Tesi sul tema "Manipulation de laboratoire"

Cette thèse traite de l'action des ondes acoustiques sur des bulles micrométriques excitées à leur fréquence de résonance. En effet, les bulles peuvent être considérées comme des oscillateurs mécaniques et les forces acoustiques à leur résonance, appelées forces de Bjerknes, ont des propriétés non triviales. De plus, les bulles interagissent entre elles par l'émission d'un champ secondaire, menant à leur auto-organisation sur un motif périodique. Ici, les bulles sont confinées dans des microcanaux, elles ne sont pas sphériques et frottent fortement sur les parois. L'étude expérimentale des forces acoustiques (primaire et secondaire) est alors précédée par la modélisation de l'écoulement des bulles, liant la friction sur les parois aux forces externes appliquées. Plusieurs applications aux laboratoires sur puce sont développées, dont le tri en taille, la division asymétrique contrôlée, l'aiguillage automatique à une bifurcation, et la manipulation de goutte.

Le travail de thèse présenté dans ce manuscrit s'inscrit dans une dynamique d'intégration de matériaux non conventionnels en systèmes microfluidiques. Il vise à démontrer le potentiel du cPDMS, un matériau nanocomposite formé d'une matrice de polydiméthylsiloxane rendu conducteur par l'ajout de nanoparticules de carbone. Compatible avec les procédés technologiques habituels, le cPDMS peut être structuré dans une large gamme d'épaisseurs et de géométries mais présente surtout l'avantage de pouvoir être collé irréversiblement sur verre, PDMS et silicium. Son intégration est parfaitement étanche, rapide à mettre en oeuvre, et très économique. La première partie du manuscrit est consacrée à la caractérisation de ce matériau. Ses propriétés électriques et de surface, pouvant être critiques pour une utilisation en microfluidique, ont été particulièrement étudiées. Les champs électriques offrant de nombreuses possibilités pour réaliser des fonctions clés en microfluidique (détection, séparation, manipulation de fluides ou de particules), nous avons choisi d'évaluer l'intérêt d'électrodes de cPDMS dans deux types d'applications. Les aspects de détection ont d'abord été mis en évidence à l'aide de mesures électrochimiques. Cette méthode a permis à la fois de caractériser la surface du cPDMS tout en validant son utilisation potentielle pour des applications d'analyses électrochimiques. Dans la dernière partie du manuscrit, le matériau a été testé pour la manipulation de particules à travers l'observation de différents phénomènes électrocinétiques. Ceux-ci ont conduit à la mise au point de dispositifs microfluidiques (intégrant des lectrodes de cPDMS) dédiés à la lyse et à l'électrofusion de cellules.

Lorsque des ondes acoustiques de surface rayonnent dans des fluides, elles provoquent deux effets non linéaires : la pression de radiation et le streaming acoustique. Ces deux effets ont trouvé un grand nombre d’applications pour la microfluidique digitale, la manipulation sans contact et le tri cellulaire. Néanmoins, ces systèmes se heurtent à deux limites. D’une part, chaque application requiert une onde acoustique spécifique : il n’existe pas de dispositif multifonction à ce jour. D’autre part, l’exploration des fonctionnalités offertes par les ondes de surface les plus simples (ondes planes, ondes focalisées) n’a pas permis de réaliser des pinces sélectives permettant de manipuler individuellement des particules ou cellules indépendamment de leurs voisines.Dans une première partie de la thèse, nous développons deux méthodologies pour synthétiser des champs complexes d’ondes de surface. La première méthode utilise un réseau de 32 peignes interdigités contrôlé par la technique du filtre inverse pour générer des champs sur demande. La seconde résout un problème inverse afin de concevoir un transducteur holographique générant spécifiquement le champ demandé. Dans la seconde partie de la thèse, nous utilisons le filtre inverse pour (i) réaliser un laboratoire sur puce multifonction et (ii) étudier le potentiel d’ondes de surface particulières appelées ondes de surface tourbillonnaires. Ces ondes permettent une manipulation sélective et sans contact d’objets microscopiques. Nous terminons la thèse en équipant un microscope d’un transducteur holographique de vortex acoustiques afin de réaliser une manipulation sélective et sans contact de cellules
When surface acoustic waves radiate in nearby fluids, they trigger two nonlinear effects: acoustic radiation pressure and acoustic streaming. These two effects find numerous applications for digital microfluidics, contactless manipulation and biological cell sorting. Nonetheless, these systems face two limitations. On the one hand, each application requires a specific acoustic wave: there is no multifunction device so far. On the other hand, search for functionalities offered by simple surface acoustic waves (plane and focused waves) has failed to provide a selective tweezers able to manipulate individual particles or cells independently of their neighbors. In the first part of this thesis, we develop two methods to synthesize complex surface acoustic wave fields. The first one employs an array of 32 interdigitated transducers controlled by the inverse filter to generate arbitrary fields on demand. The second method solves an inverse problem to design a holographic transducer to generate a predefined field. In the second part of the thesis, we use the inverse filter to (i) implement a multifunction lab on a chip and (ii) investigate the potentialities of a special type of surface acoustic waves called swirling surface waves. These waves enable a selective and contactless manipulation of microscopic objects. We conclude the thesis by integrating a holographic acoustical vortex transducer on a microscope in order to selectively manipulate biological cells without contact

