Spin transport in graphene nanostructures

Graphene is an interesting material for spintronics, showing long spin relaxation lengths even at room temperature. For future spintronic devices it is important to understand the behavior of the spins and the limitations for spin transport in structures where the dimensions are smaller than the spin relaxation length. However, the study of spin injection and transport in graphene nanostructures is highly unexplored. Here we study the spin injection and relaxation in nanostructured graphene with dimensions smaller than the spin relaxation length. For graphene nanoislands, where the edge length to area ratio is much higher than for standard devices, we show that enhanced spin-flip processes at the edges do not seem to play a major role in the spin relaxation. On the other hand, contact induced spin relaxation has a much more dramatic effect for these low dimensional structures. By studying the nonlocal spin transport through a graphene quantum dot we observe that the obtained values for spin relaxation are dominated by the connecting graphene islands and not by the quantum dot itself. Using a simple model we argue that future nonlocal Hanle precession measurements can obtain a more significant value for the spin relaxation time for the quantum dot by using high spin polarization contacts in combination with low tunneling rates

Studieadvies op basis van zelforganisatie: Dynamische wegwijzers in een veranderend onderwijslandschap

Van den Berg, B., Tattersall, C., Janssen, J., Van Es, R., & Koper, R. (2006). Studieadvies op basis van zelforganisatie: Dynamische wegwijzers in een veranderend onderwijslandschap. Unpublished manuscriptStudenten kunnen tegenwoordig kiezen uit een steeds groter aanbod van cursussen en trainingen, die vaak in de vorm van losse modules op verschillende manieren aan elkaar geschakeld kunnen worden. Dit biedt veel voordelen maar vormt ook de basis voor een keuzeprobleem: wat is de meest effectieve weg naar mijn doel? Dit artikel beschrijft de software architectuur die is ontworpen om Life-Long-Learners te ondersteunen bij het kiezen van hun leerpad in een leernetwerk. Deze architectuur sluit aan bij theorieën over zelforganisatie en indirecte sociale communicatie. De architectuur omvat de opslag, verwerking en presentatie van collectief studiegedrag en verschaft informatie over succesvolle leerpaden van medestudenten aan studenten die een vervolgkeuze voor hun studie maken. Er wordt een implementatie beschreven van een leernetwerk en verslag gedaan van de uitkomsten van een experiment met dit prototype. De resultaten leiden tot de conclusie dat er door het geven van een advies convergentie van leerpaden optreedt en dat de studenten die een studieadvies krijgen effectiever zijn

