132 research outputs found
Fault analysis and improved design of JET in-vessel Mirnov coils
No full textIn vessel Mirnov coils are an essential diagnostic in present day tokamaks. Their use in ITER and future Fusion reactors presents some disadvantages linked to the high radiation environment. Furthermore large Electro Magnetic (EM) forces can be experienced by the coil, due to the pulsed operation of the tokamak device (Van Nieuwenhove and Vermeeren, 2003, Vayakis et al., 2011 [1,2]), and disruptions (Gerasimov et al., 2015 [3]). Since the operation with the ITER-like wall, JET has experienced severe faults in the high-bandwidth Ti wire coils. During 2016-17 new coils have been designed and installed. These can be replaced using remote handling, and they use Cu alloy wire. The presented work includes the failure analysis and modelling, motivating the design differences between old and new coils. The latter will provide valuable information on the long term effects of EM loads during disruptions, as well as chemical degradation processes that will be encountered for ITER High Frequency (HF) coils, which are characterized by the same materials
Bescherming van minderheidsaandeelhouders bij een grensoverschrijdende fusie
No full textContains fulltext :
74203.pdf (Publisher’s version ) (Open Access)12 p
Use your phone to build a simple laparoscopic trainer
No full textSimulation is becoming increasingly integral to surgical training with progressive restrictions on working hours. This paper describes a unique, cable free, laparoscopic trainer that can be constructed using items readily available to the average surgical trainee. The trainer described is not a substitute for surgical practice but, nonetheless, a useful tool in developing skills such as hand-eye co-ordination, triangulation and depth queuing
Structure and functional analysis of the IGF-II/IGF2R interaction
No full textEmbryonic development and normal growth require exquisite control of insulin-like growth factors (IGFs). In mammals the extracellular region of the cation-independent mannose-6-phosphate receptor has gained an IGF-II-binding function and is termed type II IGF receptor (IGF2R). IGF2R sequesters IGF-II; imbalances occur in cancers and IGF2R is implicated in tumour suppression. We report crystal structures of IGF2R domains 11–12, 11–12–13–14 and domains 11–12–13/IGF-II complex. A distinctive juxtaposition of these domains provides the IGF-II-binding unit, with domain 11 directly interacting with IGF-II and domain 13 modulating binding site flexibility. Our complex shows that Phe19 and Leu53 of IGF-II lock into a hydrophobic pocket unique to domain 11 of mammalian IGF2Rs. Mutagenesis analyses confirm this IGF-II 'binding-hotspot', revealing that IGF-binding proteins and IGF2R have converged on the same high-affinity site.James Brown, Carlie Delaine, Oliver J Zaccheo, Christian Siebold, Robert J Gilbert, Gijs van Boxel, Adam Denley, John C Wallace, A Bassim Hassan, Briony E Forbes and E Yvonne Jone
The effect of single vegetation elements on wind speed and sediment transport in the Sahelian zone of Burkina Faso
No full textSoil loss caused by wind erosion is a widespread phenomenon in the Sahelian zone of West Africa. According to Sahelian farmers, scattered vegetation standing in amongst the crop has the potential for a wind erosion control strategy. This study was conducted to study the effect of single vegetation elements on the pattern of average wind speed and sediment transport. This was done by two experiments that were carried out during the rainy seasons of 2002 and 2003 in north Burkina Faso, West Africa. Wind speeds were measured using three sonic anemometers, at a sampling frequency of 16 Hz. Sediment transport was determined by calculating the mass fluxes from 17 MWAC catchers. In this study, a shrub was defined as a vegetation element with branches until ground and a tree as a vegetation element with a distinctive trunk below a canopy. Behind shrubs wind speed near the soil surface was reduced up to approximately seven times the height of the shrub. The observed reduction in wind speed in the area where wind speed was reduced was 15 per cent on average. At the sides of the shrub, wind speed was increased, by on average 6 per cent. As the area of increase in wind speed is one-third of the area of decrease in wind speed, the net effect of a shrub is a reduction in wind speed. A similar pattern was visible for the pattern of sediment transport around a shrub. Downwind of a shrub, sediment transport was diminished up to seven times the height of the shrub. Probably most of this material was trapped by the shrub. Trees showed a local increase of wind around the trunk, which is expected to relate to an increase in sediment transport around the trunk. Mass flux measurements of sediment transport were not made, but visual observations in the field substantiate this. Behind the canopy of a tree, a tree acts similarly to a shrub regarding its effects on average wind speed, but as a tree is generally a larger obstacle than a shrub the extent of this effect is larger than for shrubs. Thus, whereas shrubs are more effective than trees regarding their direct effect on soil loss by trapping sand particles near the soil surface, trees are more effective in affecting soil loss indirectly by reducing the wind speed downwind more effectively than shrubs. Therefore, to reduce soil loss in an area, the presence of both trees and shrubs is crucial