Les boîtes quantiques sont une technologie performante pour les diodes laser. En changeant la taille et la forme de ces boîtes et en utilisant une facette de sortie antireflet, des puces à gain peuvent être conçues pour émettre sur une large gamme de longueurs d’onde dans des lasers accordables. Cette thèse de doctorat traite à la fois de la simulation d’un laser à cavité externe et de la caractérisation expérimentale d’un laser accordable basé sur une puce à gain à boîte quantique. Un modèle d’équation d’évolution a été développé. La simulation numérique étudie les propriétés dynamiques et de bruit de ce laser. Ce travail montre l’intégration d’une puce à gain à boîte quantique dans une configuration de laser du type Littman-Metcalf. De plus, une nouvelle méthode a été développée pour résoudre spectralement l’émission spontanée en champ lointain de la puce à gain. Un mécanisme de référencement en longueur d’onde utilisant un étalon Fabry-Perot est présenté en détail. Enfin, un prototype d’un nouveau laser accordable à haute puissance sans asservissement a été testé à long terme pour un fonctionnement sans saut de mode
Quantum dots have been proven to be a high performing technology for solitary laser diodes. By varying dot sizes, shapes, and by using an antireflection output facet, gain chips can be designed to emit over a large wavelength range in tunable lasers. This PhD thesis work deals with both the simulation of an external cavity laser and the experimental characterization of a quantum dot gain chip-based tunable laser. A rate equation model has been derived. The numerical simulation investigates dynamical properties like turn-on delay, gain clamping and damping rate. This work shows the integration of a quantum dot gain chip in a Littman-Metcalf laser setup. Also, a new method has been developed to spectrally resolve the gain chip’s spontaneous emission in the far-field. A wavelength referencing mechanism utilizing a Fabry- Perot etalon is laid out in detail. Finally, a prototype of a newly developed high power tunable laser without servo control has been tested for long term mode-hop free operation

