133 research outputs found
ASO Author Reflection: Lateral Pelvic Lymph Nodes in Rectal Cancer—Not All Are Created Equal
No full textHidde M. Kroon, Miranda Kusters, and Tarik Sammou
Reply to: Lateral lymph node dissection in low rectal cancers: Call for standardized reporting of results to unify the global practice
No full textLetterHidde M. Kroona, Miranda Kusters, George J. Chang, Tarik Sammou
Systematic review and meta-analysis of long-term oncological outcomes of lateral lymph node dissection for metastatic nodes after neoadjuvant chemoradiotherapy in rectal cancer
No full textAvailable online 29 April 2022Abstract not availableHidde M. Kroon, Lotje A. Hoogervorst, Nicole Hanna-Rivero, Luke Traeger, Nagendra N. Dudi-Venkata, Sergei Bedrikovetski, Miranda Kusters, George J. Chang, Michelle L. Thomas, Tarik Sammou
Paulina vegetation model: Current attenuation by salt marsh vegetation
No full textThe present report represents the second phase of my M.Sc. dissertation. The first phase concentrated on thorough data processing of field measurements in the Paulina Polder, see Kusters et al (2003) in Appendix A. For the present phase of my end thesis I have investigated the influence of vegetation on currents in a mudflat salt marsh ecosystem in the estuary of the Westerschelde. This has been done within the framework of the Delft Cluster research program 'ecomorphology' and is part of the project Biogeomorphology of estuaries and coasts. The main objective of this thesis is to explore and evaluate the application of Delft3D, a physically-based hydrodynamic model linked with sedimentation transport in an environment where vegetation is important, e.g. a salt marsh, against field data. Once validated this Delft3D model can be used to simulate flooding and sedimentation patterns in other tidal marshes in the estuary of the Westerschelde. In a next stage this modelling can be extended to long time geomorphologic evolution simulations. The study site is the Paulina Polder, situated in the estuary of the Westerschelde in the southwest of the Netherlands. The Paulina Polder is a typically Westerschelde mudflat-salt marsh ecosystem, characterised by an extended mudflat with rich benthic community and salt marsh vegetation that contains all gradual stages from pioneer to late successively. The extended and viable zone of pioneer vegetation mainly consists of common cord grass. The sandbanks in the middle of the Schelde protect the salt marsh from extreme hydrodynamic conditions. To study the impact of vegetation on the estuarine morphodynamics, on a scale of a salt marsh the 'Paulina vegetation model' was designed. This is a three dimensional Delft3D model with an implemented routine to include vegetation. This routine incorporates an adaptation of the vertical flow distribution, turbulence generation and dissipation based on a 1DV-model. The mudflat and salt marsh system is modelled by an almost rectangular grid using a semi diurnal tide on the open sea boundary. The vegetation input is dependant on the location of the different plant types, the vertical plant structure and the number of plants per vegetation area. An important conclusion of this study is that the designed Paulina vegetation model can be used to study the effects of vegetation on flow in an estuarine environment. To obtain the most realistic simulation results detailed information about the bathymetry and vegetation is needed. The most important conclusion from the sensitivity analysis is that because of the presence of vegetation the flow area reduces, forcing the water to be pushed to the outer layers. The area is even more reduced when the vegetation is denser and the vegetation is modelled with leafs. In the upper layers, where there is no vegetation anymore, the water can overflow the plants, the velocity as a function of time increases. To al lesser degree there is an increase in velocity in the bottom layer. The changes in flow area have considerable effects on the velocities in the water column. Another finding is that because of the vegetation and the flow resistance of the marsh the water chooses a different route, the vegetation free gully. In this research the effects of waves, wind, leafs and the bending of stems are left out of the computations. In future research these effects should be investigated. Careful thought is needed about the influence of the hydraulic roughness of the vegetation on the morphological development of the salt marsh, concerning the small flow velocities.Civil Engineering and Geoscience
The effect of dendritic spine morphology on synaptic crosstalk: Two multisynapse models, integrating diffusion on curved surfaces
No full textDiffusive processes on curved surfaces are highly relevant for cellular processes and are increasingly used to characterize the behavior of proteins in cell membranes. More specifically, neurotransmitter receptors are present on the cell membranes of neurons (nerve cells) and are important for the signal transduction at synapses, which are the specializations through which neurons communicate. The morphology of the cell membrane at these synapses is nontrivial and this shape strongly affects the receptor lateral diffusion process [1]. The typical shape of a single synapse and its impact on the diffusive process have been studied [1,2]. An open question however, is how this shape affects the crosstalk between multiple synapses connected to the same dendrite. In other words, how does the release of receptors in one synapse influence the concentration in neighboring synapses. To study this we set up two diffusion models that integrate the morphology of multiple synapses. 1] Kusters, R., Kapitein, L. C., Hoogenraad, C. C., & Storm, C. (2013). Shape-induced asymmetric diffusion in dendritic spines allows efficient synaptic AMPA receptor trapping. Biophysical journal, 105(12), 2743-2750. [2] Kusters, R., & Storm, C. (2014). Impact of morphology on diffusive dynamics on curved surfaces. Physical Review E, 89(3), 032723.Numerical AnalysisApplied MathematicsElectrical Engineering, Mathematics and Computer Scienc
Some future directions in computational failure mechanics
No full textContinuum approaches are reviewed which can properly model localised deformations that act as a precursor to final fracture in quasi-brittle materials. Next, one such higher-order damaging continuum model is combined with a stochastic approach to describe the heterogeneity in quasi-brittle materials
Finite element reliability methods using DIANA
