The Historical Context of the Gender Gap in Mathematics

This chapter is based on the talk that I gave in August 2018 at the ICM in Rio de Janeiro at the panel on "The Gender Gap in Mathematical and Natural Sciences from a Historical Perspective". It provides some examples of the challenges and prejudices faced by women mathematicians during last two hundred and fifty years. I make no claim for completeness but hope that the examples will help to shed light on some of the problems many women mathematicians still face today

3D-GIS and Urban Volume: applying the third dimension in a morphological study of the Amsterdam Urban Landscape

One of the key-features of intensive urban land use is the use of the third dimension. When space is scarce, cities tend to grow vertically. At present this third dimension is not normally present in urban studies. We propose a new indicator for measuring urban morphology in all its dimensions: urban volume, based on a combination of land use maps and detailed elevation data. The Netherlands are fortunate enough to have high density information on terrain heights. Since natural elevation differences in the western part of the country are almost non-existent, height-data can provide us with information on building heights. The objective of this study is to explore the analytical possibilities for urban studies of this new elevation dataset with (3D-)GIS functionality. As a case study the changes in the urban landscape of Amsterdam in the past 50 years are studied

Development of a selective Americium Separation Process by Liquid-Liquid Extraction

International audienceRecycling americium from spent fuels is an important option considered for the future nuclear cycle as americium is the main contributor to the long-term radiotoxicity and heat power of the ultimate waste. The separation of americium alone from a PUREX raffinate can be achieved by co-extracting lanthanide (Ln) and actinide(III) cations in an organic phase containing TODGA diglycolamide extractant, and then strip Am(III) with selectivity towards curium and lanthanides. The water soluble ligand TPAEN (N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]-ethylenediamine) was tested to selectively strip Am from the loaded solvent. Used in combination with TODGA, TPAEN shows a quite high Cm/Am selectivity (SFCm/Am = 4 at 0.1M HNO3), which allows to selectively strip Am while Cm and Ln remain extracted in the organic phase. The molecule can be used at pH 1 without addition of nitrate salts.Further batch extraction data were acquired to design a process flowsheet like extraction isotherms to evaluate the influence of parameters such as americium concentration, temperature, pH, ligand concentration, etc. Kinetics experiments in batch contactors (centrifuges or mixer settlers) are also important to characterize times necessary to reach equilibrium.The impact of radiolysis on TPAEN stripping performances was also characterized after irradiating some samples up to 200 kGy showing that the ligand is particularly sensitive. Further studies should be implemented to better characterize degradation products and impact on process performances.Besides these extraction data, spectroscopic studies are in process to provide detailed knowledge about the chemical species formed in the aqueous phase with TPAEN (micro-calorimetry, UV-visible, TRLIFS, ESI-MS). These results show the formation of 11 species especially with Nd and Am

Development of a selective americium separation process using TPAEN as a water-soluble stripping agent

International audienceRecycling americium from spent fuels is an important option considered for the future nuclear fuel cycle as americium is the main contributor to the long-term radiotoxicity and heat power of the ultimate waste. The separation of americium alone from a PUREX raffinate can be achieved by co-extracting lanthanide (Ln) and actinide(III) cations in an organic phase containing TODGA diglycolamide extractant, and then strip Am(III) with selectivity towards curium and lanthanides (by analogy with the i-SANEX process for example). The water soluble ligand TPAEN (N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]-ethylenediamine) was tested to selectively strip Am from a loaded organic phase. Used in combination with TODGA in the organic phase, TPAEN shows a quite high Cm/Am selectivity (SFCm/Am = 4 at 0.1M HNO3), which allows to selectively strip Am while Cm and Ln remain extracted in the organic phase. The molecule can be used at pH 1 without addition of nitrate salts.Additional batch data were acquired to evaluate the best conditions to develop a liquid-liquid separation flowsheet with this promising TODGA/TPAEN separation system. It was observed that with macro concentrations of lanthanides, an increase of the TPAEN concentration leads to higher Cm/Am selectivity (SFCm/Am up to 5 were measured). It was also demonstrated that TPAEN has a strong complexing capacity allowing the back extraction of Am in macro concentration (1 2 mM) even with low ligand concentrations (around 1.5 equivalent of ligand is enough). TPAEN has a higher affinity for light lanthanides and the selectivity between La and Am might become low depending on the experimental conditions. The influence of parameters such as temperature, pH, ligand and cations concentrations was studied. Kinetics experiments in batch contactors (centrifuges or mixer settlers) were also performed to characterize times necessary to reach equilibrium. This set of experimental work data allowed the elaboration of a thermodynamical model which was implemented in the PAREX simulation code in order propose a flowsheet. The feasibility of this process will be evaluated during spiked tests in centrifugal contactors starting from a surrogate PUREX raffinate spiked with traces amounts of Am and Cm. A final hot test will finally be performed at ITU from a genuine PUREX raffinate.This work is the result of collaborations in the framework of the SACSESS European Project

The third dimension in urban geography; the urban volume approach

A new methodology is presented that measures density in urban systems. By combining highly detailed height measurements with, amongst others, topographical data we are able to quantify urban volume. This new approach is demonstrated in two separate case studies that relate to the temporal and spatial dimension of the urban environment, respectively. In the first study the growth of the city of Amsterdam over the past century is studied. The urban-volume indicator is used to visualise and quantify the urban extension and intensification process. To critically analyse the spatiotemporal development of Amsterdam the self-organising-map approach is applied. Special attention is given to highlighting any signs of recent polynuclear development. The second case study compares the building-height frequency and spatial distribution of high-density zones in the four major Dutch cities. Additionally, the presence of built-up areas and the actual urban-volume values are explained simultaneously using a Heckman selection model. © 2009 Pion Ltd and its Licensors

Structural and functional analysis of phosphorylation-specific binders of the kinase ERK from designed ankyrin repeat protein libraries

We have selected designed ankyrin repeat proteins (DARPins) from a synthetic library by using ribosome display that selectively bind to the mitogen-activated protein kinase ERK2 (extracellular signal-regulated kinase 2) in either its nonphosphorylated (inactive) or doubly phosphorylated (active) form. They do not bind to other kinases tested. Crystal structures of complexes with two DARPins, each specific for one of the kinase forms, were obtained. The two DARPins bind to essentially the same region of the kinase, but recognize the conformational change within the activation loop and an adjacent area, which is the key structural difference that occurs upon activation. Whereas the rigid phosphorylated activation loop remains in the same form when bound by the DARPin, the more mobile unphosphorylated loop is pushed to a new position. The DARPins can be used to selectively precipitate the cognate form of the kinases from cell lysates. They can also specifically recognize the modification status of the kinase inside the cell. By fusing the kinase with Renilla luciferase and the DARPin to GFP, an energy transfer from luciferase to GFP can be observed in COS-7 cells upon intracellular complex formation. Phosphorylated ERK2 is seen to increase by incubation of the COS-7 cells with FBS and to decrease upon adding the ERK pathway inhibitor PD98509. Furthermore, the anti-ERK2 DARPin is seen to inhibit ERK phosphorylation as it blocks the target inside the cell. This strategy of creating activation-state-specific sensors and kinase-specific inhibitors may add to the repertoire to investigate intracellular signaling in real time