Since the first microfluidic device was developed in the early 1950s, when the basics for today’s inkjet technology were set, thousands of publications have appeared related to the topic. The increasing interest on these technologies is caused by its ability to be scaled and its rapid development, which allows manipulating and detecting small quantities of analites even at the cellular scale. The integration of microfluidic technologies with specific sensors and actuators at minute scales in order to achieve a set of automated laboratory operations and perform a particular solution for a specific application, generally on the life sciences and chemistry fields, was defined as Lab-on-a-chip (LoC). LoC devices have the potential to become a powerful technology for some fields, such as health, food security or environmental control. Their low cost and portability make them also suitable to improve medical diagnosis and research in developing countries. Moreover, these systems permit also to explore new methods for manipulation and characterization of cells by means of electrical cell properties, by using techniques such as dielectrophoresis (DEP) or impedance spectroscopy (IS). In fact, the dielectrophoretic force allows manipulating cells, taking advantage of their electrical properties, by applying an electric field. Likewise, impedance allows measuring electrical properties of materials and, used wisely, inform about characteristics such as presence, composition or size of cells or other biological materials. This work aims, in its final stage, to exploit the combined potential of both techniques, DEP and IS, in a compact system for bioanalytical bench-top applications. The creation of the complete device has been a long procedure alternating theoretical calculations and experimental tests. It has included different steps such as the design of the need electronic equipment stages, the study of different microfluidic designs, an accurate bacteria concentration and manipulation protocol definition, and the study of the viability of the bacteria populations recovered with our device. These studies have made possible to finally obtain an automated bacteria concentrator for microbiology, food, water and environmental control applications while performing impedance cell analysis to monitor bacteria accumulation during the process. The system has been adjusted and proved for the real case of Escherichia Coli (E. coli) concentration and analysis. E. coli presents pathogenic variants that cause morbidity and mortality worldwide being therefore a topic of interest. E. coli is one of the main antimicrobials resistant pathogens in healthcare-associated infections reported to the National Healthcare Safety Network, being the primary cause of widespread pathologies such as significant diarrheal and extra-intestinal diseases or urinary tract infections. Furthermore, E. coli can be found as a bacterial food contamination and causes avian coli-bacillosis, one of the major bacterial diseases in the poultry industry and the most common avian disease communicable to humans. Currently, bacterium presence detection involve long time culture processes only to obtain a valid sample which could be properly detected. DEP concentration is a strong selective manipulation method which allows reducing sample preparation time. Moreover, by taking profit of IS, E. coli could be rapidly detected in the same equipment. For that reason, it is thought the proposed devices will be a useful tool for some current microbiology laboratories. Hence the mainly aims of the present thesis are: (I) to prove the feasibility of custom DEP generator for controlling bacteria and find the best signal to accomplish this, (II) to look for the best microfluidic chip option for bacteria preconcentration purposes on bioanalytical applications, (III) to test the feasibility of a custom IS device and (IV) to use the previous studies to design a complete electronic equipment, taken profit of combination of both techniques to have an autonomous system (V) To demonstrate the proof of concept of the full device with the real case of E. coli concentration.
El objetivo de esta tesis es el diseño de una instrumentación capaz de manipular y caracterizar células, a fin de realizar análisis más exhaustivos de elementos biológicos y acelerar procesos de detección de patógenos para aplicaciones de diagnóstico o de control de calidad de alimentos. El dispositivo se centra en dos tipos de técnicas eléctricas para la manipulación y detección de células: La dielectroforesis (DEP) y la medición de la bioimpedancia. La DEP permite manipular material biológico por medio de campos eléctricos, aprovechando las propiedades eléctricas de la célula y el medio en que se encuentra. La manipulación es por tanto ajustable, mediante el control de estas propiedades, así como a través de la geometría de los electrodos usados, la frecuencia y el módulo de la tensión aplicada. Por otro lado, la IS permite caracterizar material biológico mediante su comportamiento eléctrico en frecuencia. La medida se realiza a través de la aplicación de una corriente alterna controlada y la monitorización del efecto sobre el tejido mediante potencial eléctrico. Los dispositivos de IS son fácilmente integrables con técnicas dielectroforéticas de manipulación, fusionando manipulación con detección. En esta tesis, la combinación de estas técnicas permite la concentración de pequeños patógenos en grandes volúmenes de muestras y su posterior detección. Para ello, se crean diversos módulos de instrumentación electrónica. Algunos, están dedicados a generar señales alternas desfasadas a frecuencias óptimas para la manipulación de patógenos (módulo DEP). Otros, combinan módulos de generación, lectura y tratamiento digital, para la monitorización del comportamiento eléctrico de células (IS). Los módulos diseñados son validados en un entorno real controlado para concentrar y detectar la bacteria Escherichia Coli en grandes volúmenes de agua. Como resultado, se obtiene una electrónica modular válida, autónoma, portátil y de bajo coste, capaz de disminuir tiempos de preparación y detección de muestras en laboratorio.

Zebrafish has emerged as an important model for the study of embryonic hematopoiesis. It is a well-characterized model with numerous advantages. Large amount of embryos can be produced by a single pair of zebrafish and the optically transparent embryos allow direct visualization and manipulation of embryonic processes. Large-scale chemical screening using zebrafish embryos can be developed for robust screening of chemical libraries. The zebrafish hematopoiesis resembles that of mammals and occurs in two successive waves, primitive and definitive hematopoiesis. High-throughput read-outs are available to study the effects of different chemicals and genetic modifications on hematopoiesis. In first part of this study, an initial screening using O-dianisidine staining and whole-mount in-situ hybridization as read-out for chemicals that might perturb the regulation of hematopoiesis was conducted. Positive hit was further evaluated by flow cytometry of dissociated transgenic Tg(gata1:GFP) zebrafish embryos. A total of 50 compounds were screened from the "Mechanistic set" chemical libraries obtained from Developmental Therapeutics Program of the National Cancer Institute. One compound, "NSC 643834" was shown to reduce O-dianisidine staining at different concentrations tested. The second part of this study was performed to investigate the role of inca2 in zebrafish hematopoiesis. inca2 was found to be upregulated in chordin morphant zebrafish in which primitive hematopoiesis was expanded. The spatial expression of inca2 was examined by whole mount in-situ hybridization of embryos at different developmental stages. Furthermore the function of inca2 was investigated by gene knockdown using inca2 anti-sense morpholino. Primitive hematopoiesis was perturbed, suggesting that inca2 might play an important role in the regulation of this process. In conclusion, the present study demonstrated the distinct advantages and feasibility of using zebrafish as a platform of high throughput chemical screening and genetic manipulation. The result provided important ground to investigate the regulatory mechanisms of embryonic hematopoiesis.
published_or_final_version
Medicine
Master
Master of Research in Medicine