Wind erosion reduction by scattered woody vegetation in farmers’ fields in northern Burkina Faso
No full textWind erosion is an important soil degradation process on agricultural fields in the Sahel and is strongly affected by scattered woody vegetation. This paper analyses the effect of scattered vegetation on sediment transport in agricultural fields in northern Burkina Faso. A model was developed to simulate the changes in wind speed and sediment transport around shrubs and trees. The model was applied by using field measurements on wind speed, wind direction, and sediment transport, obtained from two farmers’ fields during the rainy season of 2003. Vegetation characteristics and the density of vegetation elements differed per field. The model was used for scenario studies to test the effect of height, number, element type and spatial arrangement of vegetation elements on aeolian sediment transport. The local effects of vegetation elements on wind speed and sediment transport are small compared with the effects caused by the changes in the aerodynamic roughness length and changing wind speed at a larger scale. With relatively small changes in the characteristics of scattered woody vegetation, sediment transport can change considerably. An optimal arrangement of vegetation elements in an area in itself does not exist; it is an interrelation between the number of vegetation elements, the silhouette area and the type of vegetation elements present. This interrelation makes the use of scattered vegetation as a wind erosion control strategy attractive, as it fits in a variety of farming systems and can easily be adapted to specific needs of farmers. Therefore, scattered woody vegetation can be used to reduce sediment transport
Machine learning to predict early recurrence after oesophageal cancer surgery
No full textBackground: Early cancer recurrence after oesophagectomy is a common problem, with an incidence of 20–30 per cent despite the widespread use of neoadjuvant treatment. Quantification of this risk is difficult and existing models perform poorly. This study aimed to develop a predictive model for early recurrence after surgery for oesophageal adenocarcinoma using a large multinational cohort and machine learning approaches. Methods: Consecutive patients who underwent oesophagectomy for adenocarcinoma and had neoadjuvant treatment in one Dutch and six UK oesophagogastric units were analysed. Using clinical characteristics and postoperative histopathology, models were generated using elastic net regression (ELR) and the machine learning methods random forest (RF) and extreme gradient boosting (XGB). Finally, a combined (ensemble) model of these was generated. The relative importance of factors to outcome was calculated as a percentage contribution to the model. Results: A total of 812 patients were included. The recurrence rate at less than 1 year was 29·1 per cent. All of the models demonstrated good discrimination. Internally validated areas under the receiver operating characteristic (ROC) curve (AUCs) were similar, with the ensemble model performing best (AUC 0·791 for ELR, 0·801 for RF, 0·804 for XGB, 0·805 for ensemble). Performance was similar when internal–external validation was used (validation across sites, AUC 0·804 for ensemble). In the final model, the most important variables were number of positive lymph nodes (25·7 per cent) and lymphovascular invasion (16·9 per cent). Conclusion: The model derived using machine learning approaches and an international data set provided excellent performance in quantifying the risk of early recurrence after surgery, and will be useful in prognostication for clinicians and patients.</p
Measurement of Water Drop Sizes Generated by a Dripping Rainfall Simulator with Drippers in the Form of Hypodermic Needles
No full textDripping rainfall simulators (DRS) for soil research generate water drops with different types of drippers, but metal tubes are most commonly used, often in the form of hypodermic needles. However, scientific papers using dripping rainfall simulators are often incomplete in terms of data on hypodermic needle characteristics, as well as data on drops produced by hypodermic needles under different water pressures. This study determines which drop sizes and dripping speeds are generated by various hypodermic needles at different water pressures. For the purpose of this study, a dripping rainfall simulator was designed and constructed for laboratory use. Water drops were generated with 11 different needles, ranging in size from 16 G to 32 G (tube gauge number), at different water pressures. Measured water drop sizes ranged from 1.42 to 3.69 mm at a dripping speed between 10 and 360 drops per minute and water head from 14 to over 1970 mm. Measured drop sizes, supplemented with data from previous studies, provided information on the relation between drop sizes and the size of the hypodermic needles. Van Boxel’s numerical model provided estimations of the fall velocity for different drop diameters and their kinetic energy for falling heights up to 11.5 m. The results of this research can be used to design dripping rainfall simulators for soil research
Impact of grazing and atmospheric deposition of nitrogen on vegetation development of dry dune meadows (Abstract)
No full text- …
