Percolation in the classical blockmodel

Classical blockmodel is known as the simplest among models of networks with community structure. The model can be also seen as an extremely simply example of interconnected networks. For this reason, it is surprising that the percolation transition in the classical blockmodel has not been examined so far, although the phenomenon has been studied in a variety of much more complicated models of interconnected and multiplex networks. In this paper we derive the self-consistent equation for the size the global percolation cluster in the classical blockmodel. We also find the condition for percolation threshold which characterizes the emergence of the giant component. We show that the discussed percolation phenomenon may cause unexpected problems in a simple optimization process of the multilevel network construction. Numerical simulations confirm the correctness of our theoretical derivations.Comment: 7 pages, 6 figure

In patients eligible for meniscal surgery who first receive physical therapy, multivariable prognostic models cannot predict who will eventually undergo surgery

Purpose Although physical therapy is the recommended treatment in patients over 45 years old with a degenerative meniscal tear, 24% still opt for meniscal surgery. The aim was to identify those patients with a degenerative meniscal tear who will undergo surgery following physical therapy. Methods The data for this study were generated in the physical therapy arm of the ESCAPE trial, a randomized clinical trial investigating the effectiveness of surgery versus physical therapy in patients of 45-70 years old, with a degenerative meniscal tear. At 6 and 24 months patients were divided into two groups: those who did not undergo surgery, and those who did undergo surgery. Two multivariable prognostic models were developed using candidate predictors that were selected from the list of the patients' baseline variables. A multivariable logistic regression analysis was performed with backward Wald selection and a cut-off of p < 0.157. For both models the performance was assessed and corrected for the models' optimism through an internal validation using bootstrapping technique with 500 repetitions. Results At 6 months, 32/153 patients (20.9%) underwent meniscal surgery following physical therapy. Based on the multivariable regression analysis, patients were more likely to opt for meniscal surgery within 6 months when they had worse knee function, lower education level and a better general physical health status at baseline. At 24 months, 43/153 patients (28.1%) underwent meniscal surgery following physical therapy. Patients were more likely to opt for meniscal surgery within 24 months when they had worse knee function and a lower level of education at baseline at baseline. Both models had a low explained variance (16 and 11%, respectively) and an insufficient predictive accuracy. Conclusion Not all patients with degenerative meniscal tears experience beneficial results following physical therapy. The non-responders to physical therapy could not accurately be predicted by our prognostic models.Orthopaedics, Trauma Surgery and Rehabilitatio

Evaluation of safety, performance and emissions of synthetic fuel blends in a Cessna Citation II

Prior to being used in aviation, alternative fuels have to be tested thoroughly to ensure safe operation. At Delft University of Technology, a test programme was performed to evaluate the safety, performance and emissions of synthetic fuel blends. During test preparations, compatibility of the synthetic fuel with the aircraft, a Cessna Citation II equipped with Pratt & Whitney Canada JT15D-4 jet engines, was ensured by material and component testing. When safe operation was ensured, on-ground engine test runs were performed. Results indicated good engine operation and reduced fuel consumption with increasing synthetic fuel content. Emission measurements during the engine test runs showed significantly reduced soot and sulphur dioxide emissions and small reductions in carbon monoxide and nitrogen oxides emission over a landing and take-off cycle.Aerospace Engineerin

Using Synthetic Kerosene in Civil Jet Aircraft

TU Delft in the Netherlands is performing research into the effects of the use of synthetic kerosene in aircraft. The research program consists of both desk research and tests. In the desk research gas turbine simulations will be combined with payload range performance calculations to show engine effects and fuel consumption changes. Ground and flight tests will be performed to show safe operation on synthetic fuel and to validate the calculations. Measurements during the ground tests will show the changed emissions as a result of the synthetic fuel.Aerodynamics & Wind EnergyAerospace Engineerin

Emissions testing on gas-to-liquid kerosene blends

The search for alternative fuels has lead to a number of possibilities. The most promising alternative fuels for the short term are drop-in fuels such as synthetic fuel and hydrotreated renewable jet. These fuels are similar to Jet A-1 but some differences are present. Synthetic fuels are produced using a process that results in a fuel without trace elements and almost no aromatics. Furthermore, synthetic fuels have a higher energetic content and lower gravimetric density than Jet A-1. These differences cause several effects when considering the use of synthetic fuel in aircraft. A performance model is used to show that the payload-range performance is changed and that an efficiency gain is achieved on the fuel consumption for a regular flight. Measurement of the soot emissions for several blends of synthetic fuel with Jet A-1 show that increasing the amount of synthetic fuel leads to significant reductions in soot emissions. Reductions of 50 to 70% in particle mass emitted can be reached by using 50% synthetic fuel. This might reduce the amount of contrails and aircraft induced cirrus clouds and seriously increase local air quality around airports.Aerodynamics & Wind EnergyAerospace Engineerin

Do older patients who refuse to participate in a self-management intervention in the Netherlands differ from older patients who agree to participate?

BACKGROUND AND AIMS: Refusal of patients to participate in intervention programs is an important problem in clinical trials but, in general, researchers devote relatively little attention to it. In this article, a comparison is made between patients who, after having been invited, agreed to participate in a self-management intervention (participants) and those who refused (refusers). Compared with other studies of refusers, relatively more information could be gathered with regard to both their characteristics and reasons for refusing, because all potential participants were invited personally. METHODS: Older patients from a Dutch outpatient clinic were invited to participate in a self-management intervention, and their characteristics were assessed. Demographic data were collected, as well as data on physical functioning and lack of emotional support. People who refused to participate were asked to give their reasons for refusing. RESULTS: Of the 361 patients invited, 267 (74%) refused participation. These refusers were more restricted in their mobility, lived further away from the location of the intervention, and had a partner more often than did the participants. No differences were found in level of education, age or gender. The main reasons given by respondents for refusing to participate were lack of time, travel distance, and transport problems. CONCLUSIONS: As in many studies, the refusal rate in this study is high, and seems to be related to physical mobility restrictions, travel distance and, partly, to availability of emotional support. These findings may be used to make the recruitment process more effective - for example, by offering transport to the location of the intervention

Course of distress in breast cancer patients, their partners, and matched control couples

BACKGROUND: Previous studies offer a limited perspective on the dynamic course of distress in cancer patients and their partners, owing to a restricted number of assessment points and the absence of comparison controls drawn from the general population. PURPOSE: This study investigated the course of distress among breast cancer patients and their partners (N = 92 couples) in comparison to matched control couples (N = 64). Furthermore, the influence of neuroticism on distress was investigated. METHOD: The Hospital Anxiety and Depression Scale was administered nine times over a 12-month period, and neuroticism was assessed at the beginning of the study using the Eysenck Personality Questionnaire. RESULTS: Multilevel analyses revealed that patients were more distressed during the first 15 months after diagnosis than nonpatients. A significant portion of the distress that could not be explained by the cancer experience was explained by neuroticism. CONCLUSION: Differences in distress between patients and comparison-control women are relatively small and decreased over time, while distress in male partners was not elevated in comparison to their controls