À travers des nos sens, le cerveau reçoit une énorme quantité des informations. Cette information doit être filtrée afin d'extraire les caractéristiques les plus saillantes pour guider notre comportement. La façon dont le cerveau génère différents percepts et conduit les comportements, reste comme deux des majeures questions de la neuroscience moderne. Dans ce travail, en utilisant une tâche de discrimination Go / noGo combinée à l’optogénétique pour inactiver le cortex auditif durant le comportement la souris, nous avons établi que le cortex auditif n’est pas utilisé pour les discriminations de fréquence simples, mais qu’il était nécessaire pour résoudre une tâche plus difficile. En combinant différentes techniques de cartographie et l’optogénétique sculptée pour activer des champs tonotopiques définis avec précision dans le cortex auditif, nous avons pu élucider la stratégie utilisée par les souris pour résoudre cette tâche difficile, révélant ainsi un mécanisme de discrimination de fréquence retardé. En parallèle, des observations sur la vitesse d'apprentissage et l'activité des différents sons dans le cortex auditif nous ont amenés à étudier leurs interactions et à tester de manière causale le rôle du recrutement cortical dans l'apprentissage associatif, le révélant comme un possible corrélat neurophysiologique de la saillance
Through our senses, the brain receives an enormous amount of information. This information needs to be filtered in order to extract the most salient features to guide our behavior. How the brain actually generates different percepts and drives behavior, remain the two major questions in modern neuroscience. To answer these questions, novel neural engineering approaches are now employed to map, model and finally generate, artificial sensory perception with its learned or innate associated behavioral outcome. In this work, using a Go/noGo discrimination task combined with optogenetics to silence auditory cortex during ongoing behavior in mice, we have established the dispensable role of auditory cortex for simple frequency discriminations, but also its necessary role to solve a more challenging task. By the combination of different mapping techniques and light-sculpted optogenetics to activate precisely defined tonotopic fields in auditory cortex, we could elucidate the strategy that mice use to solve this hard task, revealing a delayed frequency discrimination mechanism. In parallel, observations about learning speed and sound-triggered activity in auditory cortex, led us to study their interactions and causally test the role of cortical recruitment in associative learning, revealing it as a possible neurophysiological correlate of saliency