Chapter Genetics of Amyotrophic Lateral Sclerosis

Space scienc

Genetics of Amyotrophic Lateral Sclerosis

La sclérose latérale amyotrophique (SLA) est la maladie des neurones moteurs la plus fréquente, affectant 4-6 individus par 100,000 habitants à l’échelle mondiale. La maladie se caractérise par une faiblesse et une atrophie musculaire suite à la dégénérescence des neurones du cortex moteur, tronc cérébral et moelle épinière. Les personnes atteintes développent les premiers symptômes à l’âge adulte et la maladie progresse sur une période de trois à cinq ans. Il a été répertorié qu’environ 10% des patients ont une histoire familiale de SLA; 90% des gens affectés le sont donc de façon sporadique. La découverte il y a 19 ans de mutations dans le gène zinc/copper superoxide dismutase (SOD1), présentes dans 15-20% des cas familiaux de SLA et environ 2% du total des individus affectés, a été l’événement déclencheur pour la découverte de variations génétiques responsables de la maladie. La recherche sur la génétique de la SLA a connu une progression rapide ces quatre dernières années avec l’identification de mutations dans de nouveaux gènes. Toutefois, même si certains de ces gènes ont été démontrés comme réellement liés à la maladie, la contribution d’autres gènes demeure incertaine puisque les résultats publiés de ceux-ci n’ont pas, à ce jour, été répliqués. Une portion substantielle de cas reste cependant à être génétiquement expliquée, et aucun traitement à ce jour n’a été démontré comme étant efficace pour remédier, atténuer ou prévenir la maladie. Le but du projet de recherche de doctorat était d’identifier de nouveaux gènes mutés dans la SLA, tout en évaluant la contribution de gènes nouvellement identifiés chez une importante cohorte multiethnique de cas familiaux et sporadiques. Les résultats présentés sont organisés en trois sections différentes. Dans un premier temps, la contribution de mutations présentes dans le gène FUS est évaluée chez les patients familiaux, sporadiques et juvéniles de SLA. Précisément, de nouvelles mutations sont rapportées et la proportion de mutations retrouvées chez les cas familiaux et sporadiques de SLA est évaluée. De plus, une nouvelle mutation est rapportée dans un cas juvénile de SLA; cette étude de cas est discutée. Dans un deuxième temps, de nouvelles avenues génétiques sont explorées concernant le gène SOD1. En effet, une nouvelle mutation complexe est rapportée chez une famille française de SLA. De plus, la possibilité qu’une mutation présente dans un autre gène impliqué dans la SLA ait un impact sur l’épissage du gène SOD1 est évaluée. Finalement, la dernière section explique la contribution de nouveaux gènes candidats chez les patients atteints de SLA. Spécifiquement, le rôle des gènes OPTN, SIGMAR1 et SORT1 dans le phénotype de SLA est évalué. Il est souhaité que nos résultats combinés avec les récents développements en génétique et biologie moléculaire permettent une meilleure compréhension du mécanisme pathologique responsable de cette terrible maladie tout en guidant le déploiement de thérapies suite à l’identification des cibles appropriées.Amyotrophic lateral sclerosis (ALS) is the most common of motor neuron diseases, affecting 4-6 individuals per 100,000 individuals worldwide. ALS is characterized by muscle weakness and atrophy caused by the degeneration of neurons located in the motor cortex, brain stem and spinal cord. This fatal disease generally has an adult onset and progresses over a three to five year period. While 10% of patients affected have a family history of the disease, 90% of cases do not and are considered sporadic. The finding of mutations in the zinc/copper superoxide dismutase gene (SOD1) gene 19 years ago in about 15-20% of familial ALS (FALS) patients and approximately 2% of overall cases developed the interest of identifying rare genetics variants causing the disease. The ALS research field experienced a rapid progression during the last four years as mutations in new genes have been identified. While mutations in some of those new genes have been clearly linked to ALS, the role of others is still questionable and so far has not been positively replicated in other populations. Importantly, a significant portion of cases still need to be genetically explained and, unfortunately, there is still no effective treatment to cure, attenuate or prevent the disease. The aim of this Ph.D research project was to identify new ALS mutated genes while analysing the causative role of other newly identified genes in a large familial and sporadic ALS cohort of different origins. The results presented here are categorized into three different sections. First, the contribution of FUS mutations to familial, sporadic and juvenile ALS is analysed. Specifically, new FUS mutations are reported in ALS cases and the proportions of variants present in the tested familial and sporadic ALS cohorts are assessed. In addition, a new mutation is reported in a juvenile ALS patient, and this interesting case is discussed. Second, new genetic avenues are explored for the SOD1 gene. Precisely, a new and complex SOD1 mutation is reported in a French ALS family. Moreover, the possibility that other ALS mutated genes influence SOD1 splicing events is evaluated. Third, the contribution of new candidate genes is evaluated. Precisely, the contribution of OPTN, SIGMAR1 and SORT1 genes to the ALS phenotype is assessed. Hopefully, our different findings combined with recent developments in genetics and molecular biology will permit a better understanding of the pathological mechanisms involved in the disease and will lead to the identification of the right targets in order to develop appropriate therapeutics for ALS patients

Learners’ evaluation of a navigation support tool in distance education

Bolman, C., Tattersall, C., Waterink, W., Janssen, J., Van den Berg, B., Van Es, R., et al. (2007). Learner’s evaluation of a navigation support tool in distance education. Journal of Computer Assisted Learning, 23 (5), 384-392.This article investigates the usability of a navigation support tool developed to guide learners in a lifelong learning environment. The navigation support tool generates advice on the best next step to take in an e-learning course following completion of a course module, and was evaluated in a largescale experimental study based around an online Internet skills course. This article follows on from the experimental study and examines learners’ evaluation of the navigational support. It uses automatically generated logs of completion of course modules and learners’ answers to online questionnaires to give insight into learners’ evaluation, learners’ adherence to the advice and selfefficacy information. The article describes the theoretical underpinnings of the work, the experimental setup and results, and draws conclusions to refine the navigation tool and to increase adherence to the advice

