Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

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Applied SciencesKramers Laboratorium voor Fysische Technologi

Some investigations on low-speed anemometry

In an apparatus of the whirling arm type the use of anemometers of a semi-conducting material at low air speeds has been investigated. Some data on heat transmission from thin wires at low values of Reynold’s number are also obtained. Moreover a new method for calculating this quantity is developed

The physical properties of Fluorine-doped tindioxide coatings for Solar Collectors

Tinoxide coatings and their use for solar energy are investigate

The optical, electrical and structural properties of Fluorine-doped, Pyrolytically sprayed tindioxide coatings

Tindioxide coatings with different fluorine-doping have been produced by spray pyrolysis. The coatings have been analysed by spectrophotometry, Hall-effect measurements, X-ray diffraction and electron probe microanalysis. It is shown that the the electron mobility is limited by impurity scattering with a slight lattice scattering component for doped coatings, while the low mobility observed in undoped coatings is due to grain-boundary scattering. The diffraction measurements show a strong preferential orientation which is independent of the doping level. Electron probe microanalysis shows that it is a plausible assumption that the fluorine occupies the oxygen positions in the lattice, while the free electron density is about one third of the fluorine concentration

Transport Phenomena in Tungsten LPCVD in a Single-Wafer Reactor

The influence of the WF6 concentration on the growth rate in tungsten LPCVD from WF6 and H2 has been studied bothexperimentally in a coldwall single-wafer reactor and with the use of a mathematical simulation model, predicting the gasflow, heat transfer, species transport, and chemical reactions in the reactor. Model predictions were in very good agreementwith experimental growth rates and uniformities. The growth rate was found to be independent of the WF6 inletpressure above a certain value Pcrit, whereas for WF6 inlet pressures below Pcrit the growth rate decreases linearly with theWF6 inlet pressure. It is shown that this transition is due to mass-transfer limitations rather than a change in the reactionmechanism. The value of Pcrit depends on the reactor geometry and process conditions and may be obtained experimentallyor from model simulations as presented in this study. It is shown that large concentration gradients may be present inCVD reactors, even at low reactant conversion rates, and that criteria for "gradientless" reactor operation based on conversionrates are incorrect. We propose a better criterion, based on the value of Pcrit. It is also shown that thermal diffusionphenomena in coldwall reactors are very important. As a result, WF6 concentrations at the wafer surface will always be significantlylower than the inlet concentration

Modeling and Optimization of the Step Coverage of Tungsten LPCVD in Trenches and Contact Holes

A model is presented to calculate the step coverage of blanket tungsten low pressure chemical vapor deposition(W-LPCVD) from tungsten hexafluoride (WF6). The model can calculate tungsten growth in trenches and circular contactholes, in the case of the WF6 reduction by H2, SiH4, or both. The step coverage model predictions have been verified experimentallyby scanning electron microscopy (SEM). We found that the predictions of the step coverage model for the H2 reductionof WF6 are very accurate, if the partial pressures of the reactants at the inlet of the trench or contact hole areknown. To get these reactant inlet partial pressures, we used a reactor model which calculates the surface partial pressuresof all the reactants. These calculated surface partial pressures are used as input for our step coverage model. In this studywe showed that thermodiffusion plays a very important role in the actual surface partial pressure. In the case where SiH4was present in the gas mixture trends are predicted very well but the absolute values predicted by the step coveragemodel are too high. The partial pressure of HF, which is a by-product of the H2 reduction reaction, may be very high insidetrenches or contact holes, especially just before closing of the trench or contact hole. We found no influence of the calculatedHF partial pressure on the step coverage. Differences between step coverage in trenches and contact holes, as predictedby the step coverage model, were found to agree with the experiments. It is shown that the combination of the stepcoverage and reactor model is very useful in the optimization towards high step coverage, high throughput, and low WF6flow. We found a perfect step coverage (no void formation) in a 2 µm wide and 10 µm deep (2 × 10 µm) trench using anaverage WF6 flow of only 35 sccm, at a growth rate of 150 nm/min. In general, it is shown that the reduction of WF6 by SiH4offers no advantages over the reduction by H2 as far as step coverage is concerned.\u