The increasing number of human objects in space has laid the foundation of a novel class of orbital missions for servicing and maintenance. The main goal of this thesis is the development, building and testing of a robotic manipulator for the simulation of orbital maneuvers, with particular attention to Active Debris Removal (ADR) and On-Orbit Servicing (OOS). There are currently very few ways to reproduce microgravity in a non-orbital environment: among the main techniques, it is worth mentioning parabolic flights, pool simulations and robotic facilities. Parabolic flights allow to reproduce orbital conditions quite faithfully, but simulation conditions are very constraining. Pool simulations, on the other hand, have fewer constrictions in terms of cost, but the drag induced by the water negatively affects the simulated microgravity. Robotic facilities, finally, permit to reproduce indirectly (that is, with an appropriate control system) the physics of microgravity. State of the art on 3D robotic simulations is nowadays limited to industrial robots facilities, that bear conspicuous costs, both in terms of hardware and maintenance. This project proposes a viable alternative to these costly structures. Through dedicated algorithms, the system is able to compute in real time the consequences of these contacts in terms of trajectory modifications, which are then fed to the hardware in the loop (HIL) control system. Moreover, the governing software can be commanded to perform active maneuvers and relocations: as a consequence, the manipulator can be used as the testing bench not only for orbital servicing operations but also for attitude control systems, providing a faithful, real-time simulation of the zero-gravity behavior. Furthermore, with the aid of dynamic scaling laws, the potentialities of the facility can be exponentially increased: the simulation environment is not longer bounded to be as big as the robot workspace, but could be several orders of magnitude bigger, allowing for the reproduction of otherwise preposterous scenarios. The thesis describes the detailed mechanical design of the facility, corroborated by structural modeling, static and vibrational finite element verification. A strategy for the simulation of impedance-matched contacts is presented and an analytical control analysis defines the set of allowable inertial properties of the simulated entities. Focusing on the simulation scenarios, an innovative information theoretic approach for simultaneous localization and docking has been designed and applied for the first time to a 3D rendezvous scenario. Finally, in order to instrument the facility’s end effector with a consistent sensor suite, the design and manufacturing of an innovative Sun sensor is proposed.
Il crescente numero di oggetti umani nello spazio ha posto le basi per una nuova classe di missioni orbitali per l'assistenza e la manutenzione. L'obiettivo principale di questa tesi è lo sviluppo, la costruzione e la verifica sperimentale di un manipolatore robotico per la simulazione di manovre orbitali, con particolare attenzione alla rimozione di detriti (ADR) e la manutenzione in orbita (OOS). Allo stato dell'arte, sono poche le modalità utilizzate per la riproduzione della microgravità in un ambiente non-orbitale: fra le tecniche principali, vale la pena ricordare voli parabolici, simulazioni in piscina e simulatori robotici. I voli parabolici consentono di riprodurre le condizioni orbitali abbastanza fedelmente, ma le condizioni di simulazione sono pesantemente vincolanti. Le simulazioni in piscina, d'altra parte, hanno meno costrizioni in termini di costo, ma la resistenza indotta dall'acqua influisce negativamente sulla qualità della microgravità simulata. Gli impianti robotizzati, infine, permettono di riprodurre indirettamente (cioè attraverso un adeguato sistema di controllo) la fisica della microgravità. Lo stato dell'arte sulle simulazioni robotiche 3D è oggi limitato a robot industriali, caratterizzati da notevoli costi sia in termini di hardware che di manutenzione. Questo progetto propone un'alternativa a queste strutture: attraverso algoritmi dedicati, il sistema è in grado di calcolare in tempo reale le conseguenze dei contatti tramite le opportune modifiche alla traiettoria, che vengono poi fornite al sistema di controllo "hardware in the loop" (HIL). Inoltre, il software può essere comandato per eseguire manovre attive e di "relocation": di conseguenza, il manipolatore può essere utilizzato come test-bed non solo per operazioni di manutenzione orbitale, ma anche per sistemi di controllo di assetto, fornendo una fedele simulazione in tempo reale del rispettivo comportamento in assenza di gravità. La tesi descrive la progettazione meccanica dettagliata della struttura, corroborata dalla rispettiva modellazione strutturale, e dalla verifica agli elementi finiti delle prestazioni statiche e vibrazionali. Viene successivamente presentata una strategia per la simulazione di contatti tramite il matching tra le impedenze e un controllore dedicato definisce l'insieme delle proprietà inerziali simulabili tramite la struttura. Concentrandosi sugli scenari di simulazione, viene poi presentato un innovativo approccio SLAM (simultaneous localization and mapping) che utilizza metodi stocastici per il design di traiettorie di ispezione e riconoscimento markers applicato ad un task di rendez-vous 3D. Infine, con l'obiettivo di fornire una sensor-suite capace di stimare in real-time l'assetto dell'end-effector, viene descritto un innovativo sensore di Sole miniaturizzato. Ne vengono discusse la progettazione e la fabbricazione, corroborate dalle necessarie verifiche sperimentali.

The aim of the master thesis is to design a laboratory station and a control program operated by a collaborative robot IRB 14000 YuMi using an integrated effector camera to identify laboratory objects and control the progress of the task. In the introductory part, collaborative robots are briefly introduced, the IRB 14000 on which the task is implemented and the RobotStudio development environment together with the IntegratedVision extension are described in more detail. The following chapters describe the laboratory task itself, its solution and testing of the designed program.

Doctor of Philosophy
Department of Physics
Nobel S. Rebello
Conventional wisdom has long advised that students’ learning is best supported by interaction with physical manipulative. Thus, in the physics laboratory, students typically spend their time conducting experiments with physical equipment. However, computer simulations offer a tempting alternative to traditional physical experiments. In a virtual experiment, using a computer simulation, students can gather data quickly, and measurement errors and frictional effects can be explicitly controlled. This research investigates the relative support for students’ learning offered by physical and virtual experimentation in the context of simple machines. Specifically, I have investigated students’ learning as supported by experimentation with physical and virtual manipulative from three different angles-- what do students learn, how do students learn, and what do students think about their learning. The results indicate that the virtual manipulative better supported students’ understanding of work and potential energy than the physical manipulative did. Specifically, in responding to data analysis questions, students who used the virtual manipulative before the physical manipulative were more likely to describe work as constant across different lengths of frictionless inclined planes (or pulley systems) and were more likely to adequately compare work and potential energy, whereas students who used the physical manipulative first were more likely to talk about work and potential energy separately. On the other hand, no strong support was found to indicate that the physical manipulative better supported students’ understanding of a specific concept. In addition, students’ responses to the survey questions indicate that students tend to value data from a computer simulation more than from a physical experiment. The interview analysis indicates that the virtual environment better supported the students to create new ideas than the physical environment did. These results suggest that the traditional wisdom that students learn best from physical experiments is not necessarily true. Thus, researchers should continue to investigate how to best interweave students’ experiences with physical and virtual manipulatives. In addition, it may be useful for curriculum designers and instructors to spend more of their efforts designing learning experiences that make use of virtual manipulatives.