No full textFinite element relia.bility methods (FERM) a.re used for the analysis of a simply supported beam with a randomly distributed elastic stiffness. Two-noded Euler beam elements have been used to model the structure. The probability of exceeding a given threshold for the deflection at a certain point is calculated via FERM. The computer implementation makes use of the DIANA 5.0 finite element code
The Atlantic Meridional Overturning Circulation under Climate Forcing: An Analysis of the Community Earth System Model
No full textThe Atlantic Meridional Overturning Circulation (AMOC) is a key component in the Earth System. Given its important role in the climate system, variability in the AMOC strength is expected to have great impact on the global climate. The current observational timeseries are not long enough to make climate projections for the end of the century or even longer. Therefore, coupled climate models play an important role in the making of end of century climate projections on the AMOC strength. A known issue with the current generation of global coupled climate models is that the grid resolution is generally too coarse to resolve smaller scale processes such as mesoscale eddies. Observations and modelling studies suggest that mesoscale eddies play an important role in the exchange of water between convection regions and downwelling regions. When such processes are absent or parametrized incorrectly, it can have an influence on the climate projections based on these model simulations. This study analysed the AMOC characteristics in two different simulations of the Community Earth System Model; a reference simulation (referred to as piControl) and a simulation in which the atmospheric CO2 concentrations have been increased to four times the initial concentration (referred to as 1pctCO2). First, the AMOC characteristics in the piControl simulation are analysed using both a Eulerian and a Lagrangian approach. The Eulerian analysis shows that deep mixed layers, an indicator for convection, are present in the subpolar North Atlantic. Compared to observations and higher-resolution ocean-only models are these located closer to the West-Greenland coast. Strong vertical velocities are found over the continental slopes, especially over the steep continental slopes around Greenland. Second, the Lagrangian analysis showed the consequences of the coarse grid in the model. Only a single pathway around the subpolar gyre was observed. This implies that particles will experience convection while crossing the interior of the Labrador Sea, but only will experience downwelling when their individual pathway comes close enough to the continental slopes around Greenland. Furthermore, there is only limited exchange of particles with the regions north and south of the subpolar gyre. In the export of deep waters to the subtropical gyre, does it seem that the particles are being blocked by the North Atlantic Current. Third, the changes in the AMOC characteristics in the 1pctCO2 simulation are compared to the piControl simulation. In the 1pctCO2 simulation have deep mixed layers disappeared from the subpolar North Atlantic and convection in this region has shut down. A new fresh(er) surface layer in the Labrador Sea has intensified the stratification and prohibits the formation of deepmixed layers. Instead of the deep mixed layers in the subpolar North Atlantic have new deep mixed layers emerged between 30N and 40N. In general are velocities reduced in magnitude in the 1pctCO2 simulation, but the stronger vertical velocities can still be found over the continental slopes. In conclusion, the results show that the CESM model can reproduce the two components of the AMOC reasonably well, but the connection in the formof mesoscale eddies is missing. This illustrates that a overturning streamfunction simplifies the complexity of the overturning process. The overturning streamfunction is a measure for the overturning strength, but it does not take into account how and if the convection process and the exchange between convection and downwelling are represented.Civil Engineering | Hydraulic Engineerin
The Value and Necessity of the Project Management Plan: The pre-award phase of BVP projects from the vendor’s perspective
No full textThe research is aimed at defining the hurdles in the pre-award phase of Best Value Procurement (BVP) projects and providing a solution to overcome those problems for engineering companies. The pre-award phase includes the period between the conditional award (Dutch: voornemen tot gunning) and the definitive award (Dutch: definitieve gunning). In this phase, the vendor has approximately two months to develop a Project Management Plan (PMP) (Rijt, 2016). The pre-award phase is seen as the most important phase in BVP projects, however, a knowledge gap exists regarding control in the pre-award phase. Exploratory interviews at Witteveen+Bos have revealed that the company struggles to control the pre-award phase of projects in which they are involved, while literature suggests that particularly front-end project development is critical for outstanding project performance.Civil Engineering and GeosciencesStructural EngineeringConstruction Management and Engineerin
ARM3D: A 3D printed transhumeral arm prosthesis
No full textAim: This project aims to design a lightweight, inexpensive and easy to use upper arm prosthesis through improving the design of ARM3D, which is a 3D printed body-powered transhumeral arm prosthesis. This study will cover general shortcomings of body-powered arm prostheses as the weight, cost, amount of parts and limited accessibility of them. This study also focusses on a natural appearance of the prosthetic arm. Results: The improved design of ARM3D is made of six 3D printed and eight non-3D printed parts. It has three Degrees of Freedom (DOF’s), one control cable, a harness both to suspend and control the prosthesis, an active voluntary closing hand, a passive rotating wrist joint and a passive elbow hinge joint. The prosthesis costs €59,68 and weighs 403 g. It takes 3 days, 6 hours and 47 minutes to print and 15 minutes to assemble. The maximum open hand width is 64 mm and the prosthesis needs 15 N of tension force on the control cable to operate. Furthermore, it is possible to paint the prosthetic fingernails and to remove the nail polish. Conclusion: An improved design of the ARM3D prosthesis is presented in this paper. ARM3D is almost entirely 3D printed. It is a lightweight and inexpensive device. A field study is required to gather more information whether the prosthesis is easy to use.Biomedical Engineerin
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