigue was associated with short term but particularly with long term sickness absence. The relation between fatigue and future sickness absence holds when controlling for work related and sociodemographic confounders. Fatigue as measured with the Checklist Individual Strength can be used as a screening instrument to assess the likelihood of sickness absence in the short term.
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•Simultaneous measurement of spatially-resolved concentration-, temperature- and XAS profiles.•Predicted oxidation states could be validated with oxidation states observed from XANES ...measurements.•Kinetic model could be quickly developed by fitting complete concentration profiles.
Efficient and sustainable optimization of heterogeneous catalytic processes requires a deep understanding of catalyst structure-activity relationships that occur inside catalytic reactors in space and time. Here we introduce a catalytic profile reactor capable of simultaneously measuring spatially-resolved temperature, concentration, and X-ray absorption spectroscopy (XAS) profiles through a catalytic fixed bed. Using the oxidative dehydrogenation of ethane to ethylene over MoO3/γ-Al2O3 as a test reaction, we obtained a detailed picture of local catalyst structure and activity under realistic and well-defined reaction conditions. Concentration, temperature and XAS profiles were measured up to and beyond the point of complete O2 consumption showing a distinct transition from oxidation reactions to steam reforming and water-gas shift. Profile data up to the point of complete O2 consumption were used to develop a kinetic model for the oxidation chemistry. Structural data beyond the point of complete O2 consumption were ideal for demonstrating the correlative approach but the kinetic data in the second part were not considered during modeling because industrial selective oxidation reactors are always operated at incomplete O2 consumption. The fit of kinetic models to complete reactor profiles significantly speeds up the development and accuracy of kinetic models required for any reactor design. Further, the kinetic model considers the oxidation state of molybdenum as a dynamically changing and critical catalyst property. Hence, we could predict local catalyst oxidation states and validate our model experimentally with spatially-resolved XAS. This provides a quantitative link between catalyst structure and reactivity and allows including catalyst dynamics in reactor simulations. In the current work a widely applicable methodological approach is presented to understand and optimize heterogeneous catalytic processes, e.g. in selective oxidation.
ABSTRACTA major problem for the industrial application of supercritical water oxidation (SCWO) is to find a reactor material that can withstand both the thermo-mechanical load (high pressure, ...elevated temperature) and the chemical attack caused by the reaction medium. Especially when inorganic acids like hydrogen chloride (HCl) are formed in the course of the oxidation process, the available high-alloyed steels and Ni-based alloys suffer from severe corrosion and, from the materials investigated up to now, only ceramics (e.g., corundum) and Ti alloys exhibit a promising chemical resistance.1 However, because of their insufficient mechanical properties, ceramics (brittleness) and Ti alloys (high creep rates at elevated temperature) can only be used as the liner of a pressure-bearing tube. During the last decade, a number of commercially available materials have been tested with regard to their corrosion behavior in SCWO systems by various groups of researchers. The conditions (temperatures, pressure, pH, concentration of corrosives, etc.) and experimental techniques that have been applied differ considerably from case to case, so that a comparison of results is difficult. For the most severe SCWO environments--those including an acidic reaction medium that contains chloride ions--the essence of these investigations is that some common metallic materials (Ni-based alloys, austenitic steels, Cr-based alloys, etc.) behave better than others, but the absolute corrosion resistance is still unsatisfactory in at least one range of temperatures prevailing in a SCWO plant. To clarify the influence of the alloying elements in Ni-based materials, the authors started an investigation on model alloys, i.e., binary Ni-Cr and ternary alloys containing W and Al. These alloys were exposed to the reaction medium resulting from the oxidation of dichloromethane (CH2Cl2) with hydrogen peroxide (H2O2) at 40 MPa and various temperatures between ~100°C and ~415°C. 40 MPa is an intermediate operation pressure for the SCWO process. The critical temperature of pure water (Tc = 374°C) is within the
First experimental results of fluorescence microtomography with 6 /spl mu/m resolution obtained at ESRF, Grenoble, France, are described. The setup comprises high-quality optics (monochromator, ...mirror, focusing lenses) coupled to the high-energy/brilliance/coherence of the ID 22 undulator beamline. The tomographic setup allows precise measurements in the "pencil-beam" geometry. The image reconstruction is based on a modification of the algebraic reconstruction method but includes simplifications of the model. The quality and precision of the two-dimensional reconstructed elemental images of a phantom sample are encouraging. The method will be further refined and applied for the analysis of more complex inhomogeneous samples.