Denna studie beskriver hur en kommunal grundskola i sydvästra Indien undervisar matematik.Vår frågeställning var: Hur fungerar en indisk statlig grundskola arbetar med matematik? Vilka är lärarnas uppfattningar om skolans sätt att undervisa? För att ha möjlighet att fördjupa oss i frågorna undersökte vi även Hur lärarnas föreställningar om matematik påverkar normerna i klassrummet utifrån ramen av Yack och Cobbs normteori. Det är en kvalitativ studie där vi utförde observationer av undervisningen och intervjuer med lärare och rektorn på skolan om deras syn på matematikundervisningen, under tre veckor. Vi samlade också information om och dokumenterade deras matematikverkstad.Utifrån våra intervjuer och observationer kunde vi dra slutsatsen att samtliga på skolan arbetade med en aktivitetsbaserad undervisning där matematik lärs med hjälp av manipulativt, laborativt material. De arbetade tillsammans i ett arbetslag med en strävan att uppfylla läroplanens mål och med en gemensam arbetsmetod. Vi fann också att lärarnas värderingar och föreställningar om hur matematik ska läras ut, påverkar de normer som verkar i klassrummet.Denna studie kan inte generaliserbar eftersom detta är en fallstudie på denna skola. Dock förespråkar den indiska läroplanen att undervisningen ska ske utifrån elevnära aktiviteter, men matematikverkstaden på denna skola var speciell och utvecklad på denna skola.
For our study, we visited a Government Lower Primary School in India to inquiry about how a school in another schooling context teaches mathematics. Our research questions were: How does an Indian Government Lower Primary School work with mathematics? What are the teachers' perceptions of the school’s teaching approach? In addition to these questions and to inquire deeper into this subject, we also investigated How do the teachers’ perceptions and method of teaching connect to Yackel and Cobb’s framework of the different kinds of norms operating in the classroom?We did a qualitative study, staying at the school for three weeks to interview teachers about their method of teaching mathematics as well as observing how they were teaching mathematics and the norms that operated in the classroom. We also gathered information about their mathematics laboratory. During our interviews and observations we came to the conclusion that the school worked with activity-based learning by using manipulative materials. All teachers as well as the principal cooperatively strived to meet the curricula objectives, with the same teaching approach. We also found that the teachers’ values and beliefs about how mathematics should be taught, affect the norms operating in the classroom.This study cannot be generalised for all schools in India or even in this area. This study is a minor study which only considered one particular school which used an interesting teaching method, activity-based learning with manipulatives.

In a time when microorganisms are controlling the world, research in biology is more relevant than ever and this requires some powerful instruments. Optical tweezers use a focused laser beam to manipulate and probe objects on the nano- and microscale. This allows for the exploration of a miniature world at the border between biology, chemistry and physics. New methods for biophysical and physicochemical measurements are continuously being developed and at Umeå University there is a need for a new system that combines several of these methods. This would truly be the new Swiss army knife of biophysical and biomechanical research, extending their reach in the world of optical tweezing. My ambition with this project is to design and construct a robust system that incorporates optical trapping with high-precision force measurements and Raman spectroscopy, as well as introducing the possibility of generating multiple traps by using a spatial light modulator (SLM). The proposed design incorporates four different lasers and a novel combination of signal detection techniques. To allow for precise control of the systems components and laser beams, I designed and constructed motorized opto-mechanical components. These are controlled by an in-house developed software that handles data processing and signal analysis, while also providing a user interface for the system. The components include, motorized beam blockers and optical attenuators, which were developed using commonly available 3D printing techniques and electronic controllers. By designing the system from scratch, I could eliminate the known weaknesses of conventional systems and allow for a modular design where components can be added easily. The system is divided into two parts, a laser breadboard and a main breadboard. The former contains all the equipment needed to generate and control the laser beams, which are then coupled through optical fibers to the latter. This contains the components needed to move the optical trap inside the sample chamber, while performing measurements and providing user feedback. Construction and testing was done for one sub-system at a time, while the lack of time required a postponement for the implementation of Raman and SLM. The system performance was verified through Allan variance stability tests and the results were compared with other optical tweezers setups. The results show that the system follows the thermal limit for averaging times (τ) up to ~1 s when disturbances had been eliminated, which is similar to other systems. However, we could also show a decrease in variance all the way to τ = 2000 s, which is exceptionally good and not found in conventional systems. The force-resolution was determined to be on the order of femtonewtons, which is also exceptionally good. Thus, I conclude that this optical tweezers setup could lie as a solid foundation for future development and research in biological science at Umeå University for years to come.