Swarm-based wayfinding support in open and distance learning

Please refer to the original source: Tattersall, C. Manderveld, J., Van den Berg, B., Van Es, R., Janssen, J., & Koper, R. (2005). Swarm-based wayfinding support in open and distance learning. In Alkhalifa, E.M. (Ed). Cognitively Informed Systems: Utilizing Practical Approaches to Enrich Information Presentation and Transfer. Information Science Publishing, USA. (pp. 166-183). [http://www.silvertair.com/CIS/Contents.htm] OR Tattersall, C. Manderveld, J., Van den Berg, B., Van Es, R., Janssen, J., & Koper, R. (2008). Swarm-based Wayfinding Support in Open and Distance Learning. In Sugumaran, V. (Ed). Intelligent Information Technologies: Concepts, Methodologies, Tools, and Applications. Information Science Reference, Hershey New York. (pp 846-857).Open and Distance Learning (ODL) gives learners freedom of time, place and pace of study, putting learner self-direction centre-stage. However, increased responsibility should not come at the price of over-burdening or abandonment of learners as they progress along their learning journey. This paper introduces an approach to wayfinding support for distance learners based on self-organisation theory. It describes an architecture which supports the recording, processing and presentation of collective learner behaviour designed to create a feedback loop informing learners of successful paths towards the attainment of learning goals. The approach is presented as an alternative to methods of achieving adaptation in hypermedia-based learning environments which involve learner modelling

Isolation and function of a human endothelial cell C1q receptor

It has been shown previously that cultured human venous and arterial endothelial cells (EC) bind C1q in a time- and dose-dependent manner. Cultured human endothelial cells express an average number of 5.2 × 105 binding sites/cell. In the present study the putative receptor for C1q (C1qR) was isolated from the membranes of 1–5 × 109 human umbilical cord EC by affinity chromatography on C1q–Sepharose. During isolation, C1qR was detected by its capacity to inhibit the lysis of EAC1q in C1q-deficient serum. The eluate from C1q–Sepharose was concentrated, dialysed and subjected to QAE-A50 chromatography and subsequently to gel filtration on HPLC–TSK 3000. C1qR filtered at an apparent molecular weight of 60 kDa. Purified C1qR exhibited an apparent molecular weight of 55–62 kDa in the unreduced state and a molecular weight of 64–68 kDa in reduced form. Two IgM monoclonal antibodies (mAb) D3 and D5 were raised following immunization of mice with purified receptor preparations. Both monoclonal antibodies increased the binding of 125I-C1q to endothelial cells but F(ab')2 anti-C1qR mAb inhibited the binding of a125I-C1q to EC in a dosedependent manner. The D3 mAb recognized a band of 54–60 kDa in Western blots of membranes of human EC and polymorphonuclear leukocytes. Previously, the authors showed that C1q induces the binding of IgM-containing immune complexes to EC. Therefore, it was hypothesized that during a primary immune response generation of IgM-IC may occur, resulting in binding and activation of C1, dissociation of activated C1 by C1 inhibitor and subsequent interaction of IgM-IC bearing C1q with EC–C1qR

Swarm-based Sequencing Recommendations in E-learning

To be presented at the International Workshop on Recommender Agents and Adaptive Web-based Systems (RAAWS 2005) held in conjunction with the Intelligent Systems Design and Applications 2005 Conference (ISDA 2005), Wroclaw, Poland, September 8-10, 2005. Proceedings 5th International Conference on Intelligent Systems Design and Applications, (Eds) Kwasnicka, H. & Paprzycki, M., IEEE Computer Society, 2005, pp.488-493Open and distance Learning (ODL) gives learners freedom of time, place and pace of study, putting learner self-direction centre-stage. However, increased responsibility should not come at the price of over-burdening or abandonment of learners as they progress along their learning journey. This paper introduces an approach to recommending the sequencing of e-learning modules for distance learners based on self-organisation theory. It describes an architecture which supports the recording, processing and presentation of collective learner behaviour designed to create a feedback loop informing learners of successful paths towards the attainment of learning goals. The article includes initial results from a large-scale experiment designed to validate the approach