This paper gives an overview of investigations on the corrosion behavior of commercially available materials and nickel-chromium model alloys in chloride-containing, high-pressure aqueous solutions ...(mostly oxygenated, diluted hydrochloric acid HCl at 40 MPa), which were performed at the Institut fuer Materialforschung III in the Forschungszentrum Karlsruhe, Germany. The experimental techniques applied are introduced and the results obtained for the commercial alloys are presented and related to work published by other authors. Especially the influence of the process parameters temperature, pressure, and pH on the performance of Alloy G-30 (UNS N06030) is discussed. An internal oxidation type of material is proposed for substantial material consumption in the course of corrosion processes that start locally but eventually spread to be general (locally starting).
The corrosion behavior of structural materials in liquid lead alloys like Pb-17Li as a liquid tritium breeder for future fusion reactors and Pb-55Bi (lead-bismuth eutectic LBE) as an envisaged ...spallation target and/or coolant for accelerator-driven systems (ADS) and lead-cooled Gen IV reactors is a key issue in the road map for developing new energy systems within the next decades. Ferritic-martensitic steels of the 8 wt% to 10 wt% Cr type are considered as structural materials for use in liquid Pb-17Li at temperatures up to 550°C. Due to the specific physical chemistry of Pb-17Li, dissolution corrosion is the major corrosion mechanism of iron-based alloys. No oxide formation on steel surfaces can occur because of the very low oxygen potential. Therefore, coatings could/must be applied to minimize corrosion effects at medium (500°C) and higher operational temperatures (650°C) of advanced fusion blanket concepts. Ferritic-martensitic and austenitic CrNi steels are considered potential structural materials for ADS and Gen IV reactor applications. Nevertheless, the high nickel solubility in LBE limits the use of unprotected austenitic steels to temperatures of about 550°C. Because of the much higher oxygen potential in LBE, a totally different strategy of minimizing corrosion must be adopted. By using active oxygen control, a desired oxygen activity will be adjusted in the liquid metal via gas phase equilibrium, which enables the controlled formation of oxide layers on the steel surfaces. These in situ-formed oxides can act as corrosion barriers and make use of high-nickel alloys possible, even at temperatures around 600°C.
We have designed and built a compact x-ray microtomography system to perform element mapping and absorption imaging by exploiting scanning fluorescence tomography and full-field transmission ...microtomography, respectively. It is based on a low power microfocus tube and is potentially appropriate for x-ray diagnostics in space. Full-field transmission tomography yields the three-dimensional inner structure of an object. Fluorescence microtomography provides the element distribution on a virtual section through the sample. Both techniques can be combined for appropriate samples. Microradiography as well as fluorescence mapping are also possible. For fluorescence microtomography a small and intensive microbeam is required. It is generated using a polycapillary optic. Operating the microfocus tube with a molybdenum target at 12 W, a microbeam with a full width at half maximum lateral extension of 16 microm and a flux of about 10(8) photonss is generated. As an example of application, this beam is used to determine the element distribution inside dried plant samples. For full-field scanning tomography, the x-ray optic is removed and the sample is imaged in magnifying projection onto a two-dimensional position sensitive detector. Depending on the sample size, a spatial resolution down to about 10 microm is possible in this mode. The method is demonstrated by three-dimensional imaging of a rat humerus.
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