Je présente ici mes travaux de thèseque j’ai réalisé ces trois dernières années au seindu Laboratoire ATMosphères et Observations Spa-tiales (LATMOS) de l’Université de Versailles St-Quentin-en-Yvelines (UVSQ) et du Jet PropulsionLaboratory (JPL), California Institute of Technol-ogy. Pendant ces 3 ans je me suis intéressé à la réac-tivité chimique des composés organiques en phasegaz et solide, en utilisant des expériences de labo-ratoire simulant les conditions de l’ionosphère et dela basse atmosphère de Titan, le plus gros satellitede Saturne. Titan est la seule lune du Système So-laire qui possède sa propre atmosphère. Cette atmo-sphère est principalement composée d’azote molécu-laire (N2). Le méthane (CH4) forme le gaz sec-ondaire. D’une part, j’ai analysé les composés neu-tres et les composés chargés (ions) présents dansdes mélanges gazeux simulant la haute atmosphèrede Titan. Ces composés sont considérés commeprécurseurs chimique à la brume organique observéeentourant Titan. C’est-à-dire qu’ils forment les pre-mières étapes d’une succession de réactions chim-iques de plus en plus élaborées formant plus bas dansl’atmosphère des particules solides complexes. Lanature de ces particules dans l’atmosphère de Titanreste encore à élucider complètement. Mon travailpendant cette thèse a été d’utiliser des expériencesde laboratoire pour investiguer la réactivité chim-ique en phase gaz (Chapitres 3 & 4), précurseurs àla formation d’aérosols, ainsi que le vieillissement deces composés plus bas dans l’atmosphère lorsqu’ilsforment les premiers condensats de nucléation à laformation de nuages (Chapitre 5)
Titan is the only moon in the SolarSystem to possess its own dense and gravitationallybound atmosphere, and is even larger than planetMercury. Its rocky diameter is a mere 117 km shy ofGanymede’s. If we were to scoop up a 1 cm3 sam-ple from Titan’s upper atmosphere, we would findtwo dominant molecules: molecular nitrogen N2 andmethane CH4. Should we look a bit more carefully,we would find many neutral molecules and positiveand negative ion compounds. These chemical speciesare the outcome of processes resulting from ener-getic radiation reaching Titan’s upper atmosphere,breaking apart the initial N2 and CH4. A cascadeof subsequent reactions will trigger the formationof new gas phase products more and more com-plex. Eventually, these products mainly contain-ing hydrogen, carbon and nitrogen will form largefractal aggregates composing the opaque haze en-shrouding the surface of Titan. This haze is whatgives Titan such a unique brownish hue. Most ofthe photochemically-produced volatiles will eventu-ally condense in the lower atmosphere, where theymay aggregate to form micrometer-sized icy parti-cles and clouds. During my PhD, I have focusedmy studies on (i) the gas phase reactivity of aerosolprecursors in experimental conditions analogous toTitan’s upper atmosphere (Chapters 3 & 4), and (ii)the end of life of some of the products as they con-dense in the lower and colder atmosphere (Chapter5). I used two experiments to address these respec-tive issues: the PAMPRE plasma reactor, located atLATMOS, UVSQ, Guyancourt, France, and the Ac-quabella chamber at the Jet Propulsion Laboratory,California Institute of Technology, Pasadena, USA.In this manuscript, I present my work on the neutraland positive ion reactivity in the PAMPRE plasmadischarge, as well as ice photochemistry results usinglaser irradiation in near-UV wavelengths

The experiment reported here tests the case of so-called exclusionary manipulation of emission permit markets, i.e., when a dominant firm -- here a monopolist -- increases its holding of permits in order to raise its rivals' costs and thereby gain more on a product market. Earlier studies have claimed that this type of market manipulation is likely to substantially reduce the social gains of permit trading and even result in negative gains. The experiment designed here parallels institutional and informat ional conditions likely to hold in real trade with carbon permits among electricity producers. Although the dominant firm withheld supply from the electricity market, the outcome seems to reject the theory of exclusionary manipulation. In later trading p eriods, closing prices on both markets, permit holdings and total electricity production are near competitive levels. Social gains of emissions trading are higher than in earlier studies.
Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/)
Includes bibliographical references (p. 18-19).

The main objective of this project is to create a innovating system that allows high-school students to access and control a robotic manipulator remotely in order to finish an experiment they have started earlier in the class. The aim is to create a system that any student with a device connected to the Internet and login credentials can use. So it needs to be simple enough for easy understanding but also needs to be secure in other to minimize accidents with the experiments. It's also important for the system to be low cost so schools can afford to obtain it and introduce it to daily classes.

The main objective of this project is to create a innovating system that allows high-school students to access and control a robotic manipulator remotely in order to finish an experiment they have started earlier in the class. The aim is to create a system that any student with a device connected to the Internet and login credentials can use. So it needs to be simple enough for easy understanding but also needs to be secure in other to minimize accidents with the experiments. It's also important for the system to be low cost so schools can afford to obtain it and introduce it to daily classes.

Thesis (Ph. D.)--University of Georgia, 2002.
Directed by Valentine A. Nzengung. Includes articles submitted to Journal of environmental quality, and Environmental toxicological chemistry. Includes bibliographical references.

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Background: Falls on stairs are a common and dangerous problem for older people. This series of studies evaluated whether or not selected changes to the appearance of stairs could make them safer for older people to negotiate. Objectives: To determine the effect of (1) a step edge highlighter and its position and (2) an optimised horizontal–vertical (H–V) visual illusion placed on a step riser on gait safety during stair descent and ascent. Design: A series of studies using a repeated measures, laboratory-based design, investigating gait control and safety in independently mobile older people. Setting: The University of Bradford Vision and Mobility Laboratory. Participants: Fit and healthy older people aged 60 years of age or more, independently mobile, reasonably active and with normal healthy eyes and corrected vision. Interventions: A step edge highlighter in a variety of offsets from the stair edge and an optimised H–V visual illusion placed on the stair riser. The H–V illusion was provided on a staircase by horizontal step edge highlighters on the tread edges and vertical stripes on the step risers. Main outcome measures: Gait parameters that are important for safe stepping in ascent and descent, particularly toe clearance during stair ascent and heel clearance during stair descent. Results: The step edge highlighter increased the precision of heel clearance during stepping and its positioning relative to the tread edge determined the extent of heel clearance over the tread edge. Positioning the highlighter away from the tread edge, as is not uncommonly provided by friction strips, decreased heel clearance significantly and led to greater heel scuffs. Although psychophysics experiments suggested that higher spatial frequencies of the H–V illusion might provide greater toe clearance on stair ascent, gait trials showed similar increased toe clearances for all spatial frequencies. When a 12 cycle per step spatial frequency H–V illusion was used, toe clearance increases of approximately 1 cm (17.5%) occurred without any accompanying changes in other important gait parameters or stability measures. Conclusions: High-contrast tread edge highlighters present on steps and stairs and positioned flush with the edge of the tread or as near to this as possible should improve stair descent safety in older people. A H–V illusion positioned on the riser of a raised surface/walkway (e.g. kerbs) and/or the top and/or bottom of a stairway is likely to increase foot clearance over the associated step/stair edge, and appears not to lead to any decrement in postural stability. Thus, their use is likely to reduce trip risk and hence improve stair ascent safety. The effect of the step and stair modifications should be assessed in older people with visual impairment. The only other remaining assessment that could be made would be to assess fall prevalence on steps and stairs, perhaps in public buildings, with and without these modifications.
National Institute for Health Research, Public Health Research programme. PHR programme as project number 10/3009/06

Indiana University-Purdue University Indianapolis (IUPUI)
The present study sought to identify the effects of chronic lithium administration on ethanol intakes in high alcohol-preferring (HAP) mice. Lithium is a well-established treatment for bipolar disorder and has demonstrated efficacy in reducing impulsivity, an endophenotype of the disease. Impulsivity is also a prominent trait of alcoholism. HAP mice display a preference for consuming substantial amounts of ethanol and exhibit abnormally high levels of impulsivity. Previous work has determined that chronic lithium exposure in HAP mice reduces their levels of impulsivity. The present study analyzed fluctuations in established intake patterns after lithium exposure and how pre-exposure to lithium would affect ethanol intake acquisition. The results showed an increase in ethanol intake and no change in preference for ethanol over water in lithium treated mice. There was an increase in overall total fluid consumption in these mice, likely resulting from polydipsic effects. There also appeared to be a potentiated lithium toxicity effect found in those mice pre-exposed to lithium. The conclusion was that lithium therapy does not decrease ethanol consumption in HAP mice.